Precursory collapse in neutron star-black hole mergers

Black hole-wormhole collisions and the emergence of islands

“…The whole analysis was performed using the Ellis-Bronnikov metric and employing ray-tracing techniques. Both setups present novel features together with some already well-described phenomena occurring in the black hole-black hole [25] and the black hole-neutron star fusions [28]. We have shown that basically all of the features observed in previous studies of (non-rotating) mergers in the EMR limit are -in some cases surprisinglypresent also here: most notably, the fusion of initially disconnected horizons in Sec.…”

“…8.) The same phenomenon appears in the merger of a neutron star with a large black hole [28]. The precursor expands until it connects, at a later time, t i > t p , with the large horizon, thus closing off an 'island' region.…”

“…This limit provides a boundary condition on the null generators of the event horizon and allows one to integrate the geodesic equations back in time up to the caustic points (the set of points where the horizon generators focus). This same approach was also employed to study mergers with rotating [26] or charged [27] black holes, as well as the fusion of a neutron star with a large black hole [28].…”

Exotic marginally outer trapped surfaces in rotating spacetimes of any dimension

“…Instead, the aim was to describe the evolution of the apparent horizon during an extreme mass ratio binary black hole merger. This was based on the insights of [26][27][28], where the event horizon evolution during a merger was understood exactly in the (strict) extreme mass ratio limit. In this framework, one tracks the paths traced by a sheet of null rays-corresponding to the event horizon of the large black hole-in the spacetime of the small black hole.…”