Double polytropic cosmic acceleration from the Murnaghan equation of state
Dunsby P.K.S. Luongo O. Muccino M. Pillay V.
December 2024Elsevier B.V.
Physics of the Dark Universe
2024#46
We consider a double polytropic cosmological fluid and demonstrate that, when one constituent resembles a bare cosmological constant while the other emulates a generalized Chaplygin gas, a good description of the Universes large-scale dynamics is obtained. In particular, our double polytropic reduces to the Murnaghan equation of state, whose applications are already well established in solid state physics and classical thermodynamics. Intriguingly, our model approximates the conventional ΛCDM paradigm while reproducing the collective effects of logotropic and generalized Chaplygin fluids across different regimes. To check the goodness of our fluid description, we analyze first order density perturbations, refining our model through various orders of approximation, utilizing σ8 data alongside other cosmological data sets. Encouraging results suggest that our model, based on the Murnaghan equation of state, outperforms the standard cosmological background within specific approximate regimes and, on the whole, surpasses the standard phenomenological reconstruction of dark energy.
Dark energy , Murnaghan equation of state , Polytropic equation , Small perturbations
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Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
Cosmology and Gravity Group (CGG), University of Cape Town, Rondebosch 7701, Cape Town, South Africa
South African Astronomical Observatory, Observatory 7925, Cape Town, South Africa
Centre for Space Research, North-West University, Potchefstroom 2520, Cape Town, South Africa
Università di Camerino, Via Madonna delle Carceri 9, Camerino, 62032, Italy
SUNY Polytechnic Institute, Utica, 13502, NY, United States
Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Perugia, 06123, Italy
INAF - Osservatorio Astronomico di Brera, Milano, Italy
Al-Farabi Kazakh National University, Al-Farabi av. 71, Almaty, 050040, Kazakhstan
ICRANet, P.zza della Repubblica 10, Pescara, 65122, Italy
Department of Mathematics and Applied Mathematics
Cosmology and Gravity Group (CGG)
South African Astronomical Observatory
Centre for Space Research
Università di Camerino
SUNY Polytechnic Institute
Istituto Nazionale di Fisica Nucleare
INAF - Osservatorio Astronomico di Brera
Al-Farabi Kazakh National University
ICRANet
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