QCD Vacuum Properties in a Magnetic Field from AdS/CFT: Chiral Condensate and Goldstone Mass

Understand

Chiral condensate and $\eta^\prime$ meson mass spectrum are studied under the influence of an external Abelian magnetic field.

• We work within the D3/D7 Karch--Katz model of flavoured AdS/CFT with supersymmetry broken by the Constable--Myers deformation of the metric.
• It is shown that this setting yields a quadratic dependence of condensate on field, rather than the non-analytic (linear in field) dependence, typical for chiral perturbation theory in the exact chiral limit.
• We argue that the analytic (quadratic) result must be put into correspondence with the leading-order in the $1/N_c$ decomposition for the condensate, whereas the existing chiral perturbation theory result, which is linear in field strength, is $1/N_c$ suppressed.