Condensed Matter

We observe that boundary correlators of the elementary scalar field of the Liouville theory defined on rigid AdS2 background are the same as the correlators of the chiral stress tensor of the Liouville CFT on the complex plane restricted to the real line. The same relation generalizes to the conformal abelian Toda theory: correlators of Toda scalars on AdS2 are directly related to those of the chiral W-symmetry generators in the Toda CFT and thus are essentially controlled by the underlying infinite-dimensional symmetry. These may be viewed as examples of AdS2/CFT1 duality where the CFT1 is the chiral half of a 2d CFT. Similar relation applies also to a non-abelian Toda theory containing a Liouville scalar coupled to a 2d sigma-model originating from the SL(2,R)/U(1) gauged WZW model. Here the Liouville scalar is again dual to the chiral stress tensor T while the other two scalars are dual to the parafermionic operators V± of the non-abelian Toda CFT. The duality is checked at the next-to-leading order in the large central charge expansion by matching the chiral CFT correlators of (T,V+,V−) with the boundary correlators of the three Toda scalars given by the tree-level and one-loop Witten diagrams in AdS2. Based on arXiv:1904.12753,1907.01357.

I will overview recent results on the defect CFT corresponding to Wilson loop operators in N=4 SYM theory. In particular, I will review the calculation of defect correlators at strong coupling using the AdS2 string worldsheet, and I will present exact results for correlation functions in a subsector of the defect CFT using localization. I will also discuss a defect RG flow from the BPS to the ordinary Wilson loop, which can be used to provide a test of the "defect F-theorem" for one-dimensional defects.

In this talk, I will briefly discuss the construction of semiclassical 1/2-BPS boundary conditions and duality interfaces in 3d N=2 theories, following work with T. Dimofte and D. Gaiotto. Then, I will sketch some mathematical applications of these codimension-1 defects to the geometry of triangulated 4-manifolds and chiral algebras, based on work with T. Dimofte and building off related advances by Gadde, Gukov, and Putrov. I will also mention recent and ongoing work on generating 2d dualities from dual "sandwich" configurations of 3d theories sandwiched by both left and right boundary conditions.

A four-dimensional abelian gauge theory can be coupled to a 3d CFT with a U(1) symmetry living on a boundary. This coupling gives rise to a continuous family of boundary conformal field theories (BCFTs) parametrized by the gauge coupling \tau and by the choice of the CFT in the decoupling limit. Upon performing an Electric-Magnetic duality in the bulk and going to the decoupling limit in the new frame, one finds a different 3d CFT on the boundary, related to the original one by Witten's SL(2, Z) action. In particular the cusps on the real \tau axis correspond to the 3d gauging of the original CFT. We study general properties of this family of BCFTs. We show how to express bulk one and two-point functions, and the hemisphere free-energy, in terms of the two-point functions of the boundary electric and magnetic currents. Finally, upon assuming particle-vortex duality (and its fermionic version), we show how to turn this machinery into a powerful computational tool to study 3d gauge theories.

The partnership between 3D gravity and Chern-Simons theory is well-known and powerful, but many aspects of this relation are unclear. In this talk I'll discuss Wilson lines in Chern-Simons theory and their role in AdS3 gravity. Wilson lines are interesting objects to explore locality in Chern-Simons theory, and how they affect the partnership at the quantum level.

I will start by reviewing the definition and properties of complexity as well as the relevant holographic proposals. I will then describe the results of [1811.12549] where we studied the two holographic complexity proposals for the case of a 2d boundary CFT with a conformal defect using a Randall-Sundrum type model of a thin AdS_2 brane embedded in AdS_3. Our results indicate that this setup can be used to distinguish the two holographic proposals for the complexity. I will also describe results for simple free bosonic field theory models which include two defects on opposite sides of a periodic domain.

We review recent results on the calculation of one-point functions in dCFTs corresponding to N=4 SYM with domain walls, discussing supersymmetric as well as non-supersymmetric cases. In particular, we address the integrability properties of the theories and the status of the comparison to dual string theoretical computations.

We show that when an external magnetic field parallel to the boundary is applied, Weyl anomaly give rises to a new anomalous current transport near the boundary. Similar to the Casimir effect, this transport phenomena has its origin in the effect of the boundary on the quantum fluctuations of the vacuum. The near-boundary current takes universal form for general boundary quantum field theories, which are covariant, gauge invariant, unitary and renormalizable. We verify the universal law of current by studying free QFT and holographic BCFT. Finally, we discuss the so-called "divergence" problem and show that it can be resolved by the law of conservation of charge.