On lower bound of relaxation time for massless fluid in presence of magnetic field

TL;DR

This paper investigates the relaxation time bounds for a massless relativistic fluid under magnetic fields, linking quantum fluctuation limits to relaxation time estimates.

Contribution

It introduces a relaxation time approximation approach to determine bounds on relaxation time for massless fluids in magnetic fields.

Findings

Identifies lower and upper bounds of relaxation time.

Connects quantum fluctuation limits to relaxation time.

Provides theoretical estimates consistent with known bounds.

Abstract

Due to lowest possible quantum fluctuation, shear viscosity to entropy density ratio never reach to zero, rather has some lower bound (0.08 approx). Here, we have attempted to link our calculation, based on relaxation time approximation for massless relativistic fluid, with that value and interestingly found a lower and also an upper limit of relaxation time.