Permeable conformal walls and holography

TL;DR

This paper investigates conformal domain walls in 2D CFTs, their holographic duals in AdS3, and computes Casimir energies, revealing new insights into supersymmetry, folding, and brane configurations.

Contribution

It develops tools for analyzing conformal walls, extends folding concepts, and connects Casimir energy calculations with holographic duals and sigma models.

Findings

Casimir energy expressed via dilogarithm of reflection probability

Holographic duals involve branes connecting walls in AdS3

Casimir energy matches sigma-model expectations

Abstract

We study conformal field theories in two dimensions separated by domain walls, which preserve at least one Virasoro algebra. We develop tools to study such domain walls, extending and clarifying the concept of `folding' discussed in the condensed-matter literature. We analyze the conditions for unbroken supersymmetry, and discuss the holographic duals in AdS3 when they exist. One of the interesting observables is the Casimir energy between a wall and an anti-wall. When these separate free scalar field theories with different target-space radii, the Casimir energy is given by the dilogarithm function of the reflection probability. The walls with holographic duals in AdS3 separate two sigma models, whose target spaces are moduli spaces of Yang-Mills instantons on T4 or K3. In the supergravity limit, the Casimir energy is computable as classical energy of a brane that connects the walls through AdS3. We compare this result with expectations from the sigma-model point of view.