Back Numbers 2019-20
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  • April 12, 2019
  • Speaker: Tadashi Sasaki (Hokkaido Univ.)
    Title Topological nature of the Hawking temperature of black holes
    E-Print [1] Charles W. Robson, Leone Di Mauro Villari, Fabio Biancalana, [arXiv:1810.09322[gr-qc]]
    [2] Charles W. Robson, Leone Di Mauro Villari, Fabio Biancalana, [arXiv:1902.02547[gr-qc]]
    [3] A. Övgün, I. Sakalli, [arXiv:1902.04465[gr-qc]]

  • April 19, 2019
  • Speaker: Tomonori Ugajin (OIST)
    Title Modular Hamiltonians of excited states, OPE blocks and emergent bulk fields
    Abstract We study the entanglement entropy and the modular Hamiltonian of slightly excited states reduced to a ball shaped region in generic conformal field theories. We set up a formal expansion in the one point functions of the state in which all orders are explicitly given in terms of integrals of multi-point functions along the vacuum modular flow, without a need for replica index analytic continuation. We show that the quadratic order contributions in this expansion can be calculated in a way expected from holography, namely via the bulk canonical energy for the entanglement entropy, and its variation for the modular Hamiltonian. The bulk fields contributing to the canonical energy are defined via the HKLL procedure. In terms of CFT variables, the contribution of each such bulk field to the modular Hamiltonian is given by the OPE block corresponding to the dual operator integrated along the vacuum modular flow. These results do not rely on assuming large N or other special properties of the CFT and therefore they are purely kinematic.
    E-Print [1] G. Sarosi, T. Ugajin, [arXiv:1705.01486[hep-th]]
    [2] T. Ugajin, [arXiv:1812.01135[hep-th]]

  • April 26, 2019
  • Speaker: Kenji Shiohara (Hokkaido Univ.)
    Title Deep Learning and AdS/CFT
    E-Print [1] K. Hashiomoto, S. Sugishita, A. Tanaka and A. Tomiya, [arXiv:1802.08313[hep-th]]
    [2] K. Hashiomoto, S. Sugishita, A. Tanaka and A. Tomiya, [arXiv:1809.10536[hep-th]]


  • May 10, 2019
  • Speaker: Toshiaki Fujimori (Keio Univ.)
    Title Bions and resurgence in \(CP^N\) model
    Abstract Perturbation series in quantum field theory are generically divergent asymptotic series. Resurgence theory relates such perturbation series and non-perturbative effects which cannot be captured by the perturbative expansion. It has been shown that the so-called bion saddle points, which consist of instanton-antiinstanton pair, plays an important role in resurgence theory in a certain class of quantum systems. In this talk, I will overview the recent development of the resurgence theory based on the complexified path integral and the bion saddle points. I will talk about the bion contributions in the 2d \(CP^{N −1}\) models on \(R \times S^1\) with twisted boundary conditions and show that the semi-classical bion contributions is consistent with the expected IR-renormalon ambiguity.
    E-Print [1] T. Fujimori, S. Kamata, T. Misumi, M. Nitta, N. Sakai, [arXiv:1810.03768[hep-th]]
    [2] T. Fujimori, S. Kamata, T. Misumi, M. Nitta, N. Sakai, [arXiv:1705.10483[hep-th]]
    [3] T. Fujimori, S. Kamata, T. Misumi, M. Nitta, N. Sakai, [arXiv:1702.00589[hep-th]]
    [4] T. Fujimori, S. Kamata, T. Misumi, M. Nitta, N. Sakai, [arXiv:1607.04205[hep-th]]

  • May 17, 2019
  • Speaker: Kazuhiko Suehiro (Hokkaido Univ.)
    Title de Sitter Swampland conjecture and its implications
    E-Print [1] G. Obied, H. Ooguri, L. Spodyneiko, C. Vafa, [arXiv:1806.08362[hep-th]]
    related references

  • May 24, 2019
  • Speaker: Shintaro Takada (Hokkaido Univ.)
    Title Flux compactifications and naturalness
    E-Print [1] W.Buchmuller, M.Dierigl, E.Dudas, [arXiv:1804.07497[hep-th]]

  • May 31, 2019
  • Speaker: Takaaki Nomura (KIAS)
    Title Models with extra U(1) gauge symmetry and related phenomenology
    Abstract An extra U(1) gauge symmetry is often introduced in describing a new physics around TeV scale for some issues such as stability of dark matter, controlling flavor structure and restricting interactions in neutrino mass models. Such an U(1) gauge symmetry is considered to be spontaneously broken and gives extra neutral massive gauge boson Z’. This Z’ can be either heavier or lighter than electroweak scale depending on interaction strength, and would induce rich phenomenological consequences. In this talk, I first review models with extra U(1) gauge symmetry and discuss motivation of constructing a model, experimental constraints, and phenomenology in these models. Then I will introduce some of recent works regarding extra U(1) symmetry and show their construction as well as phenomenological consequences.
    E-Print [1] P. Ko, T. Nomura, C. Yu, [arXiv:1902.06107[hep-ph]]
    [2] T. Nomura, H. Okada, [arXiv:1806.01714[hep-ph]]
    [3] T. Nomura, H. Okada, [arXiv:1709.06406[hep-ph]]


  • June 7, 2019
  • Speaker: Hisao Suzuki (Hokkaido Univ.)
    Title Testing the rotational nature of the supermassive object M87* from the circularity and size of its first image
    E-Print [1] C. Bambi, K. Freese, S. Vagnozzi, L. Visinelli, [arXiv:1904.12983[gr-qc]]
    [2] D. Gates, D. Kapec, A. Lupsasca, Y. Shi, A. Strominger, [arXiv:1809.09092[hep-th]]

  • June 14, 2019
    Speaker: Kenzo Ishikawa (Hokkaido Univ.)
    Title Absolute transition-probability: Implications to physical phenomena
    Abstract Transition probability is one of the most important physical quantity derived from the quantum mechanics, and is given by the fomula \(P_{\alpha\beta}=<\beta|\alpha>^2\), for \(<\beta|\beta>=<\alpha|\alpha>=1\). It is not straightforward to compute the absolute probability, but a relative probability such as a rate, a cross section, and others are easier to study and have been applied successfully. Nevertheless phenomena which have origin in the absolute one can not be explained by the relative one. The absolute one is neccessary for them. In this talk, I will study the absolute transition probability, and its implications.
    E-Print [1] K. Ishikawa, Y. Tobita, PTEP (2013)
    [2] K. Ishikawa, Y. Tobita, Ann of Phys (2014)
    [3] K. Ishikawa, T. Tajima, Y. Tobita, PTEP (2015)
    [4] N. Maeda, T. Yabuki, Y. Tobita, K. Ishikawa, PTEP (2017), 素粒子論研究 (2018)
    [5] K. Ishikawa, K. Oda, PTEP (2018)
    [6] K. Ishikawa, O. Jinnouchi, A. Kubota, T. Sloan, T. Tatsuishi, R. Ushioda PTEP (2019)
    [7] R. Ushioda et al. (2019), in preparation
    [8] K. Ishikawa, K. Nishiwaki, K. Oda (2019), in preparation
    [9] 量子力学Ⅰ,Ⅱ (裳華房、石川健三、2019)

  • June 21, 2019
    Speaker: Takuya Tatsuishi (Hokkaido Univ.)
    Title How to produce antihelium from dark matter
    E-Print [1] J. Heeck, A. Rajaraman, [arXiv:1906.01667[hep-ph]]
    [2] AMS Collaboration, Phys.Rev.Lett. 117, no. 9, 091103 (2016)

  • June 28, 2019
    Speaker: Hideki Maeda (Hokkai-Gakuen Univ.)
    Title Exact black-hole formation with a conformally coupled scalar field in three dimensions
    Abstract We present exact dynamical and inhomogeneous solutions in three-dimensional AdS gravity with a conformally coupled scalar field. They contain stealth configurations of the scalar field overflying the BTZ spacetime and also solutions with a non-vanishing energy-momentum tensor. The latter non-stealth class consists of the solution obtained by Xu and its analytic extension. It is shown that this proper extension represents: (i) an eternally shrinking dynamical black hole, (ii) a curious spacetime which admits an event horizon without any trapped surface, or (iii) gravitational collapse of a scalar field in an asymptotically AdS spacetime. In the last case, by attaching the solution regularly to the past massless BTZ spacetime with a vanishing scalar field, the whole spacetime represents the black-hole formation from regular initial data in an asymptotically AdS spacetime. Depending on the parameters, the formed black hole can be asymptotically static in far future.
    E-Print [1] L. Aviles, H. Maeda, C. Martinez, [arXiv:1808.10040[gr-qc]]
    Class. Quant. Grav. 35, 245001 (2018)


  • July 5, 2019
    Speaker: Toshifumi Yamada (Shimane Univ.)
    Title Grand Unified Theory and its testability
    Abstract The Grand Unified Theory (GUT) is an interesting candidate for physics beyond the Standard Model. The only direct evidence of GUT is a proton decay, which is going to be searched for at Hyper-Kamiokande with a much improved sensitivity. We first focus on so-called “dim-6 proton decay” induced by a GUT gauge boson exchange, and investigate which types of GUT models, including supersymmetric and non-supersymmetric ones, can be tested through dim-6 proton decay at Hyper-Kamiokande. Next, we turn our attention to so-called “dim-5 proton decay” induced by a colored Higgsino exchange in supersymmetric GUT. The rate for a dim-5 proton decay depends on how the Standard Model Yukawa couplings are derived in GUT, and we discuss a correlation between dim-5 proton decay and the structure of the Yukawa couplings.
    E-Print [1] N. Haba, Y. Mimura, T. Yamada, [arXiv:1812.08521 [hep-ph]]
    Phys. Rev. D 99, no. 7, 075018 (2019)
    [2] N. Haba, Y. Mimura, T. Yamada, [arXiv:1904.11697 [hep-ph]]

  • July 12, 2019
    M2 Journal club
    Speaker: Hikaru Uchida (Hokkaido Univ.)
    Title Wavefunctions on Resolution of \(T^2/Z_2\) Orbifold
    Speaker: Yuta Mimura (Hokkaido Univ.)
    Title GAN for efficient searching MSSM-like \(Z_6\)-Ⅱ orbifold compactification parameters of \(E_8 \times E_8\) heterotic string

  • July 19, 2019
    Speaker: Shuichi Yokoyama (YITP)
    Title Holography via Flow Equation
    Abstract Recently the method of a (gradient) flow equation attracts more attention for the purpose of the study of lattice QCD and holography. In the first half I will give a pedagogical introduction of a flow equation and its application to construction of AdS geometry as a holographic space of conformal field theory (CFT). In the latter half I will speak about my latest result of the application to non-relativistic CFT and the resulting holographic geometry, and the technique to compute quantum corrections to the bulk theory in this framework.
    E-Print [1] S. Aoki, S. Yokoyama, [arXiv:1707.03982[hep-th]]
    [2] S. Aoki, S. Yokoyama, [arXiv:1709.07281[hep-th]]
    [3] S. Aoki, J. Balog, S. Yokoyama, [arXiv:1804.04636[hep-th]]
    [4] S. Aoki, S. Yokoyama, K. Yoshida, [arXiv:1902.02578[hep-th]]

  • July 26, 2019
    M2 Journal club
    Speaker: Cristopher CHUÑE (Hokkaido Univ.)
    Title Heterotic string theory and orbifold compactification
    Speaker: Yuki Kariyazono (Hokkaido Univ.)
    Title Modular symmetry in magnetic flux compactification


  • August 27-29, 2019
    Intensive lecture
    Speaker: Masahide Yamaguchi (Tokyo Inst. Tech.)
    Title  インフレーション宇宙における原始密度揺らぎと重力波

  • August 28, 2019
    Seminar (13:30-15:00)
    Speaker: Masahide Yamaguchi (Tokyo Inst. Tech.)
    Title Invertible field transformations with derivatives: necessary and sufficient conditions
    Abstract We formulate explicitly the necessary and sufficient conditions for the local invertibility of a field transformation involving derivative terms. Our approach is to apply the method of characteristics of differential equations, by treating such a transformation as differential equations that give new variables in terms of original ones. The obtained results generalise the well-known and widely used inverse function theorem. Taking into account that field transformations are ubiquitous in modern physics and mathematics, our criteria for invertibility will find many useful applications.


  • October 4, 2019
    Speaker: Noboru Kawamoto (Hokkaido Univ.)
    Title 4-dimensional \(N=4\) super Yang-Mills on the Lattice

  • October 11, 2019
    Speaker: Tatsuo Kobayashi (Hokkaido Univ.)
    Title Flavor Moonshine
    E-Print [1] S. Shiba, H. Sugawara, [arXiv:1908.11032[hep-th]]

  • October 18, 2019
    Speaker: Mitsuru Kakizaki (Univ. of Toyama)
    Title Selecting models of first-order phase transitions using the synergy between collider and gravitational-wave experiments
    Abstract We investigate the sensitivity of future space-based interferometers such as LISA and DECIGO to the parameters of new particle physics models which drive a first-order phase transition in the early Universe. We first perform a Fisher matrix analysis on the quantities characterizing the gravitational wave spectrum resulting from the phase transition, such as the peak frequency and amplitude. We next perform a Fisher analysis for the quantities which determine the properties of the phase transition, such as the latent heat and the time dependence of the bubble nucleation rate. Since these quantities are determined by the model parameters of the new physics, we can estimate the expected sensitivities to such parameters. We illustrate this point by taking three new physics models for example: (1) models with additional isospin singlet scalars (2) a model with an extra real Higgs singlet, and (3) a classically conformal B−L model. We find that future gravitational wave observations play complementary roles to future collider experiments in pinning down the parameters of new physics models driving a first-order phase transition.
    e-print [1] K. Hashino, R. Jinno, M. Kakizaki, S. Kanemura, T. Takahashi, M. Takimoto, [arXiv:1809.04994 [hep-ph]]
    Phys. Rev. D 99, no. 7, 075011 (2019)

  • October 25, 2019
    Speaker: Hiroaki Sugiyama (Toyama Pref. Univ.)
    Title Introduction to neutrino physics
    Abstract I will explain basics about the neutrino, e.g., why the neutrino was introduced.
    Title A classification of models of neutrino masses and its application
    Abstract Neutrino oscillation measurements have shown that neutrinos have non-zero masses, and then the standard model have to be extended with a mechanism for generating neutrino masses. Although there are many possible models of neutrino masses, it is an almost common feature of these models that some new scalar fields are introduced with their Yukawa interactions with leptons. In this talk, I will show a classification of models of neutrino masses according to combinations of new Yukawa interactions between new scalar fields and leptons. I will also show its possible application to discrimination of models of neutrino masses.
    e-print [1] S. Kanemura, H. Sugiyama, [arXiv:1510.08726 [hep-ph]]
    Phys.Lett. B753 (2016) 161.
    [2] S. Kanemura, K. Sakurai, H. Sugiyama, [arXiv:1603.08679 [hep-ph]]
    Phys.Lett. B758 (2016) 465.
    [3] M. Aoki, S. Kanemura, K. Sakurai, H. Sugiyama, [arXiv:1607.08548 [hep-ph]]
    Phys.Lett. B763 (2016) 352.


  • November 1, 2019
    Speaker: Ryuichi Nakayama (Hokkaido Univ.)
    Title Quantum Thermalization in 2d CFT
    e-print [1] S. Datta, P. Kraus, B. Michel, [arXiv:1904.00668[hep-th]]
    [2] M. Besken, Shouvik, P. Kraus, [arXiv:1907.06661[hep-th]]

  • November 8, 2019
    Rehearsal of M1 Journal Club, 15:00
    Speaker: Shota Kikuchi (Hokkaido Univ.)
    Title Introduction to Superstring theory and its constructions

  • November 15, 2019
    Speaker: Daniel Jeans (KEK)
    Title Physics and detectors at the ILC
    Abstract The International Linear Collider will be a "Higgs Factory", producing a large sample of Higgs particles in a well-controlled, clean environment. This will enable high precision tests of the Standard Model's Higgs sector. I will describe the physics potential of the ILC, and discuss the detectors being designed to measure the products of ILC collisions.
    Speaker: Masao Kuriki (Hiroshima Univ.)
    Title ILC加速器の概要と計画の状況
    Abstract ILC国際リニアコライダーは重心系エネルギー250 -1000 GeVの電子・陽電子コライダーです。 線形加速器を用いることでシンクロトロン輻射によるエネルギーロスをなくす一方、 ビームは衝突点を一回きりしか通過しないため、ビームパワーあたりのルミノシティを いかに高くするかが加速器設計の鍵となります。ILCでは超伝導加速器をもちいることで 加速効率を向上させ、また非対称ナノビーム衝突によりビーム間の電磁相互作用を抑えつつ ルミノシティを最大化させます。本講演では、加速器の概要と、計画の現状についてお話しいたします。
    Rehearsal of M1 Journal, 15:00
    Speaker: Chikara Tateshita (Hokkaido Univ.)
    Title Conformal Symmetry in Physics

  • November 22, 2019
    Speaker: Motoi Endo (KEK)
    Title Status and prospect for muon g-2 and new physics
    Abstract Currently, the muon anomalous magnetic moment (g-2) has >3\sigma discrepancy between the standard model (SM) and experimental results. Interestingly, a new experiment is going on at Fermilab, and the first result comes soon. In this talk, we overview the status and the prospect of the experiment and SM. Then, we discuss new physics models to explain the discrepancy.

  • November 29, 2019
    Speaker: Yuji Omura (Kindai Univ.)
    Title New Physics Possibilities in Flavor Physics
    e-print [1] S. Iguro, Y. Muramatsu, Y. Omura, Y. Shigekami, [arXiv:1804.07478[hep-ph]]
    [2] J. Kawamura, S. Okawa, Y. Omura, [arXiv:1706.04344[hep-ph]]
    Speaker: Shuhei Iguro (Nagoya Univ.)
    Title \(D^∗\) polarization vs. \(R_{D^{(∗)}}\) anomalies in the leptoquark models.
    Abstract Polarization measurements in \(\bar{B}→D^{(∗)}τ\bar{ν}\) are useful to check consistency in new physics explanations for the \(R_D\) and \(R_{D^{∗}}\) anomalies. In this talk, we investigate the \(D^∗\) and \(τ\) polarizations and focus on the new physics contributions to the fraction of a longitudinal \(D^∗\) polarization \(F_L^{D^*}\), which is recently measured by the Belle collaboration \(F_L^{D^*}= 0.60 ± 0.09\), in model-independent manner and in each single leptoquark model (\({\rm R}_2\), \({\rm S}_1\) and \({\rm U}_1\)) that can naturally explain the \(R_{D^{(∗)}}\) anomalies. It is found that BR(\(B_c  → τν\)) severely restricts deviation from the Standard Model (SM) prediction of \(F_{L,SM}^{D^*} = 0.46±0.04\) in the leptoquark models: [0.44, 0.45], [0.44, 0.49], and [0.44, 0.46] are predicted as a range of \(F_L^{D^*}\) for the \({\rm R}_2\), \({\rm S}_1\) and \({\rm U}_1\) leptoquark models, respectively, where the current data of \(R_{D^{(∗)}}\) is satisfied at \(1σ\) level. It is also shown that the \(τ\) polarization observables can much deviate from the SM predictions. The Belle II experiment, therefore, can check such correlations between \(R_{D^{(∗)}}\) and the polarization observables, and discriminate among the leptoquark models.
    e-print [1] S. Iguro, T. Kitahara, Y. Omura, R. Watanabe, K. Yamamoto, [arXiv:1811.08899[hep-ph]]


  • December 6, 2019
    Speaker: Yu Hamada (Kyoto Univ.)
    Title Stable Nambu monopole in two Higgs doublet models
    Abstract Two Higgs doublet model (2HDM), in which one more Higgs doublet is added to the Standard Model(SM), is one of the most simple extensions of the SM. We show that there is a stable magnetic monopole attached by vortex strings (called as Nambu monopole) in 2HDM. In particular, the stability of the monopole is topologically protected when the Higgs potential has a U(1) symmetry and a \(\mathbb{Z}_2\) symmetry. Since this monopole has a mass of about a few TeV, it might be discovered in future monopole searches.
    e-print [1] M. Eto, Y. Hamada, M. Kurachi, M. Nitta, [arXiv:1904.09269[hep-ph]]

  • December 13, 2019
    Speaker: Takuya Hirose (Osaka city Univ.)
    Title Cancellation of one-loop corrections to scalar masses in Yang-Mills theory with flux compactification
    Abstract We calculate one-loop corrections to the mass for the zero mode of scalar field in a six-dimensional Yang-Mills theory compactified on a torus with magnetic flux. It is shown that these corrections are exactly cancelled thanks to a shift symmetry under the translation in extra spaces. This result is expected from the fact that the zero mode of scalar field is a Nambu-Goldstone boson of the translational invariance in extra spaces.
    e-print [1] W. Buchmuller, M. Dierigl, E. Dudas, J. Schweizer, [arXiv:1611.03798[hep-th]]
    JHEP 1704 (2017) 052.
    [2] W. Buchmuller, M. Dierigl, E. Dudas, [arXiv:1804.07497[hep-th]]
    JHEP 1808 (2018) 151.
    [3] T. Hirose, N. Maru, [arXiv:1904.06028[hep-th]]
    JHEP 1908 (2019) 054.

  • December 18-20, 2019
    Intensive lecture
    Speaker: Kohei Yorita (Waseda Univ.)
    Title LHC実験物理学


  • January 10, 2020
    Speaker: Kazutoshi Ohta (Meiji Gakuin Univ.)
    Title Supersymmetric Gauge Theory on the Graph and Localization
    Abstract Supersymmetric gauge theory can be constructed on the discrete graph. Using the graph theory language, we can formulate very well supersymmetric transformations, actions and path integrals. We also apply the localization method as well as the supersymmetric gauge theory on the continuous space-time. We also discuss the continuum limit of the theory to two dimensional topological field theory, correspondence between spectrums and index theorems, some properties of the vevs of the cohomological operators, and relation to the quiver gauge theories. These lectures include basic introductions to the graph theory and localization method for beginners.
    e-print [1] S. Matsuura, T. Misumi, K. Ohta, [arXiv:1411.4466[hep-th]]
    PTEP 2015 (2015) no.3, 033B07.
    [2] K. Ohta, N. Sakai, [arXiv:1811.03824[hep-th]]
    PTEP 2019 (2019) no.4, 043B01.

  • January 17, 2020
    Master thesis presentation
    Speaker: Cristopher CHUÑE (Hokkaido Univ.)
    Title Verification of anomaly universality in \(Z_3\) heterotic orbifold models with Wilson lines
    Speaker: Yuki Kariyazono (Hokkaido Univ.)
    Title Modular symmetry anomaly in magnetic flux compactification

  • January 24, 2020
    Master thesis presentation
    Speaker: Hikaru Uchida (Hokkaido Univ.)
    Title Flavor structure of magnetized \(T^2/Z_2\) blow-up model
    Speaker: Yuta Mimura (Hokkaido Univ.)
    Title Generative Adversarial Network for efficient search of MSSM-like \(Z_6\)-Ⅱ orbifold compactification parameters of \(E_8 \times E_8\) hetrotic string

  • January 31, 2020
    Rehearsal of Master thesis presentation
    Speaker: Yuki Kariyazono (Hokkaido Univ.)
    Title Modular symmetry anomaly in magnetic flux compactification
    Speaker: Cristopher CHUÑE (Hokkaido Univ.)
    Title Anomaly universality in \(Z_3\) hetelotic orbifold models
    Speaker: Hikaru Uchida (Hokkaido Univ.)
    Title Flavor structure on the compact spaces coming from the superstring theory
    Speaker: Yuta Mimura (Hokkaido Univ.)
    Title Deep learning technology for efficient search of specific compactification parameters of string theory