AdS(AdS, duality and Strings) seminar
Student No.:50
Time:Thursday 13:30-15:00, 2017-2-23~2017-7-13
Instructor:Babak Haghighat, Hai Lin, Wei Song, Qiang Wen, Jianfei Xu  
Place:Conference room 3, Floor 2, Jin Chun Yuan West Building
Starting Date:2017-2-23
Ending Date:2017-7-13

This is a weekly seminar of the string theory group at YMSC



Date: 2017-07-13



Speaker: Ping Gao (Harvard U.)  



Time: 13:30-15:00  



Place: Conf. Room 3, Jin Chun Yuan West B., THU.




Title: Traversable Wormholes via a Double Trace Deformation



Abstract: After turning on an interaction that couples the two boundaries of an eternal BTZ black hole, we find a quantum matter stress tensor with negative average null energy, whose gravitational backreaction renders the Einstein-Rosen bridge traversable. Such a traversable wormhole has an interesting interpretation in the context of ER=EPR, which we suggest might be related to quantum teleportation. It could also be interpreted as Hayden-Preskill qubit recovery protocol. However, it cannot be used to violate causality. I will discuss some recent studies about such traversables wormholes in 2d/SYK background.




Date: 2017-07-07     


Speaker: Yingfei Gu (Stanford U)    


Time: 2017-07-07 15:00-17:00  


Place: Room 304, Jing Zhai B., THU.


Title: the butterfly effect in solvable quantum many-body systems


Abstract: the classical “butterfly effect” refers to the exponential sensitivity of the dynamics to the initial conditions. Recently, a quantum mechanical version of the butterfly effect was proposed as a diagnostic of quantum chaos. A key notion in such diagnostic is the out-of-time ordered correlator. In this talk, I will first give a review of this new tool and then apply it to some solvable quantum many-body systems, including two-dimensional rational conformal field theories and Sachdev-Ye-Kitaev model in high dimensions. It turns out the butterfly effects in these solvable models are closely related to other properties in precise forms.



Date: 2017-06-23      


Speaker: Tassos Petkou (Aristotle U. of Thessaloniki)    


Time: 2017-06-23, 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: Generalized Wilson-Fisher critical points from conformal symmetry



Abstract: Generalized massless free theories can be consistently defined as CFTs. Their nearby Wilson-Fisher critical points can be studied using the analytic structure of generic conformal blocks. This way we obtain the leading order nontrivial anomalous dimensions and critical couplings for a wide classes of theories, including generalized multicritical points, O(N) models and modes with multiple marginal deformations. Our results reveal an intriguing underlying structure in the web of generalized CFTs, which is intimately connected to higher-spin theory.




Date: 2017-05-25     


Speaker: Jia-Rui Sun (SYSU)    


Time: 2017-05-25, 13:00-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: Acoustic black holes vs real black holes--a holographic viewpoint


Abstract: Acoustic black holes are analogous models which were originally proposed to simulate various properties of real gravitational systems, such as the geometry of curved spacetime and the Hawking radiation. Despite that acoustic black holes exhibit behaviours resemble to those caused by gravity, they were mostly regarded as an analogy due to the lack of dynamical connections with the gravitational fields. In this talk, we show that, from the holographic viewpoint, an acoustic black hole in fluid can indeed be mapped to a real black hole in asymptotically AdS spacetime. The mapping is supported by the matching between their dynamics, the connection between the Hawking-like temperature and the Hawking temperature, as well as the duality between the phonon and the sound channel quasinormal mode.



Date: 2017-05-24      


Speaker: Jian-Xin LU (ICTS-USTC)    


Time: 2017-05-24, 15:30-17:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: On 1/4 BPS ((F, D1), (NS5, D5)) bound state of IIB superstring



Date: 2017-05-19       

Speaker: Gaurav Narain (ITPCAS)    


Time: 2017-05-19 15:30-17:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: Exorcising ghosts in Induced Gravity


Abstract: Unitarity of scale-invariant coupled theory of higher-derivative gravity and matter is considered. A scalar field coupled with dirac fermion is taken as matter sector. The problem is investigated along the ideas of induced gravity where the Einstein-Hilbert term is generated via dynamical symmetry breaking of scale-invariance. The renormalisation group flows are computed in 4-epsilon dimensional regularisation scheme, and one-loop RG improved effective potential of scalar is calculated. Scalar field develops a new minimum in the quantum theory via Coleman-Weinberg procedure and in turn induces Newton's constant and masses in the matter sector. The spin-2 problematic ghost and the spin-0 mode of the metric fluctuation gets a mass in the broken phase of theory. The energy-dependence of VeV in the RG improved scenario implies a running for the induced Newton's constant and masses. This sets up platform to ask the meaningful question whether it is possible to evade the problesilonmatic spin-2 ghost by keeping its   mass always above the running energy scale? In broken phase it is seen that this question can be satisfactorily answered for a large domain of coupling parameter space, where the spin-2 ghost becomes innocuous.



Date: 2017-05-11       


Speaker: Rak-Kyeong Seong (Uppsala U.)    


Time: 2017-05-11 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: Branes and 2d (0,2) Quiver Gauge Theories


Abstract: In this talk, I will present recent progress in realizing 2d (0,2) theories in terms of branes. The novel Type IIA brane configuration, which we call Brane Brick Models, consists of D4-branes suspended from a NS5-brane wrapping a holomorphic surface, tessellating a 3-torus. Brane Brick Models are T-dual to D1-branes over singular toric Calabi-Yau 4-folds and fully encode the large class of 2d (0,2) quiver gauge theories on the worldvolume of the D1-branes. By use of techniques from combinatorics and tropical geometry, I will illustrate how Brane Brick Models streamline the connection between the 2d (0,2) quiver gauge theories and the probed Calabi-Yau geometries. As an application, I will explain how Gadde-Gukov-Putrov triality is realized in terms of branes as a local mutation of Brane Brick models.



Date: 2017-05-04     


Speaker: Rong-Xin Miao (Taiwan Nati. THU)     


Time: 2017-05-04 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU


Title: A New Proposal for Holographic Boundary CFT


Abstract: We propose a new holographic dual of conformal field theory defined on a manifold with boundaries, i.e. BCFT. Our proposal can apply to general boundaries and agrees with arXiv:1105.5165 for the special case of a disk and half plane. Using the new proposal of AdS/BCFT, we successfully obtain the expected boundary Weyl anomaly and the obtained boundary central charges satisfy naturally a c-like theorem holographically. We also investigate the holographic entanglement entropy of BCFT and find that the minimal surface must be normal to the bulk spacetime boundaries when they intersect. Interestingly,the entanglement entropy depends on the boundary conditions of BCFT and the distance to the boundary. The entanglement wedge has an interesting phase transition which is important for the self-consistency of AdS/BCFT.



Date: 2017-04-26    


Speaker: Haitang Yang (Sichuan U.)    


Time: 10:00am-12:00am  


Place: Conf. room, Floor 3, Jin Chun Yuan West B., THU (近春园西楼三楼大报告厅)    


Title: Correspondence between genus expansion and alpha' expansion in string theory






Date: 2017-04-20        


Speaker: Nick Houston (ITP)


Time: 2017-04-20 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU     


Title: Supersymmetric, fermionic states in three-dimensional supergravity


Abstract: By virtue of the symmetry they preserve, BPS solutions in supergravity and string theory possess special properties and utility, and accordingly, have over many years been thoroughly investigated and classified. However despite this intense research effort, the space of these solutions is nonetheless almost entirely unexplored in one direction; that is, when fermions such as the gravitino act non-trivially. This of course needn't be the case. We detail a recent construction of novel fermionic BPS solutions in three-dimensional supergravity, and explore their properties. Possessing no purely bosonic analogue, they include fermionic black holes and solutions which would ordinarily be non-geometric in general relativity.



Date: 2017-04-13        


Speaker: Fen Zuo (Hua-Zhong U. Sci. Tech.)    


Time: 2017-04-13 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU     


Title: Stringy quantum geometry


Abstract: Around 2010, Liang Kong proposed an interesting notion of viewing 2d conformal field theories as "stringy algebraic geometry". Here we try to generalize such a notion to a 4d "stringy quantum geometry". That this could be possible is due to two important facts: first, in the mathematical construction of (rational) conformal field theories (FRS framework), the local data and the topological structure are in fact separated; secondly, the bulk-boundary correspondence could been concretely categorificated as the "bulk=center" relation, as shown recently by L. Kong and X-G. Wen.


With such a construction we try to answer two questions: what's the topological meaning of the simplicity condition which formally deforms the BF theory to general relativity? how the Bekenstein-Hawking formula for the black hole entropy is achieved?



Date: 2017-04-06

Speaker: Yan Liu (Beihang U.)    


Time: 2017-04-06 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU     


Title: Chiral matter: hydrodynamics and holography


Abstract: Chiral matter refers to a quantum many body system involving chiral fermions. Novel experimental realisations include the quark-gluon plasmas created in heavy ion collision, Weyl semimetals and so on. Theoretically a remarkable property of chiral matter is the presence of unusual (macroscopic) transport phenomena related to quantum anomalies in field theory and therefore it has attracted a lot of interest in the last few years. In this talk, I will first give a brief review on the recent progress of hydrodynamic descriptions of chiral matter, with an emphasis on the open questions of this description. Then I will talk about the holographic dual for chiral matter and the phase diagrams from holography. I will explain the puzzles on the holographic system related to the mixed gauge-gravitational anomaly.



Date: 2017-03-30        


Speaker: Shaokai Jian (IAS, THU)    


Time: 2017-03-30 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU     


Title: Solvable SYK models in higher dimensions: a new type of many-body localizationtransition


Abstract: Many aspects of many-body localization (MBL) transitions remain elusive so far. Here, we propose a higher-dimensional generalization of the Sachdev-Ye-Kitaev (SYK) model and show that itexhibits an MBL transition. The model on a bipartite lattice has N Majorana fermions with SYKinteractions on each site of A-sublattice and M free Majorana fermions on each site of B-sublattice.For rM/N rc [D(rc −r)1/2], implying a dynamical transition to an MBL phase.It is further supported by numerical calculations of level statistics which changes from Wigner-Dyson(rrc) distributions. Note that no subdiffusive phase intervenes between diffusive and MBL phases. Moreover, the critical exponent ν=0, violating the Harris criterion. Ourhigher-dimensional SYK model may provide a promising arena to explore exotic MBL transitions.



Date: 2017-03-23         

Speaker: Dmitry Polyakov (Sichuan U.)    


Time: 2017-03-23 13:30-15:00   


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU    


Title: An Analytic Formula for Numbers of Restricted Partitions from Conformal Field Theory







Date: 2017-03-15         


Speaker: Hossein Yavartanoo (ITP)    


Time: 2017-03-15 13:30-15:00  


Place: Conf. room 4, Floor 2, Jin Chun Yuan West B., THU    


Title: Combing the Horizon Fluff: Logarithmic corrections to black hole entropy from horizon fluff proposal


Abstract: According to the horizon fluff proposal microstates of a generic black hole is a certain subset ofnear horizon soft hairs that cannot be extended to beyond the near horizon region. Previously we have discussed how horizon fluff proposal works for AdS3 black holes. In this talk I will clarify furtherthe picture for BTZ black holes and their microstates arising from the proposal. In particular, I will show that BTZ black hole microstates are in general among the set of conic defects or theirVirasoro descendants and that a BTZ black hole may be viewed as a condensate, solitonicstates, of AdS3 particles. I will also provide canonical and microcanonical descriptions of statisticalmechanical system associated with BTZ black holes and their microstates and that how thetwo are related. Using the latter and as a further non-trivial check, we will se how the horizon fluffproposal precisely reproduces the logarithmic corrections to the BTZ entropy, as expected fromthe logarithmic corrections to the Cardy formula.




Date: 2017-03-16        


Speaker: Zhibin Li (IHEP)    


Time: 2017-03-16 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU     


Title: Mutual information of two intervals in AdS3/CFT2


Abstract: We consider the (Renyi) mutual information of two intervals in AdS3/CFT2. In CFT side we calculate the RMI and MI from the OPE of twist operators. For the dual AdS we need to use the partition function of handlebody. We also consider the contributions of W3 and W4 operators.




Date: 2017-03-09       


Speaker: Hui-Huang Chen (IHEP)    


Time: 2017-03-09 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU    


Title: γ-deformed ABJM theory and Y-system


Abstract: In this talk I will show some of the integrable aspects of the planar γ-deformed ABJM theory and propose the twisted asymptotic Bethe ansatz equations. A more general method through a twisted generating functional is discussed, based on which, the asymptotic large L solution of Y-system is modified in order to match the asymptotic Bethe ansatz equations. Several applications of our method in the sl(2)-like sector and some important examples in β-deformed ABJM are presented as well.



Date: 2017-03-02         

Speaker: Ling-Yan Hung (Fudan U.)    


Time: 2017-03-02 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU    


Title: Exploring the tensor network/ ads correspondence -- bulk operator reconstruction


Abstract: I will discuss some recent developments in exploring the similarities between tensor networks and the ads/cft correspondence. In this talk, we will focus particularly on the bulk operator reconstruction from the boundary. We find some very interesting parallels between the tensor network and the HKLL formula in the ads/cft dictionary. We also discuss the realization of global symmetries in the form of gauge symmetries in the tensor network bulk. We illustrate some of these ideas using the p-adic ads/cft as a toy example.



Date: 2017-02-23  


Speaker: Mei Huang (IHEP)   


Time: 2017-02-23 13:30-15:00  


Place: Conf. room 3, Floor 2, Jin Chun Yuan West B., THU   


Title: Dynamical holographic QCD model