Neural Collapse is Globally Optimal in Deep Regularized ResNets and Transformers

Fuente: arXiv
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Main Authors: Súkeník, Peter, Lampert, Christoph H., Mondelli, Marco
Format: Preprint
Published: 2025
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author Súkeník, Peter
Lampert, Christoph H.
Mondelli, Marco
author_facet Súkeník, Peter
Lampert, Christoph H.
Mondelli, Marco
contents The empirical emergence of neural collapse -- a surprising symmetry in the feature representations of the training data in the penultimate layer of deep neural networks -- has spurred a line of theoretical research aimed at its understanding. However, existing work focuses on data-agnostic models or, when data structure is taken into account, it remains limited to multi-layer perceptrons. Our paper fills both these gaps by analyzing modern architectures in a data-aware regime: we prove that global optima of deep regularized transformers and residual networks (ResNets) with LayerNorm trained with cross entropy or mean squared error loss are approximately collapsed, and the approximation gets tighter as the depth grows. More generally, we formally reduce any end-to-end large-depth ResNet or transformer training into an equivalent unconstrained features model, thus justifying its wide use in the literature even beyond data-agnostic settings. Our theoretical results are supported by experiments on computer vision and language datasets showing that, as the depth grows, neural collapse indeed becomes more prominent.
format Preprint
id arxiv_https___arxiv_org_abs_2505_15239
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Neural Collapse is Globally Optimal in Deep Regularized ResNets and Transformers
Súkeník, Peter
Lampert, Christoph H.
Mondelli, Marco
Machine Learning
Artificial Intelligence
The empirical emergence of neural collapse -- a surprising symmetry in the feature representations of the training data in the penultimate layer of deep neural networks -- has spurred a line of theoretical research aimed at its understanding. However, existing work focuses on data-agnostic models or, when data structure is taken into account, it remains limited to multi-layer perceptrons. Our paper fills both these gaps by analyzing modern architectures in a data-aware regime: we prove that global optima of deep regularized transformers and residual networks (ResNets) with LayerNorm trained with cross entropy or mean squared error loss are approximately collapsed, and the approximation gets tighter as the depth grows. More generally, we formally reduce any end-to-end large-depth ResNet or transformer training into an equivalent unconstrained features model, thus justifying its wide use in the literature even beyond data-agnostic settings. Our theoretical results are supported by experiments on computer vision and language datasets showing that, as the depth grows, neural collapse indeed becomes more prominent.
title Neural Collapse is Globally Optimal in Deep Regularized ResNets and Transformers
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2505.15239