On the cosmological effects of the Weyssenhoff spinning fluid in the Einstein-Cartan framework

TL;DR

This paper investigates how the Weyssenhoff spinning fluid and axial current influence cosmological evolution within the Einstein-Cartan framework, focusing on effects like singularity avoidance and early universe acceleration.

Contribution

It introduces a detailed analysis of cosmological models with Weyssenhoff spinning fluid and axial current, exploring their effects on universe evolution in Einstein-Cartan theory.

Findings

Spinning fluid can induce singularity avoidance.

Axial current affects early accelerated expansion.

Models with and without spinning fluid are compared.

Abstract

The effects of non-Riemannian structures in Cosmology have been studied long ago and are still a relevant subject of investigation. In the seventies, it was discovered that singularity avoidance and early accelerated expansion can be induced by torsion in the Einstein-Cartan theory. In this framework, torsion is not dynamical and is completely expressed by means of the spin sources. Thus, in order to study the effects of torsion in the Einstein-Cartan theory, one has to introduce matter with spin. In principle, this can be done in several ways. In this work we consider the cosmological evolution of the universe in the presence of a constant isotropic and homogeneous axial current and the Weyssenhoff spinning fluid. We analyse possible solutions of this model, with and without the spinning fluid.