Cosmological Dynamics on a Novel $f(Q)$ Gravity Model with Recent DESI DR2 Observation

TL;DR

This work tests a novel Starobinsky-inspired $f(Q)$ gravity model in a flat FLRW cosmology by combining Cosmic Chronometer, PantheonPlus SH0ES, and DESI DR2 BAO data. A Gong–Wang $q(z)$ parametrization yields a constrained expansion history, with best-fit values $H_0 obreak\ obreak= \nobreak 73.19$, $m \approx -0.386$, and $n \approx -1.055$, and a present-day equation of state $ obreak\omega_0 \approx -0.73$. The model exhibits a transition from deceleration to acceleration at $z_{ m tr} \approx 0.573$, and the Om(z) diagnostic supports a quintessence-like regime today. Energy conditions show NEC and DEC satisfied while SEC is violated, aligning with late-time acceleration; the results indicate the $f(Q)$ framework can account for cosmic acceleration without a cosmological constant. Future work will extend to perturbations and exploit upcoming surveys such as DESI final releases, LSST, and Euclid.

Abstract

In this article, we investigate the cosmological viability of a modified symmetric teleparallel gravity model within the $f(Q)$ framework. We derive observational constraints on the model parameters by performing a Markov Chain Monte Carlo analysis using a combined dataset consisting of cosmic chronometers, PantheonPlus SH0ES, and DESI BAO DR2. Our analysis yields the best-fit values for the model parameters $m=-0.386 \pm 0.090$ and $n=-1.055 \pm 0.047$, along with the cosmological parameters at present: $H_0 = 73.19 \pm 0.25$, $q_0 = -0.51 \pm 0.6$, and $ω_{0} = -0.73 \pm 0.3$, at 68\% CL. Furthermore, we examine the physical behavior of the model, focusing on the effective equation of state and deceleration parameter. Our findings indicate that the model experiences a transition from the early deceleration phase to the late-time cosmic acceleration, and the transition occurs at a redshift $z_{tr} = 0.573$. We also analyse the $om(z)$ diagnostic, which reflects a positive slope, supporting the behavior of the equation of state parameter in the quintessence region.

Figures (6)

• Figure 1: One-dimensional marginalized posterior distributions and two-dimensional joint contours of the model parameters.
• Figure 2: Evolution of the energy density $\rho$ as functions of redshift $z$, for the constrained coefficients from Fig. \ref{['joint']}.
• Figure 3: Evolution of the EoS parameter $\omega$ as function of redshift $z$, for the constrained coefficients from Fig. \ref{['joint']}.
• Figure 4: Evolution of the deceleration parameter $q$ as functions of redshift $z$ for the constrained coefficients from Fig. \ref{['joint']}.
• Figure 5: Evolution of energy conditions: Null [NEC, $\rho+p$], Dominant [DEC. $\rho-p$], Strong [SEC, $\rho+3p$] as functions of redshift $z$, for the constrained coefficients from Fig. \ref{['joint']}.