Speaker: Zhewei Yin
Title: On-shell constructions of the nonlinear sigma model
Host:
Zoom: https://zoom.us/j/186024391
Abstract:
The nonlinear sigma model (NLSM) can act as the effective field theory (EFT) for Nambu-Goldstone bosons. The traditional construction for the effective Lagrangian requires the ultraviolet information of the broken symmetry. Recently it becomes clear that the EFT can be universally constructed from the infrared without such information. This parallels the effort in the past years to formulate the theory from a purely on-shell perspective. The program of soft bootstrap, in which scattering amplitudes are constructed using recursion relations, is an on-shell realization of the infrared universality, and turns out to be a powerful tool for counting degrees of freedom in higher powers of the derivative expansion. On the other hand, the intriguing property of flavor-kinematics duality can also be used to determine leading order tree amplitudes of NLSM. Non-trivial generalizations of such a feature are discovered in the higher derivative interactions.
