Monique Combescure and Didier Robert
Semiclassical results in the linear response theory
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ABSTRACT.  We consider a quantum system of non-interacting fermions at 
temperature T, in the framework of linear response theory. 
We show that semiclassical theory is an appropriate framework to 
 describe some of their thermodynamic properties, in particular 
through asymptotic expansions in $\hbar$ (Planck constant) of the dynamical susceptibilities. We show how the closed orbits of 
 the classical motion in phase space manifest themselves in these 
expansions, in the regime where T is of the order of $\hbar$.