چکیده
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Our aim is studying the thermodynamics of cosmological models including initial and
final de Sitter eras. For this propose, bearing Cai–Kim temperature in mind, we investigate
the thermodynamic properties of a dark energy (DE) candidate with variable
energy density, and show that the state parameter of this dark energy candidate (ωD)
should obey the ωD = −1 constraint, whiles there is no interaction between the fluids
filled the universe, and the universe is not in the de Sitter eras. Additionally, based on
the thermal fluctuation theory, we study the possibility of inducing fluctuations to the
entropy of the DE candidate due to a mutual interaction between the cosmos sectors.
Therefore, we find a relation between the thermal fluctuations and the mutual interaction
between the cosmos sectors, whiles the DE candidate has a varying energy density.
Finally, bearing the coincidence problem in mind, we derive a constraint on the vacuum
energy, and investigate its relation with the entropy evolution of the DE candidate. We
also point to a model with initial and final de Sitter eras in which a gravitationally
induced particle production process leads to change the expansion eras, whiles the corresponding
pressure is considered as the cause of current accelerated phase. We study
its thermodynamics, and show that such processes may also leave thermal fluctuations
into the system. We also find an expression between the thermal fluctuations and the
particle production rate. Finally, we use Hayward–Kodama temperature to get a relation
for the horizon entropy in models including the gravitationally induced particle
production process. Our study shows that the first law of thermodynamics is available
on the apparent horizon whiles, the gravitationally induced particle production process,
as the DE candidate, may add an additional term to the Bekenstein limit of the horizon.
The relation between the validity of the second law of thermodynamics and the
gravitationally particle pro
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