Event details
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.