Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family
Abstract
We study degenerate-horizon limits of vacuum accelerating Kerr--NUT spacetimes with finite, nonzero NUT parameter. At cubic criticality, a2=m2+ℓ2 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.
Related
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BibTeX
@misc{hong2026critical,
title = {{Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family}},
author = {Kenneth Hong},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25031},
eprint = {2610.25031},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25031},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family
AU - Kenneth Hong
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.25031
UR - https://arxiv.org/abs/2610.25031
AB - We study degenerate-horizon limits of vacuum accelerating Kerr--NUT spacetimes with finite, nonzero NUT parameter. At cubic criticality, a^2=m^2+ℓ^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.
ER -