Nonlinear Spinor Fields in Bianchi type-I spacetime reexamined

TL;DR

This paper investigates the role of nonlinear spinor fields in the evolution of anisotropic Bianchi type-I universes, revealing two scenarios of isotropization with different restrictions on the spinor field.

Contribution

It reexamines the effects of nonlinear spinor fields on Bianchi type-I spacetime, highlighting conditions for isotropization and restrictions on the spinor field.

Findings

Universe can evolve from anisotropic to isotropic in two distinct ways.

Spinor field restrictions depend on the isotropization scenario.

Different initial conditions lead to different evolution paths.

Abstract

The specific behavior of spinor field in curve space-time with the exception of FRW model almost always gives rise to non-trivial non-diagonal components of the energy-momentum tensor. This non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions. In this paper within the scope of an anisotropic Bianchi type-I Universe we study the role of spinor field in the evolution of the Universe. It is found that there exist two possibilities. In one scenario the initially anisotropic Universe evolves into an isotropic one asymptotically, but in this case the spinor field itself undergoes some severe restrictions. In the second scenario the isotropization takes places almost at the beginning of the process.