Generalised Emergent Dark Energy Model: Confronting $Lambda$ and PEDE. (arXiv:2001.05103v1 [astro-ph.CO])

Generalised Emergent Dark Energy Model: Confronting $Lambda$ and PEDE. (arXiv:2001.05103v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Li_X/0/1/0/all/0/1">Xiaolei Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shafieloo_A/0/1/0/all/0/1">Arman Shafieloo</a>

We introduce a generalised form of an emergent dark energy model with one
degree of freedom for the dark energy sector that has the flexibility to
include both $Lambda$CDM as well as the PEDE model (Phenomenologically
Emergent Dark Energy) proposed by Li & Shafieloo (2019) as two of its special
limits. This allows us to compare statistically these models in a
straightforward way and following conventional Bayesian approach. The free
parameter for the dark energy sector, namely $Delta$, has the value of $0$ for
the case of the $Lambda$ and $1$ for the case of PEDE and its posterior
fitting the generalised parametric form to different data can directly show the
consistency of the models to the data. Fitting the introduced parametric form
to Planck CMB data and most recent $H_0$ results from local observations of
Cepheids and Supernovae (Riess et al. 2019), we show that the $Delta=0$
associated with the $Lambda$CDM model would fall out of 4$sigma$ confidence
limits of the derived posterior of the $Delta$ parameter. In contrast, PEDE
model can satisfy the combination of the observations. This is another support
for the case of PEDE model with respect to the standard $Lambda$CDM model if
we trust the reliability of both Planck CMB data and local $H_0$ observations.

We introduce a generalised form of an emergent dark energy model with one
degree of freedom for the dark energy sector that has the flexibility to
include both $Lambda$CDM as well as the PEDE model (Phenomenologically
Emergent Dark Energy) proposed by Li & Shafieloo (2019) as two of its special
limits. This allows us to compare statistically these models in a
straightforward way and following conventional Bayesian approach. The free
parameter for the dark energy sector, namely $Delta$, has the value of $0$ for
the case of the $Lambda$ and $1$ for the case of PEDE and its posterior
fitting the generalised parametric form to different data can directly show the
consistency of the models to the data. Fitting the introduced parametric form
to Planck CMB data and most recent $H_0$ results from local observations of
Cepheids and Supernovae (Riess et al. 2019), we show that the $Delta=0$
associated with the $Lambda$CDM model would fall out of 4$sigma$ confidence
limits of the derived posterior of the $Delta$ parameter. In contrast, PEDE
model can satisfy the combination of the observations. This is another support
for the case of PEDE model with respect to the standard $Lambda$CDM model if
we trust the reliability of both Planck CMB data and local $H_0$ observations.

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