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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