2026/03/20 by M. Koussour, Alnadhief H. A. Alfedeel, S. Muminov +1 · 1 voice
Physics and Astronomy · #physics.gen-ph
paper · pdf · doi:10.1016/j.jheap.2026.100578
We investigate the late-time cosmic acceleration within the framework of viscous f(T,Lm) gravity, where the gravitational action depends on both the torsion scalar T and the matter Lagrangian Lm. In this context, the Universe is modeled as a bulk viscous fluid, allowing for dissipative effects that generate an effective negative pressure capable of driving acceleration without invoking a cosmological constant. We adopt a simple linear model f(T,Lm) = αT + βLm and assume a constant bulk viscosity coefficient ζ= ζ0 > 0. The model parameters are constrained using a joint analysis of recent observational datasets, including 31 Hubble parameter measurements, the Pantheon+ sample of 1701 Type Ia Supernovae, and the latest baryon acoustic oscillation data from DESI, employing a Markov Chain Monte Carlo (MCMC) approach. The best-fit results, H0 = 68.16 ± 0.65, α= 1.53+0.49-0.61, β= 0.40 ± 0.96, and ζ0 = 2.15+0.69-0.81, are consistent with current cosmological observations and indicate that bulk viscosity plays a significant role in the late-time dynamics. The deceleration parameter q0 = -0.33 ± 0.41 confirms the current accelerated expansion, while the effective equation of state (EoS) evolves from a matter-like regime at high redshift toward a quintessence phase at late times. The Om(z) diagnostic further supports this behavior, suggesting a mild deviation from ΛCDM toward a dynamical dark energy component. Although information criteria (ΔAIC = 2.2, ΔBIC = 13.13) slightly favor the simpler ΛCDM model, the viscous f(T,Lm) framework remains a viable and physically motivated alternative capable of explaining cosmic acceleration through the combined effects of torsion-matter coupling and viscosity.