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1

Charge and spin topological insulators

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.

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

2

Asymptotic behaviour of the classical scalar fields and topological charges

NASA Astrophysics Data System (ADS)

The existence and the properties of the limit at spatial infinity are studied for the finite-energy scalar fields with respect to the topological charge introduction. The limit is shown to be constant in time and in almost all spatial directions. The proof of the existence of the limit given by Parenti, Strocchi and Velo is extended to two-dimensional space. A generalized definition of the topological charge is suggested for a ?-model as an example.

Dittrich, J.

1981-03-01

3

Gribov copies and topological charge

The existence of Gribov copies is a central feature of the field configuration space of confining gauge theories. In particular a transition between two Gribov copies with relative winding number implies a space-time configuration with topological charge. We explicitly demonstrate the proliferation of Gribov copies with relative winding number, where our focus is on localized (finite norm) configurations in Coulomb gauge. We then discuss the likelihood that some pairs of such copies are connected by Minkowski space solutions. We also comment on the relative importance of instantons and the connection to confinement.

Holdom, B. [Department of Physics, University of Toronto, Toronto, Ontario, M5S1A7 (Canada)

2010-11-15

4

Topology density correlator on dynamical domain-wall ensembles with nearly frozen topological charge

Global topological charge decorrelates very slowly or even freezes in fine lattice simulations. On the other hand, its local fluctuations are expected to survive and lead to the correct physical results as long as the volume is large enough. We investigate this issue on recently generated configurations including dynamical domain-wall fermions at lattice spacings a = 0.08 fm and finer. We utilize the Yang-Mills gradient flow to define the topological charge density operator and calculate its long-distance correlation, through which we propose a new method for extracting the topological susceptibility in a sub-volume. This method takes care of the finite volume correction, which reduces the bias caused by the global topological charge. Our lattice data clearly show a shorter auto-correlation time than that of the naive definition using the whole lattice, and are less sensitive to the global topological history. Numerical results show a clear sea-quark mass dependence, which agrees well with the prediction of chiral perturbation theory.

JLQCD collaboration; H. Fukaya; S. Aoki; G. Cossu; S. Hashimoto; T. Kaneko; J. Noaki

2014-11-06

5

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

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.

Leonardo Giusti; Silvano Petrarca; Bruno Taglienti

2007-05-22

6

Detached topological charge on capillary bridges

We numerically investigate crystalline order on negative Gaussian curvature capillary bridges. In agreement with the experimental results in [W. Irvine et al., Nature, "Pleats in crystals on curved surfaces", 2010, (468), 947]} we observe for decreasing integrated Gaussian curvature a sequence of transitions, from no defects to isolated dislocations, pleats, scars and isolated sevenfold disclinations. We especially focus on the dependency of the detached topological charge on the integrated Gaussian curvature, for which we observe, again in agreement with the experimental results, no net disclination for an integrated curvature down to -10, and a linear behaviour from there on until the disclinations match the integrated curvature of -12. The results are obtained using a phase field crystal approach on catenoid-like surfaces and are highly sensitive to the initialization.

Verena Schmid; Axel Voigt

2014-01-30

7

Topological Charge and the Laminar Structure of the QCD Vacuum

Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, coherent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. In this talk I discuss the interpretation of these Monte Carlo results in terms of our current theoretical understanding of theta-dependence and topological structure in asymptotically free gauge theories.

Thacker, H. B. [University of Virginia, Charlottesville, VA 22904 (United States)

2007-02-27

8

Topology-based Feature Definition and Analysis

Defining high-level features, detecting them, tracking them and deriving quantities based on them is an integral aspect of modern data analysis and visualization. In combustion simulations, for example, burning regions, which are characterized by high fuel-consumption, are a possible feature of interest. Detecting these regions makes it possible to derive statistics about their size and track them over time. However, features of interest in scientific simulations are extremely varied, making it challenging to develop cross-domain feature definitions. Topology-based techniques offer an extremely flexible means for general feature definitions and have proven useful in a variety of scientific domains. This paper will provide a brief introduction into topological structures like the contour tree and Morse-Smale complex and show how to apply them to define features in different science domains such as combustion. The overall goal is to provide an overview of these powerful techniques and start a discussion how these techniques can aid in the analysis of astrophysical simulations.

Weber, Gunther H.; Bremer, Peer-Timo; Gyulassy, Attila; Pascucci, Valerio

2010-12-10

9

Effect of topology on the critical charge in graphene

We show that the critical charge for the Dirac excitations in gapless graphene depends on the spatial topology of the sample. In particular, for graphene cones, the effective value of the critical charge can tend towards zero for a suitable angle of the conical sample. We discuss the nature of the scattering phase shifts, quasi-bound state energies and local density of states for a gapless graphene cone and determine the dependence of these physical quantities on the sample topology.

Baishali Chakraborty; Kumar S. Gupta; Siddhartha Sen

2010-10-28

10

Topological BPS charges in 10- and 11-dimensional supergravity

We consider the supersymmetry algebras of the maximal supergravities in 10 and 11 dimensions. We construct expressions from which the topological charge structure of the algebras can be determined in supersymmetric curved backgrounds. These are interpreted as the topological charges of the 1/2-BPS states that are found in the theories. We consider charges for all the M-, NS- and D-branes as well as the Kaluza-Klein monopoles. We also show that the dimensional reduction relations between the 11-dimensional and IIA charges, and T-duality relations of the IIA and IIB charges, match those found for the branes themselves. Finally we consider the massive versions of the IIA and 11-dimensional theories and find that the expressions for the charges, with a slight modification, are still valid in those instances.

Callister, Andrew K.; Smith, Douglas J. [Department of Mathematical Sciences, Durham University, Science Laboratories, South Road, Durham. DH1 3LE (United Kingdom)

2008-09-15

11

Diffusion of topological charge in lattice QCD simulations

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.

Greg McGlynn; Robert D. Mawhinney

2014-06-17

12

Sub-3-cycle vortex pulses of tunable topological charge.

Novel types of reflective spiral micro-electro-mechanical systems were used to generate few-cycle vortex pulses of variable topological charge from a Ti:sapphire laser oscillator. The phase profile of these components was controlled by varying the temperature. The temporal properties of the pulses were characterized with spatially resolved nonlinear autocorrelation. The beam structure resembles a slightly distorted Laguerre-Gaussian distribution. The different topological charges were indicated by detecting Poynting-vector maps with a programmable Shack-Hartmann sensor of enhanced angular sensitivity. PMID:24104835

Bock, Martin; Brunne, Jens; Treffer, Alexander; König, Stefan; Wallrabe, Ulrike; Grunwald, Ruediger

2013-09-15

13

An Evaluation of 2-phase Charge Pump Topologies with Charge Transfer Switches for

An Evaluation of 2-phase Charge Pump Topologies with Charge Transfer Switches for Green Mobile Technology Yan Chiew Wong1,2 , Nurul H. Noordin1,2 , Ahmed O. El-Rayis1,2 , Nakul Haridas1,2 , Ahmet T. The quality of the charge pump greatly depends on the effectiveness of switches to turn on and off

Arslan, Tughrul

14

Weyl and Dirac semimetals with Z2 topological charge

NASA Astrophysics Data System (ADS)

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.

Morimoto, Takahiro; Furusaki, Akira

2014-06-01

15

Charge d-wave topological insulator

Formation of a condensate of singlet electron-hole pairs in a two-dimensional metal lattice with the nesting of the Fermi contour is investigated. A numerical solution is obtained for the self-consistency equation for the insulating order parameter depending on the ratio of the coupling constants in the s- and d-wave channels of electron-hole pairing. Solutions with the pure orbital symmetry of s- and d-type are found, as well as solutions with the mixed s + d-symmetry. It is shown that in a wide range of values of the s- and d-wave coupling constants, the two-dimensional insulating order with the orbital symmetry d{sub x{sup 2}-y{sup 2}} can compete with pure ordered s- and d{sub xy}-states and mixed s + d-states. Time reversal symmetry breaking under an established real order with d{sub x{sup 2}-y{sup 2}} -wave symmetry may generate the imaginary component of the order parameter with symmetry d{sub xy} and cause a rise in topologically nontrivial d + id-wave ordering similar to the quantum Hall state in the absence of external magnetic field.

Kopaev, Yu. V.; Kapaev, V. V.; Belyavskii, V. I., E-mail: vib45@mail.ru [Russian Academy of Sciences, Lebedev Physics Institute (Russian Federation)

2013-10-15

16

C library for topological study of the electronic charge density.

The topological study of the electronic charge density is useful to obtain information about the kinds of bonds (ionic or covalent) and the atom charges on a molecule or crystal. For this study, it is necessary to calculate, at every space point, the electronic density and its electronic density derivatives values up to second order. In this work, a grid-based method for these calculations is described. The library, implemented for three dimensions, is based on a multidimensional Lagrange interpolation in a regular grid; by differentiating the resulting polynomial, the gradient vector, the Hessian matrix and the Laplacian formulas were obtained for every space point. More complex functions such as the Newton-Raphson method (to find the critical points, where the gradient is null) and the Cash-Karp Runge-Kutta method (used to make the gradient paths) were programmed. As in some crystals, the unit cell has angles different from 90°, the described library includes linear transformations to correct the gradient and Hessian when the grid is distorted (inclined). Functions were also developed to handle grid containing files (grd from DMol® program, CUBE from Gaussian® program and CHGCAR from VASP® program). Each one of these files contains the data for a molecular or crystal electronic property (such as charge density, spin density, electrostatic potential, and others) in a three-dimensional (3D) grid. The library can be adapted to make the topological study in any regular 3D grid by modifying the code of these functions. PMID:22865338

Vega, David; Aray, Yosslen; Rodríguez, Jesús

2012-12-01

17

Conduction of topologically protected charged ferroelectric domain walls.

We report on the observation of nanoscale conduction at ferroelectric domain walls in hexagonal HoMnO(3) protected by the topology of multiferroic vortices using in situ conductive atomic force microscopy, piezoresponse force microscopy, and Kelvin-probe force microscopy at low temperatures. In addition to previously observed Schottky-like rectification at low bias [Phys. Rev. Lett. 104, 217601 (2010)], conductance spectra reveal that negatively charged tail-to-tail walls exhibit enhanced conduction at high forward bias, while positively charged head-to-head walls exhibit suppressed conduction at high reverse bias. Our results pave the way for understanding the semiconducting properties of the domains and domain walls in small-gap ferroelectrics. PMID:22401247

Wu, Weida; Horibe, Y; Lee, N; Cheong, S-W; Guest, J R

2012-02-17

18

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

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.

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

2011-11-29

19

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

,12], and inspired the theoretical connection [13] between the 3D Z2 topological insulators and the 4D quantum Hall and shares the same topological origin as the quantum Hall effect. We propose an experimental setup charge pump shares the same topological origin as the two-dimensional (2D) quantum Hall effect (QHE) [7

Wang, Wei Hua

20

Maximum-Likelihood Approach to Topological Charge Fluctuations in Lattice Gauge Theory

We present a novel technique for the determination of the topological susceptibility (related to the variance of the distribution of global topological charge) from lattice gauge theory simulations, based on maximum-likelihood analysis of the Markov-chain Monte Carlo time series. This technique is expected to be particularly useful in situations where relatively few tunneling events are observed. Restriction to a lattice subvolume on which topological charge is not quantized is explored, and may lead to further improvement when the global topology is poorly sampled. We test our proposed method on a set of lattice data, and compare it to traditional methods.

R. C. Brower; M. Cheng; G. T. Fleming; M. F. Lin; E. T. Neil; J. C. Osborn; C. Rebbi; E. Rinaldi; D. Schaich; C. Schroeder; G. Voronov; P. Vranas; E. Weinberg; O. Witzel

2014-03-11

21

Charge and spin fractionalization in strongly correlated topological insulators.

We construct an effective topological Landau-Ginzburg theory that describes general SU(2) incompressible quantum liquids of strongly correlated particles in two spatial dimensions. This theory characterizes the fractionalization of quasiparticle quantum numbers and statistics in relation to the topological ground-state symmetries, and generalizes the Chern-Simons, BF ('background field') and hierarchical effective gauge theories to an arbitrary representation of the SU(2) symmetry group. We mainly focus on fractional topological insulators with time-reversal symmetry, which are treated as SU(2) generalizations of the quantum Hall effect. PMID:23209083

Nikoli?, Predrag

2013-01-16

22

NASA Astrophysics Data System (ADS)

We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

Wang, Xin; Liang, Shi-Dong

2013-02-01

23

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

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

Francisco Torrens

2004-01-01

24

P-V criticality of higher dimensional charged topological dilaton de Sitter black holes

NASA Astrophysics Data System (ADS)

There are both the black hole horizon and the cosmological horizon for the charged topological dilaton de Sitter spacetime. The thermodynamic quantities on both horizons satisfy the first law of black hole thermodynamics. Because all of these thermodynamic quantities depend on the mass M, the electric charge Q, and the cosmological constant l, the two horizons are not independent. Considering the connection between the black hole horizon and the cosmological horizon, we derive the effective thermodynamic quantities of the (n +1)-dimensional charged topological dilaton de Sitter spacetime. We find that the charged topological dilaton black hole in de Sitter spacetime has a similar phase transition and critical behavior to that in anti-de Sitter spacetime.

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

2014-09-01

25

Importance of charge fluctuations for the topological phase in SmB(6).

Typical Kondo insulators (KIs) can have a nontrivial Z_{2} topology because the energy gap opens at the Fermi energy (E_{F}) by a hybridization between odd- and even-parity bands. SmB_{6} deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in SmB_{6}. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the d-f hybridized band at the X[over ¯] point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above E_{F}. We conclude that SmB_{6} is a charge-fluctuating topological insulator. PMID:24949780

Min, Chul-Hee; Lutz, P; Fiedler, S; Kang, B Y; Cho, B K; Kim, H-D; Bentmann, H; Reinert, F

2014-06-01

26

Importance of Charge Fluctuations for the Topological Phase in SmB6

NASA Astrophysics Data System (ADS)

Typical Kondo insulators (KIs) can have a nontrivial Z2 topology because the energy gap opens at the Fermi energy (EF) by a hybridization between odd- and even-parity bands. SmB6 deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in SmB6. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the d-f hybridized band at the X ¯ point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above EF. We conclude that SmB6 is a charge-fluctuating topological insulator.

Min, Chul-Hee; Lutz, P.; Fiedler, S.; Kang, B. Y.; Cho, B. K.; Kim, H.-D.; Bentmann, H.; Reinert, F.

2014-06-01

27

Overlap fermions, which preserve exact chiral symmetry on the lattice, provide a powerful tool for investigating the topological structure of the vacuum. Applying this formulation to zero-temperature quenched SU(3) configurations generated by means of the Luescher-Weisz action, we define the topological charge density with and without UV filtering and study its properties by looking at the density profile and the

Yoshiaki Koma; E.-M. Ilgenfritz; K. Koller; G. Schierholz; T. Streuer; Volker Weinberg

2005-01-01

28

NASA Astrophysics Data System (ADS)

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.

Liu, Man

2013-11-01

29

Charge quantisation without magnetic monopoles: a topological approach to electromagnetism

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.

Romero Solha

2014-06-24

30

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

J. Bialek

1997-01-01

31

Deutsch's algorithm with topological charges of optical vortices via non-degenerate four-wave mixing

We propose a scheme to implement the Deutsch's algorithm through non-degenerate four-wave mixing process. By employing photon topological charges of optical vortices, we demonstrate the ability to realize the necessary four logic gates for all balanced and constant functions. We also analyze the feasibility of the proposed scheme on the single photon level.

Cao, Mingtao; Liu, Ruifeng; Liu, Hao; Wei, Dong; Zhang, Pei; Zhou, Yu; Guo, Wenge; Zhang, Shougang; Gao, Hong; Li, Fuli

2012-01-01

32

We propose a scheme to implement the Deutsch's algorithm through non-degenerate four-wave mixing process. By employing photon topological charges of optical vortices, we demonstrate the ability to realize the necessary four logic gates for all balanced and constant functions. We also analyze the feasibility of the proposed scheme on the single photon level. PMID:23187188

Cao, Mingtao; Han, Liang; Liu, Ruifeng; Liu, Hao; Wei, Dong; Zhang, Pei; Zhou, Yu; Guo, Wenge; Zhang, Shougang; Gao, Hong; Li, Fuli

2012-10-22

33

Charge Pump Circuits: An Overview on Design Strategies and Topologies

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

Gaetano Palumbo; Domenico Pappalardo

2010-01-01

34

A unified phase transition picture of the charged topological black hole in Horava-Lifshitz gravity

Aiming at a unified phase transition picture of the charged topological black hole in Ho\\v{r}ava-Lifshitz gravity, we investigate this issue not only in canonical ensemble with the fixed charge case but also in grand-canonical ensemble with the fixed potential case. We firstly perform the standard analysis of the specific heat, the free energy and the Gibbs potential, and then study its geometrothermodynamics. It is shown that the local phase transition points not only witness the divergence of the specific heat, but also witness the minimum temperature and the maximum free energy or Gibbs potential. They also witness the divergence of the corresponding thermodynamic scalar curvature. No matter which ensemble is chosen, the metric constructed can successfully produce the behavior of the thermodynamic interaction and phase transition structure while other metrics failed to predict the phase transition point of the charged topological black hole in former literature. In grand-canonical ensemble, we have discove...

Mo, Jie-Xiong; Li, Gu-Qiang; Jiang, Xin; Liu, Wen-Biao

2014-01-01

35

Low dimensional long range topological charge structure in the QCD vacuum

While sign-coherent 4-dimensional structures cannot dominate topological charge fluctuations in the QCD vacuum at all scales due to reflection positivity, it is possible that enhanced coherence exists over extended space-time regions of lower dimension. Using the overlap Dirac operator to calculate topological charge density, we present evidence for such structure in pure-glue SU(3) lattice gauge theory. It is found that a typical equilibrium configuration is dominated by two oppositely-charged sign-coherent connected structures (``sheets'') covering about 80% of space-time. Each sheet is built from elementary 3-d cubes connected through 2-d faces, and approximates a low-dimensional curved manifold (or possibly a fractal structure) embedded in the 4-d space. At the heart of the sheet is a ``skeleton'' formed by about 18% of the most intense space-time points organized into a global long-range structure, involving connected parts spreading over maximal possible distances. We find that the skeleton is locally 1-dimensional and propose that its geometrical properties might be relevant for understanding the possible role of topological charge fluctuations in the physics of chiral symmetry breaking.

I. Horvath; S.J. Dong; T. Draper; F.X. Lee; K.F. Liu; N. Mathur; H.B. Thacker; J.B. Zhang

2003-12-01

36

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-qubits operations on a topological 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.

Ting Mao; Z. D. Wang

2014-03-18

37

The development of charge pumps has been motivated by the power supply requirements of portable electronic devices. Charge pumps are inductorless DC-DC converters that are small size and high integration. The quality of the charge pump greatly depends on the effectiveness of switches to turn on and off at the designated clock phases. However, to date, no analysis has been

Yan Chiew Wong; Nurul H. Noordin; Ahmed O. El-Rayis; Nakul Haridas; Ahmet T. Erdogan; Tughrul Arslan

2011-01-01

38

In the great majority of genomes, the use of positive charge increases, on average, approaching protein N-termini. Such charged residues slow ribosomes by interacting with the negatively charged exit tunnel. This has been proposed to be selectively advantageous as it provides an elongation speed ramp at translational starts. Positive charges, however, are known to orientate proteins in membranes by the positive-inside rule whereby excess charge lies on the cytoplasmic side of the membrane. Which of these two models better explains the N-terminal loading of positively charged amino acids? We find strong evidence that the tendency for average positive charge use to increase at termini is exclusively due to membrane protein topology: 1) increasing N-terminal positive charge is not found in cytosolic proteins, but in transmembrane ones with cytosolic N-termini, with signal sequences contributing additional charge; 2) positive charge density at N-termini corresponds to the length of cytoplasmically exposed transmembrane tails, its usage increasing just up until the membrane; 3) membrane-related patterns are repeated at C-termini, where no ramp is expected; and 4) N-terminal positive charge patterns are no different from those seen internally in proteins in membrane-associated domains. The overall apparent increase in positive charge across all N-termini results from membrane proteins using positive charge adjacent to the cytosolic leaflet, combined with a skewed distribution of where N-termini cross the plasma membrane; 5) while Escherichia coli was predicted to have a 5' ribosomal occupancy ramp of at least 31 codons, in contrast to what is seen in yeast, we find in ribosomal footprinting data no evidence for such a ramp. In sum, we find no need to invoke a translational ramp to explain the rising positive charge densities at N-termini. The membrane orientation model makes a full account of the trend. PMID:24077849

Charneski, Catherine A; Hurst, Laurence D

2014-01-01

39

Instantons and the fixed point topological charge in the two-dimensional O(3) sigma-model

We define a fixed point topological charge for the two-dimensional O(3) lattice sigma-model which is free of topological defects. We use this operator in combination with the fixed point action to measure the topological susceptibility for a wide range of correlation lengths. The results strongly suggest that it is not a physical quantity in this model. The procedure, however, can be applied to other asymptotically free theories as well.

Marc Blatter; Rudolf Burkhalter; Peter Hasenfratz; Ferenc Niedermayer

1995-08-29

40

Comparison of converter topologies for charging capacitors used in pulsed load applications

NASA Technical Reports Server (NTRS)

The authors present a qualitative comparison of different power converter topologies which may be utilized for charging capacitors in pulsed power applications requiring voltages greater than 1 kV. The operation of the converters in capacitor charging applications is described, and relevant advantages are presented. All of the converters except one may be classified in the high-frequency switching category. One of the benefits from high-frequency operation is a reduction in size and weight. The other converter discussed is a member of the command resonant changing category. The authors first describe a boost circuit which functions as a command resonant charging circuit and utilizes a single pulse of current to charge the capacitor. The discussion of high-frequency converters begins with the flyback and Ward converters. Then, the series, parallel, and series/parallel resonant converters are examined.

Nelms, R. M.; Schatz, J. E.; Pollard, Barry

1991-01-01

41

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

42

Overlap fermions, which preserve exact chiral symmetry on the lattice, provide a powerful tool for investigating the topological structure of the vacuum. Applying this formulation to zero-temperature quenched SU(3) configurations generated by means of the Luescher-Weisz action, we define the topological charge density with and without UV filtering and study its properties by looking at the density profile and the two-point correlation function. We observe that the density possesses global sign coherent structures, which get increasingly tangled as more and more modes are included. This change of the structure is also detected by the increasing negative tail of the two-point function. We also study the inverse participation ratio of the eigenmodes and discuss their dimensionality.

Koma, Y; Koller, K; Schierholz, G; Streuer, T; Weinberg, V

2005-01-01

43

Two phase equilibrium in charged topological dilaton AdS black hole

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.

Zhao, Hui-Hua; Ma, Meng-Sen; Zhao, Ren

2014-01-01

44

NASA Astrophysics Data System (ADS)

We investigate the random wandering behavior of optical vortex over propagation distance of 5 km in weak turbulence. The multiple random phase screen simulation method and vortex extracting method are utilized to calculate the optical vortex positions (x,y) on the receiver plane. Numerical results reveal that x and y are Gaussian random variables. However, the errors of Gaussian fitting become larger and the Gaussian fitting curves become broader as topological charge of optical vortex increases through the same atmospheric turbulence. Our results are crucial for free-space optical vortex communication.

Cui, Qianru; Li, Ming; Yu, Zhongyuan

2014-10-01

45

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

NASA Astrophysics Data System (ADS)

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.

Callister, Andrew K.; Smith, Douglas J.

2009-12-01

46

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

47

A unified phase transition picture of the charged topological black hole in Horava-Lifshitz gravity

Aiming at a unified phase transition picture of the charged topological black hole in Ho\\v{r}ava-Lifshitz gravity, we investigate this issue not only in canonical ensemble with the fixed charge case but also in grand-canonical ensemble with the fixed potential case. We firstly perform the standard analysis of the specific heat, the free energy and the Gibbs potential, and then study its geometrothermodynamics. It is shown that the local phase transition points not only witness the divergence of the specific heat, but also witness the minimum temperature and the maximum free energy or Gibbs potential. They also witness the divergence of the corresponding thermodynamic scalar curvature. No matter which ensemble is chosen, the metric constructed can successfully produce the behavior of the thermodynamic interaction and phase transition structure while other metrics failed to predict the phase transition point of the charged topological black hole in former literature. In grand-canonical ensemble, we have discovered the phase transition which has not been reported before. It is similar to the canonical ensemble in which the phase transition only takes place when $k=-1$. But it also has its unique characteristics that the location of the phase transition point depends on the value of potential, which is different from the canonical ensemble where the phase transition point is independent of the parameters. After an analytical check of Ehrenfest scheme, we find that the new phase transition is a second order one. It is also found that the thermodynamics of the black hole in Horava-Lifshitz gravity is quite different from that in Einstein gravity.

Jie-Xiong Mo; Xiao-Xiong Zeng; Gu-Qiang Li; Xin Jiang; Wen-Biao Liu

2014-04-09

48

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

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

2010-04-01

49

The doubly-connected polygonal geometry of planar graphene rings is found to bring forth topological configurations for accessing nontrivial relativistic quantum field (RQF) theory models that carry beyond the constant-mass Dirac-fermion theory. These include generation of sign-alternating masses, solitonic excitations, and charge fractionization. The work integrates a RQF Lagrangian formulation with numerical tight-binding Aharonov-Bohm electronic spectra and the generalized position-dependent-mass Dirac equation. In contrast to armchair graphene rings (aGRGs) with pure metallic arms, certain classes of aGRGs with semiconducting arms, as well as with mixed metallic-semiconducting ones, are shown to exhibit properties of one-dimensional nontrivial topological insulators. This further reveals an alternative direction for realizing a graphene-based nontrivial topological insulator through the manipulation of the honeycomb lattice geometry, without a spin-orbit contribution.

Constantine Yannouleas; Igor Romanovsky; Uzi Landman

2014-01-22

50

Topology of charge density and elastic properties of Ti3SiC2 polymorphs

Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic properties of the two polymorphs, alpha and beta, of Ti3SiC2. The bonding effect was analyzed based on Bader's quantum theory of ''atoms in molecules'' (AIM). It was found that the Ti-Si bonding effect is significantly weaker in beta than in alpha, giving less stabilizing effect for beta. The Si-C bonds, which are absent in alpha, are formed in beta and provide additional stabilizing effect for beta. In contrast to conventional thinking, there is no direction interaction between Ti atoms in both alpha and beta. The calculated elastic properties are in good agreement with the experimental results, giving the bulk modulus of about 180 GPa and the Poisson's ratio of 0.2. The beta phase is generally softer than the alpha phase. As revealed by the direction dependent Young's modulus, there is only slight elastic anisotropy in Ti3SiC2. For alpha, Young's modulus is minimum in the c direction and maximum in the directions 42o from c. For beta, the maximum lies in the c direction, in part due to the formation of Si-C bonds in this direction.

Yu, Rong; Zhang, Xiao Feng; He, Lian Long; Ye, Heng Qiang

2004-06-24

51

Using ensembles generated with periodic or open boundary conditions in the temporal direction, and using Wilson flow or HYP smearing to smoothen the gauge fields, we have studied the Topological Charge Density Correlator (TCDC) and the Inverse Participation Ratio (IPR) for the topological charge density distribution in Lattice Yang-Mills theory. We have observed that at the same lattice volume and lattice spacing and at a given Wilson flow time, there is no noticeable difference between the TCDCs calculated with periodic and open boundary conditions in the temporal direction. The size of the positive core increases and the heights of the positive and negative peaks decrease with flow time, in both the cases. Open boundary condition makes it possible to compute observables at a smaller lattice spacing. On the other hand, the reference energy scale provided by Wilson flow allows us to study their scaling behaviour. At a particular Wilson flow time $t$ for all the lattice spacings investigated (except the larges...

Chowdhury, Abhishek; Maiti, Jyotirmoy

2014-01-01

52

NASA Astrophysics Data System (ADS)

Topological charged black holes coupled with a cosmological constant in R2×XD-2 spacetimes are studied, where XD-2 is an Einstein space of the form (D-2)RAB=k(D-3)hAB. The global structure for the four-dimensional spacetimes with k=0 is investigated systematically. The most general solutions that represent a type II fluid in such a high dimensional spacetime are found and show that topological charged black holes can be formed from the gravitational collapse of such a fluid. When the spacetime is (asymptotically) self-similar, the collapse always forms black holes for k=0, -1, in contrast with the case k=1, where it can form either black holes or naked singularities.

Wu, Yumei; da Silva, M. F.; Santos, N. O.; Wang, Anzhong

2003-10-01

53

Localization of overlap modes and topological charge, vortices and monopoles in SU(3) LGT

We present selected recent results of the QCDSF collaboration on the localization and dimensionality of low overlap eigenmodes and of the topological density in the quenched SU(3) vacuum. We discuss the correlations between the topological structure revealed by overlap fermions without filtering and the confining monopole and P-vortex structure obtained in the Indirect Maximal Center Gauge.

Ilgenfritz, E M; Koma, Y; Schierholz, G; Streuer, T; Weinberg, V; Quandt, M

2007-01-01

54

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 ...

Kerman, Andrew J.

55

The perihelion precession, the deflection of light, and the radar echo delay are classical tests of General Relativity here used to probe brane world topologically charged black holes in a f(R) bulk and to constrain the parameter that arises from the Shiromizu-Maeda-Sasaki procedure applied to a f(R) bulk as well. The existing Solar system observational data constrain the possible values of the tidal charge parameter and the effective cosmological constant including f(R) brane world effects. We show that the observational/experimental data for both perihelion precession and radar echo delay make the black hole space of parameters to be more strict than the ones for the Dadhich, Maartens, Papadopoulos and Rezania (DMPR) black hole geometry. Furthermore, the deflection of light constrains the tidal charge parameter similarly as the DMPR black holes due to a peculiarity in the equation of motion.

da Rocha, Roldao

2014-01-01

56

The perihelion precession, the deflection of light, and the radar echo delay are classical tests of General Relativity here used to probe brane world topologically charged black holes in a f(R) bulk and to constrain the parameter that arises from the Shiromizu-Maeda-Sasaki procedure applied to a f(R) bulk as well. The existing Solar system observational data constrain the possible values of the tidal charge parameter and the effective cosmological constant including f(R) brane world effects. We show that the observational/experimental data for both perihelion precession and radar echo delay make the black hole space of parameters to be more strict than the ones for the Dadhich, Maartens, Papadopoulos and Rezania (DMPR) black hole geometry. Furthermore, the deflection of light constrains the tidal charge parameter similarly as the DMPR black holes due to a peculiarity in the equation of motion.

Roldao da Rocha; A. M. Kuerten

2014-07-06

57

NASA Astrophysics Data System (ADS)

We study Andreev reflection and Josephson currents in topological bilayer exciton condensates (TECs). These systems can create 100% spin-entangled nonlocal currents with high amplitudes due to perfect nonlocal Andreev reflection. This Andreev reflection process can be gate tuned from a regime of purely retro reflection to purely specular reflection. We have studied the bound states in TEC-topological-insulator-TEC Josephson junctions and find a gapless dispersion for perpendicular incidence. The presence of a sharp transition in the supercurrent-phase relationship when the system is in equilibrium is a signature of fractional charge, which can be further revealed in ac measurements faster than relaxation processes via Landau-Zener processes.

Veldhorst, M.; Hoek, M.; Snelder, M.; Hilgenkamp, H.; Golubov, A. A.; Brinkman, A.

2014-07-01

58

NASA Astrophysics Data System (ADS)

Using the charge-conserving Floquet-Green function approach to open quantum systems driven by an external time-periodic potential, we analyze how spin current pumped by the precessing magnetization of a ferromagnetic (F) layer is injected laterally into the interface with strong spin-orbit coupling (SOC) and converted into charge current flowing in the same direction. In the case of a metallic interface with the Rashba SOC used in recent experiments [J. C. R. Sánchez, L. Vila, G. Desfonds, S. Gambarelli, J. P. Attané, J. M. De Teresa, C. Magén, and A. Fert, Nat. Commun. 4, 2944 (2013), 10.1038/ncomms3944], both spin IS? and charge I current flow within the interface where I /IS?? 2-8% (depending on the precession cone angle), while for a F/topological-insulator (F/TI) interface employed in related experiments [Y. Shiomi, K. Nomura, Y. Kajiwara, K. Eto, M. Novak, K. Segawa, Y. Ando, and E. Saitoh, arXiv:1312.7091] the conversion efficiency is greatly enhanced (I /IS?? 40-60%) due to perfect spin-momentum locking on the surface of a TI. The spin-to-charge conversion occurs also when spin current is pumped vertically through the F/TI interface with smaller efficiency (I /IS?˜0.001%), but with the charge current signal being sensitive to whether the Dirac fermions at the interface are massive or massless.

Mahfouzi, Farzad; Nagaosa, Naoto; Nikoli?, Branislav K.

2014-09-01

59

FAST TRACK COMMUNICATION: Semi-classical central charge in topologically massive gravity

NASA Astrophysics Data System (ADS)

It is shown that the warped black hole geometries discussed recently in arXiv:0807.3040 (Anninos et al 2008) admit an algebra of asymptotic symmetries isomorphic to the semi-direct product of a Virasoro algebra and an algebra of currents. The realization of this asymptotic symmetry by canonical charges allows us to find the central charge of the Virasoro algebra. The right-moving central charge c_R = -\\frac{(5\\hat{\

Compère, Geoffrey; Detournay, Stéphane

2009-01-01

60

Symmetry, winding number, and topological charge of vortex solitons in discrete-symmetry media

We determine the functional behavior near the discrete rotational symmetry axis of discrete vortices of the nonlinear Schroedinger equation. We show that these solutions present a central phase singularity whose charge is restricted by symmetry arguments. Consequently, we demonstrate that the existence of high-charged discrete vortices is related to the presence of other off-axis phase singularities, whose positions and charges are also restricted by symmetry arguments. To illustrate our theoretical results, we offer two numerical examples of high-charged discrete vortices in photonic crystal fibers showing hexagonal discrete rotational invariance.

Garcia-March, Miguel-Angel; Zacares, Mario [Institut Universitari de Matematica Pura i Aplicada (IUMPA), Universitat Politecnica de Valencia, Cami de Vera, s/n, E-46022 Valencia (Spain); Ferrando, Albert [Departament d'Optica, Universitat de Valencia, Dr. Moliner, 50, E-46100 Burjassot (Valencia) (Spain); Sahu, Sarira [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, C.U., A. Postal 70-543, 04510 Mexico DF (Mexico); Ceballos-Herrera, Daniel E. [Institut Universitari de Matematica Pura i Aplicada (IUMPA), Universitat Politecnica de Valencia, Cami de Vera, s/n, E-46022 Valencia (Spain); Centro de Investigaciones en Optica A.C., Leon, Gto. 37170 (Mexico)

2009-05-15

61

NASA Astrophysics Data System (ADS)

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 [U(1) or ZN] or spin-Sz rotation symmetry [U(1) or ZN] in two (2D) and three dimensions (3D) and the surface of 3D. If both are U(1), we apply external electromagnetic field/“spin gauge field” to study the charge/spin response. For the SPT examples we consider {i.e., Uc(1)?Z2T, Us(1)×Z2T, Uc(1)×[Us(1)?Z2]; subscripts c and s are short for charge and spin; Z2T and Z2 are time-reversal symmetry and ? rotation about Sy, respectively}, many variants of Witten effect in the 3D SPT bulk and various versions of anomalous surface quantum Hall effect are defined and systematically investigated. If charge or spin symmetry reduces to ZN by considering charge-N or spin-N condensate, instead of the linear response approach, we gauge the charge/spin symmetry, leading to a dynamical gauge theory with some remaining global symmetry. The 3D dynamical gauge theory describes a symmetry-enriched topological phase (SET), i.e., a topologically ordered state with global symmetry which admits nontrivial ground-state degeneracy depending on spatial manifold topology. For the SPT examples we consider, the corresponding SET states are described by dynamical topological gauge theory with topological BF term and axionic ? term in 3D bulk. In addition, the surface of SET is described by the chiral boson theory with quantum anomaly.

Ye, Peng; Wang, Juven

2013-12-01

62

An acoustic charge transport imager for high definition television applications

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

63

Using ensembles generated with periodic or open boundary conditions in the temporal direction, and using Wilson flow or HYP smearing to smoothen the gauge fields, we have studied the Topological Charge Density Correlator (TCDC) and the Inverse Participation Ratio (IPR) for the topological charge density distribution in Lattice Yang-Mills theory. We have observed that at the same lattice volume and lattice spacing and at a given Wilson flow time, there is no noticeable difference between the TCDCs calculated with periodic and open boundary conditions in the temporal direction. The size of the positive core increases and the heights of the positive and negative peaks decrease with flow time, in both the cases. Open boundary condition makes it possible to compute observables at a smaller lattice spacing. On the other hand, the reference energy scale provided by Wilson flow allows us to study their scaling behaviour. At a particular Wilson flow time $t$ for all the lattice spacings investigated (except the largest one), the TCDC data show universal behaviour within our statistical uncertainties. The behaviour of TCDC at a fixed Wilson flow time for different lattice spacings is contrasted with that of the data at a fixed HYP smearing level which show apparent scaling violation. The pseudoscalar glueball mass extracted from the TCDC appears to be insensitive to the lattice spacings (0.0345 fm $\\leq a \\leq$ 0.0667 fm) explored in this work. Expectation values of the IPR at different lattice spacings are found to be very close to each other at a given reference scale.

Abhishek Chowdhury; A. Harindranath; Jyotirmoy Maiti

2014-09-23

64

NASA Astrophysics Data System (ADS)

From 1994 to 1997, the emulsion target of the CHORUS detector was exposed to the wideband neutrino beam of the CERN SPS. In total about 100?000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events based on the data acquired by new automatic scanning systems, 2013 charm-decay events were selected by a pattern recognition program. They were confirmed as decays through visual inspection. Based on these events, the effective branching ratio of charmed particles into muons was determined to be B=[7.3±0.8(stat)±0.2(syst)]×10. In addition, the muonic branching ratios are presented for dominating charm-decay topologies. Normalization of the muonic decays to charged-current interactions provides ?/?=[3.16±0.34(stat)±0.09(syst)]×10. Selecting only events with visible energy greater than 30 GeV gives a value of B that is less affected by the charm production threshold and quasi-elastic ?c+ production. Combining this value with the current average of B×V at the leading order yields the value of V|LO=0.236±0.016.

CHORUS Collaboration; Kayis-Topaksu, A.; Önengüt, G.; van Dantzig, R.; de Jong, M.; Oldeman, R. G. C.; Güler, M.; Köse, U.; Tolun, P.; Catanesi, M. G.; Muciaccia, M. T.; Winter, K.; van de Vyver, B.; Vilain, P.; Wilquet, G.; Saitta, B.; di Capua, E.; Ogawa, S.; Shibuya, H.; Hristova, I. R.; Kawamura, T.; Kolev, D.; Meinhard, H.; Panman, J.; Rozanov, A.; Tsenov, R.; Uiterwijk, J. W. E.; Zucchelli, P.; Goldberg, J.; Chikawa, M.; Song, J. S.; Yoon, C. S.; Kodama, K.; Ushida, N.; Aoki, S.; Hara, T.; Delbar, T.; Favart, D.; Grégoire, G.; Kalinin, S.; Makhlioueva, I.; Artamonov, A.; Gorbunov, P.; Khovansky, V.; Shamanov, V.; Tsukerman, I.; Bruski, N.; Frekers, D.; Hoshino, K.; Kawada, J.; Komatsu, M.; Miyanishi, M.; Nakamura, M.; Nakano, T.; Narita, K.; Niu, K.; Niwa, K.; Nonaka, N.; Sato, O.; Toshito, T.; Buontempo, S.; Cocco, A. G.; D'Ambrosio, N.; de Lellis, G.; de Rosa, G.; di Capua, F.; Fiorillo, G.; Marotta, A.; Messina, M.; Migliozzi, P.; Scotto Lavina, L.; Strolin, P.; Tioukov, V.; Okusawa, T.; Dore, U.; Loverre, P. F.; Ludovici, L.; Rosa, G.; Santacesaria, R.; Satta, A.; Spada, F. R.; Barbuto, E.; Bozza, C.; Grella, G.; Romano, G.; Sirignano, C.; Sorrentino, S.; Sato, Y.; Tezuka, I.

2005-10-01

65

Spin torques and charge transport on the surface of topological insulator

NASA Astrophysics Data System (ADS)

We study various aspects of interplay between two-dimensional helical electrons, realized on the surface of a three-dimensional topological insulator, and the magnetization of a ferromagnet coupled to them. The magnetization is assumed to be perpendicular to the surface, with small transverse fluctuations u. In the first part of this paper, we calculate spin torques that the helical electrons exert on the magnetization. Up to first orders with respect to u, space/time derivative and electric current, we have determined all torques, which include Gilbert damping, spin renormalization, current-induced spin-orbit torques, and gradient corrections to them. Thanks to the identity between the velocity and spin in this model, these torques have exact interpretation in terms of transport phenomena, namely, diagonal conductivity, (anomalous) Hall conductivity, and corrections to them due to ordinary Hall effect on top of the anomalous one. These torque (and transport) coefficients are studied in detail with particular attention to the effects of vertex corrections and type of impurities (normal and magnetic). It is shown rigorously that the conventional current-induced torques, namely, spin-transfer torque and the so-called ? term, are absent. An electromotive force generated by spin dynamics, which is the inverse to the current-induced spin-orbit torque, is also studied. In the second part, we study the feedback effects arising as combinations of current-induced spin-orbit torques and spin-dynamics-induced electromotive force. It is demonstrated that the Gilbert damping process in this system is completely understood as a feedback effect. Another feedback effect, which may be called "magnon-drag electrical conductivity," is shown to violate the exact correspondence between spin-torque and transport phenomena demonstrated in the first part.

Sakai, Akio; Kohno, Hiroshi

2014-04-01

66

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

NASA Astrophysics Data System (ADS)

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.

Casana, R.; Lazar, G.

2014-09-01

67

Gapped symmetry preserving surface state for the electron topological insulator

NASA Astrophysics Data System (ADS)

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 implicitly assumed that if the TI surface preserves both symmetries then it must be gapless. Here we show that it is possible for the TI surface to be both gapped and symmetry preserving, at the expense of having surface-topological order. In contrast to analogous bosonic topological insulators, this symmetric surface topological order is intrinsically non-Abelian. We show that the surface-topological order provides a complete nonperturbative definition of the electron TI that transcends a free-particle band-structure picture, and could provide a useful perspective for studying strongly correlated topological Mott insulators.

Wang, Chong; Potter, Andrew C.; Senthil, T.

2013-09-01

68

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

69

An acoustic charge transport imager for high definition television applications

NASA Astrophysics Data System (ADS)

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.

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

1993-09-01

70

An acoustic charge transport imager for high definition television applications

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

71

NSDL National Science Digital Library

Geometry and Topology is "a fully refereed international journal dealing with all aspects of geometry and topology and their applications." The publisher, Geometry & Topology Publications (GTP), is a non-profit organization based in the Mathematics Department of the University of Warwick at Coventry, UK. Visitors can browse the journal, available free of charge electronically, or search by keyword or author. The moderate collection within the Geometry and Topology Monographs series includes research monographs and refereed conference proceedings.

72

A Survey of Computer Network Topology and Analysis Examples

A Survey of Computer Network Topology and Analysis Examples Brett Meador, brett an introduction to Computer Network Topology. Definitions of Physical and Logical Topologies are provided. Additionally common Computer Network realizations of Physical Topologies are reviewed. This is followed

Jain, Raj

73

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.

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

74

NASA Astrophysics Data System (ADS)

In the presence of axial magnetic fields that can be realized in deliberately buckled monolayer graphene, quasirelativistic Dirac fermions may find themselves in a variety of broken-symmetry phases even for weak repulsive interactions. Through a detailed Hartree self-consistent numerical calculation in finite strained graphene with cylindrical and open boundaries, we establish the possibility of realizing a charge-density wave order for the spinless fermions in the presence of weak nearest-neighbor repulsion. Such an instability gives rise to a staggered pattern of average fermionic density between bulk and boundary of the system as well as among two sublattices of honeycomb lattice, due to the spatial separation of the zero-energy states localized on opposite sublattices. Although with fermions spin restored, an unconventional magnetic order driven by the onsite repulsion possibly leads to the dominant instability at the Dirac point, the proposed charge-density wave order can nevertheless be realized at finite doping, which is always accompanied by a finite ferromagnetic moment. Additionally, the charge-density wave phase supports a quantized charge or spin Hall conductivity when its formation away from the Dirac point is further preceded by the appearance of topological anomalous or spin Hall insulator, respectively. The topological orders in strained graphene can be supported by weak second-neighbor repulsion, for example. Therefore, depending on the relative strength of various short-range components of the Coulomb interaction, several broken-symmetry phases can be realized within the zero-energy manifold in strained graphene.

Roy, Bitan; Sau, Jay D.

2014-08-01

75

We calculate the lattice two-point function of topological charge density in pure-glue QCD using the discretization of the operator based on the overlap Dirac matrix. Utilizing data at three lattice spacings it is shown that the continuum limit of the correlator complies with the requirement of non-positivity at non-zero distances. For our choice of the overlap operator and the Iwasaki gauge action we find that the size of the positive core is ~2a (with a being the lattice spacing) sufficiently close to the continuum limit. This result confirms that the overlap-based topological charge density is a valid local operator over realistic backgrounds contributing to the QCD path integral, and is important for the consistency of recent results indicating the existence of a low-dimensional global brane-like topological structure in the QCD vacuum. We also confirm the divergent short-distance behavior of the correlator, and the non-integrable nature of the associated contact part.

I. Horvath; A. Alexandru; J. B. Zhang; Y. Chen; S. J. Dong; T. Draper; K. F. Liu; N. Mathur; S. Tamhankar; H. B. Thacker

2005-04-07

76

Topological Solitons in Physics.

ERIC Educational Resources Information Center

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)

Parsa, Zohreh

1979-01-01

77

In this work we investigate the nature of the Cl···N interactions in complexes formed between substituted ammonium [NHn(X3-n) (with n?=?0, 1, 2, 3 and X?=?-CH3, -F] as Lewis bases and F-Cl molecule as Lewis acid. They have been chosen as a study case due to the wide range of variation of their binding energies, BEs. Møller-Plesset [MP2/6-311++G(2d,2p)] calculations show that the BEs for this set of complexes lie in the range from 1.27 kcal/mol (in F-Cl···NF3) to 27.62 kcal/mol [in F-Cl···N(CH3)3]. The intermolecular distribution of the electronic charge density and their L(r)?=?-¼?(2)?(r) function have been investigated within the framework of the atoms in molecules (AIM) theory. The intermolecular interaction energy decomposition has also been analyzed using the reduced variational space (RVS) method. The topological analysis of the L(r) function reveals that the local topological properties measured at the (3,+1) critical point [in L(r) topology] are good descriptors of the strength of the halogen bonding interactions. The results obtained from energy decomposition analysis indicate that electrostatic interactions play a key role in these halogen bonding interactions. These results allow us to establish that, when the halogen atom is bonded to a group with high electron-withdrawing capacity, the electrostatic interaction between the electron cloud of the Lewis base and the halogen atom unprotected nucleus of the Lewis acid produces the formation and determines the geometry of the halogen bonded complexes. In addition, a good linear relationship has been established between: the natural logarithm of the BEs and the electrostatic interaction energy between electron charge distribution of N atom and nucleus of Cl atom, denoted as V e-n(N,Cl) within the AIM theory. PMID:23076553

Duarte, Darío J R; Sosa, Gladis L; Peruchena, Nélida M

2013-05-01

78

As a methodology for controlling the carrier transport of topological insulators (TI's), a flexible tuning in carrier number on the surface states (SS's) of three dimensional TI's by surface modifications using organic molecules is described. The principle of the carrier tuning and its type conversion of TI's presented in this research are based on the charge transfer of holes or electrons at the TI/organic molecule interface. By employing 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) as an electron acceptor or tetracyanoquinodimethane (TCNQ) as a donor for n- and p- Bi2-xSbxTe3-ySey (BSTS) single crystals, successful carrier conversion from n to p and its reverse mode is demonstrated depending on the electron affinities of the molecules. The present method provides a nondestructive and efficient method for local tuning in carrier density of TI's, and is useful for future applications.

Tanabe, Yoichi; Nouchi, Ryo; Heguri, Satoshi; Mu, Gang; Xu, Jingtao; Shimotani, Hidekazu; Tanigaki, Katsumi

2014-01-01

79

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

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

2014-11-12

80

Individual hydrogen bond (HB) energies have been estimated in several systems involving multiple HBs such as adenine–thymine and guanine–cytosine using electron charge densities calculated at X?H hydrogen bond critical points (HBCPs) by atoms in molecules (AIM) method at B3LYP\\/6-311++G?? and MP2\\/6-311++G?? levels. A symmetrical system with two identical H bonds has been selected to search for simple relations between ?HBCP

A. Ebrahimi; S. M. Habibi Khorassani; H. Delarami

2009-01-01

81

The recent discovery of the RNA interference mechanism emphasizes the biological importance of short, isolated, double-stranded (ds) RNA helices and calls for a complete understanding of the biophysical properties of dsRNA. However, most previous studies of the electrostatics of nucleic acid duplexes have focused on DNA. Here, we present a comparative investigation of electrostatic effects in RNA and DNA. Using resonant (anomalous) and non-resonant small-angle X-ray scattering, we characterized the charge screening efficiency and counterion distribution around short (25 bp) dsDNA and RNA molecules of comparable sequence. Consistent with theoretical predictions, we find counterion mediated screening to be more efficient for dsRNA than dsDNA. Furthermore, the topology of the RNA A-form helix alters the spatial distribution of counterions relative to B-form DNA. The experimental results reported here agree well with ion-size-corrected non-linear Poisson–Boltzmann calculations. We propose that differences in electrostatic properties aid in selective recognition of different types of short nucleic acid helices by target binding partners. PMID:19395592

Pabit, Suzette A.; Qiu, Xiangyun; Lamb, Jessica S.; Li, Li; Meisburger, Steve P.; Pollack, Lois

2009-01-01

82

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.

M. Z. Hasan; C. L. Kane

2010-01-01

83

NSDL National Science Digital Library

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

Bartelt, Terry L.

2009-04-30

84

NASA Astrophysics Data System (ADS)

The application of topology, the mathematics of conserved properties under continuous deformations, is creating a range of new opportunities throughout photonics. This field was inspired by the discovery of topological insulators, in which interfacial electrons transport without dissipation, even in the presence of impurities. Similarly, the use of carefully designed wavevector-space topologies allows the creation of interfaces that support new states of light with useful and interesting properties. In particular, this suggests unidirectional waveguides that allow light to flow around large imperfections without back-reflection. This Review explains the underlying principles and highlights how topological effects can be realized in photonic crystals, coupled resonators, metamaterials and quasicrystals.

Lu, Ling; Joannopoulos, John D.; Solja?i?, Marin

2014-11-01

85

Topology is revolutionizing photonics, bringing with it new theoretical discoveries and a wealth of potential applications. This field was inspired by the discovery of topological insulators, in which interfacial electrons transport without dissipation even in the presence of impurities. Similarly, new optical mirrors of di?fferent wave-vector space topologies have been constructed to support new states of light propagating at their interfaces. These novel waveguides allow light to flow around large imperfections without back-reflection. The present review explains the underlying principles and highlights the major findings in photonic crystals, coupled resonators, metamaterials and quasicrystals.

Lu, Ling; Solja?i?, Marin

2014-01-01

86

Topological bootstrap theory of hadrons

A topological framework is constructed for anS-matrix bootstrap theory of particles. Each component of anS-matrix topological expansion is associated with a pair of intersecting “quantum” and “classical” surfaces whose complexity exhibits an entropy property. The bounded classical surface embeds graphs that carry the direct observables — energymomentum, spin and electric charge. The closed quantum surface carries a triangulation whose orientations

G. F. Chew; V. Poénaru

1981-01-01

87

Topology Explains Why Automobile Sunshades Fold Oddly

ERIC Educational Resources Information Center

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.

Feist, Curtis; Naimi, Ramin

2009-01-01

88

NASA Astrophysics Data System (ADS)

Topology may play an important role in cosmology in several different ways. First, Einstein's field equations tell us about the local geometry of the universe but not about its topology. Therefore, the universe may be multiply connected. Inflation predicts that the fluctuations that made clusters and groups of galaxies arose from random quantum fluctuations in the early universe. These should be Gaussian random phase. This can be tested by quantitatively measuring the topology of large-scale structure in the universe using the genus statistic. If the original fluctuations were Gaussian random phase then the structure we see today should have a spongelike topology. A number of studies by our group and others have shown that this is indeed the case. Future tests using the Sloan Digital Sky Survey should be possible. Microwave background fluctuations should also exhibit a characteristic symmetric pattern of hot and cold spots. The COBE data are consistent with this pattern and the MAP and PLANCK satellites should provide a definitive test. If the original inflationary state was metastable then it should decay by making an infinite number of open inflationary bubble universes. This model makes a specific prediction for the power spectrum of fluctuations in the microwave background which can be checked by the MAP and PLANCK satellites. Finally, Gott and Li have proposed how a multiply connected cosmology with an early epoch of closed timelike curves might allow the universe to be its own mother.

Gott, J. Richard, III

1998-09-01

89

Topological Pumping over a Photonic Fibonacci Quasicrystal

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.

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

2014-01-01

90

Topological Pumping over a Photonic Fibonacci Quasicrystal

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.

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

2014-03-27

91

NASA Astrophysics Data System (ADS)

A topology-intrinsic connection between the stabilities of Fermi surfaces (FSs) and topological insulators/superconductors (TIs/TSCs) is revealed. First, through revealing the topological difference of the roles played by the time-reversal (or particle-hole) symmetry respectively on FSs and TIs/TSCs, a one-to-one relation between the topological types of FSs and TIs/TSCs is rigorously derived by two distinct methods with one relying on the direct evaluation of topological invariants and the other on K theory. Secondly, we propose and prove a general index theorem that relates the topological charge of FSs on the natural boundary of a TI/TSC to its bulk topological number. In the proof, FSs of all codimensions for all symmetry classes and topological types are systematically constructed by Dirac matrices. Moreover, implications of the general index theorem on the boundary quasiparticles are also addressed.

Zhao, Y. X.; Wang, Z. D.

2014-02-01

92

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

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.

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

2005-12-27

93

Lattice QCD without topology barriers

NASA Astrophysics Data System (ADS)

As the continuum limit is approached, lattice QCD simulations tend to get trapped in the topological charge sectors of field space and may consequently give biased results in practice. We propose to bypass this problem by imposing open (Neumann) boundary conditions on the gauge field in the time direction. The topological charge can then flow in and out of the lattice, while many properties of the theory (the hadron spectrum, for example) are not affected. Extensive simulations of the SU(3) gauge theory, using the HMC and the closely related SMD algorithm, confirm the absence of topology barriers if these boundary conditions are chosen. Moreover, the calculated autocorrelation times are found to scale approximately like the square of the inverse lattice spacing, thus supporting the conjecture that the HMC algorithm is in the universality class of the Langevin equation.

Lüscher, Martin; Schaefer, Stefan

2011-07-01

94

NASA Astrophysics Data System (ADS)

Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras). In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra. A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions, on adapte ici de la même manière la définition du double quantique. Ce double topologique est alors dualisable et reflexif (même pour des algèbres de dimension infinie). Dans un cas simple on montre, en considérant le double comme la "classe zéro" d'une théorie d'extensions, l'unicité de cette structure comme algèbre quasi-Hopf.

Bonneau, Philippe

95

NSDL National Science Digital Library

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.

Workshop, Watsonville E.

2011-01-01

96

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.

Helene Porchon

2012-01-25

97

Is a color superconductor topological?

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_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(m^2+p_z^2)^(1/2). 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=(\\mu^2+\\Delta^2)^(1/2) 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.

Yusuke Nishida

2010-01-14

98

Topological extensions of the supersymmetry algebra for extended objects

NASA Astrophysics Data System (ADS)

We show that the supersymmetry algebra for supersymmetric extended objects can contain, depending on the topology of space, topological charges, the origin of which is the Wess-Zumino term in the effective action. We exhibit the consequences of these charges for the phenomenon of partial breaking of supersymmetry.

de Azcárraga, J. A.; Gauntlett, J. P.; Izquierdo, J. M.; Townsend, P. K.

1989-11-01

99

On recursion relations in topological string theory

We discuss a link between the topological recursion relations derived algebraically by Witten and the holomorphic anomaly equation of Bershadsky, Cecotti, Ooguri and Vafa. This is obtained through the definition of an operator ${\\cal{W}}_s$ that reproduces the recursion relations for topological string theory coupled to worldsheet gravity a la BCOV. This operator is contained inside an algebra that generalizes the tt* equations and whose direct consequence is the holomorphic anomaly equation itself.

Andrea Prudenziati

2012-10-16

100

Topological BF field theory description of topological insulators

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.

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

101

The topological structure of the electric topological current of the locally gauge invariant Maxwell-Chern-Simons Model and its bifurcation is studied. The electric topological charge is quantized in term of winding number. The Hopf indices and Brouwer degree labeled the local topological structure of the electric topological current. Using $\\Phi $-mapping method and implicity theory, the electric topological current is found generating or annihilating at the limit points and splitting or merging at the bifurcate points. The total electric charge holds invariant during the evolution.

Sheng Li; Yishi Duan

1998-08-28

102

Inducing magneto-electric response in topological insulator

NASA Astrophysics Data System (ADS)

Utilizing electric potential and magnetic scalar potential formulas, which contain zero-order Bessel functions of the first kind and the constitutive relations of topological insulators, we obtained the induced magnetic scalar potentials and induced magnetic monopole charges which are induced by a point charge in topological insulators. The results show that infinite image magnetic monopole charges are generated by a point electric charge. The magnitude of the induced magnetic monopole charges are determined not only by the point electric charge, but also by the material parameters.

Zeng, Lunwu; Song, Runxia; Zeng, Jing

2013-02-01

103

Soft topological objects in topological media

Topological invariants in terms of the Green's function in momentum and real space determine properties of smooth textures within topological media. In space dimension D=1 the topological invariant N_3 in terms of the Green's function G(\\omega,k_x,x) determines the fermion number of the 1D soliton, while in space dimension D=3 the topological invariant N_5 in terms of the Green's function G(\\omega,k_x,k_y,k_z,z) determines quantization of Hall conductivity in the soliton plane within the topological insulators.

Jukka I. Vayrynen; G. E. Volovik

2011-01-06

104

Topological susceptibility with the improved Asqtad action

As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.

C. Bernard et al.

2004-01-06

105

Black Holes, q-Deformed 2d Yang-Mills, and Non-perturbative Topological Strings

We count the number of bound states of BPS black holes on local Calabi-Yau three-folds involving a Riemann surface of genus g. We show that the corresponding gauge theory on the brane reduces to a q-deformed Yang-Mills theory on the Riemann surface. Following the recent connection between the black hole entropy and the topological string partition function, we find that for a large black hole charge N, up to corrections of O(e^-N), Z_BH is given as a sum of a square of chiral blocks, each of which corresponds to a specific D-brane amplitude. The leading chiral block, the vacuum block, corresponds to the closed topological string amplitudes. The sub-leading chiral blocks involve topological string amplitudes with D-brane insertions at 2g-2 points on the Riemann surface analogous to the Omega points in the large N 2d Yang-Mills theory. The finite N amplitude provides a non-perturbative definition of topological strings in these backgrounds. This also leads to a novel non-perturbative formulation of c=1 non-critical string at the self-dual radius.

Aganagic, Mina; Ooguri, Hirosi; Saulina, Natalia; Vafa, Cumrun

2005-01-28

106

Topological insulators and superconductors from string theory

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).

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

107

Topological Aspects of Differential Chains

In this paper we investigate the topological properties of the space of differential chains 'B(U) defined on an open subset U of a Riemannian manifold M. We show that 'B(U) is not generally reflexive, identifying a fundamental difference between currents and differential chains. We also give several new brief (though non-constructive) definitions of the space 'B(U), and prove that it is a separable ultrabornological (DF)-space. Differential chains are closed under dual versions of fundamental operators of the Cartan calculus on differential forms. The space has good properties some of which are not exhibited by currents B'(U) or D'(U). For example, chains supported in finitely many points are dense in 'B(U) for all open U in M, but not generally in the strong dual topology of B'(U).

Jenny Harrison; Harrison Pugh

2011-01-02

108

Topological mechanisms as classical spinor fields

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.

Vincenzo Vitelli; Nitin Upadhyaya; Bryan Gin-ge Chen

2014-07-10

109

Topological mechanisms as classical spinor fields

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.

Vitelli, Vincenzo; Chen, Bryan Ging-ge

2014-01-01

110

Exotic topological types of Majorana zero modes and their universal quantum manipulation

NASA Astrophysics Data System (ADS)

From our general index theorem, which characterizes faithfully the topological intrinsic boundary-bulk correspondence of topological superconductors and insulators, we reveal rigorously that four topologically distinct types of Majorana zero modes can emerge at the ends of superconducting wires of various symmetry classes. More intriguingly, we establish three exotic one-dimensional models that have different types of topological charge of Majorana zero modes and disclose exactly the corresponding topological properties, whose distinct topological essences may be tested experimentally. Moreover, we also address their application in universal quantum manipulation, which is promising for realizing universal topological quantum computation.

Zhao, Y. X.; Wang, Z. D.

2014-09-01

111

Deficient topological measures and functionals generated by them

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.

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

2013-05-31

112

Topological quantum matter "Topologically protected matter"

spin Hall insulators because of the analogy to quantum Hall systems 3D version: Bi2Sb3, Bi2Te3, Sb2Te3,... Bulk insulators with metallic spin-momentum locked states at the edge (2D) / surface (3D entanglement: integer quantum Hall effect, topological insulators, Chern insulators, topological

Johannesson, Henrik

113

Multimaterial topology optimization

Apr 15, 2013 ... a series of binary phase topology optimization sub-problems which are solved partially, in a .... condition) and dependency of final topology to initial design. Moreover, the ...... properties of its mother algorithm. Considering the ...

R. Tavakoli

2013-04-15

114

Boundaries and Topological Algorithms

This thesis develops a model for the topological structure of situations. In this model, the topological structure of space is altered by the presence or absence of boundaries, such as those at the edges of objects. ...

Fleck, Margaret Morrison

1988-09-01

115

Dual-wavelength laser with topological charge

NASA Astrophysics Data System (ADS)

We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ? n ? 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of n? per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

Yu, Haohai; Xu, Miaomiao; Zhao, Yongguang; Wang, Yicheng; Han, Shuo; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang

2013-09-01

116

NASA Technical Reports Server (NTRS)

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.

Lieberman, R. N.

1972-01-01

117

Detecting topological currents in graphene superlattices.

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

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

118

A hierarchy of topological tensor network states

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.

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

119

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

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

1997-01-01

120

NASA Astrophysics Data System (ADS)

We investigate modifications of the Lifshitz black hole solutions due to the presence of Maxwell charge in higher dimensions for arbitrary z and any topology. We find that the behavior of large black holes is insensitive to the topology of the solutions, whereas for small black holes significant differences emerge. We generalize a relation previously obtained for neutral Lifshitz black branes, and study more generally the thermodynamic relationship between energy, entropy, and chemical potential. We also consider the effect of Maxwell charge on the effective potential between objects in the dual theory.

Dehghani, M. H.; Mann, R. B.; Pourhasan, R.

2011-08-01

121

Gapped symmetry preserving surface state for the electron topological insulator

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 ...

Wang, Chong

122

Fractional Topological Insulators in Three Dimensions

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.

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

123

Fractional topological insulators in three dimensions.

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

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

2010-12-10

124

Membranes for topological M-theory

We formulate a theory of topological membranes on manifolds with G2 holonomy. The BRST charges of the theories are the superspace Killing vectors (the generators of global supersymmetry) on the background with reduced holonomy G2?Spin(7). In the absence of spinning formulations of supermembranes, the starting point is an N = 2 target space supersymmetric membrane in seven euclidean dimensions. The

Ling Bao; Viktor Bengtsson; Martin Cederwall; Bengt E. W. Nilsson

2006-01-01

125

Periodic table for topological insulators and superconductors

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

Alexei Kitaev; Alexei

2009-01-01

126

Nondeterministic inductive definitions Benno van den Berg

NonÂdeterministic inductive definitions Benno van den Berg 14 Apr, 2011 Abstract We study a new ``nonÂdeterministic inducÂ tive definitions''. We give applications to formal topology as well in what is called formal topology, which can be proved in MartinÂLË?of's type theory, but not in CZF

van den Berg, Benno

127

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.

Kalb, Jeffrey L.; Lee, David S.

2008-01-01

128

Inducing a magnetic monopole with topological surface States.

Existence of the magnetic monopole is compatible with the fundamental laws of nature; however, this elusive particle has yet to be detected experimentally. We show theoretically that an electric charge near a 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 may 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. PMID:19179491

Qi, Xiao-Liang; Li, Rundong; Zang, Jiadong; Zhang, Shou-Cheng

2009-02-27

129

Hopf insulators and their topologically protected surface states

NASA Astrophysics Data System (ADS)

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.

Deng, D.-L.; Wang, S.-T.; Shen, C.; Duan, L.-M.

2013-11-01

130

Topological insulators and topological nonlinear {sigma} models

In this paper we link the physics of topological nonlinear {sigma} models with that of Chern-Simons insulators. We show that corresponding to every 2n-dimensional Chern-Simons insulator there is a (n-1)-dimensional topological nonlinear {sigma} model with the Wess-Zumino-Witten term. Breaking internal symmetry in these nonlinear {sigma} models leads to nonlinear {sigma} models with the {theta} term. [This is analogous to the dimension reduction leading from 2n-dimensional Chern-Simons insulators to (2n-1) and (2n-2)-dimensional topological insulators protected by discrete symmetries.] The correspondence described in this paper allows one to derive the topological term in a theory involving fermions and order parameters (we shall referred to them as ''fermion-{sigma} models'') when the conventional gradient-expansion method fails. We also discuss the quantum number of solitons in topological nonlinear {sigma} model and the electromagnetic action of the (2n-1)-dimensional topological insulators. Throughout the paper we use a simple model to illustrate how things work.

Yao Hong; Lee, Dung-Hai [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States) and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-12-15

131

Topological crystalline insulator nanostructures.

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 Bi2Se3 and Bi2Te3, 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, Pb1-xSnxSe, and Pb1-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 Bi2Se3 and Bi2Te3. 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

Shen, Jie; Cha, Judy J

2014-11-01

132

Topological mirror superconductivity.

We demonstrate the existence of topological superconductors (SCs) protected by mirror and time-reversal symmetries. D-dimensional (D=1, 2, 3) crystalline SCs are characterized by 2(D-1) independent integer topological invariants, which take the form of mirror Berry phases. These invariants determine the distribution of Majorana modes on a mirror symmetric boundary. The parity of total mirror Berry phase is the Z(2) index of a class DIII SC, implying that a DIII topological SC with a mirror line must also be a topological mirror SC but not vice versa and that a DIII SC with a mirror plane is always time-reversal trivial but can be mirror topological. We introduce representative models and suggest experimental signatures in feasible systems. Advances in quantum computing, the case for nodal SCs, the case for class D, and topological SCs protected by rotational symmetries are pointed out. PMID:23952424

Zhang, Fan; Kane, C L; Mele, E J

2013-08-01

133

Topological Structure of the SU(3) Vacuum

We investigate the topological structure of the vacuum in SU(3) lattice gauge theory. We use under-relaxed cooling to remove the high-frequency fluctuations and a variety of "filters" to identify the topological charges in the resulting smoothened field configurations. We find a densely packed vacuum with an average instanton size, in the continuum limit, of about 0.5 fm. The density at large sizes decreases as a large inverse power of the size. At small sizes we see some sign of a trend towards the asymptotic perturbative behaviour. We find that an interesting polarisation phenomenon occurs: the large topological charges tend to have, on the average, the same sign and are over-screened by the smaller charges which tend to have, again on the average, the opposite sign to the larger instantons. We also calculate the topological susceptibility for which we obtain a continuum value of about 187 MeV. We perform the calculations for various volumes, lattice spacings and numbers of cooling sweeps, so as to obtain some control over the associated systematic errors. The coupling range is from beta=6.0 to beta=6.4 and the lattice volumes range from 16x16x16x48 to 32x32x32x64.

Douglas A. Smith; Michael J. Teper

1998-01-09

134

Static topologically-nontrivial configurations in sigma-models, for spatial dimension D \\geq 2, are unstable. The question addressed here is whether such sigma-model solitons can be stabilized by steady rotation in internal space; that is, rotation in a global SO(2) symmetry. This is the mechanism which stabilizes Q-balls (non-topological solitons). The conclusion is that the Q-mechanism can stabilize topological solitons in D=2 spatial dimensions, but not for D=3.

R. S. Ward

2003-02-07

135

Topology and Geometry Software

NSDL National Science Digital Library

The Topology and Geometry Software site provides downloads for games and interactive simulations. These help the user to understand finitely infinite systems. Many are available in multiple languages.

Weeks, Jeff

2009-06-15

136

Topology (Program Description)

... homotopy theory, ordinary and extraordinary homology and cohomology, cobordism theory, and K-theory ... geometric group theory; and general topology and continua theory. Due Dates Proposals must be ...

137

- criticality of topological black holes in Lovelock-Born-Infeld gravity

NASA Astrophysics Data System (ADS)

To understand the effect of third order Lovelock gravity, - criticality of topological AdS black holes in Lovelock-Born-Infeld gravity is investigated. The thermodynamics is further explored with some more extensions and in some more detail than the previous literature. A detailed analysis of the limit case is performed for the seven-dimensional black holes. It is shown that, for the spherical topology, - criticality exists for both the uncharged and the charged cases. Our results demonstrate again that the charge is not the indispensable condition of - criticality. It may be attributed to the effect of higher derivative terms of the curvature because similar phenomenon was also found for Gauss-Bonnet black holes. For , there would be no - criticality. Interesting findings occur in the case , in which positive solutions of critical points are found for both the uncharged and the charged cases. However, the - diagram is quite strange. To check whether these findings are physical, we give the analysis on the non-negative definiteness condition of the entropy. It is shown that, for any nontrivial value of , the entropy is always positive for any specific volume . Since no - criticality exists for in Einstein gravity and Gauss-Bonnet gravity, we can relate our findings with the peculiar property of third order Lovelock gravity. The entropy in third order Lovelock gravity consists of extra terms which are absent in the Gauss-Bonnet black holes, which makes the critical points satisfy the constraint of non-negative definiteness condition of the entropy. We also check the Gibbs free energy graph and "swallow tail" behavior can be observed. Moreover, the effect of nonlinear electrodynamics is also included in our research.

Mo, Jie-Xiong; Liu, Wen-Biao

2014-04-01

138

Game Theory and Topological Phase Transition

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.

Tieyan Si

2006-01-02

139

A new class of non-topological solitons

NASA Technical Reports Server (NTRS)

A class of non-topological solitons was constructed in renormalizable scalar field theories with nonlinear self-interactions. For large charge Q, the soliton mass increases linearly with Q, i.e., the soliton mass density is approximately independent of charge. Such objects could be naturally produced in a phase transition in the early universe or in the decay of superconducting cosmic strings.

Frieman, Joshua A.; Lynn, Bryan W.

1989-01-01

140

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.

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

2013-10-15

141

Topological Insulators & Superconductors

Topological Insulators & Superconductors New Frontiers in Low-Dimensional Systems Program 3-5 November 2010 Jadwin Hall, Fourth Floor, Room 407 Topological Insulators and Superconductors have quickly insulators but have holographic edge or surface states which are robust to disorder and impurities

142

Inet: Internet Topology Generator

Network research often involves the evaluation of new application designs, system architectures, and protocol implementations. Due to the immense scale of the Internet, deploying an Internet-wide system for the purpose of experimental study is nearly impossible. Instead, researchers evaluate their designs using generated random network topologies. In this report, we present a topology generator that is based on Autonomous System

Cheng Jin; Qian Chen; Sugih Jamin

2000-01-01

143

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

Mirkin, Sergei

144

Tunable Dirac Fermion Dynamics in Topological Insulators

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

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

145

Periodic table for topological insulators and superconductors

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 Z{sub 2}. 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.

Kitaev, Alexei [California Institute of Technology, Pasadena, CA 91125 (United States)

2009-05-14

146

Periodic table for topological insulators and superconductors

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 Z_2. 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.

Alexei Kitaev

2009-01-18

147

The interplay of topological constraints and Coulomb interactions in static and dynamic properties of charged polymers is investigated by numerical simulations and scaling arguments. In the absence of screening, the long-range interaction localizes irreducible topological constraints into tight molecular knots, while composite constraints are factored and separated. Even when the forces are screened, tight knots may survive as local (or even global) equilibria, as long as the overall rigidity of the polymer is dominated by the Coulomb interactions. As entanglements involving tight knots are not easy to eliminate, their presence greatly influences the relaxation times of the system. In particular, we find that tight knots in open polymers are removed by diffusion along the chain, rather than by opening up. The knot diffusion coefficient actually decreases with its charge density, and for highly charged polymers the knot's position appears frozen.

Paul G. Dommersnes; Yacov Kantor; Mehran Kardar

2002-07-10

148

We study a topological phase of interacting bosons in (3+1) dimensions which is protected by charge conservation and time-reversal symmetry. We present an explicit lattice model which realizes this phase and which 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 which 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.

Scott Geraedts; Olexei Motrunich

2014-08-05

149

Topology in Information Theory in Topology.

National Technical Information Service (NTIS)

We prove that timed capacity in information theory is a Euclidean continuous function of noise. This is a result based on topological methods that benefits work in information theory. Then we show that binary timing capacity is a measure of distance which...

K. Martin

2008-01-01

150

Influence of autocorrelation on the topology of the climate network

Different definitions of links in climate networks may lead to considerably different network topologies. We construct a network from climate records of surface level atmospheric temperature in different geographical sites around the globe using two commonly used definitions of links. Utilizing detrended fluctuation analysis, shuffled surrogates and separation analysis of maritime and continental records, we find that one of the major influences on the structure of climate networks is due to the auto-correlation in the records, that may introduce spurious links. This may explain why different methods could lead to different climate network topologies.

Guez, Oded C; Havlin, Shlomo

2014-01-01

151

Topological Phase Transition without Gap Closing

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

Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

2013-01-01

152

Topological susceptibility with the asqtad action

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.

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

153

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

154

Higgsless superconductivity from topological defects in compact BF terms

We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalizable 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 realized as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

M. Cristina Diamantini; Carlo A. Trugenberger

2014-08-21

155

Effect of improving the lattice gauge action on QCD topology

We use lattice topology as a laboratory to-compare the Wilson action (WA) with the Symanzik-Weisz (SW) action constructed from a combination of (1 x 1) and (1 x 2) Wilson loops, and the estimate of the renormalization trajectory (RT)[1] from a renormalization group transformation (RGT) which also includes higher representations of the (1 x 1) loop. Topological charges are computed using the geometric (Luscher`s) and plaquette methods on the uncooled lattice, and also by using cooling to remove ultraviolet artifacts. We show that as the action improves by approaching the RT, the topological charges for individual configurations, computed using these three methods become more highly correlated, suggesting that artificial lattice renormalizations to the topological susceptibility can be suppressed by improving the action.

Grandy, J. [Lawrence Livermore National Lab., CA (United States); Kilcup, G. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics

1996-08-19

156

Effect of Improving the Lattice Gauge Action on QCD Topology

We use lattice topology as a laboratory to compare the Wilson action (WA) with the Symanzik-Weisz (SW) action constructed from a combination of (1x1) and (1x2) Wilson loops, and the estimate of the renormalization trajectory (RT) from a renormalization group transformation (RGT) which also includes higher representations of the (1x1) loop. Topological charges are computed using the geometric (L\\"uscher's) and plaquette methods on the uncooled lattice, and also by using cooling to remove ultraviolet artifacts. We show that as the action improves by approaching the RT, the topological charges for individual configurations computed using these three methods become more highly correlated, suggesting that artificial lattice renormalizations to the topological susceptibility can be suppressed by improving the action.

J. Grandy; G. Kilcup

1996-09-03

157

Experimental Discovery of Topological Insulators and Related Superconductors

Most quantum states of condensed matter are categorized by the symmetries they break. The remarkable discovery of charge Quantum Hall effects (1980s) revealed that there exists an organizational principle of matter based only on the topological distinctions, but in the presence of time-reversal symmetry breaking. In the past few years, theoretical developments suggest that new classes of topological states of matter might exist that are purely topological in nature in the sense that they do not break time-reversal symmetry, and hence can be realized without any applied magnetic field: "Quantum Hall-like effects without Magnetic Fields." This talk describes our discovery of new topologically ordered states of matter (topological insulators) and discusses the unusual electro-magnetic, spin, and superconducting properties this novel phase of quantum matter might exhibit and their potential applications.

Hasan, M. Zahid (Princeton) [Princeton

2010-09-15

158

Topological black holes in Horava-Lifshitz gravity

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.

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

159

Topological solitons in 8-spinor mie electrodynamics

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.

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

2013-10-15

160

Quantum Circuit Model Topological Model

Quantum Circuit Model Topological Model Comparison of Models Topological Quantum Computation Eric Rowell Texas A&M University October 2010 Eric Rowell Topological Quantum Computation #12;Quantum Circuit Model Topological Model Comparison of Models Outline 1 Quantum Circuit Model Gates, Circuits

Rowell, Eric C.

161

Topological Quantum Computation with the universal R matrix for Ising anyons

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.

Lachezar S. Georgiev

2008-12-12

162

Photonic Floquet Topological Insulators

NASA Astrophysics Data System (ADS)

The topological insulator is a fundamentally new phase of matter, with the property that the conduction of electrons occurs only on the surface, not in the bulk. Perhaps the most fascinating and technologically important aspect of this material is ``topological protection,'' the total lack of scattering of electrons by disorder. This effect occurs at room temperature and without an external magnetic field, unlike in quantum Hall systems, which require extremely low temperatures and a strong field. 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 achieving topological protection of light at optical frequencies for applications in optical isolation and robust photon transport. Here, we theoretically propose and experimentally demonstrate the topological protection of light, without the need for an external field. The system is composed of an array of spiralling waveguides, evanescently coupled to one another, and arranged in a honeycomb lattice. The chirality of the waveguides results in scatter-free, one-way edge states that are topologically protected from scattering.

Rechtsman, Mikael; Zeuner, Julia; Plotnik, Yonatan; Segev, Mordechai; Szameit, Alexander

2013-03-01

163

on their fundamental definitions, further research has been conducted on 3D tensor topology [15, 30, 31]. MoreTopological Visualization of Brain Diffusion MRI Data Thomas Schultz, Holger Theisel, and Hans. The present work suggests a comparable method for the visualization of human brain diffusion MRI data. We

164

Geometrically induced electric polarization in conical topological insulators

We study the topological magnetoelectric effect on a conical topological insulator when a point charge $q$ is near the cone apex. The Hall current induced on the cone surface and the image charge configuration are determined. We also study a kind of gravitational Aharonov-Bohm effect in this geometry and realize a phase diference betwen the components of the wavefunctions (spinors) upon closed parallel transport around the (singular) cone tip. Concretely, a net current flowing towards cone apex (or botton) shows up, yielding electric polarization of the conical topological insulator. Such an effect may be detected, for instance, by means of the net accumulated Hall charge near the apex. Once it depends only on the geometry of the material (essetially, the cone apperture angle) this may be faced as a microscopic scale realization of (2+1)-dimensional Einstein gravity.

Jakson M. Fonseca; Winder A. Moura-Melo; Afranio R. Pereira

2011-11-29

165

Topological insulators and superconductors

NASA Astrophysics Data System (ADS)

We study theoretical properties of robust low energy electronic excitations associated with topological insulators and superconductors. The bulk materials are described by non-interacting single particle band Hamiltonians with a finite excitation gap. Their topological phases are classifed according to symmetries and dimensions, characterized by discrete bulk invariants, and correspond to topologically protected gapless excitations bounded to boundaries, interfaces or other kinds of defects. In particular, we study the metallic surface states of the three dimensional topological insulator Bi1-- xSbx, critical edge transport behavior of quantum spin Hall insulators (QSHI) using point contact geometry, Majorana bound states in three dimensions and their resemblance to Ising statistics, and various gapless modes accompanying topological defects in insulators and superconductors. We illustrate the topological phase of Bi1-- xSbx by calculating its surface energy spectrum numerically from a previously proposed tight binding model. An odd number of surface Dirac cones occupy the surface Brillouin zone and exhibit the strong topological nature of the material. We investigate the critical conductance behavior of a point contact in QSHI using a spinful Luttinger liquid description along the edges. For weak interactions, a novel intermediate fixed point controls the pinch-off transition, and the universal crossover scaling function of conductance is extracted from the solvable limits for the Luttinger parameter g = 1 -- epsilon, g = 1/2 + epsilon, and g = 1/ 3 . Majorana fermions are studied as zero energy quasiparticle excitations associated with pointlike topological defects in 3D superconductors. The low energy modes are described phenomenologically in a Dirac-type Bogoliubov de Gennes (BdG) framework, and the Majorana bound states are shown to exhibit Ising non-Abelian statistics despite living in (3 + 1) dimensions. In particular, novel braidless operations are shown to be responsible for fermion parity pumping processes, and are unique features in 3D. A unified framework to classify topological defects in insulators and superconductors is developed. A 2 + 8-fold periodic classification is discovered. A generalized bulk-boundary correspondence equates the topology to robust gapless defect modes. Physical proposals are made especially using heterostructures to achieve desirable low energy electronic excitations in line and point defects as well as adiabatic cycles.

Teo, Jeffrey C. Y.

166

NASA Astrophysics Data System (ADS)

As exotic phenomena in optics, topological states in photonic crystals have drawn much attention due to their fundamental significance and great potential applications. Because of the broken time-reversal symmetry under the influence of an external magnetic field, the photonic crystals composed of magneto-optical materials will lead to the degeneracy lifting and show particular topological characters of energy bands. The upper and lower bulk bands have nonzero integer topological numbers. The gapless edge states can be realized to connect two bulk states. This topological photonic states originated from the topological property can be analogous to the integer quantum Hall effect in an electronic system. The gapless edge state only possesses a single sign of gradient in the whole Brillouin zone, and thus the group velocity is only in one direction leading to the one-way energy flow, which is robust to disorder and impurity due to the nontrivial topological nature of the corresponding electromagnetic states. Furthermore, this one-way edge state would cross the Brillouin center with nonzero group velocity, where the negative-zero-positive phase velocity can be used to realize some interesting phenomena such as tunneling and backward phase propagation. On the other hand, under the protection of time-reversal symmetry, a pair of gapless edge states can also be constructed by using magnetic-electric coupling meta-materials, exhibiting Fermion-like spin helix topological edge states, which can be regarded as an optical counterpart of topological insulator originating from the spin-orbit coupling. The aim of this article is to have a comprehensive review of recent research literatures published in this emerging field of photonic topological phenomena. Photonic topological states and their related phenomena are presented and analyzed, including the chiral edge states, polarization dependent transportation, unidirectional waveguide and nonreciprocal optical transmission, all of which might lead to novel applications such as one-way splitter, optical isolator and delay line. In addition, the possible prospect and development of related topics are also discussed.

He, Cheng; Lin, Liang; Sun, Xiao-Chen; Liu, Xiao-Ping; Lu, Ming-Hui; Chen, Yan-Feng

2014-01-01

167

1. Theory of CW-Complexes 1. Definitions.

1. Theory of CW-Complexes 1. Definitions. A CW-complex is a topological space which * *attaching maps. They are an important ingredient of the CW-structure. Here are better def* *initions. Definition. A CW-complex is a topological space X together with a filtration

Johannson, Klaus

168

Interaction effects and quantum phase transitions in topological insulators

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.

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

169

Topology of three-dimensional separated flows

NASA Technical Reports Server (NTRS)

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.

Tobak, M.; Peake, D. J.

1981-01-01

170

Polydispersity-driven topological defects as order-restoring excitations

The engineering of defects in crystalline matter has been extensively exploited to modify the mechanical and electrical properties of many materials. Recent experiments on manipulating extended defects in graphene, for example, show that defects direct the flow of electric charges. The fascinating possibilities offered by defects in two dimensions, known as topological defects, to control material properties provide great motivation to perform fundamental investigations to uncover their role in various systems. Previous studies mostly focus on topological defects in 2D crystals on curved surfaces. On flat geometries, topological defects can be introduced via density inhomogeneities. We investigate here topological defects due to size polydispersity on flat surfaces. Size polydispersity is usually an inevitable feature of a large variety of systems. In this work, simulations show well-organized induced topological defects around an impurity particle of a wrong size. These patterns are not found in systems of identical particles. Our work demonstrates that in polydispersed systems topological defects play the role of restoring order. The simulations show a perfect hexagonal lattice beyond a small defective region around the impurity particle. Elasticity theory has demonstrated an analogy between the elementary topological defects named disclinations to electric charges by associating a charge to a disclination, whose sign depends on the number of its nearest neighbors. Size polydispersity is shown numerically here to be an essential ingredient to understand short-range attractions between like-charge disclinations. Our study suggests that size polydispersity has a promising potential to engineer defects in various systems including nanoparticles and colloidal crystals. PMID:24706918

Yao, Zhenwei; Olvera de la Cruz, Monica

2014-01-01

171

Adiabatic topological quantum computing

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.

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

2014-06-10

172

Topology and Fermionic Condensate

NASA Astrophysics Data System (ADS)

The purpose of this paper is to investigate an influence of a space-time topology on the formation of fermionic condensate in the model with four-fermion interaction ()2. The value for the space-time with topology of R1 × R1 × S1 is found. Moreover a relation of the value of fermionic condensate to a periodic length is studied. In this connection the possibility of a relation of the topologic deposits to structure of hadrons is discussed.

Kulikov, I.; Pronin, P.

173

Topology optimized microbioreactors.

This article presents the fusion of two hitherto unrelated fields--microbioreactors and topology optimization. The basis for this study is a rectangular microbioreactor with homogeneously distributed immobilized brewers yeast cells (Saccharomyces cerevisiae) that produce a recombinant protein. Topology optimization is then used to change the spatial distribution of cells in the reactor in order to optimize for maximal product flow out of the reactor. This distribution accounts for potentially negative effects of, for example, by-product inhibition. We show that the theoretical improvement in productivity is at least fivefold compared with the homogeneous reactor. The improvements obtained by applying topology optimization are largest where either nutrition is scarce or inhibition effects are pronounced. PMID:21404253

Schäpper, Daniel; Lencastre Fernandes, Rita; Lantz, Anna Eliasson; Okkels, Fridolin; Bruus, Henrik; Gernaey, Krist V

2011-04-01

174

25 CFR 700.105 - Utility charges.

Code of Federal Regulations, 2011 CFR

...Instructions Definitions § 700.105 Utility charges. Utility charges means the cost for heat, lighting, hot water, electricity, natural gas, butane, propane, wood, coal or other fuels water, sewer and trash...

2011-04-01

175

25 CFR 700.105 - Utility charges.

Code of Federal Regulations, 2013 CFR

...Instructions Definitions § 700.105 Utility charges. Utility charges means the cost for heat, lighting, hot water, electricity, natural gas, butane, propane, wood, coal or other fuels water, sewer and trash...

2013-04-01

176

25 CFR 700.105 - Utility charges.

Code of Federal Regulations, 2010 CFR

...Instructions Definitions § 700.105 Utility charges. Utility charges means the cost for heat, lighting, hot water, electricity, natural gas, butane, propane, wood, coal or other fuels water, sewer and trash...

2010-04-01

177

178

Probing the topological structure of the QCD vacuum with overlap fermions

Overlap fermions implement exact chiral symmetry on the lattice and are thus an appropriate tool for investigating the chiral and topological structure of the QCD vacuum. We study various chiral and topological aspects on Luescher-Weisz-type quenched gauge field configurations using overlap fermions as a probe. Particular emphasis is placed upon the analysis of the spectral density and the localisation properties of the eigenmodes as well as on the local structure of topological charge fluctuations.

Ilgenfritz, E M; Koma, Y; Schierholz, G; Streuer, T; Weinberg, V

2006-01-01

179

Multidimensional Topological Foam

Multidimensional cosmological model with the topology M=RxM_1xM_2x...xM_n where M_i (i=1,... ,n) undergo a chain splitting into arbitrary number of compact spaces is considered. It is shown that equations of motion can be solved exactly because they depend only on the effective curvatures and dimensions and "forget" about inner topological structure. It is proved that effective cosmological action for the model with n=1 in the case of infinite splitting of the internal space coincides with the tree-level effective action for a bosonic string.

A. Zhuk

1997-01-15

180

Systems with topological structures

NASA Astrophysics Data System (ADS)

The first chapter of this article provides the mathematical prerequisites needed. The second chapter deals with valuated objects and logics. In the third chapter the topological foundations for approximation of objects by other objects are given, e.g. valuated filter and ideal bases on partial ordered sets and uniform measures. Then it is shown, how by these classical topological concepts fuzzy set theory and fuzzy logic can be described. In the fourth chapter applications to models of I/O-systems are made, including systems with hierarchical control, complex and evolutionary systems. The final chapter includes historical remarks and comparisons with related developments.

Albrecht, Rudolf F.

1998-07-01

181

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

182

Is a color superconductor topological?

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 ...

Nishida, Yusuke

183

Topological Quantum Computing Jacob Colbert

Topological Quantum Computing Jacob Colbert 3/5/2011 Contents 1 Introduction 1 2 Typical Quantum Computing 2 2.1 What is Quantum Computing? . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Quantum Error Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Topological Quantum Computing

Rosner, Jonathan L.

184

Wild topology, hyperbolic geometry and fusion algebra of high energy particle physics

The relation between Wild Topology, Hyperbolic Geometry and Fusion Algebra on the one side and the charge and coupling constants of the standard model and quantum gravity on the other is examined.The close connection found between E(?) theory and the Topological theory of four manifolds as well as the theory of fundamental groups is elucidated using various classical theories and

M. S. El Naschie

2002-01-01

185

We study a topological phase of interacting bosons in (3+1) dimensions which is protected by charge conservation and time-reversal symmetry. We present an explicit lattice model which realizes this phase and which 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 which 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 ...

Geraedts, Scott

2014-01-01

186

Order, topology and preference

NASA Technical Reports Server (NTRS)

Some standard order-related and topological notions, facts, and methods are brought to bear on central topics in the theory of preference and the theory of optimization. Consequences of connectivity are considered, especially from the viewpoint of normally preordered spaces. Examples are given showing how the theory of preference, or utility theory, can be applied to social analysis.

Sertel, M. R.

1971-01-01

187

Holographic fractional topological insulators

We give a holographic realization of the recently proposed low-energy effective action describing a fractional topological insulator. In particular we verify that the surface of this hypothetical material supports a fractional quantum Hall current corresponding to half that of a Laughlin state.

Hoyos, Carlos; Jensen, Kristan; Karch, Andreas [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

2010-10-15

188

The quantum theory of a type of generally covariant field theory, that has no local degrees of freedom, is described. Physical observables that capture topological properties of the manifold are identified and a representation of their Poisson algebra is constructed to obtain the quantum theory. A non-Abelian generalization to SU(2) is also discussed in a similar way.

Husain, V. (Department of Physics, University of Utah, Salt Lake City, Utah 84112 (US))

1991-03-15

189

Estimation of Topological Dimension

We present two extensions of the algorithm by Broomhead et al (2) which is based on the idea that singular values that scale linearly with the radius of the data ball can be exploited to develop algorithms for computing topological dimension and for detecting whether data models based on manifolds are appropriate. We present a geometric scaling property and dimensionality

Douglas R. Hundley; Michael J. Kirby

2003-01-01

190

Collapse of topological texture

NASA Astrophysics Data System (ADS)

We study analytically the process of a topological texture collapse in the approximation of a scaling ansatz in the nonlinear sigma model. In this approximation we show that in flat space-time topological texture eventually collapses while in the case of a spatially flat expanding universe its fate depends on the rate of expansion. If the universe is inflationary, then there is a possibility that texture will expand eternally; in the case of exponential inflation the texture may also shrink or expand eternally to a finite limiting size, although this behavior is degenerate. In the case of power law noninflationary expansion topological texture eventually collapses. In a cold matter dominated universe we find that the texture which is formed comoving with the universe expansion starts collapsing when its spatial size becomes comparable to the Hubble size, a result which is in agreement with previous considerations. In the nonlinear sigma-model approximation we consider also the final stage of the collapsing ellipsoidal topological texture. We show that during the collapse of such a texture at least two of its principal dimensions shrink to zero in a similar way, so that their ratio remains finite. The third dimension may remain finite (collapse of the cigar type), or it may also shrink to zero similar to the other two dimensions (collapse of the scaling type), or shrink to zero similar to the product of the remaining two dimensions (collapse of the pancake type).

Barabash, O. V.; Shtanov, Yu. V.

1998-10-01

191

Communication Concerns 1. Topology

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 Sort, Adding Number, Sieve of Eratosthenes Star Pixel-by-Pixel Image Processing, Monte

Snir, Marc

192

Weyl semimetal from the honeycomb array of topological insulator nanowires

NASA Astrophysics Data System (ADS)

We introduce a topological semimetal phase with four isolated Weyl nodes in momentum space from a honeycomb arrangement of topological insulator nanowires. This realizes a Weyl semimetal phase in which the topological charge response is absent due to the opposite separation of two pairs of Weyl nodes in the Brillouin zone (BZ). The topological nature of the system manifests itself in the nonzero transverse “valley” current which is proportional to the length of the Weyl nodes' separation vector. In the end, we show that anomalous Hall current can also emerge by considering the Haldane term, i.e., the next-nearest-neighbour inter-wire hopping of the electrons in the presence of a modulating magnetic flux.

Vazifeh, M. M.

2013-06-01

193

Topology Change of Black Holes

The topological structure of the event horizon has been investigated in terms of the Morse theory. The elementary process of topological evolution can be understood as a handle attachment. It has been found that there are certain constraints on the nature of black hole topological evolution: (i) There are n kinds of handle attachments in (n + 1)-dimensional black hole

Daisuke Ida; Masaru Siino

2007-01-01

194

We discuss physical properties of “integer” topological phases of bosons in D = 3 + 1 dimensions, protected by internal symmetries like time reversal and/or charge conservation. These phases invoke interactions in a ...

Vishwanath, Ashvin

195

NASA Astrophysics Data System (ADS)

Topological insulators are materials with a bulk band gap, which carry conducting surface states that are protected against disorder. In three dimensions, the insulators carry 2D Dirac fermions on their surfaces. The opening of a magnetic surface gap can exhibit a topological magnetoelectric effect, and support Majorana fermions which can be manipulated for quantum computation. Previous spin and angle-resolved photoemission studies have shown that Bi 1-xSbx alloy belongs to this class of materials, with a characteristic number nu 0 = 1. Some materials challenges with Bi1-x Sbx alloy however are the significant degree of bulk disorder and a small band gap. Both problems make gating difficult for the manipulation and control of the charge carriers. While ordinary materials such as superconductors and liquid crystals can be described by an order parameter, topological insulators are not associated with a local order parameter resulting from a spontaneous broken symmetry. Rather, they manifest a topological order which requires a direct probe of how their energy bands are connected. Measurement techniques designed to detect a particular order parameter are therefore insufficient to identify the topological character of a material. Alternatively, one can look for properties analogous to the quantum Hall effect as a signature of a topologically ordered system. However, using transport probes to isolate the surface states of the topological insulator requires a pristine bulk with minimal charge carrier density. While advances have been made recently in this direction, a good candidate for such measurements has been elusive. In this thesis, we describe a systematic study of a new topological insulator class with a large band gap and a single surface state Fermi surface. Using synchrochon-based angle-resolved photoemission spectroscopy (ARPES), we measured the topological character of these materials by observing the dispersion of their metallic electronic states confined to the surface. Additionally, we confirmed the unusual spin texture of these surface states using spin-sensitive ARPES. In Chapter 1, we first give a brief summary of the theoretical developments leading to the proposal of the topological insulator. In Chapter 2, a description of the experimental techniques of spin and angle-resolved PES is provided. Chapter 3 presents experimental data for three members of the topological class: Bi2Se3, Bi2Te3 and Sb2Te3. In each of the discussions, a comparison with the respective theoretical surface state calculations is presented. Finally, in Chapter 4, we present several techniques for manipulating the metallic surface states of the topological insulators.

Xia, Yuqi

196

Manifestations of topological effects in graphene

Graphene is a monoatomic layer of graphite with Carbon atoms arranged in a two dimensional honeycomb lattice configuration. It has been known for more than sixty years that the electronic structure of graphene can be modelled by two-dimensional massless relativistic fermions. This property gives rise to numerous applications, both in applied sciences and in theoretical physics. Electronic circuits made out of graphene could take advantage of its high electron mobility that is witnessed even at room temperature. In the theoretical domain the Dirac-like behavior of graphene can simulate high energy effects, such as the relativistic Klein paradox. Even more surprisingly, topological effects can be encoded in graphene such as the generation of vortices, charge fractionalization and the emergence of anyons. The impact of the topological effects on graphene's electronic properties can be elegantly described by the Atiyah-Singer index theorem. Here we present a pedagogical encounter of this theorem and review its various applications to graphene. A direct consequence of the index theorem is charge fractionalization that is usually known from the fractional quantum Hall effect. The charge fractionalization gives rise to the exciting possibility of realizing graphene based anyons that unlike bosons or fermions exhibit fractional statistics. Besides being of theoretical interest, anyons are a strong candidate for performing error free quantum information processing.

Jiannis K. Pachos

2008-12-05

197

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

NASA Astrophysics Data System (ADS)

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.

Chen, Xie; Fidkowski, Lukasz; Vishwanath, Ashvin

2014-04-01

198

Flat bands in topological media

Topological media are systems whose properties are protected by topology and thus are robust to deformations of the system. In topological insulators and superconductors the bulk-surface and bulk-vortex correspondence gives rise to the gapless Weyl, Dirac or Majorana fermions on the surface of the system and inside vortex cores. Here we show that in gapless topological media, the bulk-surface and bulk-vortex correspondence is more effective: it produces topologically protected gapless fermions without dispersion -- the flat band. Fermion zero modes forming the flat band are localized on the surface of topological media with protected nodal lines and in the vortex core in systems with topologically protected Fermi points (Weyl points). Flat band has an extremely singular density of states, and we show that this property may give rise in particular to surface superconductivity which could exist even at room temperature.

T. T. Heikkila; N. B. Kopnin; G. E. Volovik

2010-12-04

199

Topological phases and multiqubit entanglement

Global phase factors of topological origin, resulting from cyclic local $\\rm{SU}$ evolution, called topological phases, were first described in [Phys. Rev. Lett. {\\bf 90}, 230403 (2003)], in the case of entangled qubit pairs. In this paper we investigate topological phases in multi-qubit systems as the result of cyclic local $\\rm{SU(2)}$ evolution. These phases originate from the topological structure of the local $\\rm{SU(2)}$-orbits and are an attribute of most entangled multi-qubit systems. We discuss the relation between topological phases and SLOCC-invariant polynomials and give examples where topological phases appear. A general method to find the values of the topological phases in an $n$-qubit system is described and a complete list of these phases for up to seven qubits is given.

Markus Johansson; Marie Ericsson; Kuldip Singh; Erik Sjöqvist; Mark S. Williamson

2012-02-03

200

Topological Insulators with SU(2) Landau Levels

NASA Astrophysics Data System (ADS)

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.

Li, Yi; Zhang, Shou-Cheng; Wu, Congjun

2013-11-01

201

Anomaly detection using topology

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

202

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.

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

2008-01-15

203

Spherical topological insulator

NASA Astrophysics Data System (ADS)

The electronic spectrum on the spherical surface of a topological insulator reflects an active property of the helical surface state that stems from a constraint on its spin on a curved surface. The induced spin connection can be interpreted as an effective vector potential associated with a fictitious magnetic monopole induced at the center of the sphere. The strength of the induced magnetic monopole is found to be g=±2?, being the smallest finite (absolute) value compatible with the Dirac quantization condition. We have established an explicit correspondence between the bulk Hamiltonian and the effective Dirac operator on the curved spherical surface. An explicit construction of the surface spinor wave functions implies a rich spin texture possibly realized on the surface of topological insulator nanoparticles. The electronic spectrum inferred by the obtained effective surface Dirac theory, confirmed also by the bulk tight-binding calculation, suggests a specific photoabsorption/emission spectrum of such nanoparticles.

Imura, Ken-Ichiro; Yoshimura, Yukinori; Takane, Yositake; Fukui, Takahiro

2012-12-01

204

Topological confinement and superconductivity

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.

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

2008-01-01

205

Topological Quantum Image Analysis

A new approach to analyzing visual images is proposed, based on the idea of converting an optical image into a spatially varying pattern of polarized squeezed light, which is then used to produce a pattern of chiral edge currents in a thin film topological insulator. Thin films of Bi or Bi doped with Sb which are punctured with an array of sub-micron holes may be a way of realizing this kind of optical quantum information processing.

George Chapline; Jonathan L DuBois

2009-04-28

206

Gods as Topological Invariants

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.

Daniel Schoch

2012-04-01

207

Gods as Topological Invariants

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.

Schoch, Daniel

2012-01-01

208

Battery charger and state of charge indicator. Final report

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.

Latos, T.S.

1984-04-15

209

A Battery Charger and State of Charge Indicator

NASA Technical Reports Server (NTRS)

A battery charger which 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 dc line current to be a mirror image of the ac line voltage is discussed. The power circuit operates 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 dictate the use of high power NPN Darlington switching transistors. The power circuit topology is a three switch design which utilizes 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.

Latos, T. S.

1984-01-01

210

Magnetic-topology evolution in NOAA AR 10501 on 2003 November 18

NASA Astrophysics Data System (ADS)

Context. NOAA AR 10501 produced three flares on 2003 November 18. Two of them were associated with coronal mass ejections (CMEs). Aims: We model the magnetic-field structure of the active region, study the magnetic-topology evolution, and propose a scenario of the observed events. Methods: The coronal magnetic field is reconstructed using a topological model (also called magnetic-charge model). We present an automatic method of choosing the magnetic charges for the case where the charges are located beneath the photosphere. The new method improves quantitative analysis of magnetograms and makes processing faster. Results: We demonstrate that coronal conditions became more favourable for magnetic reconnection before the flaring events. It is also shown that the magnetic-field configuration at the time of both CMEs was critical, close to what is called "topological trigger". We assume that the topological trigger played a key role in the initiation of these CMEs.

Oreshina, A. V.; Oreshina, I. V.; Somov, B. V.

2012-02-01

211

Quantifying the Topology of Large-Scale Structure

We propose and investigate a new algorithm for quantifying the topological properties of cosmological density fluctuations. We first motivate this algorithm by drawing a formal distinction between two definitions of relevant topological characteristics, based on concepts, on the one hand, from differential topology and, on the other, from integral geometry. The former approach leads one to concentrate on properties of the contour surfaces which, in turn, leads to the algorithms CONTOUR2D and CONTOUR3D familiar to cosmologists. The other approach, which we adopt here, actually leads to much simpler algorithms in both two and three dimensions. (The 2D algorithm has already been introduced to the astronomical literature.) We discuss the 3D case in some detail and compare results obtained with it to analogous results using the CONTOUR3D algorithm.

Peter Coles; Andrew G. Davies; Russell C. Pearson

1996-03-27

212

Homotopy Theory of Strong and Weak Topological Insulators

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.

Ricardo Kennedy; Charles Guggenheim

2014-09-08

213

Noncommuting momenta of topological solitons.

We show that momentum operators of a topological soliton may not commute among themselves when the soliton is associated with the second cohomology H2 of the target space. The commutation relation is proportional to the winding number, taking a constant value within each topological sector. The noncommutativity makes it impossible to specify the momentum of a topological soliton, and induces a Magnus force. PMID:24877932

Watanabe, Haruki; Murayama, Hitoshi

2014-05-16

214

Measuring ISP topologies with rocketfuel

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

Neil T. Spring; Ratul Mahajan; David Wetherall

2002-01-01

215

OPTIMAL NETWORK TOPOLOGY DESIGN

NASA Technical Reports Server (NTRS)

This program was developed as part of a research study on the topology design and performance analysis for the Space Station Information System (SSIS) network. It uses an efficient algorithm to generate candidate network designs (consisting of subsets of the set of all network components) in increasing order of their total costs, and checks each design to see if it forms an acceptable network. This technique gives the true cost-optimal network, and is particularly useful when the network has many constraints and not too many components. It is intended that this new design technique consider all important performance measures explicitly and take into account the constraints due to various technical feasibilities. In the current program, technical constraints are taken care of by the user properly forming the starting set of candidate components (e.g. nonfeasible links are not included). As subsets are generated, they are tested to see if they form an acceptable network by checking that all requirements are satisfied. Thus the first acceptable subset encountered gives the cost-optimal topology satisfying all given constraints. The user must sort the set of "feasible" link elements in increasing order of their costs. The program prompts the user for the following information for each link: 1) cost, 2) connectivity (number of stations connected by the link), and 3) the stations connected by that link. Unless instructed to stop, the program generates all possible acceptable networks in increasing order of their total costs. The program is written only to generate topologies that are simply connected. Tests on reliability, delay, and other performance measures are discussed in the documentation, but have not been incorporated into the program. This program is written in PASCAL for interactive execution and has been implemented on an IBM PC series computer operating under PC DOS. The disk contains source code only. This program was developed in 1985.

Yuen, J. H.

1994-01-01

216

NASA Astrophysics Data System (ADS)

We present a study of “nodal-semimetal” phases in which nondegenerate conduction and valence bands touch at points (the “Weyl semimetal”) or lines (the “line-node semimetal”) in three-dimensional momentum space. We discuss a general approach to such states by perturbation of the critical point between a normal insulator (NI) and a topological insulator (TI), breaking either time-reversal (TR) or inversion symmetry. We give an explicit model realization of both types of states in a NI-TI superlattice structure with broken TR symmetry. Both the Weyl and the line-node semimetals are characterized by topologically protected surface states, although in the line-node case, some additional symmetries must be imposed to retain this topological protection. The edge states have the form of “Fermi arcs” in the case of the Weyl semimetal: these are chiral gapless edge states, which exist in a finite region in momentum space, determined by the momentum-space separation of the bulk Weyl nodes. The chiral character of the edge states leads to a finite Hall conductivity. In contrast, the edge states of the line-node semimetal are “flat bands”: these states are approximately dispersionless in a subset of the two-dimensional edge Brillouin zone, given by the projection of the line node onto the plane of the edge. We discuss unusual transport properties of the nodal semimetals and, in particular, point out quantum critical-like scaling of the dc and optical conductivities of the Weyl semimetal and similarities to the conductivity of graphene in the line-node case.

Burkov, A. A.; Hook, M. D.; Balents, Leon

2011-12-01

217

Visualizing vector field topology in fluid flows

NASA Technical Reports Server (NTRS)

Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.

Helman, James L.; Hesselink, Lambertus

1991-01-01

218

Code of Federal Regulations, 2010 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Pricing Flexibility § 69.703 Definitions. For purposes of this subpart: (a) Channel terminations. (1) A channel...

2010-10-01

219

Code of Federal Regulations, 2013 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Pricing Flexibility § 69.703 Definitions. For purposes of this subpart: (a) Channel terminations. (1) A channel...

2013-10-01

220

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Pricing Flexibility § 69.703 Definitions. For purposes of this subpart: (a) Channel terminations. (1) A channel...

2011-10-01

221

Code of Federal Regulations, 2012 CFR

2012-10-01

222

Friedel sum rule in the presence of topological defects for graphene

The Friedel sum rule is extended to deal with topological defects for the case of a graphene cone in the presence of an external Coulomb charge. The dependence in the way the number of states change due to both the topological defect as well as the Coulomb charge are studied. Our analysis addresses both the cases of a subcritical as well as a supercritical value of the Coulomb charge. We also discuss the experimental implications of introducing a self-adjoint extension of the system Hamiltonian. We argue that the boundary conditions following from the self-adjoint extension encode the effect of short range interactions present in the system.

Baishali Chakraborty; Kumar S. Gupta; Siddhartha Sen

2014-03-20

223

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

NASA Astrophysics Data System (ADS)

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.

Tsurumaru, Toyohiro; Tsutsui, Izumi

1999-08-01

224

Chiral Topological Insulator on Nambu 3-Algebraic Geometry

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.

Kazuki Hasebe

2014-03-30

225

Chiral Topological Insulator on Nambu 3-Algebraic Geometry

Chiral topological insulator (AIII-class) with Landau level 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 $(l,l,l-1)$ Laughline-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.

Hasebe, Kazuki

2014-01-01

226

Concept Model on Topological Learning

NASA Astrophysics Data System (ADS)

We discuss a new model for concept based on topological learning, where the learning process on the neural network is represented by mathematical topology. The topological learning of neural networks is summarized by a quotient of input space and the hierarchical step induces a tree where each node corresponds to a quotient. In general, the concept acquisition is a difficult problem, but the emotion for a subject is represented by providing the questions to a person. Therefore, a kind of concept is captured by such data and the answer sheet can be mapped into a topology consisting of trees. In this paper, we will discuss a way of mapping the emotional concept to a topological learning model.

Ae, Tadashi; Kioi, Kazumasa

2010-11-01

227

Detecting Communities Based on Network Topology

Network methods have had profound influence in many domains and disciplines in the past decade. Community structure is a very important property of complex networks, but the accurate definition of a community remains an open problem. Here we defined community based on three properties, and then propose a simple and novel framework to detect communities based on network topology. We analyzed 16 different types of networks, and compared our partitions with Infomap, LPA, Fastgreedy and Walktrap, which are popular algorithms for community detection. Most of the partitions generated using our approach compare favorably to those generated by these other algorithms. Furthermore, we define overlapping nodes that combine community structure with shortest paths. We also analyzed the E. Coli. transcriptional regulatory network in detail, and identified modules with strong functional coherence. PMID:25033828

Liu, Wei; Pellegrini, Matteo; Wang, Xiaofan

2014-01-01

228

Dirac Quantization and Fractional Magnetoelectric Effect on Interacting Topological Insulators

We use Dirac quantization of flux to study fractional charges and axion angles \\theta in interacting topological insulators with gapless surface modes protected by time-reversal symmetry. In interacting topological insulators, there are two types of fractional axion angle due to conventional odd and nontrivial even flux quantization at the boundary. On even flux quantization in a gapped time reversal invariant system, we show that there is a halved quarter fractional quantum Hall effect on the surface with Hall conductance of p/4q e2/2h with p and q odd integers. The gapless surface modes can be characterized by a nontrivial Z2 anomaly emerged from the even flux quantization. It is suggested that the electron can be regarded as a bound state of fractionally charged quarks confined by a nonabelian color gauge field on the Dirac quantization of complex spinor fields.

K. -S. Park; H. Han

2010-10-10

229

Focus on topological quantum computation

NASA Astrophysics Data System (ADS)

Topological quantum computation started as a niche area of research aimed at employing particles with exotic statistics, called anyons, for performing quantum computation. Soon it evolved to include a wide variety of disciplines. Advances in the understanding of anyon properties inspired new quantum algorithms and helped in the characterization of topological phases of matter and their experimental realization. The conceptual appeal of topological systems as well as their promise for building fault-tolerant quantum technologies fuelled the fascination in this field. This ‘focus on’ collection brings together several of the latest developments in the field and facilitates the synergy between different approaches.

Pachos, Jiannis K.; Simon, Steven H.

2014-06-01

230

Focus on topological quantum computation

Topological quantum computation started as a niche area of research aimed at employing particles with exotic statistics, called anyons, for performing quantum computation. Soon it evolved to include a wide variety of disciplines. Advances in the understanding of anyon properties inspired new quantum algorithms and helped in the characterisation of topological phases of matter and their experimental realisation. The conceptual appeal of topological systems as well as their promise for building fault-tolerant quantum technologies fuelled the fascination in this field. This `focus on' brings together several of the latest developments in the field and facilitates the synergy between different approaches.

Jiannis K. Pachos; Steven H. Simon

2014-06-11

231

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

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

Chih-Chiang Hua; Meng-Yu Lin

2000-01-01

232

Long Range Topological Order, the Chiral Condensate, and the Berry Connection in QCD

Topological insulators are substances which are bulk insulators but which carry current via special "topologically protected" edge states. The understanding of long range topological order in these systems is built around the idea of a Berry connection, which is a gauge connection obtained from the phase of the electron wave function transported over momentum space rather than coordinate space. The phase of a closed Wilson loop of the Berry connection around the Brillouin zone defines a topological order parameter which labels discrete flux vacua. The conducting states are surface modes on the domain walls between discrete vacua. Evidence from large-$N_c$ chiral dynamics, holographic QCD, and Monte Carlo observations has pointed to a picture of the QCD vacuum that is very similar to that of a topological insulator, with discrete quasivacua labelled by $\\theta$ angles that differ by mod $2\\pi$. In this picture, the domain walls are membranes of Chern-Simons charge, and the quark condensate consists of surface ...

Thacker, H B

2014-01-01

233

Breakdown of a topological phase: quantum phase transition in a loop gas model with tension.

We study the stability of topological order against local perturbations by considering the effect of a magnetic field on a spin model--the toric code--which is in a topological phase. The model can be mapped onto a quantum loop gas where the perturbation introduces a bare loop tension. When the loop tension is small, the topological order survives. When it is large, it drives a continuous quantum phase transition into a magnetic state. The transition can be understood as the condensation of "magnetic" vortices, leading to confinement of the elementary "charge" excitations. We also show how the topological order breaks down when the system is coupled to an Ohmic heat bath and relate our results to error rates for topological quantum computations. PMID:17359006

Trebst, Simon; Werner, Philipp; Troyer, Matthias; Shtengel, Kirill; Nayak, Chetan

2007-02-16

234

Topologically induced local PandCP violation in QCD × QED

NASA Astrophysics Data System (ADS)

The existence of topological solutions and axial anomaly open a possibility of PandCP violation in QCD. For a reason that has not yet been established conclusively, this possibility is not realized in strong interactions - the experimental data indicate that a global PandCP violation in QCD is absent. Nevertheless, the fluctuations of topological charge in QCD vacuum, although not observable directly, are expected to play an important rôle in the breaking of UA(1) symmetry and in the mass spectrum and other properties of hadrons. Moreover, in the presence of very intense external electromagnetic fields topological solutions of QCD can induce localP-andCP-odd effects in the SUc(3)×Uem(1) gauge theory that can be observed in experiment directly. Here I show how these local parity-violating phenomena can be described by using the Maxwell-Chern-Simons, or axion, electrodynamics as an effective theory. Local P-andCP-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. Very recently, STAR Collaboration presented an observation of the electric charge asymmetry with respect to reaction plane in relativistic heavy ion collisions at RHIC.

Kharzeev, Dmitri E.

2010-01-01

235

Topologically induced local P and CP violation in hot QCD

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.

Kharzeev,D.E.

2009-02-01

236

Finite topology as applied to image analysis

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

V. A. Kovalevsky

1989-01-01

237

Visualizing vector field topology in fluid flows

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

James L. Helman; Lambertus Hesselink

1991-01-01

238

Evolving Neural Networks through Augmenting Topologies

An important question in neuroevolution is how to gain an advantage from evolving neural network topologies along with weights. We present a method, NeuroEvolution of Augmenting Topologies (NEAT), which outperforms the best fixed-topology method on a challenging benchmark reinforcement learning task. We claim that the increased efficiency is due to (1) employing a principled method of crossover of different topologies,

Kenneth O. Stanley; Risto Miikkulainen

2002-01-01

239

Topological Landscapes: A Terrain Metaphor

Â· Advantages: Â Intuitive: humans trained to understand landscapes Â Dimension independent Â Topology + metric of contours Edge: Evolving contour between contour creation/ merge/split/destruction events #12;Contour Tree

Geddes, Cameron Guy Robinson

240

When electrons are subject to a large external magnetic field, the conventional charge quantum Hall effect \\\\cite{Klitzing,Tsui} 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 extreme

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

2009-01-01

241

Screening and atomic-scale engineering of the potential at a topological insulator surface

NASA Astrophysics Data System (ADS)

The electrostatic behavior of a prototypical three-dimensional topological insulator, Bi2Se3(111), is investigated by a scanning tunneling microscopy (STM) study of the distribution of Rb atoms adsorbed on the surface. The positively charged ions are screened by both free electrons residing in the topological surface state as well as band bending induced quantum well states of the conduction band, leading to a surprisingly short screening length. Combining a theoretical description of the potential energy with STM-based atomic manipulation, we demonstrate the ability to create tailored electronic potential landscapes on topological surfaces with atomic-scale control.

Löptien, P.; Zhou, L.; Wiebe, J.; Khajetoorians, A. A.; Mi, J. L.; Iversen, B. B.; Hofmann, Ph.; Wiesendanger, R.

2014-02-01

242

Electric-Magnetic Duality and Topological Insulators

We work out the action of the SL(2,Z) electric-magnetic duality group for an insulator with a nontrivial 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 gauge/gravity correspondence.

Karch, A. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

2009-10-23

243

Topological insulators with SU(2) Landau levels.

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. PMID:24237548

Li, Yi; Zhang, Shou-Cheng; Wu, Congjun

2013-11-01

244

THE DUALIZING SPECTRUM TOPOLOGICAL GROUP

THE DUALIZING SPECTRUM OF A TOPOLOGICAL GROUP JOHN R. KLEIN Abstract. To a topological group G, we91, 55N91, 55P42, 57P10. Secondary: 55P25, 20J05, 18G15. 1 #12; 2 JOHN R. KLEIN 1. Introduction by the (possibly) continuous G, and the integers Z by the sphere S 0 : DG = homD(S 0 [G]) (S 0 ; S 0 [G]) ; where

Bielefeld, University of

245

Topological excitations in semiconductor heterostructures

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.

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

246

Refining the shifted topological vertex

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.

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

247

Galois conjugates of topological phases

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

248

1 A Framework for Computing Topological Network Robustness P. Van Mieghem , C. Doerr, H. Wang, J a definition and a framework to compute topological network robustness. I. INTRODUCTION Any network may on the network. Delft University of Technology, Faculty of Electrical Engineering, Math- ematics and Computer

Van Mieghem, Piet

249

Exact chiral symmetry, topological charge and related topics

It has been shown recently that Dirac operators satisfying the Ginsparg-Wilson relation provide a solution of the chirality problem in QCD at finite lattice spacing. We discuss different ways to construct these operators and their properties. The possibility to define lattice chiral gauge theories is briefly discussed as well.

Ferenc Niedermayer

1998-10-12

250

Spin-transfer torque generated by a topological insulator.

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

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

251

Code of Federal Regulations, 2012 CFR

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2012-07-01

252

Topological defects and textures in complex magnets

NASA Astrophysics Data System (ADS)

Magnetic materials support an astounding array of ordered phases, but some of the most interesting phenomena occur when conventional magnetic order is suppressed in the presence of competing interactions. Such frustrated magnets come in many forms, both classical and quantum. In this thesis I study three cases of frustrated magnetism---artificial spin ice, skyrmion crystals in chiral magnets, and the Kitaev honeycomb model, an exactly solvable quantum spin liquid. Spin ice is a phase of geometrically frustrated ferromagnets that is best known for giving rise to emergent magnetic monopoles. Spin ice on the kagome lattice finds its mesoscopic counterpart in artificial spin ice---a honeycomb network of single domain magnetic nanowires. In the first part of this work I present a model of magnetization reversal in artificial spin ice that is mediated by the magnetic charges moving through the system. The dynamics is dissipative and is influenced strongly by quenched disorder and Coulomb interactions between the charges. A skyrmion is a topologically stable magnetic texture where magnetization points in every possible direction on the sphere. Although it is tempting to think of such objects as regular point particles when solving for their low-energy dynamics, we found that due to their non-trivial topology, one has to take into account the geometric Berry phase---the time derivative term in the Lagrangian that is linear in velocity. Combining that with the elastic potential energy of a crystal, we arrive at the low-frequency spin wave spectrum for skyrmion crystals, which has two branches: a "magnetophonon" branch with a quadratic dispersion and a cyclotron branch with a finite frequency in the long-wavelength limit. Anyons are exotic quasiparticles with fractional exchange statistics that are conjectured to exist in two dimensional systems exhibiting topological order. Non-Abelian anyons are of particular interest due to their potential applications in quantum computing. The gapped phase of Kitaev's honeycomb model gives rise to Abelian anyons that are magnetic fluxes going through lattice plaquettes. In this work I demonstrate that introducing dislocations into the model enriches its properties by binding a zero energy Majorana mode to each defect. Majoranas from a dislocation pair can be combined into a non-local fermion mode that is created or annihilated whenever a flux winds around a dislocation. The nature of the flux itself also changes in this process, reflecting the non-Abelian exchange statistics associated with the dislocations.

Petrova, Olga

253

Non-topological solitons in field theories with kinetic self-coupling

We investigate some fundamental features of a class of non-linear relativistic lagrangian field theories with kinetic self-coupling. We focus our attention upon theories admitting static, spherically symmetric solutions in three space dimensions which are finite-energy and stable. We determine general conditions for the existence and stability of these non-topological soliton solutions. In particular, we perform a linear stability analysis that goes beyond the usual Derrick-like criteria. On the basis of these considerations we obtain a complete characterization of the soliton-supporting members of the aforementioned class of non-linear field theories. We then classify the family of soliton-supporting theories according to the central and asymptotic behaviors of the soliton field, and provide illustrative explicit examples of models belonging to each of the corresponding sub-families. In the present work we restrict most of our considerations to one and many-components scalar models. We show that in these cases the finite-energy static spherically symmetric solutions are stable against charge-preserving perturbations, provided that the vacuum energy of the model vanishes and the energy density is positive definite. We also discuss briefly the extension of the present approach to models involving other types of fields, but a detailed study of this more general scenario will be addressed in a separate publication.

Joaquin Diaz-Alonso; Diego Rubiera-Garcia

2007-05-01

254

Microdeletions of the 5q11.2 region are rare; in literature only two patients with a deletion in this region have been reported so far. In this study, we describe four additional patients and further define this new 5q11.2 microdeletion syndrome. A comparison of the features observed in all six patients with overlapping 5q11.2 deletions showed a phenotypic spectrum that overlaps with CHARGE syndrome and 22q11.2 deletion syndrome including choanal atresia, developmental delay, heart defects, external ear abnormalities, and short stature. No colobomas or abnormalities of semicircular canals and olfactory nerves were reported. Two male patients had genital abnormalities. We estimated a 2.0?Mb (53.0-55.0?Mb) Shortest Region of Overlap (SRO) for the main clinical characteristics of the syndrome. This region contains nine genes and two non-coding microRNAs. In this region DHX29 serves as the candidate gene as it encodes an ATP-dependent RNA-helicase that is involved in the initiation of RNA translation. Screening a small cohort of 14 patients who presented the main features, however, did not reveal any pathogenic abnormalities of DHX29. © 2014 Wiley Periodicals, Inc. PMID:25251717

Snijders Blok, Charlotte; Corsten-Janssen, Nicole; FitzPatrick, David R; Romano, Corrado; Fichera, Marco; Vitello, Girolamo Aurelio; Willemsen, Marjolein H; Schoots, Jeroen; Pfundt, Rolph; van Ravenswaaij-Arts, Conny M A; Hoefsloot, Lies; Kleefstra, Tjitske

2014-11-01

255

Communication: An approximation to Bader's topological atom.

A new, more flexible definition of fuzzy Voronoi cells is proposed as a computationally efficient alternative to Bader's Quantum Theory of Atoms in Molecules (QTAIM) partitioning of the physical space for large-scale routine calculations. The new fuzzy scheme provides atomic charges, delocalization indices, and molecular energy components very close to those obtained using QTAIM. The method is flexible enough to either ignore the presence of spurious non-nuclear attractors or to readily incorporate them by introducing additional fuzzy Voronoi cells. PMID:23968064

Salvador, Pedro; Ramos-Cordoba, Eloy

2013-08-21

256

The electric charge and magnetic moment of neutral fundamental particles

The article focuses on the issue of the two definitions of charge, mainly the gauge charge and the effective charge of fundamental particles. Most textbooks on classical electromagnetism and quantum field theory only works with the gauge charges while the concept of the induced charge remains unattended. In this article it has been shown that for intrinsically charged particles both of the charges remain the same but there can be situations where an electrically neutral particle picks up some electrical charge from its plasma surrounding. The physical origin and the scope of application of the induced charge concept has been briefly discussed in the article.

Kaushik Bhattacharya

2009-05-27

257

Topological order in a correlated three-dimensional topological insulator.

Motivated by experimental progress in the growth of heavy transition metal oxides, we theoretically study a class of lattice models of interacting fermions with strong spin-orbit coupling. Focusing on interactions of intermediate strength, we derive a low-energy effective field theory for a fully gapped, topologically ordered, fractionalized state with an eightfold ground-state degeneracy. This state is a fermionic symmetry-enriched topological phase with particle-number conservation and time-reversal symmetry. The topological terms in the effective field theory describe a quantized magnetoelectric response and nontrivial mutual braiding statistics of dynamical extended vortex loops with emergent fermions in the bulk. We explicitly compute the expected mutual statistics in a specific model on the pyrochlore lattice within a slave-particle mean-field theory. We argue that our model also provides a possible condensed-matter realization of oblique confinement. PMID:24483914

Maciejko, Joseph; Chua, Victor; Fiete, Gregory A

2014-01-10

258

Robust Transport Signatures of Topological Superconductivity in Topological Insulator Nanowires

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

259

Topological Invariants in Point Group Symmetric Photonic Topological Insulators

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.

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

2014-01-01

260

Robust transport signatures of topological superconductivity in topological insulator nanowires.

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

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

2014-09-01

261

Communication Definitions... general definition

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

Jones, Ian L.

262

Two-dimensional transport and screening in topological insulator surface states

NASA Astrophysics Data System (ADS)

We study disorder effects on the surface states of the topological insulator Bi2Se3 close to the topologically protected crossing point. Close to charge neutrality, local fluctuations in carrier density arising from the random charged disorder in the environment result in electron and hole puddles that dominate the electronic properties of these materials. By calculating the polarizability of the surface state using the random-phase approximation, and determining the characteristics of puddles using the self-consistent approximation, we find that band asymmetry plays a crucial role in determining experimentally measured quantities, including the conductivity and the puddle autocorrelation length.

Adam, S.; Hwang, E. H.; Das Sarma, S.

2012-06-01

263

Topological Insulators at Room Temperature

Topological insulators are new states of quantum matter with surface states protected by the time-reversal symmetry. In this work, we perform first-principle electronic structure calculations for Sb{sub 2}Te{sub 3}, Sb{sub 2}Se{sub 3}, Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} crystals. Our calculations predict that Sb{sub 2}Te{sub 3}, Bi{sub 2}T e{sub 3} and Bi{sub 2}Se{sub 3} are topological insulators, while Sb{sub 2}Se{sub 3} is not. In particular, Bi{sub 2}Se{sub 3} has a topologically non-trivial energy gap of 0.3eV , suitable for room temperature applications. We present a simple and unified continuum model which captures the salient topological features of this class of materials. These topological insulators have robust surface states consisting of a single Dirac cone at the {Lambda} point.

Zhang, Haijun; /Beijing, Inst. Phys.; Liu, Chao-Xing; /Tsinghua U., Beijing; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-25

264

Quartic quasi-topological gravity, black holes and holography

NASA Astrophysics Data System (ADS)

In this paper, we derive the field equations of quartic quasi-topological gravity by varying the action with respect to the metric. Also, we obtain the linearized graviton equations in the AdS background and find that it is governed by a second-order field equation as in the cases of Einstein, Lovelock or cubic quasi-topological gravities. But in contrast to the cubic quasi-topological gravity, the linearized field equation around a black hole has fourth-order radial derivative of the perturbation. Moreover, we analyze the conditions of having ghost free AdS solutions and AdS planar black holes. In addition, we compute the central charges of the dual conformal field theory of this gravity theory by studying holographic Weyl anomaly. Finally, we consider the effect of quartic term on the causality of dual theory in the tensor channel and show that, in the contrast to the trivial result of cubic quasi-topological gravity, the existence of both cubic and quartic terms leads to a non-trivial constraint. However, this constraint does not imply any lower positive bound on the viscosity/entropy ratio.

Dehghani, M. H.; Vahidinia, M. H.

2013-10-01

265

Landau theory of topological defects in multiferroic hexagonal manganites.

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. PMID:24162883

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

2014-01-01

266

Landau theory of topological defects in multiferroic hexagonal manganites

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

267

Topological approximation of the nonlinear Anderson model

NASA Astrophysics Data System (ADS)

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.

Milovanov, Alexander V.; Iomin, Alexander

2014-06-01

268

We consider Bose-Einstein condensation of massive electrically charged scalars in a uniform background of charged fermions. We focus on the case when the scalar condensate screens the background charge, while the net charge of the system resides on its boundary surface. A distinctive signature of this substance is that the photon acquires a Lorentz-violating mass in the bulk of the condensate. Due to this mass, the transverse and longitudinal gauge modes propagate with different group velocities. We give qualitative arguments that at high enough densities and low temperatures a charged system of electrons and helium-4 nuclei, if held together by laboratory devices or by force of gravity, can form such a substance. We briefly discuss possible manifestations of the charged condensate in compact astrophysical objects.

Gregory Gabadadze; Rachel A. Rosen

2007-06-15

269

Borohydrides: from sheet to framework topologies.

The five novel compounds ALiM(BH4)4 (A = K or Rb; M = Mg or Mn) and K3Li2Mg2(BH4)9 crystallizing in the space groups Aba2 and P2/c, respectively, represent the first two-dimensional topologies amongst homoleptic borohydrides. The crystal structures have been solved, refined and characterized by synchrotron X-ray powder diffraction, neutron powder diffraction and solid-state DFT calculations. Minimal energies of ordered models corroborate crystal symmetries retrieved from diffraction data. The layered Li-Mg substructure forms negatively charged uninodal 4-connected networks. It is shown that this connectivity cannot generate the long sought-after, bimetallic Li-Mg borohydrides without countercations when assuming preferred coordination polyhedra as found in Mg(BH4)2 and LiBH4. The general properties of the trimetallic compound series are analogous with the anhydrous aluminosilicates. Additionally, a relationship with zeolites is suggested, which are built from three-dimensional Al-Si-O networks with a negative charge on them. The ternary metal borohydride systems are of interest due to their potential as novel hydridic frameworks and will allow exploration of the structural chemistry of light-metal systems otherwise subject to eutectic melting. PMID:24699844

Schouwink, P; Ley, M B; Jensen, T R; Smr?ok, L'; ?erný, R

2014-06-01

270

Ring polymers with topological constraints

In the first part of this work a summary is provided of some recent experiments and theoretical results which are relevant in the research of systems of polymer rings in nontrivial topological conformations. Next, some advances in modeling the behavior of single polymer knots are presented. The numerical simulations are performed with the help of the Wang-Landau Monte Carlo algorithm. To sample the polymer conformation a set of random transformations called pivot moves is used. The crucial problem of preserving the topology of the knots after each move is tackled with the help of two new techniques which are briefly explained. As an application, the results of an investigation of the effects of topology on the thermal properties of polymer knots is reported. In the end, original results are discussed concerning the use of parallelized codes to study polymers knots composed by a large number of segments within the Wang-Landau approach.

Yani Zhao; Franco Ferrari

2014-02-02

271

Topological Mixing with Ghost Rods

Topological chaos relies on the periodic motion of obstacles in a two-dimensional flow in order to form nontrivial braids. This motion generates exponential stretching of material lines, and hence efficient mixing. Boyland et al. [P. L. Boyland, H. Aref, and M. A. Stremler, J. Fluid Mech. 403, 277 (2000)] have studied a specific periodic motion of rods that exhibits topological chaos in a viscous fluid. We show that it is possible to extend their work to cases where the motion of the stirring rods is topologically trivial by considering the dynamics of special periodic points that we call ghost rods, because they play a similar role to stirring rods. The ghost rods framework provides a new technique for quantifying chaos and gives insight into the mechanisms that produce chaos and mixing. Numerical simulations for Stokes flow support our results.

Emmanuelle Gouillart; Jean-Luc Thiffeault; Matthew D. Finn

2005-10-29

272

Nearly Flatbands with Nontrivial Topology

We report the theoretical discovery of a class of 2D tight-binding models containing nearly flatbands with nonzero Chern numbers. In contrast with previous studies, where nonlocal hoppings are usually required, the Hamiltonians of our models only require short-range hopping and have the potential to be realized in cold atomic gases. Because of the similarity with 2D continuum Landau levels, these topologically nontrivial nearly flatbands may lead to the realization of fractional anomalous quantum Hall states and fractional topological insulators in real materials. Among the models we discover, the most interesting and practical one is a square-lattice three-band model which has only nearest-neighbor hopping. To understand better the physics underlying the topological flatband aspects, we also present the studies of a minimal two-band model on the checkerboard lattice.

Sun Kai; Das Sarma, S. [Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Gu Zhengcheng [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Katsura, Hosho [Department of Physics, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588 (Japan)

2011-06-10

273

Topological gravity and transgression holography

We show that Poincare-invariant topological gravity in even dimensions can be formulated as a transgression field theory in one higher dimension whose gauge connections are associated to linear and nonlinear realizations of the Poincare group ISO(d-1,1). The resulting theory is a gauged WZW model whereby the transition functions relating gauge fields live in the coset ISO(d-1,1)/SO(d-1,1). The coordinate parametrizing the coset space is identified with the scalar field in the adjoint representation of the gauge group of the even-dimensional topological gravity theory. The supersymmetric extension leads to topological supergravity in two dimensions starting from a transgression field theory which is invariant under the supersymmetric extension of the Poincare group in three dimensions. We also apply this construction to a three-dimensional Chern-Simons theory of gravity which is invariant under the Maxwell algebra and obtain the corresponding WZW model.

Patricio Salgado; Richard J. Szabo; Omar Valdivia

2014-01-15

274

Emergent Supersymmetry in Topological Superconductors

NASA Astrophysics Data System (ADS)

In the absence of interactions, topological superconductors (TSC) host helical Majorana fermion edge states protected by time reversal symmetry. Increasing interactions can lead to spontaneous magnetic order at the boundary. We show that the associated quantum phase transition, if continuous, has emergent space-time supersymmetry at low energies. The magnetic order parameter field is identified as the superpartner of the Majorana fermions. These results are obtained using field theoretical arguments and are verified by numerical DMRG solution of a lattice model that mimics the physics of the phase transition. The emergent supersymmetry, accessed by tuning a single parameter, has striking consequences such as an exact relation between the correlation functions of fermions and those of the order parameter. Similar results are argued to hold for the 2+1 dimensional boundary of a bulk topological superconductor. Generalization to topological insulator surfaces will be mentioned.

Grover, Tarun; Sheng, Donna; Vishwanath, Ashvin

2013-03-01

275

Topology Change of Black Holes

The topological structure of the event horizon has been investigated in terms of the Morse theory. The elementary process of topological evolution can be understood as a handle attachment. It has been found that there are certain constraints on the nature of black hole topological evolution: (i) There are n kinds of handle attachments in (n+1)-dimensional black hole space-times. (ii) Handles are further classified as either of black or white type, and only black handles appear in real black hole space-times. (iii) The spatial section of an exterior of the black hole region is always connected. As a corollary, it is shown that the formation of a black hole with an S**(n-2) x S**1 horizon from that with an S**(n-1) horizon must be non-axisymmetric in asymptotically flat space-times.

Daisuke Ida; Masaru Siino

2007-04-02

276

Topology Change of Black Holes

The topological structure of the event horizon has been considered in terms of the Morse theory. The elementary process of topology changes can be understood as a handle attachment. It has been found that there are certain constraints on the black hole topology changes: (i) There are n kinds of the handle attachment in the (n+1)-dimensional black hole space-times. (ii) The handle is further classified into either black or white type and only the black handles appear in real black hole space-times. (iii) The spacial section of the exterior of the black hole region is always connected. As a corollary, it is shown that the formation of black hole with the S**(n-2) x S**1 horizon from that with the S**(n-1) horizon must be non-axisymmetric in asymptotically flat space-times.

Ida, Daisuke

2007-01-01

277

Topological Constraints on Magnetic Relaxation

The final state of turbulent magnetic relaxation in a reversed field pinch is well explained by Taylor's hypothesis. However, recent resistive-magnetohydrodynamic simulations of the relaxation of braided solar coronal loops have led to relaxed fields far from the Taylor state, despite the conservation of helicity. We point out the existence of an additional topological invariant in any flux tube with a nonzero field: the topological degree of the field line mapping. We conjecture that this constrains the relaxation, explaining why only one of three example simulations reaches the Taylor state.

Yeates, A. R.; Hornig, G.; Wilmot-Smith, A. L. [Division of Mathematics, University of Dundee, Dundee, DD1 4HN (United Kingdom)

2010-08-20

278

Topological Lensing in Spherical Spaces

This article gives the construction and complete classification of all three-dimensional spherical manifolds, and orders them by decreasing volume, in the context of multiconnected universe models with positive spatial curvature. It discusses which spherical topologies are likely to be detectable by crystallographic methods using three-dimensional catalogs of cosmic objects. The expected form of the pair separation histogram is predicted (including the location and height of the spikes) and is compared to computer simulations, showing that this method is stable with respect to observational uncertainties and is well suited for detecting spherical topologies.

Evelise Gausmann; Roland Lehoucq; Jean-Pierre Luminet; Jean-Philippe Uzan; Jeffrey Weeks

2001-06-11

279

Quantum cosmology with nontrivial topologies

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.

Vargas, T. [Department of Physics and Center for Mathematics and Theoretical Physics, National Central University, Chungli 320, Taiwan (China)

2008-10-10

280

Topological States and adiabatic pumping in quasicrystals.

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

Kraus, Yaacov E; Lahini, Yoav; Ringel, Zohar; Verbin, Mor; Zilberberg, Oded

2012-09-01

281

Topological Hochschild homology of twisted group algebras

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 ...

Vera, Daniel Joseph

2006-01-01

282

Exploring and Improving BitTorrent Topologies

]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

283

Detecting topological currents in graphene superlattices

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 ...

Gorbachev, R. V.

284

Electrical control of spin in topological insulators

NASA Astrophysics Data System (ADS)

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).

Chang, Kai

2012-02-01

285

Magnetic topology effects on Alcator C-Mod flows

The effect of magnetic topology on ion and impurity flows in a tokamak is considered by investigating the consequences of (i) the reversal of toroidal and poloidal magnetic fields and currents; (ii) a switch from lower to upper X-point operation; (iii) poloidal magnetic field or plasma current reversal, and (iv) toroidal magnetic field reversal. The general symmetries associated with magnetic topology changes in tokamaks are employed to demonstrate that the flux surface flows inside and outside the separatrix observed in Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] can be used to determine the flow features, including neoclassical and turbulent effects and in the presence of charge exchange.

Catto, Peter J.; Simakov, Andrei N. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-05-15

286

Generalized Ablowitz-Ladik hierarchy in topological string theory

This paper addresses the issue of integrable structures in topological string theory on generalized conifolds. Open string amplitudes of this theory can be expressed as the matrix elements of an operator on the Fock space of 2D charged free fermion fields. The generating function of these amplitudes with respect to the product of two independent Schur functions becomes a tau function of the 2D Toda hierarchy. The associated Lax operators turn out to have a particular factorized form. This factorized form of the Lax operators characterizes a generalization of the Ablowitz-Ladik hierarchy embedded in the 2D Toda hierarchy. The generalized Ablowitz-Ladik hierarchy is thus identified as a fundamental integrable structure of topological string theory on the generalized conifolds.

Kanehisa Takasaki

2013-12-27

287

Correlated topological insulators with mixed valence.

We propose the local density approximation+Gutzwiller method incorporating a Green's function scheme to study the topological physics of correlated materials from the first principles. Applying this method to typical mixed valence materials SmB(6), we find its nontrivial Z(2) topology, indicating that SmB(6) is a strongly correlated topological insulator. The unique feature of this compound is that its surface states contain three Dirac cones in contrast to most known topological insulators. PMID:23496729

Lu, Feng; Zhao, JianZhou; Weng, Hongming; Fang, Zhong; Dai, Xi

2013-03-01

288

Programming a Topological Quantum Computer

Topological quantum computing has recently proven itself to be a powerful computational model when constructing viable architectures for large scale computation. The topological model is constructed from the foundation of a error correction code, required to correct for inevitable hardware faults that will exist for a large scale quantum device. It is also a measurement based model of quantum computation, meaning that the quantum hardware is responsible only for the construction of a large, computationally universal quantum state. This quantum state is then strategically consumed, allowing for the realisation of a fully error corrected quantum algorithm. The number of physical qubits needed by the quantum hardware and the amount of time required to implement an algorithm is dictated by the manner in which this universal quantum state is consumed. In this paper we examine the problem of algorithmic optimisation in the topological lattice and introduce the required elements that will be needed when designing a classical software package to compile and implement a large scale algorithm on a topological quantum computer.

Simon J. Devitt; Kae Nemoto

2012-09-07

289

Magnetic Field Topology in Jets

NASA Technical Reports Server (NTRS)

We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

Gardiner, T. A.; Frank, A.

2000-01-01

290

Topological methods in quantum gravity

The main technical problem with background independent approaches to quantum gravity is inapplicability of standard quantum field theory methods. New methods are needed which would be adapted to the basic principles of General Relativity. Topological field theory is a model which provides natural tools for background independent quantum gravity. It is exactly soluble and, at the same time, diffeomorphism invariant.

Artem Starodubtsev

2005-01-01

291

Tree topologies in ATM networks

A detailed analysis of tree topologies in ATM networks is developed, by using a general model which takes into account also the problem of node coupling. The performance of the networks is evaluated, in terms of transfer delay and cell loss probability, in many different situations, so proving the flexibility and effectiveness of the proposed method

Andrea Borella; Giovanni Cancellieri; F. Chiaraluce; F. Meschini

1992-01-01

292

Topological Strings from Quantum Mechanics

We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized theta function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P2, local P1xP1 and local F1. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Phys...

Grassi, Alba; Marino, Marcos

2014-01-01

293

Topological visual mapping in robotics.

A key problem in robotics is the construction of a map from its environment. This map could be used in different tasks, like localization, recognition, obstacle avoidance, etc. Besides, the simultaneous location and mapping (SLAM) problem has had a lot of interest in the robotics community. This paper presents a new method for visual mapping, using topological instead of metric information. For that purpose, we propose prior image segmentation into regions in order to group the extracted invariant features in a graph so that each graph defines a single region of the image. Although others methods have been proposed for visual SLAM, our method is complete, in the sense that it makes all the process: it presents a new method for image matching; it defines a way to build the topological map; and it also defines a matching criterion for loop-closing. The matching process will take into account visual features and their structure using the graph transformation matching (GTM) algorithm, which allows us to process the matching and to remove out the outliers. Then, using this image comparison method, we propose an algorithm for constructing topological maps. During the experimentation phase, we will test the robustness of the method and its ability constructing topological maps. We have also introduced new hysteresis behavior in order to solve some problems found building the graph. PMID:22806678

Romero, Anna; Cazorla, Miguel

2012-08-01

294

A versatile zero ripple topology

A lightweight and efficient converter topology is described that presents zero ripple current on both input and output terminals simultaneously. The static and dynamic analyses are performed by using state representation with the current-injected method. A hardware application suitable for a space-station battery conditioner is presented as a validation of the theoretical model.

A. Capel; H. Spruyt; A. Weinberg; D. O'Sullivan; A. Crausaz; J. C. Marpinard

1988-01-01

295

Simultaneous multi-topology multi-objective sizing across thousands of analog circuit topologies

This paper presents MOJITO, a system which optimizes across thousands of analog circuit topologies simultaneously, and returns a set of sized topologies that collectively provide a performance tradeoff. MOJITO defines a space of possible topologies as a hierarchically organized combination of trusted analog building blocks. To minimize the setup burden: no topology selection rules or abstract behaviors need to be

Trent McConaghy; Pieter Palmers; Georges Gielen; Michiel Steyaert

2007-01-01

296

Simultaneous Multi-Topology Multi-Objective Sizing Across Thousands of Analog Circuit Topologies

This paper presents MOJITO, a system which optimizes across thousands of analog circuit topologies simultaneously, and returns a set of sized topologies that collectively provide a performance tradeoff. MOJITO defines a space of possible topologies as a hierarchically organized combination of trusted analog building blocks. To minimize the setup burden: no topology selection rules or abstract behaviors need to be

Trent Mcconaghy; Pieter Palmers; Georges G. E. Gielen; Michiel Steyaert

2007-01-01

297

Role of oxidation on surface conductance of the topological insulator Bi2Te2Se

NASA Astrophysics Data System (ADS)

We investigated the effect of surface oxides on charge transport properties in a topological insulator (Bi2Te2Se) using conductive probe atomic force microscopy in an ultrahigh vacuum environment. Uniform distribution of the measured friction and current were observed over a single quintuple layer terrace after exposure to the ambient environment, which is an indication of uniform surface oxide coverage. An oxide-free topological insulator surface was exposed using tip-induced etching. By comparing surface conduction on a fresh surface versus a surface exposed to air, we observed a minor change in resistance when surface oxide was present. The current density varied with applied load on the oxidized surface, which implies that the topological surface states respond to tip-induced pressure even though surface oxide is present. From these results, we conclude that surface oxidation in air has a negligible effect on surface conductance in topological insulators.

Hwang, Jin Heui; Park, Joonbum; Kwon, Sangku; Kim, Jun Sung; Park, Jeong Young

2014-12-01

298

Breakdown of a topological phase: Quantum phase transition in a loop gas model with tension

We study the stability of topological order against local perturbations by considering the effect of a magnetic field on a spin model -- the toric code -- which is in a topological phase. The model can be mapped onto a quantum loop gas where the perturbation introduces a bare loop tension. When the loop tension is small, the topological order survives. When it is large, it drives a continuous quantum phase transition into a magnetic state. The transition can be understood as the condensation of `magnetic' vortices, leading to confinement of the elementary `charge' excitations. We also show how the topological order breaks down when the system is coupled to an Ohmic heat bath and discuss our results in the context of quantum computation applications.

Simon Trebst; Philipp Werner; Matthias Troyer; Kirill Shtengel; Chetan Nayak

2006-09-03

299

Bosonic topological insulator in three dimensions and the statistical Witten effect

NASA Astrophysics Data System (ADS)

It is well known that one signature of the three-dimensional electron topological insulator is the Witten effect: if the system is coupled to a compact electromagnetic gauge field, a monopole in the bulk acquires a half-odd-integer polarization charge. In the present work, we propose a corresponding phenomenon for the topological insulator of bosons in three dimensions protected by particle number conservation and time-reversal symmetry. We claim that although a monopole inside a topological insulator of bosons can remain electrically neutral, its statistics are transmuted from bosonic to fermionic. We demonstrate that this “statistical Witten effect” directly implies that if the surface of the topological insulator is neither gapless, nor spontaneously breaks the symmetry, it necessarily supports an intrinsic two-dimensional topological order. Moreover, the surface properties can not be fully realized in a purely two-dimensional system. We also confirm that the surface phases of the bosonic topological insulator proposed by Vishwanath and Senthil [Phys. Rev. X2160-330810.1103/PhysRevX.3.011016 3, 011016 (2013)] provide a consistent termination of a bulk exhibiting the statistical Witten effect. In a forthcoming paper, we will provide an explicit field-theoretic, lattice-regularized construction of the three-dimensional topological insulator of bosons, employing a parton decomposition and subsequent condensation of parton-monopole composites.

Metlitski, Max A.; Kane, C. L.; Fisher, Matthew P. A.

2013-07-01

300

Continuity and Separation in Symmetric Topologies

ERIC Educational Resources Information Center

In this note, it is shown that in a symmetric topological space, the pairs of sets separated by the topology determine the topology itself. It is then shown that when the codomain is symmetric, functions which separate only those pairs of sets that are already separated are continuous, generalizing a result found by M. Lynch.

Harris, J.; Lynch, M.

2007-01-01

301

Topology control for multihop packet radio networks

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

Limin Hu

1993-01-01

302

An introduction to topological field theories

Topological field theories may be roughly defined as those for which the correlation functions for observables are precisely topological invariants. The study of such theories is interesting from the mathematical point of view, since they give one the possibility for finding new topological invariants within the framework of field theory. They are also physically interesting due to the interpretation of

J. Roca; Departament d'Estructura

1993-01-01

303

Free loop spaces in topology and

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

ThÃ©venaz, Jacques

304

TOPOLOGICAL STRING THEORY AND ENUMERATIVE GEOMETRY

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

Slatkin, Montgomery

305

Computing topological invariants without inversion symmetry

NASA Astrophysics Data System (ADS)

We consider the problem of calculating the weak and strong topological indices in noncentrosymmetric time-reversal (T) invariant insulators. In 2D we use a gauge corresponding to hybrid Wannier functions that are maximally localized in one dimension. Although this gauge is not smoothly defined on the two-torus,ootnotetextA. A. Soluyanov and D. Vanderbilt, arXiv:1009.1415 it respects the T symmetry of the system and allows for a definition of the Z2 invariant in terms of time-reversal polarization.ootnotetextL. Fu and C. L. Kane, Phys. Rev. B 74, 195312 (2006) In 3D we apply the 2D approach to T-invariant planes. We illustrate the method with first-principles calculations on GeTe and HgTe under [100] and [111] strain. Our approach is different from the one suggested previously by Fukui and HatsugaiootnotetextT. Fukui and Y. Hatsugai, J. Phys. Soc. Jpn. 76, 053702 (2007) and should be easier to implement in ab initio code packages. Time permitting, we will also discuss methods for decomposing the band space into T-paired Chern subspaces, and for carrying out a general construction of a Wannier representation for Z2 insulators.

Soluyanov, Alexey; Vanderbilt, David

2011-03-01

306

Polymer topology revealed by ion mobility coupled with mass spectrometry.

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

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

2014-10-01

307

Persisting topological order via geometric frustration

NASA Astrophysics Data System (ADS)

We introduce a toric code model on the dice lattice which is exactly solvable and displays topological order at zero temperature. In the presence of a magnetic field, the flux dynamics is mapped to the highly frustrated transverse field Ising model on the kagome lattice. This correspondence suggests an intriguing disorder by disorder phenomenon in a topologically ordered system implying that the topological order is extremely robust due to the geometric frustration. Furthermore, a connection between fully frustrated transverse field Ising models and topologically ordered systems is demonstrated which opens an exciting physical playground due to the interplay of topological quantum order and geometric frustration.

Schmidt, Kai Phillip

2013-07-01

308

Topological order following a quantum quench

We determine the conditions under which topological order survives a rapid quantum quench. Specifically, we consider the case where a quantum spin system is prepared in the ground state of the toric code model and, after the quench, it evolves with a Hamiltonian that does not support topological order. We provide analytical results supported by numerical evidence for a variety of quench Hamiltonians. The robustness of topological order under nonequilibrium situations is tested by studying the topological entropy and a dynamical measure, which makes use of the similarity between partial density matrices obtained from different topological sectors.

Tsomokos, Dimitris I. [School of Physics and Astronomy, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Department of Mathematics, Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); Hamma, Alioscia [Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, Ontario, Canada N2L 2Y5 (Canada); Zhang Wen; Haas, Stephan [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089 (United States); Fazio, Rosario [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Center for Quantum Technologies, National University of Singapore, Singapore (Singapore)

2009-12-15

309

Entanglement Entropy and Strongly Correlated Topological Matter

NASA Astrophysics Data System (ADS)

Topological ordered phases are gapped states of matter that are characterized by non-local entanglement in their ground state wave functions instead of a local order parameter. In this paper, we review some of the basic results on the entanglement structure of topologically ordered phases. In particular, we focus on the notion and uses of "topological entanglement entropy" in two and higher dimensions, and also briefly review the relation between entanglement spectrum and the spectrum of the physical edge states for chiral topological states. Furthermore, we discuss a curvature expansion for the entanglement entropy which sharpens the nonlocality of topological entanglement entropy.

Grover, Tarun

2013-02-01

310

CHARGE syndrome was initially defined as a non-random association of anomalies (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies\\/deafness). In 1998, an expert group defined the major (the classical 4C's: Choanal atresia, Coloboma, Characteristic ears and Cranial nerve anomalies) and minor criteria of CHARGE syndrome. Individuals with all four major characteristics or three major and

Kim D Blake; Chitra Prasad

2006-01-01

311

NSDL National Science Digital Library

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.

Kansas, University O.

2006-01-01

312

This is the report of the Intensity Frontier Charged Lepton Working Group of the 2013 Community Summer Study "Snowmass on the Mississippi", summarizing the current status and future experimental opportunities in muon and tau lepton studies and their sensitivity to new physics. These include searches for charged lepton flavor violation, measurements of magnetic and electric dipole moments, and precision measurements of the decay spectrum and parity-violating asymmetries.

J. Albrecht; M. Artuso; K. Babu; R. H. Bernstein; T. Blum; D. N. Brown; B. C. K. Casey; C. -h. Cheng; V. Cirigliano; A. Cohen; A. Deshpande; E. C. Dukes; B. Echenard; A. Gaponenko; D. Glenzinski; M. Gonzalez-Alonso; F. Grancagnolo; Y. Grossman; R. C. Group; R. Harnik; D. G. Hitlin; B. Kiburg; K. Knoepfe; K. Kumar; G. Lim; Z. -T. Lu; D. McKeen; J. P. Miller; M. Ramsey-Musolf; R. Ray; B. L. Roberts; M. Rominsky; Y. Semertzidis; D. Stoeckinger; R. Talman; R. Van De Water; P. Winter

2013-11-21

313

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along ...

Redwine, Robert P.

314

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.

Nigel Cundy; Yongmin Cho; Weonjong Lee

2014-11-04

315

Topics in Open Topological Strings

This thesis is based on some selected topics in open topological string theory which I have worked on during my Ph.D. It comprises an introductory part where I have focused on the points most needed for the later chapters, trading completeness for conciseness and clarity. Then, following [12], we discuss tadpole cancellation for topological strings where we mainly show how its implementation is needed for ensuring the same "odd" moduli decoupling encountered in the closed theory. Next we move to analyse how the open and closed effective field theories for the B model interact writing the complete Lagrangian. We first check it deriving some already known tree level amplitudes in term of target space quantities, and then we extend the recipe to new results; later we implement open closed duality from a target field theory perspective. This last subject is also analysed from a worldsheet point of view extending the analysis of [13]. Some ideas for future research are briefly reported.

Andrea Prudenziati

2010-10-16

316

A free topology safeguards network

Free Topology Network technology provides cost reduction benefits as well as flexibility in safeguards applications. Power line communications technologies have proven viability for transmission and reception of safeguards data, including surveillance photographs, the source of the largest data files. In the future, enhancements will be made to the technology that should boost both performance and flexibility. Work is already underway to achieve higher data rates over power line communications eventually, it should be possible to reach data rates of one million bits per second or higher. Also, the use of technologies such as Novell Embedded Systems Technology (NEST) and Echelon LON technology will allow a greater number of safeguards technologies to become resident on the Free Topology Safeguards Network.

Kadner, S.P.; Resnik, W.M. [Aquila Technologies Group, Inc., Albuquerque, NM (United States); Schurig, A. [Communications Foundation, Orem, UT (United States)

1995-12-31

317

Topology of modified helical gears

NASA Technical Reports Server (NTRS)

The topology of several types of modified surfaces of helical gears is proposed. The modified surfaces allow absorption of a linear or almost linear function of transmission errors. These errors are caused by gear misalignment and an improvement of the contact of gear tooth surfaces. Principles and corresponding programs for computer aided simulation of meshing and contact of gears have been developed. The results of this investigation are illustrated with numerical examples.

Litvin, F. L.; Zhang, J.; Handschuh, R. F.; Coy, J. J.

1989-01-01

318

Evaluations of topological Tutte polynomials

We find a number of new combinatorial identities for, and interpretations of evaluations of, the topological Tutte polynomials of Las Vergnas, $L(G)$, and of and Bollob\\\\'as and Riordan, $R(G)$, as well as for the classical Tutte polynomial $T(G)$. For example, we express $R(G)$ and $T(G)$ as a sum of chromatic polynomials, show that $R(G)$ counts non-crossing graph states and $k$-valuations,

Joanna A. Ellis-Monaghan; Iain Moffatt

2011-01-01

319

Topological defects in extended inflation

NASA Technical Reports Server (NTRS)

The production of topological defects, especially cosmic strings, in extended inflation models was considered. In extended inflation, the Universe passes through a first-order phase transition via bubble percolation, which naturally allows defects to form at the end of inflation. The correlation length, which determines the number density of the defects, is related to the mean size of bubbles when they collide. This mechanism allows a natural combination of inflation and large scale structure via cosmic strings.

Copeland, Edmund J.; Kolb, Edward W.; Liddle, Andrew R.

1990-01-01

320

Search for New Topological Insulators

NASA Astrophysics Data System (ADS)

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 GenBi2mTe3m+n families. [1-5] Work supported by the Office of Basic Energy Sciences, US DOE.[4pt] [1] H. Lin, R. S. Markiewicz, L. A. Wray, L. Fu, M. Z. Hasan, and A. Bansil, Physical Review Letters 105, 036404 (2010). [0pt] [2] H. Lin, L. A. Wray, Y. Xia. S. Y. Xu, S. Jia, R. J. Cava, A. Bansil, and M. Z. Hasan, Nature Materials 9, 546 (2010). [0pt] [3] W. Al-Sawai et al., Physical Review B 82, 125208 (2010). [0pt] [4] L. A. Wray et al., Nature Physics (2010, in press).[0pt] [5] S.-Y. Xu et al., arXiv:1007.5111 (2010).

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

2011-03-01

321

Testing the Topology of Reionization

The central overlap phase of cosmological hydrogen reionization is fundamentally a change in the topology of ionized regions. Before overlap, ionized bubbles grew in isolation. During overlap, they merge into a percolating ionized medium, which fills an ever-increasing volume and eventually replaces neutral gas throughout the intergalactic medium. Overlap can therefore be well studied using topological statistics, and in particular the genus number of the neutral-ionized interface. The most promising observational tools for applying such tests are (a) Lyman alpha galaxies, and (b) 21 cm tomography. Lyman alpha galaxies will be detected whenever they inhabit bubbles larger than 1 physical Mpc, and their presence can therefore be used to map such bubbles. Such large bubbles are expected during the overlap phase, and moreover, each one should contain a few detectably bright Lyman alpha galaxies. The 21cm line in principle affords better spatial resolution, but the required sensitivity and foreground subtraction may be an issue. Upcoming Lyman alpha surveys in the near-infrared could thus provide our first look at the topology of reionization.

James E. Rhoads

2007-08-21

322

Polymer Amide as an Early Topology

Hydrophobic polymer amide (HPA) could have been one of the first normal density materials to accrete in space. We present ab initio calculations of the energetics of amino acid polymerization via gas phase collisions. The initial hydrogen-bonded di-peptide is sufficiently stable to proceed in many cases via a transition state into a di-peptide with an associated bound water molecule of condensation. The energetics of polymerization are only favorable when the water remains bound. Further polymerization leads to a hydrophobic surface that is phase-separated from, but hydrogen bonded to, a small bulk water complex. The kinetics of the collision and subsequent polymerization are discussed for the low-density conditions of a molecular cloud. This polymer in the gas phase has the properties to make a topology, viz. hydrophobicity allowing phase separation from bulk water, capability to withstand large temperature ranges, versatility of form and charge separation. Its flexible tetrahedral carbon atoms that alternate with more rigid amide groups allow it to deform and reform in hazardous conditions and its density of hydrogen bonds provides adhesion that would support accretion to it of silicon and metal elements to form a stellar dust material. PMID:25048204

McGeoch, Julie E. M.; McGeoch, Malcolm W.

2014-01-01

323

Geometric background charge: dislocations on capillary bridges

Recent experiments have shown that colloidal crystals confined to weakly curved capillary bridges introduce groups of dislocations organized into `pleats' as means to relieve the stress caused by the Gaussian curvature of the surface. We consider the onset of this curvature-screening mechanism, by examining the energetics of isolated dislocations and interstitials on capillary bridges with free boundaries. The boundary provides an essential contribution to the problem, akin to a background charge that "neutralizes" the unbalanced integrated curvature of the surface. This makes it favorable for topologically neutral dislocations and groups of dislocations - rather than topologically charged disclinations and scars - to relieve the stress caused by the unbalanced gaussian curvature of the surface. This effect applies to any crystal on a surface with non-vanishing integrated Gaussian curvature and stress-free boundary conditions. We corroborate the analytic results by numerically computing the energetics of a defected lattice of springs confined to surfaces with weak positive and negative curvature

William Irvine; Vincenzo Vitelli

2012-06-19

324

Long Range Topological Order, the Chiral Condensate, and the Berry Connection in QCD

Topological insulators are substances which are bulk insulators but which carry current via special "topologically protected" edge states. The understanding of long range topological order in these systems is built around the idea of a Berry connection, which is a gauge connection obtained from the phase of the electron wave function transported over momentum space rather than coordinate space. The phase of a closed Wilson loop of the Berry connection around the Brillouin zone defines a topological order parameter which labels discrete flux vacua. The conducting states are surface modes on the domain walls between discrete vacua. Evidence from large-$N_c$ chiral dynamics, holographic QCD, and Monte Carlo observations has pointed to a picture of the QCD vacuum that is very similar to that of a topological insulator, with discrete quasivacua labelled by $\\theta$ angles that differ by mod $2\\pi$. In this picture, the domain walls are membranes of Chern-Simons charge, and the quark condensate consists of surface modes on these membranes, which are delocalized and thus support the long range propagation of Goldstone pions. The Berry phase in QED2 describes charge polarization of fermion-antifermion pairs, while in 4D QCD it describes the polarization of Chern-Simons membranes.

H. B. Thacker

2014-09-12

325

Realization of Negative Capacitance with Topological Insulator Based MOS Capacitor

NASA Astrophysics Data System (ADS)

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.

Yuan, Hui; Zhang, Kai; Zhu, Hao; Li, Haitao; Ioannou, Dimitris; Baumgart, Helmut; Richter, Curt; Li, Qiliang

2013-03-01

326

Physical meaning of the QTAIM topological parameters in hydrogen bonding.

This work examined the local topological parameters of charge density at the hydrogen bond (H-bond) critical points of a set of substituted formamide cyclic dimers and enolic tautomers. The analysis was performed not only on the total electron density of the hydrogen bonded complexes but also on the intermediate electron density differences derived from the Morokuma energy decomposition scheme. Through the connection between these intermediate electron density differences and the corresponding differences in topological parameters, the meaning of topological parameters variation due to hydrogen bonding (H-bonding) becomes evident. Thus, for example, we show in a plausible way that the potential energy density differences at the H-bond critical point properly describe the electrostatics of H-bonding, and local kinetic energy density differences account for the localization/delocalization degree of the electrons at that point. The results also support the idea that the total electronic energy density differences at the H-bond critical point describe the strength of the interaction rather than its covalent character as is commonly considered. PMID:25367044

Duarte, Darío J R; Angelina, Emilio L; Peruchena, Nélida M

2014-11-01

327

Charge separation induced by P-odd bubbles in QCD matter

We examine the recent suggestion that P- and CP-odd effects in QCD matter can induce electric charge asymmetry with respect to reaction plane in relativistic heavy ion collisions. General arguments are given which confirm that the angular momentum of QCD matter in the presence of non-zero topological charge should induce an electric field aligned along the axis of the angular momentum. A simple formula relating the magnitude of charge asymmetry to the angular momentum and topological charge is derived. The expected asymmetry is amenable to experimental observation at RHIC and LHC; we discuss the recent preliminary STAR result in light of our findings.

D. Kharzeev; A. Zhitnitsky

2007-06-07

328

Topology of "white" stars in relativistic fragmentation of light nuclei

In the present paper, experimental observations of the multifragmentation processes of light relativistic nuclei carried out by means of emulsions are reviewed. Events of the type of "white" stars in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and the target-nucleus fragments are considered. A distinctive feature of the charge topology in the dissociation of the Ne, Mg, Si, and S nuclei is an almost total suppression of the binary splitting of nuclei to fragments with charges higher than 2. The growth of the nuclear fragmentation degree is revealed in an increase in the multiplicity of singly and doubly charged fragments with decreasing charge of the non-excited part of the fragmenting nucleus. The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to charged fragments were used to study special features of the formation of systems consisting of the lightest $\\alpha$, d, and t nuclei. Clustering in form of the $^3$He nucleus can be detected in "white" stars via the dissociation of neutron-deficient Be, B, C, and N isotopes.

N. P. Andreeva; V. Bradnova; S. Vokal; A. Vokalova; A. Sh. Gaitinov; S. G. Gerasimov; L. A. Goncharova; V. A. Dronov; P. I. Zarubin; I. G. Zarubina; G. I. Orlova; A. D. Kovalenko; A. Kravchakova; V. G. Larionova; F. G. Lepekhin; O. V. Levitskaya; A. I. Malakhov; A. A. Moiseenko; G. I. Orlova; N. G. Peresadko; N. G. Polukhina; P. A. Rukoyatkin; V. V. Rusakova; N. A. Salmanova; V. R. Sarkisyan; B. B. Simonov; E. Stan; R. Stanoeva; M. M. Chernyavsky; M. Haiduc; S. P. Kharlamov; I. Tsakov; T. V. Shchedrina

2006-05-15

329

Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

330

Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields. PMID:24877965

Campbell, Michael G; Tasinkevych, Mykola; Smalyukh, Ivan I

2014-05-16

331

NASA Astrophysics Data System (ADS)

Semiconductor-superconductor hybrid systems are promising candidates for the realization of Majorana fermions and topological order, i.e. topologically protected degeneracies, in solid state devices. We show that the topological order is mirrored in the excitation spectra and can be observed in nonlinear Coulomb blockade transport through a ring-shaped nanowire. Especially, the excitation spectrum is almost independent of magnetic flux in the topologically trivial phase but acquires a characteristic h/e magnetic flux periodicity in the non-trivial phase. The transition between the trivial and non-trivial phase is reflected in the closing and reopening of an excitation gap. We show that the signatures of topological order are robust against details of the geometry, electrostatic disorder and the existence of additional subbands and only rely on the topology of the nanowire and the existence of a superconducting gap. Finally, we show that the coherence length in the non-trivial phase is much longer than in the trivial phase. This opens the possibility to coat the nanowire with superconducting nanograins and thereby significantly reduce the current due to cotunnelling of Cooper pairs and to enhance the Coulomb charging energy without destroying the superconducting gap.

Zocher, Björn; Horsdal, Mats; Rosenow, Bernd

2013-08-01

332

Topological crystalline insulators in transition metal oxides.

Topological crystalline insulators possess electronic states protected by crystal symmetries, rather than time-reversal symmetry. We show that the transition metal oxides with heavy transition metals are able to support nontrivial band topology resulting from mirror symmetry of the lattice. As an example, we consider pyrochlore oxides of the form A2M2O7. As a function of spin-orbit coupling strength, we find two Z2 topological insulator phases can be distinguished from each other by their mirror Chern numbers, indicating a different topological crystalline insulators. We also derive an effective k·p Hamiltonian, similar to the model introduced for Pb(1-x)Sn(x)Te, and discuss the effect of an on-site Hubbard interaction on the topological crystalline insulator phase using slave-rotor mean-field theory, which predicts new classes of topological quantum spin liquids. PMID:25167290

Kargarian, Mehdi; Fiete, Gregory A

2013-04-12

333

Scanning tunneling microscopy studies of topological insulators

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy (STM), with surface sensitivity, is an ideal tool to probe the intriguing properties of the surface state of topological insulators (TIs) and topological crystalline insulators (TCIs). We summarize the recent progress on those topological phases revealed by STM studies. STM observations have directly confirmed the existence of the topological surface states and clearly revealed their novel properties. We also discuss STM work on magnetic doped TIs, topological superconductors and crystalline symmetry-protected surface states in TCIs. The studies have greatly promoted our understanding of the exotic properties of the new topological phases, as well as put forward new challenges. STM will continue to play an important role in this rapidly growing field from the point view of both fundamental physics and applications.

Zhao, Kun; Lv, Yan-Feng; Ji, Shuai-Hua; Ma, Xucun; Chen, Xi; Xue, Qi-Kun

2014-10-01

334

Topological insulators and quantum spin liquids

NASA Astrophysics Data System (ADS)

In this paper we review some connections recently discovered between topological insulators and certain classes of quantum spin liquids, focusing on two and three spatial dimensions. In two dimensions we show the integer quantum Hall effect plays a key role in relating topological insulators and chiral spin liquids described by fermionic excitations, and we describe a procedure for “generating” a certain class of topological states. In three dimensions we discuss interesting relationships between certain quantum spin liquids and interacting “exotic” variants of topological insulators. We focus attention on better understanding interactions in topological insulators, and the phases nearby in parameter space that might result from moderate to strong interactions in the presence of strong spin-orbit coupling. We stress that oxides with heavy transition metal ions, which often host a competition between electron interactions and spin-orbit coupling, are an excellent place to search for unusual topological phenomena and other unconventional phases.

Fiete, Gregory A.; Chua, Victor; Kargarian, Mehdi; Lundgren, Rex; Rüegg, Andreas; Wen, Jun; Zyuzin, Vladimir

2012-02-01

335

Proximity-induced topological state in graphene

NASA Astrophysics Data System (ADS)

The appearance of topologically protected states at the surface of an ordinary insulator is a rare occurrence and to date only a handful of materials are known for having this property. An intriguing question concerns the possibility of forming topologically protected interfaces between different materials. Here we propose that a topological phase can be transferred to graphene by proximity with the three-dimensional topological insulator Bi2Se3. By using density functional and transport theory, we prove that, at the verge of the chemical bond formation, a hybrid state forms at the graphene/Bi2Se3 interface. The state has Dirac-cone-like dispersion at the ? point and a well defined helical spin texture, indicating its topologically protected nature. This demonstrates that proximity can transfer the topological phase from Bi2Se3 to graphene.

Popov, Igor; Mantega, Mauro; Narayan, Awadhesh; Sanvito, Stefano

2014-07-01

336

Photonic simulation of topological excitations in metamaterials

Condensed matter systems with topological order and metamaterials with left-handed chirality have attracted recently extensive interests in the fields of physics and optics. So far the topological order and chirality of electromagnetic wave are two independent concepts, and there is no work to address their connection. Here we propose to establish the relation between the topological order in condensed matter systems and the chirality in metamaterials, by mapping explicitly Maxwell's equations to the Dirac equation in one dimension. We report an experimental implement of the band inversion in the Dirac equation, which accompanies change of chirality of electromagnetic wave in metamaterials, and the first microwave measurement of topological excitations and topological phases in one dimension. Our finding provides a proof-of-principle example that electromagnetic wave in the metamaterials can be used to simulate the topological order in condensed matter systems and quantum phenomena in relativistic quantum mechanics in a controlled laboratory environment. PMID:24452532

Tan, Wei; Sun, Yong; Chen, Hong; Shen, Shun-Qing

2014-01-01

337

Topology control for multihop packet radio networks

NASA Astrophysics Data System (ADS)

A novel, distributed topology-control algorithm has been developed for each node in a packet radio network (PRN) to control its transmitting power and logical neighbors in order to construct 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 of edge switching to improve connectivity and throughput. The resulting triangulation at this stage is called the Delaunay triangulation, and it can be determined locally at each node. Finally, the topology is modified by negotiating among neighbors to satisfy a design requirement on the nodal degree parameter. Simulations show that (1) the final topology is degree-bounded, (2) it has a rather regular and uniform structure, and (3) its throughput and reliability are greater than that of a number of alternative topologies.

Hu, Limin

1993-10-01

338

NSDL National Science Digital Library

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).

Muller, Eric

1995-01-01

339

Electron fractionalization into spinons and chargeons plays a crucial role in 2D models of strongly correlated electrons. In this paper we show that spin-charge separation is not a phenomenon confined to lower dimensions but, rather, we present a field-theoretic model in which it is realized in 3D. The model involves two gauge fields, a standard one and a two-form gauge field. The physical picture is that of a two-fluid model of chargeons and spinons interacting by the topological BF term. When a Higgs mechanism of the second kind for the two-form gauge field takes place, chargeons and spinons are bound together into a charge 1 particle with spin 1/2. The mechanism is the same one that gives spin to quarks bound into mesons in non-critical string theories and involves the self-intersection number of surfaces in 4D space-time. A state with free chargeons and spinons is a topological insulator. When chargeons condense, the system becomes a topological superconductor; a condensate of spinons, instead realizes U(1) charge confinement.

M. Cristina Diamantini; Carlo A. Trugenberger

2011-12-14

340

Fractional electric charge and quark confinement

Owing to their fractional electric charges, quarks are blind to transformations that combine a color center phase with an appropriate electromagnetic one. Such transformations are part of a global $Z_6$-like center symmetry of the Standard Model that is lost when quantum chromodynamics (QCD) is treated as an isolated theory. This symmetry and the corresponding topological defects may be relevant to non-perturbative phenomena such as quark confinement, much like center symmetry and ordinary center vortices are in pure SU($N$) gauge theories. Here we report on our investigations of an analogous symmetry in a 2-color model with dynamical Wilson quarks carrying half-integer electric charge.

Sam R. Edwards; André Sternbeck; Lorenz von Smekal

2012-02-07

341

Algebra and topology for applications to physics

NASA Technical Reports Server (NTRS)

The principal concepts of algebra and topology are examined with emphasis on applications to physics. In particular, attention is given to sets and mapping; topological spaces and continuous mapping; manifolds; and topological groups and Lie groups. The discussion also covers the tangential spaces of the differential manifolds, including Lie algebras, vector fields, and differential forms, properties of differential forms, mapping of tangential spaces, and integration of differential forms.

Rozhkov, S. S.

1987-01-01

342

Inner topological structure of Hopf invariant

In light of $\\phi$-mapping topological current theory, the inner topological structure of Hopf invariant is investigated. It is revealed that Hopf invariant is just the winding number of Gauss mapping. According to the inner structure of topological current, a precise expression for Hopf invariant is also presented. It is the total sum of all the self-linking and all the linking numbers of the knot family.

Ji-Rong Ren; Ran Li; Yi-Shi Duan

2007-05-30

343

Measuring topological invariants in photonic systems

Motivated by the recent theoretical and experimental progress in implementing topological orders with photons, we analyze photonic systems with different topologies and present a scheme to probe their topological features. Specifically, we propose a scheme to modify the boundary phases to manipulate edge state dynamics. Such a scheme allows one to measure the winding number of the edge states. Furthermore, we discuss the effect of loss and disorder on the validity of our approach.

Mohammad Hafezi

2013-10-29

344

Some Results Related to Soft Topological Spaces

The notion of soft sets is introduced as a general mathematical tool for dealing with uncertainty. In this paper, we consider the concepts of soft compactness, countably soft compactness and obtain some results. We study some soft separation axioms that have been studied by Min and Shabir-Naz. By constructing a special soft topological space, show that some classical results in general topology are not true about soft topological spaces, for instance every compact Housdorff spaces need not be normal.

E. Peyghan; B. Samadi; A. Tayebi

2014-01-21

345

Topological Raman band in the carbon nanohorn.

Raman spectroscopy has been used in chemistry and physics to investigate the fundamental process involving light and phonons. The carbon nanohorn introduces a new subject to Raman spectroscopy, namely topology. We show theoretically that a photoexcited carrier with a nonzero winding number activates a topological D Raman band through the Aharonov-Bohm effect. The topology-induced D Raman band can be distinguished from the ordinary D Raman band for a graphene edge by its peak position. PMID:24074113

Sasaki, Ken-ichi; Sekine, Yoshiaki; Tateno, Kouta; Gotoh, Hideki

2013-09-13

346

Magnetic topological transition in transmission line metamaterials

NASA Astrophysics Data System (ADS)

We study the magnetic topological transition of the isofrequency curves in the wave vector space from a closed ellipsoid to an open hyperboloid in a metamaterial based on artificial transmission lines. In the radio frequency band we directly measure the emission pattern of a point source placed in the center of the lattice and demonstrate the elliptical wave fronts below the topological transition frequency and hyperbolic wave fronts above the topological transition frequency.

Shchelokova, Alena V.; Filonov, Dmitry S.; Kapitanova, Polina V.; Belov, Pavel A.

2014-09-01

347

Spin-Electricity Conversion Induced by Spin Injection into Topological Insulators

NASA Astrophysics Data System (ADS)

We report successful spin injection into the surface states of topological insulators by using a spin pumping technique. By measuring the voltage that shows up across the samples as a result of spin pumping, we demonstrate that a spin-electricity conversion effect takes place in the surface states of bulk-insulating topological insulators Bi1.5Sb0.5Te1.7Se1.3 and Sn-doped Bi2Te2Se . In this process, the injected spins are converted into a charge current along the Hall direction due to the spin-momentum locking on the surface state.

Shiomi, Y.; Nomura, K.; Kajiwara, Y.; Eto, K.; Novak, M.; Segawa, Kouji; Ando, Yoichi; Saitoh, E.

2014-11-01

348

Spin-electricity conversion induced by spin injection into topological insulators.

We report successful spin injection into the surface states of topological insulators by using a spin pumping technique. By measuring the voltage that shows up across the samples as a result of spin pumping, we demonstrate that a spin-electricity conversion effect takes place in the surface states of bulk-insulating topological insulators Bi_{1.5}Sb_{0.5}Te_{1.7}Se_{1.3} and Sn-doped Bi_{2}Te_{2}Se. In this process, the injected spins are converted into a charge current along the Hall direction due to the spin-momentum locking on the surface state. PMID:25415913

Shiomi, Y; Nomura, K; Kajiwara, Y; Eto, K; Novak, M; Segawa, Kouji; Ando, Yoichi; Saitoh, E

2014-11-01

349

Copying and Evolution of Neuronal Topology

We propose a mechanism for copying of neuronal networks that is of considerable interest for neuroscience for it suggests a neuronal basis for causal inference, function copying, and natural selection within the human brain. To date, no model of neuronal topology copying exists. We present three increasingly sophisticated mechanisms to demonstrate how topographic map formation coupled with Spike-Time Dependent Plasticity (STDP) can copy neuronal topology motifs. Fidelity is improved by error correction and activity-reverberation limitation. The high-fidelity topology-copying operator is used to evolve neuronal topologies. Possible roles for neuronal natural selection are discussed. PMID:19020662

Fernando, Chrisantha; Karishma, K. K.; Szathmary, Eors

2008-01-01

350

Superlattice valley engineering for designer topological insulators

A topological insulator is a novel state of quantum matter, characterized by symmetry-protected Dirac interfacial states within its bulk gap. Tremendous effort has been invested into the search for topological insulators. To date, the discovery of topological insulators has been largely limited to natural crystalline solids. Therefore, it is highly desirable to tailor-make various topological states of matter by design, starting with but a few accessible materials or elements. Here, we establish that valley-dependent dimerization of Dirac surface states can be exploited to induce topological quantum phase transitions, in a binary superlattice bearing symmetry-unrelated interfacial Dirac states. This mechanism leads to a rich phase diagram and allows for rational design of strong topological insulators, weak topological insulators, and topological crystalline insulators. Our ab initio simulations further demonstrate this mechanism in [111] and [110] superlattices of calcium and tin tellurides. While our results reveal a remarkable phase diagram for the binary superlattice, the mechanism is a general route to design various topological states. PMID:25266885

Li, Xiao; Zhang, Fan; Niu, Qian; Feng, Ji

2014-01-01

351

Superlattice valley engineering for designer topological insulators.

A topological insulator is a novel state of quantum matter, characterized by symmetry-protected Dirac interfacial states within its bulk gap. Tremendous effort has been invested into the search for topological insulators. To date, the discovery of topological insulators has been largely limited to natural crystalline solids. Therefore, it is highly desirable to tailor-make various topological states of matter by design, starting with but a few accessible materials or elements. Here, we establish that valley-dependent dimerization of Dirac surface states can be exploited to induce topological quantum phase transitions, in a binary superlattice bearing symmetry-unrelated interfacial Dirac states. This mechanism leads to a rich phase diagram and allows for rational design of strong topological insulators, weak topological insulators, and topological crystalline insulators. Our ab initio simulations further demonstrate this mechanism in [111] and [110] superlattices of calcium and tin tellurides. While our results reveal a remarkable phase diagram for the binary superlattice, the mechanism is a general route to design various topological states. PMID:25266885

Li, Xiao; Zhang, Fan; Niu, Qian; Feng, Ji

2014-01-01

352

On the topology of flux transfer events

NASA Technical Reports Server (NTRS)

A topological analysis is made of a simple model magnetic field of a perturbation at the magnetopause that shares magnetic properties with flux transfer events. The aim is to clarify a number of topological aspects that arise in the case of fully three-dimensional magnetic fields. It is shown that a localized perturbation at the magnetopause can in principle open a closed magnetosphere by establishing magnetic connections across the magnetopause by the formation of a ropelike magnetic field structure. For this purpose a global topological model of a closed magnetosphere is considered as the unperturbed state. The topological substructure of the model flux rope is discussed in detail.

Hesse, Michael; Birn, Joachim; Schindler, Karl

1990-01-01

353

Towards the topological quantization of classical mechanics

We consider the method of topological quantization for conservative systems with a finite number of degrees of freedom. Maupertuis' formalism for classical mechanics provides an appropriate scenario which permit us to adapt the method of topological quantization, originally formulated for gravitational field configurations. We show that any conservative system in classical mechanics can be associated with a principal fiber bundle. As an application of topological quantization we derive expressions for the topological spectra of some simple mechanical systems and show that they reproduce the discrete behavior of the corresponding canonical spectra.

Francisco Nettel; Hernando Quevedo; Moices Rodriguez

2008-01-16

354

Analysis of different topologies of multilevel inverters.

??This thesis compares three different topologies of inverters (one level inverter, Diode clamped inverter, Flying capacitor clamped inverter and Cascaded H-bridge inverter). The multilevel inverters… (more)

Mohammadreza, Derakhshanfar

2010-01-01

355

A FIRST COURSE IN TOPOLOGY: EXPLAINING CONTINUITY

A FIRST COURSE IN TOPOLOGY: EXPLAINING CONTINUITY (FOR MATH 112, SPRING 2005) PAUL BANKSTON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 1 #12;2 PAUL BANKSTON (18) Further Reading

Bankston, Paul

356

Spacetime G-structures I: Topological Defects

The notion of G-structure is defined and various geometrical and topological aspects of such structures are discussed. A particular chain of subgroups in the affine group for Minkowski space is chosen and the canonical geometrical and topological objects that are asssociated with each reduction of the bundle of affine frames on a four-dimensional manifold are detailed. Their physical significance is discussed in the language of topological defects in ordered media. Particular attention is paid to how one topologically characterizes the wave phase of the spacetime vacuum manifold.

D. H. Delphenich

2003-04-02

357

Geometry, topology, and string theory

A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.

Varadarajan, Uday

2003-07-10

358

Magnetic models on various topologies

NASA Astrophysics Data System (ADS)

A brief review is given on the study of the thermodynamic properties of spin models defined on different topologies like small-world, scale-free networks, random graphs and regular and random lattices. Ising, Potts and Blume-Capel models are considered. They are defined on complex lattices comprising Appolonian, Barabási-Albert, Voronoi-Delauny and small-world networks. The main emphasis is given on the corresponding phase transitions, transition temperatures, critical exponents and universality, compared to those obtained by the same models on regular Bravais lattices.

Lima, F. W. S.; Plascak, J. A.

2014-03-01

359

Nonuniversal ordering of spin and charge in stripe phases.

We study the interplay of topological excitations in stripe phases: charge dislocations, charge loops, and spin vortices. In two dimensions these defects interact logarithmically on large distances. Using a renormalization-group analysis in the Coulomb-gas representation of these defects, we calculate the phase diagram and the critical properties of the transitions. Depending on the interaction parameters, spin and charge order can disappear at a single transition or in a sequence of two transitions (spin-charge separation). These transitions are nonuniversal with continuously varying critical exponents. We also determine the nature of the points where three phases coexist. PMID:12190412

Krüger, Frank; Scheidl, Stefan

2002-08-26

360

Critical charge calculations for a bipolar SRAM array

The critical charge, Q{sub crit}, of a memory array storage cell is defined as the largest charge that can be injected without changing the cell`s logic state. The Q{sub crit} of a Schottky-coupled complementary bipolar SRAM array is evaluated in detail. An operational definition of critical charge is made, and the critical charge for the cell is determined by circuit

Leo B. Freeman

1996-01-01

361

THE IMPACT OF DYNAMIC CHANNELS ON FUNCTIONAL TOPOLOGY SKELETONS

THE IMPACT OF DYNAMIC CHANNELS ON FUNCTIONAL TOPOLOGY SKELETONS J. BERTHOLD AND R. LOOGEN topologies. This paper analyses the impact of dynamic channels on Eden's topology skeletons, i.e. skeletons which define process topologies such as rings, toroids, or hypercubes. We compare topology skeletons

Loogen, Rita

362

The high efficiency transformer-less PV inverter topologies derived from NPC topology

The grid-connected photovoltaic (PV) systems are an important part of renewable energy sources and their integration is getting more and more widespread. In order to improve the efficiency, practicality and reliability of the PV systems, many kinds of new inverter topologies have been proposed to avoid using a grid isolation transformer. The NPC topology and two other derived topologies are

Lin Ma; Tamas Kerekes; Remus Teodorescu; Xinmin Jin; Dan Floricau; Marco Liserre

2009-01-01

363

Gravity's Rainbow induces topology change

NASA Astrophysics Data System (ADS)

In this work, we explore the possibility that quantum fluctuations induce a topology change, in the context of Gravity's Rainbow. A semiclassical approach is adopted, where the graviton one-loop contribution to a classical energy in a background spacetime is computed through a variational approach with Gaussian trial wave functionals. The energy density of the graviton one-loop contribution, or equivalently the background spacetime, is then let to evolve, and consequently the classical energy is determined. More specifically, the background metric is fixed to be Minkowskian in the equation governing the quantum fluctuations, which behaves essentially as a backreaction equation, and the quantum fluctuations are let to evolve; the classical energy, which depends on the evolved metric functions, is then evaluated. Analyzing this procedure, a natural ultraviolet cutoff is obtained, which forbids the presence of an interior spacetime region, and this may result in a multiply connected spacetime. Thus, in the context of Gravity's Rainbow, this process may be interpreted as a change in topology, and in principle it results in the presence of a planckian wormhole.

Garattini, Remo; Lobo, Francisco S. N.

2014-05-01

364

Boson Stars with Nontrivial Topology

We construct boson star solutions in the presence of a phantom field, allowing for a nontrivial topology of the solutions. The wormholes residing at the core of the configurations lead to a number of qualitative changes of the boson star solutions. In particular, the typical spiraling dependence of the mass and the particle number on the frequency of the boson stars is lost. Instead, the boson stars with nontrivial topology approach a singular configuration in the limit of vanishing frequency. Depending on the value of the coupling constant, the wormhole geometry changes from a single throat configuration to a double throat configuration, featuring a belly inbetween the two throats. Depending on the mass of the boson field and its self-interaction, the mass and the size of these objects cover many orders of magnitude, making them amenable to various astrophysical observations. A stability analysis reveals, that the unstable mode of the Ellis wormhole is retained in the presence of the bosonic matter. However, the negative eigenvalue can get very close to zero, by tuning the parameters of the self-interaction potential appropriately.

Vladimir Dzhunushaliev; Vladimir Folomeev; Christian Hoffmann; Burkhard Kleihaus; Jutta Kunz

2014-09-24

365

Electronic states in disordered topological insulators

NASA Astrophysics Data System (ADS)

We present a theoretical study of electronic states in topological insulators with impurities. Chiral edge states in 2d topological insulators and helical surface states in 3d topological insulators show a robust transport against nonmagnetic impurities. Such a nontrivial character inspired physicists to come up with applications such as spintronic devices [1], thermoelectric materials [2], photovolatics[3], and quantum computation [4]. Not only has it provided new opportunities from a practical point of view, but its theoretical study has deepened the understanding of the topological nature of condensed matter systems. However, experimental realizations of topological insulators have been challenging. For example, a 2d topological insulator fabricated in a HeTe quantum well structure by Konig et al.[5] shows a longitudinal conductance which is not well quantized and varies with temperature. 3d topological insulators such as Bi2Se3 and Bi2Te3 exhibit not only a signature of surface states, but they also show a bulk conduction [6]. The series of experiments motivated us to study the effects of impurities and coexisting bulk Fermi surface in topological insulators. We first address a single impurity problem in a topological insulator using a semiclassical approach. Then we study the conductance behavior of a disordered topological-metal strip where bulk modes are associated with the transport of edge modes via impurity scattering. We verify that the conduction through a chiral edge channel retains its topological signature, and we discovered that the transmission can be succinctly expressed in a closed form as a ratio of determinants of the bulk Green's function and impurity potentials. We further study the transport of 1d systems which can be decomposed in terms of chiral modes. Lastly, the surface impurity effect on the local density of surface states over layers into the bulk is studied between weak and strong disorder strength limits.

Kim, Kun Woo

366

Bringing Definitions into High Definition

ERIC Educational Resources Information Center

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…

Mason, John

2010-01-01

367

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

NASA Technical Reports Server (NTRS)

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.

Barrett, M.

1974-01-01

368

Topological Crystalline Insulators in the SnTe Material Class

Topological crystalline insulators are new states of matter in which the topological nature of electronic structures arises from crystal symmetries. Here we predict the first material realization of topological crystalline ...

Hsieh, Timothy Hwa-wei

369

Symmetry breaking and Landau quantization in topological crystalline insulators

In the recently discovered topological crystalline insulators SnTe and Pb[subscript 1?x]Sn[subscript x](Te, Se), crystal symmetry and electronic topology intertwine to create topological surface states with many interesting ...

Serbyn, Maksym

370

Observation of Topological Phase Transitions in Photonic Quasicrystals

Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically ...

Verbin, Mor

371

Lectures on Topological Quantum Field Theory

What follows are lecture notes about Topological Quantum Field Theory. While the lectures were aimed at physicists, the content is highly mathematical in its style and motivation. The subject of Topological Quantum Field Theory is young and developing rapidly in many directions. These lectures are not at all representative of this activity, but rather reflect particular interests of the author.

Daniel S. Freed

1992-01-01

372

Bibliography. P. Alexandroff, Elementary concepts of topology,

and Bacon, Boston (1966) Â· W. Franz, Topologie I, Sammlung GÂ¨oschen Bann 1181 (1968) Â· J.G. Hacking - G. Henle, A combinatorial introduction to topology, Dover (1979) Â· K. JÂ¨anich, Topologie Â· J.L. Kelley, Topologie Â· D. Rosemann, Elementary topology, Prentice Hall (1999) Â· A.J. Sieradski, An introduction

Johannson, Klaus

373

Decomposition theorem in ideal topological spaces

NASA Astrophysics Data System (ADS)

We introduce new classes of sets called a* -I -open,A-?-I-open sets, A-pre* -I-open sets, strongly T-I -sets, A-?-T-I-sets, strongly BA -I -sets, BA -I -sets, and ??A -I -open sets in ideal topological spaces. Using these sets, to obtain decompositions of continuity in an ideal topological space.

AL-omeri, W.; Noorani, Mohd. Salmi; AL-Omari, A.

2014-06-01

374

Black holes, entropy functionals, and topological strings

This thesis is devoted to study of the connection between extremal black holes and topological strings. Important ingredient of this connection is the relation between Hartle-Hawking wave function associated to black holes and topological string partition function. This leads to a natural entropy functional defined on the moduli space of string compactifications. We discuss several examples of such entropy functionals.

Kirill Anatolyevich Saraikin

2007-01-01

375

STONE DUALITY, TOPOLOGICAL ALGEBRA, AND RECOGNITION

STONE DUALITY, TOPOLOGICAL ALGEBRA, AND RECOGNITION MAI GEHRKE Abstract. Our main result is that any topological algebra based on a Boolean space is the extended Stone dual space of a certain associated Boolean algebra with additional operations. A particular case of this result is that the profinite

Paris-Sud XI, UniversitÃ© de

376

A general circuit topology of multilevel inverter

A generalized circuit topology of multilevel voltage source inverters which is based on a direct extension of the three-level inverter to higher level is proposed. The circuit topologies up to five-level are presented. The proposed multilevel inverter can realize any multilevel pulsewidth modulation (PWM) scheme which leads to harmonic reduction and provides full utilization of semiconductor devices like GTOs, especially

Nam S. Choi; Jung G. Cho; Gyu H. Cho

1991-01-01

377

Polyhedral perturbations that preserve topological form

, and the concept appears in many applied fields. Some of the most important of these are tolerancing and metrology focus on the field of tolerancing and metrology. The requirement that two objects or sets should have modeling, tolerancing and metrology, topological equivalence, topological form, simplicial complexes

Stewart, Neil

378

A topology-based filling algorithm

In this paper we present a fast-recursive fullyautomated topology -based algorithm for filling in the interiors of objects that appear in a binaryimage. The algorithm is based on two topological properties of the image contours: perimeter coincidence and interiority. Based on these parameters the algorithm performs a tree-structured region classification. The final filling is done according to the labels of

Marcos Mart; Juan Ruiz-Alzolab

379

Topology in 4D simplicial quantum gravity

We simulate 4d simplicial gravity for three topologis S4, S3xS1, (S1)^4 and show that the free energy for these three fixed topology ensembles is the same in the thermodynamic limit. We show, that the next-to-leading order corrections, at least away from the critical point, can be described by kinematic sources.

S. Bilke; Z. Burda; B. Petersson

1996-11-22

380

Topology Simplification for Polygonal Virtual Environments

We present a topology simplifying approach that can be used for genus reductions, removal of protu- berances, and repair of cracks in polygonal models in a unified framework. Our work is complementary to the existing work on geometry simplification of polygonal datasets and we demonstrate that using topology and geometry simplifications together yields superior multiresolution hierarchies than is possi- ble

Jihad El-sana; Amitabh Varshney

1998-01-01

381

Finite Topological Spaces as a Pedagogical Tool

ERIC Educational Resources Information Center

We propose the use of finite topological spaces as examples in a point-set topology class especially suited to help students transition into abstract mathematics. We describe how carefully chosen examples involving finite spaces may be used to reinforce concepts, highlight pathologies, and develop students' non-Euclidean intuition. We end with a…

Helmstutler, Randall D.; Higginbottom, Ryan S.

2012-01-01

382

Topological SLAM Using Fast Vision Techniques

NASA Astrophysics Data System (ADS)

In this paper we propose a method for vision only topological simultaneous localisation and mapping (SLAM). Our approach does not use motion or odometric information but a sequence of noisy visual measurements observed by traversing an environment. In particular, we address the perceptual aliasing problem which occurs using external observations only in topological navigation.

Werner, Felix; Maire, Frederic; Sitte, Joaquin

383

Massive Dirac Fermion on the Surface of a Magnetically Doped Topological Insulator

Topological insulators are characterized by a massless Dirac surface state and a bulk energy gap. An insulating massive Dirac fermion state is predicted to occur if the breaking of the time reversal symmetry opens an energy gap at the Dirac point, provided that the Fermi-energy resides inside both the surface and bulk gaps. By introducing magnetic dopants into the three dimensional topological insulator Bi{sub 2}Se{sub 3} to break the time reversal symmetry, we observed the formation of a massive Dirac fermion on the surface; simultaneous magnetic and charge doping furthermore positioned the Fermi-energy inside the Dirac gap. The insulating massive Dirac Fermion state thus obtained may provide a tool for studying a range of topological phenomena relevant to both condensed matter and particle physics.

Chen, Y.L.; Chu, J.-H.; Analytis, J.G.; Liu, Z.K.; Igarashi, K.; Kuo, H.-H.; Qi, X.L.; Mo, S.K.; Moore, R.G.; Lu, D.H.; Hashimoto, M.; Sasagawa, T.; Zhang, S.C.; Fisher, I.R.; Hussain, Z.; Shen, Z.-X.; /SLAC; ,

2011-05-20

384

Two-dimensional density-matrix topological fermionic phases: topological Uhlmann numbers.

We construct a topological invariant that classifies density matrices of symmetry-protected topological orders in two-dimensional fermionic systems. As it is constructed out of the previously introduced Uhlmann phase, we refer to it as the topological Uhlmann number n_{U}. With it, we study thermal topological phases in several two-dimensional models of topological insulators and superconductors, computing phase diagrams where the temperature T is on an equal footing with the coupling constants in the Hamiltonian. Moreover, we find novel thermal-topological transitions between two nontrivial phases in a model with high Chern numbers. At small temperatures we recover the standard topological phases as the Uhlmann number approaches to the Chern number. PMID:25170721

Viyuela, O; Rivas, A; Martin-Delgado, M A

2014-08-15

385

Two-Dimensional Density-Matrix Topological Fermionic Phases: Topological Uhlmann Numbers

We construct a topological invariant that classifies density matrices of symmetry-protected topological orders in two-dimensional fermionic systems. As it is constructed out of the previously introduced Uhlmann phase, we refer to it as the topological Uhlmann number ${\\rm n}_{\\rm U}$. With it, we study thermal topological phases in several two-dimensional models of topological insulators and superconductors, computing phase diagrams where the temperature $T$ is on an equal footing with the coupling constants in the Hamiltonian. Moreover, we find novel thermal-topological transitions between two non-trivial phases in a model with high Chern numbers. At small temperature we recover the standard topological phases as the Uhlmann number approaches to the Chern number.

O. Viyuela; A. Rivas; M. A. Martin-Delgado

2014-05-23

386

Topological phonon modes in filamentary structures

NASA Astrophysics Data System (ADS)

This work describes a class of topological phonon modes, that is, mechanical vibrations localized at the edges of special structures that are robust against the deformations of the structures. A class of topological phonons was recently found in two-dimensional structures similar to that of microtubules. The present work introduces another class of topological phonons, this time occurring in quasi-one-dimensional filamentary structures with inversion symmetry. The phenomenon is exemplified using a structure inspired from that of actin microfilaments, present in most live cells. The system discussed here is probably the simplest structure that supports topological phonon modes, a fact that allows detailed analysis in both time and frequency domains. We advance the hypothesis that the topological phonon modes are ubiquitous in the biological world and that living organisms make use of them during various processes.

Berg, Nina; Joel, Kira; Koolyk, Miriam; Prodan, Emil

2011-02-01

387

ERIC Educational Resources Information Center

Ways to fund a publications office and the merits of charge-back systems are discussed. Every charge-back system differs. Some offices try to cover costs; others bill for overhead. Some alternatives to charging are described. (MLW)

Hay, Tina M.

1989-01-01

388

Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks ...

Balewski, Jan T.

389

QCD as a topologically ordered system

We argue that QCD belongs to a topologically ordered phase similar to many well-known condensed matter systems with a gap such as topological insulators or superconductors. Our arguments are based on an analysis of the so-called “deformed QCD” which is a weakly coupled gauge theory, but nevertheless preserves all the crucial elements of strongly interacting QCD, including confinement, nontrivial ? dependence, degeneracy of the topological sectors, etc. Specifically, we construct the so-called topological “BF” action which reproduces the well known infrared features of the theory such as non-dispersive contribution to the topological susceptibility which cannot be associated with any propagating degrees of freedom. Furthermore, we interpret the well known resolution of the celebrated U(1){sub A} problem where the would be ?{sup ?} Goldstone boson generates its mass as a result of mixing of the Goldstone field with a topological auxiliary field characterizing the system. We then identify the non-propagating auxiliary topological field of the BF formulation in deformed QCD with the Veneziano ghost (which plays the crucial role in resolution of the U(1){sub A} problem). Finally, we elaborate on relation between “string-net” condensation in topologically ordered condensed matter systems and long range coherent configurations, the “skeletons”, studied in QCD lattice simulations. -- Highlights: •QCD may belong to a topologically ordered phase similar to condensed matter (CM) systems. •We identify the non-propagating topological field in deformed QCD with the Veneziano ghost. •Relation between “string-net” condensates in CM systems and the “skeletons” in QCD lattice simulations is studied.

Zhitnitsky, Ariel R., E-mail: arz@physics.ubc.ca

2013-09-15

390

This Teaching Resource provides three animated lessons that describe the storage and utilization of energy across plasma membranes. The "Na,K ATPase" animation explains how these pumps establish the electrochemical gradient that stores energy across plasma membranes. The "ATP synthesizing complexes" animation shows how these complexes transfer energy from the inner mitochondrial membrane to adenosine triphosphate (ATP). The "action potential" lesson explains how charged membranes are used to propagate signals along the axons of neurons. These animations serve as valuable resources for any collegiate-level course that describes these important factors. Courses that might employ them include introductory biology, biochemistry, biophysics, cell biology, pharmacology, and physiology. PMID:23592845

Thatcher, Jack D

2013-01-01

391

NASA Astrophysics Data System (ADS)

The mean equililibrium charge of a penetrating ion can be estimated on the basis of Bohr's velocity criterion or Lamb's energy criterion. Qualitative and quantitative results are derived on the basis of the Thomas-Fermi model of the atom, which is discussed explicitly. This includes a brief introduction to the Thomas-Fermi-Dirac model. Special attention is paid to trial function approaches by Lenz and Jensen as well as Brandt and Kitagawa. The chapter also offers a preliminary discussion of the role of the stopping medium, gas-solid differences, and a survey of data compilations.

Sigmund, Peter

392

Topological Defects in Spherical Nematics

NASA Astrophysics Data System (ADS)

We study the organization of topological defects in a system of nematogens confined to the two-dimensional sphere (S2). We first perform Monte Carlo simulations of a fluid system of hard rods (spherocylinders) living in the tangent plane of S2. The sphere is adiabatically compressed until we reach a jammed nematic state with maximum packing density. The nematic state exhibits four +1/2 disclinations arrayed on a great circle. This arises from the high elastic anisotropy of the system in which splay (K1) is far softer than bending (K3). We also introduce and study a lattice nematic model on S2 with tunable elastic constants and map out the preferred defect locations as a function of elastic anisotropy. We find a one-parameter family of degenerate ground states in the extreme splay-dominated limit K3/K1??. Thus the global defect geometry is controllable by tuning the relative splay to bend modulus.

Shin, Homin; Bowick, Mark J.; Xing, Xiangjun

2008-07-01

393

Wavefunctions for topological quantum registers

We present explicit wavefunctions for quasi-hole excitations over a variety of non-abelian quantum Hall states: the Read-Rezayi states with k {>=} 3 clustering properties and a paired spin-singlet quantum Hall state. Quasi-holes over these states constitute a topological quantum register, which can be addressed by braiding quasi-holes. We obtain the braid properties by direct inspection of the quasi-hole wavefunctions. We establish that the braid properties for the paired spin-singlet state are those of 'Fibonacci anyons', and thus suitable for universal quantum computation. Our derivations in this paper rely on explicit computations in the parafermionic conformal field theories that underly these particular quantum Hall states.

Ardonne, E. [Microsoft station Q, Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States) and Center for the Physics of Information, California Institute of Technology, Pasadena, CA 91125 (United States)]. E-mail: ardonne@kitp.ucsb.edu; Schoutens, K. [Institute for Theoretical Physics, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)

2007-01-15

394

Topological Solitons and Folded Proteins

We propose that protein loops can be interpreted as topological domain-wall solitons. They interpolate between ground states that are the secondary structures like alpha-helices and beta-strands. Entire proteins can then be folded simply by assembling the solitons together, one after another. We present a simple theoretical model that realizes our proposal and apply it to a number of biologically active proteins including 1VII, 2RB8, 3EBX (Protein Data Bank codes). In all the examples that we have considered we are able to construct solitons that reproduce secondary structural motifs such as alpha-helix-loop-alpha-helix and beta-sheet-loop-beta-sheet with an overall root-mean-square-distance accuracy of around 0.7 Angstrom or less for the central alpha-carbons, i.e. within the limits of current experimental accuracy.

M. N. Chernodub; Shuangwei Hu; Antti J. Niemi

2010-03-23

395

Topological properties of integer networks

NASA Astrophysics Data System (ADS)

Inspired by Pythagoras's belief that numbers represent the reality, we study the topological properties of networks of composite numbers, in which the vertices represent the numbers and two vertices are connected if and only if there exists a divisibility relation between them. The network has a fairly large clustering coefficient C?0.34, which is insensitive to the size of the network. The average distance between two nodes is shown to have an upper bound that is independent of the size of the network, in contrast to the behavior in small-world and ultra-small-world networks. The out-degree distribution is shown to follow a power-law behavior of the form k-2. In addition, these networks possess hierarchical structure as C(k)?k-1 in accord with the observations of many real-life networks.

Zhou, Tao; Wang, Bing-Hong; Hui, P. M.; Chan, K. P.

2006-07-01

396

The formation of topological defects in phase transitions

NASA Technical Reports Server (NTRS)

It was argued, and fought through numerical work that the results of non-dynamical Monte Carlo computer simulations cannot be applied to describe the formation of topological defects when the correlation length at the Ginzburg temperature is significantly smaller than the horizon size. To test the current hypothesis that infinite strings at formation are essentially described by Brownian walks of size the correlation length at the Ginzburg temperature, fields at the Ginzburg temperature were equilibrated. Infinite structure do not exist in equilibrium for reasonable definitions of the Ginzburg temperature, and horizons must be included in a proper treatment. A phase transition, from small-scale to large-scale string or domain wall structure, is found to occur very close to the Ginzburg temperature, in agreement with recent work. The formation process of domain walls and global strings were investigated through the breaking of initially ordered states. To mimic conditions in the early Universe, cooling times are chosen so that horizons exist in the sample volume when topological structure formation occurs. The classical fields are evolved in real-time by the numerical solution of Langevin equations of motion on a three dimensional spatial lattice. The results indicate that it is possible for most of the string energy to be in small loops, rather than in long strings, at formation.

Hodges, Hardy M.

1989-01-01

397

An invariant of topologically ordered states under local unitary transformations

For an anyon model in two spatial dimensions described by a modular tensor category, the topological S-matrix encodes the mutual braiding statistics, the quantum dimensions, and the fusion rules of anyons. It is nontrivial whether one can compute the S-matrix from a single ground state wave function. Here, we define a class of Hamiltonians consisting of local commuting projectors and an associated matrix that is invariant under local unitary transformations. We argue that the invariant is equivalent to the topological S-matrix. The definition does not require degeneracy of the ground state. We prove that the invariant depends on the state only, in the sense that it can be computed by any Hamiltonian in the class of which the state is a ground state. As a corollary, we prove that any local quantum circuit that connects two ground states of quantum double models (discrete gauge theories) with non-isomorphic abelian groups, must have depth that is at least linear in the system's diameter.

Jeongwan Haah

2014-07-10

398

A General Theorem Relating the Bulk Topological Number to Edge States in Two-dimensional Insulators

We prove a general theorem on the relation between the bulk topological quantum number and the edge states in two dimensional insulators. It is shown that whenever there is a topological order in bulk, characterized by a non-vanishing Chern number, even if it is defined for a non-conserved quantity such as spin in the case of the spin Hall effect, one can always infer the existence of gapless edge states under certain twisted boundary conditions that allow tunneling between edges. This relation is robust against disorder and interactions, and it provides a unified topological classification of both the quantum (charge) Hall effect and the quantum spin Hall effect. In addition, it reconciles the apparent conflict between the stability of bulk topological order and the instability of gapless edge states in systems with open boundaries (as known happening in the spin Hall case). The consequences of time reversal invariance for bulk topological order and edge state dynamics are further studied in the present framework.

Qi, Xiao-Liang; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Wu, Yong-Shi; /Utah U.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept. /Tsinghua U., Beijing

2010-01-15

399

Conformational Properties of an Adsorbed Charged Polymer

The behavior of a strongly charged polymer adsorbed on an oppositely charged surface of low-dielectric constant is formulated by the functional integral method. By separating the translational, conformational, and fluctuational degrees of freedom, the scaling behaviors for both the height of the polymer and the thickness of the diffusion layer are determined. Unlike the results predicted by scaling theory, we identified the continuous crossover from the weak compression to the compression regime. All teh analytical results are found to be consistent with Monte-Carlo simulations. Finally, an alternative (operational) definition of a charged polymer adsorption is proposed.

Chi-Ho Cheng; Pik-Yin Lai

2004-12-02

400

Topological phases: An expedition off lattice

Highlights: > Models of topological phases where the lattice topology is a dynamical variable. > We discuss off-lattice hazards that destroy topological protection. > The Cheeger constant yields upper bound to the energy of excited states. > Baby universes meet condensed matter physics. > We study the graph Laplacian of loop gases and string nets on fluctuating lattices. - Abstract: Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of 'baby universe', here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger's theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically.

Freedman, Michael H. [Microsoft Station Q, University of California, Santa Barbara, CA 93106 (United States); Gamper, Lukas [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Gils, Charlotte [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave, Toronto, ON M5G 1X5 (Canada); Isakov, Sergei V., E-mail: isakov@itp.phys.ethz.ch [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Trebst, Simon [Microsoft Station Q, University of California, Santa Barbara, CA 93106 (United States); Troyer, Matthias [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland)

2011-08-15

401

How to model wireless mesh networks topology

NASA Astrophysics Data System (ADS)

The specification of network connectivity model or topology is the beginning of design and analysis in Computer Network researches. Wireless Mesh Networks is an autonomic network that is dynamically self-organised, self-configured while the mesh nodes establish automatic connectivity with the adjacent nodes in the relay network of wireless backbone routers. Researches in Wireless Mesh Networks range from node deployment to internetworking issues with sensor, Internet and cellular networks. These researches require modelling of relationships and interactions among nodes including technical characteristics of the links while satisfying the architectural requirements of the physical network. However, the existing topology generators model geographic topologies which constitute different architectures, thus may not be suitable in Wireless Mesh Networks scenarios. The existing methods of topology generation are explored, analysed and parameters for their characterisation are identified. Furthermore, an algorithm for the design of Wireless Mesh Networks topology based on square grid model is proposed in this paper. The performance of the topology generated is also evaluated. This research is particularly important in the generation of a close-to-real topology for ensuring relevance of design to the intended network and validity of results obtained in Wireless Mesh Networks researches.

Sanni, M. L.; Hashim, A. A.; Anwar, F.; Ahmed, G. S. M.; Ali, S.

2013-12-01

402

TRW CHARGED DROPLET SCRUBBER CORROSION STUDIES

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...

403

The switching of electric polarization induced by electric fields, a fundamental functionality of ferroelectrics, is closely associated with the motions of the domain walls that separate regions with distinct polarization directions. Therefore, understanding domain-walls dynamics is of essential importance for advancing ferroelectric applications. In this Letter, we show that the topology of the multidomain structure can have an intrinsic impact on the degree of switchable polarization. Using a combination of polarization hysteresis measurements and piezoresponse force microscopy on a uniaxial organic ferroelectric, ?-6,6'-dimethyl-2,2'-bipyridinium chloranilate, we found that the head-to-head (or tail-to-tail) charged domain walls are strongly pinned and thus impede the switching process; in contrast, if the charged domain walls are replaced with electrically neutral antiparallel domain walls, bulk polarization switching is achieved. Our findings suggest that manipulation of the multidomain topology can potentially control the switchable polarization. PMID:24329117

Kagawa, Fumitaka; Horiuchi, Sachio; Minami, Nao; Ishibashi, Shoji; Kobayashi, Kensuke; Kumai, Reiji; Murakami, Youichi; Tokura, Yoshinori

2014-01-01

404

NSDL National Science Digital Library

This Teaching Resource provides three animated lessons that describe the storage and utilization of energy across plasma membranes. The “Na,K ATPase” animation explains how these pumps establish the electrochemical gradient that stores energy across plasma membranes. The “ATP synthesizing complexes” animation shows how these complexes transfer energy from the inner mitochondrial membrane to adenosine triphosphate (ATP). The “action potential” lesson explains how charged membranes are used to propagate signals along the axons of neurons. These animations serve as valuable resources for any collegiate-level course that describes these important factors. Courses that might employ them include introductory biology, biochemistry, biophysics, cell biology, pharmacology, and physiology.

Jack D. Thatcher (Lewisburg;West Virginia School of Osteopathic Medicine REV)

2013-04-16

405

We present here a case of 17-year-old boy from Kolkata presenting with obesity, bilateral gynecomastia, mental retardation, and hypogonadotrophic hypogonadism. The patient weighed 70 kg and was of 153 cm height. Facial asymmetry (unilateral facial palsy), gynecomastia, decreased pubic and axillary hair, small penis, decreased right testicular volume, non-palpable left testis, and right-sided congenital inguinal hernia was present. The patient also had disc coloboma, convergent squint, microcornea, microphthalmia, pseudohypertelorism, low set ears, short neck, and choanalatresia. He had h/o VSD repaired with patch. Laboratory examination revealed haemoglobin 9.9 mg/dl, urea 24 mg/dl, creatinine 0.68 mg/dl. IGF1 77.80 ng/ml (decreased for age), GH <0.05 ng/ml, testosterone 0.25 ng/ml, FSH-0.95 ?IU/ml, LH 0.60 ?IU/ml. ACTH, 8:00 A.M cortisol, FT3, FT4, TSH, estradiol, DHEA-S, lipid profile, and LFT was within normal limits. Prolactin was elevated at 38.50 ng/ml. The patient's karyotype was 46XY. Echocardiography revealed ventricularseptal defect closed with patch, grade 1 aortic regurgitation, and ejection fraction 67%. Ultrasound testis showed small right testis within scrotal sac and undescended left testis within left inguinal canal. CT scan paranasal sinuses revealed choanalatresia and deviation of nasal septum to the right. Sonomammography revealed bilateral proliferation of fibroglandular elements predominantly in subareoalar region of breasts. MRI of brain and pituitary region revealed markedly atrophic pituitary gland parenchyma with preserved infundibulum and hypothalamus and widened suprasellar cistern. The CHARGE association is an increasingly recognized non-random pattern of congenital anomalies comprising of coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear abnormalities, and/or deafness.[1] These anomalies have a higher probability of occurring together. In this report, we have described a boy with CHARGE association. PMID:23565479

Chakraborty, Semanti; Chakraborty, Jayanta

2012-01-01

406

Topology and bistability in liquid crystal devices

We study nematic liquid crystal configurations in a prototype bistable device--the post aligned bistable nematic (PABN) cell. Working within the Oseen-Frank continuum model, we describe the liquid crystal configuration by a unit-vector field n, in a model version of the PABN cell. First, we identify four distinct topologies in this geometry. We explicitly construct trial configurations with these topologies which are used as initial conditions for a numerical solver, based on the finite-element method. The morphologies and energetics of the corresponding numerical solutions qualitatively agree with experimental observations and suggest a topological mechanism for bistability in the PABN cell geometry.

Majumdar, A. [School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW (United Kingdom); Hewlett-Packard Laboratories, Filton Road, Stoke Gifford, Bristol BS12 6QZ (United Kingdom); Newton, C. J. P. [Hewlett-Packard Laboratories, Filton Road, Stoke Gifford, Bristol BS12 6QZ (United Kingdom); Robbins, J. M.; Zyskin, M. [School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW (United Kingdom)

2007-05-15

407

Fibonacci topological order from quantum nets.

We analyze a model of quantum nets and show it has a non-Abelian topological order of doubled-Fibonacci type. The ground state has the same topological behavior as that of the corresponding string-net model, but our Hamiltonian can be defined on any lattice, has less complicated interactions, and its excitations are dynamical, not fixed. This Hamiltonian includes terms acting on the spins around a face, around a vertex, and special "Jones-Wenzl" terms that serve to couple long loops together. We provide strong evidence for a gap by exact diagonalization, completing the list of ingredients necessary for topological order. PMID:23848854

Fendley, Paul; Isakov, Sergei V; Troyer, Matthias

2013-06-28

408

Fibonacci topological order from quantum nets

NASA Astrophysics Data System (ADS)

We analyze a model of quantum nets and show it has a non-Abelian topological order of doubled-Fibonacci type. The ground state has the same topological behavior as that of the corresponding string-net model, but our Hamiltonian can be defined on any lattice, has less complicated interactions, and its excitations are dynamical, not fixed. This Hamiltonian includes terms acting on the spins around a face, around a vertex, and special “Jones-Wenzl” terms that serve to couple long loops together. We provide strong evidence for a gap by exact diagonalization, completing the list of ingredients necessary for topological order.

Fendley, Paul; Isakov, Sergei V.; Troyer, Matthias

2013-06-01

409

Fibonacci topological order from quantum nets

We analyze a model of quantum nets and show it has non-abelian topological order of doubled Fibonacci type. The ground state has the same topological behavior as that of the corresponding string-net model, but our Hamiltonian can be defined on any lattice, has less complicated interactions, and its excitations are dynamical, not fixed. This Hamiltonian includes terms acting on the spins around a face, around a vertex, and special "Jones-Wenzl" terms that serve to couple long loops together. We provide strong evidence for a gap by exact diagonalization, completing the list of ingredients necessary for topological order.

Paul Fendley; Sergei V. Isakov; Matthias Troyer

2012-10-19

410

Möbius Graphene Strip as Topological Insulator

We study the electronic properties of M\\"{o}bius graphene strip with a zigzag edge. We show that such graphene strip behaves as a topological insulator with a gapped bulk and a robust metallic surface, which enjoys some features due to its nontrivial topology of the spatial configuration, such as the existence of edge states and the non-Abelian induced gauge field. We predict that the topological properties of the M\\"{o}bius graphene strip can be experimentally displayed by the destructive interference in the transmission spectrum, and the robustness of edge states under certain perturbations.

Z. L. Guo; Z. R. Gong; H. Dong; C. P. Sun

2009-06-09

411

Floquet topological states in shaking optical lattices

NASA Astrophysics Data System (ADS)

In this Rapid Communication we propose realistic schemes to realize topologically nontrivial Floquet states by shaking optical lattices, using both the one-dimensional lattice and two-dimensional honeycomb lattice as examples. The topological phase in the two-dimensional model exhibits quantum anomalous Hall effect. The transition between topological trivial and nontrivial states can be easily controlled by both shaking frequency and shaking amplitude. Our schemes have two major advantages. First, both the static Hamiltonian and the shaking scheme are sufficiently simple to implement. Secondly, it requires relatively small shaking amplitude and therefore heating can be minimized. These two advantages make our schemes much more practical.

Zheng, Wei; Zhai, Hui

2014-06-01

412

Learning topological maps: An alternative approach

Our goal is autonomous real-time control of a mobile robot. In this paper we want to show a possibility to learn topological maps of a large-scale indoor environment autonomously. In the literature there are two paradigms how to store information on the environment of a robot: as a grid-based (geometric) or as a topological map. While grid-based maps are considerably easy to learn and maintain, topological maps are quite compact and facilitate fast motion-planning.

Buecken, A.; Thrun, S. [Univ. of Bonn (Germany)

1996-12-31

413

Dephasing Effect on Backscattering of Helical Surface States in 3D Topological Insulators

NASA Astrophysics Data System (ADS)

We analyze the dephasing effect on the backscattering behavior of the helical surface states in 3D topological insulators. We show that the combination of dephasing and impurity scattering can cause backscattering in the helical states. Especially for the charge impurity case, the backscattering cross section becomes extremely large around the Dirac point. This large backscattering behavior can lead to the anomalous "gaplike" features found in recent experiments [T. Sato et al., Nat. Phys. 7, 840 (2011)].

Liu, Haiwen; Jiang, Hua; Sun, Qing-feng; Xie, X. C.

2014-07-01

414

Dephasing effect on backscattering of helical surface states in 3D topological insulators.

We analyze the dephasing effect on the backscattering behavior of the helical surface states in 3D topological insulators. We show that the combination of dephasing and impurity scattering can cause backscattering in the helical states. Especially for the charge impurity case, the backscattering cross section becomes extremely large around the Dirac point. This large backscattering behavior can lead to the anomalous "gaplike" features found in recent experiments [T. Sato et al., Nat. Phys. 7, 840 (2011)]. PMID:25105645

Liu, Haiwen; Jiang, Hua; Sun, Qing-Feng; Xie, X C

2014-07-25

415

Tunable multifunctional topological insulators in ternary Heusler compounds.

Recently the quantum spin Hall effect was theoretically predicted and experimentally realized in quantum wells based on the binary semiconductor HgTe (refs 1-3). The quantum spin Hall state and topological insulators are new states of quantum matter interesting for both fundamental condensed-matter physics and material science. Many Heusler compounds with C1(b) structure are ternary semiconductors that are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the bandgap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by the lattice parameter) and magnitude of spin-orbit coupling (by the atomic charge). Based on first-principle calculations we demonstrate that around 50 Heusler compounds show band inversion similar to that of HgTe. The topological state in these zero-gap semiconductors can be created by applying strain or by designing an appropriate quantum-well structure, similar to the case of HgTe. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from superconductivity (for example LaPtBi; ref. 12) to magnetism (for example GdPtBi; ref. 13) and heavy fermion behaviour (for example YbPtBi; ref. 14). These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors. PMID:20512154

Chadov, Stanislav; Qi, Xiaoliang; Kübler, Jürgen; Fecher, Gerhard H; Felser, Claudia; Zhang, Shou Cheng

2010-07-01

416

Critical Points of the Electric Field from a Collection of Point Charges

The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.

Max, N; Weinkauf, T

2007-02-16

417

Modeling Prosecutors' Charging Decisions in Domestic Violence Cases

ERIC Educational Resources Information Center

Relatively little research explaining prosecutors' charging decisions in criminal cases is available. Even less has focused on charging decisions in domestic violence cases. Past studies have also relied on restrictive definitions of domestic violence, notably cases with male offenders and female victims, and they have not considered prosecutors'…

Worrall, John L.; Ross, Jay W.; McCord, Eric S.

2006-01-01

418

. A total of 628 bp-1 of data collected with the ALEPH detector at centre-of-mass energies from 189 to 209 GeV is analysed in the search for gauge\\u000a mediated SUSY breaking (GMSB) topologies. These topologies include two acoplanar photons, non-pointing single photons, acoplanar\\u000a leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and multi-leptons\\u000a plus missing

S Schael; R Barate; R Brunelière; I De Bonis; D Décamp; C Goy; S Jézéquel; J P Lees; F Martin; E Merle; M N Minard; B Pietrzyk; B Trocmé; G Boix; S Bravo; M P Casado; M Chmeissani; J M Crespo; E Fernández; M Fernández-Bosman; L Garrido; E Graugès-Pous; J López; M Martínez; G Merino; R Miquel; L M Mir; A Pacheco; D Paneque; H Ruiz; A Colaleo; D Creanza; N De Filippis; M De Palma; Giuseppe Iaselli; G Maggi; M Maggi; S Nuzzo; A Ranieri; G Raso; F Ruggieri; G Selvaggi; L Silvestris; P Tempesta; A Tricomi; G Zito; X Huang; J Lin; Q Ouyang; T Wang; Y Xie; R Xu; S Xue; J Zhang; L Zhang; W Zhao; D Abbaneo; P Azzurri; Timothy L Barklow; O L Buchmüller; M Cattaneo; F Cerutti; B Clerbaux; H Drevermann; Roger W Forty; M Frank; F Gianotti; T C Greening; J B Hansen; J Harvey; D E Hutchcroft; P Janot; B Jost; M Kado; P Mato; A Moutoussi; F Ranjard; Luigi Rolandi; W D Schlatter; G Sguazzoni; W Tejessy; F Teubert; Andrea Valassi; I Videau; J J Ward; F Badaud; S Dessagne; A Falvard; D Fayolle; P Gay; J Jousset; B Michel; S Monteil; D Pallin; J M Pascolo; P Perret; J D Hansen; P H Hansen; B S Nilsson; A Kyriakis; C Markou; Errietta Simopoulou; Anna Vayaki; K Zachariadou; A Blondel; J C Brient; F P Machefert; A Rougé; M Swynghedauw; R Tanaka; H L Videau; V Ciulli; E Focardi; G Parrini; A Antonelli; M Antonelli; G Bencivenni; F Bossi; P Campana; G Capon; V Chiarella; P Laurelli; G Mannocchi; F Murtas; G P Murtas; L Passalacqua; A Halley; J Kennedy; J G Lynch; P Negus; V O'Shea; A S Thompson; S R Wasserbaech; R J Cavanaugh; S Dhamotharan; C Geweniger; P Hanke; V Hepp; E E Kluge; G Leibenguth; A Putzer; H Stenzel; K Tittel; M Wunsch; R Beuselinck; W Cameron; G Davies; Peter J Dornan; M Girone; R D Hill; N Marinelli; J Nowell; S A Rutherford; J K Sedgbeer; J C Thompson; R White; V M Ghete; P Girtler; E Kneringer; D Kuhn; G Rudolph; E Bouhova-Thacker; C K Bowdery; D P Clarke; G Ellis; A J Finch; F Foster; G Hughes; R W L Jones; M R Pearson; N A Robertson; M Smizanska; O van der Aa; C Delaere; V Lemaître; U Blumenschein; F Hölldorfer; K Jakobs; F J Kayser; K Kleinknecht; A S Müller; G Quast; B Renk; H G Sander; S Schmeling; H W Wachsmuth; C Zeitnitz; T Ziegler; A Bonissent; P Coyle; C Curtil; A Ealet; D Fouchez; P Payre; A Tilquin; F Ragusa; A David; H Dietl; G Ganis; K Hüttmann; G Lütjens; W Männer; H G Moser; Ronald Settles; G Wolf; J Boucrot; O Callot; M Davier; L Duflot; J F Grivaz; P Heusse; A Jacholkowska; C Loomis; L Serin; J J Veillet; J B De Vivie de Régie; C Yuan; G Bagliesi; T Boccali; L Foà; A Giammanco; A Giassi; F Ligabue; A Messineo; Fabrizio Palla; G Sanguinetti; A Sciabà; Roberto Tenchini; A Venturi; P G Verdini; O Awunor; G A Blair; G Cowan; A García-Bellido; M G Green; L T Jones; T Medcalf; A Misiejuk; J A Strong; P Teixeira-Dias; R W Clifft; T R Edgecock; P R Norton; I R Tomalin; B Bloch-Devaux; D E Boumediene; P Colas; B Fabbro; E Lançon; M C Lemaire; E Locci; P Pérez; J Rander; J F Renardy; A Rosowsky; P Seager; A Trabelsi; B Tuchming; B Vallage; N P Konstantinidis; A M Litke; G Taylor; C N Booth; S L Cartwright; F Combley; P N Hodgson; M H Lehto; L F Thompson; K Affholderbach; A Böhrer; S Brandt; Claus Grupen; J Hess; A Ngac; G Prange; U Sieler; C Borean; G Giannini; H He; J Pütz; J E Rothberg; S R Armstrong; K Berkelman; K Cranmer; D P S Ferguson; Y Gao; S González; O J Hayes; H Hu; S Jin; J Kile; P A McNamara; J Nielsen; Y B Pan; J H Von Wimmersperg-Töller; W Wiedenmann; J Wu; Wu Sau Lan; X Wu; G Zobernig; G Dissertori

2002-01-01

419

Topological mid-gap states of px+ipy topological superconductor with vortex square superlattice

NASA Astrophysics Data System (ADS)

In this paper, the px+ipy topological superconductor with vortex square superlattice is studied. We calculated the edge spectrum in the presence of vortex superlattice, and found that there exist mid-gap vortex fermion bands induced by the vortex superlattice with nontrivial topological properties, which relate to gapless edge mode and non-zero winding number. Moreover, we proposed a topological anisotropic tight-binding Majorana lattice model to describe the mid-gap states.

Zhou, Jiang; Wang, Shi-Zhu; Wu, Ya-Jie; Li, Rong-Wu; Kou, Su-Peng

2014-07-01

420

Topologically induced local PandCP violation in QCD x QED

The existence of topological solutions and axial anomaly open a possibility of PandCP violation in QCD. For a reason that has not yet been established conclusively, this possibility is not realized in strong interactions - the experimental data indicate that a global PandCP violation in QCD is absent. Nevertheless, the fluctuations of topological charge in QCD vacuum, although not observable directly, are expected to play an important role in the breaking of U{sub A}(1) symmetry and in the mass spectrum and other properties of hadrons. Moreover, in the presence of very intense external electromagnetic fields topological solutions of QCD can induce localP-andCP-odd effects in the SU{sub c}(3)xU{sub em}(1) gauge theory that can be observed in experiment directly. Here I show how these local parity-violating phenomena can be described by using the Maxwell-Chern-Simons, or axion, electrodynamics as an effective theory. Local P-andCP-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. Very recently, STAR Collaboration presented an observation of the electric charge asymmetry with respect to reaction plane in relativistic heavy ion collisions at RHIC.

Kharzeev, Dmitri E. [Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Physics, Yale University, New Haven, CT 06520-8120 (United States)], E-mail: kharzeev@bnl.gov

2010-01-15

421

Helix periodicity, topology, and dynamics of membrane-associated ?-Synuclein

The protein ?-Synuclein (aS) is a synaptic vesicle-associated regulator of synaptic strength and dopamine homeostasis with a pathological role in Parkinson’s disease. The normal function of aS depends on a membrane-associated conformation that is adopted upon binding to negatively charged lipid surfaces. Previously we found that the membrane-binding domain of aS is helical and suggested that it may exhibit an unusual structural periodicity. Here we present a study of the periodicity, topology, and dynamics of detergent micelle-bound aS using paramagnetic spin labels embedded in the micelle or attached to the protein. We show that the helical region of aS completes three full turns every 11 residues, demonstrating the proposed 11/3 periodicity. We also find that the membrane-binding domain is partially buried in the micelle surface and bends toward the hydrophobic interior, but does not traverse the micelle. Deeper submersion of certain regions within the micelle, including the unique lysine-free sixth 11-residue repeat, is observed and may be functionally important. There are no long-range tertiary contacts within this domain, indicating a highly extended configuration. The backbone dynamics of the micelle-bound region are relatively uniform with a slight decrease in flexibility observed toward the C-terminal end. These results clarify the topological features of aS bound to membrane-mimicking detergent micelles, with implications for aS function and pathology. PMID:15741347

Bussell, Robert; Ramlall, Trudy Fiona; Eliezer, David

2005-01-01

422

Things Fall Apart Topology Change from Winding Tachyons

We argue that closed string tachyons drive two spacetime topology changing transitions -- loss of genus in a Riemann surface and separation of a Riemann surface into two components. The tachyons of interest are localized versions of Scherk-Schwarz winding string tachyons arising on Riemann surfaces in regions of moduli space where string-scale tubes develop. Spacetime and world-sheet renormalization group analyses provide strong evidence that the decay of these tachyons removes a portion of the spacetime, splitting the tube into two pieces. We address the fate of the gauge fields and charges lost in the process, generalize it to situations with weak flux backgrounds, and use this process to study the type 0 tachyon, providing further evidence that its decay drives the theory sub-critical. Finally, we discuss the time-dependent dynamics of this topology-changing transition and find that it can occur more efficiently than analogous transitions on extended supersymmetric moduli spaces, which are limited by modul...

Adams, A; McGreevy, J; Saltman, A; Silverstein, E

2005-01-01

423

Things Fall Apart: Topology Change from Winding Tachyons

We argue that closed string tachyons drive two spacetime topology changing transitions -- loss of genus in a Riemann surface and separation of a Riemann surface into two components. The tachyons of interest are localized versions of Scherk-Schwarz winding string tachyons arising on Riemann surfaces in regions of moduli space where string-scale tubes develop. Spacetime and world-sheet renormalization group analyses provide strong evidence that the decay of these tachyons removes a portion of the spacetime, splitting the tube into two pieces. We address the fate of the gauge fields and charges lost in the process, generalize it to situations with weak flux backgrounds, and use this process to study the type 0 tachyon, providing further evidence that its decay drives the theory sub-critical. Finally, we discuss the time-dependent dynamics of this topology-changing transition and find that it can occur more efficiently than analogous transitions on extended supersymmetric moduli spaces, which are limited by moduli trapping.

A. Adams; X. Liu; J. McGreevy; A. Saltman; E. Silverstein

2005-02-02

424

Things Fall Apart: Topology Change From Winding Tachyons

We argue that closed string tachyons drive two spacetime topology changing transitions--loss of genus in a Riemann surface and separation of a Riemann surface into two components. The tachyons of interest are localized versions of Scherk-Schwarz winding string tachyons arising on Riemann surfaces in regions of moduli space where string-scale tubes develop. Spacetime and world-sheet renormalization group analyses provide strong evidence that the decay of these tachyons removes a portion of the spacetime, splitting the tube into two pieces. We address the fate of the gauge fields and charges lost in the process, generalize it to situations with weak flux backgrounds, and use this process to study the type 0 tachyon, providing further evidence that its decay drives the theory sub-critical. Finally, we discuss the time-dependent dynamics of this topology-changing transition and find that it can occur more efficiently than analogous transitions on extended supersymmetric moduli spaces, which are limited by moduli trapping.

Adams, A.

2005-02-04

425

Topological Field Theories in 2 dimensions Constantin Teleman

Topological Field Theories in 2 dimensions Constantin Teleman UC Berkeley Amsterdam, 14 July 2008 Constantin Teleman 2D Topological Field Theories #12;Origins The notion of a Topological Field Theory (TFT space). This space of fields is "multiplicative in pieces of X". Constantin Teleman 2D Topological Field

Teleman, Constantin

426

C*-Algebras over Topological Spaces: The Bootstrap Class.

We carefully define and study C*-algebras over topological spaces, possibly non-Hausdorff, and review some relevant results from point-set topology along the way. We explain the triangulated category structure on the bivariant Kasparov theory over a topological space. We introduce and describe an analogue of the bootstrap class for C*-algebras over a finite topological space.

Ralf Meyer; Ryszard Nest

427

A List of Recommended Books in Topology Allen Hatcher

for getting the big picture. Perhaps not as easy for a beginner as the preceding book. Â· G E Bredon. TopologyA List of Recommended Books in Topology Allen Hatcher These are books that I personally like't cover absolutely all areas of Topology. The number of Topology books has been increasing rather rapidly

Hatcher, Allen

428

Topologies on quantum topoi induced by quantization

In the present paper, we consider effects of quantization in a topos approach of quantum theory. A quantum system is assumed to be coded in a quantum topos, by which we mean the topos of presheaves on the context category of commutative subalgebras of a von Neumann algebra of bounded operators on a Hilbert space. A classical system is modeled by a Lie algebra of classical observables. It is shown that a quantization map from the classical observables to self-adjoint operators on the Hilbert space naturally induces geometric morphisms from presheaf topoi related to the classical system to the quantum topos. By means of the geometric morphisms, we give Lawvere-Tierney topologies on the quantum topos (and their equivalent Grothendieck topologies on the context category). We show that, among them, there exists a canonical one which we call a quantization topology. We furthermore give an explicit expression of a sheafification functor associated with the quantization topology.

Nakayama, Kunji [Faculty of Law, Ryukoku University, Fushimi-ku, Kyoto 612-8577 (Japan)] [Faculty of Law, Ryukoku University, Fushimi-ku, Kyoto 612-8577 (Japan)

2013-07-15

429

Information topology identifies emergent model classes

We introduce the concept of information topology by considering the information geometry of models of the same physical system under different experimental conditions. By varying the experimental conditions, statistical inference imposes different metrics on the system's parameter space, leading to different geometric properties, such as distance and curvature. Experimental conditions that preserve the structural identifiability of the parameters are related by diffeomorphisms and form an information topology. Experimental conditions that lead to a manifold collapse correspond to a different topology and require a modification of the underlying theory in order to construct a model whose parameters are identifiable (either structurally or practically). For many models the relevant topological feature is a hierarchical structure of boundaries (faces, edges, corners, etc.) which we represent as a hierarchical graph. The tips of this hierarchical graph correspond to dominant modes that govern the macroscopic, col...

Transtrum, Mark K; Qiu, Peng

2014-01-01

430

Topology optimisation for natural convection problems

This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation. In order to facilitate topology optimisation, the Brinkman approach is taken to penalise velocities inside the solid domain and the effective thermal conductivity is interpolated in order to accommodate differences in thermal conductivity of the solid and fluid phases. The governing equations are discretised using stabilised finite elements and topology optimisation is performed for two different problems using discrete adjoint sensitivity analysis. The study shows that topology optimisation is a viable approach for designing heat sink geometries cooled by natural convection and micropumps powered by natural convection.

Alexandersen, Joe; Andreasen, Casper Schousboe; Sigmund, Ole

2014-01-01

431

Statistical analysis of protein interaction network topology

Complex networks arise in diverse areas of natural and social sciences and network topology is a key determinant of such systems. In this work we investigate the protein-protein interaction network of the KSHV herpesvirus, ...

Dong, Yu-An, 1974-

2005-01-01

432

HgTe as a Topological Insulator

NASA Astrophysics Data System (ADS)

HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the compound into a topological insulator. The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures exhibit the quantum spin Hall effect, where a pair of spin polarized helical edge channels develops when the bulk of the material is insulating. Our transport data provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topological insulator. To turn the material into a 3-dimensional topological insulator, we utilize growth induced strain in relatively thick (ca. 100 nm) HgTe epitaxial layers. The high electronic quality of such layers allows a direct observation of the quantum transport properties of the 2-dimensional topological surface states.

Molenkamp, Laurens W.

2012-02-01

433

Band geometry of fractional topological insulators

NASA Astrophysics Data System (ADS)

Recent numerical simulations of flat-band models with interactions which show clear evidence of fractionalized topological phases in the absence of a net magnetic field have generated a great deal of interest. We provide an explanation for these observations by showing that the physics of these systems is the same as that of conventional fractional quantum Hall phases in the lowest Landau level under certain ideal conditions which can be specified in terms of the Berry curvature and the Fubini-Study or quantum metric of the topological band. In particular, we show that when these ideal conditions hold, the density operators projected to the topological band obey the W? algebra. Our approach leads us to propose a way of testing the suitability of topological bands for hosting fractionalized phases.

Roy, Rahul

2014-10-01

434

Extracting hadron masses from fixed topology simulations

NASA Astrophysics Data System (ADS)

Lattice QCD simulations tend to become stuck in a single topological sector at fine lattice spacing or when using chirally symmetric overlap quarks. In such cases physical observables differ from their full QCD counterparts by finite volume corrections. These systematic errors need to be understood on a quantitative level and possibly removed. In this paper we extend an existing relation from the literature between two-point correlation functions at fixed and the corresponding hadron masses at unfixed topology by calculating all terms proportional to 1/V2 and 1/V3, where V is the spacetime volume. Since parity is not a symmetry at fixed topology, parity mixing is comprehensively discussed. In the second part of this work we apply our equations to a simple model, quantum mechanics on a circle both for a free particle and for a square-well potential, where we demonstrate in detail, how to extract physically meaningful masses from computations or simulations at fixed topology.

Dromard, Arthur; Wagner, Marc

2014-10-01

435

Quantum algebraic approach to refined topological vertex

NASA Astrophysics Data System (ADS)

We establish the equivalence between the refined topological vertex of Iqbal-Kozcaz-Vafa and a certain representation theory of the quantum algebra of type W 1+? introduced by Miki. Our construction involves trivalent intertwining operators ? and ?* associated with triples of the bosonic Fock modules. Resembling the topological vertex, a triple of vectors ? {mathbb{Z}^2} is attached to each intertwining operator, which satisfy the Calabi-Yau and smoothness conditions. It is shown that certain matrix elements of ? and ?* give the refined topological vertex C ? ?? ( t, q) of Iqbal-Kozcaz-Vafa. With another choice of basis, we recover the refined topological vertex C ? ? ? ( q, t) of Awata-Kanno. The gluing factors appears correctly when we consider any compositions of ? and ?*. The spectral parameters attached to Fock spaces play the role of the Kähler parameters.

Awata, H.; Feigin, B.; Shiraishi, J.

2012-03-01

436

THE TOPOLOGICAL IHX RELATION NATHAN HABEGGER

THE TOPOLOGICAL IHX RELATION NATHAN HABEGGER Abstract. We give an exposition of the classification, to a perturbative expansion in terms of Feynman diagrams for the objects of study. 1 #12; 2 NATHAN HABEGGER

Habegger, Nathan

437

Generalized gauge field theories with non-topological soliton solutions

We perform a systematic analysis of the conditions under which \\textit{generalized} gauge field theories of compact semisimple Lie groups exhibit electrostatic spherically symmetric non-topological soliton solutions in three space dimensions. By the term \\textit{generalized}, we mean that the dynamics of the concerned fields is governed by lagrangian densities which are general functions of the quadratic field invariants, leading to physically consistent models. The analysis defines exhaustively the class of this kind of lagrangian models supporting those soliton solutions and leads to methods for their explicit determination. The necessary and sufficient conditions for the linear stability of the finite-energy solutions against charge-preserving perturbations are established, going beyond the usual Derrick-like criteria, which only provides necessary conditions.

Joaquin Diaz-Alonso; Diego Rubiera-Garcia

2007-08-04

438

The general supersymmetric solution of topologically massive supergravity

NASA Astrophysics Data System (ADS)

We find the general fully nonlinear solution of topologically massive supergravity admitting a Killing spinor. It is of plane-wave type, with a null Killing vector field. Conversely, we show that all solutions with a null Killing vector are supersymmetric for one or the other choice of sign for the Chern Simons coupling constant ?. If ? does not take the critical value, ? = ±1, these solutions are asymptotically regular on a Poincaré patch, but do not admit a smooth global compactification with boundary S^1 \\times \\R . In the critical case, the solutions have a logarithmic singularity on the boundary of the Poincaré patch. We derive a Nester Witten identity, which allows us to identify the associated charges, but we conclude that the presence of the Chern Simons term prevents us from making a statement about their positivity. The Nester Witten procedure is applied to the BTZ black hole.

Gibbons, G. W.; Pope, C. N.; Sezgin, E.

2008-10-01

439

Topological similarities in electrical and hydrological drainage networks

NASA Astrophysics Data System (ADS)

Under an electric field, spherical conducting particles in a dielectric liquid assemble into a dendritic tree in order to dissipate charge. Several topological measures characterize such networks, including degree distributions, Strahler numbers, and total external pathlengths. Here, scaling laws relating these measures to the number of nodes in the system are presented and shown to match diffusion limited aggregation (DLA) structures. Experimental bifurcation and stream-length ratios in this easily reproducible laboratory experiment are found to agree with DLA simulations and Horton's laws for river networks. Certain scaling relations in transportation networks are known to originate from general features of networks. Here we find the experimental structures share properties with hydrological drainage networks.

Soni, Vishal H.; Ketisch, Pia M.; Rodríguez, Juan D.; Shpunt, Alexander; Hübler, Alfred W.

2011-02-01

440

Topology Based Flow Analysis and Superposition Effects

Using topology for feature analysis in flow fields faces several problems. First of all, not all features can be detected\\u000a using topology based methods. Second, while in flow feature analysis the user is interested in a quantification of feature\\u000a parameters like position, size, shape, radial velocity and other parameters of feature models, many of these parameters can\\u000a not be determined

Julia Ebling; Alexander Wiebel; Christoph Garth; Gerik Scheuermann

441

Geometry and Topology: Volume 6 (2002)

NSDL National Science Digital Library

Geometry and Topology is a yearly journal published in association with the Mathematics Department of the University of Warwick. The latest volume was recently posted and can be downloaded from this Web site. Each section discusses current research into proofs and algorithms involving geometry and topology. Surface bundles, 3-manifolds, bounded cohomology, and mapping class groups are among the topics for this volume. All five earlier volumes are available from the main page, as well as some research monographs.

1997-01-01

442

Topological censorship and higher genus black holes

NASA Astrophysics Data System (ADS)

Motivated by recent interest in black holes whose asymptotic geometry approaches that of anti-de Sitter spacetime, we give a proof of topological censorship applicable to spacetimes with such asymptotic behavior. Employing a useful rephrasing of topological censorship as a property of homotopies of arbitrary loops, we then explore the consequences of topological censorship for the horizon topology of black holes. We find that the genera of horizons are controled by the genus of the space at infinity. Our results make it clear that there is no conflict between topological censorship and the nonspherical horizon topologies of locally anti-de Sitter black holes. More specifically, let D be the domain of outer communications of a boundary at infinity ``scri.'' We show that the principle of topological censorship (PTC), which is that every causal curve in D having end points on scri can be deformed to scri, holds under reasonable conditions for timelike scri, as it is known to do for a simply connected null scri. We then show that the PTC implies that the fundamental group of scri maps, via inclusion, onto the fundamental group of D: i.e., every loop in D is homotopic to a loop in scri. We use this to determine the integral homology of preferred spacelike hypersurfaces (Cauchy surfaces or analogues thereof) in the domain of outer communications of any four-dimensional spacetime obeying the PTC. From this, we establish that the sum of the genera of the cross sections in which such a hypersurface meets black hole horizons is bounded above by the genus of the cut of infinity defined by the hypersurface. Our results generalize familiar theorems valid for asymptotically flat spacetimes requiring simple connectivity of the domain of outer communications and spherical topology for stationary and evolving black holes.

Galloway, G. J.; Schleich, K.; Witt, D. M.; Woolgar, E.

1999-11-01

443

Fractional Topological Phase for Entangled Qudits

NASA Astrophysics Data System (ADS)

We investigate the topological structure of entangled qudits under unitary local operations. Different sectors are identified in the evolution, and their topological aspects are analyzed. The geometric phase is explicitly calculated in terms of the concurrence. As a main result, we predict a fractional phase for cyclic evolutions in the multiply connected space of maximally entangled states. This result is potentially useful for noise robust implementations of quantum gates.

Oxman, L. E.; Khoury, A. Z.

2011-06-01

444

Cosmological topologically massive gravitons and photons

We study topologically massive (2+1)-dimensional gravity with a negative cosmological constant. The masses of the linearized curvature excitations about AdS3 backgrounds are not only shifted from their flat background values but also, more surprisingly, split according to chirality. For all finite values of the topological mass, we find a single bulk degree of freedom with positive energy, and exhibit a

S. Carlip; S. Deser; A. Waldron; D. K. Wise

2009-01-01

445

Introduction to Dirac materials and topological insulators

NASA Astrophysics Data System (ADS)

We present a short pedagogical introduction to the physics of Dirac materials, restricted to graphene and two-dimensional topological insulators. We start with a brief reminder of the Dirac and Weyl equations in the particle physics context. Turning to condensed matter systems, semimetallic graphene and various Dirac insulators are introduced, including the Haldane and the Kane-Mele topological insulators. We also discuss briefly experimental realizations in materials with strong spin-orbit coupling.

Cayssol, Jérôme

2013-11-01

446

Topology of plane arrangements and their complements

NASA Astrophysics Data System (ADS)

This paper is a glossary of notions and methods related to the topological theory of affine plane arrangements, including braid groups, configuration spaces, order complexes, stratified Morse theory, simplicial resolutions, complexes of graphs, Orlik-Solomon rings, Salvetti complexes, matroids, Spanier-Whitehead duality, twisted homology groups, monodromy theory, and multidimensional hypergeometric functions. The emphasis is upon making the presentation as geometric as possible. Applications and analogies in differential topology are outlined, and some recent results of the theory are presented.

Vasiliev, V. A.

2001-04-01

447

Topological holes in space-time

Summary We consider the solution of Einstein’s field equations on a manifold with a topological hole in the 3-geometry. We find that\\u000a such a hole is repelled by ordinary matter and behaves as if it had negative gravitational mass and positive inertial mass\\u000a even though it has no actual energy content. Topological holes do not radiate or absorb energy if placed

D. K. Ross

1984-01-01

448

Geometry and groups for cosmic topology

The Cosmic Microwave Background is measured by satellite observation with great precision. It offers insight into its origin in early states of the universe. Unexpected low multipole amplitudes of the incoming CMB radiation may be due to a multiply connected topology of cosmic 3-space. We present and analyze the geometry and homotopy for the family of Platonic spherical 3-manifolds, provide their harmonic analysis, and formulate topological selection rules.

Kramer, Peter [Institut fuer Theoretische Physik der Universitaet Tuebingen (Germany)

2011-03-21

449

Topology of crystalline insulators and superconductors

NASA Astrophysics Data System (ADS)

We complete a classification of topological phases and their topological defects in crystalline insulators and superconductors. We consider topological phases and defects described by noninteracting Bloch and Bogoliubov-de Gennes Hamiltonians that support additional order-two spatial symmetry, besides any of 10 classes of symmetries defined by time-reversal symmetry and particle-hole symmetry. The additional order-two spatial symmetry we consider is general and it includes Z2 global symmetry, mirror reflection, twofold rotation, inversion, and their magnetic point group symmetries. We find that the topological periodic table shows a periodicity in the number of flipped coordinates under the order-two spatial symmetry, in addition to the Bott periodicity in the space dimensions. Various symmetry-protected topological phases and gapless modes will be identified and discussed in a unified framework. We also present topological classification of symmetry-protected Fermi points. The bulk classification and the surface Fermi point classification provide a realization of the bulk-boundary correspondence in terms of the K theory.

Shiozaki, Ken; Sato, Masatoshi

2014-10-01

450

Thermodynamics of quasi-topological cosmology

NASA Astrophysics Data System (ADS)

In this Letter, we study thermodynamical properties of the apparent horizon in a universe governed by quasi-topological gravity. Our aim is twofold. First, by using the variational method we derive the general form of Friedmann equation in quasi-topological gravity. Then, by applying the first law of thermodynamics on the apparent horizon, after using the entropy expression associated with the black hole horizon in quasi-topological gravity, and replacing the horizon radius, r+, with the apparent horizon radius, r, we derive the corresponding Friedmann equation in quasi-topological gravity. We find that these two different approaches yield the same result which shows the profound connection between the first law of thermodynamics and the gravitational field equations of quasi-topological gravity. We also study the validity of the generalized second law of thermodynamics in quasi-topological cosmology. We find that, with the assumption of the local equilibrium hypothesis, the generalized second law of thermodynamics is fulfilled for the universe enveloped by the apparent horizon for the late time cosmology.

Dehghani, M. H.; Sheykhi, A.; Dehghani, R.

2013-07-01

451

Topology of crystalline insulators and superconductors

We complete a classification of topological phases and their topological defects in crystalline insulators and superconductors. We consider topological phases and defects described by non-interacting Bloch and Bogoliubov de Gennes Hamiltonians that support additional order-two spatial symmetry, besides any of ten classes of symmetries defined by time-reversal symmetry and particle-hole symmetry. The additional order-two spatial symmetry we consider is general and it includes $Z_2$ global symmetry, mirror reflection, two-fold rotation, inversion, and their magnetic point group symmetries. We find that the topological periodic table shows a novel periodicity in the number of flipped coordinates under the order-two spatial symmetry, in addition to the Bott-periodicity in the space dimensions. Various symmetry protected topological phases and gapless modes will be identified and discussed in a unified framework. We also present topological classification of symmetry protected Fermi points. The bulk classification and the surface Fermi point classification provide a novel realization of the bulk-boundary correspondence in terms of the K-theory.

Ken Shiozaki; Masatoshi Sato

2014-03-13

452

The net charge at interfaces between insulators

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

453

Modeling Prosecutors' Charging Decisions in Domestic Violence Cases

Relatively little research explaining prosecutors'charging decisions in criminal cases is available. Even less has focused on charging decisions in domestic violence cases. Past studies have also relied on restrictive definitions of domestic violence, notablycases with male offenders and female victims, and they have not considered prosecutors'decisions to pursue misdemeanor instead of felony charges—or vice versa. In response to these limitations,

John L. Worrall; Jay W. Ross; Eric S. McCord

2006-01-01

454

Electromagnetic moments of the bound system of charged particles

NASA Astrophysics Data System (ADS)

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.

Wienczek, Albert; Puchalski, Mariusz; Pachucki, Krzysztof

2014-08-01

455

PROTECTED VETERAN DEFINITIONS TITLE DEFINITION

if the veteran has been determined to have a serious employment handicap). Disabled Veteran Veteran who servedPROTECTED VETERAN DEFINITIONS TITLE DEFINITION Veteran of the Vietnam Era Veteran of the U because of a service connected disability. "Vietnam era veteran" also includes any veteran of the U

Tipple, Brett

456

Measurement of the B{sup +} and B{sup 0} lifetimes with topological vertexing at SLD

The lifetimes of the B{sup +} (B{sub u}) and B{sup 0} (B{sub d}) mesons have been measured using a sample of 150,000 hadronic Z{sup 0} decays collected by the SLD experiment at the SLC between 1993 and 1995. The analysis reconstructs the decay length and charge of the B meson using a novel topological technique. This method results in a high statistics sample of 6,033 (3,665) charged (neutral) vertices. The ratio of B{sup +}:B{sup 0} decays in the charged (neutral) sample is 1.8:1 (1:2.3).

Abe, K. [Nagoya Univ. (Japan); Abe, K. [Tohoku Univ., Sendai (Japan); Abt, I. [Univ. of Illinois, Urbana, IL (United States)] [and others; SLD Collaboration

1996-07-01

457

Systematic physical verification with topological patterns

NASA Astrophysics Data System (ADS)

Design rule checks (DRC) are the industry workhorse for constraining design to ensure both physical and electrical manufacturability. Where DRCs fail to fully capture the concept of manufacturability, pattern-based approaches, such as DRC Plus, fill the gap using a library of patterns to capture and identify problematic 2D configurations. Today, both a DRC deck and a pattern matching deck may be found in advanced node process development kits. Major electronic design automation (EDA) vendors offer both DRC and pattern matching solutions for physical verification; in fact, both are frequently integrated into the same physical verification tool. In physical verification, DRCs represent dimensional constraints relating directly to process limitations. On the other hand, patterns represent the 2D placement of surrounding geometries that can introduce systematic process effects. It is possible to combine both DRCs and patterns in a single topological pattern representation. A topological pattern has two separate components: a bitmap representing the placement and alignment of polygon edges, and a vector of dimensional constraints. The topological pattern is unique and unambiguous; there is no code to write, and no two different ways to represent the same physical structure. Furthermore, markers aligned to the pattern can be generated to designate specific layout optimizations for improving manufacturability. In this paper, we describe how to do systematic physical verification with just topological patterns. Common mappings between traditional design rules and topological pattern rules are presented. We describe techniques that can be used during the development of a topological rule deck such as: taking constraints defined on one rule, and systematically projecting it onto other related rules; systematically separating a single rule into two or more rules, when the single rule is not sufficient to capture manufacturability constraints; creating test layout which represents the corners of what is allowed, or not allowed by a rule; improving manufacturability by systematically changing certain patterns; and quantifying how a design uses design rules. Performance of topological pattern search is demonstrated to be production full-chip capable.

Dai, Vito; Lai, Ya-Chieh; Gennari, Frank; Teoh, Edward; Capodieci, Luigi

2014-03-01

458

Photons as quasi-charged particles

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.

K. -P. Marzlin; Juergen Appel; A. I. Lvovsky

2007-04-05

459

Topological phase transition in a topological crystalline insulator induced by finite-size effects

NASA Astrophysics Data System (ADS)

We study electronic states and topological invariants of (001) films of the topological crystalline insulator (TCI) PbxSn1-xTe. Gapless surface Dirac cones on bulk TCIs become gapped in thin films due to the finite-size effect, which is the hybridization between the states on the top and bottom surfaces. We clarify that the TCI film has a strong finite-size effect as compared to three-dimensional topological insulators such as Bi2Se3. Moreover, the energy gap oscillates with the thickness of film. The oscillation stems from topological phase transitions in two dimensions. The obtained data of the topological invariants and energy gap serve as guide to TCI-device applications.

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

2014-07-01

460

NASA Astrophysics Data System (ADS)

In density-based topological design, one expects that the final result consists of elements either black (solid material) or white (void), without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multi- displacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.

Rong, J. H.; Yi, J. H.

2010-10-01

461

Advanced Accessory Power Supply Topologies

This Cooperative Research and Development Agreement (CRADA) began December 8, 2000 and ended September 30, 2009. The total funding provided by the Participant (General Motors Advanced Technology Vehicles [GM]) during the course of the CRADA totaled $1.2M enabling the Contractor (UT-Battelle, LLC [Oak Ridge National Laboratory, a.k.a. ORNL]) to contribute significantly to the joint project. The initial task was to work with GM on the feasibility of developing their conceptual approach of modifying major components of the existing traction inverter/drive to develop low cost, robust, accessory power. Two alternate methods for implementation were suggested by ORNL and both were proven successful through simulations and then extensive testing of prototypes designed and fabricated during the project. This validated the GM overall concept. Moreover, three joint U.S. patents were issued and subsequently licensed by GM. After successfully fulfilling the initial objective, the direction and duration of the CRADA was modified and GM provided funding for two additional tasks. The first new task was to provide the basic development for implementing a cascaded inverter technology into hybrid vehicles (including plug-in hybrid, fuel cell, and electric). The second new task was to continue the basic development for implementing inverter and converter topologies and new technology assessments for hybrid vehicle applications. Additionally, this task was to address the use of high temperature components in drive systems. Under this CRADA, ORNL conducted further research based on GM’s idea of using the motor magnetic core and windings to produce bidirectional accessory power supply that is nongalvanically coupled to the terminals of the high voltage dc-link battery of hybrid vehicles. In order not to interfere with the motor’s torque, ORNL suggested to use the zero-sequence, highfrequency harmonics carried by the main fundamental motor current for producing the accessory power. Two studies were conducted at ORNL. One was to put an additional winding in the motor slots to magnetically link with the high frequency of the controllable zero-sequence stator currents that do not produce any zero-sequence harmonic torques. The second approach was to utilize the corners of the square stator punching for the high-frequency transformers of the dc/dc inverter. Both approaches were successful. This CRADA validated the feasibility of GM’s desire to use the motor’s magnetic core and windings to produce bidirectional accessory power supply. Three joint U.S. patents with GM were issued to ORNL and GM by the U.S. Patent Office for the research results produced by this CRADA.

Marlino, L.D.

2010-06-15