Page Curve from Defect Extremal Surface and Island in Higher Dimensions

TL;DR

This paper derives the Page curve in higher-dimensional AdS/BCFT setups using defect extremal surfaces and island formulas, showing their agreement in 3D and differences in higher dimensions, highlighting the impact of UV completion.

Contribution

It extends the defect extremal surface and island formula analysis from AdS$_3$/BCFT$_2$ to higher dimensions, revealing new insights into entropy calculations.

Findings

Page curve derived from defect extremal surface matches island formula in AdS$_3$/BCFT$_2$.

In higher dimensions, defect extremal surface entropy is generally larger than island formula entropy.

UV completion of the island formula results in smaller entropy in higher dimensions.

Abstract

Defect extremal surface is defined by minimizing the Ryu-Takayanagi surface corrected by the defect theory, which is useful when the RT surface crosses or terminates on the defect. Based on the decomposition procedure of a AdS bulk with a defect brane, proposed in arXiv:2012.07612, we derive Page curve in a time dependent set up of AdS$_3$/BCFT$_2$, and find that the result from island formula agrees with defect extremal surface formula precisely. We then extend the study to higher dimensions and find that the entropy computed from bulk defect extremal surface is generally less than that from island formula in boundary low energy effective theory, which implies that the UV completion of island formula gives a smaller entropy in higher dimensions.