Based on well-known lectures given at Scuola Normale Superiore in Pisa,
this book introduces analysis in a separable Hilbert space of infinite
dimension. It starts from the definition of Gaussian measures in Hilbert
spaces, concepts such as the Cameron-Martin formula, Brownian motion and
Wiener integral are introduced in a simple way. These concepts are then
used to illustrate basic stochastic dynamical systems and Markov
semi-groups, paying attention to their long-time behavior.