Bianchi type I cosmology with scalar and spinor fields

TL;DR

This paper explores Bianchi type-I cosmology with interacting scalar and spinor fields, analyzing initial singularity, isotropization, and oscillatory behavior influenced by a cosmological constant.

Contribution

It introduces a derivative coupling interaction in Bianchi I cosmology with scalar and spinor fields and finds self-consistent solutions including effects of a cosmological constant.

Findings

Existence of regular solutions without broken energy conditions.

Cosmological constant induces oscillations in the BI model.

Analysis of initial singularity and isotropization processes.

Abstract

We consider a system of interacting spinor and scalar fields in a gravitational field given by a Bianchi type-I cosmological model filled with perfect fluid. The interacting term in the Lagrangian is chosen in the form of derivative coupling, i.e., ${\cal L}_{\rm int} = \frac{\lambda}{2} \vf_{,\alpha}\vf^{,\alpha} F$, with $F$ being a function of the invariants $I$ an $J$ constructed from bilinear spinor forms $S$ and $P$. We consider the cases when $F$ is the power or trigonometric functions of its arguments. Self-consistent solutions to the spinor, scalar and BI gravitational field equations are obtained. The problems of initial singularity and asymptotically isotropization process of the initially anisotropic space-time are studied. It is also shown that the introduction of the Cosmological constant ($\Lambda$-term) in the Lagrangian generates oscillations of the BI model, which is not the case in absence of $\Lambda$ term. Unlike the case when spinor field nonlinearity is induced by self-action, in the case in question, wehere nonlinearity is induced by the scalar field, there exist regular solutions even without broken dominant energy condition.