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Abstract：
When the curvature perturbation R is enhanced in the single field inflation, the deviation to the slow-roll attractor usually leads to significant nonlinear effects. I will show how to derive the fully nonlinear relation of R(δφ) in a single-field inflation with a piecewise-quadratic potential, which is a sum of logarithms contributed by all the non-attractor stages. When only one non-attractor stage dominates, the probability distribution function of R shows the renowned "exponential tail”, or the Gumbel-distribution-like tail, depending on the signature of the inflaton mass. Such a result will be useful when calculating the primordial black hole abundance and the induced gravitational waves. I will also briefly discuss the implication on the recent pulsar timing array signals.
Biography:
Shi Pi is an associate professor in Institute of Theoretical Physics, Chinese Academy of Sciences (ITP-CAS). He got the PhD in Peking University in 2013, and then went to APCTP in Korea (2013-2015), ITP-CAS (2015-2017), YITP in Kyoto University (2017), and Kavli IPMU in the University of Tokyo (2017-2020) as a postdoc. His research interests are cosmology and gravity, including but not limited to inflation model building, cosmological perturbation theory, modified gravity, dark energy, as well as the gravitational wave astronomy/cosmology.
Host：Prof. Yifeng Sun
Alternative online link: https://meeting.tencent.com/dm/wxC17OIr7Fpq
(id: 423480770 passcode: 123456）