Xinyu Sun

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Conformal field theories (CFTs) capture universal features of critical and gapless systems through compact conformal data—scaling dimensions and OPE coefficients. Introducing a boundary or defect preserves a subgroup of conformal symmetry and enriches this data via boundary primaries and the boundary operator expansion (BOE). In this talk I survey boundary CFTs (BCFTs) and their holographic duals with an emphasis on phase transitions and conformal data. I will (i) present results on boundary criticality, including the novel extraordinary transition in the tricritical O(N) model, which is the first nontrivial example of spontaneous continuous symmetry breaking confined to a two-dimensional boundary; (ii) discuss analytic bootstrap for BCFTs with interacting boundaries, including nonunitary-boundary CFTs that were previously inaccessible to conformal bootstrap; and (iii) briefly introduce our AdS/BCFT results, showing how weak measurements in QFT creates an interface brane in the dual geometry, and if time allows, how boundary condition changing operators and cusps can be characterized by corners on the interface branes in a general DCFT. Taken together, these threads provide an overview of novel phase transitions and structures in BCFTs and clarify the role of AdS/CFT duality in understanding the properties of boundaries and defects in CFTs.

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Tsinghua University
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Contact: Simon Trebst