A ghost and a naked singularity; facing our demons
arXiv:1905.08849
Abstract
We encounter these demons on the path towards a UV complete QFT of gravity and a horizonless replacement for black holes. The fate of the ghost is discussed in the strong coupling version of classically-scale-invariant quadratic gravity. Rather than a propagating ghost, the full graviton propagator ends up with a slight acausal behavior. We then turn to the 2-2-hole solutions appearing in a classical approximation of the gravity theory. We present a new solution that is sourced by a relativistic gas, where a benign timelike singularity is shrouded by a fireball. Calculating the standard entropy gives an area law, and the entropy of a 2-2-hole can exceed that of the same size black hole. Finally, an observational consequence of 2-2-holes takes the form of gravitational wave echoes that can be generated by a newly formed 2-2-hole after a 2-2-hole merger. LIGO is sensitive to such a signal. We update the evidence from our previous search with five additional events reported more recently by LIGO.
13 pages, 23 figures, talk given at CERN workshop "Scale Invariance in Particle Physics and Cosmology", Jan 28 - Feb 1, 2019