Reproducing classic Kovacs experiments on polydisperse hard sphere system

In a classic set of experiments A. Kovacs in 1964 demonstrated several characteristic features of the relaxation behavior of glasses – the nonlinearity and asymmetry of approach to equilibrium as well as the memory effect. Although multiple phenomenological models exist, the physics behind these ubiquitous features remains unexplained. Therefore, it is of interest to find the most stripped-down glassy system for which the Kovacs features still hold. Here we report on an attempt to reproduce the Kovacs suite of experiments on a polydisperse hard sphere system. In the original experiments, specific volume was the quantity whose evolution following up and down temperature jumps was observed. For an athermal hard sphere system the up and down jumps in the packing fraction are exercised and the subsequent pressure relaxation is monitored. The polydisperse hard sphere system exhibits the characteristic intrinsic isotherm behavior where upon an abrupt increase in packing fraction the pressure relaxes linearly with the logarithm of time for multiple decades. The memory effect is also observed. Implications for modeling the relaxation behavior of glasses will be discussed.