"Largest Time Equation in Non-Equilibrium Effective Field Theories"
One challenge of effective field theory (EFT) is to characterize the low-energy behavior of a quantum system while accounting for the fundamental properties of quantum mechanics. In this talk, I will first show how the Schwinger-Keldysh formalism provides the natural language to formulate a genuine EFT for systems in local equilibrium. I will then focus on the role of the largest time equation, which comes from unitarity and implies causality. One particular feature of non-equilibrium EFTs is that they display an emergent BRST supersymmetry, with associated ghost fields. While this led recently to uncovering new, unexpected geometrical structures, I will show that, due to causality and unitarity, at perturbative level, ghosts are not necessary for the consistency of the theory. Even if the ghost fields are introduced, their contributions vanish to all loops, drastically simplifying the EFT at quantum level.
HEP May30 Glorioso flyer