Chemical potential and the nature of dark energy: The case of a phantom field

Lima, J. A. S.; Pereira, S. H.

doi:10.1103/physrevd.78.083504

Cited by 41 publications

(38 citation statements)

References 76 publications

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“…and as can be observed for the phantom regime we have T S < 0 since ω < −1, this implies a negative entropy for the phantom cosmology. Within the scheme of standard cosmology was found that the aforementioned problem for the entropy can be solved if a chemical potential, denoted as μ, it is introduced at cosmological level [61,62], i.e., the Euler relation takes the form…”

Section: Thermodynamicsmentioning

confidence: 99%

Non-zero torsion and late cosmology

2020

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In this work, we study some thermodynamical aspects associated with torsion in a flat FLRW spacetime cosmic evolution. By implementing two Ansatze for the torsion term, we find that the model admits a phantom regime or a quintessence behavior. This scheme differs from the CDM model at the thermodynamical level. The resulting cosmic expansion is not adiabatic, the fulfillment of the second law of thermodynamics requires a positive torsion term, and the temperature of the cosmic fluid is always positive. The entropy of the torsion phantom scenario is negative, but introducing chemical potential solves this issue. For a Dirac-Milne type Universe, the torsion leads to a growing behavior for the temperature of the fluid but has no incidence on the rate of expansion.

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Section: Thermodynamicsmentioning

confidence: 99%

Non-zero torsion and late cosmology

2020

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“…The evolutions of all effective EoS, whose early-time asymptotic values are ω 1e f f = 0. 44, ω 2e f f = −1. 47 and ω t = 0, are shown in Fig.…”

Section: α =mentioning

confidence: 99%

On extended sign-changeable interactions in the dark sector

Forte

2014

Gen Relativ Gravit

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We extend the cosmological couplings proposed in Sun et al. and Wei, where they suggested interactions with change of signs along the cosmological evolution. Our extension liberates the changes of sign of the interaction from the deceleration parameter and from the relation of energy densities of the dark sector and considers the presence of non interactive matter. In three cases we obtain the general solutions and the results obtained in models fitted with Hubble's function and SNe Ia data, are analyzed regarding the problem of the cosmological coincidence, the problem of the crisis of the cosmological age and the magnitude of the energy density of dark energy at early universe. Also we graphically study the range of variation of, the actual dark matter density parameter, the effective equation of state of the dark energy and the redshift of transition to the accelerated regimen, generated by variations at order $1\sigma$ in the coupling parameters.Comment: 20 pages, 26 figures,title shortened, new references added, to be published in General Relativity and Gravitation journal. The final publication will be available at Springer via link.springer.com/article/10.1007/s10714-014-1811-

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“…Thus, this idea of negative temperature is discarded because the temperature of a fluid should be positive-definite. Another possible way is the establishment of a negative potential to the fluid [42] to validate the hypothesis of the phantom. However, the generalized second law of thermodynamics postulates that the total entropy S of the universe should increase with time during cosmological evolution, i.e.…”

Section: Field Equations and Thermodynamicsmentioning

confidence: 99%

Thermodynamics of cosmological models with generalized G and Λ

Singh¹,

Singh²

2018

Turk J Phys

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Abstract:Here we investigate spatially flat Friedmann-Robertson-Walker space-time models of the universe to study the thermodynamic behaviors in light of variables G and Λ . A particular method to find the solutions of Einstein's field equations and mathematical expressions for temperature and entropy of the perfect fluid cosmological models is introduced by using both the equation of state and the assumption G = G0 a n . It is observed that the phantom field of ( ω < −1) is thermodynamically not viable when the temperature increases with the evolution of the universe. The second law of thermodynamics is also constrained by cosmological models with time-dependent G and Λ . The mathematical expressions for the look-back time, proper distance, luminosity distance, and angular diameter distances are obtained for an isotropic stiff-fluid model and their significances are investigated. The most interesting part of the investigation is that the dynamical and physical behaviors of the models are less constrained by the second law of thermodynamics.

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Chemical potential and the nature of dark energy: The case of a phantom field

Cited by 41 publications

References 76 publications

Non-zero torsion and late cosmology

Non-zero torsion and late cosmology

On extended sign-changeable interactions in the dark sector

Thermodynamics of cosmological models with generalized G and Λ

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