分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：We propose the SUSY SU(7) unification of the SU(3)_C* SU(4)_W* U(1)_{B-L} model. Such unification scenario has rich symmetry breaking chains in a five-dimensional orbifold. We study in detail the SUSY SU(7) symmetry breaking into SU(3)_C* SU(4)_W* U(1)_{B
分类： 地球科学 >> 空间物理学 提交时间： 2016-12-22
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要：We propose to embed de Sitter space into five dimensional anti-de Sitter space to compute some physical quantities of interest, using the AdS/CFT correspondence. The static de Sitter can be considered as the conformal structure of the boundary of the hyperbolic AdS(5) with a horizon, thus energy as well as entropy can be computed. The global dS can be embedded into a half-global AdS(5), and the dS entropy can be regarded as entanglement entropy in this case. Finally, the inflationary dS can also be regarded as the boundary of AdS(5), and this can be extended to include general cosmology with a positive cosmological constant, however at the price of introducing a naked null singularity in the bulk unless the cosmology is pure de Sitter space.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-08
摘要：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.
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