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Highly non-Gaussian tails and primordial black holes from single-field inflation
Abstract For primordial perturbations, deviations from Gaussian statistics on the tail of the probability distribution can be associated with non-perturbative effects of inflation. In this paper, we present some particular examples in which the tail of the distribution becomes highly non-Gaussian al...
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Published in: | Journal of cosmology and astroparticle physics 2022-12, Vol.2022 (12), p.34 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Abstract
For primordial perturbations, deviations from Gaussian statistics on the tail of the
probability distribution can be associated with non-perturbative effects of inflation. In this
paper, we present some particular examples in which the tail of the distribution becomes highly
non-Gaussian although the statistics remains almost Gaussian in the perturbative regime. We begin
with an extension of the ultra-slow-roll inflation that incorporates a transition process, where
the inflaton climbs up a tiny potential step at the end of the non-attractor stage before it
converges to the slow-roll attractor. Through this example, we identify the key role of the
off-attractor behaviour for the upward-step transition, and then extend the analysis to another
type of the transition with two slow-roll stages connected by a tiny step. We perform both the
perturbative and non-perturbative analyses of primordial fluctuations generated around the step in
detail, and show that the tiny but nontrivial transition may affect large perturbations in the
tail of the distribution, while the perturbative non-Gaussianity remains small. Our result
indicates that the non-Gaussian tails can have rich phenomenology which has been overlooked in
conventional analyses. We also study the implications of this non-Gaussian tail for the formation
of primordial black holes, and find that their mass fraction can be parametrically amplified by
several orders of magnitudes in comparison with the case of the Gaussian
distribution. Additionally, we also discuss a mechanism of primordial black holes formation for
this upward step inflation model by trapping the inflaton in the bottom of the step. |
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ISSN: | 1475-7516 1475-7516 |
DOI: | 10.1088/1475-7516/2022/12/034 |