Past events, Spring 2019
Monday Feb. 25
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Welcome back! On the first journal club meeting we will decide on a topic and reading material.
Thursday Feb. 28
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Dan Xie, Tsinghua University
"W algebra and four dimensional N=2 Argyres-Douglas theory"
Abstract: One can associate a two dimensional vertex operator algebra (VOA) to a four dimensional N=2 SCFT. In this talk, I will discuss the associated VOA for 4d N=2 SCFTs engineered using 6d (2,0) theory, and the result is a class of W algebras which has been intensively studied by physicists and mathematicians in the past few years. Various interesting results of 4d theory and 2d theory will be discussed. This is a joint work with Wenbin Yan.
Monday Mar. 4
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Hongji Gao, Tsinghua University Sections 1 - 3.3 of Witten's A mini-introduction to information theory
Thursday Mar. 7
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Song He, ITP
"ABCD of causal diamonds, cluster associahedra and scattering amplitudes"
Abstract: Recently it has been realized that scattering amplitudes in various theories can be viewed as "volume" of certain polytopes that live in kinematic space, which can make properties/symmetries of amplitudes manifest. I will introduce perhaps the simplest class of such polytopes, namely generalized associahedra for finite-type cluster algebra. It is remarkable even combinatorially trivalent scalar Feynman diagrams at tree and one-loop level form polytopes of type A, B/C and D, and our realizations of the latter in kinematic space provide new representation for these scalar amplitudes. As a byproduct, such realizations are naturally related to causal diamonds and positive solutions of wave equations in 1+1 D, which can be viewed as the continuum limit of our associahedra. (Based on part I of series of works in progress with Arkani-Hamed et al, which aim to provide a combinatorial origin for scattering of particles and strings and connect them with positive geometries, cluster algebra, periods etc.)
Monday Mar. 11
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Hongji Gao, Tsinghua University Sections 1 - 3.3 of Witten's A mini-introduction to information theory
Thursday Mar. 14
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Song He, ITP
"ABCD of causal diamonds, cluster associahedra and scattering amplitudes (part 2)"
Abstract: Recently it has been realized that scattering amplitudes in various theories can be viewed as "volume" of certain polytopes that live in kinematic space, which can make properties/symmetries of amplitudes manifest. I will introduce perhaps the simplest class of such polytopes, namely generalized associahedra for finite-type cluster algebra. It is remarkable even combinatorially trivalent scalar Feynman diagrams at tree and one-loop level form polytopes of type A, B/C and D, and our realizations of the latter in kinematic space provide new representation for these scalar amplitudes. As a byproduct, such realizations are naturally related to causal diamonds and positive solutions of wave equations in 1+1 D, which can be viewed as the continuum limit of our associahedra. (Based on part I of series of works in progress with Arkani-Hamed et al, which aim to provide a combinatorial origin for scattering of particles and strings and connect them with positive geometries, cluster algebra, periods etc.)
Monday Mar. 18
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Shuwei Liu, Tsinghua University
"Introduction to quantum information theory and selected topics"
Abstract: First, I will continue introducing some concepts in quantum information theory, like monotonicity of relative entropy and quantum channels. Then I will talk about three topics to give some hints on the physical meaning of various entropies in quantum information theory. The topics we will consider are quantum teleportation and conditional entropy, relative entropy and quantum hypothesis testing, and the use of quantum state to encode classical information.
Reference: A mini-introduction to information theory
Thursday Mar. 21
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Junbao Wu, Tianjin University
"Holographic Wilson Loops in AdS4/CFT3 Correspondence Revisited"
Abstract: The duality between bosonic 1/2-BPS Wilson loops and probe M2-branes in dual M-theories were proposed in Farquet and Sparks in 2013. Though passed some checks, we found this duality should be reconsidered. The reason is that we found fermionic BPS Wilson loops in such theories including ones coupled with all nodes and the arrows in the quiver diagrams. The precise duality between fermionic BPS Wilson loops and probe M2-branes are found for N=2 orbifold ABJM theory. The duality in more general theories are to be studied. This talk is based on joint work done with A. Mauri, H. Ouyang, S. Penati and J.-j. Zhang.
IASTU Seminar
3.30 pm at Conference Hall 322, Science Building
Michal Heller, Max Planck Institute for Gravitational Physics Potsdam (Albert Einstein Institute)
"Circuit complexity for path integral optimization"
Abstract: The talk will review recent progress on defining complexity using unitary circuits in the setting of quantum field theory (1707.08582, 1807.07075, 1810.05151) and discuss an ongoing effort to generalize it to euclidean path integrals. The latter results provide a further justification for the path integral optimization program.
Monday Mar. 25
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Shuwei Liu, Tsinghua University
"Introduction to quantum information theory and selected topics". Reference: A mini-introduction to information theory
&
Wenxin Lai, Peking University
Chapter 2 of Holographic Entanglement Entropy
Wednesday Mar. 27
IASTU Seminar
3.30 pm at Conference Hall 322, Science Building
Bartek Czech, IASTU
"Modular Berry Connection and How Holographic Spacetimes Acquire Curvature"
Abstract: In the AdS/CFT correspondence, it is believed that the bulk AdS spacetime is built out of quantum entanglement in the dual conformal field theory (CFT). If so, what feature of the CFT entanglement is responsible for the curvature of the bulk spacetime? In this talk, I will explain that the answer is the modular Berry connection. This is a Berry connection constructed out of modular Hamiltonians--operators that encode how complementary subregions of the CFT are entangled with one another. The modular Berry connection is a novel concept, with potential applications outside the AdS/CFT correspondence.
Monday Apr. 1
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Wenxin Lai (赖文昕), Peking University
Summary of Chapters 1~4 of Holographic Entanglement Entropy
Thursday Apr. 4
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Xuening Bai, IASTU
"Cosmic-ray Streaming Instability: Introduction and ab initio Simulations"
Abstract: The interstellar medium in the Galaxy is filled with gas, magnetic fields, and cosmic-rays (CRs). Being relativistic particles, the CRs naturally tends to escape from thee Galaxy. Howeveer, CRs streaming along magnetic fields are subject to the cosmic-ray (CR) streaming instability, which is gyro-resonant in nature and occurs when the bulk CR streaming speed exceeds the Alfven velocity of background gas. It is believed to play a crucial role in CR transport, leading to growth of Alfven waves at small scales that scatter CRs, and impacts the interaction of CRs with the interstellar medium on large scales. Employing our recently developed magnetohydrodynamic-particle-in-cell (MHD-PIC) method, we conduct the first simulations that quantitatively demonstrate the growth and saturation of the instability. By implementing the delta-f method, we are able to accurately capture wave growth over a broad spectrum, and accurately follow the subsequent quasi-linear diffusion. Full isotropization of the CRs in the wave frame requires pitch angles of most CRs to efficiently cross 90deg, which is achieved by non-linear wave-particle interaction. We anticipate our methodology will open up opportunities for future investigations that incorporate additional physics.
Monday Apr. 8
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Haoxin Wang, Tsinghua University
Chapters 3 and 4 of Holographic Entanglement Entropy
Thursday Apr. 11
AdS, DUALITY AND STRINGS SEMINAR
10.30 am at Jinchunyuan West 3rd floor
Joonho Kim, KIAS
"Cardy Formula of 4d N=1 SCFT"
Abstract: We study the asymptotic behavior of the modified superconformal index in 4d N=1 gauge theory. This index has the same amount of information as the conventional one, and only differs by an extra phase factor dressing each short multiplet’s contribution. The high ‘temperature' limit of this index can be written in terms of the conformal anomalies, (3c-2a). We find that the entropy from our asymptotic free energy is always positive for interacting SCFTs. Especially for the holographic SCFTs dual to AdS_5 × Y^{p,p}, the entropy from the index accounts for the Bekenstein-Hawking entropy of large BPS black holes.
Monday Apr. 15
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Zi-Zhi Wang, IASTU
Chapter 5 of Holographic Entanglement Entropy
Thursday Apr. 18
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Alejandra Castro, University of Amsterdam
"New aspects of nAdS2/nCFT1 correspondence"
Abstract: The linchpin of nAdS2/nCFT1 is the non-linear realisation of symmetries, where the conformal symmetry of AdS2 is spontaneously broken and also broken by an anomaly. In this talk I'll discuss aspects of this correspondence that are relevant for the holographic description of near-extremal rotating black holes. And if time allows, I will discuss the role of gravitational anomalies in nAdS2 holography.
Monday Apr. 22
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Yuan Zhong, YMSC
Chapter 6 of Holographic Entanglement Entropy
Thursday Apr. 25
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Marcus Sperling, YMSC
"From discrete quotients of Coulomb branches to magnetic quivers"
Abstract: Coulomb branches of 3-dimensional N=4 gauge theories are hyper-Kähler singularities with non-trivial quantum corrections; in contrast to Higgs branches of theories with 8 supercharges. The monopole formula, defined as Hilbert series of the Coulomb branch chiral ring, provides one approach to study these moduli spaces. Remarkably, Coulomb branches have been used recently to describe Higgs branches of 5d and 6d theories with 8 supercharges at infinite gauge coupling, where no classical Higgs branch description is applicable. After a brief reminder of the set-up, I discuss discrete quotients of 3d N=4 Coulomb branches and prove equalities of Hilbert series for a number of different cases. Among others, the results prove a recent 'discrete gauging' conjecture on Higgs branches of certain 6-dimensional N=(0,1) theories. In the second half, I focus on Higgs branches of 6d N=(1,0) theories associated to the physics of M5 branes placed near an M9 plane on an A-type ALE singularity. There are tensionless strings whenever two M5 branes coincide or whenever an M5 brane approaches the M9 plane. Previous works suggest the conjecture that a new Higgs branch arises whenever a BPS-string becomes tensionless. Previewing joint work with Santiago Cabrera and Amihay Hanany, a formalism is proposed that allows to derive a novel object from a brane configuration, called the 'magnetic quiver'. The main features are (i) the 3d Coulomb branch of the magnetic quiver yields the Higgs branch of the 6d system, (ii) all 'discrete gauging' and 'small E8 instanton transitions' have an explicit brane realisation, and (iii) exceptional symmetries arise directly from brane configurations.
Monday Apr. 29
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Bowen Chen, IASTU
Chapter 7 of Holographic Entanglement Entropy
Monday May 6
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Yuan Zhong, YMSC
Chapter 8 of Holographic Entanglement Entropy
Thursday May 9
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Babak Haghighat, YMSC
"M5 branes and theta functions"
Abstract: We propose quantum states for Little String Theories (LSTs) arising from M5 branes probing A- and D-type singularities. This extends Witten's picture of M5 brane partition functions as theta functions to this more general setup. Compactifying the world-volume of the five-branes on a two-torus, we find that the corresponding theta functions are sections of line bundles over complex 4-tori. This formalism allows us to derive Seiberg-Witten curves for the resulting four-dimensional theories. Along the way, we prove a duality for LSTs observed by Iqbal, Hohenegger and Rey.
Monday May 13
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Yuan Zhong, YMSC
Chapter 8 of Holographic Entanglement Entropy
Thursday May 16
SEMINAR
10.30 am at Jinchunyuan West Conference Room 1
Dongmin Gang, KIAS
"Magnetically charged Ads4 (Ads5) black hole from class R (class S) theories"
Abstract: I will talk about twisted index computation of 3d theory of class R associated hyperbolic 3-manifold M. Using 3d-3d relation, the index is given in terms of simple 3-manifold invariant, analytic torsion. From the expression, we found 1) a curious integral properties of analytic torsion at finite N, 2) full perturbative 1/N corrections at large N. The leading and log N subleading nicely match the supergravity computation and other perturbative terms give predictions on holographic dual gravity computation. I briefly comment on similar story for 4d class R theory on S1xM.
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Ben Heidenreich, University of Massachusetts Amherst
"The Weak Gravity Conjecture and Repulsive Forces"
Abstract: The Weak Gravity Conjecture postulates the existence of a particle with charge-to-mass ratio larger than that of an extremal black hole in any consistent quantum gravity. I review the evidence for the conjecture and some of its strong forms, and compare it with a subtly different conjecture that requires a charged particle that repels its identical copy at large separations. I discuss the evidence for this "repulsive force conjecture" and comment on its relationship to black holes, as well as its potential application to theories without gravity.
Monday May 20
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Boyang Yu, YMSC
Chapter 9 of Holographic Entanglement Entropy
Thursday May 23
IASTU SEMINAR
11 am at Conference Hall 322, Science Building (高等研究院)
Vijay Balasubramanian, University of Pennsylvania
"Quantum entanglement as a probe of hidden physics"
Abstract: A basic challenge facing the construction of fundamental theories of physics is that we have only have experimental access to coarse, low-energy probes. However, low-energy particles interact with high-energy degrees of freedom, and thus must be quantum mechanically entangled with them. In this talk I will suggest that we can use this entanglement between energy scales as a novel probe of high energy physics. In some scenarios in string theory, the consequence of this entanglement will be that low-energy observers will measure coupling constants of nature that appear to statistically variable.
AdS, DUALITY AND STRINGS SEMINAR
1.20 pm (starts 10 minutes earlier) at Jinchunyuan West 3rd floor
Dandan Xu, IASTU
"Legend of Sealed Book"
Abstract: In this talk, I will review a brief history of cosmology studies since the beginning of last century, in particular how the current cosmological picture is reached, its success and drawbacks. In particular, I will talk about a powerful astronomical tool named gravitational lensing, using which various theories on cosmology and galaxy formation can be tested and constrained.
Monday May 27
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Zi-Zhi Wang, IASTU
"On Renormalization Group Flows in Four Dimensions"
Thursday May 30
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Bartek Czech, IASTU
"Holographic Entropy Cone with Time Dependence"
Abstract: In the AdS/CFT correspondence, if a CFT state is dual to a semiclassical spacetime, its entanglement entropies (minimal surface areas) must obey certain inequalities. The best-known examples are the strong subadditivity of entanglement entropy (SSA) and the monogamy of mutual information (MMI). Together, such inequalities define the so-called holographic entropy cone. It is an interesting object because (a) it quantifies what is special about holography--how holographic CFTs are different from general quantum mechanical systems, and (b) it highlights special entanglement structures (bipartite, perfect tensor), which are the atomic ingredients for building up holographic spacetimes.
The holographic entropy cone is known for static states, but it is not known for time-dependent states. Is it possible to use time dependence to construct more general bulk spacetimes, which violate conditions that hold in static geometries? I will show that this does not happen in the AdS3/CFT2 correspondence. The argument has many interesting aspects: (a) it completely dispenses with any notion of a bulk slice, (b) it operates directly in kinematic space (space of CFT intervals), (c) it reduces to repeated applications of the strong subadditivity of entanglement entropy. I hope we will discuss the significance of these facts together.
Monday June 3
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Luis Apolo, YMSC
Chapter 12 of Holographic Entanglement Entropy
Thursday June 6
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Sung-Soo Kim, UESTC
"New developments in 5d SCFTs and 5-brane webs"
Abstract: In this talk, we will first review 5d superconformal theories (SCFTs) and its salient features. As geometric engineering, we then discuss how one can construct 5d SCFTs from Type II string theory or M-theory. We finally report recent developments in 5-brane web in Type II string theory including constructions of spinor representations and rank-3 antisymmetric hypermultiplets and their connection to 6d SCFTs.
Past events, Fall 2018
Tuesday Sep. 25
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Ju Zhu Chapters 1 & 2 of Ginsparg's Applied Conformal Field Theory
Thursday Sep. 27
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Bin Chen, Peking University
"Entanglement Entropy in TTbar-Deformed CFT"
Abstract: The TTbar-deformation of CFT presents an one-parameter class of integrable quantum field theory. In this talk, I would like to give a brief review on the recent development of TTbar deformed 2D CFT. In particular, I will discuss the holographic dual of the deformed CFT, and introduce our recent work on the entanglement entropy in the TTbar deformed CFT.
Monday Oct. 8
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Shuwei Liu, Tsinghua University
Chapters 3 & 4 of Ginsparg's Applied Conformal Field Theory
Thursday Oct. 11
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Hossein Yavartanoo, ITP
"H0 Tension & Swampland Conjectures"
Abstract: I will review some recent arguments on measuring Hubble parameter and H0 tension. Further, borrowing from the string theory tool- kit, I will present a holographic model that relieves the tension and predicts a turning point in the Hubble parameter at small redshift. This feature is easily falsified by upcoming
Monday Oct. 15
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Gongwang Yan, IASTU
Chapters 3 & 4 of Ginsparg's Applied Conformal Field Theory
Thursday Oct. 18
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Bartek Czech, IASTU
"Modular Berry Connection in CFT and Transport in AdS"
Abstract: A leading hypothesis about the emergence of a gravitational bulk spacetime in holographic duality is that spacetime is built out of quantum entanglement in the boundary theory. I will review one example of how the bulk "geometrizes" the boundary entanglement: lengths of spacelike curves in AdS3 compute a boundary quantity called differential entropy, which appropriately isolates IR contributions to entanglement entropies of CFT subregions. I will then explain a novel perspective on this older story: that differential entropy (and lengths of curves in AdS) are manifestations of the famous Berry phase -- a quantum phase, generated by a sequence of changing modular Hamiltonians in the CFT. As an illustration, we will look at the transport of CFT operators called OPE blocks (geodesic operators in AdS), where the Berry connection generates translations in AdS. A conjecture is that bulk transport in holography, perhaps in all generality, originates from modular Berry transformations.
Monday Oct. 22
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Shuhang Yang, YMSC
Chapters 4 & 5 of Ginsparg's Applied Conformal Field Theory
Thursday Oct. 25
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Andreas Braun, Oxford
"What's new in G_2?"
Abstract: Compact manifolds with the exceptional holonomy groups G_2 and Spin(7) can be used in M-Theory to geometrically engineer theories in 4D and 3D
with minimal supersymmetry. Building on new results in mathematics, we
review recent progress in the construction of such geometries, the
associated physics, and dualities to other string compactifications.
Monday Oct. 29
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Luis Apolo, YMSC
Chapter 5 of Ginsparg's Applied Conformal Field Theory
Wednesday Oct. 31
COLLOQUIUM
4.30 pm at Jinchunyuan West 3rd floor
Dieter Luest, MPI & LMU Munich
“Quantum Aspects of Black Holes”
Abstract: Although there is direct experimental evidence for the existence of black holes from the recent measurements of gravitational waves, black holes are still mysterious objects from the theoretical point of view. According to the seminal work of Stephen Hawking, all information about the collapsing matter that forms a black hole is lost during the evaporation of Hawking radiation. This loss of information is in sharp conflict with the rules of quantum mechanics. It is also closely related to the no hair theorem of classical black holes, which states a black hole cannot carry any other quantum numbers other than its mass, charge or its angular momentum. Hence it is mandatory to understand in a quantum theory of gravity what are the carriers of information in a black hole and which kind of quantum hair can be attributed to black holes. In this talk, I will first review how the quantum entropy of black holes emerges in string theory. Furthermore, I will also discuss a complementary picture for the hair of neutral Schwarzschild black holes. This part is based on some recent developments related to asymptotic symmetries in gravity. Finally I give some remarks on black holes as quantum computers.
Thursday Nov. 1
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Dieter Luest, MPI & LMU Munich
"Non-geometric fluxes and non-associativity in string/M-theory"
Abstract: In this talk I will discuss compactifications with geometric and non-geometric fluxes in string and in M-theory. These can be described by generalized geometry, double field theory and exceptional field theory. In particular I will discuss how non-geometric fluxes lead to a non-associative phase space structure, which is closely related to the non-associative algebra of the imaginary octonions.
Monday Nov. 5
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Boyang Yu, Tsinghua University
Chapter 7 of Ginsparg's Applied Conformal Field Theory
Thursday Nov. 8
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Falk Hassler, University of Oviedo
"Poisson-Lie T-duality in double field theory"
Abstract: A formulation of double field theory is presented which makes Poisson-Lie T-duality manifest. It allows to identify the doubled space with a Drinfeld double and provides a powerful tool to extract the transformation of the metric, B-field, dilaton and R/R potentials under Poisson-Lie T-duality.
Monday Nov. 12
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Yuan Zhong, Tsinghua University
Chapter 8 of Ginsparg's Applied Conformal Field Theory
Thursday Nov. 15
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Ioannis Papadimitriou, KIAS
"SQFTs on curved backgrounds and supersymmetry anomalies"
Abstract: I will discuss a new quantum anomaly for rigid supersymmetry on even dimensional curved backgrounds that admit Killing spinors and will show how it is related to the superconfomal anomalies that are determined by the Wess-Zumino consistency conditions. I will then explore the implications of this anomaly for the dependence of supersymmetric partition functions on the geometric data of the background, for the supersymmetric Casimir energy, as well as for supersymmetric localization.
Monday Nov. 19
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Zi-Zhi Wang, IASTU
Chapter 9 of Ginsparg's Applied Conformal Field Theory
Sections 11.4, 11.5, 15.4, and 15.5 of Polchinski's String Theory, volume 2.
Thursday Nov. 22
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Yiwen Pan, Zhongshan University
"Fiber-base duality and 3d dualities"
Abstract: 5d supersymmetric gauge theories often admit (p,q) web construction, and therefore enjoy the fiber-base duality which descends from the IIB S-duality. Such duality further leads to dualities in lower dimensional gauge theories. In this talk I will discuss simple examples where 5d fiber-base duality reduces to 3d mirror symmetry of gauge theories on intersecting spaces, and also possible connections to 3d-3d correspondence.
COLLOQUIUM
4 pm at Zheng Yutong Lecture Hall (郑裕彤讲堂)
Song He, ITP
"New structures and formulations for S-matrices"
Abstract: In the past decades and especially the last one, powerful new tools and remarkable new structures for perturbative scattering amplitudes in QFT have been discovered. Apart from playing a prominent role in high-energy particle physics, these developments have important implications for a wide range of subjects: from string perturbation theory to multi-loop calculations in (super)-gravity, from new mathematics to all-loop amplitudes in N=4 SYM. I will review some recent progress, focusing on two topics: (1) a string-inspired new formulation for amplitudes in gauge theories and gravity, and "double-copy” between them (2) new geometric structures underlying amplitudes which may hint at a ``theory at infinity” for S-matrices.
Thursday Nov. 29
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Max Riegler, ULB
"Warped Black Holes in Lower-Spin Gravity"
Abstract: In this talk I will talk about recent work (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 how to compute the thermodynamic properties of warped black holes in this theory.
Monday Dec. 3
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Bowen Chen, IASTU
WZW models
Thursday Dec. 6
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Alex Belin, University of Amsterdam
"Holographic Symplectic forms and extremal volumes: a new York time story"
Abstract: In this talk, I will explain how the gravitational symplectic form between nearby AAdS geometries is dual to a quantum Kahler form on the space of euclidean path integral states with sources turned on. As an application, I will show that variations of extremal volumes can be computed using this symplectic form by considering a particular variation: the “new York” variation, which I will describe in detail. Finally, I will discuss the CFT interpretation of this deformation in some concrete examples like the vacuum and the TFD state at late times.
Monday Dec. 10
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Pankaj Chaturvedi, YMSC
WZW models and Chern-Simons theories
Thursday Dec. 13
AdS, DUALITY AND STRINGS SEMINAR
1.30 pm at Jinchunyuan West 3rd floor
Sangmin Lee, SNU
"Brane brick models, colored quivers, and calibrated geometry"
Abstract: Brane brick model (BBM) is a dictionary between toric Calabi-Yau 4-fold cones and 2d (0,2) quiver gauge theories. It arises from D1-branes probing the Calabi-Yau cones. In the first half of the talk, we explain what has been done to establish BBM.In the second half, we explain how BBM and its generalizations make contact with various mathematical objects such as colored quivers and a co-associative 4-cycle in a manifold with a G2 structure.
Monday Dec. 17
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Wenxin Lai (赖文昕), PKU & Yu Hao (郝雨), NKU
Introduction to orbifolds and its applications in CFT
Thursday Dec. 20
AdS, DUALITY AND STRINGS SEMINAR
11.45 am at Jinchunyuan West 3rd floor
Si Li, YMSC
“Homotopy Algebras in Higher Spin Theory”
Abstract: Motivated by string field theory, we explain various algebraic aspects of higher spin theory and Vasiliev equation in terms of homotopy algebras. We present a systematic study of unfolded formulation developed for the higher spin equation in terms of the Maurer-Cartan equation associated to differential forms valued in L-infinity algebras. The elimination of auxiliary variables of Vasiliev equation is analyzed through homological perturbation theory. We also discover a topological quantum mechanics model whose correlation functions give deformed higher spin vertices at first order. This is joint work with Keyou Zeng
Monday Dec. 24
JOURNAL CLUB
12 pm at Jinchunyuan West Conference Room 1
Shunyu Yao, THU
On space of integrable quantum field theories
Thursday Dec. 27
AdS, DUALITY AND STRINGS SEMINAR
1:30 pm at Jinchunyuan West 3rd floor
Jihuan Tian, Northeastern University
"Non-simply-laced symmetry algebras in F-theory on singular spaces"
Abstract: We demonstrate how non-simply-laced gauge and flavor symmetries arise in F-theory on spaces with non-isolated singularities. The breaking from a simply-laced symmetry to one that is non-simply-laced is induced by Calabi-Yau complex structure deformation. In all examples the deformation maintains non-isolated singularities but is accompanied by a splitting of an I_1 sevenbrane that opens new loops in the geometry near a non-abelian seven-brane. The splitting also arises in the moduli space of a probe D3-brane, which upon traversing the new loop experiences a monodromy that acts on 3-7 string junctions on the singular space. The monodromy reduces the symmetry algebra, which is the flavor symmetry of the D3-brane and the gauge symmetry of the seven-brane, to one that is non-simply-laced. A collision of the D3-brane with the seven-brane gives rise to a 4d N = 1 SCFT with a non-simply-laced flavor symmetry.
Thursday Jan. 3, 2019
AdS, DUALITY AND STRINGS SEMINAR
1:30 pm at Jinchunyuan West 3rd floor
Zhihao Duan, ENS
"Computing the elliptic genus of higher rank E strings from genus 0 GW invariants"
Abstract: In this talk, I will discuss the elliptic genera of BPS strings in 6d SCFTs. As we shall see, they are determined by a finite amount of data thanks to their modular property. Therefore, a crucial step is to impose suitable boundary conditions to fix them. Different from the vanishing conditions explored in arXiv: 1701.00764 and arXiv:1712.07017, we analyse the pole structure of the elliptic genera and reconstruct them using only their polar parts. The main goal of this talk is to show that the elliptic genus of higher rank E-strings can be computed based solely on the genus 0 Gromov-Witten invariants of the corresponding elliptic geometry. The talk is based on arXiv: 1810.01280.