Sharp Lower Bounds for Linearized ReLU^k Approximation on the Sphere

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Hauptverfasser: Mao, Tong, Xu, Jinchao
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Veröffentlicht: 2025
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author Mao, Tong
Xu, Jinchao
author_facet Mao, Tong
Xu, Jinchao
contents We prove a saturation theorem for linearized shallow ReLU$^k$ neural networks on the unit sphere $\mathbb S^d$. For any antipodally quasi-uniform set of centers, if the target function has smoothness $r>\tfrac{d+2k+1}{2}$, then the best $\mathcal{L}^2(\mathbb S^d)$ approximation cannot converge faster than order $n^{-\frac{d+2k+1}{2d}}$. This lower bound matches existing upper bounds, thereby establishing the exact saturation order $\tfrac{d+2k+1}{2d}$ for such networks. Our results place linearized neural-network approximation firmly within the classical saturation framework and show that, although ReLU$^k$ networks outperform finite elements under equal degrees $k$, this advantage is intrinsically limited.
format Preprint
id arxiv_https___arxiv_org_abs_2510_04060
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Sharp Lower Bounds for Linearized ReLU^k Approximation on the Sphere
Mao, Tong
Xu, Jinchao
Numerical Analysis
Machine Learning
We prove a saturation theorem for linearized shallow ReLU$^k$ neural networks on the unit sphere $\mathbb S^d$. For any antipodally quasi-uniform set of centers, if the target function has smoothness $r>\tfrac{d+2k+1}{2}$, then the best $\mathcal{L}^2(\mathbb S^d)$ approximation cannot converge faster than order $n^{-\frac{d+2k+1}{2d}}$. This lower bound matches existing upper bounds, thereby establishing the exact saturation order $\tfrac{d+2k+1}{2d}$ for such networks. Our results place linearized neural-network approximation firmly within the classical saturation framework and show that, although ReLU$^k$ networks outperform finite elements under equal degrees $k$, this advantage is intrinsically limited.
title Sharp Lower Bounds for Linearized ReLU^k Approximation on the Sphere
topic Numerical Analysis
Machine Learning
url https://arxiv.org/abs/2510.04060