3 citations · 7 across the 7 of their papers we have counts for
8 papers
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…
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…
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…
Geometric phase from encircling an exceptional point of a quantum resonance in the complex-scaling method
Okuto Morikawa, Shoya Ogawa, Soma Onoda
Non-Hermitian operators are now routinely used to describe few-mode systems such as optical resonators and superconducting qubits, and exceptional points (EPs) are defective spectr…
Exact WKB method for radial Schrödinger equation
Okuto Morikawa, Shoya Ogawa
We revisit exact WKB quantization for radial Schrödinger problems from the modern resurgence perspective, with emphasis on how ``physically meaningful'' quantization paths should b…
On continuum and resonant spectra from exact WKB analysis
Okuto Morikawa, Shoya Ogawa
Resonance phenomena are central to many quantum systems, where resonant states are typically characterized by pole singularities of the S-matrix. In this work, we employ the comple…
Unified exact WKB framework for resonance -- Zel'dovich/complex-scaling regularization and rigged Hilbert space
Okuto Morikawa, Shoya Ogawa
We develop a unified framework for analyzing quantum mechanical resonances using the exact WKB method. The non-perturbative formulation based on the exact WKB method works for inco…
Nonperturbative Formulation of Resonances in Quantum Mechanics Based on Exact WKB Method
Okuto Morikawa, Shoya Ogawa
We study quasi-stationary states in quantum mechanics using the exact Wentzel--Kramers--Brillouin (WKB) analysis as a nonperturbative framework. Whereas previous works focused main…