### Abstract

Original language | English |
---|---|

Pages (from-to) | 732-738 |

Number of pages | 7 |

Journal | Письма в Журнал экспериментальной и теоретической физики |

Volume | 102 |

Issue number | 9-10 |

Publication status | Published - 2015 |

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*Письма в Журнал экспериментальной и теоретической физики*,

*102*(9-10), 732-738.

}

*Письма в Журнал экспериментальной и теоретической физики*, vol. 102, no. 9-10, pp. 732-738.

**COMPLEX SINGULARITIES OF FLUID VELOCITY AUTOCORRELATION FUNCTION.** / Chtchelkatchev, N. M.; Ryltsev, R. E.

Research output: Contribution to journal › Article › Research › peer-review

TY - JOUR

T1 - COMPLEX SINGULARITIES OF FLUID VELOCITY AUTOCORRELATION FUNCTION

AU - Chtchelkatchev, N. M.

AU - Ryltsev, R. E.

PY - 2015

Y1 - 2015

N2 - 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(ω) 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.

AB - 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(ω) 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.

UR - https://elibrary.ru/item.asp?id=25021522

M3 - Article

VL - 102

SP - 732

EP - 738

JO - Письма в Журнал экспериментальной и теоретической физики

JF - Письма в Журнал экспериментальной и теоретической физики

SN - 0370-274X

IS - 9-10

ER -