Open string attractors

Abstract

We present a simple example of a supersymmetric attractor mechanism in the purely open string context of D-branes embedded in curved space-time. Our example involves a class of D3-branes embedded in the 2-charge D1-D5 background of type IIB whose worldvolume contains a 2-sphere. Turning on worldvolume fluxes, these branes carry induced (p,q) string charges. Supersymmetric configurations display a flow of the open string moduli towards an attractor solution independent of their asymptotics. The equations governing this mechanism closely resemble the attractor flow equations for supersymmetric black holes in closed string theory. The BPS equations take the form of a gradient flow and describe worldvolume solitons interpolating between an AdS_2 geometry where the two-sphere has collapsed, and an attractor solution with AdS_2 x S^2 geometry. In these limiting solutions, the preserved supersymmetry is enhanced from 4 to 8 supercharges. We also discuss the interpretation of our solutions as intersecting brane configurations placed in the D1-D5 background, as well as the S-duality transformation to the F1-NS5 background.