Vorticity and entropy production in tilted Szekeres spacetimes

TL;DR

This paper investigates the tilted Szekeres spacetime, revealing nonreversible fluid evolution with entropy production and vorticity detection by tilted observers, highlighting differences from non-tilted cases and discussing physical implications.

Contribution

It provides a detailed analysis of the kinematical and thermodynamical properties of tilted Szekeres spacetimes, including vorticity and entropy production, which were not previously characterized.

Findings

Tilted observers detect vorticity in the fluid congruence.

The fluid exhibits nonvanishing entropy production and is nongeodesic.

Magnetic part of the Weyl tensor vanishes, indicating nonradiative spacetime.

Abstract

We analyze the properties of the tilted Szekeres spacetime, i.e. the version of such spacetime as seen by a congruence of observers with respect to which the fluid is moving. The imperfect fluid and the kinematical variables associated to the four-velocity of the fluid assigned by tilted observers are studied in detail. As it happens for the case of the Lemaitre--Tolman--Bondi spacetime, the fluid evolves nonreversibly (with nonvanishing entropy production) and is nongeodesic. However unlike that later case, the tilted observer detects vorticity in the congruence of the fluid world lines. Also, as for the nontilted congruence the magnetic part of the Weyl tensor vanishes, reinforcing the nonradiative character of this kind of spacetime. Possible physical implications of these results are discussed.