Speaker
Description
The group field theory formalism provides a powerful embedding of canonical LQG states, spin foam amplitudes and lattice gravity path integrals, offering in particular suitable tools for the extraction of continuum, spatiotemporal physics. After reviewing the key aspects of this embedding, the challenges of bridging the gap between fundamental quantum gravity dynamics and effective continuum physics, and outlining the (novel) approximations that it allows, I discuss recent results showing how an effective scalar field theory, on a cosmological background, can be extracted from the fundamental quantum gravity dynamics. The tools used combine: mean field techniques from quantum many-body systems and relational observables constructed via quantum reference frames, in addition to the control over the quantum geometric aspects of the theory. I will also indicate the quantum gravity modifications to usual QFT that this effective field theory shows, of potential interest for quantum gravity phenomenology, and draw some more general lessons about the non-trivial relation between fundamental quantum gravity models and their emergent continuum physics.