Holography, Unfolding and Higher-Spin Theory
Holographic duality is argued to relate classes of models that have equivalent unfolded formulation, hence exhibiting different space-time visualizations for the same theory. This general phenomenon is illustrated by the AdS_4 higher-spin gauge theory shown to be dual to the theory of 3d conformal currents of all spins interacting with 3d conformal higher-spin fields of Chern-Simons type. The resulting 3d boundary conformal theory is nonlinear, providing an interacting version of the 3d boundary sigma model conjectured by Klebanov and Polyakov to be dual to the AdS_4 HS theory in the large N limit. Higher-spin holographic duality will be also discussed for the AdS_3/CFT_2 case and duality between higher-spin theories and nonrelativistic quantum mechanics.