SXS Collaboration's video: Event horizon for head-on BBH in two coordinate systems

Event horizon for a head-on binary black hole merger in two different coordinate systems. The top row shows the coordinate system used to merge the black holes (where the coordinate system and spacetime is axisymmetric), and the bottom row shows another coordinate system. The two are related with a simple coordinate transformation where the time coordinate satisfies t' = t + Gaussian. The first half of the video shows the event horizon surfaces, where orange represents the true event horizon, and translucent purple represents "future generators" of the horizon. The second half of the video shows a zoomed in spatial cut through the middle of the event horizon, showing there is no torus forming in either coordinate system. There is no coordinate system where this binary has a toroidal topology. For more information about the binary or the methodology, please see our website or our paper https://www.black-holes.org/for-researchers/event-horizon-topologies