7,409 research outputs found

    Bulk matter fields on two-field thick branes

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    In this paper we obtain a new solution of a brane made up of a scalar field coupled to a dilaton. There is a unique parameter bb in the solution, which decides the distribution of the energy density and will effect the localization of bulk matter fields. For free vector fields, we find that the zero mode can be localized on the brane. And for vector fields coupled with the dilaton via eτπFMNFMN\text{e}^{\tau\pi}F_{MN}F^{MN}, the condition for localizing the zero mode is τb/3\tau\geq-\sqrt{b/3} with 01/3b0-1/\sqrt{3b} with b>1b>1, which includes the case τ=0\tau=0. While the zero mode for free Kalb-Ramond fields can not be localized on the brane, if only we introduce a coupling between the Kalb-Ramond fields and the dilaton via eζπHMNLHMNL\text{e}^{\zeta \pi}H_{MNL}H^{MNL}. When the coupling constant satisfies ζ>1/3b\zeta>1/\sqrt{3b} with b1b\geq1 or ζ>2b3b\zeta>\frac{2-b}{\sqrt{3b}} with 0<b<10<b<1, the zero mode for the KR fields can be localized on the brane. For spin half fermion fields, we consider the coupling ηΨˉeλπϕΨ\eta\bar{\Psi}\text{e}^{\lambda \pi}\phi\Psi between the fermions and the background scalars with positive Yukawa coupling η\eta. The effective potentials for both chiral fermions have three types of shapes decided by the relation between the dilaton-fermion coupling constant λ\lambda and the parameter bb. For λ1/3b\lambda\leq-1/\sqrt{3b}, the zero mode of left-chiral fermion can be localized on the brane. While for λ>1/3b\lambda>-1/\sqrt{3b} with b>1b>1 or 1/3b<λ<b/3-1/\sqrt{3b}<\lambda<-\sqrt{b/3} with 0<b10<b\leq1, the zero mode for left-chiral fermion also can be localized.Comment: 22 pages, 8 figures, improved version, accepted by Physical Review

    First Principles Study of Adsorption of O2O_{2} on Al Surface with Hybrid Functionals

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    Adsorption of O2O_{2} molecule on Al surface has been a long standing puzzle for the first principles calculation. We have studied the adsorption of O2O_{2} molecule on the Al(111) surface using hybrid functionals. In contrast to the previous LDA/GGA, the present calculations with hybrid functionals successfully predict that O2O_{2} molecule can be absorbed on the Al(111) surface with a barrier around 0.2\thicksim0.4 eV, which is in good agreement with experiments. Our calculations predict that the LUMO of O2O_{2} molecule is higher than the Fermi level of the Al(111) surface, which is responsible for the barrier of the O2O_{2} adsorption.Comment: 14 pages, 5 figure

    Domain Wall Brane in Eddington Inspired Born-Infeld Gravity

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    Recently, inspired by Eddington's theory, an alternative gravity called Eddington-inspired Born-Infeld gravity was proposed by Ban~\tilde{\text{n}}ados and Ferreira. It is equivalent to Einstein's general relativity in vacuum, but deviates from it when matter is included. Interestingly, it seems that the cosmological singularities are prevented in this theory. Based on the new theory, we investigate a thick brane model with a scalar field presenting in the five-dimensional background. A domain wall solution is obtained, and further, we find that at low energy the four-dimensional Einstein gravity is recovered on the brane. Moreover, the stability of gravitational perturbations is ensured in this model.Comment: 16 pages, 2 figures, improved versio

    Very large magnetoresistance in Fe0.28_{0.28}TaS2_{2} single crystals

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    Magnetic moments intercalated into layered transition metal dichalcogenides are an excellent system for investigating the rich physics associated with magnetic ordering in a strongly anisotropic, strong spin-orbit coupling environment. We examine electronic transport and magnetization in Fe0.28_{0.28}TaS2_{2}, a highly anisotropic ferromagnet with a Curie temperature TC68.8 T_{\mathrm{C}} \sim 68.8~K. We find anomalous Hall data confirming a dominance of spin-orbit coupling in the magnetotransport properties of this material, and a remarkably large field-perpendicular-to-plane MR exceeding 60% at 2 K, much larger than the typical MR for bulk metals, and comparable to state-of-the-art GMR in thin film heterostructures, and smaller only than CMR in Mn perovskites or high mobility semiconductors. Even within the Fex_xTaS2_2 series, for the current xx = 0.28 single crystals the MR is nearly 100×100\times higher than that found previously in the commensurate compound Fe0.25_{0.25}TaS2_{2}. After considering alternatives, we argue that the large MR arises from spin disorder scattering in the strong spin-orbit coupling environment, and suggest that this can be a design principle for materials with large MR.Comment: 8 pages, 8 figures, accepted in PR

    Deterministic quantum teleportation between distant atomic objects

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    Quantum teleportation is a key ingredient of quantum networks and a building block for quantum computation. Teleportation between distant material objects using light as the quantum information carrier has been a particularly exciting goal. Here we demonstrate a new element of the quantum teleportation landscape, the deterministic continuous variable (cv) teleportation between distant material objects. The objects are macroscopic atomic ensembles at room temperature. Entanglement required for teleportation is distributed by light propagating from one ensemble to the other. Quantum states encoded in a collective spin state of one ensemble are teleported onto another ensemble using this entanglement and homodyne measurements on light. By implementing process tomography, we demonstrate that the experimental fidelity of the quantum teleportation is higher than that achievable by any classical process. Furthermore, we demonstrate the benefits of deterministic teleportation by teleporting a dynamically changing sequence of spin states from one distant object onto another

    Localization of Bulk Matters on a Thick Anti-de Sitter Brane

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    In this paper, we investigate the localization and the mass spectra of gravity and various bulk matter fields on a thick anti-de Sitter (AdS) brane, by presenting the mass-independent potentials of the Kaluza-Klein (KK) modes in the corresponding Schr\"{o}dinger equations. For gravity, the potential of the KK modes tends to infinity at the boundaries of the extra dimension, which leads to an infinite number of the bound KK modes. Although the gravity zero mode cannot be localized on the AdS brane, the massive modes are trapped on the brane. The scalar perturbations of the thick AdS brane have been analyzed, and the brane is stable under the scalar perturbations. For spin-0 scalar fields and spin-1 vector fields, the potentials of the KK modes also tend to infinity at the boundaries of the extra dimension, and the characteristic of the localization is the same as the case of gravity. For spin-1/2 fermions, by introducing the usual Yukawa coupling ηΨˉϕΨ\eta\bar{\Psi}\phi\Psi with the positive coupling constant η\eta, the four-dimensional massless left-chiral fermion and massive Dirac fermions are obtained on the AdS thick brane.Comment: 23 pages, 9 figure

    Approximating the monomer-dimer constants through matrix permanent

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    The monomer-dimer model is fundamental in statistical mechanics. However, it is #P-complete in computation, even for two dimensional problems. A formulation in matrix permanent for the partition function of the monomer-dimer model is proposed in this paper, by transforming the number of all matchings of a bipartite graph into the number of perfect matchings of an extended bipartite graph, which can be given by a matrix permanent. Sequential importance sampling algorithm is applied to compute the permanents. For two-dimensional lattice with periodic condition, we obtain 0.6627±0.0002 0.6627\pm0.0002, where the exact value is h2=0.662798972834h_2=0.662798972834. For three-dimensional lattice with periodic condition, our numerical result is 0.7847±0.0014 0.7847\pm0.0014, {which agrees with the best known bound 0.7653h30.78620.7653 \leq h_3 \leq 0.7862.}Comment: 6 pages, 2 figure

    Controlling complex networks: How much energy is needed?

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    The outstanding problem of controlling complex networks is relevant to many areas of science and engineering, and has the potential to generate technological breakthroughs as well. We address the physically important issue of the energy required for achieving control by deriving and validating scaling laws for the lower and upper energy bounds. These bounds represent a reasonable estimate of the energy cost associated with control, and provide a step forward from the current research on controllability toward ultimate control of complex networked dynamical systems.Comment: 4 pages paper + 5 pages supplement. accepted for publication in Physical Review Letters; http://link.aps.org/doi/10.1103/PhysRevLett.108.21870

    Understanding Lung Carcinogenesis from a Morphostatic Perspective:Prevention and Therapeutic Potential of Phytochemicals for Targeting Cancer Stem Cells

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    Lung cancer is still one of the deadliest cancers, with over two million incidences annually. Prevention is regarded as the most efficient way to reduce both the incidence and death figures. Nevertheless, treatment should still be improved, particularly in addressing therapeutic resistance due to cancer stem cells—the assumed drivers of tumor initiation and progression. Phytochemicals in plant-based diets are thought to contribute substantially to lung cancer prevention and may be efficacious for targeting lung cancer stem cells. In this review, we collect recent literature on lung homeostasis, carcinogenesis, and phytochemicals studied in lung cancers. We provide a comprehensive overview of how normal lung tissue operates and relate it with lung carcinogenesis to redefine better targets for lung cancer stem cells. Nine well-studied phytochemical compounds, namely curcumin, resveratrol, quercetin, epigallocatechin-3-gallate, luteolin, sulforaphane, berberine, genistein, and capsaicin, are discussed in terms of their chemopreventive and anticancer mechanisms in lung cancer and potential use in the clinic. How the use of phytochemicals can be improved by structural manipulations, targeted delivery, concentration adjustments, and combinatorial treatments is also highlighted. We propose that lung carcinomas should be treated differently based on their respective cellular origins. Targeting quiescence-inducing, inflammation-dampening, or reactive oxygen species-balancing pathways appears particularly interesting
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