[ 素粒子論セミナー ]

Callan-Rubakov effect and non-invertible defects

講演者

Masataka Watanabe (YITP)

日時

2022年11月29日(火)15:40-16:40

場所

H701

概要

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There is a famous puzzle in QED coupled to N massless Dirac fermions that the scattering of afermion off a monopole creates an out-state which cannot be any of the elementary particles in the theory. We give a new understanding of the s-wave reduced version of the phenomena by interpreting the magnetic defect as a Tambara-Yamagami line defect.

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[ 素粒子論セミナー ]

Explicit Late Time Correlation Functions in de Sitter from CFT

講演者

Heng-Yu Chen (National Taiwan U.)

日時

2022年11月22日(火)15:40-16:40

場所

H701

概要

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In this talk, we will discuss recent work on constructing an explicit example of dS3/CFT2 correspondence via analytic continuation, then we will use it to obtain the late time correlation functions in the three dimensional de Sitter spacetime from two dimensional CFT. We will also discuss how to reproduce them from the suitable holographic configurations, and future directions.

[ 素粒子論セミナー ]

Comment on the subtlety of defining real-time path integral in lattice gauge theories

講演者

Nobuyuki Matsumoto (RIKEN / BNL)

日時

2022年11月8日(火)15:40-16:40

場所

Online(H701)

概要

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Recently, Hoshina, Fujii, and Kikukawa [1] pointed out that the naive lattice gauge theory action in Minkowski signature does not result in a unitary theory in the continuum limit, and Kanwar and Wagman [2] proposed alternative lattice actions to the Wilson action without divergences. We here show that the subtlety can be understood from the asymptotic expansion of the modified Bessel function, which has been discussed for path integral of compact variables in nonrelativistic quantum mechanics [3,4]. The essential ingredient for defining the appropriate continuum theory is the iε prescription, which we show is applicable also for the Wilson action. It is here important that the iε should be implemented for both timelike and spacelike plaquettes. We then argue that such iε can be given a physical meaning that they remove singular paths having nontrivial winding for an infinitesimal time evolution that do not have corresponding paths in the continuum. Such point of view is only apparent in systems with compact variables as lattice gauge theories. This talk is based on [5].

[1] H. Hoshina, H. Fujii and Y. Kikukawa, "Schwinger-Keldysh formalism for Lattice Gauge Theories," PoS LATTICE2019, 190 (2020)
[2] G. Kanwar and M. L. Wagman, "Real-time lattice gauge theory actions: Unitarity, convergence, and path integral contour deformations," Phys. Rev. D 104, no.1, 014513 (2021) [arXiv:2103.02602 [hep-lat]]
[3] W. Langguth and A. Inomata, "Remarks on the Hamiltonian path integral in polar coordinates," J. Math. Phys. 20, 499-504 (1979)
[4] M. Bohm and G. Junker, "Path integration over compact and noncompact rotation groups," J. Math. Phys. 28, 1978-1994 (1987)
[5] N. M. "Comment on the subtlety of defining real-time path integral in lattice gauge theories," [arXiv:2206.00865 [hep-lat]]

[ 素粒子論セミナー ]

Tensor renormalization group analysis for the phase structure of the CP(1) model with the theta term

講演者

Katsumasa Nakayama (RIKEN)

日時

2022年11月1日(火)15:40-16:40

場所

H701

概要

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We study the phase structure of the CP(1) model by using several kinds of the tensor renormalization group. The phase structure of the CP(1) model is investigated by the strong coupling expansion, analytical continuation with the assumption, possibly sign problematic Monte Carlo simulation and the simple TRG. These predictions show the first-order transition at θ = π at the strong coupling region, but there are contradicted in the weak and intermediate coupling region because of the limitation of the systematic error. In this work, we extend the TRG method to the intermediate coupling region by carefully discussing the systematic error in TRG. We apply the recently developed TRG method, such as the anisotropic TRG and bond-weighted TRG, to reduce the systematic errors in the coarse-graining step. In order to show the importance of systematic error estimation, we start from the θ = 0 calculation as a demonstration.The larger bond size is strongly required for a reliable result, depending on the initial tensor size. After the demonstration, we calculate the CP(1) model with the theta term. With the controlled systematic error, the TRG method shows the first order transition at the θ = π up to β < 1.1.

[ 素粒子論セミナー ]

Effective field theory in light of relative entropy

講演者

Naoto Kan(Osaka U.)

日時

2022年10月25日(火)15:40-16:40

場所

H701

概要

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We consider the relative entropy between two theories (or systems) described by heavy and light degrees of freedom. The non-negativity of the relative entropy gives inequalities for the difference between the two EFTs obtained by integrating the heavy degrees of freedom. Using the inequalities, we consider the entropy constraint on higher-dimensional operators arising from integration over the heavy degrees of freedom.

[ 素粒子論セミナー ]

Models of the muonium to antimuonium transition

講演者

Yuichi Uesaka (Kyushu Sangyo U.)

日時

2022年10月18日(火)15:40-16:40

場所

Online

概要

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Muonium is a bound state composed of an antimuon and an electron, which constitutes a hydrogen-like atom.The process of the muonium-to-antimuonium transition is considered to be effective to identify fundamental interactions which relate to the lepton flavor and lepton number violation.New experiments are being planned at J-PARC in Japan and CSNS in China, and it is expected to attract more attention in the near future.We have studied what kind of model can be verified in the next generation of the muonium-to-antimuonium transition search experiments while escaping the constraints by other experiments.Though the transition probability is strongly suppressed by the lepton flavor conservation in the standard model, it can be much larger by the exchanges of neutral and doubly charged bosons, and by box loop diagrams in new physics beyond the standard model. In this talk, I will show the analyses for some neutrino models which can be tested in the forthcoming experiments for the muonium to antimuonium transition.

[ 素粒子論セミナー ]

Lattice fermions as spectral graphs -Toward a new theorem-

講演者

Tatsuhiro Misumi (Kindai U.)

日時

2022年10月11日(火)15:40-16:40

場所

H701

概要

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We study lattice fermions from the viewpoint of spectral graph theory (SGT). We find that a fermion defined on a certain lattice is identified as a spectral graph. SGT helps us investigate the number of zero eigenvalues of lattice Dirac operators even on the non-torus and non-regular lattice, leading to understanding of the number of fermion species (doublers) on lattices with arbitrary topologies. We apply this idea to the known lattice fermion formulations including Naive fermions, Wilson fermions and Domain-wall fermions, and reproduce the known fact on the number of species. We also apply it to the lattice fermion on the discretized four-dimensional hyperball and discuss the number of fermion species on the bulk. In the end of the paper, we discuss the application of the analysis to lattice fermions on generic lattices with arbitrary topologies, leading to conjecturing a new theorem regarding the number of fermion species on the lattice.

[ 素粒子論セミナー ]

Is energy conserved in general relativity ? — Noether’s 1st theorem with local symmetries —

講演者

Shinya Aoki (YITP)

日時

2022年10月4日(火)15:40-16:40

場所

H701

概要

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To answer the question in the title is rather non-trivial. In a flat spacetime, as a consequence of Noether's 1st theorem, a time translation symmetry not only defines a corresponding energy density as the time component of the Noether current, but also tells that a total energy given by a volume integral of the energy density is conserved. This construction of a conserved energy does not work in general relativity, since a time translational symmetry is a part of local symmetries, general coordinate transformations, to which Noether's first theorem can not be directly applied. Recently we propose a general method to derive a conserved current associated with a global symmetry which is a part of local symmetries. We apply the method to general relativity and obtain the following answer to the question. “No, the matter energy is not conserved in general. However there always exist a more general conserved charge associated with matters.” In my talk, I will explain how this conclusion is derived.

[ 素粒子論セミナー ]

Coleman-Weinberg Abrikosov-Nielsen-Olesen strings

講演者

Yu Hamada (KEK)

日時

2022年7月26日(火)15:40-16:40

場所

H701

概要

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Vortex strings are topological solitons in field theories and appear in various systems, such as superconductor, neutron star, early universe and so on. We clarify the nature of vortex strings in the Abelian-Higgs-like model with a Coleman-Weinberg type Higgs potential, which is inspired by the argument of the naturalness problem in particle physics. This model has the gauge U(1) symmetry and the classical scale invariance. The model has no vortex string solution at the classical level, while quantum corrections spontaneously break the U(1) symmetry and stable vortex strings exist. The interaction between the two vortex strings is found to be very different from that of the Abelian-Higgs model with the conventional second- and fourth-order type potentials. Implications for particle physics and cosmology are also discussed.

[ 素粒子論セミナー ]

Emergence of time from unitary equivalence

講演者

Chris Lau (Kobe U.)

日時

2022年7月5日(火)15:40-16:40

場所

H701

概要

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In this talk, I want to motivate a possible way to realise time as an emergent concept. I will introduce a general fermionic system and demonstrate how a modular flow can be interpreted as a physical time flow. I will provide support for this interpretation using the thermofield double state together with the relations between various quantum chaos diagnostic quantities. I will explain how these concepts can be linked together and realise an emergence of time. I will end by discussing some limitations of our example.

[ 素粒子論セミナー ]

The W-boson mass anomaly and new physics interpretations

講演者

Teppei Kitahara (Nagoya U.)

日時

2022年6月21日(火)15:40-16:40

場所

H701

概要

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The CDF collaboration recently announced the most precise measurement of the W-boson mass by using the proton-antiproton collision data at the Fermilab Tevatron. This data provides a significant inconsistency between the measured mass and the Standard Model prediction. In this talk, first, I will summarize the current circumstances of the W-boson mass measurements and the Standard Model prediction. Next, I will present several explanations of this anomaly by the new physics beyond the Standard Model. Finally, a model with the vector-like quark will be introduced, based on our recent work arXiv:2204.05962.

[ 素粒子論セミナー ]

Muon g-2

講演者

Motoi Endo (KEK)

日時

2022年6月17日(金)15:40-16:40

場所

Hybrid (E204+Online)

概要

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In the last year, the Fermilab experiment has reported their first result on the measurement of the muon anomalous magnetic moment (g-2). The result was consistent with the Brookhaven E821 experiment, and the deviation from the standard model prediction becomes 4.2sigma, which is planned to be revised soon. In this talk, we will overview the status and prospect of the theoretical side of the muon g-2. I will first review the standard model prediction and explain the issues explored today. Then, new physics interpretations will be discussed, especially focusing on the supersymmetric models.

[ 素粒子論セミナー ]

Narain CFTs and error-correcting codes

講演者

Shinichiro Yahagi (Tokyo U.)

日時

2022年6月7日(火)15:40-16:40

場所

オンライン

概要

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A Narain CFT is a conformal field theory (CFT) that describes a compactified spacetime. On the other hand, an error-correcting code is a concept in information theory for transmitting information correctly in spite of errors. In this talk, I will discuss the relation between Narain CFTs and error-correcting codes on finite fields through lattices. Using this correspondence, we can consider the spectrum and the symmetries of the CFT in the language of the code. In particular, the spectral gap of the CFT and the error correction capability of the code are roughly proportional, which helps to find CFTs with large spectral gaps.

[ 素粒子論セミナー ]

Implications of anomaly-free axion for Higgs bosons in 3HDM

講演者

Kodai Sakurai (Tohoku U.)

日時

2022年5月24日(火)15:40-16:40

場所

H701

概要

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Axion (or axion-like particle) is a prominent candidate of light dark matter (DM). It emerged as the pseudo Nambu-Goldstone boson originated from the breaking of global U(1) symmetry. If the mass scale is keV, axion usually suffers from the severe constraint from the X-ray bounds. However, a fascinating axion, which can evade such a severe constraint, was proposed as an anomaly-free axion. In this talk, I will discuss a three Higgs doublet model (3HDM) as a UV complete model where the anomaly-free axion is embodied. I will show the synergy between the anomaly-free axion and the heavy Higgs bosons predicted in this concrete model.

[ 素粒子論セミナー ]

Symmetry Protected Topological Criticality

講演者

Linhao Li (Tokyo U.)

日時

2022年5月10日(火)15:40-16:40

場所

Online (D501)

概要

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Symmetry protected topological (SPT) phases are one of the simplest, yet nontrivial, gapped systems that go beyond the Landau paradigm. In this work, we study the notion of SPT for critical systems, namely, symmetry protected topological criticality (SPTC). We discuss a systematic way of constructing a large class of SPTCs using decorated defect construction, study the physical observables that characterize the nontrivial topological signatures of SPTCs, and discuss the stability under symmetric perturbations. Our exploration of SPTC is mainly based on several previous studies of gapless SPT: gapless symmetry protected topological order, symmetry enriched quantum criticality and intrinsically gapless topological phases. We partially reinterpret these previous studies in terms of decorated defect construction, and discuss their generalizations.

[ 素粒子論セミナー ]

CFT duals of three-dimensional de Sitter gravity

講演者

Tatsuma Nishioka (Osaka U.)

日時

2022年4月26日(火)15:40-16:40

場所

H701

概要

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We present a class of dS/CFT correspondence between two-dimensional CFTs and three-dimensional de Sitter spaces. We argue that such a CFT includes an SU(2) WZW model in the critical level limit k → −2, which corresponds to the classical gravity limit. We can generalize this dS/CFT by considering the SU(N) WZW model in the critical level limit k →−N, dual to the higher spin gravity on a three-dimensional de Sitter space. We confirm that under this proposed duality the classical partition function in the gravity side can be reproduced from CFT calculations.

[ 素粒子論セミナー ]

Some phenomenological aspects of 2HDM

講演者

Tanmoy Mondal (Osaka U.)

日時

2022年4月19日(火)15:40-16:40

場所

H701

概要

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I will talk about some phenomenological aspects of the two Higgs doublet model(2HDM). The 2HDM can explain the muon anomalous magnetic moment with a light pseudoscalar. I will discuss the prospect of discovering such particles at the lepton collider like ILC. Then I will discuss how an extension of 2HDM can connect neutrino mass and muon anomalous magnetic moment.

[ 原子核実験セミナー ]

Nuclear Incompressibility: 
How Collective Excitation Modes of a Nucleus Characterize Astrophysical Processes

講演者

Dr. Umesh Garg
(Professor, Department of Physics, University of Notre Dame)

日時

2022年2月3日(木)11:15-12:45

場所

オンライン

概要

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The Nuclear Incompressibility parameter is one of three important components characterizing the nuclear equation of state (EOS). It has crucial bearing on diverse nuclear and astrophysical phenomena, including radii of neutron stars, strength of supernova collapse, emission of neutrinos in supernova explosions, and collective flow in medium- and high-energy nuclear collisions. In this talk I will review current status of the research on direct experimental determination of nuclear incompressibility via the compressional-mode giant resonances. In particular, measurements on a series of Sn and Cd isotopes have provided an "experimental" value for the asymmetry term of the nuclear incompressibility; this term is important for the EOS of neutron stars. We also find that the GMR centroid energies of the in both Sn and Cd isotopes are significantly lower than the theoretical predictions, pointing to the possible role of superfluidity in nuclear incompressibility.
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IPC intensive lecture will be also given online by Prof. Umesh Garg during Feb 1-4.
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問い合わせ先:川畑 貴裕 (理学研究科物理学専攻)

スクール

高エネルギー物理春の学校

2015年6月10-12日

物理院生春の学校

2015年3月9-11日

ICEPPシンポジウム

2015年2月8-11日