Aspects of Instanton Dynamics in AdS / CFT Duality

We consider aspects of instanton dynamics in the large-N limit using the AdS/CFT duality for D0/D4 bound states. In the supergravity picture of wrapped D0-brane worldlines on D4-branes, we find the single-instanton measure and discuss its dependence on compactification finite-size effects, as well as its matching to perturbative results. In the non-supersymmetric case, the same dynamical effects that produce the theta-angle dependence perturbatively in 1/N , render the instantons unstable, although approximate instantons of very small size still exist. The smeared D0/D4 black-brane supergravity solution can be interpreted as dual to a field theory configuration of an instanton condensate in the vacuum. In this case, we derive a holographic relation between the bare theta angle and the topological charge density of the instanton condensate.