Renormalization and continuum limit:

Benjamin Bahr, University of Hamburg, Renormalization group flow in truncated spin foam models

I will give details on recent results of the RG flow in symmetry restricted spin foam models. I will in particular discuss the existence of an interacting fixed point, as well as its connection to diffeomorphism symmetry.

Norbert Bodendorfer, Ludwig Maximilian University of Munich, Coarse graining and LQC

Within a full theory embedding of LQC using highly symmetric quantum states inspired by GFT condensates, the question of coarse graining simplifies significantly. We discuss how invariance of the dynamics under coarse graining or refining is mapped to a scaling property of LQC quantum states relevant for fiducial cell independence. These results allow to address coarse graining in a simplified setting using LQC techniques.

Giovanni Rabuffo, University of Hamburg, Towards a Cosmological subsector of Spin Foam Quantum Gravity

I will examine the EPRL-FK spin foam model by restricting the state sum to certain symmetric configurations which resemble the geometry of a flat homogeneous and isotropic universe. The asymptotic form of the vertex amplitude will be derived, recovering in this limit a Regge-type action, as well as an explicit form of the Hessian matrix, which captures quantum corrections.
I will show that this model presents a large intersection with computations done in the context of cosmological modelling with Regge Calculus. I will also discuss some results concerning the renormalization properties of the EPRL-FK spin foam model in the symmetry restricted setting.

Saeed Rastgoo, Universidad Autonoma Metropolitana, Mexico, Emergent space(time) from renormalizing discrete metric spaces

I present a novel "geometric renormalization method", in the spirit of the Wilsonian RG, by which we aim at formulating the emergence of smooth space(time) from discrete metric spaces, specifically graphs, interpreted as discrete structure(s) underlying the smooth space(time). This method introduces a RG flow in the space of locally compact metric spaces -a parallel to the concept of the "theory space"- possibly leading to fixed points and attractors, whose continuum limit would be the classical spacetime. I will discuss the basic contents of the model and its current most important results, including the conditions on the existence of the continuum limit of relevant graphs, dimension and its integerness, as well as its stability under this RG flow.

Fleur Versteegen, Heidelberg University, An asymptotically safe gauge coupling

In the search for a fundamental theory of quantum gravity and matter, we use non-perturbative functional Renormalization Group methods to examine a system composed of a charged scalar and a U(1) gauge field, coupled to asymptotically safe quantum gravity. Without quantum gravity, the system features a Landau pole at high energies, i.e., the model features the so-called triviality problem and breaks down in the ultraviolet and ``new physics" is needed. We explore the hypothesis, that the ``new physics" is quantum gravity. Preliminary results for the flow of the gauge coupling show evidence for the existence of two fixed points, providing a possible solution to the triviality problem. The most significant result is the irrelevant nature of the coupling at one of the fixed points, hinting towards the possibility of predicting its value at low energies.