Fluctuation Theorem, non linear response and the regularity of time reversal symmetry

The Gallavotti - Cohen Fluctuation Theorem (FT) implies an infinite set of identities between correlation functions that can be seen as a generalization of Green Kubo formula to the nonlinear regime. As an application, we discuss a perturbative check of the FT relation through these identities for a simple Anosov reversible system; we find that the lack of differentiability of the time reversal symmetry implies a violation of the Gallavotti - Cohen fluctuation relation. Finally, a brief comparison with Lebowitz - Spohn FT is reported.