セミナー 2017年

Yuhma Asano, Dublin Institute for Advanced Studie

Phase transitions in the BMN matrix model

Seminar room, Kenkyu honkan 3F
Formulating string theory or M-theory by a gauge theory is an attractive idea which has been extensively studied. Especially, realisation of geometries from the lower dimensional gauge theory is an intriguing and challenging problem. The necessity of such emergent geometry suggests that there should be a phase transition in the gauge theory and that a geometry would appear as its temperature decreases. In this talk, we focus on the BMN matrix model, which is considered as a non-perturbative formulation of M-theory on the pp-wave geometry and also conjectured to have a gauge/gravity duality, which relates the vacua on the gauge theory side to bubbling geometries in the type IIA supergravity. Our preliminary results of Monte Carlo simulations show two phase transitions and one of them looks related with emergent geometry.

加藤政博, 自然科学研究機構分子科学研究所

[光渦についての特別セミナー] 自由電子による光渦の放射

研究本館3階 セミナー室



梶田隆章, 東京大学                  

[第四回KEK連携コロキウム] 重力波の観測に挑むKAGRAプロジェクト


Yoshiyuki Inoue, RIKEN

[Cosmophysics group seminar] Toward the understanding of magnetic fields in the vicinity of active supermassive black holes

Meeting room 1, Kenkyu honkan 1F
Magnetic fields of active supermassive black holes have not been measured yet, although it is one of the most fundamental parameters in black hole physics such as for launching mechanism of relativistic jets and generation of hot coronae. In this talk, I will report our new measurements of magnetic fields in several tens Schwarzschild radii of central black holes. Utilizing ALMA and NuSTAR, we successfully detected coronal synchrotron emission. The estimated magnetic field strength is not strong enough to keep corona hot.

Naoki Yamamoto, Keio University 

Chirality, Topology, and Astrophysics

Meeting room 1, Kenkyu honkan 1F
Chirality of fermions has a topological nature. This microscopic property modifies the macroscopic hydrodynamic behavior and leads to unusual transport protected by topology in relativistic systems. We argue that these topological tranport phenomena should play important roles in the evolution of supernovae and could potentially solve the problems in astrophysics, such as the origins of supernova explosions and magnetars.

Matsuo Sato, Hirosaki University


Meeting room1, Kenkyu honkan 1F
弦幾何、つまり、相互作用を含めた超弦の集合、その位相、チャート、計量を定義する。弦位相空間上の漸近的な軌跡の集合はターゲット多様体中の超リーマン面のモジュライを正しく再現する。弦幾何に基づいてゲージ場と結合するアインシュタイン-ヒルベルト作用を定式化し、弦空間上の位相、計量、ゲージ場について足し上げる事によって、超弦理論を非摂動論的に定義する。この理論は背景(ターゲット空間を含む)に依存しない。理論は弦多様体上の一般座標変換対称性の一部として超対称性を持つ。T双対も一般座標変換対称性の一部である。結果、IIA超弦とIIB超弦の違いは弦多様体上でどの座標系を選ぶかである。弦多様体においてDブレーンとOプレーンがある配位をとる場合はSO(32) I型超弦との違いも同様である。この一つの理論において摂動論的真空を表す背景を固定し、その周りの揺らぎから、IIA、IIB、SO(32) I型超弦の全オーダーの摂動論的散乱振幅を超モジュライを含めて導出する。理論は、粒子だけでなく時空の点も、ミクロに観測すると弦が観測されることを予言する。つまり、この理論は粒子と時空を統一する。新しい概念の説明のため黒板を用いて日本語で行う。

齊藤英治, 東北大学

[第三回KEK連携コロキウム] スピン流とスピントロニクスの物理

つくばキャンパス3号館1階セミナー ホール/東海キャンパス(TV会議中継) 東海1号館324号室

Kazuo Hosomichi, National Defense Academy

Supersymmetric vortex defects in two dimensions

Meeting room1, Kenkyu honkan 1F, slides (kek.jp only)
We study codimension-two BPS defects in 2d N=(2,2) supersymmetric gauge theories, focusing especially on those characterized by vortex-like singularities in the dynamical or non-dynamical gauge field. We classify possible SUSY-preserving boundary conditions on charged matter fields around the vortex defects, and derive a formula for defect correlators on the squashed sphere. We also prove an equivalence relation between vortex defects and 0d-2d coupled systems. Our defect correlators are shown to be consistent with the mirror symmetry duality between Abelian gauged linear sigma models and Landau-Ginzburg models, as well as that between the minimal model and its orbifold. We also study the vortex defects inserted at conical singularities.

Yasha Neiman, Okinawa Institute of Science and Technology

From infinity to the horizon through twistor space

Meeting room 1, Kenkyu honkan 1F
I will outline an ongoing research program, aimed at deriving the physics inside an observable patch of de Sitter space from dS/CFT. The approach is a marriage between the higher-spin realization of dS_4/CFT_3 by Strominger et.al. and the suggestion by Verlinde et.al. to consider a folded-in-half version of de Sitter space, where the information content in a causal patch is the same as at the asymptotic boundary. I will briefly describe two threads of results. The first is a completed dictionary between the CFT and the bulk causal-patch physics, in the limit of free bulk fields. The second is a new dictionary between the full boundary theory and twistor space, which should take us beyond the linearized bulk limit.

Jnanadeva Maharana, Institute of Physics, Bhubaneswar

Analyticity of Scattering Amplitude in Higher Dimensional Theories

Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
Theories in higher spacetime dimensions (D>4) have been topics of research for several years. Moreover, there are models where the extra compact dimension might have large radius and we might discover new phenomena even at LHC. I shall discuss field theories in higher dimensions and derive analyticity property of scattering amplitude within the frame works of LSZ formalism. The analog of Froissart bound will be derived.
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