Instantons and Emergent AdS_3 x S^3 Geometry
  Two dimensional N=(4,4) gauge theories flow to interacting superconformal field theories on their Higgs branch. We examine worldsheet instantons in these theories through the eyes of a D-brane construction. The effective instanton partition function is shown to reveal an emergent background AdS_3 x S^3 geometry. 
Heng-Yu Chen and David Tong