Eur. Phys. J. B (2018) 91: 226
https://doi.org/10.1140/epjb/e2018-90105-x

Regular Article

Unraveling the Landau’s consistence criterion and the meaning of interpenetration in the “Two-Fluid” Model

¹ Departamento de Física Teórica, Universidad de Zaragoza, 50009 Zaragoza, Spain
² Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, 50018 Zaragoza, Spain
³ Unidad asociada IQFR-BIFI, 50018 Zaragoza, Spain

^a e-mail: ares@unizar.es

Received: 28 February 2018
Published online: 3 October 2018

Abstract

In this letter, we show that it is possible to unravel both the physical origin of the Landau’s consistence criterion and the specific and subtle meaning of interpenetration of the “two fluids” if one takes into account that in the hydrodynamic regime one needs a coarse-graining in time to bring the system into local equilibrium. That is, the fuzziness in time is relevant for the phenomenological Landau’s consistency criterion and the meaning of interpenetration. Note also that we are not questioning the validity of the “Two-Fluid” Model.