Chameleon Early Dark Energy and the Hubble Tension. (arXiv:2106.13290v2 [astro-ph.CO] UPDATED)

Chameleon Early Dark Energy and the Hubble Tension. (arXiv:2106.13290v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Karwal_T/0/1/0/all/0/1">Tanvi Karwal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raveri_M/0/1/0/all/0/1">Marco Raveri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jain_B/0/1/0/all/0/1">Bhuvnesh Jain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khoury_J/0/1/0/all/0/1">Justin Khoury</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trodden_M/0/1/0/all/0/1">Mark Trodden</a>

Early dark energy (EDE) offers a particularly interesting theoretical
approach to the Hubble tension, albeit one that introduces its own set of
challenges, including a new `why then’ problem related to the EDE injection
time at matter-radiation equality, and a mild worsening of the large-scale
structure (LSS) tension. Both these challenges center on the properties of dark
matter, which becomes the dominant component of the Universe at EDE injection
and is also responsible for seeding LSS. Motivated by this, we present the
potential of couplings between EDE and dark matter to address these challenges,
focusing on a mechanism similar to chameleon dark energy theories, deeming this
chameleon early dark energy (CEDE). We present relevant background and
perturbation equations and study the dynamics of the case of a quartic scalar
potential and an exponential coupling.

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