Back Numbers 2018-19
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  • April 13, 2018
  • Speaker:T. tatsuishi (Hokkaido Univ.)
    TitleNeutrino Mixing and Leptonic CP Violation from 𝑆_4 and Generalised CP Symmetries
    E-Print [1] J. T. Pendo, S. T. Petcov, and A. V. Titov, [arXiv:1803.11009[hep-ph]]
    [2] N. Delsate, A. Compère, arXiv:1112.1304
    [3] J. T. Penedo, S. T. Petcov, A. V. Titov arXiv:1705.00309

  • April 20, 2018
  • Morning
    Speaker:M. Tanimoto (Niigata Univ.)
    TitlePredicting CP violation of neutrinos in Non-Abelian Flavor Symmetries
    Abstract Finite groups are applied to understand the flavor structure of quarks and leptons. Flavor symmetry can predict the flavor mixing and mass spectrum. Indeed, the CP violating phase of neutrino oscillations was predicted clearly by some kind of finite groups. I introduce some recent works and discuss the perspective in this field.
    Speaker:Y. Shimizu (Hiroshima Univ.)
    TitleCP violation of neutrinos and sign of the baryon asymmetry
    Abstract We discuss the correlation between the CP violating Dirac phase of neutrinos and the cosmological baryon asymmetry based on the leptogenesis. In this seminar, we introduce the minimal seesaw model with two right-handed Majorana neutrinos and the trimaximal mixing pattern for neutrino flavors. In the model, the sign of the CP violating Dirac phase at low energy scale is fixed by the observed cosmological baryon asymmetry. The model is also fixed only for the normal hierarchy of neutrino masses from recent T2K and NOνA data.

  • April 27, 2018
  • Speaker:N. Oshita (RESCEU)
    TitleShedding light on the initial condition problem for cosmological inflation
    Abstract The inflationary scenario solves fine-tuning problems. However, in order for the inflationary scenario to be counted as a real success, inflation should arise without having to impose highly fine-tuned initial conditions. On the other hand, it has been proved that inflationary spacetimes are incomplete in past directions. I will give a talk on how we could solve the initial condition problem for cosmological inflation while avoiding the initial singularity by taking into account the quantum tunneling of gravitational filed with inhomogeneous initial conditions.


  • May 11, 2018
  • Speaker:K. Hotta (Hokkaido Univ.)
    TitlePre-Hawking Radiation Cannot Prevent the Formation of Apparent Horizon
    E-Print [1] P. Chen, W. G. Unruh, C. Wu and D. Yeom [arXiv:1710.01533[gr-qc]]

  • May 18, 2018
  • Speaker:T. Tatsuishi and T. Sasaki (Hokkaido University)
    TitleReport on Emallia Conference 2017

  • May 25, 2018
  • Speaker:K. Ishikawa (Hokkaido University)
    TitleProbability principle and rigorous transition probability: beyond the Fermi's golden rule
    Abstract A transition probability is one of the fundamental quantities that determine natural phenomena and a revised formula "P(T)= \Gamma T +P^d" beyond the standard Fermi's golden rule derived by the present author and collaborators is discussed. The new term "P^d" has the origin in overlap of the waves, and induces unique phenomena of the waves not only at short time but also at long time in wide area. Various experimental and theoretical developments on P^d will be presented.
    E-Print [1] K.Ishikawa and Y.Tobita, Prog.Theor. Exp.Phys.,073B02,doi:10.1093/ptep/ptt049(2013), and others.
    [2] K.Ishikawa,O.Jinnouchi,A.Kubota,T.Sloan,T.H.Tatsuishi, R.Ushioda, "On experimental confirmation of the corrections to the Fermi's golden rule" JPS Spring meeting, Noda, 2018, and in preparation.
    [3] K.Ishikawa, H.Nakatsuka, and K.Oda,"Particle decay in wave-packet formalism revised" JPS Spring meeting, Noda, 2018, and in preparation.
    [4] N.Maeda et al, Prog.Theor.Exp.Phys.,053J01(2017)


  • June 1, 2018
  • Speaker:N. Kawamoto (Hokkaido Univ.)
    TitleAn Alternative Lattice Field Theory Formulation Inspired by Lattice Supersymmetry
    Abstract I summarize our recent conclusion of exact lattice supersymmetry based on our papers. I try to explain the motivations and basic ideas in a concrete and simple way.
    E-Print [1] A. D'Adda, N. Kawamoto, and J. Saito, "An alternative lattice field theory formulation inspired by lattice supersymmetry", JHEP 1712 (2017) 089, arXiv:1706.02615 [hep-lat]
    [2] A. D'Adda, N. Kawamoto, and J. Saito, "An Alternative Lattice Field Theory Formulation Inspired by Lattice Supersymmetry-Summary of the Formulation-", EPJ Web Conf. 175 (2018) 11020, arXiv:1710.06072 [hep-lat]

  • June 8, 2018
    Speaker:H. Maeda (Hokkai-Gakuen Univ.)
    (Morning session only)
    TitleDecreasing entropy of dynamical black holes in critical gravity
    Abstract Critical gravity is a quadratic curvature gravity in four dimensions which is ghost-free around the AdS background. Constructing a Vaidya-type exact solution, we show that the area of a black hole defined by a future outer trapping horizon can shrink by injecting a charged null fluid with positive energy density, so that a black hole is no more a one-way membrane even under the null energy condition. In addition, the solution shows that the Wald-Kodama dynamical entropy of a black hole is negative and can decrease. These properties expose the pathological aspects of critical gravity at the non-perturbative level.
    E-Print [1] Hideki Maeda, Robert Svarc, and Jiri Podolsky, "Decreasing entropy of dynamical black holes in critical gravity" [arXiv:1805.00026 [gr-qc]]
    [2] Hideki Maeda, "Black-hole dynamics in BHT massive gravity" [JHEP 1102,039(2011)], arXiv:1012.5048[hep-th]
    [3] Masato Nozawa and Hideki Maeda, "Dynamical black holes with symmetry in Einstein-Gauss-Bonnet gravity" [Class. Quant. Grav. 25, 055009(2008)], arXiv0710.2709[gr-qc]

  • June 15, 2018
    Speaker:Y. Yokokura (RIKEN)
    TitleA Self-consistent Solution of Evaporating Black Holes
    Abstract Black holes evaporate by nature. We obtain a self-consistent solution of the semi-classical Einstein equation including the backreaction of the collapsing matter and evaporation. It indicates that a collapsing matter becomes a dense object without horizon or singularity, and it has a surface and looks like a usual black hole from the outside. Hawking radiation and a strong tangential pressure occur inside the object, which is consistent with 4D Weyl anomaly. Any object we recognize as a black hole should be such an object. In the morning, I will review the basic of Hawking radiation. In the afternoon, I will explain how the above picture appears directly by solving the semi-classical Einstein equation.
    E-Print [1]Hikaru Kawai, Yuki Yokokura, "A Model of Black Hole Evaporation and 4D Weyl Anomaly" [arXiv:1701.03455[hep-th]]

  • June 22, 2018
    Speaker:S. Terashima (YITP)
    TitleGeometry from Matrices via D-branes
    Abstract We give a map from matrices to a commutative geometry from a bound state of a D2-brane and N D0-branes. For this, tachyons in auxiliary unstable D-brane system describing the bound state play crucial roles. We found the map obtained in this way coincides with the recent proposals. We also consider the map from the geometry to matrices in a large N limit and argue that the map is a matrix regularization of geometry.

  • June 29, 2018
    Speaker:M. Tachibana (Saga Univ.)
    Title review physics of neutron stars, mainly focusing on particle/nuclear physics aspects.
    Abstract I review physics of neutron stars, especially focusing on particle/nuclear physics viewpoints.
    Title Capture of Dark Matter by Neutron Stars
    Abstract In this talk, I address possible interesting connection between physics of neutron stars and that of dark matter.
    Refferences [1] Motoi Tachibana, Marco Ruggieri, "Comment on Dark Matter Capture in Neutron Stars with Exotic Phases" arXiv:1312.5802[hep-ph]
    [2] Yusuke Sanematsu, Motoi Tachibana, "Generalized thermalization time of dark matter captured by neutron stars" arXiv:1511.00249[hep-ph]


  • July 6, 2018
    Speaker:K. Umemoto (YITP)
    title Entanglement of Purification in Holography
    Abstract Entanglement entropy has a clear geometrical counterpart in holography ( Ryu-Takayanagi formula), which implies potential relationship between quantum entanglement and quantum gravity. We discuss two successive generalizations of Ryu-Takayanagi formula by proposing that so-called entanglement of purification for mixed or multipartite states also have clear gravitational counterparts. We show that these conjectures pass various tests and also are supported by an heuristic explanation from tensor network.
    E-Print [1] T. Takayanagi and K. Umemoto, “Holographic Entanglement of Purification,”[Nature Physics 14, pages573–577 (2018)], arXiv:1708.09393[hep-th]
    [2] K. Umemoto and Y. Zhou, “Entanglement of Purification for Multipartite States and its Holographic Dual,” [arXiv:1805.02625[hep-th]]

  • July 13, 2018
    Speaker:K. Nakayama (Univ. of Tokyo)
    TitleAxion-photon conversion and effects on 21cm observation
    Abstract Recently the EDGES experiment reported an enhanced 21cm absorption signal in the radio wave observation, which may be interpreted as either anomalous cooling of baryons or heating of cosmic microwave background photons. In the first part of the talk, I will review the basics of 21cm cosmology. In the second part, I will explain our model that possibly explains the EDGES anomaly: axion-photon conversion effectively heats up the radiation in the frequency range relevant for the EDGES experiment.
    E-Print [1] Takeo Moroi, Kazunori Nakayama, Yong Tang, "Axion-Photon Conversion and Effects on 21cm Observation," [arXiv:1804.10378[hep-ph]]

  • July 20, 2018
    M2 Journal club
    Speaker:D. Sasaki (Hokkaido Univ.)
    TitleBulk reconstruction beyond classical limit in AdS_3/CFT_2
    Speaker:S. Tamba (Hokkaido Univ.)
    TitleDiscrete flavor symmetry in magnetized Compactification model
    Speaker:S. Takada (Hokkaido Univ.)
    TitleSpontaneous localization of bulk fields: the six-dimensional case

  • July 27, 2018
    Morning session only
    Speaker:Y. Hasegawa (Hokkaido University, TU Wien)
    Title 量子力学の基礎問題への実験的アプローチ
    ~ 中性子を用いた量子光学実験 ~
    Abstract ミクロの世界の実験事実を説明するために、様々な試みがなされ、 現在われわれが手にしている量子力学が出来上がった。 この量子力学は相対性理論と並んで「現代」物理学で大きな役割を果たしており,その適用範囲は物理学のみならず, 化学や生物学の領域にもわたっている.また、量子力学の予測が高精度に正しいことは多くに実験で立証されたきた。 ところが、量子系で何が起こっているかといった、量子力学の解釈に関してはいまだに統一的な見解があるとは言い難い。 とくに、量子力学の予測が決定論的ではなく確率論的であること、 シュレディンガーの猫として知られている逆説的な現象などが、一般の人々のみならず多くの物理学者をも惑わし続けている。 今回のセミナーでは、粒子としてイメージしやすい中性子を使った最近の光学実験を紹介する。 中性子の干渉とスピンを用いた実験を通して、我々の慣れ親しんでいる世界から直感的には理解しがたい、 波動と量子の二重性、あるいは実在性、局所性や因果律などといった量子力学独特のミスティーに挑戦する。 特に、不確定性関係に関する最近の動向および不思議の国のアリスに出てくる猫にちなんで名づけられた、 「量子チェシャ猫」と呼ばれる、 マッハ・ツェンダー干渉計内で中性子とそのスピンがそれぞれのパスで透明化あるいは分離する実験を重点的に紹介する。


  • October 5, 2018
    M2 Journal club
    Speaker:Y. Ohie (Hokkaido Univ.)
    Title Equivariant Localization of Cohomological Field Theory
    Speaker:T. Hasegawa (Hokkaido Univ.)
    Title Probing seesaw scale with gravitational waves
    E-Print [1] Nobuchika Okada and Osamu Seto, ''Probing seesaw scale with gravitational waves'', [arXiv:1807.00336[hep-ph]]

  • October 12, 2018
    Speaker:T. Kobayashi (Hokkaido Univ.)
    Title Flavor Symmetry and CP Violation from String Theory
    E-Print [1] H. P. Nilles,, ''CP Violation from String Theory'', arXiv:1808.07060[hep-th]
    [2] S. Ramos-Sanchez,, ''Charting the flavor landscape of MSSM-like Abelian heterotic orbifolds'', arXiv:1808.06622[hep-th]
    M1 Journal Club
    Speaker:H. Uchida (Hokkaido University)
    Title Standard model and grand unified theory

  • October 19, 2018
    Speaker:T. Morita (Shizuoka Univ.)
    Title Bound on chaos in a semi-classical regime
    Title Microscopic understanding of acoustic Hawking radiation in a free fermi Fluid
    Abstract In the first talk, I will give an introduction of chaos and the idea of the bound on the Lyapunov exponent which might be related to black hole physics. Then I will argue that this bound might imply the emergence of a novel Hawking radiation like phenomena in dynamical chaotic systems. The mechanism of this phenomena may be very simple and they might be realized in laboratories. In the second talk, as an application of this phenomenon, we consider a microscopic understanding of acoustic Hawking radiation in quantum fluid.  I will derive acoustic Hawking radiation through a quantum mechanical calculation of the constitute particles of the fluid. We may gain some insights in to Hawking radiation from it.
    e-print [1] Takeshi Morita,, "Semi-classical bound on Lyapunov exponent and acoustic Hawking radiation in c=1 matrix model", arXiv:1801.00967[hep-th]

  • October 26, 2018
    Speaker:N. Maru (Osaka City Univ.)
    Title Basic of gauge-Higgs unification
    Abstract In this talk, the basics for model building in gauge-Higgs unification is discussed.
    Title Dark matter in gauge-Higgs unification
    Abstract In this talk, I will talk about the recent work on dark matter physics in a context of gauge-Higgs unification.
    e-print [1] N. Maru, T. Miyaji, N. Okada and S. Okada, "Fermion Dark Matter in Gauge-Higgs Unification ", JHEP1707 (2017) 048
    [2] N. Maru, N. Okada and S. Okada, "Fermionic Minimal Dark Matter in 5D Gauge-Higgs Unification", Phys. Rev. D96 (2017) 115023
    [3] N. Maru, N. Okada and S. Okada, "$SU(2)_L$ Doublet Vector Dark Matter from Gauge-Higgs Unification", arXiv:1803.01274[hep-ph](Accepted in PRD)


  • November 2, 2018
    Speaker:R. Nakayama (Hokkaido Univ.)
    Title A theory of reparametrizations for AdS_3 gravity
    e-print [1] J. Cotler and K. Jensen, "A theory of reparametrizations for AdS_3 gravity ", arXiv:1808.03263[hep-th]

  • November 9, 2018
    Speaker:M. Miyaji (YITP)
    Title Averaged Null Energy Condition, Wormhole, and Double Trace Deformation

    Averaged Null Energy Condition (ANEC) is a generic condition hold in unitary QFT on Minkowski spacetime, intimately related to locality and causality of the theory. The violation of ANEC indicates, for example formation of traversable wormhole. Recent study by [Gao, Jafferis, Wall [1608.05687]]showed that by adding non local double trace deformation to two sided black hole, which is holographically dual to tensor product of CFTs, ANEC can be violated and traversable wormhole can be formed.

    In the first part of this talk, I will review averaged null energy condition, and explain the consequences of null energy condition such as Focussing, Singularity theorem, prohibition of traversable wormhole. Then I will review two proofs of Averaged Null Energy condition on flat space [ Faulkner, Leigh, Parrikar, Wang[1605.08072] and [Hartman, Kundu, Tajdini [1610.05308]].

    In the second part, I will consider CFT dual to global AdS, and pursue time evolution of both CFT and AdS after addition of non local double deformation to the CFT Hamiltonian [Miyaji[1806.10807]]. I computed time evolution of null energy and averaged null energy in AdS, and confirmed that both can be negative. This implies that, causal structure in AdS is modified, so that originally spacelike separated points can be timelike after double trace deformation. Finally, I will also explain the time evolution of entanglement entropy and Renyi entropy in the CFT.

  • November 13-15, 2018
    Intensive Lecture
    Speaker:H. Kodama (YITP)
    Title 多様な次元における超重力理論とその応用I, II

  • November 14, 2018
    Seminar (Start at 16:30)
    Speaker:H. Kodama (YITP)
    Title 重力波観測による究極理論探査
    Abstract 超弦理論は,現時点で,自然界の最も根源的な基本理論の最有力候補であるが, そのことを直接示す証拠はない.現在,その証拠を求めて,様々な努力がなされているが, それらは大まかに3つに分類される.一つは,加速器実験を含む地上実験,二つ目は, インフレーションのCMBによる観測的研究,最後は超弦理論の予言する隠れたセクターの 引き起こす宇宙現象を用いるアプローチである.この講演では,この最後のアプローチに ついて,その基本的なアイデアを説明し,さらに超弦理論コンパクト化により生み出される 超弦アクシオンとブラックホールの相互作用が引き起こす宇宙現象の重力波観測により, 超弦理論コンパクト化についての情報を得る可能性についての我々の最近研究を紹介する.
    Rehearsal of M1 Journal Club
    Speaker:Cristopher CHUÑE (Hokkaido University)
    Title Superstrings, compactification and gauge symmetry

  • November 30, 2018
    Speaker:T. Terada (KEK)
    Title Unitarity constraint on the Kähler curvature
    Abstract In supersymmetric theories, the signs of quartic terms in the Kähler potential control the stability of non-supersymmetric field configurations.  In particular, in supersymmetric inflation models, the signs are important for the stability of an inflationary trajectory as well as for the prediction of the spectral index.  In this paper, we clarify what properties of a UV theory determine the sign from unitarity arguments of scattering amplitudes.  As non-trivial examples, we discuss the sign of a four-meson term in large N supersymmetric gauge theories and also those of the quartic terms obtained in the intersecting D-brane models in superstring theory.  The UV origins of inflationary models and supersymmetry breaking models are constrained by this discussion.
    e-print [1] Ema, Kitano, and Terada, JHEP 1809 (2018) 075, arXiv:1807.06940[hep-th] and references therein.
    In particular, Ref. [4] serves as an invaluable introduction. Appendices of Ref. [45] summarize basic and useful things. See also the textbook by S. Wenberg, "The Quantum Theory of Fields Vol. 1", Sec. 10.7 - 10.8. In addition, an easy-to-read review of large N expansion by E. Witten is also useful, Nucl.Phys. B160 (1979) 57-115.


  • December 7, 2018
    Speaker:E. K. Park (Hokkaido University)
    Title Light Fermionic WIMP Dark Matter with Light Scalar Mediator
    e-print [1] Shigeki Matsumoto, Yue-Lin Sming Tsai and Po-Yan Tseng, "Light Fermionic WIMP Dark Matter with Light Scalar Mediator ", arXiv:1811.03292v1[hep-ph]


  • January 11, 2019
    Speaker:S. Chigusa (Univ. of Tokyo)
    Title Solutions to Domain Wall Problem in Models with Discrete Flavor Symmetry

  • January 18, 2019
    Master thesis presentation
    Speaker: Y. Ohie (Hokkaido Univ.)
    Title Mirror Symmetry in 3D Gauge Theories via Equivariant Localization
    Speaker: S. Tamba (Hokkaido Univ.)
    Title Modular and Discrete Flavor Symmetry in Magnetized D-brane Models
    Speaker: S. Takada (Hokkaido Univ.)
    Title Spontaneous localization of bulk fields: the six dimensional case

  • January 25, 2019
    Master thesis presentation
    Speaker: T. Hasegawa (Hokkaido Univ.)
    Title Minimal B-L model
    Speaker: D. Sasaki (Hokkaido Univ.)
    Title Bulk reconstruction beyond the classical limit in AdS3/CFT2 and application to BTZ black hole


  • February 1, 2019
    Rehearsal of Master thesis presentation
    Speaker:Y. Ohie (Hokkaido Univ.)
    Title 同変局所化を用いた3次元ミラー対称性の研究
    Speaker:D. Sasaki (Hokkaido Univ.)
    Title AdS3/CFT2対応における重力の量子効果を考慮したバルクの再構成と3次元ブラックホールへの適用
    Speaker:S. Takada (Hokkaido Univ.)
    Title TBA
    Speaker:S. Tamba (Hokkaido Univ.)
    Title 超弦理論におけるモジュラー対称性と離散フレーバー対称性
    Speaker:T. Hasegawa (Hokkaido Univ.)
    Title ミニマルB-Lモデル由来の重力波