Journal of High Energy Physics (Jul 2024)

Entanglement islands and cutoff branes from path-integral optimization

  • Ashish Chandra,
  • Zhengjiang Li,
  • Qiang Wen

DOI
https://doi.org/10.1007/JHEP07(2024)069
Journal volume & issue
Vol. 2024, no. 7
pp. 1 – 41

Abstract

Read online

Abstract Recently it was proposed that, the AdS/BCFT correspondence can be simulated by a holographic Weyl transformed CFT2, where the cut-off brane plays the role of the Karch-Randall (KR) brane [1]. In this paper, we focus on the Weyl transformation that optimizes the path integral computation of the reduced density matrix for a single interval in a holographic CFT2. When we take the limit that one of the endpoint of the interval goes to infinity (a half line), such a holographic Weyl transformed CFT2 matches the AdS/BCFT configuration for a BCFT with one boundary. Without taking the limit, the induced cutoff brane becomes a circle passing through the two endpoints of the interval. We assume that the cutoff brane also plays the same role as the KR brane in AdS/BCFT, hence the path-integral-optimized purification for the interval is in the island phase. This explains the appearance of negative mutual information observed in [2]. We check that, the entanglement entropy and the balanced partial entanglement entropy (BPE) calculated via the island formulas, exactly match with the RT formula and the entanglement wedge cross-section (EWCS), which are allowed to anchor on the cutoff brane.

Keywords