Subjects: Geosciences >> Space Physics submitted time 2016-12-22
Abstract： We study a holographic model with vector condensate by coupling the anti-de Sitter gravity to an Abelian gauge field and a charged vector field in (3 + 1) dimensional spacetime. In this model there exists a non-minimal coupling of the vector field to the gauge field. We find that there is a critical temperature below which the charged vector condenses via a second order phase transition. The DC conductivity becomes infinite and the AC conductivity develops a gap in the condensed phase. We study the effect of a background magnetic field on the system. It is found that the background magnetic field can induce the condensate of the vector field even in the case without chemical potential/charge density. In the case with non-vanishing charge density, the transition temperature raises with the applied magnetic field, and the condensate of the charged vector operator forms a vortex lattice structure in the spatial directions perpendicular to the magnetic field.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-12-22
Abstract： We continue to study the holographic p-wave superconductor model in the Einstein-Maxwell-complex vector field theory with a non-minimal coupling between the complex vector field and the Maxwell field. In this paper we work in the AdS soliton background which describes a conformal field theory in the confined phase and focus on the probe approximation. We find that an applied magnetic field can lead to the condensate of the vector field and the AdS soliton instability. As a result, a vortex lattice structure forms in the spatial directions perpendicular to the applied magnetic field. As a comparison, we also discuss the vector condensate in the Einstein-SU(2) Yang-Mills theory and find that in the setup of the present paper, the Einstein-Maxwell-complex vector field model is a generalization of the SU(2) model in the sense that the vector field has a general mass and gyromagnetic ratio.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-12-22
Abstract： We study competition between s-wave order and d-wave order through two holographic superconductor models. We find that once the coexisting phase appears, it is always thermodynamically favored, and that the coexistence phase is narrow and one condensate tends to kill the other. The phase diagram is constructed for each model in terms of temperature and the ratio of charges of two orders. We further compare the behaviors of some thermodynamic quantities, and discuss the different aspects and identical ones between two models.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-12-22
Abstract： In a recent paper, arXiv:1309.4877, a holographic p-wave model has been proposed in an Einstein Maxwell-complex vector field theory with a negative cosmological constant. The model exhibits rich phase structure depending on the mass and the charge of the vector field. We investigate the behavior of the entanglement entropy of dual field theory in this model. When the above two model parameters change, we observe the second order, first order and zeroth order phase transitions from the behavior of the entanglement entropy at some intermediate temperatures. These imply that the entanglement entropy can indicate not only the occurrence of the phase transition, but also the order of the phase transition. The entanglement entropy is indeed a good probe to phase transition. Furthermore, the "retrograde condensation" which is a sub-dominated phase is also reflected on the entanglement entropy. (C) 2015 The Authors. Published by Elsevier B.V.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We continue to study the holographic p-wave superconductor model in the Einstein-Maxwell-complex vector field theory with a non-minimal coupling between the complex vector field and the Maxwell field. In this paper we work in the AdS soliton background which describes a conformal field theory in the confined phase and focus on the probe approximation. We find that an applied magnetic field can lead to the condensate of the vector field and the AdS soliton instability. As a result, a vortex lattice structure forms in the spatial directions perpendicular to the applied magnetic field. As a comparison, we also discuss the vector condensate in the Einstein-SU(2) Yang-Mills theory and find that in the setup of the present paper, the Einstein-Maxwell-complex vector field model is a generalization of the SU(2) model in the sense that the vector field has a general mass and gyromagnetic ratio.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We study a holographic p-wave superconductor model in a four dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. The complex vector field is charged under the Maxwell field. We solve the full coupled equations of motion of the system and find black hole solutions with the vector hair. The vector hairy black hole solutions are dual to a thermal state with the U(1) symmetry as well as the spatial rotational symmetry broken spontaneously. Depending on two parameters, the mass and charge of the vector field, we find a rich phase structure: zeroth order, first order and second order phase transitions can happen in this model. We also find "retrograde condensation" in which the hairy black hole solution exists only for the temperatures above a critical value with the free energy much larger than the one of the black hole without the vector hair. We construct the phase diagram for this system in terms of the temperature and charge of the vector field.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We study a holographic model with vector condensate by coupling the anti-de Sitter gravity to an Abelian gauge field and a charged vector field in (3 + 1) dimensional spacetime. In this model there exists a non-minimal coupling of the vector field to the gauge field. We find that there is a critical temperature below which the charged vector condenses via a second order phase transition. The DC conductivity becomes infinite and the AC conductivity develops a gap in the condensed phase. We study the effect of a background magnetic field on the system. It is found that the background magnetic field can induce the condensate of the vector field even in the case without chemical potential/charge density. In the case with non-vanishing charge density, the transition temperature raises with the applied magnetic field, and the condensate of the charged vector operator forms a vortex lattice structure in the spatial directions perpendicular to the magnetic field.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We construct a holographic multi-band superconductor model with each complex scalar field in the bulk minimally coupled to a same gauge field. Taking into account the back reaction of matter fields on the background geometry and focusing on the two band case with two scalar order parameters, we find that depending on the strength of the back reaction and the charge ratio of the two bulk scalars, five different superconducting phases exist, and three of five phases exhibit some region where both orders coexist and are thermodynamically favored. The other two superconducting phases have only one scalar order. The model exhibits rich phase structure and we construct the full diagram for the five superconducting phases. Our analysis indicates that the equivalent attractive interaction mediated by gravity between the two order parameters tends to make the coexistence of two orders much more easy rather than more difficult.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We continue our study of entanglement entropy in the holographic superconducting phase transitions. In this paper we consider the holographic p-wave superconductor/insulator model, where as the back reaction increases, the transition is changed from second order to first order. We find that unlike the s-wave case, there is no additional first order transition in the superconducting phase. We calculate the entanglement entropy for two strip geometries. One is parallel to the super current, and the other is orthogonal to the super current. In both cases, we find that the entanglement entropy monotonically increases with respect to the chemical potential.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： Recently Lysov and Strominger [arXiv:1104.5502] showed that imposing Petrov type I condition on a (p+1)-dimensional time like hypersurface embedded in a (p+2)-dimensional vacuum Einstein gravity reduces the degrees of freedom in the extrinsic curvature of the hypersurface to that of a fluid on the hypersurface, and that the leading-order Einstein constraint equations in terms of the mean curvature of the embedding give the in compressible Navier-Stokes equations of the dual fluid. In this paper we show that the non-relativistic fluid dual to vacuum Einstein gravity does not satisfy the Petrov type I condition at next order, unless additional constraint such as their rotational condition is added. In addition, we show that this procedure can be inversed to derive the non-relativistic hydrodynamics with higher order corrections through imposing the Petrov type I condition, and that some second order transport coefficients can be extracted, but the dual "Petrov type I fluid" does not match the dual fluid constructed from the geometry of vacuum Einstein gravity in the non-relativistic limit. We discuss the procedure both on the finite cut off surface via the non-relativistic hydrodynamic expansion and on the highly accelerated surface via the near horizon expansion.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We study the Wilson line response in the holographic superconducting phase transitions in the Gauss-Bonnet gravity. In the black brane background case, the Little-Parks periodicity is independent of the Gauss-Bonnet parameter, while in the anti-de Sitter soliton case, there is no evidence for the Little-Parks periodicity. We further study the impact of the Gauss-Bonnet term on the holographic phase transitions quantitatively. For a given Wilson line, a bigger Gauss-Bonnet coefficient makes the phase transition easier for the black brane background while harder for the soliton background. For a given chemical potential, the response to the Wilson line is less sensitive for a bigger Gauss-Bonnet coefficient in the black brane case while the response is more sensitive in the soliton case. And more, a bigger Gauss-Bonnet coefficient makes the superconducting state more stable for both the black brane and the soliton backgrounds. DOI: 10.1103/PhysRevD.87.026002
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We continue to study the holographic QCD (hQCD) model, proposed in a previous paper, in an Einstein-Maxwell-Dilaton (EMD) system. In this paper we discuss some aspects of quark gluon plasma (QGP) in the hQCD model, such as drag force, jet quenching parameter and screening length. The results turn out to be consistent with those as expected in QCD qualitatively. By calculating free energy of the background black hole solution, we find that there exists a phase transition between small black hole and large black hole when chemical potential it is less than the critical one pc, and the phase transition is absent when chemical potential is beyond the critical one.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We study the behaviors of entanglement entropy and vacuum expectation value of Wilson loop in the Stuckelberg holographic insulator/superconductor model. This model has rich phase structures depending on model parameters. Both the entanglement entropy for a strip geometry and the heavy quark potential from the Wilson loop show that there exists a "confinement/deconfinement phase transition. In addition, we find that the non-monotonic behavior of the entanglement entropy with respect to chemical potential is universal in this model. The pseudo potential from the spatial Wilson loop also has a similar non-monotonic behavior. It turns out that the entanglement entropy and Wilson loop are good probes to study the properties of the holographic superconductor phase transition.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We investigate the behaviors of entanglement entropy in the holographical insulator/superconductor phase transition. We calculate the holographic entanglement entropy for two kinds of geometry configurations in a completely back-reacted gravitational background describing the insulator/superconductor phase transition. The non-monotonic behavior of the entanglement entropy is found in tins system. In the belt geometry case, there exist four phases characterized by the chemical potential and belt width.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We study the thermodynamics and non-relativistic hydrodynamics of the holographic fluid on a finite cutoff surface in the Gauss-Bonnet gravity. It is shown that the isentropic flow of the fluid is equivalent to a radial component of gravitational field equations. We use the non-relativistic fluid expansion method to study the Einstein-Maxwell-dilaton system with a negative cosmological constant, and obtain the holographic incompressible forced Navier-Stokes equations of the dual fluid at AdS boundary and at a finite cutoff surface, respectively. The concrete forms of external forces are given. (c) 2012 Elsevier B.V. All rights reserved.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： We investigate the scalar perturbations in an anti-de Sitter soliton background coupled to a Maxwell field via marginally stable modes. In the probe limit, we study the magnetic field effect on the holographic insulator/superconductor phase transition numerically and analytically. The condensate will be localized in a finite circular region for any finite constant magnetic field. Near the critical point, we find that there exists a simple relation among the critical chemical potential, magnetic field, the charge, and mass of the scalar field. This relation indicates that the presence of the magnetic field causes the transition from insulator to superconductor to be difficult.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-09
Abstract： Using the non-relativistic hydrodynamic limit, we solve equations of motion for Einstein gravity and Gauss-Bonnet gravity with a negative cosmological constant within the region between a finite cutoff surface and a black brane horizon, up to second order of the non-relativistic hydrodynamic expansion parameter. Through the Brown-York tensor, we calculate the stress energy tensor of dual fluids living on the cutoff surface. With the black brane solutions, we show that for both Einstein gravity and Gauss-Bonnet gravity, the ratio of shear viscosity to entropy density of dual fluid does not run with the cutoff surface. The incompressible Navier-Stokes equations are also obtained in both cases.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-08
Abstract： The gravitational collapse of a massless scalar field with a self-interaction term lambda phi(4) in anti-de Sitter space is investigated. We numerically investigate the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island, and energy transformation. The results show that a positive A suppresses the formation of black hole, while a negative A enhances the process. We define two susceptibilities to characterize the effect of the self-interaction on the black hole formation, and find that near the critical amplitude, there exists a universal scaling relation with the critical exponent alpha approximate to 0.74 for the time of black hole formation.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-08
Abstract： Within massive gravity, we construct a gravity dual for the insulator/metal phase transition and colossal magnetoresistance effect found in some manganese oxides materials. In the heavy graviton limit, a remarkable magnetic-field-sensitive DC resistivity peak appears at the Curie temperature, where an insulator/metal phase transition happens and the magnetoresistance is scaled with the square of field-induced magnetization. We find that metallic and insulating phases coexist below the Curie point and the relation with the electronic phase separation is discussed.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-05-08
Abstract： In this paper we investigate in some detail the holographic ferromagnetic phase transition in an AdS(4) black brane background by introducing a massive 2-form field coupled to the Maxwell field strength in the bulk. In two probe limits, one is to neglect the back reaction of the 2-form field to the background geometry and to the Maxwell field, and the other to neglect the back reaction of both the Maxwell field and the 2-form field, we find that the spontaneous magnetization and the ferromagnetic phase transition always happen when the temperature gets low enough with similar critical behavior. We calculate the DC resistivity in a semi-analytical method in the second probe limit and find it behaves as the colossal magnetic resistance effect in some materials. In the case with the first probe limit, we obtain the off-shell free energy of the holographic model near the critical temperature and compare with the Ising-like model. We also study the back reaction effect and find that the phase transition is always second order. In addition, we find an analytical Reissner-Norstrom-like black brane solution in the Einstein-Maxwell-2-form field theory with a negative cosmological constant.
Peer Review Status:Awaiting Review
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