Magnetic catalysis with massive dynamical flavours

Abstract

Within gauge/gravity duality, we construct a backreacted supergravity background dual to SU(Nc) N=4 SYM coupled to Nf massive fundamental flavours in the presence of an external magnetic field. Our solution is perturbative in a parameter that counts the number of the internal flavour loops. The background has a hollow cavity in the bulk of the geometry, where it is similar to the supergravity dual of a non-commutative SYM. The radius of this cavity is related to the dynamically generated mass of the fundamental fields. We apply our construction to study the effect of magnetic catalysis and develop an appropriate renormalization scheme to compute the free energy and the fundamental condensate of the dual gauge theory as a function of the bare mass. While at leading order in the expansion of the perturbative parameter, the free energy and the fundamental condensate agree with the results obtained in the quenched approximation, at next order we show that the effect of magnetic catalysis is enhanced and the contribution to the condensate of the theory from internal fundamental loops runs logarithmically with the finite cutoff Lambda_UV.