Dynamics of BPS States in the Dirac-Born-Infeld Theory

The Dirac-Born-Infeld action with transverse scalar fields is considered to study the dynamics of various BPS states. We first describe the characteristic properties of the so-called 1/2 and 1/4 BPS states on the D3 brane, which can be interpreted as F/D-strings ending on a D3-brane in Type IIB string theory picture. We then study the response of the BPS states to low energy excitations of massless fields on the brane, the scalar fields representing the shape fluctuation of the brane and U(1) gauge fields describing the open string excitations on the D-brane. This leads to an identification of interactions between BPS states including the static potentials and the kinetic interactions.