Thermodynamic constraints and observational validation of the deceleration parameter
Myrzakulov Y. Donmez O. Koussour M. Muminov S. Dauletov A. Rayimbaev J.
July 2025Elsevier B.V.
Nuclear Physics B
2025#1016
In this work, we propose a two-parameter parametrization for the deceleration parameter q(z) grounded in thermodynamic constraints and applied it to explore the evolution of the universe. The second law of thermodynamics imposes essential conditions to ensure that the system approaches equilibrium in late times, requiring q(z)≥−1 and [Formula presented] as z→−1. These constraints ensure that entropy does not decrease, stabilize the system, and facilitate a smooth transition from deceleration to acceleration, consistent with the observed cosmic expansion. Furthermore, the model avoids the phantom regime (ω<−1), preventing catastrophic future scenarios such as the Big Rip. Using the combined CC, Pantheon, SH0ES, and BAO datasets, we constrain the model parameters and compare the results with the standard ΛCDM model. Our findings indicate H0=70.82±0.88, with a transition redshift of zt=0.597±0.214, suggesting an earlier onset of acceleration compared to ΛCDM. The present deceleration parameter, q0=−0.364±0.032, implies a weaker acceleration than in ΛCDM. Moreover, we analyze the evolution of total energy density, pressure, and the effective equation of state parameter, confirming a quintessence-like behavior with ω0=−0.570±0.056. Our results provide a thermodynamically consistent framework for cosmic expansion, supporting a dark-energy-driven acceleration.
Dark energy , Deceleration parameter , Equation of state parameter , Observational cosmology , Thermodynamic 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
Department of Digital Technologies, Alfraganus University, Yukori Karakamish Street 2a, Tashkent, 100190, Uzbekistan
New Uzbekistan University, Movarounnahr Street 1, Tashkent, 100007, Uzbekistan
Urgench State University, Kh. Alimjan Str. 14, Urgench, 221100, Uzbekistan
Department of General & Theoretical Physics
College of Engineering and Technology
Department of Physics
Mamun University
Department of Digital Technologies
New Uzbekistan University
Urgench State University
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