Post-Planck dark energy constraints

Abstract

Abstract. We constrain plausible dark energy models, parametrized by multiple candidate equation of state, using the recently published Cosmic Microwave Background (CMB) temperature anisotropy data from Planck together with the WMAP-9 low-ℓ polarization data and data from low redshift surveys. To circumvent the limitations of any particular equation of state towards describing all existing dark energy models, we work with three different equation of state covering a broader class of dark energy models and, hence, provide more robust and generic constraints on the dark energy properties. We show that a clear tension exists between dark energy constraints from CMB and non-CMB observations when one allows for dark energy models having both phantom and non-phantom behavior; while CMB is more favorable to phantom models, the low-z data prefers model with behavior close to a Cosmological Constant. Further, we reconstruct the equation of state of dark energy as a function of redshift using the results from combined CMB and non-CMB data and find that Cosmological Constant lies outside the 1σ band for multiple dark energy models allowing phantom behavior. A considerable fine tuning is needed to keep models with strict non-phantom history inside 2σ allowed range. This result might motivate one to construct phantom models of dark energy, which is achievable in the presence of higher derivative operators as in string theory. However, disallowing phantom behavior, based only on strong theoretical prior, leads to both CMB and non-CMB datasets agree on the nature of dark energy, with the mean equation of state being very close to the Cosmological Constant. Finally, to illustrate the impact of additional dark energy parameters on other cosmological parameters, we provide the cosmological parameter constraints for the "Standard Model of Cosmology" including an evolving dark energy component, for the different dark energy models.

Study of non-canonical scalar field model using various parametrizations of dark energy equation of state

“…It should be noted that the GCG model has been studied by many authors for the parameter range, 0 ≤ α ≤ 1 [17,18]. However, in this work, we have obtained the best fit values of the parameter A s and Ω m0 by fixing the value of other parameter α within the range, −1 < α < 0 (shown in Table 4), as α < 0, is in good agreement with the work of Sen and Scherrer [104], Gong [105] and Hazra et al [41]. It has also been noticed from Table 4 that the range of the allowed values of Ω m0 match well with the previous results obtained by Riess et al [106] and Sahni et al [107].…”

“…It may be noted that the standard flat CDM model is represented by this parametrization with the choice of ω 0 = −1 and ω 1 = 0. In fact, many functional forms of f (z) have been considered in literature [33][34][35][36][37][38][39][40][41][42][43]. In this present work, we shall use four popular parametrizations of ω φ (z) to study the behavior of the deceleration parameter q(z) of this noncanonical scalar field model.…”

“…In this context, a large number of parametrizations of DE equation of state have been proposed [33][34][35][36][37][38][39][40][41][42][43][44], which could provide solutions to a number of cosmological problems. However, most of these analysis have been carried out for canonical scalar field models of DE.…”

Inflationary generalized Chaplygin gas and dark energy in light of the Planck and BICEP2 experiments

“…This is consistent with the earlier results obtained by Hazra et al [13]. But with the addition of BICEP2 data, the improvement in χ 2 is roughly 4.3 for CPLDE models which is roughly three times of what one gets without BICEP2.…”

“…Initially considered as a natural candidate for a unification of dark matter and dark energy (UDM), it was later shown that this particular UDM behaviour is not suitable for the structure formation of the Universe [12]. But this fluid can be a possible dark energy candidate which tracks the background fluid initially and subsequently exits the tracking regime and starts acting as a dark energy candidate [13].…”