I am following the lecture notes on F-theory by T. Weigand . On page 7 he states that when considering F-theory as the strong coupling limit of type IIB orientifolds with D-branes, the axio-dilaton field defined on the coordinates perpendicular to the brane has to depend holomorphically on these coordinates.

My question is: what are these conditions? A reference would be greatly appreciated as well.

This post imported from StackExchange Physics at 2016-06-17 12:19 (UTC), posted by SE-user saesori