**Author**
: Giovanni Gallavotti

**Title:
Fluctuation Theorem and Chaos
**

**Abstract**:
The heat theorem (i.e. the second law of
thermodynamics or the existence of entropy) is a manifestation of a
general property of hamiltonian mechanics and of the ergodic
Hypothesis. In nonequilibrium thermodynamics of stationary states
the chaotic hypothesis plays a similar role: it allows a unique
determination of the probability distribution (called {\rm SRB}
distribution on phase space providing the time averages of the
observables. It also implies an expression for a few averages
concrete enough to derive consequences of symmetry properties like
the fluctuation theorem or to formulate a theory of coarse graining
unifying the foundations of equilibrium and of nonequilibrium.

**Keywords**:
Statistical Mechanics, Nonequilibrium, Fluctuation Theorem, Chaotic Hypothesis

Giovanni Gallavotti,

Dipartimento di Fisica,

Universita` di Roma 1

Ple Moro 2, 00185, Roma, Italy

giovanni.gallavotti@roma1.infn.it