2025/07/14 by G. K. Goswami, Goswami, G. K., J. P. Saini +1
Earth and Planetary Sciences · Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Geophysics and Gravity Measurements
paper · pdf · doi:10.48550/arxiv.2507.10101
openalex publication_date 2025/07/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate a specific gravity model of the form f(R, Lm) = αR + Lmβ + γ, where the nonlinear dependence on the matter Lagrangian Lm introduces an effective curvature-matter interaction, leading to the non-conservation of the energy-momentum tensor. Using distance modulus data, we constrain the parameters through χ2 minimization and Bayesian MCMC analysis, obtaining statistically robust best-fit values: H0 = 73.75 ± 0.16~\mathrmkm s-1 Mpc-1, λ= 0.262 ± 0.007, and w = -0.005 ± 0.001. This study presents a comprehensive and statistically rigorous comparison of three key early-Universe epochs: structure formation, recombination, and matter-radiation equality between the f(R,Lm) model and the standard ΛCDM cosmology. The model predicts an earlier onset of nonlinear structure formation (zcf(R,Lm) ≈ 25.6) and a higher matter-radiation equality redshift (zeqf(R,Lm) ≈ 4203) compared to ΛCDM (zeqΛCDM ≈ 2779), while maintaining consistency with the observed recombination redshift (zrec ≈ 1092). The recombination visibility function, derived using standard microphysical expressions with the modified expansion history, exhibits a slightly broader full width at half maximum, suggesting an extended photon decoupling period.