Constraining model parameters in f(Q,C) gravity: Observational analysis and geometric diagnostics

TL;DR

This paper explores a modified gravity model using observational data to constrain parameters, analyze cosmic acceleration, and assess dark energy behavior, finding consistency with current acceleration and stability of the model.

Contribution

It introduces a specific $f(Q,C)$ gravity model with three dark energy parameterizations and constrains them using multiple cosmological datasets, providing new insights into cosmic acceleration mechanisms.

Findings

Supports late-time cosmic acceleration with a transition from deceleration.

Dark energy exhibits negative pressure and positive energy density.

Model remains physically stable across parameterizations.

Abstract

We investigate the cosmological implications of $f(Q,C)$ gravity with $f(Q,C)=\alpha Q+\beta C$, where $Q$ is the non-metricity scalar and $C$ encapsulates cosmological expansion terms. Three parameterizations of the EoS for dark energy, $\omega=\omega_{0}+\omega_{1}z$, $\omega=\omega_{0}+\frac{\omega_{1}z(1+z)}{1+z^{2}}$ and $\omega=\omega_{0}+\frac{\omega_{1}z^{2}}{1+z^{2}}$ are tested using the Hubble, Hubble plus BAO, and Hubble plus BAO plus Pantheon datasets to constrain model parameters. The resulting Hubble and deceleration parameters reveal a transition from deceleration to acceleration, supporting current cosmic acceleration observations. Analysis of the energy density and pressure confirms positive energy density and a negative pressure for dark energy, potentially driving the late-time acceleration. We examine energy conditions, showing compliance with NEC, WEC and DEC, while SEC remains negative, supporting an accelerated expansion. Statefinder diagnostics suggest that two of the EoS parameterizations lead to Quintessence-like behavior with a time-varying dark energy component, while the third closely approaches $\Lambda$CDM showing slight deviations consistent with recent observations. Sound speed analysis demonstrates the physical stability of all parameterizations.