Abstract
We present a conjugate analysis of two different dark energy models, namely the Barboza–Alcaniz parameterization and the phenomenologically-motivated Hobbit model, investigating both their agreement with observational data and their thermodynamical properties. We successfully fit a wide dataset including the Hubble diagram of Type Ia Supernovae, the Hubble rate expansion parameter as measured from cosmic chronometers, the baryon acoustic oscillations (BAO) standard ruler data and the Planck distance priors. This analysis allows us to constrain the model parameters, thus pointing at the region of the wide parameters space, which is worth focusing on. As a novel step, we exploit the strong connection between gravity and thermodynamics to further check models’ viability by investigating their thermodynamical quantities. In particular, we study whether the cosmological scenario fulfills the generalized second law of thermodynamics, and moreover, we contrast the two models, asking whether the evolution of the total entropy is in agreement with the expectation for a closed system. As a general result, we discuss whether thermodynamic constraints can be a valid complementary way to both constrain dark energy models and differentiate among rival scenarios.
Highlights
That the universe is presently undergoing a phase of accelerated expansion is nowadays an observationally unquestionable fact [1,2,3,4,5,6,7,8,9]
While the best fit values for the BA model are expected since they are close to the ΛCDM limit (w0, wa ) = (−1, 0), the (α, β) values for the Hobbit model are somewhat surprising, being quite different from the case (α, β) = (3, 4), which we have identified as interesting
The best fit β is set in such a way that w Hob ( a) asymptotes to w dark energy (DE) = −0.85, which is still close to the ΛCDM w = −1 value
Summary
That the universe is presently undergoing a phase of accelerated expansion is nowadays an observationally unquestionable fact [1,2,3,4,5,6,7,8,9]. On the one hand, it has been shown that applying the first law of thermodynamics to the apparent horizon of an FRW universe with any spatial curvature, once assuming a relation for temperature and entropy, the Friedmann equations can be obtained. This works in general relativity, and in Gauss–Bonnet and Lovelock gravity theories [35]. The accelerating universe enveloped by the apparent horizon satisfies the generalized second law Deviations from this behavior can be observed in relation to the temperature of fluids within the horizon [38] and to the value of the barotropic factor ω.
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