Supernova constraints on decaying vacuum cosmology

Carneiro, S.; Pigozzo, C.; Borges, H. A.; Alcaniz, J. S.

doi:10.1103/physrevd.74.023532

“…As discussed in [17,18,19], for non-zero Ω r0 the expression (7) is an approximate solution, differing only 1% from the exact one, since Ω r0 ≈ 8 × 10 −5 ≪ 1. For Ω r0 = 0, the solution (7) is exact.…”

mentioning

confidence: 99%

“…The corresponding cosmological model has a simple analytical solution, which reduces to the CDM model for early times and to a de Sitter universe for t → ∞ [16]. It has the same free parameters of the standard model and presents good concordance when tested against type Ia supernovas, baryonic acoustic oscillations, the position of the first peak of CMB and the matter power spectrum [12,17,18,19,20,21]. Furthermore, the coincidence problem is alleviated, because the matter density contrast is suppressed in the asymptotic future, owing to the matter production [12,20].…”

mentioning

confidence: 99%

“…With the concordance values of Ω m0 in hand, we can obtain the age parameter of the Universe. It is given by [16,17,18,19] H 0 t 0 = 2 ln Ω m0 3(Ω m0 − 1)…”

mentioning

confidence: 99%

“…The Hubble function (7) can be used to test the model against background observations like SNIa, BAO and the position of the first peak in the CMB spectrum [17,18,19]. The analysis of the matter power spectrum was performed in [20], where, for simplicity, baryons were not included and the cosmological term was not perturbed.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Concordance Cosmology with Particle Creation

Carneiro

¹

2013

Springer Proceedings in Mathematics &Amp; Statistics

View full text Add to dashboard Cite

A constant-rate creation of dark particles in the late-time FLRW spacetime provides a cosmological model in accordance with precise observational tests. The matter creation backreaction implies in this context a vacuum energy density scaling linearly with the Hubble parameter, which is consistent with the vacuum expectation value of the QCD condensate in a low-energy expanding spacetime. Both the cosmological constant and coincidence problems are alleviated in this scenario. We discuss the cosmological model that arises in this context and present a joint analysis of observations of the first acoustic peak in the cosmic microwave background (CMB) anisotropy spectrum, the Hubble diagram for supernovas of type Ia (SNIa), the distance scale of baryonic acoustic oscillations (BAO) and the distribution of large scale structures (LSS). We show that a good concordance is obtained, albeit with a higher value of the present matter abundance than in the standard model.The gravitation of vacuum fluctuations is in general a difficult problem, since their energy density usually depends on the renormalization procedure and on an adequate definition of the vacuum state in the curved background. In the case of conformal fields in de Sitter spacetime, the renormalized vacuum density is Λ ≈ H 4 [1,2,3,4], which in a low-energy universe leads to a too tiny cosmological term.In the case we consider the vacuum energy of interacting fields, it has been suggested that in a low energy, approximately de Sitter background the vacuum condensate originated from the QCD phase transition leads to Λ ≈ m 3 H, where m ≈ 150 MeV is the energy scale of the transition [5,6,7,8,9,10,11]. These results are in fact intuitive. In a de Sitter background the energy per observable degree of freedom is given by the temperature of the horizon, E ≈ H. For a massless free field this energy is distributed in a volume 1/H 3 , leading to a density Λ ≈ H 4 , as above. For a strongly interacting field in a low energy space-time, on the other hand, the occupied volume is 1/m 3 , owing to confinement, and the expected density is Λ ≈ m 3 H.

show abstract

“…We are, in this case, inferring a variation law for the cosmological term, which has already been considered in the literature on the basis of different arguments [16]- [23] (for other variation laws for the cosmological term, see, for instance, [24]- [27]). We will show that this ansatz leads to a set of solutions larger than the first one, containing its solutions as a particular case.…”

Section: Introductionmentioning

confidence: 99%

Exact solutions of Brans–Dicke cosmology with decaying vacuum density

Montenegro¹,

Carneiro²

2006

Class. Quantum Grav.

View full text Add to dashboard Cite

We investigate cosmological solutions of Brans-Dicke theory with both the vacuum energy density and the gravitational constant decaying linearly with the Hubble parameter. A particular class of them, with constant deceleration factor, sheds light on the cosmological constant problems, leading to a presently small vacuum term, and to a constant ratio between the vacuum and matter energy densities. By fixing the only free parameter of these solutions, we obtain cosmological parameters in accordance with observations of both the relative matter density and the universe age. In addition, we have three other solutions, with Brans-Dicke parameter ω = −1 and negative cosmological term, two of them with a future singularity of big-rip type. Although interesting from the theoretical point of view, two of them are not in agreement with the observed universe. The third one leads, in the limit of large times, to a constant relative matter density, being also a possible solution to the cosmic coincidence problem.

show abstract

A Cosmological Concordance Model with Particle Creation

Alcaniz

¹

,

Borges

²

,

Carneiro

³

et al. 2014

Springer Proceedings in Physics

Self Cite

View full text Add to dashboard Cite

A constant-rate creation of dark particles in the late-time FLRW spacetime provides a cosmological model in accordance with precise observational tests. The matter creation backreaction implies in this context a vacuum energy density scaling linearly with the Hubble parameter, which is consistent with the vacuum expectation value of the QCD condensate in a low-energy expanding spacetime. Both the cosmological constant and coincidence problems are alleviated in this scenario. We discuss the cosmological model that arises in this context and present a joint analysis of observations of the first acoustic peak in the cosmic microwave background (CMB) anisotropy spectrum, the Hubble diagram for supernovas of type Ia (SNIa), the distance scale of baryonic acoustic oscillations (BAO) and the distribution of large scale structures (LSS). We show that a good concordance is obtained, albeit with a higher value of the present matter abundance than in the standard model.The gravitation of vacuum fluctuations is in general a difficult problem, since their energy density usually depends on the renormalization procedure and on an adequate definition of the vacuum state in the curved background. In the case of conformal fields in de Sitter spacetime, the renormalized vacuum density is Λ ≈ H 4 [1,2,3,4], which in a low-energy universe leads to a too tiny cosmological term.In the case we consider the vacuum energy of interacting fields, it has been suggested that in a low energy, approximately de Sitter background the vacuum condensate originated from the QCD phase transition leads to Λ ≈ m 3 H, where m ≈ 150 MeV is the energy scale of the transition [5,6,7,8,9,10,11]. These results are in fact intuitive. In a de Sitter background the energy per observable degree of freedom is given by the temperature of the horizon, E ≈ H. For a massless free field this energy is distributed in a volume 1/H 3 , leading to a density Λ ≈ H 4 , as above. For a strongly interacting field in a low energy space-time, on the other hand, the occupied volume is 1/m 3 , owing to confinement, and the expected density is Λ ≈ m 3 H.

show abstract

Supernova constraints on decaying vacuum cosmology

Cited by 61 publications

References 73 publications

Concordance Cosmology with Particle Creation

Concordance Cosmology with Particle Creation

Exact solutions of Brans–Dicke cosmology with decaying vacuum density

A Cosmological Concordance Model with Particle Creation

Contact Info

Product

Resources

About