Integrating Out Heavy Modes in the In-in Formalism

Abstract

Effective field theory has been a very fruitful framework in theoretical physics. However, most of its applications focus on the calculation of scattering amplitudes, rather than correlation functions. In this talk, the speaker will discuss several different ways to calculate the in-in correlator starting from the Lagrangian, and show that discrepancies arise between the calculation using the full theory and that from a naive effective Lagrangian. The discrepancies can be cured by carefully taking into account the boundary conditions of the path integral. Finally, it will be shown that in de Sitter background the discrepancies vanish, rendering the calculations of cosmological correlators tractable when coupled with a heavy field.

About the Speaker

Dr. SUN Guanhao is currently a postdoc in the physics department of University of California, San Diego. He obtained his PhD in physics from Columbia University in 2022, and his Bachelor's degree from Hong Kong University of Science and Technology in 2016. Dr. Sun's research focuses on the application of effective field theories in cosmology and condensed matter systems. His works span a variety of topics, including inflationary physics, effective field theory of condensed matter systems, formal QFT, and black hole superradiance. 

About the Program

For more information, please refer to the program website at http://iasprogram.ust.hk/particle_theory.

For Attendees' Attention

• Seating is on a first come, first served basis.