Frozen stars: Black hole mimickers sourced by a string fluid

I will present the Frozen Star model: a model of a "black hole mimicker" – an object whose exterior geometry resembles that of a general relativity black hole but differs in its interior. To an external observer, a static frozen star looks exactly like a Schwarzschild black hole and a rotating frozen star looks exactly like a Kerr black hole, but its interior geometry differs from the general relativity one at the horizon scale. I will show that the exotic matter sourcing the frozen star can be effectively described as a “string fluid” originating from the decay of an unstable D-brane at the end point of tachyon condensation. I will end by showing that frozen stars are stable and that the internal modes that they possess may lead to observable effects during astrophysical black hole mergers.