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2011年度セミナー (Seminar Schedule 2011)

Inflation in Supergravity: the Meeting Point of Cosmology and High-Energy Physics

When:2011/04/27 (Wed.) 16:00-17:00
Where:H1-36
Speaker:Sergei Ketov (Tokyo Metropolitan U.)
Abstract:A simple (most economic) and viable realization of cosmological inflation of early Universe in supergravity theory represents the important challenge to unifying cosmology with supersymmetry beyond the Standard Model. We propose a new, simple and viable realization of chaotic inflation in supergravity, based on the new theory of supergravity that we call F(R) supergravity. The F(R) supergravity can be understood as the N=1 locally supersymmetric extension of the popular theories of f(R) gravity in four spacetime dimensions. Our proposal to inflation uses the supersymmetric realization of the famous Starobinsky inflation. The F(R) supergravity theory was originally invented for that purpose too. In my talk I review the Starobinsky inflation, the F(R) supergravity in superspace, and their applications to the Early Universe cosmology. The reheating and particle production after inflation are discussed too. We believe that our findings may find many applications in High-Energy Physics of the early Universe.
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Deformation of half-BPS solution in ABJM model and instability of supermembrane

When:2011/05/11 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H1-36
Speaker:Tsunehide Kuroki (Rikkyo U.)
Abstract:It is well-known that a supermembrane in the light-cone gauge has a continuous spectrum and is unstable. Physical interpretation of this instability is that a supermembrane can have a long thin tube without cost of energy and consequently it becomes a spiky configuration in which multiple membranes are connected by thin tubes. On the other hand, the ABJM model was proposed as a low-energy description of multiple M2-branes in the static gauge. It is natural that an M2-brane is also unstable in this gauge if we believe the physical picture in the light-cone gauge. In order to examine this, we construct a BPS solution explicitly both in the Nambu-Goto action of a supermembrane in the static gauge and in the U(1){\times}U(1) ABJM model, which represents intersecting M2-branes. Since this configuration is regarded as a single M2-brane emitting another one, we study the instability of an M2-brane by analyzing fluctuations around it. We show that a zero mode exists which can deform the configuration. For comparison, we also examine a similar configuration on the D2-brane and check that it does not have such zero modes under a fixed string charge. Furthermore we confirm that the novel Higgs mechanism translates our BPS solution in the ABJM model into that in the D2-brane world volume theory, where the winding number of the former around the fixed point of the orbifold becomes the number of strings ending on the D2-brane in the latter.
Reference:arXiv:1102.3277

Statistical model and BPS D4-D2-D0 counting

When:2011/05/18 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H1-36
Speaker:Takahiro Nishinaka (KEK)
Abstract:Recently, there has been various studies on the statistical model description of BPS D6-D2-D0 bound states on a Calabi-Yau three-fold, which is called the crystal melting model.

In this talk, I will talk about a new statistical model that describes the BPS D4-D2-D0 bound states on the resolved conidold. Our model is a D4-D2-D0 counterpart of the crystal melting model for the D6-D2-D0 system. Wall-crossing phenomena in our model will also be discussed briefly. I will also mention the possibility to understand our model in a quiver quantum mechanics.
Reference:arXiv:1102.2992

Exact Results for ’t Hooft Loops in Gauge Theories on a Four-Sphere

When:2011/05/25 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H1-36
Speaker:Takuya Okuda (U. of Tokyo, Komaba)
Abstract:We exactly evaluate the path integral of a general N=2 supersymmetric gauge theory on a four-sphere in the presence of a supersymmetric ’t Hooft loop operator. Besides instantons localized at the north and south poles, monopoles produce important non-perturbative contributions localized at the equator of S^4, where the loop operator is inserted. I will discuss in detail how to compute such monopole contributions to the path-integral. As a by-product, our results confirm predictions obtained from Liouville/Toda conformal field theory via the AGT relation.
Reference:arXiv:1105.2568

On Non-Chiral Extension of Kerr/CFT

When:2011/06/03 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H1-36
Speaker:Noriaki Ogawa (IPMU)
Abstract:Kerr/CFT対応は臨界(零温度)ブラックホールに2次元カイラルCFTが双対であるとする予想である。これを非臨界系に拡張できれば現実的な系の記述にまで応用できることが期待されるが、現状では、CFTがカイラルである(left moverのみを含む)ことに起因して、これにより記述される状態は臨界直上のものに限られている。

我々は臨界ブラックホールの零エントロピー極限を考え、その場合にはKerr/CFTが非カイラルに拡張されることを示した。また、このような場合のright moving sectorのセントラルチャージ計算には従来困難があったが、適切な正則化の方法を提案し、それによって正しい値が計算可能であることを示す。

一般の臨界ブラックホールに対して同様の結果を得ることが次の課題といえるが、その展望と困難についても簡単に説明する。
Reference:arXiv:1010.4291, arXiv:1102.3423

弦の場の理論における多重Ｄブレイン解

When:2011/06/08 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H284A
Speaker:Masaki Murata (RIKEN)
Abstract:弦の場の理論において，Ｄブレインが複数枚あるような状況に相当する解の存在について示唆を得た．具体的には，ソリトン解のエネルギーや閉弦との相互作用を見ることで，ブレインの枚数を勘定し，多重ブレイン解について議論する．
　Ｄブレインはゲージ重力対応など，さまざまな分野へ応用されており，本研究はその基礎研究である．なお，本講演は Martin Schnabl氏との共同研究に基づく．
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ヒッグス粒子の正体？～階層性問題を手がかりとして～

When:2011/06/17 (Fri.) 14:00-15:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Nobuhito Maru (Keio U.)
Abstract:１９７０年代初頭に完成した素粒子とその相互作用を記述する標準模型は、現在まで観測されている実験データをよく説明し非常に成功を収めている。しかし、標準模型は様々な問題を抱えているために基本理論とは考えにくく、(ある基本理論の)低エネルギー有効理論と考えられている。その問題の多くは、標準模型の中で唯一の未発見粒子であるヒッグス粒子に関連しており、その中でも「階層性問題」と呼ばれる問題の解決へのアプローチの方法によって、様々な「標準模型を超える新しい物理」が提案されている。

この講演では、標準模型を超える新しい物理につながる代表的なアイデアを紹介し、素粒子模型構築のレシピを概観する。
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Dp-branes, NS5-branes and U-duality from nonabelian (2,0) theory with Lie 3-algebra

When:2011/06/22 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Yoshinori Honma (Sokendai (KEK))
Abstract:最近、LambertとPapageorgakisによって Lie 3-代数を用いたnonabelian (2,0)理論の運動方程式の記述法が提唱された。この模型には新しい補助場が導入されており、この場に真空期待値をもたせることでD4ブレーンの低エネルギー有効理論を再現することができるが、M5ブレーンの情報を完全に保った定式化になっているかどうかなどの謎も多い。そこで我々はLie 3-代数の具体例を用いることでDpブレーン(p＞4)やNS5-ブレーンの導出やU-dualityの再現性について着目した。
Reference:arXiv:1103.1327

BPS状態の数え上げとbrane配位

When:2011/06/29 (Wed.) 15:00-16:30
Where:Honkan (Main Bldg.) H284A
Speaker:Satoshi Yamaguchi (Osaka U.)
Abstract:Type IIA 弦理論をCalabi-Yau多様体でコンパクト化すると４次元でN=2の超対称性を持つ理論になる。このような理論にはBPS状態と呼ばれる超対称性を半分保つ状態があり、これは、Calabi-Yau多様体のKaehler moduliを変えていくと変化する（壁越え現象）。我々は、Type IIA 弦理論をConifoldでコンパクト化した際のD4,D2,D0-braneの結合状態のBPS状態の数え上げをKontsevich-Soibelmanの壁越え公式を用いた場合と、この系に双対なbrane配位での弦のスペクトラムを考えた場合で行った。この結果、この両者は壁越えを含めて完全に一致することが確かめられた。これは、KSの壁越え公式が有効であること、および双対性が正しいことの非自明な証拠となる。
Reference:

N=1 curves for trifundamentals

When:2011/07/13 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kazuya Yonekura (IPMU)
Abstract:We study the Coulomb phase of N=1 SU(2)^3 gauge theory coupled to one trifundamental field, and generalizations thereof. The moduli space of vacua is always one-dimensional with multiple unbroken U(1) fields. We find that the N=1 Seiberg-Witten curve which encodes the U(1) couplings is given by the double cover of a Riemann surface branched at the poles and the zeros of a meromorphic function.
Reference:arXiv:1105.3215

Renormalization effects on MSSM from a calculable model of strongly coupled hidden sector

When:2011/07/20 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Masato Arai (Czech Technical University )
Abstract:We investigate renormalization effects on the low energy mass spectrum of the minimal supersymmetric standard model (MSSM), using a calculable model of strongly coupled hidden sector. We model the hidden sector by ${\cal N}=2$ supersymmetric quantum chromodynamics with gauge group $SU(2)\times U(1)$ and $N_f=2$ matter hypermultiplets, perturbed by a Fayet-Iliopoulos term which breaks the supersymmetry down to ${\cal N}=0$ on a meta-stable vacuum. The hidden sector K\"{a}hler metric is renormalized, contributing to the MSSM renormalization group flows via gauge mediation. In contrast to perturbative examples of hidden sector renormalization studied in the literature, we find that our strongly coupled model exhibits rather intricate effects on the MSSM soft scalar mass spectrum, depending sensitively on how the hidden sector fields are coupled to the messenger fields. This model provides a concrete example in which the low energy spectrum of MSSM particles that are expected to be accessible in collider experiments can be directly computed using strongly coupled hidden sector dynamics.
Reference:

Beta-ensemble matrix models for orbifold partition function

When:2011/10/05 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Taro Kimura (Univ. of Tokyo, Komaba)
Abstract:We would like to discuss combinatorial treatment, and its matrix model
description of the instanton partition function for the orbifold
theory. The partition function is obtained by extracting the invariant
sector of the standard partition function under the discrete orbifold
action. We will show the q-deformation, and its root of unity limit of
the partition function is useful to study the combinatorial aspects of
the orbifold partition function. It is also shown that the
beta-ensemble matrix model is derived from the asymptotic behavior of
the combinatorial partition function for generic $\beta = - \epsilon_1
/ \epsilon_2$. and then the Seiberg-Witten curve arises from the
spectral curve of the corresponding matrix model.
Reference:arXiv:1105.6091, arXiv:1109.0004

Classical integrability of Schrodinger sigma models and q-deformed Poincare symmetry

When:2011/10/12 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Io Kawaguchi (Kyoto U.)
Abstract:近年、AdS/CFT対応を拡張して、非相対論的共形場理論に適用しようという試みがなされてきた。Schrodinger時空はその際に現れる背景時空の一つである。ここでは、3次元Schrodinger時空を考え、その上の非線形シグマ模型の古典的な可積分構造について議論する。この模型の運動方程式は2通りのLax対を用いて記述できることを示した。それぞれの記述の背後にある対称性を同定し、古典r行列も求めた。両者は異なる対称性に基づく記述であるが、互いに等価で、非局所写像により関係している。また、この可積分構造は、3次元warped AdS空間上の非線形シグマ模型の持つ可積分構造と関係しており、両者の関係についても議論する。
Reference:arXiv:1109.0872

${\cal W}_{1+\infty}$ algebra as a symmetry behind AGT relation

When:2011/10/19 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Shotaro Shiba (KEK)
Abstract:AGT(-W) relation claims that the partition functions of 4-dim ${\cal N}=2$ supersymmetric quiver gauge theories correspond to the correlation functions of Liouville (Toda) field theory times so-called "$U(1)$ factor". We take notice of this factor, and then find some evidences which imply that ${\cal W}_{1+\infty}$ algebra describes the symmetry behind AGT(-W) relation. In this seminar, I want to start from the concrete form of AGT(-W) relation, and to explain clearly why this $U(1)$ factor is related to ${\cal W}_{1+\infty}$ algebra.
Reference:arXiv:1105.1667

Solutions from boundary condition changing operators in open superstring field theory

When:2011/10/26 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Toshifumi Noumi (Univ. of Tokyo, Komaba)
Abstract:Since Schnable's construction of an analytic solution for tachyon
condensation, a lot of classical solutions in open string field theory
have been analytically constructed. In this talk, I will introduce an
approach using boundary condition changing (bcc) operators. After
reviewing previous solutions in the bosonic string using bcc operators,
I will discuss their relation to boundary conformal field theories by
considering the gauge-invariant observables corresponding to closed
string one-point functions on the disk. And then, I will talk about our
construction of solutions in the superstring.
Reference:arXiv:1108.5317

3d/3d 関係について

When:2011/11/04 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Yuji Terashima (Tokyo Tech)
Abstract:3d/3d 関係は3次元のゲージ理論と3次元の Chern-Simons 理論の等価性を主張する．この講演では，この主張の量的な証拠として，3次元のゲージ理論の分配関数から3次元双曲多様体の体積をどのように導けるか，について述べる．
Reference:arXiv:1103.5748, arXiv:1106.3066

On S-duality of 5d super Yang-Mills on $S^1$

When:2011/11/09 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Yuji Tachikawa (IPMU)
Abstract:After reviewing the basics of the S-duality of 4d N=4 super Yang-Mills with general gauge groups, its extension to 5d maximally supersymmetric Yang-Mills on $S^1$ will be discussed. It will be shown to be closely related to the reversal of arrows of Dynkin diagrams of affine Lie algebras. If we have time, the most subtle case involving the SU(odd) gauge theory with $Z_2$ twist and the USp theory with nontrivial 5d theta angle will also be discussed.
Reference:arXiv:1110.0531

Worldsheet formulation for the refined topological string theory

When:2011/11/16 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Yu Nakayama (Caltech/IPMU)
Abstract:Nekrasov's partition function is defined on a flat bundle of R^4 over S^1 called the Omega background. When the fibration is self-dual, the partition function is known to be equal to the topological string partition function, which computes scattering amplitudes of self-dual gravitons and graviphotons in type II superstring compactified on a Calabi-Yau manifold. We propose a generalization of this correspondence when the fibration is not necessarily self-dual.
Reference:arXiv:1106.5503

Selberg Integral and SU(N) AGT Conjecture

When:2011/12/14 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Hong Zhang (Univ. of Tokyo, Hongo)
Abstract:An intriguing coincidence between the partition function of super Yang-Mills theory and correlation functions of 2d Toda system has been heavily studied recently. While the partition function of gauge theory was explored by Nekrasov, the correlation functions of Toda equation has not been completely understood. In this paper, we study the latter in the form of Dotsenko-Fateev integral and reduce it in the form of Selberg integral of several Jack polynomials. We conjecture a formula for such Selberg average which satisfies some consistency conditions and show that it reproduces the SU(N) version of AGT conjecture.
Reference:arXiv:1110.5255, arXiv:1012.3137

Chern-Simons Theories with a Vector Fermion

When:2011/12/21 (Wed.) 13:30-14:30
Where:Honkan (Main Bldg.) H284A
Speaker:Shuichi Yokoyama (TIFR)
Abstract:We investigate Chern-Simons theories coupling to vector matter. These kinds of model are quite interesting in the following sense. First, they provide us with infinitely many interacting conformal field theories (CFT) with Lagrangian description, which enables us to study CFT in a direct calculation. Second, these kinds of model are likely to be dual to higher spin theories in AdS4, which would have potential or possibility to reveal rich structure in high energy physics. After belief introduction of these backgrounds, I will talk about U(N) Chern-Simons theories coupling to a vector-like (fundamental/anti-fundamental) fermion. It turns out that this model can be handled exactly in 't Hooft limit. I will explain how to deal with it by means of large N technique.
Reference:arXiv:1110.4386

博士論文発表会

When:2012/01/05 (Thu.) 13:30-18:00
Where:Honkan (Main Bldg.) H284A
Speaker:Takuya Saka, Koh Iwasaki (Tokyo Tech)
Abstract:13:30-15:30
Takuya Saka,
"Instanton Caluculus in $\Omega$-deformed $\mathcal{N}=4$ Super Yang-Mills Theory."

16:00-18:00
Koh Iwasaki, "BPS States in World-volume Theories of M-branes and D-branes."
Reference:

Atomic nucleus from string theory

When:2012/01/11 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Koji Hashimoto (RIKEN)
Abstract:In generic holographic QCD, we find that baryons are bound to form a nucleus, and that its radius obeys the empirically-known mass number (A) dependence r A1/3 for large A. Our result is robust, since we use only a generic property of D-brane actions in string theory. We also show that nucleons are bound completely in a finite volume. Furthermore, employing a concrete holographic model (derived by Hashimoto, Iizuka, and Yi, describing a multi-baryon system in the Sakai-Sugimoto model), the nuclear radius is evaluated as O(1)×A1/3 [fm], which is consistent with experiments.
Reference:arXiv:1103.5688

A Note on Kahler Potential of Charged Matter in F-theory

When:2012/01/18 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Teruhiko Kawano (Univ. of Tokyo, Hongo)
Abstract:We study the Kahler potential of charged matter fields, whose profiles have a peak on their matter curve --- on an "intersection" of 7-branes, in an F-theory compactification. It is shown that the Kahler potential is exactly given by the integral over the matter curve, but not by the integral over the whole GUT surface of 7-branes.
Reference:

Line operators on $S^1 \times \mathbb{R}^3$ and AGT correspondence

When:2012/01/25 (Wed.) 13:30-14:30
Where:Honkan (Main Bldg.) H284A
Speaker:Yuto Ito (Univ. of Tokyo, Komaba)
Abstract:We perform an exact localization calculation for the expectation values of Wilson-'t Hooft line operators in $\mathcal{N} = 2$ supersymmetric gauge theories on $S^1 \times \mathbb{R}^3$. We twist the periodic boundary condition around $S^1$ and check the correspondence between the 't Hooft line operators with the twisted boundary condition and the Verlinde loop operators in Liouville field theory with a general value of the parameter appearing in the action. We also observe that the values of the line operators on $S^1 \times \mathbb{R}^3$ coincide with holonomies of flat connections on Riemann surfaces whose space is quantized Hitchin moduli space.
Reference:arXiv:1111.4221

Holographic three point functions for GKP strings from integrability

When:2012/02/01 (Wed.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Shota Komatsu (Univ. of Tokyo, Komaba)
Abstract:I will describe a holographic computation of a three point function of twist 2 operators with large spin in N=4 super Yang-Mills at strong coupling. In AdS/CFT correspondence, three point functions of non-BPS operators in the gauge theory correspond to three point functions of a worldsheet sigma model of string theory on AdS. When the gauge theory is strongly coupled and operators have large quantum numbers, the worldsheet sigma model becomes classical. In this limit, there are two different contributions to the three point functions: One is from the action of the sigma model and the other is from vertex operators. I will show that the contribution from the action can be computed by adapting integrability-based techniques invented previously for the gluon scattering problem. If time permits, I would also like to sketch how to calculate the contribution from vertex operators and show, if possible, a tentative result.
Reference:arXiv:1110.3949

Gauge Fixing of Open Superstring Field Theory

When:2012/02/22 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Shingo Torii (Univ. of Tokyo, Komaba)
Abstract:We consider gauge fixing of the Wess-Zumino-Witten-type open superstring field theory. Analyzing the free theory, we find that there appear infinitely many ghost string fields and antighost string fields carrying various world-sheet ghost numbers and picture numbers. We propose a variety of gauge-fixing conditions, one of which manifests the relation to Witten's original superstring field theory, and calculate the corresponding propagators. We also determine the field-antifield content and the free master action in the Batalin-Vilkovisky formalism.
Unlike in the bosonic string field theory, the master action does not take the same form as the original gauge-invariant action.
Reference:arXiv:1201.1761, arXiv:1201.1762

Towards q-deformations of the Mirror TBA

When:2012/03/23 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:G. E. Arutyunov (Utrecht U.)
Abstract:The mirror Thermodynamic Bethe Ansatz (TBA) is a tool to determine the spectrum of the AdS_5 x S^5 superstring. After an extensive introduction, I will discuss work in progress towards constructing a q-deformed version of the mirror TBA.
Reference: