Magnetized Einstein-Maxwell-dilaton model under external electric fields

Abstract

We employ an analytic solution of a magnetized Einstein-Maxwell-dilaton gravity system whose parameters have been determined so that its holographic dual has the most similarity to a confining QCD-like theory influenced by a background magnetic field. Analyzing the total potential of a quark-antiquark pair in an external electric field, we are able to investigate the effect of the electric field on the different phases of the background which are the thermal AdS and the black hole phases. This is helpful for better understanding the confining character and also the phase transitions of the system. We find out that the field theory dual to the black hole solution is always deconfined. However, although the thermal AdS phase describes the confining phase in general, for the quark pairs parallel to $B$ (longitudinal case) and $B>B_{\mathrm{critical}}$ the response of the system to the electric field mimics the deconfinement. We moreover consider the effect of the magnetic field and the chemical potential on the Schwinger effect. We observe that when we are in the black hole phase with sufficiently small values of $\mu$ or in the thermal AdS phase, and for both longitudinal and transverse cases, the magnetic field increase leads to the enhancement of the Schwinger effect, which can be termed as the inverse magnetic catalysis. This is deduced both from the decrease of the critical electric fields and from the decreasing the height and width of the total potential barrier that the quarks are facing with. However, by increasing $\mu$ to high enough values, the inverse magnetic catalysis turns into magnetic catalysis, as can also be observed from the diagram of the Hawking-Page phase transition temperature versus $B$ for the background geometry itself.