Consistency of dynamic heterogeneities characterized by X-ray experiments and MD simulations

To understand the origin of slow dynamics near the glass transition, "dynamic heterogeneity" plays a crucial role. In the previous studies, quantitative evaluation of dynamical heterogeneity has been attempted from analyzing speckle patterns in X-ray scattering experiments or from four-body correlation functions in molecular dynamics (MD) simulations. However, the physical relationship between those observed dynamic heterogeneities has not been clarified. This study proposes a connection between the dynamic heterogeneities characterized by the speckle pattern and those followed by the four-body correlation function. The validity of the relationship has also been clarified.