Holographic Interfaces in Symmetric Product Orbifolds

The study of non-local operators in gauge theory and holography, such as line-operators or interfaces, has attracted significant attention. Two-dimensional symmetric product orbifolds are close cousins of higher-dimensional gauge theory. In this work, we construct a novel family of interfaces in symmetric product orbifolds. These may be regarded as two-dimensional analogues of Wilson-line operators or Karch-Randall interfaces at the same time. The construction of the interfaces entails the choice of boundary conditions of the seed theory. For a generic seed theory, we construct the boundary states associated to the interfaces via the folding trick, compute their overlaps and extract the spectrum of interface changing operators through modular transformation. Then, we specialise to the supersymmetric four-torus $\mathbb{T}^4$ and show that the corresponding interfaces of the symmetric product orbifold are dual to $AdS_2$ branes in the tensionless limit of type IIB superstring theory on $AdS_3 \times S^3 \times \mathbb{T}^4$.