YITP Workshop
Strings and Fields 2018

July 30 (Mon) - August 3 (Fri), 2018

Panasonic Auditorium 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 .

July 30 (Mon)
Afternoon Session 1 (13:30-14:40)
Sotaro Sugishita	Osaka University	Memory effects and the related infrared physics *
A burst of gravitational radiation causes the gravitational memory effect. It has been found that the memory effect is related to the soft graviton theorem and the asymptotic symmetry in asymptotically flat spacetime. Such relations hold in other theories containing massless particles. In this talk, I will explain what the memory effects are, and give an overview of the relations to soft theorems and asymptotic symmetries, especially in electrodynamics.
Afternoon Session 2 (15:00-16:15)
Hayato Hirai	Osaka University	Asymptotic Symmetry and Subleading Charges in QED
We present several results on asymptotic symmetries and soft theorems in massive QED. We show that some parts of the large gauge transformations are physical symmetries by justifying that they are not gauge redundancies in the BRST formalism. We also explain the expression of new charges associated with the subleading soft photon theorem in massive scalar QED. This presentation is based on joint work with Sotaro Sugishita.
Max Riegler	Université libre de Bruxelles	Warped Black Holes in Lower-Spin Gravity
In this talk I will talk about recent work (arXiv:1801.07263) showing that (spacelike) warped $AdS_3$ black hole solutions can be consistently described in a lower-spin gravity theory. This model provides a very simple playground to explore warped black holes and at the same time warped conformal field theories at finite temperature. I will put an emphasis on the basic ideas that are needed to translate geometric statements into a gauge-theoretic language as well as explain how to compute the thermodynamic properties of warped black holes in this theory.
Yuki Yokokura	RIKEN	Energy-momentum tensor inside evaporating black holes
Recently, we have constructed a self-consistent model of evaporating black holes, which indicates that a black hole is a dense object that evaporates without horizon or singularity. In this talk, we solve Heisenberg equation in the interior metric by a systematic perturbation technique, and directly evaluate the expectation value of energy-momentum tensor by dimensional regularization and renormalization. Then, we show that the metric satisfies the semi-classical Einstein equation. This result builds a foundation of a full field-theoretic description of quantum black holes.
Afternoon Session 3 (16:30-17:45)
Katsumi Itoh	Niigata University	Functional flows in QED and the modified Ward-Takahashi identity
In the functional renormalisation group approach to gauge theory,the Ward-Takahashi identity is modified due to the presence of an infrared cutoff. Using both the Wilsonian and the one-particle-irreducible effectiveactions, we study flows for QED with a massless fermion and the modified Ward-Takahashi identity.The critical exponents are calculated and compared with the known results.
Yu Hamada	Kyoto University	Gauge invariant regularization for perturbative chiral gauge theory
We propose a novel gauge-invariant regularization for the perturbative chiral gauge theory. Our method consists of the two ingredients: use of the domain-wall fermion to describe a chiral fermion with Pauli-Villars regulators and application of the dimensional regularization only to the gauge field. This regularization is implemented in the Lagrangian level, unlike other gauge-invariant regularizations (eg. the covariant regularizations).We show that the abelian (fermion number) anomaly is reproduced correctly in this formulation.This work is based on the collaboration with Hikaru Kawai and Katsuta Sakai.
Takaki Matsumoto	University of Tsukuba	Diffeomorphism for fuzzy sphere
Matrix geometry is known as a typical example of Non-commutative geometry and expected to describe the fundamental structure of space-time. However, the mechanism to describe gravity in terms of matrices remains to be completely elucidated. To understand the mechanism, we focus on the diffeomorphisms of Riemannian manifolds which play a key role in the classical theory of gravity. Using Berezin-Toeplitz quantization map, we translate diffeomorphisms into transformations of matrices and define diffeomorphic configurations of matrices. In this formulation, we consider the case of 2-sphere and show a concrete configuration of matrices that is diffeomorphic to fuzzy sphere. This talk is based on the work in collaboration with Goro Ishiki (University of Tsukuba).
July 31 (Tue)
Morning Session 1 (9:00-10:10)
Akinori Tanaka	RIKEN	Machine learning techniques to probe theoretical physics *
Nowadays, machine learning is one of the hot topics both in academia and industry. The trend is mainly driven by recent development of training techniques for layered structured artificial neural networks called multi-layer perceptrons, and the collection of various techniques is called deep learning in general. If we want to use it in science,iIt is natural to apply it to simplify the procedures on experimental science, and in fact, it has been applied to various real experiments already. In this talk, on the other hand, I would like to introduce various attempts trying to apply machine learning techniques to the study of 'theoretical' physics including condensed matter physics, quantum field theory and string theory including my own works.
Morning Session 2 (10:30-11:20)
Koji Hashimoto	Osaka University	Deep Learning and holographic QCD
We present a deep neural network representation of the AdS/CFT correspondence, and demonstrate the emergence of the bulk metric function via the learning process for given data sets of response in boundary quantum field theories. In particular, we apply the method to holographic QCD.
Masamichi Miyaji	Yukawa Institute for Theoretical Physics	Time Shifts via Double Trace Deformations
In my talk, I will introduce several types of double trace deformations in zero temperature CFT. One double trace deformation is by boundary local operators, and the other is by bulk local operators. In both cases, with suitable choice of sign of the deformation, creation of negative null energy shocks and violation of ANEC are observed. We also compute time evolution of entanglement entropy.
Morning Session 3 (11:35-12:50)
Tomoki Nosaka	Korea Institute for Advanced Study	The Thouless time for mass-deformed SYK
We studied the Random-Matrix-Theory(RMT)-like behavior of the SYK model deformed with a mass term (quadratic random interaction). This model is suggested to exhibit a chaotic/integrable transition as the mass parameter increases. We evaluated the Thouless time, a characterization of the onset of RMT behavior, from the connected unfolded spectral form factor and found that it shows a qualitative agreement with the chaotic/integrable transition. By comparing the same transition suggested from other several quantities, we also conclude that the chaotic/integrable transition is not uniform in the spectrum; it takes place earlier in the tails than in the bulk.
Chen-Te Ma	National Taiwan University	Two Dimensional Dilaton Gravity Theory and Lattice Schwarzian Theory
We present a holographic study in the AdS$_2$ dilaton gravity theory with the Dirichlet boundary condition and the higher derivative term $R^2$, where $R$ is the scalar curvature linearly coupled to a dilaton field. Our result shows that the form of the boundary theory is the same as the Schwarzian theory without any modification from the higher derivative term. Finally, we construct the lattice Schwarzian theory and show that the action of the lattice Schwarzian theory is the same as the action of the discretized AdS$_2$ dilaton gravity theory from a perturbative study up to the second order of the boundary cut-off $\epsilon^2$ through identification between the lattice spacing $a$ and the boundary cut-off $\epsilon$.
Takeshi Morita	Shizuoka University	Thermal emission from semi-classical chaotic systems
Recently the bound on the Lyapunov exponent $\lambda_L \le 2\pi T/ \hbar$ in thermal quantum systems was conjectured by Maldacena, Shenker and Stanford.If we naively apply this bound to a system with a Lyapunov exponent $\lambda_L$, it might predict the existence of the lower bound on temperature $T \ge \hbar \lambda_L/ 2\pi $.Particularly, it might mean that chaotic systems cannot be zero temperature quantum mechanically.Even classical dynamical systems which are deterministic might exhibit thermal behaviors once we turn on quantum corrections.We elaborate this possibility by investigating semi-classical particle motions near the hyperbolic fixed point and show that indeed quantum corrections may induce energy emission which obeys a Boltzmann distribution. We also argue that this emission is related to the acoustic Hawking radiation in quantum fluid.In addition, we discuss when the bound is saturated, and show that a particle motion in an inverse harmonic potential and $c=1$ matrix model may saturate the bound in some sense although they are integrable.
Afternoon Session 1 (14:30-15:45)
Koji Umemoto	Yukawa Institute for Theoretical Physics	Holographic Entanglement of Purification and its Multipartite generalization
We present the conjectured dual relationship between quantum information and gravity, $E_P=E_W$, in the AdS/CFT correspondence. Here $E_P$ is entanglement of purification, which is a generalization of entanglement entropy, and measures an amount of information-theoretic total correlation for (bipartite) mixed states in CFT. On the other hand, $E_W$ is called entanglement wedge cross-section, given by a certain minimal area of codimension-2 surface in AdS. This $E_P=E_W$ relation gives a novel generalization of Ryu-Takayanagi (holographic entanglement entropy) formula for bipartite mixed states. Furthermore, we define new information-theoretic/geometrical quantity by extending both of them for multipartite setups, denoted by $\Delta_P$ and $\Delta_W$, and show properties of them separately. It turns out that all properties of $\Delta_P\ (E_P)$ we proved are coincide with that of $\Delta_W\ (E_W)$. These facts strongly support the $E_P=E_W$ conjecture, or the generalized $\Delta_P=\Delta_W$ conjecture.
Kotaro Tamaoka	Osaka University	Towards Entanglement of Purification for Conformal Field Theories
We argue that the entanglement of purification for two dimensional holographic CFT can be obtained from conformal blocks with internal twist operators. First, we explain our formula from the view point of tensor network model of holography. Then, we apply it to bipartite mixed states dual to subregion of AdS${}_3$ and the static BTZ blackhole geometries. The formula in CFT agrees with the entanglement wedge cross section in the bulk, which has been recently conjectured to be equivalent to the entanglement of purification.
Matsuo Sato	Hirosaki University	String Geometry and Non-perturbative Formulation of Superstring Theory
We define string geometry: spaces of superstrings including the interactions, their topologies, charts, and metrics. Trajectories in asymptotic processes on a topological space of strings reproduce the right moduli space of the super Riemann surfaces in a target manifold. Based on the string geometry, we formulate Einstein-Hilbert action coupled with gauge fields, and define superstring theory non-perturbatively by summing over metrics and the gauge fields on the spaces of strings. This theory does not depend on backgrounds. The theory has a supersymmetry as a part of the diffeomorphisms symmetry on the superstring manifolds. We derive the all-order scattering amplitudes that possess the super moduli in perturbative type IIA, type IIB and SO(32) type I superstring theories from the single theory, by considering fluctuations around fixed backgrounds representing type IIA, type IIB and SO(32) type I perturbative vacua, respectively. The theory predicts that we can see a string if we microscopically observe not only a particle but also a point in the space-time. That is, this theory unifies particles and the space-time.
Afternoon Session 2 (16:00-17:15)
Hiroaki Matsunaga	Institute of Physics, Czech Academy of Sciences	BV master action for superstring field theory in the large Hilbert space
We construct several BV master action for superstring field theory in the large Hilbert space.
Yuho Sakatani	Kyoto Prefectural University of Medicine	Weaving the Exotic Web
Toroidally compactified M-theory or type II string theory contains a rich variety of exotic branes. In this talk, I will review these exotic branes and construct their supergravity solutions utilizing the framework of the double/exceptional field theory. Some of the obtained solutions depend on the winding coordinates although the section condition is not violated. The mixed-symmetry potentials and the locally non-geometric fluxes in the exotic domain-wall backgrounds, and deformations of supergravity are also discussed. This talk is based on a collaboration with Jose J. Fernandez-Melgarejo and Tetsuji Kimura, arXiv:1805.12117.
Tetsuji Kimura	Nihon University	Double dualization of twisted chiral and another GLSM for five-branes of codimension two
We obtain another formulation of five-branes of codimension two via double dualization of a twised chiral multiplet.In this dualization we introduce a twisted linear multiplet which is useful to perform T-duality without isometry. By using these multiplets we reformulate the GLSM for exotic five-branes discussed in arXiv:1304.4061. In this new model, we obtain an additional instanton corrections to the five-branes along the smeared directions. They are interpreted as the string worldsheet corrections to the five-branes of codimension two. This result supports the analysis of the winding corrections in the framework of double field theory.
August 1 (Wed)
Morning Session 1 (9:00-10:10)
Konstantin Zarembo	Nordita	Quantum String Corrections to Holographic Wilson Loops *
One of the central elements of the gauge-string correspondence is that the expectation value of the Wilson loop operator should be given by the string path integral. In the context of the AdS/CFT correspondence, some Wilson loop expectation values are known exactly, circular Wilson loop being the prototypical example. These exact results, when continued to string coupling, perfectly agree with the area law in $AdS_5\times S_5$, while for quantum corrections the situations was not so clear. I will described how the expectation of the circular Wilson loop can be reproduced at strong coupling from the instanton-like calculus in the string sigma-model.
Morning Session 2 (10:30-11:45)
Takahiro Uetoko	Ritsumeikan University	Conformal blocks from Wilson lines with loop corrections
We compute the conformal blocks of Virasoro minimal model with large central charge from Wilson line networks in a Chern-Simons theory including loop corrections. We propose a new prescription to regularize divergences from loops attached to Wilson lines. Using this, we discuss general light-light blocks with the Wilson line method and compare the results with known ones obtained using a different prescription. This presentation is based on the collaboration with Yasuaki Hikida.
Yuya Kusuki	Yukawa Institute for Theoretical Physics	New Properties of Large-c Conformal Blocks from Recursion Relation
We study large $c$ conformal blocks outside the known limits. This work seems to be hard, but it is possible numerically by using the Zamolodchikov recursion relation.As a result, we find new some properties of large $c$ conformal blocks with a pair of two different dimensions for any channel and with various internal dimensions. With light intermediate states, we find a Cardy-like asymptotic formula for large $c$ conformal blocks and also we find that the qualitative behavior of various large $c$ blocks drastically changes when the dimensions of external primary states reach the value $c/32$. And we proceed to the study of blocks with heavy intermediate states $h_p$ and we find some simple dependence on heavy $h_p$ for large $c$ blocks. Our results can be applied to, for example, the calculation of OTOC or Entanglement Entropy. In the end, we comment on the application to the conformal bootstrap in large $c$ CFTs.
Yoshiki Sato	University of Tokyo	Conformal manifolds with boundaries or defects
In this talk, I discuss conformal manifolds with boundaries or defects.Using conformal perturbation theory we derive constraints such that conformal manifolds exist perturbatively.I also comment on beta-functions in a mixed dimensional QED and its extension to jumping coupling constant using a differential regularization.
Morning Session 3 (12:00-12:50)
Junichi Sakamoto	Kyoto University	Local $\beta$-deformations and Yang-Baxter sigma model
Homogeneous Yang-Baxter (YB) deformation of AdS$_5\times$ S$^5$ superstring is revisited.In this talk, I explain that homogeneous YB deformations are equivalent to $\beta$-deformations of the AdS$_5\times$ S$^5$ background when the classical $r$-matrices consist of bosonic generators.If time permitted, I also discuss $\beta$-deformations of the AdS$_3\times$ S$^3\times$T$^4$ with $H$-flux and proviede various solutions of (generalized) type II supergravity.This talk is based on arXiv:1803.05903.
Hajime Otsuka	Waseda University	Hypercharge flux in SO(32) heterotic string theory
We study SO(32) heterotic line bundle models where SO(32) gauge group is directly broken to the standard model gauge group by a hypercharge flux. It turns out that the line bundle background leads to three-generation standard-like models on general Calabi-Yau three-folds.
Afternoon Session 1 (14:30-15:20)
Nobuyoshi Ohta	Kindai University	Asymptotic safety and field parametrization dependence in the $f(R)$ truncation
We study the dependence on field parametrization of the functional renormalization group equation in the $f(R)$ truncation for the effective average action. We perform a systematic analysis of the dependence of fixed points and critical exponents on different choices of field parametrization and gauge parameter in polynomial truncations. We find that, for a given truncation, different qualitative results are obtained for different choices of parametrization. In particular, we observe that two cases that have three relevant directions and two directions. The computations are performed in the background approximation. We compare our findings with those available in the literature and conclude that within the background approximation, the discrepancies reported in previous works are due to regulator dependence.
Kenji Hotta	Hokkaido University	Creation of D9-brane--anti-D9-brane Pairs in Rindler Spacetime
Recently, we investitated Unruh effect for open strings on D9-brane--anti-D9-brane pairs. We calculated the expectation value of the Rindler string number in the Minkowski vacuum state, and obtained Bose-Einstein spectrum and Fermi-Dirac one for radiation at Unruh temperature. Previously, we calculated the finite temperature effective potential for open strings on D9-brane--anti-D9-brane pairs at finite temperature in flat spacetime, and shown that the potential minimum moves from closed string vacuum towards open string vacuum. This means that D9-brane--anti-D9-brane pairs are half-formed before the Hagedorn transition. Here we calculate the finite temperature effective potential for open strings on D9-brane--anti-D9-brane pairs in each orbit of accelerated observers, and show that the potential minimum moves from closed string vacuum towards open string vacuum as the acceleration of observers increases. This means that highly accelerated observers see the creation of D9-brane--anti-D9-brane pairs.
Poster Session 1 (15:35-18:00)
Yi-Hsien Du	National Cheng Kung University & Imperial College London	Butterfly Effect and Holographic Mutual Informationunder External Field and Spatial Noncommutativity
We apply the transformation of mixing azimuthal and internal coordinate or mixing time and internal coordinate to a stack of N black M-branes to find the Melvin spacetime of a stack of N black D-branes with magnetic or electric flux in string theory, after the Kaluza-Klein reduction. We slightly extend previous formulas to investigate the external magnetic and electric effects on the butterfly effect and holographic mutual information. It shows that the Melvin fields do not modify the scrambling time and will enhance the mutual information. In addition, we also T-dualize and twist a stack of N black D-branes to find a Melvin Universe supported by the flux of the NSNS b-field, which describes a non-comutative spacetime. It also shows that the spatial noncommutativity does not modify the scrambling time and will enhance the mutual information. We also study the corrected mutual information in the backreaction geometry due to the shock wave in our three model spacetimes.
Tomohiro Furukawa	Osaka City University	Jacobi-Trudi identity in ABJM matrix model
Jacobi-Trudi identity and Giambelli identity are the equality relations for Schur functions and so on. And these also appear in integrable system. In ABJM matrix model, one-point functions of 1/2-BPS Wilson loop satisfy these identities. This fact strongly suggests integrable structure for this matrix model.
Debabrata Ghorai	S. N. Bose National Centre for Basic Sciences	Non-linear effect on Holographic Superconductors
We have investigated the properties of holographic superconductors in Born-Infeld electrodynamics with backreaction using Sturm-Liouville eigenvalue approach. We have showed that the inclusion of the BI parameter, the GB coupling parameter and the backreaction of the matter fields on the spacetime metric makes the scalar hair formation harder. We have then investigated the role of noncommutativity of spacetime in holographic superconductors. It is observed that the noncommuativity of spacetime plays an important role only when black hole mass is small. The properties of 3-dimensional holographic superconductors using the formalism of thermodynamic geometry is studied. The matching method is employed to obtain the behaviour of the matter fields near the horizon of the black hole. We then proceed to compute the free energy of this system which is to relate the free energy of the theory on the boundary to the value of the on-shell action of the Abelian-Higgs sector of the full Euclideanaction. From this, we compute the thermodynamic metric and calculate the scalar curvature. The temperature at which the scalar curvature diverges is said to be the critical temperature.
Sota Hanazawa	Ibaraki University	Born-Infeld Equations in Diverse Dimensions from Pure Spinor Superstring
Berkovits and Pershin have shown that in a general background, the ten-dimensional Born-Infeld equations of motion for the background fields are extracted from BRS charge conservation in an open pure spinor superstring. We improve their result to include even contribution of Dirichlet boundary conditions for the open superstring. It is expected that the resulting abelian Born-Infeld equations contain higher-derivative correction in the BI field strength and have manifest supersymmetry on D-brane world-volumes.
Kohta Hatakeyama	Shizuoka University	Large-N volume independence on group manifolds
It was shown in arXiv:0912.1456 that the large-$N$ reduction holds on group manifoldsin the sense that a large-$N$ gauge theory on a group manifoldis realized by a matrix modelwhich is obtained by dimensionally reducing the original theory to zero dimension.In this poster, generalizing the above statement,we show that a large-$N$ gauge theory on a group manifoldis equivalent to a theory which is obtained by reducing the original theory toits coset space. This is analogous to the statement of the large-$N$ reduction onflat spaces that large-$N$ gauge theories are independent of the volume.
Keita Kanno	Kavli IPMU	Phenomenology and Arithmetic: F-theory vacua on K3 x K3 orbifolds
We studied F-theory compactifications on orbifolds of K3 x K3,which contain dense sets of so-called CM-points in their complex structure moduli spaces.A CM-point is defined by an arithmetic property of the cohomology group of the variety corresponding to the point. CM-points are shown, by our previous study on type-IIB theory [arXiv:1705.05110], to be highly preferred when one focuses on supersymmetric and Minkowski flux vacua, which are suitable for phenomenology.We first studied the families of K3 surfaces that have some symmetries (automorphisms) suitable for orbifolding. We found that even after taking the orbifold,often some symmetries, that may relevant to the low-energy effective theory, are automatically left.We further studied the physical aspects of the vacua, extending the previous study.
Takumi Kato	Kitasato University	Symmetric calorons of higher charges revisited
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".In this study, we reconsider the analytic Nahm data of calorons of higher monopole charges with particular symmetry.
Shoichi Kawamoto	Chung Yuan Christian University	Momentum space entanglement for scalar field theory on the fuzzy sphere
We consider the entanglement in momentum space for scalar $\phi^4$ theory on the fuzzy two-sphere. The scalar field theory can be described by a matrix model, and we study the entanglement for high and low momentum (or energy) modes in perturbation theory. The UV/IR mixing phenomenon will be discussed in terms of the entanglement of different degrees of freedom.
Naoki Kiryu	University of Tokyo	Correlation Functions on the Half-BPS Wilson Loop: Perturbation and Hexagonalization
We study correlation functions of protected primaries on the $1/2$-BPS Wilson loop in $\cal{N}=4$ super Yang-Mills theory from two different perspectives; perturbation and integrability. We first perform direct perturbative computation at one loop in the planar limit and present compact formulae for general three- and four-point functions. We then reproduce them from integrability by generalizing the ``hexagonalization'' approach, which was introduced previously to study the correlation functions in the absence of the Wilson loop. This work is based on the collaboration with Shota Komatsu.
Tomomi Kitade	Nara Women’s University	Closed String Symmetries in Open String Field Theories
We consider open string field theories expanded around identity-based tachyon vacuum solutions. As a result, we find a certain symmetry in the theory, which is same as that should be included in closed string theories. This suggests the possibility of formulating a pure closed string theory in terms of open string fields.
Toru Masuda	Institute of Physics, Czech Academy of Sciences	Revisiting light-like rolling tachyon in open string field theory
We study a classical solution for light-like tachyon condensation constructed by Hellerman and Schnabl in arXiv:0803.1184 [hep-th]. In particular, we found that the late time ($x^+\to\infty$) behavior of the solution can be understood using a formal power series with respect to the negative power of the marginal operator, which results in an asymptotic series of the tachyon profile around $x^+=\infty$. (This presentation is based on a collaborative work with Ted Erler and Martin Schnabl.)
Masahiro Nozaki	University of Chicago	Entanglement Spreading and Oscillation
Many researchers have been studying the time evolution of entanglement entropy in the sudden quenches where a characteristic mass scale suddenly changes. It is well-know that in these quenches, the change of entanglement entropy become thermal entropy which is proportional to a subsystem size in the late time. However, we do not know which quenches thermalize a subsystem. In our works, we have been studied the time evolution of quantum entanglement in the global quenches with finite quench rate (smooth quenches). Thus, we found that diabaticity plays an important role, so that quenches thermalize the subsystem.
Toshihiro Ota	Osaka University	QCD chaos via the D-brane dynamics in higher dimensions
We define a chaos phase diagram of QCD allowing us to locate chaos in the parameter space of energy of homogeneous meson condensates and the QCD parameters such as pion/quark mass.We draw the chaos phase diagrams obtained in two ways: first, by using a linear sigma model, varying parameters of the potential, and second, by using the D4/D6 holographic QCD, varying the number of colors $N_c$ and the 't Hooft coupling constant $\lambda$.A scaling law drastically simplifies our analyses, and we discovered that the chaos originates in the maximum of the potential, and larger $N_c$ or larger $\lambda$ diminishes the chaos.
Rodolfo Abraham Sanchez Isidro	Institute of Nuclear Sciences, UNAM	Double Field Theory and The Double Space
In this poster I show how the double space works in the double field theory. This is a string theory based in superstring theory IIB with a torus compactification fixed background. Such theory contains new degrees of freedom related to the winding numbers of the string, hence the name double field theory. My research consists in the study of the Bianchi identities in the structure of double space.
Mohamed Ali Seridi	Constantine Mentouri University	Paraquantum Strings in Noncommutative Spacetime.
A parabosonic string is assumed to propagate in a total noncommutative target phasespace. open strings between two parallel Dp–Dq branes and closed ones. This leads to a generalization of the oscillators algebra of the string and the corresponding Virasoro algebra.The mass operator is no more diagonal in the ordinary Fock space, a redefinition of this later will modify the mass spectrum, so that, neither massless vector state nor massless tensor state are present.The restoration of the photon and the graviton imposes specific forms of the noncommutativity parameter matrices, partially removes the mass degeneracy and gives new additional ones. In particular, for the D-branes, one can have a tachyon free model with a photon state when more strict conditions on these parameters are imposed, while, thematch level condition of the closed string model induces the reduction of the spectrum.
Kenta Shiozawa	Kitasato University	Worldsheet Instanton Corrections to Five-branes and Waves in Double Field Theory
We make a comprehensive study on the string winding corrections to supergravity solutions in double field theory (DFT). We find five-brane and wave solutions of diverse codimensions in which the winding coordinates are naturally included. We discuss a physical interpretation of the winding coordinate dependence. The analysis based on the geometric structures behind the solutions leads to an interpretation of the winding dependence as string worldsheet instanton corrections. We also give a brief discussion on the origins of these winding corrections in gauged linear sigma model. Our analysis reveals that for every supergravity solution, one has DFT solutions that include string winding corrections.
Hongfei Shu	Tokyo Institute of Technology	Generalized ODE/IM correspondence and its application to N=2 gauge theories
We study the quantum spectral curve of four dimensional N=2 gauge theories in the Nekrasov-Shatashvili limit of the Omega-background. Using the generalized ODE/IM correspondence, we first derive the T-/Y-system and Thermodynamic Bethe Ansatz (TBA) equation for $A_n$-type Argyres-Douglas theory. Based on the Stokes phenomena of the quantum spectral curve, we then construct functional relation for N=2 gauge theory with SU(2) gauge group. We also compare our functional relation and TBA equation with the ones in the study of BPS spectrum and wall-crossing. This talk is based on the collaboration with Katsushi Ito and arXiv:1707.03596.
Masaki Tezuka	Kyoto University	Quantum Lyapunov spectrum: random-matrix behavior and application to the Sachdev-Ye-Kitaev model and many-body localization
We have proposed the existence of a universality in classical chaotic systems when the number of degrees of freedom is large: the statistical property of the Lyapunov spectrum is described by random matrix theory. In this work we examine the case of quantum systems, comparing the maximally chaotic Sachdev-Ye-Kitaev model and models of many-body localization, by extending the definition of the Lyapunov spectrum to the quantum mechanical case.
Gaurav Verma	University of Hawaii-Manoa	Analysis and application of Superstring S-matrix elements and Ward Identities calculated from a 1PI Theory
We study the expression for S-matrix elements and Ward Identities for Superstrings as calculated from the proposed 1PI Theory, that has a built in subtraction procedure which removes the IR divergences coming from Tadpoles and Mass Renormalization-Unlike the usual Polyakov procedure(On-Shell) for calculating Amplitudes that suffers from possible IR divergences coming from separating type degeneration where the momentum conservation restricts the momentum flowing through the long tube connecting the two Riemann surface (via plumbing fixture) to be either zero or equal to one of the momenta carried by external states (divergences associated with tadpoles or mass renormalization). Full Superstring amplitudes are calculated from the tree amplitude of the 1PI Theory and since the 1PI Theory has gauge symmetry, we derive appropriate Ward Identities(associated with Supersymmetry). Ward Identities derived here are in : 1)general vacuum which may not be perturbative vacuum (previous results were restricted to Amplitudes in perturbative vacuum) but a nearby shifted vacuum obtained by condensation of some scalar field and : 2) for general external states (previous results were restricted to Amplitudes for external states which do not undergo mass renormalization). Ward Identities corresponding to global supersymmetry : give rise to equality of renormalized masses of bosons and fermions, and global supersymmetry to a given order in perturbation theory gives vanishing of tadpoles to one higher order. More explicitly in SO(32) heterotic superstring on CY-3 fold where a Fayet-Iliopoulos(D-term) term breaks supersymmetry in the perturbative vacuum at one loop, however a shifted vacuum exists(obtained by solving classical equation of motion of 1PI Theory) that restores supersymmetry. One loop calculation (in 1PI Theory) shows the equality of masses of bosons and fermions at shifted vacuum which is absent at the perturbative vacuum(due to broken supersymmetry at one loop). Two loop calculation (in 1PI Theory) of dilaton tadpole vanishes in shifted vacuum however is non-vanishing in perturbative vacuum(due to broken supersymmetry at one loop).
Kazushi Yamashiro	Shizuoka University	Critical behavior of scalar field theory on the fuzzy sphere
We study critical behavior of scaler field theory on the fuzzy sphere by Monte Carlo simulation. By measuring the susceptibility, we identify the phase boundary. By calculating multi-point correlation functions defined by the Berezin symbol, we show that the theory on the phase boundary is universal. We find that the theory behaves as a CFT at short distances and shows an effect of the UV/IR mixing at long distances.
Shota Yanai	Tokyo University of Science	Large variety of geometrical structures of Harbor for the Schwarzschild Black hole in a CP$^{2n+1}$ model
No-hair conjecture is well known as elementary nature of black hole. However, there are some counterexamples such as the skyrmion hair. Another is so called a harbor;in which blackhole is surrounded by compact boson shells. We examine compact boson $Q$-stars and $Q$-shells of a $CP^{2n+1}$ model and investigate their gravitating solutions. We have found several type of solutions which can harbor Schwarzschild black holes.
August 2 (Thu)
Morning Session 1 (9:00-10:10)
Kazuya Yonekura	Kyushu University	Anomalies and topological phases in QFT *
I will talk about recent developments in QFT related to anomalies and topological phases. In particular, I will talk about how the standard perturbative anomalies described in standard textbooks are generalized/refined in various directions, and their applications to strong coupling dynamics, string theory, and so on.
Morning Session 2 (10:30-11:45)
Bhupendra Nath Tiwari	University of Information Science and Technology & INFN-Laboratori Nazionali di Frascati	Thermodynamic Geometry of Yang-Mills Gauge Theory
We study vacuum fluctuation properties of an ensemble of SU(N) gauge theory configurations in the limit of a large number of colors. We explore statistical properties of moduli fluctuations by analyzing the critical behavior and geometric invariants at a given vacuum parameter. Further, we discuss the nature of long-range correlations, interacting/ noninteracting domains, and associated phase transitions. Finally, we provide possible directions towards its phenomenological developments.
Takafumi Okubo	Tokyo Institute of Technology	Quantum periods for ${\mathcal{N}}=2$ $SU(2)$ SQCD around the superconformal point
We study the Argyres-Douglas theories realized at the superconformal point in the Coulomb moduli space of $\mathcal{N}=2$ supersymmetric $SU(2)$ QCD with $N_f=1,2,3$ hypermultiplets in the Nekrasov-Shatashvili limit of the Omega-background. The Seiberg-Witten curve of the theory is quantized in this limit and the periods receive the quantum corrections. By applying the WKB method for the quantum Seiberg-Witten curve, we calculate the quantum corrections to the Seiberg-Witten periods around the superconformal point up to the fourth order in the parameter of the Omega background. This talk is based on arXiv:1804.04815.
Katsuya Yano	Osaka City University	Discrete Painlevé system and the double scaling limit of the matrix model for irregular conformal block and gauge theory
We study the partition function of the matrix model of finite size that realizes the irregular conformal block for the case of the ${\cal N}=2$ supersymmetric $SU(2)$ gauge theory with $N_f =2$. This model has been obtained in [arXiv:1008.1861 [hep-th]] as the massive scaling limit of the $\beta$ deformed matrix model representing the conformal block. We point out that the model for the case of $\beta =1$ can be recast into a unitary matrix model with log potential and show that it is exhibited as a discrete Painlevé system by the method of orthogonal polynomials. We derive the Painlevé II equation, taking the double scaling limit in the vicinity of the critical point which is the Argyres-Douglas type point of the corresponding spectral curve. By the $0$d-$4$d dictionary, we obtain the time variable and the parameter of the double scaled theory respectively from the sum and the difference of the two mass parameters scaled to their critical values.
Morning Session 3 (12:00-12:50)
Justin Kaidi	Unversity of California, Los Angeles	Mass deformations of 5d SCFTs via holography
Using six-dimensional Euclidean F(4) gauged supergravity, we construct a holographic renormalization group flow for a CFT on $S^5$. The free energy of the theory on $S^5$ is determined holographically by calculation of the renormalized on-shell supergravity action, and in the process a number of subtleties in the holographic renormalization procedure are encountered. We then propose a candidate field theory dual to our solutions. A localization calculation of the free energy is performed in this dual field theory, and is found to match with the free energy calculated holographically. Based on [arXiv:1801.00730].
Hong Zhang	Institute of Theoretical Physics, Chinese Academy of Sciences	Supersymmetric Yangian, DIM algebra, and Gaiotto states
The affine Yangian of gl$_1$ is known to be isomorphic to W$_{1+\infty}$, the W-algebra that characterizes the bosonic higher spin -- CFT duality.We propose defining relations of the Yangian that is relevant for the N=2 superconformal version of W$_{1+\infty}$. Our construction is based on the observation that the N=2 superconformal W$_{1+\infty}$ algebra contains two commuting bosonic W$_{1+\infty}$ algebras, and that the additional generators transform in bi-minimal representations with respect to these two algebras. The corresponding affine Yangian can therefore be built up from two affine Yangians of gl$_1$ by adding in generators that transform appropriately. On the other hand, we know Argyres-Douglas theory involves Gaiotto states, which could be constructed by the AFLT basis. We will discuss their further deformed version, and the relation with Yangian and Ding-Iohara-Miki algebra.
Afternoon Session 1 (14:30-15:45)
Ariunzul Davgadorj	Masaryk University	N=2 super Yang-Mills theory in Projective superspace
Projective superspace is a manifestly supersymmetric formulation for theories with 8 supercharges. In this formalism standard $\mathbb{R}^{4\|8}$ superspace is enforced by an extra bosonic coordinates on $\mathbb{CP}^1$. The advantage of this description is that there will be infinite number of auxilaries and consequently one can describe the $\mathcal{N}=2$ multiplets off-shell in terms of unconstrained superfields.In this presentation I will describe $\mathcal{N}=2$ super Yang-Mills theory using Projective methods particularly YAng-Mills field strength will be described in terms of unconstrained gauge prepotential and write the Yang-Mills action manifestly in $\mathcal{N}=2$ superspace.The advantage of using Projective superspace in manifest $\mathcal{N}=2$ calculations is that here we deal with simpler contour integrals holomorphically depending on the auxuliar $\mathbb{CP}^1$ factor. This feature is important in cases where the competing Harmonic superspace method is too complicated or produce coinciding singularities. Also in Projective superspace formalism one can readily describe the theory in $\mathcal{N}=1$ components.
Yuta Sekiguchi	University of Bern	Extended Gauge Theory Deformations From Flux Backgrounds
We constructed supersymmetric deformations of gauge theories in various dimensions using probe branes embedded in flux backgrounds. In particular we obtained deformations which take the form of Wilson line defects, where the R-symmetry is twisted into the gauge symmetry. Furthermore we considered higher-order generalisations, which involve a twisting of the R-symmetry and have symmetry associated with defects of co-dimension two and three.
Ryo Yokokura	Keio University	Ghost-free vector superfield actions in supersymmetric higher-derivative theories
We systematically construct ghost-free higher-derivative actions of Abelian vector supermultiplets in four-dimensional N=1 global supersymmetric theories. We discuss possible building blocks for a ghost-free action and explicitly show that their bosonic parts have no ghost mode and the auxiliary field does not propagate. Higher-derivative terms yield higher powers of the auxiliary field in the actions, and the D-term equations of motion consequently admit multiple solutions in general. We confirm that the well-known supersymmetric Dirac-Born-Infeld action falls into this class. We further give another example in which the standard quadratic kinetic term (Maxwell term) is corrected by a quartic term of the field strength. We also discuss possible couplings to matter fields and a deformed D-term potential. This talk is based on JHEP 1709 (2017) 143 [arXiv:1708.05129].
Afternoon Session 2 (16:00-16:50)
Inori Ueba	Kobe University	Extended quantum mechanical supersymmetry in Dirac action with extra dimensions
We show that $\mathcal{N}$-extended quantum mechanical supersymmetry is hidden in the 4D spectrum of the KK decomposition for the higher dimensional Dirac field. This supersymmetry can explain degeneracy of the spectrum and relate the degenerate KK mode functions with each other. We also discuss a possibility whether the supersymmetry can reduce depending on boundary conditions.
Haoyu Sun	University of California, Berkeley	S-Duality, Quadratic Reciprocity, and Janus Configurations
Quadratic reciprocity in number theory maps the question "does the equation $x^2=q$ (mod p), for given odd primes p and q, have an integer solution x?" to a mirror question with p and q interchanged, and numbers of solutions are encoded in the quadratic residue. We first show that this reciprocity is a direct consequence of T-duality, by recasting the quadratic Gauss sum as the partition function of N=4 U(1) SYM on a mapping-torus $M_3$ with coupling constant $g^2$ and theta-angle varying along the base $S^1$. With an R-symmetry twist, $M_3$ preserves SUSY, and an Olive-Montonen SL(2;Z) twist on $S^1$ connects $g^2$ and theta smoothly. In our setting, we compactify Gaiotto-Witten Janus of N=4 SYM on $T^2$ to obtain 2d SUSY sigma-models with target space $T^2$ with complex structure varying along one worldsheet direction and Kahler modulus varying along another. For these double-Janus configurations, topological partition functions can be written as quadratic Gauss sums. The limit where the Janus circle is much larger than the base of $M_3$ and the opposite limit provide two ways of calculating the same partition function. For gauge group G=U(1), the equivalence of the two methods leads to the L-S relation, from which quadratic reciprocity follows; for more complicated SL(2;Z) twists, we obtain 2- and 3-variable generalizations of L-S relation, whose analytical proof will be sketched. More abelian number-theoretic identities can be systematically generated. Since quadratic reciprocity is generalized by Artin reciprocity, which is the starting point of Langlands' conjectures, we may probe some features in arithmetic Langlands program. This talk is based on arXiv:1403.2365 and an ongoing work with Ori J. Ganor.
August 3 (Fri)
Morning Session 1 (9:00-10:10)
Masazumi Honda	Weizmann Institute of Science	Resurgence, complex saddles and Lefschetz thimbles *
Resurgence is a technique to resum asymptotic perturbative series which has often reproduced exact results in various problems. In this talk I will mainly review applications of resurgence to weak coupling expansions in quantum field theories. I will start with a toy example in order to explain basic ideas of resurgence, and emphasize importance of Lefschetz thimbles (steepest descents) and saddle points which are not on original (path) integral contour. Then I will introduce my recent works on applications of resurgence to 3d N=2 supersymmetric Chern-Simons matter theories. I will also discuss whether or not one can apply to QCD-like theories and their possible subtleties. Finally I will briefly mention applications of resurgence to other types of problems such as 1/N-expansions, strong coupling expansions, perturbative series in quantum gravity and so on.
Morning Session 2 (10:30-11:20)
Toshiaki Fujimori	Keio University	Bion and resurgence in 2d ${\mathbb C}P^N$ sigma model
We discuss semiclassical contributions of the complex bion solutions by evaluating one-loop quantum fluctuation and quasi-moduli integral in the ${\mathbb C}P^N$ model on $R × S^1$ with a twisted boundary condition. We derive the renormalized bion effective action characterized by the dynamical scale by calculating the one-loop determinant as a sum over the contributions from Kaluza-Klein modes. Based on the effective action, we calculate the contribution from the complex bion solution in a weak coupling limit, whose imaginary ambiguity is consistent with the expected infrared renormalon. This is the first explicit result indicating the relation between complex bion solutions and infrared renormalons in quantum field theories.
Keisuke Ohashi	Keio University	Effective theory of Jackiw-Pi vortex in a harmonic potential
We discuss a supersymmetric extension of a non-relativistic Chern-Simons matter theory, known as the SUSY Jackiw-Pi model, in a harmonic trap. We show that the non-relativistic version of the superconformal symmetry, called the super-Schrödinger symmetry, is not spoiled by an external field including the harmonic potential. It survives as a modified symmetry whose generators have explicit time dependences determined by the strength of the trap, the rotation velocity of the system and the fermion number chemical potential. We construct 1/3 BPS states of trapped Jackiw-Pi vortices preserving a part of the modified superconformal symmetry and discuss fluctuations around static BPS configurations. In addition to the bosonic massive Nambu-Goldstone modes, we find that there exist massive Nambu-Goldstone fermions associated with broken generators of the modified super-Schrödinger symmetry.
Morning Session 3 (11:35-12:25)
Naotaka Kubo	Yukawa Institute for Theoretical Physics	Two-Point Functions in ABJM Matrix Model
We introduce non-trivial two-point functions of the super Schur polynomials in the ABJM matrix model and study their exact values with the Fermi gas formalism. We find that, although defined non-trivially, these two-point functions enjoy two simple relations with the one-point functions. One of them is associated with the Littlewood-Richardson rule, while the other is more novel.
Kento Sugiyama	Shizuoka University	Toward the construction of the general multi-cut solutions in Chern-Simons Matrix Models
We study Chern-Simons matrix models 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 talk, we show the existence of novel types of multi-cut solutions in Chern-Simons matrix models and propose an ansatz which may allow us to derive the analytic expressions for all these solutions. These solutions might also be related to the non-perturbative effects in string theory / M-theory. In particular, we discuss the relations between our novel multi-cut solutions and the D2 brane instanton in ABJM matrix model.

YITP WorkshopStrings and Fields 2018

Program

July 30 (Mon)

July 31 (Tue)

August 1 (Wed)

August 2 (Thu)

August 3 (Fri)

YITP Workshop
Strings and Fields 2018