The interior of a neutron star is expected to be occupied by neutron superfluids. While the outer region should be filled by 1S0 superfluids consisting of a conventional singlet pairs of neutrons, the inner core may be 3P2 superfluids consisting of a condensate of spin-triplet p-wave Cooper pairs of neutrons with total angular momentum J=2 . This has rich topological structures in both momentum and real spaces: it is a topological superfluid and admits various topological defects such as half-quantum non-Abelian vortices, domain walls, surface topological defects, boojums, and so on. I will give a review of the current status of 3P2 superfluids with a particular attention to vortices and possible applications to pulsar glitches.

※Zoom情報：https://zoom.us/meeting/register/6aN7eizNRL–W58_kNle8A

連絡教員：物理学系　関澤　一之（内線2463）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/432.pdf

The superradiant phase transition (SRPT) is a second-order phase transition where a static electric or magnetic field is ordered spontaneously due to an ultrastrong interaction with matters in thermal equilibrium. Although the SRPT has not been observed since its first prediction in 1973, its magnonic (spin-wave) version was confirmed in a magnetic material ErFeO3 recent years [1-3]. In this seminar, we will present experimental results [1,3] and theoretical background [2] of this magnonic SRPT. In addition, thermal-equilibrium quantum squeezing obtained at the SRPT critical point [4] will also be presented. The quantum technologies like quantum computing have been developed basically based on non-equilibrium phenomena. Because quantum states in those phenomena are usually excited states in systems of interest, such states are easily destroyed due to a variety of decoherence phenomena. In contrast, the SRPT provides quantum squeezing in the most stable state of systems in thermal equilibrium, thus its squeezing is robust against decoherence, which might give us a foundation of decoherence-robust quantum technologies.

[1] X. Li, M. Bamba, N. Yuan, Q. Zhang, Y. Zhao, M. Xiang, K. Xu, Z. Jin, W. Ren, G. Ma, S. Cao, D. Turchinovich, and J. Kono, Observation of Dicke cooperativity in magnetic interactions. Science 361, 794–797 (2018).
[2] M. Bamba, X. Li, N. Marquez Peraca, and J. Kono, Magnonic superradiant phase transition. Communications Physics 5, 3 (2022).
[3] D. Kim, S. Dasgupta, X. Ma, J.-M. Park, H.-T. Wei, X. Li, L. Luo, J. Doumani, W. Yang, D. Cheng, R. H. J. Kim, H. O. Everitt, S. Kimura, H. Nojiri, J. Wang, S. Cao, M. Bamba, K. R. A. Hazzard, and J. Kono, Observation of the magnonic Dicke superradiant phase transition. Sci. Adv. 11, eadt1691 (2025).
[4] K. Hayashida, T. Makihara, N. Marquez Peraca, D. Fallas Padilla, H. Pu, J. Kono, and M. Bamba, Perfect intrinsic squeezing at the superradiant phase transition critical point. Sci. Rep. 13, 2526 (2023).

連絡教員：藤井　啓資（内線2136）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/431.pdf

マヨラナ準粒子を始めとする非自明なエッジ状態を有するトポロジカル超伝導は様々な非従来型超伝導体において実現されることが明らかになってきた。このエッジ状態の起源は、ハミルトニアンの有するトポロジカル不変量に帰することが知られている[1-2]。
講演では、トポロジカル超伝導の持つ顕著な性質である1)常伝導金属との接合における零電圧コンダクタンスピーク[3]、2)ジョセフソン電流[3]、3)常伝導金属中の準粒子状態密度がゼロエネルギーでピークを持つ奇周波数電子対による異常近接効果[2,4-5]を紹介する。

[1] Y. Tanaka, M. Sato, N. Nagaosa, J. Phys. Soc. Jpn. 81, 011013, 2012.
[2] 超伝導接合の物理　田仲由喜夫著　名古屋大学出版会　2021年
[3] Y. Tanaka and S. Kashiwaya, Phys. Rev. Lett., 74, 3451, 1995; Phys. Rev. B 56, 892, 1997.
[4] Y. Tanaka and S. Kashiwaya, Phys. Rev. B, 70, 012507, 2004.
[5] Y. Tanaka S. Tamura and J. Cayao, Prog. Theor. Exp. Phys., 08C105 2024.

※「物理学特別講義（発展）第九」を履修する学生は本セミナーも聴講すること。

連絡教員　　打田　正輝（内線2756）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/430.pdf

Our lab uses quantitative microscopy and theory to develop constitutive and closure relations that bridge the particle-to-continuum field scales. In this seminar, I describe our application of feedback control on self-propelled agents to create spatiotemporal patterns and user-specified population distributions. We demonstrate the use of “gray-box models” that incorporate partially-known dynamics and learn the difficult-to-model terms (e.g., many-body interactions). We use the concepts of observability and time-delay embedding to model, forecast, and control the complex behaviors of active matter using continuum density data alone. By forcing the system to sample rare configurations, we can develop new constitutive field relations with appropriate closures. This project is aimed at deepening our understanding of mode coupling in nonlinear dynamics across the length and time scales.

連絡教員：物理学系　西口　大貴（内線2447）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/117tokubetsu.pdf

ソフトマテリアルのナノ粒子（ミセルやベシクル）は、近年ドラッグデリバリーや生体親和性材料およびバイオ診断といった応用に向けて盛んに研究されている。これらの粒子は溶液中でのみナノスケールの構造体として存在し、その機能を発現するため、真空下の電子顕微鏡測定などではなく溶液中において粒径を決定することが重要である。この目的のために最も広く用いられている動的光散乱法では、溶液試料にレーザー光を照射し、その散乱光の強度のゆらぎを計測する。市販の動的光散乱装置では数nm～数百nmの粒径分布の推定が可能であるが、市販装置には以下のような問題点がある。

これらの問題を克服するために、当研究室では新たな動的光散乱装置の開発を行ない、これまで困難であった白濁した系や汚染物質を含む系、および多成分系溶液中での粒径分布計測に成功した。本講演では、動的光散乱法の測定原理を説明した上で、当研究室で開発した様々な動的光散乱装置および今後の研究展望について紹介する。

連絡教員：物理学系　西口　大貴（内線2447）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/11/429.pdf

The neutron star binary GW170817 detected via gravitational waves and the neutron star observed by NICER provide astronomical constraints on the equation of state (EoS) of dense matter. More precise and diverse astronomical observations are expected to further strengthen constraints on the EoS of dense matter. This presentation will focus on gravitational-wave observations and comprehensively discuss related topics. It will also include a brief introduction to research utilising next-generation gravitational-wave detectors.

連絡教員：物理学系　関澤　一之（内線2463）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/11/428.pdf

・量子情報、量子コンピューティングの理論で世界的に著名なMITのSeth Lloyd教授の講演会です。

・Lloyd教授の話は大変分かりやすいことで有名ですので、学生さんを含めどなたもご参加ください。事前登録不要、英語です。

・前半（第１部）は量子コンピューティングについての全般的なイントロ、第2部は最新の研究成果についてです。

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/10/Seminar_-Seth-Lloyd.pdf

For open quantum systems obeying a Lindblad equation, it is a challenging problem to clarify and classify what kind of non-equilibrium steady state (NESS) the system relaxes to after a sufficiently long time. In this talk, we consider open quantum spin systems on infinite lattices described by the Lindblad equation and present a definition of the NESS in such infinite systems. The NESS in infinite systems is not necessarily equivalent to the thermodynamic limit of the NESS in finite systems; the former may correspond in finite systems to a metastable state, not a NESS. We see this in a solvable model. We also find a sufficient condition for equivalence of them, which relates to both the Liouvillian gap and nonnormality, i.e., nonorthogonality among eigenmodes of the Liouvillian. The enhancement of nonnormality can cause spontaneous symmetry breaking (SSB) for the NESS in infinite systems, which we dub nonnormality-induced SSB. Since a Liouvillian is normal in unitary dynamics, such a type of SSB is unique to open quantum systems. Furthermore, the nonnormality-induced SSB can occur even when the Liouvillian is gapped. This work uncovers a novel phase of matter in open quantum systems and establishes a way to classify it by focusing on nonnormality. This talk is based on the preprint arXiv:2508.07448.

連絡教員：物理学系　山本　和樹（内線2724）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/11/427.pdf

This seminar will discuss applications of exact WKB analysis in physics and explore how it can differ from conventional calculations. After explaining the Landau–Zener transition, on which our analysis is based, we will expand the model to see how the difference manifests itself in the calculation. In the first part [1], we provide specific examples where the linear approximation at the level crossing, commonly used in Landau-Zener transitions, does not yield a good approximation. We will also mention the possibility that the Stokes lines may differ depending on whether the interacting electric field is a classical electromagnetic field or a photon[1]. As applied examples, we also explain particle creation in the early universe[2], the emergence of asymmetry due to CP violation[3], the Schwinger effect[4], the Unruh effect[4], and Hawking radiation[4]. For CP violation to affect the asymmetry between particles and antiparticles in baryon number generation, it is shown that multiple Stokes phenomena must undergo quantum interference[3]. Particle production in steady states, such as the Schwinger effect and Hawking radiation, can be solved “locally” by examining in detail how degrees of freedom like gauge and Lorentz symmetries are treated in differential geometry[4].

[1] Phys. Rev. A 112 (2025) 3, 032224, e-Print:2505.09240
[2] JHEP 03 (2021) 090, e-Print: 2010. 14835
[3] JHEP 02 (2022) 131, e-Print: 2104. 02312, JHEP 01 (2023) 088, e-Print: 2203.04497
[4] JHEP 05 (2025) 216, e-Print: 2404.19160, Int. J. Mod. Phys. A 40 (2025) 28, 2550130, e-Print:2501, 09919

連絡教員：物理学系　藤井　啓資（内線2136）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/11/426.pdf

AI やロボットアームなどに代表される先端技術の急速な発展による影響は多くの分野へと波及しつつあり、材料科学にも新たな視点と研究開発手法をもたらしている。私はこれまでに、材料特性の実験データと計算データを機械学習によって統合し、物性と構造の類似度を同時に反映する材料マップを開発してきた[1]。さらに、ロボットアーム、電動ピペット、3Dプリンタを用いた自動実験システムを構築し、金属有機構造体（MOF）などのナノ材料合成の自動化を推進している。これらの自動実験を通じて得られる再現性の高い信頼性のある材料データベースは、今後のデータ駆動型材料開発の基盤となる。加えて、生成AIを活用したマルチエージェントシステムにより、自動かつ自律的なデータ分析手法の開発も進めている。本セミナーでは、これらの新技術を統合することで実現されつつある、材料研究開発の新しい枠組みについて紹介する。

References
[1] Y. Hashimoto, et al., APL Machine Learning 3, 036104 (2025)

連絡教員：物理学系　佐藤　琢哉（内線2716）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/10/425.pdf