Abstract
Using field theory techniques we analyze the perfect fluid limit, defined as fastest possible local equilibration, in a medium with polarizability, defined as a nonzero local equilibrium partition of angular momentum into spin and vorticity. We show that to restore causality a relaxation term linking vorticity and polarization, analogous to the Israel-Stewart term linking viscous forces and gradients, is required. This term provides the minimum amount of dissipation a locally thermalized relativistic medium with polarizability must have, independently of its underlying degrees of freedom. For materials susceptible to spin alignment an infrared acausal mode remains, which we interpret as a Banks-Casher mode signaling spontaneous transition to a polarized phase. With these ingredients, we propose a candidate for a fully causal Lagrangian of a relativistic polarizable system near the perfect fluid limit, and close with some phenomenological considerations.
- Received 10 July 2018
DOI:https://doi.org/10.1103/PhysRevD.100.056011
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society