Infrared limit of quantum gravity

Understand

We explore the infrared limit of quantum gravity in presence of a cosmological constant or effective potential for scalar fields.

• For a positive effective scalar potential, one-loop perturbation theory around flat space is divergent due to an instability of the graviton propagator.
• Functional renormalization solves this problem by a flow of couplings avoiding instabilities.
• This leads to a graviton barrier limiting the maximal growth of the effective potential for large values of scalar fields.