# FUNCTIONAL ITÔ VERSUS BANACH SPACE STOCHASTIC CALCULUS AND STRICT SOLUTIONS OF SEMILINEAR PATH-DEPENDENT EQUATIONS

Abstract : Functional It\^o calculus was introduced in order to expand a functional $F(t, X_{\cdot+t}, X_t)$ depending on time $t$, past and present values of the process $X$. Another possibility to expand $F(t, X_{\cdot+t}, X_t)$ consists in considering the path $X_{\cdot+t}=\{X_{x+t},\,x\in[-T,0]\}$ as an element of the Banach space of continuous functions on $C([-T,0])$ and to use Banach space stochastic calculus. The aim of this paper is threefold. 1) To reformulate functional It\^o calculus, separating time and past, making use of the regularization procedures which matches more naturally the notion of horizontal derivative which is one of the tools of that calculus. 2) To exploit this reformulation in order to discuss the (not obvious) relation between the functional and the Banach space approaches. 3) To study existence and uniqueness of smooth solutions to path-dependent partial differential equations which naturally arise in the study of functional It\^o calculus. More precisely, we study a path-dependent equation of Kolmogorov type which is related to the window process of the solution to an It\^o stochastic differential equation with path-dependent coefficients. We also study a semilinear version of that equation.
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Type de document :
Pré-publication, Document de travail
2015
Domaine :

https://hal-ensta.archives-ouvertes.fr/hal-01145300
Contributeur : Francesco Russo <>
Soumis le : jeudi 23 avril 2015 - 17:24:05
Dernière modification le : vendredi 28 avril 2017 - 01:07:57
Document(s) archivé(s) le : lundi 14 septembre 2015 - 13:01:18

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### Identifiants

• HAL Id : hal-01145300, version 1
• ARXIV : 1505.02926

### Citation

Andrea Cosso, Francesco Russo. FUNCTIONAL ITÔ VERSUS BANACH SPACE STOCHASTIC CALCULUS AND STRICT SOLUTIONS OF SEMILINEAR PATH-DEPENDENT EQUATIONS. 2015. <hal-01145300>

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