Interactions among particles in dense liquids confine the particles, allowing them to move only cooperatively and making their displacements correlated. Such correlations in dense liquids persist beyond the alpha-relaxation time and even in only slightly glassy liquids.
Recently, we reported that displacement correlations in a 2D model liquid, made of Brownian disks, behave logarithmically with regard to the spatial distance. This correlation occurs in spite of the absence of momentum conservation and therefore must have an origin different from that of Alder’s backflow.
We argue that the logarithmic correlations can be understood as originating from short-scale elasticity of the 2D liquid, in a way mathematically analogous to the theory of correlated displacements for 1D chain of Brownian particles confined in a channel.
We discuss how the measurements of such displacement correlations may shed light to shorter-scale elasticity of liquids.