  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.
