Quantum Field Theory on compact stars near the Buchdahl limit

Understand

Very compact stars seem to be forbidden in General Relativity.

• While Buchdahl's theorem sets an upper bound on compactness, further no-go results rely on the existence of two light rings, the inner of which has been associated to gravitational instabilities.
• However, little is known about the role of quantum fields in these strong gravity regimes.
• Here, we consider the particularly simple model of a constant density star and we work in the probe approximation where the backreaction is ignored.