Exploring the CMB Power Suppression in Canonical Inflation Models. (arXiv:1904.07249v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gonzalez_M/0/1/0/all/0/1">Mark Gonzalez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hertzberg_M/0/1/0/all/0/1">Mark P. Hertzberg</a>

There exists some evidence of a suppression in power in the CMB multipoles
around $l sim 20-30$. If taken seriously, this is in tension with the simplest
inflationary models driven by a single scalar field with a standard type of
slowly varying potential function $V(phi)$. Such potential functions generate
a nearly scale invariant spectrum and so they do not possess the requisite
suppression in power. In this paper we explore if canonical two-derivative
inflation models, with a step-like feature in the potential, can improve
agreement with data. We find that improvement can be made when one utilizes the
standard slow-roll approximation formula for the power spectrum. However, we
find that in order to have a feature in the power spectrum that is sufficiently
localized so as to not significantly disrupt higher $l$ or lower $l$, the
potential’s step-like feature must be so sharp that the standard slow-roll
approximations break down. This leads us to perform an exact computation of the
power spectrum by solving for the Bunch-Davies mode functions numerically. We
find that the corresponding CMB multipoles do not provide a good agreement with
the data. We conclude that, unless there is fine-tuning, canonical inflation
models do not fit this suppression in the data.

There exists some evidence of a suppression in power in the CMB multipoles
around $l sim 20-30$. If taken seriously, this is in tension with the simplest
inflationary models driven by a single scalar field with a standard type of
slowly varying potential function $V(phi)$. Such potential functions generate
a nearly scale invariant spectrum and so they do not possess the requisite
suppression in power. In this paper we explore if canonical two-derivative
inflation models, with a step-like feature in the potential, can improve
agreement with data. We find that improvement can be made when one utilizes the
standard slow-roll approximation formula for the power spectrum. However, we
find that in order to have a feature in the power spectrum that is sufficiently
localized so as to not significantly disrupt higher $l$ or lower $l$, the
potential’s step-like feature must be so sharp that the standard slow-roll
approximations break down. This leads us to perform an exact computation of the
power spectrum by solving for the Bunch-Davies mode functions numerically. We
find that the corresponding CMB multipoles do not provide a good agreement with
the data. We conclude that, unless there is fine-tuning, canonical inflation
models do not fit this suppression in the data.

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