Parametrizing the transition to the phantom epoch with supernovae Ia and standard rulers

Abstract

The reconstruction of a (non)canonical scalar field Lagrangian from the dark energy Equation of State (EoS) parameter is studied, where it is shown that any EoS parametrization can be well reconstructed in terms of scalar fields. Several examples of EoS parameters are studied and the particular scalar field Lagrangian is reconstructed. Then, we propose some new parametrizations that may present a (fast) transition to a phantom dark energy EoS (where wDE < −1) and the scalar field Lagrangian is also reconstructed numerically. Furthermore, the properties of these parametrizations of the dark energy EoS are studied by using supernovae Ia data (HST Cluster Supernova Survey) combined with Standard Ruler datasets [Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO)] and its comparison with the ΛCDM model is analyzed. Then, the best fit of the models is obtained, which provides some information about whether a phantom transition may be supported by the observations. In this regard, the crossing of the phantom barrier is allowed statistically but the occurrence of a future singularity seems unlikely.PACS numbers: 98.80 -k, 98.80.Es

Observational constraints on cosmological future singularities

“…This was not obvious a priori, since none of our parameterizations contain CDM in its parameter space. Hence, as shown in previous references [38][39][40][41][42], a singular scenario cannot be discarded right away from tests of the background evolution and the time remaining for the occurrence of a future singularity may be shorter than expected. However, we need to stress that CDM has become the standard model of cosmology because of its outstanding performance in fitting most cosmological observations, not only the ones considered in our analysis, so that in order to be able to establish a com-pelling scenario with a future singularity on equal footing as CDM, we would need to show its ability to fit the rest of cosmological observations, including those sensitive to the perturbations.…”

“…However, it will be useful to have some estimation on how close to us a given singularity can be and, therefore, have an idea of how far in the future we could extrapolate a model with a certain type of future singularity. It is important to notice that an effective equation of state for dark energy w < −1 is within the confidence regions of observational data [38][39][40][41][42], so the possibility of having a future singularity is plausible. Moreover, such models have also received attention because of some theoretical implications, since possible quantum effects close to the singularity become important.…”

Constrainingf(T,T)gravity models using type Ia supernovae

“…Alternatively,μ can be fixed to a value. Following the reasoning in [30], we expand χ 2 in Eq. (4.5) as 6) where the coefficients are given by Marginalizing overμ amounts to considering the follow-…”

Crossing the phantom divide line as an effect of quantum transitions

“…Nonetheless, the cosmological observations does not provide a lower limit for the value of w. While it has a value close to −1, the values in the range w < −1 are not excluded by the cosmological observations [37][38][39][40][41][42]. Hence, scalar fields with phantom kinetic energy have been introduced in the literature [43,44].…”