Observational constraints on viscous cosmology in $f(T,L_m)$ gravity

Abstract

We investigate the late-time cosmic acceleration within the framework of viscous $f(T,L_m)$ gravity, where the gravitational action depends on both the torsion scalar $T$ and the matter Lagrangian $L_m$. 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 $f(T,L_m)=\alpha T+\beta L_m$ and assume a constant bulk viscosity coefficient $\zeta ={\zeta }_0>0$. 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, $H_0=68.16\pm 0.65$, $\alpha =1.53_{-0.61}^{+0.49}$, $\beta =0.40\pm 0.96$, and ${\zeta }_0=2.15_{-0.81}^{+0.69}$, are consistent with current cosmological observations and indicate that bulk viscosity plays a significant role in the late-time dynamics. The deceleration parameter $q_0=-0.33\pm 0.41$ 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 $\Lambda$CDM toward a dynamical dark energy component. Although information criteria ($\Delta \mathrm{AIC}=2.2$, $\Delta \mathrm{BIC}=13.13$) slightly favor the simpler $\Lambda$CDM model, the viscous $f(T,L_m)$ framework remains a viable and physically motivated alternative capable of explaining cosmic acceleration through the combined effects of torsion-matter coupling and viscosity.

Journal of High Energy Astrophysics published version

References in corpus (22)

• f(R,T) gravity
• A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
• The Pantheon+ Analysis: Cosmological Constraints
• Dark torsion as the cosmic speed-up
• Modified teleparallel gravity: inflation without inflaton
• Einstein's Other Gravity and the Acceleration of the Universe
• Extra force in $f(R)$ modified theories of gravity
• The Pantheon+ Analysis: The Full Dataset and Light-Curve Release
• Two new diagnostics of dark energy
• f(R,L_m) gravity
• On Born-Infeld Gravity in Weitzenbock spacetime
• Large Scale Structure as a Probe of Gravitational Slip
• Modified gravity with arbitrary coupling between matter and geometry
• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• Dark matter as a geometric effect in f(R) gravity
• New classes of modified teleparallel gravity models
• Palatini formulation of modified gravity with a nonminimal curvature-matter coupling
• Crossing of the w=-1 barrier in viscous modified gravity
• Crossing of the w=-1 Barrier in Two-Fluid Viscous Modified Gravity
• Is Teleparallel Gravity really equivalent to General Relativity?
• Viscosity in modified gravity
• Bulk viscous matter in $f(T)$ gravity: A path to cosmic acceleration

Cited by in corpus (1)

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