Taku Matsui and Yoshiko Ogata
Variational Principle for Non-Equilibrium Steady States 
of the XX Model
(376K, Postscript)

ABSTRACT.  We show that non-equilibrium steady states of 
 the one dimensional exactly solved XY model 
can be characterized by the variational principle 
of free energy of a long range interaction and that they cannot 
be a KMS state for any C$^*$-dynamical system.