Nonlinear Spinor Fields in Bianchi type-$VI_0$ spacetime

TL;DR

This paper investigates how nonlinear spinor fields influence the evolution of the Universe within Bianchi type-VI_0 spacetime, revealing scenarios where the spinor field causes expansion or contraction depending on its properties.

Contribution

It demonstrates the significant impact of non-diagonal energy-momentum components of spinor fields on cosmological evolution, highlighting the role of nonlinear and massive terms.

Findings

Spinor fields can lead to either universe expansion or contraction.

Nontrivial spinor energy-momentum components critically affect spacetime dynamics.

The behavior depends on the coupling constants and invariants of the spinor field.

Abstract

Within the scope of Bianchi type-$VI_0$ spacetime we study the role of spinor field on the evolution of the Universe. It is found that the presence of nontrivial non-diagonal components of energy-momentum tensor of the spinor field plays vital role on the evolution of the Universe. As a result of their mutual influence there occur two different scenarios. In one case the invariants constructed from the bilinear forms of the spinor field become trivial, thus giving rise to a massless and linear spinor field Lagrangian. According to the second scenario massive and nonlinear terms do not vanish and depending on the sign of coupling constants we have either an expanding mode of expansion or the one that after obtaining some maximum value contracts and ends in big crunch generating spacetime singularity. This result shows that the spinor field is highly sensitive to the gravitational one.