# What is the origin of the five-form field in bubbling Ads geometries?

I have been reading the paper: Bubbling Ads space and the 1/2 BPS geometries[hep-th/0409174]. In the paper they look at 1/2 BPS states in the field theory which are dual to D3 branes IIB supegravity. The D3 branes couple to a four form potential . I would like to ask, why is it that the D3 brane couples to a four form potential?

• All type II D$p$-branes couple to the $(p+1)$-form potential - whose physical excitations appear in the Ramond-Ramond sector of closed strings. This is the biggest insight of Joe Polchinski's, 1995, which has now over 3,000 citations: scholar.google.com/… arxiv.org/abs/hep-th/9510017 - One really can't do anything meaningful with D-branes without knowing this coupling. – Luboš Motl May 18 '16 at 15:56