BPS states and minimal surfaces

It was observed recently, that the low-energy effective action of the four-dimensional supersymmetric theories may be obtained as a certain limit of M-theory. From this point of view, the BPS states correspond to the minimal area membranes ending on the M-theory 5-brane. We prove that for the configuration, corresponding to the SU(2) super-Yang-Mills theory, the BPS spectrum is correctly reproduced, and develop techniques for analyzing the BPS spectrum in more general cases. We show that the type of the supermultiplet is related to the topology of the membrane: disks correspond to hypermultiplets, and cylinders to vector multiplets. We explain the relation between minimal surfaces and geodesic lines, which shows that our description of BPS states is closely related to one arising in type II string compactification on Calabi-Yau threefolds. (orig.)