Infrared divergences in the EPRL-FK Spin Foam model

Understand

We provide an algorithm to estimate the divergence degree of the Lorentzian EPRL-FK spin foam amplitudes for arbitrary 2-complexes.

• We focus on the "self-energy" and "vertex renormalization" diagrams and find an upper bound estimate.
• We argue that our upper bound must be close to the actual value, and explain what numerical improvements are needed to verify this numerically.
• For the self-energy, this turns out to be significantly more divergent than the lower bound estimate present in the literature.