Back Numbers 2016-17
Back to Home (Japanese)      Back-Numbers etc.



  • April 15, 2016
  • Speaker:O. Seto (Hokkaido Univ.)
    E-Printmany references

  • April 22, 2016
  • Speaker:ヤン ジャクリン (KEK)『ILCの物理と測定器』
    高橋 徹 (Hiroshima Univ.) 『ILCの加速器と計画の概要』
    Abstract 国際リニアコライダー(ILC)は次世代の電子陽電子衝突エネルギーフロンティア加速器として、世界中の研究者の国際協力のもと研究開発 ・設計が行われています。国際プロジェクトILCの日本国内誘致に向けた動きも加速しています。本セミナーでは、ILCで期待されるヒッグス粒子や トップクォークの研究と新粒子発見の可能性、最先端の超伝導加速技術を用いた加速器設計、及びILC計画を実現するための国内外の取り組みについて、 ILC計画に携わる若手研究者を含む講師陣が解説します。


  • May 13, 2016
    Speaker:D. Takahashi (OIST)
    TitleLHC Run-2 bound on the Z' boson mass in the Classically conformal U(1)' extended Standard Model with electroweak vacuum stability
    Abstract With the LHC Run-2 results at 13 TeV, we perform the calculation on the lower bound on the Z' boson mass in the context of the general U(1) gauged extension of the standard model with classically scale invariance and the electroweak vacuum stability at 2-loop level. The model is called the classically conformal U(1)' extended standard model which is a phenomenologically viable one that realizes Coleman-Weinberg-type breaking of the electroweak symmetry. The model can naturally provide a solution to one of the most important problem in the standard model, gauge hierarchy problem, and also solving the SM Higgs vacuum instability with having nonzero U(1)' charge of the SM Higgs, which is contrast to the U(1)\(_{B-L}\) case. In this study, we perform the calculation at 2-loop level where we find the parameter regions for solving the SM Higgs instability. We plot the allowed parameter regions with three free parameters, the U(1)' gauge coupling, the U(1)' charge of the SM higgs, and the vacuum expectation value of the new additional singlet Higgs. We find that U(1)\(_{B-L}\) and orthogonal model are excluded from having the electroweak vacuum stability with the current world average of the experimental data, \(m_t=173.34\) GeV and \(m_h=125.09\) GeV. Finally, we find that the current collider bounds are around \(m_Z' \gtrsim 3.5\) TeV, and naturalness bounds are around \(m_Z' \lesssim 7\) TeV in order to avoid a fine-tuning severer than 10\(%\) level, where the Z' boson can be detected at the current LHC Run-2 experiment in the near future.
    E-Print [1] Satsuki Oda, Nobuchika Okada, and Dai-suke Takahashi, Phys. Rev. D 92, 015026 "Classically conformal U(1)' extended standard model and Higgs vacuum stability"
    [2] Arindam Das, Satsuki Oda, Nobuchika Okada, Dai-suke Takahashi [arXiv:1605.01157]

  • May 20, 2016
  • Speaker:T. Suzuki (Hokkaido Univ.)
    TitleBulk Reconstruction in the Entanglement Wedge in AdS/CFT
    E-Print [1] Xi Dong, Daniel Harlow, Aron C. Wall, "Bulk Reconstruction in the Entanglement Wedge in AdS/CFT" [arXiv:1601.05416]

  • May 27, 2016
  • Speaker:K. Suehiro (Hokkaido Univ.)
    TitleInflation from string field theory
    E-Print [1] Alexey S. Koshelev, K. Sravan Kumar, Paulo Vargas Moniz, "Inflation from string field theory" [arXiv:1604.01440]


  • June 3, 2016
  • Speaker:M. Kakizaki (University of Toyama)
    TitleGravitational waves from first order phase transitions
    Abstract At early times, the Universe experienced several phase transitions. If such phase transitions are of strongly first order, gravitational waves are produced and contribute to the stochastic gravitational wave background. Therefore, observation of gravitational wave signals serves as a probe for new physics beyond the standard model. In this talk, I give a pedagogical introduction to gravitational waves generated by strongly first order phase transitions, focusing mainly on the electroweak phase transition.
    Title Probing physics behind the electroweak symmetry breaking at future gravitational wave and collider experiments
    Abstract Revealing dynamics of the electroweak phase transition is essential for probing new physics at the early Universe such as electroweak baryogenesis, which requires strongly first order phase transition. It is expected that the strongly first order electroweak phase transition is tested through precision measurement of the triple Higgs boson coupling at future colliders such as the International Linear Collider. Future space-based interferometers such as eLISA and DECIGO can also explore the phase transition through observation of generated gravitational waves signals. In this talk, complementarity of both the approaches in probing the strongly first order electroweak phase transition is discussed in models with additional isospin singlet scalar fields with and without classical scale invariance. It is pointed out that that they are synergetic in distinguishing specific models of electroweak symmetry breaking.
    E-Print [1] K. Hashino, M. Kakizaki, S. Kanemura and T. Matsui, "Synergy between measurements of the gravitational wave and the triple Higgs coupling in probing first order phase transition"[arXiv:1604.02069 [hep-th]]
    [2] M. Kakizaki, S. Kanemura and T. Matsui, "Gravitational waves as a probe of extended scalar sectors with the first order electroweak phase transition," Phys. Rev. D 92, no. 11, 115007 (2015) [arXiv:1509.08394 [hep-ph]]

  • June 10, 2016
    Speaker:H. Maeda (Hokkai-Gakuen Univ.)
    TitleUnitary evolution of the quantum Universe with a Brown-Kuchar dust
    Abstract We study the time evolution of a wave function for the spatially flat Friedmann-Lemaitre-Robertson-Walker universe governed by the Wheeler-DeWitt equation in both analytical and numerical methods. We consider a Brown-Kuchar dust as a matter field in order to introduce a "clock" in quantum cosmology and adopt the Laplace-Beltrami operator-ordering. The Hamiltonian operator admits an infinite number of self-adjoint extensions corresponding to a one-parameter family of boundary conditions at the origin in the minisuperspace. For any value of the extension parameter in the boundary condition, the evolution of a wave function is unitary and the classical initial singularity is avoided and replaced by the big bounce in the quantum system. Exact wave functions show that the expectation value of the spatial volume of the universe obeys the classical time evolution in the late time but its variance diverges.
    E-Print [1] H. Maeda, "Unitary evolution of the quantum universe with a Broun-Kuchar dast" [arXiv:1502.06954 [gr-qc]]

  • June 17, 2016
    Speaker:H. Suzuki (Hokkaido Univ.)
    TitleSoft Hair on Black Holes
    E-Print [1]Stephen W. Hawking, Malcolm J. Perry, Andrew Strominger, "Soft Hair on Black Holes" [arXiv:1601.00921[hep-th]]

  • June 24, 2016
    Speaker:Y. Takano (Hokkaido Univ.)
    TitleConstrained superfields from an anti-D3-brane in KKLT
    E-Print [1] Bert Vercnocke, Timm Wrase, "Constrained superfields from an anti-D3-brane in KKLT" [arXiv:1605.03961[hep-th]]


  • July 1, 2016
    Speaker:G. Ishiki (University of Tsukuba)
    TitleMatrix geometry and Kahler structure
    Abstract We consider the commutative limit of matrix geometry described by a large-N sequence of some Hermitian matrices. Under some assumptions, we show that the commutative geometry possesses a Kahler structure. We find an explicit relation between the Kahler structure and the matrix configurations which define the matrix geometry. We also test this relation in the case of a fuzzy sphere plus some fluctuation.

  • July 8, 2016
    (M2 Journal club)
    Speaker:T. Sasaki (Hokkaido Univ.)
    TitleA review of black hole information loss paradox
    (M2 Journal club)
    Speaker:Y. Nishimura (Hokkaido Univ.)
    TitleEntanglement entropy

  • July 15, 2016
    (M2 Journal club)
    Speaker:N. Fukuhara (Hokkaido Univ.)
    TitleHiggs spectrums in MSSM and NMSSM

  • July 22, 2016
    Speaker:Y. Yamada (Keio Univ.)
    TitleSupersymmetric models with higher-derivatives
    Abstract Supersymmetry (SUSY) has received significant interest since it has theoretically and phenomenologically interesting features. In particular, a local SUSY called supergravity (SUGRA) is known as an effective theory of superstring. In the effective theory of superstring, higher-order derivative interactions would appear e.g. in the effective action of D-branes. As a bottom-up approach, it would be useful to understand higher-order derivative terms in 4D SUSY. In this talk, I review and show some global SUSY models with higher-order derivative interactions. First, I briefly review the superspace formulation and a general problem in higher-derivative interactions, known as the ghost instability. Then, I show some ghost-free higher derivative models such as the Dirac-Born-Infeld (DBI) type action.
    Title DBI action in conformal supergravity
    Abstract DBI action is originally an interesting extension of Maxwell action, and is also known as the effective action of D-brane in superstring theory. It can also be regarded as a SUGRA action with infinite numbers of derivatives but without ghost modes. In this talk, I show how to construct the DBI type action in SUGRA. First, I briefly review conformal SUGRA formulation. Then, I discuss how the global SUSY action can be embedded into conformal SUGRA. We find that the SUGRA realization of the DBI actions depends on the formulations of SUGRA, which can be understood as the choice of compensators in conformal SUGRA. I also discuss an application of SUGRA DBI action to inflationary models in SUGRA.
    E-Print [1] R. P. Woodard, "Avoiding dark energy with 1/r modifications of gravity," Lect. Notes Phys. 720, 403 (2007) [astro-ph/0601672]
    [2] H. Abe, Y. Sakamura and Y. Yamada, "Matter coupled Dirac-Born-Infeld action in four-dimensional N=1 conformal supergravity", Phys. Rev. D 92, no. 2, 025017 (2015) [arXiv:1504.01221 [hep-th]]
    [3] S. Aoki and Y. Yamada, "Impacts of supersymmetric higher derivative terms on inflation models in supergravity," JCAP 1507, no. 07, 020 (2015) [arXiv:1504.07023 [hep-th]]
    [4] H. Abe, Y. Sakamura and Y. Yamada, "Massive vector multiplet inflation with Dirac-Born-Infeld type action,"Phys. Rev. D 91, no. 12, 125042 (2015) [arXiv:1505.02235 [hep-th]]
    [5] S. Aoki and Y. Yamada, "DBI action of real linear superfield in 4D N=1 conformal supergravity," JHEP 1606, 168 (2015) [arXiv:1603.06770 [hep-th]]

  • July 29, 2016
    Speaker:J. H. Park (KIAS)
    TitleFlexibleSUSY: a meta spectrum calculator
    Abstract FlexibleSUSY is a software package that takes as input descriptions of (non-)minimal supersymmetric models written in Wolfram/Mathematica and generates a set of spectrum calculator libraries and executables, with the aid of SARAH. The design goals are precision, reliability, modularity, speed, and readability of the code. The boundary conditions are independent C++ objects that are plugged into the boundary value problem solver together with the model objects. This clean separation makes it easy to adapt the generated code for individual projects. The latest efforts are focused on the implementation of Higgs mass calculation through the EFT approach.


  • October 7, 2016
    Speaker:D. Shiota (ISEE)
    TitleSolar magnetic activities and their long-term variations
    Abstract Various types of activities occur in the solar atmosphere and they are caused by highly structured magnetic field of the Sun. In this talk, I would like to introduce the magnetic activities of the Sun and their relation to the long-term variation of the solar magnetism.
    TitleModeling of solar wind and eruptive events for space weather forecast
    Abstract Solar wind and transient eruptive events (coronal mass ejections) escape from the Sun. Some of them reach to the Earth orbit and make disturbances in magnetosphere and ionosphere of the Earth (space weather). We have been developing a modeling system named as SUSANOO to forecast the Earth coming solar wind and coronal mass ejections on the basis of only observations of the Sun.

  • October 14, 2016
    Speaker:Y. Shoji (ICRR)
    TitleRenormalization-Scale Uncertainty in the Decay Rate of False Vacuum

  • October 21, 2016
    Speaker:Y. Kaneko (Tohoku Univ.)
    TitleBatalin-Vilkovisky formalism and AKSZ construction
    Abstract The Batalin-Vilkovisky formalism tells us the ghost structure of gauge theories. The AKSZ construction is a method for constructing actions in the BV formalism. First, I briefly review the BRST formalism. Second, I explain general aspects of the BV formalism and the AKSZ construction. Finally, I apply these methods to the 2d BF theory and the 3d Chern-Simons theory.
    TitleHigher Gauge Theories from Lie n-algebras and Off-Shell Covariantization
    Abstract We analyze higher gauge theories in various dimensions using a supergeometric method based on a differential graded symplectic manifold, called a QP-manifold, which is closely related to the BRST-BV formalism in gauge theories. Extensions of the Lie 2-algebra gauge structure are formulated within the Lie n-algebra induced by the QP-structure. We find that in 5 and 6 dimensions there are special extensions of the gauge algebra. In these cases, a restriction of the gauge symmetry by imposing constraints on the auxiliary gauge fields leads to a covariantized theory. As an example we show that we can obtain an off-shell covariantized higher gauge theory in 5 dimensions, which is similar to the one proposed in arXiv: 1206:5643.
    E-Print Ursula Carow-Watamura, Marc Andre Heller, Noriaki Ikeda, Yukio Kaneko, Satoshi Watamura, "Higher Gauge Theories from Lie n-algebras and Off-Shell Covariantization" [arXiv:1606.03861]

  • October 28, 2016
    (M2 Journal club)
    Speaker:K. Ueda (Hokkaido Univ.)
    TitleClassification of SUSY breaking
    (M1 Journal club)
    Speaker:S. Nagamoto (Hokkaido Univ.)
    TitlePhenomenology of Superstring theory
    References [1] L.E. Ibanez, A.M. Uranga, "String Theory and Particle Physics", Cambridge University Press, 2012
    [2] D. Cremades, L.E. Ibanez and F. Marchesano, "Computing Yukawa couplings from magnetized extra dimensions", JHEP 0405:079, 2004
    (M2 Journal club)
    Speaker:H. Kato (Hokkaido Univ.)
    TitleRelaxation of the higgs mass by the relaxion
    E-Print [1] Peter W. Graham, David E. Kaplan, Surjeet Rajendran "Cosmological Relaxation of the Electroweak Scale" [arXiv:1504.07551v2]
    [2] Tatsuo Kobayashi, Osamu Seto, Takashi Shimomura, Yuko Urakawa "Relaxion window" [arXiv:1605.06908v1]


  • November 4, 2016
    Speaker:K.A.S. Croker (University of Hawai'i at Mānoa)
    TitleA Smolin-like branching multiverse from multiscalar-tensor theory
    Abstract In 1992, Lee Smolin proposed that the Universe we observe is a branching multiverse. His branching process stochastically explores Standard Model parameter space and selects for Universes which are somehow "more fit" than other Universes, in analogy to Darwin's famous biological thesis. Smolin's original notion of fitness, however, lacks interactions between Universes and ultimately disagrees with observation. We remedy this situation and implement an interacting population of clones via a multiscalar-tensor extension to General Relativity. Our phenomenological model naturally features a big bang initial condition, dark matter candidates, and exhibits a novel decoupling of the scalar fields from the source stress. In the weak-field, slow-motion limit, Newton's law of gravitation is exactly reproduced.
    E-Print K.A.S. Croker, "A Smolin-like branching multiverse from multiscalar-tensor theory" [arXiv:1609.03159]

  • November 11, 2016
    Speaker:K. Hamada (KEK)
    TitleRenormalizable Quantum Gravity and Inflation
    TitleBRST Conformal Symmetry and Quantum Gravity

  • November 18, 2016
    Speaker:T. Tatsuishi (Hokkaido Univ.)
    TitleGauge Higgs Unification
    E-Print [1] Y. Hosotani, "Gauge Higgs EW and Grand Unification," Int. J. Mod. Phys. A31 (2016) no.20n21, 1630031, [arXiv:1606.08108]
    [2] H. Hatanaka, T. Inami and C. S. Lim, Mod. Phys. Lett. A13 (1998) 2601, [arXiv:hep-th/9805067]
    [3] N. S. Manton, Nucl. Phys. B158 (1979) 141.

  • November 25, 2016
    Speaker:Y. Sato (Hokkaido Univ.)
    TitleRelativistic Matter Density Ontology
    E-Print [1] Daniel Bedingham, Detlef Dürr, GianCarlo Ghirardi, Sheldon Goldstein, Roderich Tumulka and Nino Zanghi, Journal of Statistical Physics 154: 623-631 (2014), [arXiv:1111.1425]
    M1 Journal club
    Speaker:K. Tanaka (Hokkaido Univ.)
    TitleRenormalization and running of electric charge
    References [1] Lewis H. Ryder, "QUANTUM FIELD THEORY", Second edition, Cambridge University Press (1996)
    [2] Michael E. Peskin, Daniel V. Schroeder, "An Introduction To Quantum Field Theory", Westview Press (1995)
    [3] 江沢洋, 渡辺敬二, 鈴木増雄, 田崎晴明, "岩波講座現代の物理学<13>くりこみ群の方法", 岩波書店


  • December 2, 2016
    Speaker:N. Tanahashi (Osaka Univ.)
    TitleClassical and Quantum Chaos
    Abstract Studies on chaos has a long history beginning from its discovery by Poincare, and even today it is an important target of theoretical and experimental physics in various contexts. As a brief overview of studies on classical and quantum chaos, in this talk I will explain basics of classical chaos, chaos in general relativity, definition of quantum chaos, and chaos in string theory.
    References [1] 前田恵一, 「重力理論講義」, サイエンス社
    [2] 中村勝弘, 「量子物理学におけるカオス」, 岩波書店
    [3] J. Maldacena, S. H. Shenker, and D. Stanford, "A bound on chaos", [arXiv:1503.01409]
    TitleBlack Hole Horizon is a Nest of Chaos
    Abstract Motion of a particle near a horizon of a spherically symmetric black hole is shown to possess a universal Lyapunov exponent of a chaos provided by its surface gravity. To probe the horizon, we introduce electromagnetic or scalar force to the particle so that it does not fall into the horizon. There appears an unstable maximum of the total potential where the evaluated maximal Lyapunov exponent is found to be independent of the external forces and the particle mass. The Lyapunov exponent is universally given by the surface gravity of the black hole. Unless there are other sources of a chaos, the Lyapunov exponent λ is subject to an inequality λ < 2π TBH, which is identical to the bound recently discovered by Maldacena, Shenker and Stanford.
    E-Print [1] Koji Hashimoto and Norihiro Tanahashi, "Universality in Chaos of Particle Motion near Black Hole Horizon", [arXiv:1610.06070]

  • December 9, 2016
    Speaker:W. Akutsu (Hokkaido Univ.)
    TitleKnot homologies and topological string
    E-Print [1] Hiroshi Ooguri, Cumrun Vafa, "Knot Invariants and Topological Strings", [arXiv:hep-th/9912123]
    [2] Sergei Gukov, Albert Schwarz, Cumrun Vafa, "Khovanov-Rozansky Homology and Topological Strings", [arXiv:hep-th/0412243]
    M1 Journal club
    Speaker:K. Shiohara (Hokkaido Univ.)
    TitleAdS/CFT correspondence and Schwinger-Keldysh formalism
    References [1] Alex Kamenev, "Field Theory of Non-Equilibrium Systems," Cambridge University Press, 2011
    [2] C.P. Herzog and D.T. Son, "Schwinger-Keldysh Propagators from AdS/CFT Correspondence," [arXiv:hep-th/0212072]


  • January 10-12, 2017 (Intensive lecture)
    Speaker:Y. Hayato (ICRR)

  • January 12, 2017 (M1 Journal club)
    Speaker:I. Saga (Hokkaido Univ.)
    TitleSmall-field axion inflation

  • January 20, 2017 (Rehearsal of Master Thesis Presentation)
    Speaker:Y. Nishimura (Hokkaido Univ.)
    TitleEntanglement and Complexity
    Speaker:T. Sasaki (Hokkaido Univ.)
    TitleSupertranslation and Newman-Janis Algorithm

  • January 24-26, 2017 (Intensive lecture)
    Speaker:S. Aoki (YITP)

  • January 27, 2017 (Rehearsal of Master Thesis Presentation)
    Speaker:K. Ueda (Hokkaido Univ.)
    TitleSearch for SUSY breaking model
    Speaker:N. Fukuhara (Hokkaido Univ.)
    TitleHiggs mass in NMSSM-like model motivated from SO(32) heterotic string theory
    Speaker:H. Kato (Hokkaido Univ.)
    TitleRelaxation of the higgs mass by the relaxion


  • February 3, 2017 (Short Rehearsal of Master Thesis Presentation)
    Speaker:K. Ueda (Hokkaido Univ.)
    Speaker:H. Kato (Hokkaido Univ.)
    Speaker:N. Fukuhara (Hokkaido Univ.)
    Speaker:Y. Nishimura (Hokkaido Univ.)
    Speaker:T. Sasaki (Hokkaido Univ.)

  • February 17, 2017
    Speaker:K. Hotta (Hokkaido Univ.)
    TitleClassical Limit of Black Hole Quantum N-Portrait and BMS symmetry
    E-Print [1] Gia Dvali, Cesar Gomez, Dieter Lüst, "Classical Limit of Black Hole Quantum N-Portrait and BMS symmetry", [arXiv:1509.02114]

  • February 24, 2017
    Speaker:K. Ishikawa (Hokkaido Univ.)
    TitleFinite-size corrections to Fermi's golden rule and quasi-stationary composite states
    Abstract 量子力学の基本原理に基づいた遷移確率\(P(T)\)は, 2時刻間\(T>T_0\)の平均\(\Gamma=\frac{P(T)-P(T_0)}{T-T_0}\)と, \(T_0\)での値から, \(P(T)=(P(T_0)-\Gamma T_0)+\Gamma T\)と表される. 右辺第1項は波の重なりに起源をもつ速い 遷移, 第2項は粒子に起源をもつ平均寿命の遷移を表す. シュレーディンガー方程式の定常解より計算される\(\Gamma\)と 異なり, \(P(T)\)は規格化された解で正しく計算され, 対応する現象の発現する頻度を決定する. 特に, 波の重なりが大きい 超前方領域で, \(\Gamma T\)からは導かれない顕著な効果が発現する. これらは, 光反応やニュートリノ反応で, 実験値に 寄与すると共に, マクロな自然現象に新たな発現機構を与える. 以下の諸反応や, 他の量子的な現象で, 量子的な波動効果 が表れる.
    • ニュートリノ反応: パイ中間子崩壊ニュートリノ, ミューオン崩壊ニュートリノ, ニュートリノの電弱 ホール効果, 他
    • 光反応: 分子・原子の光の放射・吸収, 光合成, トムソン散乱, ラーマン散乱, 中性パイ中間子 2光子崩壊, 他
    • 様々なハローの形成機構
    References [1] K. Ishikawa and Y. Tobita, Prog. Theor. Exp.Phys.(2013),073B02; Ann of Phys. 344(2014) 118-178 ; K. Ishikawa, T. Tajima, and Y. Tobita, Prog. Theor. Exp.Phys.(2015),013B02;
    [2] K. Ishikawa, T. Nozaki, M. Sentoku, and Y. Tobita," Transition probability for the neutrino wave in muon decay and oscillation experiments." [arXiv:1405.0582[hep-ph]]
    [3] K. Ishikawa and Y. Tobita, "Finite-size corrections to Fermi's golden rule II," [arXif:1607.08522[hep-ph]]
    [4] N. Maeda, T. Yabuki, Y. Tobita and K. Ishikawa, "Finite-size corrections to the Excitation energy transfer", [arXiv:1609.00160[physics.chem-ph]]