Towards the Breakdown of Perturbation Theory at High Energies
Abstract: Calculations of high-energy processes involving the production of a large number of particles in weakly-coupled quantum field theories have previously sparked ideas towards the need for novel non-perturbative behavior or even new physical phenomena. In this talk, I will review some scenarios where already tree-level computations may enter the regime of large-order perturbation theory and therefore require a careful investigation. I will argue that in scalar quantum field theories with a unique global minimum, where suitably resummed perturbative expansions are expected to capture all relevant physical effects, perturbation theory may still suffer from severe shortcomings in the high-energy regime. As an example, I will consider the computation of multiparticle threshold amplitudes in scalar field theories with (higher-order) self-interactions and demonstrate they these may violate unitarity of the quantum theory, even after the resummation of all leading quantum corrections. Among the plethora of viable scalar theories, this renders SM-like Higgs bosons unique.
Zoom link: IPPP Seminars (Friday at 2 pm UK time)
Meeting ID: 994 2012 4988