Three thermodynamically based parametrizations of the deceleration parameter

Campo, Sérgio del; Herrera, Ramón; Durán, I.; Pavón, Diego

doi:10.1103/physrevd.86.083509

Cited by 94 publications

(59 citation statements)

References 55 publications

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“…Now, let us examine whether the universe with signchangeable interaction in the dark sectors will result to thermodynamic equilibrium. As it is discussed extensively in the literature (see for instance [120,121]), in order for this to be achieved one needs to have a total entropy whose first derivative is positive, while at late times its second derivative should be negative [122], and thus the entropy asymptotically tends towards a constant value. Using x = ln a as the independent variable the above require that S ≥ 0 and S < 0, where S = S r + S b + S c + S x + S h , with primes denoting differentiation with respect to x.…”

Section: Laws Of Thermodynamics In Sign-changeable Interaction Momentioning

confidence: 99%

Observational constraints on sign-changeable interaction models and alleviation of the H0 tension

et al. 2019

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We investigate various scenarios which include interaction forms between dark matter and dark energy that exhibit sign reverse, namely where the transfer of energy between the dark fluids changes sign during evolution. We study the large-scale inhomogeneities in such interacting scenarios and we confront them with the latest astronomical data. Our analysis shows that the sign-changeable interaction models are able to produce stable perturbations. Additionally, the data seem to slightly favor a non-zero interaction, however, within 1σ confidence level (CL) the scenarios cannot be distinguished from non-interacting cosmologies. We find that the best-fit value of the dark-energy equation-of-state parameter lies in the phantom regime, while the quintessence region is also allowed nevertheless at more than 2σ CL. Examining the effect of the interaction on the CMB TT and matter power spectra we show that while from the simple spectra it is hard to distinguish the interacting case from ΛCDM scenario, in the residual graphs the interaction is indeed traceable. Moreover, we find that sign-changeable interaction models can reconcile the H0 tension, however the σ8 tension is still persisting. Finally, we examine the validity of the laws of thermodynamics and we show that the generalized second law is always satisfied, while the second derivative of the total entropy becomes negative at late times which implies that the universe tends towards thermodynamic equilibrium. 95.36.+x, 95.35.+d, 98.80.Es

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Section: Laws Of Thermodynamics In Sign-changeable Interaction Momentioning

confidence: 99%

Observational constraints on sign-changeable interaction models and alleviation of the H0 tension

et al. 2019

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“…There are several parameterizations for q(z) reported in the literature, see refs. [17][18][19][20][21][22][23][25][26][27][28][29][30]. We propose a new one as follows where, q 0 and q 1 are the values for the deceleration parameter at the present epoch, and at high redshift, respectively.…”

Section: Proposed Parameterization For the Deceleration Parametermentioning

confidence: 99%

“…By probing the cosmographic parameters using cosmological data, it is possible to associate them to a given dynamical DE entity and reconstruct its features as well as the Universe dynamics. In this vein, several authors have proposed a number of functions to parameterize the deceleration parameter q(z) (see for example [17][18][19][20][21][22] for recent studies) and reconstructed the features of any kind of dark energy.…”

Section: Introductionmentioning

confidence: 99%

Constraints on barotropic dark energy models by a new phenomenological q(z) parameterization

et al. 2019

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In this paper, we propose a new phenomenological two parameter parametrization of q(z) to constrain barotropic dark energy models by considering a spatially flat FRW universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis type Ia Supernovae sample and a joint analysis from these data. We obtain a value of q(z) today, q 0 = −0.48 +0.10 −0.11 , and a transition redshift, z t = 0.71 +0.12 −0.12 (when the Universe change from an decelerated phase to an accelerated one). The effective EoS reconstruction and the ω -ω plane analysis pointed out a quintom dark energy, which is consistent with a non parametric EoS reconstruction, reported by other authors, and using the latest cosmological observations.

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“…However, in the literature other approaches suggest different points of views, motivated by physical requirements, different from assuming the above radius r u . In particular, one can imagine to have r u ∝ H −1 [33][34][35]. In general such a choice would reproduce a causal region different from the sphere ∝ a 3 , albeit at small redshift regime, i.e., z 1, one can continue to approximate the volume with the simplest choice of V ∝ a 3 .…”

Section: The Volume and Its Evolution In Terms Of The Redshiftmentioning

confidence: 99%

Cosmographic Thermodynamics of Dark Energy

Luongo

2017

Entropy

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Dark energy's thermodynamics is here revised giving particular attention to the role played by specific heats and entropy in a flat Friedmann-Robertson-Walker universe. Under the hypothesis of adiabatic heat exchanges, we rewrite the specific heats through cosmographic, model-independent quantities and we trace their evolutions in terms of z. We demonstrate that dark energy may be modeled as perfect gas, only as the Mayer relation is preserved. In particular, we find that the Mayer relation holds if j − q > 1 2 . The former result turns out to be general so that, even at the transition time, the jerk parameter j cannot violate the condition: j tr > 1 2 . This outcome rules out those models which predict opposite cases, whereas it turns out to be compatible with the concordance paradigm. We thus compare our bounds with the ΛCDM model, highlighting that a constant dark energy term seems to be compatible with the so-obtained specific heat thermodynamics, after a precise redshift domain. In our treatment, we show the degeneracy between unified dark energy models with zero sound speed and the concordance paradigm. Under this scheme, we suggest that the cosmological constant may be viewed as an effective approach to dark energy either at small or high redshift domains. Last but not least, we discuss how to reconstruct dark energy's entropy from specific heats and we finally compute both entropy and specific heats into the luminosity distance d L , in order to fix constraints over them through cosmic data.

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Three thermodynamically based parametrizations of the deceleration parameter

Cited by 94 publications

References 55 publications

Observational constraints on sign-changeable interaction models and alleviation of the H0 tension

Observational constraints on sign-changeable interaction models and alleviation of the H0 tension

Constraints on barotropic dark energy models by a new phenomenological q(z) parameterization

Cosmographic Thermodynamics of Dark Energy

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