Verification theorem related to a zero sum stochastic differential game, based on a chain rule for non-smooth functions

Fuente: arXiv
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Autori principali: Ciccarella, Carlo, Russo, Francesco
Natura: Preprint
Pubblicazione: 2024
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author Ciccarella, Carlo
Russo, Francesco
author_facet Ciccarella, Carlo
Russo, Francesco
contents In the framework of stochastic zero-sum differential games, we establish a verification theorem, inspired by those existing in stochastic control, to provide sufficient conditions for a pair of feedback controls to form a Nash equilibrium. Suppose the validity of the classical Isaacs' condition and the existence of a (what is termed) quasi-strong solution to the Bellman-Isaacs (BI) equations. If the diffusion coefficient of the state equation is non-degenerate, we are able to show the existence of a saddle point constituted by a couple of feedback controls that achieve the value of the game: moreover, the latter is equal to the (necessarily unique) solution of the BI equations. A suitable generalization is available when the diffusion is possibly degenerate. Similarly we have also improved a well-known verification theorem in stochastic control theory. The techniques of stochastic calculus via regularization we use, in particular specific chain rules, are borrowed from a companion paper of the authors.
format Preprint
id arxiv_https___arxiv_org_abs_2407_06243
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Verification theorem related to a zero sum stochastic differential game, based on a chain rule for non-smooth functions
Ciccarella, Carlo
Russo, Francesco
Optimization and Control
Probability
In the framework of stochastic zero-sum differential games, we establish a verification theorem, inspired by those existing in stochastic control, to provide sufficient conditions for a pair of feedback controls to form a Nash equilibrium. Suppose the validity of the classical Isaacs' condition and the existence of a (what is termed) quasi-strong solution to the Bellman-Isaacs (BI) equations. If the diffusion coefficient of the state equation is non-degenerate, we are able to show the existence of a saddle point constituted by a couple of feedback controls that achieve the value of the game: moreover, the latter is equal to the (necessarily unique) solution of the BI equations. A suitable generalization is available when the diffusion is possibly degenerate. Similarly we have also improved a well-known verification theorem in stochastic control theory. The techniques of stochastic calculus via regularization we use, in particular specific chain rules, are borrowed from a companion paper of the authors.
title Verification theorem related to a zero sum stochastic differential game, based on a chain rule for non-smooth functions
topic Optimization and Control
Probability
url https://arxiv.org/abs/2407.06243