Mechanisms for primordial black hole production in string theory

Ozsoy, Ogan, Parameswaran, Susha, Tasinato, Gianmassimo and Zavala, Ivonne
(2018) Mechanisms for primordial black hole production in string theory. Journal of Cosmology and Astroparticle Physics, 2018 (July).

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We consider mechanisms for producing a significant population of primordial black holes (PBHs) within string inspired single field models of inflation. The production of PBHs requires a large amplification in the power spectrum of curvature perturbations between scales associated with CMB and PBH formation. In principle, this can be achieved by temporarily breaking the slow-roll conditions during inflation. In this work, we identify two string setups that can realise this process. In string axion models of inflation, subleading non-perturbative effects can superimpose steep cliffs and gentle plateaus onto the leading axion potential. The cliffs can momentarily violate the slow-roll conditions, and the plateaus can lead to phases of ultra slow-roll inflation. We thus achieve a string motivated model which both matches the Planck observations at CMB scales and produces a population of light PBHs, which can account for an order one fraction of dark matter. In DBI models of inflation, a sharp increase in the speed of sound sourced by a steep downward step in the warp factor can drive the amplification. In this scenario, discovery of PBHs could indicate non-trivial dynamics in the bulk, such as flux-antibrane annihilation at the tip of a warped throat.

Item Type: Article
Uncontrolled Keywords: inflation, primordial black holes, string theory and cosmology, axions
Depositing User: Symplectic Admin
Date Deposited: 10 Dec 2018 11:18
Last Modified: 16 Sep 2022 10:54
DOI: 10.1088/1475-7516/2018/07/005
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