Diffeomorphism-invariant observables and nonlocality

          @misc{ scivideos_PIRSA:15080078,
            doi = {10.48660/15080078},
            url = {https://pirsa.org/15080078},
            author = {},
            keywords = {Quantum Fields and Strings, Quantum Gravity, Quantum Information},
            language = {en},
            title = {Diffeomorphism-invariant observables and nonlocality},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2015},
            month = {aug},
            note = {PIRSA:15080078 see, \url{https://scivideos.org/index.php/pirsa/15080078}}
          }
          

Abstract

In a theory of gravity, observables must be diffeomorphism-invariant. Such observables are nonlocal, in contrast with the usual formulation of local quantum field theory. Working to leading order in Newtons constant G, I'll describe a construction of diffeomorphism-invariant observables for a scalar field coupled to gravity that closely parallels an analogous construction for charged particles in electrodynamics. These observables acting on the vacuum create scalar particles together with their (linearized) gravitational dressing. The commutator of two such spacelike-separated observables is nonvanishing at order G, and is related to the gravitational potential between two masses. Based on arXiv:1507.07921 with Steve Giddings.