期刊
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
卷 -, 期 7, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2018/07/005
关键词
inflation; primordial black holes; string theory and cosmology; axions
资金
- STFC [ST/P00055X/1]
- STFC [ST/P00055X/1] Funding Source: UKRI
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.
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