Null test for interactions in the dark sector. (arXiv:1812.02333v1 [astro-ph.CO])

Null test for interactions in the dark sector. (arXiv:1812.02333v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Marttens_R/0/1/0/all/0/1">Rodrigo von Marttens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marra_V/0/1/0/all/0/1">Valerio Marra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casarini_L/0/1/0/all/0/1">Luciano Casarini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzalez_J/0/1/0/all/0/1">J. E. Gonzalez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alcaniz_J/0/1/0/all/0/1">Jailson Alcaniz</a>

Since there is no known symmetry in Nature that prevents a non-minimal
coupling between the dark energy (DE) and cold dark matter (CDM) components,
such a possibility constitutes an alternative to standard cosmology, with its
theoretical and observational consequences being of great interest. In this
paper we propose a new null test on the standard evolution of the dark sector
based on the time dependence of the ratio between the CDM and DE energy
densities which, in the standard $Lambda$CDM scenario, scales necessarily as
$a^{-3}$. We use the latest measurements of type Ia supernovae, cosmic
chronometers and angular baryonic acoustic oscillations to reconstruct the
expansion history using model-independent Machine Learning techniques, namely,
the Linear Model formalism and Gaussian Processes. We find that while the
standard evolution is consistent with the data at $3sigma$ level, some
deviations from the $Lambda$CDM model are found at low redshifts, which may be
associated with the current tension between local and global determinations of
$H_0$.

Since there is no known symmetry in Nature that prevents a non-minimal
coupling between the dark energy (DE) and cold dark matter (CDM) components,
such a possibility constitutes an alternative to standard cosmology, with its
theoretical and observational consequences being of great interest. In this
paper we propose a new null test on the standard evolution of the dark sector
based on the time dependence of the ratio between the CDM and DE energy
densities which, in the standard $Lambda$CDM scenario, scales necessarily as
$a^{-3}$. We use the latest measurements of type Ia supernovae, cosmic
chronometers and angular baryonic acoustic oscillations to reconstruct the
expansion history using model-independent Machine Learning techniques, namely,
the Linear Model formalism and Gaussian Processes. We find that while the
standard evolution is consistent with the data at $3sigma$ level, some
deviations from the $Lambda$CDM model are found at low redshifts, which may be
associated with the current tension between local and global determinations of
$H_0$.

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