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The success of deep networks has been attributed in part to their expressivity: per parameter, deep networks can approximate a richer class of functions than shallow networks. In ReLU networks, the number of activation patterns is one…

Machine Learning · Statistics 2019-10-22 Boris Hanin , David Rolnick

It is well-known that the parameterized family of functions representable by fully-connected feedforward neural networks with ReLU activation function is precisely the class of piecewise linear functions with finitely many pieces. It is…

Metric Geometry · Mathematics 2026-01-21 J. Elisenda Grigsby , Kathryn Lindsey , Robert Meyerhoff , Chenxi Wu

We analyze a simple one-hidden-layer neural network with ReLU activation functions and fixed biases, with one-dimensional input and output. We study both continuous and discrete versions of the model, and we rigorously prove the convergence…

Machine Learning · Computer Science 2026-04-10 Fabricio Macià , Shu Nakamura

In neural networks, non-linearity is introduced by activation functions. One commonly used activation function is Rectified Linear Unit (ReLU). ReLU has been a popular choice as an activation but has flaws. State-of-the-art functions like…

Machine Learning · Computer Science 2021-12-23 Advait Vagerwal

This paper studies the problem of how efficiently functions in the Sobolev spaces $\mathcal{W}^{s,q}([0,1]^d)$ and Besov spaces $\mathcal{B}^s_{q,r}([0,1]^d)$ can be approximated by deep ReLU neural networks with width $W$ and depth $L$,…

Machine Learning · Statistics 2025-07-21 Yunfei Yang

In this paper we investigate the performance of different types of rectified activation functions in convolutional neural network: standard rectified linear unit (ReLU), leaky rectified linear unit (Leaky ReLU), parametric rectified linear…

Machine Learning · Computer Science 2015-11-30 Bing Xu , Naiyan Wang , Tianqi Chen , Mu Li

As modern deep learning architectures grow in complexity, representational ambiguity emerges as a critical barrier to their interpretability and reliable merging. For ReLU networks, identical functional mappings can be achieved through…

Machine Learning · Computer Science 2026-04-21 Kutomanov Hennadii

We present a fully constructive analysis of deep ReLU neural networks for classification and function approximation tasks. First, we prove that any dataset with $N$ distinct points in $\mathbb{R}^d$ and $M$ output classes can be exactly…

Machine Learning · Statistics 2025-06-25 Martín Hernández , Enrique Zuazua

In this paper, we investigate the relationship between deep neural networks (DNN) with rectified linear unit (ReLU) function as the activation function and continuous piecewise linear (CPWL) functions, especially CPWL functions from the…

Numerical Analysis · Mathematics 2020-06-02 Juncai He , Lin Li , Jinchao Xu , Chunyue Zheng

The activation functions are fundamental to neural networks as they introduce non-linearity into data relationships, thereby enabling deep networks to approximate complex data relations. Existing efforts to enhance neural network…

Machine Learning · Computer Science 2024-09-26 Jiayu Li , Zilong Zhao , Kevin Yee , Uzair Javaid , Biplab Sikdar

Activation function is a key component in deep learning that performs non-linear mappings between the inputs and outputs. Rectified Linear Unit (ReLU) has been the most popular activation function across the deep learning community.…

Machine Learning · Computer Science 2022-03-01 Hock Hung Chieng , Noorhaniza Wahid , Pauline Ong

It is shown that over-parameterized neural networks can achieve minimax optimal rates of convergence (up to logarithmic factors) for learning functions from certain smooth function classes, if the weights are suitably constrained or…

Machine Learning · Statistics 2024-06-05 Yunfei Yang , Ding-Xuan Zhou

In this paper, we develop a wavelet-based theoretical framework for analyzing the universal approximation capabilities of neural networks over a wide range of activation functions. Leveraging wavelet frame theory on the spaces of…

Machine Learning · Computer Science 2025-04-24 Youngmi Hur , Hyojae Lim , Mikyoung Lim

The purpose of the present paper is to study the computation complexity of deep ReLU neural networks to approximate functions in H\"older-Nikol'skii spaces of mixed smoothness $H_\infty^\alpha(\mathbb{I}^d)$ on the unit cube…

Numerical Analysis · Mathematics 2021-03-02 Dinh Dũng , Van Kien Nguyen , Mai Xuan Thao

We show that suitably regular functions can be approximated in the $\mathcal{C}^1$-norm both with rational functions and rational neural networks, including approximation rates with respect to width and depth of the network, and degree of…

Machine Learning · Computer Science 2025-08-28 Erion Morina , Martin Holler

We investigate to what extent it is possible to solve linear inverse problems with $ReLu$ networks. Due to the scaling invariance arising from the linearity, an optimal reconstruction function $f$ for such a problem is positive homogeneous,…

Machine Learning · Computer Science 2023-08-08 Stefan Bamberger , Reinhard Heckel , Felix Krahmer

We consider functions from the real numbers to the real numbers, output by a neural network with 1 hidden activation layer, arbitrary width, and ReLU activation function. We assume that the parameters of the neural network are chosen…

Machine Learning · Computer Science 2023-04-20 David Holmes

This paper considers the following question: how well can depth-two ReLU networks with randomly initialized bottom-level weights represent smooth functions? We give near-matching upper- and lower-bounds for $L_2$-approximation in terms of…

Machine Learning · Computer Science 2021-09-09 Daniel Hsu , Clayton Sanford , Rocco A. Servedio , Emmanouil-Vasileios Vlatakis-Gkaragkounis

We study the realization map of deep ReLU networks, focusing on when a function determines its parameters up to scaling and permutation. To analyze hidden redundancies beyond these standard symmetries, we introduce a framework based on…

Machine Learning · Computer Science 2026-05-21 Moritz Grillo , Guido Montúfar

In this study, we establish that deep neural networks employing ReLU and ReLU$^2$ activation functions can effectively represent Lagrange finite element functions of any order on various simplicial meshes in arbitrary dimensions. We…

Numerical Analysis · Mathematics 2024-01-15 Juncai He , Jinchao Xu