Fractional Parabolic Partial Differential Equations in Anisotropic Spectral Barron Spaces: Regularity and Neural Approximation
Abstract
We study fractional parabolic initial-value problems with lower-order drift and potential terms in anisotropic spectral Barron spaces, defined by weighted space--time Fourier L1 norms adapted to parabolic scaling. We prove existence, uniqueness, and maximal regularity with a gain of one derivative in time and γ derivatives in space, where γ>0 is the order of the fractional Laplacian. The evolution is defined only for t≥0, whereas the finite-time norm requires a global extension with sufficient temporal Fourier decay. We construct a finite reflected semigroup extension using a Vandermonde system to match derivatives at t=0, obtaining temporal Fourier estimates uniform in the semigroup parameter. Combined with Fourier multiplier estimates for the damped principal operator, it yields maximal regularity. Dimension-independent multiplication estimates support a finite regularity bootstrap, while interpolation and sufficient damping absorb the lower-order terms in the base estimate. The a priori estimate and the method of continuity yield maximal regularity without smallness assumptions on the lower-order coefficients. A frequency-localized counterexample shows that a uniform-in-time spatial Barron bound on the forcing does not imply the corresponding two-derivative solution bound, even for the one-dimensional heat equation. Using this regularity, Fourier sampling yields n−1/2 approximation rates for the solution in mixed space--time Sobolev norms using shallow networks with suitable activations. Sampling in a product Hilbert space yields a population-level PINN consistency estimate for shallow cosine networks on a bounded cylinder. There exists a single width-n network for which the sum of the squared mixed-Sobolev solution error, the squared L2-norm of the residual for the whole-space fractional equation, and the squared initial-data error is O(n−1).
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BibTeX
@misc{choi2026fractional,
title = {{Fractional Parabolic Partial Differential Equations in Anisotropic Spectral Barron Spaces: Regularity and Neural Approximation}},
author = {Jae-Hwan Choi and Hyojae Lim and Jinsol Seo and Young-Jin Sim and Changhoon Song},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.27781},
eprint = {2607.27781},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.27781},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Fractional Parabolic Partial Differential Equations in Anisotropic Spectral Barron Spaces: Regularity and Neural Approximation
AU - Jae-Hwan Choi
AU - Hyojae Lim
AU - Jinsol Seo
AU - Young-Jin Sim
AU - Changhoon Song
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2607.27781
UR - https://arxiv.org/abs/2607.27781
AB - We study fractional parabolic initial-value problems with lower-order drift and potential terms in anisotropic spectral Barron spaces, defined by weighted space--time Fourier L^1 norms adapted to parabolic scaling. We prove existence, uniqueness, and maximal regularity with a gain of one derivative in time and γ derivatives in space, where γ>0 is the order of the fractional Laplacian. The evolution is defined only for t≥0, whereas the finite-time norm requires a global extension with sufficient temporal Fourier decay. We construct a finite reflected semigroup extension using a Vandermonde system to match derivatives at t=0, obtaining temporal Fourier estimates uniform in the semigroup parameter. Combined with Fourier multiplier estimates for the damped principal operator, it yields maximal regularity. Dimension-independent multiplication estimates support a finite regularity bootstrap, while interpolation and sufficient damping absorb the lower-order terms in the base estimate. The a priori estimate and the method of continuity yield maximal regularity without smallness assumptions on the lower-order coefficients. A frequency-localized counterexample shows that a uniform-in-time spatial Barron bound on the forcing does not imply the corresponding two-derivative solution bound, even for the one-dimensional heat equation. Using this regularity, Fourier sampling yields n^−1/2 approximation rates for the solution in mixed space--time Sobolev norms using shallow networks with suitable activations. Sampling in a product Hilbert space yields a population-level PINN consistency estimate for shallow cosine networks on a bounded cylinder. There exists a single width-n network for which the sum of the squared mixed-Sobolev solution error, the squared L^2-norm of the residual for the whole-space fractional equation, and the squared initial-data error is O(n^−1).
ER -