Dropping a diary into semiclassical black hole microstates

We study the impact of the infalling matter on the semiclassical microstate structure of black holes in general relativity with negative cosmological constant in arbitrary spacetime dimension. The matter is taken to be a sequence of thin heavy shells, which are infalling into the microstate geometry from outside the horizon. We show that the coarse-grained entropy of the quantum black hole described by these microstates in the presence of infalling shells behaves in agreement with the expectation for the Bekenstein-Hawking entropy from classical black hole thermodynamics. Meanwhile, we also demonstrate that the finer characteristics of the overlap structure of the microstates depend on the entropies of the black hole after consuming every individual shell, thus recording the history of the black hole matter consumption during its evolution.