PIRSA:25050045

Video URL

https://pirsa.org/25050045

Flatness and spikes in Ponzano-Regge

Engle, J. (2025). Flatness and spikes in Ponzano-Regge. Perimeter Institute for Theoretical Physics. https://pirsa.org/25050045

Engle, Jonathan. Flatness and spikes in Ponzano-Regge. Perimeter Institute for Theoretical Physics, May. 29, 2025, https://pirsa.org/25050045 

          @misc{ scivideos_PIRSA:25050045,
            doi = {10.48660/25050045},
            url = {https://pirsa.org/25050045},
            author = {Engle, Jonathan},
            keywords = {Quantum Gravity},
            language = {en},
            title = {Flatness and spikes in Ponzano-Regge},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2025},
            month = {may},
            note = {PIRSA:25050045 see, \url{https://scivideos.org/pirsa/25050045}}
          }

Jonathan Engle

Talk numberPIRSA:25050045
DOI10.48660/25050045
Source RepositoryPIRSA
Collection
Talk Type Scientific Series
Subject

Abstract

The original spinfoam amplitude, Ponzano-Regge, has two properties in seeming contradiction: (1.) It can be written as an integral of a product of Dirac delta functions imposing that holonomies be exactly flat, and (2.) In its original sum-over-spins form, its leading order large spin asymptotics consist in Regge calculus, modified to include an additional local discrete orientation variable for each tetrahedron, which, when fixed inhomogeneously, leads to critical point equations for the edge lengths which do not necessarily imply flatness, but allow spikes. Of course, this apparent contradiction between flatness and spikes appears only for triangulations with bubbles, for which both of these formulations of the model are divergent and ill-defined anyway, and this may be the resolution of the paradox. However, we explore the possibility of another resolution of this paradox which may also have relevance for the semiclassical regime of 4D spinfoams, in which a similar sum over local orientations appears.