Schrödinger Bridge with Quadratic State Cost is Exactly Solvable

Fuente: arXiv
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Autori principali: Teter, Alexis M. H., Wang, Wenqing, Halder, Abhishek
Natura: Preprint
Pubblicazione: 2024
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author Teter, Alexis M. H.
Wang, Wenqing
Halder, Abhishek
author_facet Teter, Alexis M. H.
Wang, Wenqing
Halder, Abhishek
contents Schrödinger bridge is a diffusion process that steers a given distribution to another in a prescribed time while minimizing the effort to do so. It can be seen as the stochastic dynamical version of the optimal mass transport, and has growing applications in generative diffusion models and stochastic optimal control. {\black{We say a Schrödinger bridge is ``exactly solvable'' if the associated uncontrolled Markov kernel is available in closed form, since then the bridge can be numerically computed using dynamic Sinkhorn recursion for arbitrary endpoint distributions with finite second moments.}} In this work, we propose a regularized variant of the Schrödinger bridge with a quadratic state cost-to-go that incentivizes the optimal sample paths to stay close to a nominal level. Unlike the conventional Schrödinger bridge, the regularization induces a state-dependent rate of killing and creation of probability mass, and its solution requires determining the Markov kernel of a reaction-diffusion partial differential equation. We derive this Markov kernel in closed form, {\black{showing that the regularized Schrödinger bridge is exactly solvable, even for non-Gaussian endpoints. This advances the state-of-the-art because closed form Markov kernel for the regularized Schrödinger bridge is available in existing literature only for Gaussian endpoints}}. Our solution recovers the heat kernel in the vanishing regularization (i.e., diffusion without reaction) limit, thereby recovering the solution of the conventional Schrödinger bridge {\black{as a special case}}. We deduce properties of the new kernel and explain its connections with certain exactly solvable models in quantum mechanics.
format Preprint
id arxiv_https___arxiv_org_abs_2406_00503
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Schrödinger Bridge with Quadratic State Cost is Exactly Solvable
Teter, Alexis M. H.
Wang, Wenqing
Halder, Abhishek
Optimization and Control
Machine Learning
Systems and Control
Mathematical Physics
Schrödinger bridge is a diffusion process that steers a given distribution to another in a prescribed time while minimizing the effort to do so. It can be seen as the stochastic dynamical version of the optimal mass transport, and has growing applications in generative diffusion models and stochastic optimal control. {\black{We say a Schrödinger bridge is ``exactly solvable'' if the associated uncontrolled Markov kernel is available in closed form, since then the bridge can be numerically computed using dynamic Sinkhorn recursion for arbitrary endpoint distributions with finite second moments.}} In this work, we propose a regularized variant of the Schrödinger bridge with a quadratic state cost-to-go that incentivizes the optimal sample paths to stay close to a nominal level. Unlike the conventional Schrödinger bridge, the regularization induces a state-dependent rate of killing and creation of probability mass, and its solution requires determining the Markov kernel of a reaction-diffusion partial differential equation. We derive this Markov kernel in closed form, {\black{showing that the regularized Schrödinger bridge is exactly solvable, even for non-Gaussian endpoints. This advances the state-of-the-art because closed form Markov kernel for the regularized Schrödinger bridge is available in existing literature only for Gaussian endpoints}}. Our solution recovers the heat kernel in the vanishing regularization (i.e., diffusion without reaction) limit, thereby recovering the solution of the conventional Schrödinger bridge {\black{as a special case}}. We deduce properties of the new kernel and explain its connections with certain exactly solvable models in quantum mechanics.
title Schrödinger Bridge with Quadratic State Cost is Exactly Solvable
topic Optimization and Control
Machine Learning
Systems and Control
Mathematical Physics
url https://arxiv.org/abs/2406.00503