Singularity avoidance in classical gravity from four-fermion interaction

Understand

We derive the dynamics of the gravitational collapse of a homogeneous and spherically symmetric cloud in a classical set-up endowed with a topological sector of gravity and a non-minimal coupling to fermions.

• The effective theory consists of the Einstein-Hilbert action plus Dirac fermions interacting through a four-fermion vertex.
• At the classical level, we obtain the same picture that has been recently studied by some of us within a wide range of effective theories inspired by a super-renormalizable and asymptotically free theory of gravity.
• The classical singularity is replaced by a bounce, beyond which the cloud re-expands indefinitely.