Fluctuation dissipation ratio in an aging Lennard-Jones glass
  By using extensive Molecular Dynamics simulations, we have determined the violation of the fluctuation-dissipation theorem in a Lennard-Jones liquid quenched to low temperatures. For this we have calculated $X(C)$, the ratio between a one particle time-correlation function $C$ and the associated response function. Our results are best fitted by assuming that $X(C)$ is a discontinuous, piecewise constant function. This is similar to what is found in spin systems with one step replica symmetry breaking. This strengthen the conjecture of a similarity between the phase space structure of structural glasses and such spin systems. 
Jean-Louis Barrat (Departement de Physique des Materiaux, Lyon,   France) and Walter Kob (Institute of Physics, Mainz, Germany)