Constraints on the BPS spectrum of N = 2, D = 4 theories with ADE flavor symmetry Original Research Article

BPS states of N = 2, D = 4 super Yang-Mills theories with ADE flavor symmetry arise as junctions joining a D3-brane to a set of 7-branes defining the enhanced flavor algebra. We show that the familiar BPS spectrum of SU(2) theories with Nf ⩽ 4 is simply given by the set of junctions whose self-intersection is bounded below as required by supersymmetry. This constraint, together with the relations between junction and weight lattices, is used to establish the appearance of arbitrarily large flavor representations for the case of Dn⩾5 and En symmetries. Such representations are required by consistency with decoupling down to smaller flavor symmetries.