)_L \times SU (N_f )_R$ and the vector part $U(1)_V$ . There is no explicit breaking of this group since the model only contains massless quarks. Spontaneous chiral symmetry breaking is realized when the D8- and D8-branes connect in the bulk. They always connect in the confined phase whether they connect in the deconfined phase depends on the separation L of the D8- and D8-branes in the extra dimension $x_4$.

The Sakai-Sugimoto model is particularly suited for phenomenon related to chirality as chiral magnetic effect (CME) \[21-25\] since it has a well defined concept for chirality and the chiral phase transition. It is straightforward to introduce right- and left-handed chemical potentials independently.

The chiral magnetic effect is a hypothetical phenomenon which states that, in the presence of a magnetic field B, a nonzero axial charge density will lead to an electric current along the direction of the B field \[26-28\]. Analysis of RHIC data appears to favor the presence of a CME in the quark-gluon plasma, although a better understanding of systematic errors and backgrounds is still needed. CME is studied in many holographic systems, following refs. \[29-34\], including systems without confinement or chiral symmetry breaking in vacuum.

Also, predictions 