Testing an anisotropic spinor field--based Modified Chaplygin Gas model in Kantowski--Sachs spacetime with observational constraints

Abstract: We investigate a cosmological model based on a massless nonlinear spinor field coupled to a Modified Chaplygin Gas (MCG) in the Kantowski--Sachs spacetime, aiming to probe anisotropies and unified dark sector dynamics. The model parameters are constrained using recent observational data, including Pantheon+, cosmic chronometers, DESI DR2, and CMB distance priors, via a Markov Chain Monte Carlo analysis. We find $H_0 \sim 67$--$68~\mathrm{km\,s^{-1}\,Mpc^{-1}}$, while the shear parameter is consistent with zero, indicating an effectively isotropic Universe at late times. The model reproduces late-time cosmic acceleration with a present-day deceleration parameter $q_0 \sim -0.49$, and provides a good fit to the data, yielding a lower minimum $χ^2$ than $Λ$CDM, and is favored by the Akaike Information Criterion. Overall, the spinor field MCG model in Kantowski--Sachs spacetime offers a viable framework that naturally incorporates anisotropy and a unified description of dark matter and dark energy, consistent with current observations.