Constraining f(Q,Lm) gravity with bulk viscosity


Myrzakulov Y. Donmez O. Koussour M. Muminov S. Davletov I.Y. Rayimbaev J.
May 2025Elsevier B.V.

Physics of the Dark Universe
2025#48

We investigate the influence of bulk viscosity on late-time cosmic acceleration within an extended f(Q,Lm) gravity framework, where the non-metricity Q is non-minimally coupled with the matter Lagrangian Lm. Analyzing the function f(Q,Lm)=αQ+βLm, we derive exact solutions under non-relativistic matter domination. Using observational datasets (H(z), Pantheon supernovae, and their combination), we constrain the model parameters H0, α, β, and ζ. The deceleration parameter transitions from positive to negative values around redshifts zt≈0.80 to 0.99, indicating current accelerated expansion. Moreover, the effective equation of state parameter, ωeff, resembles quintessence dark energy ([Formula presented]), with corresponding values from respective datasets. Finally, we use the Om(z) diagnostic, which confirms that our model demonstrates quintessence-like behavior. Our findings underscore the significant role of bulk viscosity in understanding accelerated expansion in the universe within alternative gravity theories.

Bulk viscosity , Dark energy , f(Q, Lm) gravity , Observational constraints

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Department of General & Theoretical Physics, L.N. Gumilyov Eurasian National University, Astana, 010008, Kazakhstan
College of Engineering and Technology, American University of the Middle East, Egaila, 54200, Kuwait
Department of Physics, University of Hassan II Casablanca, Morocco
Mamun University, Bolkhovuz Street 2, Khiva, 220900, Uzbekistan
Technical Faculty, Urganch State University, Urgench, Uzbekistan
Institute of Fundamental and Applied Research, National Research University TIIAME, Kori Niyoziy 39, Tashkent, 100000, Uzbekistan
University of Tashkent for Applied Sciences, Str. Gavhar 1, Tashkent, 100149, Uzbekistan
Shahrisabz State Pedagogical Institute, Shahrisabz Str. 10, Shahrisabz, 181301, Uzbekistan
Tashkent State Technical University, Tashkent, 100095, Uzbekistan
Department of Nuclear Physics and Astronomy, Samarkand State University, Samarkand, 140104, Uzbekistan

Department of General & Theoretical Physics
College of Engineering and Technology
Department of Physics
Mamun University
Technical Faculty
Institute of Fundamental and Applied Research
University of Tashkent for Applied Sciences
Shahrisabz State Pedagogical Institute
Tashkent State Technical University
Department of Nuclear Physics and Astronomy

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