CONSTRAINTS ON THE BPS SPECTRUM OF NU=2, D=4 THEORIES WITH ADE FLAVORSYMMETRY

BPS states of N = 2, D = 4 super Yang-Mills theories with ADE flavor s ymmetry arise as junctions joining a D3-brane to a set of 7-branes def ining the enhanced flavor algebra. We show that the familiar BPS spect rum of SU(2) theories with N-f less than or equal to 4 is simply given by the set of junctions whose self-intersection is bounded below as r equired by supersymmetry. This constraint, together with the relations between junction and weight lattices, is used to establish the appear ance of arbitrarily large flavor representations for the case of D-n g reater than or equal to 5 and E-n symmetries. Such representations are required by consistency with decoupling down to smaller flavor symmet ries. (C) 1998 Published by Elsevier Science B.V.