Holographic Entanglement Entropy in the FLRW Universe
When:
2025/05/23 (Fri.) 12:30-13:30
Where:
Honkan (Main Bldg.) B61
Speaker:
Toshifumi Noumi (University Tokyo)
Abstract:
We discuss properties of the holographic entanglement entropy in the three-dimensional Friedmann--Lemaitre--Robertson--Walker universe. We consider two types of holographic scenarios analogous to the static patch holography and the half de Sitter holography, in which the holographic boundary is timelike and placed in the bulk. We find in general that the strong subadditivity can be satisfied only in the former type and in addition the holographic boundary has to fit inside the apparent horizon. Also, for the universe filled with an ideal fluid of constant equation of state w < −1, the condition is sharpened as that the holographic boundary has to fit inside the event horizon instead. These conditions provide a necessary condition for the dual quantum field theory to be standard and compatible with the strong subadditivity.
Higgsing procedure of line defect half-indices in N=4 SYM theories
When:
2025/04/25 (Fri.) 13:30-14:30
Where:
Honkan (Main Bldg.) B61
Speaker:
Tadashi Okazaki (Southeast University)
Abstract:
We demonstrate that the line defect half-indices of the ’t Hooft lines of magnetic charges corresponding to the minuscule representations in the presence of the Nahm pole boundary conditions can be obtained by applying the Higgsing prescription to the half-indices of the Dirichlet boundary conditions. Accordingly, we find precise matching of the indices for pairs of the S-dual configurations with the Wilson lines and Neumann boundary conditions and those with the ’t Hooft lines and Nahm pole boundary conditions.
The Schur index in four-dimensional N=4 super Yang-Mills theory with U(N) gauge group has a natural two-parameter deformation. We find that a matrix integral in such a deformed Schur index can be exactly evaluated by using Macdonald polynomials. The resulting expression is a simple combinatorial summation over partitions. An extension to line operator indices is straightforward. In particular, for an anti-symmetric representation, the line operator index has a relatively simple form. We further discuss infinite N analysis and finite N giant graviton expansions.
Exploring Complex Saddles and Geometries through Holography
When:
2025/03/10 (Mon.) 13:30-14:30
Where:
Honkan (Main Bldg.) H227C
Speaker:
Heng-Yu Chen (National Taiwan University)
Abstract:
Studying gravitational path integral often leads one to encounter complex saddles and the corresponding geometries, some may have interesting physical interpretations while others may be unphysical, it is therefore interesting to study them through the lens of holography. In this talk, I will report some recent progresses in this direction by applying holography correspondence for both asymptotically Anti de-Sitter and de-Sitter spacetimes. We employ the suitable analytic continuations of dual CFT correlation functions, the method of mini-superspace, and resurgence to explore these complex saddles. In the process we will provide the geometric interpretations for them, which are consistent with the holography correspondences. The work was done in collaborations with Yasuaki Hikida, Yusuke Taki and Takahiro Uetoko.
Reference:
Giant Gravitons and Volume Minimisation
When:
2025/02/21 (Fri.) 13:30-14:30
Where:
Honkan (Main Bldg.) 227B
Speaker:
Sanefumi Moriyama (Osaka Metropolitan University)
Abstract:
The giant graviton expansion of the superconformal index of field theories and the master volume in volume minimization exhibit notable similarities. In our recent work, we establish a precise correspondence between these two concepts. In this talk, I will explain this correspondence and discuss its consistency with the simple sum reduction and the parallelogram ansatz.
Folding QQ-relations and transfer matrix eigenvalues: towards a unified approach to Bethe ansatz for super spin chains
When:
2025/01/29 (Wed.) 16:00-17:00
Where:
Zoom Online
Speaker:
Zengo Tsuboi ()
Abstract:
We derive QQ-relations (functional relations among Baxter Q-functions) and T-functions (eigenvalues of transfer matrices) for fusion vertex models associated with twisted quantum affine superalgebras and untwisted quantum affine orthosymplectic superalgebras (and their Yangian counterparts) as reductions (a kind of folding) of those associated with the quantum affine general linear superalgebra $U_{q}(gl(M|N)^{(1)})$. In particular, we reproduce previously proposed generating functions (difference operators) of the T-functions for the symmetric or anti-symmetric representations, and tableau sum expressions for more general representations for orthosymplectic superalgebras, and obtain Wronskian-type expressions (analogues of Weyl-type character formulas) for them. T-functions for spinorial representations are related to reductions of those for asymptotic limits of typical representations of $U_{q}(gl(M|N)^{(1)})$.
Genus 2 Superstring Chiral Measure From The 3-Dimensional Gelca-Hamilton TQFT
When:
2025/01/22 (Wed.) 16:00-17:00
Where:
Zoom & Honkan (Main Bldg.) H227B
Speaker:
Saki Koizumi (DIAS)
Abstract:
In the path integral formulation of the superstring, the chiral measure acquires a phase under the modular transformation of a Riemann surface.
This motivated the use of anomaly inflow to define the superstring chiral measure by a path integral formalism of a modular invariant $3$-dimensional theory.
A Gelca-Hamilton topological field theory (TQFT) is one of the Atiyah’s TQFT on a $3$-dimensional extended manifold with the boundary Jacobi variety of a Riemann surface, whose Hilbert space is spanned by the theta series.
We show that genus $g\leq 2$ superstring chiral measure in the path integral can be obtained by the path integral of the Gelca-Hamilton TQFT on some $3$-dimensional bulk extended manifolds.
The modular transformation of the superstring chiral measure can be understood as the action of the extended mapping class group on the bulk $3$-dimensional extended manifolds.
Heterotic string theory has nonsupersymmetric branes whose existence is suggested by the cobordism conjecture. We numerically construct static, spherically symmetric and asymptotically flat black brane solutions in ten dimensional heterotic string theories for 0- and 4-branes. These branes carry charges that are measured by Chern classes on the sphere surrounding the branes. For the extremal case, the solution have a throat region with a linear dilaton profile as expected from the corresponding world sheet theory. We also construct non-extremal solutions by compactifying the time direction. To verify the reliability of our numerical calculations, we confirm that they reproduce the known analytical solutions for the 6-brane. Our black brane solutions provide evidence supporting the existence of such branes in heterotic string theory. In this talk, I will explain our motivation for constructing these solutions in heterotic string theory, and then discuss how to realize them.
Gauge origami is a generalized supersymmetric quiver gauge theory where intersecting D-branes appear. The simplest setup is the gauge origami system in $\mathbb{C}^4$, where D2/D4/D6/D8 branes are present. Instantons are D0-branes bound to the D(2p)-branes, and the partition functions are the flavored Witten indices of the supersymmetric quantum mechanics of the D0-branes. We demonstrate that the contour integral formulas of the partition functions have free field interpretations, leading to the operator formalism of $qq$-characters, which we generally call BPS $qq$-characters. On one hand, the $qq$-characters of D2-D0 and D4-D0 bound states correspond to screening charges and generators of the affine quiver W-algebra, respectively. On the other hand, the $qq$-characters of D6-D0 and D8-D0 bound states give new types of $qq$-characters, where the monomial terms are characterized by plane partitions and solid partitions. The D4, D6, D8 $qq$-characters automatically reproduce the partition function of the spiked instanton, tetrahedron instanton, and the magnificent four, which eventually establish the BPS/CFT correspondence. We also discuss the relation with quantum toroidal algebras and generalizations to toric Calabi-Yau four-folds. This talk is based on arXiv: 2310.08545, 2404.17061, 2411.01987
Hawking-Page and entanglement phase transition in 2d CFT on curved backgrounds
When:
2024/12/11 (Wed.) 16:00-17:00
Where:
Zoom
Speaker:
Akihiro Miyata (YITP)
Abstract:
The thermodynamics and the entanglement properties of two-dimensional conformal field theories (2d CFTs) on curved backgrounds are studied. By means of conformal mapping we study the equivalent system on flat space governed by the deformed Hamiltonian, which is a spatial integral of the Hamiltonian density modulated by an enveloping function. Focusing on holographic CFTs, we observe Hawking-Page like phase transition for the thermal and the entanglement entropy as we vary the background metric. We also compute the mutual information to study the information theoretic correlation between parts of the curved spacetime. The gravity dual of 2d CFTs on curved background is also discussed.
This presentation is based on the paper, A. Miyata, M. Nozaki, K. Tamaoka, and M. Watanabe, JHEP 08 (2024) 190. [arXiv: 2406.06121]
A concrete construction of topological operator in factorization algebras
When:
2024/11/13 (Wed.) 16:00-17:00
Where:
Honkan (Main Bldg.) H227B
Speaker:
Masashi Kawahira (YITP)
Abstract:
In this talk, we will discuss a concrete construction of a topological operator in factorization algebras. Factorization algebras play an important role in modern mathematics and physics in the formulation of quantum field theories by K. Costello and his collaborators. We will provide a definition of topological operators and a construction of the topological operator corresponding to shift symmetry, in one-dimensional massless scalar field theory.
Investigating 9d/8d non-supersymmetric branes and theories from supersymmetric heterotic strings
When:
2024/11/06 (Wed.) 16:00-17:00
Where:
Honkan (Main Bldg.) H227B
Speaker:
Arata Ishige (SOKENDAI)
Abstract:
Superstring theory is expected to derive the Standard Model from fundamental principles. With this hope in mind, the vacua of superstring theories have been studied extensively over the years. Among various string theories, heterotic strings have attracted interest from a phenomenological perspective since the early stage.
It is well known that there are two types of heterotic strings in 10 dimensions: E8×E8 and SO(32). This is the case when spacetime supersymmetry (SUSY) was postulated.
It is also known that in 10 dimensions, there are various heterotic strings without spacetime SUSY. All of them can be constructed from 10d SUSY heterotic strings through a process called asymmetric orbifolding.
Recently, the maximal gauge symmetries of SUSY heterotic strings on T^d have been identified. Therefore, it is quite natural to wonder what 9d non-SUSY heterotic strings can be obtained from them through asymmetric orbifolding.
In this talk, I will first review the basics of 10d/9d SUSY and 10d non-SUSY heterotic strings. Then, I will explain the method to construct 9d non-SUSY theories and present our result.
Exact WKB (EWKB) is one of the most powerful tools to study differential equations and has many applications including quantum mechanics, SUSY gauge theories, integrable models, topological string theory etc. Being an incorporation of resurgence theory and the traditional WKB method, EWKB method reveals the exact quantization of the physical systems. However, in its standard treatment, the EWKB techniques are restricted to only a single sector which is bounded by singular points on the moduli space. In this talk, I will introduce a novel EWKB approach which displays the continuous connection between different sectors via an analytical continuation preventing the singularities. My focus will be on one dimensional potentials with degenerate saddles. With the Airy-type EWKB method, I will show the smooth transition of the spectrum between different sectors. In addition to that with the Weber-type EWKB method, I will present exact estimations to WKB actions in relation with multi-instanton configurations. This reveals the S-duality between minima and maxima of the degenerate potentials in the language of EWKB method. I also show an S-transformation of resurgence relations of genus-1 potentials.
Reference:
Exact quantization conditions and full transseries structures for ${\cal PT}$ symmetric anharmonic oscillators
When:
2024/07/26 (Fri.) 13:30-14:30
Where:
227B Honkan (Main Bldg.)
Speaker:
Syo Kamata (U.Tokyo)
Abstract:
We study exact Wentzel–Kramers–Brillouin analysis (EWKB) for a ${\cal PT}$ symmetric quantum mechanics (QM) defined by the potential $V_{\cal PT}(x) = \omega^2 x^2 + g x^{2 K} (i x)^{\varepsilon}$ with $\omega \in {\mathbb R}_{\ge 0}$, $g \in {\mathbb R}_{>0}$ and $K, \varepsilon \in {\mathbb N}$ to clarify its perturbative/non-perturbative structure. In our analysis, we mainly consider the massless cases, i.e., $\omega = 0$, and derive the exact quantization conditions (QCs) for arbitrary $(K,\varepsilon)$ including all perturbative/non-perturbative corrections. From the exact QCs, we clarify full transseries structure of the energy spectra with respect to the inverse energy level expansion, and then formulate the Gutzwiller trace formula, the spectral summation form, and the Euclidean path-integral. For the massive cases, i.e., $\omega > 0$, we show the fact that, by requiring existence of solution of the exact QCs, the path of analytic continuation in EWKB is uniquely determined for a given $N = 2K + \varepsilon$, and in consequence the exact QCs, the energy spectra, and the three formulas are all perturbative. Similarities to Hermitian QMs and resurgence are also discussed as additional remarks.
Reference:
https://arxiv.org/abs/2406.01230
Exact Non-Abelian Supertubes
When:
2024/06/26 (Wed.) 16:00-17:00
Where:
zoom
Speaker:
Masaki Shigemori (Nagoya University)
Abstract:
Supertubes are supersymmetric configurations in string theory in which branes are extending along a closed curve. For a supertube of codimension two, its dipole charge is characterized by the duality monodromy around the closed curve. When multiple codimension-2 supertubes are present, the monodromies around different supertubes can be non-commuting, namely non-Abelian. Non-Abelian configurations of supertubes are expected to play an important role in non-perturbative physics of string theory, especially black holes. In this paper, in the framework of five-dimensional supergravity, we construct exact solutions describing codimension-2 supertubes in three-dimensional space. We use an extension formula to construct a three-dimensional solution from a two-dimensional seed solution. The two-dimensional seed is an F-theory like configuration in which a torus is nontrivially fibered over a complex plane. In the first example, there is a stack of circular supertubes around which there is a non-trivial monodromy. In some cases this can be thought of as a microstate of a black hole in $AdS_2 \times S^2$. The second example is an axi-symmetric solution with two stacks of circular supertubes with non-Abelian monodromies. In addition, there is a continuous distribution of charges on the symmetry axis.
We employ double holography to examine a system of two entangled gravitating universes that live on two codimension-one branes in an asymptotically AdS3 spacetime with two disjoint conformal boundaries. There are distinct brane configurations depending on the temperature of the thermofield double (TFD) state between the left and right systems. The topology transition between two branes is naturally identified with the emergence of an Einstein-Rosen bridge connecting the two entangled universes. This doubly holographic construction offers a holographic perspective on gravitational collapse and black hole formation in brane universes. Through this holographic framework, we analyze the quantum information structure of the two gravitating universes. Specifically, we calculate the mutual information between defects present in the boundary theories on the left and right sides. Furthermore, we investigate the decoupling process in the Hayden-Preskill protocol applied to the two copies of the defect field theory and discuss the interpretation of the Yoshida-Kitaev decoding protocol.
End of the world branes from dimensional reduction
When:
2024/05/31 (Fri.) 12:30-13:30
Where:
zoom
Speaker:
Yu-ki Suzuki (Kyoto University)
Abstract:
We consider dimensional reduction of cigar geometries which are obtained by a Wick rotation of black hole solutions. Originally the cigar geometry is smooth around the tip, but after the dimensional reduction along the Euclidean time direction, there appears an end-of-the-world brane (ETW brane). We derive the tension of the brane by two methods: bulk equations of motion and boundary equations of motion.In particular, for AdS7-soliton×S4 and AdS4-soliton ×S7 backgrounds in M-theory, we find that the tension of the emerging ETW branes behaves as t(Φ) ~ e−3Φ in the string frame. This indicates the existence of such ETW branes in the strongly coupled regime of type 0A string theory.
Gauge Symmetries and Conserved Currents in AdS/BCFT
When:
2024/05/15 (Wed.) 16:00-17:00
Where:
Honkan (Main Bldg.) H227B
Speaker:
Kenta Suzuki (Rikkyo University)
Abstract:
The AdS/BCFT correspondence is a simple variation of the ordinary AdS/CFT correspondence, which claims a duality between a quantum gravity in AdS spacetime with an end-of-the-world brane and a conformal filed theory defined on a spacetime with a boundary. This AdS/BCFT correspondence recently found interesting applications for black hole information paradox, as well as strong coupling dynamics of boundary conformal field theory (BCFT).
In this talk, we study massless/massive vector field perturbations in AdS spacetime with an end-of-the-world brane. By imposing U(1) preserving Neumann boundary condition on the end-of-the-world brane, we study their spectrum and discuss their implications for dual BCFT operators. When the perturbation is massless, the dual BCFT operator is a conserved current and we show that such an operator indeed satisfies the U(1) preserving conformal boundary condition. On the other hand, when the perturbation is massive, in general there exists non-vanishing perpendicular components of the dual BCFT operator, even in the massless limit. We explain this difference between massless and massive perturbations from the point of view of the bulk gauge symmetry, or equivalently from different structure of equations of motion. We also find several brane-tension-independent modes in massless perturbations, and these are understood as boundary-condition-independent modes from the dual BCFT point of view.
Reference:
arxiv:2403.07325
When:
2024/01/22 (Mon.) 16:00-17:00
Where:
Speaker:
Saki Koizumi ()
Abstract:
Reference:
Supersymmetric CFTs from quantum stabilizer codes
When:
2024/01/10 (Wed.) 16:00-17:00
Where:
Honkan (Main Bldg.) 227B
Speaker:
Kohki Kawabata (University of Tokyo)
Abstract:
We construct fermionic conformal field theories (CFTs) whose spectra are characterized by quantum stabilizer codes. We exploit our construction to search for fermionic CFTs with supersymmetry by focusing on quantum stabilizer codes of the Calderbank-Shor-Steane type, and derive simple criteria for the theories to be supersymmetric. We provide several examples of fermionic CFTs that meet the criteria, and find quantum codes that realize N=4 supersymmetry. Our work constitutes a new application of quantum codes and paves the way for the methodical search for supersymmetric CFTs.
