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Kinetic Heterogeneities in a Highly Supercooled Liquid

We study a highly supercooled two-dimensional fluid mixture via molecular dynamics simulation. We follow bond breakage events among particle pairs, which occur on the scale of the $α$ relaxation time $τ_α$. Large scale heterogeneities analogous to the critical fluctuations in Ising systems are found in the spatial distribution of bonds which are broken in a time interval with a width of order $0.05τ_α$. The structure factor of the broken bond density is well approximated by the Ornstein-Zernike form. The correlation length is of order $100 σ_1$ at the lowest temperature studied, $σ_1$ being the particle size. The weakly bonded regions thus identified evolve in time with strong spatial correlations.