Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family
Year: 2026
Type: preprint
Abstract: We study degenerate-horizon limits of vacuum accelerating Kerr--NUT spacetimes with finite, nonzero NUT parameter. At cubic criticality, $a^2=m^2+\ell^2$ and $αm=1$, a projective coordinate transformation relates the complete critical parent metrics by a local homothety. The cubic horizon has one finite axis and a noncompact angular end, and its near-horizon limit is locally homothetic to the swirling universe. Explicit four-dimensional coordinate transformations place the ordinary extremal, Nariai and cubic near-horizon metrics in the negative-, positive- and zero-curvature longitudinal sectors of the non-expanding Plebański--Demiański family. The Nariai correspondence includes an exceptional endpoint that requires a separate Killing chart. Under a cubic-adapted near-critical scaling, fixed first-order separations between the approaching horizons do not affect the leading metric. The global Killing identifications and regular completion of the critical parent remain open.
Source: arXiv (Cornell University)
Author: Hong, Kenneth
Institution: National University of Singapore
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223034746