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ЖУРНАЛЫ // Письма в Журнал экспериментальной и теоретической физики // Архив

Письма в ЖЭТФ, 2015, том 102, выпуск 10, страницы 732–738 (Mi jetpl4788)

Эта публикация цитируется в 14 статьях

ПЛАЗМА, ГИДРО- И ГАЗОДИНАМИКА

Complex singularities of fluid velocity autocorrelation function

N. M. Chtchelkatcheva, R. E. Ryltsevbac

a Landau Institute for Theoretical Physics of the RAS, 142432 Chernogolovka, Russia
b Institute of Metallurgy UB of the RAS, 620016 Ekaterinburg, Russia
c Ural Federal University, 620002 Ekaterinburg, Russia

Аннотация: There are intensive debates regarding the nature of supercritical fluids: if their evolution from liquid-like to gas-like behavior is a continuous multistage process or there is a sharp well defined crossover. Velocity autocorrelation function $Z$ is the established detector of evolution of fluid particles dynamics. Usually, complex singularities of correlation functions give more information. So we investigate $Z$ in complex plane of frequencies using numerical analytical continuation. We have found that naive picture with few isolated poles fails describing $Z(\omega)$ of one-component Lennard–Jones (LJ) fluid. Instead we see the singularity manifold forming branch cuts extending approximately parallel to the real frequency axis. That suggests LJ velocity autocorrelation function is a multiple-valued function of complex frequency. The branch cuts are separated from the real axis by the well-defined “gap” whose width corresponds to an important time scale of a fluid characterizing crossover of system dynamics from kinetic to hydrodynamic regime. Our working hypothesis is that the branch cut origin is related to competition between one-particle dynamics and hydrodynamics. The observed analytical structure of $Z$ is very stable under changes of temperature; it survives at temperatures which are by the two orders of magnitude higher than the critical one.

Поступила в редакцию: 18.09.2015
Исправленный вариант: 05.10.2015

Язык публикации: английский

DOI: 10.7868/S0370274X15220038


 Англоязычная версия: Journal of Experimental and Theoretical Physics Letters, 2015, 102:10, 643–649

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