Flavoured largeNgauge theory in an external magnetic field

Abstract

We consider a D7-brane probe of AdS 5 × S 5 in the presence of pure gauge B-field. In the dual gauge theory, the B-field couples to the fundamental matter introduced by the D7-brane and acts as an external magnetic field. The B-field supports a 6-form Ramond-Ramond potential on the D7-branes world volume that breaks the supersymmetry and enables the dual gauge theory to develop a non-zero fermionic condensate. We explore the dependence of the fermionic condensate on the bare quark mass m q and show that at zero bare quark mass a chiral symmetry is spontaneously broken. A study of the meson spectrum reveals a coupling between the vector and scalar modes, and in the limit of weak magnetic field we observe Zeeman splitting of the states. We also observe the characteristic √ m q dependence of the ground state corresponding to the Goldstone boson of spontaneously broken chiral symmetry.

Mesons in gauge/gravity duals

“…Such a B field breaks supersymmetry completely. As shown in [23,218], it induces spontaneous chiral symmetry breaking and Goldstone bosons by virtue of a similar mechanism as discussed in sect. 6 above.…”

“…Several similar scenarios in which supersymmetry breaking leads to chiral symmetry breaking have also been found -for example a set-up of D4 and D6 branes [21], by placing the gauge theory on an anti-de-Sitter space [22], or introducing a background magnetic field [23].…”

“…7.1, there is no spontaneous chiral symmetry breaking in the finite-temperature field theory dual of the AdS-Schwarzschild black-hole background. However, if a B field of the form of [23] of sufficient strength is switched on, the chiral symmetry-breaking mechanism induced by this B field dominates and is present even in the black-hole background [219,220]. This is shown in fig.…”

“…A Zeeman splitting is observed if a pure gauge-external B field is turned on in two spatial directions parallel to the AdS boundary [23,218]. Such a B field breaks supersymmetry completely.…”

Non-equilibrium physics at a holographic chiral phase transition

“…Several mechanisms for triggering this condensation have been explored. The cleanest is when a background magnetic field is introduced [15][16][17][18][19][20][21][22][23] so we will use that mechanism here. The reader might want to loosely view the B field as simply the introduction of a conformal symmetry and supersymmetry breaking parameter that triggers the strong dynamics to cause the symmetry breaking.…”