书摘
The theory of Malliavin Calculus was initiated by P. Malliavin in 1976, to study the Hrmander hypoellipticity problem. Since then the research on infinite dimensional analysis became very active. The theory was well developed during 1980s in the framework of Grosss Abstract Wiener space. The application to the study of the loop space over a compact Lie group or more generally over a compact Riemannian manifold started at the beginning of 1990.
The functionals defined by It stochastic calculus are the typical examples of smooth functions in Malliavin calculus. In this note, we shall pay much attention to classical Wiener spaces. Not only it does give more direct connections with Analysis, Geometry and others through It stochastic differential equations, but also it has a particular structure: It filtration. In this framework, Girsanov theorem plays a central role.
The existence of divergence operator allows to do the integration by parts on the Wiener space. In L2 case, it is in connection with the fundamental geometric formula: Weitzenbck formula. The establishment in Lp needs the tool of Riesz transform. The proof given in this note is heavily dependent on the linear structure of the Wiener space. The problem for Riemannian path spaces is open.
This note was based on a course given at Beijing Normal University during JuneJuly 2002, some materials were talked at the seminar “Dynamic system and Probability” at Mathematical Institute of Burgundy, Dijon. The author is grateful to Professor Fengyu Wang for giving him the opportunity to visit and work at “Stochastic Center” in Beijing Normal University. The presence and the interest of Professor Mufa Chen in the course was an encouragement to the author. The author would like also to express many thanks to Professor Bernard Schmitt for inviting him to give a series of talks at his seminar on the subject at Dijon.