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- 2025| World Scientific Pub...This study investigates the cosmological implications of the 𝑓(𝑅,𝑇)=𝑅+2𝜆𝑇 gravity model. 𝑓(𝑅,𝑇) gravity is a modification of General Relativity (GR) that introduces a coupling between the Ricci scalar R and the trace of the energy–momentum tensor T. This work provides a comprehensive analysis of the model’s predictions using updated observational data, including uncorrelated Baryon Acoustic Oscillations and Cosmic Chronometers. By employing the Markov Chain Monte Carlo technique, we constrain the model parameters, demonstrating their compatibility with current observational datasets. Our findings reveal that the model naturally extends the ΛCDM model, with the parameter 𝜆 from 𝑓(𝑅,𝑇) gravity quantifying deviations from GR. Additionally, we provide a critical discussion on the challenges and limitations of the 𝑓(𝑅,𝑇) framework, addressing issues such as observational constraints, systematic uncertainties and model dependencies. This work not only refines parameter constraints for 𝑓(𝑅,𝑇) gravity, but also bridges the gap between theoretical predictions and observational tests, offering a powerful framework for exploring deviations from GR in a cosmological context.
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- 2025| World Scientific Pub...In this work, we investigate the cosmological implications of f(Q) gravity by introducing a nonlinear equation of state of the form p = βρ2 - ρ. This modified gravity framework, based on the non-metricity scalar Q, offers an alternative to General Relativity and provides new insights into cosmic acceleration. To test the validity of our model, we use a combined observational dataset consisting of 31 cosmic chronometer data points, 1701 Type Ia supernova measurements, and 26 baryon acoustic oscillation observations, leading to a total of 1758 data points. The statistical analysis based on this dataset allows for a viable comparison with the standard ΛCDM model. We analyze cosmographic parameters such as the deceleration parameter, jerk parameter, and statefinder parameters, to determine the impact of the model on the evolution of the universe. The results indicate that our model successfully describes cosmic expansion while presenting deviations from the standard ΛCDM scenario. Statistical comparisons based on the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) further suggest that the proposed model provides a competitive fit to observational data. Our findings show the potential of f(Q) gravity with a nonlinear EoS in the quadratic form as an alternative to the ΛCDM model. This work contributes to efforts to explore modified gravity theories as possible explanations for late cosmic acceleration and provides commentary on their implications.
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