Casting Shadows on Holographic Reconstruction

TL;DR

This paper investigates regions in holographic spacetimes, called shadows, that are not accessible via known bulk probes, and explores their implications for the bulk-boundary correspondence in AdS/CFT.

Contribution

It introduces the concept of bulk shadows in holography, quantifies their size near black holes and dense stars, and discusses their significance for the bulk-boundary dictionary.

Findings

Identification of shadow regions in holographic spacetimes.

Quantification of shadow size near black holes and dense stars.

Implications for the bulk-boundary correspondence and dual field theory.

Abstract

In the context of the AdS/CFT correspondence, we study several holographic probes that relate information about the bulk spacetime to CFT data. The best-known example is the relation between minimal surfaces in the bulk and entanglement entropy of a subregion in the CFT. Building on earlier work, we identify "shadows" in the bulk: regions that are not illuminated by any of the bulk probes we consider, in the sense that the bulk surfaces do not pass through these regions. We quantify the size of the shadow in the near horizon region of a black hole and in the vicinity of a sufficiently dense star. The existence of shadows motivates further study of the bulk-boundary dictionary in order to identify CFT quantities that encode information about the shadow regions in the bulk. We speculate on the interpretation of our results from a dual field theory perspective.