YITP Workshop
Strings and Fields 2017

August 7 (Mon) - 11 (Fri), 2017

Panasonic Hall and Rooms Y206 & Y306, Yukawa Memorial Building,
Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, Japan

Program

Invited talks including overviews are marked with ^*.
Length of talks: 60 mins for invited talk and 20 mins for short talk.
At the beginning of each poster session, there are 1-min talks by the presenters of the posters.
Individual abstracts can be shown by clicking/touching the entry.
You can also .

August 7 (Mon)
Afternoon Session 1 (13:00-14:10)
Vladimir Rosenhaus ^*	KITP, UC Santa Barbara	SYK Model ^*
The SYK model, a quantum mechanical model of $N\gg 1$ Majorana fermions $\chi_i$ with a $q$-body, random interaction, is a novel realization of holography. We discuss recent progress in finding the bulk dual of SYK.
Afternoon Session 2 (14:30-15:20)
Tatsuo Azeyanagi	Universite Libre de Bruxelles	Aspects of large D matrix models and tensor models
In this talk, I will investigate a new type of (enhanced) large D limit for complex/Hermitian matrix models and its generalizations. I will explain physical properties of the models, including their phase structures. I will also comment on some connections to the tensor models proposed as implementation of the SYK model without relying on disorder.
Suguru Okumura	Kyoto University	Deformations of the Almheiri-Polchinski model
We study Yang-Baxter deformations of a specific 1+1 D dilaton gravity model called the Almheiri-Polchinski model. We present a deformed black hole solution and compute the Bekenstein-Hawking entropy. The entropy can also be reproduced holographically by evaluating the renormalized stress tensor on a regularized screen close to a singularity which is generated by the deformation. This work is based on the collaboration arXiv:1701.06340 and arXiv:1704.07410 with Hideki Kyono and Kentaroh Yoshida.
Afternoon Session 3 (15:35-16:50)
Masaki Shigemori	Queen Mary University of London & Yukawa Institute for Theoretical Physics	Recent developments in the black hole microstate geometry program
I will discuss recent developments in the black hole microstate geometry program, including a new class of superstratum solutions, and their implications for black hole microphysics.
Minkyu Park	Yukawa Institute for Theoretical Physics	Non-Abelian supertubes
We found an example of non-Abelian supertubes which are natural extensions of all known (Abelian) supertubes so far. By non-Abelian, we mean noncommute monodromy matrices which belong to each supertube, $[M_1,M_2]\ne0$. The solution is obtained in the limit where two supertubes can be regarded as one supertube. We also study the physical properties of this solution and discuss some implications of it in the context of black hole microstate.
Yoshinori Matsuo	National Taiwan University	Static black holes with back reaction from vacuum energy
We study spherically symmetric static solutions to the semi-classical Einstein equation sourced by the vacuum energy of quantum fields in the curved space-time of the same solution. We found solutions that are small deformations of the Schwarzschild metric for distant observers, but without horizon. Instead of being a robust feature of objects with high densities, the horizon is sensitive to the energy-momentum tensor in the near-horizon region.
Afternoon Session 4 (17:05-18:20)
Yuki Yokokura	RIKEN	A Model of Black Hole Evaporation and 4D Weyl Anomaly
We analyze time evolution of a spherically-symmetric collapsing matter from a point of view that black holes evaporate by nature. We consider conformal matters and solve the semi-classical Einstein equation $G_{\mu\nu}=8\pi G \langle T_{\mu\nu} \rangle$ by using the 4-dimensional Weyl anomaly with a large $c$ coefficient. Here $\langle T_{\mu\nu} \rangle$ contains the contribution from both the collapsing matter and Hawking radiation. The solution indicates that the collapsing matter forms a dense object and evaporates without horizon or singularity, and it has a surface but looks like an ordinary black hole from the outside. Any object we recognize as a black hole should be such an object.
Nobuyoshi Ohta	Kindai University	Gauge and Parametrization dependence in Renormalization group approach to Quantum Gravity
We perform a general computation of the off-shell one-loop divergences in a higher-derivative theory of gravity in addition to the Hilbert and cosmological terms in a two-parameter family of path integral measures, corresponding to different ways of parametrizing the graviton field, and a two-parameter family of gauges. Trying to reduce the gauge- and measure-dependence selects certain classes of measures and gauges respectively. There is a choice of two parameters (corresponding to the exponential parametrization and the partial gauge condition that the quantum field be traceless) that automatically eliminates the dependence on the remaining two parameters and on the cosmological constant. We observe that the divergences are invariant under a $Z_2$ "duality" transformation that involves the replacement of the densitized metric by a densitized inverse metric as the fundamental quantum variable. This singles out a formulation of unimodular gravity as the unique "self-dual" theory in this class.
Kazunari Shima	Saitama Institute of Technology	Nonlinear-supersymmetric general relativity theory for a model of nature
Considering unstable Riemann space-time inspired by nonlinear representation of SUSY(NLSUSY) whose tangent space possesses Grassmann SL(2,C) degrees of freedom besides the ordinary Minkowski (SO(1,3)) ones and performing the ordinary geometric arguments of Einstein general relativity(GR) principle, we obtain NLSUSY invariant Einstein-Hilbert-type general relativity action(nonlinear supersymmetric general relativity (NLSUSYGR)) equipped with the cosmological term. NLSUSYGR would collapse spontaneously(Big Collapse) to ordinary Riemann space-time and Nambu-oldstone fermion corresponding to [superGL(4,R)/GL(4,R)] of Grassmann degrees of freedom. It gives a new paradigm for the SUSY unification of space- time and matter with the robust SUSY breaking encoded in space-time itself, where the standard model(SM) of the low energy particle physics is anticipated to emerge in the true vacuum of NLSUSYGR as the effective theory composed of NG fermion. From these viewpoints the linearization of NLSUSY and the relation(equivalence) of NLSUSY theory with the LSUSY theory are discussed in detail by the systematic and algebraic argument. SUSYGR paradigm can bridge naturally the cosmology and the low energy particle physics and gives new insights into unsolved problems of cosmology and SM and explains naturally mysterious relations among them, e.g. the space-time dimension four, the dark energy density≃( neutrino mass)4 , the three-generations structure of quarks and leptons, etc.. The Grassmann nature of space-time and the NLSUSY Lie algebra play crucial roles.
August 8 (Tue)
Morning Session 1 (9:00-10:10)
Shinya Kanemura^*	Osaka University	Higgs as a Probe of New Physics^*
We discuss physics of the Higgs sector, new physics models beyond the standard model and their relation, from the viewpoint that the Higgs sector is a key to new physics. We discuss how we can approach to the new physics beyond the standard model via exploring the structure and the property of the Higgs sector using current LHC experiments, precision studies at the future International Linear Collider and the future gravitational wave interferometers such as LISA and DECIGO.
Morning Session 2 (10:30-11:20)
Naoki Yamatsu	Maskawa Institute, Kyoto Sangyo University	Special Grand Unification
I will propose new-type grand unified theories (GUTs) based on GUT gauge groups broken to their special subgroups. In the framework, 4D gauge anomaly cancellation restricts the minimal number of generations of the 4D the Standard Model (SM) Weyl fermions. In this talk, I will show that in an SU(16) GUT on 6D orbifold space whose GUT group is broken to its special subgroup SO(10) and further SM gauge groups, three generations of the SM fermions are allowed by the 6D and 4D gauge anomaly cancellation on the bulk and fixed points without exotic 4D chiral fermions. This talk is based on arXiv:1704.08827.
Masatoshi Yamada	Heidelberg University	Gauge hierarchy problem in asymptotically safe gravity--the resurgence mechanism
The gauge hierarchy problem could find a solution within the scenario of asymptotic safety for quantum gravity. We discuss a "resurgence mechanism" where the running dimensionless coupling responsible for the Higgs scalar mass first decreases in the ultraviolet regime and subsequently increases in the infrared regime. A gravity induced large anomalous dimension plays a crucial role for the required "self-tuned criticality" in the ultraviolet regime beyond the Planck scale.
Morning Session 3 (11:35-12:25)
Keita Kanno	Kavli IPMU	Revisiting arithmetic solutions to the W=0 condition
The gravitino mass is expected not to be much smaller than the Planck scale for a large fraction of vacua in flux compactifications. There is no continuous parameter to tune even by hand, and it seems that the gravitino mass can be small only as a result of accidental cancellation between period integrals weighted by integer-valued flux quanta. DeWolfe et.al. (2005) proposed to pay close attention to vacua where the Hodge decomposition is possible within a number field, so that the precise cancellation takes place as a result of algebra. We focus on a subclass of those vacua---those with complex multiplications---and explore more on the idea in this article. It turns out, in Type IIB compactifications, that those vacua admit non-trivial supersymmetric flux configurations if and only if the reflex field of the Weil intermediate Jacobian is isomorphic to the quadratic imaginary field generated by the axidilaton vacuum expectation value. We also found that flux statistics is highly enriched on such vacua, as F-term conditions become linearly dependent.
Hajime Otsuka	Waseda University	SO(32) heterotic line bundle models
We search for the three-generation standard-like models from $SO(32)$ heterotic string theory on smooth, quotient complete intersection Calabi-Yau threefolds with multiple line bundles. The stable line bundles lead to the three chiral generations of quarks and leptons without chiral exotics. The Higgs doublets appear as the vector-like particles under the standard model gauge groups. It is found that the Yukawa couplings of quarks and leptons are allowed at the renormalizable level.
Afternoon Session 1 (14:05-15:20)
Tomoki Nosaka	Korea Institute for Advanced Study	Instanton in rank-deformed Chern-Simons matter theory from topological string
We studied the partition function of U(N)^4 circular quiver superconformal Chern-Simons theory which preserves N=4 supersymmetry. The N=4 supersymmetry restricts the four Chern-Simons levels to be (k,0,-k,0) or (k,-k,k,-k), which are unified through the Hanany-Witten transition in the generalization with non-equal ranks U(N+M_1)xU(N+M_2)xU(N+M_3)xU(N+M_4). We explicitly showed that the generating function of this partition function coincides for special M_i with the free energy of topological string on local D_5 del Pezzo geometry, with the non-perturbative completion proposed by Hatsuda, Marino, Moriyama and Okuyama in arXiv:1306.1734.
Sanefumi Moriyama	Osaka City University	Superconformal Chern-Simons Theories from del Pezzo Geometries
In the talk by Tomoki Nosaka, it was found that the so-called (2,2) model (which is a superconformal Chern-Simons theory with the gauge group U(N)^4 and the Chern-Simons level (k,0,-k,0)) is described by the free energy of topological strings. Here I would like to present a geometrical interpretation to this analysis and discuss its implication.
Takao Suyama	KEK	Strong Coupling Limit of A Family of Chern-Simons-matter Theories
We investigate the strong coupling limit of a family of Chern-Simons-matter theories in the planar limit. The family consists of ${\cal N}=3$ theories with the gauge group ${\rm U}(N_1)_{k_1}\times{\rm U}(N_2)_{k_2}$ coupled to $n$ bi-fundamental hypermultiplets. All observables obtainable from the planar resolvent turns out to have finite limits in the large 't~Hooft coupling limit. Possible gravity duals are briefly discussed. We observe that Kac-Moody algebras govern the structure of the planar spectral curves of the theories.
Afternoon Session 2 (15:35-16:50)
Kazuma Shimizu	Yukawa Institute for Theoretical Physics	Mass Deformed ABJM Theory in Finite and large N
We study the mass deformed ABJM theory by using localization method. We studied this theory in the large N limit with help of the saddle point approximation. This work suggests that there is a singularity of the solution of the saddle point at a certain finite value of mass parameter. In this time, we study this theory in finite N region by the numerical analysis. The result suggests that there are zero locus of the partition function of this theory at certain values of the mass parameter and the first zero point becomes the singular point of the solution of the saddle point equation in our previous work. This presentation is based on the collaboration with Masazumi,Honda, Tomoki, Nosaka and Seiji,Terashima.
Shuichi Yokoyama	Yukawa Institute for Theoretical Physics	Complete factorization in minimal N=4 Chern-Simons-matter theory
I will speak about my recent work with T.Nosaka on the study of a minimal N=4 Chern-Simons matter theory, that is, N=4 U(N)_k x U(N+M)_{-k} Chern-Simons theory coupling to one bifundamental hypermultiplet employing its partition function, which is given by 2N+M dimensional integration via localization. Surprisingly, by performing the integration explicitly the partition function completely factorizes into that of pure Chern-Simons theory for two gauge groups and an analogous contribution from the hypermultiplet. Using the factorized partition function we argue the level/rank duality, which is also expected from the Hanany-Witten transition of type IIB brane realization. If time permits, I also comment on the connection to the higher-spin theory in the 't Hooft limit.
Hironori Mori	Yukawa Institute for Theoretical Physics	Refined geometric transition and qq-characters
We provide the refined prescription for the geometric transition in the refined topological string theory and show how to apply it to constructing doubly quantized Seiberg-Witten curves called qq- characters. In the arguments of literatures for the refined geometric transition, it was not seriously considered that the choice of the preferred direction may affect the open string amplitude. Our prescription given here for the refined geometric transition is involved in nontrivial effects from sensitivity to the preferred direction. As its application, we discuss the description of the qq-character that was recently well-developed but whose stringy origin is still unclear. It is proposed that it can be engineered by the refined geometric transition, which may possibly give interpretation in terms of string theory.
Afternoon Session 3 (17:05-18:20)
Yuji Sugimoto	Osaka University	Calabi--Yau geometry and electrons on 2d lattices
The B-model approach of topological string theory leads to difference equations by quantizing algebraic mirror curves. It is known that these quantum mechanical systems are solved by the refined topological strings. Recently, it was pointed out that the quantum eigenvalue problem for a particular Calabi--Yau manifold, known as local $\mathbb{F}_0$, is closely related to the Hofstadter problem for electrons on a two- dimensional square lattice. In this paper, we generalize this idea to a more complicated Calabi--Yau manifold. We find that the local $\mathcal{B}_3$ geometry, which is a three-point blow-up of local $\mathbb{P}^2$, is associated with electrons on a triangular lattice. This correspondence allows us to use known results in condensed matter physics to investigate the quantum geometry of the toric Calabi--Yau manifold.
Kohta Hatakeyama	Shizuoka University	Correlation functions and renormalization in a scalar field theory on the fuzzy sphere
We study correlation functions in a scalar field theory on the fuzzy sphere, which is realized by a matrix model where the matrix size plays a role of the UV cutoff. We identify the Berezin symbol for a matrix with a field, and we calculate the correlation functions of the fields by Monte Carlo simulation. By tuning a parameter of the theory, we find that the two-point and four-point correlation functions agree for different matrix sizes. This result strongly suggests that the theory is renormalizable.
Takaki Matsumoto	Tsukuba University	Information metric and Berry phase in matrix geometry
Matrix geometry is defined by a sequence of some Hermitian matrices and known as a typical example of noncommutative geometry which is a promising candidate for the quantum geometry of space-time. We introduce a recently proposed method which makes it possible to relate matrix geometry to smooth differential geometry. In this formulation, we introduce the information metric and Berry phase and show that they work as a Riemannian metric and gauge field on the corresponding smooth geometry respectively. They are expressed in terms of given matrices and therefore regarded as a new objects that characterize the matrix geometry. This talk is based on a work in collaboration with Goro Ishiki and Hisayoshi Muraki.
August 9 (Wed)
Morning Session 1 (9:00-10:10)
Christopher Herzog ^*	Stony brook University	Boundary Trace Anomalies and Boundary Conformal Field Theory^*
I discuss some aspects of boundary conformal field theories (bCFTs). I will demonstrate that free bCFTs have a universal way of satisfying crossing symmetry constraints. I will introduce a simple class of interacting bCFTs where the interaction is restricted to the boundary. Finally, I will discuss possible relationships between boundary trace anomalies and boundary limits of stress- tensor correlation functions.
Morning Session 2 (10:30-11:45)
Noburo Shiba	Harvard University	The Aharonov-Bohm Effect on Entanglement Entropy in Conformal Field Theory
We consider the Aharonov-Bohm effect on entanglement entropy for one interval in (1+1) dimensional conformal field theory on a one dimensional ring. The magnetic field is confined inside the ring, i.e. there is a Wilson loop on the ring. The Aharonov-Bohm phase factor which is proportional to the Wilson loop is represented as insertion of twist operators. We compute exactly the Renyi entropy from a four point function of twist operators in a free charged scalar field.
Kotaro Tamaoka	Osaka University	Entanglement Entropy for 2D Gauge Theories with Matters
Entanglement entropy (EE) for gauge theories have rich structures due to the gauge constraints. In this talk, first we explain the difference of EE between usual spin systems and gauge theories by using the extended Hilbert space definition. Next, we discuss the EE in 1+1-dimensional $SU(N)$ gauge theories with various matter fields on the lattice. Especially, we consider how the ground state EE in the continuum limit can be understood from the lattice ground state. This talk is based on the work arXiv:1705.01549 in collaboration with Sinya Aoki, Norihiro Iizuka, and Tsuyoshi Yokoya.
Ken Kikuchi	Nagoya University	Exactly marginal deformations of supersymmetric Renyi entropy
Conformal field theories (CFTs) often appear in continuous families. These CFTs are connected by exactly marginal deformations. Therefore, their parameters, called exactly marginal couplings, label CFTs, and can be considered as coordinates of manifolds called conformal manifolds. It is known that sphere partition functions of various CFTs with nontrivial conformal manifolds compute Kahler potentials of exactly marginal couplings. On the other hand, an object called supersymmetric Renyi entropy (SRE) is defined via partition functions on branched sphares, which are one parameter generalization of ordinary spheres. Thus it is expected that similar structures would be observed if one considers exactly marginal deformations of SRE (at least in the limit that branched spheres reduce to the ordinary ones). We would like to address this question.
Morning Session 3 (12:00-12:50)
Sotaro Sugishita	Osaka University	Entanglement entropy for free scalar fields in AdS
We consider entanglement entropy (EE) of QFT in AdS space in order to evaluate quantum corrections to the holographic EE of CFT. For a holographic CFT, when the theory is a large N theory, EE can be computed by the area of the minimal surface in the bulk AdS space. However, for a finite N theory, we need to consider the quantum corrections in the bulk. It is proposed that the quantum corrections are given by the bulk EE and back reaction. We evaluate these corrections for the scalar field in AdS at the 1-loop level and see that the result is consistent with the 1/N expansion of the dual CFT.
Satoshi Ohya	Nihon University	Conformal Ward-Takahashi Identity at Finite Temperature
It is widely believed that conformal symmetry is always broken at finite temperature. This is true in most cases, however, this is not the whole truth: if CFTs are thermalized via the Unruh effect, conformal symmetry remains intact. In this talk I shall discuss the conformal Ward-Takahashi identities in $d$-dimensional CFT thermalized via the Unruh effect. I shall show that, for the case of two-point functions, the conformal Ward-Takahashi identities are translated into certain recurrence relations in the complex momentum space. It can be shown that all the real-time two-point functions are obtained by solving these recurrence relations in any spacetime dimension $d\geq3$.
Afternoon Session 1 (14:05-15:20)
Taro Kimura	Keio University	Non-simply-laced quiver gauge theory from Omega-background
We introduce quiver gauge theory associated with the non-simply-laced type fractional quiver, and define fractional quiver W-algebras by using construction of arXiv:1512.08533 and arXiv:1608.04651 with representation of fractional quivers. This talk is based on a collaboration with V. Pestun (IHES).
Toshiaki Fujimori	Keio University	Resurgence Structure to All Orders of Multi-bions in Deformed SUSY Quantum Mechanics
Perturbation series in quantum theory are usually divergent asymptotic series which give rise to ambiguities when they are resummed by using the Borel resummation. Those ambiguities are expected to be canceled when non-perturbative corrections from non-trivial saddle points are correctly added to form so-called resurgent trans-series. I will talk about the full resurgent trans-series in the (nearly) supersymmetric ${\mathbb C}P^1$ quantum mechanics reduced from the 2d $\mathcal N=(2,0)$ model. We obtain exact results for the first and second susceptibility of the ground state energy under a SUSY breaking deformation. We obtain all multi-bion exact solutions in the complexified theory and construct the resurgent trans-series to all orders in the multi-bion contributions. We show that it reproduces the exact result, which supports the resurgence to all orders.
Antonino Flachi	Keio University	Gross-Neveu model on the interval: exact solutions and quantum vacuum energy
In this talk I will present discuss a fermion system of finite size. Fermions are allowed to interact and are forced to obey rigid boundary conditions. I will approach this problem by using a self-consistent method based on the non-linear Schr\"odinger equation and show how this alters the process of condensation and the quantum vacuum energy for this system. A nontrivial behaviour in the Casimir force, displaying a switch from an attractive to a repulsive regime, is observed. This sign flip originates from the competition between the attractive contribution from the usual fermionic Casimir effect and a repulsive one coming from the condensate.
Afternoon Session 2 (15:35-18:20)
Poster Session
List of Posters
Jaewang Choi	Yukawa Institute for Theoretical Physics	Super Yang-Mills theory with position dependent couplings
When the coupling depends on the position, whether supersymmetry is preserved or not is not manifest. We found some conditions to preserve supersymmetry with position dependent coupling by deforming the N=4 SYM theory. And we got some non-trivial solutions to satisfy these conditions in some specific case. And also in perspective of supergravity in 10 dimension, we can guess that our deformed SYM action have relations with D3 branes' world-volume action in general supergravity background. So, we also discuss about relation with our new deformation terms and 10 dimensional supergravity fields.
Sota Hanazawa	Ibaraki University	Dirichlet-branes from BRST-invariance in Pure Spinor Formalism
In the pure spinor formalism, the kappa-symmetry in Green- Schwarz (GS) superstring is replaced with the BRST symmetry. In this talk, we find that boundary conditions to eliminate BRST surface term of pure spinor superstring in an ${\rm AdS_5}\times{\rm S^5}$ background lead to a classification of possible configurations of 1/2-BPS Dirichlet-branes. Our result turns out to be consistent with the one obtained by the boundary kappa-invariance of GS superstring. We also discuss an open pure spinor supermembrane in the presence of a constant three-form flux. It is shown that a noncommutative M5-brane and a noncommutative M9-brane are possible as boundary conditions.
Yasuyuki Hatsuda	Rikkyo University	Solving Integrable Systems by String Theory
I will explain that a class of integrable systems is solved by topological string theory. It turns out that there exists a remarkable symmetric structure in these integrable systems.
Masaya Iida	Tokyo University of Science	Fermions coupled with a vortex skyrmion
Fermions that interact with the baby skyrmion are already studied. And it is known that energy level continuously travel between positive/negative levels by variation of the baby skyrmion size and the fermion become localizing mode during the level crossing. In this poster, we study behavior of the fermion interacting with vortex skyrmion. The vortex skyrmion is consisting of the baby skyrmions piled along the three dimensional direction. We discuss behavior of the fermion by spectral flow analysis and solving the Dirac equation. The specific energy level is affected by the topological information of the vortex skyrmion. We obtain the traveling wave solution as well as bound state solution. And we discuss close connection between the statistics of the vortex skyrmion and the winding number.
Hiroshi Isono	Chulalongkorn University	Inflation from Supersymmetry Breaking
We explore the possibility that inflation is driven by supersymmetry breaking with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Moreover, we impose an R-symmetry that allows to satisfy easily the slow-roll conditions, avoiding the so-called $\eta$-problem, and leads to two different classes of small field inflation models; they are characterised by an inflationary plateau around the maximum of the scalar potential, where R- symmetry is either restored or spontaneously broken, with the inflaton rolling down to a minimum describing the present phase of our Universe. To avoid the Goldstone boson and remain with a single (real) scalar field (the inflaton), R- symmetry is gauged with the corresponding gauge boson becoming massive. This framework generalises a model studied recently by the present authors, with the inflaton identified by the string dilaton and R-symmetry together with supersymmetry restored at weak coupling, at infinity of the dilaton potential. The presence of the D-term allows a tuning of the vacuum energy at the minimum. The proposed models agree with cosmological observations and predict a tensor-to-scalar ratio of primordial perturbations $10^{-9}\lt r\lt 10^{-4}$ and an inflation scale $10^{10}$ GeV $\lt H_\lt 10^{12}$ GeV. $H_$ may be lowered up to electroweak energies only at the expense of fine-tuning the scalar potential.
Nahomi Kan	National Institute of Technology, Gifu College	Boson stars in interacting scalar models associated with graphs
We study solutions for boson stars in the multi-scalar field theory with global symmetry $[U(1)]^N$. The properties of the boson stars are investigated by the Newtonian approximation with the large coupling limit. Our purpose is to study the models bringing about exotic mass distributions which explain flat rotation curves of galaxies. We propose plausible models in which coupling matrices are associated with various graphs in graph theory.
Shoichi Kawamoto	Chung Yuan Christian University	Charged rotating BTZ black holes in noncommutative space and torsion gravity
We consider charged rotating BTZ black holes in noncommutative space by use of Chern-Simons theory formulation of $2+1$ dimensional gravity. The noncommutativity between the radial and the angle variables is introduced through the Seiberg-Witten map for gauge fields, and the deformed geometry to the first order in the noncommutative parameter is calculated. It is found that the deformation also induces nontrivial torsion, and the framework of Einstein-Cartan theory appears to be suitable to investigate the equations of motion. Though the deformation is indeed nontrivial, the deformed and the original Einstein equations are found to be related by a rather simple coordinate change.
Yuta Kikuchi	Kyoto University & Stony Brook University	Mixed anomaly and global inconsistency in quantum mechanics
We discuss energy spectrum of several quantum mechanical models at finite $\theta$ angle, which share certain properties in common with $SU(n)$ Yang-Mills theory and $SU(n)\times SU(n)$ bifundamental gauge theory. In order to give a precise constraint, mixed 't~Hooft anomaly and global inconsistency are studied in detail by gauging the continuous and discrete global symmetries. We compute the energy spectrum of the models numerically and confirm the constraints are satisfied.
Tetsuji Kimura	Tokyo Institute of Technology	Nonlocal N=1 Supersymmetry
We construct ${\cal N}=1$ supersymmetric nonlocal theories in four dimension. We discuss higher derivative extensions of chiral and vector superfields, and write down generic forms of Kahler potential and superpotential up to quadratic order. We derive the condition in which an auxiliary field remains non-dynamical, and the dynamical scalars and fermions are free from the ghost degrees of freedom. We also investigate the nonlocal effects on the supersymmetry breaking and find that supertrace (mass) formula is significantly modified even at the tree level. This is a work in collaboration with Anupam Mazumdar, Toshifumi Noumi, and Masahide Yamaguchi.
Naoki Kiryu	University of Tokyo	Structure constants of operators on the Wilson loop at weak coupling
We study structure constants of local operators inserted on the Wilson loop in ${\cal N}=4$ super Yang-Mills theory. We compute the structure constants in the SU(2) sector at tree level using the correspondence between operators on the Wilson loop and the open spin chain. The results are interpreted as the summation over all possible ways of changing the signs of magnon momenta in the hexagon form factors. This is consistent with a holographic description of the correlator as the cubic open string vertex, which consists of one hexagonal patch and three boundaries. We then conjecture that a similar expression should hold also at finite coupling.
Toru Masuda	Nara Women's University	Vector profile of classical solutions for constant magnetic field background in open string field theory
Recently Ishibashi, Kishimoto and Takahashi constructed a classical solution representing constant magnetic background, following the method of Erler and Maccaferri. For the toroidally compactified background, we investigate the vector profile of the solution. By a numerical computation, we find that the vector profile of the solution has no discontinuity in the both directions of the torus. This continuity is a feature never seen in a gauge field theory on the torus.
Hiroaki Matsunaga	Institute of Physics, Czech Academy of Sciences	New loop-propagating degrees in superstring field theory
In this presentation, we show that there exists a hidden gauge reducibility in superstring field theory based on the small dynamical string field $\Psi \in \mathcal{H}_{\beta \gamma }$ whose gauge variation is also small $\delta \Psi \in \mathcal{H}_{\beta \gamma }$. It requires additional ghost-antighost fields in the gauge fixed or quantum gauge theory, and thus changes the Batalin-Vilkovisky master action, which implies that additional propagating degrees of freedom appear in the loop superstring amplitudes via gauge choice of the field theory. We present that the resultant master action can take a different and enlarged form, and that there exist canonical transformations getting it back to the canonical form. On the basis of Batalin-Vilkovisky formalism, we clarify some exact relations in this hidden or extended gauge structure of superstring field theory.
Atsushi Nakamula	Kitasato University	On magnetically charged limits of calorons
Instantons in pure Yang-Mills theories on partially periodic space $S^1\times\mathbb{R}^3$ are usually called calorons. For the case of gauge group $SU(2)$, they are generally composed of two constituent ``monopoles" with opposite magnetic charges. This constituent structure often appears in the topological soliton systems on periodic background, and makes many curious facts such as fractional topological charge, etc.. For calorons, it occasionally occurs the cases that they have net magnetic charges in $\mathbb{R}^3$. In this study, we consider the mechanism how the magnetic charges appear for certain types of calorons.
Toshifumi Noumi	Kobe University	Coset for BMS: Graviton as a Nambu-Goldstone boson
It has been known that graviton can be thought of as a Nambu-Goldstone (NG) boson for spontaneously broken GL(4) symmetry, which is a part of large gauge transformations associated to general covariance. In this interpretation all the components of the metric are identified with NG bosons, so that these NG modes include gauge degrees of freedom in addition to the two physical helicity modes of graviton. In this presentation I would like to revisit such a property of graviton based on the Bondi-Metzner-Sachs (BMS) symmetry, an infinite dimensional symmetry of asymptotically flat spacetimes. In particular I will illustrate that the viewpoint of asympotics resolves the mismatch between the number of broken symmetries and physical helicity modes. [Based on a collaboration with Y.Huang, T.Inami, K.Izumi and T.Kitamura]
Takayoshi Ootsuka	Ochanomizu University	Finsler connection on general Finsler manifold
We give a Finsler connection on general Finsler manifold $(M,F)$, whose Finsler metric may not be singular, as a non-linear connection on point manifold $M$ not on line-element space $TM-{0}$. In mathematics, Finsler connection is usually defined on a linear connection on $TTM$, but our non-linear connection is defined directly from Finsler metric $F$ and becomes a little easier calculation than conventional treatments. If the Finsler metric $F(x,dx)$ is a Riemannian $F(x,dx)=\sqrt{g_{\mu\nu} (x)dx^\mu dx^\nu}$, then our connection becomes Riemannian connection on $TM$, and if $F$ is regular, which means rank of $\left(\frac{\partial^2 F} {\partial dx^\mu \partial dx^\nu}\right)$ is less than ${\rm dim}M-1$, then our connection becomes non-linear connection of Berwald's. In physics problems, our Finsler connection can be applicable to Lagrangian systems which include constrained dynamical systems, and suits to constructions of deformed Einstein's theory because we do not use line element space but point manifold, our spacetime.
Kazuhiro Sugita	Nihon University	On Multiple-Brane Solution in Berkovits’ Open Superstring Field Theory
The tachyon vacuum solution is constructed in Berkovits' string field theory. The tachyon vacuum solution can be written in the pure-gauge form by using a singular gauge transformation. We propose a candidate for the double-brane solution by using the inverse of the gauge transformation. We should confirm that the energy of the solution is increased by a tension of a D9-brane. However, since the computation of the energy may be difficult, we try to compute the Ellwood invariant.
Kento Sugiyama	Shizuoka University	Multi-cut solutions in Chern-Simons Matrix Models
We study Chern-Simons matrix models including ABJM matrix model at large N.In general, the behaviors of matrix models at large N are characterized by solutions of saddle point equations of matrix eigenvalues. In this poster, we show the existence of novel types of multi-cut solutions in Chern-Simons matrix models.These solutions appear by curious structure in these models.In ABJM matrix models, we particularly argue that the one of our multi-cut solutions might corresponds to a condensation of the membrane instantons.
Takahiro Uetoko	Ritsumeikan University	Non-SUSY D-branes with Vanishing Cylinder Amplitudes in Asymmetric Orbifolds
We study the type II string vacua with chiral space-time SUSY constructed as asymmetric orbifolds of torus and K3 compactifications. Despite the fact that all the D-branes are non-BPS in any chiral SUSY vacua, we show that the relevant non- geometric vacua of asymmetric orbifolds allow rather generally configurations of D-branes which lead to vanishing cylinder amplitudes, implying the bose-fermi cancellation at each mass level of the open string spectrum.
Tsuyoshi Yokoya	Osaka University	Entanglement Entropy for 2D Gauge Theories with Matters
We investigate the entanglement entropy in 1+1-dimensional SU(N) gauge theories with various matter fields using the lattice regularization. Here we use extended Hilbert space definition for entanglement entropy, which contains three contributions; (1) classical Shannon entropy, (2) logarithm of the dimensions of their representations, and (3) EPR Bell pairs. We explicitly show that entanglement entropies (1) and (2) above indeed appear for various multiple "meson" states in gauge theories with matter fields. Furthermore, we employ transfer matrix formalism for gauge theory with fundamental matter field and analyze its ground state using hopping parameter expansion (HPE). We evaluate the entanglement entropy for the ground state and show that all (1), (2), (3) above appear in the HPE. With these results, we discuss how the ground state entanglement entropy in the continuum limit can be understood from the lattice ground state obtained in the HPE. The work is in collaboration with Sinya Aoki, Norihiro Iizuka, and Kotaro Tamaoka.
Ruidong Zhu	University of Tokyo	Orientifold realization of D-type quiver gauge theories in topological vertex formalism and boundary state
It is known that one can compute the instanton partition function of 5d N=1A-type quiver gauge theories (with A-type gauge groups) by using the refined topological vertex. However, the generalization to other types of quivers is not clear from the viewpoint of topological string context. In this poster presentation, we propose a prescription to realize the partition function of D-type quiver gauge theories (with A-type gauge groups), in which a boundary state (for associated 2d Virasoro algebra) is used to represent the "effect" of orientifold in the topological vertex formalism. Supporting evidence is provided by checking that we have the correct double-quantized Seiberg-Witten curve (qq-character) for D-type quiver gauge theories.
August 10 (Thu)
Morning Session 1 (9:00-10:10)
Hiroshi Suzuki^*	Kyushu University	A new domain-wall lattice formulation of chiral gauge theories ^*
Recently, a new domain-wall type lattice formulation of chiral gauge theories was proposed by Grabowska and Kaplan. I review some aspects of this formulation, especially on its gauge (non-)invariance.
Morning Session 2 (10:30-11:45)
Hidenori Fukaya	Osaka University	Atiyah-Patodi-Singer index theorem for physicists
The Atiyah-Patodi-Singer (APS) index theorem attracts attention for understanding physics on surface of materials in topological phases. The original theorem written by the mathematicians is, however, too abstract and too general (allowing non- trivial metric and so on). In particular, the theorem imposes on the Dirac operator the so-called APS boundary condition, which is non-local and unlikely to be realized in physics. In this work, we attempt to reformulate the APS index in a “physicist-friendly” way, for the Dirac fermion operator with U(1) or SU(N) gauge group on a flat four-dimensional Euclidean space. Our method corresponds to a generalization of the Fujikawa method on closed manifolds to that on manifolds with boundary. We show that the same index can be obtained from the massive Dirac operator, even when its boundary condition is local. This presentation is based on a work in collaboration with T. Onogi (Osaka U.) and S. Yamaguchi (Osaka U.).
Faisal Etminan	University of Birjand	Auxiliary-field Monte Carlo method for strongly paired fermions
We present calculations for spin 1/2 fermions at unitarity limit, where the effective range of the interaction is zero and the scattering length is infinite. We compute the ground-state energy for a system of 6, 10,14 and 18 particles, with equal numbers of up and down spins in a periodic cube in the full ground-state constrained-path Monte Carlo (CPMC) method using the extended, attractive Hubbard model, obtaining result for the universal parameter \xi.
Kazuya Yonekura	Kavli IPMU	Anomaly constraints on deconfinement and chiral phase transition
We study constraints on thermal phase transitions of ${\rm SU}(N_c)$ gauge theories by using the 't~Hooft anomaly involving the center symmetry and chiral symmetry. We consider two cases of massless fermions: (i) adjoint fermions, and (ii) $N_f$ flavors of fundamental fermions with a nontrivial greatest common divisor ${\rm gcd}(N_c,N_f) \neq 1$. For the first case (i), we show that the chiral symmetry restoration in terms of the standard Landau-Ginzburg effective action is impossible at a temperature lower than that of deconfinement. For the second case (ii), we introduce a modified version of the center symmetry which we call center-flavor symmetry, and draw similar conclusions under a certain technical definition of (de)confinement. At zero temperature, our results give a partial explanation of the appearance of dual magnetic gauge group in (supersymmetric) QCD when ${\rm gcd}(N_c,N_f) \neq 1$.
Morning Session 3 (12:00-12:50)
Ryo Yokokura	Keio University	Abelian tensor hierarchy and Chern-Simons actions in 4D N=1 conformal supergravity
We consider Chern-Simons actions of Abelian tensor hierarchy of p-form gauge fields in four-dimensional N = 1 supergravity. Using conformal superspace formalism, we solve the constraints on the field strengths of the p-form gauge superfields in the presence of the tensor hierarchy. The solutions are expressed by the prepotentials of the p-form gauge superfields. We show the internal and superconformal transformation laws of the prepotentials. The descent formalism for the Chern-Simons actions is exhibited.
Ryoko Yahagi	Ochanomizu University	Geodesic Equations of Superparticle using Super Finsler Connection
We extend the Brink-Schwarz superparticle model in 2-dimensional spacetime to curved spacetime. We identify its Lagrangian as a super Finsler metric $F$ on (2,2)-dimensional supermanifold $M$. From this super Finsler metric $F$, we define a super Finsler connection. Our connection defines parallel transports on the manifold $M$, while most other Finsler connections are defined on $TM$, which have less physical meaning. The equations of motion of superparticle are reconstructed in the form of geodesic equations by means of super Finsler connection. We consider these geodesics equations lead a supergravity in the same way of Einstein .gravity.
Afternoon Session 1 (14:05-15:15)
Kallol Sen^*	Kavli IPMU	A Mellin space approach to the conformal bootstrap ^*
We describe in more detail our approach to the conformal bootstrap which uses the Mellin representation of CFTd four point functions and expands them in terms of crossing symmetric combinations of AdS$_{d+1}$ Witten exchange functions. We consider arbitrary external scalar operators and set up the conditions for consistency with the operator product expansion. Namely, we demand cancellation of spurious powers (of the cross ratios, in position space) which translate into spurious poles in Mellin space. We discuss two contexts in which we can immediately apply this method by imposing the simplest set of constraint equations. The first is the epsilon expansion. We mostly focus on the Wilson-Fisher fixed point as studied in an epsilon expansion about d=4. We reproduce Feynman diagram results for operator dimensions to $O(e^3)$ rather straightforwardly. This approach also yields new analytic predictions for OPE coefficients to the same order which fit nicely with recent numerical estimates for the Ising model (at e=1). We will also mention some leading order results for scalar theories near three and six dimensions. The second context is a large spin expansion, in any dimension, where we are able to reproduce and go a bit beyond some of the results recently obtained using the (double) light cone expansion. We also have a preliminary discussion about numerical implementation of the above bootstrap scheme in the absence of a small parameter.
Afternoon Session 2 (15:35-16:50)
Chika Hasegawa	Rikkyo University	Crosscap Bootstrap and $\epsilon$-Expansion from Conformal Field Theory in $4-\epsilon$ Dimensional Critical $\phi^4$-Theory
In this talk, we will explain to solve a conformal bootstrap equation in the critical $\phi^4$ theory on the $4-\epsilon$ dimensional real projective space by $\epsilon$-expansion and to evaluate the $\phi$-$\phi$ two points-function to the first non- trivial order in $\epsilon$. We will also mention that our results are consistent with both the results from perturbation theory and the results of the $\epsilon$-expansion from conformal field theory. This talk is based on a current work in progress collaborated with Yu Nakayama.
Hideki Kyono	Kyoto University	Spinning Geodesic Witten diagrams
We consider the so-called geodesic Witten diagrams (GWDs). GWDs are proposed recently as the gravity dual of conformal blocks in CFT in previous work (arXiv:1508.00501). We generalize this relation to Witten diagrams with spinning external and internal fields and we also consider its Mellin representation.
Junichi Sakamoto	Kyoto University	Yang-Baxter sigma models, conformal twists and noncommutative Yang-Mills
The Yang-Baxter sigma model is a systematic way to generate integrable deformations of AdS$_{5}\times$S$^5$. In this talk, we recast the deformations as seen by open strings, where the metric is undeformed AdS$_{5}\times$S$^5$ with constant string coupling, and all information about the deformation is encoded in the noncommutative (NC) parameter. In addition, we show that the unimodularity conditon on $r$- matrices for supergravity solutions translates into the NC parameter being divergence-free. This talk is based on arXiv:1702.02861, 1705.02063.
Afternoon Session 3 (17:05-18:20)
Ivan Arraut	Tokyo University of Science	The triangular formulation of the Nambu-Goldstone theorem
The formulation of the Nambu-Goldstone theorem based on triangle relations between pairs of Goldstone bosons with the degenerate vacuum is based on the Quantum Yang Baxter equations (QYBE). The number of Goldstone bosons as well as their corresponding dispersion relations are natural consequences of this approach. Here we evaluate the triangle relations by using them in order to explain the physics of different systems starting with the Kaon condensation, etc. We also make an analogy with the way how pairs of D-branes interact inside the scenario of String Theory.
Kenji Hotta	Hokkaido University	Thermal Vacuum State for Open Strings on Brane-Antibrane Pairs in the Framework of Thermo Field Dynamics
Previously we have calculated the thermal vacuum state and the partition function for a single open superstring on D-brane--anti-D-brane pairs in the framework of thermo field dynamics. From this we can reproduce the free energy for multiple strings in the case of Matsubara method. We have computed the finite temperature effective potential and concluded that D9-brane--anti-D9-brane pairs are created near the Hagedorn temperature. However it is unsatisfactory to derive free energy in such a way, since the free energy for multiple strings should be obtained by only calculating the expectation value of the corresponding operator in the thermal vacuum state. In this talk, we compute the thermal vacuum state for multiple open superstrings based on free light-cone superstring field theory inspired by boundary string field theory. From this we can reproduce the free energy for open superstrings in the case of Matsubara method. On the other hand, we have already inverstigated the closed superstrings in the framework of thermo field dynamics. We discuss the possibility that open superstrings on D9-brane--anti-D9-brane pairs and closed superstrings play roles of 'holes' each others in the double copy states of thermo field dynamics.
Yukihiro Fujimoto	National Institute of Technology, Oita College	Dynamical generation of fermion mass hierarchy on an interval
In the context of five-dimensional gauge theories with an interval extra dimension, we propose a new mechanism to produce a fermion mass hierarchy dynamically with yielding generations. Point interactions, which are regarded as zero-width branes and provide extra boundary points, are responsible for producing　fermion generations and make chiral massless zero modes to be localized into segments. Then extra-dimensional-coordinate dependent VEV of the scalar, which is produced by the Robin boundary condition, yields an exponential mass hierarchy to the fermions through overlap integrals. Positions of the point interactions are key ingredient to control the fermion mass hierarchy and can be determined by minimizing the Casimir energy. We show that fermion mass hierarchy appear dynamically after deriving the VEV of the scalar and determining the positions of the point interactions by the Casimir energy minimization.
August 11 (Fri)
Morning Session 1 (9:00-10:10)
Takahiro Nishinaka ^*	Ritsumeikan University	Chiral algebras for 4d N≥2 superconformal field theories ^*
It has recently been discovered (in arXiv:1312.5344) that every 4d N=2 or N>2 superconformal field theory (SCFT) has a special set of BPS local operators whose OPEs are isomorphic to a 2d chiral algebra (or, vertex operator algebra). Among other things, this new 4d-2d relation is an extremely powerful tool to study 4d N=2 or N>2 SCFTs without Lagrangian description. In the main part of this talk, I will review how this 4d-2d relation emerges, how useful it is, and what is still to be understood. I will also talk about our recent work on an exotic 4d N=2 SCFT and its associated 2d chiral algebra.
Morning Session 2 (10:30-11:45)
Hirotaka Hayashi	Tokai University	5d/6d DE instantons from trivalent gluing of web diagrams
We propose a new prescription for computing the Nekrasov partition functions of five-dimensional theories with eight supercharges realized by gauging non-perturbative flavor symmetries of three five-dimensional superconformal field theories. The topological vertex formalism gives a way to compute the partition functions of the matter theories with flavor instanton backgrounds, and the gauging is achieved by summing over Young diagrams. We apply the prescription to calculate the Nekrasov partition functions of various five- dimensional gauge theories such as $SO(2N)$ gauge theories with or without hypermultiplets in the vector representation and also pure $E_6$, $E_7$, $E_8$ gauge theories. Furthermore, the technique can be applied to computations of the Nekrasov partition functions of five-dimensional theories which arise from circle compactifications of six-dimensional minimal superconformal field theories characterized by the gauge groups $SU(3)$, $SO(8)$, $E_6$, $E_7$, $E_8$. We exemplify our method by comparing some of the obtained partition functions with known results and find perfect agreement.
Futoshi Yagi	Technion	Discrete theta angle from O5-plane
We consider 5d $\mathcal{N}=1$ $Sp(1)$ gauge theory with no matter field based on a brane configuration with an $O5$- plane. It is known that two different theories exist depending on the discrete theta angle $\theta=0, \pi$ (mod $2\pi$). A naive brane configuration with an $O5$-plane in a weak coupling region, however, does not distinguish two different theories. By considering We devise a technique for computing 5d Seiberg-Witten curve of the two theories based on the brane configuration and show two theories have distinct phase structures in their Coulomb branch by taking a decompactification limit of each Seiberg-Witten curve, leading to different strong coupling behavior.
Hiroyuki Shimizu	Kavli IPMU	Small instanton transitions for M5 fractions
M5-branes on an ADE singularity are described by certain six-dimensional superconformal eld theories. Their Higgs moduli spaces contain information about various dynamical processes for the M5s. However, they are not directly accessible due to the lack of a Lagrangian formulation. Using anomaly matching, we compute their dimensions. The result implies that M5 fractions can recombine in several different ways, where the M5s are leaving behind frozen versions of the singularity. We also check the Higgs dimension formula by comparing it with various existing conjectures for the CFTs one obtains by torus compactifications down to four and three dimensions. As byproducts, we also make some new conjectures about compactifications of theories not previously considered.
Morning Session 3 (12:00-13:15)
Tadashi Okazaki	National Taiwan University	Emergence of Supergroups from Junctions of M-Branes
It has been recently argued that supergroups emerge from junctions of branes in string theory and M-theory (arXiv:1410.1175, arXiv:1703.00982, arXiv:1512.06646). We study the BPS indices of the supergroup WZW models which may describe certain junctions of M2-branes and M5-branes. We find that the vacuum configurations of the brane system are in one-to-one correspondence with the weight diagrams of the associated Lie superalgebras. For the case arising from the BLG model an explicit expression can be given in terms of a mock modular form. We discuss the physical implications of the mock modularity and its modular completion of the index, at the cost of a holomorphic anomaly. We will also consider the alternative matrix quantum mechanical descriptions of the supergroup WZW models.
Yuta Sekiguchi	University of Bern	Twisted Wilson Line Defects from Flux Backgrounds
We construct supersymmetric gauge theories with Wilson lines for a connection from branes in a flux background in string theory.
Takafumi Okubo	Tokyo Institute of Technology	Quantum periods and prepotential in N=2 SU(2) SQCD
The Seiberg-Witten solution of the $\mathcal{N}=2$ supersymmetric gauge theory enables us to understand both weak and strong coupling physics of the theory. When we quantize the Seiberg- Witten curve, the solution describes the theory in the Nekrasov- Shatashvili (NS) limit of the $\Omega $ background. We study $\mathcal{N}=2$ $SU(2)$ supersymmetric QCD with massive hypermultiplets in the NS limit. The prepotential of the low- energy effective theory is determined by the WKB solution of the quantum Seiberg-Witten curve. We calculate the deformed Seiberg- Witten periods around the massless monoplole point explicitly up to the fourth order in the deformation parameter.

YITP WorkshopStrings and Fields 2017

Program

August 7 (Mon)

August 8 (Tue)

August 9 (Wed)

Poster Session

August 10 (Thu)

August 11 (Fri)

YITP Workshop
Strings and Fields 2017