On the Son-Yamamoto relation in the soft-wall holographic model of QCD

We study the vertex function of two vector and one axial-vector operators in the soft-wall holographic model of QCD. In particular, we discuss the possible relation, introduced by Son and Yamamoto, between the structure function $w_T$ describing such a vertex when one of the two vector currents represents an on-shell soft photon and the the two-point ${\mathrm{\Pi }}_{\perp }^{VV}-{\mathrm{\Pi }}_{\perp }^{AA}$ correlation function.