## 2008年度のセミナー

 date 21 April. (Tue) 15:30〜 H711 清水 明(東大駒場) Modern theory of quantum measurement and its applications Since quantum systems exhibit probabilistic natures, one has to perform many runs of measurements in an experiment. In ordinary experiments, one resets the system before each run in order to prepare the same quantum state |psi> for all runs. Or, alternatively, one prepares many equivalent systems in the same state |psi>, and performs the same measurement independently for each system. In either case, one does not need to know the post-measurement state |psi'> (i.e., the state after the measurement) in order to predict or analyze the results of the experiment.However, one can perform another measurement (of either the same observable or a different observable) on |psi'> before he resets the system. That is, one can perform two subsequent measurements in each run, one for the pre-measurement state |psi> and the other for the post-measurement state |psi'>.In order to preedict or analyze the results of such subsequent measurements, one needs to know |psi'>. To calculate it, one must use something like the so-called projection postulate. By many studies in the last several decades, it has been revealed both theoretically and experimentally that a naive application of the projection postulate gives wrong results that do not agree with experiments on subsequent measurements. To resolve this discrepancy, the quantum measurement theory has been developed. The power of the quantum measurement theory has been demonstrated by many experiments (mostly on quantum optics). In this talk, I will review basic things of the quantum measurement theory. I will also present briefly some applications, such as Quantum Nondemolitoin Measurement, Fundamental Limits of quantum intereference devices, Symmetry breaking when the order parameter does not commute with Hamiltonian.
 date 14 April. (Tue) 15:30〜 H711 畦柳 竜生(京大理) Worldsheet analysis of gauge/gravity dualities 2007年に川合-須山により、D3ブレーンの場合のゲージ/重力対応を弦の世界面の立場から直接的に理解する方法が提案された。本セミナーではこの方法を説明すると共に、低次元Dブレーンの場合への拡張を紹介する。そして、特にWilson loopおよびエントロピーの対応が弦の世界面の立場からどのように理解できるかを議論する(花田政範氏、川合光氏、および松尾善典氏との共同研究に基づく)。
 date 6 April. (Mon) 15:30〜 H711 新田 宗人(慶応日吉) Non-Abelian Vortices - Five Years Since the Discovery - Five years ago, non-Abelian vortices were discovered in supersymmetric gauge theories and string theory independently. Those were suggested to be a key to understand confinement and duality of supersymmetric QCD, as a generalization of the old idea of Nambu and Mandelstam. In 2005 similar but a bit different non-Abelian vortices happened to be found in the color-flavor locked phase (color superconductor) of dense QCD, which is expected to be realized in core of neutron stars. It has turned out that the moduli space of the vortex solutions in the BPS case has very ample structures, like the one of Yang-Mills instantons. There has been a lot of developments in various directions. For instance, those vortices are candidates of non-Abelian cosmic strings; When two of them collide, their reconnection is inevitable. Vortices in SO and USp generalization has been found recently, and these may offer a fundamental tool toward a proof of the GNO duality. I will explain those developments in these five years.
 date 5 Mar. (Thu) 15:30〜 H711 横井直人(東大駒場) Superstring in the plane-wave background with RR flux as a conformal field theory AdS/CFT 対応の観点からも重要である Ramond-Ramond flux が存在し、かつ、曲がった時空上の超弦理論の一例として pp-wave と呼ばれる時空上の超弦理論を、その世界面上の共形不変な理論として定式化する。その定式化を用いて BRST 量子化を行い、光円錐ゲージで得られていたmassive な理論のスペクトラムを再現する。 3 Mar. (Tue) 15:30〜 H711 濱口幸一(東大本郷) Supersymmetric Models with Gravitino LSP I discuss several topics on SUSY models with gravitino LSP. (i) Gravitino LSP Dark Matter with mass around 1.2 TeV with small R-parity violation, which may explain the observed anomaly of PAMELA and ATIC. (ii) Gravitino LSP Dark Matter with stau NLSP, which may solve the Lithium Problem in Big-Bang Nucleosynthesis, and its LHC phenomenology. (iii) Gravitino LSP with O(eV) mass in Gauge Mediation and its LHC phenomenology, and composite Dark Matter. 24 Feb. (Tue) 15:30〜 H711 木村哲士(基研) Realization of AdS Vacua on Generalized Geometries フラックスコンパクト化の最も一般的な議論を、typeII弦を用いて展開する。コンパクト化される空間が Hitchinのgeneralized geometryで記述されると、すべてのfluxの寄与を自然に導入することが可能となる。実現される超対称真空は、このコンパクト化で得られる4次元超重力理論のsuperpotentialの数学的構造を調べるだけで、反ド・ジッターか平坦かが選定される。また理論に制限を課す事で、RRfluxが内在しない模型や、Heterotic弦の配位などを考察する事が可能になる。(arXiv:0810.0937) 5 Feb. (Thu) 15:30〜 H711 Pyungwon Ko(KIAS) Electroweak symmetry breaking (EWSB) and cold dark matter (CDM) from hidden sector technicolor interaction I describe a class of models with hidden sector technicolor interaction, where EWSB and CDM originate from the hidden sector. 27 Jan. (Tue) 15:30〜 H711 伊藤 悦子(工学院大) 格子シミュレーションによる共形場の理論の探索 格子シミュレーションのを用い、大きなフレーバー数をもつゲージ理論に非自明な赤外固定点が存在するかどうか調べる。そのために、まず効率的に計算でき、小さい系統誤差をもつ新しい繰りこみスキームを提案した。そして、その新しい繰りこみスキームの有用性を調べ、最後にその新しい繰りこみスキームを用いて非摂動論的なrunning coupling constant を測定した。 20 Jan. (Tue) 15:30〜 H711 Dongsu Bak(Seoul) Nonequilibrium Thermodynamics and Time Dependent Black Holes We discuss aspects of the exact time dependent black hole solution of IIB string theory using the AdS/CFT correspondence. The dual field theory is a thermal system in which initially a vacuum density for a non-conserved operator is turned on. We can see that in agreement with general thermal field theory expectation the system equilibrates: the expectation value of the non-conserved operator goes to zero exponentially and the entropy increases. In the field theory the process can be described quantitatively in terms of a thermofield state and exact agreement with the gravity answers is found. 13 Jan. (Tue) 15:30〜 H711 両角卓也(広島大) CP violation of hadronic tau decays and the hadronic form factors We study direct CP violation of tau -> K pi(eta,eta')nu decays. By studying the forward and backward asymmetry, the interference of L=0 and L=1 amplitudes of the hadronic system can be extracted. By including the scalar and vector mesons into the chiral Lagrangian, we compute the form factors which correspond to L=0 and L=1 angular momentum state of the hadronic system. We include real and imaginary parts of the one loop corrections to the self-energies of the scalar and vector mesons. The direct CP violation of the forward and backward asymmetry is computed using a two Higgs doublet model in which a new CP violating phase is introduced. We show how the CP violation of the forward and the backward asymmetry may depend on the new CP violating phase and the strong phase of the form factors. 6 Jan. (Tue) 15:30〜 H711 細道和男(KIAS) Chern-Simons-matter theories and M2-branes I will review the recent progress in three-dimensional Chern-Simons matter theories, focusing mainly on the so-called ABJM model, and their relation to M2-brane physics. 22 Dec. (Mon) 15:30〜 H711 津村浩二(The Abdus Salam ICTP) Flavonの現象論 フレーバー対称性の導入はフェルミオンの質量階層性を解決する可能性がある。その際に導入されるスカラー粒子をFlavonと呼び、その現象論について議論する。FCNC過程およびg-2からの制限を調べ比較的軽いFlavonが存在できることを示す。そのような軽いFlavonはLHCでの生成が可能であり、また特徴的な崩壊パターンを持つ。 16 Dec. (Tue) 15:30〜 H711 吉村太彦(岡山大) ニュートリノ質量分光と宇宙背景ニュートリノ検出に向けて 原子または分子集団の低温固体状態を準安定状態へ励起することにより、1光子＋ニュートリノ対生成の検出が可能になる。1光子エネルギースペクトルの測定からすべてのニュートリノ質量絶対値、すべての混合角とマヨラナかディラック型質量の区別ができる。この手段によりニュートリノ質量分光を組織的に展開したい。この実験手法の原理とミリグラム以下の試料で測定可能な増幅原理を紹介する。超放射現象に類似したコヒーラント過程が増幅に関わり、プロセスのレートは標的数の高い冪依存性をもつ。もっとも軽いニュートリノ対閾値付近では、パウリ排他原理を利用して宇宙背景ニュートリノを検出する可能性もある。理論面とともに、岡山大学を中心に推進している実験研究の現状と今後の展望を簡単に紹介したい。 9 Dec. (Tue) 15:30〜 H711 森山翔文(名大多元) Instanton Calculus and Loop Operator in Supersymmetric Gauge Theory 物理学において対称性は常に重要な役割を果たしている。N=2超対称ゲージ理論の低エネルギー有効理論はサイバーグとウィッテンによって対称性などの議論から完全に決定された。しかし、それだけでは理解が表面的に留まり、むしろ同じ結果を経路積分から再現することが望ましい。ネクラソフを含む多くの物理学者の努力によって、有効理論の結果がインスタントン効果の足し上げから再現された。このトークでは、ネクラソフの手法を簡単に紹介し、それがどのようにN=1の相関関数計算に応用され、ダイグラーフとバッファの行列模型による結果を再現するのかについて説明したい。 28 Nov. (Fri) 15:30〜 H711 綿引芳之(東工大) Causal dynamical triangulation TBA 25 Nov. (Tue) 15:30〜 H711 Wei Li(IPMU) Aspects of Three-dimensional Quantum Gravity TBA 11 Nov. (Tue) 15:30〜 H711 寺口俊介(名大) On the general action of boundary (super)string field theory We reformulate (super)boundary string field theory in terms of boundary state. In our formulation, we can formally perform the integration of target space equations of motion for arbitrary field configurations without assuming decoupling of matter and ghost. Thus, we obtain the general form of the action of boundary string field theory. This formulation may help us to understand possible interactions between boundary string field theory and the closed string sector. 4 Nov. (Tue) 15:30〜 H711 丸信人(中央大) S and T Parameters at 1-loop in the Gauge-Higgs Unification We investigate the one-loop contributions to S and T oblique parameters in the gauge-Higgs unification. We show that these parameters are finite in five dimensional space-time, but are divergent in more than five dimensions. Remarkably, however, we find that a particular linear combination of S and T parameters, $S - 4 \cos \theta_{W} \ T$, becomes finite for six dimensional space-time, though each of these parameters are divergent. This is because, in the Gauge-Higgs unification scenario, the operators relevant for S and T parameters are not independent, but are included in a unique higher dimensional gauge invariant operator. Thus the predictable linear combination is model independent, irrespectively of the detail of the matter content. 29 Oct. (Wed) 16:00〜 大阪駅前第2ビル6階 大阪市立大学文化交流センター　大セミナー室 藤井保憲(東大) Scalar-tensor theory and the accelerating universe The observational discovery in 1998 of the accelerating universe has shed a new light on the cosmological constant problem, a purely theoretical issue now in today's version consisting of the two questions, fine-tuning and coincidence problems. I argue that the issue can be understood consistently in terms of the scalar-tensor theory of gravitation. The key word is $10^{-120}=(10^{60})^{-2}$. 28 Oct. (Tue) 15:30〜 H711 Chung-Lin Shan(Seoul National Univ.) Identifying Weakly Interacting Massive Particles from Direct Dark Matter Detection Data Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Cold Dark Matter. Currently, the most promising method for searching for different WIMP candidates is the direct detection of the recoil energy deposited in a low-background laboratory detector by elastic scattering of ambient WIMPs off the target nuclei. For understanding properties of WIMPs and identifying them among new particles produced at colliders (hopefully in the near future), determinations of their mass and their couplings on nucleons from direct detection experiments are essential. We developed new model-independent processes for determining the mass and the couplings of WIMPs by using experimental data (i.e., measured recoil energies) directly. Our method are independent of the as yet unknown WIMP density near the Earth, of the form of the WIMP velocity distribution, as well as of the WIMP-nucleus cross section or the WIMP mass. Once two (or more) experiments with different target nuclei obtain posotive signals, one should in principle be able to estimate these quantities with an error of ~30% with only ~50 events from each experiment. 14 Oct. (Tue) 15:30〜 H711 植草 宣弘(阪大) The lightest Higgs boson mass in effective field theory with bulk and brane supersymmetry breaking ヒッグス質量へのループ補正を、バルクとブレイン上で超対称性が破られる模型で議論する。余次元の効果のうちKaluza-Kleinモードのレベルやコンパクト化の半径の大きさがあらわにわかる表式で補正の性質を見出す。0806.3229[hep-ph] 7 Oct. (Tue) 15:30〜 H711 長尾 桂子(名大) Neutralino dark matter in the light Higgs scenario Minimal supersymmetric standard modelにおいて、低いSUSY breaking scaleをとる領域は、little hierarchy problemに関するfine tuningを軽減することから理論的に自然なパラメータ領域だと考えられる。そのような領域を実現するため、この研究ではlight Higgs senarioを採用し、Neutralino dark matterの残存量を計算した。その結果、light Higgs scenarioでこれまで知られていたものとは傾向が異なるパラメータ領域が存在し、allowed regionが広がることがわかった。 16 Sept. (Tue) 15:30〜 H711 進藤　哲央(DESY) Superparticle Mass Window from Thermal Leptogenesis and Decaying Gravitino Dark Matter The thermal leptogenesis is explored in gravitino dark matter scenarios. High reheating temperature is achieved by introducing R-parity violations. Low-energy observables put an upper limit on the reheating temperature. Assuming the universal gaugino mass at the grand-unified scale, we found that the reheating temperature can reach $O(10^9)$GeV for a gravitino mass of $O(100)$GeV. We also showed that superparticles of the standard model are expected to be detected in the Large Hadron Collider. 22 July (Tue) 15:30〜 H711 大田 武志(大阪市大) Kerr-NUT-de Sitter spacetimes and conformal Killing Yano tensor The Kerr-NUT-de Sitter (KNdS) metrics are the most general, known higher-dimensional black hole solutions with a spherical horizon. It is known that the geodesic motion in the KNdS spacetime is integrable in all dimensions. Also, the Hamilton-Jacobi equations, the Klein-Gordon equations and the Dirac equations in these background allow the separation of variables. These properties are a consequence of existence of a non-degenerate, second-rank conformal Killing Yano (CKY) tensor. Generalization to a degenerate CKY tensor case is also reported. 15 July (Tue) 15:30〜 H711 兼村晋哉(富山大学) TeV Scale Physics as Origin of Neutrino Mass and Mixing, Dark Matter, and Baryon Asymmetry Today we know new phenomena which the SM definitely cannot explain; i.e., neutrino oscillation, origin of dark matter, and baryon asymmetry of universe. We propose a new model at a TeV-scale that can explain all the above new phenomena simultaneously without fine tuning. This is based on the physics of extended Higgs sector with a new exact discrete Z_2 symmetry and TeV-scale right-handed neutrinos. Observed tiny neutrino masses are explained as 3-loop quantum effects. Additional lightest Z_2 odd scalar field is a candidate of cold dark matter, and furthermore a strong coupling property and extra CP-phases in the extended Higgs sectors can generate baryon asymmetry at the electroweak phase transition. The model can provide a scenario without any contradiction against all the current experimental data as well as theoretical constraints, and predict very distinctive phenomenology from any other new physics model in lepton flavor physics, Higgs physics and also in dark matter physics. The model is well testable at current and future experiments. 8 July (Tue) 15:30〜 H711 山崎雅人(東京大学) Intersecting Solitons, Amoeba and Tropical Geometry 今回のセミナーでは、5次元N=1超対称ゲージ理論のHiggs相において存在する、vortexとinstantonからなる複合ソリトン系を議論したい。このソリトン系は、8SUSYのゲージ理論の1/4 BPSソリトンの親玉とでもいうべき重要な系であるが、これまでほとんど調べられていなかった。今回は、このソリトン系を一般的に解析し、それがアメーバ、トロピカル幾何と呼ばれる数学的枠組みによって自然にとらえられることを示した我々の研究について述べたい。（太田和俊氏、坂井典佑氏、新田宗士氏、藤森俊明氏との共同研究arXiv:0805.1194 [hep-th]に基づく） 1 July (Tue) 15:30〜 H711 Manu Paranjape (Universit醇P de Montr醇Pal) Path Integration, Perturbation Theory and Complex Actions We consider Euclidean functional integrals involving actions which are not exclusively real. This situation arises, for example, when there are $t$-odd terms in the the Minkowski action. Writing the action in terms of only real fields (which is always possible), such terms appear as explicitly imaginary terms in the Euclidean action. The usual quanization procedure which involves finding the critical points of the action and then quantizing the spectrum of fluctuations about these critical points fails. In the case of complex actions, there do not exist, in general, any critical points of the action on the space of real fields, the critical points are in general complex. The proper definition of the function integral then requires the analytic continuation of the functional integration into the space of complex fields so as to pass through the complex critical points according to the method of steepest descent. We show a simple example where this procedure can be carried out explicitly. The procedure of finding the critical points of the real part of the action and quantizing the corresponding fluctuations, treating the (exponential of the) complex part of the action as a bounded integrable function is shown to fail in our explicit example, at least perturbatively. 24 June (Tue) 15:30〜 H711 竹内建(Virginia Tech.） Constraints on New Physics from Various Neutrino Experiments TBA 17 June (Tue) 15:30〜 H711 松尾泰(東京大学) Lie 3-Algebra and Multiple M2-branes Recently Bagger-Lambert and Gustavsson (BLK) proposed a maximally supersymmetric action which describe the multiple M2 branes. This model is based on a new symmetry based on Lie 3-algebra. We classify possible Lie 3-algebras. When we assume the metric is positive definite and the algebra contains finite number of generators, we found that only the direct sum of the simplest algebra (so called A_4) is possible as long as the number of generators are less than 8. Next, if we allow the number of generators to be infinite, we found that Nambu-Poisson bracket on three dimensional manifold gives a varieties of Lie 3-algebras. We show that for this choice BLK model defines an action for M5 where various fields in BLK model are recombined into the self-dual two form field on M5. Finally we use the milder constraint for the positive definiteness on the metric, we found that there are again variety of Lie 3-algebras. In particular for one of them we show that BLK model does not contain ghost and has a gauge symmetry based on arbitrary type of Lie algebras. 10 June. (Tue) 15:30〜 H711 笹井裕也(京都大学) Noncommutative field theories and Hopf algebraic symmetires 最近の進展である非可換時空上の場の理論におけるHopf代数的対称性に関する話題を話す。以前までは古典論における話であったが、量子場の理論においてはbraidと呼ばれる非自明な統計性を場に与えることで、それらの対称性が満たされることがいくつかの例で調べられていた。我々は一般にHopf代数的対称性が量子場の理論の対称性であるために必要な条件を調べ、そのうちの１つが非自明なbraidの条件であることを確かめた。また、その物理的な側面として、Hopf代数的な並進対称性を持つLie代数的な非可換性を持つ時空上の場の理論を取り上げ、ドメインウォール解とそのモジュライ空間を調べ、モジュライ場がmasslessであることを確かめた。 5 June (Thur) 12:00〜 (Tentative) (ATTENTION) H711 菅野浩明(名古屋大学) Refined BPS state counting and Macdonald function It has been argued that the Nekrasov's partition function gives the generating function of refined BPS state counting in the compactification of M theory on local Calabi-Yau spaces. We show that a refined version of the topological vertex we proposed before is a building block of the Nekrasov's partition function with two equivariant parameters. Our refined vertex is expressed entirely in terms of the specialization of the Macdonald symmetric functions and has a simple transformation law under the flop operation, which suggests that homological invariants of the Hopf link are related to the Macdonald functions. 27 May. (Tue) 15:30〜 H711 西岡辰磨(京都大学) Near Extremal Black Hole Entropy as Entanglement Entropy via　AdS(2)/CFT(1) We point out that the entropy of (near) extremal black holes can be interpreted as the entanglement entropy of dual conformal quantum mechanics via AdS2/CFT1. As an explicit example, we study near extremal BTZ black holes and derive this claim from AdS3/CFT2. We also analytically compute the entanglement entropy in the two dimensional CFT of a free Dirac fermion compactified on a circle at finite temperature. From this result, we clarify the relation between the thermal entropy and entanglement entropy, which is essential for the entanglement interpretation of black hole entropy. 20 May. (Tue) 13:30〜(ショートレクチャー) 小澤 正直(名古屋大学) （非数学屋・物理屋むけの）量子測定理論・解釈問題入門、および最近の進展 重力波検出の標準量子限界を巡る論争、量子測定の数学的特徴付け、不確定性原理と小澤の不等式、Wigner-Araki-Yanaseの定理と量子計算の限界などについて述べる。 参考文献：物理学会誌 59, 157-165 (2004) 及びその引用文献など 13 May. (Tue) 15:30〜 石橋　明浩　(KEK) Symmetry Properties of Higher Dimensional Black Holes In the first part of this talk, I will attempt to give a brief overview of basic properties of 4- and higher-dimensional black holes within the context of general relativity. 　In the second part, I will focus on symmetry properties that a stationary, rotating vacuum black hole must be axisymmetric in any spacetime dimensions greater than or equal to 4. This result---called the "Rigidity"---generalizes the classical result due to Hawking to higher dimensions and applies to, in particular, non-spherical black holes, known to occur in higher dimensions but not in 4. However, the proof would not appear to work for extremal black holes with a degenerate horizon, i.e., black holes with "zero-temperature." I will discuss whether or not higher dimensional, extremal (zero-temperature) black holes also can enjoy the rigidity property. 22 Apr. (Tue) 15:30〜 K.R. Ito (Setsunan U.) Present Status of Quark Confinement in Lattice Gauge Theory T.B.A. 15 Apr. (Tue) 15:30〜 So Matsuura (Niels Bohr Institute) Relation among Supersymmetric Lattice Gauge Theories and Matrix Theories Recently, several schemes to define gauge theories with exact supersymmetry on a space-time lattice have been developed. In this talk, I show that these seemingly different schemes are related with each other and so-called the orbifolding procedure gives the unifying framework. I also mention on the relation between the orbifold procedure and matrix theories.