Giovanni Gallavotti
Fluctuation patterns and conditional
reversibility in nonequilibrium systems
(46K, Absolutely Plain TeX)
ABSTRACT. Fluctuations of observables as functions of
time, or "fluctuation patterns", are studied in a
chaotic microscopically reversible system that has
irreversibly reached a nonequilibrium stationary state.
Supposing that during a certain, long enough, time
interval the average entropy creation rate has a value
$s$ and that during another time interval of the same
length it has value $-s$ then we show that the relative
probabilities of fluctuation patterns in the first time
interval are the same as those of the reversed patterns
in the second time interval. The system is
``conditionally reversible'' or irreversibility in a
reversible system is "driven" by the entropy creation:
while a very rare fluctuation happens to change the
sign of the entropy creation rate it also happens that
the time reversed fluctuations of all other observables
acquire the same relative probability of the
corresponding fluctuations in presence of normal
entropy creation. A mathematical proof is sketched.