Date: September 3

Time: 09:30 IST (UTC + 5:30) Rescheduled on Sep 24

Speaker: Kristan Jensen (San Francisco State University)

Title: AdS3 gravity and random CFT (Euclidean wormholes in D > 2 and AdS/CFT)

• Abstract: We compute the path integral of three-dimensional gravity with negative cosmological constant on spaces which are topologically a torus times an interval. These are Euclidean wormholes, which smoothly interpolate between two asymptotically Euclidean AdS3 regions with torus boundary. From our results we obtain the spectral correlations between BTZ black hole microstates near threshold, as well as extract the spectral form factor at fixed momentum, which has linear growth in time with small fluctuations around it. The low-energy limit of these correlations is precisely that of a double-scaled random matrix ensemble with Virasoro symmetry. Our findings suggest that if pure three-dimensional gravity has a holographic dual, then the dual is an ensemble which generalizes random matrix theory.

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Date: September 10

Time: 17:30 IST (UTC + 5:30)

Speaker: Francisco Peña-Benitez (MPI Dresden)

Title: Weyl Semimetals

• Abstract: After the discovery of Graphene a new fauna of materials with a semi-metallic spectrum, have been predicted, some of them showing a linear dispersion relation. Actually, in Weyl semimetals the low energy excitations are described in term of Weyl fermions. Therefore, the phenomenology of these systems is enriched by the presence of quantum anomalies, and more generally “relativistic” quantum mechanics. Notice, that even though the dispersion relation is linear, electrons inside a Weyl semimetal usually propagate with a velocity three orders of magnitude smaller than the speed of light. In this seminar, I will introduce the properties of Weyl semimetals and their exotic cousins, usually called multi-Weyl semimetals. In addition, I will discuss the current experimental status of the so-called anomaly induced transport, which happens to be a macroscopic manifestation in transport of chiral anomalies. Finally, on a more theoretical ground I will comment on the holographic realisation of these systems, as a toy model for the cases in which electrons suffer of strong interactions.

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Date: September 17

Time: 17:30 IST (UTC + 5:30)

Speaker: Yun-Long Zhang (YITP, Kyoto University)

Title: Fluid/Gravity on Finite Cutoff and Accelerating Universe

• Abstract: Based on the fluid/gravity on the finite cutoff surface, the Rindler fluid has been proposed as a good approximation of the black hole membrane paradigm. I will introduce the properties and transports of the dual Rindler fluid as well as cutoff AdS fluid from our investigations. Besides, this approach can also be generalized to the de Sitter universe on a dynamical cutoff surface, which is similar to the braneworld scenarios. I will discuss the effective description of the dual fluid with the induced metric as dS or FRW background, as well as their connection with swampland conjecture on the accelerating universe. [Refs: 1705.05078 & 1812.11105 & 1905.10950].

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Date: September 29

Time: 17:30 IST (UTC + 5:30)

Speaker: Rajesh Gopakumar (ICTS-TIFR)

Title: The AdS_3/CFT_2 Correspondence

• Abstract: I will give a pedagogical description of recent work on deriving the AdS_3/CFT_2 correspondence in a special tensionless limit. This is a duality between string theory on AdS_3\times S^3\times T^4 with one unit of NS-NS flux and a free symmetric orbifold 2d CFT (T^4)N/S_N (in a large N limit). I will mainly focus on how correlators in the worldsheet theory go over into those of the symmetric orbifold CFT due to a rather remarkable localisation on the worldsheet moduli space. This, in some sense, tautologises the AdS/CFT correspondence in this particular case and reveals a novel connection between the worldsheet and boundary spacetime theories.

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