2025/05/23 by Goswami, G. K., Pradhan, Anirudh · 3 citations
#FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2505.18226
We investigate a spatially flat FLRW cosmological model in the framework of modified gravity described by the function \( f(R, Lm) = αR + Lmβ+ γ\), where \( Lm \) is the matter Lagrangian density. The modified Friedmann equations yield the Hubble parameter as H(z) = H0 √(1 - λ) + λ(1 + z)3(1 + w), with the parameters \( λ= \fracγ6αH02 + 1 \) and \( w = (β(n - 2) + 1)/(2β- 1) \). Using a Bayesian Markov Chain Monte Carlo (MCMC) approach, we constrain the model parameters with recent observational data, including cosmic chronometers, the Pantheon+ Supernovae dataset, Baryon Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB) shift parameters. The best-fit values are found to be \( H0 = 72.773+0.148-0.152 \) km/s/Mpc, \( λ= 0.289+0.007-0.007 \), and \( w = -0.002+0.002-0.002 \), all quoted at the 1\(σ\) confidence level.This model predicts a transition redshift of \( zt ≈ 0.76 \) for the onset of cosmic acceleration and an estimated universe age of 13.21 Gyr. The higher inferred value of \( H0 \) compared to the Planck 2018 result offers a potential resolution to the Hubble tension. Additionally, using \( ρ0 = 0.534 × 10-30 g/cm3 \) and assuming \( n = 1 \), we derive the model constants as \( β= 1.00201 \), \( α= 512247 \), and \( γ= -1.215 × 10-29 \). We also evaluate the Bayesian Information Criterion (BIC) to compare the model's performance with that of the standard \(Λ\)CDM model. The small BIC difference (\( ΔBIC = 0.16 \)) indicates comparable statistical support for both models. Thus, the \( f(R, Lm) \) gravity scenario serves as a consistent and viable alternative to \(Λ\)CDM, potentially addressing open questions in late-time cosmology.