Test of the Chevallier-Polarski-Linder parametrization for rapid dark energy equation of state transitions

Abstract

We test the robustness and flexibility of the Chevallier-Polarski-Linder (CPL) parameterization of the Dark Energy equation of state w(z) = w0 + wa z 1+z in recovering a four-parameter step-like fiducial model. We constrain the parameter space region of the underlying fiducial model where the CPL parameterization offers a reliable reconstruction. It turns out that non negligible biases leak into the results for recent (z < 2.5) rapid transitions, but that CPL yields a good reconstruction in all other cases. The presented analysis is performed with supernova Ia data as forecasted for a space mission like SNAP/JDEM, combined with future expectations for the CMB shift parameter R and the BAO parameter A.

Model independent constraints on mass-varying neutrino scenarios

“…In this sense, it seemed to us that Eq. (18) would give us the best ''priceto-earnings ratio'' among the possibilities to use phenomenologically motivated parametrizations for the massvarying neutrinos, although certainly there could be similar proposals equally viable, such as for instance the possibil- ity of adapting for the mass variation the parametrization used for the dark energy equation of state in [42,43]. There, the transition between two constant values of the equation of state exhibits a tanh½À t ðu À u t Þ dependence, where À t is responsible for the duration of the transition and u t is related to its halfway point.…”

The Measurement of and in Bianchi Type-I Anisotropic Dark Energy Cosmological Model with Constant Deceleration Parameter in Bimetric Theory of Gravitation

“…These measurements combined with red-shift data for the supernovae and predicted an accelerating universe. For closed universe, the Hubble parameter , H the matter energy density parameter M  and the dark energy density parameter ,   predicted by Tegmark [12] by Sahni et al [23][24].This parameter ) ( t  have been calculated with some reasoning with reduced to some simple parameterization of the dependences by many authors [25][26][27][28][29][30]. The results from SNe Ia data collaborated with CMBR anisotropy and galaxy clustering statistics (Tegmark et al [12] [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54].…”

“…Thus the law of variation of Hubble parameter gives two types of the expansion in the universe i.e., (i) power law expansion given by (26) and (ii) exponential law expansion given by (27).…”

“…Integrate (23), we obtain the laws of variation of parameter for the average scale factor a as (27) where 1 c and 2 c are integrating constants. Thus the law of variation of Hubble parameter gives two types of the expansion in the universe i.e., (i) power law expansion given by (26) and (ii) exponential law expansion given by (27).…”

“…The solutions have been obtained in power law (26) and in exponential law (27) for accelerating as well as for decelerating phase of the universe. 2.…”