Description:

Loop corrections in interacting quantum field theories (QFTs) on a time-dependent background often diverge in time, hence obscuring the notion of renormalizability. In the first part of my talk, I will consider a toy model of out-of-equilibrium QFT in Minkowski spacetime where time-dependence is introduced by performing an interaction quench at some initial time. I will show that additional initial state counterterms may be needed to renormalize correlations in this case, depending on the type of interaction. I will also show that loop corrections to the unequal-time two-point correlation diverge in time and that late-time divergences can be resummed into decays. In the second part of my talk, I will relate initial state counterterms to entanglement between ultraviolet (UV)-infrared (IR) modes and argue that mutual information between momentum shells should capture any UV-IR correlation. Specifically, I will show that mutual information is a reliable indicator of renormalizability in QFT, demonstrating different behavior as a function of scale separation for different interactions. Lastly, I will generalize the results to interacting QFTs in de Sitter spacetime and discuss how background dynamics affect renormalizability.

Nishant Agarwal, Associate Professor, University of Massachusetts, Lowell

Host: Andre de Gouvea