Analytic Formulae for Inflationary Correlators with Dynamical Mass

Abstract

Massive fields can imprint distinct oscillatory features, known as the cosmological collider signal, onto primordial correlation functions or inflationary correlators. In this work, we delve into an analytical exploration of the effects of a time-dependent mass of a scalar field on inflationary correlators, which uncover novel phenomenological implications that have remained obscured in previous studies. The time-dependent mass for the heavy particle is naturally induced by couplings to the slow-roll inflaton background, leading to sizable effects, particularly when the couplings do not respect the shift symmetry of the inflaton. Our calculation incorporates techniques developed in the cosmological bootstrap program. Furthermore, by employing a linear order approximation for the time dependence, we obtain an analytical expression for mode functions of the massive scalar. Based on these foundations, we derive analytical formulae for two-, three-, and four-point correlators with the tree-level exchange of the massive scalar. The formulae enable a comprehensive analysis of the phenomenological impact. Notably, our findings reveal modifications in the scaling behavior of the bispectrum in the squeezed configuration, i.e., the cosmological collider signal, characterized by a scale-dependent Boltzmann suppression. We also emphasize that couplings between the inflation and the massive particle can be determined in principle by observing the scaling behavior in detail.

About the Speaker

Mr. Fumiya SANO is a first-year PhD student at Tokyo Institute of Technology, Japan, and he is working as a Student Research Assistant at Cosmology, Gravity and Astroparticle Group in the Center for Theoretical Physics of the Universe (CTPU-CGA), Institute for Basic Science, Korea. His research interest lies mostly in early universe cosmology and its connection to high energy physics, as well as observational signatures of quantum nature in gravitational theories.

About the Program

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