# Non-minimally coupled nonlinear spinor field in Bianchi type-I cosmology

## TL;DR

This paper investigates how non-minimal coupling of nonlinear spinor fields influences the evolution of Bianchi type-I universes, revealing that such coupling can lead to closed universe scenarios with eventual contraction.

## Contribution

It demonstrates that non-minimal coupling alters the universe's evolution, enabling nonlinear spinor fields to produce closed universes, unlike minimal coupling cases which lead to open universes.

## Key findings

- Non-minimal coupling maintains the same restrictions on spacetime geometry as minimal coupling.
- Diagonal components of energy-momentum tensor differ with non-minimal coupling, affecting universe evolution.
- Nonlinear spinor fields with non-minimal coupling can cause a universe to expand and then recollapse.

## Abstract

Within the scope of Bianchi type-$I$ cosmological model we have studied the role of spinor field in the evolution of the Universe. In doing so we have considered the case with non-minimal coupling. It was found that the non-diagonal components of the energy-momentum tensor of the spinor field, hence the restrictions on the space-time geometry remain the same as in case of minimal coupling. Since in this case the diagonal components of the energy-momentum tensor differ, the evolution of the corresponding universe also differs. For example, while a linear spinor field with non-minimal coupling or nonlinear spinor field with minimal coupling give rise to open universe, a nonlinear spinor field with non-minimal coupling with the same parameters can generate close universe that at the beginning expands, and after attaining some maximum value begin to contract and finally ends in a Big Crunch.