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/2026/04/439.pdf

最初の重力波観測から10年後の今と未来

約13億年前、宇宙で起きたブラックホール同士の衝突。その衝突によって生じた時空のゆらぎは、2015年に地球で初めて観測されました。本講演では、人類が初めて「宇宙の調べ」を聴いた重力波観測の舞台裏と、その画期的な意義について、アメリカで実際に研究開発に携わっていた講師が解説します。光では捉えられなかったブラックホール連星の世界が、なぜ今わかるようになったのか。原子よりも小さな揺れを測る最先端技術と、100年にわたる科学者たちの挑戦をご紹介します。さらに、この10年で進歩した観測技術の成果と、今後さらに数十年をかけて改良を重ね、より遠い宇宙を見つめようとする将来計画についてもお話しします。

連絡教員　宗宮　健太郎（内線3546）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/04/438.pdf

We propose first-principle calculations of an open system based on the real-time path integral formalism, treating the environment as well as the system of interest together on a computer. We focus on the Caldeira-Leggett model, which is well known, in particular, as a model of quantum decoherence. The calculation simplifies for typical initial conditions, and the relevant complex saddle point can be determined by solving a linear equation. The integration over the saddles can be performed analytically, and the reduced density matrix can be obtained by tracing out a large number of harmonic oscillators in the environment. In particular, we confirm the dependence of the decoherence time on the coupling constant and the temperature that has been predicted from the Lindblad-type master equation in a certain parameter regime. If time allows, we also discuss how to extend this framework to general models, e.g., by using the generalized Lefschetz thimble method to overcome the sign problem.

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/2026/04/437.pdf

When metals are magnetized, emulsions phase separate, or galaxies cluster, domain walls and patterns form and irremediably coarsen over time. Such coarsening is universally driven by diffusive relaxation toward equilibrium. Here, we discover a vibrational counterpart—wave coarsening—in active elastic media: vibrations emerge and spontaneously grow in wavelength, period, and amplitude, before a globally synchronized state called a time crystal forms. We observe wave coarsening in one- and two-dimensional mechatronic metamaterials and capture its dynamical scaling. We further arrest the process by breaking momentum conservation and reveal a far-from-equilibrium nonlinear analogue to chiral topological edge modes. Our results open new questions about the transient physics of systems with non-potential interactions and suggest an organizing principle for nonlinear waves in acoustics, optomechanics, living matter, and soft robotics.  

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https://zoom.us/meeting/register/K4FBE190TqeWm0CoObrn8Q  

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※本セミナーは学術変革領域(A)「動的物質科学の創成 量子と古典の枠を超える」および
学術変革領域(A)「進化情報アセンブリによる生命機能の創出原理」との共催です。

連絡教員：物理学系　花井　亮（内線2070）・西口　大貴（内線2447）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/03/436.pdf

One-dimensional models are a theoretical playground for the investigation of strongly interacting many-body dynamics that have in recent years become experimentally realizable. While mean-field methods and other standard approaches are not applicable, they can often be investigated with techniques of integrability and generalized hydrodynamics that have revolutionized our understanding of their large-scale behavior. Fluctuations around hydrodynamic values display remarkable robustness and have recently been observed to be anomalous, indicating additional processes besides normal diffusion.
We study a family of cellular automata with ballistically propagating charged particles and stochastic scattering. By mapping the dynamics to a “vacancy-dressed” stochastic six-vertex model we derive the exact anomalous distribution of the charge current. Building on macroscopic fluctuation theory, we also give a hydrodynamic description of the model’s anomalous fluctuations. Linear degeneracy arising from charge inertness allows for simultaneous contributions from convective and normal diffusion. 
Similar phenomenology of dynamical criticality is observed in equilibrium spin current fluctuations in the easy-axis and isotropic regimes of the XXZ spin chain. The easy-axis regime supports the non-Gaussian distribution of the charged single-file class despite not manifestly satisfying a kinetic constraint. We argue anomalous fluctuations instead arise due to linear degeneracy of the vacuum polarization in the quasi-particle description. At the Heisenberg point the spin structure factor matches that of the Kardar-Parisi-Zhang universality class while spin fluctuations are anomalous but distinct from those of the KPZ class. 

連絡教員：物理学系　笹本　智弘（内線2736）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/02/435.pdf

This seminar will review experimental searches for the H-dibaryon through various reactions, focusing specifically on the latest results from the J-PARC E42 experiment. This experiment investigates the H-dibaryon near the Lambda Lambda and Xi- p mass thresholds. The E42 has collected thousands of Lambda Lambda production events from (K-, K+) reactions off a 12C target at 1.8 GeV/c. We are on the verge of publishing our results, and this talk will discuss the nature of the H-dibaryon, offering insights into exotic baryon spectroscopy and extending our understanding to further multiquark states.

連絡教員：物理学系　慈道　大介（内線2083）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/01/434.pdf

Standard hydrodynamics serves as a successful macroscopic description of fluid motion, ranging from engineering applications to turbulent flows. However, this framework is inherently deterministic and neglects the fluctuations that inevitably arise due to their underlying atomic structure. In particular, these fluctuations govern fluid phenomena at the mesoscopic scale between the microscopic and macroscopic scales. Fluctuating hydrodynamics extends the classical description by incorporating thermal fluctuations, leading to a more accurate description of such mesoscopic transport phenomena.
Recently, we analyzed the strong non-equilibrium fluctuations exhibited by fluids subjected to uniform gradients, such as single-component fluids under a shear flow or a temperature gradient and multi-component fluids under a concentration gradient [1-3]. These phenomena are one of the most well-established examples requiring a fluctuating hydrodynamic description, having been precisely observed in microgravity experiments. We performed direct numerical simulations (DNS) of the fluctuating hydrodynamic equations, and investigated the properties of energy dissipation and fluid behavior in the inviscid limit. In this seminar, I will present these findings alongside a historical review of the development and analysis of fluctuating hydrodynamics.

[1] HN, and K. Yokota, Phys. Rev. E 111, L063401 (2025)
[2] HN, Y. Minami, and K. Saito, arXiv:2502.15241(2025)
[3] HN, and Y. Minami, arXiv:2511.17851 (2025)

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/2026/01/433ーhenkou.pdf

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-henkou.pdf