The dual twistor theory of self-dual black holes
Tim Adamo, Bernardo Araneda, Sean Seet
TL;DR
This work develops a complete, explicit map between holomorphic quadrics in flat dual twistor space and self-dual black hole geometries, showing that every such metric is encoded in flat-space data. It leverages the Penrose transform and Tod's Kerr-Schild construction to produce SD hyperkähler metrics that admit both Kerr-Schild and Gibbons-Hawking forms, with the dual twistor quadric determining all Killing spinors and symmetries. The authors classify generic dual twistor quadrics into three cases, revealing a precise one-to-one correspondence with self-dual Taub-NUT, Eguchi-Hanson, and self-dual Plebański-Demiański metrics, and they demonstrate that each case yields a single Kerr-Schild representation. This framework unifies previously known SDBHs under a flat-twistor data paradigm and provides a concrete platform for exploring perturbations and holographic connections in self-dual backgrounds. The results have potential implications for analytic gravitational scattering on self-dual backgrounds and for linking twistor methods with Teukolsky-type perturbation analyses in black hole physics.
Abstract
The Taub-NUT and Eguchi-Hanson gravitational instantons, along with the self-dual Plebanski-Demianski metric, form a set of Euclidean metrics which can naturally be called `self-dual black holes', as they arise from self-dual slices of the most general vacuum, asymptotically flat black hole metric. These self-dual black holes are of interest for many reasons, and can famously be described through the non-linear graviton construction of twistor theory. However, the implicit nature of this twistor description obscures some features of the underlying geometry, particularly for the most general self-dual black holes. In this paper, we give a new construction of all asymptotically flat self-dual black holes based on holomorphic quadrics in flat dual twistor space, rather than the usual twistor space associated with self-duality. Remarkably, the geometry of the self-dual black holes -- including their hyperkahler structure, as well as Kerr-Schild and Gibbons-Hawking forms -- is directly encoded in the corresponding quadric. As a consequence, we obtain a previously unknown single Kerr-Schild form of the self-dual Plebanski-Demianski metric.
