Absence of a local rest frame in far from equilibrium quantum matter

TL;DR

This paper demonstrates that in strongly coupled quantum matter far from equilibrium, certain regions lack a local rest frame due to quantum effects, which could be relevant for understanding heavy ion collisions.

Contribution

It reveals the existence of regions without a local rest frame in quantum matter post-collision, a phenomenon absent in classical systems, and explores its relation to energy conditions.

Findings

Regions without a local rest frame are identified in quantum matter.

Such regions violate the null and weak energy conditions.

No instabilities or pathologies are observed in these regions.

Abstract

In a collision of strongly coupled quantum matter we find that the dynamics of the collision produces regions where a local rest frame cannot be defined because the energy-momentum tensor does not have a real time-like eigenvector. This effect is purely quantum mechanical, since for classical systems, a local rest frame can always be defined. We study the relation with the null and weak energy condition, which are violated in even larger regions, and compare with previously known examples. While no pathologies or instabilities arise, it is interesting that regions without a rest frame are possibly present in heavy ion collisions.