arXiv subjects

Mahendra Goray

Publications and source records attributed to Mahendra Goray.

4 recordsLinked to original sources

arXiv2026

Cosmological Perturbations and Observational Constraints on Spinor Field Quintessence Dark Energy

We investigate the linear perturbation cosmology of a spinor-field realization of quintessence dark energy by implementing the model in the Einstein--Boltzmann solver \texttt{CLASS}. The model parameters are constrained using a Markov Chain Monte Carlo analysis with Pantheon$^{+}$ Type Ia supernovae, cosmic chronometers, DESI DR2 baryon acoustic oscillations, redshift-space distortions, and Planck 2018 CMB distance-prior data. For the full combined dataset, we obtain $w_{\rm de}=-0.9710^{+0.0206}_{-0.0206}$, $Ω_{m0}=0.2939^{+0.0047}_{-0.0047}$, and $H_0=66.23^{+0.55}_{-0.53},\mathrm{kms^{-1}Mpc^{-1}}$. The corresponding perturbation quantities are $σ_8=0.7537^{+0.0076}_{-0.0075}$ and $S_8=0.7459^{+0.0067}_{-0.0065}$. We find that the spinor-quintessence model closely reproduces the predictions of a phenomenological constant-$w$ model in the matter power spectrum, growth-rate observable $fσ_8$, growth index, and CMB temperature anisotropy spectrum, with deviations generally below the percent level. A comparison with $Λ$CDM and $w$CDM shows statistically indistinguishable fits, although the Bayesian information criterion favors the simpler $Λ$CDM model. Our results demonstrate that the spinor-field quintessence scenario remains consistent with current expansion-history and structure-growth observations when its perturbation evolution is treated consistently, providing a field-theoretically motivated realization of constant-$w$ dark energy at the background and linear perturbation levels.

physics.gen-ph↗

arXiv2026

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

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.

gr-qc↗

arXiv2025

Observational Constraints on a Spinor Field Generalized Chaplygin Gas Model in a Spherically Symmetric FLRW Spacetime

Despite the remarkable success of the standard LambdaCDM model in describing the evolution of the universe, several unresolved issues remain, such as the true nature of dark energy, fine-tuning problems, and the persistent Hubble tension. Motivated by these shortcomings, we construct a spinor field-based Generalized Chaplygin Gas (GCG) model that unifies dark matter and dark energy within a spherically symmetric Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. This framework incorporates a nonlinear spinor field and considers an open universe geometry. We constrain the model parameters using the latest observational datasets, including Type Ia supernovae from the binned Pantheon compilation, Hubble parameter measurements from cosmic chronometers (CC) and SDSS, including baryon acoustic oscillation (BAO) data. Employing Markov Chain Monte Carlo (MCMC) sampling techniques, we obtain best-fit values that indicate the spinor GCG model provides a competitive and viable alternative to the LambdaCDM, particularly in the late-time universe. Furthermore, the model predicts a lower present-day Hubble constant, offering a potential resolution to the Hubble tension. The results highlight the rich phenomenology of spinor fields and their possible role in the dynamics of dark energy through spacetime interaction.

gr-qc↗

arXiv2025

Constraining parameters of spinor field dark energy: An alternative to $Λ$CDM model under the spherically symmetric FLRW space-time

This study constrains the cosmological parameters within the scope of a spherically symmetric FLRW cosmological model, the role of a nonlinear spinor field in the universe's evolution. To test this approach, we incorporate the recent Cosmic chronometers, Supernova, and Sloan Digital Sky Survey data. It is found that if spherical coordinates give the FLRW model, the energy-momentum tensor (EMT) of the spinor field possesses nontrivial non-diagonal components. These non-diagonal components of EMT neither depend on the spinor field nonlinearity nor the value of the parameter $k$ defining the type of curvature of the FLRW model. In this context, we construct a dark energy model and perform an MCMC simulation to obtain the best-fit values of the parameters. The results are well comparable to the present Hubble parameter and deceleration parameter, indicating the accelerated expansion of the universe.

physics.gen-ph↗