Lifetime of dynamical heterogeneity in a highly supercooled liquid.

We numerically examine dynamical heterogeneity in a highly supercooled three-dimensional liquid via molecular-dynamics simulations. To define the local dynamics, we consider two time intervals: τ(α) and τ(ngp). τ(α) is the α relaxation time, and τ(ngp) is the time at which non-gaussian parameter of the Van Hove self-correlation function is maximized. We determine the lifetimes of the heterogeneous dynamics in these two different time intervals, τ(hetero)(τ(α)) and τ(hetero)(τ(ngp)), by calculating the time correlation function of the particle dynamics, i.e., the four-point correlation function. We find that the difference between τ(hetero)(τ(α)) and τ(hetero)(τ(ngp)) increases with decreasing temperature. At low temperatures, τ(hetero)(τ(α)) is considerably larger than τ(α), while τ(hetero)(τ(ngp)) remains comparable to τ(α). Thus, the lifetime of the heterogeneous dynamics depends strongly on the time interval.