  The problem of stationary heat transport in the Fermi-Pasta-Ulam chain is
numerically studied showing that the conductivity diverges in the thermodynamic
limit. Simulations were performed with time-reversible thermostats, both for
small and large temperature gradients. In the latter case, fluctuations of the
heat current are shown to be in agreement with the recent conjectures of
Gallavotti and Cohen.
