Local dynamical heterogeneity in glass formers

Assessing the role of local order and of more extended static correlations on the dynamics of deeply supercooled liquids is one of the foremost open problems in the physics of glasses. We here study the local dynamical fluctuations in glass-forming models. Our calculation for d→∞ systems reveals that single-particle observables, such as squared particle displacements, display diverging fluctuations around the dynamical (or mode-coupling) transition, due to the emergence of nontrivial correlations between displacements along different directions. This effect also gives rise to a diverging non-Gaussian parameter, α₂(t). The local dynamics therefore becomes quite rich upon approaching the glass transition. The finite-d remnant of this phenomenon further provides a long sought-after, first-principle explanation for the growth of α₂(t) around the glass transition that is not based on multi-particle correlations.