Q‐branes in type IIB supergravity

The notion of Q7‐branes and Q‐instantons is introduced. These are one‐half BPS solutions of the type IIB supergravity theory characterized by a set of three parameters p,q,r such that r^2>4pq. The numbers p,q,r parameterize the electric and magnetic couplings of, respectively, the Q7‐branes and Q‐instantons to a triplet of 8‐forms. The (p,q) 7‐branes and instantons including the D7‐brane and the D‐instanton have r 2 = 4pq. Seven‐brane solutions containing Q7‐branes are discussed and the Q‐instanton on‐shell action is computed. The Q7‐branes are either novel bound states of a (p,q) 7‐brane and a (p′,q′) 7‐brane with (p,q) ≠ (p′,q′) or they form an independent new object in the theory.