Complete total-transmission modes of Kerr black holes

Abstract

We construct the complete spectrum of gravitational total-transmission modes (TTMs) of Kerr black holes and find four globally continuous families, $n_\infty=1,2,3,4$. Compared with the three-family classification of Cook and Lu [Phys. Rev. D 107, 044043 (2023)], our global continuation separates complex conjugation at fixed $m$ from the mirror symmetry connecting the $m$ and $-m$ spectra, yielding a uniform four-family classification without additional symmetry-unrelated roots. The $n_\infty=3$ family approaches the Schwarzschild algebraically special frequency, whereas the $n_\infty=1,2,$ and $4$ families diverge as $ω\propto a^{-4/3}$ along lower-half-plane directions $-150^\circ$, $-90^\circ$, and $-30^\circ$. High-precision data up to $\ell=32$ recover the Cook--Lu small-spin asymptotics and show how the divergent branches are embedded in the global four-family spectrum. The spherical-limit polar labeling and large-$|aω|$ angular ordering are related in a family-dependent manner. For axisymmetric perturbations, we show that the $n_\infty=2$ and $n_\infty=3$ branches coalesce at exceptional points and subsequently evolve toward distinct small-spin limits, rather than exhibiting the overtone-multiplet splitting proposed by Cook and Lu. Finally, we identify a previously unreported anomalous proximity between the $n_\infty=3$ TTM family and the unconventional Kerr quasinormal-mode sequence, with separations reaching order $10^{-8}$ while remaining numerically well resolved.