Parametrized Papapetrou equations: Applications in cosmological evolution and astrophysics

The classical Papapetrou equations describe the motion of spinning test particles within curved spacetimes, capturing the interplay between spin and spacetime curvature. In this study, we extend these equations to incorporate the effects of torsion by adopting the framework of Parameterized Absolute Parallelism geometry. We derive the generalized spin-precession and force equations, explicitly introducing the torsion parameter b, and show how these modifications reduce to the classical Papapetrou equations when torsion vanishes. We apply these generalized equations to cosmological contexts, specifically examining their implications within radiation-dominated and matter-dominated FLRW universes. Our analysis reveals that torsion significantly alters the decay rates of spin components and the evolution of particle momentum, potentially affecting the dynamics of the early universe. These findings suggest novel avenues for probing spin-torsion interactions within modified gravity theories, offering possible observational consequences in cosmological scenarios. The parameterized equations were also utilized to examine the motion of spinning particles in a gravitational field with torsion, allowing for an investigation into how torsion influences the dynamics of these particles.