Amjad Ashoorioon

School of Physics, Institute for Research in Fundamental Sciences (IPM)

Tossin’ and Turnin’ in the Landscape: Primordial Black Holes and Gravitational Waves

Abstract: The landscape of String Theory could not only contain a lot of metastable vacua, but also a lot of troughs connecting them. These troughs are separated by barriers. Primordial inflation could have happened through rolling on one of these troughs.  While rolling slowly on the false vacuum trough during inflation, bubbles of true vacuum nucleate. These bubbles can collapse to primordial black holes (PBHs) after the end of slow-roll inflation. With this picture in mind, we explicitly construct double-field inflationary models at relatively small energy scales, which realizes this picture and satisfies the latest Planck constraints at the scales that contribute to the cosmic microwave background (CMB). We will show that the shape of the mass distribution of the PBHs is dependent on how inflation ends and the Universe settles from the false trough to the true one. The end of inflation can also be probed by examining the gravitational waves spectrum, which could be generated from both a first or second-order phase transition during or after the end of slow-roll inflation. The spectra that these two ways of settling to the true vacuum leave behind, could be distinguished from the shape, and sometimes from the amplitude. In particular, we apply this framework to PBHs in the mass range, 10^{-17}–10^{-13} M_{\odot}, which can constitute the whole dark matter budget and identify a correlated SGWB signal within the DECIGO and BBO sensitivity bands. Alternatively trying to interpret the recently claimed NANOGrav 12.5 year signal within this framework, lead us to LIGO mass and heavier PBHs. We discover that in the latter case, only a first-order phase transition can generate a signal as strong as NANOGrav.

یکشنبه 24  بهمن 1400، ساعت 19:00

Sunday 13 February 2022 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest