| 1: Yoshihiko Abe |
Kyoto university |
Implications of the weak gravity conjecture in anomalous quiver gauge theories |
We argue a smallness of gauge couplings in abelian quiver gauge theories, taking the anomaly cancellation condition into account. In theories of our interest there exist chiral fermions leading to chiral gauge anomalies, and an anomaly-free gauge coupling tends to be small, and hence can give a non-trivial condition of the weak gravity conjecture. As concrete examples, we consider $U(1)^k$ gauge theories with a discrete symmetry associated with cyclic permutations between the gauge groups, and identify anomaly-free $U(1)$ gauge symmetries and the corresponding gauge couplings. Owing to this discrete symmetry, we can systematically study the models and we find that the models would be examples of the weak coupling conjecture. It is conjectured that a certain class of chiral gauge theories with too many $U(1)$ symmetries may be in the swampland. We also numerically study constraints on the couplings from the scalar weak gravity conjecture in a concrete model. These constraints may have a phenomenological implication to model building of a chiral hidden sector as well as the visible sector.
Based on 2004.14917
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| 2: Sinya Aoki |
Yukawa Institute for Theoretical Physics, Kyoto Univwersity |
Conserved charges in gravity |
We propose a manifestly covariant definition of a conserved charge in gravity. We define a charge density from the energy momentum tensor with a Killing vector, if exists in the system, and calculate the mass (and angular momentum) of the black hole by a volume integral. Our definition leads to a correction of the known mass formula of a compact star, which is shown to be 68\% of the leading term in some case. We then propose a new method to define a conserved charge in the absence of Killing vectors, and argue its physical meaning. We apply the definition to the expanding universe and gravitational plane waves. We discuss future directions of our research.
Based on 2005.13233
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| 3: Yuichi Enoki |
The University of Tokyo |
Modular Forms as Classification Invariants of 4D N=2 Heterotic--IIA Dual Vacua |
We focus on 4D $\mathcal{N}=2$ string vacua described both byperturbative Heterotic theory and by Type IIA theory; a Calabi--Yau three-fold$X_{\rm IIA}$ in the Type IIA language is further assumed to have a regular K3-fibration.It is well-known that one can assign a modular form $\Phi$ to such a vacuumby counting perturbative BPS states in Heterotic theory or collectingNoether--Lefschetz numbers associated with the K3-fibration of $X_{\mathrm{IIA}}$.We expand the observations and ideas (using gauge thresholdcorrection) in the literature and formulate a modular form $\Psi$ for the class of vacua above, which can be usedalong with $\Phi$ for the purpose of classification of those vacua.Topological invariants of $X_{\mathrm{IIA}}$ can be extracted from $\Phi$ and$\Psi$, and even a pair of diffeomorphic Calabi--Yau's with differentKahler cones may be distinguished by introducing the notion of"the set of $\Psi$'s for Higgs cascades/for curve classes''.
Based on 1911.09934
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| 4: Eric Howard |
Macquarie University |
Low-energy conditions for string and superstring theories |
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We aim to analyze the validity and consistency conditions as well as the generic predictions for string and superstring theory models in low energy physics context, covering a range of challenging ideas that are part of the field, from the Weak Gravity Conjecture, compactifications, string vacua, low-energy supersymmetry, gauge-symmetry breaking and supersymmetry breaking to heterotic strings, D-branes, M-Theory and large dimensions. We identify the theoretical implications, current concerns and experimental constraints of candidate string theories in the low energy limit, that are underlying certain solutions to several nontrivial problems such as the dimensionality of space-time, naturalness, supersymmetry and supergravity, axions and the strong CP problem, Yukawa couplings, black hole information paradox or grand unification. We finally discuss the effective field theory relevant for low energy precision physics at scales probed in table-top laboratory experiments and justify its relevance for string phenomenology in the submillimeter region.
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| 5: Noriaki Ikeda |
Ritsumeikan university |
Geometry of double field theory and (pre-)rackoid |
New geometric structures have appeared in T-duality in string theory, such as a generalized geometry, a para-Hermitian geometry, the doubled geometry. Especially, a geometry of double field theory is not well understood. For analysis of T-duality, we propose a new geometric structure, a Lie (pre-)rackoid, which is a generalization of a Lie group. A sigma model description of the above new structure is proposed.
Based on 2006.08158
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| 6: Keita Imaizumi |
Tokyo institute of technology |
Exact WKB analysis and TBA equations for the Mathieu equation |
We derive Thermodynamic Bethe Ansatz (TBA) equations governing the Borel resummation of WKB periods for the Mathieu equation. By using the resulting TBA equations, we will calculate the band spectrum of the Mathieu equation numerically. The WKB periods for the Mathieu equation can also be regarded as the quantum periods which determine the low energy effective theory of N=2 SU(2) super Yang-Mills theory. The TBA equations clarify a non-trivial relation between 4-dimensional gauge theory and 2-dimensional CFT.
Based on 2002.06829
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| 7: Shoichi Kawamoto |
National Tsing Hua University |
Momentum-space entanglement in scalar field theory on the fuzzy sphere |
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In this talk, I will study the quantum entanglement in the momentum space for scalar field theory on a fuzzy sphere. In an interacting quantum field theory, the degrees of freedom in momentum space show entanglement; it quantifies the correlation between the high/low momentum modes. On a fuzzy sphere, an example of noncommutative space, it is known that the UV and IR degrees of freedom show a characteristic correlation known as UV/IR mixing. I thus study the entanglement entropy in the momentum space for quantum field theory defined on the fuzzy sphere and examine the difference from the theory on the ordinary sphere.
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| 8: Omar Kidwai |
University of Tokyo |
Topological recursion and uncoupled BPS structures for hypergeometric spectral curves |
We describe joint work with K. Iwaki relating the computation of free energies in the topological recursion formalism to the counting of BPS states in 4d N=2 QFTs in the uncoupled case. For the "hypergeometric spectral curve" and its confluent degenerations, we obtain a simple formula expressing the topological recursion free energies as a sum over BPS states (degenerate spectral networks) for the relevant quadratic differential. In doing so, we count degenerations of spectral networks occurring in several concrete examples of quadratic differentials on P^1. We conjecture that a similar relation should hold more generally whenever the corresponding BPS structure is uncoupled.
Based on 2010.05596
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| 9: Isao Kishimoto |
Sanyo-Onoda City University |
On numerical solutions in open string field theory around the identity-based solution |
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Using the level truncation method, we construct numerical solutions, which are twist even and SU(1,1) singlet, in the theory around the Takahashi-Tanimoto identity-based solution (TT solution) with a real parameter $a$ in the framework of bosonic open string field theory. We find solutions corresponding to ``double brane" and ``ghost brane" solutions which were constructed by Kudrna and Schnabl in the conventional theory around the perturbative vacuum. Our solutions show somewhat similar $a$-dependence to tachyon vacuum and single brane solutions, which we found in the earlier works. In this sense, we might be able to expect that they are consistent with the interpretation of $a$-dependence of the TT solution. We observe that numerical complex solutions at low levels become real ones at higher level for some region of the parameter $a$.
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| 10: Sujoy Mahato |
Institute of Mathematical Sciences |
Surface Defect from Fractional Branes |
We show that the Gukov-Witten monodromy defects of supersymmetric Yang-Mills theory can be realized in perturbative string theory by considering an orbifold background of the Kanno-Tachikawa type and placing stacks of fractional D3-branes whose world-volume partially extends along the orbifold directions. In particular, we show that turning on a constant background value for some scalar fields in the closed string twisted sectors induces a non-trivial profile for the gauge field and one of the complex scalars of the world-volume theory, and that this profile exactly matches the singular behavior that one expects for a Gukov-Witten surface defect in the $ \mathcal N=4 $ super Yang-Mills theory. To keep the presentation as simple as possible, in this work we restrict our analysis to surface defects corresponding to a $ ℤ_2 $ orbifold and defer the study of the most general case to a companion paper.
Based on 2005.02050
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| 11: Taha Malik |
The University of Texas at San Antonio |
Proof of the quantum null energy condition for free fermionic field theories |
The quantum null energy condition (QNEC) is a quantum generalization of the null energy condition which gives a lower bound on the null energy in terms of the second derivative of the von Neumann entropy or entanglement entropy of some region with respect to a null direction. The QNEC states that $\langle T_{kk}\rangle _{p}\geq \lim_{A\rightarrow 0}\left(\frac{\hbar}{2\pi A}S_{\text{out}}^{\prime\prime}\right)$ where $S_{\text{out}}$ is the entanglement entropy restricted to one side of a codimension-2 surface $\Sigma$ which is deformed in the null direction about a neighborhood of point $p$ with area $A$. A proof of QNEC has been given which applies to free and super-renormalizable bosonic field theories, and to any points that lie on a stationary null surface. Using similar assumptions and methods, we prove the QNEC for fermionic field theories.
Based on 1910.07594
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| 12: Miguel Angel Martin-Contreras |
Universidad de Valparaiso |
Non-linear Regge trajectories with bottom-up AdS/QCD |
In this work, we consider a non-quadratic dilaton $\Phi(z)=(\kappa\,z)^{2-\alpha}$ in the context of the static soft wall model to describe the mass spectrum of a wide range of vector mesons from the light up to the heavy sectors. The effect of this non-quadratic approach is translated into non-linear Regge trajectories with the generic form $M^2=a\,(n+b)^\nu$. We apply this sort of fits for the isovector states of $\omega$, $\phi$, $J/\psi$, and $\Upsilon$ mesons and compare with the corresponding holographic duals. We also extend these ideas to the heavy-light sector by using the isovector set of parameters to extrapolate the proper values of $ \kappa $ and $ \alpha $ through the average constituent mass $\bar{m}$ for each mesonic specie considered. In the same direction, we address the description of possible non-$q\,\bar{q}$ candidates using $\bar{m}$ as a holographic threshold, associated with the structure of the exotic state, to define the values of $\kappa$ and $\alpha$. We study the $\pi_1$ mesons in the light sector and the $Z_c$, $Y$, and $Z_b$ mesons in the heavy sector as possible exotic vector states. Finally, the RMS error for describing these twenty-seven states with fifteen parameters (four values for $\kappa$ and $\alpha$ respectively and seven values for $\bar{m}$) is $12.61\%$.
Based on 2004.10286
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| 13: Tatsuya Mori |
Tokyo Institute of Technology |
Superconformal indices of $6$D $A_{N-1}$ theories |
We study the superconformal indices of the theories realized on M$2$- and M$5$-branes by using AdS/CFT correspondence in the finite-$N$ region. Based on our works so far, we propose that the superconformal index on the gravity side consists of the contributions from not only the Kaluza-Klein particles but also suitable M-branes wrapped on the compact space. We need to consider all configurations of the wrapped branes but only analyze the single-wrapping case for the simplicity. To confirm that this proposal is correct, we compare the index of ABJM theory with the index on the corresponding gravity side and find the agreement up to the expected terms for single-wrapping. We apply the proposition to the gravity dual to $A_{N-1}$ theories and derive the first few terms in the indices of $A_{N-1}$ theories.
Based on 2007.05213
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| 14: Ian Nagle |
Macquarie University |
Conserved charges for evaporating black holes |
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Using the covariant phase space formalism, we present some new results on conserved charges and thermodynamics (or lack thereof) for evaporating black holes in 3 and 4 dimensions.
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| 15: Sota Nakajima |
Osaka City University |
Stability, enhanced gauge symmetry and suppressed cosmological constant in heterotic interpolating models |
We investigate the moduli space of heterotic interpolating models by computing the one-loop partition functions and deriving the massless spectra, paying attention to the region where supersymmetry is asymptotically restoring. We find some special points in the moduli space where the gauge symmetry is enhanced and the cosmological constant is exponentially suppressed. We discuss the stability of the Wilson line moduli.
Based on 2003.11217
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| 16: Yasunori Nomura |
UC Berkeley |
From the Black Hole Conundrum to the Structure of Quantum Gravity |
A quantum system with a black hole accommodates two widely different, though physically equivalent, descriptions. In one description, based on global spacetime of general relativity, the existence of the interior region is manifest, while understanding unitarity requires nonperturbative quantum gravity effects such as Euclidean wormholes. The other description adopts a manifestly unitary, or holographic, description, in which the interior emerges effectively as a collective phenomenon of fundamental degrees of freedom.In this paper we study the latter approach, which we refer to as the unitary gauge construction. In this picture, the formation of a black hole is signaled by the emergence of a surface (stretched horizon) possessing special dynamical properties: quantum chaos, fast scrambling, and low energy universality. These properties allow for constructing interior operators, as we do explicitly, without relying on details of microscopic physics. A key role is played by certain coarse modes in the zone region (hard modes), which determine the degrees of freedom relevant for the emergence of the interior.We study how the interior operators can or cannot be extended in the space of microstates and analyze irreducible errors associated with such extension. This reveals an intrinsic ambiguity of semiclassical theory formulated with a finite number of degrees of freedom. We provide an explicit prescription of calculating interior correlators in the effective theory, which describes only a finite region of spacetime. We study the issue of state dependence of interior operators in detail and discuss a connection of the resulting picture with the quantum error correction interpretation of holography.
Based on 2010.15827
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| 17: Toshihiro Ota |
Osaka university |
Wilson-'t Hooft lines as transfer matrices |
We establish a correspondence between a class of Wilson-'t Hooft lines in four-dimensional $\mathcal{N} = 2$ supersymmetric gauge theories described by circular quivers and transfer matrices constructed from dynamical L-operators for trigonometric quantum integrable systems. We compute the vacuum expectation values of the Wilson--'t Hooft lines in a twisted product space $S^1 \times_{\epsilon} \mathbb{R}^2 \times \mathbb{R}$ by supersymmetric localization and show that they are equal to the Wigner transforms of the transfer matrices. A variant of the AGT correspondence implies an identification of the transfer matrices with Verlinde operators in Toda theory, which we also verify. We explain how these field theory setups are related to four-dimensional Chern-Simons theory via embedding into string theory and dualities.
Based on 2009.12391
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| 18: Koichi Saito |
The University of Tokyo, Komaba |
U(1) spin Chern-Simons theory and Arf invariants in two dimensions |
In this talk, I will discuss the construction of a candidate of the 2d theory, which lives in the boudnary of a spin U(1) Chern-Simons theory, and check whether they are in the bulk-edge correspondence from several points of view. We anticipate that the 2-dimensional theory. is the 2d CFT of a compact boson modified by the Arf invariant. Also, I will talk about the derivation of the partition function of a U(1) Chern-Simons theory on the lens space.
Based on 2005.03203
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| 19: Noburo Shiba |
Yukawa Institute for Theoretical Physics, Kyoto University |
Pseudo entropy in free scalar field theory |
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Pseudo entropy is a generalization of entanglement entropy via post-selection. We develop computational methods of pseudo entropy in free scalar field theory. We study pseudo entropy in Lifshitz free scalar theory and massive free scalar theory. This talk is based on work in progress.
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| 20: Kenta Shiozawa |
Kitasato University |
World-volume Effective Theories of Locally Non-geometric Branes |
We study world-volume effective theories of five-branes in type II string theories. We determine the bosonic zero-modes of the NS5-brane, the Kaluza-Klein monopole, the exotic Q5-, R5-branes and a space-filling brane, by direct calculations within the formalism of double field theory (DFT). We show that these zero-modes are Nambu-Goldstone modes associated with the spontaneously broken gauge symmetries in DFT. They are organized into the bosonic part of the six-dimensional $\mathcal{N} = (1,1)$ vector and the $\mathcal{N} = (2,0)$ tensor multiplets. Among other things, we examine the locally non-geometric R5-branes and space-filling branes that are characterized by the winding space. We also study effective theories of five-branes with string worldsheet instanton corrections.
Based on 2010.02701
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| 21: Akimi Watanabe |
University of Tokyo |
Dimensional oxidization on coset space |
In the matrix model approaches of string/M theories, one starts from a generic symmetry gl(∞) to reproduce the space-time manifold. In this paper, we consider the generalization in which the space-time manifold emerges from a gauge symmetry algebra which is not necessarily gl(∞). We focus on the second nontrivial example after the toroidal compactification, the coset space G/H, and propose a specific infinite-dimensional symmetry which realizes the geometry. It consists of the gauge-algebra valued functions on the coset and Lorentzian generator pairs associated with the isometry. We show that the 0-dimensional gauge theory with the mass and Chern-Simons terms gives the gauge theory on the coset with scalar fields associated with H.
Based on 2005.13936
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| 22: Ryota Watanabe |
Osaka University |
Chaos and scrambling in simple quantum systems via OTOC |
Exponential growth of thermal out-of-time-order correlator (OTOC) is an indicator of a possible gravity dual, and a simple toy quantum model showing the growth is being looked for. The growth, which we call scrambling, is the quantum version of the butterfly effect and is sometimes regarded as a characteristic of quantum chaos. However, the scrambling can occur in some systems without classical chaos. We numerically study the thermal OTOC in a coupled harmonic oscillator and an inverted harmonic oscillator, and show that quantum chaos, classical chaos and scrambling are not always simultaneously observed.
Based on 2004.04381, 2007.04746
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| 23: Zixia Wei |
Yukawa Institute for Theoretical Physics |
Holographic Pseudo Entropy |
We introduce a quantity, called pseudo entropy, as a generalization of entanglement entropy via post-selection. In the AdS/CFT correspondence, this quantity is dual to areas of minimal area surfaces in time-dependent Euclidean spaces which are asymptotically AdS. We study its basic properties and classifications in qubit systems. In specific examples, we provide a quantum information theoretic meaning of this new quantity as an averaged number of Bell pairs when the post-selection is performed. We also present properties of the pseudo entropy for random states. We then calculate the pseudo entropy in the presence of local operator excitations for both the two dimensional free massless scalar CFT and two dimensional holographic CFTs. We find a general property in CFTs that the pseudo entropy is highly reduced when the local operators get closer to the boundary of the subsystem. We also compute the holographic pseudo entropy for a Janus solution, dual to an exactly marginal perturbation of a two dimensional CFT and find its agreement with a perturbative calculation in the dual CFT. We show the linearity property holds for holographic states, where the holographic pseudo entropy coincides with a weak value of the area operator. Finally, we propose a mixed state generalization of pseudo entropy and give its gravity dual.
Based on 2005.13801
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| Shiraz Minwalla |
TIFR |
Constraining Tree Level Gravitational Scattering |
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I will use the chaos bound to motivate a conjecture - the so called CRG conjecture - for a universal constraint on tree level scattering in 'consistent' classical theories. I will then demonstrate that in six and lower dimensions, the only local (i.e finite number of derivatives) tree level gravitational four point function with a finite number of poles that obeys the CRG conjecture is the Einstein S matrix.
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| Sotaro Sugishita |
KEK |
IR finite S-matrix by gauge invariant dressed states |
Dressed states were proposed to define the IR finite $S$-matrix in QED or gravity. However, we show that known dressed states still cause IR divergences in QED. This fact is also related to inconsistency between these dressed states and the asymptotic symmetry in QED. We propose new dressed states which are consistent with the asymptotic symmetry in QED. We conclude that the $S$-matrix for the new dressed states is IR finite.
Based on 2009.11716
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| Junsei Tokuda |
Kobe University |
Positivity bounds on low-energy gravitational EFTs |
It has been suggested that not every consistent-looking effective field theories (EFTs) can be embedded into UV complete theories of quantum gravity such as string theory. We show that EFTs which can be embedded into quantum gravity must satisfy a certain set of inequalities (so-called positivity bounds), assuming that the scattering amplitude exhibits the Regge behavior in the high energy limit as realized in string theory. Our work provides the reliable bounds on the predictions of quantum gravity on low energy physics.
Based on 2007.15009
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| Sudip Ghosh |
Okinawa Institute of Science and Technology |
MHV Graviton Scattering Amplitudes and Current Algebra on the Celestial Sphere |
We consider the implications of asymptotic symmetries associated to soft theorems for the OPE of graviton primaries in $2$-$d$ celestial conformal field theories (CCFTs), the conjectured holographic dual of quantum gravitational theories in $4$-$d$ asymptotically flat spacetime. We show that the subleading soft graviton theorem for a positive helicity soft graviton naturally gives rise to a $\overline{SL(2,\mathbb{C})}$ current algebra that resides on the celestial sphere at null infinity. This forms an extended closed algebra with super-translations coming from the leading soft theorem for a positive helicity soft graviton. We find that the celestial OPE of gravitons, extracted from the Mellin transform of tree level MHV amplitudes in Einstein gravity can be organised according to representations of this algebra. We also study the role of two particular null states admitted by this local symmetry algebra. Their decoupling leads to two sets of partial differential equations (PDEs) for $n$-point MHV amplitudes. These PDEs can be used to completely determine the leading structure of the OPE of two graviton primaries in the CCFT. All descendant OPE’s can then be obtained in terms of the leading OPE coefficient by demanding invariance of the OPE under the extended local symmetry algebra. Remarkably, our results suggest the existence of an autonomous sector of the CCFT which holographically computes tree level MHV graviton amplitudes in Einstein gravity and is entirely governed by the $\overline{SL(2,\mathbb{C})}$ current algebra and super-translations. This MHV sector of the CCFT resembles minimal models of $2$-d CFT.
Based on 2008.04330
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| Subham Dutta Chowdhury |
Tata Institute of Fundamental Research |
Classification of four-point local gluon S-matrices |
In this paper, we classify four-point local gluon S-matrices in arbitrary dimensions. This is along the same lines as \cite{Chowdhury:2019kaq} where four-point local photon S-matrices and graviton S-matrices were classified. We do the classification explicitly for gauge groups $SO(N)$ and $SU(N)$ for all $N$ but our method is easily generalizable to other Lie groups. The construction involves combining not-necessarily-permutation-symmetric four-point S-matrices of photons and those of adjoint scalars into permutation symmetric four-point gluon S-matrix. We explicitly list both the components of the construction, i.e permutation symmetric as well as non-symmetric four point S-matrices, for both the photons as well as the adjoint scalars for arbitrary dimensions and for gauge groups $SO(N)$ and $SU(N)$ for all $N$. In this paper, we explicitly list the local Lagrangians that generate the local gluon S-matrices for $D\geq 9$ and present the relevant counting for lower dimensions. Local Lagrangians for gluon S-matrices in lower dimensions can be written down following the same method. We also express the Yang-Mills four gluon S-matrix with gluon exchange in terms of our basis structures.
Based on 2006.12458
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| Antonio Gallerati |
Politecnico di Torino, Italy |
Supersymmetry, holography and applications |
I discuss a 1+2 dimensional model holographically realized as the boundary theory of a four-dimensional supergravity model in Anti de Sitter spacetime. The result is achieved through suitable boundary conditions for the D=4 fields, and an effective model for massive spin-1/2 fields on a curved background is obtained.The (unconventional) supersymmetry of the boundary model allows to introduce extra internal degrees of freedom, which can provide an application to the description of the charge carriers properties of graphene-like 2D materials at the Dirac points. In particular, the two valleys correspond to the two independent sectors of the boundary model, connected by a parity transformation, and the fermion masses entering the corresponding Dirac equations are related to the torsion parameters in the three-dimensional model.The construction follows a top-down approach, in that the effective 1+2 dimensional theory for a condensed matter system at the boundary originates from a well-defined supersymmetric effective supergravity in the bulk.
Based on 1910.03508
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