Holographic Probes of Anti-de Sitter Spacetimes

TL;DR

Balasubramanian, Kraus, Lawrence, and Trivedi develop a concrete framework to describe bulk AdS probes in terms of boundary CFT data, using the AdS/CFT correspondence to relate bulk field behavior to boundary operator expectation values. They demonstrate a scale-radius duality where bulk radial positions map to boundary scales, showing, for example, that bulk D-instantons correspond to boundary YM instantons and bulk strings to boundary flux tubes. The paper provides both Euclidean and Lorentzian formalisms, an operator-level mapping of bulk and boundary quanta, and explicit analyses of dilaton couplings and wave packets, thereby clarifying how bulk locality and horizon physics might emerge from boundary dynamics in the large-N limit. These results lay groundwork for understanding how spacetime locality and causal structure arise and how horizons could be described holographically in the boundary theory.

Abstract

We describe probes of anti-de Sitter spacetimes in terms of conformal field theories on the AdS boundary. Our basic tool is a formula that relates bulk and boundary states -- classical bulk field configurations are dual to expectation values of operators on the boundary. At the quantum level we relate the operator expansions of bulk and boundary fields. Using our methods, we discuss the CFT description of local bulk probes including normalizable wavepackets, fundamental and D-strings, and D-instantons. Radial motions of probes in the bulk spacetime are related to motions in scale on the boundary, demonstrating a scale-radius duality. We discuss the implications of these results for the holographic description of black hole horizons in the boundary field theory.