Topological action at a distance and the magnetic moment of point-like anyons

In (2+1) dimensions, a point-like particle with no spin degree of freedom can carry its proper magnetic moment. It is shown that, for a particular value of this magnetic moment, the Maxwell-Chern-Simons electrodynamics of a system of N point-like charges exactly reduces to an effective action at a distance that is a topological invariant of particle world-lines. The resulting action differs from the standard action of ideal anyons by a velocity-dependent attractive contact term. (orig.)