Hockey-stick dark energy is not a solution to the $H_0$ crisis. (arXiv:2101.08641v1 [astro-ph.CO])

<a href="http://arxiv.org/find/astro-ph/1/au:+Camarena_D/0/1/0/all/0/1">David Camarena</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marra_V/0/1/0/all/0/1">Valerio Marra</a>

A dark-energy which behaves as the cosmological constant until a sudden

phantom transition at very-low redshift ($z<0.1$) seems to solve the >4$sigma$

disagreement between the local and high-redshift determinations of the Hubble

constant, while maintaining the phenomenological success of the $Lambda$CDM

model with respect to the other observables. Here, we show that such a

hockey-stick dark energy cannot solve the $H_0$ crisis. The basic reason is

that the supernova absolute magnitude $M_B$ that is used to derive the local

$H_0$ constraint is not compatible with the $M_B$ that is necessary to fit

supernova, BAO and CMB data, and this disagreement is not solved by a sudden

phantom transition at very-low redshift. Finally, we encourage the community to

adopt in the statistical analyses the prior on the supernova absolute magnitude

$M_B$ as an alternative to the prior on $H_0$. The three reasons are: i) one

avoids double counting of low-redshift supernovae, ii) one avoids fixing the

deceleration parameter to the standard model value $q_0=-0.55$, iii) one

includes in the analysis the fact that $M_B$ is constrained by local

calibration, an information which would otherwise be neglected in the analysis,

biasing both model selection and parameter constraints.

A dark-energy which behaves as the cosmological constant until a sudden

phantom transition at very-low redshift ($z<0.1$) seems to solve the >4$sigma$

disagreement between the local and high-redshift determinations of the Hubble

constant, while maintaining the phenomenological success of the $Lambda$CDM

model with respect to the other observables. Here, we show that such a

hockey-stick dark energy cannot solve the $H_0$ crisis. The basic reason is

that the supernova absolute magnitude $M_B$ that is used to derive the local

$H_0$ constraint is not compatible with the $M_B$ that is necessary to fit

supernova, BAO and CMB data, and this disagreement is not solved by a sudden

phantom transition at very-low redshift. Finally, we encourage the community to

adopt in the statistical analyses the prior on the supernova absolute magnitude

$M_B$ as an alternative to the prior on $H_0$. The three reasons are: i) one

avoids double counting of low-redshift supernovae, ii) one avoids fixing the

deceleration parameter to the standard model value $q_0=-0.55$, iii) one

includes in the analysis the fact that $M_B$ is constrained by local

calibration, an information which would otherwise be neglected in the analysis,

biasing both model selection and parameter constraints.

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