More on the Tensor Response of the QCD Vacuum to an External Magnetic   Field
  In this Letter we discuss a few issues concerning the magnetic susceptibility of the quark condensate and the Son-Yamamoto (SY) anomaly matching equation. It is shown that the SY relation in the IR implies a nontrivial interplay between the kinetic and WZW terms in the chiral Lagrangian. It is also demonstrated that in a holographic framework an external magnetic field triggers mixing between scalar and tensor fields. Accounting for this, one may calculate the magnetic susceptibility of the quark condensate to all orders in the magnetic field. 
A. Gorsky, P. N. Kopnin, A. Krikun, and A. Vainshtein
hep-ph hep-th