Holographic Schwinger effect

We study tunneling pair creation of W bosons by an external electric field on the Coulomb branch of N=4 supersymmetric Yang-Mills theory. We use AdS/CFT holography to find a generalization of Schwinger's formula for the pair production rate to the strong coupling, planar limit which includes the exchange of virtual massless particles to all orders. We find that the pair creation formula has an upper critical electric field beyond which the process is no longer exponentially suppressed. The value of the critical field is identical to that which occurs in the Born-Infeld action of probe D3-branes in the AdS(5)×S(5) background, where AdS(5) and S(5) are 5-dimensional anti-de Sitter space and the 5-sphere, respectively.     

Holographic Schwinger effect in spinning black hole backgrounds

We perform a potential analysis for the holographic Schwinger effect in spinning Myers-Perry black holes.We compute the potential between the produced pair by evaluating the classical action of a string attached on a probe D3-brane at an intermediate position in the AdS bulk.We find that increasing the angular momentum reduces the potential barrier,thus enhancing the Schwinger effect,consistent with previous findings obtained via the local Lorentz transformation.In particular,these effects are m...     

R~4 corrections to holographic Schwinger effect

We consider R4 corrections to the holographic Schwinger effect in an AdS black hole background and a confining D3-brane background. The potential between a test particle pair are performed for both backgrounds. We find there is no potential barrier in the critical electric field, which means that the system becomes catastrophically unstable. It is shown that for both backgrounds, increasing the inverse 't Hooft coupling parameter 1/λ enhances the Schwinger effect. We also discuss the possible relation between the Schwinger effect and the viscosity-entropy ratioη/s in strong coupling.     

Holographic Schwinger effect in a soft wall AdS/QCD model

We perform a potential analysis for the holographic Schwinger effect in a deformed AdS5 model with conformal invariance broken by a background dilaton.We evaluated the static potential by analyzing the classical action of a string attached to a rectangular Wilson loop on a probe D3 brane located at an intermediate position in the bulk AdS space.We observed that the inclusion of the chemical potential tends to enhance the production rate,which is opposite to the effect of the confining scale.In addition,we calculated the critical electric field based on the Dirac-Born-Infeld(DBI)action.     

Holographic p-wave superfluid with Weyl corrections

In this work,we study the effects of the Weyl corrections on the p-wave superfluid phase transition in terms of an EinsteinMaxwell theory coupled to a complex vector field.In the probe limit,it is observed that the phase structure is significantly modified owing to the presence of the higher order Weyl corrections.The latter,in general,facilitates the emergence of the superfluid phase as the condensate increases with the Weyl coupling measured byγ.Moreover,several features about the phase structure of the holographic superfluid are carefully investigated.In a specific region,the phase transition from the normal phase to the superfluid phase is identified to be the first order,instead of being the second order,as in the cases for many holographic superconductors.By carrying out a numerical scan of model parameters,the boundary dividing these two types of transitions is located and shown to be rather sensitive to the strength of Weyl coupling.Also,a feature known as"Cave of Winds",associated with the emergence of a second superfluid phase,is observed for specific choices of model parameters.However,it becomes less prominent and eventually disappears asγincreases.Furthermore,for temperature in the vicinity of the critical one for vanishing superfluid velocity,denoted by T0,the supercurrent is found to be independent of the Weyl coupling.The calculated ratio,of the condensate with vanishing superfluid velocity to that with maximal superfluid velocity,is in good agreement with that predicted by Ginzburg-Landau theory.While compared with the impact on the phase structure owing to the higher curvature corrections,the findings in our present study demonstrate entirely different characteristics.Further implications are discussed.     

Interacting Holographic Dark Energy in the Scalar Gauss-Bonnet Gravity

We study cosmological application of interacting holographic dark energy density in the scalar Gauss-Bonnet framework. We employ the interacting holographic model of dark energy to obtain the equation of state for the interacting holographic energy density in a spatially fiat universe. Our calculations show that taking Ω∧ = 0.73 for the present time, it is possible to have w∧^eff crossing -1. This implies that one can generate a phantom-like equation of state from the interacting holographic dark energy model in flat universe in the scalar Gauss-Bonnet cosmology framework. Then we reconstruct the potential of the scalar field.     

Gravitational decoupled charged anisotropic solutions in modified Gauss-Bonnet gravity

This paper is devoted to the study of charged anisotropic exact solutions for spherical geometry in the context of modified Gauss-Bonnet gravity using the gravitational decoupling technique. We take Krori-Barua solution in the presence of charge for a spherically symmetric self-gravitating system and extend it to obtain two anisotropic solutions through some constraints. We study the stability as well as the physical viability criterion of the resulting solutions using anisotropy, squared speed of sound parameter and energy bounds. Both models turn out to be physically viable and stable as they fulfill the required energy conditions and stability criterion. We conclude that the stability of both anisotropic solutions increases with a decrease in charge.     

Holographic conductivity of holographic superconductors with higher-order corrections

We analytically and numerically disclose the effects of the higher-order correction terms in the gravity and in the gauge field on the properties of s-wave holographic superconductors. On the gravity side, we consider the higher curvature Gauss–Bonnet corrections and on the gauge field side, we add a quadratic correction term to the Maxwell Lagrangian. We show that, for this system, one can still obtain an analytical relation between the critical temperature and the charge density. We also calculate the critical exponent and the condensation value both analytically and numerically. We use a variational method, based on the Sturm–Liouville eigenvalue problem for our analytical study, as well as a numerical shooting method in order to compare with our analytical results. For a fixed value of the Gauss–Bonnet parameter, we observe that the critical temperature decreases with increasing the nonlinearity of the gauge field. This implies that the nonlinear correction term to the Maxwell electrodynamics makes the condensation harder. We also study the holographic conductivity of the system and disclose the effects of the Gauss–Bonnet and nonlinear parameters \(\alpha \) and b on the superconducting gap. We observe that, for various values of \(\alpha \) and b, the real part of the conductivity is proportional to the frequency per temperature, \(\omega /T\), as the frequency is large enough. Besides, the conductivity has a minimum in the imaginary part which is shifted toward greater frequency with decreasing temperature.     

Holographic superconductor developed in BTZ black hole background with backreactions

We develop a holographic superconductor in BTZ black hole background with backreactions. We investigate the influence of the backreaction on the condensation of the scalar hair and the dynamics of perturbation in the background spacetime. When the Breitenlohner-Freedman bound is approached, we argue that only one of two possible operators can reflect the real property of the condensation in the holographic superconductor. This argument is supported by the investigation in dynamics.     

Holographic thermalization in a quark confining background

Journal of Experimental and Theoretical Physics - We study holographic thermalization of a strongly coupled theory inspired by two colliding shock waves in a vacuum confining background....     

Quantum electrodynamics with anisotropic scaling: Heisenberg-Euler action and Schwinger pair production in the bilayer graphene

We discuss quantum electrodynamics emerging in the vacua with anisotropic scaling. Systems with anisotropic scaling were suggested by Hořava in relation to the quantum theory of gravity. In such vacua, the space and time are not equivalent, and moreover they obey different scaling laws, called the anisotropic scaling. Such anisotropic scaling takes place for fermions in bilayer graphene, where if one neglects the trigonal warping effects the massless Dirac fermions have quadratic dispersion. This results in the anisotropic quantum electrodynamics, in which electric and magnetic fields obey different scaling laws. Here we discuss the Heisenberg-Euler action and Schwinger pair production in such anisotropic QED.     

Behavior of Holographic Ricci Dark Energy in Scalar Gauss-Bonnet Gravity for Different Choices of the Scale Factor

In this paper, we studied the cosmological application of the interacting Ricci Dark Energy (RDE) model in the framework of the scalar Gauss-Bonnet modified gravity model. We studied the properties of the reconstructed potential \(V\left (t \right )\) , the Strong Energy Condition (SEC), the Weak Energy Condition (WEC) and the deceleration parameter q for three different models of scale factor, i.e. the emergent, the intermediate and the logamediate one. We obtained that \(V\left (t \right )\) , for the emergent scenario, has a decreasing behavior, while, for the logamediate scenario, the potential start with an increasing behavior then, for later times, it shows a slowly decreasing behavior. Finally, for the intermediate scenario, the potential has an initial increasing behavior, then for a time of t≈1.2, it starts to decrease. We also found that both SEC and WEC are violated for all the three scale factors considered. Finally, studying the plots of q, we derived that an accelerated universe can be achieved for the three models of scale factor considered.     

Properties of an Accelerating Gauss-Bonnet Vacuum in Five Dimensions

The causal structure of a five-dimensional C-metric like vacuum solution of Gauss-Bonnet gravity is analyzed in detail, the Gauss-Bonnet parameter make it more complex than that of a C-metric like solution of Einstein gravity. The acceleration of the observer fixed at a spatial position is calculated, the effect of the Gauss-Bonnet parameter comes in, but the acceleration of the origin is not affected by the parameter. The geodesics of the test particles in the spacetime are investigated, it is found that objects accelerate to go to the horizon in the accelerating spacetime.     

Wormholes in higher dimensions with Gauss-Bonnet terms

A class of wormhole solutions permitted in a theory with Gauss-Bonnet terms in the gravitational action in higher dimensions have been studied. The case of de-Sitter type instantons, with a compact inner space, are of particular interest here. Some of the configurations, when continued analytically to the Lorentzian metric lead to the standard inflationary universe. Some multiple-sphere configurations of the type studied by Myers have also been noted. The Euclidean action for the solutions has been calculated and the relevance of the solutions in the quantum creation of the universe has been considered.