**Author**
: Giovanni Gallavotti

**Title::** *
Finite thermostats in classical and quantum nonequilibrium*

**Abstract**:*
Models for studying systems in stationary states but out of
equilibrium have often empirical nature and very often break the
fundamental time reversal symmetry. Here a formal interpretation will
be discussed of the widespread idea that, in any event, the particular friction model choice should not matter physically. The proposal is,
quite generally, that for the same physical system a time reversible
model should be possible. Examples about the Navier-Stokes equations
are given.*

**Keywords**: Fluids, Irreversibility, Reversibility, Friction, Nonequilibrium Ensembles, Navier-Stokes, Fluctuation Relation

Giovanni Gallavotti

INFN Fisica, Rutgers University e Accademia dei Lincei

Universita di Roma Sapienza, 00185 Roma, Italy

giovanni.gallavotti@roma1.infn.it