Constraints on anisotropic properties of the universe in $f(Q, T)$ gravity theory

TL;DR

This paper explores how $f(Q, T)$ gravity affects the anisotropic properties of the universe, using observational data to constrain models and revealing a transition to accelerated expansion with phantom-like energy behavior.

Contribution

It introduces a novel analysis of $f(Q, T)$ gravity in Bianchi type-I spacetime, combining observational constraints with anisotropic cosmological modeling.

Findings

Universe transitions from deceleration to acceleration.

Energy density approaches zero over time.

Spacetime anisotropy influences dark energy behavior.

Abstract

Motivated by anomalies in cosmic microwave background observations, we investigate the implications of $f(Q, T)$ gravity in Bianchi type-I spacetime, aiming to characterize the universe's spatially homogeneous and anisotropic properties. By using a linear combination of non-metricity $Q$ and the energy-momentum tensor trace $T$, we parametrize the deceleration parameter and derive the Hubble solution, which we then impose in the Friedmann equations of $f(Q, T)$ gravity. Bayesian analysis is employed to find the best-fit values of model parameters, with $1-\sigma$ and $2-\sigma$ contour plots illustrating the constraints from observational data, including $H(z)$ data and the Pantheon+ sample. Our analysis reveals a transition from a decelerated to an accelerated expansion phase, with the present deceleration parameter indicating an accelerating universe. The energy density gradually decreases over time, approaching zero for the present and future, indicating continuous expansion. The anisotropic pressure, initially notably negative, transitions to slightly negative values, suggesting the presence of dark energy. The evolving equation of state parameter $\omega$ exhibits behavior akin to phantom energy, influenced by spacetime anisotropy. Violations of the null energy condition and the strong energy condition imply phantom-like behavior and accelerated expansion.