Inverse magnetic catalysis in bottom-up holographic QCD

Abstract

We explore the effect of magnetic field on chiral condensation in QCD via a simple bottom up holographic model which inputs QCD dynamics through the running of the anomalous dimension of the quark bilinear. Bottom up holography is a form of effective field theory and we use it to explore the dependence on the coefficients of the two lowest order terms linking the magnetic field and the quark condensate. In the massless theory, we identify a region of parameter space where magnetic catalysis occurs at zero temperature but inverse magnetic catalysis at temperatures of order the thermal phase transition. The model shows similar non-monotonic behaviour in the condensate with B at intermediate T as the lattice data. This behaviour is due to the separation of the meson melting and chiral transitions in the holographic framework. The introduction of quark mass raises the scale of B where inverse catalysis takes over from catalysis until the inverse catalysis lies outside the regime of validity of the effective description leaving just catalysis.

Quarkyonic phase from quenched dynamical holographic QCD model

“…The deconfinement phase transition has been widely discussed with the expectation value of Polyakov loop as the order parameter of deconfinement phase transition. However, till recently, the dynamical spontaneous chiral symmetry breaking and chiral phase transition have been realized in soft-wall holographic QCD model [99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116] with the chiral condensate as the order parameter.…”

Chiral phase transition of QCD with N f = 2 + 1 flavors from holography

“…Different from top-down approach, bottom-up holographic QCD starts from QCD phenomena and try to build up more realistic holographic models. In this approach, chiral phase transition has been studied in several different models [5,[58][59][60][61][62][63][64][65][66][67]. Most of these studies considered the case with equal quark masses for all quarks.…”

Improved Holographic QCD and the Quark--Gluon Plasma

“…The question has been addressed in the various papers in holography [96,97,98,99,100,101,102,103], or with smeared backreacted flavor branes in the Veneziano limit [104] but most of these works are either for adjoint flavors or consider small values of fundamental quarks. Very recently, the question is addressed in [86] for ihQCD in the Veneziano limit (95).…”

“…Finally, when one cranks up T further, the quark-condensate melts trough a second-order phase transition (blue, dashed curve) at T χ (µ) and one obtains a deconfined state where the chiral symmetry is restored. This phase holographically corresponds to a generalization of the blackbrane background of the previous section for finite (103) and τ = 0. In section 8 we shall see how this phase diagram is altered for vanishing chemical potential µ = 0 but a finite external magnetic field B turned on instead.…”