title: Collective excitations in 2D hard-disc fluid.
abstract: Collective dynamics of a two-dimensional (2D) hard-disc fluid was studied by molecular dynamics simulations in the range of packing fractions that covers states up to the freezing. Some striking features concerning collective excitations in this system were observed. In particular, the short-wavelength shear waves while being absent at low packing fractions were observed in the range of high packing fractions, just before the freezing transition in a 2D hard-disc fluid. In contrast, the so-called "positive sound dispersion" typically observed in dense Lennard-Jones-like fluids, was not detected for the 2D hard-disc fluid. The ratio of specific heats in the 2D hard-disc fluid shows a monotonic increase with density approaching the freezing, resembling in this way the similar behavior in the vicinity of the Widom line in the case of supercritical fluids.
authors.affiliation: Departamento de Fisica, Universidad Veracruzana, Xalapa, Mexico.
authors.forename: Adrian
authors.initials: A
authors.lastname: Huerta
authors.affiliation: Institute for Condensed Matter Physics of National Academy of Sciences of Ukraine, 79011 Lviv, Ukraine; Institute of Applied Mathematics and Fundamental Sciences, Lviv Polytechnic National University, Lviv 79013, Ukraine.
authors.forename: Taras
authors.initials: T
authors.lastname: Bryk
authors.affiliation: Institute for Condensed Matter Physics of National Academy of Sciences of Ukraine, 79011 Lviv, Ukraine; Institute of Applied Mathematics and Fundamental Sciences, Lviv Polytechnic National University, Lviv 79013, Ukraine. Electronic address: adt@icmp.lviv.ua.
authors.forename: Andrij
authors.initials: A
authors.lastname: Trokhymchuk
keywords: Collective excitations; Hard-core colloids; Hard-disc fluid; Molecular dynamics; Sound velocity; Structure factor