Is there supernova evidence for dark energy metamorphosis?

Alam, Ujjaini; Sahni, Varun; Saini, Tarun Deep; Starobinsky, Alexei A.

doi:10.1111/j.1365-2966.2004.08189.x

Cited by 484 publications

(494 citation statements)

References 86 publications

Supporting

Mentioning

433

Contrasting

Unclassified

Order By: Relevance

“…Note that this ansatz for the Hubble parameter has been tested and found to give accurate results for a variety of cosmological models [18,19]. Its main features are: (i) it accounts for a matter dominated regime at high redshift, (ii) it is exact for DE being the mixture of a cosmological constant and non-relativistic domain walls and cosmic strings (in other words, for DE consisting of 3 components with with w = −1, w = −1/3 and w = −2/3), (iii) it can satisfactorily emulate DE with an evolving equation of state including Braneworld models and phantom models admitting regions with w < −1 (moreover, the DE effective energy density ρ DE may even become negative in such models).…”

Section: Methodsmentioning

confidence: 99%

Exploring the properties of dark energy using type-Ia supernovae and other datasets

Alam

Sahni

Starobinsky

2007

J. Cosmol. Astropart. Phys.

Self Cite

115

View full text Add to dashboard Cite

We reconstruct dark energy properties from two complementary supernova datasets -the newly released Gold+HST sample and SNLS. The results obtained are consistent with standard ΛCDM model within 2σ error bars although the Gold+HST data favour evolving dark energy slightly more than SNLS. Using complementary data from baryon acoustic oscillations and the cosmic microwave background to constrain dark energy, we find that our results in this case are strongly dependent on the present value of the matter density Ω0m. Consequently, no firm conclusions regarding constancy or variability of dark energy density can be drawn from these data alone unless the value of Ω0m is known to an accuracy of a few percent. However, possible variability is significantly restricted if this data is used in conjunction with supernova data. INTRODUCTIONThere is a growing consensus in cosmology that the Universe is currently accelerating. Perhaps the simplest explanation of this property is the presence of a positive cosmological constant Λ. Although Λ appears to explain all current observations satisfactorily, to do so its value must necessarily be very small Λ/8πG ≃ 10 −47 GeV 4 . So, it represents a new small constant of nature in addition to those known from elementary particle physics. However, since it is not known at present how to derive it from these other small constants and it is even unclear if it should be exactly constant, other phenomenological explanations for cosmic acceleration have been suggested. Collectively called dark energy (DE) models, they are based either on the introduction of new physical fields (quintessence and phantom models, the Chaplygin gas, etc.), or on geometrical approaches which attempt to generate acceleration by means of a change in the laws of gravity and, therefore, the geometry of space-time [1]. Scalar-tensor gravity, R+ f (R) gravity and higher dimensional 'Braneworld' models are prominent members of this second category.The growing number of DE models has inspired a complementary approach whose aim is to reconstruct properties of DE directly from observations in a quasi-model independent manner, see the recent review [2] and the extensive list of references therein. The aim of this paper is to investigate what new insights can be obtained about DE using the most recent data, and to see whether or not these data strengthen previously obtained results on the closeness of DE to Λ. We study two different supernova samples -the newly released Gold+HST sample [3] and SNLS data [4] to see what constraints follow from them on possible evolution of DE. We also investigate the possibility of extracting information about the nature of DE from datasets other than the supernova data. To this end, we consider what follows from the value of the R parameter characterizing acoustic peaks in the angular power spectrum of the cosmic microwave background (CMB) [5,6] and from the SDSS result on the baryon acoustic oscillation peak (BAO) [7]. DATA AND METHODOLOGYIn this paper, we shall compare the reconstruction re...

show abstract

Section: Methodsmentioning

confidence: 99%

Exploring the properties of dark energy using type-Ia supernovae and other datasets

Alam

Sahni

Starobinsky

2007

J. Cosmol. Astropart. Phys.

Self Cite

115

View full text Add to dashboard Cite

show abstract

“…Granted that string gas cosmologies are capable of crossing the "phantom divide" in one direction, it seems natural to suppose that they can cross in the other, from w ≥ −1 to w < −1. In fact, as Hu has recently stressed [41], such a crossing must occur if, as has been proposed [38], the observational data suggest that w is evolving rapidly. The question is far from academic, since a recent period of NEC violation is entirely compatible with the observational data [46].…”

Section: String Gases Topology and The Null Energy Conditionmentioning

confidence: 99%

The phantom divide in string gas cosmology

McInnes

2005

Nuclear Physics B

102

View full text Add to dashboard Cite

One of the main virtues of string gas cosmology is that it resolves cosmological singularities. Since the Universe can be approximated by a locally asymptotically de Sitter spacetime by the end of the inflationary era, a singularity theorem implies that these cosmologies effectively violate the Null Energy Condition [not just the Strong Energy Condition]. We stress that this is an extremely robust result, which does not depend on assuming that the spatial sections remain precisely flat in the early Universe. This means, however, that it must be possible for string cosmologies to cross the recently much-discussed phantom divide [from w < −1 to w > −1, where w is the equation-ofstate parameter]. This naturally raises the question as to whether the phantom divide can be crossed again, to account for recent observations suggesting that w < −1 at the present time. We argue that non-perturbative string effects rule out this possibility, even if the NEC violation in question is only "effective".

show abstract

“…Thus for instance, it is known that the Gold dataset [1] prefers models with w X < ÿ1 [17,18], the so called phantom dark energy models, whereas for the more recent Supernova Legacy Survey (SNLS) [2], the best fit is closer to a pure cosmological constant [19,20]. Therefore it is worth exploring what kind of constraints are imposed in each case, and this is the aim of the present work.…”

Section: Introductionmentioning

confidence: 99%

Confronting quintessence models with recent high-redshift supernovae data

Barro

Maroto

2006

Phys. Rev. D

View full text Add to dashboard Cite

We confront the predictions of different quintessence models with recent measurements of the luminosity distance from two sets of supernovae type Ia. In particular, we consider the 157 SNe Ia in the Gold dataset with z < 1:7, and the more recent data containing 71 supernovae obtained by the Supernova Legacy Survey (SNLS) with z < 1. We numerically solve the evolution equations for the Ratra-Peebles inverse power-law model, the double exponential and the hyperbolic cosine quintessence models. We obtain confidence regions from the two datasets in the M ÿ and M ÿ w planes for the different models and compare their predictions with dark energy models with constant equation of state.

show abstract

Is there supernova evidence for dark energy metamorphosis?

Cited by 484 publications

References 86 publications

Exploring the properties of dark energy using type-Ia supernovae and other datasets

Exploring the properties of dark energy using type-Ia supernovae and other datasets

The phantom divide in string gas cosmology

Confronting quintessence models with recent high-redshift supernovae data

Contact Info

Product

Resources

About