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<title>Fabian Ruehle — Neckpinch</title><link>https://neckpinch.com/authors/fabian-ruehle/</link><description>New arXiv papers by Fabian Ruehle, from Neckpinch</description>
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<item><title>Rigor with Machine Learning from Field Theory to the Poincaré Conjecture</title><link>https://neckpinch.com/papers/2402.13321/</link><guid isPermaLink="false">arxiv:2402.13321</guid><pubDate>Tue, 20 Feb 2024 00:00:00 GMT</pubDate><description>Sergei Gukov, James Halverson, Fabian Ruehle — Machine learning techniques are increasingly powerful, leading to many breakthroughs in the natural sciences, but they are often stochastic, error-prone, and blackbox. How, then, should they be utilized in fields such as theoretical physics and pure mathematics that place a premium on rigor and understanding? In this Perspective we discuss techniques for obtaining rigor in the natural sciences with machine learning. Non-rigorous methods may lead to rigorous results via conjecture generation or verification by reinforcement learning. We survey applications of these techniques-for-rigor ranging from string theory to the smooth 4d Poincaré conjecture in low-dimensional topology. One can also imagine building direct bridges between machine learning theory and either mathematics or theoretical physics. As examples, we describe a new approach to field theory motivated by neural network theory, and a theory of Riemannian metric flows induced by neural network gradient descent, which encompasses Perelman&apos;s formulation of the Ricci flow that was utilized to resolve the 3d Poincaré conjecture.</description><category>Ricci flow</category><category>Poincaré conjecture</category><category>Physics</category><category>Discrete &amp; graph Ricci</category></item>
<item><title>Metric Flows with Neural Networks</title><link>https://neckpinch.com/papers/2310.19870/</link><guid isPermaLink="false">arxiv:2310.19870</guid><pubDate>Mon, 30 Oct 2023 00:00:00 GMT</pubDate><description>James Halverson, Fabian Ruehle — We develop a general theory of flows in the space of Riemannian metrics induced by neural network gradient descent. This is motivated in part by recent advances in approximating Calabi-Yau metrics with neural networks and is enabled by recent advances in understanding flows in the space of neural networks. We derive the corresponding metric flow equations, which are governed by a metric neural tangent kernel, a complicated, non-local object that evolves in time. However, many architectures admit an infinite-width limit in which the kernel becomes fixed and the dynamics simplify. Additional assumptions can induce locality in the flow, which allows for the realization of Perelman&apos;s formulation of Ricci flow that was used to resolve the 3d Poincaré conjecture. We demonstrate that such fixed kernel regimes lead to poor learning of numerical Calabi-Yau metrics, as is expected since the associated neural networks do not learn features. Conversely, we demonstrate that well-learned numerical metrics at finite-width exhibit an evolving metric-NTK, associated with feature learning. Our theory of neural network metric flows therefore explains why neural networks are better at learning Calabi-Yau metrics than fixed kernel methods, such as the Ricci flow.</description><category>Ricci flow</category><category>Ricci-flat &amp; Calabi–Yau</category><category>Poincaré conjecture</category><category>3-manifolds</category><category>Kähler geometry</category><category>Discrete &amp; graph Ricci</category><category>Numerics &amp; visualization</category></item>
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