Observational evidence of bulk viscosity effects in f(R,T) cosmological models
Zhadyranova A. Kanibekova Z. Zhumabekova V. Koussour M. Anshokova D. Muminov S. Rayimbaev J.
15 July 2025Elsevier B.V.
Physics Letters, Section A: General, Atomic and Solid State Physics
2025#548
In this study, we explore an f(R,T) cosmological model incorporating bulk viscosity, focusing on scenarios where the matter sector is minimally and linearly coupled to the geometry, specifically f(R,T)=R+2λT, with λ as the coupling constant. Two cases of bulk viscosity are examined: Case I with a time-dependent coefficient ζ=ζ0+ζ1H (ζ1≠0) and Case II with a constant viscosity ζ=ζ0 (ζ1=0). By employing Bayesian methods, including MCMC techniques, we constrain the model parameters H0, λ, ζ0, and ζ1 using the Hubble H(z) and Pantheon+SH0ES datasets. Our analysis reveals a transition from a decelerating to an accelerating universe driven by bulk viscosity. Case I exhibits a present-day deceleration parameter q0=−0.51, indicating moderate acceleration, while Case II shows a slightly stronger acceleration with q0=−0.53. The evolution of the energy density ρ and effective pressure p¯ aligns with standard cosmological expectations, with positive energy density and consistently negative effective pressure, characteristic of DE. Furthermore, the effective equation of state parameter ωeff and the Om(z) diagnostic suggest quintessence-like behavior, with the violation of the strong energy condition supporting the observed accelerated expansion of the universe. These findings suggest that the f(R,T) model with bulk viscosity offers a consistent and plausible description of late-time cosmic acceleration, aligning well with observational data.
Bayesian analysis , Bulk viscosity , Cosmic acceleration , Dark energy , f(R,T) gravity
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General and Theoretical Physics Department, L. N. Gumilyov Eurasian National University, Astana, 010008, Kazakhstan
Theoretical and Nuclear Physics Department, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Department of Physics, University of Hassan II, Casablanca, Morocco
Mamun University, Bolkhovuz Street 2, Khiva, 220900, Uzbekistan
New Uzbekistan University, Movarounnahr Street 1, Tashkent, 100007, Uzbekistan
Urgench State University, Kh. Alimjan Str. 14, Urgench, 221100, Uzbekistan
General and Theoretical Physics Department
Theoretical and Nuclear Physics Department
Department of Physics
Mamun University
New Uzbekistan University
Urgench State University
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