Modified cosmology through nonextensive horizon thermodynamics

Lymperis, Andreas (Aff1, 0000 0004 0576 5395, grid.11047.33, Department of Physics, University of Patras, 26500, Patras, Greece) ; Saridakis, Emmanuel N. (Aff2, 0000 0001 2185 9808, grid.4241.3, Department of Physics, National Technical University of Athens, Zografou Campus GR, 157 73, Athens, Greece) (Aff3, 0000 0001 2111 2894, grid.252890.4, CASPER, Physics Department, Baylor University, 76798-7310, Waco, TX, USA)

05 December 2018

Abstract: We construct modified cosmological scenarios through the application of the first law of thermodynamics on the universe horizon, but using the generalized, nonextensive Tsallis entropy instead of the usual Bekenstein–Hawking one. We result to modified cosmological equations that possess the usual ones as a particular limit, but which in the general case contain extra terms that appear for the first time, that constitute an effective dark energy sector quantified by the nonextensive parameter δ . When the matter sector is dust, we extract analytical expressions for the dark energy density and equation-of-state parameters, and we extend these solutions to the case where radiation is present too. We show that the universe exhibits the usual thermal history, with the sequence of matter and dark-energy eras, and according to the value of δ the dark-energy equation-of-state parameter can be quintessence-like, phantom-like, or experience the phantom-divide crossing during the evolution. Even in the case where the explicit cosmological constant is absent, the scenario at hand can very efficiently mimic ΛCDM cosmology, and is in excellent agreement with Supernovae type Ia observational data.

Published in: EPJC 78 (2018) 993
Published by: Springer/Società Italiana di Fisica
DOI: 10.1140/epjc/s10052-018-6480-y
License: CC-BY-3.0

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