Spin fluids in Bianchi-I f(R)-cosmology with torsion

TL;DR

This paper investigates the effects of spin fluids in Bianchi-I cosmological models within torsional f(R)-gravity, analyzing the field equations in different frames and exploring the role of spin and non-linear gravity in torsion dynamics.

Contribution

It provides a detailed derivation and discussion of the field equations for Weyssenhoff spin fluids in Bianchi-I models within torsional f(R)-gravity, including analysis in Jordan and Einstein frames.

Findings

Clarified the role of spin and non-linearity in torsion dynamics.

Derived conditions for the preservation of the Hamiltonian constraint.

Presented specific examples illustrating the theoretical framework.

Abstract

We study Weyssenhoff spin fluids in Bianchi type-I cosmological models, within the framework of torsional f(R)-gravity; the resulting field equations are derived and discussed in both Jordan and Einstein frames, clarifying the role played by the spin and the non-linearity of the gravitational Lagrangian f(R) in generating the torsional dynamical contributions. The general conservation laws holding for f(R)-gravity with torsion are employed to provide the conditions needed to ensure the preservation of the Hamiltonian constraint and the consequent correct formulation of the associated initial value problem. Examples are eventually given.