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SUMMARY:Pierre Auclair (U. Paris\, CNRS)
DTSTART:20201112T150000Z
DTEND:20201112T160000Z
DTSTAMP:20260423T003234Z
UID:IFTWeb/15
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/IFTWeb/15/">
 Primordial black holes from metric preheating: mass fraction in the excurs
 ion-set approach</a>\nby Pierre Auclair (U. Paris\, CNRS) as part of IFT-M
 adrid Webinars\n\n\nAbstract\nAfter inflation\, the oscillations of the in
 flaton at the bottom of its potential source a parametric instability in t
 he equation of motion of scalar perturbations. In a recent paper by Martin
  et al. 2020\, it was shown that the production of ultra-light PBHs from t
 his instability is so efficient that they can quickly come to dominate the
  universe content. However their abundance is usually computed by assuming
  that they are rare objects that are formed at around a single scale\, and
  the probability that a given region of the universe ends up in a black ho
 le can be inferred from the knowledge of the primordial curvature power sp
 ectrum at that scale. Such an approach may however fail in cases where PBH
 s are abundantly produced\, and/or if they arise over a wide range of mass
 es.\n\nIn the present seminar\, I will first briefly describe the mechanis
 m of metric preheating and the production of PBHs that is associated to it
 . Then I will give a short introduction on the calculation of the mass fra
 ction and more particularly the excursion set formalism. This framework tr
 anslates the estimation of a mass fraction to the study of a Langevin equa
 tion\; more particularly to the first crossing distribution of a Langevin 
 trajectory with a moving barrier. Finally\, I will present the result of a
 pplying this formalism to the calculation of the mass fraction of PBHs ari
 sing from metric preheating.\n
LOCATION:https://researchseminars.org/talk/IFTWeb/15/
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