AdS(Algeometry, duality and Strings) seminar
Student No.:20
Time:Thu 13:30-15:00
Instructor:Song Wei, Yan Wenbin, Lin Hai, Xu Jianfei  
Place:Lecture Hall, Jin Chun Yuan West Bldg.
Starting Date:2018-3-8
Ending Date:2018-6-21


Speaker:Prof. Massimo Porrati [NTU]

Title: A proposal for the CFT dual for superstrings on ADS3 at the string radius

Abstract:After a review of the spectrum of superstrings on the AdS3 WZW background, I will review evidence for a phase transition when the AdS radius becomes of order of the string length. I will then propose a holographic dual CFT that matches exactly the entire continuous spectrum of the superstring. I will conclude with a few observations on the role of discrete, short-string states and on interactions.



Speaker:Prof. Ya-wen Sun [University of Chinese Academy of Sciences]

Title: Holographic semimetals and topological invariants

Abstract:In this talk I will present how machine learning techniques can be useful in string theory. In the first example I discuss a novel algorithm for obtaining finding regular, fine-star triangulations for reflexive polytopes. Our algorithm utilises successful techniques from object recognition. The second example utilises generative adversarial networks which are a powerful tool to generate (fake) data with desired properties. I present a framework to generate new SUSY models using GANs. As a proof of principle, we construct a GAN which generates superpotentials. The features of these superpotentials go beyond the polynomial examples known to the network.


Speaker:Dr. Sven Krippendorf [LMU]

Title: Exploration of parameter space in supersymmetry and string theory using machine learning

Abstract:Topological states of matter have been a research focus in condensed matter physics for the past decade. I will introduce a framework in holography to generate gapless topological semimetal states. As explicit examples, we introduce the holographic model of Weyl semimetals and topological nodal-line semimetals. In each of these systems, there exists a quantum phase transition between the topologically trivial semimetal states and the topologically nontrivial Weyl/nodal-line semimetal states. Evidence including anomalous transport properties and "ARPES" calculations as well as predictions for possible new transport properties, including the presence of Hall viscosity associated with the mixed gauge gravitational anomaly, will be discussed. Finally we will specially focus on the calculation of nontrivial topological invariants from the dual fermion Green functions. This suggests that at strong coupling we could still have a physical system with the essential properties of the weakly coupled topology semimetals.


Speaker:Vishnu Jejjala [University of the Witwatersrand]

Title: Hot Attractors

Abstract:Non-extremal black holes, which emit thermal Hawking radiation, have two horizons: the event horizon or outer horizon and the Cauchy horizon or inner horizon. Surprisingly, for a broad class of solutions to the Einstein equations, the product of the areas of the inner and outer horizons is the square of the area of the horizon of the zero temperature black hole obtained from taking the smooth extremal limit. We use the attractor mechanism in supergravity to motivate this statement. Non-extremal geometries at the Reissner-Nordström point, where the scalar moduli are held fixed, can be lifted to solutions in supergravity with a near-horizon AdS3×S2. These solutions have the same entropy and temperature as the original black hole and therefore allow an interpretation of the underlying gravitational degrees of freedom in terms of CFT2. Symmetries of the moduli space enable us to explicate the origin of entropy in the extremal limit. We consider various generalizations of these results.


Speaker:Ivano Lodato [Fudan University]

Title: The BMS_3/GCA_2 boostrap set-up

Abstract:I will start with an introduction to BMS symmetries, and the BMS_3/GCA_2 correspondence. After explaining the motivation behind our studies, I will show how these ultra (BMS) and non (GCA)-relativistic algebras can be derived from a consistent Inonu-Wigner contractions of the Virasoro algebra. In the second part I will present in detail how to set-up the bootstrap procedure for the two N=2 supersymmetric extensions of the Galilean conformal algebra, the democratic and despotic Susy algebras, and in particular I will give the explicit expression for the (super-)GCA blocks and comment on interesting future directions.


Speaker: Taoli Cheng [University of Chinese Academy of Sciences]

Title: Introduction to Deep Neural Networks in Jet Tagging at the LHC

Abstract: In this talk we will introduce recent applications of deep neural networks in high energy physics, especially in jet tagging. As a specific example, we will talk about using recursive neural networks to discriminate quark and gluon jets at the LHC.



Speaker: Sung-Soo Kim

Title: 5d rank 2 SCFTs, Brane webs, and Dualities

Abstract: In this talk, we will review brane constructions for 5d superconformal theories (SCFTs) of rank 2, based on Type IIB (p,q) 5-branes. We then discuss various dualities from the perspective 5-brane webs.




Speaker: Wen Qiang [YMSC]

Title: Fine structure in holographic entanglement

Abstract: We explore the fine structure of the holographic entanglement entropy proposal in  AdS33/CFT2. With the guidance from the boundary and bulk modular flows we find a natural slicing of the entanglement wedge with the modular planes, which are co-dimension one bulk surfaces tangent to the modular flow everywhere. This gives an one-to-one correspondence between the points on the boundary interval A and the points on the Ryu-Takayanagi (RT) surface EA. In the same sense an arbitrary part A2 of the interval A will correspond to a part E2 of EA.




Speaker: Qing-Guo Huang [ITP CAS]

Title: Gravitational Wave: a probe to the early universe

Abstract: I will focus on two kinds of gravitational waves in our Universe. One is the so-called primordial gravitational wave generated from vacuum during inflation and the other is the gravitational wave from merger of primordial black hole binaries. And we will discuss how we can learn a lot about the physics in the early universe from them.





Speaker: Ioannis  Papadimitriou [KIAS, Korea]

Title: 5D Rotating Black Holes and the nAdS2/nCFT1 Correspondence

Abstract: I will discuss a consistent Kaluza-Klein reduction of 5D Einstein gravity on warped S^2 x S^1 that includes the Myers-Perry or Kerr-AdS black holes with two equal angular momenta as special cases. The effective 2D theory admits an AdS2 vacuum corresponding to the extremal Kerr black hole. I will holographically derive the quantum effective action of the dual 1D theory in conformal perturbation theory around the extremal solution and will show how the presence of a conformal anomaly gives rise to the Schwarzian effective action. I will conclude with some comments on black hole thermodynamics.





Speaker: Kowshik Bettadapura [Australian Natl. U.]

Title: On splitting deformations of super Riemann surfaces

Abstract: In this talk I will introduce super Riemann surfaces and their deformations. The goal is to classify them as complex superspaces, thereby studying aspects of the local geometry of the corresponding moduli space. I will present some recent results and open questions in this direction.




Speaker: Joonho Kim [KIAS, Seoul]

Title: Wilson surface in M5-branes

Abstract: In this talk, I will discuss about Wilson surface defects in 6d (2,0) superconformal field theories, engineered by semi-infinite M2-branes intersecting M5-branes. I will explain two field-theoretic ways to compute Wilson surface observables on R4 X T2; One way is to study 5d N=1* instanton partition functions in the presence of Wilson lines, using the fact that 5d maximal SYM instantons capture Kaluza-Klein momentum modes along the (reduced) 6th circle; The other way is to study the elliptic genera of a 2d gauge theory, which we propose as describing the worldsheet physics of 6d BPS strings in the presence of Wilson surfaces. Both results are precisely in agreement for Wilson surfaces in minuscule representations. However, for non-minuscule representations, I will describe a subtlety (and a challenge) arising in computation of the elliptic genera.