Singularity band of velocity auto correlation function of LennardJones fluid in complex $\omega$plain
Abstract
It is well known from the quantum theory of strongly correlated systems that poles (or more subtle singularities) of dynamic correlation functions in complex plane usually correspond to the collective or localized modes. Here we address singularities of velocity autocorrelation function $Z$ in complex $\omega$plain for the onecomponent particle system with isotropic pair potential. We have found that naive few poles picture fails to describe analytical structure of $Z(\omega)$ of LennardJones particle system in complex plain. Instead of few isolated poles we see the singularity manifold of $Z(\omega)$ forming branch cuts that suggests LennardJones velocity autocorrelation function is a multiplevalued function of complex frequency. The brunch cuts are separated from the real axis by the welldefined "gap". The gap edges extend approximately parallel to the real frequency axis. The singularity structure is very stable under increase of the temperature; we have found its trace at temperatures even several orders of magnitude higher than the melting point. Our working hypothesis that the branch cut origin is related to the "interference" in $Z$ of oneparticle kinetics and collective hydrodynamic motion.
 Publication:

arXiv eprints
 Pub Date:
 July 2015
 DOI:
 10.48550/arXiv.1507.04532
 arXiv:
 arXiv:1507.04532
 Bibcode:
 2015arXiv150704532C
 Keywords:

 Condensed Matter  Soft Condensed Matter;
 Physics  Chemical Physics;
 Physics  Computational Physics;
 Physics  Data Analysis;
 Statistics and Probability
 EPrint:
 9 pages, 11 figures