The most general renormalizable quantum field theory one can write down for a finite spectrum of spin-0, 1/2, and 1 particles is a gauge theory, with possible spontaneously broken symmetries. The existence of Lie group structures in such a theory is determined by perturbative unitarity of the on-shell scattering amplitudes. Armed with new tools developed for scattering amplitudes, we demonstrate very explicitly how broken symmetries emerge from the constraints of tree unitarity. Such constraints result in relations dictating the couplings to be invariant tensors of the gauge group, and each of these relations has a counterpart for kinematic numerators of on-shell amplitudes. This facilitates the extension of color-kinematics duality to spontaneously broken gauge theories.

报告人简介：Dr Zhewei Yin obtained his BSc degree in 2015 at Peking University, China, and his PhD degree in 2020 at Northwestern University, USA. He has since then been a postdoctoral researcher at Uppsala University, Sweden. He works in the field of theoretical high energy physics, with a focus on discovering new properties and developing modern methods in scattering amplitudes and effective field theories (EFTs). He has been working on understanding the phenomenon of spontaneously broken symmetry in modern contexts such as soft theorems of EFTs and extensions of the color-kinematics duality, as well as applications of these formal development to particle phenomenology and gravitational wave physics.