A duality of Ryu-Takayanagi surfaces inside and outside the horizon

Abstract: We study the Ryu-Takayanagi (RT) surfaces associated with timelike subregions in static spacetimes with a horizon. These RT surfaces can extend into the horizon, allowing us to probe the interior of the black hole. The horizon typically divides the RT surface into two distinct parts. We demonstrate that the area of the RT surface inside the horizon can be reconstructed from the contributions of the RT surfaces outside the horizon, along with additional RT surfaces for spacelike subregions that are causally related to the timelike subregions. This result provides a concrete realization of black hole complementarity, where the information from the black hole interior can be reconstructed from the degrees of freedom outside the horizon.