Emergence of Lorentzian Geometries from Spin-Foams and Group Field Theories

by Alexander Jercher (Friedrich-Schiller-Universität Jena)

Thursday 30 Jan 2025, 14:15 → 15:45 Europe/Berlin

Abbeanum/Ground floor-HS 2 - Hörsaal 2 (TPI, FSU Jena)

In this talk, I will examine the recovery of Lorentzian continuum geometries from the two closely related non-perturbative and background independent quantum gravity (QG) approaches of spin-foams and group field theories (GFTs). The talk is commenced by motivating the search for a theory of QG and showing why the most immediate quantization strategies fail. Thereafter, spin-foams and GFTs are introduced at length. It is demonstrated that their degrees of freedom are radically different from those of GR, marking a key challenge in reconnecting to continuum metric geometries. Two possibilities of bridging this gap are being discussed in more detail: 1) an effective model for spin-foam cosmology in (2+1) dimension, and 2) the extraction of scalar cosmological perturbations from entangled GFT coherent states.