Théorique, numérique
Dense liquids gradually solidify at low temperature via a physical process called the glass transition. While well-known and understood at the macrosopic scale, very little is known from direct experimental measurements about the dynamics of molecules in the vicinity of the glass transition. A microscopic understanding of this important process remains a lively research problem, which has resisted several decades of careful studies. In the last decade, non-linear dielectric measurements have been performed in molecular systems, that are interpreted as a unique way to probe emerging glassy correlations in these systems. In parallel, modern computer simulations techniques were recently developed to study the motion of molecular models at very long times, revealing the existence of a complex hierarchy of correlated molecular motion in these dense glassy fluids. In this project we propose to use newly developed numerical approaches to systematically measure non-linear response functions similar to the ones determined experimentally, while resolving in space and time the molecular dynamics that give rise to this signal. By measuring systematically static and dynamic correlations, and their relation to non-linear response functions, a microscopic interpretation of the physical content of non-linear response functions will be available. Ultimately, this work will provide the missing link between the competing theoretical approaches and the available experimental observations.