Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.25031

Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family

Kenneth Hong
View original source ↗Read source document ↗Export metadata ↓

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.

Explore related subjects

gr-qc

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Kenneth Hong. 2026-10-18. Critical limits of accelerating Kerr--NUT spacetimes and the non-expanding Plebański--Demiański family. https://arxiv.org/abs/2610.25031

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Self-consistent Hubble expansion in exponential teleparallel gravity: confrontation with recent observations

We reconstruct the Hubble expansion history in exponential teleparallel gravity using recent cosmological observations, including Observational Hubble Data (OHD), the Dark Energy Spectroscopic Instrument Data Release 2 (DESI DR2) baryon acoustic oscillation (BAO) measurements, gravitational-wave (GW) standard-siren data, and the Pantheon Plus and SH0ES Type Ia supernova compilations. We explicitly demonstrate that exponential teleparallel gravity can be consistent with current cosmological observations through statistical analyses based on the reduced $χ^2$, Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). In addition, we show that the present model of exponential teleparallel gravity can be viable cosmologically by analysing the dynamical evolution, stability conditions, and linear matter perturbations.

gr-qc↗
arXiv2026

Dyonic black holes supporting nearly-black self-gravitating thin shells

It has recently been revealed that dyonic black-hole spacetimes of a quasitopological non-linear electrodynamic field theory may be characterized by discrete radial regions with the property $dg_{tt}(r)/dr=0$ in which spherically symmetric massive {\it test} shells (Dyson shells with negligible self-gravity) can be supported in static equilibrium states. In the present paper we prove that the dyonic spacetimes of the non-linear electrodynamic field theory may also be characterized by the presence of radial regions with the dimensionless property $d[r\cdot g_{tt}(r)]/dr\to0^+$ in which massive {\it self-gravitating} thin shells that are on the verge of becoming black holes can be supported in static equilibrium states. Intriguingly, it is proved that the discrete radii of these self-gravitating nearly-black Dyson shells are universal in the sense that they are independent of the masses of the central supporting dyonic compact objects.

gr-qc↗
arXiv2026

A dark-matter-sensitive orientation clock near rotating black holes

A coherent triaxial structure has an intrinsic orientation clock because rotation about its intermediate principal axis is unstable. I ask how this clock changes when the structure moves on a circular equatorial orbit near a rotating black hole in an effective dark matter (DM) environment. The calculation uses a comoving orthonormal tetrad, the electric part of the Riemann tensor, Euler--quaternion dynamics, and the conversion from proper time to stationary coordinate time. The clock shift separates exactly into a local proper-time response and a geometric time-conversion response. I compute a direct grid of 600 DM models for Einasto, regularized cored Navarro--Frenk--White, and Hernquist profiles. Across the scanned domain, the total fractional frequency shift lies between about $-3\times10^{-7}$ and $-3\times10^{-4}$. For the fiducial body model, most of the shift comes from the time conversion. Synthetic timing tests show that a shift near $10^{-4}$ is recoverable only when the clock is highly coherent and its Kerr baseline is known independently. This gives a theoretical timing diagnostic and a synthetic observational forecast. I do not fit real data.

gr-qc↗