  The IR limit of a planar static D3-brane in AdS5 x S5 is a tensionless
D3-brane at the AdS horizon, with dynamics governed by a strong-field limit of
the Dirac-Born-Infeld action analogous to that found from the Born-Infeld
action by Bialynicki-Birula. As in that case, the field equations are those of
an interacting 4D conformal invariant field theory with an Sl(2;R)
electromagnetic duality invariance, but the D3-brane origin makes these
properties manifest. We also find an Sl(2;R)-invariant action for these
equations.
