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

Abstract

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...

Interacting F(R, T) gravity with modified Chaplygin gas

“…We note that reconstruction of dark energy models was fulfilled in Refs. [56][57][58][59][60] for a minimally scalar field with a potential. Therefore, we take the following parametrization as The value of EoS of late time confirms the result of [63] in a flat Universe.…”

Perturbative quantum gravity comes of age

“…[57][58][59][60] Note that adding the matter couplings required to produce reheating puts 2-4 at risk because matter loop effects induce Coleman-Weinberg corrections to the inflaton effective potential. Nor does fundamental theory provide any explanation for why the cosmological constant is so small.…”

Reconstruction of the equation of state for the cyclic universes in homogeneous and isotropic cosmology

“…ForḢ = 0, eff = −1, which corresponds to the cosmological constant. It is significant to remark that recent various observational data [139][140][141][142][143][144] implies that the crossing of the phantom divide line of DE = −1 occurred in the near past. Here, DE is the EoS for dark energy and at the dark energy dominated stage, it can be regarded that ≈ DE ≈ eff .…”