Title: Analytic Formulae for Inflationary Correlators with Dynamical Mass

Speaker: Fumiya Sano (Tokyo Institute of Technology)

Time: 2:00 pm, Nov 23 (Thursday) 2023

Location: 理科楼C302

Abstract: Massive fields can imprint unique oscillatory features on primordial correlation functions or inflationary correlators, which is dubbed the cosmological collider signal. In this work, we analytically investigate the effects of a time-dependent mass of a scalar field on inflationary correlators, extending previous numerical studies and implementing techniques developed in the cosmological bootstrap program. The time-dependent mass is in general induced by couplings to the slow-roll inflaton background, with particularly significant effects in the case of non-derivative couplings. By linearly approximating the time dependence, the mode function of the massive scalar is computed analytically, on which we derive analytic formulae for two-, three-, and four-point correlators with the tree-level exchange of the massive scalar. The obtained formulae are utilized to discuss the phenomenological impacts on the power spectrum and bispectrum, and it is found that the scaling behavior of the bispectrum in the squeezed configuration, i.e., the cosmological collider signal, is modified from a time-dependent Boltzmann suppression. By investigating the scaling behavior in detail, we are in principle able to determine the non-derivative couplings between the inflaton and the massive particle. 

Bio: I am a first-year PhD student at Tokyo Institute of Technology, Japan, and I am working as a Student Research Assistant at Cosmology, Gravity and Astroparticle Group in Center for Theoretical Physics of the Universe (CTPU-CGA), Institute for Basic Science, Korea.

My research interest lies mostly on early universe cosmology and its connection to high energy physics, especially beyond-Standard-Model particle theory as well as observational signatures of quantum nature in gravity.