Okuto Morikawa

学振dc1の書類の内容を sites.google.com/view/o-morikaw… で公開しました。 後輩の皆さんの参考になれば嬉しい限りです。

@AnilZenginoglu @gabrielmjonk @FaustOrpheu @star_stufff Thank you, this is a fair question. I think this requires a more careful discussion than I can give properly in a short reply. We will revise the manuscript to clarify its relation and to state more precisely what the CSM/spectral-deformation viewpoint is intended.

Both approaches get you a non-self-adjoint spectral theory. In the hyperboloidal case, you get this because the physical problem is open (radiation to horizon and infinity). In your case, you're rotating the continuum spectrum, which turns resonance poles into isolated eigenvalues. Could you explain in a few words why one would want to do that? What are the expected benefits over existing approaches?

@gabrielmjonk @FaustOrpheu @star_stufff They appear as singularities of the analytically continued resolvent, so the domain/boundary-condition issue is essential.

@AnilZenginoglu @gabrielmjonk @FaustOrpheu @star_stufff Thank you for sharing your interesting works. Our motivation is somewhat different: an Aguilar--Balslev--Combes-type spectral-deformation of the continuum, aimed at treating QNMs within a non-self-adjoint spectral framework rather than as a boundary-condition problem.

@o_morikawa @gabrielmjonk @FaustOrpheu @star_stufff Hyperboloidal also works in time-domain. You can use the same method whether in frequency or time domain once you recognize the underlying geometric idea. I don't think complex scaling extends to time domain naturally. arxiv.org/abs/1102.2451 arxiv.org/abs/2409.11478

@gabrielmjonk @FaustOrpheu @star_stufff Since the original differential operator still has good elliptic regularity, this provides a rather controlled way to study the QNM/resonance structure and the continuum response.

@gabrielmjonk @FaustOrpheu @star_stufff In our approach, complex scaling gives a non-unitary similarity transformation which turns the outgoing-wave problem into a mathematically well-defined non-self-adjoint eigenvalue problem.

@gabrielmjonk @FaustOrpheu @star_stufff Thanks a lot for the comments and references! One point I find especially interesting is that the starting operator may look rather standard/self-adjoint, but QNMs are not ordinary eigenvalues in the original Hilbert space.

Our new paper is out! arxiv.org/abs/2605.03277 S. Ogawa, O. Morikawa, and T. Hirose Quasinormal modes and continuum response of de Sitter black holes via complex scaling method

@FaustOrpheu For black holes, quasinormal modes are one concrete manifestation of this. Also, the high precision of gravitational-wave observations makes the theory–experiment interplay very active, which is certainly an important motivation. Thank you for your interest!

@FaustOrpheu I’m still a beginner, so I cannot give a grand overview. But personally I’m interested in constructive approaches to QFT and quantum resonance/scattering theory. It is fascinating that essentially the same mathematical structures appear universally in different physical contexts.

@dwba369 Why not!

ブラックホール摂動論で毎回つらい 「この (r_*) どう定義するんだっけ？」 を少しでも減らしたい。

全世界が感動する亀座標自動計算システム、AutoTortoise.jl を公開しました。 Laurent-polynomial 型の static spherical metric function を入れると、horizon data の抽出、tortoise coordinate の構成、inverse map まで面倒を見ます。 github.com/o-morikawa/Aut…

Given a Laurent-polynomial static spherical metric function, it takes care of extracting horizon data, constructing the tortoise coordinate, and building the inverse map. I want to reduce the recurring pain in BH theory: “Wait, how exactly should I define r_* here?”

I have released AutoTortoise.jl, an automatic tortoise-coordinate construction system that will move the entire world. github.com/o-morikawa/Aut…

Mathematical Ideas and Notions of Quantum Field Theory という本がAMSから出るらしい テンソル圏や表現論の本で有名なPavel Etingof氏が書いた arXivでも公開されている arxiv.org/abs/2409.03117

Accepted in JPhysA: Math. Theor. O. Morikawa and S. Ogawa, ``On continuum and resonant spectra from exact WKB analysis'' arxiv.org/abs/2508.09211

これ書くのを人生の目標の一つにしよう

@Zzzyt9k どうせ関係なく聴覚過敏なので、ノイキャンしながらじゃないと寝れない。

うつ病とか精神疾患になってから 音楽聞けなくなった人っていますか？

In modern times, browser-based editors such as Atom have become widespread. However, it is also true that various frustrations remain unresolved, which is why Vim still persists. Taking a reverse perspective, wouldn’t it make sense for the browser itself to incorporate Emacs?

Historically, Emacs was an environment. It has also remained an excellent editor ever since.