Holographic BCFT with a Defect on the End-of-the-World Brane

TL;DR

This paper introduces a new gravity dual for 2D BCFTs with a defect connecting two boundaries, revealing a richer spectrum, phase structure, and wormhole solutions, expanding the understanding of holographic BCFT models.

Contribution

It proposes a novel bulk model with a defect connecting End-of-the-World branes, leading to new spectral and entanglement features in holographic BCFTs.

Findings

The lowest energy spectrum can interpolate between negative and zero values.

Holographic entanglement entropy exhibits three distinct phases.

A wormhole saddle exists only in non-unitary BCFTs, but is subdominant.

Abstract

In this paper, we propose a new gravity dual for a $2$d BCFT with two conformal boundaries by introducing a defect that connects the two End-of-the-World branes. We demonstrate that the BCFT dual to this bulk model exhibits a richer lowest spectrum. The corresponding lowest energy eigenvalue can continuously interpolate between $-\frac{\pi c}{24\Delta x}$ and $0$ where $\Delta x$ is the distance between the boundaries. This range was inaccessible to the conventional AdS/BCFT model with distinct boundary conditions. We compute the holographic entanglement entropy and find that it exhibits three different phases, one of which breaks the time reflection symmetry. We also construct a wormhole saddle, analogous to a $3$d replica wormhole, which connects different boundaries through the AdS bulk. This saddle is present only if the BCFT is non-unitary and is always subdominant compared to the disconnected saddle.