Minimax Response Recovery under Global Overlap Tails
The verified contribution is substantial and generally represented faithfully, but extensive repetition and an underdeveloped econometric motivation require substantial editorial revision.
- Introduction; Main results; Identification and upper-bound proofs; Source-model transfer and comparison scope; Proofs of the main results The manuscript repeatedly presents the same material at substantial length. The Dorn comparison appears in the introduction, related work, geometric discussion, source appendix, and deferred proofs; the template is defined in three overlapping environments; and the main-result proof substantially repeats the selected-mesh and coefficient-envelope analysis already presented in its auxiliary lemma. This organization makes the new statistical argument difficult to distinguish from routine supporting detail.
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- 1 Oct 2026 (v1) · last revised 1 Oct 2026 (v3)
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CSWP-2026-026· https://causalsmith.org/papers/stat_weakoverlap_unisolvent_rate_v1/
@techreport{causalsmith_stat_weakoverlap_unisolvent_rate_v1,
title = {Minimax response recovery under global overlap tails},
author = {{CausalSmith}},
year = {2026},
month = oct,
institution = {CausalSmith Working Papers},
number = {CSWP-2026-026},
url = {https://causalsmith.org/papers/stat_weakoverlap_unisolvent_rate_v1/},
note = {Version 3, 1 Oct 2026. Machine-generated; formal statements verified in Lean 4 at commit d07574d}
} https://causalsmith.org/papers/stat_weakoverlap_unisolvent_rate_v1/ Cites version 3 of 1 Oct 2026. Abstract
We characterize minimax recovery of the treated causal response under a global propensity-tail restriction. The model combines consistency and conditional exchangeability with a covariate density bounded below on a cube, intrinsic Hölder response smoothness of known order , a bounded treated conditional mean, and uniformly conditional sub-Gaussian residuals. If is the covariate dimension, is the sample size, and is the overlap exponent, the pointwise and expected spatial-supremum minimax risks have scale An explicit estimator fits local polynomials with equal aggregate weight across fixed template microcells and selects its mesh through treated observation counts. With model constants fixed, its expected spatial-supremum guarantee attains this pure-power rate uniformly over fixed compact overlap intervals with distinct endpoints in , using the known smoothness and observed treatment design. A bounded, two-valued potential-outcome experiment supplies the matching pointwise lower bound at every fixed point of the closed cube. In dimensions at least two, a thin-strip construction exhibits admissible treatment geometry with degenerating local treated variation. An affine transfer also establishes the expected spatial-supremum upper guarantee for fixed-constant Gaussian source envelopes satisfying Dorn’s retained moment, variance, smoothness, uniform-design, and global-tail restrictions.
Introduction
This paper establishes the minimax rate for recovering a treated causal response throughout a covariate cube when treatment availability is governed by a global propensity tail. Under consistency and conditional exchangeability, the target is the conditional mean of the treated potential outcome, identified through treated outcome regression. We study laws with a covariate density bounded below, a response in an intrinsic cube Hölder ball of known order, a uniformly bounded treated conditional mean, and uniformly conditional sub-Gaussian residuals. Write for sample size, for response smoothness, for covariate dimension, and for the overlap exponent. Within this fixed-constant class, one explicit estimator attains the expected spatial-supremum rate The upper guarantee is uniform over any fixed compact exponent interval with distinct endpoints contained in . For each fixed exponent and each fixed evaluation point, a matching lower bound establishes the same minimax scale for pointwise expected absolute error.
Response recovery is a basic component of causal adjustment in the potential-outcome framework (Rubin, 1974; Rosenbaum et al., 1983; Imbens et al., 2015). Its statistical difficulty depends on where treated observations are available. Our overlap restriction bounds the covariate probability of low-propensity regions by a power of the propensity threshold. This restriction quantifies the prevalence of treatment scarcity while accommodating measurable propensities and heterogeneous local treatment geometry. The target remains the continuous treated response over the entire closed cube, and the spatial loss measures the largest estimation error within each sample realization before taking expectation.
The construction separates polynomial conditioning from treatment-count precision. Each partition cube contains scaled copies of a fixed collection of small microcells around polynomial interpolation nodes. The fit gives every microcell the same aggregate weight, averaging treated observations within each cell. This weighting keeps the empirical Gram matrix close to a fixed positive-definite template whenever the cells are occupied. A count selector chooses the finest candidate mesh at which every microcell contains enough treated observations relative to the approximation scale. The resulting estimator uses the observed sample, sample size, dimension, known smoothness, and response bound, as specified in Algorithms 1 and 2.
The statistical explanation rests on an ordered information profile. The density lower bound assigns covariate mass to each template microcell, and the global propensity tail controls the treated mass of unions of disjoint microcells. Together, they imply a polynomial lower bound in rank for the weakest treated-cell masses across partition cubes. This profile distinguishes the least-informed cubes from the progressively better-informed cubes. Combining its rank-dependent stochastic control with the common scale cap supplied by count feasibility yields the pure-power expected spatial-supremum guarantee in Theorem 1. Local polynomial approximation and deterministic template conditioning complete the upper bound.
The converse uses a bounded causal experiment. For every fixed evaluation point, including points on faces and corners, a pair of laws places a smooth response perturbation near that point and shares a radial propensity satisfying the global tail envelope. The laws admit potential outcomes taking values in a common two-point set. Their response separation and bounded relative entropy give the pointwise lower bound in Lemma 6. Thus the minimax characterization applies to the full conditional sub-Gaussian response class, with the converse already supported by a bounded subclass.
The closest theorem-level comparison is Dorn (2026). For a fixed Gaussian uniform-design setup satisfying Dorn’s retained restrictions and local anti-concentration condition, Dorn establishes a probability upper bound at the same pure-power scale in an essential-supremum criterion. The source describes a count-based estimator computable without the overlap exponent, while its probability upper guarantee fixes the source family, its common constants, and that exponent before selecting the estimator and threshold constant (Dorn, 2026). That construction provides a direct antecedent for mesh selection. Dorn’s local anti-concentration condition additionally links every sufficiently small neighborhood’s largest selected propensity to a common positive fraction of its covariate mass, with constants common across the fixed family and its selected propensity representatives. Our expected spatial-supremum guarantee is established over the global-tail class in Definition 2, using one estimator and common constants across the stated compact exponent range.
The geometric and source-model comparisons make this distinction precise. In dimensions at least two, Proposition 1 constructs a thin-strip law within the causal class whose displayed propensity violates the selected-version local anti-concentration condition and whose normalized treated-design second-coordinate moment tends to zero. Separately, Proposition 2 transfers the upper guarantee to fixed-constant Gaussian envelopes satisfying the retained source restrictions from Dorn (2026). Affine transport and fixed-cube smoothness completion supply the common full Hölder radius. The transferred guarantee controls expected spatial-supremum error uniformly over those envelopes and the compact exponent range. Its Gaussian geometric witnesses use constants selected separately for each exponent.
Related regression results characterize other aspects of heterogeneous information. Gaïffas (2005) derives pointwise rates under locally symmetric, regularly varying design densities in a one-dimensional Gaussian experiment. Gaïffas (2009) and Schmidt-Hieber et al. (2024) retain spatial variation through location-dependent loss normalization. Our criterion instead evaluates expected unweighted spatial-supremum error over a global overlap envelope. The causal target also differs from the smooth treatment contrast studied under strict overlap by Kennedy et al. (2024): here smoothness is imposed directly on the treatment-specific response.
An appendix documents the precise scope of the mathematical results.
The exposition proceeds through related work, the model and risk criteria, and the estimator and recovery guarantee. It then develops the local treatment-geometry comparison and Gaussian transfer, followed by discussion and future work. The appendices present auxiliary identification, upper-bound, testing, geometry, and source-comparison arguments, followed by the complete main-result proofs.
Related work
The closest theorem-level comparator is Dorn (2026). In a fixed setup with uniform covariates on a cube, Gaussian outcomes, and Hölder response curves, satisfying Dorn’s retained restrictions and local anti-concentration condition, Dorn establishes an essential-supremum probability upper bound uniformly over the source family. Writing for the covariate dimension, for response smoothness, for the overlap exponent, and for sample size, the pure-power rate in this paper’s notation is For each probability tolerance, the source result supplies a finite threshold constant within that fixed setup. Dorn describes a count-based grid and bandwidth estimator computable from the known smoothness and observed treatment design without the overlap exponent (Dorn, 2026). The probability upper guarantee fixes the source family, its common constants, and the exponent before selecting the estimator and threshold constant. The construction is a direct antecedent for the present mesh selector; the new uniformity statement concerns one estimator and common risk constants across a prescribed compact exponent interval.
The present comparison concerns the guarantee and its model domain. Under the fixed model indices and class constants, Theorem 1 gives an expected spatial-supremum guarantee over the envelopes in Definition 2, uniformly across a compact range of overlap exponents, with response smoothness fixed. These envelopes impose a bounded treated conditional mean and uniformly conditional sub-Gaussian residuals, intrinsic cube Hölder smoothness, a covariate density lower bound, and a global propensity-tail bound. Bounded potential outcomes are used for the testing subclass and the thin-strip example, rather than for the full upper-bound class. Dorn’s local anti-concentration condition additionally requires a common positive fraction of the covariate mass in every sufficiently small neighborhood to have propensity comparable to that neighborhood’s propensity supremum. Here, the global tail and the density lower bound support the equal-cell construction under the conditions in Assumptions 4 and 7. The distinction in admissible local treatment geometry is made precise in Definition 9 and Proposition 1, while Proposition 2 states the corresponding Gaussian-envelope upper guarantee.
Degenerate-design regression supplies a complementary comparison at a single location. In a one-dimensional Gaussian regression experiment, Gaïffas (2005) derives pointwise minimax moment rates for a fixed design density that is locally symmetric and regularly varying around the evaluation point. The regression class is specified through a local polynomial approximation modulus, together with a bound on the function; regular variation of the design and modulus yields a power rate multiplied by a slowly varying factor. In the separate adaptive experiment, Gaïffas (2005) constructs a local polynomial procedure adaptive to design degeneracy and Hölder smoothness, and identifies the logarithmic cost of that pointwise adaptation. These results characterize local information through the behavior of a specified design near one point. The present envelopes instead organize treatment-specific recovery through a global distributional restriction on the propensity.
Spatially normalized losses provide another way to express heterogeneous information. In one-dimensional Gaussian regression over Hölder classes, Gaïffas (2009) studies the supremum of estimation error divided by a location-dependent rate obtained from a local bias–variance balance. The adaptive upper result assumes a continuous design density that is positive everywhere or has finitely many zeros with specified local power behavior; the lower result uses an interval-mass condition and establishes optimality over intervals of prescribed shrinking size. Likewise, Schmidt-Hieber et al. (2024) analyzes a weighted uniform criterion in one-dimensional Gaussian regression under a local doubling condition on the design distribution. Least squares over the unit-Lipschitz class attains the local rate for truths in a strictly smaller Lipschitz ball. Both comparisons retain the design’s spatial variation in the loss normalization. Our criterion in Definition 3 measures expected unweighted spatial-supremum error, with worst-case difficulty indexed by the global overlap envelope.
The estimator combines familiar polynomial approximation with a particular treatment-design weighting rule. Local polynomial fitting approximates a smooth response within a neighborhood (Fan et al., 1996); series methods approximate conditional expectations in finite-dimensional spaces, including polynomial and spline spaces (Newey, 1997). Partitioning-based series estimation develops this approach through locally supported bases (Cattaneo et al., 2020). The construction in Definition 6 and Algorithm 2 fits polynomials on partition cubes, assigns equal aggregate weight to the reference microcells, and selects its mesh through the treated-count feasibility rule in Algorithm 1.
The causal estimand also determines the relevant comparison. Kennedy et al. (2024) studies pointwise expected absolute error for the conditional average treatment effect under strict overlap, with separate Hölder restrictions on the treatment effect, propensity, and control response. Its attainable rates depend on their relative smoothness and on conditions controlling covariate-distribution estimation and the local fitting matrices. Our target is a treatment-specific response curve, with smoothness imposed directly on that response and information scarcity described by a global overlap tail. For functional estimation, Mou et al. (2023) derives local minimax mean-squared-error bounds for linear functionals over convex symmetric regression classes, together with attaining procedures for reproducing kernel Hilbert space classes under the stated noise, spectral, and sample-size conditions. That experiment measures accuracy through a specified functional and its observational coverage. The present minimax criterion evaluates recovery of the response throughout the covariate cube.
Setup and assumptions
Generic positive constants may change between displays; the model constants introduced below remain fixed across laws and sample sizes. For a vector, denotes the maximum absolute coordinate, and for a function it denotes the supremum of its absolute value over its stated domain. Multi-indices have nonnegative integer coordinates, with denoting their sum. Observation indices range from to , and . The notation denotes an inequality up to a positive constant depending on the fixed model parameters, and denotes inequalities in both directions. For comparisons uniform over the overlap range specified below, these constants are independent of both the sample size and the overlap exponent.
Sample and target
Consider an observational causal model indexed by a probability law . The covariate vector takes values in the covariate cube , where and . The binary treatment indicator takes values in . Write for the control potential outcome, for the treated potential outcome, and for the observed outcome. The observed triple is . When specifying the sampling law, denotes the observed-data marginal of the causal law, and denotes its covariate marginal.
The covariate density is the density of with respect to Lebesgue measure on , and the propensity is a measurable version of . Our target is the treated causal response , the continuous Hölder representative of We write when the indexing law needs to be explicit.
The sample and estimator convention uses the observed sample , defined by , where . Every estimator is measurable with respect to this sample. Scalar-valued estimators estimate the response at a specified covariate point; function-valued estimators recover the response over and are required to have measurable spatial-supremum loss. Expectations of their losses refer to the observed-sample distribution.
Fix a smoothness order , a Hölder radius with , and a treated-response bound with . Also fix a density lower bound with and a global-tail constant with . The overlap exponent ranges over the compact interval , defined by Its lower endpoint and upper endpoint satisfy . Throughout, , and .
Intrinsic cube smoothness
Smoothness is measured directly on the closed covariate cube. For the fixed smoothness order, the derivative order is . For a generic function on , denotes its coordinate derivative, interpreted through continuous boundary traces as specified below. The intrinsic cube Hölder ball combines a uniform derivative bound with a modulus restriction on the highest-order derivatives. We first state these two restrictions.
⊢ Lean
The uniform derivative bound controls the function itself and all coordinate derivatives through order , using a common radius. This standard Hölder-ball condition gives a common scale for response levels and local polynomial coefficients (Dorn, 2026). The corresponding restriction on variation across covariate points is as follows.
⊢ Lean
The Hölder modulus condition bounds changes in the highest-order derivatives by the covariate distance raised to . Together with the derivative bound, this standard restriction controls local approximation error at smoothness order (Dorn, 2026). The next definition fixes the boundary convention used throughout.
The intrinsic cube Hölder ball is Here is a nonnegative integer and . The integer is the derivative order, and the top-order modulus has exponent . The class consists of functions whose classical coordinate partial derivatives through order on the interior of the cube admit unique continuous traces on . Every derivative , supremum, and difference quotient in the defining restrictions uses these traces. At positive integer , this convention uses Lipschitz derivatives of order .
⊢ LeanFor the maintained domain , the derivative order in Definition 1 agrees with the order fixed above. Its trace convention makes smoothness restrictions meaningful at boundary points as well as in the interior.
Sampling and observational restrictions
The statistical experiment combines independent sampling with restrictions on covariate coverage, causal identification, treatment availability, and the treated response. We begin with the sampling law.
The observed sample consists of independent observations with common law , so that
⊢ LeanIndependent and identically distributed sampling gives the product experiment used to evaluate estimation risk. It is a standard sampling condition for nonparametric regression (Stone, 1982). Covariate coverage is controlled separately.
The covariate density satisfies for Lebesgue-almost every .
⊢ LeanThe random-design density lower bound ensures that each measurable covariate region has probability at least times its volume. This standard coverage condition supports response recovery throughout the cube (Stone, 1982). To connect that response to observed treated outcomes, we impose consistency and conditional exchangeability.
The observed outcome , binary treatment indicator , and potential outcomes and satisfy almost surely.
⊢ LeanConsistency links each observed outcome to the potential outcome corresponding to the realized treatment. It is the standard condition that gives the observed treatment groups their potential-outcome interpretation (Kennedy et al., 2024). The next condition makes treatment assignment comparable within covariate strata.
The potential outcomes and are jointly independent of the treatment indicator conditional on the covariate vector :
⊢ LeanConditional exchangeability is the standard identification condition under which conditioning on removes dependence between treatment assignment and potential outcomes (Kennedy et al., 2024). Together with consistency, it identifies the treated causal response from the treated conditional mean wherever the propensity is positive. Treatment availability is quantified by a global tail restriction.
The propensity , evaluated at the covariate vector , satisfies
⊢ LeanThe polynomial global propensity-tail bound controls the covariate probability assigned to regions with low treatment probability, a standard overlap restriction in this setting (Dorn, 2026). Since , its value at implies positive propensity almost surely under . Consequently, consistency and exchangeability identify with for -almost every . The smoothness convention selects a continuous representative over the entire cube.
We next control the magnitude and fluctuations of the treated conditional outcome distribution.
The observed outcome , binary treatment indicator , and covariate vector satisfy
⊢ LeanThe uniformly bounded treated conditional mean and conditional sub-Gaussian residual condition supplies a common scale for response levels and sampling fluctuations (Dorn, 2026). In particular, the treated conditional mean has absolute value at most , and the centered treated residual has conditional moment-generating function bounded by . These bounds hold essentially uniformly over the covariate distribution. The response curve also satisfies the following smoothness restriction.
The treated causal response belongs to the intrinsic cube Hölder ball :
⊢ LeanIsotropic Hölder response smoothness imposes the same order across covariate directions, with the common derivative and modulus bounds specified in Definition 1 (Dorn, 2026). It supplies the regularity through which nearby treated observations inform the target response. Combined with identification and the density lower bound, continuity extends the treated-mean magnitude bound to throughout .
Law class and risk scales
We collect the observational restrictions into a fixed-constant class. The dimension, smoothness order, and constants remain common across its members; indexes the overlap restriction. The observational causal law class is defined as follows.
The class consists of observational causal laws satisfying the following restrictions, with common fixed constants:
(Covariate density.) The density of the covariate vector satisfies Assumption 4.
(Consistency.) The observed outcome , binary treatment indicator , and potential outcomes and satisfy Assumption 5.
(Exchangeability.) The potential outcomes and treatment satisfy Assumption 6.
(Overlap.) The propensity satisfies Assumption 7.
(Response bound.) The treated conditional outcome distribution satisfies Assumption 8.
(Response smoothness.) The treated causal response satisfies Assumption 9.
For each member of Definition 2, the sample is drawn according to Assumption 3. Fix an evaluation point in the closed cube, including its boundary. We measure recovery through the pointwise minimax risk and the spatial-supremum minimax risk . Both criteria use expected absolute error, with the latter evaluating the largest error across the cube within each sample realization.
The minimax expected absolute error at and the minimax expected spatial-supremum error are, respectively, and Here is the treated response under law , and each infimum ranges over estimators measurable with respect to the observed sample . The first infimum uses scalar-valued estimators, and the second uses function-valued estimators.
⊢ LeanThe order of supremum and expectation in Definition 3 makes the functional criterion sensitive to the largest spatial error in each realized estimate. Its spatial supremum ranges over all points of , using the continuous response representative fixed above.
To express the subsequent risk comparisons, define the overlap-dependent effective dimension , the oracle mesh scale , and the response-recovery scale by These deterministic scales depend on the sample size, smoothness order, dimension, and overlap exponent. They satisfy which expresses the balance between a smoothness scale and an overlap-adjusted sampling scale. The term “oracle” indicates that the mesh scale is indexed by ; it provides the benchmark for comparing risk and selecting a mesh from the observed treatment design.
Main results
The oracle scales introduced in the setup suggest selecting a resolution from the observed treatment information. We implement this choice with local polynomial fits whose conditioning is controlled by a fixed interpolation template. The construction uses the known smoothness order , with polynomial degree , and selects a mesh through treated observation counts.
Construction
The tensor nodes specify the locations around which the fitting observations are collected. Their placement leaves room for small neighborhoods inside the reference cube.
The tensor node , for nonnegative integers and an index vector , is defined by
⊢ LeanWe use total-degree monomials indexed by to form the polynomial vector . The node count determines the equal weights in the reference Gram matrix. The following construction fixes both the polynomial basis and the neighborhoods used to fit it.
Fix a dimension and a polynomial degree . Let with the coordinates of ordered lexicographically. For , define and set The template Lipschitz constant is where is the matrix operator norm induced by the Euclidean vector norm. This finite constant gives the bound Define the microcell width and reference microcubes by In particular, for , the bound entering the width rule is
The reference Gram matrix is positive definite because the tensor grid identifies every polynomial in the chosen basis. Its least eigenvalue provides a deterministic conditioning benchmark. The matrix Lipschitz constant controls the perturbation caused by moving observations away from the nodes. Accordingly, the width makes the reference microcubes small enough to preserve that benchmark; the conditioning argument is recorded in Lemma 4.
For the fitting formulas, we enumerate the tensor nodes by a single index from to . The template notation under this enumeration is collected below.
The equally weighted template Gram matrix and its least eigenvalue are where is the polynomial template vector, are its tensor nodes, and is the number of nodes. With denoting the polynomial order and the constant entering the width rule, define the microcube width The disjoint reference microcubes are
⊢ LeanEach partition cube receives a scaled copy of this same template. We search over the finite dyadic mesh collection , with denoting the partition at mesh .
For a sample size , dimension , and smoothness parameter , define the finite candidate mesh collection For , let be the dyadic partition of into cubes of side length . Each coordinate interval is half-open, with the right endpoint included in the last interval of that coordinate. Write for the lower-left corner of .
The corner supplies the translation for placing the reference template in a partition cube. The resulting microcells have treated observation counts . We require each count to reach the smoothness-dependent threshold . The feasible mesh set collects the resolutions meeting this requirement, and the selected width is the finest feasible resolution, with the exceptional-sample convention specified below.
Given the candidate meshes , the observed sample , the smoothness parameter , and the reference microcubes , proceed as follows.
For each , form the cube partition . For each partition cube , with corner , define its microcells and treated observation counts by
Define the set of feasible meshes by where is the number of reference microcubes.
Output the numerically smallest feasible mesh, with zero assigned when the feasible set is empty:
Selection depends on the sampled covariates and treatment indicators. The threshold calibrates the amount of treatment information to the approximation scale . At a feasible mesh, each microcell receives the same total fitting weight, so the template geometry governs the empirical matrix even when treated observations are distributed unevenly across microcells.
The empirical equal-cell Gram matrix and coefficient estimate make this weighting explicit.
Let be the observed sample. Fix a feasible mesh , a partition cube with lower-left corner , the polynomial template vector , and its reference microcubes . Define Feasibility means that for every partition cube and template microcell, so these counts are positive. The equal-cell empirical Gram matrix is Using the polynomial template and its microcell width, this matrix is invertible at every feasible mesh. Define the equal-cell local polynomial coefficient estimate by Thus each microcell receives weight , and the treated observations within that microcell receive equal weights.
Invertibility follows from the deterministic template perturbation bound whenever the count requirement is met. The fitted polynomial is evaluated throughout its partition cube, including points outside the fitting microcells. Projection onto the response-bound interval completes the response estimator and controls its magnitude on every sample realization.
Given the selected mesh , the polynomial template vector , and the response bound , proceed as follows.
If , output
Otherwise, set For every , compute the empirical equal-cell Gram matrix and the equal-cell polynomial coefficient estimate .
For , let be the unique half-open partition cube containing , and let be its corner. Output
Recovery guarantee
The count-selected estimator attains the overlap-dependent oracle rate uniformly over a compact range of overlap exponents. A matching converse holds within the model’s bounded, two-valued potential-outcome subclass.
Fix the model parameters subject to the following conditions:
(Dimension and smoothness.) , , and .
(Response and smoothness bounds.) and .
(Overlap and density constants.) and .
(Adaptation interval.) The real endpoints satisfy , and the adaptation interval is
Let be the covariate cube, and let be the observational causal model of Definition 2, with fixed parameters , including the propensity-tail envelope in Assumption 7. Define the effective dimension , oracle mesh , and oracle response-recovery scale , for , by
The count-selected equal-cell estimator of Algorithm 2 takes and the observed sample as inputs. There exist and such that, for every integer , every , and every , Here is the sampling law of independent observed triples , and is the treated causal response under .
For every real and every , there exist finite constants , possibly depending on and the fixed model parameters, such that, for every integer , The infimum ranges over sample-measurable estimators ; the pointwise and expected supremum minimax risks and are those of Definition 3.
⊢ LeanThe rate reflects a balance between polynomial approximation and the treatment information available at a given resolution. Smoothness supplies the approximation scale , while the global overlap tail determines the effective dimension . At the oracle mesh these scales satisfy The count threshold implements this balance through the realized treatment design, and the fixed template turns feasible counts into stable polynomial fits.
Adaptation in Theorem 1 concerns the overlap exponent at a known smoothness order. For fixed and a fixed compact interval with distinct endpoints, one estimator and common constants provide the upper bound for every . Its inputs are the observed sample and . Thus the overlap exponent is accommodated through count selection, while determines the polynomial degree, candidate resolutions, and feasibility threshold.
The upper bound controls expected spatial-supremum error: the largest error over the closed covariate cube is evaluated within each sample realization and then averaged over samples. This criterion matches Definition 3 and covers boundary points as well as interior points. For each fixed , the converse establishes the same rate at every fixed evaluation point, already among laws admitting potential outcomes in . Consequently, both pointwise recovery and recovery under expected spatial-supremum loss have minimax scale The constants in the fixed-exponent comparison may depend on the evaluation point and fixed model parameters, as specified in Theorem 1.
Statistical explanation
Two features of the construction account for the guarantee. First, equal-cell weighting separates polynomial conditioning from the distribution of treated observations within a cube. Every microcell contributes total weight , and every normalized fitting location remains near its reference node. The empirical Gram matrix therefore stays close to the same positive-definite template at every feasible resolution. Lemma 4 supplies this deterministic step, while Lemma 5 connects count feasibility to the oracle resolution.
Second, the global overlap restriction controls the spatial distribution of scarce treatment information. To describe this distribution, fix a law and a candidate mesh . Let the population treated microcell mass and the weakest such mass in a partition cube be Write for these weakest-cell masses arranged in ascending order, with . This ordering records how treatment information improves as one moves beyond the least-informed cubes.
The density lower bound in Assumption 4 assigns covariate probability to each microcell, and the global tail envelope in Assumption 7 limits how much of that probability can carry very small propensities. Their combination yields the ordered treatment-information bound uniformly over the compact overlap range; this is Lemma 3. On the count-concentration event of Lemma 5, the conditional variance proxy for every fitted coefficient in the cube of rank is bounded, up to a common constant, by The first term is the feasibility cap; the second decreases with rank according to the ordered-mass profile. Their equality marks the ranks at which the envelope leaves the common cap. Applying the ordered maximal inequality across these ranks and comparing the selected mesh with the oracle mesh gives Thus the few least-informed cubes are controlled by feasibility, while the improving ranks pay progressively smaller stochastic scales. Deterministic template conditioning then transfers this coefficient bound to expected spatial-supremum response error at the oracle rate. The appendix proves the concentration event and the maximal inequality in full.
The appendix develops the corresponding probability bounds and the bounded testing experiment. Their roles are complementary: the selected-mesh analysis establishes the estimator’s recovery guarantee, and Lemma 6 supplies the bounded-response comparison underlying the minimax converse.
Local treatment geometry and the Gaussian transfer
Global tail control and local treatment geometry
The recovery guarantee in Theorem 1 rests on global tail control and the equal-cell construction. To clarify the geometric scope of this guarantee, we compare the model with the local anti-concentration condition . This condition relates a neighborhood’s largest selected propensity to the covariate probability assigned to propensities of comparable size. Its formulation fixes both the family of laws and the pointwise propensity representatives.
The family-level condition is defined for a family and selected propensity versions satisfying:
(Family.) is a nonempty family of probability laws with common covariate cube .
(Versions.) For each , is a fixed, pointwise-defined measurable version of .
(Overlap.) For each , -almost surely.
The condition holds when there exist constants and , common to the family, such that, for every , every , and every , Here denotes probability under , and the supremum is the pointwise supremum of the selected version. Thus the condition is a property of the family together with its selected propensity versions; its truth can depend on their values on -null sets. The covariate cube is in Dorn’s source and after affine transport. For a single displayed law and propensity, abbreviates the condition for the singleton family equipped with that selected version.
⊢ LeanThe common constants in Definition 9 require this comparison to persist across laws, locations, and sufficiently small neighborhoods. The pointwise supremum also makes the selected representative part of the condition. By contrast, the global tail restriction in Assumption 7 controls the probability of small propensity values under the covariate distribution. A thin-strip construction makes the distinction concrete: it combines a radial propensity component with additional treatment probability concentrated in a narrowing strip.
The observed-data law is defined by the following construction, under these conditions:
(Dimension.) .
(Covariates.) is uniform on .
(Strip exponent.) Choose satisfying
Define the cube center, radial distance, and its continuous distribution function by Define the strip and selected propensity by Given , draw Set Draw and conditionally independently given , each with conditional distribution , and define Then is the law of .
⊢ LeanThe thin-strip law of Definition 10 has constant potential-outcome means and bounded outcomes. It therefore isolates the treatment geometry while keeping the response smooth. The strip exponent makes the strip narrow relative to the surrounding neighborhood as its radius decreases. Under the displayed exponent range, Proposition 1 establishes the coexistence of global tail control and a vanishing normalized treated-design moment.
Suppose the parameters satisfy:
(Dimension and smoothness.) , , and .
(Model constants.) , , , and .
(Overlap and strip exponent.) and
For every such , let and its displayed selected propensity be the construction in Definition 10, and let denote the model class with the fixed parameters . Then , and
On the unit cube , the numerical anti-concentration clause fails: there are no such that, for every and every , This failure applies to the numerical clause allowing propensity values equal to one. Consequently, the full singleton-family predicate , evaluated using , also fails.
Moreover, writing , the normalized treated-design second moment in the second coordinate satisfies In particular, contains a law whose full singleton-family Dorn predicate fails for the displayed selected propensity .
⊢ LeanThe global tail inequality controls the prevalence of small propensities, while the displayed moment records the shape of the treated design near the cube center. Its limit shows that, after normalization by neighborhood width, treated observations concentrate increasingly close to the strip’s central hyperplane. The local second-coordinate variation consequently degenerates even though the law satisfies the global model restrictions. For dimensions at least two, Proposition 1 thus establishes a strict enlargement relative to imposing the selected-version predicate within the causal class. The equal-cell estimator’s guarantee in Theorem 1 covers this geometry through its template and count-feasibility conditions.
Transfer to fixed-constant Gaussian source envelopes
The geometric distinction also has a source-model consequence. Under the retained restrictions in Dorn (2026), affine transport maps each fixed-constant Gaussian source envelope to the causal class used by Theorem 1. A common response bound controls the transported mean and noise scale, while fixed-cube smoothness completion supplies a common full Hölder radius. Consequently, one transformed equal-cell estimator attains the expected spatial-supremum rate uniformly over the source envelope and the prescribed compact exponent range. The exact envelope, transport constants, exponent-specific Gaussian witness, and family-richness qualifications are stated in Proposition 2 and proved in the source-comparison appendix.
The transfer aligns the source restrictions with the components needed for response recovery. Uniform covariates supply the density lower bound after transport, the propensity tail inequality supplies global overlap control, and the Gaussian and treated-moment restrictions supply common response bounds. Fixed-cube smoothness completion converts the source’s top-derivative seminorm restriction, together with a function bound, into the full Hölder radius used by the estimator. The precise completion argument is given in Lemma 7.
The upper guarantee controls the expected spatial supremum over the entire unit cube, uniformly over the fixed-constant envelopes and the compact exponent range. This loss criterion is stronger than the displayed essential-supremum probability criterion: it controls the magnitude of the largest spatial error in expectation and yields the stated probability guarantee at every positive tolerance. The same constants apply to each source subfamily satisfying the retained restrictions because each such family lies within the corresponding envelope.
The Gaussian existence assertion has a separate quantifier structure. In dimensions at least two, it supplies, for each overlap exponent, a source tuple satisfying the retained restrictions with positive finite constants chosen for that exponent and with local anti-concentration failure for its selected representative. These witnesses establish the geometric scope of the retained Gaussian restrictions; the envelope-wide upper guarantee applies with the fixed constants specified at the start of Proposition 2.
The converse statements likewise identify their comparison classes explicitly. A source family with a common treated curve has zero minimax pointwise miss probability, whereas the full causal class in Definition 3 admits the displayed positive expected absolute-error lower bound at the oracle scale, supported by its two-valued potential-outcome subclass. Family richness therefore determines the scope of a minimax converse, while the transferred upper guarantee remains valid for every qualifying source subfamily. The technical source-family comparison is developed in Lemma 8 and Proposition 3.
Discussion
The guarantees in Theorem 1 describe response recovery with known smoothness and adaptation to overlap. The known smoothness parameter determines the polynomial degree and the approximation order used in constructing the estimator. Treatment counts then select a feasible mesh through Algorithm 1. Thus response regularity supplies the approximation benchmark, while the observed treatment design determines the spatial resolution.
The compact range for the overlap parameter , contained in , specifies the domain over which the risk constants are uniform. With the remaining model constants fixed, a single estimator attains the corresponding oracle scale throughout that range. The pointwise and expected spatial-supremum guarantees therefore share an overlap-dependent scale, including the spatial-supremum guarantee without an additional logarithmic factor.
For comparison, the classical regular-design spatial-supremum benchmark includes a logarithmic factor, with scale under its regular coverage conditions (Stone, 1982). The present theorem instead takes a worst case over the larger global-tail class at each fixed finite , giving the pure power . The theorem supplies one estimator and common risk constants on every prescribed compact interval of finite overlap exponents.
Equal-cell weighting connects the deterministic geometry in Definition 6 to the fitted polynomials in Algorithm 2. Each microcell contributes the same total weight, so the conditioning argument is governed by the template geometry, while differences in treatment counts govern stochastic precision; Lemmas 4 and 3 give the two bounds.
Conditional sub-Gaussian residuals supply exponential control of fluctuations after conditioning on the sampled covariates and treatment indicators. That control supports the upper-bound argument and its Gaussian-envelope transfer in Proposition 2. Together, the response smoothness, template geometry, and treatment-count information determine approximation, conditioning, and stochastic error, respectively.
Limitations and future work
Joint adaptation would replace the known smoothness benchmark with a comparison across response regularities as well as treatment-count-feasible resolutions. The following proposal describes an architecture for that extension.
A proposed direction for future work is to construct a single response estimator with an adaptive-risk envelope over compact rectangles of the smoothness parameter and the overlap parameter . The proposed architecture uses sample splitting to compare equal-cell fits across polynomial degrees and treatment-count-feasible meshes, with the count selector controlling adaptation to overlap and held-out Lepski inequalities controlling adaptation to smoothness. The sample split, degree-and-mesh comparison rule, Lepski threshold, estimator, and envelope functional remain to be specified; estimator existence and the corresponding risk bounds remain open.
⊢ LeanThe proposed split would allocate separate observations to fitting and comparison, while the degree-and-mesh rule would compare candidates along both parameter axes. Lepski comparisons provide a natural perspective on smoothness selection (Lepski et al., 1997); smoothness adaptation under degenerate random design, studied by Gaïffas (2005), supplies a related setting in which to interpret the adaptation question. These comparisons motivate the proposal rather than establish its risk envelope.
The absence of an additional spatial-supremum logarithm in the known-smoothness guarantee makes the cost of the proposed two-axis comparison particularly relevant. The question concerns both attainability of the oracle scale and any unavoidable adaptation penalty.
For a compact rectangle of smoothness and overlap parameters contained in , can a procedure adapting along both parameter axes produce a single estimator whose pointwise and expected spatial-supremum risks attain the oracle scale for every pair in the rectangle? What logarithmic penalty, if any, is minimax unavoidable?
⊢ LeanResolving Remark 2 requires specifying the procedure and establishing its risk bounds, together with an appropriate converse for any claimed unavoidable logarithmic price. The existing common-class bounded-response converse and Gaussian-envelope upper transfer address distinct comparison domains: the former supplies the minimax lower bound in Theorem 1, while the latter supplies the upper guarantee in Proposition 2. The transferred upper bound does not furnish a matching converse for every Gaussian source subfamily. As Lemma 8 and Proposition 3 clarify, a lower-bound analysis must account for family richness. These distinctions also govern how a future joint-adaptation result could characterize an unavoidable logarithmic penalty.
Appendices
Identification and upper-bound proofs
The upper bound in Theorem 1 combines causal identification with control of approximation error, conditional stochastic error, and exceptional samples. The auxiliary statements below follow that order: identification fixes the population target, cube smoothness admits a controlled global extension, the global overlap tail supplies an ordered information profile, and the template and mesh bounds translate that profile into stable response estimation.
Identification of the continuous response
Under the causal conditions in Definition 2, the treated conditional mean identifies the causal response almost everywhere. The density and smoothness restrictions then determine its continuous representative throughout the covariate cube. The following statement records both levels of identification.
Let satisfy the parameter restrictions and causal model conditions of Definition 2, with . Write for its covariate marginal and for the covariate cube. Then Moreover, every function that is continuous on and satisfies obeys
⊢ LeanLet be the joint causal law on : Its observed marginal is , and its covariate marginal is . Define the joint conditioning law and conditional probability kernels by Choose measurable versions defined at every conditioning input, with arbitrary probability values on exceptional conditioning sets.
By Assumption 5, Conditioning this equality on gives By Assumption 6, and are conditionally independent given . Consequently,
Applying Assumption 7 at , and using , yields Since , To express positivity through the conditioning kernel, define again as a measurable probability kernel defined everywhere. The observed marginal relation and the definition of the propensity give Combining these identities with the null-set calculation proves
Disintegration of the joint conditioning law gives We use the following consequence of this identity. For any predicate holding -almost everywhere, disintegration implies At any such with , failure of would imply Thus holds -almost everywhere. Applying this argument to the conjunction of the two conditional-kernel identities above gives
Now define the observed outcome kernel and its treated slice by The observed marginal relation gives Applying the same positive-slice argument once more, we obtain
Define the treated regression on all of by using value zero wherever the integrand is not integrable. By Assumption 8 and the kernel equality just proved, for -almost every , and each exponential integrand in this display is integrable.
The choices and control the absolute first moment. Indeed, for every , so The right-hand side is integrable under . Integrating the inequality and using the exponential bounds yields This bound is uniform on a set of full -measure. Disintegration therefore gives In particular, is integrable under .
Define with value zero wherever the integrand is not integrable. The conditional-distribution formula for conditional expectation, together with the defining conditional-mean relation for the treated causal response, gives The kernel integral is measurable. Continuity of on , supplied by Assumption 9 and Definition 1, and supply a measurable representative of under . Using these representatives, the covariate pushforward identity transfers the preceding equality to The equality then gives
It remains to establish the asserted equality for every point of the cube. Define the restricted Lebesgue measure by The parameter restrictions give . Absolute continuity of with respect to and Assumption 4 yield Consequently, For completeness, if a Borel set satisfies , then Since is nonnegative, this forces -almost everywhere on ; its strict positivity -almost everywhere gives .
Let satisfy the continuity and almost-everywhere agreement required in the statement. The identifying equality already established implies and hence, by , Both functions are continuous on . Thus a nonzero difference at an interior point would, by continuity, persist on an open ball contained in the cube, whose positive Lebesgue measure contradicts the preceding almost-everywhere equality. Finally, Continuity therefore extends the equality to every , as required.
The pointwise and spatial-supremum losses in Definition 3 therefore concern a uniquely identified continuous response, including at boundary points. This separates the identification of the target from the statistical difficulty created by small treated probabilities.
Global extension of cube smoothness
The intrinsic smoothness convention in Definition 1 specifies coordinate derivatives through their continuous boundary traces. For an integer derivative order and a top-derivative Hölder exponent , the following statement supplies a global representative with controlled Fréchet derivatives. In the response class, these orders are and .
Fix an integer , an integer , and an exponent . There exists a constant , depending only on , , and , with the following property. Let and let satisfy:
(Intrinsic smoothness.) The function belongs to in the intrinsic closed-cube sense of Definition 1, transported to . Its coordinate derivatives , for , exist on the interior and admit continuous traces on the closed cube.
(Derivative bounds.) With derivatives evaluated through their continuous traces,
(Hölder continuity.) For every and all ,
Then there exists such that and Here denotes the Fréchet derivative of order , with order zero interpreted as the function itself, and denotes the operator norm of a -linear form on equipped with the supremum norm .
⊢ LeanWrite All intrinsic derivatives below are evaluated through their continuous traces, as in Definition 1.
Order zero. Suppose . Define the coordinatewise retraction and the extension by Projection onto an interval is nonexpansive. Consequently, The hypotheses therefore give Since , the last bound implies continuity. Thus works in this case. The same construction applies when , with the empty coordinate tuple interpreted as the unique point of .
From coordinate bounds to multilinear bounds. Henceforth assume . Set For endpoints satisfying , define For an intrinsic response on this box, its full intrinsic derivative is the multilinear form At order zero this is ; at positive order in dimension zero the sum is empty and the form is zero.
To see the relevant norm estimate, define the coordinate basis by If a -linear form satisfies multilinearity gives Here the order-zero sum has one term, including when . Applying this estimate to the derivative and to the difference of two top derivatives shows that coordinate bounds of radius imply and
Affine transport between boxes. Consider two nondegenerate boxes Define their affine identification and its coordinate slopes by This map carries bijectively onto . Define and Coordinatewise subtraction yields hence, because , For a response with intrinsic radius on , define The affine chain rule, including continuous boundary traces, gives Since , for , It follows that and, for , Composition with the affine map also preserves intrinsic regularity. These formulas establish the claimed radius factor over the whole closed box.
Moment-matched reflection across a normalized face. Choose real coefficients , , satisfying Such coefficients exist: the matrix is a Vandermonde matrix at distinct nodes. Its determinant is nonzero, so the system has a solution depending only on .
Regularity and bounds on a one-face collar. Fix a coordinate , and define For each , define an affine inward sample on all of by If , then so . The weak inequalities likewise show that the closed exterior slab maps into .
For an auxiliary response with intrinsic radius on , define This defines the response on all of , and it agrees with on .
On the closed exterior slab, the finite sum is intrinsically , by composition with the affine samples. At , every sample equals , and the moment equation at identifies that sum with the second branch. Moreover, for , the exterior derivative trace at this face is Indeed, the affine chain rule gives the factors , and continuity of the original derivative traces gives the limit at the face. Coordinate expansion then identifies the full multilinear traces. This argument includes the edges and corners.
The two closed pieces therefore have matching derivatives through order . They glue to an intrinsic response on : at a common face point, the derivative remainders on both pieces use the same linear approximation and are ; on their union the same remainder estimate holds. Applying this observation successively to the derivative fields, and using continuity of the matching fields, establishes regularity through order .
For the quantitative estimates, define the linear part of each sample by Then On the open exterior slab, the chain rule gives Using the full intrinsic bounds from [proof:global-holder-extension:coordinate-bounds] at the inward samples yields and Define Differentiating the finite reflection sum and applying the triangle inequality gives and on the open exterior slab. Its closure is . Continuity of the within-collar derivatives therefore extends the first bound to that closure, and successive limits in the two points extend the second bound.
On , agreement of the responses identifies their derivatives in the interior. Continuity extends this identity to the closed cube: Thus the corresponding full derivative and top-modulus bounds on the cube have coefficient .
For a pair , , choose Existence follows from ; if both coordinates equal , take . The other coordinates remain in , so The two side estimates and the triangle inequality now give Pairs on the same side satisfy the same enlarged bound; reversing the points treats the other crossing order. Evaluating on coordinate basis tuples converts these full-jet estimates to coordinate estimates. Consequently, with the reflected response has intrinsic radius on . All these constants are positive and depend only on .
A fixed larger box. For a nondegenerate box and a coordinate , define its lower enlargement by Normalize a response on , reflect it, and transport it back: The chosen collar width gives the affine identity Therefore give its radius factor
For the upper enlargement, define Apply the lower construction to the negated box and then negate back. This transport preserves the radius, since Thus the upper construction agrees on and has factor Applying the lower construction first and the upper construction to its enlarged box gives agreement on the original box and factor
Iterate this two-face construction through coordinates . More precisely, define At stage , apply the lower enlargement in coordinate , followed by the upper enlargement using the new lower endpoint, and denote the resulting box by . Define The lower and upper increments are positive. Previously enlarged coordinates remain unchanged, and every intermediate box contains . Induction consequently gives Set For every admissible , the same induction produces a response satisfying and For definiteness, the starting ambient representative is Subsequent representatives are defined everywhere by the displayed reflection and affine formulas. When , the iteration is empty: and . The final box and radius factor depend only on .
A fixed smooth cutoff and its zero extension. Define and The strict margins imply Choose a smooth bump with where support denotes closed support. Smooth bump existence in a finite-dimensional normed space supplies this choice. In particular, with Compact support and continuity of the derivatives make the constant finite and positive.
For any response of intrinsic radius on , define At an interior point this is locally a product of functions. At every point outside the open box, a neighborhood misses the closed support of , so the extension is locally zero. Hence and
Uniform derivatives of the cutoff extension. We make the product estimate explicit. Define For an -linear form and a -linear form , where , define At , the permutation set has one element and the expression is ordinary multiplication. Each summand is bounded by , so Repeated differentiation along a line gives the scalar Leibniz formula on repeated arguments. Both sides below are symmetric multilinear forms, and polarization therefore gives the full product identity Thus [proof:global-holder-extension:coordinate-bounds] gives Outside the open box the derivative is zero. Consequently, defining we obtain the global bound
The global top-order modulus. For in the open box, define The box is convex. For , the bound on the next full intrinsic derivative and the mean-value inequality give The uniform bounds also give a difference bound . For , the condition implies ; for , positivity of implies . Therefore For , [proof:global-holder-extension:coordinate-bounds] gives the sharper bound with coefficient , and hence the same displayed bound with coefficient .
Likewise, the cutoff derivatives through order give, for , The same two distance ranges yield
Bilinearity of the pairings in [proof:global-holder-extension:cutoff-derivatives] splits each product difference into a cutoff difference times a response jet, and a cutoff jet times a response difference. Subtracting the two product identities and applying their contraction bounds gives Define The open box is dense in the closed box, including in dimension zero. Since is globally , its top derivative is continuous. Passing to limits in both points, using continuity of the distance power for , gives
Now let and . Some coordinate satisfies or . Define Then makes the top derivative zero at both and . Hence Reversing the points treats the opposite crossing order. If both points lie outside the closed box, both derivatives are zero. Together with the closed-box estimate, these cases establish the displayed modulus for all . In dimension zero the outside cases are empty.
Composition of the two radius factors. Define the fixed constants The box, cutoff, and all constants depend only on . For the given , choose the neighborhood response from [proof:global-holder-extension:larger-box] and set Its agreement on the cube is and [proof:global-holder-extension:cutoff] gives . give and Every estimate uses multiplication by nonnegative radii, so the construction and bounds also apply when .
The extension preserves every value on the closed cube and converts the coordinate-derivative restrictions into global operator-norm bounds. Its smoothness factor depends on dimension and smoothness order, uniformly over functions satisfying the displayed radius bound. This supplies a controlled global representation of intrinsic cube smoothness while preserving the response values relevant to approximation.
The ordered treated-mass profile
For a dyadic mesh , let denote the population treated probability of template microcell in partition cube . The quantity is the smallest of these microcell probabilities within , and is the th smallest entry among the cube-level quantities . Ties may be ordered arbitrarily. These masses concern the scaled microcells of Definition 6, rather than the total treated probability of each partition cube.
The global-tail restriction in Assumption 7 controls treated probability on every measurable covariate region. Its implication for the ordered weakest-cell masses supplies the information profile used in the stochastic analysis.
Fix the model parameters and an overlap interval satisfying
(Parameter domain.) , , , , , , and .
(Overlap range.) , with .
There exists , depending only on these fixed parameters and interval endpoints, such that the following two bounds hold for every and every causal law satisfying Definition 2.
For every measurable , writing ,
For each , set Let be the dyadic cube partition of , with . Using the degree- polynomial template microcells within each , define their treated masses and each cube’s weakest mass by where is the number of template microcells. Let be the th entry of the list of these ’s sorted in nondecreasing order. Then, for every integer ,
⊢ LeanUniform coefficient. Set using the template of Definitions 4, 5, and 6. Its polynomial coordinates and node set are We first establish positivity of the template width. Define For , at least one coefficient is nonzero, and The node values in each coordinate are distinct. If vanished at every tensor node, fixing the other coordinates at node values and applying the univariate root bound would make it vanish identically in the first coordinate. Repeating this argument in each coordinate would give . Thus
The set is nonempty, since it contains the coefficient vector of the constant polynomial . It is closed and bounded: for every , Consequently it is compact. The continuous quadratic form attains its minimum there, and the Rayleigh characterization gives
Every quotient defining is nonnegative; the indexing set contains distinct cube points because . Hence the width rule supplies
For , define Since , , and , this function is continuous and strictly positive on the nonempty compact interval . Therefore This constant depends only on the fixed parameters and interval endpoints.
Setwise treated mass. Fix and , and write Then . Let be measurable and set If , the claimed lower bound is zero, while the treated probability is nonnegative. Suppose henceforth that , and define The inequalities and give
Define the weak level-set mass function on all real thresholds by It is nonnegative and nonincreasing: As a version of the conditional treatment probability, the propensity satisfies Disintegration of the treatment probability therefore gives Moreover, Tonelli’s theorem yields the weak-level-set representation The propensity is integrable on , and the bounded monotone level-set functions are integrable on the threshold intervals used below.
For comparison, define For , Assumption 7 and monotonicity of measure give The two threshold sets cover , so subadditivity implies Since , it follows that Integrating over the cutoff interval gives
The cutoff balances the tail envelope and set mass: Also . Thus direct integration gives
Combining these bounds, using and , proves
A ranked union and its upper bound. Fix and an integer in the stated range, and set Use the dyadic partition , whose coordinate intervals are half-open with the global right boundary included. For each cube, write its lower corner and scaled microcells as Because the finite collection of microcell masses is nonempty, choose Define the threshold collection The first entries of the sorted mass list are all at most . Sorting preserves the multiplicity of each mass, so Choose a collection and define its selected union by Subadditivity of the treated probability then gives
The selected union’s lower bound. The node coordinates and width bound satisfy Hence, for every and every coordinate , After scaling, every microcell lies strictly between its cube’s coordinate faces: In particular, . Distinct dyadic cubes have lower corners differing by at least in some coordinate. The strict bounds therefore imply
More explicitly, each microcell is the rectangle Each coordinate interval has length , so
By Assumption 4, integration of the density over each microcell yields The selected microcells are measurable and pairwise disjoint. Thus
The exponent and the setwise coefficient are positive. Applying monotonicity of this power and the setwise estimate already established gives
Power identity and conclusion. The factorization and exponent identity are Using multiplicativity of real powers on positive bases and , we obtain
Multiplying the uniform coefficient bound by the positive mesh and rank factors therefore gives The lower and upper bounds on the same selected union give Dividing by and combining the two inequalities proves The choices of , , , and were arbitrary in their stated ranges, so the bound holds uniformly as claimed.
The rank factor quantifies how information improves across the ordered cubes. At a fixed mesh, the weakest treated mass grows at least polynomially with rank, so the corresponding variance envelope decreases with rank. The constant is common to the stated compact overlap range; this uniformity carries the mass comparison into the adaptive upper bound.
Deterministic conditioning of the template
Write for the vector of monomials of total degree at most , with in the statistical application. The tensor nodes , reference microcubes , and reference Gram matrix are those of Definition 6. Its least eigenvalue is denoted by . The empirical matrix assigns equal weight to the microcells and averages within each cell over its treated observations. The next statement gives the conditioning bound for every feasible sampled configuration.
Let be nonnegative integers, let , and let be any sample with , , and . Write for the vector of total-degree- monomials. For the polynomial template’s tensor nodes and reference microcubes , indexed by , define Here .
Let , with a nonnegative integer, be a feasible candidate dyadic mesh: , the candidate mesh collection, and where is the dyadic cube partition at mesh . For a cube with corner , the microcell and its treated count are Define the equal-cell empirical Gram matrix by Then , and for every , where .
⊢ LeanFix . Since , feasibility gives Thus every microcell count is positive, and its reciprocal is well defined. We establish the conditioning bounds using these positive counts.
Define the coefficient and node index sets, and the polynomial associated with a coefficient vector, by Expanding the definition of yields
The nodes in Definition 4 form the Cartesian product of the one-dimensional set Each coordinate degree of is at most . Consequently, vanishing at every tensor node implies that is the zero polynomial. Indeed, fixing all but one coordinate at node values gives a univariate polynomial with distinct roots and degree at most , so it vanishes identically. Repeating this argument coordinate by coordinate extends the vanishing to all of . Hence For , both index sets have one element and is constant, so the same implication follows directly. A unit coefficient vector has a nonzero coordinate; therefore at least one summand is strictly positive, and
To obtain strict positivity of the infimum, define The zero multi-index belongs to for every , and . Thus is nonempty. It is closed, and each of its coordinates satisfies so it is bounded and hence compact. The continuous quadratic form attains its minimum there: for some ,
Fix an arbitrary . Write the supremum norm, including its zero-dimensional convention, as The template Lipschitz constant described in Definition 5 is with value zero when the set of quotients is empty. For , Definition 5 supplies its finiteness; for , the cube is a singleton and the stated convention applies. Every quotient is nonnegative, so .
By Definition 6, the width and microcubes satisfy In particular, The coordinate inequalities are vacuous when . They imply, for every ,
Define the perturbation matrix and the coefficient-dependent error by If , the desired squared-evaluation inequality follows immediately from . If , the definition of and the preceding distance bound give For , the quadratic-form bound below is immediate. For , define The operator-norm definition and homogeneity give Cauchy–Schwarz therefore yields Combining the two cases for , we obtain
Define the normalized observations and the treated index sets by Then . Since and , every satisfies . Averaging the pointwise inequality within each cell gives Expansion of the empirical Gram matrix, followed by equal averaging across the cells, now gives The last equality uses , so the equally averaged error remains .
For , the template lower bound is an equality. For , the unit vector defined above and the defining infimum give The width rule also implies Consequently, Combining these inequalities with the equal-cell transfer proves
If , there is a nonzero coefficient vector with Applying the quadratic lower bound gives the contradiction Thus .
For an arbitrary input vector , define Invertibility gives . The quadratic lower bound and Cauchy–Schwarz imply If , the following bound is immediate; otherwise, divide by its positive norm and then by . In both cases, The coefficient unit sphere is nonempty, as witnessed by . Taking the supremum over its vectors therefore gives Since was arbitrary, all the asserted bounds hold throughout .
Equal weighting preserves the reference template’s conditioning even when the treated counts differ across microcells. The bound is deterministic once feasibility holds, and it controls the amplification of both approximation residuals and outcome fluctuations in the fitted coefficients. Its geometric requirement is supplied by the occupied template microcells and their prescribed widths.
Selected-mesh concentration and maximal error
Let be the observed sample. Conditional expectations below condition on the sampled design , comprising the covariates and treatment indicators. Under this conditioning, the selected mesh of Algorithm 1 is fixed. The coefficient vector is the equal-cell polynomial fit used in Algorithm 2; centering it by its conditional expectation isolates the stochastic coefficient error.
The oracle mesh is , and the oracle response-recovery scale is . The sample event below controls both selection and the comparison of empirical counts with population treated masses. For the accompanying maximal inequality, denotes a generic family of centered real variables under a probability law . The positive quantities and specify a common scale cap and an ordered decay scale, respectively.
Fix the dimension , smoothness parameter , model constants , and adaptation endpoints , satisfying
(Dimension and smoothness.) , , and .
(Model constants.) , , , and .
(Adaptation interval.) , with
There exist constants and such that the following holds uniformly for every , , and observed law , with the displayed fixed model constants. Let the sample have the iid law specified in Assumption 3, and use the mesh selector of Algorithm 1. Write where is the effective dimension governing the model’s overlap-dependent rate, and let denote its oracle response-recovery risk scale.
For each partition cube and template microcell , define the population treated mass, its empirical count, and the weakest treated microcell mass by There is a measurable sample event such that For every sample in , the selected mesh satisfies
Order the selected cubes by increasing , with ranks starting at . Conditional on the sampled design , evaluate all coefficient estimators at the selected mesh of the given sample. For the cube of rank , every monomial coefficient indexed by a multiindex of total degree at most , and every , These conditional exponential moments are integrable for every coefficient and every , and the maximum coefficient-vector error is conditionally integrable. With denoting the maximum absolute coordinate over those monomial indices, its conditional expectation satisfies
Moreover, for every exponent , there exists such that the following maximal inequality holds. Let be a probability law on a measurable space, let , and let be real random variables satisfying
(Scales.) and .
(Exponential integrability.) For every and , is integrable under .
(Moment envelope.) For every and ,
Then
⊢ LeanThroughout the proof, write and use the template width and least eigenvalue from Definition 6. Also write
Membership in , as specified by Definition 2, supplies the treated response bound in Assumption 8. In particular, with the treated conditional law satisfies, for -almost every , and every displayed exponential moment is integrable. These are the outcome properties used below.
We first construct the uniform count bound. Define the positive mass coefficient The minimum exists and is positive because the displayed function is continuous and positive on the compact interval . Every template microcell at mesh has volume . Consequently, Assumption 4 and the setwise bound in Lemma 3 give
Choose a fixed enlargement such that Such a choice exists because . Since the effective dimension decreases with , and hence
The candidate collection in Definition 7 has largest dyadic index The floor inequality yields Moreover, The positive power in the last display tends to infinity when applied to . Thus, for all sufficiently large , Rounding upward within the finite dyadic collection therefore gives a candidate satisfying Indeed, successive candidate widths differ by a factor of two; the smallest candidate width at least satisfies these inequalities, including when either endpoint is itself a candidate.
For the simultaneous concentration budget, define Here counts the partition cubes and counts the microcells within each cube. Since , and therefore For , this implies
To make the count threshold dominate this budget, set The elementary bound and divergence of the positive powers allow one common starting sample size for which Together with the endpoint and candidate bounds, these give Fix large enough that all these bounds hold uniformly for .
Finally, the oracle balance identity is Thus every microcell at satisfies or equivalently .
Under Assumption 3, a treated microcell count is a sum of independent Bernoulli indicators. Each indicator has mean , its centered absolute value is at most one, and its variance is . The Bernstein bound for these bounded centered summands gives, for every , For , the numerical inequality follows by expanding both sides. Hence Define This finite intersection is measurable. The union bound gives
On this event, the candidate from the preceding step satisfies It is therefore feasible. The selector in Algorithm 1 then gives At the selected mesh, feasibility and the budget imply Using the upper deviation inequality first gives The lower deviation inequality now yields These arguments apply to every partition cube, with the boundary convention of Definition 7.
We next obtain the actual conditional coefficient bound. Define the sampled design and its conditional sample law by Under the iid product law, disintegration coordinate by coordinate gives for almost every . To see the product structure, conditional probabilities of response rectangles factor into the product of the coordinate conditional probabilities; these rectangles determine the conditional response law.
For such a design, define the treated residuals on a conditional sample by They are independent under , and the treated conditional bound from the first step, together with the zero residual in the second case, gives with integrable exponential moments.
Fix a feasible candidate , a cube , and . Define The equal-cell formula in Definition 8 is understood with , and with the zero matrix assigned as the inverse of a singular Gram matrix. On the feasible meshes considered here, Lemma 4 supplies the ordinary inverse and
The conditional sample has the same design as almost surely. Expanding the coefficient formula therefore gives The residuals are integrable and have mean zero, so integration proves In particular, defining we have the conditional identity and moment bound Independence and coordinate exponential integrability also show that every exponential moment in this display is integrable.
The normalized covariates appearing in a microcell lie in . Since every coordinate of has absolute value at most one there, Consequently, if then for observations counted in a microcell. Applying to the cell contributions to each weight, and then summing over the observations, gives
For the mass comparison, define, at the fixed mesh, and select weakest microcells by The selected microcells in different cubes are disjoint. Their union has covariate mass at least , whereas its treated mass is at most . The setwise inequality of Lemma 3 thus gives Dividing by and collecting powers yields the explicit mass-rank bound At a feasible mesh satisfying the count lower bound from the preceding step, each inverse count consequently satisfies Define the fixed template factor The conditional coefficient bound is therefore
Choose a measurable full-measure set on which the conditional identities, exponential integrability, and bounds just established hold simultaneously for all feasible candidate indices and coefficient coordinates. Define Intersecting with this full-measure set preserves the failure bound: All subsequent conditional assertions hold for every , at the selected mesh of that sample.
We normalize the two variance scales uniformly. Define For , , and , we have For the second inequality, if , the left side is at most ; if , it is at most . Applying this with the displayed mass coefficient and collecting inverse powers gives Set The selected mesh and conditional moments thus obey If the cubes are enumerated in nondecreasing mass order, the first cubes all belong to . Hence This converts the displayed bound to the rank- envelope, including ties.
We establish the scalar maximal estimate used to control the coefficient vectors. Begin with a clipped Gaussian integral. For an integer and a scale , define We have and . For , For , put The nonnegativity of and the elementary quadratic inequality give Therefore Integrating this exponential majorant proves
Fix any exponent . For an integer , retain and define the clipped suffix envelope Partition its indices into dyadic blocks by and define Each block has at most indices, and within it The preceding clipped Gaussian calculation, at scale , consequently gives Since and , Define Convergence follows from the geometric series and its linearly weighted series.
The dyadic blocks partition the suffix. For nonnegative summands, clipping a sum at one is bounded by the sum of the individually clipped block sums. Only finitely many blocks meet , so integration gives The finite Gaussian sums and their clipped versions are integrable, so all these integrations are legitimate.
Now let be a probability law, let , and let have the exponential integrability and moment envelope with exponent . Define For , this definition gives , and the maximal inequality follows immediately. Suppose , and define Exponential Markov bounds for and , optimized at , give The finite union bound, together with the probability bound by one, therefore yields Exponential moments at and imply integrability of every , and hence of . The layer-cake identity gives
To bound the last integral, set Then The latter bound follows by taking logarithms of the preceding inequality, using and . It implies Furthermore, Split the sum defining at and . The prefix has at most terms, each with variance at most . The suffix has the preceding decaying variance bound. Since we obtain The two integral estimates prove where the positive constant may be taken as
To obtain a constant uniform over the adaptation interval, define Taking reciprocals of positive denominators shows
For any and , Thus the scalar estimate at applies to the envelope with exponent . Its logarithmic factor satisfies Indeed, if , use if , both positive-part logarithms vanish and the inequality is . Taking square roots establishes a uniform scalar constant
For a finite nonempty family of vectors with coordinates in , the pointwise inequality is Coordinate exponential integrability implies integrability of these finite maxima and of the vector maximum. For example, and each finite maximum is bounded by the sum of the corresponding absolute values. Applying the uniform scalar estimate coordinatewise and integrating the pointwise inequality gives
The preceding vector estimate applies to mass-ranked cube envelopes. Enumerate the cubes in nondecreasing , breaking ties by any fixed ordering of the finite cube family. This enumeration is a bijection, so As established above, . For any nonnegative variance factor , Therefore an envelope with variance proxy has the ordered envelope required by the vector estimate whenever The cube family is nonempty at every dyadic mesh, so the vector estimate applies throughout the selected-mesh argument.
We now fix the final constants. Define These constants are positive and depend only on the fixed parameters and interval endpoints.
Fix , , , and . Conditional on its sampled design, keep fixed and define the scales All three are positive, and Applying the ranked vector estimate under gives The same exponential integrability supplies integrability of the maximum on the left.
The oracle definition and imply After cancelling , this gives Define the resulting logarithmic exponent by Its reciprocal dependence cancels, and
For a positive ratio and an exponent , If , this follows from . If , both positive parts vanish and the assertion is . Applying these two cases to the oracle ratio proves
Combining the preceding estimates and the definition of yields Since , the mesh bound also becomes The variance proxies are nonnegative, so increasing to in the conditional exponential bound preserves that inequality. Together with the rank comparison, this gives precisely The count bound and all exponential integrability assertions are retained on the same event .
For the deterministic comparison with the oracle rate, define If , then and consequently Since , If , the positive-part logarithm vanishes, and The two cases give Multiplying by proves the asserted bound with .
Finally, for the additional maximal assertion, take and in the scalar calculation above, and set Its hypotheses are exactly the stated exponential integrability and moment envelope. Thus, including the case , This completes all assertions.
The two parts of the coefficient envelope have distinct statistical roles. Count feasibility caps every coefficient’s stochastic scale at a constant times . The population-mass comparison and Lemma 3 additionally supply the rank-dependent scale . The ordered maximal inequality combines these two controls. Its logarithm measures the number of ranks at which the common cap is relevant, through the scale ratio .
For the coefficient application, the decay exponent is , and, apart from fixed multiplicative constants, the two scales are Their ratio is governed by the selected mesh relative to the oracle mesh. Thus the conditional maximum is controlled at the statistical scale . The final inequality in Lemma 5 places this expression at the oracle scale even for finer selected meshes. In this application, the decay exponent ranges over and the lemma supplies common constants and a common threshold over the stated overlap interval. The fixed number of polynomial coordinates is included in those constants.
The three components of the upper bound
The approximation component uses the intrinsic Hölder regularity in Definition 1 and Assumption 9 at degree . The deterministic inverse-Gram bound in Lemma 4 keeps the fitted conditional mean stable relative to its local polynomial approximation. On , the selected-mesh comparison in Lemma 5 places the resulting mesh-dependent approximation error at the oracle response-recovery scale.
The conditional stochastic component is controlled by the coefficient maximum in Lemma 5. On normalized partition cubes, polynomial evaluation transfers this coefficient control to spatial-supremum control, with constants determined by the fixed dimension and degree. Conditioning on the sampled design accommodates the count-based mesh selection while retaining the ordered information profile.
Finally, the clipping rule in Algorithm 2 and the response bound in Definition 2 bound the loss on exceptional samples by . Consequently, the exceptional-sample contribution is at most . These three controls furnish the uniform spatial-supremum upper guarantee in Theorem 1; the pointwise upper guarantee follows from the same spatial-supremum control.
Bounded testing experiment and geometry proofs
The bounded testing construction
The minimax converse in Theorem 1 is supported by a pair of causal laws with two-valued potential outcomes. The construction places a smooth response perturbation around the evaluation point and uses a common radial propensity to control the treatment information available there. Its radial distribution accounts for intersection with the covariate cube, so the experiment accommodates evaluation points on faces and corners as well as in the interior. The following definition specifies both the observed laws and their causal completions.
The bounded testing construction is the measure-valued family on observations , indexed by and , with parameters , , , and constants . Set where is the oracle mesh for the smoothness and overlap parameters. Define the radial distance, cube-truncated radial function, and common propensity by For and , is the probability of under uniform covariates. Define the smooth product bump and treated success parameters by
The totalized construction uses the positive-part weights For each covariate , take the product of the three two-point measures with weights where the potential-outcome measures place their masses at and , respectively. Integrate this product measure against Lebesgue measure restricted to , and let be its image under
The admissible domain consists exactly of the constants for which for every and every , with . On this domain, is the observed law obtained from uniform and conditionally mutually independent given , with For fixed admissible , define the sample-size-indexed collection
⊢ LeanThe positive-part weights in Definition 11 specify a common measure-family construction across parameter values. On the admissible domain, each conditional two-point measure has total mass one and the construction yields the displayed Bernoulli probability laws. The sample-size-indexed collection uses fixed amplitude and mesh constants; sample size changes the perturbation through the oracle mesh.
Admissibility supplies the probability interpretation, while membership in the model of Definition 2 additionally requires the response and overlap restrictions. The next result makes these requirements compatible with small statistical information and separation of the chosen response representatives at the evaluation point.
Suppose that:
(Dimension and exponents.) , , , and .
(Response constants.) and .
(Model constants.) and .
(Evaluation point.) .
There exist constants , fixed across sample sizes, such that, for every integer , with , where is the oracle mesh, the construction in Definition 11 satisfies Both observed laws and belong to , the model class with parameters . Under each of their constructed causal completions, Moreover, , the log likelihood ratio is integrable under , and For the chosen Hölder response representatives and associated with their model-class memberships, where is the oracle response-recovery risk scale.
⊢ LeanWe first obtain a Hölder radius for the scaled bump that is uniform in its scale and center. Set For each derivative order , write where denotes the -th Fréchet derivative, with the operator norm induced by the supremum norm.
The coordinate factors defining are smooth across their endpoints: their derivatives from inside vanish at the endpoints because the exponential factor decays faster than every inverse power of the distance to the endpoint. Consequently, Every is continuous and compactly supported. Thus the constants are finite and nonnegative. Define The derivative bound of order , applied along a line segment, gives If , then If , then These two cases include .
For , define the scaled bump by Translation and dilation give, for , and hence For the top derivative, the preceding modulus bound yields since . Set Coordinate derivatives are evaluations of these multilinear derivatives on coordinate unit vectors, so their magnitudes and differences are bounded by the corresponding operator norms. Restricting the ambient smooth functions to the cube supplies their continuous boundary traces. Therefore, with the convention of Definition 1,
Using the baseline probability from Definition 11, choose Since , Define the effective dimension and entropy coefficient by Here , , and . Choose Then and . Because and , so All these constants are fixed independently of .
Fix an integer . The oracle mesh and the selected bump scale are Since , , and , Use and as defined in Definition 11. Every factor defining lies in , and the exponent is positive. Thus For each coordinate factor of , the exponent is nonpositive when the coordinate has absolute value less than one, and the factor is zero otherwise. Hence Together with , this gives and therefore In particular, lie in the admissible domain of Definition 11, simultaneously for every .
Write the constructed completion laws as where the joint law is the product-kernel construction in Definition 11. The cube has Lebesgue volume The admissible weights sum to one in each two-point factor. The kernels are measurable, so integrating them over the cube gives probability laws , whose observed images are .
Define the displayed treated-response curves by The choices of and give and consequently For the baseline curve, all positive-order derivatives vanish and For the perturbed curve, For every multi-index with , The bounds from the first step imply For , the constant term cancels in the difference, giving Their ambient smoothness supplies the required boundary traces. It follows from Definition 1 that
The treated potential-outcome marginal of the conditional product kernel is . Thus, under the constructed completion, for Lebesgue-almost every . This establishes the response smoothness requirement in Assumption 9.
We next establish the propensity tail bound. For every , the intersection of the radial sublevel set with the cube is Since , these intervals are nonempty. Their product volume gives under uniform . The displayed formula for is continuous, and the nested sublevel sets show that it is nondecreasing on . Also, The first identity uses ; the second follows because every coordinate interval at radius one is .
For , define The set contains zero, is closed by continuity, and is bounded above by one because for . Its supremum therefore belongs to the set. Consequently, For , the same upper bound follows from total probability one.
For , raising to the positive power gives Since , the preceding bound yields At , this shows Together with , it follows that almost surely.
We verify the remaining model requirements for the constructed completions. Their covariate marginal is uniform on the cube, so The conditional product kernel has the factorization Thus , and almost everywhere. The observation map enforces
The endpoint-supported potential-outcome kernels and this observation map imply almost surely. To apply this support bound to the treated conditional distribution, define Disintegrating the support statement first over and then over , and using almost surely, gives For such , put Integrating the support bounds gives The bounded-variable sub-Gaussian moment bound gives, for every , The exponential is integrable because almost surely. These bounds establish Assumption 8. The density, consistency, exchangeability, propensity-tail, and smoothness properties proved above establish the other requirements of Definition 2. Therefore, with these exact completion witnesses and response curves,
For completeness, the two potential-outcome factors at every covariate point assign total mass one to . Integrating their product over the cube therefore gives This is the required endpoint support under each constructed completion.
We now bound the entropy of the conditional observation laws. For , define Both parameters lie in , and Applying , for , to each likelihood-ratio term gives Also,
Define the laws of the treatment and binary selected outcome by on . Their scaled and recorded versions are Here the first map has domain , the second has domain , and denotes image measure. The product construction shows that is the conditional observation law at covariate .
The control parameters agree, so the control contribution to entropy is zero. The treated contribution satisfies the preceding quadratic bound. Conditioning on the binary treatment therefore gives Applying entropy contraction first to recording the covariate and then to scaling the binary outcome yields In particular, the conditional entropies are finite.
Define the open bump box by Outside , at least one coordinate factor of the bump is zero. Hence For every , each truncated coordinate interval has length at most , so For , we have , and thus Moreover,
Both observed laws are obtained by integrating against the same uniform covariate law, and each conditional law records its covariate in the first coordinate. The entropy disintegration identity therefore gives On , apply the conditional entropy and propensity bounds; on its complement, the integrand is zero. Consequently, The last equality uses The finite entropy bound supplies both
Finally, the oracle mesh satisfies The fixed calibration from the second step therefore gives
It remains to identify the chosen response representatives at . The constructed memberships have the continuous Hölder representatives . By Lemma 1, both these representatives and the chosen representatives associated with the same observed laws agree almost everywhere with the treated conditional regression. Its pointwise uniqueness conclusion gives This includes boundary points of the cube.
Every coordinate factor of equals one at zero, so Writing we conclude that The positivity of justifies the second equality. Since was arbitrary, the fixed constants satisfy all the stated requirements.
Lemma 6 supplies the three components of the testing comparison: two laws within the fixed-constant model, a bound on their relative entropy, and response separation at the oracle scale. Here denotes Kullback–Leibler relative entropy. The absolute-continuity and integrability clauses support the information comparison for independent samples, whose laws are and . The chosen Hölder representatives specify the pointwise targets, including their values on the cube boundary.
The lower guarantee in Theorem 1 uses this pair through the two-point testing principle (Tsybakov, 2009). The information bound and target separation provide the comparison for expected absolute error within the subclass admitting potential outcomes in . The risk ordering in Theorem 1 then places the same oracle scale below the pointwise and expected spatial-supremum minimax risks of Definition 3.
The quantifiers of the construction preserve the pointwise scope of the converse. For each fixed and each fixed in the closed cube, the constants are chosen once and apply to every integer . Their permitted dependence on the evaluation point and fixed model parameters matches Theorem 1. Cube truncation in Definition 11 and the intrinsic smoothness convention in Definition 1 keep boundary evaluation within this same comparison.
The thin-strip geometry
The geometry assertions in Proposition 1 concern the strip law of Definition 10. That construction uses the cube center and a radial-plus-strip propensity; its strip exponent is the parameter specified there, separately from the amplitude constant in the testing pair. Constant potential-outcome means keep response smoothness fixed while the propensity determines the local treated design.
The model-membership and tail clauses of Proposition 1 place this law within the global-tail causal class. Its remaining clauses describe two distinct aspects of local geometry. The anti-concentration statement concerns the displayed selected propensity and the pointwise supremum over Euclidean neighborhoods, as specified in Definition 9. The numerical clause has a counterexample even when propensity values equal to one are permitted. This establishes the selected-version failure underlying the strict enlargement within the causal class.
The second-moment clause instead concerns treatment-weighted variation in supremum-norm neighborhoods of the cube center. Its denominator is the probability of both treatment and neighborhood membership, so the ratio measures the conditional second moment of the second coordinate after normalization by neighborhood width. The zero limit in Proposition 1 records degeneration of that coordinate’s local treated variation under the stated strip-exponent range.
These conclusions have complementary roles. The selected-version statement establishes the comparison with the local anti-concentration predicate, while the normalized moment describes the shape of the treated distribution itself. Together with model membership and the global tail inequality, they characterize the treatment geometry covered by Theorem 1.
Source-model transfer and comparison scope
The retained source restrictions fix a nonempty family , common class constants, and selected regression and propensity representatives before stating a uniform recovery guarantee. Under Dorn (2026), each member has uniform covariates on and a selected measurable propensity satisfying Writing for the selected treated regression, the common constants , , and finite overlap exponent satisfy with conditional inequalities holding almost surely, and Conditional outcomes in both treatment arms are Gaussian with their selected regression means and common variance . Both regression curves belong to , the source smoothness class with common .
The source smoothness convention uses derivative order and bounds the -Hölder seminorm of derivatives of order by , using Euclidean distance. For the intrinsic cube interpretation used in Proposition 2, interior derivatives through order have continuous traces on the closed cube. The source upper comparison additionally imposes the family-level local condition in Definition 9, with common positive constants and the selected pointwise propensity representatives, as in Dorn (2026). These restrictions distinguish the retained source envelope from the fixed families to which the published upper comparison applies.
Fixed-cube smoothness completion
For the transfer in Proposition 2, the treated-moment restriction supplies the function bound that complements the source seminorm. The full response class in Definition 1 also controls the function and all lower derivatives. The following completion statement connects these two smoothness descriptions for the paper’s range .
Fix an integer and a real number , and set . There exists a constant , depending only on and , such that the following holds for every and satisfying:
(Nonnegative bounds.) and .
(Intrinsic regularity.) , with interior derivatives through order admitting continuous traces on the closed cube.
(Top derivative modulus.) For every multi-index with and every , the coordinate derivatives, interpreted through their continuous boundary traces, satisfy
(Response bound.) for every .
For the affine transport the transported function satisfies on , with the intrinsic Hölder ball defined in Definition 1.
⊢ Lean1. Parameters and derivative notation. Set Since and , For each integer , define the set of ordered coordinate indices and the associated derivative by Here contains the empty index and . On a closed cube, these derivatives use their continuous interior traces. Symmetry of the interior derivatives identifies an ordered derivative with the multi-index derivative having the same coordinate multiplicities; continuity preserves this identity on the boundary.
2. Completion on the source cube. We first derive a constant , depending only on , with the following property. For arbitrary suppose that and The desired completion estimates are and
To obtain the interpolation estimate used in this completion, first consider a function whose ordinary coordinate derivatives on satisfy the displayed top-order modulus. Multilinearity gives, for a direction vector , Consequently, Define for and . The segment lies in , and its points with lie in . The chain rule therefore gives Using the diagonal estimate and we obtain Taylor’s Lagrange remainder of degree , applied on , supplies such that After subtracting the degree- term, Since and , this proves
We next bound this Taylor polynomial on a fixed tensor grid. Define Every belongs to . Compactness supplies a finite number satisfying Set For the Taylor polynomial the response bound and remainder estimate yield
Here is the polynomial estimate that converts these grid bounds into derivative bounds. Define the univariate Lagrange polynomials, their coefficients, and the tensor weights by where and . For any polynomial of degree at most in each coordinate, define Univariate Lagrange interpolation, applied to each monomial, gives Taking products over the coordinates and then expanding proves the coefficient recovery identity
The weights admit a uniform bound. Define the coefficient one-norm of a univariate polynomial by The coefficient convolution formula and the triangle inequality imply Since , each numerator factor has coefficient one-norm at most . Splitting the denominator factors below and above gives Thus The binomial identity and the elementary binomial coefficient bounds give Consequently, Define Factoring the finite tensor sums now yields Hence, whenever and for every ,
For each , the monomial is smooth. Continuity of its iterated differentials on the compact cube, followed by a maximum over the finitely many and , supplies such that Each coordinate unit vector has supremum norm , so Define Differentiating the finite expansion therefore gives for , , and .
The polynomial has total degree at most , as is also seen from its coordinate expansion Its derivatives at the expansion point agree with those of . Indeed, a homogeneous term of degree has zero -th derivative; a term of degree retains a vanishing factor at ; and for , symmetry of the differential produces identical contributions, cancelling . Thus Set Combining the grid bound, polynomial derivative bound, and derivative agreement proves under the ordinary-derivative modulus used above.
To apply this estimate to intrinsic cube derivatives, define the inward contractions For every , . The chain rule on this interior region gives The assumed intrinsic top-order modulus implies because and . The preceding interpolation estimate therefore applies to , yielding Continuity of the derivative traces allows , giving Since , the same continuity extends this bound to every .
Finally, define Nonnegativity of the bounds gives These inequalities prove both completion estimates stated at the beginning of this step, together with the original regularity.
3. Affine transport of a completed radius. Define Suppose that a function has derivative and top-order modulus bounds of radius : The affine map maps into . Composition preserves the intrinsic regularity, and the chain rule gives This identity holds on the interior and extends to the boundary by the continuous traces. Hence Moreover, so Thus affine transport multiplies the completed radius by at most .
4. Conversion of the given modulus. Choose These constants depend only on and . For any , define its coordinate multiplicities by Then The hypothesis therefore bounds every ordered top derivative. For , Since , raising the latter inequality to the power gives Multiplication by now yields
5. Completion and transport for . Define the source radius The source-cube completion estimates apply with the response bound and modulus constant . They give and Applying the affine transport estimate with radius proves and
6. Calibration of the final radius. The nonnegative bounds imply Multiplying by gives Consequently, and, for every and , Together with the transported intrinsic regularity, these are precisely the restrictions in Assumptions 1 and 2. By Definition 1, All estimates include zero values of either bound, and the argument uses , including .
∎Fix parameters satisfying:
(Dimension and smoothness.) , , and .
(Source constants.) and .
(Adaptation range.) , with
For each , let be the maximal envelope of source-law tuples consisting of an observed law , treated and control mean functions, and a selected propensity , satisfying the following retained restrictions from Dorn (2026): is uniform on ; the selected propensity belongs to almost surely; conditional on , the outcome is Gaussian with variance ; both conditional mean functions belong to ; and Here is the selected treated mean. The source class consists of functions in , with continuous boundary traces of their derivatives, whose derivatives of order have -Hölder seminorm at most , using the source’s convention.
Let , the affine transport from the unit cube to the source cube, and the common response bound be Define the common transported Hölder radius and the interpolation constant by The functional is the full Hölder-radius functional on , including the function, lower derivatives, and top-derivative modulus. Then
Every member of , after replacing by , belongs to the global-tail causal class with constants In particular, its transported observed law admits a consistency-and-exchangeability causal completion with these constants.
Let be the equal-cell estimator of Algorithm 2, with smoothness and response bound , applied to independent transported observations. Write , the oracle risk scale, as There exist and such that, for every , every , and every source tuple in , Every source family satisfying the cited Assumptions 1–2 with the fixed displayed constants is nonempty and contained in . The same therefore satisfy
For every , there exist and such that, simultaneously for all , , and source tuples in , Here the norm is the essential supremum under the source covariate law, and the estimator is computed from the transported sample.
If , then for each there exist positive finite constants and a source tuple with uniform covariates, Gaussian conditional outcomes, and a selected pointwise propensity representative satisfying all the retained restrictions with these constants, for which where the family-level condition is defined in Definition 9. The constants in this existence assertion are selected separately for each .
For any nonempty family of source-law tuples sharing a common treated regression curve , meaning the minimax pointwise miss-probability value at any evaluation point , sample size , and positive threshold , with , equals zero.
Finally, for every and every , there exists such that where is the pointwise minimax expected absolute-error risk of Definition 3 over the causal class with constants , and . The displayed lower bound is first established for the two-valued potential-outcome subclass risk; monotonicity under class inclusion transfers it to . The constant may depend on the evaluation point and the fixed parameters.
⊢ LeanThe completion constant depends on dimension and smoothness alone. Consequently, a common function bound and a common top-derivative modulus yield a common full Hölder radius after affine transport. Applied to the treated regression curves in Proposition 2, this statement supplies the finite radius needed by the equal-cell estimator. The continuous boundary traces make the completion applicable on the entire closed cube, including its faces and corners.
Source loss and the fixed-family criterion
For the source comparisons, the regression target is , with the selected version understood. Let denote the sample of independent observed triples, whose sampling law is . For a regression estimator , the source loss is Thus the essential supremum is taken under the source covariate marginal. For a fixed finite overlap exponent , write for the source comparison scale. The fixed-family probability criterion bounds the probability that the source loss exceeds , where is a positive threshold constant allowed to depend on the fixed setup.
A pointwise minimax miss probability also depends on which regression curves the family contains. The next statement records the common-curve obstruction once; later comparisons invoke it by reference.
Fix parameters satisfying
(Dimension.) and .
(Smoothness.) and .
(Overlap.) and .
Let be any nonempty source family equipped with selected treated and control regression functions and propensity representatives. Suppose its selected treated regression is the same known function throughout the family: For a sample size , let denote the observed sample and its product sampling law. Then, for every evaluation point , every , and every , where is an arbitrary positive comparison scale, The infimum ranges over all measurable real-valued sample estimators , and the minimax value is taken in the extended nonnegative reals.
In particular, consider the singleton family whose observed law has mutually independent coordinates with selected treated and control regression functions identically zero and selected propensity . There exist common constants , , and for which this law satisfies all of the following:
(Selected propensity.) The selected propensity is a measurable version of the conditional treatment probability and lies in almost surely.
(Moment and variance bounds.) The treated conditional absolute -moment is integrable and satisfies
(Source smoothness.) Both selected regression functions belong to the source top-derivative seminorm class specified in Proposition 2.
(Global overlap.) The selected propensity satisfies
(Conditional Gaussian outcomes.) For -almost every , the conditional outcome distribution in each treatment arm is Gaussian with its selected regression mean and variance one.
(Common local anti-concentration.) The singleton satisfies with the local ball-ratio inequalities and common positive constants specified in Definition 9.
At the cube center , for every and every , this singleton’s displayed minimax miss probability equals zero.
⊢ LeanFix the family, evaluation point, sample size, and positive constants in the first assertion. Define the constant estimator It is measurable for every , including . For every and every sample, Since , its miss event is empty. Consequently, in the extended nonnegative reals, This proves the first assertion.
For the explicit witness, define the cube and component measures by The cube-volume formula gives Also, Thus is a probability law with the independent coordinates specified in the statement. Its covariate marginal is Select the treated regression, control regression, and propensity, respectively, as
The Gaussian fourth absolute moment is finite. Define Then Monotonicity of powers in the exponent for a base at least one yields Hence Choose the common constants They satisfy , , and .
We verify the remaining model restrictions with these constants. The product law gives This is the joint law obtained from and the constant conditional distribution . Uniqueness of conditional distributions therefore gives Thus the selected propensity is a measurable version, with
Similarly, reassociating the product law gives Uniqueness of conditional distributions identifies the conditional outcome law with for -almost every . Fubini’s theorem gives this identity for -almost every , for -almost every . Since both arms satisfy, simultaneously, In particular, the treated conditional absolute fourth moment is integrable and The regression variance satisfies
Both selected regressions have continuous derivatives of every order, and for every multi-index and every , Their continuous boundary traces are also zero. Every defining top-derivative difference therefore vanishes, while its prescribed modulus bound is nonnegative. Thus
For the global overlap bound, fix . If , monotonicity of the power with positive exponent gives The propensity event is then the whole covariate space, so If , that event is empty, and Finally, the conditional outcome identities already established give Gaussian distributions in both arms with their selected zero means and variance one: for -almost every .
Define the selected singleton family and common local constants by The family is nonempty, its selected propensity has the required properties, and We verify the local ratio in Definition 9. For and , define Since , this intersection is nonempty, and the constant selected propensity has supremum
The denominator in the local ratio is positive, including when lies on the cube boundary. Indeed, the coordinatewise closure identity and the finite-product closure and interior identities give The set is open and contains , because . It therefore meets . Their intersection is a nonempty open set, so its Lebesgue measure is positive. Since we obtain Consequently, Because the propensity is identically on all of , Thus, for every and , This proves
The singleton has the common known treated regression Applying the constant-estimator argument above with this regression and gives, for every and every ,
The decision underlying Lemma 8 is the constant sample estimator . Its pointwise error is identically zero throughout the family: The Gaussian singleton shows that the obstruction is compatible with the source moment, smoothness, overlap, and local anti-concentration restrictions.
The source upper comparison
The cited upper comparison concerns an estimator selected for an already fixed family and its common constants. Its probability bound is uniform over members of that family, with the comparison scale determined by the family’s fixed overlap exponent. The following proposition retains that quantifier order; its common-regression clause is the application of Lemma 8 needed to delimit the converse scope.
Fix an integer , constants , and . For every fixed finite , consider a nonempty source family of observed-data laws, equipped with selected treated and control regression curves and selected propensity representatives . Suppose that:
(Design and propensity.) Under every , is uniform on , and the selected measurable representative satisfies
(Moment and variance.) Writing for the selected treated regression curve, every member satisfies with the conditional inequalities holding almost surely in each applicable arm.
(Gaussian regression and smoothness.) Almost surely with respect to the covariate marginal, the conditional outcome distributions in the treated and control arms are Gaussian with their respective selected regression means and common variance . Both selected regression curves belong to the source seminorm class : their derivatives of order satisfy Dorn’s Hölder-seminorm bound , with exponent .
(Global overlap tail.) For every and ,
(Family-level local condition.) On the original cube , the selected propensity representatives satisfy as defined in Definition 9, including its common positive constants and uniform local-ball mass-ratio inequality.
Define the fixed-setup comparison scale by There exists a regression estimator , where is the sample of independent observations, selected after the family, its common constants, and its propensity representatives have been fixed, such that its dependence on the sample is measurable for every and . For every sample size , member , and real threshold , the event is measurable, where the norm is the essential supremum with respect to the covariate marginal of . For every , there exists a finite constant such that where is the product sampling law. The estimator and may depend on the fixed setup. This upper comparison is the assertion of Dorn (2026).
For every , the following two pointwise conclusions also hold. First, let be any nonempty source family whose selected treated regression curves equal a common known function at every point: For every evaluation point , sample size , and constants , its extended nonnegative minimax miss risk is Here the infimum ranges over all measurable real-valued functions of the sample.
Second, there exist constants and for which the singleton Gaussian experiment with mutually independent and selected treated mean, control mean, and propensity respectively , satisfies the displayed design, propensity, moment, variance, Gaussian, smoothness, and global-tail conditions with parameter tuple and satisfies the family-level condition of Definition 9 on the original cube. For this singleton, at , every sample size and every satisfy
⊢ LeanThe source upper assertion in Proposition 3 is the fixed-setup, uniform-in- probability guarantee of Dorn (2026). Its displayed scale has no logarithmic factor. The estimator, threshold constant, and overlap exponent remain indexed by the fixed setup, while sample measurability and exceedance-event measurability give the displayed probabilities their ordinary sampling interpretation.
The common-regression clauses give the model-family qualification relevant to the pointwise lower attribution printed in Dorn (2026). The positive pointwise converse in Proposition 2 instead concerns the full causal class of Definition 3, with expected absolute-error loss; its lower bound is supported by the two-valued potential-outcome subclass in Definition 11 and Lemma 6.
The affine transfer
The transfer component of Proposition 2 uses the retained source restrictions from Dorn (2026). The maximal envelopes and the constants are defined in that statement. Their role is to place every qualifying source tuple within one response-recovery class after transporting covariates by , where .
The ingredients have distinct mathematical functions. Uniform source covariates become uniform covariates on the unit cube, supplying density constant . The retained propensity tail controls global overlap at the same exponent. The treated-moment and Gaussian restrictions supply the common response bound , and Lemma 7 supplies the finite full Hölder radius . The causal-completion clause of Proposition 2 then identifies the transported observed laws as members of the model in Definition 2.
With this membership established, the equal-cell estimator of Algorithm 2 has the expected spatial-supremum guarantee stated in Proposition 2, uniformly over the fixed-constant envelopes and the compact overlap range. At , its oracle scale equals the source scale . The accompanying essential-supremum probability bound supplies a comparison in the source loss criterion, with constants common to those envelopes and that exponent range. Every qualifying source subfamily inherits the envelope guarantee through the containment asserted in Proposition 2.
The Gaussian strictness construction
The Gaussian existence component of Proposition 2 concerns the geometric scope of the retained restrictions. For each overlap exponent in the stated range and dimension , it supplies a source tuple with uniform covariates, Gaussian conditional outcomes, smooth means, and the required moment and global-tail bounds, together with failure of the selected-version local predicate in Definition 9. Its positive finite constants are selected separately for each exponent.
This quantifier structure distinguishes the existence construction from the upper guarantee over a prescribed fixed-constant envelope. The construction establishes that the retained Gaussian restrictions accommodate the selected-propensity geometry described by the corollary. The affine-transfer component supplies recovery guarantees for each envelope with its displayed common constants, while Proposition 3 supplies the preprint comparator for fixed families satisfying the additional local condition. Together, these components identify the smoothness completion, family scope, and treatment geometry underlying Proposition 2.
Verification note
The theorem and lemma environments carrying declaration links are machine-checked in Lean 4.33.0 (compiler commit d8b18978322de05a8f3dba51ef03cf5461676c17) against mathlib revision db584cd6d46c92f209a44c0f1c829460d327499d and the adjacent Causalean library. The Lean sources are under CausalSmith/Stat/STAT_WeakoverlapUnisolventRate_Research; the bundle’s lean_snippets.json and formal_layer.json record the complete object-to-declaration map. The verification record identifies repository revision d07574d7eb0a903c2a049c6ae28702de46193ec0; this is distinct from the Lean compiler commit and the mathlib revision above. The emitted paper checksum is recorded separately in meta.json.
The checked results include causal identification, ordered treated-cell masses, template conditioning, and mesh selection in Lemmas 1, 3, 4, and 5; the bounded testing experiment in Lemma 6; and the adaptive minimax conclusion in Theorem 1. They also include the treatment-geometry and Gaussian-transfer conclusions in Propositions 1 and 2, together with smoothness completion, the family-richness obstruction, and the source comparison scope in Lemma 7, Lemma 8, and Proposition 3. The synthesized notation environments and explanatory transitions are presentation-level material. The joint-adaptation entries in Remarks 1 and 2 describe future work and assert no proved risk bound.
These checks certify deductions under the stated assumptions. Response recovery uses the sampling, causal, density, global-tail, outcome, and smoothness restrictions defining Definition 2, with the fixed constants and compact overlap range specified in Theorem 1. The geometry and transfer conclusions retain their stated dimension restrictions, selected propensity versions, and source-family conditions. External-source transcriptions and generated theorem-local dependency footnotes delimit the trust boundary for cited inputs: the checked deductions use the recorded source conclusions under their recorded assumptions, while the source proofs of those conclusions remain external. The consolidated account here complements those local disclosures.
Proofs of the main results
1. Uniform local approximation. We first establish the estimator bound uniformly over the prescribed adaptation interval. Set Then and . By the identification and uniqueness conclusions of Lemma 1, every Hölder response witnessing membership of in agrees with throughout .
Here is the local approximation bound used below, including at cube boundaries. Define the affine map and transported response by Repeated coordinate differentiation of the affine composition gives, for every multiindex with , The chain rule proves this identity in the interior, and continuity of the derivative traces extends it to the boundary. Thus Assumption 1 gives For and , the identity and Assumption 2 give Affine composition also preserves the continuous derivative traces through order . Consequently, defining we obtain intrinsic Hölder radius for on . Lemma 2, applied with derivative order , exponent , and radius , supplies a constant and a function satisfying and Here denotes the Fréchet derivative of the indicated order, with order zero interpreted as the function itself.
For a partition cube of mesh , define and We derive the remainder bound along the expansion segment. Since , we have . For , define The chain rule gives with order zero interpreted as the function value. Expanding the symmetric derivatives in coordinate directions and using the definition of yields Taylor’s theorem with the order- Lagrange remainder gives a point satisfying Choose such a point and define the degree- remainder by The displayed Hölder modulus for the extended function therefore implies since , , and . This bound also applies when . Define Because , we obtain, uniformly in the expansion centre, where The normalized coordinates belong to , and the affine image of belongs to , which justify the equality and the approximation. This construction also covers integer , for which .
2. Conditional bias and supremum loss. Apply Lemma 5. Denote its uniform mesh and coefficient constants by , and its sample-size threshold by . Enlarge these constants and the threshold as required by the constructions below, taking . Define For , , and , choose the simultaneous treated-count event underlying the mesh and coefficient bounds as follows. For all candidate microcells, define and take The Bernstein bound for each treated count and the finite union bound give We establish the selected-mesh and treated-count bounds on this particular intersection. Let be the reference microcube width in Definition 6. Each microcell at mesh has volume , so Assumption 4 and the measurable-set bound in Lemma 3 give where The positivity of the minimum follows from continuity and positivity of the displayed coefficient on the compact interval . Choose a fixed enlargement constant satisfying Such a choice exists because . Since we have
The candidate collection in Definition 7 has largest index The floor inequality gives Because and , After enlarging , these relations ensure, uniformly over , that Define an oracle candidate by The set defining the maximum contains zero. If its maximum is smaller than , the next dyadic width is smaller than ; if the maximum equals , the preceding lower bound on the finest width forces equality with the target width. Thus
We next verify the logarithmic budget. The template and dyadic partition have Since , the definition of gives For , using and , we obtain Define The elementary bound and divergence of positive powers allow a further uniform enlargement of such that Consequently, The population-mass bound also gives, for every microcell of this oracle candidate, where .
On , the defining deviation inequality therefore yields, at the oracle candidate, Thus this candidate is feasible. The smallest-feasible-mesh rule of Algorithm 1 gives For a microcell of the selected mesh, feasibility and the same deviation inequality imply In particular, Taking , we have established on the displayed count intersection that
Every count in the defining finite intersection is measurable with respect to , and every population mass is fixed under . Hence . Conditioning therefore fixes the sampled design, the selected mesh, its treated counts, and membership in .
First, the response bound holds everywhere on the cube. Define The conditional-mean bound in Assumption 8 and identification give Both functions are continuous on the cube. The uniqueness conclusion of Lemma 1 therefore gives
On , set At each fixed design, this conditional expectation evaluates the coefficients at that design’s selected mesh. Feasibility gives positive treated counts. For each treated observation used in the fit on , define The local polynomial approximation gives Identification and the equal-cell normal equations yield, almost surely, Every monomial coordinate has absolute value at most one on the normalized cube, so Consequently, Lemma 4 implies Define the fixed constants
For the selected design, define the maximum coefficient fluctuation by This maximum uses the selected mesh fixed by the conditioning design. Since and clipping contracts distance to every value in , we obtain We derive the conditional coefficient envelope on this same count event. For the selected design, define and order the selected cubes so that Here . The ordered-mass conclusion of Lemma 3 supplies a fixed constant satisfying
Define the treated residuals and coefficient weights by These weights are evaluated only at the positive feasible mesh on , where every denominator is positive. Conditional on , the residuals are independent by iid sampling, and identification together with Assumption 8 gives, almost surely, For an untreated observation the residual is zero. The equal-cell coefficient formula consequently gives The inverse bound in Lemma 4 and imply Cauchy–Schwarz over the microcells, followed by summation over their treated observations, gives The last line uses both and the established bound . Multiplying the conditional exponential moments of the independent weighted residuals yields Define The ordered-mass bound and for nonnegative now give All these exponential moments are finite; their two-sided finiteness also gives conditional integrability of the finite coefficient maxima.
To apply the maximal inequality in Lemma 5 with a constant uniform in , define Then Since for , the same moment bound satisfies the maximal inequality at the fixed exponent . Let be its constant, and define The logarithmic factors satisfy Indeed, when , expand the logarithms and use ; when this ratio is smaller than one, both positive-part logarithms vanish. Applying the scalar maximal inequality to each coefficient and using we obtain
The oracle-mesh identity gives Define Then and hence To absorb the remaining logarithm, define If , then so their product is at most one. If , the positive-part logarithm vanishes and . Thus Choose the initially enlarged coefficient constant to satisfy We have therefore established, almost surely on the explicitly chosen count event,
Also, Thus, defining we have and The finite mesh selection and polynomial fits are measurable, and the conditional integrability needed here is supplied by Lemma 5.
3. Uniform expected risk. For every sample, including samples with , the estimator in Algorithm 2 takes values in . Define, on the entire sample space, The preceding response bound gives The supremum loss is measurable and bounded. The tower property and the bounds on the event and its complement therefore give For every , , and , so monotonicity of powers with base gives Set Then , and uniformly for , , and . The count rule and clipped fit in Algorithms 1 and 2 use the stated inputs .
4. The bounded-subclass lower bound. Fix and . Define the subclass and its pointwise minimax risk by The infimum is over sample-measurable scalar estimators.
Apply Lemma 6. It supplies fixed such that, for every , the pair from Definition 11, with belongs to and satisfies Define The separation supplied by Lemma 6 is
For an arbitrary sample-measurable estimator , define its clipped version by The response bound established above gives, for , Thus the clipped losses are integrable under both sample laws.
Product entropy tensorization and Pinsker’s inequality give Define the two large-error events by The triangle inequality and target separation imply Hence For each , integration over yields Combining the two inequalities and the clipping contraction gives Both laws belong to the restricted subclass. Taking the infimum over , and defining proves
5. Constants for all positive sample sizes. For the fixed , define a local adaptation interval by Since , Applying the uniform estimator bound to this interval supplies and such that Define These constants are finite, , , and
Fix . If , the measurable estimator is an admissible witness in the supremum minimax infimum, so If , then . Monotonicity of the inverse square and give Therefore The same clipped estimator has loss at most for every sample, so Thus the upper bound holds for every .
6. Comparison of the risks. The inclusion implies, for each scalar estimator , Taking infima over the same estimators gives For any admissible function-valued estimator , define its evaluation by This is a measurable scalar estimator, and gives Taking expectations, worst-case risks, and then the infimum over function-valued estimators yields Combining the bounded-subclass lower bound, the upper bound for every positive sample size, and these comparisons proves
∎Fix an admissible strip exponent , and use the construction and selected propensity in Definition 10 throughout.
Let the completed-data law and its treated response be The construction gives The radial term and strip increment are nonnegative, and truncation at one therefore gives Thus all conditional Bernoulli distributions are probability distributions. Integrating their product against the uniform covariate distribution shows that and its observed-data marginal are probability laws, with
The conditional distribution of is the constant scaled Bernoulli distribution, so For the derivative order in Definition 1, the constant function satisfies Its derivatives have continuous boundary traces. Hence as defined in Definition 1, and it supplies the response required by Assumption 9.
We verify the remaining restrictions in Definition 2. The uniform marginal gives which supplies Assumption 4. The completed construction gives and, for almost every , These identities verify Assumptions 5 and 6, and the treatment marginal gives
For the overlap calculation, define the radial propensity and radial exponent by The centered cube of radius has side length , whence In particular , so the nonnegative strip increment gives
To bound the last event over its whole range, for define Then , and monotonicity of the -th power on nonnegative reals gives Consequently, This includes ; at , the same upper bound follows from total probability one. Taking therefore yields This verifies Assumption 7. At , the sharp bound and nonnegativity of also give
The equal-arm product construction identifies the treated conditional distribution wherever treatment has positive conditional probability: for -almost every . Its support is contained in . The bounded-range exponential-moment inequality, followed by enlargement of its exponent, gives Also . For every , it follows that The centered exponential moment is at least one by Jensen’s inequality, so the square root is well defined. These estimates supply Assumption 8. Together with the smoothness already established and the stated parameter conditions, they prove The uniform covariate marginal also supplies the asserted sharp bound
Fix arbitrary . For , define the centered Euclidean ball and local propensity supremum by For , every coordinate displacement in has magnitude at most . On , the strip inequality further gives Thus this intersection is contained in a rectangular box with second-coordinate side length and all other side lengths . Uniformity implies For the denominator, the centered box with every coordinate displacement at most lies in and in , since Its volume therefore supplies Dividing these bounds yields Because and , Choose satisfying
The center belongs to , and its radial term is zero. Hence For , the propensity equals its radial component and , giving Therefore and This contradicts the numerical clause for the proposed triple. Since the triple was arbitrary, the numerical anti-concentration clause fails. The argument uses the pointwise bound , so it applies with propensity values equal to one admitted.
The full singleton-family condition in Definition 9 entails its numerical clause with the same constants . Thus the preceding contradiction gives for the selected propensity .
For the design limit, define, for every , For this definition, a quotient with zero denominator is assigned value zero.
Introduce the positive constants and envelope Factoring powers of gives The strip-exponent restrictions give so both powers tend to zero and
We bound the moment by this envelope. Suppose . On , the normalized second-coordinate square is at most one. If , the strip inequality and give If , the radial bound gives Combining these two cases and integrating, Here , and its volume is . The same rectangular enclosure used above bounds the strip intersection, so
For the treated-mass lower bound, define Since and , The coordinate bounds place in , and they imply Thus Its second-coordinate side length is , and each other side length is . Since on ,
Finally, conditioning on and using gives the numerator and denominator identities All integrands are nonnegative. Dividing the numerator upper bound by the positive denominator lower bound therefore yields The squeeze theorem proves which is exactly the asserted normalized treated-design limit.
The law itself supplies the final existence claim: it belongs to , and its full singleton-family Dorn predicate fails for .
The source mean is bounded throughout the cube. Fix and a source tuple in . Write and let be its selected control mean. Continuity of on the compact source cube gives For -almost every , the treated conditional distribution is . Its mean identity, the absolute-integral inequality, and Jensen’s inequality give and Since and , this implies almost everywhere.
To extend this inequality to the boundary as well, define The function is continuous on the source cube and vanishes Lebesgue-almost everywhere there. Moreover, Continuity first forces to vanish on the interior, since a positive value would give a neighborhood of positive Lebesgue measure on which it remains positive. Taking limits from the interior then gives
Completion and comparison of the common radii. By Lemma 7, there is a constant such that, for every nonnegative amplitude bound , nonnegative seminorm bound , and function satisfying the corresponding source regularity and bounds, For a function admitting a nonnegative Hölder radius, write its set of admissible radii as Consequently, In particular, the two suprema in the proposition are bounded above:
Every admissible radius bounds the function itself. Taking the infimum of those bounds gives Constant functions satisfy the source seminorm restriction because their derivative differences vanish. Applying the preceding inequality to the constant functions and , which admit radii by the completion result, yields The constant function , with amplitude and seminorm bounds both equal to , is admissible in the definition of . The constant function is admissible in the definition of . Hence Finally, every function contributing to also contributes, after normalization, to : Taking the supremum over these functions proves
Gaussian source witnesses for the local-condition assertion. Suppose , and fix . Then . Choose so that For the fixed moment exponent, set Gaussian moments are finite, so is positive and finite. Since and , All four chosen source constants are positive and finite.
Use the center, radial function, strip, and propensity from Definition 10. For the ambient arguments needed below, the same coordinate formulas are Here . Define the capped propensity on all of by Thus, on the unit cube,
Construct random variables with conditional product distribution Set These measurable product kernels define a probability law. The affine change of variables and the conditional product distribution give and Since the radial term is positive away from , a set of full covariate probability, The zero means satisfy the source smoothness restriction, and Together with the bound on , these establish the moment, variance, Gaussian, and smoothness restrictions.
The uniform-covariate propensity bound in Proposition 1 supplies For , capping leaves this sublevel event unchanged. Since , For , monotonicity of the positive power gives The affine transport therefore yields Thus the tuple satisfies every retained source restriction with the chosen constants.
It remains to establish the failure of the numerical clause in Definition 9 for this capped representative. Define the closed centered Euclidean ball by For , the ball lies in the unit cube. On , the second coordinate has width at most , and each other coordinate has width at most . Conversely, because the squared Euclidean distance of any point in this box is at most . These box bounds give and hence
Consider any proposed constants , and set Both and tend to zero as . Choose with For every , , so Consequently, At the center the propensity equals , giving the pointwise bound For , the strip term vanishes, and It follows that The resulting local mass ratio is therefore at most , contradicting the required strict inequality.
Finally, the affine identities preserve the pointwise suprema and the numerator and denominator probabilities in these ratios. A source-cube local condition with radius bound would thus give a unit-cube condition with radius bound , which the preceding argument contradicts. Hence The construction selects its constants separately for the chosen .
Transport and causal completion of each source tuple. Return to an arbitrary tuple in , with . Define globally measurable versions by Continuity on the closed source cube makes the mean extensions measurable. The clamped propensity is measurable and takes values in . Since the source covariate is supported on the cube and the selected propensity lies in almost surely,
Construct a completion law by retaining covariate marginal and using the conditional product distribution with All factors are probability kernels, so this defines a probability law.
To identify its observed marginal, take any bounded measurable function Conditioning first on the covariate and treatment and then on the covariate alone gives Here the selected propensity and both Gaussian arm kernels identify the two conditional distributions. Thus
Define the transported covariate, completion, and observed law by The observed marginal of is exactly . The source tail inequality at also gives Together with , , and , this verifies the required parameter domain.
The affine change of variables has Jacobian , and hence The transported selected propensity is and satisfies The treated conditional kernel under is almost everywhere. The displayed bound on the source cube gives Translation of a Gaussian by its mean produces a centered Gaussian. Its moment-generating function therefore gives, for every , These inequalities verify Assumption 8.
The treated potential outcome is integrable, by integrability of the source mean and the Gaussian residual. Its Gaussian conditional distribution yields Since is a measurable bijection with measurable inverse, conditioning on gives
We next verify smoothness at the precise radius . Completion supplies at least one admissible radius for , and its defining supremum gives For completeness, the infimum defining the full radius is attained whenever its admissible-radius set is nonempty. Indeed, regularity follows from any one admissible radius, and every derivative bound satisfies For distinct , every admissible radius bounds the quotient, so For , both sides of the corresponding modulus inequality have zero left-hand side and zero distance factor; it follows directly from any admissible radius. Thus Increasing a radius preserves its defining inequalities. Applying this to the transported response proves The measurable mean extension agrees with the selected source mean throughout the source cube, so its transported version agrees with throughout the unit cube. Their intrinsic derivative traces and modulus restrictions therefore coincide. Since is supported there, this also preserves the conditional-mean identity.
Finally, the product construction and its affine transport give These are Assumptions 5 and 6. Together with the density, tail, response-bound, and smoothness calculations, they verify every restriction in Definition 2. Consequently, with the exhibited causal completion .
A common expected-supremum bound. Define the enlarged tail constant by Increasing the tail constant preserves the tail restriction, since Thus every transported tuple belongs to the model with parameters . These parameters satisfy the hypotheses of Theorem 1.
To state the sampling identity explicitly, define, for , For , this is the identity on the singleton empty sample. For every source tuple, define the transported-sample loss by where is the estimator of Algorithm 2 with parameters .
By Lemma 1, the continuous treated response associated with agrees throughout the cube with the response of the displayed completion: Hence the estimator risk supplied by Theorem 1 is exactly That result supplies and a common integer such that The constants are common because the model parameters and adaptation interval are fixed.
Restriction to source families. The source setting permits an arbitrary nonempty family whose members satisfy the retained restrictions with common constants (Dorn, 2026). Therefore every such family satisfies Taking the supremum of the preceding memberwise estimate over this family gives, with the same , This is the asserted family expected-supremum bound.
The probability bound on the source cube. Fix , and choose For every , the oracle scale is positive: For each partition cell at each fixed dyadic mesh, choose a countable subset dense in the relative topology: On a sample with positive selected mesh, the fitted function restricted to each selected cell is a clipped polynomial. Together with continuity of the transported response, this gives For each fixed mesh and cell, the fitted value at a fixed point is sample-measurable, so the right-hand side is a countable supremum of measurable functions. Taking the maximum over the finitely many cells preserves measurability. The mesh selector is measurable and takes values in a countable set of dyadic meshes together with zero, so selecting among these measurable losses also preserves measurability. On the zero-mesh branch, which is deterministic. Thus is measurable.
For every transported sample and every source-cube point , The source covariate law is supported on that cube, so Markov’s inequality and the common expectation bound now give The sampling identity for expresses the same probability under when the estimator is computed from the transported sample. Every bound is simultaneous over and source tuples in .
Families with a common regression curve. Let be the stated nonempty family with common treated curve . For any and evaluation point , define the constant sample estimator It is measurable, including when . For every family member and every sample, Since , its miss event is empty. Consequently, This proves the asserted equality in the extended nonnegative reals.
The causal-class pointwise lower bound. Apply the pointwise lower conclusion, supported by the two-valued potential-outcome subclass, of Theorem 1 with the fixed parameters Their required positivity and range conditions were established above. Distinguish the restricted pointwise risk by defining For every and every , the cited conclusion supplies such that The second inequality follows because the restricted laws form a subset of the full causal class in Definition 3: for each measurable estimator, restriction decreases the worst-case risk, and taking the infimum preserves this inequality. This gives the final assertion.
Fix a finite , the source family , its common constants, and its selected propensity representatives. The design, moment, variance, Gaussian, smoothness, and global-tail hypotheses give Dorn’s Assumption 2, including the restrictions retained from Assumption 1. The family-level condition in Definition 9 gives Assumption 3 on the original cube.
Dorn’s fixed-setup upper comparison (Dorn, 2026) therefore supplies an estimator , measurable as a function of the sample for every and , with comparison scale Its admissibility also gives measurability, for every , , and , of For every , the cited comparison supplies a finite such that The setup was fixed before selecting the estimator and threshold constant, so both may depend on that setup. This proves the upper comparison.
Fix . The hypotheses , , and permit application of Lemma 8. Its known-regression conclusion gives, for every nonempty family with selected treated curves equal pointwise to , every evaluation point , every sample size , and every , with the minimax value taken in the extended nonnegative reals.
The singleton conclusion of the same result supplies and for the independent experiment displayed in the statement. It supplies the uniform design, selected propensity , moment and regression-variance bounds, zero treated and control curves with the required source smoothness, global-tail bound, Gaussian conditional outcomes, and the family-level condition of Definition 9. The conditional Gaussian distributions have variance one, hence Thus the conditional-variance restriction also holds for the asserted parameter tuple. Finally, the singleton conclusion at gives These are the two pointwise conclusions.
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