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gr-qc2026
Riesz--Laurent representation of black-hole scattering and sourced response at exceptional points
Okuto Morikawa, Shoya Ogawa, Takuya Hirose
At a black-hole exceptional point (EP), two quasinormal modes coalesce and their separate residues become ill-conditioned. Rather than postulating a near-degenerate modal fit, we d…
hep-th2026
Quasinormal modes and continuum response of de Sitter black holes via complex scaling method
Shoya Ogawa, Okuto Morikawa, Takuya Hirose
We apply the complex scaling method to black-hole perturbations in four-dimensional Schwarzschild--de~Sitter (dS) spacetimes. The method converts the outgoing-wave boundary-value p…
hep-th2026
Complex scaling approach to quasinormal modes of Schwarzschild and Reissner--Nordström black holes
Shoya Ogawa, Takuya Hirose, Okuto Morikawa
We study black-hole quasinormal modes by applying the complex scaling method (CSM) to the perturbation equations of Schwarzschild and Reissner--Nordström black holes. The method co…