Math-Physセミナー
22 イベント
-
セミナー
Operational Quantum Frames: from quantum mechanics to quantum field theory and beyond
2025年10月30日(木) 16:00 - 17:00
Jan Głowacki (Postdoc, Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Austria)
In this talk I will begin with a concise overview of the development of the operational approach to quantum reference frames (QRFs), tracing the line from its foundational contributions to its most recent applications. I will then introduce the central ideas of the research direction that I am pursuing which aims at developing relational foundations for relativistic quantum physics. The starting point is the application of the operational QRF formalism to the context of the Poincaré group, and establishing connections between this emerging framework and existing formalisms in quantum field theory. This part of the talk will summarize results from a recent preprint written with Samuel Fedida [1]. I will conclude by outlining a number of open research directions, highlighting selected topics in more detail depending on the available time and the interests of the audience
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Foundations of Relational Quantum Field Theory — scalars
2025年9月9日(火) 16:30 - 17:30
Samuel Fedida (PhD, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK)
We develop foundations for a relational approach to quantum field theory (RQFT) based on the operational quantum reference frames (QRFs) framework considered in a relativistic setting. We focus on scalar fields in Minkowski spacetime and discuss the emergence of relational local observables and pointwise fields from the consideration of Poincaré-covariant frame observables defined over the space of inertial reference frames. We recover a relational notion of Poincaré covariance, with transformations on the system directly linked to the state preparations of the QRF. We introduce various causality conditions which mirror standard Einstein causality and microcausality, now seen in a relational context. The theory makes direct contact with established foundational approaches to QFT: the vacuum expectation values derived within our framework reproduce many of the essential properties of Wightman functions, and we compare the proposed formalism with Wightman QFT with the frame smearing functions describing the QRF's localisation uncertainty playing the role of the Wightmanian test functions. We show how the algebras generated by relational local observables satisfy all of the core axioms of Algebraic QFT. This work is an early step in revisiting the mathematical foundations of QFT from a relational and operational perspective.
会場: via Zoom / セミナー室 (359号室)
イベント公式言語: 英語
-
セミナー
Supersymmetric field theories and homotopy theory
2025年7月23日(水) 13:00 - 14:30
山下 真由子 (Junior Research Faculty member, Perimeter Institute for Theoretical Physics, Canada)
I will give a general introduction and overview on the Segal-Stolz-Teichner program, which tries to relate supersymmetric field theories in physics with homotopy theory in mathematics.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Exact WKB as unified analytic structure for resonance physics
2025年6月27日(金) 15:00 - 17:00
森川 億人 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 基礎科学特別研究員)
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 incorporating well-established phenomenological regularizations, the ABC theorem (proof of the completeness of Hilbert space), and the rigged Hilbert space in resonant phenomena. By examining the inverted Rosen-Morse potential, we illustrate how the exact WKB analysis captures resonant phenomena rigorously. Also, we clarify the corresponding linear spaces defined in each step of the exact WKB manipulations. The complementarity between the essential analyticity for resonance and the ABC theorem leads us to construct a modified Hilbert space called the rigged Hilbert space within the exact WKB framework. This offers a deeper understanding of resonant states and their analytic structures. Our results provide a concrete demonstration of the non-perturbative accuracy of exact WKB methods in unstable quantum systems.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Stable homotopy theory of invertible quantum spin systems
2025年5月16日(金) 16:00 - 18:00
窪田 陽介 (京都大学 大学院理学研究科 准教授)
In the past decade, A. Kitaev proposed that the set of invertible gapped quantum spin systems would form an \Omega-spectrum. This conjecture is considered to have potentially significant application to the study of SPT phases. Recently, we give a mathematically rigorous realization of this proposal with the language of functional analysis and operator algebra. This gives a unified proof of a series of existing researches. The proof also suggests to understand Kitaev's proposal from the viewpoint of coarse geometry of metric spaces. This association leads us to the concept of localization flow.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
The index of lattice Dirac operators and K-theory
2025年5月15日(木) 13:30 - 15:00
深谷 英則 (大阪大学 大学院理学研究科 助教)
We show that the Wilson Dirac operator in lattice gauge theory can be identified as a mathematical object in K-theory and that its associated spectral flow is equal to the index. In comparison to the standard lattice Dirac operator index, our formulation does not require the Ginsparg-Wilson relation and has broader applicability to systems with boundaries and to the mod-two version of the indices in general dimensions. We numerically verify that the K and KO group formulas reproduce the known index theorems in continuum theory. We examine the Atiyah-Singer index on a flat two-dimensional torus and, for the first time, demonstrate that the Atiyah-Patodi-Singer index with nontrivial curved boundaries, as well as the mod-two versions, can be computed on a lattice (This seminar is co-organized with FQSP).
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Foliation Matter Phase and Godbillon-Vey Invariant
2024年10月16日(水) 15:00 - 17:00
中西 泰一 (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 博士課程)
It has been a main topic in today's physics to classify matter phases. Especially, topologically ordered phases are attracting much attension from broad perspective. However, most of mathematical structures other than the topology are not investigated yet in physics. In this talk, we present a physical model which is strongly connected to the foliation structure of the space manifold, and its field theoretical description. In such a foliation field theory, we can see the structure is highly connected to the mathematical invariant of foliation structures called Godbillon-Vey invariant. This work would be a fiest step toward shining a light on mathematical structures used in physics. This work is based on arXiv:2408.05048 with Hiromi Ebisu, Masazumi Honda, and Soichiro Shimamori.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Prefactorization algebra and theta term
2024年5月21日(火) 16:00 - 17:30
川平 将志 (京都大学 基礎物理学研究所 博士課程)
Quantum field theories (QFTs) describe a lot of physical phenomena in our world. And giving a mathematical definition of QFTs is a long-standing problem. There are several mathematical formulations: Wightman formulation, Osterwalder–Schrader formulation and Atiyah-Segal formulation. And each of them cover different aspects of QFTs. Recently, Costello and their collabolators formulate QFTs by using prefactorization algbras. This formulaion cover a lot of classes of QFTs: TQFTs, 2d CFTs and perturbative QFTs. And they reproduce various results such as asymptotic freedom in non-Abelian gauge theories. Prefactorization algbras can be given by Batalin–Vilkovisky quantization (BV quantization) of the Lagrangian. However the original BV quantizations are perturbative and they do not have non-perturbative effects like instantons. In this talk, we propose the way to include Abelian-instanton effects. In modern language, it is the same as ℤgauging.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
A Selective Survey of Ideas, Tools and Results in Constructive QFT II
2024年4月1日(月) 13:00 - 14:30
クリスティ・コウジ・ケリー (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)
In this talk we continue to discuss the constructive programme in rigorous QFT. Our aim is discuss a few points on difficulties in relation to the definition of Euclidean path integrals and the general strategy of constructive field theory from a constructive perspective. This will motivate a discussion of the fundamental results in probability theory which are the main tools for the construction of Euclidean path integral measures. We might also discuss some points in relation to free fields, including in particular difficulties in the characterisation of massless fields.
会場: via Zoom / セミナー室 (359号室)
イベント公式言語: 英語
-
セミナー
A Selective Survey of Ideas, Tools and Results in Constructive Field Theory
2024年2月26日(月) 13:00 - 14:30
クリスティ・コウジ・ケリー (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)
In this talk we discuss some aspects of constructive field theory with an emphasis on analytical and probabilistic methods and results. In particular after an overview of some points in the history of constructive QFT we plan to discuss some early achievements in axiomatic QFT, some features of the theory of distributions and the basic structure of the Wightman reconstruction theorem. We also introduce the Osterwalder-Schrader axioms and overview the strategy for the construction of nontrivial measures describing path-integrals for interacting QFTs. Depending on time constraints we might also discuss probabilistic tools (weak convergence of measures, the Bochner-Minlos theorem etc), Gaussian measures, UV regularity of simple QFTs and the construction of (infinite volume) Euclidean P(phi)_2 measures. The plan is to discuss some of these topics in some detail after the end of the official seminar.
会場: via Zoom / セミナー室 (359号室)
イベント公式言語: 英語
-
セミナー
Application of Modular tensor category to Lattice gauge theory
2023年12月29日(金) 10:30 - 16:00
早田 智也 (慶應義塾大学 経済学部 助教)
Inspired by the recent development in quantum computers, much efforts have been devoted to exploring their potential applications in lattice gauge theories. However, in contrast to condensed matter systems, we face many challenges in applications of quantum computations to lattice gauge theories, where one of the major obstructions lies in implementation of gauge symmetries in quantum computations. In this seminar, I talk about a possible solution to the problem based on a unitary modular tensor category, expressing the Hamiltonian of lattice gauge theories in terms of the so called F moves, and implementing the F moves on quantum computers. References: TH, Y. Hidaka, JHEP 09 (2023) 126; JHEP 09 (2023) 123.
会場: セミナー室 (359号室)
イベント公式言語: 英語
-
セミナー
Vortex Reconnection in Classical and Quantum Fluids
2023年11月10日(金) 15:00 - 16:30
木村 芳文 (名古屋大学 大学院多元数理科学研究科 特任教授)
As a fundamental process in turbulence, vortex reconnection has been studied widely not only in classical fluids but also in quantum fluids. For the latter, the first real observation of vortex reconnection was rather recent, and since then active analyses have been continued. On the other hand, vortex reconnection in the former has a long history, and it is now studied intensively as a candidate for a solution to the problem of the regularity/Singularity of the Navier-Stokes equations, which is one of the seven millennium prize problems of the Clay Mathematical Institute. In this talk, after introducing the problem, we will present some results of analysis and simulations of the dynamical system which has been proposed to describe a vortex reconnection of two vortex rings located symmetrically on two tilted planes [1], [2], [3]. Then it will be shown that this dynamical system can be written in noncanonical Hamiltonian form with Hamiltonian, H, and a Casimir invariant, C in the limit of zero viscosity [4].
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
-
セミナー
Feynman’s proof of integrability of Calogero system from a modern point of view
2023年3月10日(金) 10:00 - 11:30
Yehao Zhou (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)
In his last year of life Feynman was interested in integrable system, and in his study of Calogero models he came up with his own proof of the commutativity of integrals of motions of these models, which remains unpublished until it was transcribed by Polychronakos in 2018. His idea is to organize integrals of motions of a Calogero model into a generating function of differential operators which look like a correlation function in a certain free theory, then he showed that the generating function of differential operators commute for all spectral values, which leads to a proof of commutativity of integrals of motions. He commented on his proof “I learn nothing, no real clue as to why all this works, and what it means”. Recently in a joint work with Davide Gaiotto and Miroslav Rapcek we identify Feynman’s generating function as the correlation function of Miura operators in a W-algebra of type A, and in the rational and trigonometric cases we show that they equal to certain elements in the Dunkl representation of corresponding spherical Cherednik algebras in type A, which make the commutativity self-evident. This progress is a byproduct of a project in the study of M2-M5 brane junction in the M-theory.
会場: コモンルーム (246-248号室) / via Zoom
イベント公式言語: 英語
-
セミナー
String theory, N=4 SYM and Riemann hypothesis
2023年2月16日(木) 14:00 - 16:10
本多 正純 (京都大学 基礎物理学研究所 助教)
We discuss new relations among string theory, four-dimensional N=4 supersymmetric Yang-Mills theory (SYM) and the Riemann hypothesis. It is known that the Riemann hypothesis is equivalent to an inequality for the sum of divisors function σ(n). Based on previous results in literature, we focus on the fact that σ(n) appears in a problem of counting supersymmetric states in the N=4 SYM with SU(3) gauge group: the Schur limit of the superconformal index plays a role of a generating function of σ(n). Then assuming the Riemann hypothesis gives bounds on information on the 1/8-BPS states in the N=4 SYM. The AdS/CFT correspondence further connects the Riemann hypothesis to the type IIB superstring theory on AdS5×S5. In particular, the Riemann hypothesis implies a miraculous cancellation among Kaluza-Klein modes of the supergravity multiplet and D3-branes wrapping supersymmetric cycles in the string theory. We also discuss possibilities to gain new insights on the Riemann hypothesis from the physics side. This talk is based on a collaboration with Takuya Yoda (arXiv:220317091).
会場: コモンルーム 246-248号室 とZoomのハイブリッド開催
イベント公式言語: 英語
-
セミナー
An Introduction to Rough Geometry (with a view to Euclidean Gravity)
2022年10月14日(金) 14:00 - 16:30
クリスティ・コウジ・ケリー (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)
The mathematical formulation of Einstein gravity typically utilises differentiable manifolds as models of smooth spacetimes. In many scenarios, however, it is desirable to have coarser models of spacetime and a correspondingly rough theory of geometry applicable to these coarser spacetime structures. In 2D Euclidean quantum gravity, for instance, the use of Regge calculus allows one to treat triangulations as regularisations of smooth spacetimes. There has been much recent progress in the mathematical (rigorous) understanding of this theory which we briefly review. We also introduce a rich alternative framework for the study coarse Euclidean geometry in the form of metric geometry augmented by optimal transport theory. In particular we introduce several optimal transport theoretic curvatures and demonstrate that these recover the familiar smooth notions under suitable limits.
会場: コモンルーム 246-248号室 とZoomのハイブリッド開催
イベント公式言語: 英語
-
セミナー
Implications of singularity theorem for non-singular universe
2022年6月16日(木) 13:30 - 15:00
吉田 大介 (名古屋大学 大学院多元数理科学研究科 特任助教)
The singularity theorem by Penrose shows that a spacetime singularity arises in certain universal situations. The existence of a spacetime singularity is thought to represent a breakdown in the validity of theories such as general relativity and the phenomenological models of the universe. Thus, if we could build a correct model that describes the beginning of the universe, the universe predicted by that model should be non-singular. In this talk, we will discuss general properties that a non-singular universe must satisfy in order to avoid the singularity theorem. In particular, we will see that the universe must be, in some sense, smaller than the corresponding closed de Sitter spacetime.
会場: コモンルーム 246-248号室 とZoomのハイブリッド開催
イベント公式言語: 英語
-
セミナー
Recent Progress in the Swampland Program
2022年5月19日(木) 14:00 - 15:30
野海 俊文 (神戸大学 大学院理学研究科 物理学専攻 宇宙論研究室 准教授)
In the past years, it has become increasingly clear that there exist nontrivial consistency conditions on symmetries in quantum gravity, that are invisible in classical gravity. The Swampland program aims at identifying such quantum gravity constraints and their implications for particle physics and cosmology, toward quantum gravity phenomenology. In this talk, I will review recent progress in this program, including my own works.
会場: コモンルーム 246-248号室 とZoomのハイブリッド開催
イベント公式言語: 英語
-
セミナー
Self-adjoint extension in quantum mechanics and non-Rydberg spectra of one-dimensional hydrogen atom
2021年4月13日(火) 16:00 - 18:10
全 卓樹 (高知工科大学 環境理工学群 教授)
We offer a beginner’s guide to the functional-analytical techniques in quantum mechanics, and cover its application to the 1D Coulomb problem. It is shown that the wave function at the diverging point of the Coulomb potential is mathematically described by three-parameter family of generalized connection conditions. A scheme is devised to physically implement the generalized conditions, which provides the way to experimentally realize non-Rydberg spectra in 1D Hydrogen atom. Schedule: Part 1, Self-adjoint extension of Hilbert space operator Part 2, 1D Coulomb problem
会場: via Zoom
イベント公式言語: 英語
-
セミナー
Non-perturbative tests of duality cascades in three dimensional supersymmetric gauge theories
2020年12月14日(月) 16:00 - 18:10
久保 尚敬 (京都大学 基礎物理学研究所 特別研究員)
M2-brane is an interesting object in M-theory and string theory. A three-dimensional ?=6 super conformal Chern Simons theory with gauge group U(?1)×?(?2), called ABJ theory, describes the low energy behavior of M2-brane On the one hand, it has been considered that when |?1−?2| is larger than the absolute value of Chern Simons level, the supersymmetry is broken. On the other hand, it was predicted that an interesting phenomenon called duality cascade occurs, and supersymmetry is not broken in some cases. Motivated by this situation, we performed non-perturbative tests by focusing on the partitionfunction on ?3. The result strongly suggests that the duality cascade indeed occurs. We also proposed that the duality cascade occurs in theories with more general gauge groups and we performed non-perturbative tests in the same way. I will review and explain our physical prediction in the first half of my talk. In the second half of my talk , I will explain the non-perturbative tests . This part is mathematical because the partition function reduces to a matrix model by using the supersymmetric localization technique.
会場: via Zoom
イベント公式言語: 英語
-
セミナー
Mathematics of thermalization in isolated quantum systems
2020年11月10日(火) 16:00 - 18:10
白石 直人 (学習院大学 理学部 物理学科 助教)
If an isolated macroscopic quantum system is left at a nonequilibrium state, then this system will relax to the unique equilibrium state, which is called thermalization. Most of quantum many-body systems thermalize, while some many-body systems including integrable systems do not thermalize. What determines the presence/absence of thermalization and how to understand thermalization from microscopic quantum mechanics are profound long-standing problems. In the first part of my talk, I briefly review some established results of quantum thermalization. I first clarify the problem of thermalization in a mathematical manner, and then introduce several important results and insights: typicality of equilibrium states [1], relaxation caused by large effective dimension [2], and eigenstate thermalization hypothesis (ETH) [3,4] and weak-ETH [5]. In the second part of my talk, I explain some of my results. First, I introduce a model which is non-integrable and thermalizes but does not satisfy the ETH [6,7]. This finding disproves the conjectures that all nonintegrable systems satisfy the ETH and that the ETH is a necessary condition for thermalization. I also discuss the hardness of the problem of thermalization from the viewpoint of computational science [8]. Then, I move to an analytical approach to a concrete model, and prove that S=1/2 XYZ chain with a magnetic field is nonintegrable [9]. This is the first example of proof of nonintegrability in a concrete quantum many-body system, which will help a mathematical approach to thermalization.
会場: via Zoom
イベント公式言語: 英語
22 イベント