Sample records for topological charge definitions

  1. Fixed point action and topological charge for SU(2) gauge theory

    E-print Network

    Thomas A. DeGrand; Anna Hasenfratz; Decai Zhu

    1996-07-30

    We present a theoretically consistent definition of the topological charge operator based on renormalization group arguments. Results of the measurement of the topological susceptibility at zero and finite temperature for SU(2) gauge theory are presented.

  2. Charge and spin topological insulators

    SciTech Connect

    Kopaev, Yu. V., E-mail: kopaev@sci.lebedev.ru; Gorbatsevich, A. A.; Belyavskii, V. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2011-09-15

    The topologically nontrivial states of matter-charge and spin topological insulators, which exhibit, respectively, properties of the integer quantum Hall effect and the quantum spin Hall effect-are discussed. The topological characteristics (invariant with respect to weak adiabatic changes in the Hamiltonian parameters) which lead to such states are considered. The model of a 2D hexagonal lattice having symmetries broken with respect to time reversal and spatial inversion which was proposed by Haldane and marked the beginning of unprecedented activity in the study of topologically nontrivial states is discussed. This model relates the microscopic nature of the symmetry breaking with respect to the time reversal to the occurrence of spontaneous orbital currents which circulate within a unit cell. Such currents become zero upon summation over the unit cell, but they may form spreading current states at the surface which are similar to the edge current states under the quantum Hall effect. The first model of spontaneous currents (exciton insulator model) is considered, and the possibility of implementing new topologically nontrivial states in this model is discussed.

  3. Thermodynamics of charged topological dilaton black holes

    E-print Network

    Ahmad Sheykhi

    2007-10-15

    A class of $(n+1)$-dimensional topological black hole solutions in Einstein-Maxwell-dilaton theory with Liouville-type potentials for the dilaton field is presented. In these spacetimes, black hole horizon and cosmological horizon can be an $(n-1)$-dimensional positive, zero or negative constant curvature hypersurface. Because of the presence of the dilaton field, these topological black holes are neither asymptotically flat nor (anti)-de Sitter. We calculate the charge, mass, temperature, entropy and electric potential of these solutions. We also analyze thermodynamics of these topological black holes and disclose the effect of the dilaton field on the thermal stability of the solutions.

  4. Large statistics study of the topological charge distribution in the SU(3) gauge theory

    E-print Network

    Leonardo Giusti; Silvano Petrarca; Bruno Taglienti

    2007-05-22

    We present preliminary results for a high statistics study of the topological charge distribution in the SU(3) Yang-Mills theory obtained by using the definition of the charge suggested by Neuberger fermions. We find statistical evidence for deviations from a gaussian distribution. The large statistics required has been obtained by using PCs of the INFN-GRID.

  5. Particles of One-Half Topological Charge

    E-print Network

    Rosy Teh; Ban-Loong Ng; Khai-Ming Wong

    2012-08-07

    We would like to show the existence of finite energy SU(2) Yang-Mills-Higgs particles of one-half topological charge. The magnetic fields of these solutions at spatial infinity correspond to the magnetic field of a positive one-half magnetic monopole located at the origin and a semi-infinite Dirac string which carries a magnetic flux of $\\frac{2\\pi}{g}$ going into the center of the sphere at infinity. Hence the net magnetic charge of the configuration is zero. The solutions possess gauge potentials that are singular along one-half of the z-axis, elsewhere they are regular. There are two distinct configurations of these particles with different total energies and magnetic dipole moments. Their total energies are found to increase with the strength of the Higgs field self-coupling constant $\\lambda$.

  6. Comparison of topologies suitable for Capacitor Charging Systems

    E-print Network

    Maestri, S; Uicich, G; Benedetti, M; Cravero, JM

    2014-01-01

    This paper presents a comparison between topologies suitable for capacitor charging systems. The topologies under evaluation are a flyback converter, a half-bridge series resonant converter and a full-bridge phase-shifted converter. The main features of these topologies are highlighted, which allows the proper topology selection according to the application requirements. Moreover, the performed analysis permits to characterize the operational range of the main components thus allowing their appropriate sizing and selection. Simulation results are provided.

  7. Non-Gaussianities in the topological charge distribution of the SU(3) Yang--Mills theory

    E-print Network

    Marco Cé; Cristian Consonni; Georg P. Engel; Leonardo Giusti

    2015-06-19

    We study the topological charge distribution of the SU(3) Yang--Mills theory with high precision in order to be able to detect deviations from Gaussianity. The computation is carried out on the lattice with high statistics Monte Carlo simulations by implementing a naive discretization of the topological charge evolved with the Yang--Mills gradient flow. This definition is far less demanding than the one suggested from Neuberger's fermions and, as shown in this paper, in the continuum limit its cumulants coincide with those of the universal definition appearing in the chiral Ward identities. Thanks to the range of lattice volumes and spacings considered, we can extrapolate the results for the second and fourth cumulant of the topological charge distribution to the continuum limit with confidence by keeping finite volume effects negligible with respect to the statistical errors. Our best results for the topological susceptibility is t_0^2*chi=6.67(7)*10^-4, where t_0 is a standard reference scale, while for the ratio of the forth cumulant over the second we obtain R=0.233(45). The latter is compatible with the expectations from the large Nc expansion, while it rules out the theta-behavior of the vacuum energy predicted by the dilute instanton model. Its large distance from 1 implies that, in the ensemble of gauge configurations that dominate the path integral, the fluctuations of the topological charge are of quantum non-perturbative nature.

  8. Charged Topological Black Hole Pair Creation

    E-print Network

    R. B. Mann

    1997-05-28

    I examine the pair creation of black holes in spacetimes with a cosmological constant of either sign. I consider cosmological C-metrics and show that the conical singularities in this metric vanish only for three distinct classes of black hole metric, two of which have compact event horizons on each spatial slice. One class is a generalization of the Reissner-Nordstrom (anti) de Sitter black holes in which the event horizons are the direct product of a null line with a 2-surface with topology of genus $g$. The other class consists of neutral black holes whose event horizons are the direct product of a null conoid with a circle. In the presence of a domain wall, black hole pairs of all possible types will be pair created for a wide range of mass and charge, including even negative mass black holes. I determine the relevant instantons and Euclidean actions for each case. Only for spherical are non-static solutions possible.

  9. Stable structures with high topological charge in nonlinear photonic quasicrystals

    E-print Network

    Law, K J H; Kevrekidis, P G; Bishop, A R

    2010-01-01

    Stable vortices with topological charge of 3 and 4 are examined numerically and analytically in photonic quasicrystals created by interference of 5 as well as 8 beams, in the cases of cubic as well as saturable nonlinearities. These structures are experimentally realizable, including a prototypical example of a stable charge 4 vortex. Direct numerical simulations corroborate the analytical and numerical linear stability analysis predictions.

  10. Non-Gaussianities in the topological charge distribution of the SU(3) Yang--Mills theory

    E-print Network

    Cé, Marco; Engel, Georg P; Giusti, Leonardo

    2015-01-01

    We study the topological charge distribution of the SU(3) Yang--Mills theory with high precision in order to be able to detect deviations from Gaussianity. The computation is carried out on the lattice with high statistics Monte Carlo simulations by implementing a naive discretization of the topological charge evolved with the Yang--Mills gradient flow. This definition is far less demanding than the one suggested from Neuberger's fermions and, as shown in this paper, in the continuum limit its cumulants coincide with those of the universal definition appearing in the chiral Ward identities. Thanks to the range of lattice volumes and spacings considered, we can extrapolate the results for the second and fourth cumulant of the topological charge distribution to the continuum limit with confidence by keeping finite volume effects negligible with respect to the statistical errors. Our best results for the topological susceptibility is t_0^2*chi=6.67(7)*10^-4, where t_0 is a standard reference scale, while for the...

  11. The anomalous transport of axial charge: topological vs non-topological fluctuations

    E-print Network

    Iatrakis, Ioannis; Yin, Yi

    2015-01-01

    Axial charge imbalance is an essential ingredient in novel effects associated with chiral anomaly such as chiral magnetic effects (CME). In a non-Abelian plasma with chiral fermions, local axial charge can be generated a) by topological fluctuations which would create domains with non-zero winding number b) by conventional non-topological thermal fluctuations. We provide a holographic evaluations of medium's response to dynamically generated axial charge density in hydrodynamic limit and examine if medium's response depends on the microscopic origins of axial charge imbalance. We show a local domain with non-zero winding number would induce a non-dissipative axial current due to chiral anomaly. We illustrate holographically that a local axial charge imbalance would be damped out with the damping rate related to Chern-Simon diffusive constant. By computing chiral magnetic current in the presence of dynamically generated axial charge density, we found that the ratio of CME current over the axial charge density ...

  12. Diffusion of topological charge in lattice QCD simulations

    E-print Network

    Greg McGlynn; Robert D. Mawhinney

    2014-06-17

    We study the autocorrelations of observables constructed from the topological charge density, such as the topological charge on a time slice or in a subvolume, using a series of hybrid Monte Carlo simulations of pure SU(3) gauge theory with both periodic and open boundary conditions. We show that the autocorrelation functions of these observables obey a simple diffusion equation and we measure the diffusion coefficient, finding that it scales like the square of the lattice spacing. We use this result and measurements of the rate of tunneling between topological charge sectors to calculate the scaling behavior of the autocorrelation times of these observables on periodic and open lattices. There is a characteristic lattice spacing at which open boundary conditions become worthwhile for reducing autocorrelations and we show how this lattice spacing is related to the diffusion coefficient, the tunneling rate, and the lattice Euclidean time extent.

  13. Charge and the topology of spacetime

    E-print Network

    Tammo Diemer; Mark J Hadley

    1999-09-02

    A new class of electrically charged wormholes is described in which the outer two sphere is not spanned by a compact coorientable hypersurface. These wormholes can therefore display net electric charge from the source free Maxwell's equation. This extends the work of Sorkin on non-space orientable manifolds, to spacetimes which do not admit a time orientation. The work is motivated by the suggestion that quantum theory can be explained by modelling elementary particles as regions of spacetime with non-trivial causal structure. The simplest example of an electrically charged spacetime carries a spherical symmetry.

  14. Role of topological charge stabilization in protomeric tautomerism.

    PubMed

    Hatanaka, Masashi

    2015-02-12

    Protomeric tautomerism is analyzed in view of the topological charge stabilization rules. Based on Hückel molecular orbital considerations and modern DFT calculations, it was found that the branching of amino or hydroxyl groups significantly contributes to the stability of major species through the first- and second-order perturbations with respect to the isoelectronic hydrocarbon. While amino-imino tautomerism is almost completely dominated by topological charge stabilization, hydroxyl-oxo tautomerism is affected by changes in the resonance integral of C-O/C?O bonds. Nevertheless, apart from side effects such as hydrogen bonds or solvent effects, a quantitative preference rule for the prediction of the tautomeric stability can be developed using topological ?-electron energetics. As well as the analyses of simple bases, applications to complex or extended systems are exemplified analyzing purine bases, polyguanide, and polyuret. The present approach can be useful in conjunction with chemical intuition that comes from conventional valence bond theory. PMID:25619937

  15. Weyl and Dirac semimetals with Z2 topological charge

    NASA Astrophysics Data System (ADS)

    Morimoto, Takahiro; Furusaki, Akira

    2014-06-01

    We study the stability of gap-closing (Weyl or Dirac) points in the three-dimensional Brillouin zone of semimetals using Clifford algebras and their representation theory. We show that a pair of Weyl points with Z2 topological charge are stable in a semimetal with time-reversal and reflection symmetries when the square of the product of the two symmetry transformations equals minus identity. We present toy models of Z2 Weyl semimetals which have surface modes forming helical Fermi arcs. We also show that Dirac points with Z2 topological charge are stable in a semimetal with time-reversal, inversion, and SU(2) spin rotation symmetries when the square of the product of time-reversal and inversion equals plus identity. Furthermore, we briefly discuss the topological stability of point nodes in superconductors using Clifford algebras.

  16. Charge distributions and effective atomic charges in transition-metal complexes using generalized atomic polar tensors and topological analysis

    SciTech Connect

    Cioslowski, J.; Hay, P.J.; Ritchie, J.P. (Los Alamos National Laboratory, NM (USA))

    1990-01-11

    Advantages and shortcomings of three different definitions of the atomic charges, namely, the Mulliken, the generalized atomic polar tensors (GAPT), and the topological ones, are judged by applying them to the results of ab initio calculations on the TiF{sub 4}, Ni(CO){sub 4}, and FeH{sub 6}{sup 4{minus}} molecules. In agreement with previous reports, we find that the Mulliken charges vary widely with the choice of basis sets and therefore their utilization for the analysis of electronic structure of the transition-metal complexes is of little practical importance. On the other hand, both the GAPT and Bader's charges show a remarkable insensitivity to the quality of the basis sets.

  17. Valence topological charge-transfer indices for dipole moments

    Microsoft Academic Search

    Francisco Torrens

    2003-01-01

    New topological valence charge-transfer (CT) indices are applied to the calculation of dipole moments. The dipole moments calculated by algebraic and vector semisums of the CT indices are defined. The combination of the CT indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the

  18. Implementing a Magnetic Charge Topology Model for Solar Active Regions

    E-print Network

    Longcope, Dana

    , as well as uncorrelated noise. We determine the reliability of our method and estimate the uncertainties test this prediction. Magnetic charge topology (MCT) models assume that the photospheric magnetic field MCT models to observations, photospheric fields must be somehow represented as a set of distinct

  19. Rotating One-Half Topological Charge Dyon

    E-print Network

    Rosy Teh; Ban-Loong Ng; Khai-Ming Wong

    2012-10-01

    Recently, we have shown the existence of a finite energy one-half monopole. In this paper, we would like to introduce electric charge into the one-half monopole configuration, thus creating a one-half dyon. This one-half dyon possesses finite energy, magnetic dipole moment and angular momentum. Hence it is able to rotate in the presence of an external magnetic field. Similar to the single pole dyons and the MAP dyons, this one-half dyon possesses critical (maximum) electric charge, total energy, and magnetic dipole moment when the Higgs self-coupling constant is nonvanishing, and the electric charge parameter approaches one. This one-half dyon solution does not satisfy the first order Bogomol'nyi equations and is a non-BPS solution in the limit of vanishing Higgs self-coupling constant.

  20. Topology of event distributions as a generalized definition of phase transitions in finite systems

    Microsoft Academic Search

    Ph. Chomaz; F. Gulminelli; V. Duflot

    2001-01-01

    We propose a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. This generalizes the definitions based on the curvature anomalies of thermodynamical potentials, provides a natural definition of order parameters, and can be related to the Yang-Lee theorem in the thermodynamical limit. It is directly operational

  1. Topological charge and the spectrum of exactly massless fermions on the lattice

    NASA Astrophysics Data System (ADS)

    Chiu, Ting-Wai

    1998-10-01

    The square root of the positive definite Hermitian operator D†wDw in Neuberger's proposal of exactly massless quarks on the lattice is implemented by the recursion formula Yk+1=12(Yk+D†wDwY-1k) with Y0=1, where Y2k converges to D†wDw quadratically. The spectrum of the lattice Dirac operator for single massless fermion in two dimensional background U(1) gauge fields is investigated. For smooth background gauge fields with nonzero topological charge, the exact zero modes with definite chirality are reproduced to a very high precision on a finite lattice and the index theorem is satisfied exactly. The fermionic determinants are also computed and they are in good agreement with the continuum exact solution.

  2. Simultaneous magnetic and charge doping of topological insulators with carbon.

    PubMed

    Shen, Lei; Zeng, Minggang; Lu, Yunhao; Yang, Ming; Feng, Yuan Ping

    2013-12-01

    A two-step doping process, magnetic followed by charge or vice versa, is required to produce massive topological surface states (TSS) in topological insulators for many physics and device applications. Here, we demonstrate simultaneous magnetic and hole doping achieved with a single dopant, carbon, in Bi2Se3 by first-principles calculations. Carbon substitution for Se (C(Se)) results in an opening of a sizable surface Dirac gap (up to 82 meV), while the Fermi level remains inside the bulk gap and close to the Dirac point at moderate doping concentrations. The strong localization of 2p states of C(Se) favors spontaneous spin polarization via a p-p interaction and formation of ordered magnetic moments mediated by surface states. Meanwhile, holes are introduced into the system by C(Se). This dual function of carbon doping suggests a simple way to realize insulating massive TSS. PMID:24476296

  3. Local topological charge analysis of electromagnetic vortex beam based on empirical mode decomposition

    E-print Network

    Hui, Xiaonan; Zhang, Weite; Jin, Xiaofeng; Chi, Hao; Zhang, Xianmin

    2015-01-01

    The topological charge of an electromagnetic vortex beam depends on its wavefront helicity. For mixed vortex beams composed of several different coaxial vortices, the topological charge spectrum can be obtained by Fourier transform. However, the vortex beam is generally divergent and imperfect. It makes it significant to investigate the local topological charges, especially in radio frequency regime. Fourier transform based methods are restrained by the uncertainty principle and cannot achieve high angular resolution and mode resolution simultaneously. In this letter, an analysis method for local topological charges of vortex beams is presented based on the empirical mode decomposition (EMD). From EMD, the intrinsic mode functions (IMFs) can be obtained to construct the bases of the electromagnetic wave, and each local topological charge can be respectively defined. With this method the local value achieves both high resolution of azimuth angle and topological charge, meanwhile the amplitudes of each OAM mode...

  4. Glueballs and topological charge in the presence of dynamical quarks

    SciTech Connect

    Bitar, K.M.; Edwards, R.; Heller, U.M.; Kennedy, A.D. (Florida State Univ., Tallahassee, FL (USA). Supercomputer Computations Research Inst.); DeGrand, T.A. (Colorado Univ., Boulder, CO (USA). Dept. of Physics); Gottlieb, S.; Kraznitz, A. (Indiana Univ., Bloomington, IN (USA). Dept. of Physics); Kogut, J.B.; Renken, R.L. (Illinois Univ., Urbana, IL (USA). Dept. of Physics); Liu, W.; Rossi, P. (Thinking

    1990-11-01

    We have estimated the string tension and the masses of the 0{sup ++} and 2{sup ++} glueballs in lattice QCD with 2 light flavours of staggered quarks. In addition we have measured the topological charge and hence susceptibility of our gauge field configurations. The simulations were performed at 6/g{sup 2}=5.6 and quark masses m=0.01 and 0.025 (lattice units) on lattice sizes ranging from 12{sup 4} to 16{sup 4}. 7 refs., 5 figs.

  5. Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics

    E-print Network

    P. V. Buividovich; T. Kalaydzhyan; M. I. Polikarpov

    2012-10-21

    We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d = 2..3 towards the total space dimension. Therefore, the cooling procedure destroys some of the essential properties of the topological charge distribution.

  6. Thermodynamics of topological nonlinear charged Lifshitz black holes

    E-print Network

    Zangeneh, M Kord; Dehghani, M H

    2015-01-01

    In this paper, we construct a new class of analytic topological Lifshitz black holes with constant curvature horizon in the presence of power-law Maxwell field in four and higher dimensions. We find that in order to obtain these exact Lifshitz solutions, we need a dilaton and at least three electromagnetic fields. Interestingly enough, we find that the reality of the charge of the electromagnetic field which is needed for having solutions with curved horizon rules out black holes with hyperbolic horizon. Next, we study the thermodynamics of these nonlinear charged Lifshitz black holes with spherical and flat horizons by calculating all the conserved and thermodynamic quantities of the solutions. Furthermore, we obtain a generalized Smarr formula and show that the first law of thermodynamics is satisfied. Finally, we perform a stability analysis in both canonical and grand-canonical ensembles. We find that the solutions are thermally stable in a proper ranges of the metric parameters.

  7. Definitions, examples The polyhedral product functor (Stable) homotopy type Homotopy Lie algebras Topological aspects of partial product spaces: a

    E-print Network

    Denham, Graham

    Definitions, examples The polyhedral product functor (Stable) homotopy type Homotopy Lie algebras Topological aspects of partial product spaces: a survey Graham Denham Department of Mathematics University, November 2010 #12;Definitions, examples The polyhedral product functor (Stable) homotopy type Homotopy Lie

  8. Charged skyrmions on the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Hurst, Hilary M.; Efimkin, Dmitry K.; Zang, Jiadong; Galitski, Victor

    2015-02-01

    We consider the interplay between magnetic skyrmions in an insulating thin film and the Dirac surface states of a three-dimensional topological insulator (TI), coupled by the proximity effect. The magnetic texture of skyrmions can lead to confinement of Dirac states at the skyrmion radius, where out-of-plane magnetization vanishes. This confinement can result in charging of the skyrmion texture. The presence of bound states is robust in an external magnetic field, which is needed to stabilize skyrmions. It is expected that, for relevant experimental parameters, skyrmions will have a few bound states that can be tuned using an external magnetic field. We argue that these charged skyrmions can be manipulated directly by an electric field, with skyrmion mobility proportional to the number of bound states at the skyrmion radius. Coupling skyrmionic thin films to a TI surface can provide a more direct and efficient way of controlling skyrmion motion in insulating materials. This provides a different dimension in the study of skyrmion manipulation.

  9. Charged Particle Environment Definition for NGST: Model Development

    NASA Technical Reports Server (NTRS)

    Blackwell, William C.; Minow, Joseph I.; Evans, Steven W.; Hardage, Donna M.; Suggs, Robert M.

    2000-01-01

    NGST will operate in a halo orbit about the L2 point, 1.5 million km from the Earth, where the spacecraft will periodically travel through the magnetotail region. There are a number of tools available to calculate the high energy, ionizing radiation particle environment from galactic cosmic rays and from solar disturbances. However, space environment tools are not generally available to provide assessments of charged particle environment and its variations in the solar wind, magnetosheath, and magnetotail at L2 distances. An engineering-level phenomenology code (LRAD) was therefore developed to facilitate the definition of charged particle environments in the vicinity of the L2 point in support of the NGST program. LRAD contains models tied to satellite measurement data of the solar wind and magnetotail regions. The model provides particle flux and fluence calculations necessary to predict spacecraft charging conditions and the degradation of materials used in the construction of NGST. This paper describes the LRAD environment models for the deep magnetotail (XGSE < -100 Re) and solar wind, and presents predictions of the charged particle environment for NGST.

  10. Skyrmion Manipulation and Spin/Charge Transport in Topological insulators

    NASA Astrophysics Data System (ADS)

    Ndiaye, Papa Birame; Manchon, Aurelien; Spintronics Theory Group Team

    2015-03-01

    We study the diffusive spin dynamics at the interface between a 3D topological insulator and a topological magnetic texture using Keldysh formalism, supplemented by the gradient expansion. Following the work by Wang and Manchon, one cannot avoid the comparison between the 2D electron gas with Rashba SOC and the surface of a topological insulator, the analogy between the Rashba/ other SO torques and the intrinsic/extrinsic torque arising from a topological Dirac cone. The similarity between the Hamiltonian in the two cases can bridge the unique material properties of topological insulators and spintronics. We first derive the diffusion equation for the non-equilibrium spin accumulation. This approach provides a direct access to the diffusive dynamic equation, but we also evaluate the spin torque originated from the interaction between a topological magnetic texture like a Skyrmion and the TI interface.

  11. Exciton Condensation and Charge Fractionalization in a Topological Insulator Film

    Microsoft Academic Search

    B. Seradjeh; J. E. Moore; M. Franz

    2009-01-01

    An odd number of gapless Dirac fermions is guaranteed to exist at a surface of a strong topological insulator. We show that in a thin-film geometry and under external bias, electron-hole pairs that reside in these surface states can condense to form a novel exotic quantum state which we propose to call ``topological exciton condensate'' (TEC). This TEC is similar

  12. Valence Topological Charge-Transfer Indices for Dipole Moments: Percutaneous Enhancers

    Microsoft Academic Search

    Francisco Torrens

    2004-01-01

    Valence topological charge-transfer (CT) indices are applied to the calculation of dipole moments. The algebraic and vector semisum CT indices are defined. The combination of CT indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the molecular charge distribution is established by comparing them

  13. Topology and shape optimization of induced-charge electro-osmotic micropumps

    E-print Network

    Gregersen, Misha Marie; Bazant, Martin Z; Bruus, Henrik

    2009-01-01

    For a dielectric solid surrounded by an electrolyte and positioned inside an externally biased parallel-plate capacitor, we study numerically how the resulting induced-charge electro-osmotic (ICEO) flow depends on the topology and shape of the dielectric solid. In particular, we extend existing conventional electrokinetic models with an artificial design field to describe the transition from the liquid electrolyte to the solid dielectric. Using this design field, we have succeeded in applying the method of topology optimization to find system geometries with non-trivial topologies that maximize the net induced electro-osmotic flow rate through the electrolytic capacitor in the direction parallel to the capacitor plates. Once found, the performance of the topology optimized geometries has been validated by transferring them to conventional electrokinetic models not relying on the artificial design field. Our results show the importance of the topology and shape of the dielectric solid in ICEO systems and point...

  14. Electronegativities in situ, bond hardnesses, and charge-transfer components of bond energies from the topological theory of atoms in molecules

    SciTech Connect

    Cioslowski, J.; Mixon, S.T. (Florida State Univ., Tallahassee (United States))

    1993-02-10

    Rigorous definitions for electronegativities of atoms and functional groups in molecules, bond hardnesses, and the charge-transfer components of the bond energies are proposed. The definitions rely upon values of total energies and their derivatives calculated for molecules composed of fragments with a controlled degree of charge transfer. Such calculations, in which the atomic or fragment charges are obtained with the help of the topological theory of atoms in molecules, are easily accomplished by adding appropriate Lagrange multiplier terms to the electronic Hamiltonian. Numerical examples that are given for 23 different systems indicate that the bond hardnesses are mostly transferable, but because of the electric field generated by the molecular environment the electronegativity differences are not. 27 refs., 1 fig., 1 tab.

  15. Probing the vortex beams with fractional and integral topological charges using weak random scattering screen

    NASA Astrophysics Data System (ADS)

    Liu, Man

    2013-11-01

    By use of the numerical calculation based on the Kirchhoff Green's integral theorem, we study the intensity distributions of speckle fields behind the weak random scattering screens illuminated by the Laguerre-Gaussian beams. It is found that the profile of bright spot similar to the peacock-feather-like in intensity distributions of speckle field, those bright spots show uniform distribution around the central dark spots, and the number of bright spots is related to the topological charges of the vortex beams. We are able to probe the topological charges of Laguerre-Gaussian beams directly by observing the bright spots in the intensity distributions patterns.

  16. An Acoustic Charge Transport Imager for High Definition Television

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin; May, Gary; Glenn, William E.; Richardson, Mike; Solomon, Richard

    1999-01-01

    This project, over its term, included funding to a variety of companies and organizations. In addition to Georgia Tech these included Florida Atlantic University with Dr. William E. Glenn as the P.I., Kodak with Mr. Mike Richardson as the P.I. and M.I.T./Polaroid with Dr. Richard Solomon as the P.I. The focus of the work conducted by these organizations was the development of camera hardware for High Definition Television (HDTV). The focus of the research at Georgia Tech was the development of new semiconductor technology to achieve a next generation solid state imager chip that would operate at a high frame rate (I 70 frames per second), operate at low light levels (via the use of avalanche photodiodes as the detector element) and contain 2 million pixels. The actual cost required to create this new semiconductor technology was probably at least 5 or 6 times the investment made under this program and hence we fell short of achieving this rather grand goal. We did, however, produce a number of spin-off technologies as a result of our efforts. These include, among others, improved avalanche photodiode structures, significant advancement of the state of understanding of ZnO/GaAs structures and significant contributions to the analysis of general GaAs semiconductor devices and the design of Surface Acoustic Wave resonator filters for wireless communication. More of these will be described in the report. The work conducted at the partner sites resulted in the development of 4 prototype HDTV cameras. The HDTV camera developed by Kodak uses the Kodak KAI-2091M high- definition monochrome image sensor. This progressively-scanned charge-coupled device (CCD) can operate at video frame rates and has 9 gm square pixels. The photosensitive area has a 16:9 aspect ratio and is consistent with the "Common Image Format" (CIF). It features an active image area of 1928 horizontal by 1084 vertical pixels and has a 55% fill factor. The camera is designed to operate in continuous mode with an output data rate of 5MHz, which gives a maximum frame rate of 4 frames per second. The MIT/Polaroid group developed two cameras under this program. The cameras have effectively four times the current video spatial resolution and at 60 frames per second are double the normal video frame rate.

  17. Topological charge renormalization: A test case for 3-loop vacuum calculations using overlap fermions and Symanzik improved gluons

    Microsoft Academic Search

    Apostolos Skouroupathis; Haralambos Panagopoulos

    2005-01-01

    We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the Symanzik improved gluon action for 4- and 6-link loops. We compute the multiplicative renormalization of the topological charge density to one loop; this involves only the gluon part

  18. Topological charge renormalization: A test case for 3-loop vacuum calculations using overlap fermions and Symanzik improved gluons

    E-print Network

    A. Skouroupathis; H. Panagopoulos

    2005-09-07

    We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the Symanzik improved gluon action for 4- and 6-link loops. We compute the multiplicative renormalization of the topological charge density to one loop; this involves only the gluon part of the action. The power divergent additive renormalization of the topological susceptibility is calculated to 3 loops.

  19. Topological generation and load distribution factors for supplement charge allocation in transmission open access

    Microsoft Academic Search

    J. Bialek

    1997-01-01

    This paper introduces a simple novel method of transmission supplement charge allocation based on topological analysis of power flows in the network. The method uses the MW-MILE methodology but analyses the share, not the impact of, individual loads and generators in line flows. This results in positive contributions from all the users hence rescinding the problem of counterflows

  20. Charge quantisation without magnetic monopoles: a topological approach to electromagnetism

    E-print Network

    Romero Solha

    2014-06-24

    The present work provides a theoretical explanation for the quantisation of electric charges, an open problem since Millikan's oil drop experiment in 1909. This explanation is based solely on Maxwell's theory, it recasts Electromagnetic theory under the language of complex line bundles; therefore, neither magnetic monopoles nor quantum mechanics are invoked. Essentially, the existence of magnetic monopoles was the only theoretical explanation for charge quantisation (e.g. Dirac's monopole), and there is no experimental data supporting their existence ---on the contrary, they have nerver been observed.

  1. Charge Pump Circuits: An Overview on Design Strategies and Topologies

    Microsoft Academic Search

    Gaetano Palumbo; Domenico Pappalardo

    2010-01-01

    Due to the continuous power supply reduction, charge pumps circuits are widely used in integrated circuits (ICs) devoted to several kind of applications such as smart power, nonvolatile memories, switched capacitor circuits, operational amplifiers, voltage regulators, SRAMs, LCD drivers, piezoelectric actuators, RF antenna switch controllers, etc. The main focus of this tutorial manuscript is to provide a deep understanding of

  2. Topology of drift trajectories of charged particles in a tokamak

    NASA Astrophysics Data System (ADS)

    Gott, Yu. V.; Yurchenko, E. I.

    2014-04-01

    The topology of drift orbits in a tokamak is analyzed in the entire cross section of the device both near the magnetic axis and at the periphery of the plasma column. The use of invariants of the drift equations (the generalized momentum, magnetic moment, and total energy) as variables for the entire cross section of the plasma column and self-similar variables near the magnetic axis makes it possible to comprehensively classify closed drift orbits in a tokamak. When describing orbits of different types and domains of their existence, discriminant and locus curves obtained by the methods of differential geometry are used to determine the ranges in which the invariants vary. The influence of the nonuniformity of the longitudinal current on the drift trajectories of fast particles is studied. The works in which, together with known types of orbits, trajectories along which particles leave the plasma column and can fall on the chamber wall are analyzed.

  3. Direct Observation of Chiral Topological Solitons in 1D Charge-Density Waves

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hwan; Cheon, Sangmo; Lee, Sung-Hoon; Yeom, Han Woong

    2015-03-01

    Macroscopic and classical solitons are easily and ubiquitously found, from tsunami to blood pressure pulses, but those in microscopic scale are hard to observe. While the existence of such topological solitons were predicted theoretically and evidenced indirectly by the transport and infrared spectroscopy measurements, the direct observation has been hampered by their high mobility and small dimension. In this talk, we show direct observation of topological solitons in the quasi-1D charge-density wave (CDW) ground state of indium atomic wires, which are consisting of interacting double Peierls chains. Such solitons exhibit a characteristic spatial variation of the CDW amplitudes as expected from the electronic structure. Furthermore, these solitons have an exotic hidden topology originated by topologically different 4-fold degenerate CDW ground states. Their exotic topology leads to the chirality of 1D topological solitons through interaction between two solitons in the double Peierls chains. Detailed scanning tunneling microscopy and spectroscopy reveal their chiral nature at the atomic scale. This work paves the avenue toward the microscopic exploitation of the peculiar properties of nanoscale chiral solitons.

  4. Effects of Reasonable Doubt Definition and Inclusion of a Lesser Charge on Jury Verdicts

    Microsoft Academic Search

    Chantal Mees Koch; Dennis J. Devine

    1999-01-01

    The impact of two procedural factors on jury verdicts was assessed in a mock jury study: (1) definition of the term “reasonable doubt” and (2) inclusion of a “lesser” charge against the defendant in addition to a primary charge. Mock juries of 4-7 persons read an edited transcript from a real murder trial and deliberated to a unanimous verdict. Juries

  5. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin F.; Summers, Chris J.

    1992-01-01

    In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program.

  6. Equations of motion of Dirac-like topological charges in Yang-Mills fields

    SciTech Connect

    Hong-Mo, C. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX (United Kingdom)] [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX (United Kingdom); Faridani, J. [Department of Theoretical Physics, Oxford University, 1 Keble Road, Oxford, OX1 3NP (United Kingdom)] [Department of Theoretical Physics, Oxford University, 1 Keble Road, Oxford, OX1 3NP (United Kingdom); Sheung Tsun, T. [Mathematical Institute, Oxford University, 24-29 St. Giles`, Oxford, OX1 3LB (United Kingdom)] [Mathematical Institute, Oxford University, 24-29 St. Giles`, Oxford, OX1 3LB (United Kingdom)

    1995-06-15

    Most non-Abelian gauge theories admit the existence of conserved and quantized topological charges as generalizations of the Dirac monopole. Their interactions are dictated by topology. In this paper, previous work in deriving classical equations of motion for these charges is extended to quantized particles described by Dirac wave functions. The resulting equations show intriguing similarities to the Yang-Mills theory. Further, although the system is not dual symmetric, its gauge symmetry is nevertheless doubled as in the Abelian case from {ital G} to {ital G}{times}{ital G}, where the second {ital G} has opposite parity to the first but is mediated instead by an antisymmetric second-rank tensor potential.

  7. No P- V criticality for charged topological black holes in Ho?ava-Lifshitz gravity

    NASA Astrophysics Data System (ADS)

    Mo, Jie-Xiong

    2015-04-01

    Searching for the unusual characteristics of Ho?ava-Lifshitz gravity, we generalize our former research of charged topological black holes in Ho?ava-Lifshitz gravity to the extended phase space. By treating cosmological constant as thermodynamic pressure, thermodynamic volume is derived as the conjugate quantity. P- V criticality is investigated by carrying out analytic analysis not only for the uncharged case but also for the charged case. All the topologies are considered. Unfortunately, no physical critical point has been found in all the cases. The results suggests again that the van der Waals like P- V criticality is not a universal phenomenon by providing one more example other than BTZ black holes. Our results also show that the existence of cosmological constant in the black hole metric is not sufficient for the existence of van der Waals like P- V criticality.

  8. Persistent Hall voltages across thin planar charged quantum rings on the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Durganandini, P.

    2015-03-01

    We consider thin planar charged quantum rings on the surface of a three dimensional topological insulator coated with a thin ferromagnetic layer. We show theoretically, that when the ring is threaded by a magnetic field, then, due to the Aharanov-Bohm effect, there are not only the well known circulating persistent currents in the ring but also oscillating persistent Hall voltages across the thin ring. Such oscillating persistent Hall voltages arise due to the topological magneto-electric effect associated with the axion electrodynamics exhibited by the surface electronic states of the three dimensional topological insulator when time reversal symmetry is broken. We further generalize to the case of dipole currents and show that analogous Hall dipole voltages arise. We also discuss the robustness of the effect and suggest possible experimental realizations in quantum rings made of semiconductor heterostructures. Such experiments could also provide new ways of observing the predicted topological magneto-electric effect in three dimensional topological insulators with time reversal symmetry breaking. I thank BCUD, Pune University, Pune for financial support through research grant.

  9. Charge and spin edge currents in two-dimensional Floquet topological superconductors

    NASA Astrophysics Data System (ADS)

    Sacramento, P. D.

    2015-06-01

    A time periodic driving on a topologically trivial system induces edge modes and topological properties. In this work we consider triplet and singlet superconductors subject to periodic variations of the chemical potential, spin-orbit coupling, and magnetization in both topologically trivial and nontrivial phases, and study their influence on the charge and spin currents that propagate along the edges of the two-dimensional system, for moderate to large driving frequencies. Currents associated with the edge modes are induced in the trivial phases and enhanced in the topological phases. In some cases there is a sign reversal of the currents as a consequence of the periodic driving. The edge states associated with the finite quasienergy states at the edge of the Floquet zone are in general robust, while the stability of the zero quasienergy states depends on the parameters. Also, the spin polarization of the Floquet spectrum quasienergies is strong as for the unperturbed topological phases. It is found that in some cases the unperturbed edge states are immersed in a continuum of states due to the perturbation, particularly if the driving frequency is not large enough. However, their contribution to the edge currents and spin polarization is still significant.

  10. Transfer and computation of optical topological charges via light pulse buffer memory in an electromagnetically-induced-transparency solid

    NASA Astrophysics Data System (ADS)

    Zhai, Zhaohui; Li, Zhixiang; Xu, Jingjun; Zhang, Guoquan

    2013-09-01

    We verified that optical topological charges are conserved in a two-step light-pulse storage and retrieval process based on the electromagnetically-induced-transparency (EIT) effect in a Pr3+:Y2SiO5 crystal. Based on this conservation law, one could transfer topological charges from the interacting beams, which may not be overlapped in space and time domains, to the targeted output signal beam, and algebraic operations such as summation and subtraction of topological charges carried by the interacting beams were demonstrated via the EIT-assisted two-step light-pulse storage-retrieval process. The results may be useful for classical and quantum information processing based on optical topological charge buffer memory in EIT media.

  11. Direct observation of the topological charge of a terahertz vortex beam generated by a Tsurupica spiral phase plate

    SciTech Connect

    Miyamoto, K., E-mail: k-miyamoto@faculty.chiba-u.jp [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Suizu, K.; Akiba, T. [Department of Electrical, Electronics and Computer Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016 (Japan); Omatsu, T. [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); CREST Japan Science and Technology Agency, Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2014-06-30

    A terahertz (THz) spiral phase plate with high transmission (>90% after Fresnel correction) and low dispersion has been developed based on the Tsurupica olefin polymer. Direct observations of the topological charge (both magnitude and sign) of a THz vortex beam are performed by using a THz camera with tilted lens focusing and radial defect introduction. The vortex outputs with a topological charge of ±1 (or ±2) are obtained at a frequency of 2 (or 4) THz.

  12. Quantum simulation of topological Majorana bound states and their universal quantum operations using charge-qubit arrays

    NASA Astrophysics Data System (ADS)

    Mao, Ting; Wang, Z. D.

    2015-01-01

    Majorana bound states have been a focus of condensed matter research for their potential applications in topological quantum computation. Here we utilize two charge-qubit arrays to explicitly simulate a DIII class one-dimensional superconductor model where Majorana end states can appear. Combined with one braiding operation, universal single-qubit operations on a Majorana-based qubit can be implemented by a controllable inductive coupling between two charge qubits at the ends of the arrays. We further show that in a similar way, a controlled-not gate for two topological qubits can be simulated in four charge-qubit arrays. Although the current scheme may not truly realize topological quantum operations, we elaborate that the operations in charge-qubit arrays are indeed robust against certain local perturbations.

  13. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin F.; Summers, Christopher J.

    1993-01-01

    This report covers: (1) invention of a new, ultra-low noise, low operating voltage APD which is expected to offer far better performance than the existing volume doped APD device; (2) performance of a comprehensive series of experiments on the acoustic and piezoelectric properties of ZnO films sputtered on GaAs which can possibly lead to a decrease in the required rf drive power for ACT devices by 15dB; (3) development of an advanced, hydrodynamic, macroscopic simulator used for evaluating the performance of ACT and CTD devices and aiding in the development of the next generation of devices; (4) experimental development of CTD devices which utilize a p-doped top barrier demonstrating charge storage capacity and low leakage currents; (5) refinements in materials growth techniques and in situ controls to lower surface defect densities to record levels as well as increase material uniformity and quality.

  14. Two phase equilibrium in charged topological dilaton AdS black hole

    E-print Network

    Hui-Hua Zhao; Li-Chun Zhang; Meng-Sen Ma; Ren Zhao

    2014-12-01

    In this paper we discuss the phase transition of the charged topological dilaton AdS black holes by Maxwell equal area law. Using Maxwell equal area law we found the border of the region of two phase coexistence in $P-v$ diagrams and analyze the parameters which affect the extent of the region. We also plot the $P-T$ phase diagram and derive the Clapeyron equation for the black hole, and investigate the phase change latent heat. The results show the phase transition characteristic is similar to that of usual non-gravity thermodynamic systems.

  15. Topological charges in SL(2,R) covariant massive 11-dimensional and type IIB supergravity

    NASA Astrophysics Data System (ADS)

    Callister, Andrew K.; Smith, Douglas J.

    2009-12-01

    In this paper we construct closed expressions that correspond to the topological charges of the various 1/2-BPS states of the maximal 10- and 11-dimensional supergravity theories. These expressions are related to the structure of the supersymmetry algebras in curved spacetimes. We mainly focus on IIB supergravity and 11-dimensional supergravity in a double M9-brane background, with an emphasis on the SL(2,R) multiplet structure of the charges and how these map between theories. This includes the charges corresponding to the multiplets of 7- and 9-branes in IIB. We find that examining the possible multiplet structures of the charges provides another tool for exploring the spectrum of BPS states that appear in these theories. As a prerequisite to constructing the charges we determine the field equations and multiplet structure of the 11-dimensional gauge potentials, extending previous results on the subject. The massive gauge transformations of the fields are also discussed. We also demonstrate how these massive gauge transformations are compatible with the construction of an SL(2,R) covariant kinetic term in the 11-dimensional Kaluza-Klein monopole worldvolume action.

  16. Full electrical control of Charge and Spin conductance through Interferometry of Edge States in Topological Insulators

    E-print Network

    Fabrizio Dolcini

    2011-05-13

    We investigate electron interferometry of edge states in Topological Insulators. We show that, when inter-boundary coupling is induced at two quantum point contacts of a four terminal setup, both Fabry-P\\'erot-like and Aharonov-Bohm-like loop processes arise. These underlying interference effects lead to a full electrically controllable system, where the magnitude of charge and spin linear conductances can be tuned by gate voltages, without applying magnetic fields. In particular we find that, under appropriate conditions, inter-boundary coupling can lead to negative values of the conductance. Furthermore, the setup also allows to selectively generate pure charge or pure spin currents, by choosing the voltage bias configuration.

  17. Spin-charge separation of plasmonic excitations in thin topological insulators

    NASA Astrophysics Data System (ADS)

    Stauber, T.; Gómez-Santos, G.; Brey, L.

    2013-11-01

    We discuss plasmonic excitations in a thin slab of topological insulators. In the limit of no hybridization of the surface states and same electronic density of the two layers, the electrostatic coupling between the top and bottom layers leads to optical and acoustic plasmons which are purely charge and spin collective oscillations. We then argue that a recent experiment on the plasmonic excitations of Bi2Se3 [Di Pietro , Nat. Nanotechnol.1748-338710.1038/nnano.2013.134 8, 556 (2013)] must be explained by including the charge response of the two-dimensional electron gas of the depletion layer underneath the two surfaces. We also present an analytic formula to fit their data.

  18. Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)

    NASA Astrophysics Data System (ADS)

    Delacroix, Christian; Absil, Olivier; Carlomagno, Brunella; Piron, Pierre; Forsberg, Pontus; Karlsson, Mikael; Mawet, Dimitri; Habraken, Serge; Surdej, Jean

    2014-08-01

    One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2? radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation.

  19. Gel’fand-Yaglom equations with charge or energy density of definite sign

    Microsoft Academic Search

    V. Amar; U. Dozzio

    1972-01-01

    Summary  We consider finite-dimensional Gel’fand-Yaglom equations with the supplementary requirement that for half-odd spin the charge\\u000a density and for integer spin the energy density be positive definite. We derive, in general, a necessary condition to satisfy\\u000a this requirement, in terms of a restriction on the structure of the Gel’fand chains. For equations with unique mass and spin\\u000a this necessary condition is

  20. Phase Fluctuations and the Absence of Topological Defects in Photo-excited Charge Ordered Nickelate

    SciTech Connect

    Lee, W.S.; Chuang, Y.D.; Moore, R.G.; Zhu, Y.; Patthey, L.; Trigo, M.; Lu, D.H.; Kirchmann, P.S.; Krupin, O.; Yi, M.; Langner, M.; Huse, N.; Robinson, J.S.; Chen, Y.; Zhou, S.Y.; Coslovich, G.; Huber, B.; Reis, D.A.; Kaindl, R.A.; Schoenlein, R.W.; Doering, D.

    2012-05-15

    The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La{sub 1.75}Sr{sub 0.25}NiO{sub 4} to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter.

  1. Additive and multiplicative renormalization of topological charge with improved gluon and fermion actions: A test case for 3-loop vacuum calculations, using overlap or clover fermions

    Microsoft Academic Search

    A. Skouroupathis; H. Panagopoulos

    2005-01-01

    We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the Symanzik improved gluon action for 4- and 6-link loops. We compute the multiplicative renormalization of the topological charge density to one loop; this involves only the gluon part

  2. Topological analysis of aromatic halogen/hydrogen bonds by electron charge density and electrostatic potentials.

    PubMed

    Duarte, Darío J R; de las Vallejos, Margarita M; Peruchena, Nélida M

    2010-04-01

    In this work, the intermolecular distribution of the electronic charge density in the aromatic hydrogen/halogen bonds is studied within the framework of the atoms in molecules (AIM) theory and the molecular electrostatic potentials (MEP) analysis. The study is carried out in nine complexes formed between benzene and simple lineal molecules, where hydrogen, fluorine and chlorine atoms act as bridge atoms. All the results are obtained at MP2 level theory using cc-pVTZ basis set. Attention is focused on topological features observed at the intermolecular region such as bond, ring and cage critical points of the electron density, as well as the bond path, the gradient of the density maps, molecular graphs and interatomic surfaces. The strength of the interaction increases in the following order: F[Symbol: see text]pi < Cl[Symbol: see text]pi < H[Symbol: see text]pi. Our results show that the fluorine atom has the capability to interact with the pi-cloud to form an aromatic halogen bond, as long as the donor group is highly electron withdrawing. The Laplacian topology allows us to state that the halogen atoms can act as nucleophiles as well as electrophiles, showing clearly their dual character. PMID:19820973

  3. Propagation of a topologically half-charge vortex light beam in a self-focusing photorefractive medium.

    PubMed

    Chen, Chih-Rong; Yeh, Chih-Hung; Shih, Ming-Feng

    2014-02-10

    While a fundamental Gaussian light beam can form stably a spatial soliton in certain self-focusing medium, a single-wave topologically integer-n-charge vortex light beam cannot. It breaks up into 2n filaments due to symmetry breaking and azimuthal instability, in which every azimuthal section of a ? phase range from a soliton and repels itself from its azimuthal neighboring soliton. Then what happens to the half-charge vortex light beam, which contains only one section of a ? phase range? We investigate experimentally and theoretically the propagation and stability of a topologically half-charge vortex light beam in a self-focusing photorefractive medium. We observed that the light beam propagates unstably in a self-focusing medium and breaks up into three filaments. This result is confirmed by numerical simulation and perturbation analysis. PMID:24663609

  4. Charged Particle Environment Definition for NGST: L2 Plasma Environment Statistics

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Blackwell, William C.; Neergaard, Linda F.; Evans, Steven W.; Hardage, Donna M.; Owens, Jerry K.

    2000-01-01

    The plasma environment encountered by the Next Generation Space Telescope satellite in a halo orbit about L2 can include the Earth's magnetotail and magnetosheath in addition to the solar wind depending on the orbital radius chosen for the mission. Analysis of plasma environment impacts on the satellite requires knowledge of the average and extreme plasma characteristics to assess the magnitude of spacecraft charging and materials degradation expected for the mission lifetime. This report describes the analysis of plasma data from instruments onboard the IMP 8 and Geotail spacecraft used to produce the plasma database for the LRAD engineering-level phenomenology code developed to provide the NGST L2 environment definition.

  5. Carrier control via charge transfer at the topological-insulator/organic-molecule interface

    NASA Astrophysics Data System (ADS)

    Tanigaki, Katsumi; Tanabe, Yoichi; Kuynh, Khuong; Urata, Takahiro; Nouchi, Ryo; Heguri, Satoshi; Shimotani, Hidekazu; AIMR, Tohoku University Collaboration; Department of Pysics, Graduate School of Science, Tohoku University Collaboration; Osaka Prefecture University Collaboration

    2013-03-01

    A topological insulator is a material that behaves as an insulator as a bulk state, while permitting metallicity on its Dirac cone surface state. One of the most serious issues of recent researches in this field, however, has been the fact that the Fermi levels in many TIs actually fall in either the conduction or valence band due to the naturally occurring defects and must be controlled by further doping. We report here that the major electron carriers on the SS of a Bi2-xSbxTe3-ySey(BSTS) single crystal can be converted to the hole carriers via interface control using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F4-TCNQ), with strong electron affinity. The evidence can be elucidated using a detailed three-carrier model. The results apparently demonstrate that the charge transfer at the TI/organic-molecule interface is very efficient in order to control the carrier density of TIs, particularly on the SS. Our present results will be very important for studying the fundamental aspects of TIs as well as their future device applications. A topological insulator is a material that behaves as an insulator as a bulk state, while permitting metallicity on its Dirac cone surface state. One of the most serious issues of recent researches in this field, however, has been the fact that the Fermi levels in many TIs actually fall in either the conduction or valence band due to the naturally occurring defects and must be controlled by further doping. We report here that the major electron carriers on the SS of a Bi2-xSbxTe3-ySey(BSTS) single crystal can be converted to the hole carriers via interface control using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F4-TCNQ), with strong electron affinity. The evidence can be elucidated using a detailed three-carrier model. The results apparently demonstrate that the charge transfer at the TI/organic-molecule interface is very efficient in order to control the carrier density of TIs, particularly on the SS. Our present results will be very important for studying the fundamental aspects of TIs as well as their future device applications. Osaka Prefecture University

  6. Scalar and tensorial topological matter coupled to (2+1)-dimensional gravity:A.Classical theory and global charges

    E-print Network

    R. B. Mann; E. M. Popescu

    2005-11-27

    We consider the coupling of scalar topological matter to (2+1)-dimensional gravity. The matter fields consist of a 0-form scalar field and a 2-form tensor field. We carry out a canonical analysis of the classical theory, investigating its sectors and solutions. We show that the model admits both BTZ-like black-hole solutions and homogeneous/inhomogeneous FRW cosmological solutions.We also investigate the global charges associated with the model and show that the algebra of charges is the extension of the Kac-Moody algebra for the field-rigid gauge charges, and the Virasoro algebrafor the diffeomorphism charges. Finally, we show that the model can be written as a generalized Chern-Simons theory, opening the perspective for its formulation as a generalized higher gauge theory.

  7. Use of topological charge to determine filament location and dynamics in a numerical model of scroll wave activity.

    PubMed

    Bray, Mark-Anthony; Wikswo, John P

    2002-10-01

    The unique time course of an excitable element in cardiac tissue can be represented as the phase of its trajectory in state space. A phase singularity is defined as a spatial point where the surrounding phase values changes by a total of 2 pi, thereby forming the organizing center for a reentrant excitatory wave, a phenomenon which occurs in cardiac fibrillation. In this paper, we describe a methodology to detect the singular filament in numeric simulations of three-dimensional (3-D) scroll waves by using the concept of topological charge. Here, we use simple two-variable models of cardiac activity to construct the state space, generate the phase field, and calculate the topological charge as a summation of 3-D convolution operations. We illustrate the usage of the algorithm on the basic dynamics of vortex ring filament behavior as well as the more complex spatiotemporal behavior observed in fibrillation. We also compare the motion of filament wavetips as determined by the phase field produced by two-variable state space and single-variable, time-delay embedded state space. Finally, we examine the state spaces produced by a more complex three-variable model. We conclude that the use of state-space analysis, along with the unique properties of topological charge, allows for a novel means of filament localization. PMID:12374332

  8. Symmetry-protected topological phases with charge and spin symmetries: Response theory and dynamical gauge theory in two and three dimensions

    E-print Network

    Ye, Peng

    A large class of symmetry-protected topological phases (SPT) in boson/spin systems have been recently predicted by the group cohomology theory. In this work, we consider bosonic SPT states at least with charge symmetry ...

  9. Additive and multiplicative renormalization of topological charge with improved gluon/fermion actions: A test case for 3-loop vacuum calculations, using overlap or clover fermions

    E-print Network

    A. Skouroupathis; H. Panagopoulos

    2006-01-02

    We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the Symanzik improved gluon action for 4- and 6-link loops. We compute the multiplicative renormalization of the topological charge density to one loop; this involves only the gluon part of the action. The power divergent additive renormalization of the topological susceptibility is calculated to 3 loops. Our work serves also as a test case of the techniques and limitations of lattice perturbation theory, it being the first 3-loop computation in the literature involving overlap fermions.

  10. Topological phases in Iridium oxide superlattices: quantized anomalous charge or valley Hall insulators

    NASA Astrophysics Data System (ADS)

    Kee, Hae-Young; Chen, Yige

    2015-03-01

    Designing materials is one of intense topics in modern condensed matter physics. Recently, how to achieve a topological insulator in transition metal oxides with strong spin-orbit coupling became an interesting subject. We have investigated possible topological phases in orthorhombic perovskite Iridium (Ir) oxide superlattices grown along the [001] crystallographic axis. We found that bilayer Ir oxide superlattices exhibit quantized anomalous Hall effects in magnetic topological insulating phases. We also found, depending on the stacking of two layers, a valley Hall insulator with nontrivial valley dependent surface modes and a topological crystalline insulator with the crystal symmetry protected edge states can be realized. Experimental tools to detect such topological phases are also discussed.

  11. Flux–charge duality and topological quantum phase fluctuations in quasi-one-dimensional superconductors

    E-print Network

    Kerman, Andrew J.

    It has long been thought that macroscopic phase coherence breaks down in effectively lower-dimensional superconducting systems even at zero temperature due to enhanced topological quantum phase fluctuations. In ...

  12. Surface state charge dynamics of a high-mobility three-dimensional topological insulator.

    PubMed

    Hancock, Jason N; van Mechelen, J L M; Kuzmenko, Alexey B; van der Marel, Dirk; Brüne, Christoph; Novik, Elena G; Astakhov, Georgy V; Buhmann, Hartmut; Molenkamp, Laurens W

    2011-09-23

    We present a magneto-optical study of the three-dimensional topological insulator, strained HgTe, using a technique which capitalizes on advantages of time-domain spectroscopy to amplify the signal from the surface states. This measurement delivers valuable and precise information regarding the surface-state dispersion within <1 meV of the Fermi level. The technique is highly suitable for the pursuit of the topological magnetoelectric effect and axion electrodynamics. PMID:22026887

  13. 140 Basic Differential Topology Definition 5.28 For 0 r Cr(M, N) denote the space of Cr maps

    E-print Network

    Hurtubise, David E.

    140 Basic Differential Topology Definition 5.28 For 0 r Cr(M, N) denote the space of Cr maps between two Cr manifolds M and N. Let f Cr(M, N), and let (, U) and (, V ) be charts on M and N (f; (, U), (, V ), ) to be the set of Cr maps g : M N such that g(K) V and Dk (f-1 )(x) - Dk (g-1

  14. The self-energy of a charged particle in the presence of a topological defect distribution

    E-print Network

    A. M. de M. Carvalho; Fernando Moraes; Claudio Furtado

    2004-01-09

    In this work we study a charged particle in the presence of both a continuous distribution of disclinations and a continuous distribution of edge dislocations in the framework of the geometrical theory of defects. We obtain the self-energy for a single charge both in the internal and external regions of either distribution. For both distributions the result outside the defect distribution is the self-energy that a single charge experiments in the presence of a single defect.

  15. Scaling and Topological Charge of a Fixed Point Action for $SU(2)$ Gauge Theory

    E-print Network

    Thomas DeGrand; Anna Hasenfratz; Decai Zhu

    1996-04-18

    We construct a few parameter approximate fixed point action for SU(2) pure gauge theory and subject it to scaling tests, via Monte Carlo simulation. We measure the critical coupling for deconfinement for lattices of temporal extent $N_t=2$, 3, 4, the torelon mass at fixed physical volume, and the string tension (and heavy quark potential) from Wilson loops. We calculate the topological susceptibility using inverse blocking and show that it scales over the observed range of lattice spacings.

  16. Charge transport in organic crystals: role of disorder and topological connectivity.

    PubMed

    Vehoff, Thorsten; Baumeier, Björn; Troisi, Alessandro; Andrienko, Denis

    2010-08-25

    We analyze the relationship among the molecular structure, morphology, percolation network, and charge carrier mobility in four organic crystals: rubrene, indolo[2,3-b]carbazole with CH(3) side chains, and benzo[1,2-b:4,5-b']bis[b]benzothiophene derivatives with and without C(4)H(9) side chains. Morphologies are generated using an all-atom force field, while charge dynamics is simulated within the framework of high-temperature nonadiabatic Marcus theory or using semiclassical dynamics. We conclude that, on the length scales reachable by molecular dynamics simulations, the charge transport in bulk molecular crystals is mostly limited by the dynamic disorder, while in self-assembled monolayers the static disorder, which is due to the slow motion of the side chains, enhances charge localization and influences the transport dynamics. We find that the presence of disorder can either reduce or increase charge carrier mobility, depending on the dimensionality of the charge percolation network. The advantages of charge transporting materials with two- or three-dimensional networks are clearly shown. PMID:20666495

  17. Probing Membrane Topology of the Antimicrobial Peptide Distinctin by Solid-State NMR Spectroscopy in Zwitterionic and Charged Lipid Bilayers

    PubMed Central

    Verardi, Raffaello; Traaseth, Nathaniel J.; Shi, Lei; Porcelli, Fernando; Monfregola, Luca; De Luca, Stefania; Amodeo, Pietro; Veglia, Gianluigi; Scaloni, Andrea

    2010-01-01

    Distinctin is a 47-residue antimicrobial peptide, which interacts with negatively charged membranes and is active against Gram-positive and Gram-negative bacteria. Its primary sequence comprises two linear chains of 22 (chain 1) and 25 (chain 2) residues, linked by a disulfide bridge between Cys19 of chain 1 and Cys23 of chain 2. Unlike other antimicrobial peptides, distinctin in the absence of the lipid membrane has a well-defined three-dimensional structure, which protects it from protease degradation. Here, we used static solid-state NMR spectroscopy to study the topology of distinctin in lipid bilayers. We found that In mechanically aligned lipid bilayers (charged or zwitterionic) this heterodimeric peptide adopts an ordered conformation absorbed on the surface of the membrane, with the long helix (chain 2), approximately parallel to the lipid bilayer (?5° from the membrane plane) and the short helix (chain 1) forming a ?24° angle. Since at lipid-to-protein molar ratio of 50:1 the peptide does not disrupt the macroscopic alignment of either charged or zwitterionic lipid bilayers, it is possible that higher concentrations might be needed for the hypothesized pore formation, or alternatively, distinctin elicits its cell disruption action by other mechanisms. PMID:20719234

  18. Charge and spin transport in edge channels of a ?=0 quantum Hall system on the surface of topological insulators.

    PubMed

    Morimoto, Takahiro; Furusaki, Akira; Nagaosa, Naoto

    2015-04-10

    Three-dimensional topological insulators of finite thickness can show the quantum Hall effect (QHE) at the filling factor ?=0 under an external magnetic field if there is a finite potential difference between the top and bottom surfaces. We calculate energy spectra of surface Weyl fermions in the ?=0 QHE and find that gapped edge states with helical spin structure are formed from Weyl fermions on the side surfaces under certain conditions. These edge channels account for the nonlocal charge transport in the ?=0 QHE which is observed in a recent experiment on (Bi_{1-x}Sb_{x})_{2}Te_{3} films. The edge channels also support spin transport due to the spin-momentum locking. We propose an experimental setup to observe various spintronics functions such as spin transport and spin conversion. PMID:25910149

  19. Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges

    E-print Network

    Bouchard, Frédéric; Schulz, Sebastian A; Upham, Jeremy; Karimi, Ebrahim; Boyd, Robert W

    2014-01-01

    Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded \\qo{space} for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states of light, coupling between spin and orbital angular momentum allows a faster manipulation of orbital angular momentum states because it depends on manipulating the polarisation state of light, which is simpler and generally faster than manipulating conventional orbital angular momentum generators. In this work, we design and fabricate an ultra-thin spin-to-orbital angular momentum converter, based on plasmonic nano-antennas and operating in the visible wavelength range that is capable of converting spin to an arbitrary value of OAM $\\ell$. The nano-antennas are arranged in an array with a well-defined geometry in the transverse plane of the beam, possessing a specific integer or half-integer topological charge $q$. When a circularly polarised light beam traverse...

  20. Topological Charge Pumping in a One-Dimensional Optical Lattice Lei Wang,1,2

    E-print Network

    Wang, Wei Hua

    a similarity to the famous Archimedes screw [6], where water is pumped by a rotat- ing spiral tube. However of condensed matter phys- ics, the theory of quantized charge pumping also lays a firm foundation for the modern theory of polarization of crys- talline solids [9,10], the theory for Z2 spin pump [11

  1. Charge Transport in 3D topological insulators in the presence of surface potential fluctuation

    NASA Astrophysics Data System (ADS)

    Peng, Xingyue; Yang, Yiming; Singh, Rajiv; Savrasov, Sergey; Yu, Dong

    2015-03-01

    Field effect measurements on the surface of a 3D topological insulator (TI) have often shown a high minimum conductivity as the Fermi level is shifted to Dirac point. Not only does this minimum conductivity vary from 5 to 50 e2/h strongly dependent on sample details but the gate dependent conductivity also exhibits anomalous non-monotonic behavior which is not yet understood. Understanding the nature of this minimum conductivity is crucial for the design and fabrication of novel spintronic devices based on 3D TIs. We propose a theoretic model to explain this anomalous behavior, considering the existence of surface potential fluctuations as indicated by scanning tunneling spectroscopy (STS) and scanning photocurrent microscopy (SPCM) measurements on the surface of a 3D TI. Our model agrees well with preexisting experiments and our own transport measurements in field effect transistors (FETs) incorporating Sb-doped single Bi2Se3 nanoribbons.

  2. Topological influence and backaction between topological excitations

    NASA Astrophysics Data System (ADS)

    Kobayashi, Shingo; Tarantino, Nicolas; Ueda, Masahito

    2014-03-01

    Topological objects can influence each other if the underlying homotopy groups are non-Abelian. Under such circumstances, the topological charge of each individual object is no longer a conserved quantity and can be transformed to each other. Yet we can identify the conservation law by considering the backaction of topological influence. We develop a general theory of topological influence and backaction based on the commutators of the underlying homotopy groups. In the case of the topological influence of a half-quantum vortex on a point defect, we point out that the topological backaction from the point defect is a twisting of the vortex. The total twist of the vortex line compensates for the change in the point-defect charge to conserve the total charge. We use this theory to classify charge transfers in condensed matter systems and show that a non-Abelian charge transfer can be realized in a spin-2 Bose-Einstein condensate.

  3. Magnetotransport in disordered two-dimensional topological insulators: signatures of charge puddles

    NASA Astrophysics Data System (ADS)

    Essert, Sven; Richter, Klaus

    2015-06-01

    In this numerical study we investigate the influence and interplay of disorder, spin–orbit coupling and magnetic field on the edge-transport in HgTe/CdTe quantum wells in the framework of coherent elastic scattering. We show that the edge states remain unaffected by the combined effect of moderate disorder and a weak magnetic field at realistic spin–orbit coupling strengths. Agreement with the experimentally observed linear magnetic field dependence for the conductance of long samples is obtained when considering the existence of charge puddles.

  4. Topological charged BPS vortices in Lorentz-violating Maxwell-Higgs electrodynamics

    E-print Network

    R. Casana; G. Lazar

    2014-10-23

    We have performed a complete study of BPS vortex solutions in the Abelian sector of the standard model extension (SME). Specifically, we have coupled the SME electromagnetism with a Higgs field which is supplemented with a Lorentz-violating CPT-even term. We have verified that Lorentz violation (LV) belonging to the Higgs sector allows to interpolate between some well known models like, Maxwell-Higgs, Chern-Simons-Higgs and Maxwell-Chern-Simons-Higgs. We can also observed that the electrical charged density distribution is nonnull in both CPT-even and CPT-odd models; however, the total electric charge in the CPT-even case is null, whereas in the CPT-odd one it is proportional to the quantized magnetic flux. The following general results can be established in relation to the LV introduced in the Higgs sector: it changes the vortex ansatz and the gauge field boundary conditions. A direct consequence is that the magnetic flux, besides being proportional to the winding number, also depends explicitly on the Lorentz-violation belonging to the Higgs sector.

  5. Topological charged BPS vortices in Lorentz-violating Maxwell-Higgs electrodynamics

    NASA Astrophysics Data System (ADS)

    Casana, R.; Lazar, G.

    2014-09-01

    We have performed a complete study of BPS vortex solutions in the Abelian sector of the standard model extension (SME). Specifically, we have coupled the SME electromagnetism with a Higgs field which is supplemented with a Lorentz-violating CPT-even term. We have verified that Lorentz violation (LV) belonging to the Higgs sector allows us to interpolate between some well-known models like Maxwell-Higgs, Chern-Simons-Higgs, and Maxwell-Chern-Simons-Higgs. We can also observe that the electrical charged density distribution is non-null in both CPT-even and CPT-odd models; however, the total electric charge in the CPT-even case is null, whereas in the CPT-odd one it is proportional to the quantized magnetic flux. The following general results can be established in relation to the LV introduced in the Higgs sector: it changes the vortex ansatz and the gauge field boundary conditions. A direct consequence is that the magnetic flux, besides being proportional to the winding number, also depends explicitly on the Lorentz-violation belonging to the Higgs sector.

  6. Anomalies, gauge field topology, and the lattice

    SciTech Connect

    Creutz, Michael, E-mail: creutz@bnl.gov [Physics Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2011-04-15

    Motivated by the connection between gauge field topology and the axial anomaly in fermion currents, I suggest that the fourth power of the naive Dirac operator can provide a natural method to define a local lattice measure of topological charge. For smooth gauge fields this reduces to the usual topological density. For typical gauge field configurations in a numerical simulation, however, quantum fluctuations dominate, and the sum of this density over the system does not generally give an integer winding. On cooling with respect to the Wilson gauge action, instanton like structures do emerge. As cooling proceeds, these objects tend shrink and finally 'fall through the lattice.' Modifying the action can block the shrinking at the expense of a loss of reflection positivity. The cooling procedure is highly sensitive to the details of the initial steps, suggesting that quantum fluctuations induce a small but fundamental ambiguity in the definition of topological susceptibility.

  7. Reproducability and transferability of topological properties; experimental charge density of the hexapeptide cyclo-(D,L-Pro)2-(L-Ala)4 monohydrate.

    PubMed

    Dittrich, B; Koritsánszky, T; Grosche, M; Scherer, W; Flaig, R; Wagner, A; Krane, H G; Kessler, H; Riemer, C; Schreurs, A M M; Luger, P

    2002-08-01

    The charge density of a hexapeptide was determined from high-resolution CCD area-detector experiments at 100 K. Two datasets, one from a rotating anode and a second one from synchrotron radiation, were measured and the results are compared. The data are interpreted in terms of the 'rigid pseudoatom' model. The topology of the experimental density is analyzed and compared with the topology of the constituting amino acids, and shows good agreement. All critical points of the electron density at the covalent and hydrogen bonds, as well as those of the Laplacian, were located. With respect to the transferability of electronic and bond topological properties the six peptide bonds were compared with values given in the literature. PMID:12149563

  8. Topological properties of hydrogen bonds and covalent bonds from charge densities obtained by the maximum entropy method (MEM)

    PubMed Central

    Netzel, Jeanette; van Smaalen, Sander

    2009-01-01

    Charge densities have been determined by the Maximum Entropy Method (MEM) from the high-resolution, low-temperature (T ? 20?K) X-ray diffraction data of six different crystals of amino acids and peptides. A comparison of dynamic deformation densities of the MEM with static and dynamic deformation densities of multipole models shows that the MEM may lead to a better description of the electron density in hydrogen bonds in cases where the multipole model has been restricted to isotropic displacement parameters and low-order multipoles (l max = 1) for the H atoms. Topological properties at bond critical points (BCPs) are found to depend systematically on the bond length, but with different functions for covalent C—C, C—N and C—O bonds, and for hydrogen bonds together with covalent C—H and N—H bonds. Similar dependencies are known for AIM properties derived from static multipole densities. The ratio of potential and kinetic energy densities |V(BCP)|/G(BCP) is successfully used for a classification of hydrogen bonds according to their distance d(H?O) between the H atom and the acceptor atom. The classification based on MEM densities coincides with the usual classification of hydrogen bonds as strong, intermediate and weak [Jeffrey (1997) ?. An Introduction to Hydrogen Bonding. Oxford University Press]. MEM and procrystal densities lead to similar values of the densities at the BCPs of hydrogen bonds, but differences are shown to prevail, such that it is found that only the true charge density, represented by MEM densities, the multipole model or some other method can lead to the correct characterization of chemical bonding. Our results do not confirm suggestions in the literature that the promolecule density might be sufficient for a characterization of hydrogen bonds. PMID:19767685

  9. Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges

    NASA Astrophysics Data System (ADS)

    Bouchard, Frédéric; De Leon, Israel; Schulz, Sebastian A.; Upham, Jeremy; Karimi, Ebrahim; Boyd, Robert W.

    2014-09-01

    Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded "space" for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states of light, coupling between spin and orbital angular momentum allows a faster manipulation of orbital angular momentum states because it depends on manipulating the polarisation state of light, which is simpler and generally faster than manipulating conventional orbital angular momentum generators. In this work, we design and fabricate an ultra-thin spin-to-orbital angular momentum converter, based on plasmonic nano-antennas and operating in the visible wavelength range that is capable of converting spin to an arbitrary value of orbital angular momentum ?. The nano-antennas are arranged in an array with a well-defined geometry in the transverse plane of the beam, possessing a specific integer or half-integer topological charge q. When a circularly polarised light beam traverses this metasurface, the output beam polarisation switches handedness and the orbital angular momentum changes in value by ? = ± 2 q ? per photon. We experimentally demonstrate ? values ranging from ±1 to ±25 with conversion efficiencies of 8.6% ± 0.4%. Our ultra-thin devices are integratable and thus suitable for applications in quantum communications, quantum computations, and nano-scale sensing.

  10. Charging Dirac states at antiphase domain boundaries in the three-dimensional topological insulator Bi2Se3.

    PubMed

    Liu, Y; Li, Y Y; Gilks, D; Lazarov, V K; Weinert, M; Li, L

    2013-05-01

    Using scanning tunneling microscopy and transmission electron microscopy, we demonstrate the existence of antiphase boundaries between neighboring grains shifted by a fraction of a quintuple layer in epitaxial (0001) films of the three-dimensional topological insulator Bi(2)Se(3). Scanning tunneling spectroscopy and first-principles calculations reveal that these antiphase boundaries provide electrostatic fields on the order of 10(8) V/m that locally charge the Dirac states, modulating the carrier density, and shift the Dirac point by up to 120 meV. This intrinsic electric field effect, demonstrated here near interfaces between Bi(2)Se(3) grains, provides direct experimental evidence at the atomic scale that the Dirac states are indeed robust against extended structural defects and tunable by electric field. These results also shed light on the recent observation of coexistence of Dirac states and two-dimensional electron gas on Bi(2)Se(3) (0001) after adsorption of metal atoms and gas molecules. PMID:23683233

  11. Signatures of charge inhomogeneities in the infrared spectra of topological insulators Bi2Se3, Bi2Te3 and Sb2Te3.

    PubMed

    Dordevic, S V; Wolf, M S; Stojilovic, N; Lei, Hechang; Petrovic, C

    2013-02-20

    We present the results of an infrared spectroscopy study of topological insulators Bi(2)Se(3), Bi(2)Te(3) and Sb(2)Te(3). Reflectance spectra of all three materials look similar, with a well defined plasma edge. However, there are some important differences. Most notably, as temperature decreases the plasma edge shifts to lower frequencies in Bi(2)Se(3), whereas in Bi(2)Te(3) and Sb(2)Te(3) it shifts to higher frequencies. In the loss function spectra we identify asymmetric broadening of the plasmon, and assign it to the presence of charge inhomogeneities. It remains to be seen if charge inhomogeneities are characteristic of all topological insulators, and whether they are of intrinsic or extrinsic nature. PMID:23328626

  12. Effects of bulk charged impurities on the bulk and surface transport in three-dimensional topological insulators

    SciTech Connect

    Skinner, B.; Chen, T.; Shklovskii, B. I., E-mail: shklovsk@physics.spa.umn.edu [University of Minnesota, Fine Theoretical Physics Institute (United States)

    2013-09-15

    In the three-dimensional topological insulator (TI), the physics of doped semiconductors exists literally side-by-side with the physics of ultrarelativistic Dirac fermions. This unusual pairing creates a novel playground for studying the interplay between disorder and electronic transport. In this mini-review, we focus on the disorder caused by the three-dimensionally distributed charged impurities that are ubiquitous in TIs, and we outline the effects it has on both the bulk and surface transport in TIs. We present self-consistent theories for Coulomb screening both in the bulk and at the surface, discuss the magnitude of the disorder potential in each case, and present results for the conductivity. In the bulk, where the band gap leads to thermally activated transport, we show how disorder leads to a smaller-than-expected activation energy that gives way to variable-range hopping at low temperatures. We confirm this enhanced conductivity with numerical simulations that also allow us to explore different degrees of impurity compensation. For the surface, where the TI has gapless Dirac modes, we present a theory of disorder and screening of deep impurities, and we calculate the corresponding zero-temperature conductivity. We also comment on the growth of the disorder potential in passing from the surface of the TI into the bulk. Finally, we discuss how the presence of a gap at the Dirac point, introduced by some source of time-reversal symmetry breaking, affects the disorder potential at the surface and the mid-gap density of states.

  13. Fractional Topological Insulators

    Microsoft Academic Search

    Michael Levin; Ady Stern

    2009-01-01

    We analyze generalizations of two-dimensional topological insulators which can be realized in interacting, time reversal invariant electron systems. These states, which we call fractional topological insulators, contain excitations with fractional charge and statistics in addition to protected edge modes. In the case of sz conserving toy models, we show that a system is a fractional topological insulator if and only

  14. Ambipolar charge injection and transport of few-layer topological insulator Bi2Te3 and Bi2Se3 nanoplates

    NASA Astrophysics Data System (ADS)

    Hao, Guolin; Qi, Xiang; Liu, Yundan; Huang, Zongyu; Li, Hongxing; Huang, Kai; Li, Jun; Yang, Liwen; Zhong, Jianxin

    2012-06-01

    We report the electrostatic properties of few-layer Bi2Te3 and Bi2Se3 nanoplates (NPs) grown on 300 nm SiO2/Si substrate. Electrons and holes are locally injected in Bi2Te3 and Bi2Se3 nanoplates by the apex of an atomic force microscope tip. Both carriers are delocalized uniformly over the whole nanoplate. The electrostatic property of topological insulator Bi2Te3 and Bi2Se3 nanoplates after charge injection is characterized by Kelvin probe force microscopy under ambient environment and exhibits an ambipolar surface potential behavior. These results provide insight into the electronic properties of topological insulators at the nanometer scale.

  15. A DFT study on the correlation between topology and Bader charges: Part I, effects of compression and expansion of As2O5

    NASA Astrophysics Data System (ADS)

    Beck, Horst P.

    2015-03-01

    Starting from known structures of the modifications of As2O5 we investigate the results of relaxations in DFT calculations performed at different fixed volumes per formula unit on keeping the axis relations and the symmetry of the original space group. We analyse the correlation between the topology of a structure, i.e. the co-ordination geometry and the distances observed, with the charges of the atoms as derived form a Bader analysis of the electron distribution resulting from a DFT relaxation. A similar study is done on the changes of the structure and the charges as a result of a relaxation without such a symmetry bias giving a new hitherto unknown possible high pressure structure.

  16. Topological Solitons in Physics.

    ERIC Educational Resources Information Center

    Parsa, Zohreh

    1979-01-01

    A broad definition of solitons and a discussion of their role in physics is given. Vortices and magnetic monopoles which are examples of topological solitons in two and three spatial dimensions are described in some detail. (BB)

  17. Spanning set of silica cluster isomer topologies from QTAIM.

    PubMed

    Jenkins, Samantha; Rong, Chunying; Kirk, Steven R; Yin, Dulin; Liu, Shubin

    2011-11-17

    Structural and chemical properties of the building block of silica nanowires, (SiO(2))(6), are investigated with the theory of atoms and molecules (QTAIM). Twenty-five conformers have been analyzed, ten of which have not been reported before. We extend the silica (SiO(2))(6) topology phase space using QTAIM; the Poincaré-Hopf topological sum rules are applied and used to identify the spanning set of topologies, and this includes finding eight new distinct topologies that satisfy the Poincaré-Hopf relation. A simple phase diagram of the solutions of the Poincaré-Hopf relation is created with the aid of a new classification scheme to determine the boundary between topological stability and instability. Sum rules are then found to be applicable to any set of isomers. We determine that O-O bonding interactions exist for the silica (SiO(2))(6) conformers in regions where the energy surface is flattest. In addition, we identify unstable local minima in the topology of the charge density in order to further compare conformer instabilities. We quantify the dimensionality of a molecule using the Poincaré-Hopf relation instead of Euclidean geometry. This quantum topological definition of geometry shows that the four most energetically stable (SiO(2))(6) conformers are quantified as two-dimensional within the new quantum topology. PMID:21557588

  18. On neutrosophic paraconsistent topology

    Microsoft Academic Search

    Francisco Gallego Lupiáñez

    2010-01-01

    Purpose – Recently, F. Smarandache generalized the Atanassov's intuitionistic fuzzy sets and other kinds of sets to neutrosophic sets (NSs). Also, this author introduced a general definition of neutrosophic topology. On the other hand, there exist various kinds of paraconsistent logics, where some contradiction is admissible. The purpose of this paper is to show that a Smarandache's definition of neutrosophic

  19. Electrical detection of the spin polarization due to charge flow in the surface state of the topological insulator Bi(1.5)Sb(0.5)Te(1.7)Se(1.3).

    PubMed

    Ando, Yuichiro; Hamasaki, Takahiro; Kurokawa, Takayuki; Ichiba, Kouki; Yang, Fan; Novak, Mario; Sasaki, Satoshi; Segawa, Kouji; Ando, Yoichi; Shiraishi, Masashi

    2014-11-12

    We detected the spin polarization due to charge flow in the spin nondegenerate surface state of a three-dimensional topological insulator by means of an all-electrical method. The charge current in the bulk-insulating topological insulator Bi1.5Sb0.5Te1.7Se1.3 (BSTS) was injected/extracted through a ferromagnetic electrode made of Ni80Fe20, and an unusual current-direction-dependent magnetoresistance gave evidence for the appearance of spin polarization, which leads to a spin-dependent resistance at the BSTS/Ni80Fe20 interface. In contrast, our control experiment on Bi2Se3 gave null result. These observations demonstrate the importance of the Fermi-level control for the electrical detection of the spin polarization in topological insulators. PMID:25330016

  20. Topology in Ordered Phases

    NASA Astrophysics Data System (ADS)

    Tanda, Satoshi; Matsuyama, Toyoki; Oda, Migaku; Asano, Yasuhiro; Yakubo, Kousuke

    2006-08-01

    I. Topology as universal concept. Optical vorticulture / M. V. Berry. On universality of mathematical structure in nature: topology / T. Matsuyama. Topology in physics / R. Jackiw. Isoholonomic problem and holonomic quantum computation / S. Tanimura -- II. Topological crystals. Topological crystals of NbSe[symbol] / S. Tanda ... [et al.]. Superconducting states on a Möbius strip / M. Hayashi ... [et al.]. Structure analyses of topological crystals using synchrotron radiation / Y. Nogami ... [et al.]. Transport measurement for topological charge density waves / T. Matsuura ... [et al.]. Theoretical study on Little-Parks oscillation in nanoscale superconducting ring / T. Suzuki, M. Hayashi and H. Ebisawa. Frustrated CDW states in topological crystals / K. Kuboki ... [et al.]. Law of growth in topological crystal / M. Tsubota ... [et al.]. Synthesis and electric properties of NbS[symbol]: possibility of room temperature charge density wave devices / H. Nobukane ... [et al.]. How does a single crystal become a Möbius strip? / T. Matsuura ... [et al.]. Development of X-ray analysis method for topological crystals / K. Yamamoto ... [et al.] -- III. Topological materials. Femtosecond-timescale structure dynamics in complex materials: the case of (NbSe[symbol])[symbol]I / D. Dvorsek and D. Mihailovic. Ultrafast dynamics of charge-density-wave in topological crystals / K. Shimatake ... [et al.]. Topology in morphologies of a folded single-chain polymer / Y. Takenaka, D. Baigl and K. Yoshikawa. One to two-dimensional conversion in topological crystals / T. Toshima, K. Inagaki and S. Tanda. Topological change of Fermi surface in Bismuth under high pressure / M. Kasami ... [et al.]. Topological change of 4, 4'-bis[9-dicarbazolyl]-2, 2'-biphenyl (CBP) by international rearrangement / K. S. Son ... [et al.]. Spin dynamics in Heisenberg triangular system VI5 cluster studied by [symbol]H-NMR / Y. Furukawa ... [et al.]. STM/STS on NbSe[symbol] nanotubes / K. Ichimura ...[et al.]. Nanofibers of hydrogen storage alloy / I. Saita ... [et al.]. Synthesis of stable icosahedral quasicrystals in Zn-Sc based alloys and their magnetic properties / S. Kashimoto and T. Ishimasa. One-armed spiral wave excited by eam pressure in accretion disks in Be/X-Ray binaries / K. Hayasaki and A. T. Okazaki -- IV. Topological defects and excitations. Topological excitations in the ground state of charge density wave systems / P. Monceau. Soliton transport in nanoscale charge-density-wave systems / K. Inagaki, T. Toshima and S. Tanda. Topological defects in triplet superconductors UPt3, Sr[symbol]RuO[symbol], etc. / K. Maki ... [et al.]. Microscopic structure of vortices in type II superconductors / K. Machida ... [et al.]. Microscopic neutron investigation of the Abrikosov state of high-temperature superconductors / J. Mesot. Energy dissipation at nano-scale topological defects of high-Tc superconductors: microwave study / A. Maeda. Pressure induced topological phase transition in the heavy Fermion compound CeAl[symbol] / H. Miyagawa ... [et al.]. Explanation for the unusual orientation of LSCO square vortex lattice in terms of nodal superconductivity / M. Oda. Local electronic states in Bi[symbol]Sr[symbol]CaCu[symbol]O[symbol] / A. Hashimoto ... [et al.] -- V. Topology in quantum phenomena. Topological vortex formation in a Bose-Einstein condensate of alkali-metal atoms / M. Nakahara. Quantum phase transition of [symbol]He confined in nano-porous media / K. Shirahama, K. Yamamoto and Y. Shibayama. A new mean-field theory for Bose-Einstein condensates / T. Kita. Spin current in topological cristals / Y. Asano. Antiferromagnetic defects in non-magnetic hidden order of the heavy-electron system URu[symbol]Si[symbol] / H. Amitsuka, K. Tenya and M. Yokoyama. Magnetic-field dependences of thermodynamic quantities in the vortex state of Type-II superconductors / K. Watanabe, T. Kita and M. Arai. Three-magnon-mediated nuclear spin relaxation in quantum ferrimagnets of topological origin / H. Hori and S, Yamamoto. Topological aspects of wave function statistics at t

  1. Novel converter topology and algorithm for simultaneous charging and individual cell balancing of multiple Li-ion batteries

    Microsoft Academic Search

    Sombuddha Chakraborty; Amit Kumar Jain; Ned Mohan

    2004-01-01

    This work presents a novel lithium-ion battery charger based on pulse charging technique. A central power supply acting as a controlled current source is sequentially connected in parallel with different batteries through an array of switches. A forward converter realizes the controlled current source. Magnetics are restricted to the inductor and transformer of the forward converter. Each battery contains plurality

  2. Magnetic-field control of topological charge-transport properties in Nd2Ir2O7

    NASA Astrophysics Data System (ADS)

    Ueda, Kentaro; Yang, Bohm-Jung; Fujioka, Jun; Shiogai, Junichi; Tsukazaki, Atsushi; Nagaosa, Naoto; Tokura, Yoshinori

    2015-03-01

    Weyl semimetal is a novel quantum phase with topological properties where the linear-dispersive band with a surface Fermi arc state is realized in a three-dimensional bulk. Pyrochlore-type R2Ir2O7 is one of the promising candidates for realization of the Weyl semimetal. In this system, the magnetic ordering pattern is predicted to play a key role for characterizing its electronic band structure. We report the magneto-transport properties in Nd2Ir2O7 single crystals for several magnetic field directions. We reveal that all-in all-out type magnetic domain walls, at which the conductive mode inherent to the surface state of Weyl semimetal may be preserved, are finely controlled by an applied field along [111] direction showing unique hysteresis in resistivity. With applied field along [001] direction, the Nd-4 f moment forms 2-in 2-out configuration that turns the insulating state into the anomalous metallic one near the Weyl (semi-)metal phase. A mean-field calculation consistent with our experimental findings suggests that there are a plenty of exotic states in pyrochlore iridates as functions of electron correlation and external magnetic field that tunes Ir-5 d spin texture.

  3. Topological pumping over a photonic Fibonacci quasicrystal

    E-print Network

    Verbin, Mor

    Quasiperiodic lattices have recently been shown to be a nontrivial topological phase of matter. Charge pumping—one of the hallmarks of topological states of matter—was recently realized for photons in a one-dimensional ...

  4. Kinetic interaction analysis of human interleukin 5 receptor alpha mutants reveals a unique binding topology and charge distribution for cytokine recognition.

    PubMed

    Ishino, Tetsuya; Pasut, Gianfranco; Scibek, Jeffery; Chaiken, Irwin

    2004-03-01

    Human interleukin 5 receptor alpha (IL5Ralpha) comprises three fibronectin type III domains (D1, D2, and D3) in the extracellular region. Previous results have indicated that residues in the D1D2 domains are crucial for high affinity interaction with human interleukin 5 (IL5). Yet, it is the D2D3 domains that have sequence homology with the classic cytokine recognition motif that is generally assumed to be the minimum cytokine-recognizing unit. In the present study, we used kinetic interaction analysis of alanine-scanning mutational variants of IL5Ralpha to define the residues involved in IL5 recognition. Soluble forms of IL5Ralpha variants were expressed in S2 cells, selectively captured via their C-terminal V5 tag by anti-V5 tag antibody immobilized onto the sensor chip and examined for IL5 interaction by using a sandwich surface plasmon resonance biosensor method. Marked effects on the interaction kinetics were observed not only in D1 (Asp(55), Asp(56), and Glu(58)) and D2 (Lys(186) and Arg(188)) domains, but also in the D3 (Arg(297)) domain. Modeling of the tertiary structure of IL5Ralpha indicated that these binding residues fell into two clusters. The first cluster consists of D1 domain residues that form a negatively charged patch, whereas the second cluster consists of residues that form a positively charged patch at the interface of D2 and D3 domains. These results suggest that the IL5 x IL5Ralpha system adopts a unique binding topology, in which the cytokine is recognized by a D2D3 tandem domain combined with a D1 domain, to form an extended cytokine recognition interface. PMID:14662768

  5. Analyzing topological defects in disordered charge density waves in transition-metal dichalcogenides TaSe2 and TaS2 using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Schaper, Danielle; McElroy, Kyle; Calleja, Eduardo; Dai, Jixia; Li, Lijun; Lu, Wenjian; Sun, Yuping; Zhu, Xiangde

    2014-03-01

    Charged ordered states are becoming a common feature in the phase diagrams of correlated materials. In many cased there are indications that doping controlled quantum critical points between the CO state and others are related to interesting properties including superconductivity. An interesting test case is the ordered 2D CDW found in the transition metal dichalcogenides. We performed an analytical study on the dichalcogenides tantalum disulfide (TaS2) and tantalum diselenide (TaSe2) to observe how CDWs present in the material can be melted as disorder is introduced into the system via copper doping. Data was taken using a scanning tunneling microscope (STM) below the transition to the CDW state, both with and without copper dopants added. The resulting topographs were then analyzed to investigate the relationship between the phase and the amplitude of the disordered CDW. We found that the copper doping caused disorder in the CDW state characterized by phase wanderings and 2 ? phase winding ``point defects'' in the CDW not present in the undoped parent compound. The locations of these point defects and windings were, in turn, found to have the characteristics of topological defects. Implications for studies of other disordered CO states seen in STM will be discussed.

  6. Topological X-Rays Revisited

    ERIC Educational Resources Information Center

    Lynch, Mark

    2012-01-01

    We continue our study of topological X-rays begun in Lynch ["Topological X-rays and MRI's," iJMEST 33(3) (2002), pp. 389-392]. We modify our definition of a topological magnetic resonance imaging and give an affirmative answer to the question posed there: Can we identify a closed set in a box by defining X-rays to probe the interior and without…

  7. Symmetry and Topological Order

    E-print Network

    Zohar Nussinov; Gerardo Ortiz

    2014-10-22

    We prove sufficient conditions for Topological Quantum Order at both zero and finite temperatures. The crux of the proof hinges on the existence of low-dimensional Gauge-Like Symmetries (that notably extend and differ from standard local gauge symmetries) and their associated defects, thus providing a unifying framework based on a symmetry principle. These symmetries may be actual invariances of the system, or may emerge in the low-energy sector. Prominent examples of Topological Quantum Order display Gauge-Like Symmetries. New systems exhibiting such symmetries include Hamiltonians depicting orbital-dependent spin exchange and Jahn-Teller effects in transition metal orbital compounds, short-range frustrated Klein spin models, and p+ip superconducting arrays. We analyze the physical consequences of Gauge-Like Symmetries (including topological terms and charges), discuss associated braiding, and show the insufficiency of the energy spectrum, topological entanglement entropy, maximal string correlators, and fractionalization in establishing Topological Quantum Order. General symmetry considerations illustrate that not withstanding spectral gaps, thermal fluctuations may impose restrictions on certain suggested quantum computing schemes and lead to "thermal fragility". Our results allow us to go beyond standard topological field theories and engineer systems with Topological Quantum Order.

  8. Topological activity in Bragg elliptical twisted fibers.

    PubMed

    Alexeyev, Constantine N; Fadeyeva, Tatyana A; Lapin, Boris P; Yavorsky, Maxim A

    2012-04-01

    We have theoretically shown that Bragg twisted elliptical fibers manifest, in certain spectral regions, the property of topological activity--the ability to change in the reflected field the topological charge of incoming optical vortices and fundamental modes by two units. This property could be used for narrowband generation of optical vortices from Gaussian beams and for changing the topological charge of incoming optical vortices. PMID:22505114

  9. Fractional charges and Misner-Wheeler charge without charge effect in metamaterials

    E-print Network

    Igor I. Smolyaninov

    2014-12-08

    Optical space in metamaterials may be engineered to emulate four dimensional Kaluza-Klein theory. Nonlinear optics of such metamaterials mimics interaction of quantized electric charges. An electromagnetic wormhole is designed, which connects two points of such an optical space and changes its effective topology. Electromagnetic field configurations which exhibit fractional charges appear as a result of such topology change. Moreover, such effects as Misner-Wheeler charge without charge may be replicated.

  10. Nonequilibrium green function approach to elastic and inelastic spin-charge transport in topological insulator-based heterostructures and magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad

    Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single ferromagnet (FM). I show that this could be due to the existence of Rashba spin-orbit coupling (SOC) at the interface of the FM and insulator. Assuming that the measured signals are quantum mechanical effect where a solution to the time dependent Schrodinger equation is required, I use Keldysh Green function formalism to introduce a "multi-photon" approach which takes into account the effects of time-dependent term exactly up to scatterings from a finite number of photons. We then proceed to find the corresponding Green function numerically using a recursive method which allows us to increase the size of the system significantly. We also implement other approximations such as adiabatic and rotating frame approaches and compared them with our approach. In Chapter 4, I investigate the spin and charge pumping from a precessing magnetization attached to the edge of a 2-dimensional topological insulator (2DTI). We show that, in this system a huge spin current (or voltage signal if the FM covers only one edge) can be pumped for very small cone angles of the precessing FM (proportional to the intensity of the applied microwave). In Chapter 5 I present the third project in this field of research, where, I investigated the pumping from FM attached to a 3-dimensional TI. Spin-transfer torque: Presented in Chapter 6, in this work I investigate the torque induced by a flow of spin-polarized current into a FM and check the condition in which it can cause the magnetization to flip. Motivated by recent experimental developments in the field, here I consider systems with strong SOC such as TIs within a magnetic tunnel junction (MTJ) heterostructure. In the theoretical part I show the correct way (as opposed to the conventional approach used in some theoretical works which suffers from violation of the gauge invariance) to calculate linear-response torque to the external applied voltage and for the numerical calculation I adopted a parallelized adaptive integration algorithm in order to take care of very sharp changes that appear in momentum and energy dependence of t

  11. On-column 2p bound state with topological charge \\pm1 excited by an atomic-size vortex beam in an aberration-corrected scanning transmission electron microscope

    E-print Network

    Xin, Huolin L

    2012-01-01

    Atomic-size vortex beams have great potential in probing materials' magnetic moment at atomic scales. However, the limited depth of field of vortex beams constrains the probing depth in which the helical phase front is preserved. On the other hand, electron channeling in crystals can counteract beam divergence and extend the vortex beam without disrupting its topological charge. Specifically, in this paper, we report atomic vortex beams with topological charge \\pm1 can be coupled to the 2p columnar bound states and propagate for more 50 nm without being dispersed and losing its helical phase front. We gave numerical solutions to the 2p columnar orbitals and tabulated the characteristic size of the 2p states of two typical elements, Co and Dy, for various incident beam energies and various atomic densities. The tabulated numbers allow estimates of the optimal convergence angle for maximal coupling to 2p columnar orbital. We also have developed analytic formulae for beam energy, convergence-angle, and hologram ...

  12. Topology Explains Why Automobile Sunshades Fold Oddly

    ERIC Educational Resources Information Center

    Feist, Curtis; Naimi, Ramin

    2009-01-01

    Automobile sunshades always fold into an "odd" number of loops. The explanation why involves elementary topology (braid theory and linking number, both explained in detail here with definitions and examples), and an elementary fact from algebra about symmetric group.

  13. The topological description of coronal magnetic fields

    NASA Technical Reports Server (NTRS)

    Berger, Mitchell A.

    1986-01-01

    Determining the structure and behavior of solar coronal magnetic fields is a central problem in solar physics. At the photosphere, the field is believed to be strongly localized into discrete flux tubes. After providing a rigorous definition of field topology, how the topology of a finite collection of flux tubes may be classified is discussed.

  14. Anderson localization of light with topological dislocations

    NASA Astrophysics Data System (ADS)

    Lobanov, Valery E.; Kartashov, Yaroslav V.; Vysloukh, Victor A.; Torner, Lluis

    2013-11-01

    We predict Anderson localization of light with nested screw topological dislocations propagating in disordered two-dimensional arrays of hollow waveguides illuminated by vortex beams. The phenomenon manifests itself in the statistical presence of topological dislocations in ensemble-averaged output distributions accompanying standard disorder-induced localization of light spots. Remarkably, screw dislocations are captured by the light spots despite the fast and irregular transverse displacements and topological charge flipping undertaken by the dislocations due to the disorder. The statistical averaged modulus of the output local topological charge depends on the initial vorticity carried by the beam.

  15. Communication Definitions... general definition

    E-print Network

    Jones, Ian L.

    Communication Definitions... general definition "the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood the same way by both sender and receiver" (Wikipedia)! Biological communication Action by one organism (individual

  16. Topological Insulators

    Microsoft Academic Search

    M. Z. Hasan; C. L. Kane

    2010-01-01

    Topological insulators are electronic materials that have a bulk band gap\\u000alike an ordinary insulator, but have protected conducting states on their edge\\u000aor surface. The 2D topological insulator is a quantum spin Hall insulator,\\u000awhich is a close cousin of the integer quantum Hall state. A 3D topological\\u000ainsulator supports novel spin polarized 2D Dirac fermions on its surface.

  17. Network Topologies

    NSDL National Science Digital Library

    Bartelt, Terry L. M.

    Network topology is the physical arrangement of the switching devices of a network connecting a group of computers or buildings. This brief interactive activity, by the Electromechanical Digital Library and Wisconsin Technical College System faculty, explains how and why these connections are made. It showcases common topologies including mesh, bus, star, and ring topologies. Users can click through these various categories at their own speed, replaying animations and rereading explanations as many times as the individual needs. This is a great resource for students and teachers alike to familiarize themselves with network topologies. [ES

  18. Manipulating surface states in topological insulator nanoribbons

    Microsoft Academic Search

    Faxian Xiu; Liang He; Yong Wang; Lina Cheng; Li-Te Chang; Murong Lang; Guan Huang; Xufeng Kou; Yi Zhou; Xiaowei Jiang; Zhigang Chen; Jin Zou; Alexandros Shailos; Kang L. Wang

    2011-01-01

    Topological insulators display unique properties, such as the quantum spin Hall effect, because time-reversal symmetry allows charges and spins to propagate along the edge or surface of the topological insulator without scattering. However, the direct manipulation of these edge\\/surface states is difficult because they are significantly outnumbered by bulk carriers. Here, we report experimental evidence for the modulation of these

  19. IMPLEMENTING A MAGNETIC CHARGE TOPOLOGY MODEL FOR SOLAR ACTIVE REGIONS Colorado Research Associates Division, NorthWest Research Associates, Inc., 3380 Mitchell Lane, Boulder, CO 80301;

    E-print Network

    Barnes, Graham

    changes due to variations in atmospheric seeing, as well as un- correlated noise. We determine (MCT) models, are versatile enough to apply to realistic coronal geometries and thereby test this prediction. MCT models assume that the photospheric magnetic field consists of distinct sources or ``charges

  20. Topological pumping over a photonic Fibonacci quasicrystal

    NASA Astrophysics Data System (ADS)

    Verbin, Mor; Zilberberg, Oded; Lahini, Yoav; Kraus, Yaacov E.; Silberberg, Yaron

    2015-02-01

    Quasiperiodic lattices have recently been shown to be a nontrivial topological phase of matter. Charge pumping—one of the hallmarks of topological states of matter—was recently realized for photons in a one-dimensional off-diagonal Harper model implemented in a photonic waveguide array. However, if the relationship between topological pumps and quasiperiodic systems is generic, one might wonder how to observe it in the canonical and most studied quasicrystalline system in one dimension—the Fibonacci chain. This chain is expected to facilitate a similar phenomenon, yet its discrete nature hinders the experimental study of such topological effects. Here, we overcome this obstacle by utilizing the topological equivalence of a family of quasiperiodic models which ranges from the Fibonacci chain to the Harper model. Implemented in photonic waveguide arrays, we observe the topological properties of this family, and perform a topological pumping of photons across a Fibonacci chain.

  1. Topological Pumping over a Photonic Fibonacci Quasicrystal

    E-print Network

    Mor Verbin; Oded Zilberberg; Yoav Lahini; Yaacov E. Kraus; Yaron Silberberg

    2014-03-27

    Quasiperiodic lattices have recently been shown to be a non-trivial topological phase of matter. Charge pumping -- one of the hallmarks of topological states of matter -- was recently realized for photons in a one-dimensional (1D) off-diagonal Harper model implemented in a photonic waveguide array. The topologically nontrivial 1D Fibonacci quasicrystal (QC) is expected to facilitate a similar phenomenon, but its discrete nature and lack of pumping parameter hinder the experimental study of such topological effects. In this work we overcome these obstacles by utilizing a family of topologically equivalent QCs which ranges from the Fibonacci QC to the Harper model. Implemented in photonic waveguide arrays, we observe the topological properties of this family, and perform a topological pumping of photons across a Fibonacci QC.

  2. Topological Pumping over a Photonic Fibonacci Quasicrystal

    E-print Network

    Verbin, Mor; Lahini, Yoav; Kraus, Yaacov E; Silberberg, Yaron

    2014-01-01

    Quasiperiodic lattices have recently been shown to be a non-trivial topological phase of matter. Charge pumping -- one of the hallmarks of topological states of matter -- was recently realized for photons in a one-dimensional (1D) off-diagonal Harper model implemented in a photonic waveguide array. The topologically nontrivial 1D Fibonacci quasicrystal (QC) is expected to facilitate a similar phenomenon, but its discrete nature and lack of pumping parameter hinder the experimental study of such topological effects. In this work we overcome these obstacles by utilizing a family of topologically equivalent QCs which ranges from the Fibonacci QC to the Harper model. Implemented in photonic waveguide arrays, we observe the topological properties of this family, and perform a topological pumping of photons across a Fibonacci QC.

  3. The U(1) Topological Gauge Field Theory for Topological Defects in Liquid Crystals

    E-print Network

    Yi-shi Duan; Li Zhao; Xin-hui Zhang; Tie-yan Si

    2005-12-27

    A novel U(1) topological gauge field theory for topological defects in liquid crystals is constructed by considering the U(1) gauge field is invariant under the director inversion. Via the U(1) gauge potential decomposition theory and the $\\phi$-mapping topological current theory, the decomposition expression of U(1) gauge field and the unified topological current for monopoles and strings in liquid crystals are obtained. It is revealed that monopoles and strings are located in different spatial dimensions and their topological charges are just the winding numbers of $\\phi$-mapping.

  4. Topological forms of information

    NASA Astrophysics Data System (ADS)

    Baudot, Pierre; Bennequin, Daniel

    2015-01-01

    We propose that entropy is a universal co-homological class in a theory associated to a family of observable quantities and a family of probability distributions. Three cases are presented: 1) classical probabilities and random variables; 2) quantum probabilities and observable operators; 3) dynamic probabilities and observation trees. This gives rise to a new kind of topology for information processes. We discuss briefly its application to complex data, in particular to the structures of information flows in biological systems. This short note summarizes results obtained during the last years by the authors. The proofs are not included, but the definitions and theorems are stated with precision.

  5. Introduction Definitions

    E-print Network

    Herwig, Wendt

    Introduction Definitions Bootstrap Results Conclusions and Perspectives Bootstrap for Log Wavelet;Introduction Definitions Bootstrap Results Conclusions and Perspectives Motivation Motivation Multifractal, Patrice Abry Bootstrap for Log Wavelet Leaders Cumulant based MFA #12;Introduction Definitions Bootstrap

  6. Topological Acoustics

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-01

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  7. Topological insulators/Isolants topologiques An introduction to topological insulators

    E-print Network

    Paris-Sud XI, Université de

    Topological insulators/Isolants topologiques An introduction to topological insulators Introduction topology, the insulator is called a topological insulator. We introduce this notion of topological order sont finalement discutées. Keywords: topological insulator, topological band theory, quantum anomalous

  8. Measurement-only topological quantum computation via anyonic interferometry

    SciTech Connect

    Bonderson, Parsa [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: parsab@microsoft.com; Freedman, Michael [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: michaelf@microsoft.com; Nayak, Chetan [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States); Department of Physics, University of California, Santa Barbara, CA 93106 (United States)], E-mail: nayak@kitp.ucsb.edu

    2009-04-15

    We describe measurement-only topological quantum computation using both projective and interferometrical measurement of topological charge. We demonstrate how anyonic teleportation can be achieved using 'forced measurement' protocols for both types of measurement. Using this, it is shown how topological charge measurements can be used to generate the braiding transformations used in topological quantum computation, and hence that the physical transportation of computational anyons is unnecessary. We give a detailed discussion of the anyonics for implementation of topological quantum computation (particularly, using the measurement-only approach) in fractional quantum Hall systems.

  9. Quasi-topological Reissner-Nordström Black Holes

    E-print Network

    W. G. Brenna; R. B. Mann

    2012-07-04

    We consider Reissner-Nordstrom solutions in quasi-topological gravity, obtaining exact solutions to the field equations yielding charged quasi-topological black holes. We study their thermodynamic behaviour over a range of parameters that yield ghost-free and stable space times. We find that a sufficiently negative quasi-topological parameter can yield black holes with 2 horizons, even for zero charge. We discuss the thermodynamic stability for the class of solutions we obtain. We also describe the structure of exact charged solutions to $k^{th}$ order quasi-topological gravity.

  10. From topological insulators to superconductors and Confinement

    E-print Network

    M. Cristina Diamantini; Pasquale Sodano; Carlo A. Trugenberger

    2012-02-01

    Topological matter in 3D is characterized by the presence of a topological BF term in its long-distance effective action. We show that, in 3D, there is another marginal term that must be added to the action in order to fully determine the physical content of the model. The quantum phase structure is governed by three parameters that drive the condensation of topological defects: the BF coupling, the electric permittivity and the magnetic permeability of the material. For intermediate levels of electric permittivity and magnetic permeability the material is a topological insulator. We predict, however, new states of matter when these parameters cross critical values: a topological superconductor when electric permittivity is increased and magnetic permeability is lowered and a charge confinement phase in the opposite case of low electric permittivity and high magnetic permeability. Synthetic topological matter may be fabricated as 3D arrays of Josephson junctions.

  11. Band structure engineering in topological insulator based heterostructures.

    PubMed

    Menshchikova, T V; Otrokov, M M; Tsirkin, S S; Samorokov, D A; Bebneva, V V; Ernst, A; Kuznetsov, V M; Chulkov, E V

    2013-01-01

    The ability to engineer an electronic band structure of topological insulators would allow the production of topological materials with tailor-made properties. Using ab initio calculations, we show a promising way to control the conducting surface state in topological insulator based heterostructures representing an insulator ultrathin films on the topological insulator substrates. Because of a specific relation between work functions and band gaps of the topological insulator substrate and the insulator ultrathin film overlayer, a sizable shift of the Dirac point occurs resulting in a significant increase in the number of the topological surface state charge carriers as compared to that of the substrate itself. Such an effect can also be realized by applying the external electric field that allows a gradual tuning of the topological surface state. A simultaneous use of both approaches makes it possible to obtain a topological insulator based heterostructure with a highly tunable topological surface state. PMID:24274792

  12. Topological BF field theory description of topological insulators

    E-print Network

    Gil Young Cho; Joel E. Moore

    2010-12-03

    Topological phases of matter are described universally by topological field theories in the same way that symmetry-breaking phases of matter are described by Landau-Ginzburg field theories. We propose that topological insulators in two and three dimensions are described by a version of abelian $BF$ theory. For the two-dimensional topological insulator or quantum spin Hall state, this description is essentially equivalent to a pair of Chern-Simons theories, consistent with the realization of this phase as paired integer quantum Hall effect states. The $BF$ description can be motivated from the local excitations produced when a $\\pi$ flux is threaded through this state. For the three-dimensional topological insulator, the $BF$ description is less obvious but quite versatile: it contains a gapless surface Dirac fermion when time-reversal-symmetry is preserved and yields "axion electrodynamics", i.e., an electromagnetic $E \\cdot B$ term, when time-reversal symmetry is broken and the surfaces are gapped. Just as changing the coefficients and charges of 2D Chern-Simons theory allows one to obtain fractional quantum Hall states starting from integer states, $BF$ theory could also describe (at a macroscopic level) fractional 3D topological insulators with fractional statistics of point-like and line-like objects.

  13. Is a color superconductor topological?

    SciTech Connect

    Nishida, Yusuke [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2010-04-01

    A fully gapped state of matter, whether insulator or superconductor, can be asked if it is topologically trivial or nontrivial. Here we investigate topological properties of superconducting Dirac fermions in 3D having a color superconductor as an application. In the chiral limit, when the pairing gap is parity even, the right-handed and left-handed sectors of the free space Hamiltonian have nontrivial topological charges with opposite signs. Accordingly, a vortex line in the superconductor supports localized gapless right-handed and left-handed fermions with the dispersion relations E={+-}vp{sub z} (v is a parameter dependent velocity) and thus propagating in opposite directions along the vortex line. However, the presence of the fermion mass immediately opens up a mass gap for such localized fermions and the dispersion relations become E={+-}v{radical}(m{sup 2}+p{sub z}{sup 2}). When the pairing gap is parity odd, the situation is qualitatively different. The right-handed and left-handed sectors of the free space Hamiltonian in the chiral limit have nontrivial topological charges with the same sign and therefore the presence of the small fermion mass does not open up a mass gap for the fermions localized around the vortex line. When the fermion mass is increased further, there is a topological phase transition at m={radical}({mu}{sup 2}+{Delta}{sup 2}) and the localized gapless fermions disappear. We also elucidate the existence of gapless surface fermions localized at a boundary when two phases with different topological charges are connected. A part of our results is relevant to the color superconductivity of quarks.

  14. Introduction -Definition

    E-print Network

    Aslaksen, Helmer

    #12;Introduction - Definition - Characteristics - Good kaleidoscope angle The two-mirror system - process of reflection The three-mirror system - summation of good kaleidoscope angles - process kaleidoscopes Steps in making a kaleidoscope Bibliography #12;Introduction Definition Kaleidoscopes are devices

  15. Fractal Topology Foundations

    E-print Network

    Helene Porchon

    2012-01-25

    In this paper, we introduce the foundation of a fractal topological space constructed via a family of nested topological spaces endowed with subspace topologies, where the number of topological spaces involved in this family is related to the appearance of new structures on it. The greater the number of topological spaces we use, the stronger the subspace topologies we obtain. The fractal manifold model is brought up as an illustration of space that is locally homeomorphic to the fractal topological space.

  16. Topological Puzzles

    NSDL National Science Digital Library

    Watsonville Environmental Science Workshop

    2011-01-01

    In this activity, learners construct three math puzzles out of simple materials like wood, string, and Styrofoam. The first two puzzles, called "Remove the Loop" and "Two Washers," are examples of topology, an area of math about how geometric figures are different and similar. The third puzzle, "Towers of Hanoi," uses a mathematical tool called an algorithm and is also a good example of an exponential function.

  17. Bringing Definitions into High Definition

    ERIC Educational Resources Information Center

    Mason, John

    2010-01-01

    Why do definitions play such a central role in mathematics? It may seem obvious that precision about the terms one uses is necessary in order to use those terms reasonably (while reasoning). Definitions are chosen so as to be definite about the terms one uses, but also to make both the statement of, and the reasoning to justify, theorems as…

  18. Topological BF field theory description of topological insulators

    SciTech Connect

    Cho, Gil Young [Department of Physics, University of California, Berkeley, CA 94720 (United States); Moore, Joel E., E-mail: jemoore@berkeley.edu [Department of Physics, University of California, Berkeley, CA 94720 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2011-06-15

    Research Highlights: > We show that a BF theory is the effective theory of 2D and 3D topological insulators. > The non-gauge-invariance of the bulk theory yields surface terms for a bosonized Dirac fermion. > The 'axion' term in electromagnetism is correctly obtained from gapped surfaces. > Generalizations to possible fractional phases are discussed in closing. - Abstract: Topological phases of matter are described universally by topological field theories in the same way that symmetry-breaking phases of matter are described by Landau-Ginzburg field theories. We propose that topological insulators in two and three dimensions are described by a version of abelian BF theory. For the two-dimensional topological insulator or quantum spin Hall state, this description is essentially equivalent to a pair of Chern-Simons theories, consistent with the realization of this phase as paired integer quantum Hall effect states. The BF description can be motivated from the local excitations produced when a {pi} flux is threaded through this state. For the three-dimensional topological insulator, the BF description is less obvious but quite versatile: it contains a gapless surface Dirac fermion when time-reversal-symmetry is preserved and yields 'axion electrodynamics', i.e., an electromagnetic E . B term, when time-reversal symmetry is broken and the surfaces are gapped. Just as changing the coefficients and charges of 2D Chern-Simons theory allows one to obtain fractional quantum Hall states starting from integer states, BF theory could also describe (at a macroscopic level) fractional 3D topological insulators with fractional statistics of point-like and line-like objects.

  19. Proposal for direct measurement of topological invariants in optical lattices.

    PubMed

    Wang, Lei; Soluyanov, Alexey A; Troyer, Matthias

    2013-04-19

    We propose an experimental technique for classifying the topology of band structures realized in optical lattices, based on a generalization of topological charge pumping in quantum Hall systems to cold atoms in optical lattices. Time-of-flight measurement along one spatial direction combined with in situ detection along the transverse direction provides a direct measure of the system's Chern number, as we illustrate by calculations for the Hofstadter lattice. Based on an analogy with Wannier function techniques of topological band theory, the method is very general and also allows the measurement of other topological invariants, such as the Z(2) topological invariant of time-reversal symmetric insulators. PMID:23679630

  20. Universal characterizing topological insulator and topological semi-metal with Wannier functions

    E-print Network

    Ye Xiong; Peiqing Tong

    2015-04-22

    The nontrivial evolution of Wannier functions (WF) for the occupied bands is a good starting point to understand topological insulator. By modifying the definition of WFs from the eigenstates of the projected position operator to those of the projected modular position operator, we are able to extend the usage of WFs to Weyl metal where the WFs in the old definition fails because of the lack of band gap at the Fermi energy. This extension helps us to universally understand topological insulator and topological semi-metal in a same framework. Another advantage of using the modular position operators in the definition is that the higher dimensional WFs for the occupied bands can be easily obtained. We show one of their applications by schematically explaining why the winding numbers $\

  1. T-Duality and Topological Insulators

    E-print Network

    Mathai, Varghese

    2015-01-01

    It is well known that topological insulators are classified by a family of groups, which coincidentally also classifies D-brane charges on orientifolds in string theory. In this letter, we extend this correlation via a geometric analog of the real Fourier transform to obtain a novel duality of topological insulators that can be viewed as a condensed matter analog of T-duality in string theory.

  2. T-Duality of Topological Insulators

    E-print Network

    Varghese Mathai; Guo Chuan Thiang

    2015-04-08

    Topological insulators and D-brane charges in string theory can both be classified by the same family of groups. In this letter, we extend this connection via a geometric transform, giving a novel duality of topological insulators which can be viewed as a condensed matter analog of T-duality in string theory. For 2D Chern insulators, this duality exchanges the rank and Chern number of the valence bands.

  3. Topological properties in topological insulators and superconductors

    E-print Network

    Chunbo Zhao

    2013-09-09

    We give a self-contained and enriched review about topology properties in the rapidly growing field of topological states of matter (TSM). This review is mainly focus on the beautiful interplay of topology mathematics and condensed matter physics that issuing TSM. Fiber bundle theory is a powerful concept to describe the non-trivial topology properties underlying the physical system. So we briefly present some motivation of fiber bundle theory and following that several effective topological methods have been introduced to judge whether a fiber bundle is trivial or not. Next, we give some topological invariants that characterizes the non-trivial TSM in the non-interacting systems in all dimensions, which is called topological band theory. Following that, we review and generalize the topological response using topological field theory called Chern-Simons effective theory. Finally, the classification of free-fermion systems have been studied by loop space and K-theory.

  4. Topological Black Holes -- Outside Looking In

    E-print Network

    R. B. Mann

    1997-09-15

    I describe the general mathematical construction and physical picture of topological black holes, which are black holes whose event horizons are surfaces of non-trivial topology. The construction is carried out in an arbitrary number of dimensions, and includes all known special cases which have appeared before in the literature. I describe the basic features of massive charged topological black holes in $(3+1)$ dimensions, from both an exterior and interior point of view. To investigate their interiors, it is necessary to understand the radiative falloff behaviour of a given massless field at late times in the background of a topological black hole. I describe the results of a numerical investigation of such behaviour for a conformally coupled scalar field. Significant differences emerge between spherical and higher genus topologies.

  5. Topological Aspects of Quantum Chromodynamics

    Microsoft Academic Search

    Gerard't Hooft

    1998-01-01

    Absolute confinement of its color charges is a natural property of gauge\\u000atheories such as quantum chromodynamics. On the one hand, it can be attributed\\u000ato the existence of color-magnetic monopoles, a topological feature of the\\u000atheory, but one can also maintain that all non-Abelian gauge theories confine.\\u000aIt is illustrated how ``confinement'' works in the SU(2) sector of the

  6. Topological and geometric decomposition of nematic textures

    E-print Network

    Simon ?opar; Slobodan Žumer

    2012-01-20

    Directional media, such as nematic liquid crystals and ferromagnets, are characterized by their topologically stabilized defects in directional order. In nematics, boundary conditions and surface-treated inclusions often create complex structures, which are difficult to classify. Topological charge of point defects in nematics has ambiguously defined sign and its additivity cannot be ensured when defects are observed separately. We demonstrate how the topological charge of complex defect structures can be determined by identifying and counting parts of the texture that satisfy simple geometric rules. We introduce a parameter called the defect rank and show that it corresponds to what is intuitively perceived as a point charge based on the properties of the director field. Finally, we discuss the role of free energy constraints in validity of the classification with the defect rank.

  7. 5 CFR 630.206 - Minimum charge.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS ABSENCE AND LEAVE Definitions and General Provisions for Annual and Sick Leave § 630.206 Minimum charge. (a) Unless an agency establishes a minimum charge of less than one hour,...

  8. BPA Definitions

    SciTech Connect

    United States. Bonneville Power Administration.

    1993-12-01

    The Bonneville Power Administration`s definition of terms are documented here. The terms primarily focus on transmission, generation and distribution, but also cover BPA services and responsibilities.

  9. Chapter 0: Topological Groups..........................................................................................................2 Chapter 1: Manifolds..................................................................................................

    E-print Network

    Sengun, Mehmet Haluk

    by . Proof a. Take any element then for . Then and as by definition, . b. ( ) ( ) ( ) . c. We need to check that if then and then . As and are products of elements of , clearly is a product of elements of . If and we have . Lemma 0: Manifolds Definition 1.1 A chart ( ) on a topological space of dimension is a non-empty open set

  10. Topological mechanisms as classical spinor fields

    E-print Network

    Vincenzo Vitelli; Nitin Upadhyaya; Bryan Gin-ge Chen

    2014-07-11

    A mechanism is a zero-energy motion of a mechanical structure that does not stretch or compress any of its components. Here, we focus on a special class of mechanisms that we dub topological because they are insensitive to smooth changes in material parameters. Topological mechanisms do not arise from local under-coordination, but they can be localized to solitons in the underlying structure. In this letter, we exploit supersymmetry to develop a real-space formalism whereby a topological mechanism can be described as a classical spinor whose real components are the soliton-induced displacement and stress fields. Our analytical approach goes beyond topological band theory by addressing the non-linearity and inhomogeneity of the underlying structure key to the very definition of a mechanism. We apply this general method to an activated mechanism, inspired by the organic molecule polyacetylene, that can propagate down an assembly line without deploying the whole structure.

  11. Topological Insulators and Superconductors from String Theory

    E-print Network

    Shinsei Ryu; Tadashi Takayanagi

    2010-08-01

    Topological insulators and superconductors in different spatial dimensions and with different discrete symmetries have been fully classified recently, revealing a periodic structure for the pattern of possible types of topological insulators and supercondutors, both in terms of spatial dimensions and in terms of symmetry classes. It was proposed that K-theory is behind the periodicity. On the other hand, D-branes, a solitonic object in string theory, are also known to be classified by K-theory. In this paper, by inspecting low-energy effective field theories realized by two parallel D-branes, we establish a one-to-one correspondence between the K-theory classification of topological insulators/superconductors and D-brane charges. In addition, the string theory realization of topological insulators and superconductors comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature, such as ones with the Chern-Simons term or the $\\theta$-term in various dimensions. This sheds light on topological insulators and superconductors beyond non-interacting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions. Increasing the number of D-branes naturally leads to a realization of topological insulators and superconductors in terms of holography (AdS/CFT).

  12. Topological insulators and superconductors from string theory

    SciTech Connect

    Ryu, Shinsei; Takayanagi, Tadashi [Department of Physics, University of California, Berkeley, California 94720 (United States); Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)

    2010-10-15

    Topological insulators and superconductors in different spatial dimensions and with different discrete symmetries have been fully classified recently, revealing a periodic structure for the pattern of possible types of topological insulators and superconductors, both in terms of spatial dimensions and in terms of symmetry classes. It was proposed that K theory is behind the periodicity. On the other hand, D-branes, a solitonic object in string theory, are also known to be classified by K theory. In this paper, by inspecting low-energy effective field theories realized by two parallel D-branes, we establish a one-to-one correspondence between the K-theory classification of topological insulators/superconductors and D-brane charges. In addition, the string theory realization of topological insulators and superconductors comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature, such as ones with the Chern-Simons term or the {theta} term in various dimensions. This sheds light on topological insulators and superconductors beyond noninteracting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions. Increasing the number of D-branes naturally leads to a realization of topological insulators and superconductors in terms of holography (AdS/CFT).

  13. Deficient topological measures and functionals generated by them

    SciTech Connect

    Svistula, Marina G [Samara State University, Samara (Russian Federation)

    2013-05-31

    This paper looks at the properties of deficient topological measures, which are a generalization of topological measures. Integration of a real function that is continuous on a compact set with respect to a deficient topological measure is also investigated. The notions of r- and l-functionals are introduced and an analogue of the Riesz representation theorem is obtained for them. As corollaries, both well-known and new results for quasi-integrals and topological measures are presented (for example, a new version of the definition of a quasi-integral). Bibliography: 16 titles.

  14. Gapped symmetry preserving surface state for the electron topological insulator

    E-print Network

    Wang, Chong

    It is well known that the three-dimensional (3D) electronic topological insulator (TI) with charge-conservation and time-reversal symmetry cannot have a trivial insulating surface that preserves symmetry. It is often ...

  15. PROTECTED VETERAN DEFINITIONS TITLE DEFINITION

    E-print Network

    Tipple, Brett

    .S. military, ground, naval, or air service who served in the Republic of Vietnam between February 28, 1961PROTECTED VETERAN DEFINITIONS TITLE DEFINITION Veteran of the Vietnam Era Veteran of the U through May7, 1975, who: 1. served on active duty for a period of more than 180 days and was discharged

  16. Submitted to Topology Proceedings

    E-print Network

    Gauld, David

    Submitted to Topology Proceedings TOPOLOGY PROCEEDINGS EXAMPLE FOR THE AUTHORS AUTHOR ONE Abstract. This paper contains a sample article in the Topology Proceedings format. 1. Introduction This is a sample article in the TOPOLOGY PROCEEDINGS for- mat. Prepare your paper in a similar manner before submitting

  17. Topological binding and elastic interactions of microspheres and fibres in a nematic liquid crystal.

    PubMed

    Nikkhou, M; Škarabot, M; Muševi?, I

    2015-03-01

    We present a detailed analysis of topological binding and elastic interactions between a long, and micrometer-diameter fiber, and a microsphere in a homogeneously aligned nematic liquid crystal. Both objects are surface treated to produce strong perpendicular anchoring of the nematic liquid crystal. We use the opto-thermal micro-quench of the laser tweezers to produce topological defects with prescribed topological charge, such as pairs of a Saturn ring and an anti-ring, hyperbolic and radial hedgehogs on a fiber, as well as zero-charge loops. We study the entanglement and topological charge interaction between the topological defects of the fiber and sphere and we observe a huge variety of different entanglement topologies and defect-mediated elastic bindings. We explain all observed phenomena with simple topological rule: like topological charges repel each other and opposite topological charges attract. These binding mechanisms not only demonstrate the fascinating topology of nematic colloids, but also open a novel route to the assembly of very complex topological networks of fibers, spheres and other objects for applications in liquid crystal photonics. PMID:25813607

  18. Bosonic topological insulator in three dimensions and the statistical Witten effect

    E-print Network

    Bosonic topological insulator in three dimensions and the statistical Witten effect Max A-known that one signature of the three-dimensional electron topological insulator is the Witten effect-odd-integer polarization charge. In the present work, we propose a corre- sponding phenomenon for the topological insulator

  19. Fractional topological insulators in three dimensions.

    PubMed

    Maciejko, Joseph; Qi, Xiao-Liang; Karch, Andreas; Zhang, Shou-Cheng

    2010-12-10

    Topological insulators can be generally defined by a topological field theory with an axion angle ? of 0 or ?. In this work, we introduce the concept of fractional topological insulator defined by a fractional axion angle and show that it can be consistent with time reversal T invariance if ground state degeneracies are present. The fractional axion angle can be measured experimentally by the quantized fractional bulk magnetoelectric polarization P?, and a "halved" fractional quantum Hall effect on the surface with Hall conductance of the form ?H=p/q e²/2h with p, q odd. In the simplest of these states the electron behaves as a bound state of three fractionally charged "quarks" coupled to a deconfined non-Abelian SU(3) "color" gauge field, where the fractional charge of the quarks changes the quantization condition of P? and allows fractional values consistent with T invariance. PMID:21231552

  20. Fractional Topological Insulators in Three Dimensions

    SciTech Connect

    Maciejko, Joseph; Zhang Shoucheng [Department of Physics, Stanford University, Stanford, California 94305 (United States); Qi Xiaoliang [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, California 93106 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); Karch, Andreas [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

    2010-12-10

    Topological insulators can be generally defined by a topological field theory with an axion angle {theta} of 0 or {pi}. In this work, we introduce the concept of fractional topological insulator defined by a fractional axion angle and show that it can be consistent with time reversal T invariance if ground state degeneracies are present. The fractional axion angle can be measured experimentally by the quantized fractional bulk magnetoelectric polarization P{sub 3}, and a 'halved' fractional quantum Hall effect on the surface with Hall conductance of the form {sigma}{sub H}=(p/q)(e{sup 2}/2h) with p, q odd. In the simplest of these states the electron behaves as a bound state of three fractionally charged 'quarks' coupled to a deconfined non-Abelian SU(3) 'color' gauge field, where the fractional charge of the quarks changes the quantization condition of P{sub 3} and allows fractional values consistent with T invariance.

  1. Fractional topological insulators in three dimensions

    E-print Network

    Joseph Maciejko; Xiao-Liang Qi; Andreas Karch; Shou-Cheng Zhang

    2010-11-14

    Topological insulators can be generally defined by a topological field theory with an axion angle theta of 0 or pi. In this work, we introduce the concept of fractional topological insulator defined by a fractional axion angle and show that it can be consistent with time reversal (T) invariance if ground state degeneracies are present. The fractional axion angle can be measured experimentally by the quantized fractional bulk magnetoelectric polarization P_3, and a `halved' fractional quantum Hall effect on the surface with Hall conductance of the form (p/q)(e^2/2h) with p,q odd. In the simplest of these states the electron behaves as a bound state of three fractionally charged `quarks' coupled to a deconfined non-Abelian SU(3) `color' gauge field, where the fractional charge of the quarks changes the quantization condition of P_3 and allows fractional values consistent with T-invariance.

  2. Electrically Tunable Magnetism in Magnetic Topological Insulators

    NASA Astrophysics Data System (ADS)

    Zhang, Shou-Cheng; Wang, Jing; Lian, Biao

    2015-03-01

    The external controllability of the magnetic properties in topological insulators would be important both for fundamental and practical interests. Here we predict the electric-field control of ferromagnetism in a thin film of insulating magnetic topological insulators. The decrease of band inversion by the application of electric fields results in a reduction of magnetic susceptibility, and hence in the modication of magnetism. Remarkably, the electric field could even induce the magnetic quantum phase transition from ferromagnetism to paramagnetism. We further propose a topological transistor device in which the dissipationless charge transport of chiral edge states is controlled by an electric field. The simultaneous electrical control of magnetic order and chiral edge transport in such a device may lead to electronic and spintronic applications for topological insulators. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515.

  3. A hierarchy of topological tensor network states

    SciTech Connect

    Buerschaper, Oliver [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario, Canada N2L 2Y5 (Canada) [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario, Canada N2L 2Y5 (Canada); Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Mombelli, Juan Martin [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Medina Allende s/n, Ciudad Universitaria, 5000 Cordoba (Argentina)] [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Medina Allende s/n, Ciudad Universitaria, 5000 Cordoba (Argentina); Christandl, Matthias [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich (Switzerland)] [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich (Switzerland); Aguado, Miguel [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)] [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)

    2013-01-15

    We present a hierarchy of quantum many-body states among which many examples of topological order can be identified by construction. We define these states in terms of a general, basis-independent framework of tensor networks based on the algebraic setting of finite-dimensional Hopf C*-algebras. At the top of the hierarchy we identify ground states of new topological lattice models extending Kitaev's quantum double models [Ann. Phys. 303, 2 (2003)]. For these states we exhibit the mechanism responsible for their non-zero topological entanglement entropy by constructing an entanglement renormalization flow. Furthermore, we argue that the hierarchy states are related to each other by the condensation of topological charges.

  4. Detecting topological currents in graphene superlattices.

    PubMed

    Gorbachev, R V; Song, J C W; Yu, G L; Kretinin, A V; Withers, F; Cao, Y; Mishchenko, A; Grigorieva, I V; Novoselov, K S; Levitov, L S; Geim, A K

    2014-10-24

    Topological materials may exhibit Hall-like currents flowing transversely to the applied electric field even in the absence of a magnetic field. In graphene superlattices, which have broken inversion symmetry, topological currents originating from graphene's two valleys are predicted to flow in opposite directions and combine to produce long-range charge neutral flow. We observed this effect as a nonlocal voltage at zero magnetic field in a narrow energy range near Dirac points at distances as large as several micrometers away from the nominal current path. Locally, topological currents are comparable in strength with the applied current, indicating large valley-Hall angles. The long-range character of topological currents and their transistor-like control by means of gate voltage can be exploited for information processing based on valley degrees of freedom. PMID:25342798

  5. POTLUCK FOOD SAFETY 1. Definition

    E-print Network

    POTLUCK FOOD SAFETY 1. Definition: (i) Campus Potluck is a closed food event that is privately funded by the participants, where all group members bring food dishes to share with others in the group. All food provided for the potluck event shall be consumed by members of the group at no charge

  6. Effective field theories for topological insulators by functional bosonization

    NASA Astrophysics Data System (ADS)

    Chan, AtMa; Hughes, Taylor L.; Ryu, Shinsei; Fradkin, Eduardo

    2013-02-01

    Effective field theories that describe the dynamics of a conserved U(1) current in terms of “hydrodynamic” degrees of freedom of topological phases in condensed matter are discussed in general dimension D=d+1 using the functional bosonization technique. For noninteracting topological insulators (superconductors) with a conserved U(1) charge and characterized by an integer topological invariant [more specifically, they are topological insulators in the complex symmetry classes (class A and AIII), and in the “primary series” of topological insulators, in the eight real symmetry classes], we derive the BF-type topological field theories supplemented with the Chern-Simons (when D is odd) or the ? (when D is even) terms. For topological insulators characterized by a Z2 topological invariant (the first and second descendants of the primary series), their topological field theories are obtained by dimensional reduction. Building on this effective field theory description for noninteracting topological phases, we also discuss, following the spirit of the parton construction of the fractional quantum Hall effect by Block and Wen, the putative “fractional” topological insulators and their possible effective field theories, and use them to determine the physical properties of these nontrivial quantum phases.

  7. Hopf insulators and their topologically protected surface states

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Tao; Deng, Dong-Ling; Shen, Chao; Duan, Lu-Ming

    2014-03-01

    Three-dimensional (3D) topological insulators in general need to be protected by certain kinds of symmetries other than the presumed U(1) charge conservation. A peculiar exception is the Hopf insulators which are 3D topological insulators characterized by an integer Hopf index. To demonstrate the existence and physical relevance of the Hopf insulators, we construct a class of tight-binding model Hamiltonians which realize all kinds of Hopf insulators with arbitrary integer Hopf index. These Hopf insulator phases have topologically protected surface states and we numerically demonstrate the robustness of these topologically protected states under general random perturbations without any symmetry other than the U(1) charge conservation that is implicit in all kinds of topological insulators. NBR-PC (973 Program) 2011CBA00300 (2011CBA00302), the DARPA OLE program, the IARPA MUSIQC program, the ARO and the AFOSR MURI program.

  8. Topological quantization of the spin Hall effect in two-dimensional paramagnetic semiconductors

    SciTech Connect

    Qi, X.-L.

    2010-03-02

    We propose models of two-dimensional paramagnetic semiconductors where the intrinsic spin Hall effect is exactly quantized in integer units of a topological charge. The model describes a topological insulator in the bulk and a 'holographic metal' at the edge, where the number of extended edge states crossing the Fermi level is dictated by (exactly equal to) the bulk topological charge. We also demonstrate the spin Hall effect explicitly in terms of the spin accumulation caused by the adiabatic flux insertion.

  9. Circuital characterisation of space-charge motion with a time-varying applied bias

    PubMed Central

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-01-01

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes. PMID:26133999

  10. Circuital characterisation of space-charge motion with a time-varying applied bias.

    PubMed

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-01-01

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes. PMID:26133999

  11. 4D Topological Mass by Gauging Spin

    E-print Network

    Choudhury, Ishita D; Guarnaccia, Giuseppe; Lahiri, Amitabha; Trugenberger, Carlo A

    2015-01-01

    We propose a spin gauge field theory in which the curl of a Dirac fermion current density plays the role of the pseudovector charge density. In this field-theoretic model, spin interactions are mediated by a single scalar gauge boson in its antisymmetric tensor formulation. We show that these long range spin interactions induce a gauge invariant photon mass in the one-loop effective action. The fermion loop generates a coupling between photons and the spin gauge boson, which acquires thus charge. This coupling represents also an induced, gauge invariant, topological mass for the photons, leading to the Meissner effect. The one-loop effective equations of motion for the charged spin gauge boson are the London equations. We propose thus spin gauge interactions as an alternative, topological mechanism for superconductivity in which no spontaneous symmetry breaking is involved.

  12. Topological wave functions and the 4D-5D lift

    E-print Network

    Gao, Peng

    2008-01-01

    We revisit the holomorphic anomaly equations satisfied by the topological string amplitude from the perspective of the 4D-5D lift, in the context of ``magic'' N=2 supergravity theories. In particular, we interpret the Gopakumar-Vafa relation between 5D black hole degeneracies and the topological string amplitude as the result of a canonical transformation from 4D to 5D charges. Moreover we use the known Bekenstein-Hawking entropy of 5D black holes to constrain the asymptotic behavior of the topological wave function at finite topological coupling but large K\\"ahler classes. In the process, some subtleties in the relation between 5D black hole degeneracies and the topological string amplitude are uncovered, but not resolved. Finally we extend these considerations to the putative one-parameter generalization of the topological string amplitude, and identify the canonical transformation as a Weyl reflection inside the 3D duality group.

  13. Topological wave functions and the 4D-5D lift

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Pioline, Boris

    2008-07-01

    We revisit the holomorphic anomaly equations satisfied by the topological string amplitude from the perspective of the 4D-5D lift, in the context of ``magic'' Script N = 2 supergravity theories. In particular, we interpret the Gopakumar-Vafa relation between 5D black hole degeneracies and the topological string amplitude as the result of a canonical transformation from 4D to 5D charges. Moreover we use the known Bekenstein-Hawking entropy of 5D black holes to constrain the asymptotic behavior of the topological wave function at finite topological coupling but large Kähler classes. In the process, some subtleties in the relation between 5D black hole degeneracies and the topological string amplitude are uncovered, but not resolved. Finally we extend these considerations to the putative one-parameter generalization of the topological string amplitude, and identify the canonical transformation as a Weyl reflection inside the 3D duality group.

  14. Topological wave functions and the 4D-5D lift

    E-print Network

    Peng Gao; Boris Pioline

    2008-07-14

    We revisit the holomorphic anomaly equations satisfied by the topological string amplitude from the perspective of the 4D-5D lift, in the context of ''magic'' N=2 supergravity theories. In particular, we interpret the Gopakumar-Vafa relation between 5D black hole degeneracies and the topological string amplitude as the result of a canonical transformation from 4D to 5D charges. Moreover we use the known Bekenstein-Hawking entropy of 5D black holes to constrain the asymptotic behavior of the topological wave function at finite topological coupling but large K\\"ahler classes. In the process, some subtleties in the relation between 5D black hole degeneracies and the topological string amplitude are uncovered, but not resolved. Finally we extend these considerations to the putative one-parameter generalization of the topological string amplitude, and identify the canonical transformation as a Weyl reflection inside the 3D duality group.

  15. Wannier center sheets in topological insulators

    NASA Astrophysics Data System (ADS)

    Taherinejad, Maryam; Garrity, Kevin F.; Vanderbilt, David

    2014-03-01

    We argue that various kinds of topological insulators (TIs) can be insightfully characterized by an inspection of the charge centers of the hybrid Wannier functions, defined as the orbitals obtained by carrying out a Wannier transform on the Bloch functions in one dimension while leaving them Bloch-like in the other two. From this procedure, one can obtain the Wannier charge centers (WCCs) and plot them in the two-dimensional projected Brillouin zone. We show that these WCC sheets contain the same kind of topological information as is carried in the surface energy bands, with the crucial advantage that the topological properties of the bulk can be deduced from bulk calculations alone. The distinct topological behaviors of these WCC sheets in trivial, Chern, weak, strong, and crystalline TIs are first illustrated by calculating them for simple tight-binding models. We then present the results of first-principles calculations of the WCC sheets in the trivial insulator Sb2Se3, the weak TI KHgSb, and the strong TI Bi2Se3, confirming the ability of this approach to distinguish between different topological behaviors in an advantageous way.

  16. Optical image encryption topology.

    PubMed

    Yong-Liang, Xiao; Xin, Zhou; Qiong-Hua, Wang; Sheng, Yuan; Yao-Yao, Chen

    2009-10-15

    Optical image encryption topology is proposed based on the principle of random-phase encoding. Various encryption topological units, involving peer-to-peer, ring, star, and tree topologies, can be realized by an optical 6f system. These topological units can be interconnected to constitute an optical image encryption network. The encryption and decryption can be performed in both digital and optical methods. PMID:19838280

  17. Topologies on directed graphs

    NASA Technical Reports Server (NTRS)

    Lieberman, R. N.

    1972-01-01

    Given a directed graph, a natural topology is defined and relationships between standard topological properties and graph theoretical concepts are studied. In particular, the properties of connectivity and separatedness are investigated. A metric is introduced which is shown to be related to separatedness. The topological notions of continuity and homeomorphism. A class of maps is studied which preserve both graph and topological properties. Applications involving strong maps and contractions are also presented.

  18. A remark on gapped domain walls between topological phases

    E-print Network

    Kawahigashi, Yasuyuki

    2015-01-01

    We give a mathematical definition of a gapped domain wall between topological phases and a gapped boundary of a topological phase. We then provide answers to some recent questions studied by Lan, Wang and Wen in condensed matter physics based on works of Davydov, M\\"uger, Nikshych and Ostrik. In particular, we identify their tunneling matrix and a coupling matrix of Rehren, and show that their conjecture does not hold.

  19. A remark on gapped domain walls between topological phases

    E-print Network

    Yasuyuki Kawahigashi

    2015-05-07

    We give a mathematical definition of a gapped domain wall between topological phases and a gapped boundary of a topological phase. We then provide answers to some recent questions studied by Lan, Wang and Wen in condensed matter physics based on works of Davydov, M\\"uger, Nikshych and Ostrik. In particular, we identify their tunneling matrix and a coupling matrix of Rehren, and show that their conjecture does not hold.

  20. Modeling Internet topology

    Microsoft Academic Search

    K. I. Calvert; M. B. Doar; E. W. Zegura

    1997-01-01

    The topology of a network, or a group of networks such as the Internet, has a strong bearing on many management and performance issues. Good models of the topological structure of a network are essential for developing and analyzing internetworking technology. This article discusses how graph-based models can be used to represent the topology of large networks, particularly aspects of

  1. On various neutrosophic topologies

    Microsoft Academic Search

    2009-01-01

    Purpose – Recently, F. Smarandache generalized the Atanassov's intuitionistic fuzzy sets (IFSs) and other kinds of sets to neutrosophic sets (NSs) and also defined various notions of neutrosophic topologies on the non-standard interval. One can expect some relation between the intuitionistic fuzzy topology (IFT) on an IFS and neutrosophic topologies on the non-standard interval. The purpose of this paper is

  2. On neutrosophic topology

    Microsoft Academic Search

    Francisco Gallego Lupianez

    2008-01-01

    Purpose – Recently, Smarandache generalized the Atanassov's intuitionistic fuzzy sets (IFSs) and other kinds of sets to neutrosophic sets (NSs). Also, this author defined the notion of neutrosophic topology on the non-standard interval. One can expect some relation between the intuitionistic fuzzy topology (IFT) on an IFS and the neutrosophic topology. This paper aims to show that this is false.

  3. Time-Reversal-Invariant Topological Superconductivity in n-type Doped BiH

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Liu, Cheng-Cheng; Zhang, Yu-Zhong; Yao, Yugui; Lee, Dung-Hai

    2015-03-01

    Intrinsic and symmetry protected topological states have attracted lots of interest in condensed matter physics recently. In particular, time reversal symmetry protected fermion topological insulators have been theoretically predicted and experimentally verified. However despite considerable experimental and theoretical works, definitive evidence for time reversal invariant topological superconductivity is still lacking. Here we propose that upon electron doping the hydrogenated single bilayer Bi, namely BiH, will exhibit time reversal invariant topological superconductivity. If confirmed experimentally this material will constitute the first example of TRI topological superconductor.

  4. Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides

    NASA Astrophysics Data System (ADS)

    Pardo, V.; Smith, J. C.; Pickett, W. E.

    2012-06-01

    It was reported earlier [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.106.056401 106, 056401 (2011)] that the skutterudite structure compound CoSb3 displays a unique band structure with a topological transition versus a symmetry-preserving sublattice (Sb) displacement very near the structural ground state. The transition is through a massless Dirac-Weyl semimetal, point Fermi surface phase which is unique in that (1) it appears in a three-dimensional crystal, (2) the band critical point occurs at k=0, and (3) linear bands are degenerate with conventional (massive) bands at the critical point (before inclusion of spin-orbit coupling). Further interest arises because the critical point separates a conventional (trivial) phase from a topological phase. In the native cubic structure this is a zero-gap topological semimetal; we show how spin-orbit coupling and uniaxial strain converts the system to a topological insulator (TI). We also analyze the origin of the linear band in this class of materials, which is the characteristic that makes them potentially useful in thermoelectric applications or possibly as transparent conductors. We characterize the formal charge as Co+ d8, consistent with the gap, with its 3¯ site symmetry, and with its lack of moment. The Sb states are characterized as px (separately, py) ?-bonded Sb4 ring states occupied and the corresponding antibonding states empty. The remaining (locally) pz orbitals form molecular orbitals with definite parity centered on the empty 2a site in the skutterudite structure. Eight such orbitals must be occupied; the one giving the linear band is an odd orbital singlet A2u at the zone center. We observe that the provocative linearity of the band within the gap is a consequence of the aforementioned near-degeneracy, which is also responsible for the small band gap.

  5. Game Theory and Topological Phase Transition

    E-print Network

    Tieyan Si

    2008-03-29

    Phase transition is a war game. It widely exists in different kinds of complex system beyond physics. Where there is revolution, there is phase transition. The renormalization group transformation, which was proved to be a powerful tool to study the critical phenomena, is actually a game process. The phase boundary between the old phase and new phase is the outcome of many rounds of negotiation between the old force and new force. The order of phase transition is determined by the cutoff of renormalization group transformation. This definition unified Ehrenfest's definition of phase transition in thermodynamic physics. If the strategy manifold has nontrivial topology, the topological relation would put a constrain on the surviving strategies, the transition occurred under this constrain may be called a topological one. If the strategy manifold is open and noncompact, phase transition is simply a game process, there is no table for topology. An universal phase coexistence equation is found, it sits at the Nash equilibrium point. Inspired by the fractal space structure demonstrated by renormalization group theory, a conjecture is proposed that the universal scaling law of a general phase transition in a complex system comes from the coexistence equation around Nash equilibrium point. Game theory also provide us new understanding to pairing mechanism and entanglement in many body physics.

  6. Quartic Quasi-Topological-Born-Infeld Gravity

    E-print Network

    Ghanaatian, Mohammad

    2015-01-01

    In this paper, quartic quasi-topological black holes in the presence of a nonlinear electromagnetic Born-Infeld field is presented. By using the metric parameters, the charged black hole solutions of quasi-topological Born-Infeld gravity is considered. The thermodynamics of these black holes are investigated and I show that the thermodynamics and conserved quantities verify the first law of thermodynamics. I also introduce the thermodynamics of asymptotically AdS rotating black branes with flat horizon of these class of solutions and I calculate the finite action by use of the counterterm method inspired by AdS/CFT correspondence.

  7. Topological Valley Currents in Gapped Dirac Materials

    NASA Astrophysics Data System (ADS)

    Lensky, Yuri D.; Song, Justin C. W.; Samutpraphoot, Polnop; Levitov, Leonid S.

    2015-06-01

    Gapped 2D Dirac materials, in which inversion symmetry is broken by a gap-opening perturbation, feature a unique valley transport regime. Topological valley currents in such materials are dominated by bulk currents produced by electronic states just beneath the gap rather than by edge modes. The system ground state hosts dissipationless persistent valley currents existing even when topologically protected edge modes are absent. Valley currents induced by an external bias are characterized by a quantized half-integer valley Hall conductivity. The undergap currents dominate magnetization and the charge Hall effect in a light-induced valley-polarized state.

  8. TRANSFORMER DESIGN FOR CHARGING DEFIBRILLATOR CAPACITORS

    Microsoft Academic Search

    Kirby Creel

    Generating high voltage by means of flyback topology is a common approach. Using the generated voltage to charge a capacitor for a high energy pulse are used in defibrillators, photo- flashs, strobes and ignition circuits to name a few. The procedure outlined in this article is useful in the initial transformer design phase for charging a capacitor in a stated

  9. Monopole-charge instability

    E-print Network

    Horváthy, P A; Rawnsley, J H

    2009-01-01

    For monopoles with nonvanishing Higgs potential it is shown that with respect to "Brand-Neri-Coleman type" variations (a) the stability problem reduces to that of a pure gauge theory on the two-sphere (b) each topological sector admits one, and only one, stable monopole charge, and (c) each unstable monopole admits $2\\sum_{q<0} (2|q|-1)$ negative modes, where the sum goes over all negative eigenvalues $q$ of the non-Abelian charge $Q$. An explicit construction for (i) the unique stable charge (ii) the negative modes and (iii) the spectrum of the Hessian, on the 2-sphere, is then given. The relation to loops in the residual group is explained. The negative modes are tangent to suitable energy-reducing two-spheres. The general theory is illustrated for the little groups U(2), U(3), SU(3)/Z_3 and O(5).

  10. Battery charger and state of charge indicator. Final report

    SciTech Connect

    Latos, T.S.

    1984-04-15

    The battery charger has a full-wave rectifier in series with a transformer isolated 20 kHz dc-dc converter with high frequency switches which are programmed to actively shape the input ac line current to be a mirror image of the ac line voltage. The power circuit is capable of operating at 2 kW peak and 1 kW average power. The BC/SCI has two major subsystems: (1) the battery charger power electronics with its controls; and (2) a microcomputer subsystem which is used to acquire battery terminal data and exercise the state-of-charge software programs. The state-of-charge definition employed is the energy remaining in the battery when extracted at a 10 kW rate divided by the energy capacity of a fully charged new battery. The battery charger circuit is an isolated boost converter operating at an internal frequency of 20 kHz. The switches selected for the battery charger are the single most important item in determining its efficiency. The combination of voltage and current requirements dictated the use of high power NPN Darlington switching transistors. The power circuit topology developed is a three switch design utilizing a power FET on the center tap of the isolation transformer and the power Darlingtons on each of the two ends. An analog control system is employed to accomplish active input current waveshaping as well as the necessary regulation.

  11. Network topology analysis.

    SciTech Connect

    Kalb, Jeffrey L.; Lee, David S.

    2008-01-01

    Emerging high-bandwidth, low-latency network technology has made network-based architectures both feasible and potentially desirable for use in satellite payload architectures. The selection of network topology is a critical component when developing these multi-node or multi-point architectures. This study examines network topologies and their effect on overall network performance. Numerous topologies were reviewed against a number of performance, reliability, and cost metrics. This document identifies a handful of good network topologies for satellite applications and the metrics used to justify them as such. Since often multiple topologies will meet the requirements of the satellite payload architecture under development, the choice of network topology is not easy, and in the end the choice of topology is influenced by both the design characteristics and requirements of the overall system and the experience of the developer.

  12. Model Realization and Numerical Studies of a Three-Dimensional Bosonic Topological Insulator and Symmetry-Enriched Topological Phases

    NASA Astrophysics Data System (ADS)

    Geraedts, Scott D.; Motrunich, Olexei I.

    2014-10-01

    We study a topological phase of interacting bosons in (3 +1 ) dimensions that is protected by charge conservation and time-reversal symmetry. We present an explicit lattice model that realizes this phase and that can be studied in sign-free Monte Carlo simulations. The idea behind our model is to bind bosons to topological defects called hedgehogs. We determine the phase diagram of the model and identify a phase where such bound states are proliferated. In this phase, we observe a Witten effect in the bulk whereby an external monopole binds half of the elementary boson charge, which confirms that it is a bosonic topological insulator. We also study the boundary between the topological insulator and a trivial insulator. We find a surface phase diagram that includes exotic superfluids, a topologically ordered phase, and a phase with a Hall effect quantized to one-half of the value possible in a purely two-dimensional system. We also present models that realize symmetry-enriched topologically ordered phases by binding multiple hedgehogs to each boson; these phases show charge fractionalization and intrinsic topological order as well as a fractional Witten effect.

  13. Generating charge from diffeomorphisms

    NASA Astrophysics Data System (ADS)

    Hansen, James; Kraus, Per

    2006-12-01

    We unravel some subtleties involving the definition of sphere angular momentum charges in AdSq × Sp spacetimes, or equivalently, R-symmetry charges in the dual boundary CFT. In the AdS3 context, it is known that charges can be generated by coordinate transformations, even though the underlying theory is diffeomorphism invariant. This is the bulk version of spectral flow in the boundary CFT. We trace this behavior back to special properties of the p-form field strength supporting the solution, and derive the explicit formulas for angular momentum charges. This analysis also reveals the higher dimensional origin of three dimensional Chern-Simons terms and of chiral anomalies in the boundary theory.

  14. Generating Charge from Diffeomorphisms

    E-print Network

    James Hansen; Per Kraus

    2006-09-18

    We unravel some subtleties involving the definition of sphere angular momentum charges in AdS_q \\times S^p spacetimes, or equivalently, R-symmetry charges in the dual boundary CFT. In the AdS_3 context, it is known that charges can be generated by coordinate transformations, even though the underlying theory is diffeomorphism invariant. This is the bulk version of spectral flow in the boundary CFT. We trace this behavior back to special properties of the p-form field strength supporting the solution, and derive the explicit formulas for angular momentum charges. This analysis also reveals the higher dimensional origin of three dimensional Chern-Simons terms and of chiral anomalies in the boundary theory.

  15. Higgsless superconductivity from topological defects in compact BF terms

    NASA Astrophysics Data System (ADS)

    Diamantini, M. Cristina; Trugenberger, Carlo A.

    2015-02-01

    We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalisable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D - 1)-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact low-energy effective BF theories. In the average field approximation, the corresponding uniform emergent charge creates a gap for the (D - 2)-dimensional branes via the Magnus force, the dual of the Lorentz force. One particular combination of intrinsic and emergent charge fluctuations that leaves the total charge distribution invariant constitutes an isolated gapless mode leading to superfluidity. The remaining massive modes organise themselves into a D-dimensional charged, massive vector. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2) and the topological order (4) are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D this type of superconductivity is explicitly realised as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

  16. Topological Quantum Computation with the universal R matrix for Ising anyons

    E-print Network

    Lachezar S. Georgiev

    2008-12-12

    We show that the braid-group extension of the monodromy-based topological quantum computation scheme of Das Sarma et al. can be understood in terms of the universal R matrix for the Ising model giving similar results to those obtained by direct analytic continuation of multi-anyon Pfaffian wave functions. It is necessary, however, to take into account the projection on spinor states with definite total parity which is responsible for the topological entanglement in the Pfaffian topological quantum computer.

  17. Topological crystalline insulator nanostructures.

    PubMed

    Shen, Jie; Cha, Judy J

    2014-11-01

    Topological crystalline insulators are topological insulators whose surface states are protected by the crystalline symmetry, instead of the time reversal symmetry. Similar to the first generation of three-dimensional topological insulators such as Bi?Se? and Bi?Te?, topological crystalline insulators also possess surface states with exotic electronic properties such as spin-momentum locking and Dirac dispersion. Experimentally verified topological crystalline insulators to date are SnTe, Pb?-xSnxSe, and Pb?-xSnxTe. Because topological protection comes from the crystal symmetry, magnetic impurities or in-plane magnetic fields are not expected to open a gap in the surface states in topological crystalline insulators. Additionally, because they have a cubic structure instead of a layered structure, branched structures or strong coupling with other materials for large proximity effects are possible, which are difficult with layered Bi?Se? and Bi?Te?. Thus, additional fundamental phenomena inaccessible in three-dimensional topological insulators can be pursued. In this review, topological crystalline insulator SnTe nanostructures will be discussed. For comparison, experimental results based on SnTe thin films will be covered. Surface state properties of topological crystalline insulators will be discussed briefly. PMID:25350386

  18. Periodic table for topological insulators and superconductors

    NASA Astrophysics Data System (ADS)

    Kitaev, Alexei

    2009-05-01

    Gapped phases of noninteracting fermions, with and without charge conservation and time-reversal symmetry, are classified using Bott periodicity. The symmetry and spatial dimension determines a general universality class, which corresponds to one of the 2 types of complex and 8 types of real Clifford algebras. The phases within a given class are further characterized by a topological invariant, an element of some Abelian group that can be 0, Z, or Z2. The interface between two infinite phases with different topological numbers must carry some gapless mode. Topological properties of finite systems are described in terms of K-homology. This classification is robust with respect to disorder, provided electron states near the Fermi energy are absent or localized. In some cases (e.g., integer quantum Hall systems) the K-theoretic classification is stable to interactions, but a counterexample is also given.

  19. Tunable Dirac Fermion Dynamics in Topological Insulators

    PubMed Central

    Chen, Chaoyu; Xie, Zhuojin; Feng, Ya; Yi, Hemian; Liang, Aiji; He, Shaolong; Mou, Daixiang; He, Junfeng; Peng, Yingying; Liu, Xu; Liu, Yan; Zhao, Lin; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Yu, Li; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Zhou, X. J.

    2013-01-01

    Three-dimensional topological insulators are characterized by insulating bulk state and metallic surface state involving relativistic Dirac fermions which are responsible for exotic quantum phenomena and potential applications in spintronics and quantum computations. It is essential to understand how the Dirac fermions interact with other electrons, phonons and disorders. Here we report super-high resolution angle-resolved photoemission studies on the Dirac fermion dynamics in the prototypical Bi2(Te,Se)3 topological insulators. We have directly revealed signatures of the electron-phonon coupling and found that the electron-disorder interaction dominates the scattering process. The Dirac fermion dynamics in Bi2(Te3?xSex) topological insulators can be tuned by varying the composition, x, or by controlling the charge carriers. Our findings provide crucial information in understanding and engineering the electron dynamics of the Dirac fermions for fundamental studies and potential applications. PMID:23934507

  20. Manipulating Topological States by Imprinting Non-Collinear Spin Textures

    DOE PAGESBeta

    Streubel, Robert; Han, Luyang; Im, Mi-Young; Kronast, Florian; Rößler, Ulrich K.; Radu, Florin; Abrudan, Radu; Lin, Gungun; Schmidt, Oliver G.; Fischer, Peter; et al

    2015-03-05

    Topological magnetic states, such as chiral skyrmions, are of great scientific interest and show huge potential for novel spintronics applications, provided their topological charges can be fully controlled. So far skyrmionic textures have been observed in noncentrosymmetric crystalline materials with low symmetry and at low temperatures. We propose theoretically and demonstrate experimentally the design of spin textures with topological charge densities that can be tailored at ambient temperatures. Tuning the interlayer coupling in vertically stacked nanopatterned magnetic heterostructures, such as a model system of a Co/Pd multilayer coupled to Permalloy, the in-plane non-collinear spin texture of one layer can bemore »imprinted into the out-of-plane magnetised material. We observe distinct spin textures, e.g. vortices, magnetic swirls with tunable opening angle, donut states and skyrmion core configurations. We show that applying a small magnetic field, a reliable switching between topologically distinct textures can be achieved at remanence« less

  1. CHARGE syndrome: an update

    Microsoft Academic Search

    Damien Sanlaville; Alain Verloes

    2007-01-01

    CHARGE syndrome is a rare, usually sporadic autosomal dominant disorder due in 2\\/3 of cases to mutations within the CHD7 gene. The clinical definition has evolved with time. The 3C triad (Coloboma-Choanal atresia-abnormal semicircular Canals), arhinencephaly and rhombencephalic dysfunctions are now considered the most important and constant clues to the diagnosis. We will discuss here recent aspects of the phenotypic

  2. Photonic Floquet Topological Insulators

    E-print Network

    Rechtsman, Mikael C; Plotnik, Yonatan; Lumer, Yaakov; Nolte, Stefan; Segev, Mordechai; Szameit, Alexander

    2012-01-01

    The topological insulator is a fundamentally new phase of matter, with the striking property that the conduction of electrons occurs only on its surface, not within the bulk, and that conduction is topologically protected. Topological protection, the total lack of scattering of electron waves by disorder, is perhaps the most fascinating and technologically important aspect of this material: it provides robustness that is otherwise known only for superconductors. However, unlike superconductivity and the quantum Hall effect, which necessitate low temperatures or magnetic fields, the immunity to disorder of topological insulators occurs at room temperature and without any external magnetic field. For this reason, topological protection is predicted to have wide-ranging applications in fault-tolerant quantum computing and spintronics. Recently, a large theoretical effort has been directed towards bringing the concept into the domain of photonics: achieving topological protection of light at optical frequencies. ...

  3. Supersymmetric black holes with lens-space topology.

    PubMed

    Kunduri, Hari K; Lucietti, James

    2014-11-21

    We present a new supersymmetric, asymptotically flat, black hole solution to five-dimensional supergravity. It is regular on and outside an event horizon of lens-space topology L(2,1). It is the first example of an asymptotically flat black hole with lens-space topology. The solution is characterized by a charge, two angular momenta, and a magnetic flux through a noncontractible disk region ending on the horizon, with one constraint relating these. PMID:25479484

  4. Topological wave functions and the 4D-5D lift

    Microsoft Academic Search

    Peng Gao; Boris Pioline

    2008-01-01

    We revisit the holomorphic anomaly equations satisfied by the topological string amplitude from the perspective of the 4D-5D lift, in the context of ``magic'' Script N = 2 supergravity theories. In particular, we interpret the Gopakumar-Vafa relation between 5D black hole degeneracies and the topological string amplitude as the result of a canonical transformation from 4D to 5D charges. Moreover

  5. 42 CFR 405.509 - Determining the inflation-indexed charge.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Determining the inflation-indexed charge. 405.509... § 405.509 Determining the inflation-indexed charge. (a) Definition. For purposes of this section, inflation-indexed charge means...

  6. 42 CFR 405.509 - Determining the inflation-indexed charge.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Determining the inflation-indexed charge. 405.509... § 405.509 Determining the inflation-indexed charge. (a) Definition. For purposes of this section, inflation-indexed charge means...

  7. 42 CFR 405.509 - Determining the inflation-indexed charge.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Determining the inflation-indexed charge. 405.509... § 405.509 Determining the inflation-indexed charge. (a) Definition. For purposes of this section, inflation-indexed charge means...

  8. 42 CFR 405.509 - Determining the inflation-indexed charge.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Determining the inflation-indexed charge. 405.509... § 405.509 Determining the inflation-indexed charge. (a) Definition. For purposes of this section, inflation-indexed charge means...

  9. 42 CFR 405.509 - Determining the inflation-indexed charge.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Determining the inflation-indexed charge. 405.509... § 405.509 Determining the inflation-indexed charge. (a) Definition. For purposes of this section, inflation-indexed charge means...

  10. Topological black holes in Horava-Lifshitz gravity

    SciTech Connect

    Cai Ronggen [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China) and Kavli Institute for Theoretical Physics China (KITPC), Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Cao Liming [Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Ohta, Nobuyoshi [Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan)

    2009-07-15

    We find topological (charged) black holes whose horizon has an arbitrary constant scalar curvature 2k in Horava-Lifshitz theory. Without loss of generality, one may take k=1, 0, and -1. The black hole solution is asymptotically anti-de Sitter with a nonstandard asymptotic behavior. Using the Hamiltonian approach, we define a finite mass associated with the solution. We discuss the thermodynamics of the topological black holes and find that the black hole entropy has a logarithmic term in addition to an area term. We find a duality in Hawking temperature between topological black holes in Horava-Lifshitz theory and Einstein's general relativity: the temperature behaviors of black holes with k=1, 0, and -1 in Horava-Lifshitz theory are, respectively, dual to those of topological black holes with k=-1, 0, and 1 in Einstein's general relativity. The topological black holes in Horava-Lifshitz theory are thermodynamically stable.

  11. Destroying a topological quantum bit by condensing Ising vortices

    NASA Astrophysics Data System (ADS)

    Hao, Zhihao; Inglis, Stephen; Melko, Roger

    2014-12-01

    The imminent realization of topologically protected qubits in fabricated systems will provide not only an elementary implementation of fault-tolerant quantum computing architecture, but also an experimental vehicle for the general study of topological order. The simplest topological qubit harbours what is known as a Z2 liquid phase, which encodes information via a degeneracy depending on the system’s topology. Elementary excitations of the phase are fractionally charged objects called spinons, or Ising flux vortices called visons. At zero temperature, a Z2 liquid is stable under deformations of the Hamiltonian until spinon or vison condensation induces a quantum-phase transition destroying the topological order. Here we use quantum Monte Carlo to study a vison-induced transition from a Z2 liquid to a valence-bond solid in a quantum dimer model on the kagome lattice. Our results indicate that this critical point is beyond the description of the standard Landau paradigm.

  12. Cubic topological Kondo insulators.

    PubMed

    Alexandrov, Victor; Dzero, Maxim; Coleman, Piers

    2013-11-27

    Current theories of Kondo insulators employ the interaction of conduction electrons with localized Kramers doublets originating from a tetragonal crystalline environment, yet all Kondo insulators are cubic. Here we develop a theory of cubic topological Kondo insulators involving the interaction of ?(8) spin quartets with a conduction sea. The spin quartets greatly increase the potential for strong topological insulators, entirely eliminating the weak topological phases from the diagram. We show that the relevant topological behavior in cubic Kondo insulators can only reside at the lower symmetry X or M points in the Brillouin zone, leading to three Dirac cones with heavy quasiparticles. PMID:24329462

  13. Topological Domain Theory 

    E-print Network

    Battenfeld, Ingo

    2008-01-01

    This thesis presents Topological Domain Theory as a powerful and flexible framework for denotational semantics. Topological Domain Theory models a wide range of type constructions and can interpret many computational features. Furthermore, it has...We begin by describing the categories of Topological Domain Theory, and their categorical structure. In particular, we recover the basic constructions of domain theory, such as products, function spaces, fixed points and recursive types, in the context of Topological Domain Theory....As a central contribution, we give a detailed account of how computational effects can be modelled in Topological Domain Theory. Following recent work of Plotkin and Power, who proposed to construct effect monads via free algebra functors, this is done by showing that free algebras for a large class of parametrised equational theories exist in Topological Domain Theory. These parametrised equational theories are expressive enough to generate most of the standard examples of effect monads. Moreover, the free algebras in Topological Domain Theory are obtained by an explicit inductive construction, using only basic topological and set-theoretical principles....We also give a comparison of Topological and Classical Domain Theory. The category of omega-continuous dcpos embeds into Topological Domain Theory, and we prove that this embedding preserves the basic domain-theoretic constructions in most cases. We show that the classical powerdomain constructions on omega-continuous dcpos, including the probabilistic powerdomain, can be recovered in Topological Domain Theory....Finally, we give a synthetic account of Topological Domain Theory. We show that Topological Domain Theory is a specific model of Synthetic Domain Theory in the realizability topos over Scott's graph model. We give internal characterisations of the categories of Topological Domain Theory in this realizability topos, and prove the corresponding categories to be internally complete and weakly small. This enables us to show that Topological Domain Theory can model the polymorphic lambda-calculus, and to obtain a richer collection of free algebras than those constructed earlier....In summary, this thesis shows that Topological Domain Theory supports a wide range of semantic constructions, including the standard domain-theoretic constructions, computational effects and polymorphism, all within a single setting....

  14. Notes on topological insulators

    E-print Network

    Dan Li; Ralph M. Kaufmann; Birgit Wehefritz-Kaufmann

    2015-06-15

    This paper is a survey of the $\\mathbb{Z}/\\mathbb{Z}_2$-valued invariants of topological insulators in condensed matter physics. The $\\mathbb{Z}$-valued topological invariant was originally called the TKNN invariant in physics, which has been fully understood as the first Chern number. The $\\mathbb{Z}_2$ invariant is more mysterious, we will devote our efforts to reviewing its equivalent descriptions from different points of view. We emphasize that both invariants are realizations of some index theorems in condensed matter physics. Topological K-theory also plays an important role in the classification of topological insulators with different symmetries.

  15. Notes on topological insulators

    E-print Network

    Dan Li; Ralph M. Kaufmann; Birgit Wehefritz-Kaufmann

    2015-01-13

    This paper is a survey of the $\\mathbb{Z}/\\mathbb{Z}_2$-valued invariants of topological insulators in condensed matter physics. The $\\mathbb{Z}$-valued topological invariant was originally called the TKNN invariant in physics, which has been fully understood as the first Chern number. The $\\mathbb{Z}_2$ invariant is more mysterious, we will devote our efforts to reviewing its equivalent descriptions from different point of views. We emphasize that both invariants are realizations of the Atiyah--Singer index theorem in condensed matter physics. The topological K-theory also plays an important role in the classification of topological insulators with different symmetries.

  16. Black hole attractors and the topological string

    Microsoft Academic Search

    Hirosi Ooguri; Andrew Strominger; Cumrun Vafa

    2004-01-01

    A simple relationship of the form ZBH=|Ztop|2 is conjectured, where ZBH is a supersymmetric partition function for a four-dimensional BPS black hole in a Calabi-Yau compactification of Type II superstring theory and Ztop is a second-quantized topological string partition function evaluated at the attractor point in moduli space associated to the black hole charges. Evidence for the conjecture in a

  17. Topological solitons in 8-spinor mie electrodynamics

    SciTech Connect

    Rybakov, Yu. P., E-mail: soliton4@mail.ru [Peoples' Friendship University of Russia, Department of Theoretical Physics (Russian Federation)

    2013-10-15

    We investigate the effective 8-spinor field model suggested earlier as the generalization of nonlinear Mie electrodynamics. We first study in pure spinorial model the existence of topological solitons endowed with the nontrivial Hopf invariant Q{sub H}, which can be interpreted as the lepton number. Electromagnetic field being included as the perturbation, we estimate the energy and the spin of the localized charged configuration.

  18. Wormhole effect in a strong topological insulator

    Microsoft Academic Search

    G. Rosenberg; M. Franz

    2010-01-01

    When the surface of a strong topological insulator (STI) is coated by a ferromagnetic film the surface state acquires a gap and becomes a quantum Hall liquid with the Hall conductance (n+1\\/2)e^2\\/h, n integer. Applying the Laughlin flux-insertion argument to such a surface implies the existence of quasiparticles with fractional charge ±e\\/2. This result however contradicts the microscopic theory of

  19. Topological susceptibility with the asqtad action

    SciTech Connect

    Bazavov, A.; Toussaint, D. [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Bernard, C.; Laiho, J. [Department of Physics, Washington University, St. Louis, Missouri 63130 (United States); Billeter, B.; DeTar, C.; Levkova, L.; Oktay, M. B. [Physics Department, University of Utah, Salt Lake City, Utah 84112 (United States); Gottlieb, Steven [Department of Physics, Indiana University, Bloomington, Indiana 47405, USA, NCSA, University of Illinois, Urbana, Illinois 61801 (United States); Heller, U. M. [American Physical Society, One Research Road, Ridge, New York 11961 (United States); Hetrick, J. E. [Physics Department, University of the Pacific, Stockton, California 95211 (United States); Osborn, J. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Sugar, R. L. [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Van de Water, R. S. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2010-06-01

    Chiral perturbation theory predicts that in quantum chromodynamics (QCD), light dynamical quarks suppress the gauge-field topological susceptibility of the vacuum. The degree of suppression depends on quark multiplicity and masses. It provides a strong consistency test for fermion formulations in lattice QCD. Such tests are especially important for staggered fermion formulations that lack a full chiral symmetry and use the 'fourth-root' procedure to achieve the desired number of sea quarks. Over the past few years we have measured the topological susceptibility on a large database of 18 gauge-field ensembles, generated in the presence of 2+1 flavors of dynamical asqtad quarks with up and down quark masses ranging from 0.05 to 1 in units of the strange quark mass and lattice spacings ranging from 0.045 fm to 0.12 fm. Our study also includes three quenched ensembles with lattice spacings ranging from 0.06 to 0.12 fm. We construct the topological susceptibility from the integrated point-to-point correlator of the discretized topological charge density FF-tilde. To reduce its variance, we model the asymptotic tail of the correlator. The continuum extrapolation of our results for the topological susceptibility agrees nicely at small quark mass with the predictions of lowest-order SU(3) chiral perturbation theory, thus lending support to the validity of the fourth-root procedure.

  20. Topological Phase Transition without Gap Closing

    PubMed Central

    Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2013-01-01

    Topological phase transition is accompanied with a change of topological numbers. According to the bulk-edge correspondence, the gap closing and the breakdown of the adiabaticity are necessary at the phase transition point to make the topological number ill-defined. However, the gap closing is not always needed. In this paper, we show that two topological distinct phases can be continuously connected without gap closing, provided the symmetry of the system changes during the process. Here we propose the generic principles how this is possible by demonstrating various examples such as 1D polyacetylene with the charge-density-wave order, 2D silicene with the antiferromagnetic order, 2D silicene or quantum well made of HgTe with superconducting proximity effects and 3D superconductor Cu doped Bi2Se3. It is argued that such an unusual phenomenon can occur when we detour around the gap closing point provided the connection of the topological numbers is lost along the detour path. PMID:24071900

  1. Topological phase transition without gap closing.

    PubMed

    Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2013-01-01

    Topological phase transition is accompanied with a change of topological numbers. According to the bulk-edge correspondence, the gap closing and the breakdown of the adiabaticity are necessary at the phase transition point to make the topological number ill-defined. However, the gap closing is not always needed. In this paper, we show that two topological distinct phases can be continuously connected without gap closing, provided the symmetry of the system changes during the process. Here we propose the generic principles how this is possible by demonstrating various examples such as 1D polyacetylene with the charge-density-wave order, 2D silicene with the antiferromagnetic order, 2D silicene or quantum well made of HgTe with superconducting proximity effects and 3D superconductor Cu doped Bi2Se3. It is argued that such an unusual phenomenon can occur when we detour around the gap closing point provided the connection of the topological numbers is lost along the detour path. PMID:24071900

  2. Probing the Chiral Anomaly with Nonlocal Transport in Three-Dimensional Topological Semimetals

    NASA Astrophysics Data System (ADS)

    Parameswaran, S. A.; Grover, T.; Abanin, D. A.; Pesin, D. A.; Vishwanath, A.

    2014-07-01

    Weyl semimetals are three-dimensional crystalline systems where pairs of bands touch at points in momentum space, termed Weyl nodes, that are characterized by a definite topological charge: the chirality. Consequently, they exhibit the Adler-Bell-Jackiw anomaly, which in this condensed-matter realization implies that the application of parallel electric (E) and magnetic (B) fields pumps electrons between nodes of opposite chirality at a rate proportional to E .B. We argue that this pumping is measurable via nonlocal transport experiments, in the limit of weak internode scattering. Specifically, we show that as a consequence of the anomaly, applying a local magnetic field parallel to an injected current induces a valley imbalance that diffuses over long distances. A probe magnetic field can then convert this imbalance into a measurable voltage drop far from source and drain. Such nonlocal transport vanishes when the injected current and magnetic field are orthogonal and therefore serves as a test of the chiral anomaly. We further demonstrate that a similar effect should also characterize Dirac semimetals—recently reported to have been observed in experiments—where the coexistence of a pair of Weyl nodes at a single point in the Brillouin zone is protected by a crystal symmetry. Since the nodes are analogous to valley degrees of freedom in semiconductors, the existence of the anomaly suggests that valley currents in three-dimensional topological semimetals can be controlled using electric fields, which has potential practical "valleytronic" applications.

  3. Fermionic symmetry-protected topological phase induced by interactions

    NASA Astrophysics Data System (ADS)

    Ning, Shang-Qiang; Jiang, Hong-Chen; Liu, Zheng-Xin

    2015-06-01

    Strong interactions can give rise to new fermionic symmetry-protected topological phases which have no analogs in free fermion systems. As an example, we have systematically studied a spinless fermion model with U (1 ) charge conservation and time-reversal symmetry on a three-leg ladder using density-matrix renormalization group. In the noninteracting limit, there are no topological phases. Turning on interactions, we found two gapped phases. One is trivial and is adiabatically connected to a band insulator, while another one is a nontrivial symmetry-protected topological phase resulting from strong interactions.

  4. Topological color code and symmetry-protected topological phases

    NASA Astrophysics Data System (ADS)

    Yoshida, Beni

    2015-06-01

    We study (d -1 ) -dimensional excitations in the d -dimensional color code that are created by transversal application of the Rd phase operators on connected subregions of qubits. We find that such excitations are the superpositions of electric charges and can be characterized by the fixed-point wave functions of (d -1 ) -dimensional bosonic symmetry-protected topological (SPT) phases with (Z2) ?d symmetry. While these SPT excitations are localized on (d -1 ) -dimensional boundaries, their creation requires operations acting on all qubits inside the boundaries, reflecting the nontriviality of emerging SPT wave functions. Moreover, these SPT excitations can be physically realized as transparent gapped domain walls which exchange excitations in the color code. Namely, in the three-dimensional color code, the domain wall, associated with the transversal R3 operator, exchanges a magnetic flux and a composite of a magnetic flux and the looplike SPT excitation, revealing rich possibilities of boundaries in higher-dimensional TQFTs. We also find that magnetic fluxes and the looplike SPT excitations exhibit nontrivial three-loop braiding statistics in three dimensions as a result of the fact that the R3 phase operator belongs to the third level of the Clifford hierarchy. We believe that the connection between SPT excitations, fault-tolerant logical gates and gapped domain walls, established in this paper, can be generalized to a large class of topological quantum codes and TQFTs.

  5. Topological defects in CFT

    SciTech Connect

    Petkova, V. B., E-mail: petkova@inrne.bas.bg [Bulgarian Academy of Sciences, Institute of Nuclear Research and Nuclear Energy (Bulgaria)

    2013-10-15

    Areview of the notion, properties and the use of topological defects in 2d conformal field theories is presented. An emphasis is made on the recent interpretation of such operators in non-rational theories, as describing Wilson-'t Hooft loop operators of N = 2 supersymmetric 4d topological theories.

  6. STABLE ALGEBRAIC TOPOLOGY AND

    E-print Network

    May, J. Peter

    subject, and its foundations are not yet firmly* * in place. I shall give some history, examples theory. This i* *s by far the most calculationally accessible part of algebraic topology, although it been central to this part of algeb* *raic topology since the early 1960's, but that have only been

  7. Computational Topology Afra Zomorodian

    E-print Network

    Zomorodian, Afra

    in combinatorial and algebraic topology, areas that had been overshadowed by point set topology in the last one formalize in Section 3, classifying all sur- faces, and introducing both combinatorial and algebraic invariants in the process. Sections 4 and 5 focus on homology and persistent homology, algebraic invariants

  8. Topologically Adaptable Snakes

    Microsoft Academic Search

    Tim Mcinerney; Demetri Terzopoulos

    1995-01-01

    This paper presents a topologically adaptable snakes model for image segmentation and object representation. The model is embedded in the framework of domain subdi- vision using simplicial decomposition. This framework ex- tends the geometric and topological adaptability of snakes while retaining all of the features of traditional snakes, s uch as user interaction, and overcoming many of the limitations of

  9. DNA Topology: Fundamentals

    E-print Network

    Mirkin, Sergei

    DNA Topology: Fundamentals Sergei M Mirkin, University of Illinois at Chicago, Illinois, USA Topological characteristics of DNA and specifically DNA supercoiling influence all major DNA transactions in living cells. DNA supercoiling induces the formation of unusual secondary structure by specific DNA

  10. Topological Defects in Cosmology

    Microsoft Academic Search

    Alejandro Gangui; F ´ õsica del Espacio

    2001-01-01

    Topological defects are ubiquitous in condensed-matter physics but only hypothetical in the early universe. In spite of this, even an indirect evidence for one of these cosmic objects would revolutionize our vision of the cosmos. We give here an introduction to the subject of cosmic topological defects and their possible observable signatures. Beginning with a review of the basics of

  11. Cosmology from Topological Defects

    Microsoft Academic Search

    Alejandro Gangui; F ´ õsica del Espacio

    2003-01-01

    The potential role of cosmic topological defects has raised interest in the astrophysical community for many years now. In this set of notes, we give an introduction to the subject of cosmic topological defects and some of their possible observable signatures. We begin with a review of the basics of general defect formation and evolution, we briefly comment on some

  12. Superconducting doped topological materials

    NASA Astrophysics Data System (ADS)

    Sasaki, Satoshi; Mizushima, Takeshi

    2015-07-01

    Recently, the search for Majorana fermions (MFs) has become one of the most important and exciting issues in condensed matter physics since such an exotic quasiparticle is expected to potentially give rise to unprecedented quantum phenomena whose functional properties will be used to develop future quantum technology. Theoretically, the MFs may reside in various types of topological superconductor materials that is characterized by the topologically protected gapless surface state which are essentially an Andreev bound state. Superconducting doped topological insulators and topological crystalline insulators are promising candidates to harbor the MFs. In this review, we discuss recent progress and understanding on the research of MFs based on time-reversal-invariant superconducting topological materials to deepen our understanding and have a better outlook on both the search for and realization of MFs in these systems. We also discuss some advantages of these bulk systems to realize MFs including remarkable superconducting robustness against nonmagnetic impurities.

  13. Interaction effects and quantum phase transitions in topological insulators

    SciTech Connect

    Varney, Christopher N. [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Joint Quantum Institute and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Sun Kai; Galitski, Victor [Joint Quantum Institute and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Rigol, Marcos [Department of Physics, Georgetown University, Washington, DC 20057 (United States)

    2010-09-15

    We study strong correlation effects in topological insulators via the Lanczos algorithm, which we utilize to calculate the exact many-particle ground-state wave function and its topological properties. We analyze the simple, noninteracting Haldane model on a honeycomb lattice with known topological properties and demonstrate that these properties are already evident in small clusters. Next, we consider interacting fermions by introducing repulsive nearest-neighbor interactions. A first-order quantum phase transition was discovered at finite interaction strength between the topological band insulator and a topologically trivial Mott insulating phase by use of the fidelity metric and the charge-density-wave structure factor. We construct the phase diagram at T=0 as a function of the interaction strength and the complex phase for the next-nearest-neighbor hoppings. Finally, we consider the Haldane model with interacting hard-core bosons, where no evidence for a topological phase is observed. An important general conclusion of our work is that despite the intrinsic nonlocality of topological phases their key topological properties manifest themselves already in small systems and therefore can be studied numerically via exact diagonalization and observed experimentally, e.g., with trapped ions and cold atoms in optical lattices.

  14. Topological solitons in helical strings

    NASA Astrophysics Data System (ADS)

    Nisoli, Cristiano; Balatsky, Alexander V.

    2015-06-01

    The low-energy physics of (quasi)degenerate one-dimensional systems is typically understood as the particle-like dynamics of kinks between stable, ordered structures. Such dynamics, we show, becomes highly nontrivial when the ground states are topologically constrained: a dynamics of the domains rather than on the domains which the kinks separate. Motivated by recently reported observations of charged polymers physio-adsorbed on nanotubes, we study kinks between helical structures of a string wrapping around a cylinder. While their motion cannot be disentangled from domain dynamics, and energy and momentum is not concentrated in the solitons, the dynamics of the domains can be folded back into a particle-like description of the local excitations.

  15. Symmetry-protected topological invariant and Majorana impurity states in time-reversal-invariant superconductors

    NASA Astrophysics Data System (ADS)

    Kimme, Lukas; Hyart, Timo; Rosenow, Bernd

    2015-06-01

    We address the question of whether individual nonmagnetic impurities can induce zero-energy states in time-reversal-invariant topological superconductors, and define a class of symmetries which guarantee the existence of such states for a specific value of the impurity strength. These symmetries allow the definition of a position-space topological Z2 invariant, which is related to the standard bulk topological Z2 invariant. Our general results are applied to the time-reversal-invariant p -wave phase of the doped Kitaev-Heisenberg model, where we demonstrate how a lattice of impurities can drive a topologically trivial system into the nontrivial phase.

  16. Time-reversal-invariant topological superconductivity in n -doped BiH

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Liu, Cheng-Cheng; Zhang, Yu-Zhong; Yao, Yugui; Lee, Dung-Hai

    2015-04-01

    Despite intense interest and considerable works, definitive experimental evidence for time-reversal-invariant topological superconductivity is still lacking. Hence searching for such superconductivity in real materials remains one of the main challenges in the field of topological material. Previously it has been shown that in the buckled honeycomb lattice structure, hydrogenated single bilayer Bi, namely BiH, is a topological insulator. Here we predict that upon n -type doping, BiH is a time-reversal-invariant topological superconductor. Interestingly the edge states of such a superconductor consist of both helical complex fermion modes and helical Majorana fermion modes.

  17. Dynamics of topological multipoles: II. Creation, annihilation, and evolution of nonparaxial optical vortices

    Microsoft Academic Search

    A. V. Volyar; T. A. Fadeeva

    2002-01-01

    The behavior of nonparaxial combined beams transferring two or four optical vortices with opposite topological charges (topological\\u000a dipole or quadrupole) is studied. The paraxial and nonparaxial approaches are compared. It is shown that the behavior of a\\u000a topologically neutral wave system is well characterized by the position of a representative point on the parametric plane.\\u000a It is found that there

  18. a Research on the Hierarchy and Completeness of Roof Topology for Robust Building Reconstruction from Airborne Point Cloud

    NASA Astrophysics Data System (ADS)

    Xu, B.; Jiang, W. S.; Zhu, Q. S.

    2015-05-01

    In this work, we concentrate on the hierarchy and completeness of roof topology, and the aim is to avoid or correct the errors in roof topology. The hierarchy of topology is expressed by the hierarchical roof topology graph (HRTG) in accord with the definition of CityGML LOD (level of details). We decompose the roof topology graph (RTG) with a progressive approach while maintain the integrality and consistency of the data set simultaneously. Common feathers like collinear ridges or boundaries are calculated integrally to maintain their completeness. The roof items will only detected locally to decrease the error caused by data spare or mutual interference. Finally, a topology completeness test is adopted to detect and correct errors in roof topology, which results in a complete and hierarchical building model. Experiments shows that our methods have obvious improvements to the RTG based reconstruction method, especially for sparse data or roof topology with ambiguous.

  19. 4. System Definition 16 4. System Definition

    E-print Network

    Berlin,Technische Universität

    4. System Definition 16 _____________________________________________________________________________ 4. System Definition Based on our knowledge that we can "join" the dynamic characteristics-up, complete system. A general and simple example of substructuring is the source-transmission element

  20. Topology of three-dimensional separated flows

    NASA Technical Reports Server (NTRS)

    Tobak, M.; Peake, D. J.

    1981-01-01

    Based on the hypothesis that patterns of skin-friction lines and external streamlines reflect the properties of continuous vector fields, topology rules define a small number of singular points (nodes, saddle points, and foci) that characterize the patterns on the surface and on particular projections of the flow (e.g., the crossflow plane). The restricted number of singular points and the rules that they obey are considered as an organizing principle whose finite number of elements can be combined in various ways to connect together the properties common to all steady three dimensional viscous flows. Introduction of a distinction between local and global properties of the flow resolves an ambiguity in the proper definition of a three dimensional separated flow. Adoption of the notions of topological structure, structural stability, and bifurcation provides a framework to describe how three dimensional separated flows originate and succeed each other as the relevant parameters of the problem are varied.

  1. Opportunities in chemistry and materials science for topological insulators and their nanostructures

    Microsoft Academic Search

    Desheng Kong; Yi Cui

    2011-01-01

    Electrical charges on the boundaries of topological insulators favour forward motion over back-scattering at impurities, producing low-dissipation, metallic states that exist up to room temperature in ambient conditions. These states have the promise to impact a broad range of applications from electronics to the production of energy, which is one reason why topological insulators have become the rising star in

  2. Modifying the molecular dynamics action to increase topological tunnelling rate for dynamical overlap fermions

    E-print Network

    Nigel Cundy; Weonjong Lee

    2012-02-27

    We describe a new Hybrid Monte Carlo (HMC) algorithm for dynamical overlap fermions, which improves the rate of topological index changes by adding an additional (intensive) term to the action for the molecular dynamics part of the algorithm. The metropolis step still uses the exact action, so that the Monte Carlo algorithm still generates the correct ensemble. By tuning this new term, we hope to be able to balance the acceptance rate of the HMC algorithm and the rate of topological index changes. We also describe how suppressing, but not eliminating, the small eigenvalues of the kernel operator may improve the volume scaling of the cost per trajectory for overlap HMC while still allowing topological index changes. We test this operator on small lattices, comparing our new algorithm with an old overlap HMC algorithm with a slower rate of topological charge changes, and an overlap HMC algorithm which fixes the topology. Our new HMC algorithm more than doubles the rate of topological index changes compared to the previous state of the art, while maintaining the same metropolis acceptance rate. We investigate the effect of topological index changes on the local topological charge density, measured using an improved field theoretic operator after heavy smearing. We find that the creation and annihilation of large lumps of topological charge is increased with the new algorithm.

  3. A study of charging control of lead-acid battery for electric vehicles

    Microsoft Academic Search

    Chih-Chiang Hua; Meng-Yu Lin

    2000-01-01

    The object of this paper is to investigate the circuit topologies and control techniques for fast charging of battery for the electric vehicle (EV). Analysis and comparison of fast charging characteristics for different charging controls are presented. A charging and discharging monitoring system was implemented based on a DSP. To improve the utilization of EV, it is necessary to design

  4. Take Charge!

    NSDL National Science Digital Library

    Integrated Teaching and Learning Program,

    Students come to understand static electricity by learning about the nature of electric charge, and different methods for charging objects. In a hands-on activity, students induce an electrical charge on various objects, and experiment with electrical repulsion and attraction.

  5. Seeing the magnetic monopole through the mirror of topological surface states

    SciTech Connect

    Qi, Xiao-Liang; Li, Rundong; /Stanford U., Phys. Dept.; Zang, Jiadong; /Fudan U.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept. /Fudan U.

    2010-03-25

    Existence of the magnetic monopole is compatible with the fundamental laws of nature, however, this illusive particle has yet to be detected experimentally. In this work, we show that an electric charge near the topological surface state induces an image magnetic monopole charge due to the topological magneto-electric effect. The magnetic field generated by the image magnetic monopole can be experimentally measured, and the inverse square law of the field dependence can be determined quantitatively. We propose that this effect can be used to experimentally realize a gas of quantum particles carrying fractional statistics, consisting of the bound states of the electric charge and the image magnetic monopole charge.

  6. Witten effect in a crystalline topological insulator

    SciTech Connect

    Rosenberg, G.; Franz, M. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

    2010-07-15

    It has been noted a long time ago that a term of the form theta(e{sup 2}/2pih)Bcentre dotE may be added to the standard Maxwell Lagrangian without modifying the familiar laws of electricity and magnetism. theta is known to particle physicists as the 'axion' field and whether or not it has a nonzero expectation value in vacuum remains a fundamental open question of the standard model. A key manifestation of the axion term is the Witten effect: a unit magnetic monopole placed inside a medium with thetanot =0 is predicted to bind a (generally fractional) electric charge -e(theta/2pi+n) with n integer. Here we conduct a test of the Witten effect based on the recently established fact that the axion term with theta=pi emerges naturally in the description of the electromagnetic response of a class of crystalline solids called topological insulators--materials distinguished by strong spin-orbit coupling and nontrivial band structures. Using a simple physical model for a topological insulator we demonstrate the existence of a fractional charge bound to a monopole by an explicit numerical calculation. We also propose a scheme for generating an 'artificial' magnetic monopole in a topological insulator film that may be used to facilitate an experimental test of Witten's prediction.

  7. Wannier Center Sheets in Topological Insulators

    NASA Astrophysics Data System (ADS)

    Taherinejad, Maryam; Garrity, Kevin; Vanderbilt, David

    2014-03-01

    The electronic ground state in a periodic crystalline insulator can be described by hybrid Wannier functions | Wnlz(kx ,ky) > which are maximally localized in one direction and Bloch-like in the other two. In 3D insulators the Wannier charge centers (WCCs), defined as zn(kx ,ky) = < Wn 0(kx ,ky) | z& circ; |Wn 0(kx ,ky) > , are functions of momentum in two dimensions and can be plotted as sheets over the 2D Brillouin zone. We show that the symmetry group of the WCCs zn(kx ,ky) includes all the symmetries of surface energy bands ?n(kx ,ky) . More importantly, the WCCs contain the same kind of topological information as is carried in the surface energy bands, with the crucial advantage that the topological properties of the bulk can be deduced from bulk properties alone. The distinct topological behavior of these WCC sheets in trivial, Chern, weak, strong, and crystalline topological insulators are demonstrated using different tight-binding models. The WCC sheets calculated from first-principles calculations in Z2-even Sb2Se3, weak Z2-odd KHgSb, and strong Z2-odd Bi2Se3 confirm the results from the tight-binding models. Supported by NSF Grant DMR-10-05838.

  8. Topologically massive magnetic monopoles

    E-print Network

    A. N. Aliev; Y. Nutku; K. Sayg?l?

    2000-05-15

    We show that in the Maxwell-Chern-Simons theory of topologically massive electrodynamics the Dirac string of a monopole becomes a cone in anti-de Sitter space with the opening angle of the cone determined by the topological mass which in turn is related to the square root of the cosmological constant. This proves to be an example of a physical system, {\\it a priory} completely unrelated to gravity, which nevertheless requires curved spacetime for its very existence. We extend this result to topologically massive gravity coupled to topologically massive electrodynamics in the framework of the theory of Deser, Jackiw and Templeton. These are homogeneous spaces with conical deficit. Pure Einstein gravity coupled to Maxwell-Chern-Simons field does not admit such a monopole solution.

  9. Multimaterial topology optimization

    E-print Network

    R. Tavakoli

    2013-04-15

    Apr 15, 2013 ... listings are provided as the supplementary materials. The success .... materials is an- other candidate to solve multiphase topology optimization problems. ..... It is mainly because of their promising efficiency to solve special ...

  10. Polariton Z Topological Insulator

    NASA Astrophysics Data System (ADS)

    Nalitov, A. V.; Solnyshkov, D. D.; Malpuech, G.

    2015-03-01

    We demonstrate that honeycomb arrays of microcavity pillars behave as an optical-frequency two-dimensional photonic topological insulator. We show that the interplay between the photonic spin-orbit coupling natively present in this system and the Zeeman splitting of exciton polaritons in external magnetic fields leads to the opening of a nontrivial gap characterized by a C =±2 set of band Chern numbers and to the formation of topologically protected one-way edge states.

  11. Polariton Z topological insulator.

    PubMed

    Nalitov, A V; Solnyshkov, D D; Malpuech, G

    2015-03-20

    We demonstrate that honeycomb arrays of microcavity pillars behave as an optical-frequency two-dimensional photonic topological insulator. We show that the interplay between the photonic spin-orbit coupling natively present in this system and the Zeeman splitting of exciton polaritons in external magnetic fields leads to the opening of a nontrivial gap characterized by a C=±2 set of band Chern numbers and to the formation of topologically protected one-way edge states. PMID:25839295

  12. Topological insulators and superconductors

    Microsoft Academic Search

    Xiao-Liang Qi; Shou-Cheng Zhang

    2010-01-01

    Topological insulators are new states of quantum matter which can not be\\u000aadiabatically connected to conventional insulators and semiconductors. They are\\u000acharacterized by a full insulating gap in the bulk and gapless edge or surface\\u000astates which are protected by time-reversal symmetry. These topological\\u000amaterials have been theoretically predicted and experimentally observed in a\\u000avariety of systems, including HgTe quantum

  13. Recipe for Topological Polaritons

    NASA Astrophysics Data System (ADS)

    Karzig, Torsten; Bardyn, Charles-Edouard; Lindner, Netanel; Refael, Gil

    2015-03-01

    The interaction between light and matter can give rise to novel topological states. This principle was recently exemplified in Floquet topological insulators, where classical light was used to induce a topological electronic band structure. Here, in contrast, we show that mixing single photons with excitons can result in new topological polaritonic states -- or ``topolaritons''. Taken separately, the underlying photons and excitons are topologically trivial. Combined appropriately, however, they give rise to non-trivial polaritonic bands with chiral edge modes allowing for unidirectional polariton propagation. The main ingredient in our construction is an exciton-photon coupling with a phase that winds in momentum space. We demonstrate how this winding emerges from spin-orbit coupling in the electronic system and an applied Zeeman field. We discuss the requirements for obtaining a sizable topological gap in the polariton spectrum. Funded by the Institute for Quantum Information and Matter, the Bi-National Science Foundation and I-Core: the Israeli Excellence Center ``Circle of Light'', and Darpa under funding for FENA, and the Swiss National Science Foundation.

  14. Photonic topological insulators

    NASA Astrophysics Data System (ADS)

    Khanikaev, Alexander B.; Hossein Mousavi, S.; Tse, Wang-Kong; Kargarian, Mehdi; MacDonald, Allan H.; Shvets, Gennady

    2013-03-01

    Recent progress in understanding the topological properties of condensed matter has led to the discovery of time-reversal-invariant topological insulators. A remarkable and useful property of these materials is that they support unidirectional spin-polarized propagation at their surfaces. Unfortunately topological insulators are rare among solid-state materials. Using suitably designed electromagnetic media (metamaterials) we theoretically demonstrate a photonic analogue of a topological insulator. We show that metacrystals—superlattices of metamaterials with judiciously designed properties—provide a platform for designing topologically non-trivial photonic states, similar to those that have been identified for condensed-matter topological insulators. The interfaces of the metacrystals support helical edge states that exhibit spin-polarized one-way propagation of photons, robust against disorder. Our results demonstrate the possibility of attaining one-way photon transport without application of external magnetic fields or breaking of time-reversal symmetry. Such spin-polarized one-way transport enables exotic spin-cloaked photon sources that do not obscure each other.

  15. Topology of density matrices

    NASA Astrophysics Data System (ADS)

    Budich, Jan Carl; Diehl, Sebastian

    2015-04-01

    We investigate the topological properties of density matrices, motivated by the question to what extent phenomena such as topological insulators and superconductors can be generalized to mixed states in the framework of open quantum systems. The notion of geometric phases has been extended from pure to mixed states by Uhlmann [Rep. Math. Phys. 24, 229 (1986), 10.1016/0034-4877(86)90055-8], who discovered an emergent gauge theory over the density matrices based on their pure state representation in a larger Hilbert space. However, since the uniquely defined square root ?{? } of a density matrix ? provides a global gauge, this construction is always topologically trivial. Here, we study a more restrictive gauge structure which can be topologically nontrivial and is capable of resolving homotopically distinct mappings of density matrices subject to various spectral constraints. Remarkably, in this framework, topological invariants can be directly defined and calculated for mixed states. In the limit of pure states, the well-known system of topological invariants for gapped band structures at zero temperature is reproduced. We compare our construction with recent approaches to Chern insulators at finite temperature.

  16. 40 CFR 61.171 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...Inorganic Arsenic Emissions From Primary Copper Smelters § 61.171 Definitions...addition of a molten or solid material to a copper converter. Control device means...rate at which arsenic is charged to the copper converters in the copper converter...

  17. 40 CFR 61.171 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Inorganic Arsenic Emissions From Primary Copper Smelters § 61.171 Definitions...addition of a molten or solid material to a copper converter. Control device means...rate at which arsenic is charged to the copper converters in the copper converter...

  18. 40 CFR 61.171 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Inorganic Arsenic Emissions From Primary Copper Smelters § 61.171 Definitions...addition of a molten or solid material to a copper converter. Control device means...rate at which arsenic is charged to the copper converters in the copper converter...

  19. Topological Insulators and Superconductors from D-branes

    E-print Network

    Shinsei Ryu; Tadashi Takayanagi

    2010-08-08

    Realization of topological insulators (TIs) and superconductors (TSCs), such as the quantum spin Hall effect and the Z_2 topological insulator, in terms of D-branes in string theory is proposed. We establish a one-to-one correspondence between the K-theory classification of TIs/TSCs and D-brane charges. The string theory realization of TIs and TSCs comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature. This sheds light on TIs and TSCs beyond non-interacting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions.

  20. Pair Production of Topological anti de Sitter Black Holes

    E-print Network

    R. B. Mann

    1996-07-28

    The pair creation of black holes with event horizons of non-trivial topology is described. The spacetimes are all limiting cases of the cosmological $C$ metric. They are generalizations of the $(2+1)$ dimensional black hole and have asymptotically anti de Sitter behaviour. Domain walls instantons can mediate their pair creation for a wide range of mass and charge.

  1. Positive topological entropy for multi-bump magnetic fields

    E-print Network

    Andreas Knauf; Frank Schulz; Karl Friedrich Siburg

    2012-08-27

    We study the dynamics of a charged particle in a planar magnetic field which consists of $n\\geq 2$ disjoint localized peaks. We show that, under mild geometric conditions, this system is semi-conjugated to the full shift on $n$ symbols and, hence, carries positive topological entropy.

  2. A topological Dirac insulator in a quantum spin Hall phase

    Microsoft Academic Search

    D. Hsieh; D. Qian; L. Wray; Y. Xia; Y. S. Hor; R. J. Cava; M. Z. Hasan

    2008-01-01

    When electrons are subject to a large external magnetic field, the conventional charge quantum Hall effect dictates that an electronic excitation gap is generated in the sample bulk, but metallic conduction is permitted at the boundary. Recent theoretical models suggest that certain bulk insulators with large spin-orbit interactions may also naturally support conducting topological boundary states in the quantum limit,

  3. Experimental Realization of a Three-Dimensional Topological Insulator

    Microsoft Academic Search

    Yulin Chen

    2010-01-01

    Three-dimensional(3D) topological insulators (TIs) are a new state of quantum matter with a bulk gap generated by the spin orbit interaction and odd number of relativistic Dirac fermions on the surface. The robust surface states of TIs can be the host for many striking quantum phenomena, such as an image magnetic monopole induced by an electric charge and Majorana fermions

  4. Topological Insulators Avoid the Parity Anomaly

    E-print Network

    Michael Mulligan; F. J. Burnell

    2013-01-17

    The surface of a 3+1d topological insulator hosts an odd number of gapless Dirac fermions when charge conjugation and time-reversal symmetries are preserved. Viewed as a purely 2+1d system, this surface theory would necessarily explicitly break parity and time-reversal when coupled to a fluctuating gauge field. Here we explain why such a state can exist on the boundary of a 3+1d system without breaking these symmetries, even if the number of boundary components is odd. This is accomplished from two complementary perspectives: topological quantization conditions and regularization. We first discuss the conditions under which (continuous) large gauge transformations may exist when the theory lives on a boundary of a higher-dimensional spacetime. Next, we show how the higher-dimensional bulk theory is essential in providing a parity-invariant regularization of the theory living on the lower-dimensional boundary or defect.

  5. Topological Insulators Avoid the Parity Anomaly

    E-print Network

    Mulligan, Michael

    2013-01-01

    The surface of a 3+1d topological insulator hosts an odd number of gapless Dirac fermions when charge conjugation and time-reversal symmetries are preserved. Viewed as a purely 2+1d system, this surface theory would necessarily explicitly break parity and time-reversal when coupled to a fluctuating gauge field. Here we explain why such a state can exist on the boundary of a 3+1d system without breaking these symmetries, even if the number of boundary components is odd. This is accomplished from two complementary perspectives: topological quantization conditions and regularization. We first discuss the conditions under which (continuous) large gauge transformations may exist when the theory lives on a boundary of a higher-dimensional spacetime. Next, we show how the higher-dimensional bulk theory is essential in providing a parity-invariant regularization of the theory living on the lower-dimensional boundary or defect.

  6. Extended topological defects as sources and outlets of dislocations in spherical hexagonal crystals

    NASA Astrophysics Data System (ADS)

    Roshal, D. S.; Petrov, K. Yu.; Myasnikova, A. E.; Rochal, S. B.

    2014-04-01

    Extended topological defects (ETDs) arising in spherical hexagonal crystals due to their curvature are considered. These prevalent defects carry a unit total topological charge and are surrounded by scalene pentagonal boundaries. Topological peculiarities of reactions between ETDs and dislocations are considered. Similarly to boundaries of the usual planar crystalline order the ETDs emit and absorb the dislocations without preservation of their dislocational charge. Dislocations located inside the ETD area lose it and the enforced ETD decay can proceed in different ways without conservation of the total Burgers vector of the dislocations emitted.

  7. Nonlinear scattering in photonic crystals having dislocations with fractional topological character and multiple dislocations

    NASA Astrophysics Data System (ADS)

    Naor, Liran; Sharabi, Shani; Juwiler, Irit; Arie, Ady

    2015-05-01

    The spectrum of the second harmonic signal generated in quadratic nonlinear photonic crystals, having different types of edge dislocations, was studied theoretically and experimentally. In the case of a dislocation with a fractional topological charge, we observed an asymmetric spectral conversion efficiency response, where the degree of asymmetry depends on the value of the fractional charge. Moreover, we have found that the conversion efficiency spectrum exhibits a periodic dependence on the topological charge value. In addition, nonlinear photonic crystals with multiple edge dislocations were studied. We show that for any number of dislocations characterized by even topological charge, the nonlinear spectral response will be identical to the response of the ideal, dislocation-free structure. This is a generalization of a previous observation that was made for crystals with a single even charge dislocation. Furthermore, for any number of dislocations with odd topological charge, two new peaks of maximal efficiency are observed in the second harmonic spectrum, in addition to a series of local efficiency peaks that are governed by the total number of dislocations. This is also a generalization of a previous observation that was made for a single dislocation case having an odd topological charge.

  8. Internal Charging

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.

    2014-01-01

    (1) High energy (>100keV) electrons penetrate spacecraft walls and accumulate in dielectrics or isolated conductors; (2) Threat environment is energetic electrons with sufficient flux to charge circuit boards, cable insulation, and ungrounded metal faster than charge can dissipate; (3) Accumulating charge density generates electric fields in excess of material breakdown strenght resulting in electrostatic discharge; and (4) System impact is material damage, discharge currents inside of spacecraft Faraday cage on or near critical circuitry, and RF noise.

  9. Topological phase transition in thin-film topological crystalline insulators

    NASA Astrophysics Data System (ADS)

    Yamakage, Ai; Ozawa, Hideyuki; Sato, Masatoshi; Tanaka, Yukio

    2015-03-01

    Topological crystalline insulator is one of the recent breakthrough ideas, in which Dirac fermions on the surface protected by crystalline symmetry, not by time-reversal symmetry. Another direction of the topological expansion is nanofabrication. In this work, we reveal the topological phase diagram of a thin-film topological crystalline insulator PbxSn1-xTe. Odd numbers of layers of PbxSn1-xTe exhibit the topological phase transition between two-dimensional trivial and topological crystalline insulators protected by the mirror-Chern number, which is consistent with the previous work. In addition, we have found a new topological phase in the even numbers of layers, which is protected by the glide symmetry. This glide topological phase can be realized in the thin film not in the bulk system.

  10. 40 CFR 98.430 - Definition of the source category.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.430 Definition of the...contained in pre-charged equipment or closed-cell foams, consists of any entity that imports...entity that imports or exports closed-cell foams that contain a fluorinated...

  11. A Torsional Topological Invariant

    E-print Network

    H. T Nieh

    2013-09-04

    Curvature and torsion are the two tensors characterizing a general Riemannian spacetime. In Einstein's general theory of gravitation, with torsion postulated to vanish and the affine connection identified to the Christoffel symbol, only the curvature tensor plays the central role. For such a purely metric geometry, two well-known topological invariants, namely the Euler class and the Pontryagin class, are useful in characterizing the topological properties of the spacetime. From a gauge theory point of view, and especially in the presence of spin, torsion naturally comes into play, and the underlying spacetime is no longer purely metric. We describe a torsional topological invariant, discovered in 1982, that has now found increasing usefulness in recent developments.

  12. Adiabatic topological quantum computing

    E-print Network

    Chris Cesare; Andrew J. Landahl; Dave Bacon; Steven T. Flammia; Alice Neels

    2014-06-10

    Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev's surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computation size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.

  13. a Torsional Topological Invariant

    NASA Astrophysics Data System (ADS)

    Nieh, H. T.

    2008-12-01

    Curvature and torsion are the two tensors characterizing a general Riemannian space-time. In Einstein's general theory of gravitation, with torsion postulated to vanish and the affine connection identified to the Christoffel symbol, only the curvature tensor plays the central role. For such a purely metric geometry, two well-known topological invariants, namely the Euler class and the Pontryagin class, are useful in characterizing the topological properties of the space-time. From a gauge theory point of view, and especially in the presence of spin, torsion naturally comes into play, and the underlying space-time is no longer purely metric. We describe a torsional topological invariant, discovered in 1982, that has now found increasing usefulness in recent developments.

  14. Topological insulators with SU(2) Landau levels

    E-print Network

    Yi Li; Shou-Cheng Zhang; Congjun Wu

    2013-10-23

    We construct continuum models of 3D and 4D topological insulators by coupling spin-1/2 fermions to an SU(2) background gauge field, which is equivalent to a spatially dependent spin-orbit coupling. Higher dimensional generalizations of flat Landau levels are obtained in the Landau-like gauge. The 2D helical Dirac modes with opposite helicities and 3D Weyl modes with opposite chiralities are spatially separated along the third and fourth dimensions, respectively. Stable 2D helical Fermi surfaces and 3D chiral Fermi surfaces appear on open boundaries, respectively. The charge pumping in 4D Landau level systems shows quantized 4D quantum Hall effect.

  15. Topological insulators with SU(2) Landau levels

    E-print Network

    Li, Yi; Wu, Congjun

    2013-01-01

    We construct continuum models of 3d and 4d topological insulators by coupling spin-1/2 fermions to an SU(2) background gauge field, which is equivalent to a spatially dependent spin-orbit coupling. Higher dimensional generalizations of flat Landau levels are obtained in the Landau-like gauge. The 2d helical Dirac modes with opposite helicities and 3d Weyl modes with opposite chiralities are spatially separated along the third and fourth dimensions, respectively. Stable 2d helical Fermi surfaces and 3d chiral Fermi surfaces appear on open boundaries, respectively. The charge pumping in 4d Landau level systems shows quantized 4d quantum Hall effect.

  16. Topology Preserving and Controlled Topology Simplifying Multiresolution Isosurface Extraction

    E-print Network

    Sminchisescu, Cristian

    Topology Preserving and Controlled Topology Simplifying Multiresolution Isosurface Extraction@iam.uni-bonn.de Information and Computer Science University of California Irvine pajarola@acm.org Abstract Multiresolution is often ne- glected in multiresolution algorithms. This results in uncontrolled topological changes which

  17. Symmetry enforced non-Abelian topological order at the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Chen, Xie; Fidkowski, Lukasz; Vishwanath, Ashvin

    2014-04-01

    The surfaces of three-dimensional topological insulators (3D TIs) are generally described as Dirac metals, with a single Dirac cone. It was previously believed that a gapped surface implied breaking of either time-reversal T or U(1) charge conservation symmetry. Here, we discuss a possibility in the presence of interactions, a surface phase that preserves all symmetries but is nevertheless gapped and insulating. Then, the surface must develop topological order of a kind that can not be realized in a two-dimensional (2D) system with the same symmetries. We discuss candidate surface states, non-Abelian quantum Hall states which, when realized in 2D, have ?xy=1/2 and hence break T symmetry. However, by constructing an exactly soluble 3D lattice model, we show they can be realized as T-symmetric surface states. The corresponding 3D phases are confined, and have ? =? magnetoelectric response. Two candidate states have the same 12-particle topological order, the (Read-Moore) Pfaffian state with the neutral sector reversed, which we term T-Pfaffian topological order, but differ in their T transformation. Although we are unable to connect either of these states directly to the superconducting TI surface, we argue that one of them describes the 3D TI surface, while the other differs from it by a bosonic topological phase. We also discuss the 24-particle Pfaffian-antisemion topological order (which can be connected to the superconducting TI surface) and demonstrate that it can be realized as a T-symmetric surface state.

  18. Topological Supersymmetry Breaking as the Origin of the Butterfly Effect

    E-print Network

    Igor V. Ovchinnikov

    2015-04-08

    Previously, there existed no clear explanation why chaotic dynamics is always accompanied by the infinitely long memory of perturbations (and/or initial conditions) known as the butterfly effect (BE). As a result, it was often believed that the BE must be a part of the definition of the concept of dynamical chaos. Here, it is shown that within the recently found approximation-free cohomological theory of stochastic and deterministic (partial) differential equations (SDE), the BE is a derivable consequence of dynamical chaos, a rigorous definition of which is the spontaneous breakdown of topological supersymmetry that all SDEs possess.

  19. Is a color superconductor topological?

    E-print Network

    Nishida, Yusuke

    A fully gapped state of matter, whether insulator or superconductor, can be asked if it is topologically trivial or nontrivial. Here we investigate topological properties of superconducting Dirac fermions in 3D having a ...

  20. A Survey of Computer Network Topology and Analysis Examples

    E-print Network

    Jain, Raj

    Spanning Tree, Graph Theory, Bus Network Topology, Ring Network Topology, Star Network Topology, Tree Topologies 2.1 Bus Network Topology 2.2 Ring Network Topology 2.3 Star Network Topology 2.4 Tree Network, Star, Tree and Mesh Network Topologies are presented. 2.1 Bus Network Topology In Bus Network Topology

  1. Homotopy Theory of Strong and Weak Topological Insulators

    E-print Network

    Ricardo Kennedy; Charles Guggenheim

    2014-09-08

    We use homotopy theory to extend the notion of strong and weak topological insulators to the non-stable regime (low numbers of occupied/empty energy bands). We show that for strong topological insulators in d spatial dimensions to be "truly d-dimensional", i.e. not realizable by stacking lower-dimensional insulators, a more restrictive definition of "strong" is required. However, this does not exclude weak topological insulators from being "truly d-dimensional", which we demonstrate by an example. Additionally, we prove some useful technical results, including the homotopy theoretic derivation of the factorization of invariants over the torus into invariants over spheres in the stable regime, as well as the rigorous justification of replacing $T^d$ by $S^d$ and $T^{d_k}\\times S^{d_x}$ by $S^{d_k+d_x}$ as is common in the current literature.

  2. Homotopy theory of strong and weak topological insulators

    NASA Astrophysics Data System (ADS)

    Kennedy, Ricardo; Guggenheim, Charles

    2015-06-01

    We use homotopy theory to extend the notion of strong and weak topological insulators to the nonstable regime (low numbers of occupied/empty energy bands). We show that for strong topological insulators in d spatial dimensions to be "truly d -dimensional," i.e., not realizable by stacking lower-dimensional insulators, a more restrictive definition of "strong" is required outside the stable regime. However, this does not exclude weak topological insulators from being "truly d -dimensional," which we demonstrate by an example. Additionally, we prove some useful technical results, including the homotopy theoretic derivation of the factorization of invariants over the torus into invariants over spheres in the stable regime, as well as the rigorous justification of the parameter space replacements Td?Sd and Tdk×Sdx?Sdk+dx used widely in the current literature.

  3. 7 CFR 62.301 - Payment of fees and other charges.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AGRICULTURAL MARKETING SERVICE (Standards, Inspections...AGRICULTURAL COMMODITIES (QUALITY SYSTEMS VERIFICATION PROGRAMS) Quality Systems Verification Programs Definitions Charges for Service § 62.301 Payment of...

  4. Definitions of dwelling

    E-print Network

    Olgyay, Victor W. (Victor Wayne)

    1986-01-01

    Home is an elusive concept. In one manner it is highly specific and individual in its definition, and in other aspects it is ubiquitous, present in our every act. In this thesis I explore several possible definitions of ...

  5. Numerical Study of a Bosonic Topological Insulator in three dimensions

    NASA Astrophysics Data System (ADS)

    Geraedts, Scott; Motrunich, Olexei

    2014-03-01

    We construct a model which realizes a (3+1)-dimensional symmetry-protected topological phase of bosons with U(1) charge conservation and time reversal symmetry, envisioned by A. Vishwanath and T. Senthil [PRX 4 011016]. Our model works by introducing an additional O(3) degree of freedom, and binding its hedgehogs to a species of charged bosons; the continuous symmetry is thus enlarged to SO(3) × U(1) . We study the model using Monte Carlo and determine its bulk phase diagram; the phase where the bound states of hedgehogs and charges condense is the topological phase. We also study surface phase diagram on a (2+1)-dimensional boundary between the topological and trivial insulators. The theory for the surface is the same as for a (2+1)D hedgehog-suppressed non-linear sigma model, which confirms the proposed so-called NCCP1 field theory. We apply a Zeeman field to the surface, which breaks time reversal on the surface only, and observe a surface Hall conductivity which is half of a quantized value allowed for bosons in strictly (2+1)D, thus establishing topological nature of the (3+1)D bulk phase. Support from NSF Grant DMR-1206096; Caltech Institute of Quantum Imformation and Matter, and an NSERC PGS fellowship.

  6. Topological censorship and chronology protection

    E-print Network

    John L. Friedman; Atsushi Higuchi

    2008-06-03

    Over the past two decades, substantial efforts have been made to understand the way in which physics enforces the ordinary topology and causal structure that we observe, from subnuclear to cosmological scales. We review the status of topological censorship and the topology of event horizons; chronology protection in classical and semiclassical gravity; and related progress in establishing quantum energy inequalities.

  7. Topological Insulator Nanowires and Nanoribbons

    E-print Network

    Cui, Yi

    Topological Insulator Nanowires and Nanoribbons Desheng Kong, Jason C. Randel,,| Hailin Peng,, Judy material show that it is a three-dimensional topological insulator possessing conductive surface states topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface

  8. Physics World Archive Topological insulators

    E-print Network

    Johannesson, Henrik

    Physics World Archive Topological insulators Charles Kane, Joel Moore From Physics World February, how- ever, now uncovered a new electronic phase called a topological insulator. Putting the name; this "spin current" is a milestone in the realization of practical "spintronics". Topological insulators have

  9. Topological Insulators in Three Dimensions

    Microsoft Academic Search

    Liang Fu; Charles Kane; Eugene Mele

    2007-01-01

    We study three dimensional generalizations of the quantum spin Hall (QSH) effect. Unlike two dimensions, where the QSH effect is distinguished by a single Z2 topological invariant, in three dimensions there are 4 invariants distinguishing 16 ``topological insulator'' phases. There are two general classes: weak (WTI) and strong (STI) topological insulators. The WTI states are equivalent to layered 2D QSH

  10. Decomposition Properties of Hyperspace Topologies

    Microsoft Academic Search

    L. Holà; S. Levi

    1997-01-01

    Let X be a T1 topological space and ? a nonempty family of closed subsets of X. We study the hit-and-miss hyperspace topology generated by ? in terms of its upper and lower parts, focusing on first and second countability and quasi-uniformization. We also obtain some new results on the Vietoris and Fell topologies.

  11. $Z^{'0}Z^{'0}$, $K^{+}K^{-}$ and $K^{0}\\bar{K}^{0}$ boson production with definite helicity amplitudes through $e^{+}e^{-}$ collisions in the 3-3-1 models without exotic electric charges

    E-print Network

    Flórez, Juan B

    2007-01-01

    A detailed analysis of $Z^{'0}Z^{'0}$, $K^{+}K^{-}$ and $K^{0}\\bar{K}^{0}$ pair production in $e^{+}e^{-}$ collisions is presented by using helicity amplitudes. The trilinear bosons couplings in the $SU(3)_{C}\\otimes SU(3)_{L}\\otimes U(1)_{X}$ models without exotic electric charges are also calculated. We carry out the mentioned analysis for two models, one of them is a one family model which is an $E_6$ subgroup \\cite{b1} and the other one is a three family model with right handed neutrinos\\cite{b2,b3}. These models do not contain exotic electric charges. For them, we give explicit formulae and the corresponding numerical estimates of the cross-sections and angular distributions occurred in the processes $e^{+}e^{-}\\to Z^{'0}Z^{'0}$, $e^{+}e^{-} \\to K^{+}K^{-}$ and $e^{+}e^{-}\\to K^{0}\\bar{K}^{0}$ present in our models. We suppose these processes are invariant under $C$, $P$ and $T$ transformation.

  12. A symmetry-respecting topologically-ordered surface phase of 3d electron topological insulators

    NASA Astrophysics Data System (ADS)

    Metlitski, Max

    2014-03-01

    A 3d electron topological insulator (ETI) is a phase of matter protected by particle-number conservation and time-reversal symmetry. It was previously believed that the surface of an ETI must be gapless unless one of these symmetries is broken. A well-known symmetry-preserving, gapless surface termination of an ETI supports an odd number of Dirac cones. In this talk, I will show that in the presence of strong interactions, an ETI surface can actually be gapped and symmetry preserving, at the cost of carrying an intrinsic two-dimensional topological order. I will argue that such a topologically ordered phase can be obtained from the surface superconductor by proliferating the flux 2hc/e vortex. The resulting topological order consists of two sectors: a Moore-Read sector, which supports non-Abelian charge e/4 anyons, and an Abelian anti-semion sector, which is electrically neutral. The time-reversal and particle number symmetries are realized in this surface phase in an ``anomalous'' way: one which is impossible in a strictly 2d system.

  13. Definitions Main Result

    E-print Network

    Heubach, Silvia

    Background Definitions Main Result Special Types of Patterns Summary Avoidance of partially ordered Avoidance of partially ordered patterns in compositions #12;Background Definitions Main Result Special Types of Patterns Summary Outline 1 Background 2 Definitions 3 Main Result Preliminaries Main Result 4 Special Types

  14. Definitions Appendix B

    E-print Network

    APPENDIX B Definitions #12;Appendix B Definitions Adsorption - partitioning of a dissolved species.e., smaller than clay size), that can be easily suspended. original sense, the definition of a colloid different from that of the uncontaminated portion of the aquifer. Fulvic Acids - breakdown products

  15. Relation Definition Theory.

    ERIC Educational Resources Information Center

    Herrmann, Douglas J.; Chaffin, Roger

    The relation definition theory proposed in this paper is explicitly different from previous semantic memory theories since it is the first to make a relation's definition the basis of semantic processing. The paper suggests that this relation definition theory successfully predicts relation similarity on the basis of one key primary assumption:…

  16. Communication Concerns 1. Topology

    E-print Network

    Snir, Marc

    is determined, and it stays fixed throughout the life cycle of execution. Topology changes in phases. Determined is always fixed at certain amount throughout the life cycle of the program. Previous received data and Multicast, Find Maximum Butterfly FFT, Prefix Sum Tree Mergesort, Barnes-Hutt, Bucket Sort, Adaptive

  17. Topology discovery in PROFINET

    Microsoft Academic Search

    I. Schafer; M. Felser

    2007-01-01

    PROFINET, an automation network based on Ethernet, includes the automatic discovery of the physical topology with the link layer discovery protocol (LLDP) in its newest specifications. In this paper we present the objectives of LLDP in PROFINET and general information about the protocol and other parts of IEEE 802.1AB, which describes LLDP. During the analysis of different implementations on the

  18. Topological Anderson Insulator

    Microsoft Academic Search

    Jian Li; Rui-Lin Chu; J. K. Jain; Shun-Qing Shen

    2009-01-01

    Disorder plays an important role in two dimensions, and is responsible for striking phenomena such as metal-insulator transition and the integral and fractional quantum Hall effects. In this Letter, we investigate the role of disorder in the context of the recently discovered topological insulator, which possesses a pair of helical edge states with opposing spins moving in opposite directions and

  19. Hypersensitivity to hypercapnia: definition/(s).

    PubMed

    Vickers, Kristin

    2012-05-15

    Empirical evidence indicates that panic disorder (PD) patients experience hypersensitivity to hypercapnia, a condition in which the blood level of carbon dioxide exceeds the normal value. The importance of this research line is substantial and indeed, hypercapnic hypersensitivity has been advanced as a possible endophenotype of panic. Definitions of "hypersensitivity," however, have varied. The purpose of this brief review is to delineate and critique different definitions of hypercapnic hypersensitivity. Several definitions - panic attack rate, panic symptoms including dyspnea, subjective anxiety, and respiratory disturbance - are explored. The review concludes that although no ideal definition has emerged, marked anxiety post-hypercapnia has substantial support as a putative trait marker of PD. The term "subjective hypersensitivity" (Coryell et al., 2001) is re-introduced to denote pronounced anxiety post-hypercapnia and recommended for use along with its previous definition: increased self-reported anxiety measured on a continuous visual analog scale, already widely in use. Due to the well-established link between panic and respiration, definitional candidates focusing on aberrant respiratory response - less investigated as trait markers of PD in high risk studies - warrant scrutiny as well. Several reasons why definitional clarity might be beneficial are presented, along with ideas for future research. PMID:22401967

  20. Optically engineering the topological properties of a spin Hall insulator.

    PubMed

    Dóra, Balázs; Cayssol, Jérôme; Simon, Ferenc; Moessner, Roderich

    2012-02-01

    Time-periodic perturbations can be used to engineer topological properties of matter by altering the Floquet band structure. This is demonstrated for the helical edge state of a spin Hall insulator in the presence of monochromatic circularly polarized light. The inherent spin structure of the edge state is influenced by the Zeeman coupling and not by the orbital effect. The photocurrent (and the magnetization along the edge) develops a finite, helicity-dependent expectation value and turns from dissipationless to dissipative with increasing radiation frequency, signalling a change in the topological properties. The connection with Thouless' charge pumping and nonequilibrium zitterbewegung is discussed, together with possible experiments. PMID:22400947

  1. Electrically detected interferometry of Majorana fermions in a topological insulator

    E-print Network

    A. R. Akhmerov; Johan Nilsson; C. W. J. Beenakker

    2009-03-12

    We show how a chiral Dirac fermion (a massless electron or hole) can be converted into a pair of neutral chiral Majorana fermions (a particle equal to its own antiparticle). These two types of fermions exist on the metallic surface of a topological insulator, respectively, at a magnetic domain wall and at a magnet-superconductor interface. Interferometry of Majorana fermions is a key operation in topological quantum computation, but the detection is problematic since these particles have no charge. The Dirac-Majorana converter enables electrical detection of the interferometric signal.

  2. Topological Hall Effect in Skyrmions: A Nonequilibrium Coherent Transport Approach

    NASA Astrophysics Data System (ADS)

    Yin, Gen; Zang, Jiadong; Lake, Roger

    2014-03-01

    Skyrmion is a topological spin texture recently observed in many materials with broken inversion symmetry. In experiments, one effective method to detect the skyrmion crystal phase is the topological Hall measurement. At adiabatic approximation, previous theoretical studies show that the Hall signal is provided by an emergent magnetic field, which explains the topological Hall effect in the classical level. Motivated by the potential device application of skyrmions as digital bits, it is important to understand the topological Hall effect in the mesoscopic level, where the electron coherence should be considered. In this talk, we will discuss the quantum aspects of the topological Hall effect on a tight binding setup solved by nonequilibrium Green's function (NEGF). The charge distribution, Hall potential distribution, thermal broadening effect and the Hall resistivity are investigated in detail. The relation between the Hall resistance and the DM interaction is investigated. Driven by the spin transferred torque (SST), Skyrmion dynamics is previously studied within the adiabatic approximation. At the quantum transport level, this talk will also discuss the non-adiabatic effect in the skyrmion motion with the presence of the topological Hall effect. This material is based upon work supported by the National Science Foundation under Grant Nos. NSF 1128304 and NSF 1124733. It was also supported in part by FAME, one of six centers of STARnet, an SRC program sponsored by MARCO and DARPA.

  3. Tailoring the topology of an artificial magnetic skyrmion

    NASA Astrophysics Data System (ADS)

    Li, Jia

    2015-03-01

    A skyrmion is a topological twist of a continuous field that was first proposed by Skyrme to describe discrete nucleons. In condensed-matter physics, skyrmions emerge as topological invariant spin textures in a two dimensional Heisenberg spin lattice. Evidence of skyrmions in condensed matter physics appeared after the discovery of the Quantum Hall Effect in which the lowest energy charged excitations can be mapped onto two-dimensional magnetic skyrmion states. Despite theoretical predictions, it remains an experimental challenge to realize an artificial magnetic skyrmion whose topology can be well controlled and tailored so that its topological effect can be revealed explicitly in a deformation of the spin textures. Here we report epitaxial magnetic thin films in which an artificial skyrmion is created by embedding a magnetic vortex into an out-of-plane aligned spin environment. By changing the relative orientation between the central vortex core polarity and the surrounding out-of-plane spins, we are able to control and tailor the system between two skyrmion topological states. An in-plane magnetic field is used to annihilate the skyrmion core by converting the central vortex state into a single domain state. Our result shows distinct annihilation behaviour of the skyrmion core for the two different skyrmion states, suggesting a topological effect of the magnetic skyrmions in the core annihilation process.

  4. Electrokinetic motion of heterogeneous particles Electrophoresis, induced-charge electrophoresis, transverse electrophoresis.

    E-print Network

    Bazant, Martin Z.

    Electrokinetic motion of heterogeneous particles Synonyms Electrophoresis, induced-charge electrophoresis, transverse electrophoresis. Definition The electrokinetic motion of heterogeneous particles due to the combined effects of electrophoresis, induced-charge electrophoresis, and dielectrophoresis

  5. Charge Challenge

    NSDL National Science Digital Library

    University of Kansas

    2006-01-01

    In this activity, learners explore how objects can have positive, negative, or neutral charges, which attract, repel and move between objects. Learners charge various materials and observe their interactions. Winter is an ideal time to perform these experiments (because there is less water vapor in the air); if it is humid, use a hair dryer to dry the objects, surfaces, and air around the work area.

  6. A model recognition approach to the prediction of all-helical membrane protein structure and topology.

    PubMed

    Jones, D T; Taylor, W R; Thornton, J M

    1994-03-15

    This paper describes a new method for the prediction of the secondary structure and topology of integral membrane proteins based on the recognition of topological models. The method employs a set of statistical tables (log likelihoods) complied from well-characterized membrane protein data, and a novel dynamic programming algorithm to recognize membrane topology models by expectation maximization. The statistical tables show definite biases toward certain amino acid species on the inside, middle, and outside of a cellular membrane. Using a set of 83 integral membrane protein sequences taken from a variety of bacterial, plant, and animal species, and a strict jackknifing procedure, where each protein (along with any detectable homologues) is removed from the training set used to calculate the tables before prediction, the method successfully predicted 64 of the 83 topologies, and of the 37 complex multispanning topologies 34 were predicted correctly. PMID:8130217

  7. Energy Harvesting by Sweeping Voltage-Escalated Charging of a Reconfigurable Supercapacitor Array

    E-print Network

    Shinozuka, Masanobu

    Energy Harvesting by Sweeping Voltage-Escalated Charging of a Reconfigurable Supercapacitor Array charge pump to perform maximum power-transfer track- ing (MPTT) while charging a reservoir supercapacitor. The supercapacitors in the RSA can be dynamically configured for series or parallel topologies by means of a switch

  8. Algebraic methods for multidimensional digital topology

    NASA Astrophysics Data System (ADS)

    McAndrew, Alasdair; Osborne, Charles F.

    1993-12-01

    We show how algebraic methods can be used to provide a mathematical framework suitable for the definition of multidimensional hypersurfaces in digital space, and for proofs of separation theorems. Our work is motivated by the need for a mathematical basis to provide a strong foundation for the creation of image processing algorithms in multidimensions; multidimensional images have been shown to arise naturally in areas as diverse as medical diagnosis and agricultural imaging. Whereas previous work in the area has been either combinatorial or has used the tools of point-set topology, we show how homology and cohomology groups can be defined in digital space. Our definitions are of a broad nature encompassing many of the standard adjacencies used to define digital objects. Given that in Euclidean space these groups satisfy conditions which provide for very neat proofs of separation theorems, we conjecture that an analogous theorem is true in digital space. We further show that the concept of orientability can be given a meaning in digital space more closely analogous to its classical meaning than definitions given previously in the image processing literature.

  9. Isospin of topological defects in Dirac systems

    NASA Astrophysics Data System (ADS)

    Herbut, Igor F.

    2012-02-01

    We study the Dirac quasiparticles in d-dimensional lattice systems of electrons in the presence of domain walls (d=1), vortices (d=2), or hedgehogs (d=3) of superconducting and/or insulating, order parameters, which appear as mass terms in the Dirac equation. Such topological defects have been known to carry nontrivial quantum numbers, such as charge and spin. Here we discuss their additional internal degree of freedom: irrespective of the dimensionality of space and the nature of orders that support the defect, an extra mass order parameter is found to emerge in their core. Six linearly independent local orders, which close two mutually commuting three-dimensional Clifford algebras, are proven to be in general possible. We show how the particle-hole symmetry restricts the defects to always carry the quantum numbers of a single effective isospin 1/2, quite independently of the values of their electric charge or true spin. Examples of this new degree of freedom in graphene and on surfaces of topological insulators are discussed.

  10. Quantum algorithm for topological and geometric analysis of data

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth; Zanardi, Paolo; Garnerone, Silvano

    2015-03-01

    Topological methods for analyzing data sets provide a powerful technique for extracting useful information from data. Data that represents geometric features of the world typically gives a distorted picture of those features, if only because the devices and systems that sense the world and that generate the data by their very nature induce distortions. By definition, topological features are those that persist under continuous distortions of the data. Topological methods can therefore identify features of the real system from which the data was collected, but that have been distorted by the data collection process. Persistent homology is a sophisticated tool for identifying such topological features -connected components, holes, or voids - and for determining how such features persist as the data is viewed at different scales. This talk presents quantum machine learning algorithms for calculating Betti numbers in persistent homology, and for finding eigenvectors and eigenvalues of the combinatorial Laplacian (the quantities that famously allow one to ``hear the shape of a drum''). The algorithms provide an exponential speedup over classical algorithms for topological and geometrical data analysis.

  11. EDITORIAL: Topological data analysis Topological data analysis

    NASA Astrophysics Data System (ADS)

    Epstein, Charles; Carlsson, Gunnar; Edelsbrunner, Herbert

    2011-12-01

    Inverse problems can be defined as the area of mathematics that attempts to reconstruct a physical or mathematical object from derived data. Frequently, this means the evaluation of parameters or other numerical quantities (such as eigenvalues) that characterize or provide information about the system. There are, however, other aspects of a system that are important, but are not as readily summarized by numerical quantities. If one considers observations of diabetic patients (using metabolic quantities), one will find that the data breaks up into components, or pieces, corresponding to distinct forms of the disease. The decomposition of data sets into disjoint pieces, or clustering, is an aspect of the study of the shape of the data, albeit one that has been extensively studied. A more complex notion of shape appears in observations of a predator-prey system governed by a Lotka-Volterra equation. One would find that exact observations, consisting of (prey population, predator population) pairs, appear to lie along a simple closed curve in the plane. The fact that the data lies along such a closed curve is an important piece of information, since it suggests that the system displays recurrent behavior. If one did not know, a priori, that the system is governed by a Lotka-Volterra equation, then it would not be immediately obvious that the system is undergoing recurrent motion, and this deduction would constitute a significant insight. In this case, it is again the shape of the data, namely the fact that it lies on a simple closed curve, which is the key insight. Shape is a somewhat nebulous concept, which at first blush may be too intuitive to make precise mathematically, and describe quantitatively. Within pure mathematics, the disciplines of topology and differential geometry are designed exactly to address this problem. They provide explicit signatures which, in precise senses, quantify and describe the shape of a geometric object. In addition, they provide methods for discretizing and compressing the information present in a geometric object so as to provide a useful, small representation of the object. The articles in this special issue are concerned with the applications of topology to the analysis of data sets. The adaptation of topological techniques from pure mathematics to the study of data from real systems is a project which has been undertaken during the past two decades, and the present volume contains various contributions to that project. At the current state of development, homology and persistence are two of the most popular topological techniques used in this context. Homology goes back to the beginnings of topology in Poincaré's influential papers. It is the idea that the connectivity of a space is determined by its cycles of different dimensions, and that these cycles organize themselves into abelian groups, called homology groups. Better known than these groups are their ranks, the Betti numbers of the space, which are non-negative integers that count the number of independent cycles in each dimension. To give an example, the zeroth Betti number counts the components, and the first counts the loops. A crucial feature of homology groups is that, given a reasonably explicit description of a space, their computation is an exercise in linear algebra. Even better known than the Betti numbers is the Euler characteristic, which we know from Poincaré's work, is equal to the alternating sum of the Betti numbers, which can be computed without computing the homology groups themselves. To give evidence that these numbers have relevant practical applications, we mention that integrating the Euler characteristic over a domain with sensor information can be used to count objects in the domain. This alone would not explain the popularity of homology groups, which we see rooted in the fact that they hit a sweet-spot that offers relatively strong discriminative power, and a clear intuitive meaning, all at a surprisingly low computational cost. Even these desirable qualities would not be sufficient if it were not pos

  12. Assessment and control of electrostatic charges. [hazards to space missions

    NASA Technical Reports Server (NTRS)

    Barrett, M.

    1974-01-01

    The experience is described of NASA and DOD with electrostatic problems, generation mechanisms, and type of electrostatic hazards. Guidelines for judging possible effects of electrostatic charges on space missions are presented along with mathematical formulas and definitions.

  13. Network topology mapper

    DOEpatents

    Quist, Daniel A. (Los Alamos, NM); Gavrilov, Eugene M. (Los Alamos, NM); Fisk, Michael E. (Jemez, NM)

    2008-01-15

    A method enables the topology of an acyclic fully propagated network to be discovered. A list of switches that comprise the network is formed and the MAC address cache for each one of the switches is determined. For each pair of switches, from the MAC address caches the remaining switches that see the pair of switches are located. For each pair of switches the remaining switches are determined that see one of the pair of switches on a first port and the second one of the pair of switches on a second port. A list of insiders is formed for every pair of switches. It is determined whether the insider for each pair of switches is a graph edge and adjacent ones of the graph edges are determined. A symmetric adjacency matrix is formed from the graph edges to represent the topology of the data link network.

  14. Anomaly detection using topology

    NASA Astrophysics Data System (ADS)

    Basener, Bill; Ientilucci, Emmett J.; Messinger, David W.

    2007-04-01

    In this paper we present a new topology-based algorithm for anomaly detection in dimensionally large datasets. The motivating application is hyperspectral imaging where the dataset can be a collection of ~ 10 6 points in R k, representing the reflected (or radiometric) spectra of electromagnetic radiation. The algorithm begins by building a graph whose edges connect close pairs of points. The background points are the points in the largest components of this graph and all other points are designated as anomalies. The anomalies are ranked according to their distance to the background. The algorithm is termed Topological Anomaly Detection (TAD). The algorithm is tested on hyperspectral imagery collected with the HYDICE sensor which contains targets of known reflectance and spatial location. Anomaly maps are created and compared to results from the common anomaly detection algorithm RX. We show that the TAD algorithm performs better than RX by achieving greater separation of the anomalies from the background for this dataset.

  15. Topological Structure of the Magnetic Solar Corona

    NASA Astrophysics Data System (ADS)

    Maclean, R. C.

    2007-12-01

    The solar corona is a highly complex and active plasma environment, containing many exotic phenomena such as solar flares, coronal mass ejections, prominences, coronal loops, and bright points. The fundamental element giving coherence to all this apparent diversity is the strong coronal magnetic field, the dominant force shaping the plasma there. In this thesis, I model the 3D magnetic fields of various coronal features using the techniques of magnetic charge topology (MCT) in a potential field. Often the real coronal field has departures from its potential state, but these are so small that the potential field method is accurate enough to pick out the essential information about the structure and evolution of the magnetic field. First I perform a topological analysis of the magnetic breakout model for an eruptive solar flare. Breakout is represented by a topological bifurcation that allows initially enclosed flux from the newly emerging region in my MCT model of a delta sunspot to reconnect out to large distances. I produce bifurcation diagrams showing how this behaviour can be caused by changing the strength or position of the emerging flux source, or the force-free parameter ?. I also apply MCT techniques to observational data of a coronal bright point, and compare the results to 3D numerical MHD simulations of the effects of rotating the sources that underlie the bright point. The separatrix surfaces that surround each rotating source are found to correspond to locations of high parallel electric field in the simulations, which is a signature of magnetic reconnection. The large-scale topological structure of the magnetic field is robust to changes in the method of deriving point magnetic sources from the magnetogram. Next, I use a Green's function expression for the magnetic field to relax the standard topological assumption of a flat photosphere and extend the concept of MCT into a spherical geometry, enabling it to be applied to the entire global coronal magnetic field. I perform a comprehensive study of quadrupolar topologies in this new geometry, producing several detailed bifurcation diagrams. These results are compared to the equivalent study for a flat photosphere. A new topological state is found on the sphere which has no flat photosphere analogue; it is named the dual intersecting state because of its twin separators joining a pair of magnetic null points. The new spherical techniques are then applied to develop a simple six-source topological model of global magnetic field reversal during the solar cycle. The evolution of the large-scale global magnetic field is modelled through one complete eleven-year cycle, beginning at solar minimum. Several distinct topological stages are exhibited: active region flux connecting across the equator to produce transequatorial loops; the dominance of first the leading and then the following polarities of the active regions; the magnetic isolation of the poles; the reversal of the polar field; the new polar field connecting back to the active regions; the polar flux regaining its dominance; and the disappearance of the transequatorial loops.

  16. On topological terms in the O(3) nonlinear sigma model

    NASA Astrophysics Data System (ADS)

    Tsurumaru, Toyohiro; Tsutsui, Izumi

    1999-08-01

    Topological terms in the O(3) nonlinear sigma model in (1+1) and (2+1) dimensions are re-examined based on the description of the SU(2)-valued field g. We first show that the topological soliton term in (1+1) dimensions arises from the unitary representations of the group characterizing the global structure of the symmetry inherent in the description, in a manner analogous to the appearance of the ?-term in Yang-Mills theory in (3+1) dimensions. We then present a detailed argument as to why the conventional Hopf term, which is the topological counterpart in (2+1) dimensions and has been widely used to realize fractional spin and statistics, is ill-defined unless the soliton charge vanishes. We show how this restriction can be lifted by means of a procedure proposed recently, and provide its physical interpretation as well.

  17. Topological gap states of semiconducting armchair graphene ribbons

    E-print Network

    Y. H. Jeong; S. C. Kim; S. -R. Eric Yang

    2015-05-31

    In semiconducting armchair graphene ribbons a chiral lattice deformation can induce pairs of topological gap states with opposite energies. Near the critical value of the deformation potential these kink and antikink states become almost degenerate with zero energy and have a fractional charge one-half. Such a semiconducting armchair ribbon represents a one-dimensional topological insulator with nearly zero energy end states. Using data collapse of numerical results we find that the shape of the kink displays an anomalous power-law dependence on the width of the local lattice deformation. We suggest that these gap states may be probed in optical measurements. However, "metallic" armchair graphene ribbons with a gap induced by many-electron interactions have no gap states and are not topological insulators.

  18. Topological gap states of semiconducting armchair graphene ribbons

    E-print Network

    Jeong, Y H; Yang, S -R Eric

    2015-01-01

    In semiconducting armchair graphene ribbons a chiral lattice deformation can induce pairs of topological gap states with opposite energies. Near the critical value of the deformation potential these kink and antikink states become almost degenerate with zero energy and have a fractional charge one-half. Such a semiconducting armchair ribbon represents a one-dimensional topological insulator with nearly zero energy end states. Using data collapse of numerical results we find that the shape of the kink displays an anomalous power-law dependence on the width of the local lattice deformation. We suggest that these gap states may be probed in optical measurements. However, "metallic" armchair graphene ribbons with a gap induced by many-electron interactions have no gap states and are not topological insulators.

  19. Chiral Topological Insulator on Nambu 3-Algebraic Geometry

    E-print Network

    Kazuki Hasebe

    2014-08-02

    Chiral topological insulator (AIII-class) with Landau levels is constructed based on the Nambu 3-algebraic geometry. We clarify the geometric origin of the chiral symmetry of the AIII-class topological insulator in the context of non-commutative geometry of 4D quantum Hall effect. The many-body groundstate wavefunction is explicitly derived as a $(l,l,l-1)$ Laughlin-Halperin type wavefunction with unique $K$-matrix structure. Fundamental excitation is identified with anyonic string-like object with fractional charge ${1}/({1+2(l-1)^2})$. The Hall effect of the chiral topological insulators turns out be a color version of Hall effect, which exhibits a dual property of the Hall and spin-Hall effects.

  20. Topological confinement and superconductivity

    SciTech Connect

    Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

    2008-01-01

    We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.

  1. Topological Mott Insulators

    Microsoft Academic Search

    Srinivas Raghu; Xiao-Liang Qi; Carsten Honerkamp; Shou-Cheng Zhang

    2008-01-01

    We consider extended Hubbard models with repulsive interactions on a honeycomb lattice, and the transitions from the semimetal to Mott insulating phases at half-filling. Because of the frustrated nature of the second-neighbor interactions, topological Mott phases displaying the quantum Hall and the quantum spin Hall effects are found for spinless and spin fermion models, respectively. The mean-field phase diagram is

  2. Gods as Topological Invariants

    E-print Network

    Daniel Schoch

    2012-04-01

    We show that the number of gods in a universe must equal the Euler characteristics of its underlying manifold. By incorporating the classical cosmological argument for creation, this result builds a bridge between theology and physics and makes theism a testable hypothesis. Theological implications are profound since the theorem gives us new insights in the topological structure of heavens and hells. Recent astronomical observations can not reject theism, but data are slightly in favor of atheism.

  3. Gods as Topological Invariants

    E-print Network

    Schoch, Daniel

    2012-01-01

    We show that the number of gods in a universe must equal the Euler characteristics of its underlying manifold. By incorporating the classical cosmological argument for creation, this result builds a bridge between theology and physics and makes theism a testable hypothesis. Theological implications are profound since the theorem gives us new insights in the topological structure of heavens and hells. Recent astronomical observations can not reject theism, but data are slightly in favor of atheism.

  4. Towards Phononic Topological Insulators

    NASA Astrophysics Data System (ADS)

    Wang, Pai; Bertoldi, Katia

    2014-03-01

    Recent studies in optics have shown that the concept of topological insulators can be extended to band theories of classical waves and bosonic systems. Here, we present some design considerations in realization and observation of topological edge states for phonons. The goal is to achieve topologically protected one-way propagation of surface acoustic / elastic waves against back-scattering and localization due to defects and disorders by utilizing phononic crystals, which have micro-structures with periodicity comparable to the wavelength of the propagating elastic waves. Both theoretical and practical challenges in creating non-reciprocal elastic media will be discussed. Possible candidates include temporal modulation of phononic crystals, coupled wave guides, chiral local resonators, artificial magneto-acoustic effects and asymmetric body forces induced by external fields. These symmetry breaking mechanisms can potentially lead to the phononic analogue of electronic quantum hall effect. The robustness of reflection-immune unidirectional elastic wave has promising applications in surface acoustic wave (SAW) devices that are widely used in modern telecommunication, geophysics as well as micro-fluidics.

  5. Topological proximity effect in a topological insulator hybrid.

    PubMed

    Shoman, T; Takayama, A; Sato, T; Souma, S; Takahashi, T; Oguchi, T; Segawa, Kouji; Ando, Yoichi

    2015-01-01

    It is well known that a topologically protected gapless state appears at an interface between a topological insulator and an ordinary insulator; however, the physics of the interface between a topological insulator and a metal has largely been left unexplored. Here we report a novel phenomenon termed topological proximity effect, which occurs between a metallic ultrathin film and a three-dimensional topological insulator. We study one bilayer of bismuth metal grown on the three-dimensional topological insulator material TlBiSe2, and by using spin- and angle-resolved photoemission spectroscopy, we found evidence that the topological Dirac-cone state migrates from the surface of TlBiSe2 to the attached one-bilayer Bi. We show that such a migration of the topological state occurs as a result of strong spin-dependent hybridization of the wave functions at the interface, which is also supported by our first-principles calculations. This discovery points to a new route to manipulating the topological properties of materials. PMID:25761780

  6. Topological proximity effect in a topological insulator hybrid

    NASA Astrophysics Data System (ADS)

    Shoman, T.; Takayama, A.; Sato, T.; Souma, S.; Takahashi, T.; Oguchi, T.; Segawa, Kouji; Ando, Yoichi

    2015-03-01

    It is well known that a topologically protected gapless state appears at an interface between a topological insulator and an ordinary insulator; however, the physics of the interface between a topological insulator and a metal has largely been left unexplored. Here we report a novel phenomenon termed topological proximity effect, which occurs between a metallic ultrathin film and a three-dimensional topological insulator. We study one bilayer of bismuth metal grown on the three-dimensional topological insulator material TlBiSe2, and by using spin- and angle-resolved photoemission spectroscopy, we found evidence that the topological Dirac-cone state migrates from the surface of TlBiSe2 to the attached one-bilayer Bi. We show that such a migration of the topological state occurs as a result of strong spin-dependent hybridization of the wave functions at the interface, which is also supported by our first-principles calculations. This discovery points to a new route to manipulating the topological properties of materials.

  7. Transportation Network Topologies

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.; Scott, John

    2004-01-01

    A discomforting reality has materialized on the transportation scene: our existing air and ground infrastructures will not scale to meet our nation's 21st century demands and expectations for mobility, commerce, safety, and security. The consequence of inaction is diminished quality of life and economic opportunity in the 21st century. Clearly, new thinking is required for transportation that can scale to meet to the realities of a networked, knowledge-based economy in which the value of time is a new coin of the realm. This paper proposes a framework, or topology, for thinking about the problem of scalability of the system of networks that comprise the aviation system. This framework highlights the role of integrated communication-navigation-surveillance systems in enabling scalability of future air transportation networks. Scalability, in this vein, is a goal of the recently formed Joint Planning and Development Office for the Next Generation Air Transportation System. New foundations for 21st thinking about air transportation are underpinned by several technological developments in the traditional aircraft disciplines as well as in communication, navigation, surveillance and information systems. Complexity science and modern network theory give rise to one of the technological developments of importance. Scale-free (i.e., scalable) networks represent a promising concept space for modeling airspace system architectures, and for assessing network performance in terms of scalability, efficiency, robustness, resilience, and other metrics. The paper offers an air transportation system topology as framework for transportation system innovation. Successful outcomes of innovation in air transportation could lay the foundations for new paradigms for aircraft and their operating capabilities, air transportation system architectures, and airspace architectures and procedural concepts. The topology proposed considers air transportation as a system of networks, within which strategies for scalability of the topology may be enabled by technologies and policies. In particular, the effects of scalable ICNS concepts are evaluated within this proposed topology. Alternative business models are appearing on the scene as the old centralized hub-and-spoke model reaches the limits of its scalability. These models include growth of point-to-point scheduled air transportation service (e.g., the RJ phenomenon and the Southwest Effect). Another is a new business model for on-demand, widely distributed, air mobility in jet taxi services. The new businesses forming around this vision are targeting personal air mobility to virtually any of the thousands of origins and destinations throughout suburban, rural, and remote communities and regions. Such advancement in air mobility has many implications for requirements for airports, airspace, and consumers. These new paradigms could support scalable alternatives for the expansion of future air mobility to more consumers in more places.

  8. Transportation Network Topologies

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.; Scott, John M.

    2004-01-01

    A discomforting reality has materialized on the transportation scene: our existing air and ground infrastructures will not scale to meet our nation's 21st century demands and expectations for mobility, commerce, safety, and security. The consequence of inaction is diminished quality of life and economic opportunity in the 21st century. Clearly, new thinking is required for transportation that can scale to meet to the realities of a networked, knowledge-based economy in which the value of time is a new coin of the realm. This paper proposes a framework, or topology, for thinking about the problem of scalability of the system of networks that comprise the aviation system. This framework highlights the role of integrated communication-navigation-surveillance systems in enabling scalability of future air transportation networks. Scalability, in this vein, is a goal of the recently formed Joint Planning and Development Office for the Next Generation Air Transportation System. New foundations for 21PstP thinking about air transportation are underpinned by several technological developments in the traditional aircraft disciplines as well as in communication, navigation, surveillance and information systems. Complexity science and modern network theory give rise to one of the technological developments of importance. Scale-free (i.e., scalable) networks represent a promising concept space for modeling airspace system architectures, and for assessing network performance in terms of scalability, efficiency, robustness, resilience, and other metrics. The paper offers an air transportation system topology as framework for transportation system innovation. Successful outcomes of innovation in air transportation could lay the foundations for new paradigms for aircraft and their operating capabilities, air transportation system architectures, and airspace architectures and procedural concepts. The topology proposed considers air transportation as a system of networks, within which strategies for scalability of the topology may be enabled by technologies and policies. In particular, the effects of scalable ICNS concepts are evaluated within this proposed topology. Alternative business models are appearing on the scene as the old centralized hub-and-spoke model reaches the limits of its scalability. These models include growth of point-to-point scheduled air transportation service (e.g., the RJ phenomenon and the 'Southwest Effect'). Another is a new business model for on-demand, widely distributed, air mobility in jet taxi services. The new businesses forming around this vision are targeting personal air mobility to virtually any of the thousands of origins and destinations throughout suburban, rural, and remote communities and regions. Such advancement in air mobility has many implications for requirements for airports, airspace, and consumers. These new paradigms could support scalable alternatives for the expansion of future air mobility to more consumers in more places.

  9. ON TOPOLOGICAL TITS BUILDINGS AND THEIR CLASSIFICATION

    E-print Network

    Spatzier, Ralf

    ON TOPOLOGICAL TITS BUILDINGS AND THEIR CLASSIFICATION by KEITH BURNS (1) and RA*F SPATZIER (2) Abstract We define topological Tits buildings. If a topological building A satisfies some technical the notion of a topological Tits building. Roughly speaking, this is a Tits building A with a topology which

  10. Continuous-variable topological codes

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2013-10-01

    Topological code is a stabilizer quantum error correcting code whose generators are local but logical operators are topologically nontrivial and nonlocal. It offers interesting features such as the homological deformations of string operators and anyonic excitations on it. Topological codes are also closely related to the “topological order,” which has been an important concept in condensed-matter physics. In this paper, we consider continuous-variable versions of topological codes, including the toric code by Kitaev [A. Y. Kitaev, Ann. Phys.APNYA60003-491610.1016/S0003-4916(02)00018-0 303, 2 (2003)] with a single type of stabilizer on the checkerboard lattice, and the color code by Bombin and Martin-Delgado [H. Bombin and M. A. Martin-Delgado, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.97.180501 97, 180501 (2006)]. We show that it is possible to consider continuous-variable analog of these topological codes.

  11. Supernovae observations and cosmic topology

    E-print Network

    M. J. Reboucas; J. S. Alcaniz; B. Mota; M. Makler

    2006-04-14

    Two fundamental questions regarding our description of the Universe concern the geometry and topology of its 3-dimensional space. While geometry is a local characteristic that gives the intrinsic curvature, topology is a global feature that characterizes the shape and size of the 3-space. The geometry constrains, but does not dictate the the spatial topology. We show that, besides determining the spatial geometry, the knowledge of the spatial topology allows to place tight constraints on the density parameters associated with dark matter ($\\Omega_m$) and dark energy ($\\Omega_{\\Lambda}$). By using the Poincar\\'e dodecahedral space as the observable spatial topology, we reanalyze the current type Ia supenovae (SNe Ia) constraints on the density parametric space $\\Omega_{m} - \\Omega_{\\Lambda}$. From this SNe Ia plus cosmic topology analysis, we found best fit values for the density parameters, which are in agreement with a number of independent cosmological observations.

  12. Supernovae observations and cosmic topology

    E-print Network

    Rebouças, M J; Mota, B; Makler, M

    2006-01-01

    Two fundamental questions regarding our description of the Universe concern the geometry and topology of its 3-dimensional space. While geometry is a local characteristic that gives the intrinsic curvature, topology is a global feature that characterizes the shape and size of the 3-space. The geometry constrains, but does not dictate the the spatial topology. We show that, besides determining the spatial geometry, the knowledge of the spatial topology allows to place tight constraints on the density parameters associated with dark matter ($\\Omega_m$) and dark energy ($\\Omega_{\\Lambda}$). By using the Poincar\\'e dodecahedral space as the observable spatial topology, we reanalyze the current type Ia supenovae (SNe Ia) constraints on the density parametric space $\\Omega_{m} - \\Omega_{\\Lambda}$. From this SNe Ia plus cosmic topology analysis, we found best fit values for the density parameters, which are in agreement with a number of independent cosmological observations.

  13. Adiabatic Preparation of Topological Order

    E-print Network

    Alioscia Hamma; Daniel A. Lidar

    2007-10-13

    Topological order characterizes those phases of matter that defy a description in terms of symmetry and cannot be distinguished in terms local order parameters. This type of order plays a key role in the theory of the fractional quantum Hall effect, as well as in topological quantum information processing. Here we show that a system of n spins forming a lattice on a Riemann surface can undergo a second order quantum phase transition between a spin-polarized phase and a string-net condensed phase. This is an example of a phase transition between magnetic and topological order. We furthermore show how to prepare the topologically ordered phase through adiabatic evolution in a time that is upper bounded by O(\\sqrt{n}). This provides a physically plausible method for constructing a topological quantum memory. We discuss applications to topological and adiabatic quantum computing.

  14. Controlled Spin Transport in Planar Systems Through Topological Exciton

    E-print Network

    Abhinav, Kumar

    2015-01-01

    It is shown that a charge-neutral spin-1 exciton, possibly realizable only in planar systems like graphene and topological insulators, can be effectively used for controlled spin transport in such media. The effect of quantum and thermal fluctuations yield a parametric excitation threshold for its realization. This planar exciton differs from the conventional ones, as it owes its existence to the topological Chern-Simons (CS) term. The parity and time-reversal violating CS term can arise from quantum effects in systems with parity-breaking mass-gap. The spinning exciton naturally couples to magnetic field, leading to the possibility of controlled spin transport. Being neutral, it is immune to a host of effect, which afflicts spin transport through charged fermions.

  15. Controlled Spin Transport in Planar Systems Through Topological Exciton

    E-print Network

    Kumar Abhinav; Prasanta K. Panigrahi

    2015-04-29

    It is shown that a charge-neutral spin-1 exciton, possibly realizable only in planar systems like graphene and topological insulators, can be effectively used for controlled spin transport in such media. The effect of quantum and thermal fluctuations yield a parametric excitation threshold for its realization. This planar exciton differs from the conventional ones, as it owes its existence to the topological Chern-Simons (CS) term. The parity and time-reversal violating CS term can arise from quantum effects in systems with parity-breaking mass-gap. The spinning exciton naturally couples to magnetic field, leading to the possibility of controlled spin transport. Being neutral, it is immune to a host of effect, which afflicts spin transport through charged fermions.

  16. Z2 anomaly and boundaries of topological insulators

    NASA Astrophysics Data System (ADS)

    Ringel, Zohar; Stern, Ady

    2013-09-01

    We study the edge and surface theories of topological insulators from the perspective of anomalies and identify a Z2 anomaly associated with charge conservation. The anomaly is manifested through a two-point correlation function involving creation and annihilation operators on two decoupled boundaries. Although charge conservation on each boundary requires this quantity to vanish, we find that it diverges. A corollary result is that under an insertion of a flux quantum, the ground state evolves to an exactly orthogonal state independent of the rate at which the flux is inserted. The anomaly persists in the presence of disorder and imposes sharp restrictions on possible low-energy theories. Being formulated in a many-body, field-theoretical language, the anomaly allows one to test the robustness of topological insulators to interactions in a concise way.

  17. Models of three-dimensional fractional topological insulators

    NASA Astrophysics Data System (ADS)

    Maciejko, Joseph; Qi, Xiao-Liang; Karch, Andreas; Zhang, Shou-Cheng

    2012-12-01

    Time-reversal invariant three-dimensional topological insulators can be defined fundamentally by a topological field theory with a quantized axion angle ? of 0 or ?. It was recently shown that fractional quantized values of ? are consistent with time-reversal invariance if deconfined, gapped, fractionally charged bulk excitations appear in the low-energy spectrum due to strong correlation effects, leading to the concept of a fractional topological insulator. These fractionally charged excitations are coupled to emergent gauge fields, which ensure that the microscopic degrees of freedom, the original electrons, are gauge-invariant objects. A first step towards the construction of microscopic models of fractional topological insulators is to understand the nature of these emergent gauge theories and their corresponding phases. In this work, we show that low-energy effective gauge theories of both Abelian or non-Abelian type are consistent with a fractional quantized axion angle if they admit a Coulomb phase or a Higgs phase with gauge group broken down to a discrete subgroup. The Coulomb phases support gapless but electrically neutral bulk excitations while the Higgs phases are fully gapped. The Higgs and non-Abelian Coulomb phases exhibit multiple ground states on boundaryless spatial three-manifolds with nontrivial first homology, while the Abelian Coulomb phase has a unique ground state. The ground-state degeneracy receives an additional contribution on manifolds with boundary due to the induced boundary Chern-Simons term.

  18. Models of three-dimensional fractional topological insulators

    E-print Network

    Joseph Maciejko; Xiao-Liang Qi; Andreas Karch; Shou-Cheng Zhang

    2012-12-20

    Time-reversal invariant three-dimensional topological insulators can be defined fundamentally by a topological field theory with a quantized axion angle theta of zero or pi. It was recently shown that fractional quantized values of theta are consistent with time-reversal invariance if deconfined, gapped, fractionally charged bulk excitations appear in the low-energy spectrum due to strong correlation effects, leading to the concept of a fractional topological insulator. These fractionally charged excitations are coupled to emergent gauge fields which ensure that the microscopic degrees of freedom, the original electrons, are gauge-invariant objects. A first step towards the construction of microscopic models of fractional topological insulators is to understand the nature of these emergent gauge theories and their corresponding phases. In this work, we show that low-energy effective gauge theories of both Abelian or non-Abelian type are consistent with a fractional quantized axion angle if they admit a Coulomb phase or a Higgs phase with gauge group broken down to a discrete subgroup. The Coulomb phases support gapless but electrically neutral bulk excitations while the Higgs phases are fully gapped. The Higgs and non-Abelian Coulomb phases exhibit multiple ground states on boundaryless spatial 3-manifolds with nontrivial first homology, while the Abelian Coulomb phase has a unique ground state. The ground state degeneracy receives an additional contribution on manifolds with boundary due to the induced boundary Chern-Simons term.

  19. The Topological Open String Wavefunction

    NASA Astrophysics Data System (ADS)

    Grassi, Alba; Källén, Johan; Mariño, Marcos

    2015-05-01

    We show that, in local Calabi-Yau manifolds, the topological open string partition function transforms as a wavefunction under modular transformations. Our derivation is based on the topological recursion for matrix models, and it generalizes in a natural way the known result for the closed topological string sector. As an application, we derive results for vacuum expectation values of 1/2 BPS Wilson loops in ABJM theory at all genera in a strong coupling expansion, for various representations.

  20. Measuring ISP topologies with rocketfuel

    Microsoft Academic Search

    Neil T. Spring; Ratul Mahajan; David Wetherall

    2002-01-01

    To date, realistic ISP topologies have not been accessible to the research community, leaving work that depends on topology on an uncertain footing. In this paper, we present new Internet mapping techniques that have enabled us to directly measure router-level ISP topologies. Our techniques reduce the number of required traces compared to a brute-force, all-to-all approach by three orders of

  1. Measuring ISP topologies with rocketfuel

    Microsoft Academic Search

    Neil T. Spring; Ratul Mahajan; David Wetherall; Thomas E. Anderson

    2004-01-01

    To date, realistic ISP topologies have not been accessible to the research community, leaving work that depends on topology on an uncertain footing. In this paper, we present new Internet mapping techniques that have enabled us to measure router-level ISP topologies. Our techniques reduce the number of required traces compared to a brute-force, all-to-all approach by three orders of magnitude

  2. Supernovae observations and cosmic topology

    Microsoft Academic Search

    M. J. Reboucas; J. S. Alcaniz; B. Mota; M. Makler

    2005-01-01

    Two fundamental questions regarding our description of the Universe concern\\u000athe geometry and topology of its 3-dimensional space. While geometry is a local\\u000acharacteristic that gives the intrinsic curvature, topology is a global feature\\u000athat characterizes the shape and size of the 3-space. The geometry constrains,\\u000abut does not dictate the the spatial topology. We show that, besides\\u000adetermining the

  3. Holding Charge

    NSDL National Science Digital Library

    Eric Muller

    1995-01-01

    In this trick, learners discover how to stick a straw to the palm of their hand, window door, or anywhere using static electricity. This activity introduces learners to negative and positive charges and shows how opposites attract. Note: this trick works best in low humidity (dry air).

  4. Fractional topological insulators of Cooper pairs induced by the proximity effect.

    PubMed

    Nikoli?, Predrag; Duric, Tanja; Tešanovi?, Zlatko

    2013-04-26

    Certain insulating materials with strong spin-orbit interaction can conduct currents along their edges or surfaces owing to the nontrivial topological properties of their electronic band structure. This phenomenon is somewhat similar to the integer quantum Hall effect of electrons in strong magnetic fields. Topological insulators analogous to the fractional quantum Hall effect are also possible, but have not yet been observed in any material. Here we show that a quantum well made from a topological band insulator such as Bi2Se3 or Bi2Te3, placed in contact with a superconductor, can be used to realize a two-dimensional topological state with macroscopic many-body quantum entanglement whose excitations carry fractional amounts of an electron's charge and spin. This fractional topological insulator is a "pseudogap" state of induced spinful p-wave Cooper pairs, a new strongly correlated quantum phase with possible applications to spintronic devices and quantum computing. PMID:23679757

  5. Section 19 The Product Topology We will consider these products of topological spaces

    E-print Network

    Scannell, Kevin Patrick

    Section 19 ­ The Product Topology We will consider these products of topological spaces : The finite Cartesian product ! X1 " X2 " ..." Xn The infinite Cartesian Product ! X1 " X2 " X3 " ... There are two topologies: the box topology and the product topology. Basis for the box topology: sets

  6. Semi Compactness in Multiset Topology

    E-print Network

    J. Mahanta; D. Das

    2014-11-21

    In this paper, we introduce and study the concepts of semi open SOM) and semi closed (SCM) M-sets in multiset topological spaces.With this generalization of the notions of open and closed sets in M-topology, we generalize the concept of compactness in M-topology as semi compactness. Further semi compactness is generalized as semi whole compactness, semi partial whole compactness and semi full compactness. Some characterizations of these compact spaces are studied in the setting of multiset theory. In each step, several remarks with proper justifications are provided taking the well existing theories of general topology as the base of our study.

  7. Experimental Evidence for Topological Doping in the Cuprates

    SciTech Connect

    Tranquada, J. M.

    1999-04-06

    Some recent experiments that provide support for the concept of topological doping in cuprate superconductors are discussed. Consistent with the idea of charge segregation, it is argued that the scattering associated with the ''resonance'' peak found in YBa{sub 2}Cu{sub 3}O{sub 6+x} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} comes from the Cu spins and not from the doped holes.

  8. Monopole current and unconventional Hall response on a topological insulator

    Microsoft Academic Search

    Jiadong Zang; Naoto Nagaosa

    2010-01-01

    We study theoretically the charged current above a topological insulator (TI) separated by a ferromagnetic insulating layer. An unconventional Hall response occurs in the conducting layer on top of the TI which approaches to a constant value independent of R for R≪l and decays with ?R-1 for R≫l , where R is the separation between TI and conducting layer and

  9. A V2G vector control model of electric car charging and discharging machine

    Microsoft Academic Search

    Xiaolei Wang; Pan Yan; Liang Yang; Wendao Yao; Guangwen Shi

    2011-01-01

    circuit topology structure of electric vehicle charging and discharging inverter based on space vector is presented. The control strategy uses rotation vector of the directional three-phase active tide reversible PWM converter, and the circuit topology is two-way control DC\\/DC converter with double buck reversible structure. In order to improve the efficiency of the charging and discharging machine, the main circuit

  10. Weak symmetry breaking in two-dimensional topological insulators

    NASA Astrophysics Data System (ADS)

    Wang, Chenjie; Levin, Michael

    2013-12-01

    We show that there exist two-dimensional (2D) time-reversal invariant fractionalized insulators with the property that both their boundary with the vacuum and their boundary with a topological insulator can be fully gapped without breaking time-reversal or charge conservation symmetry. This result leads us to an apparent paradox: we consider a geometry in which a disklike region made up of a topological insulator is surrounded by an annular strip of a fractionalized insulator, which is, in turn, surrounded by the vacuum. If we gap both boundaries of the strip, we naively obtain an example of a gapped interface between a topological insulator and the vacuum that does not break any symmetries—an impossibility. The resolution of this paradox is that this system spontaneously breaks time-reversal symmetry in an unusual way, which we call weak symmetry breaking. In particular, we find that the only order parameters that are sensitive to the symmetry breaking are nonlocal operators that describe quasiparticle tunneling processes between the two edges of the strip; expectation values of local order parameters vanish exponentially in the limit of a wide strip. Also, we find that the symmetry breaking in our system comes with a ground-state degeneracy, but this ground-state degeneracy is topologically protected, rather than symmetry protected. We show that this kind of symmetry breaking can also occur at the edge of 2D fractional topological insulators.

  11. Interaction-driven topological and nematic phases on the Lieb lattice

    NASA Astrophysics Data System (ADS)

    Tsai, Wei-Feng; Fang, Chen; Yao, Hong; Hu, Jiangping

    2015-05-01

    We show that topological states are often developed in two-dimensional semimetals with quadratic band crossing points (BCPs) by electron–electron interactions. To illustrate this, we construct a concrete model with the BCP on an extended Lieb lattice and investigate the interaction-driven topological instabilities. We find that the BCP is marginally unstable against infinitesimal repulsions. Depending on the interaction strengths, topological quantum anomalous/spin Hall, charge nematic, and nematic-spin-nematic phases develop separately. Possible physical realizations of quadratic BCPs are provided.

  12. Family of non-Abelian Kitaev models on a lattice: Topological condensation and confinement

    SciTech Connect

    Bombin, H.; Martin-Delgado, M. A. [Departamento de Fisica Teorica I, Universidad Complutense, 28040 Madrid (Spain)

    2008-09-15

    We study a family of non-Abelian topological models in a lattice that arise by modifying the Kitaev model through the introduction of single-qudit terms. The effect of these terms amounts to a reduction in the discrete gauge symmetry with respect to the original systems, which corresponds to a generalized mechanism of explicit symmetry breaking. The topological order is either partially lost or completely destroyed throughout the various models. The systems display condensation and confinement of the topological charges present in the standard non-Abelian Kitaev models, which we study in terms of ribbon operator algebras.

  13. Topologically induced local P and CP violation in hot QCD

    SciTech Connect

    Kharzeev,D.E.

    2009-02-01

    Very stringent experimental bounds exist on the amount of P and CP violation in strong interactions. Nevertheless, the presence of non-Abelian topological solutions and the axial anomaly make the issue of CP invariance in QCD non-trivial ('the strong CP problem'). Even in the absence of a global P and CP violation the fluctuations of topological charge in the QCD vacuum are expected to play an important role in the breaking of chiral symmetry, and in the mass spectrum and other properties of hadrons. Here I argue that topological fluctuations in hot QCD matter can become directly observable in the presence of a very intense external magnetic field by inducing local P- and CP-odd effects. These local parity-violating phenomena can be described by using the Maxwell-Chern-Simons, or axion, electrodynamics as an effective theory. Local P and CP violation in hot QCD matter can be observed in experiment through the 'chiral magnetic effect' - the separation of electric charge along the axis of magnetic field that is created by the colliding relativistic ions. There is a recent evidence for the electric charge separation relative to the reaction plane of heavy ion collisions from the STAR Collaboration at RHIC.

  14. SHAPE AND TOPOLOGY OPTIMIZATION TECHNIQUES IN EIT

    E-print Network

    Hintermüller, Michael

    method Topological expansion Applications medicine blood clots in the lungs breast cancer geophysics Theory Introduction in EIT 2 (Shape) Gradient method Topological expansion Numerics Fast sweeping Finite Numerics Results Introduction in EIT 2 (Shape) Gradient method Topological expansion Detect objects

  15. Definitions of Entomological Terms

    NSDL National Science Digital Library

    0000-00-00

    A list of of morphological definitions and word roots useful to Entomology students and teachers. The list contains concise and easily understandable definitions for a number of morphological and physiological terms and specifies where on the insect these terms apply. A good reference for students in introductory entomology or insect morphology classes. Requires Adobe Acrobat Reader or equivalent software to read .pdf documents.

  16. Cachexia: A new definition

    Microsoft Academic Search

    William J. Evans; John E. Morley; Josep Argiles; Connie Bales; Vickie Baracos; Denis Guttridge; Aminah Jatoi; Kamyar Kalantar-Zadeh; Herbert Lochs; Giovanni Mantovani; Daniel Marks; William E. Mitch; Maurizio Muscaritoli; Armine Najand; Piotr Ponikowski; Filippo Rossi Fanelli; Morrie Schambelan; Annemie Schols; Michael Schuster; David Thomas; Robert Wolfe; Stefan D. Anker

    2008-01-01

    Summary On December 13th and 14th a group of scientists and clinicians met in Washington, DC, for the cachexia consensus conference. At the present time, there is no widely agreed upon operational definition of cachexia. The lack of a definition accepted by clinician and researchers has limited identification and treatment of cachectic patient as well as the development and approval

  17. Dynamics of Situation Definition

    ERIC Educational Resources Information Center

    Park, Dongseop; Moro, Yuji

    2006-01-01

    Situation definition is the process and product of actors' interpretive activities toward a given situation. By reviewing a number of psychological studies conducted in experimental settings, we found that the studies have only explicated a part of the situation definition process and have neglected its dynamic aspects. We need to focus on the…

  18. Observation of topological surface state quantum Hall effect in an intrinsic three-dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Xu, Yang; Miotkowski, Ireneusz; Liu, Chang; Tian, Jifa; Nam, Hyoungdo; Alidoust, Nasser; Hu, Jiuning; Shih, Chih-Kang; Hasan, M. Zahid; Chen, Yong P.

    2014-12-01

    A three-dimensional (3D) topological insulator (TI) is a quantum state of matter with a gapped insulating bulk yet a conducting surface hosting topologically protected gapless surface states. One of the most distinct electronic transport signatures predicted for such topological surface states (TSS) is a well-defined half-integer quantum Hall effect (QHE) in a magnetic field, where the surface Hall conductivities become quantized in units of (1/2)e2/h (e being the electron charge, h the Planck constant) concomitant with vanishing resistance. Here, we observe a well-developed QHE arising from TSS in an intrinsic TI of BiSbTeSe2. Our samples exhibit surface-dominated conduction even close to room temperature, whereas the bulk conduction is negligible. At low temperatures and high magnetic fields perpendicular to the top and bottom surfaces, we observe well-developed integer quantized Hall plateaux, where the two parallel surfaces each contribute a half-integer e2/h quantized Hall conductance, accompanied by vanishing longitudinal resistance. When the bottom surface is gated to match the top surface in carrier density, only odd integer QH plateaux are observed, representing a half-integer QHE of two degenerate Dirac gases. This system provides an excellent platform to pursue a plethora of exotic physics and novel device applications predicted for TIs, ranging from magnetic monopoles and Majorana particles to dissipationless electronics and fault-tolerant quantum computers.

  19. TRW CHARGED DROPLET SCRUBBER CORROSION STUDIES

    EPA Science Inventory

    The report gives results of corrosion studies to provide definitive data concerning the corrosive nature of coke-oven waste-heat flue gas and its effects on wet electrostatic precipitators, and specifically on TRW's Charged Droplet Scrubber (CDS). The study characterized the chem...

  20. Finding topological center of a geographic space via road network

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Miao, Yanan; Qin, Yuhao; Zhao, Xiaomei; Gao, Zi-You

    2015-02-01

    Previous studies show that the center of a geographic space is of great importance in urban and regional studies, including study of population distribution, urban growth modeling, and scaling properties of urban systems, etc. But how to well define and how to efficiently extract the center of a geographic space are still largely unknown. Recently, Jiang et al. have presented a definition of topological center by their block detection (BD) algorithm. Despite the fact that they first introduced the definition and discovered the 'true center', in human minds, their algorithm left several redundancies in its traversal process. Here, we propose an alternative road-cycle detection (RCD) algorithm to find the topological center, which extracts the outmost road-cycle recursively. To foster the application of the topological center in related research fields, we first reproduce the BD algorithm in Python (pyBD), then implement the RCD algorithm in two ways: the ArcPy implementation (arcRCD) and the Python implementation (pyRCD). After the experiments on twenty-four typical road networks, we find that the results of our RCD algorithm are consistent with those of Jiang's BD algorithm. We also find that the RCD algorithm is at least seven times more efficient than the BD algorithm on all the ten typical road networks.

  1. Charged Balanced Black Rings in Five Dimensions

    E-print Network

    Burkhard Kleihaus; Jutta Kunz; Kirsten Schnülle

    2010-12-22

    We present balanced black ring solutions of pure Einstein-Maxwell theory in five dimensions. The solutions are asymptotically flat, and their tension and gravitational self-attraction are balanced by the repulsion due to rotation and electrical charge. Hence the solutions are free of conical singularities and possess a regular horizon which exhibits the topology S1 x S2 of a torus. We discuss the global charges and the horizon properties of the solutions and show that they satisfy a Smarr relation. We construct these black rings numerically, restricting to the case of black rings with a rotation in the direction of the S1.

  2. Dense topological spaces and dense continuity

    NASA Astrophysics Data System (ADS)

    Aldwoah, Khaled A.

    2013-09-01

    There are several attempts to generalize (or "widen") the concept of topological space. This paper uses equivalence relations to generalize the concept of topological space via the concept of equivalence relations. By the generalization, we can introduce from particular topology on a nonempty set X many new topologies, we call anyone of these new topologies a dense topology. In addition, we formulate some simple properties of dense topologies and study suitable generalizations of the concepts of limit points, closeness and continuity, as well as Jackson, Nörlund and Hahn dense topologies.

  3. MORPHOLOGICAL ANTIALIASING AND TOPOLOGICAL RECONSTRUCTION

    E-print Network

    Paris-Sud XI, Université de

    MORPHOLOGICAL ANTIALIASING AND TOPOLOGICAL RECONSTRUCTION Adrien Herubel, Venceslas Biri LIGM: Morphological antialiasing is a post-processing approach which does note require additional samples compu to line length com- putation. We also introduce in the method the notion of topological reconstruction

  4. Topological Insulator Nanoribbons and Nanocrystals

    NASA Astrophysics Data System (ADS)

    Cui, Yi

    2010-03-01

    Following the discovery of two-dimensional topological insulator edge states in HgTe quantum wells at cryogenic temperatures, three dimensional (3D) topological insulators were recently discovered in Bismuth Selenide (Bi2Se3) and related compounds. Theoretical prediction and angle resolved photon emission spectroscopy studies show quantum spin Hall surface states in these 3D topological insulator materials. However, all the studies thus far have been on bulk size materials and it is challenging to observe directly the surface topological state conduction since its effects are masked by the residue bulk carrier. Here I present our study on topological insulator nanostructures, which can manifest the surface conduction states due their large surface-to-volume ratios. We show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coverage of two-dimensional electrons on the entire surface. I will discuss our recent exciting study on topological insulator nanocrystals. Our results suggest that topological insulator nanoribbons and nanocrystals afford novel promising materials for future spintronic devices.

  5. The birth of topological insulators

    Microsoft Academic Search

    Joel E. Moore

    2010-01-01

    Certain insulators have exotic metallic states on their surfaces. These states are formed by topological effects that also render the electrons travelling on such surfaces insensitive to scattering by impurities. Such topological insulators may provide new routes to generating novel phases and particles, possibly finding uses in technological applications in spintronics and quantum computing.

  6. Topological Sweep in Degenerate Cases

    Microsoft Academic Search

    Eynat Rafalin; Diane L. Souvaine; Ileana Streinu

    2002-01-01

    Abstract: Topological sweep can contribute to efficient implementationsof various algorithms for data analysis. Real data, however, hasdegeneracies. The modification of the topological sweep algorithm presentedhere handles degenerate cases such as parallel or multiply concurrentlines without requiring numerical perturbations to achieve generalposition. Our method maintains the O(n) and O(n) time and space complexitiesof the original algorithm, and is robust and easy

  7. Topological Fermi-liquid theory

    E-print Network

    Yong-Soo Jho; Ki-Seok Kim

    2015-04-06

    Quantum anomalies have been playing an essential role not only in particle physics but also in modern condensed matter physics, in particular, for topological states of matter. They are responsible for quantum number fractionalization in solitonic objects (Goldstone-Wilczek currents), deconfined quantum criticality (emergent non-abelian chiral anomaly) gapless boundary states and anomalous (quantized) electrical and thermal (Hall) transport phenomena, and etc, driving one branch of condensed matter physics. Furthermore, recent advances on topological states of matter have blurring out the boundary between high energy physics and condensed matter physics besides the string-theory application of the AdS/CFT conjecture. In this study, we generalize physics of insulating topological states of matter into a metallic phase, where effects of electron correlations can be incorporated to cause exotica. We propose a novel metallic state identified with a topological Fermi-liquid fixed point and described by a topological Fermi-liquid theory, where electromagnetic properties are governed by axion electrodynamics originating from chiral anomaly, thus which should be distinguished from the Landau's Fermi-liquid fixed point described by Landau's Fermi-liquid theory. We speculate that the topological Fermi-liquid theory lays the foundation stone of a topological Landau-Ginzburg theory for phase transitions from the topological Fermi-liquid state, which generalizes the Landau-Ginzburg theory for phase transitions from the Landau's Fermi-liquid state.

  8. Topology Change in General Relativity

    E-print Network

    Gary T. Horowitz

    1991-09-18

    A review is given of recent work on topology changing solutions to the first order form of general relativity. These solutions have metrics which are smooth everywhere, invertible almost everywhere, and have bounded curvature. The importance of considering degenerate metrics is discussed, and the possibility that quantum effects can suppress topology change is briefly examined.

  9. Fast topological imaging.

    PubMed

    Rodriguez, Samuel; Sahuguet, Perrine; Gibiat, Vincent; Jacob, Xavier

    2012-12-01

    Mathematical optimization methods based on the topological sensitivity analysis have been used to develop innovative ultrasonic imaging methods. With a single illumination of the medium, they have proved experimentally to yield a lateral resolution comparable to classical multiple-illumination techniques. As these methods are based on the numerical simulations of two wave fields, they require extensive computation. A time-domain finite-difference scheme is usually used for that purpose. This paper presents the development of an experimental imaging method based on the topological sensitivity. The numerical cost is reduced by replacing the numerical simulations by simple mathematical operations between the radiation patterns of the array's transducers and the frequency-domain signals to be emitted. These radiation patterns are preliminary computed once and for all. They were obtained with a finite element model for the anisotropic elastodynamic case and with semi-analytical integrations for the acoustic case. Experimental results are presented for a composite material sample and for a prefractal network immersed in water. A lateral resolution below 2.5 times the wavelength is obtained with a single plane wave illumination. The method is also applied with multiple illuminations, so that objects hidden in complex media can be investigated. PMID:22989947

  10. Propagators and topology

    NASA Astrophysics Data System (ADS)

    Maas, Axel

    2015-03-01

    Two popular perspectives on the non-perturbative domain of Yang-Mills theories are either in terms of the gluons themselves or in terms of collective gluonic excitations, i.e. topological excitations. If both views are correct, then they are only two different representations of the same underlying physics. One possibility to investigate this connection is by the determination of gluon correlation functions in topological background fields, as created by the smearing of lattice configurations. This is performed here for the minimal Landau gauge gluon propagator, ghost propagator, and running coupling, both in momentum and position space for SU(2) Yang-Mills theory. The results show that the salient low-momentum features of the propagators are qualitatively retained under smearing at sufficiently small momenta, in agreement with an equivalence of both perspectives. However, the mid-momentum behavior is significantly affected. These results are also relevant for the construction of truncations in functional methods, as they provide hints on necessary properties to be retained in truncations.

  11. Abelian Chern-Simons theory. I. A topological quantum field theory

    NASA Astrophysics Data System (ADS)

    Manoliu, Mihaela

    1998-01-01

    We give a construction of the Abelian Chern-Simons gauge theory from the point of view of a 2+1-dimensional topological quantum field theory. The definition of the quantum theory relies on geometric quantization ideas that have been previously explored in connection to the non-Abelian Chern-Simons theory [J. Diff. Geom. 33, 787-902 (1991); Topology 32, 509-529 (1993)]. We formulate the topological quantum field theory in terms of the category of extended 2- and 3-manifolds introduced in a preprint by Walker in 1991 and prove that it satisfies the axioms of unitary topological quantum field theories formulated by Atiyah [Publ. Math. Inst. Hautes Etudes Sci. Pans 68, 175-186 (1989)].

  12. Quantum Chemical Topology: Knowledgeable atoms in peptides

    NASA Astrophysics Data System (ADS)

    Popelier, Paul L. A.

    2012-06-01

    The need to improve atomistic biomolecular force fields remains acute. Fortunately, the abundance of contemporary computing power enables an overhaul of the architecture of current force fields, which typically base their electrostatics on fixed atomic partial charges. We discuss the principles behind the electrostatics of a more realistic force field under construction, called QCTFF. At the heart of QCTFF lies the so-called topological atom, which is a malleable box, whose shape and electrostatics changes in response to a changing environment. This response is captured by a machine learning method called Kriging. Kriging directly predicts each multipole moment of a given atom (i.e. the output) from the coordinates of the nuclei surrounding this atom (i.e. the input). This procedure yields accurate interatomic electrostatic energies, which form the basis for future-proof progress in force field design.

  13. Surface conduction in encapsulated topological gated structures

    NASA Astrophysics Data System (ADS)

    Deshko, Yury; Korzhovska, Inna; Zhao, Lukas; Arefe, Ghidewon; Konczykowski, Marcin; Krusin-Elbaum, Lia

    2015-03-01

    In three-dimensional (3D) topological insulators (TIs), the surface Dirac fermions intermix with the conducting bulk, thereby complicating access to the low-energy surface charge transport or magnetic response. The subsurface 2D states of bulk origin are vulnerable to bandbending due to surface adatoms, a band modification thought to be responsible for the `ageing' effect. To minimize this effect, we have developed an inert environment mechanical exfoliation technique to fabricate transistor-like gated structures in which prototypical binary TIs as well as ultra-low bulk carrier density ternaries (such as Bi2Te2Se) were encapsulated by thin h-BN layers, with electrical contacts made using exfoliated graphene. The effects of electrostatic tuning by the gate bias voltage on surface conductivity as a function of thickness of the TI layers and the variation with disorder will be presented. Supported by NSF-DMR-1312483, and DOD-W911NF-13-1-0159.

  14. Electric-Magnetic Duality and Topological Insulators

    E-print Network

    Andreas Karch

    2009-10-03

    We work out the action of the SL(2,Z) electric-magnetic duality group for an insulator with a non-trivial permittivity, permeability and theta-angle. This theory has recently been proposed to be the correct low-energy effective action for topological insulators. As applications, we give manifestly SL(2,Z) covariant expressions for the Faraday rotation at orthogonal incidence at the interface of two such materials, as well as for the induced magnetic and electric charges, slightly clarifying the meaning of expressions previously derived in the literature. We also use electric-magnetic duality to find a gravitational dual for a strongly coupled version of this theory using the AdS/CFT correspondence.

  15. Spin-transfer torque generated by a topological insulator.

    PubMed

    Mellnik, A R; Lee, J S; Richardella, A; Grab, J L; Mintun, P J; Fischer, M H; Vaezi, A; Manchon, A; Kim, E-A; Samarth, N; Ralph, D C

    2014-07-24

    Magnetic devices are a leading contender for the implementation of memory and logic technologies that are non-volatile, that can scale to high density and high speed, and that do not wear out. However, widespread application of magnetic memory and logic devices will require the development of efficient mechanisms for reorienting their magnetization using the least possible current and power. There has been considerable recent progress in this effort; in particular, it has been discovered that spin-orbit interactions in heavy-metal/ferromagnet bilayers can produce strong current-driven torques on the magnetic layer, via the spin Hall effect in the heavy metal or the Rashba-Edelstein effect in the ferromagnet. In the search for materials to provide even more efficient spin-orbit-induced torques, some proposals have suggested topological insulators, which possess a surface state in which the effects of spin-orbit coupling are maximal in the sense that an electron's spin orientation is fixed relative to its propagation direction. Here we report experiments showing that charge current flowing in-plane in a thin film of the topological insulator bismuth selenide (Bi2Se3) at room temperature can indeed exert a strong spin-transfer torque on an adjacent ferromagnetic permalloy (Ni81Fe19) thin film, with a direction consistent with that expected from the topological surface state. We find that the strength of the torque per unit charge current density in Bi2Se3 is greater than for any source of spin-transfer torque measured so far, even for non-ideal topological insulator films in which the surface states coexist with bulk conduction. Our data suggest that topological insulators could enable very efficient electrical manipulation of magnetic materials at room temperature, for memory and logic applications. PMID:25056062

  16. Electromagnetic moments of the bound system of charged particles

    E-print Network

    Albert Wienczek; Mariusz Puchalski; Krzysztof Pachucki

    2014-07-28

    We consider a bound system of particles interacting via electromagnetic forces in an external electromagnetic field, including leading relativistic corrections. Each particle has a definite mass, charge, spin, and charge radius. We introduce suitable canonical transformations and a perturbation scheme to obtain a Hamiltonian which describes the global dynamics of the system. This enables the derivation of formulas for various electromagnetic moments, such as the magnetic dipole moment, the mean square charge radius, and the electric dipole polarizability.

  17. Geometric aspects of charged black holes in Palatini theories

    E-print Network

    Olmo, Gonzalo J; Sanchez-Puente, A

    2015-01-01

    Charged black holes in gravity theories in the Palatini formalism present a number of unique properties. Their innermost structure is topologically nontrivial, representing a wormhole supported by a sourceless electric flux. For certain values of their effective mass and charge curvature divergences may be absent, and their event horizon may also disappear yielding a remnant. We give an overview of the mathematical derivation of these solutions and discuss their geodesic structure and other geometric properties.

  18. Transportation Network Topologies

    NASA Technical Reports Server (NTRS)

    Alexandrov, Natalia (Editor)

    2004-01-01

    The existing U.S. hub-and-spoke air transportation system is reaching saturation. Major aspects of the current system, such as capacity, safety, mobility, customer satisfaction, security, communications, and ecological effects, require improvements. The changing dynamics - increased presence of general aviation, unmanned autonomous vehicles, military aircraft in civil airspace as part of homeland defense - contributes to growing complexity of airspace. The system has proven remarkably resistant to change. NASA Langley Research Center and the National Institute of Aerospace conducted a workshop on Transportation Network Topologies on 9-10 December 2003 in Williamsburg, Virginia. The workshop aimed to examine the feasibility of traditional methods for complex system analysis and design as well as potential novel alternatives in application to transportation systems, identify state-of-the-art models and methods, conduct gap analysis, and thus to lay a foundation for establishing a focused research program in complex systems applied to air transportation.

  19. Gear tooth topological modification

    NASA Technical Reports Server (NTRS)

    Kish, Jules G. (Inventor); Isabelle, Charles (Inventor)

    1994-01-01

    The topology of parallel axis gears, such as spur and helical gears is modified to produce quieter and more smoothly operating gear sets with more uniform load distribution. A finite element analysis of the gear in its operating mode is made to produce a plot of radial and tangential deflections of the pinion and gear tooth surfaces which will occur when the gears are loaded during operation. The resultant plot is then inverted to produce a plot, or set of coordinates, which will define the path of travel of the gear tooth grinding wheel, which path is a mirror image of the plot of the finite element analysis. The resulting gears, when subjected to operating loads, will thus be deflected tangentially and radially to their optimum operating, or theoretical true involute, positions so as to produce quieter, smoother, and more evenly loaded gear trains.

  20. Definitions Derived from Neutrosophics

    E-print Network

    Florentin Smarandache

    2003-01-28

    Thirty-three new definitions are presented, derived from neutrosophic set, neutrosophic probability, neutrosophic statistics, and neutrosophic logic. Each one is independent, short, with references and cross references like in a dictionary style.

  1. Definitions Derived from Neutrosophics

    Microsoft Academic Search

    Florentin Smarandache

    2003-01-01

    Thirty-three new definitions are presented, derived from neutrosophic set, neutrosophic probability, neutrosophic statistics, and neutrosophic logic. Each one is independent, short, with references and cross references like in a dictionary style.

  2. Genomic definition of species

    SciTech Connect

    Crkvenjakov, R.; Drmanac, R.

    1991-07-01

    The subject of this paper is the definition of species based on the assumption that genome is the fundamental level for the origin and maintenance of biological diversity. For this view to be logically consistent it is necessary to assume the existence and operation of the new law which we call genome law. For this reason the genome law is included in the explanation of species phenomenon presented here even if its precise formulation and elaboration are left for the future. The intellectual underpinnings of this definition can be traced to Goldschmidt. We wish to explore some philosophical aspects of the definition of species in terms of the genome. The point of proposing the definition on these grounds is that any real advance in evolutionary theory has to be correct in both its philosophy and its science.

  3. The net charge at interfaces between insulators.

    PubMed

    Bristowe, N C; Littlewood, P B; Artacho, Emilio

    2011-03-01

    The issue of the net charge at insulating oxide interfaces is briefly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarization of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO(3) over SrTiO(3) in the absence of free carriers, for which the net charge is exactly 0.5e per interface formula unit, if the polarization response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt (2009 Phys. Rev. B 80 241103) of using formal polarization values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith (1993 Phys. Rev. B 48 4442-55). Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarization quanta. PMID:21411891

  4. The net charge at interfaces between insulators

    NASA Astrophysics Data System (ADS)

    Bristowe, N. C.; Littlewood, P. B.; Artacho, Emilio

    2011-03-01

    The issue of the net charge at insulating oxide interfaces is briefly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarization of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO3 over SrTiO3 in the absence of free carriers, for which the net charge is exactly 0.5e per interface formula unit, if the polarization response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt (2009 Phys. Rev. B 80 241103) of using formal polarization values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith (1993 Phys. Rev. B 48 4442-55). Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarization quanta.

  5. Energy versus topology: Competing defect structures in 2D complex vector field

    NASA Astrophysics Data System (ADS)

    Pismen, L. M.

    1994-04-01

    The topology of minimal orbits of the energy functional of a complex 2D vector field depends on the sign of nonlinear terms breaking the SU(2) symmetry, giving rise to either linearly or circularly polarized states (LP and CP) which possess different sets of defects. The CP vortices have two alternative core structures, with either vanishing amplitude or reversed polarization in the inner core. In the LP state, there are two distinct topological charges. Vortices carrying two half-unit charges have a circularly polarized core. Unit-charged vortices have a core with a vanishing amplitude, and may suffer a core instability splitting into a pair of half-unit-charged vortices.

  6. Does Zeeman's Fine Topology Exist?

    E-print Network

    Norberto Sainz

    2012-01-23

    We work on the family of topologies for the Minkowski manifold M. We partially order this family by inclusion to form the lattice \\Sigma(M), and focus on the sublattice Z of topologies that induce the Euclidean metric space on every time axis and every space axis. We analyze the bounds of Z in the lattice \\Sigma(M), in search for its supremum. Our conclusion --that such a supremum does not belong in Z-- is compared with constructive proofs of existence of the fine topology, defined as the maximum of Z and conceived to play an essential role in contemporary physical theories. Essential mathematical and physical questions arise.

  7. Entangled topological features of light

    E-print Network

    J. Romero; J. Leach; B. Jack; M. R. Dennis; S. Franke-Arnold; S. M. Barnett; M. J. Padgett

    2010-08-26

    We report the entanglement of topological features, namely, isolated, linked optical vortex loops in the light from spontaneous parametric down-conversion (SPDC). In three dimensions, optical vortices are lines of phase singularity and vortices of energy flow which percolate through all optical fields. This example of entanglement is between features that extend over macroscopic and finite volumes, furthermore, topological features are robust to perturbation . The entanglement of photons in complex three-dimensional(3D) topological states suggests the possibility of entanglement of similar structures in other quantum systems describable by complex scalar functions, such as superconductors, superfluids and Bose-Einstein condensates.

  8. Spherical Orbifolds for Cosmic Topology

    NASA Astrophysics Data System (ADS)

    Kramer, Peter

    2012-08-01

    Harmonic analysis is a tool to infer cosmic topology from the measured astrophysical cosmic microwave background CMB radiation. For overall positive curvature, Platonic spherical manifolds are candidates for this analysis. We combine the specific point symmetry of the Platonic manifolds with their deck transformations. This analysis in topology leads from manifolds to orbifolds. We discuss the deck transformations of the orbifolds and give eigenmodes for the harmonic analysis as linear combinations of Wigner polynomials on the 3-sphere. These provide new tools for detecting cosmic topology from the CMB radiation.

  9. Gravity From Topological Field Theory

    E-print Network

    J. Gegenberg; R. B. Mann

    1999-02-04

    We construct a topological field theory which, on the one hand, generalizes BF theories in that there is non-trivial coupling to `topological matter fields'; and, on the other, generalizes the three-dimensional model of Carlip and Gegenberg to arbitrary dimensional manifolds. Like the three dimensional model, the theory can be considered to describe a gravitational field interacting with topological matter. In particular, in two dimensions, the model is that of gravity on a torus. In four dimensions, the model is shown to admit constant curvature black hole solutions.

  10. Finite topology as applied to image analysis

    Microsoft Academic Search

    V. A. Kovalevsky

    1989-01-01

    The notion of a cellular complex which is well known in the topology is applied to describe the structure of images. It is shown that the topology of cellular complexes is the only possible topology of finite sets. Under this topology no contradictions or paradoxes arise when defining connected subsets and their boundaries. Ways of encoding images as cellular complexes

  11. Visualizing vector field topology in fluid flows

    Microsoft Academic Search

    James L. Helman; Lambertus Hesselink

    1991-01-01

    Methods for automating the analysis and display of vector field topology in general, and flow topology in particular, are described. By using techniques to extract and visualize topological information, it is possible to combine the simplicity of schematic depictions with the quantitative accuracy of curves and surfaces computed directly from the data. Two-dimensional vector field topology is discussed, covering critical

  12. Amplified topological characteristics of MBE-grown Bi2Se3/II-VI semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Chen, Zhiyi; Zhao, Lukas; Korzhovska, Inna; Tamargo, Maria; Krusin, Lia

    2015-03-01

    Access to charge transport in Dirac surface states of topological insulators (TIs) such as Bi2Se3 is faced with two big challenges: one is significant bulk conduction and another is intermixing of topological states with nontopological 2DEG quantum well states formed by bending of bulk electronic bands near the surface. The latter effect is thought to arise via charge transfer from surface adatoms and, therefore, the choice of layers abutting topological surfaces can be critical. Here we report a successful molecular beam epitaxy growth of Bi2Se3/ZnxCd1-xSe superlattices that improve topological characteristics of individual 8 - 10 nm thick TI layers. We show that in these superlattices the two-dimensional (2D) weak antilocalization quantum correction to classical magnetoresistance, associated with topological Berry phase, scales with the number of TI layers, with one quantum channel per layer. The Berry phase of ? obtained independently from Shubnikov de Haas quantum oscillations demonstrates robust topological interfaces in the multilayer structure. Supported by NSF-DMR-1122594 and DOD-W911NF-13-1-0159.

  13. Elec 331 -Bio-Potential Electrodes Review Definitions

    E-print Network

    Pulfrey, David L.

    Elec 331 - Bio-Potential Electrodes 1 Review Definitions · Ion Charged particle (molecule / atom- ­ Holes h+ · Electrode ­ Electron / ion transducer To monitor Cl h e #12;Elec 331 - Bio;Elec 331 - Bio-Potential Electrodes 3 Polarizeable Electrodes · Series capacitance effect · High pass

  14. Structured Analysis for Requirements Definition

    Microsoft Academic Search

    Douglas T. Ross; Kenneth E. Schoman Jr.

    1977-01-01

    Requirements definition encompasses all aspects of system development prior to actual system design. We see the lack of an adequate approach to requirements definition as the source of major difficulties in current systems worlk This paper examines the needs for requirements definition, and proposes meeting those objectives with three interrelated subjects: context analysis, functional specification, and design constraints. Requirements definition

  15. Topological fluctuations and susceptibility in SU(3) lattice gauge theory

    NASA Astrophysics Data System (ADS)

    Hoek, Jaap; Teper, M.; Waterhouse, J.

    We measure the topological charge density of the (Monte Carlo generated) SU(3) vacuum. Our algorithm involves first smoothening the generated configurations in a way that conserves the total charge in the continuum limit. We work in a range of couplings 5.6 ? ? ? 6/ g2 ? 6.0 and on lattice sizes up to 16 4. We find that the topological susceptibility scales like the string tension (within errors). This allows us to extract a value in physical units, X t{1}/{4} = 191 ± 16 MeV, in good agreement with the Witten-Veneziano mass formula. We also show how Xt is strongly suppressed as the temperature is increased through the deconfining transition, so that the U A(1) symmetry is effectively restored in the deconfined phase. Our results leave open the possibility that Xt is an order parameter for this transition. We carefully monitor finite size effects and perform a variety of calculations - reproducibility, stability under Monte Carlo, distribution of core sizes, etc. - which give us a direct insight into the approach to continuum topology.

  16. String flux mechanism for fractionalization in topologically ordered phases

    NASA Astrophysics Data System (ADS)

    Hermele, Michael

    2014-11-01

    We construct a family of exactly solvable spin models that illustrate a mechanism for fractionalization in topologically ordered phases, dubbed the string flux mechanism. The essential idea is that an anyon of a topological phase can be endowed with fractional quantum numbers when the string attached to it slides over a background pattern of flux in the ground state. The string flux models that illustrate this mechanism are Zn quantum double models defined on specially constructed d -dimensional lattices, and possess Zn topological order for d ?2 . The models have a unitary, internal symmetry G , where G is an arbitrary finite group. The simplest string flux model is a Z2 toric code defined on a bilayer square lattice, where G =Z2 is layer-exchange symmetry. In general, by varying the pattern of Zn flux in the ground state, any desired fractionalization class [element of H2(G ,Zn) ] can be realized for the Zn charge excitations. While the string flux models are not gauge theories, they map to Zn gauge theories in a certain limit, where they follow a magnetic route for the emergence of low-energy gauge structure. The models are analyzed by studying the action of G symmetry on Zn charge excitations, and by gauging the G symmetry. The latter analysis confirms that distinct fractionalization classes give rise to distinct quantum phases, except that classes [? ] ,[?] -1?H2(G ,Zn) give rise to the same phase. We conclude with a discussion of open issues and future directions.

  17. Spin-transfer torque generated by a topological insulator

    NASA Astrophysics Data System (ADS)

    Mellnik, Alex

    2015-03-01

    Magnetic devices are a leading contender for the implementation of memory and logic technologies that are non-volatile, that can scale to high density and high speed, and that do not wear out. However, widespread application of magnetic memory and logic devices will require the development of efficient mechanisms for reorienting their magnetization using the least possible current and power. We report experiments showing that charge current flowing in-plane in a thin film of the topological insulator Bi2Se3 at room temperature can exert a strong spin-transfer torque on an adjacent metallic ferromagnetic layer, with a direction consistent with that expected from a topological surface state. The spin torque efficiency per unit charge current density in the Bi2Se3 is larger than any previously measured at room temperature. Our data suggest that topological insulators could enable very efficient electrical manipulation of magnetic materials at room temperature, for memory and logic applications. Related publications: A. R. Mellnik, J. S. Lee, A. Richardella, J. L. Grab, P. J. Mintun, M. H. Fischer, A. Vaezi, A. Manchon, E.-A. Kim, N. Samarth, D. C. Ralph, Nature 511, 449-451 (2014).

  18. Topological insulators and Mott physics from the Hubbard interaction

    NASA Astrophysics Data System (ADS)

    Rachel, Stephan; Le Hur, Karyn

    2010-08-01

    We investigate the Hubbard model on the honeycomb lattice with intrinsic spin-orbit interactions as a paradigm for two-dimensional topological band insulators in the presence of interactions. Applying a combination of Hartree-Fock theory, slave-rotor techniques, and topological arguments, we show that the topological band insulating phase persists up to quite strong interactions. Then we apply the slave-rotor mean-field theory and find a Mott transition at which the charge degrees of freedom become localized on the lattice sites. The spin degrees of freedom, however, are still described by the original Kane-Mele band structure. Gauge-field effects in this region play an important role. When the honeycomb layer is isolated then the spin sector becomes already unstable toward an easy-plane Neel order. In contrast, if the honeycomb lattice is surrounded by extra “screening” layers with gapless spinons, then the system will support a fractionalized topological insulator phase with gapless spinons at the edges. For large interactions, we derive an effective spin Hamiltonian.

  19. Landau theory of topological defects in multiferroic hexagonal manganites

    NASA Astrophysics Data System (ADS)

    Artyukhin, Sergey; Delaney, Kris T.; Spaldin, Nicola A.; Mostovoy, Maxim

    2014-01-01

    Topological defects in ordered states with spontaneously broken symmetry often have unusual physical properties, such as fractional electric charge or a quantized magnetic field flux, originating from their non-trivial topology. Coupled topological defects in systems with several coexisting orders give rise to unconventional functionalities, such as the electric-field control of magnetization in multiferroics resulting from the coupling between the ferroelectric and ferromagnetic domain walls. Hexagonal manganites provide an extra degree of freedom: in these materials, both ferroelectricity and magnetism are coupled to an additional, non-ferroelectric structural order parameter. Here we present a theoretical study of topological defects in hexagonal manganites based on Landau theory with parameters determined from first-principles calculations. We explain the observed flip of electric polarization at the boundaries of structural domains, the origin of the observed discrete vortices, and the clamping between ferroelectric and antiferromagnetic domain walls. We show that structural vortices induce magnetic ones and that, consistent with a recent experimental report, ferroelectric domain walls can carry a magnetic moment.

  20. Boundary degeneracy of topological order

    E-print Network

    Wen, Xiao-Gang

    We introduce the concept of boundary degeneracy, as the ground state degeneracy of topologically ordered states on a compact orientable spatial manifold with gapped boundaries. We emphasize that the boundary degeneracy ...

  1. The topological filtration of ?-structures.

    PubMed

    Li, Thomas J X; Reidys, Christian M

    2013-01-01

    In this paper we study ?-structures filtered by topological genus. ?-structures are a class of RNA pseudoknot structures that plays a key role in the context of polynomial time folding of RNA pseudoknot structures. A ?-structure is composed by specific building blocks, that have topological genus less than or equal to ?, where composition means concatenation and nesting of such blocks. Our main results are the derivation of a new bivariate generating function for ?-structures via symbolic methods, the singularity analysis of the solutions and a central limit theorem for the distribution of topological genus in ?-structures of given length. In our derivation specific bivariate polynomials play a central role. Their coefficients count particular motifs of fixed topological genus and they are of relevance in the context of genus recursion and novel folding algorithms. PMID:23022027

  2. Topological insulators: The next generation

    Microsoft Academic Search

    Joel Moore

    2009-01-01

    Spin-orbit coupling in some materials leads to the formation of surface states that are topologically protected from scattering. Theory and experiments have found an important new family of such materials.

  3. Correlation effects on topological insulator

    E-print Network

    Xiong-Jun Liu; Yang Liu; Xin Liu

    2010-11-24

    The strong correlation effects on topological insulator are studied in a two-sublattice system with an onsite single-particle energy difference $\\Delta$ between two sublattices. At $\\Delta=0$, increasing the onsite interaction strength $U$ drives the transition from the quantum spin Hall insulating state to the non-topological antiferromagnetic Mott-insulating (AFMI) state. When $\\Delta$ is larger than a certain value, a topologically trivial band insulator or AFMI at small values of $U$ may change into a quantum anomalous Hall state with antiferromagnetic ordering at intermediate values of $U$. Further increasing $U$ drives the system back into the topologically trivial state of AFMI. The corresponding phenomena is observable in the solid state and cold atom systems. We also propose a scheme to realize and detect these effects in cold atom systems.

  4. On the riesz charge of the lower envelope of ?-subharmonic functions

    Microsoft Academic Search

    Alexandre Eremenko; Bent Fuglede; Mikhail Sodin

    1992-01-01

    By potential theoretic methods involving the Cartan fine topology a recent result by two of the authors is extended as follows: The Riesz charge of the lower envelope of a family of 3 or more d-subharmonic functions (no longer supposed continuous) in the plane equals the infimum of the charges of the lower envelopes of all pairs of functions from

  5. Search for New Topological Insulators

    Microsoft Academic Search

    Hsin Lin; L. A. Wray; S.-Y. Xu; M. Z. Hasan; T. Das; Y. J. Wang; R. S. Markiewicz; Arun Bansil

    2011-01-01

    Topological insulators (TIs) host a novel quantum phase of electrons which is characterized by topologically protected surface states originating from the effects of spin-orbit and time-reversal symmetries. While several families of TIs have already been found, the intense world-wide search for new classes of TIs continues unabated. This interest is driven by the need for materials with greater structural flexibility

  6. Data Traffic, Topology and Congestion

    Microsoft Academic Search

    David Arrowsmith; R. J. Mondrag; M. Woolf

    We consider the interaction between the topology of a network and the tra.c carried along its channels. The binding elements\\u000a between the topology and the traffic dynamics are the routing mechanisms. In a packet-based network, like the Internet, the\\u000a transmission of information is carried out in discrete packets. The path that a packet follows when travelling the network\\u000a is determined

  7. Topological excitations in semiconductor heterostructures

    SciTech Connect

    Koushik, R.; Mukerjee, Subroto; Ghosh, Arindam [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Baenninger, Matthias [Cavendish laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK and Department of Physics, Stanford University, Stanford, CA 94305 (United States); Narayan, Vijay [Department of Physics, Indian Institute of Science, Bangalore 560012, India and Cavendish laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Pepper, Michael [Cavendish laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK and Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Farrer, Ian; Ritchie, David A. [Cavendish laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2013-12-04

    Topological defects play an important role in the melting phenomena in two-dimensions. In this work, we report experimental observation of topological defect induced melting in two-dimensional electron systems (2DES) in the presence of strong Coulomb interaction and disorder. The phenomenon is characterised by measurement of conductivity which goes to zero in a Berezinskii-Kosterlitz-Thouless like transition. Further evidence is provided via low-frequency conductivity noise measurements.

  8. Topological insulators with inversion symmetry

    Microsoft Academic Search

    Liang Fu; C. L. Kane

    2007-01-01

    Topological insulators are materials with a bulk excitation gap generated by the spin-orbit interaction that are different from conventional insulators. This distinction is characterized by Z2 topological invariants, which characterize the ground state. In two dimensions, there is a single Z2 invariant that distinguishes the ordinary insulator from the quantum spin-Hall phase. In three dimensions, there are four Z2 invariants

  9. Topology independent protein structural alignment

    Microsoft Academic Search

    Joe Dundas; TA Binkowski; Bhaskar DasGupta; Jie Liang

    2007-01-01

    BACKGROUND: Identifying structurally similar proteins with different chain topologies can aid studies in homology modeling, protein folding, protein design, and protein evolution. These include circular permuted protein structures, and the more general cases of non-cyclic permutations between similar structures, which are related by non-topological rearrangement beyond circular permutation. We present a method based on an approximation algorithm that finds sequence-order

  10. Refining the shifted topological vertex

    SciTech Connect

    Drissi, L. B.; Jehjouh, H.; Saidi, E. H. [Faculte des Sciences, Laboratory/UFR-Physique des Hautes Energies, Rabat, 1014 (Morocco); Groupement National de Physique des Hautes Energies (GNPHE), Siege focal:FS, Rabat, 1014 (Morocco)

    2009-01-15

    We study aspects of the refining and shifting properties of the 3d MacMahon function C{sub 3}(q) used in topological string theory and BKP hierarchy. We derive the explicit expressions of the shifted topological vertex S{sub {lambda}}{sub {mu}}{sub {nu}}(q) and its refined version T{sub {lambda}}{sub {mu}}{sub {nu}}(q,t). These vertices complete results in literature.

  11. Cosmological Parameters and Cosmic Topology

    Microsoft Academic Search

    M. J. Reboucas; J. S. Alcaniz

    2006-01-01

    Geometry constrains but does not dictate the topology of the 3--dimensional\\u000aspace. In a locally spatially homogeneous and isotropic universe, however, the\\u000atopology of its spatial section dictates its geometry. We show that, besides\\u000adetermining the geometry, the knowledge of the spatial topology through the\\u000acircles--in--the--sky offers an effective way of setting constraints on the\\u000adensity parameters associated with dark

  12. Search for Topological Superconductivity in Superconducting Doped Topological Insulators

    NASA Astrophysics Data System (ADS)

    Sasaki, Satoshi

    2013-03-01

    Recent discovery of topological insulators (TIs) which can be characterized by topologically protected gapless surface states stimulated the search for an even more exotic state of matter, a topological superconductor (TSC), which is also predicted to have a topologically protected gapless surface state consisting of massless Majorana fermions as its distinctive characteristic. Low-carrier-density semiconductors with a strong spin-orbit coupling and a Fermi surface that is centered around time-reversal-invariant momenta, such as superconducting doped TIs, are predicted to be prime candidates for TSCs. Following this prediction, we studied the nature of superconductivity in doped TIs, CuxBi2Se3 and Sn1-xInxTe, by employing a conductance spectroscopy. I will present our latest results together with recent spectroscopy data from other groups, and summarize the current understanding of topological superconductivity in superconducting doped TIs. Work in collaboration with M. Kriener, Z. Ren, A. A. Taskin, K. Segawa, Y. Ando (Osaka Univ.), K. Yada, M. Sato, Y. Tanaka (Nagoya), and L. Fu (MIT). Recent discovery of topological insulators (TIs) which can be characterized by topologically protected gapless surface states stimulated the search for an even more exotic state of matter, a topological superconductor (TSC), which is also predicted to have a topologically protected gapless surface state consisting of massless Majorana fermions as its distinctive characteristic. Low-carrier-density semiconductors with a strong spin-orbit coupling and a Fermi surface that is centered around time-reversal-invariant momenta, such as superconducting doped TIs, are predicted to be prime candidates for TSCs. Following this prediction, we studied the nature of superconductivity in doped TIs, CuxBi2Se3 and Sn1-xInxTe, by employing a conductance spectroscopy. I will present our latest results together with recent spectroscopy data from other groups, and summarize the current understanding of topological superconductivity in superconducting doped TIs. Work in collaboration with M. Kriener, Z. Ren, A. A. Taskin, K. Segawa, Y. Ando (Osaka Univ.), K. Yada, M. Sato, Y. Tanaka (Nagoya), and L. Fu (MIT). Supported by JSPS (KAKENHI 24740237 and NEXT Program) and AFOSR (AOARD 124038)

  13. Topological approximation of the nonlinear Anderson model.

    PubMed

    Milovanov, Alexander V; Iomin, Alexander

    2014-06-01

    We study the phenomena of Anderson localization in the presence of nonlinear interaction on a lattice. A class of nonlinear Schrödinger models with arbitrary power nonlinearity is analyzed. We conceive the various regimes of behavior, depending on the topology of resonance overlap in phase space, ranging from a fully developed chaos involving Lévy flights to pseudochaotic dynamics at the onset of delocalization. It is demonstrated that the quadratic nonlinearity plays a dynamically very distinguished role in that it is the only type of power nonlinearity permitting an abrupt localization-delocalization transition with unlimited spreading already at the delocalization border. We describe this localization-delocalization transition as a percolation transition on the infinite Cayley tree (Bethe lattice). It is found in the vicinity of the criticality that the spreading of the wave field is subdiffusive in the limit t?+?. The second moment of the associated probability distribution grows with time as a power law ? t^{?}, with the exponent ?=1/3 exactly. Also we find for superquadratic nonlinearity that the analog pseudochaotic regime at the edge of chaos is self-controlling in that it has feedback on the topology of the structure on which the transport processes concentrate. Then the system automatically (without tuning of parameters) develops its percolation point. We classify this type of behavior in terms of self-organized criticality dynamics in Hilbert space. For subquadratic nonlinearities, the behavior is shown to be sensitive to the details of definition of the nonlinear term. A transport model is proposed based on modified nonlinearity, using the idea of "stripes" propagating the wave process to large distances. Theoretical investigations, presented here, are the basis for consistency analysis of the different localization-delocalization patterns in systems with many coupled degrees of freedom in association with the asymptotic properties of the transport. PMID:25019865

  14. Galois conjugates of topological phases

    NASA Astrophysics Data System (ADS)

    Freedman, M. H.; Gukelberger, J.; Hastings, M. B.; Trebst, S.; Troyer, M.; Wang, Z.

    2012-01-01

    Galois conjugation relates unitary conformal field theories and topological quantum field theories (TQFTs) to their nonunitary counterparts. Here we investigate Galois conjugates of quantum double models, such as the Levin-Wen model. While these Galois-conjugated Hamiltonians are typically non-Hermitian, we find that their ground-state wave functions still obey a generalized version of the usual code property (local operators do not act on the ground-state manifold) and hence enjoy a generalized topological protection. The key question addressed in this paper is whether such nonunitary topological phases can also appear as the ground states of Hermitian Hamiltonians. Specific attempts at constructing Hermitian Hamiltonians with these ground states lead to a loss of the code property and topological protection of the degenerate ground states. Beyond this, we rigorously prove that no local change of basis can transform the ground states of the Galois-conjugated doubled Fibonacci theory into the ground states of a topological model whose Hermitian Hamiltonian satisfies Lieb-Robinson bounds. These include all gapped local or quasilocal Hamiltonians. A similar statement holds for many other nonunitary TQFTs. One consequence is that these nonunitary TQFTs do not describe physical realizations of topological phases. In particular, this implies that the “Gaffnian” wave function can not be the ground state of a gapped fractional quantum Hall state.

  15. Topological Surface States Originated Spin-Orbit Torques in Bi2Se3

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Deorani, Praveen; Banerjee, Karan; Koirala, Nikesh; Brahlek, Matthew; Oh, Seongshik; Yang, Hyunsoo

    2015-06-01

    The three dimensional topological insulator bismuth selenide (Bi2Se3 ) is expected to possess strong spin-orbit coupling and spin-textured topological surface states and, thus, exhibit a high charge to spin current conversion efficiency. We evaluate spin-orbit torques in Bi2Se3/Co40Fe40B20 devices at different temperatures by spin torque ferromagnetic resonance measurements. As the temperature decreases, the spin-orbit torque ratio increases from ˜0 .047 at 300 K to ˜0 .42 below 50 K. Moreover, we observe a significant out-of-plane torque at low temperatures. Detailed analysis indicates that the origin of the observed spin-orbit torques is topological surface states in Bi2Se3 . Our results suggest that topological insulators with strong spin-orbit coupling could be promising candidates as highly efficient spin current sources for exploring the next generation of spintronic applications.

  16. Holographic Wilson loops, dielectric interfaces, and topological insulators

    NASA Astrophysics Data System (ADS)

    Estes, John; O'Bannon, Andy; Tsatis, Efstratios; Wrase, Timm

    2013-05-01

    We use holography to study (3+1)-dimensional N=4 supersymmetric SU(Nc) Yang-Mills theory (SYM) in the large-Nc and large-coupling limits, with a (2+1)-dimensional interface where the Yang-Mills coupling or ? angle changes value, or “jumps.” We consider interfaces that either break all supersymmetry or that preserve half of the N=4 supersymmetry thanks to certain operators localized to the interface. Specifically, we compute the expectation values of a straight timelike Wilson line and of a rectangular Wilson loop in the fundamental representation of SU(Nc). The former gives us the self-energy of a heavy test charge while the latter gives us the potential between heavy test charges. A jumping coupling or ? angle acts much like a dielectric interface in electromagnetism: the self-energy or potential includes the effects of image charges. N=4 SYM with a jumping ? angle may also be interpreted as the low-energy effective description of a fractional topological insulator, as we explain in detail. For nonsupersymmetric interfaces, we find that the self-energy and potential are qualitatively similar to those in electromagnetism, despite the differences between N=4 SYM and electromagnetism. For supersymmetric interfaces, we find dramatic differences from electromagnetism which depend sensitively on the coupling of the test charge to the adjoint scalars of N=4 SYM. In particular, we find one special case where a test charge has a vanishing image charge.

  17. Holographic Wilson Loops, Dielectric Interfaces, and Topological Insulators

    E-print Network

    John Estes; Andy O'Bannon; Efstratios Tsatis; Timm Wrase

    2013-06-02

    We use holography to study (3+1)-dimensional N=4 supersymmetric SU(Nc) Yang-Mills theory (SYM) in the large-Nc and large coupling limits, with a (2+1)-dimensional interface where the Yang-Mills coupling or theta-angle changes value, or "jumps." We consider interfaces that either break all supersymmetry or that preserve half of the N=4 supersymmetry thanks to certain operators localized to the interface. Specifically, we compute the expectation values of a straight timelike Wilson line and of a rectangular Wilson loop in the fundamental representation of SU(Nc). The former gives us the self-energy of a heavy test charge while the latter gives us the potential between heavy test charges. A jumping coupling or theta-angle acts much like a dielectric interface in electromagnetism: a self-energy or potential includes the effects of image charges. N=4 SYM with a jumping theta-angle may also be interpreted as the low-energy effective description of a fractional topological insulator, as we explain in detail. For non-supersymmetric interfaces, we find that the self-energy and potential are qualitatively similar to those in electromagnetism, despite the differences between N=4 SYM and electromagnetism. For supersymmetric interfaces, we find dramatic differences from electromagnetism which depend sensitively on the coupling of the test charge to the adjoint scalars of N=4 SYM. In particular, we find one special case where a test charge has vanishing image charge.

  18. Scanning Tunnelling Spectroscopic Studies of Dirac Fermions in Graphene and Topological Insulators

    E-print Network

    Yeh, Nai-Chang

    by chemical vapour deposition (CVD), strain-induced scalar and gauge potentials are manifested by the charging graphene [1] and the surface state (SS) of three- dimensional (3D) strong topological insulators (STI) [2 evidences for strain-induced scalar and gauge potentials [7]. The gauge potentials result in both integer

  19. Surface States of Topological Insulators: The Dirac Fermion in Curved Two-Dimensional Spaces

    Microsoft Academic Search

    Dung-Hai Lee

    2009-01-01

    The surface of a topological insulator is a closed two-dimensional manifold. The surface states are described by the Dirac Hamiltonian in curved two-dimensional spaces. For a slablike sample with a magnetic field perpendicular to its top and bottom surfaces, there are chiral states delocalized on the four side faces. These ``chiral sheets'' carry both charge and spin currents. In strong

  20. Symmetry-protected topological (SPT) phases in gapped electronic systems can host robust surface states that

    E-print Network

    McQuade, D. Tyler

    Symmetry-protected topological (SPT) phases in gapped electronic systems can host robust surface states that remain gapless as long as the relevant global symmetry remains unbroken. The nature of the charge carriers in SPT surface states is intimately tied to the symmetry of the bulk, resulting in one

  1. Identifying non-Abelian topological ordered state and transition by momentum polarization

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Qi, Xiao-Liang

    2014-05-01

    Using a method called momentum polarization, we study the quasiparticle topological spin and the edge-state chiral central charge of non-Abelian topological ordered states described by Gutzwiller-projected wave functions. Our results verify that the fractional Chern insulator state obtained by Gutzwiller projection of two partons in bands of Chern number 2 is described by SU(2)2 Chern-Simons theory coupled to fermions, rather than the pure SU(2)2 Chern-Simons theory. In addition, by introducing an adiabatic deformation between one Chern-number-2 band and two Chern-number-1 bands, we show that the topological order in the Gutzwiller-projected state does not always agree with the expectation of topological field theory. Even if the parton mean-field state is adiabatically deformed, the Gutzwiller projection can introduce a topological phase transition between Abelian and non-Abelian topologically ordered states. Our approach applies to more general topologically ordered states described by Gutzwiller-projected wave functions.

  2. Exotic quantum phase transitions of strongly interacting topological insulators

    NASA Astrophysics Data System (ADS)

    Slagle, Kevin; You, Yi-Zhuang; Xu, Cenke

    2015-03-01

    Using determinant quantum Monte Carlo simulations, we demonstrate that an extended Hubbard model on a bilayer honeycomb lattice has two novel quantum phase transitions. The first is a quantum phase transition between the weakly interacting gapless Dirac fermion phase and a strongly interacting fully gapped and symmetric trivial phase, which cannot be described by the standard Gross-Neveu model. The second is a quantum critical point between a quantum spin Hall insulator with spin Sz conservation and the previously mentioned strongly interacting fully gapped phase. At the latter quantum critical point the single-particle excitations remain gapped, while spin and charge gaps both close. We argue that the first quantum phase transition is related to the Z16 classification of the topological superconductor 3He-B phase with interactions, while the second quantum phase transition is a topological phase transition described by a bosonic O (4 ) nonlinear sigma model field theory with a ? term.

  3. Quantum Hall superfluids in topological insulator thin films.

    PubMed

    Tilahun, Dagim; Lee, Byounghak; Hankiewicz, E M; MacDonald, A H

    2011-12-01

    Three-dimensional topological insulators have protected Dirac-cone surface states. In this Letter we argue that gapped excitonic superfluids with spontaneous coherence between top and bottom surfaces can occur in the topological insulator (TI)-thin-film quantum Hall regime. We find that the large dielectric constants of TI materials increase the layer separation range over which coherence survives and decrease the superfluid sound velocity, but have little influence on the superfluid density or on the charge gap. The coherent state at total Landau-level filling factor ?T=0 is predicted to be free of edge modes, qualitatively altering its transport phenomenology compared to the widely studied case of ?T=1 in GaAs double-quantum wells. PMID:22243013

  4. A magnetic monopole in topological insulator: exact solution

    E-print Network

    Yuan-Yuan Zhao; Shun-Qing Shen

    2012-11-15

    The Witten effect tells that a unit magnetic monopole can bind a half elementary charge in an axion media. We present an exact solution of a magnetic monopole in a topological insulator that was proposed to be an axion media recently. It is found that a magnetic monopole can induce one zero energy state bound to it and one surface state of zero energy. The two states are quite robust, but the degeneracy can be removed by external fields. For a finite size system, the interference of two states may lift the degeneracy, and the resulting states have one half near the origin and another half around the surface, which realizes the Witten effect. However, the energy difference decays exponentially with the size of the system. The exact solution does not fully support the realization of the Witten effect in a topological insulator.

  5. Charged particle periodicity in the Saturnian magnetosphere

    NASA Technical Reports Server (NTRS)

    Carbary, J. F.; Krimigis, S. M.

    1982-01-01

    The present investigation is concerned with the first definitive evidence for charged particle modulations near the magnetic rotation period at Saturn. This periodicity is apparent in the ratios (and spectra) of low energy charged particles in the Saturnian magnetosphere. Most of the data presented were taken during the Voyager 2 outbound portion of the Saturn encounter. During this time the spacecraft was at high latitudes (approximately 30 deg) in the southern hemisphere of the Saturnian magnetosphere. The probe's trajectory was approximately along the dawn meridian at an essentially constant local time. The observation that the charged particle modulation is consistent with the Saturn Kilometric Radiation (SKR) period provides a basic input for the resolution of a puzzle which has existed ever since the discovery of the SKR modulation. The charged particle periodicity identified suggests that a basic asymmetry must exist in the Saturnian magnetosphere.

  6. SEDS experiment design definition

    NASA Technical Reports Server (NTRS)

    Carroll, Joseph A.; Alexander, Charles M.; Oldson, John C.

    1990-01-01

    The Small Expendable-tether Deployment System (SEDS) was developed to design, build, integrate, fly, and safely deploy and release an expendable tether. A suitable concept for an on-orbit test of SEDS was developed. The following tasks were performed: (1) Define experiment objectives and requirements; (2) Define experiment concepts to reach those objectives; (3) Support NASA in experiment concept selection and definition; (4) Perform analyses and tests of SEDS hardware; (5) Refine the selected SEDS experiment concept; and (6) Support interactive SEDS system definition process. Results and conclusions are given.

  7. DEFINITION FOR ASBESTOS.

    USGS Publications Warehouse

    Ross, Malcolm; Kuntze, Richard A.; Clifton, Robert A.

    1984-01-01

    A definition of asbestos is proposed. Under this definition, the term asbestos applies to six naturally occurring minerals exploited commercially for their desirable physical properties, which are in part derived from their asbestiform habit. The six minerals are the serpentine mineral chrysotile and the amphibole minerals grunerite asbestos (also referred to as amosite), riebeckite asbestos (also referred to as crocidolite), anthophyllite asbestos, tremolite asbestos, and actinolite asbestos. Individual mineral particles, however processed and regardless of their mineral name, are not demonstrated to be asbestos if the length-to-width ratio is less than 20:1.

  8. Experimental Realizations of Magnetic Topological Insulator and Topological Crystalline Insulator

    NASA Astrophysics Data System (ADS)

    Xu, Suyang

    2013-03-01

    Over the past few years the experimental research on three-dimensional topological insulators have emerged as one of the most rapidly developing fields in condensed matter physics. In this talk, we report on two new developments in the field: The first part is on the dynamic interplay between ferromagnetism and the Z2 topological insulator state (leading to a magnetic topological insulator). We present our spin-resolved photoemission and magnetic dichroic experiments on MBE grown films where a hedgehog-like spin texture is revealed on the magnetically ordered surface of Mn-Bi2Se3 revealing a Berry's phase gradient in energy-momentum space of the crystal. A chemically/electrically tunable Berry's phase switch is further demonstrated via the tuning of the spin groundstate in Mn-Bi2Se3 revealed in our data (Nature Physics 8, 616 (2012)). The second part of this talk describes our experimental observation of a new topological phase of matter, namely a topological crystalline insulator where space group symmetries replace the role of time-reversal symmetry in an otherwise Z2 topological insulator predicted in theory. We experimentally investigate the possibility of a mirror symmetry protected topological phase transition in the Pb1-xSnxTe alloy system, which has long been known to contain an even number of band inversions based on band theory. Our experimental results show that at a composition below the theoretically predicted band inversion, the system is fully gapped, whereas in the band-inverted regime, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order (Nature Communications 3, 1192 (2012)) distinct from that observed in Z2 topological insulators. We discuss future experimental possibilities opened up by these new developments in topological insulators research. This work is in collaboration with M. Neupane, C. Liu, N. Alidoust, I. Belopolski, D. Qian, D.M. Zhang, A. Richardella, A. Marcinkova, Q. Gibson, R. Sankar, Y.J. Wang, T. Chang, H. Jeng, H. Lin, L.A. Wray, J.D. Denlinger, M. Leandersson, T. Balasubramanian, J. Sánchez-Barriga, O. Rader, G. Landolt, B. Slomski, J.H. Dil, F.C. Chou, E. Morosan, N. Samarth, R.J. Cava and M.Z. Hasan. Over the past few years the experimental research on three-dimensional topological insulators have emerged as one of the most rapidly developing fields in condensed matter physics. In this talk, we report on two new developments in the field: The first part is on the dynamic interplay between ferromagnetism and the Z2 topological insulator state (leading to a magnetic topological insulator). We present our spin-resolved photoemission and magnetic dichroic experiments on MBE grown films where a hedgehog-like spin texture is revealed on the magnetically ordered surface of Mn-Bi2Se3 revealing a Berry's phase gradient in energy-momentum space of the crystal. A chemically/electrically tunable Berry's phase switch is further demonstrated via the tuning of the spin groundstate in Mn-Bi2Se3 revealed in our data (Nature Physics 8, 616 (2012)). The second part of this talk describes our experimental observation of a new topological phase of matter, namely a topological crystalline insulator where space group symmetries replace the role of time-reversal symmetry in an otherwise Z2 topological insulator predicted in theory. We experimentally investigate the possibility of a mirror symmetry protected topological phase transition in the Pb1-xSnxTe alloy system, which has long been known to contain an even number of band inversions based on band theory. Our experimental results show that at a composition below the theoretically predicted band inversion, the system is fully gapped, whereas in the band-inverted regime, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order (Nature Communications 3, 1192 (2012)) distinct from that observed in Z2 topological insulators. We discuss future experimental possibilities opened up by these new developments in topological insulators research.

  9. Stability of Topological Superconductors to Interactions and Surface Topological Order

    NASA Astrophysics Data System (ADS)

    Fidkowski, Lukasz

    2014-03-01

    Three-dimensional topological superconductors protected by time reversal symmetry are characterized by gapless Majorana cones on their surface. Free-fermion phases with this symmetry (class DIII) are indexed by an integer Z, of which ? = 1 is realized by the B phase of superfluid 3 He . Previously, it was believed that the surface must be gapless unless time-reversal symmetry is broken. In this talk, we argue that a fully symmetric and gapped surface is possible in the presence of strong interactions, if a special type of topological order appears on the surface. The topological order realizes time reversal symmetry in an anomalous way, one that is impossible to achieve in purely two dimensions. For odd ?, the surface topological order must be non-Abelian, and propose the simplest non-Abelian topological order that contains electronlike excitations, SO(3)6 , with four quasiparticles, as a candidate surface state. We also discuss Abelian theories for the surface ? = 2 , 4 , 8 one particular consequence of our scheme is that ? = 16 admits a trivially gapped time reversal symmetric surface.

  10. Synthesis and characterization of 3D topological insulators: a case TlBi(S1?xSex)2

    NASA Astrophysics Data System (ADS)

    Segawa, Kouji

    2015-02-01

    In this article, practical methods for synthesizing Tl-based ternary III-V-VI2 chalcogenide TlBi(S1-xSex)2 are described in detail, along with characterization by x-ray diffraction and charge transport properties. The TlBi(S1-xSex)2 system is interesting because it shows a topological phase transition, where a topologically nontrivial phase changes to a trivial phase without changing the crystal structure qualitatively. In addition, Dirac semimetals whose bulk band structure shows a Dirac-like dispersion are considered to exist near the topological phase transition. The technique shown here is also generally applicable for other chalcogenide topological insulators, and will be useful for studying topological insulators and related materials.

  11. Polymer topology revealed by ion mobility coupled with mass spectrometry.

    PubMed

    Morsa, Denis; Defize, Thomas; Dehareng, Dominique; Jérôme, Christine; De Pauw, Edwin

    2014-10-01

    Hyperbranched and star shaped polymers have raised tremendous interest because of their unusual structural and photochemical properties, which provide them potent applications in various domains, namely in the biomedical field. In this context, the development of adequate tools aiming to probe particular three-dimensional features of such polymers is of crucial importance. In this present work, ion mobility coupled with mass spectrometry was used to experimentally derive structural information related to cationized linear and star shaped poly-?-caprolactones as a function of their charge state and chain length. Two major conformations were observed and identified using theoretical modeling: (1) near spherical conformations whose sizes are invariant with the polymer topology for long and lightly charged chains and (2) elongated conformations whose sizes vary with the polymer topology for short and highly charged chains. These conformations were further confirmed by collisional activation experiments based on the ejection thresholds of the coordinated cations that vary according to the elongation amplitude of the polymer chains. Finally, a comparison between solution and gas-phase conformations highlights a compaction of the structure with a loss of specific chain arrangements during the ionization and desolvation steps of the electrospray process, fueling the long-time debated question related to the preservation of the analyte structure during the transfer into the mass spectrometer. PMID:25188877

  12. Nonperturbative comparison of QCD effective charges

    SciTech Connect

    Aguilar, A. C. [Federal University of ABC, CCNH, Rua Santa Adelia 166, CEP 09210-170, Santo Andre (Brazil); Binosi, D. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT), Villa Tambosi, Strada delle Tabarelle 286, I-38050 Villazzano (Italy); Papavassiliou, J. [Department of Theoretical Physics and IFIC, University of Valencia-CSIC, E-46100, Valencia (Spain); Rodriguez-Quintero, J. [Department of Applied Physics, University of Huelva, E-21071 Huelva (Spain)

    2009-10-15

    We study the nonperturbative behavior of two versions of the QCD effective charge, one obtained from the pinch technique gluon self-energy, and one from the ghost-gluon vertex. Despite their distinct theoretical origin, due to a fundamental identity relating various ingredients appearing in their respective definitions, the two effective charges are almost identical in the entire range of physical momenta, and coincide exactly in the deep infrared, where they freeze at a common finite value. Specifically, the dressing function of the ghost propagator is related to the two form factors in the Lorentz decomposition of a certain Green's function, appearing in a variety of field-theoretic contexts. The central identity, which is valid only in the Landau gauge, is derived from the Schwinger-Dyson equations governing the dynamics of the aforementioned quantities. The renormalization procedure that preserves the validity of the identity is carried out, and various relevant kinematic limits and physically motivated approximations are studied in detail. A crucial ingredient in this analysis is the infrared finiteness of the gluon propagator, which is inextricably connected with the aforementioned freezing of the effective charges. Some important issues related to the consistent definition of the effective charge in the presence of such a gluon propagator are resolved. We finally present a detailed numerical study of a special set of Schwinger-Dyson equations, whose solutions determine the nonperturbative dynamics of the quantities composing the two effective charges.

  13. Topological Invariants in Point Group Symmetric Photonic Topological Insulators

    E-print Network

    Chen, Xiao-Dong; Chen, Wen-Jie; Wang, Jia-Rong; Dong, Jian-Wen

    2014-01-01

    We proposed a group-theory method to calculate topological invariant in bi-isotropic photonic crystals invariant under crystallographic point group symmetries. Spin Chern number has been evaluated by the eigenvalues of rotation operators at high symmetry k-points after the pseudo-spin polarized fields are retrieved. Topological characters of photonic edge states and photonic band gaps can be well predicted by total spin Chern number. Nontrivial phase transition is found in large magnetoelectric coupling due to the jump of total spin Chern number. Light transport is also issued at the {\\epsilon}/{\\mu} mismatching boundary between air and the bi-isotropic photonic crystal. This finding presents the relationship between group symmetry and photonic topological systems, which enables the design of photonic nontrivial states in a rational manner.

  14. Robust transport signatures of topological superconductivity in topological insulator nanowires.

    PubMed

    de Juan, Fernando; Ilan, Roni; Bardarson, Jens H

    2014-09-01

    Finding a clear signature of topological superconductivity in transport experiments remains an outstanding challenge. In this work, we propose exploiting the unique properties of three-dimensional topological insulator nanowires to generate a normal-superconductor junction in the single-mode regime where an exactly quantized 2e2/h zero-bias conductance can be observed over a wide range of realistic system parameters. This is achieved by inducing superconductivity in half of the wire, which can be tuned at will from trivial to topological with a parallel magnetic field, while a perpendicular field is used to gap out the normal part, except for two spatially separated chiral channels. The combination of chiral mode transport and perfect Andreev reflection makes the measurement robust to moderate disorder, and the quantization of conductance survives to much higher temperatures than in tunnel junction experiments. Our proposal may be understood as a variant of a Majorana interferometer which is easily realizable in experiments. PMID:25238379

  15. The Definition of Abstinence

    Microsoft Academic Search

    Angela Nicoletti

    2005-01-01

    A teen's definition of sexual activity most often does not include oral or anal sex. Abstinence only programs vary widely as to how they define sexual behavior and may be contributing to misinformation about STD transmission. Unknown is the extent to which declining teen pregnancy rates are due to non-coital activities replacing vaginal intercourse.

  16. FAMILY MEDICINE* Definition Of

    E-print Network

    Finley Jr., Russell L.

    FAMILY MEDICINE* Definition Of Family medicine is the medical specialty which provides continuing the biological, clinical and behavioral sciences. The scope of family medicine encompasses all ages, both sexes, each organ system and every disease entity. (1986) (2003) Quality Healthcare In Family Medicine Quality

  17. Definition Is it real?

    E-print Network

    Boisvert, Jeff

    declines Oil Discoveries #12;01-4 Important points · No more very large oil fields. Nearly all new oil01-1 · Definition · Is it real? · Consequences MinE 422: Peak Oil Background · How an oil field has that name for a reason, it is difficult oil · Alternatives ­ Natural gas ­ Coal ­ Biofuels

  18. Developmental Education: A Definition.

    ERIC Educational Resources Information Center

    Beckett, Gene

    A discussion is provided of the distinguishing characteristics of developmental education. First, the reasons for the lack of a clear definition are discussed, and the consequences of this ambiguity are highlighted in terms of the existing confusion over the purposes of developmental education. Next, the linguistic and theoretical bases of…

  19. 3 Library Regulations Definitions

    E-print Network

    Mottram, Nigel

    3 Library Regulations Definitions In Regulation 3: 'Library' means the University Library as defined in Regulation 3.1; 'Library staff' means the staff of the University Library; 'Librarian' means the University Librarian and Head of Information Resources Directorate or nominee; `Library Committee' means

  20. Topological Invariant and Quantum Spin Models from Magnetic ? Fluxes in Correlated Topological Insulators

    E-print Network

    F. F. Assaad; M. Bercx; M. Hohenadler

    2013-02-28

    The adiabatic insertion of a \\pi flux into a quantum spin Hall insulator gives rise to localized spin and charge fluxon states. We demonstrate that \\pi fluxes can be used in exact quantum Monte Carlo simulations to identify a correlated Z_2 topological insulator using the example of the Kane-Mele-Hubbard model. In the presence of repulsive interactions, a \\pi flux gives rise to a Kramers doublet of spinon states with a Curie law signature in the magnetic susceptibility. Electronic correlations also provide a bosonic mode of magnetic excitons with tunable energy that act as exchange particles and mediate a dynamical interaction of adjustable range and strength between spinons. \\pi fluxes can therefore be used to build models of interacting spins. This idea is applied to a three-spin ring and to one-dimensional spin chains. Due to the freedom to create almost arbitrary spin lattices, correlated topological insulators with \\pi fluxes represent a novel kind of quantum simulator potentially useful for numerical simulations and experiments.

  1. Symmetry Enforced Non-Abelian Topological Order at the Surface of a Topological Insulator

    E-print Network

    Chen, Xie; Vishwanath, Ashvin

    2013-01-01

    The surfaces of three dimensional topological insulators (3D TIs) are generally described as Dirac metals, with a single Dirac cone. It was previously believed that a gapped surface implied breaking of either time reversal T or U(1) charge conservation symmetry. Here we discuss a novel possibility in the presence of interactions, a surface phase that preserves all symmetries but is nevertheless gapped and insulating. A requirement is that the surface develops topological order of a kind that cannot be realized in a purely 2D system with the same symmetries. We discuss two candidate surface states - both of which are non-Abelian Fractional Quantum Hall states which, when realized in 2D, have \\sigma_{xy}=1/2 and hence break T symmetry. However, by constructing an exactly soluble 3D lattice model, we show they can be realized as T symmetric surface states. Both the corresponding 3D phases are confined, have \\theta=\\pi magnetoelectric response, and require electrons that are Kramers doublets. The first, the T-Pfa...

  2. Realization of Negative Capacitance with Topological Insulator Based MOS Capacitor

    NASA Astrophysics Data System (ADS)

    Yuan, Hui; Zhang, Kai; Zhu, Hao; Li, Haitao; Ioannou, Dimitris; Baumgart, Helmut; Richter, Curt; Li, Qiliang; ECE, George Mason University Team; Semiconductor and Dimensional Metrology Division of NIST Team; ECE, Old Dominion University Team

    2013-03-01

    Negative capacitance is one of way to achieve steep subthreshold slope exceeding its thermal limit in metal-oxide-semiconductor field effect transistor (MOSFET). The common materials under study for negative capacitance are ferroelectric thin films. However, the integration of regular ferroelectric materials (e.g., PZT) into semiconductor based devices is usually difficult due to the high temperature required for crystallization and precise control of oxygen percentage in ferroelectric materials. In this work, we found that negative capacitance can be achieved by introducing a topological insulator interlayer into a conventional MOS capacitor. Three-dimensional topological insulators inherently contain a insulator/semiconductor bulk and a gapless conducting surface. When an electric field is added to topological insulator interlayer, imbalanced charge carriers (electrons and holes) would be generated and then accumulate on either surface of the film, resulting in a temporary residual polarization. As a result, a ferroelectric-like hysteresis and negative capacitance are achieved. We believe this approach will be very attractive to achieve steep subthreshold using negative capacitance. Negative capacitance is one of way to achieve steep subthreshold slope exceeding its thermal limit in metal-oxide-semiconductor field effect transistor (MOSFET). The common materials under study for negative capacitance are ferroelectric thin films. However, the integration of regular ferroelectric materials (e.g., PZT) into semiconductor based devices is usually difficult due to the high temperature required for crystallization and precise control of oxygen percentage in ferroelectric materials. In this work, we found that negative capacitance can be achieved by introducing a topological insulator interlayer into a conventional MOS capacitor. Three-dimensional topological insulators inherently contain a insulator/semiconductor bulk and a gapless conducting surface. When an electric field is added to topological insulator interlayer, imbalanced charge carriers (electrons and holes) would be generated and then accumulate on either surface of the film, resulting in a temporary residual polarization. As a result, a ferroelectric-like hysteresis and negative capacitance are achieved. We believe this approach will be very attractive to achieve steep subthreshold using negative capacitance. Supported by NSF Career grant 0846649.

  3. Topological interface physics in spinor Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Borgh, Magnus; Ruostekoski, Janne

    2013-05-01

    We present an experimentally viable scheme whereby the physics of coherent interfaces between topologically distinct regions can be studied in an atomic quantum gas. The interface engineering is achieved using the internal spin structures of atoms together with local control over interaction strengths. We consider a coherent interface between polar and ferromagnetic regions of a spin-1 Bose-Einstein condensate and show that defects representing different topologies can connect continuously across the boundary. We show that energy minimization leads to nontrivial interface-crossing defect structures, demonstrating how the method can be used to study stability properties of field-theoretical solitons. We demonstrate, e.g., the formation of a half-quantum vortex arch, an Alice arch, on the interface, exhibiting the topological charge of a point defect. We also demonstrate an energetically stable connection of a coreless vortex to two half-quantum vortices. Our method can be extended to study interface physics in spin-2 and spin-3 BECs with richer phenomenology, or in strongly correlated optical-lattice systems. We present an experimentally viable scheme whereby the physics of coherent interfaces between topologically distinct regions can be studied in an atomic quantum gas. The interface engineering is achieved using the internal spin structures of atoms together with local control over interaction strengths. We consider a coherent interface between polar and ferromagnetic regions of a spin-1 Bose-Einstein condensate and show that defects representing different topologies can connect continuously across the boundary. We show that energy minimization leads to nontrivial interface-crossing defect structures, demonstrating how the method can be used to study stability properties of field-theoretical solitons. We demonstrate, e.g., the formation of a half-quantum vortex arch, an Alice arch, on the interface, exhibiting the topological charge of a point defect. We also demonstrate an energetically stable connection of a coreless vortex to two half-quantum vortices. Our method can be extended to study interface physics in spin-2 and spin-3 BECs with richer phenomenology, or in strongly correlated optical-lattice systems. We acknowledge financial support from the Leverhulme Trust.

  4. Confinement, the Abelian Decomposition, and the Contribution of Topology to the Static Quark Potential

    E-print Network

    Nigel Cundy; Yongmin Cho; Weonjong Lee

    2014-11-04

    In the past few years, we have presented a new way of considering quark confinement. Through a careful choice of a Cho-Duan-Ge Abelian Decomposition, we can construct the QCD Wilson Loop in terms of an Abelian restricted field. The relationship between the QCD and restricted string tensions is exact; and we do not need to gauge fix, apply any path ordering of gauge links, or additional path integrals. This hints at why mesons are colour neutral. Furthermore, the Abelian restricted field contains two parts: a Maxwell term, and a topological term. The topological term can describe magnetic monopoles and other topological objects, which can be studied both numerically and theoretically. By examining the topological part of the restricted field strength we have found evidence suggesting that these objects, which will contribute to confinement if present, are indeed there. Previous studies have used simplifications, breaking the exact relationship between the restricted and QCD string tensions, but it was found that the topological term dominated the restricted string tension. Here we remove those simplifications, and show that the Abelian restricted field does indeed fully explain confinement. However, our results for how much of the restricted string tension arises from the topological objects show strong dependence on the lattice spacing and level of smearing, so we are not yet able to draw a definitive conclusion.

  5. Topological Strings and Integrable Hierarchies

    NASA Astrophysics Data System (ADS)

    Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Mariño, Marcos; Vafa, Cumrun

    2006-01-01

    We consider the topological B-model on local Calabi-Yau geometries. We show how one can solve for the amplitudes by using -algebra symmetries which encode the symmetries of holomorphic diffeomorphisms of the Calabi-Yau. In the highly effective fermionic/brane formulation this leads to a free fermion description of the amplitudes. Furthermore we argue that topological strings on Calabi-Yau geometries provide a unifying picture connecting non-critical (super)strings, integrable hierarchies, and various matrix models. In particular we show how the ordinary matrix model, the double scaling limit of matrix models, and Kontsevich-like matrix model are all related and arise from studying branes in specific local Calabi-Yau three-folds. We also show how an A-model topological string on P1 and local toric threefolds (and in particular the topological vertex) can be realized and solved as B-model topological string amplitudes on a Calabi-Yau manifold.

  6. Cosmological Parameters and Cosmic Topology

    E-print Network

    M. J. Reboucas; J. S. Alcaniz

    2006-04-04

    Geometry constrains but does not dictate the topology of the 3--dimensional space. In a locally spatially homogeneous and isotropic universe, however, the topology of its spatial section dictates its geometry. We show that, besides determining the geometry, the knowledge of the spatial topology through the circles--in--the--sky offers an effective way of setting constraints on the density parameters associated with dark matter ($\\Omega_m$) and dark energy ($\\Omega_{\\Lambda}$). By assuming the Poincar\\'e dodecahedral space as the circles--in--the--sky detectable topology of the spatial sections of the Universe, we re-analyze the constraints on the density parametric plane $\\Omega_{m}$--$ \\Omega_{\\Lambda} $ from the current type Ia supenovae (SNe Ia) plus X-ray gas mass fraction data, and show that a circles--in--the sky detection of the dodecahedral space topology give rise to strong and complementary constraints on the region of the density parameter plane currently allowed by these observational data sets.

  7. Cosmological Parameters and Cosmic Topology

    E-print Network

    Rebouças, M J

    2006-01-01

    Geometry constrains but does not dictate the topology of the 3--dimensional space. In a locally spatially homogeneous and isotropic universe, however, the topology of its spatial section dictates its geometry. We show that, besides determining the geometry, the knowledge of the spatial topology through the circles--in--the--sky offers an effective way of setting constraints on the density parameters associated with dark matter ($\\Omega_m$) and dark energy ($\\Omega_{\\Lambda}$). By assuming the Poincar\\'e dodecahedral space as the circles--in--the--sky detectable topology of the spatial sections of the Universe, we re-analyze the constraints on the density parametric plane $\\Omega_{m}$--$ \\Omega_{\\Lambda} $ from the current type Ia supenovae (SNe Ia) plus X-ray gas mass fraction data, and show that a circles--in--the sky detection of the dodecahedral space topology give rise to strong and complementary constraints on the region of the density parameter plane currently allowed by these observational data sets.

  8. Lifshitz Topological Black Holes

    E-print Network

    R. B. Mann

    2009-05-07

    I find a class of black hole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These black holes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large black holes is almost the same regardless of genus, but differs considerably for small black holes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small black holes.

  9. Quark masses, the Dashen phase, and gauge field topology

    SciTech Connect

    Creutz, Michael, E-mail: creutz@bnl.gov

    2013-12-15

    The CP violating Dashen phase in QCD is predicted by chiral perturbation theory to occur when the up–down quark mass difference becomes sufficiently large at fixed down-quark mass. Before reaching this phase, all physical hadronic masses and scattering amplitudes are expected to behave smoothly with the up-quark mass, even as this mass passes through zero. In Euclidean space, the topological susceptibility of the gauge fields is positive at positive quark masses but diverges to negative infinity as the Dashen phase is approached. A zero in this susceptibility provides a tentative signal for the point where the mass of the up quark vanishes. I discuss potential ambiguities with this determination. -- Highlights: •The CP violating Dashen phase in QCD occurs when the up quark mass becomes sufficiently negative. •Before reaching this phase, all physical hadronic masses and scattering amplitudes behave smoothly with the up-quark mass. •The topological susceptibility of the gauge fields diverges to negative infinity as the Dashen phase is approached. •A zero in the topological susceptibility provides a tentative signal for the point where the mass of the up quark vanishes. •The universality of this definition remains unproven. Potential ambiguities are discussed.

  10. Topological invariants and the ground state wavefunction of topological insulators

    NASA Astrophysics Data System (ADS)

    Wang, Zhong; Zhang, Shou-Cheng

    2014-03-01

    We will talk about precise topological invariants defined in terms of the ground state wavefuntion. The Hall coefficients in even spatial dimensions and the magnetoelectric theta terms in odd spatial dimensions are expressed in terms of the ground state wavefunctions under generalized twisted-boundary conditions. This formulation is valid in the presence of arbitrary interaction and disorder, in particular, it is applicable to both integer and fractional topological insulators. (arXiv:1308.4900) Supported by Tsinghua University Initiative Scientific Research Program (No. 20121087986).

  11. Electrical control of spin in topological insulators

    NASA Astrophysics Data System (ADS)

    Chang, Kai

    2012-02-01

    All-electrical manipulation of electron spin in solids becomes a central issue of quantum information processing and quantum computing. The many previous proposals are based on spin-orbit interactions in semiconductors. Topological insulator, a strong spin-orbit coupling system, make it possible to control the spin transport electrically. Recent calculations proved that external electric fields can drive a HgTe quantum well from normal band insulator phase to topological insulator phase [1]. Since the topological edge states are robust against local perturbation, the controlling of edge states using local fields is a challenging task. We demonstrate that a p-n junction created electrically in HgTe quantum wells with inverted band structure exhibits interesting intraband and interband tunneling processes. We find a perfect intraband transmission for electrons injected perpendicularly to the interface of the p-n junction. The opacity and transparency of electrons through the p-n junction can be tuned by changing the incidence angle, the Fermi energy and the strength of the Rashba spin-orbit interaction (RSOI). The occurrence of a conductance plateau due to the formation of topological edge states in a quasi-one-dimensional p-n junction can be switched on and off by tuning the gate voltage. The spin orientation can be substantially rotated when the samples exhibit a moderately strong RSOI [2]. An electrical switching of the edge-state transport can also be realized using quantum point contacts in quantum spin Hall bars. The switch-on/off of the edge channel is caused by the finite size effect of the quantum point contact and therefore can be manipulated by tuning the voltage applied on the split gate [3,4]. The magnetic ions doped on the surface of 3D TI can be correlated through the helical electrons. The RKKY interaction mediated by the helical Dirac electrons consists of the Heisenberg-like, Ising-like, and Dzyaloshinskii-Moriya (DM)-like terms, which can be tuned by changing the gate voltage. It provides us a new way to control surface magnetism electrically. The gap opened by doped magnetic ions can lead to a short-range Bloembergen-Rowland interaction. The competition among the Heisenberg, Ising, and DM terms leads to rich spin configurations and an anomalous Hall effect on different lattices [4]. There are many proposals for quantum computation scheme are based on the spin in semiconductor quantum dots. Topological insulator quantum dots display a very different behavior with that of conventional semiconductor quantum dots [5]. In sharp contrast to conventional semiconductor quantum dots, the quantum states in the gap of the HgTe QD are fully spin-polarized and show ring-like density distributions near the boundary of the QD and optically dark. The persistent charge currents and magnetic moments, i.e., the Aharonov-Bohm effect, can be observed in such a QD structure. This feature offers us a practical way to detect these exotic ring-like edge states by using the SQUID technique. [0pt]Refs: [1] W. Yang, Kai Chang, and S. C. Zhang, Phys. Rev. Lett. 100, 056602 (2008); J. Li and Kai Chang, Appl. Phys. Lett. 95, 222110 (2009). [2] L. B. Zhang, Kai Chang, X. C. Xie, H. Buhmann and L. W. Molenkamp, New J. Phys. 12, 083058 (2010). [3] L. B. Zhang, F. Cheng, F. Zhai and Kai Chang, Phys. Rev. B 83 081402(R) (2011); Z. H. Wu, F. Zhai, F. M. Peeters, H. Q. Xu and Kai Chang, Phys, Rev. Lett. 106, 176802 (2011). [4] J. J. Zhu, D. X. Yao, S. C. Zhang, and Kai Chang, Phys. Rev. Lett. 106, 097201 (2011). [5] Kai Chang, and Wen-Kai Lou, Phys. Rev. Lett. 106, 206802 (2011).

  12. APPENDIX C. USEFUL DEFINITE INTEGRALS 1 Useful Definite Integrals

    E-print Network

    Callen, James D.

    APPENDIX C. USEFUL DEFINITE INTEGRALS 1 Appendix C Useful Definite Integrals Definite integrals that often arise in plasma physics are summarized in this appendix. C.1 Integrals Involving A Decaying/) often result in integrals of the form 0 dt tn e-t/ = n+1 0 dx xn e-x (C.1) in which x t/. The most

  13. Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3

    NASA Astrophysics Data System (ADS)

    Kim, Dohun; Cho, Sungjae; Butch, Nicholas P.; Syers, Paul; Kirshenbaum, Kevin; Adam, Shaffique; Paglione, Johnpierre; Fuhrer, Michael S.

    2012-06-01

    The newly discovered three-dimensional strong topological insulators (STIs) exhibit topologically protected Dirac surface states. Although the STI surface state has been studied spectroscopically, for example, by photoemission and scanned probes, transport experiments have failed to demonstrate the most fundamental signature of the STI: ambipolar metallic electronic transport in the topological surface of an insulating bulk. Here we show that the surfaces of thin (~ 10nm), low-doped Bi2Se3 (~1017cm-3) crystals are strongly electrostatically coupled, and a gate electrode can completely remove bulk charge carriers and bring both surfaces through the Dirac point simultaneously. We observe clear surface band conduction with a linear Hall resistivity and a well-defined ambipolar field effect, as well as a charge-inhomogeneous minimum conductivity region. A theory of charge disorder in a Dirac band explains well both the magnitude and the variation with disorder strength of the minimum conductivity (2 to 5 e2/h per surface) and the residual (puddle) carrier density (0.4×1012 to 4×1012cm-2). From the measured carrier mobilities 320-1,500cm2V-1s-1, the charged impurity densities 0.5×1013 to 2.3×1013cm-2 are inferred. They are of a similar magnitude to the measured doping levels at zero gate voltage (1×1013 to 3×1013cm-2), identifying dopants as the charged impurities.

  14. Formation of a topological non-Fermi liquid in MnSi.

    PubMed

    Ritz, R; Halder, M; Wagner, M; Franz, C; Bauer, A; Pfleiderer, C

    2013-05-01

    Fermi liquid theory provides a remarkably powerful framework for the description of the conduction electrons in metals and their ordering phenomena, such as superconductivity, ferromagnetism, and spin- and charge-density-wave order. A different class of ordering phenomena of great interest concerns spin configurations that are topologically protected, that is, their topology can be destroyed only by forcing the average magnetization locally to zero. Examples of such configurations are hedgehogs (points at which all spins are either pointing inwards or outwards) and vortices. A central question concerns the nature of the metallic state in the presence of such topologically distinct spin textures. Here we report a high-pressure study of the metallic state at the border of the skyrmion lattice in MnSi, which represents a new form of magnetic order composed of topologically non-trivial vortices. When long-range magnetic order is suppressed under pressure, the key characteristic of the skyrmion lattice--that is, the topological Hall signal due to the emergent magnetic flux associated with the topological winding--is unaffected in sign or magnitude and becomes an important characteristic of the metallic state. The regime of the topological Hall signal in temperature, pressure and magnetic field coincides thereby with the exceptionally extended regime of a pronounced non-Fermi-liquid resistivity. The observation of this topological Hall signal in the regime of the NFL resistivity suggests empirically that spin correlations with non-trivial topological character may drive a breakdown of Fermi liquid theory in pure metals. PMID:23636328

  15. Topological insulators and the QCD vacuum: the theta parameter as a Berry phase

    E-print Network

    Thacker, H B

    2013-01-01

    There is considerable evidence, based on large $N_c$ chiral dynamics, holographic QCD, and Monte Carlo studies, that the QCD vacuum is permeated by discrete quasivacua separated by domain walls across which the local value of the topological $\\theta$ parameter jumps by $\\pm2\\pi$. In the 2-dimensional $CP^{N-1}$ sigma model, a pointlike charge is a domain wall, and $\\theta$ describes the background electric flux and the polarization of charged pairs in the vacuum. We show that the screening process, and the role of $\\theta$ as an order parameter describing electric polarization, are naturally formulated in terms of Bloch wave eigenstates of the Dirac Hamiltonian in the background gauge field. This formulation is similar to the Berry phase description of electric polarization and quantized charge transport in topological insulators. The Bloch waves are quasiperiodic superpositions of localized Dirac zero modes. They define a Berry connection around the Brillouin zone of the zero mode band which describes the lo...

  16. Positive Topological Quantum Field Theories

    E-print Network

    Markus Banagl

    2013-03-18

    We propose a new notion of positivity for topological field theories (TFTs), based on S. Eilenberg's concept of completeness for semirings. We show that a complete ground semiring, a system of fields on manifolds and a system of action functionals on these fields determine a positive TFT. The main feature of such a theory is a semiring-valued topologically invariant state sum that satisfies a gluing formula. The abstract framework has been carefully designed to cover a wide range of phenomena. For instance, we derive Polya's counting theory in combinatorics from state sum identities in a suitable positive TFT. Several other concrete examples are discussed, among them Novikov signatures of fiber bundles over spacetimes and arithmetic functions in number theory. In the future, we will employ the framework presented here in constructing a new differential topological invariant that detects exotic smooth structures on spheres.

  17. Search for New Topological Insulators

    NASA Astrophysics Data System (ADS)

    Lin, Hsin; Wray, L. A.; Xu, S.-Y.; Hasan, M. Z.; Das, T.; Wang, Y. J.; Markiewicz, R. S.; Bansil, Arun

    2011-03-01

    Topological insulators (TIs) host a novel quantum phase of electrons which is characterized by topologically protected surface states originating from the effects of spin-orbit and time-reversal symmetries. While several families of TIs have already been found, the intense world-wide search for new classes of TIs continues unabated. This interest is driven by the need for materials with greater structural flexibility and tunability to enable viable applications in spintronics and quantum computing. We have used first-principles band theory computations in combination with angle-resolved photoemission experiments to successfully predict many new classes of topologically interesting materials, including Bi2Se3 series, the ternary half-Heusler compounds, thallium-based chalcogenides, and the Li2AgSb and Ge n Bi 2m Te 3m+n families. [1-5] Work supported by the Office of Basic Energy Sciences, US DOE.

  18. Accurately modeling the internet topology.

    PubMed

    Zhou, Shi; Mondragón, Raúl J

    2004-12-01

    Based on measurements of the internet topology data, we found that there are two mechanisms which are necessary for the correct modeling of the internet topology at the autonomous systems (AS) level: the interactive growth of new nodes and new internal links, and a nonlinear preferential attachment, where the preference probability is described by a positive-feedback mechanism. Based on the above mechanisms, we introduce the positive-feedback preference (PFP) model which accurately reproduces many topological properties of the AS-level internet, including degree distribution, rich-club connectivity, the maximum degree, shortest path length, short cycles, disassortative mixing, and betweenness centrality. The PFP model is a phenomenological model which provides an insight into the evolutionary dynamics of real complex networks. PMID:15697435

  19. Interaction effects of a topological Dirac semimetal Na3Bi

    NASA Astrophysics Data System (ADS)

    Zhang, Ruixing; Hutasoit, Jimmy; Liu, Chaoxing

    2015-03-01

    We study the interaction effects of a topological Dirac semimetal Na3Bi based on the mean field theory. The phase diagram can be classified by two kinds of chiral-symmetry-breaking order parameters: nematic orders that break rotational symmetry and charge-density-wave (CDW) order that break translational symmetry. Under strong magnetic field, gapless Landau levels will be formed and result in instabilities due to the above order parameters. These order parameters are generally complex, and are identified as complex mass terms, which introduce axions into the low energy theory. The possible experimental consequence is also studied.

  20. Topological interactions in spacetimes with thick line defects

    NASA Astrophysics Data System (ADS)

    Moraes, Fernando; Carvalho, A. M.; Costa, Ismael V.; Oliveira, F. A.; Furtado, Claudio

    2003-08-01

    In this work we study the topologically induced electric self-energy and self-force on a long, straight, wire in two distinct, but similar, spacetimes: (i) the Gott-Hiscock thick cosmic string spacetime, and (ii) the spacetime of a continuous distribution of infinitely thin cosmic strings over a disk of finite radius. In each case we obtain the electric self-energy and self-force both in the internal and external regions of the defect distribution. The self-force is always repulsive, independently of the sign of the charge, and is maximum on the string’s surface, in both cases.

  1. (De)confinement of supercurrent in Z_2 Topological Insulators

    E-print Network

    Jun Goryo; Nobuki Maeda; Ken-Ichiro Imura

    2010-07-12

    It is shown that the electric supercurrent flows in a Z_2 topological insulator with U_em(1) X U_z(1) (electromagnetic and spin) gauge symmetries. When U_z(1) is broken, a dissipationless electric current is still possible to flow locally but net charge transfer is absent, i.e., current is confined. In the Kane-Mele model for graphene, this confining-deconfining (superconducting) transition is driven by the Rashba spin-orbit interaction, which breaks U_z(1).

  2. Heliumlike and lithiumlike ionic sequences: Critical charges

    SciTech Connect

    Guevara, N. L.; Turbiner, A. V. [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico, D.F. (Mexico)

    2011-12-15

    In nonrelativistic quantum mechanics we study the Coulomb systems of infinitely massive center of charge Z and two-three electrons: (Z,e,e) and (Z,e,e,e). It is shown that in both cases the total energy curve in Z is smooth, without any visible irregularities. Thus, for both systems the physical integer charges Z=1, 2,... do not play a distinguished role as would be associated with charge quantization. By definition, a critical charge Z{sub cr} is a charge which separates a domain of the existence of bound states from a domain of unbound ones (continuum). For both systems the critical charges are found, Z{sub cr,2e}=0.910850 and Z{sub cr,3e}=2.0090, respectively. Based on numerical analysis, the Puiseux expansion in fractional powers of (Z-Z{sub cr}) is constructed for both systems. Our results indicate the existence of a square-root branch point singularity at Z{sub cr} with exponent 3/2. A connection between the critical charge and the radius of convergence of 1/Z expansion is briefly discussed.

  3. Magnetotransport in Thin Films and Heterostructures of Topological Matter

    NASA Astrophysics Data System (ADS)

    Assaf, Badih Assaf

    Topological insulators are semiconducting materials that host spin-momentum locked surface Dirac Fermions. These massless surface states occur as a result of a symmetry-protected band crossing. The effective mass of surface electrons can be tuned by breaking that symmetry. Such materials are thus attractive for technological applications as they allow one to manipulate the charge, spin and effective mass of electrons in devices. The surface states are, however, difficult to access and manipulate using conventional electrical probes, as the underlying bulk is not usually insulating. In this thesis, we have studied electrical transport in two prototypical topological systems, Bi2Te2Se---belonging to the class of Z2 topological insulators, and SnTe---a topological crystalline insulator. We also looked at how the breaking of crystalline symmetry by proximity to a ferromagnet alters the transport in SnTe. We grew Bi2Te2Se thin films by molecular beam epitaxy (MBE) on Si(111) and studied the magnetoresistance (MR), which was found to exhibit weak antilocalization (WAL) at low fields and linear MR at high fields. By proposing a model that accounts for both WAL and the linear MR simultaneously, we were able to separate the MR contribution of topological surface-states from that of Rashba spin-orbit split bulk states. In SnTe thin films, also grown by MBE on BaF2(001) and Si(001), we demonstrated that film crystallinity, morphology, carrier density and mobility all improve with increasing growth temperature. By studying WAL in different films, it was found that valley coupling reduced the measured number of WAL channels. This is a direct consequence of the degenerate surface bands of SnTe. Changes in the shape of the bulk Fermi surface were also seen to influence the measured number of WAL channels. Proximity-induced magnetism was observed in a SnTe-EuS heterostructure though the anomalous Hall effect. The observation of an isotropic hysteretic MR was shown to be evidence of domain-wall-supported, one-dimensional conduction as previously hypothesized for Bi2Se3-EuS. As we enter the exciting era of topological condensed matter physics, these results will be important to the development of future device ideas relying on the manipulation of topological surface states.

  4. Electronic transport in bismuth selenide in the topological insulator regime

    NASA Astrophysics Data System (ADS)

    Kim, Dohun

    The 3D topological insulators (TIs) have an insulating bulk but spin-momentum coupled metallic surface states stemming from band inversion due to strong spin-orbit interaction, whose existence is guaranteed by the topology of the band structure of the insulator. While the STI surface state has been studied spectroscopically by e.g. photoemission and scanned probes, transport experiments have failed to demonstrate clear signature of the STI due to high level of bulk conduction. In this thesis, I present experimental results on the transport properties of TI material Bi2Se3 in the absence of bulk conduction (TI regime), achieved by applying novel p-type doping methods. Field effect transistors consisting of thin (thickness: 5-17 nm) Bi2Se3 are fabricated by mechanical exfoliation of single crystals, and a combination of conventional dielectric (300 nm thick SiO2) and electrochemical or chemical gating methods are used to move the Fermi energy through the surface Dirac point inside bulk band gap, revealing the ambipolar gapless nature of transport in the Bi2Se3 surface states. The minimum conductivity of the topological surface state is understood within the self-consistent theory of Dirac electrons in the presence of charged impurities. The intrinsic finite-temperature resistivity of the topological surface state due to electron-acoustic phonon scattering is measured to be 60 times larger than that of graphene largely due to the smaller Fermi and sound velocities in Bi2Se 3, which will have implications for topological electronic devices operating at room temperature. Along with semi-classical Boltzmann transport, I also discuss 2D weak anti-localization (WAL) behavior of the topological surface states. By investigating gate-tuned WAL behavior in thin (5-17 nm) TI films, I show that WAL in the TI regime is extraordinarily sensitive to the hybridization induced quantum mechanical tunneling between top and bottom topological surfaces, and interplay of phase coherence time and inter-surface tunneling time results in a crossover from two decoupled (top and bottom) symplectic 2D metal surfaces to a coherently coupled single channel. Furthermore, a complete suppression of WAL is observed in the 5 nm thick Bi2Se 3 film which was found to occur when the hybridization gap becomes comparable to the disorder strength.

  5. The definition of cross polarization.

    NASA Technical Reports Server (NTRS)

    Ludwig, A. C.

    1973-01-01

    Consideration of three alternate definitions of cross-polarization known to the author. The three definitions are expressed precisely in terms of the same antenna pattern coordinate system, and the relative merits of the various definitions are discussed. One of the definitions is shown to be the proper choice for describing source current polarizations, another is suitable for relating source current distributions to secondary patterns, and the third is the best choice for describing antenna patterns.

  6. Exploring and Improving BitTorrent Topologies

    E-print Network

    ]CDFofconnections #12;Evaluation: topology sample size 58% peers cannot be scanned 42% 58% #12;Evaluation: topology sample size 58% peers cannot be scanned 42% 58% But we can scan either endpoint of a connection: 67% 33

  7. Topological Hochschild homology of twisted group algebras

    E-print Network

    Vera, Daniel Joseph

    2006-01-01

    Let G be a group and A be a ring. There is a stable equivalence of orthogonal spectra ... between the topological Hochschild homology of the group algebra A[G] and the smash product of the topological Hochschild homology ...

  8. Topological States and Adiabatic Pumping in Quasicrystals

    E-print Network

    Yaacov E. Kraus; Yoav Lahini; Zohar Ringel; Mor Verbin; Oded Zilberberg

    2012-09-17

    The unrelated discoveries of quasicrystals and topological insulators have in turn challenged prevailing paradigms in condensed-matter physics. We find a surprising connection between quasicrystals and topological phases of matter: (i) quasicrystals exhibit nontrivial topological properties and (ii) these properties are attributed to dimensions higher than that of the quasicrystal. Specifically, we show, both theoretically and experimentally, that one-dimensional quasicrystals are assigned two-dimensional Chern numbers and, respectively, exhibit topologically protected boundary states equivalent to the edge states of a two-dimensional quantum Hall system.We harness the topological nature of these states to adiabatically pump light across the quasicrystal. We generalize our results to higher-dimensional systems and other topological indices. Hence, quasicrystals offer a new platform for the study of topological phases while their topology may better explain their surface properties.

  9. Topological States and adiabatic pumping in quasicrystals.

    PubMed

    Kraus, Yaacov E; Lahini, Yoav; Ringel, Zohar; Verbin, Mor; Zilberberg, Oded

    2012-09-01

    The unrelated discoveries of quasicrystals and topological insulators have in turn challenged prevailing paradigms in condensed-matter physics. We find a surprising connection between quasicrystals and topological phases of matter: (i) quasicrystals exhibit nontrivial topological properties and (ii) these properties are attributed to dimensions higher than that of the quasicrystal. Specifically, we show, both theoretically and experimentally, that one-dimensional quasicrystals are assigned two-dimensional Chern numbers and, respectively, exhibit topologically protected boundary states equivalent to the edge states of a two-dimensional quantum Hall system. We harness the topological nature of these states to adiabatically pump light across the quasicrystal. We generalize our results to higher-dimensional systems and other topological indices. Hence, quasicrystals offer a new platform for the study of topological phases while their topology may better explain their surface properties. PMID:23005308

  10. Topological States and Adiabatic Pumping in Quasicrystals

    E-print Network

    Kraus, Yaacov E; Ringel, Zohar; Verbin, Mor; Zilberberg, Oded

    2011-01-01

    The discovery of topological insulators has sparked considerable interest in the study of topological phases of matter. The hallmark of these novel phases is the emergence of topologically protected boundary phenomena, e.g. quantum pumping, surface states related to exotic models from particle physics, and quasi-particles with non-Abelian statistics. Yet, realizations of these phases of matter are scarce. Moreover, one-dimensional systems without any additional symmetries are considered to lack such topological phenomena. Here we show, both theoretically and experimentally, that quasicrystals reveal new types of topological phases. We demonstrate that one-dimensional quasicrystals exhibit topological properties that were, thus far, thought to be limited to two-dimensional systems. Using photonic quasicrystals, we observe localized boundary states, which manifest these topological properties. These topological boundary states are used to realize an adiabatic optical pumping effect in which photons are uni-dire...

  11. Topology-Aware Vulnerability Mitigation Worms

    E-print Network

    Sheldon, Nathan D.

    Topology-Aware Vulnerability Mitigation Worms Defensive Worms Ziyad S. AL-Salloum Thesis submitted-set. Clear area Royal Holloway logo guidelines 2011 #12;#12;Topology-Aware Vulnerability Mitigation Worms

  12. Quantum cosmology with nontrivial topologies

    SciTech Connect

    Vargas, T. [Department of Physics and Center for Mathematics and Theoretical Physics, National Central University, Chungli 320, Taiwan (China)

    2008-10-10

    Quantum creation of a universe with a nontrivial spatial topology is considered. Using the Euclidean functional integral prescription, we calculate the wave function of such a universe with cosmological constant and without matter. The minisuperspace path integral is calculated in the semiclassical approximation, and it is shown that in order to include the nontrivial topologies in the path integral approach to quantum cosmology, it is necessary to generalize the sum over compact and smooth 4-manifolds to sum over finite-volume compact 4-orbifolds.

  13. Topological transitions in spin interferometers

    NASA Astrophysics Data System (ADS)

    Saarikoski, Henri; Vázquez-Lozano, J. Enrique; Baltanás, José Pablo; Nagasawa, Fumiya; Nitta, Junsaku; Frustaglia, Diego

    2015-06-01

    We show that topological transitions in electronic spin transport are feasible by a controlled manipulation of spin-guiding fields. The transitions are determined by the topology of the fields texture through an effective Berry phase (related to the winding parity of spin modes around poles in the Bloch sphere), irrespective of the actual complexity of the nonadiabatic spin dynamics. This manifests as a distinct dislocation of the interference pattern in the quantum conductance of mesoscopic loops. The phenomenon is robust against disorder, and can be experimentally exploited to determine the magnitude of inner spin-orbit fields.

  14. Conserved charges of order-parameter textures in Dirac systems

    E-print Network

    Igor F. Herbut; Chi-Ken Lu; Bitan Roy

    2012-08-31

    A simple expression for the induced fermion current in the presence of a texture in mass-order-parameters in two-dimensional condensed-matter Dirac systems is derived using the representation theory of Clifford algebras. In particular, it is shown that every texture in three mutually anticommuting order parameters, in graphene for example, implies an induced density of a properly defined conserved charge. The sufficient condition for the general charge to be the familiar electrical charge is that the remaining two anticommuting order parameters allowed by the particle-hole symmetry are the two phase components of some superconducting order. This allows eight different types of electrically charged textures in graphene or in the $\\pi$-flux Hamiltonian on the square lattice. Generalized charge of mass-textures on the surfaces of thin films of topological insulators, or in spinless Dirac fermions hopping on the honeycomb lattice is also discussed.

  15. Magnetic End States in a Strongly Interacting One-Dimensional Topological Kondo Insulator

    NASA Astrophysics Data System (ADS)

    Lobos, Alejandro M.; Dobry, Ariel O.; Galitski, Victor

    2015-04-01

    Topological Kondo insulators are strongly correlated materials where itinerant electrons hybridize with localized spins, giving rise to a topologically nontrivial band structure. Here, we use nonperturbative bosonization and renormalization-group techniques to study theoretically a one-dimensional topological Kondo insulator, described as a Kondo-Heisenberg model, where the Heisenberg spin-1 /2 chain is coupled to a Hubbard chain through a Kondo exchange interaction in the p -wave channel (i.e., a strongly correlated version of the prototypical Tamm-Schockley model). We derive and solve renormalization-group equations at two-loop order in the Kondo parameter, and find that, at half filling, the charge degrees of freedom in the Hubbard chain acquire a Mott gap, even in the case of a noninteracting conduction band (Hubbard parameter U =0 ). Furthermore, at low enough temperatures, the system maps onto a spin-1 /2 ladder with local ferromagnetic interactions along the rungs, effectively locking the spin degrees of freedom into a spin-1 chain with frozen charge degrees of freedom. This structure behaves as a spin-1 Haldane chain, a prototypical interacting topological spin model, and features two magnetic spin-1 /2 end states for chains with open boundary conditions. Our analysis allows us to derive an insightful connection between topological Kondo insulators in one spatial dimension and the well-known physics of the Haldane chain, showing that the ground state of the former is qualitatively different from the predictions of the naive mean-field theory.

  16. Non-topological nature of the edge current in a chiral p-wave superconductor

    NASA Astrophysics Data System (ADS)

    Taylor, Edward; Huang, Wen; Lederer, Samuel; Kallin, Catherine

    2015-03-01

    The edges of time reversal symmetry breaking topological superconductors support chiral Majorana bound states as well as spontaneous charge currents. The Majorana modes are a robust, topological property, but the charge currents are non-topological-and therefore sensitive to microscopic details-even if we neglect Meissner screening. We give insight into the non-topological nature of edge currents in chiral p-wave superconductors using a variety of theoretical techniques, including lattice Bogoliubov-de Gennes equations, the quasiclassical approximation, and the gradient expansion, and describe those special cases where edge currents do have a topological character. While edge currents are not quantized, they are generically large, but can be substantially reduced for a sufficiently anisotropic gap function, a scenario of possible relevance for the putative chiral p-wave superconductor Sr2RuO4 . Supported by NSERC and CIFAR at McMaster and by the Canada Research Chair and Canada Council Killam programs and NSF Grant No. NSF PHY11-25915 (CK). SL is supported by the DOE Office of Basic Energy Sciences, contract DEAC02-76SF00515

  17. The discovery of topological insulators and possible topological superconductors has greatly expanded research into

    E-print Network

    Weston, Ken

    The discovery of topological insulators and possible topological superconductors has greatly Superconductor, a Copper-doped Topological Insulator: Cu1/4Bi2Se3 Ben J. Lawson1, Y. S. Hor2, J. Mannhart3, Lu Li in CuxBi2Se3 and its implications for pairing in the undoped topological insulator" PRL, 104, 057001

  18. Robustness of topological order and formation of quantum well states in topological insulators

    E-print Network

    Wang, Wei Hua

    Robustness of topological order and formation of quantum well states in topological insulators (like transport measurements) and ultimate application of the topological insulators usually in- volve-resolved photoemission measurements to directly probe the surface state of the prototypical topological insulators, Bi2Se

  19. Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator

    Microsoft Academic Search

    Su-Yang Xu; Y. Xia; L. A. Wray; S. Jia; F. Meier; J. H. Dil; J. Osterwalder; B. Slomski; A. Bansil; H. Lin; R. J. Cava; M. Z. Hasan

    2011-01-01

    The recently discovered three-dimensional or bulk topological insulators are expected to exhibit exotic quantum phenomena. It is believed that a trivial insulator can be twisted into a topological state by modulating the spin-orbit interaction or the crystal lattice, driving the system through a topological quantum phase transition. By directly measuring the topological quantum numbers and invariants, we report the observation

  20. Classification of Intelligent Agent Network Topologies and a New Topological Description Language for Agent Networks

    Microsoft Academic Search

    Hao Lan Zhang; Clement H. C. Leung; Gitesh K. Raikundalia

    2006-01-01

    Topological theory of intelligent agent networks provides crucial information about the structure of agent distribution over a network. Agent network topologies not only take agent distribution into consideration but also consider agent mobility and intelligence in a network. Current research in the agent network topology area adopts topological theory from the distributed system and computing network fields without considering mobility

  1. Definitions Algebra of complex numbers

    E-print Network

    Lega, Joceline

    Definitions Algebra of complex numbers Polar coordinates form of complex numbers Check your knowledge Review of Complex Numbers Definitions, Algebra of complex numbers, Polar coordinates Review of Complex Numbers #12;Definitions Algebra of complex numbers Polar coordinates form of complex numbers Check

  2. THE DEFINITE INTEGRAL AND COMPUTER

    Microsoft Academic Search

    Dragoslav Herceg

    2009-01-01

    In this paper the results of the learning concept of definite integral and numeric integration with the computer is presented. The tested students attend ?Sabac Chemical Technological college. The aim of this test was to check the student's theoretical, visual and practical knowledge of definite integral. In almost all secondary schools definite integral and its applications are studied. The concept

  3. Integrated Charger with Wireless Charging and Boost Function for PHEV and EV Applications

    SciTech Connect

    Chinthavali, Madhu Sudhan [ORNL; Onar, Omer C [ORNL; Campbell, Steven L [ORNL

    2015-01-01

    Integrated charger topologies that have been researched so far with dc-dc converters and the charging functionality have no isolation in the system. Isolation is an important feature that is required for user interface systems that have grid connections and therefore is a major limitation that needs to be addressed along with the integrated functionality. The topology proposed in this paper is a unique and a first of its kind topology that integrates a wireless charging system and the boost converter for the traction drive system. The new topology is also compared with an on-board charger system from a commercial electric vehicle (EV). The ac-dc efficiency of the proposed system is 85.05% and the specific power and power density of the onboard components is ~455 W/kg and ~302 W/ .

  4. Universal transport signatures of topological superconductivity in quantum spin Hall architectures

    NASA Astrophysics Data System (ADS)

    Lee, Shu-Ping; Aasen, David; Karzig, Torsten; Alicea, Jason

    2015-03-01

    Interfacing s-wave superconductors with quantum spin Hall systems provides a promising route to ``engineered'' topological superconductivity. Given exciting recent progress on the fabrication side, identifying experiments that definitively expose the topological superconducting phase (and clearly distinguish it from a trivial state) raises an increasingly important problem. With this goal in mind we use renormalization group methods to extract universal transport characteristics of superconductor/quantum spin Hall heterostructures where the native edge states serve as a lead. Interestingly, arbitrarily weak interactions induce qualitative changes in the behavior relative to the free-fermion limit, leading to a sharp dichotomy in conductance for the trivial (narrow superconductor) and topological (wide superconductor) cases. Furthermore, we find that strong interactions can in principle induce power-law-localized ``parafermion'' excitations at a superconductor/quantum spin Hall junction. NSF Grant DMR-1341822. (2) Institute for Quantum Information and Matter, an NSF physics frontier center with support from the Moore Foundation.

  5. Research and Implement of an Algorithm for Physical Topology Automatic Discovery in Switched Ethernet

    NASA Astrophysics Data System (ADS)

    Xiong, Yuting; Gu, Zhaojun; Jin, Wei

    In this paper, a novel practical algorithmic solution for automatic discovering the physical topology of switched Ethernet was proposed. Our algorithm collects standard SNMP MIB information that is widely supported in modern IP networks and then builds the physical topology of the active network. We described the relative definitions, system model and proved the correctness of the algorithm. Practically, the algorithm was implemented in our visualization network monitoring system. We also presented the main steps of the algorithm, core codes and running results on the lab network. The experimental results clearly validate our approach, demonstrating that our algorithm is simple and effective which can discover the accurate up-to-date physical network topology.

  6. CT number definition

    NASA Astrophysics Data System (ADS)

    Bryant, J. A.; Drage, N. A.; Richmond, S.

    2012-04-01

    The accuracy of CT number plots has been found lacking in several medical applications. This is of concern since the ability to compare and evaluate results on a reproducible and standard basis is essential to long term development. Apart from the technical limitations arising from the CT scanner and the data treatment, there are fundamental issues with the definition of the Hounsfield number, namely the absence of a standard photon energy and the need to specify the attenuation mechanism for standard measurements. This paper presents calculations to demonstrate the shortcomings of the present definition with a brief discussion. The remedy is straightforward, but probably of long duration as it would require an international agreement.

  7. Information systems definition architecture

    SciTech Connect

    Calapristi, A.J.

    1996-06-20

    The Tank Waste Remediation System (TWRS) Information Systems Definition architecture evaluated information Management (IM) processes in several key organizations. The intent of the study is to identify improvements in TWRS IM processes that will enable better support to the TWRS mission, and accommodate changes in TWRS business environment. The ultimate goals of the study are to reduce IM costs, Manage the configuration of TWRS IM elements, and improve IM-related process performance.

  8. Definitions: Types of Commissioning

    E-print Network

    Martinez, J. T.

    2014-01-01

    Workshop on the Continuous Commissioning® Process Joseph T. Martinez, PCC Carlos Yagua, PE Hiroko Masuda, Juan-Carlos Baltazar, PhD, PE Ahmet Ugursal, PhD Clean Air Through Energy Efficiency (CATEE) Conference, Dallas, Texas. November 18, 2014... 5. Continuous Commissioning Measures 6. Measurement and Verification ESL-KT-14-11-41 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas Nov. 18-20 Definitions: Types of Commissioning Joseph T. Martinez, PCC Carlos Yagua, PE Hiroko...

  9. Photons as quasi-charged particles

    E-print Network

    K. -P. Marzlin; Juergen Appel; A. I. Lvovsky

    2007-10-16

    The Schrodinger motion of a charged quantum particle in an electromagnetic potential can be simulated by the paraxial dynamics of photons propagating through a spatially inhomogeneous medium. The inhomogeneity induces geometric effects that generate an artificial vector potential to which signal photons are coupled. This phenomenon can be implemented with slow light propagating through an a gas of double-Lambda atoms in an electromagnetically-induced transparency setting with spatially varied control fields. It can lead to a reduced dispersion of signal photons and a topological phase shift of Aharonov-Bohm type.

  10. A computational investigation of topological insulator Bi2Se3 film

    NASA Astrophysics Data System (ADS)

    Hu, Yi-Bin; Zhao, Yong-Hong; Wang, Xue-Feng

    2014-12-01

    Topological insulators have a bulk band gap like an ordinary insulator and conducting states on their edge or surface which are formed by spin-orbit coupling and protected by time-reversal symmetry. We report theoretical analyses of the electronic properties of three-dimensional topological insulator Bi2Se3 film on different energies. We choose five different energies (-123, -75, 0, 180, 350 meV) around the Dirac cone (-113 meV). When energy is close to the Dirac cone, the properties of wave function match the topological insulator's hallmark perfectly. When energy is far way from the Dirac cone, the hallmark of topological insulator is broken and the helical states disappear. The electronic properties of helical states are dug out from the calculation results. The spin-momentum locking of the helical states are confirmed. A 3-fold symmetry of the helical states in Brillouin zone is also revealed. The penetration depth of the helical states is two quintuple layers which can be identified from layer projection. The charge contribution on each quintuple layer depends on the energy, and has completely different behavior along K and M direction in Brillouin zone. From orbital projection, we can find that the maximum charge contribution of the helical states is p z orbit and the charge contribution on p y and p x orbits have 2-fold symmetry.

  11. ?-relaxed approach in structural topology optimization

    Microsoft Academic Search

    G. D. Cheng; X. Guo

    1997-01-01

    This paper presents a so-called e-relaxed approach for structural topology optimization problems of discrete structures. The distinctive feature of this new approach is that unlike the typical treatment of topology optimization problems based on the ground structure approach, we eliminate the singular optima from the problem formulation and thus unify the sizing and topology optimization within the same framework. As

  12. Topologies for hybrid solutions Dmitry Gokhman

    E-print Network

    Gokhman, Dmitry

    analysis of hybrid systems was carried out by Tavernini (1987), who introduced the conceptTopologies for hybrid solutions Dmitry Gokhman Department of Mathematics The University of Texas The Tavernini metric for hybrid solutions the Skorohod J1 topology. 1 Introduction The Skorohod topology, used

  13. Topology control for multihop packet radio networks

    Microsoft Academic Search

    Limin Hu

    1993-01-01

    A distributed topology-control algorithm has been developed for each node in a packet radio network (PRN) to control its transmitting power and logical neighbors for a reliable high-throughput topology. The algorithm first constructs a planar triangulation from locations of all nodes as a starting topology. Then, the minimum angles of all triangles in the planar triangulation are maximized by means

  14. Free loop spaces in topology and

    E-print Network

    Thévenaz, Jacques

    Free loop spaces in topology and physics Kathryn Hess What is the space of free loops? Enumeration of geodesics Hochschild and cyclic homology Homological conformal field theories Free loop spaces in topology Meeting of the Edinburgh Mathematical Society Glasgow, 14 November 2008 #12;Free loop spaces in topology

  15. SPINES OF TOPOLOGICAL MANIFOLDS ERIK KJR PEDERSEN

    E-print Network

    Pedersen, Erik Kjær

    SPINES OF TOPOLOGICAL MANIFOLDS ERIK KJÃ?R PEDERSEN In this paper we prove that a closed 2-connected topological manifold has a PL-spine, i. e. there is a locally tamely embedded complex such that a regular). This "spine method" together with the relative edition of regular neighborhoods of complexes in topological

  16. Topologies on the Planar Orthogonal Grid

    Microsoft Academic Search

    Reinhard Klette

    2002-01-01

    This paper discusses different topologies on the planar orthogonal grid and shows homeomorphy between cellular models. It also discusses graph-theoretical options defined by planar extensions of the 4-adjacency graph. The topology of digital images, and topological prob- lems related to image analysis have been studied over the last thirty years. This article shows that cellular models in 2D, commonly discussed

  17. Dynamics of Dirac Fermions in Topological Insulators

    E-print Network

    Arnold, Anton

    Dynamics of Dirac Fermions in Topological Insulators R. Hammer1 , C. Ertler1 , W. P¨otz1 , and A.hammer@uni-graz.at Abstract We study the coherent dynamics of Dirac fermions on the surface of topological insulators in one topological insulators (TI) we investigate theoretically the dynamics of Dirac fermion wave packets on their 2

  18. Tunable Dirac Fermion Dynamics in Topological Insulators

    E-print Network

    Wang, Wei Hua

    Tunable Dirac Fermion Dynamics in Topological Insulators Chaoyu Chen1 , Zhuojin Xie1 , Ya Feng1, Beijing 100190, China. Three-dimensional topological insulators are characterized by insulating bulk state topological insulators. We have directly revealed signatures of the electron-phonon coupling and found

  19. Fractional Topological Insulators in Three Dimensions

    Microsoft Academic Search

    Joseph Maciejko; Xiao-Liang Qi; Andreas Karch; Shou-Cheng Zhang

    2010-01-01

    Topological insulators can be generally defined by a topological field theory with an axion angle theta of 0 or pi. In this work, we introduce the concept of fractional topological insulator defined by a fractional axion angle and show that it can be consistent with time reversal T invariance if ground state degeneracies are present. The fractional axion angle can

  20. TOPOLOGICAL STRING THEORY AND ENUMERATIVE GEOMETRY

    E-print Network

    Slatkin, Montgomery

    TOPOLOGICAL STRING THEORY AND ENUMERATIVE GEOMETRY a dissertation submitted to the department) Approved for the University Committee on Graduate Studies: iii #12;TOPOLOGICAL STRING THEORY In this thesis we investigate several problems which have their roots in both topolog- ical string theory