High Energy Theory Seminar

In (asymptotically) flat spacetime, the symmetry group of EM and gravity is infinite dimensional and their associated conservation laws have been an important organizing principle in studying the IR behavior of quantum fields and gravity. In this talk, I will explain the consequences arising from "superselection" of these large gauge charges on local physics. We show that the only physical states in QED scattering theory are maximally entangled states, in which electron (or positron) momenta at timelike infinity are entangled with soft (on-shell) radiation at null infinity. Indeed we show that the "bare" electron (i.e. an electron with just its Coulomb field) does not localize anywhere in spacetime and is not a physical state. We explain why collider predictions are insensitive to this total delocalization. In the case of quantum gravity, these results necessitate the non-local nature of  quantum gravity observables. Some resulting fundamental bounds on quantum coherence are presented.

The talk is in 469 Lauritsen.

Contact [email protected] for Zoom information.