D-particle dynamics and bound states

We study the low energy effective theory describing the dynamics of D-particles. This corresponds to the quantum-mechanical system obtained by dimensional reduction of (9 + 1)-dimensional supersymmetric Yang-Mills theory to 0 + 1 dimensions and can be interpreted as the nonrelativistic limit of the Born-Infeld action. We study the system of two like-charged D-particles and find evidence for the existence of non-BPS states whose mass grows like lambda(1/3) over the BPS mass. We give a string interpretation of this phenomenon in terms of a linear potential generated by strings stretching from the two D-particles. Some comments on the possible relations to black hole entropy and eleven-dimensional supergravity are also given.