A Defect in AdS3/CFT2 Duality

TL;DR

This paper explores an explicit example of AdS3/BCFT2 duality by extending string theory in AdS3 to include open strings via a D-brane, revealing a deformed symmetric product structure in the dual boundary theory.

Contribution

It introduces a semi-classical D-brane in AdS3 to model open strings, extending the duality to include boundary conformal field theories with explicit boundary deformations.

Findings

Constructs an AdS3/BCFT2 duality with open strings.

Shows the boundary theory is a deformed symmetric product.

Provides a framework for open/closed string transitions.

Abstract

$AdS_3$ string theory in the stringy regime $k=(R_{AdS}/\ell_{str})^2 < 1$ provides a laboratory for the study of holography in which both sides of AdS/CFT duality are under fairly good control. Worldsheet string theory is solvable, and for closed strings the dual spacetime CFT is a deformation of a symmetric product orbifold. Here we extend this construction to include open strings by adding a probe D-string, described semi-classically by an $AdS_2$ D-brane in $AdS_3$. The dual defect or boundary conformal field theory (BCFT) is again a deformed symmetric product, which now describes the Fock space of long open and closed strings near the AdS boundary, with a boundary deformation implementing the open/closed transition in addition to the symmetric product ${\mathbb Z}_2$ twist deformation that implements closed string joining/splitting. The construction thus provides an explicit example of an $AdS_3/BCFT_2$ duality.