Emergent D5-brane background from D-strings

We solve the worldsheet theory describing the near-horizon dynamics of a D-string in the presence of a very large number N of D5-branes. The model is pre-geometric in the sense that the near-horizon worldsheet Lagrangian does not have dynamical fields associated with the dimensions transverse to the D5-branes. The solution at large N is shown to be given by a classical action for the D-string moving in a curved ten-dimensional spacetime. The four dimensions transverse to the D5-branes emerge from the quantum loops of the original strongly coupled quantum worldsheet field theory. By comparing with the Dirac-Born-Infeld plus Chern-Simons action for a D-string in a general type IIB background, we identify the string-frame metric, dilaton and Ramond-Ramond three-form field strength and find a match with the near-horizon geometry of a stack of D5-branes.