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- 2025| Springer NatureWe present an investigation of a scalar field dark energy model in the context of the FLRW universe, focusing on the parameterization of the deceleration parameter q(z) to study the evolution of cosmic acceleration. By employing extensive observational datasets—including 30 independent cosmic chronometer measurements, 17 additional baryon acoustic oscillation data points, and standard candle datasets from Pantheon Type Ia supernovae, Quasars, and Gamma-Ray Bursts—we provide constraints on cosmological parameters using advanced Markov chain Monte Carlo methods. Our analysis identifies a transition redshift of , marking the shift from decelerated to accelerated expansion, with a current deceleration parameter of . The equation of state parameter confirms the dynamical behavior of quintessence, deviating slightly from a cosmological constant. Furthermore, the model demonstrates strong consistency with CDM at lower redshifts while revealing distinct deviations at higher redshifts, which provides valuable insights into the late-time dynamics of the universe. By examining the evolution of cosmography parameters, energy density, pressure, and the scalar field equation of state, this study contributes the relevance of scalar field models as promising candidates for dark energy.
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- 2025| ElsevierThe ongoing Hubble tension, a significant discrepancy between early-and late-universe measurements of the Hubble constant 𝐻0, challenges the foundations of modern cosmology. A closely related issue, the 𝐻0−𝑟𝑑 tension, arises from the dependency of BAO-based inferences of 𝐻0on the assumed sound horizon at the drag epoch 𝑟𝑑. In this work, we investigate the cosmological implications of the 𝑓(𝑅,𝑇)=𝑅+2𝜆𝑇gravity model, which introduces a direct coupling between the Ricci scalar (𝑅) and the trace of the energy-momentum tensor (𝑇). By utilizing a Markov Chain Monte Carlo (MCMC) analysis with observational datasets, such as Baryon Acoustic Oscillations (BAO), Cosmic Chronometers (CC), and Standard Candles (SC), we constrain the model parameters and assess their compatibility with current cosmological observations. Our findings indicate a strong correlation between 𝐻0and 𝑟𝑑, confirming that different dataset combinations lead to systematically varying constraints on these parameters. The inclusion of the Riess 2019 prior (R19) results in higher values of 𝐻0, reinforcing the Hubble tension, while BAO-only data favors lower values, consistent with early-universe measurements. Additionally, we analyze the evolution of the main cosmologic parameters such as the deceleration parameter 𝑞(𝑧)and the equation of state parameter 𝜔(𝑧). Our results suggest that the 𝑓(𝑅,𝑇)model exhibits a quintessence-like behavior, with 𝜔(𝑧)>−1at present, indicating a dynamical dark energy component rather than a simple cosmological constant. Furthermore, we confirm that the present-day values of the matter and dark energy density parameters, Ω𝑚≈0.3and ΩΛ≈0.7, remain consistent with a spatially flat universe. These results highlight the role of modified gravity in addressing key tensions in cosmology and demonstrate that the 𝑓(𝑅,𝑇)framework provides a natural extension of ΛCDM.
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