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1

Charge conservation protected topological phases  

NASA Astrophysics Data System (ADS)

We discuss the relation between particle number conservation and topological phases. In four spatial dimensions, we find that systems belonging to different topological phases in the presence of a U(1) charge conservation can be connected adiabatically, i.e., without closing the gap, upon intermediately breaking this local symmetry by a superconducting term. The time reversal preserving topological insulator states in two and three dimensions which can be obtained from the four-dimensional parent state by dimensional reduction inherit this protection by charge conservation. Hence, all topological insulators can be adiabatically connected to a trivial insulating state without breaking time reversal symmetry, provided an intermediate superconducting term is allowed during the adiabatic deformation. Conversely, in one spatial dimension, non-symmetry-protected topological phases occur only in systems that break U(1) charge conservation. These results can intuitively be understood by considering a natural embedding of the classifying spaces of charge conserving Hamiltonians into the corresponding Bogoliubov-de Gennes classes.

Budich, Jan Carl

2013-04-01

2

Charge and spin topological insulators  

SciTech Connect

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

3

Gribov copies and topological charge  

SciTech Connect

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

Improved lattice operators: Case of the topological charge density  

SciTech Connect

We analyze the properties of a class of improved lattice topological charge density operators, constructed by a smearinglike procedure. By optimizing the choice of the parameters introduced in their definition we find operators having (i) a better statistical behavior as estimators of the topological charge density on the lattice, i.e., less noisy, (ii) a multiplicative renormalization much closer to one, and (iii) a large suppression of the perturbative tail (and other unphysical mixings) in the corresponding lattice topological susceptibility. {copyright} {ital 1996 The American Physical Society.}

Christou, C.; Giacomo, A.D.; Panagopoulos, H.; Vicari, E. [Department of Natural Sciences, University of Cyprus, CY-1678, Nicosia (Cyprus)]|[Dipartimento di Fisica dellUniversita and INFN, Pisa (Italy)

1996-03-01

5

Critical analysis of topological charge determination in the background of center vortices in SU(2) lattice gauge theory  

NASA Astrophysics Data System (ADS)

We analyze topological charge contributions from classical SU(2) center vortices with shapes of planes and spheres using different topological charge definitions, namely the center vortex picture of topological charge, a discrete version of FF˜ in the plaquette or hypercube definitions and the lattice index theorem. For the latter the zero modes of the Dirac operator in the fundamental and adjoint representations using both the overlap and asqtad staggered fermion formulations are investigated. We find several problems for the individual definitions and discuss the discrepancies between the different topological charge definitions. Our results show that the interpretation of topological charge in the background of center vortices is rather subtle.

Höllwieser, R.; Faber, M.; Heller, U. M.

2012-07-01

6

Fractional Charge Definitions and Conditions  

SciTech Connect

Fractional charge is known through theoretical and experimental discoveries of isolable objects carrying fractions of familiar charge units--electric charge Q, spin S, and the difference of baryon and lepton numbers B-L. With a few simple assumptions all these effects may be described using a generalized version of charge renormalization for locally conserved charges, in which medium correlations yield familiar adiabatic, continuous renormalization, or sometimes nonadiabatic, discrete renormalization. Fractional charges may be carried by fundamental particles or fundamental solitons. Either picture works for the simplest fractional-quantum-Hall-effect quasiholes, though the particle description is far more general. The only known fundamental solitons in three or fewer space dimensions d are the kink (d = 1), the vortex (d = 2), and the magnetic monopole (d = 3). Further, for a charge not intrinsically coupled to the topological charge of a soliton, only the kink and the monopole may carry fractional values. The same reasoning enforces fractional values of B-L for electrically charged elementary particles.

Goldhaber, A.S.

2004-06-04

7

Effect of topology on the critical charge in graphene  

SciTech Connect

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 toward zero for a suitable angle of the conical sample. We discuss the nature of the scattering phase shifts, quasibound state energies, and local density of states for a gapless graphene cone and determine the dependence of these physical quantities on the sample topology.

Chakraborty, Baishali; Gupta, Kumar S. [Theory Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700064 (India); Sen, Siddhartha [CRANN School of Physics, Trinity College, Dublin 2 (Ireland)

2011-03-15

8

Induced Fermionic Charges from Topological Actions,  

National Technical Information Service (NTIS)

The author examines various theories of fermions interacting with static topological soliton backgrounds in which fermion fractionization occurs. While induced fermion currents can, in general, be calculated from the effective action by a variation with r...

J. A. Zuk

1987-01-01

9

Thermodynamics of charged topological dilaton black holes  

Microsoft Academic Search

A class of (n+1)-dimensional (n>=3) topological black hole solutions in Einstein-Maxwell-dilaton theory with Liouville-type potentials for the dilaton field is presented. In these spacetimes, the black hole horizon and the cosmological horizon can be an (n-1)-dimensional positive, zero, or negative constant curvature hypersurface. Because of the presence of the dilaton field, these topological black holes are neither asymptotically flat nor

Ahmad Sheykhi

2007-01-01

10

Thermodynamics of charged topological dilaton black holes  

Microsoft Academic Search

A class of (n+1)-dimensional (n{>=}3) topological black hole solutions in Einstein-Maxwell-dilaton theory with Liouville-type potentials for the dilaton field is presented. In these spacetimes, the black hole horizon and the cosmological horizon can be an (n-1)-dimensional positive, zero, or negative constant curvature hypersurface. Because of the presence of the dilaton field, these topological black holes are neither asymptotically flat nor

Sheykhi

2007-01-01

11

Are topological charge fluctuations in QCD instanton dominated?  

NASA Astrophysics Data System (ADS)

We consider a recent proposal by Horváth et al. to address the question of whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings, we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD.

Edwards, Robert G.; Heller, Urs M.

2002-01-01

12

Scattering from multicomponent charged ramified polymeric networks of arbitrary topology  

Microsoft Academic Search

The scattering and critical properties of weakly charged ramified polymeric systems for any arbitrary topology are investigated by using the random phase approximation. The interaction matrix is modeled as the sum of the short-range excluded volume matrix and the long-range Debye–Hûckel matrix. We consider three kinds of systems, namely weakly charged ramified polymers in solution when the scattering behavior is

N. Ghaouar; M. Benhamou; A. Gharbi

2006-01-01

13

Valence topological charge-transfer indices for dipole moments  

Microsoft Academic Search

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

Francisco Torrens

2003-01-01

14

Stable structures with high topological charge in nonlinear photonic quasicrystals  

SciTech Connect

Stable vortices with topological charges of 3 and 4 are examined numerically and analytically in photonic quasicrystals created by interference of five as well as eight beams, for cubic as well as saturable nonlinearities. Direct numerical simulations corroborate the analytical and numerical linear stability analysis predictions for such experimentally realizable structures.

Law, K. J. H. [Warwick Mathematics Institute, University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515 (United States); Saxena, Avadh; Bishop, A. R. [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Kevrekidis, P. G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515 (United States)

2010-09-15

15

Nuclear charge form factor in the topological soliton model  

NASA Astrophysics Data System (ADS)

The isoscalar electromagnetic current in the topological soliton model based on the Skyrme model for baryons is related to the topological current which is conserved for purely algebraic reasons. It reflects the chiral symmetry governing the low-energy hadron physics in the u- and d-quark sector and therefore relevant also for the properties of finite nuclei. Here the charge form factor of doubly closed shell nuclei such as 4He, 16O and 40Ca is studied by taking into account both the one- and two-body isoscalar charge operators. The results are compared with those obtained in the frame of meson exchange currents. The role of short-range correlation is also considered.

Boffi, S.; Nicrosini, O.; Radici, M.

1988-12-01

16

Instanton dominance of topological charge fluctuations in QCD?  

NASA Astrophysics Data System (ADS)

We consider the local chirality of near-zero eigenvectors from Wilson-Dirac and clover improved Wilson-Dirac lattice operators as proposed recently by Horváth et al. We study finer lattices and repair for the loss of orthogonality due to the non-normality of the Wilson-Dirac matrix. As a result we do see a clear double peak structure on lattices with resolutions higher than 0.1 fm. We find that the lattice artifacts can be considerably reduced by exploiting the biorthogonal system of left and right eigenvectors. We conclude that the dominance of instantons in topological charge fluctuations is not ruled out by local chirality measurements.

Hip, I.; Lippert, Th.; Neff, H.; Schilling, K.; Schroers, W.

2002-01-01

17

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

NASA Astrophysics Data System (ADS)

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

Chiu, Ting-Wai

1998-10-01

18

Nonlinear Charged Black Holes in AdS Quasi-Topological Gravity  

NASA Astrophysics Data System (ADS)

In this paper, we present the static charged solutions of quartic quasi-topological gravity in the presence of a nonlinear electromagnetic field. Two branches of these solutions present black holes with one or two horizons or a naked singularity depending on the charge and mass of the black hole. The entropy of the charged black holes of fourth-order quasi-topological gravity through the use of Wald formula is computed and the mass, temperature and the charge of these black holes are found as well. We show that black holes with spherical, flat and hyperbolical horizon in quasi-topological gravity are stable for any allowed quasi-topological parameters. We also investigate the stability of nonlinear charged black holes.

Ghanaatian, Mohammad; Bazrafshan, Afsaneh

2013-11-01

19

Topology of the Spin-Polarized Charge Density in bcc and fcc Iron  

Microsoft Academic Search

We report the first investigation of the topology of spin-polarized charge density, specifically in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical. In these cases, the two spin densities are correlated: the spin-minority electrons have directional bond

Travis E. Jones; Mark E. Eberhart; Dennis P. Clougherty

2008-01-01

20

Topological charge pumping effect by the magnetization dynamics on the Surface of Three-Dimensional Topological Insulators  

NASA Astrophysics Data System (ADS)

We discuss a current dynamics on the surface of a 3-dimensional topological insulator induced by magnetization precession of a ferromagnet attached. It is found that the magnetization dynamics generates a direct charge current when the precession axis is within the surface plane. This rectification effect is due to a quantum anomaly (parity anomaly) and is topologically protected. The robustness of the rectification effect against first-varying exchange field is confirmed by the explicit calculation, where we adopt the dimensional regularization to remove the divergence which is inevitable in the study on the electromagnetic response of the Dirac system.

Ueda, Hiroaki; Takeuchi, Akihito; Tatara, Gen; Yokoyama, Takehito

2012-02-01

21

Topology of the Spin-Polarized Charge Density in bcc and fcc Iron  

Microsoft Academic Search

We investigate the topology of the spin-polarized charge density in bcc and\\u000afcc iron. While the total spin-density is found to possess the topology of the\\u000anon-magnetic prototypical structures, in some cases the spin-polarized\\u000adensities are characterized by unique topologies; for example, the\\u000aspin-polarized charge densities of bcc and high-spin fcc iron are atypical of\\u000aany known for non-magnetic materials.

Travis E. Jones; Dennis P. Cloughertyyz; Dennis P. Clougherty

2008-01-01

22

Topology of the Spin-Polarized Charge Density in bcc and fcc Iron  

NASA Astrophysics Data System (ADS)

We report the first investigation of the topology of spin-polarized charge density, specifically in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical. In these cases, the two spin densities are correlated: the spin-minority electrons have directional bond paths and deep minima, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of distinct spin topologies allows us to show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetry-breaking paradigm and proceeds without a topological transformation, while the latter involves a topological catastrophe.

Jones, Travis E.; Eberhart, Mark E.; Clougherty, Dennis P.

2008-01-01

23

Topology of the spin-polarized charge density in bcc and fcc iron.  

PubMed

We report the first investigation of the topology of spin-polarized charge density, specifically in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical. In these cases, the two spin densities are correlated: the spin-minority electrons have directional bond paths and deep minima, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of distinct spin topologies allows us to show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetry-breaking paradigm and proceeds without a topological transformation, while the latter involves a topological catastrophe. PMID:18232817

Jones, Travis E; Eberhart, Mark E; Clougherty, Dennis P

2008-01-10

24

Topological Effects of Charge Transfer in Telomere G-Quadruplex Mechanism on Telomerase Activation and Inhibition  

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

25

Continuum limit of HP{sup 1}-based topological charge density distribution  

SciTech Connect

The bulk distribution of the topological charge density, constructed via the HP{sup 1} {sigma}-model embedding method, is investigated. We argue that the specific pattern of leading power corrections to gluon condensate hints on a particular UV divergent structure of HP{sup 1} {sigma}-model fields, which in turn implies the linear divergence of the corresponding topological density in the continuum limit. We show that under testable assumptions, the topological charge is to be distributed within three-dimensional sign-coherent domains and, conversely, the dimensionality of sign-coherent regions dictates the leading divergence of the topological density. Confronting the proposed scenario with lattice data we present evidence for indeed peculiar divergence of the embedded fields. Then the UV behavior of the topological density is studied directly and is found to agree with our proposition. Finally, we introduce a method to investigate the dimensionality of relevant topological fluctuations and show that indeed topological charge sign-coherent regions are likely to be three-dimensional.

Boyko, P.Yu.; Gubarev, F.V. [Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation)

2006-06-01

26

Topological insulator magnetic tunnel junctions: quantum Hall effect and fractional charge via folding.  

PubMed

We provide a characterization of tunneling between coupled topological insulators in 2D and 3D under the influence of a ferromagnetic layer. We explore conditions for such systems to exhibit integer quantum Hall physics and localized fractional charge, also taking into account interaction effects for the 2D case. We show that the effects of tunneling are topologically equivalent to a certain deformation or folding of the sample geometry. Our key advance is the realization that the quantum Hall or fractional charge physics can appear in the presence of only a single magnet unlike previous proposals which involve magnetic domain walls on the surface or edges of topological insulators, respectively. We give illustrative topological folding arguments to prove our results and show that for the 2D case our results are robust even in the presence of interactions. PMID:23215214

Meng, Qinglei; Vishveshwara, Smitha; Hughes, Taylor L

2012-10-25

27

A rotating one-half topological charge dyon  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

28

Topology  

NSDL National Science Digital Library

A unit designed to develop logical reasoning through topology, using sorting, classifying, and patterning. Topology is about points, lines, and the figures they make; but length, area, curvature and angle can be altered as much as you wish. Thus topology is sometimes called Rubber-Sheet Geometry. Topics chosen are presented in a way that requires a minimum mathematical background and maturity; it is not assumed that students who use this unit know how to solve even simple equations or that they have much acquaintance with geometric figures.

Kaeley, Bhim S.

2007-04-03

29

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

NASA Astrophysics Data System (ADS)

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

Gregersen, M. M.; Okkels, F.; Bazant, M. Z.; Bruus, H.

2009-07-01

30

Scaling Algebras for Charged Fields and Short-Distance Analysis for Localizable and Topological Charges  

Microsoft Academic Search

The method of scaling algebras, which has been introduced earlier as a means for analyzing the short-distance behavior of quantum field theories in the setting of the model-independent, operator algebraic approach, is extended to the case of fields carrying superselection charges. In doing so, consideration will be given to strictly localizable charges (“DHR-type” superselection charges) as well as to charges

Claudio D’Antoni; Gerardo Morsella; Rainer Verch

2004-01-01

31

An evaluation of 2-phase charge pump topologies with charge transfer switches for green mobile technology  

Microsoft Academic Search

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

32

Computation of topological charges of optical vortices via nondegenerate four-wave mixing  

SciTech Connect

In this paper, we report an experiment, which demonstrates computation of topological charges of two optical vortices via a nondegenerate four-wave-mixing process. We show that the output signal photon carries orbital angular momentum which equals to the subtraction of the orbital angular momenta of the probe light photon and the backward pump light photon. The {sup 85}Rb atoms are used as the nonlinear medium, which transfers the orbital angular momenta of lights.

Jiang Wei; Chen Qunfeng; Zhang Yongsheng; Guo, G.-C. [Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026 (China)

2006-10-15

33

Computation of topological charges of optical vortices via nondegenerate four-wave mixing  

Microsoft Academic Search

In this paper, we report an experiment, which demonstrates computation of topological charges of two optical vortices via a nondegenerate four-wave-mixing process. We show that the output signal photon carries orbital angular momentum which equals to the subtraction of the orbital angular momenta of the probe light photon and the backward pump light photon. The ⁸⁵Rb atoms are used as

Jiang Wei; Chen Qunfeng; Zhang Yongsheng; G.-C. Guo

2006-01-01

34

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

NASA Astrophysics Data System (ADS)

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

35

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

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

36

Reading Charge Transport from the Spin Dynamics on the Surface of a Topological Insulator  

NASA Astrophysics Data System (ADS)

Resolving the conductance of the topological surface states (TSSs) from the bulk contribution has been a great challenge for studying the transport properties of topological insulators. By developing a nonperturbative diffusion equation that describes fully the spin-charge dynamics in the strong spin-orbit coupling regime, we present a proposal to read the charge transport information of TSSs from its spin dynamics which can be isolated from the bulk contribution by the time-resolved second harmonic generation pump-probe measurement. We demonstrate the qualitatively different Dyaknov-Perel spin relaxation behavior between the TSSs and the two-dimensional spin-orbit coupling electron gas. The decay time of both in-plane and out-of-plane spin polarization is naturally proved to be identical to the charge transport time. The out-of-plane spin dynamics is shown to be in the experimentally reachable regime of the femtosecond pump-probe spectroscopy and thereby we suggest experiments to detect the charge transport properties of the TSSs from their unique spin dynamics.

Liu, Xin; Sinova, Jairo

2013-10-01

37

Spin and charge transport on the surface of a topological insulator.  

PubMed

We derive diffusion equations, which describe spin-charge coupled transport on the helical metal surface of a three-dimensional topological insulator. The main feature of these equations is a large magnitude of the spin-charge coupling, which leads to interesting and observable effects. In particular, we predict a new magnetoresistance effect, which manifests in a non-Ohmic correction to a voltage drop between a ferromagnetic spin-polarized electrode and a nonmagnetic electrode, placed on top of the helical metal. This correction is proportional to the cross product of the spin polarization of the ferromagnetic electrode and the charge current between the two electrodes. We also demonstrate tunability of this effect by applying a gate voltage, which makes it possible to operate the proposed device as a transistor. PMID:20867997

Burkov, A A; Hawthorn, D G

2010-08-06

38

Comparative investigation of surface charge transport in graphene and topological insulator  

NASA Astrophysics Data System (ADS)

The surface state of topological insulator (TI) and graphene show similar two dimensional ambipolar electronic transport. The Dirac electrons on these surfaces share common transport properties. In this study we provide a comparative investigation based on Boltzmann transport theory to identify similarities and differences between the transport mechanisms in graphene and TI. The band structure of graphene has symmetry between the electron and hole bands, however the band structure of the surface states of TI has asymmetry between the electron and hole bands. This asymmetry in band structure results asymmetric ambipolar behavior in the charge transport. We provide a device model which includes the Dirac equation and band asymmetry to obtain the transfer and output characteristics. We anticipate that, having an enormous progress in graphene based electronics, this comparative investigation could provide a road map for electronic devices based on topological insulators.

Pince, Ercag; Kocabas, Coskun

2013-03-01

39

Topological phase effect on a superconductivity model: Generalized Jahn-teller problems and fractional charge  

NASA Astrophysics Data System (ADS)

Using a toy model of the pairing hamiltonian, we show that the topological (Berry) phase leads to the fractional quantization of the pairing mode in superconductivity, which implies a fractional charge of the Cooper pair. The author would like to thank Dr. S. Iida for his fruitful comments. He is also grateful to Mr. S. Yatsuda and Mr. S. Kakigi for their preparing the manuscript in TEX. This work was carried out under auspices of the Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture No. 62540216.

Kuratsuji, Hiroshi

1988-04-01

40

Spin and charge structure of the surface states in topological insulators  

NASA Astrophysics Data System (ADS)

We investigate the spin and charge densities of surface states of the three-dimensional topological insulator Bi2Se3, starting from the continuum description of the material [Zhang , Nat. Phys.1745-247310.1038/nphys1270 5, 438 (2009)]. The spin structure on surfaces other than the (111) surface has additional complexity because of a misalignment of the contributions coming from the two sublattices of the crystal. For these surfaces we expect new features to be seen in the spin-resolved angular resolved photoemission spectroscopy (ARPES) experiments, caused by a nonhelical spin polarization of electrons at the individual sublattices as well as by the interference of the electron waves emitted coherently from two sublattices. We also show that the position of the Dirac crossing in the spectrum of the surface states depends on the orientation of the interface. This leads to contact potentials and surface charge redistribution at edges between different facets of the crystal.

Silvestrov, P. G.; Brouwer, P. W.; Mishchenko, E. G.

2012-08-01

41

The geometry and electronic topology of higher-order charged Möbius annulenes.  

PubMed

Higher-order aromatic charged Möbius-type annulenes have been L(k) realized computationally. These charged species are based on strips with more than one electronic half-twist, as defined by their linking numbers. The B3LYP/6-311+G(d,p) optimized structures and properties of annulene rings with such multiple half-twists (C(12)H(12)(2+), C(12)H(12)(2-), C(14)H(14), C(18)H(18)(2+), C(18)H(18)(2-), C(21)H(21)(+), C(24)H(24)(2-), C(28)H(28)(2+), and C(28)H(28)(2-)) have the nearly equal C-C bond lengths, small dihedral angles around the circuits, stabilization energies, and nucleus-independent chemical shift values associated with aromaticity. The topology and nature of Möbius annulene systems are analyzed in terms of the torus curves defined by electron density functions (rho(r)(pi), ELF(pi)) constructed using only the occupied pi-MOs. The pi-torus subdivides into a torus knot for annulenes defined by an odd linking number (L(k) = 1, 3pi) and a torus link for those with an even linking number (L(k) = 2, 4pi). The torus topology is shown to map onto single canonical pi-MOs only for even values of L(k). Incomplete and misleading descriptions of the topology of pi-electronic Möbius systems with an odd number of half twists result when only signed orbital diagrams are considered, as is often done for the iconic single half twist system. PMID:19637872

Wannere, Chaitanya S; Rzepa, Henry S; Rinderspacher, B Christopher; Paul, Ankan; Allan, Charlotte S M; Schaefer, Henry F; Schleyer, Paul v R

2009-10-29

42

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

Microsoft Academic Search

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

Chantal Mees Koch; Dennis J. Devine

1999-01-01

43

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

SciTech Connect

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

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

2012-05-15

44

Charge instabilities and topological phases in the extended Hubbard model on the honeycomb lattice with enlarged unit cell  

NASA Astrophysics Data System (ADS)

We study spontaneous symmetry breaking in a system of spinless fermions in the honeycomb lattice paying special emphasis to the role of an enlarged unit cell on time reversal symmetry broken phases. We use a tight-binding model with nearest-neighbor hopping t and Hubbard interaction V1 and V2 and extract the phase diagram as a function of electron density and interaction within a mean-field variational approach. The analysis completes the previous work done in Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.106402 107, 106402 (2011) where phases with nontrivial topological properties were found with only a nearest-neighbor interaction V1 in the absence of charge decouplings. We see that the topological phases are suppressed by the presence of metallic charge density fluctuations. The addition of next to nearest-neighbor interaction V2 restores the topological nontrivial phases.

Grushin, Adolfo G.; Castro, Eduardo V.; Cortijo, Alberto; de Juan, Fernando; Vozmediano, María A. H.; Valenzuela, Belén

2013-02-01

45

An acoustic charge transport imager for high definition television applications  

NASA Astrophysics Data System (ADS)

The progress during the third six month period of the project is presented. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modeling of the avalanche photodiode (APD) and the charge overflow transistor, and the materials growth and fabrication part of the program. Among other results from a comprehensive experimental study, it was found that the use of a ZnO thin film piezoelectric overlay can reduce the RF power consumption of a typical ACT device from 28 dBm to 8 dBm.

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

1993-05-01

46

Topological extensions of Noether charge algebras carried by Dp-branes  

NASA Astrophysics Data System (ADS)

We derive an extension of the supersymmetry algebra carried by D-branes in a massless type IIA superspace vacuum. We find that the extended algebra contains not only topological charges that probe the presence of compact space-time dimensions but also pieces that measure non-trivial configurations of the gauge field on the world-volume of the brane. Furthermore there are terms that measure the coupling of the non-triviality of the world-volume regarded as a U(1) bundle of the gauge field to possible compact space-time dimensions. In particular, the extended algebra carried by the D2-brane can contain the charge of a Dirac monopole of the gauge field. In the course of this work we derive a set of generalized Gamma-matrix identities that include the ones presently known for the IIA case. In the first part of the paper we give an introduction to the basic notions of Noether current algebras and charge algebras; furthermore we find a theorem that describes in a general context how the presence of a gauge field on the world-volume of an embedded object transforming under the symmetry group on the target space alters the algebra of the Noether charges, which otherwise would be the same as the algebra of the symmetry group. This is a phenomenon recently found by Sorokin and Townsend in the case of the M5-brane, but here we show that it holds quite generally, and in particular also in the case of D-branes.

Hammer, Hanno

1998-06-01

47

Investigating the power architectures and circuit topologies for megawatt superfast electric vehicle charging stations with enhanced grid support functionality  

Microsoft Academic Search

In this paper, the power architectures and the power electronics circuit topologies for future megawatt electric vehicle (EV) superfast charging stations with enhanced grid support functionality are discussed and a promising power architecture is proposed. The paper first does a literature research. Based on the literature research, the disadvantages of the existing technologies are identified. A power architecture is proposed

Shuo Wang; Russell Crosier; Yongbin Chu

2012-01-01

48

Membranes with topological charge and AdS{sub 4}/CFT{sub 3} correspondence  

SciTech Connect

If the second Betti number b{sub 2} of a Sasaki-Einstein manifold Y{sup 7} does not vanish, then M-theory on AdS{sub 4}xY{sup 7} possesses 'topological' U(1){sup b}{sub 2} gauge symmetry. The corresponding Abelian gauge fields come from three-form fluctuations with one index in AdS{sub 4} and the other two in Y{sup 7}. We find black membrane solutions carrying one of these U(1) charges. In the zero-temperature limit, our solutions interpolate between AdS{sub 4}xY{sup 7} in the UV and AdS{sub 2}xR{sup 2}xsquashed Y{sup 7} in the IR. In fact, the AdS{sub 2}xR{sup 2}xsquashed Y{sup 7} background is by itself a solution of the supergravity equations of motion. These solutions do not appear to preserve any supersymmetry. We search for their possible instabilities and do not find any. We also discuss the meaning of our charged membrane backgrounds in a dual quiver Chern-Simons gauge theory with a global U(1) charge density. Finally, we present a simple analytic solution which has the same IR but different UV behavior. We reduce this solution to type IIA string theory, and perform T-duality to type IIB. The type IIB metric turns out to be a product of the squashed Y{sup 7} and the extremal Banados-Teitelboim-Zanelli black hole. We discuss an interpretation of this type IIB background in terms of the (1+1)-dimensional conformal field theory on D3-branes partially wrapped over the squashed Y{sup 7}.

Klebanov, Igor R. [Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States); Center for Theoretical Science, Princeton University, Princeton, New Jersey 08544 (United States); Pufu, Silviu S.; Tesileanu, Tiberiu [Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States)

2010-06-15

49

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

NASA Astrophysics Data System (ADS)

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 quasi-one-dimensional wires, these fluctuations are described in terms of ‘quantum phase-slip’ (QPS): tunneling of the superconducting order parameter for the wire between states differing by ±2? in their relative phase between the wire's ends. Over the last several decades, many deviations from conventional bulk superconducting behavior have been observed in ultra-narrow superconducting nanowires, some of which have been identified with QPS. While at least some of the observations are consistent with existing theories for QPS, other observations in many cases point to contradictory conclusions or cannot be explained by these theories. Hence, our understanding of the nature of QPS, and its relationship to the various observations, has remained imcomplete. In this paper we present a new model for QPS which takes as its starting point an idea originally postulated by Mooij and Nazarov (2006 Nature Phys. 2 169): that flux–charge duality, a classical symmetry of Maxwell's equations, can be used to relate QPS to the well-known Josephson tunneling of Cooper pairs. Our model provides an alternative, and qualitatively different, conceptual basis for QPS and the phenomena which arise from it in experiments, and it appears to permit for the first time a unified understanding of observations across several different types of experiments and materials systems.

Kerman, Andrew J.

2013-10-01

50

Topology of charge density and elastic properties of Ti3SiC2 polymorphs  

SciTech Connect

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

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

NASA Astrophysics Data System (ADS)

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

Tanigaki, Katsumi; Tanabe, Yoichi; Kuynh, Khuong; Urata, Takahiro; Nouchi, Ryo; Heguri, Satoshi; Shimotani, Hidekazu

2013-03-01

52

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

SciTech Connect

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

Skouroupathis, A.; Panagopoulos, H. [Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia CY-1678 (Cyprus)

2005-11-01

53

Construction of a topological charge on fuzzy S{sup 2}xS{sup 2} via a Ginsparg-Wilson relation  

SciTech Connect

We construct a topological charge of gauge field configurations on a fuzzy S{sup 2}xS{sup 2} by using a Dirac operator satisfying the Ginsparg-Wilson relation. The topological charge defined on the fuzzy S{sup 2}xS{sup 2} can be interpreted as a noncommutative (or matrix) generalization of the 2nd Chern character on S{sup 2}xS{sup 2}. We further calculate the number of chiral zero modes of the Dirac operator in topologically nontrivial gauge configurations. Generalizations of our formulation to fuzzy (S{sup 2}){sup k} are also discussed.

Aoki, Hajime [Department of Physics, Saga University, Saga 840-8502 (Japan); Hirayama, Yoshiko [Miyazaki Information Processing Center Limited, Fukuoka 812-0011 (Japan); Iso, Satoshi [KEK Theory Center, High Energy Accelerator Research Organization (KEK) and the Graduate University for Advanced Studies (SOKENDAI), Ibaraki 305-0801 (Japan)

2009-12-15

54

Interrelation between monopoles, vortices, topological charge, and chiral symmetry breaking: Analysis using overlap fermions for SU(2)  

NASA Astrophysics Data System (ADS)

We study the properties of configurations from which P-vortices on one hand or Abelian monopoles on the other hand have been removed. We find that the zero modes and the band of nonzero modes close to zero disappear from the spectrum of the overlap Dirac operator, confirming the absence of topological charge and quark condensate. The different behavior of the modified ensembles under smearing compared to the unmodified Monte Carlo ensemble corroborates these findings. The gluonic topological susceptibility rapidly approaches zero in accordance with Qindex=0. The remaining (ultraviolet) monopoles without vortices and—to a less extent—the remaining vortices without monopoles are unstable under smearing whereas smearing of the unmodified Monte Carlo ensemble affects the monopoles and vortices only by smoothing, reducing the density only slightly.

Bornyakov, V. G.; Ilgenfritz, E.-M.; Müller-Preussker, M.; Martemyanov, B. V.; Morozov, S. M.; Veselov, A. I.

2008-04-01

55

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

56

Quantum Charges and Spacetime Topology: The Emergence of New Superselection Sectors  

Microsoft Academic Search

A new form of superselection sectors of topological origin is developed. By that it is meant a new investigation that includes\\u000a several extensions of the traditional framework of Doplicher, Haag and Roberts in local quantum theories. At first we generalize\\u000a the notion of representations of nets of C*–algebras, then we provide a brand new view on selection criteria by adopting

Romeo Brunetti; Giuseppe Ruzzi

2009-01-01

57

Experimental Charge Densities and Intermolecular Interactions:  Electrostatic and Topological Analysis of dl Histidine  

Microsoft Academic Search

A high-resolution, low-temperature X-ray diffraction data set on DL-histidine, collected with a CCD detector, is used in the analysis of molecular bonding and intermolecular interactions. The molecular dipole moment in the crystal is enhanced relative to that from HF and DFT calculations. Topological properties of the molecular electron density differ from theory for the polar bonds but generally agree well

Philip Coppens; Yuriy Abramov; Michael Carducci; Boris Korjov; Irina Novozhilova; Cristobal Alhambra; Mark R. Pressprich

1999-01-01

58

A unified phase transition picture of the charged topological black hole in Ho?ava-Lifshitz gravity  

NASA Astrophysics Data System (ADS)

Aiming at a unified phase transition picture of the charged topological black hole in Ho?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.

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

2013-10-01

59

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

PubMed

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

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

2010-08-25

60

[ital S][sup 1][times][ital S][sup 2] wormholes and topological charge  

SciTech Connect

I investigate solutions to the Euclidean Einstein-matter field equations with the topology [ital S][sup 1][times][ital S][sup 2][times][ital R] in a theory with a massless periodic scalar field and electromagnetism. These solutions carry the winding number of the periodic scalar as well as magnetic flux. They induce violations of a quasitopological conservation law which conserves the product of the magnetic flux and winding number on the background spacetime. I extend these solutions to a model with stable loops of superconducting cosmic string and interpret them as contributing to the decay of such loops.

Ridgway, S.A. (Physics Department, Columbia University, New York, New York 10027 (United States))

1994-07-15

61

Phase fluctuations and the absence of topological defects in a photo-excited charge-ordered nickelate.  

PubMed

The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La(1.75)Sr(0.25)NiO(4) to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter. PMID:22588300

Lee, W S; Chuang, Y D; Moore, R G; Zhu, Y; Patthey, L; Trigo, M; Lu, D H; Kirchmann, P S; Krupin, O; Yi, M; Langner, M; Huse, N; Robinson, J S; Chen, Y; Zhou, S Y; Coslovich, G; Huber, B; Reis, D A; Kaindl, R A; Schoenlein, R W; Doering, D; Denes, P; Schlotter, W F; Turner, J J; Johnson, S L; Först, M; Sasagawa, T; Kung, Y F; Sorini, A P; Kemper, A F; Moritz, B; Devereaux, T P; Lee, D-H; Shen, Z X; Hussain, Z

2012-05-15

62

Diffraction of plane waves by finite-radius spiral phase plates of integer and fractional topological charge.  

PubMed

A detailed analysis of the plane-wave diffraction by a finite-radius circular spiral phase plate (SPP) with integer and fractional topological charge and with variable transmission coefficients inside and outside of the plate edge is presented. We characterize the effect of varying the transmission coefficients and the parameters of the SPP on the propagated field. The vortex structure for integer and fractional phase step of the SPPs with and without phase apodization at the plate edge is also analyzed. The consideration of the interference between the light crossing the SPP and the light that undergoes no phase alteration at the aperture plane reveals new and interesting phenomena associated to this classical problem. PMID:19340254

Garcia-Gracia, Hipolito; Gutiérrez-Vega, Julio C

2009-04-01

63

Diffraction of plane waves by apodized finite-radius spiral phase plates of integer and fractional topological charge  

NASA Astrophysics Data System (ADS)

An analysis of the diffraction of plane waves by an apodized finite-radius circular spiral phase plate (SPP) with integer and fractional topological charge and with variable transmission coefficients inside and outside of the plate edge is presented. We introduce a sinusoidal apodization function at the edge of the plate to allow for a continuous transition between the transmission coefficients, and between the spiral and uniform phase distributions inside and outside of the plate edge. The interference between the light crossing the SPP and the light which undergoes no phase alteration at the aperture plane, and the presence of an apodization at the edge of the plate, cause some interesting phenomena previously unobserved in this widely known problem.

Garcia-Gracia, Hipolito; Gutiérrez-Vega, Julio C.

2009-08-01

64

Quantum molecular dynamics of the topological properties of the electron density: charge transfer in H3(+) and LiF.  

PubMed

This paper presents a method to analyze the time evolution of electron density descriptors defined by the quantum theory of atoms in molecules. The wave packet nuclear dynamics was followed solving the time-dependent Schrödinger equation. The time evolution of the nuclear wave packets was combined with the electronic wave functions to follow the time dependence of the average values of topological electron density descriptors. The method was applied to the reactive collision of H(+) + H(2) under different initial conditions and the photodissociation of LiF for either diabatic or adiabatic processes, with emphasis on the information provided by the time evolution of the atomic charges. These examples illustrate how this approach allows for a detailed analysis of the electronic structure in the time domain. PMID:21942735

Chávez-Calvillo, Rodrigo; Hernández-Trujillo, Jesús

2011-09-26

65

Charging Dirac States at Antiphase Domain Boundaries in the Three-Dimensional Topological Insulator Bi2Se3  

NASA Astrophysics Data System (ADS)

Using scanning tunneling microscopy and transmission electron microscopy, we demonstrate the existence of antiphase boundaries between neighboring grains shifted by a fraction of a quintuple layer in epitaxial (0001) films of the three-dimensional topological insulator Bi2Se3. Scanning tunneling spectroscopy and first-principles calculations reveal that these antiphase boundaries provide electrostatic fields on the order of 108V/m that locally charge the Dirac states, modulating the carrier density, and shift the Dirac point by up to 120 meV. This intrinsic electric field effect, demonstrated here near interfaces between Bi2Se3 grains, provides direct experimental evidence at the atomic scale that the Dirac states are indeed robust against extended structural defects and tunable by electric field. These results also shed light on the recent observation of coexistence of Dirac states and two-dimensional electron gas on Bi2Se3(0001) after adsorption of metal atoms and gas molecules.

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

2013-05-01

66

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

67

Topological black holes dressed with a conformally coupled scalar field and electric charge  

SciTech Connect

Electrically charged solutions for gravity with a conformally coupled scalar field are found in four dimensions in the presence of a cosmological constant. If a quartic self-interaction term for the scalar field is considered, there is a solution describing an asymptotically locally AdS charged black hole dressed with a scalar field that is regular on and outside the event horizon, which is a surface of negative constant curvature. This black hole can have negative mass, which is bounded from below for the extremal case, and its causal structure shows that the solution describes a ''black hole inside a black hole''. The thermodynamics of the nonextremal black hole is analyzed in the grand canonical ensemble. The entropy does not follow the area law, and there is an effective Newton constant which depends on the value of the scalar field at the horizon. If the base manifold is locally flat, the solution has no electric charge, and the scalar field has a vanishing stress-energy tensor so that it dresses a locally AdS spacetime with a nut at the origin. In the case of vanishing self interaction, the solutions also dress locally AdS spacetimes, and if the base manifold is of negative constant curvature a massless electrically charged hairy black hole is obtained. The thermodynamics of this black hole is also analyzed. It is found that the bounds for the black holes parameters in the conformal frame obtained from requiring the entropy to be positive are mapped into the ones that guarantee cosmic censorship in the Einstein frame.

Martinez, Cristian; Troncoso, Ricardo; Staforelli, Juan Pablo [Centro de Estudios Cientificos (CECS), Casilla 1469, Valdivia (Chile); Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Departamento de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Centro de Estudios Cientificos (CECS), Casilla 1469, Valdivia (Chile)

2006-08-15

68

Topological Solitons versus Nonsolitonic Phase Defects in a Quasi-One-Dimensional Charge-Density Wave  

NASA Astrophysics Data System (ADS)

We investigated phase defects in a quasi-one-dimensional commensurate charge-density wave (CDW) system, an In atomic wire array on Si(111), using low temperature scanning tunneling microscopy. The unique fourfold degeneracy of the CDW state leads to various phase defects, among which intrinsic solitons are clearly distinguished. The solitons exhibit a characteristic variation of the CDW amplitude with a coherence length of about 4 nm, as expected from the electronic structure, and a localized electronic state within the CDW gap. While most of the observed solitons are trapped by extrinsic defects, moving solitons are also identified and their novel interaction with extrinsic defects is disclosed.

Kim, Tae-Hwan; Yeom, Han Woong

2012-12-01

69

On the definition of dielectric permittivity for media with temporal dispersion in the presence of free charge carriers  

Microsoft Academic Search

We show that in the presence of free charge carriers the definition of the frequency-dependent dielectric permittivity requires additional regularization. As an example, the dielectric permittivity of the Drude model is considered and its time-dependent counterpart is derived and analyzed. The respective electric displacement cannot be represented in terms of the standard Fourier integral. The regularization procedure allowing the circumvention

M. Bordag; B. Geyer; G. L. Klimchitskaya; V. M. Mostepanenko

2010-01-01

70

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

NASA Astrophysics Data System (ADS)

We present the results of an infrared spectroscopy study of topological insulators Bi2Se3, Bi2Te3 and Sb2Te3. Reflectance spectra of all three materials look similar, with a well defined plasma edge. However, there are some important differences. Most notably, as temperature decreases the plasma edge shifts to lower frequencies in Bi2Se3, whereas in Bi2Te3 and Sb2Te3 it shifts to higher frequencies. In the loss function spectra we identify asymmetric broadening of the plasmon, and assign it to the presence of charge inhomogeneities. It remains to be seen if charge inhomogeneities are characteristic of all topological insulators, and whether they are of intrinsic or extrinsic nature.

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

2013-02-01

71

Topological and differential geometrical gauge field theory  

NASA Astrophysics Data System (ADS)

Recent Quantum Field Theory books have defined the topological charge (Q) in terms of the winding number (N). Contrary to this definition, my proof defines Q in terms of the quantum number (n). Defining Q in terms of n, instead of in terms of N, enables me to determine a precise value for Q. The solutions of all kinds of homotopy classification are referred to as instanton solutions, hence the terms homotopy classification and instanton solution will be used interchangeably. My proof replaces the use of these techniques with the use of the Dirac quantization condition, the covariant Dirac's equation, and the covariant Maxwell's equation. Unlike the earlier approaches, my proof accounts for the concept of the spin quantum number and the concept of time. Using the three methods noted above, my proof yields results not obtained by earlier methods. I have dealt similarly with the Pontryagin Index. I have used the Covariant Electrodynamics, in place of homotopy classification techniques, to create for the Pontryagin Index a proof that is alternative to the one cited in recent literature. The homotopy classification techniques gives an expression that excludes the fact that particles have spin quantum number. Therefore, the homotopy classification techniques does not really describe what the topological charge is in reality. I did derive an expression which does include the spin quantum numbers for particles and this has not been done before. Therefore, this will give a better idea for theoretical physicists about the nature of the topological charge. Contribution to knowledge includes creativity. I created an alternative method to the instanton solution for deriving an expression for the topological charge and this method led to new discoveries as a contribution to knowledge in which I found that topological charge for fermions cannot be quantized (to be quantized means to take discrete values only in integer steps), whereas the instanton solution cannot distinguish between bosons (quantized) and fermions (not quantized). Thus I produced results that were previously unobtainable. Furthermore, since topological charge takes place in Flat Spacetime, I investigated the quantization of the Curved Spacetime version of topological charge (Differential Geometrical Charge) by developing the differential geometrical Gauge Field Theory. It should be noted that the homotopy classification method is not at all applicable to Curved Spacetime. I also modified the Dirac equation in Curved Spacetime by using Einstein's field equation in order to account for the presence of matter. As a result, my method has allowed me to address four cases of topological charge (both spinless and spin one- half, in both Flat and in Curved Spacetime) whereas earlier methods had been blind to all but one of these cases (spinless in Flat Spacetime). (Abstract shortened by UMI.)

Saaty, Joseph

72

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

73

Topological characteristics of brainstem lesions in clinically definite and clinically probable cases of multiple sclerosis: an MRI-study.  

PubMed

Disseminated lesions in the white matter of the cerebral hemispheres and confluent lesions at the borders of the lateral ventricles as seen on MRI are both considered acceptable paraclinical evidence for the diagnosis of multiple sclerosis. Similar changes are, however, also found in vascular diseases of the brain. We therefore aimed at identifying those additional traits in the infratentorial region, which in our experience are not frequently found in cerebrovascular pathology. We evaluated MR brain scans of 68 patients and found pontine lesions in 71% of cases with a clinically definite diagnosis (17 out of 24) and in 33% of cases with a probable diagnosis (14 out of 43). Lesions in the medulla oblongata were present in 50% and 16%, respectively, and in the midbrain in 25% and 7%, respectively. With rare exceptions all brainstem lesions were contiguous with the cisternal or ventricular cerebrospinal fluid spaces. In keeping with post-mortem reports the morphological spectrum ranged from large confluent patches to solitary, well delineated paramedian lesions or discrete linings of the cerebrospinal fluid border zones and were most clearly depicted form horizontal and sagittal T2 weighted SE-sequences. If there is a predilection for the outer or inner surfaces of the brainstem, such lesions can be considered an additional typical feature of multiple sclerosis and can be more reliably weighted as paraclinical evidence for a definite diagnosis. PMID:3431697

Brainin, M; Reisner, T; Neuhold, A; Omasits, M; Wicke, L

1987-01-01

74

Topology in Ordered Phases  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

75

Exploring the bond topological properties and the charge depletion-impact sensitivity relationship of high energetic TNT molecule via theoretical charge density analysis  

Microsoft Academic Search

To understand the energetic properties of 2,3,4-Trinitrotolune (TNT) molecule, a quantum chemical calculation and the electronic charge density analysis have been performed. The density functional theory (B3P86\\/6-311G??) calculation was carried out using Gaussian03 software. The energy-minimized wave function obtained from DFT was used for the charge density analysis. The inductive and steric effects of methyl and nitro substituents are not

Arputharaj David Stephen; Rajesh B. Pawar; Poomani Kumaradhas

2010-01-01

76

SU(2) gluodynamics and HP{sup 1} {sigma}-model embedding: Scaling, topology, and confinement  

SciTech Connect

We investigate recently proposed HP{sup 1} {sigma}-model embedding method aimed to study the topology of SU(2) gauge fields. The HP{sup 1} based topological charge is shown to be fairly compatible with various known definitions. We study the corresponding topological susceptibility and estimate its value in the continuum limit. The geometrical clarity of HP{sup 1} approach allows to investigate nonperturbative aspects of SU(2) gauge theory on a qualitatively new level. In particular, we obtain a numerically precise estimation of gluon condensate and its leading quadratic correction. Furthermore, we present clear evidences that the string tension is to be associated with global (percolating) regions of sign-coherent topological charge. As a by-product of our analysis we estimate the continuum value of quenched chiral condensate and the dimensionality of regions, which localize the lowest eigenmodes of overlap Dirac operator.

Boyko, P.Yu.; Gubarev, F.V.; Morozov, S.M. [Institute of Theoretical and Experimental Physics, B.Cheremushkinskaya 25, Moscow, 117218 (Russian Federation)

2006-01-01

77

Topological approach to Alice electrodynamics  

NASA Astrophysics Data System (ADS)

We analyze the unlocalized ``Cheshire charge'' carried by ``Alice strings.'' The magnetic charge on a string loop is carefully defined, and the transfer of magnetic charge from a monopole to a string loop is analyzed using global topological methods. A semiclassical theory of electric charge transfer is also described.

Bucher, Martin; Lo, Hoi-Kwong; Preskill, John

1992-11-01

78

Topological X-Rays Revisited  

ERIC Educational Resources Information Center

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

Lynch, Mark

2012-01-01

79

New Notions for Discrete Topology  

Microsoft Academic Search

Some new notions based on orders and discrete topology are introduced. We investigate the notions of unipolar and free points,\\u000a we propose some discrete definitions for homotopy and a generalization of the notion of simple point.

Gilles Bertrand; Cite Descartes

1999-01-01

80

Design and development of repetitive capacitor charging power supply based on series-parallel resonant converter topology  

NASA Astrophysics Data System (ADS)

LCL resonant converter based repetitive capacitor charging power supply (CCPS) is designed and developed in the division. The LCL converter acts as a constant current source when switching frequency is equal to the resonant frequency. When both resonant inductors' values of LCL converter are same, it results in inherent zero current switching (ZCS) in switches. In this paper, ac analysis with fundamental frequency approximation of LCL resonant tank circuit, frequency dependent of current gain converter followed by design, development, simulation, and practical result is described. Effect of change in switching frequency and resonant frequency and change in resonant inductors ratio on CCPS will be discussed. An efficient CCPS of average output power of 1.2 kJ/s, output voltage 3 kV, and 300 Hz repetition rate is developed in the division. The performance of this CCPS has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. These results indicate that this design is very feasible for use in capacitor-charging applications.

Patel, Ankur; Nagesh, K. V.; Kolge, Tanmay; Chakravarthy, D. P.

2011-04-01

81

Design and development of repetitive capacitor charging power supply based on series-parallel resonant converter topology.  

PubMed

LCL resonant converter based repetitive capacitor charging power supply (CCPS) is designed and developed in the division. The LCL converter acts as a constant current source when switching frequency is equal to the resonant frequency. When both resonant inductors' values of LCL converter are same, it results in inherent zero current switching (ZCS) in switches. In this paper, ac analysis with fundamental frequency approximation of LCL resonant tank circuit, frequency dependent of current gain converter followed by design, development, simulation, and practical result is described. Effect of change in switching frequency and resonant frequency and change in resonant inductors ratio on CCPS will be discussed. An efficient CCPS of average output power of 1.2 kJ/s, output voltage 3 kV, and 300 Hz repetition rate is developed in the division. The performance of this CCPS has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. These results indicate that this design is very feasible for use in capacitor-charging applications. PMID:21529043

Patel, Ankur; Nagesh, K V; Kolge, Tanmay; Chakravarthy, D P

2011-04-01

82

Topological superconductivity, topological confinement, and the vortex quantum Hall effect  

SciTech Connect

Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.

Diamantini, M. Cristina; Trugenberger, Carlo A. [INFN and Dipartimento di Fisica, University of Perugia, via A. Pascoli, I-06100 Perugia (Italy); SwissScientific, chemin Diodati 10, CH-1223 Cologny (Switzerland)

2011-09-01

83

Effect of charge, topology and orientation of the electric field on the interaction of peptides with the ?-hemolysin pore.  

PubMed

Nanopore analysis is an emerging technique of structural biology which employs nanopores, such as the ?-hemolysin pore, as a biosensor. A voltage applied across a membrane containing a nanopore generates a current, which is partially blocked when a molecule interacts with the pore. The magnitude (I) and the duration (T) of the current blockade provide an event signature for that molecule. Two peptides, CY12(+)T1 and CY12(-)T1 with net charges + 2 and - 2, respectively, were analysed using different applied voltages and all four possible orientations of the electrodes and pore. The four orientations were vestibule downstream (VD), vestibule upstream (VU), stem downstream (SD) and stem upstream (SU) where vestibule and stem refer to the side of the pore on which the peptide was placed and downstream and upstream refer to the application of a positive or negative electrophoretic force, respectively. For CY12(+)T1, the effect of voltage on the event duration was consistent with translocation in the VD and SD configurations, but only intercalation events were observed in the VU and SU configurations. For CY12(-)T1, translocations were only observed in the VD and VU configurations. The results are interpreted in terms of two energy barriers on either side of the lumen of the pore. The difference in height of the barriers determines the preferred direction of exit. Electroosmotic flow and current rectification due to the pore as well as the dipole moment and charge of the peptide also play significant roles. Thus, factors other than simple electrophoresis are important for determining the interaction of small peptides with the pore. PMID:21766390

Christensen, Christopher; Baran, Christian; Krasniqi, Besnik; Stefureac, Radu I; Nokhrin, Sergiy; Lee, Jeremy S

2011-07-18

84

Genetic neural network modeling of the selective inhibition of the intermediate-conductance Ca2+ -activated K+ channel by some triarylmethanes using topological charge indexes descriptors.  

PubMed

Selective inhibition of the intermediate-conductance Ca(2+)-activated K(+ )channel (IK (Ca)) by some clotrimazole analogs has been successfully modeled using topological charge indexes (TCI) and genetic neural networks (GNNs). A neural network monitoring scheme evidenced a highly non-linear dependence between the IK (Ca) blocking activity and TCI descriptors. Suitable subsets of descriptors were selected by means of genetic algorithm. Bayesian regularization was implemented in the network training function with the aim of assuring good generalization qualities to the predictors. GNNs were able to yield a reliable predictor that explained about 97% data variance with good predictive ability. On the contrary, the best multivariate linear equation with descriptors selected by linear genetic search, only explained about 60%. In spite of when using the descriptors from the linear equations to train neural networks yielded higher fitted models, such networks were very unstable and had relative low predictive ability. However, the best GNN BRANN 2 had a Q ( 2 ) of LOO of cross-validation equal to 0.901 and at the same time exhibited outstanding stability when calculating 80 randomly constructed training/test sets partitions. Our model suggested that structural fragments of size three and seven have relevant influence on the inhibitory potency of the studied IK (Ca) channel blockers. Furthermore, inhibitors were well distributed regarding its activity levels in a Kohonen self-organizing map (KSOM) built using the inputs of the best neural network predictor. PMID:16374673

Caballero, Julio; Garriga, Miguel; Fernández, Michael

2005-12-23

85

AdS Boundary Conditions and the Topologically Massive Gravity/CFT Correspondence  

SciTech Connect

The AdS/CFT correspondence provides a new perspective on recurrent questions in General Relativity such as the allowed boundary conditions at infinity and the definition of gravitational conserved charges. Here we review the main insights obtained in this direction over the last decade and apply the new techniques to Topologically Massive Gravity. We show that this theory is dual to a non-unitary CFT for any value of its parameter mu and becomes a Logarithmic CFT at mu = 1.

Skenderis, Kostas; Taylor, Marika; Rees, Balt C. van [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)

2009-12-15

86

Topological censorship.  

NASA Astrophysics Data System (ADS)

Classically, all topologies are allowed as solutions to the Einstein equations. However, one does not observe any topological structures on medium range distance scales, that is scales that are smaller than the size of the observed universe but larger than the microscopic scales for which quantum gravity becomes important. Recently, Friedman, Schleich and Witt (1993) have proven that there is topological censorship on these medium range distance scales: the Einstein equations, locally positive energy, and local predictability of physics imply that any medium distance scale topological structures cannot be seen. More precisely we show that the topology of physically reasonable isolated systems is shrouded from distant observers, or in other words there is a topological censorship principle.

Schleich, K.; Witt, D. M.

87

Topological activity in Bragg elliptical twisted fibers.  

PubMed

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

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

2012-04-01

88

Knot topology in QCD  

NASA Astrophysics Data System (ADS)

We consider topological structure of classical vacuum solutions in quantum chromodynamics. Topologically non-equivalent vacuum configurations are classified by non-trivial second and third homotopy groups for coset of the color group SU(N) (N=2,3) under the action of maximal Abelian stability group. Starting with explicit vacuum knot configurations we study possible exact classical solutions. Exact analytic non-static knot solution in a simple CP1 model in Euclidean space-time has been obtained. We construct an ansatz based on knot and monopole topological vacuum structure for searching new solutions in SU(2) and SU(3) QCD. We show that singular knot-like solutions in QCD in Minkowski space-time can be naturally obtained from knot solitons in integrable CP1 models. A family of Skyrme type low energy effective theories of QCD admitting exact analytic solutions with non-vanishing Hopf charge is proposed.

Zou, L. P.; Zhang, P. M.; Pak, D. G.

2013-10-01

89

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

90

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

91

Quantum gates with topological phases  

SciTech Connect

We investigate two models for performing topological quantum gates with the Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects. Topological one- and two-qubit Abelian phases can be enacted with the AB effect using charge qubits, whereas the AC effect can be used to perform all single-qubit gates (Abelian and non-Abelian) for spin qubits. Possible experimental setups suitable for a solid-state implementation are briefly discussed.

Ionicioiu, Radu [Institute for Scientific Interchange (ISI), Villa Gualino, Viale Settimio Severo 65, I-10133 Torino, (Italy)

2003-09-01

92

Topological construction of mesoporous materials  

Microsoft Academic Search

Major advances in the field of ordered mesoporous materials have been achieved in topological structure definition at the meso phase, and macroscale levels (shape and morphology) using molecular control during mesoporous materials synthesis. Examples include the use of block copolymers for the preparation of mesoporous materials with large pore sizes ($?30 nm), the formation of mesoporous silica with 3D periodically

Dongyuan Zhao; Yang Peidong; Huo Qisheng; Chmelka Bradley F; Stucky Galen D

1998-01-01

93

Preliminary Experimental Work on Nanocomposite Polymers: Small Partial Discharges at Inception Voltage, The Existence of Possible Charging Mechanisms Below Inception Voltage and the Problem of Definitions  

NASA Astrophysics Data System (ADS)

In this paper, some results are presented from experiments concerning partial discharge (PD) behaviour of epoxy resin samples having 3 wt% nano- and 3 wt% micro-fillers, as well as epoxy samples having 3 wt%and1 wt% nanoparticles. The nano- and micro-fillers were TiO2 (titania). The main idea is to see whether a sample with PD at its inception voltage, still presents some tendency to charging effects below inception. An effort is being made to relate the present work with previous publications on the same main idea, as well as to previous research performed recently at Xian Jiaotong University, State Key Laboratory of Electrical Insulation and Power Equipment. It is indicated that with the samples investigated, although on some occasions random charging phenomena were observed below the inception voltage, it was not noted the same behaviour as with pure epoxy samples. Finally, a discussion ensues as to the definitions of the phenomena taking place below inception voltage.

Zhang, Yuan; Danikas, Michael G.; Zhao, Xu; Cheng, Yonghong

2012-03-01

94

An introduction to intuitionistic fuzzy topological spaces  

Microsoft Academic Search

The purpose of this paper is to construct the basic concepts of the so-called “intuitionistic fuzzy topological spaces”. After giving the fundamental definitions and the necessary examples we introduce the definitions of fuzzy continuity, fuzzy compactness, fuzzy connectedness and fuzzy Hausdorff space, and obtain several preservation properties and some characterizations concerning fuzzy compactness and fuzzy connectedness.

Do?an Çoker

1997-01-01

95

Linking the historical and chemical definitions of diabatic states for charge and excitation energy transfer reactions in condensed phase  

NASA Astrophysics Data System (ADS)

Marcus theory of electron transfer (ET) and Förster theory of excitation energy transfer (EET) rely on the Condon approximation and the theoretical availability of initial and final states of ET and EET reactions, often called diabatic states. Recently [Subotnik et al., J. Chem. Phys. 130, 234102 (2009)], diabatic states for practical calculations of ET and EET reactions were defined in terms of their interactions with the surrounding environment. However, from a purely theoretical standpoint, the definition of diabatic states must arise from the minimization of the dynamic couplings between the trial diabatic states. In this work, we show that if the Condon approximation is valid, then a minimization of the derived dynamic couplings leads to corresponding diabatic states for ET reactions taking place in solution by diagonalization of the dipole moment matrix, which is equivalent to a Boys localization algorithm; while for EET reactions in solution, diabatic states are found through the Edmiston-Ruedenberg localization algorithm. In the derivation, we find interesting expressions for the environmental contribution to the dynamic coupling of the adiabatic states in condensed-phase processes. In one of the cases considered, we find that such a contribution is trivially evaluable as a scalar product of the transition dipole moment with a quantity directly derivable from the geometry arrangement of the nuclei in the molecular environment. Possibly, this has applications in the evaluation of dynamic couplings for large scale simulations.

Pavanello, Michele; Neugebauer, Johannes

2011-10-01

96

Topological Quantum Double  

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

97

Coil Array Structures Compared for Contactless Battery Charging Platform  

Microsoft Academic Search

We propose two new coil topologies for a contactless battery charging platform. The new topologies consist of square printed circuit board (PCB) coils, grouped in two layers on a PCB. We compare the new topologies to each other and to a previously published topology that consists of three layers of hexagonal coils. For each topology, the magnetic flux density is

Jaron Achterberg; Elena A. Lomonova; Jeroen de Boeij

2008-01-01

98

Measurement-only topological quantum computation via anyonic interferometry  

SciTech Connect

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

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

2009-04-15

99

Is a color superconductor topological?  

SciTech Connect

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

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

2010-04-01

100

Experimental charge density of L-alanyl-L-prolyl-L-alanine hydrate: classical multipole and invariom approach, analysis of intra- and intermolecular topological properties.  

PubMed

A high-resolution dataset of the tripeptide L-alanyl-L-prolyl-L-alanine hydrate was measured at 100 K using synchrotron radiation and CCD area detection. Electron densities were obtained from a full multipole refinement of the X-ray experimental data, from an invariom transfer and from a theoretical calculation. Topological and atomic properties were derived via an AIM analysis [Atoms in Molecules; see Bader (1990). Atoms in Molecules: A Quantum Theory, No. 22 in International Series of Monographs on Chemistry, 1st ed. Oxford: Clarendon Press] of these densities and compared with each other, as well as with results from the literature of other oligopeptides and amino acids. By application of the invariom formalism to a dataset of limited resolution, its performance was compared with a conventional spherical refinement, highlighting the possibility of aspherically modelling routine structure-determination experiments. The hydrogen-bonding scheme was subject to a detailed analysis according to the criteria of Koch & Popelier [(1995), J. Phys. Chem. 99, 9747-9754] as well as to the characterization of Espinosa et al. [(1998), Chem. Phys. Lett. 285, 170-173; (1999), Acta Cryst. B55, 563-572; (2002), J. Chem. Phys. 117, 5529-5542] using the results from the refined and invariom multipole densities as well as the spherical-density model, which are critically compared. PMID:17873445

Kalinowski, Roman; Dittrich, Birger; Hübschle, Christian B; Paulmann, Carsten; Luger, Peter

2007-09-14

101

Topology, Holes and Sources  

NASA Astrophysics Data System (ADS)

The Aharonov-Bohm effect is often called "topological." But it seems no more topological than magnetostatics, electrostatics or Newton-Poisson gravity (or just about any radiation, propagation from a source). I distinguish between two senses of "topological."

Afriat, Alexander

2013-03-01

102

Topological BF field theory description of topological insulators  

SciTech Connect

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

103

A time-reversal invariant topological phase at the surface of a 3D topological insulator  

NASA Astrophysics Data System (ADS)

A 3D fermionic topological insulator has a gapless Dirac surface state protected by time-reversal symmetry and charge conservation symmetry. The surface state can be gapped by introducing ferromagnetism to break time-reversal symmetry, introducing superconductivity to break charge conservation, or entering a topological phase. In this paper, we construct a minimal gapped topological phase that preserves both time-reversal and charge conservation symmetries and supports Ising-type non-Abelian anyons. This phase can be understood heuristically as emerging from a surface s-wave superconducting state via the condensation of eight-vortex composites. The topological phase inherits vortices supporting Majorana zero modes from the surface superconducting state. However, since it is time-reversal invariant, the surface topological phase is a distinct phase from the Ising topological phase, which can be viewed as a quantum-disordered spin-polarized px + ipy superconductor. We discuss the anyon model of this topological phase and the manner in which time-reversal symmetry is realized in it. We also study the interfaces between the topological state and other surface gapped phases.

Bonderson, Parsa; Nayak, Chetan; Qi, Xiao-Liang

2013-09-01

104

Energetic charged particles as probes of the geometry and topology of the interplanetary magnetic field: The detection of coronal mass ejections  

SciTech Connect

The large-scale structure of the interplanetary magnetic field has been inferred almost exclusively from single point measurements obtained by spacecraft. It has recently been appreciated that energetic charged particles can yield new information about the interplanetary fields since they originate at the sun and are constrained to follow the field lines out to the points of observation. The author reviews the results of particle probes, particularly bidirectional flows (BDFs), to detect coronal mass ejections (CMEs). While a good association, possibly one-to-one, has been assumed between BDFs and CMEs, there is now evidence to suggest that some CMEs do not produce BDFs and that many BDFs are not due to CMEs.

Kahler, S.W.

1994-09-01

105

Topological qubits in graphenelike systems  

NASA Astrophysics Data System (ADS)

The fermion-doubling problem can be an obstacle to getting half a qubit in two-dimensional fermionic tight-binding models in the form of Majorana zero modes bound to the core of superconducting vortices. We argue that the number of such Majorana zero modes is determined by a Z2×Z2 topological charge for a family of two-dimensional fermionic tight-binding models ranging from noncentrosymmetric materials to graphene. This charge depends on the dimension of the representation (i.e., the number of species of Dirac fermions—where the doubling problem enters) and the parity of the Chern number induced by breaking time-reversal symmetry. We show that in graphene there are as many as ten order parameters that can be used in groups of four to change the topological number from even to odd.

Santos, Luiz; Ryu, Shinsei; Chamon, Claudio; Mudry, Christopher

2010-10-01

106

Linear response theory of interacting topological insulators  

NASA Astrophysics Data System (ADS)

Chiral surface states in topological insulators are robust against interactions, nonmagnetic disorder, and localization, yet topology does not yield protection in transport. This work presents a theory of interacting topological insulators in an external electric field, starting from the quantum Liouville equation for the many-body density matrix. Out of equilibrium, topological insulators acquire a current-induced spin polarization. Electron-electron interactions renormalize the nonequilibrium spin polarization and charge conductivity, and disorder in turn enhances this renormalization by a factor of 2. Topological insulator phenomenology remains intact in the presence of interactions out of equilibrium, and an exact correspondence exists between the mathematical frameworks necessary for the understanding of the interacting and noninteracting problems.

Culcer, Dimitrie

2011-12-01

107

Topological susceptibility with the improved Asqtad action  

SciTech Connect

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

108

Topological Magnetoelectric Effect Decay  

NASA Astrophysics Data System (ADS)

We address the influence of realistic disorder and finite doping on the effective magnetic monopole induced near the surface of an ideal topological insulator (TI) by currents that flow in response to a suddenly introduced external electric charge. We show that when the longitudinal conductivity ?xx=g(e2/h)?0, the apparent position of a magnetic monopole initially retreats from the TI surface at speed vM=?cg, where ? is the fine structure constant and c is the speed of light. For the particular case of TI surface states described by a massive Dirac model, we further find that the temperature T=0 Hall currents vanish when the external potential is screened.

Pesin, D. A.; MacDonald, A. H.

2013-07-01

109

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

SciTech Connect

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

110

Disordered Floquet topological insulators  

NASA Astrophysics Data System (ADS)

In the presence of an external periodic field some materials become Floquet topological insulators. Introducing disorder into these systems may alter their electronic properties, which may critically affect their applications. We investigate the effects of disorder on Floquet topological insulators using a Green's function formalism. We find that in the presence of disorder, the transport properties of Floquet topological insulators differ from those of standard topological insulators. We further investigate the robustness of the topological phase to disorder.

Baruch, Shirit; Pereg-Barnea, Tami

2013-03-01

111

Observation of unconventional quantum spin textures in topological insulators.  

PubMed

A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry-based classification of condensed matter. Exotic spin-transport phenomena, such as the dissipationless quantum spin Hall effect, have been speculated to originate from a topological order whose identification requires a spin-sensitive measurement, which does not exist to this date in any system. Using Mott polarimetry, we probed the spin degrees of freedom and demonstrated that topological quantum numbers are completely determined from spin texture-imaging measurements. Applying this method to Sb and Bi(1-x)Sb(x), we identified the origin of its topological order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a topological quantum Berry's phase and definite spin chirality, which are the key electronic properties component for realizing topological quantum computing bits with intrinsic spin Hall-like topological phenomena. PMID:19213915

Hsieh, D; Xia, Y; Wray, L; Qian, D; Pal, A; Dil, J H; Osterwalder, J; Meier, F; Bihlmayer, G; Kane, C L; Hor, Y S; Cava, R J; Hasan, M Z

2009-02-13

112

Topological insulators and superconductors from string theory  

SciTech Connect

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

113

Digitization constraints that preserve topology and geometry  

Microsoft Academic Search

Our definition of a digitization approximates many real digitization processes. We present conditions which guarantee that a digitization process preserves topology of a digitized object. Moreover, these conditions guarantee the invariance of convexity features of the object contour. A useful consequence of this result is the computation of a digitization resolution and a camera distance from a planar object such

Longin Latecki; Ari Gross

1995-01-01

114

Equivalent topological invariants of topological insulators  

NASA Astrophysics Data System (ADS)

A time-reversal (TR) invariant topological insulator can be generally defined by the effective topological field theory with a quantized ? coefficient, which can only take values of 0 or ?. This theory is generally valid for an arbitrarily interacting system and the quantization of the ? invariant can be directly measured experimentally. Reduced to the case of a non-interacting system, the ? invariant can be expressed as an integral over the entire three-dimensional Brillouin zone. Alternatively, non-interacting insulators can be classified by topological invariants defined over discrete TR invariant momenta. In this paper, we show the complete equivalence between the integral and the discrete invariants of the topological insulator.

Wang, Zhong; Qi, Xiao-Liang; Zhang, Shou-Cheng

2010-06-01

115

Topological phases and topological entropy of two-dimensional systems with finite correlation length  

SciTech Connect

We elucidate the topological features of the entanglement entropy of a region in two-dimensional quantum systems in a topological phase with a finite correlation length {xi}. First, we suggest that simpler reduced quantities, related to the von Neumann entropy, could be defined to compute the topological entropy. We use our methods to compute the entanglement entropy for the ground-state wave function of a quantum eight-vertex model in its topological phase and show that a finite correlation length adds corrections of the same order as the topological entropy which come from sharp features of the boundary of the region under study. We also calculate the topological entropy for the ground state of the quantum dimer model on a triangular lattice by using a mapping to a loop model. The topological entropy of the state is determined by loop configurations with a nontrivial winding number around the region under study. Finally, we consider extensions of the Kitaev wave function, which incorporate the effects of electric and magnetic charge fluctuations, and use it to investigate the stability of the topological phase by calculating the topological entropy.

Papanikolaou, Stefanos; Fradkin, Eduardo [Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green St., Urbana, Illinois 61801-3080 (United States); Raman, Kumar S. [Department of Physics and Astronomy, University of California at Riverside, Riverside, California 92521 (United States)

2007-12-01

116

PWM converter topologies  

NASA Astrophysics Data System (ADS)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is defined followed by two universal rules allowing for derivation of a wide variety of different topologies. A summary of different topology types is provided with steady state and small signal relations given for each. The survey shows 46 converter topologies of which 18 are known and 28 are new (under, patent application). The number of topologies could be increased to 68 if negative input voltages are considered.

Meerman, E. R. W.; Spruyt, H. J. N.

1989-08-01

117

Topological density wave states of nonzero angular momentum  

NASA Astrophysics Data System (ADS)

The pseudogap state of high-temperature superconductors is a profound mystery. It contains tantalizing evidence of a number of broken symmetry states, not necessarily conventional charge- and spin-density waves. Here we explore a class of more exotic density wave states characterized by topological properties observed in recently discovered topological insulators. We suggest that these rich topological density wave states deserve closer attention not only in high-temperature superconductors but in other correlated electron states as well.

Hsu, Chen-Hsuan; Raghu, S.; Chakravarty, Sudip

2011-10-01

118

A hierarchy of topological tensor network states  

NASA Astrophysics Data System (ADS)

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; Mombelli, Juan Martín; Christandl, Matthias; Aguado, Miguel

2013-01-01

119

Sufficient symmetry conditions for Topological Quantum Order  

PubMed Central

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

Nussinov, Zohar; Ortiz, Gerardo

2009-01-01

120

Topological Quantum Information Theory  

Microsoft Academic Search

This paper is an introduction to relationships between quantum topology and quantum computing. In this paper we discuss unitary solutions to the Yang- Baxter equation that are universal quantum gates, quantum entanglement and topological entanglement, and we give an exposition of knot-theoretic recoupling theory, its relationship with topological quantum fleld theory and apply these methods to produce unitary representations of

Louis H. Kaufiman; Samuel J. Lomonaco Jr

121

Topological Noise Removal  

Microsoft Academic Search

Meshes obtained from laser scanner data often contain topological noise due to inaccuracies in the scanning and merging process. This topological noise complicates sub- sequent operations such as remeshing, parameterization and smoothing. We introduce an approach that removes unnecessary nontrivial topology from meshes. Using a local wave front traversal, we discover the local topolo- gies of the mesh and identify

Igor Guskov; Zoë J. Wood

2001-01-01

122

Fractional Topological Insulators in Three Dimensions  

SciTech Connect

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

Convergence in topological molecular lattices  

Microsoft Academic Search

The theory of topological molecular lattices introduced by Wang has general topology and fuzzy topology as special cases. In this paper, the author establishes the theory of ideal convergence in topological molecular lattices, and gives characterizations of some topological notions, e.g. closed elements, Hausdorffness, continuous GOH in topological molecular lattices, etc. in terms of ideals. The author establishes the relation

Yixiang Chen

1996-01-01

124

49 CFR 242.7 - Definitions.  

Code of Federal Regulations, 2012 CFR

... QUALIFICATION AND CERTIFICATION OF CONDUCTORS General § 242.7 Definitions...preparation containing ethyl alcohol. Conductor means the crewmember in charge of a...also the definition of âpassenger conductorâ in this section. Controlled...

2012-10-01

125

Periodic table for topological insulators and superconductors  

Microsoft Academic Search

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

Effective field theories for topological insulators by functional bosonization  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

127

Network topology analysis.  

SciTech Connect

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

Photonic Floquet topological insulators  

NASA Astrophysics Data System (ADS)

Topological insulators are a new phase of matter, with the striking property that conduction of electrons occurs only on the surface. In two dimensions, surface electrons in topological insulators do not scatter despite defects and disorder, providing robustness akin to superconductors. Topological insulators are predicted to have wideranging applications in fault-tolerant quantum computing and spintronics. Recently, large theoretical efforts were directed towards achieving topological insulation for electromagnetic waves. One-dimensional systems with topological edge states have been demonstrated, but these states are zero-dimensional, and therefore exhibit no transport properties. Topological protection of microwaves has been observed using a mechanism similar to the quantum Hall effect, by placing a gyromagnetic photonic crystal in an external magnetic field. However, since magnetic effects are very weak at optical frequencies, realizing photonic topological insulators with scatterfree edge states requires a fundamentally different mechanism - one that is free of magnetic fields. Recently, a number of proposals for photonic topological transport have been put forward. Specifically, one suggested temporally modulating a photonic crystal, thus breaking time-reversal symmetry and inducing one-way edge states. This is in the spirit of the proposed Floquet topological insulators, where temporal variations in solidstate systems induce topological edge states. Here, we propose and experimentally demonstrate the first external field-free photonic topological insulator with scatter-free edge transport: a photonic lattice exhibiting topologically protected transport of visible light on the lattice edges. Our system is composed of an array of evanescently coupled helical waveguides arranged in a graphene-like honeycomb lattice. Paraxial diffraction of light is described by a Schrödinger equation where the propagation coordinate acts as `time'. Thus the waveguides' helicity breaks zreversal symmetry in the sense akin to Floquet Topological Insulators. This structure results in scatter-free, oneway edge states that are topologically protected from scattering.

Rechtsman, Mikael C.; Zeuner, Julia M.; Plotnik, Yonatan; Lumer, Yaakov; Podolsky, Daniel; Dreisow, Felix; Nolte, Stefan; Segev, Mordechai; Szameit, Alexander

2013-09-01

129

Topological insulators and topological nonlinear {sigma} models  

SciTech Connect

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

130

Definitive evidence for the existence of isomeric chlorophenyl radicals (C 6H 4Cl ) from charge inversion mass spectrometry and DFT calculations  

Microsoft Academic Search

Free radical species are much more reactive than stable molecules, and so usually exist only as transient intermediates in chemical reactions. Charge inversion mass spectrometry using alkali metal targets is an effective method for determining the structure and dissociation processes of radicals, and can also enable differentiation between isomeric forms of compounds whose parent ions have similar mass spectra and

Shigeo Hayakawa; Hiroshi Matsubara; Yoshiaki Kawamura; Kenichi Iwamoto

2007-01-01

131

Topological Hamiltonian as an exact tool for topological invariants.  

PubMed

We propose the concept of 'topological Hamiltonian' for topological insulators and superconductors in interacting systems. The eigenvalues of the topological Hamiltonian are significantly different from the physical energy spectra, but we show that the topological Hamiltonian contains the information of gapless surface states, therefore it is an exact tool for topological invariants. PMID:23507711

Wang, Zhong; Yan, Binghai

2013-03-19

132

Topological mirror superconductivity.  

PubMed

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

2013-08-02

133

A Similarity Search Using Molecular Topological Graphs  

PubMed Central

A molecular similarity measure has been developed using molecular topological graphs and atomic partial charges. Two kinds of topological graphs were used. One is the ordinary adjacency matrix and the other is a matrix which represents the minimum path length between two atoms of the molecule. The ordinary adjacency matrix is suitable to compare the local structures of molecules such as functional groups, and the other matrix is suitable to compare the global structures of molecules. The combination of these two matrices gave a similarity measure. This method was applied to in silico drug screening, and the results showed that it was effective as a similarity measure.

Fukunishi, Yoshifumi; Nakamura, Haruki

2009-01-01

134

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

135

Stress-based topology optimization for continua  

Microsoft Academic Search

We propose an effective algorithm to resolve the stress-constrained topology optimization problem. Our procedure combines\\u000a a density filter for length scale control, the solid isotropic material with penalization (SIMP) to generate black-and-white\\u000a designs, a SIMP-motivated stress definition to resolve the stress singularity phenomenon, and a global\\/regional stress measure\\u000a combined with an adaptive normalization scheme to control the local stress level.

Chau Le; Julian Norato; Tyler Bruns; Christopher Ha; Daniel Tortorelli

2010-01-01

136

Topological Response Theory of Doped Topological Insulators  

NASA Astrophysics Data System (ADS)

We generalize the topological response theory of three-dimensional topological insulators (TI) to metallic systems—specifically, doped TI with finite bulk carrier density and a time-reversal symmetry breaking field near the surface. We show that there is an inhomogeneity-induced Berry phase contribution to the surface Hall conductivity that is completely determined by the occupied states and is independent of other details such as band dispersion and impurities. In the limit of zero bulk carrier density, this intrinsic surface Hall conductivity reduces to the half-integer quantized surface Hall conductivity of TI. Based on our theory we predict the behavior of the surface Hall conductivity for a doped topological insulator with a top gate, which can be directly compared with experiments.

Barkeshli, Maissam; Qi, Xiao-Liang

2011-11-01

137

Periodic table for topological insulators and superconductors  

SciTech Connect

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

138

Tunable Dirac fermion dynamics in topological insulators.  

PubMed

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

2013-08-12

139

Hypercovers in topology  

Microsoft Academic Search

We show that if U is a hypercover of a topological space X then the natural map from hocolim U to X is a weak equivalence. This fact is used to construct topological realization functors for the A^1-homotopy theory of schemes over real and complex fields.

Daniel Dugger; Daniel C. Isaksen

2001-01-01

140

Inet: Internet Topology Generator  

Microsoft Academic Search

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

141

PWM Converter Topologies.  

National Technical Information Service (NTIS)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is d...

E. R. W. Meerman H. J. N. Spruyt

1989-01-01

142

Topologically Adaptable Snakes  

Microsoft Academic Search

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

Tim Mcinerney; Demetri Terzopoulos

1995-01-01

143

TERRITORIAL AND TOPOLOGICAL LEVELS  

Microsoft Academic Search

The aim of this study is to characterize territorial and topological levels in the structure and evolution of the global air transportation network. Using data from the ITA database for both 2000 and 2004, we analyze the topology of these networks with a new approach based on weighted graphs from a small world perspective (Watts, 1999 ; Barabasi, 2002 ;

Carine DISCAZEAUX; Celine ROZENBLAT; Pierre-Yves KOENIG; Guy MELANCON

144

Definitive evidence for the existence of isomeric chlorophenyl radicals (C6H4Cl) from charge inversion mass spectrometry and DFT calculations  

NASA Astrophysics Data System (ADS)

Free radical species are much more reactive than stable molecules, and so usually exist only as transient intermediates in chemical reactions. Charge inversion mass spectrometry using alkali metal targets is an effective method for determining the structure and dissociation processes of radicals, and can also enable differentiation between isomeric forms of compounds whose parent ions have similar mass spectra and similar collisionally activated dissociation spectra, such as the isomers of dichlorobenzene and chlorophenol. The charge inversion process using alkali metal targets proceeds via near-resonant neutralization, followed by spontaneous dissociation of the excited neutrals, and then endothermic negative ion formation. In the normalized charge inversion spectra of ortho-, meta-, and para-dichlorobenzene (C6H4Cl2) measured in this work, the intensities of the peaks associated with chlorine anions (Cl-) are almost same for each of the isomers, whereas the intensities of the peaks associated with the chlorophenyl anions (C6H4Cl-) display a strong dependence on the isomeric structure of the parent compound. The similarities of the Cl- ion peak intensities indicate that neutralization cross-sections and branching ratios to produce Cl radicals are the same for each of the isomeric precursor C6H4Cl2+ ions. The strong isomer-dependence of the peak intensities of C6H4Cl- anions suggests that the chlorophenyl radicals (C6H4Cl) formed from C6H4Cl2 by loss of Cl do not undergo isomerization, and that the electron transfer cross-sections to form the negative ions are strongly isomer-dependent. Density functional theory (DFT) calculations on the o-, m-, and p-C6H4Cl radicals show that the barriers to isomerization are in excess of 2.8 eV, and these high isomerization barriers are believed to be the reason for the absence of isomerization among the C6H4Cl radicals during the charge inversion process. Calculated adiabatic electron affinities and vertical electron affinities both show differences for the o-, m-, and p-isomers, but the trend in the magnitude of the electron affinities has an inverse relation to the peak intensities of the isomeric C6H4Cl- ions in the charge inversion spectra. It is, therefore, assumed that the cross-sections for negative ion formation are influenced by many factors other than the electron affinity, such as the relatively large geometrical distortion in the chlorophenyl radicals predicted in this work. The good agreement between the experimental results and the theoretical predictions obtained in this work provides compelling evidence for the existence of isomeric C6H4Cl radicals that do not undergo isomerization during charge inversion mass spectrometry.

Hayakawa, Shigeo; Matsubara, Hiroshi; Kawamura, Yoshiaki; Iwamoto, Kenichi

2007-05-01

145

Dynamic topology representing networks.  

PubMed

In the present paper, we propose a new algorithm, namely the Dynamic Topology Representing Networks (DTRN) for learning both topology and clustering information from input data. In contrast to other models with adaptive architecture of this kind, the DTRN algorithm adaptively grows the number of output nodes by applying a vigilance test. The clustering procedure is based on a winner-take-quota learning strategy in conjunction with an annealing process in order to minimize the associated mean square error. A competitive Hebbian rule is applied to learn the global topology information concurrently with the clustering process. The topology information learned is also utilized for dynamically deleting the nodes and for the annealing process. Properties of the DTRN algorithm will be discussed. Extensive simulations will be provided to characterize the effectiveness of the new algorithm in topology preserving, learning speed, and classification tasks as compared to other algorithms of the same nature. PMID:10987515

Si, J; Lin, S; Vuong, M A

2000-07-01

146

Floquet topological insulators  

NASA Astrophysics Data System (ADS)

Topological insulators represent unique phases of matter with insulating bulk and conducting edge or surface states, immune to small perturbations such as backscattering due to disorder. This stems from their peculiar band structure, which provides topological protections. While conventional tools (pressure, doping etc.) to modify the band structure are available, time periodic perturbations can provide tunability by adding time as an extra dimension enhanced to the problem. In this short review, we outline the recent research on topological insulators in non equilibrium situations. Firstly, we introduce briefly the Floquet formalism that allows to describe steady states of the electronic system with an effective time-independent Hamiltonian. Secondly, we summarize recent theoretical work on how light irradiation drives semi-metallic graphene or a trivial semiconducting system into a topological phase. Finally, we show how photons can be used to probe topological edge or surface states.

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

2013-02-01

147

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

148

The Scott Topology Induces the Weak Topology  

Microsoft Academic Search

Given a probability measure on a compact metric space, we construct an increasing chain of valuations on the upper space of the metric space whose least upper bound is the measure. We then obtain the expected value of any Holder continuous function with respect to the measure up to any precision. We prove that the Scott topology induces the weak

Abbas Edalat

1996-01-01

149

Topological Phase Transition without Gap Closing  

PubMed Central

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.

Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

2013-01-01

150

Topological magnon insulator in insulating ferromagnet  

NASA Astrophysics Data System (ADS)

In the ferromagnetic insulator with the Dzyaloshinskii-Moriya interaction, we theoretically predict and numerically verify a topological magnon insulator, where the charge-free magnon is topologically protected for transporting along the edge/surface while it is insulating in the bulk. The chiral edge states form a connected loop as a 4?- or 8?-period Möbius strip in the spin-wave vector space, showing the nontrivial topology of magnonic bands. Using the nonequilibrium Green's function method, we explicitly demonstrate that the one-way chiral edge transport is indeed topologically protected from defects or disorders. Moreover, we show that the topological edge state mainly localizes around edges and leaks into the bulk with oscillatory decay. Although the chiral edge magnons and energy current prefer to travel along one edge from the hot region to the cold one, the anomalous transports are identified in the opposite edge, which reversely flow from the cold region to the hot one. Our findings could be validated within wide energy ranges in various magnonic crystals, such as Lu2V2O7.

Zhang, Lifa; Ren, Jie; Wang, Jian-Sheng; Li, Baowen

2013-04-01

151

Topological Phase Transition without Gap Closing.  

PubMed

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

2013-09-27

152

Black hole attractors and the topological string  

SciTech Connect

A simple relationship of the form Z{sub BH}= vertical bar Z{sub top} vertical bar{sup 2} is conjectured, where Z{sub BH} is a supersymmetric partition function for a four-dimensional BPS black hole in a Calabi-Yau compactification of Type II superstring theory and Z{sub top} is a second-quantized topological string partition function evaluated at the attractor point in moduli space associated to the black hole charges. Evidence for the conjecture in a perturbation expansion about large graviphoton charge is given. The microcanonical ensemble of BPS black holes can be viewed as the Wigner function associated to the wave function defined by the topological string partition function.

Ooguri, Hirosi [California Institute of Technology, Pasadena, California 91125 (United States); Strominger, Andrew; Vafa, Cumrun [Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States)

2004-11-15

153

Topological qubits in graphene-like systems  

NASA Astrophysics Data System (ADS)

The fermion-doubling problem can be an obstacle to getting half-a-qubit in two-dimensional fermionic tight-binding models in the form of Majorana zero modes bound to the core of superconducting vortices. We argue that the number of such Majorana zero modes is determined by a Z2xZ2 topological charge for a family of two-dimensional fermionic tight-binding models ranging from noncentrosymmetric materials to graphene. This charge depends on the dimension of the representation (i.e., the number of species of Dirac fermions -- where the doubling problem enters) and the parity of the Chern number induced by breaking time-reversal symmetry. We show that in graphene there are as many as 10 order parameters that can be used in groups of 4 to change the topological number from even to odd.

Santos, Luiz; Ryu, Shinsei; Chamon, Claudio; Mudry, Christopher

2010-03-01

154

Effect of improving the lattice gauge action on QCD topology  

SciTech Connect

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

155

Topological black holes in Horava-Lifshitz gravity  

SciTech Connect

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

156

Experimental Discovery of Topological Insulators and Related Superconductors  

SciTech Connect

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

2010-09-15

157

Experimental Discovery of Topological Insulators and Related Superconductors  

ScienceCinema

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.

158

Black hole attractors and the topological string  

Microsoft Academic Search

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

Hirosi Ooguri; Andrew Strominger; Cumrun Vafa

2004-01-01

159

Fractional charge in perspective  

SciTech Connect

The concept of fractional charge has been recognized and developed in the past fifteen years. Under suitable circumstances an isolated object may display an eigenvalue of charge which is a fraction of the value carried by any elementary' excitation of the system. This phenomenon may be understood as due to vacuum polarization generated by couplings of the isolated object to elementary currents. One might expect that solitons or defects almost invariably would exhibit fractional charge, but this turns out to be the exception rather than the rule in 3+1 dimensions, both for quantum field theory and condensed matter systems. It is suggested that fractional charges are uncommon because some surprisingly weak general conditions are sufficient to assure integer charges. Thus the introduction of fractional charge has been far indeed from an opening of Pandora's box. Examples are reviewed where past proposals of fractional charge appear tenuous, or refer to an unconventional definition of charge.

Goldhaber, A.S. (Institute for Theoretical Physics, State University of New York, Stony Brook, New York 11794-3840 (United States))

1992-02-05

160

Fractional Topological Insulators in 2 and 3 dimensions  

NASA Astrophysics Data System (ADS)

I will present a family of exactly solvable models whose low energy physics is that of a 3D topological band insulator of fractionally charged fermions. When time reversal is broken at the surface, these insulators display a fractional magnetoelectric effect, leading to fractional quantum Hall surface states. Further, some -- but not all -- of them can be shown to be genuine topological insulators, whose gapless surface states are protected by time reversal. This gives an explicit construction of fractional topological insulators in 3D. This work has been done in collaboration with Michael Levin (University of Maryland), Maciej Koch-Janusz (Weizmann Institute), and Ady Stern (Weizmann Institute).

Burnell, F. J.

2012-02-01

161

Offsetting operations on non-manifold topological models  

Microsoft Academic Search

This paper describes non-manifold offsetting operations that add or remove a uniform thickness from a given non-manifold topological model. The mathematical definitions and properties of the non-manifold offsetting operations are investigated first, and then an offset algorithm based on the definitions is proposed and implemented using the non-manifold Euler operators proposed in this paper. In this algorithm, the offset elements

Sang Hun Lee

2009-01-01

162

Topological Image Matcher.  

National Technical Information Service (NTIS)

Computer vision tasks to determine whether two patches are similar or dissimilar are addressed. The assignation of a topological structure, induced by boundary locations, to images is shown. It is proposed that this structure be preserved locally during t...

M. M. Fleck

1989-01-01

163

Topological Response Theory of Doped Topological Insulators  

NASA Astrophysics Data System (ADS)

We generalize the topological response theory of three-dimensional topological insulators (TI) to metallic systems -- specifically, doped TI with finite bulk carrier density and a time-reversal symmetry breaking field near the surface. We show that there is an inhomogeneity-induced Berry phase contribution to the surface Hall conductivity that is completely determined by the occupied states and is independent of other details such as band dispersion and impurities. In the limit of zero bulk carrier density, this intrinsic surface Hall conductivity reduces to the half-integer quantized surface Hall conductivity of TI. Our theory is directly related to the TI materials currently under experimental investigation, which have finite residual bulk carrier densities.

Barkeshli, Maissam; Qi, Xiaoliang

2011-03-01

164

Topological dilaton black holes  

Microsoft Academic Search

In four-dimensional spacetime, when the two-sphere of black hole event horizons is replaced by a two-dimensional hypersurface with zero or negative constant curvature, the black hole is referred to as a topological black hole. In this paper we present some exact topological black hole solutions in the Einstein-Maxwell dilaton theory with a Liouville-type dilaton potential.

Rong-Gen Cai; Jeong-Young Ji; Kwang-Sup Soh

1998-01-01

165

The refined topological vertex  

NASA Astrophysics Data System (ADS)

We define a refined topological vertex which depends in addition on a parameter, which physically corresponds to extending the self-dual graviphoton field strength to a more general configuration. Using this refined topological vertex we compute, using geometric engineering, a two-parameter (equivariant) instanton expansion of gauge theories which reproduce the results of Nekrasov. The refined vertex is also expected to be related to Khovanov knot invariants.

Iqbal, Amer; Kozçaz, Can; Vafa, Cumrun

2009-10-01

166

Manufacturing tolerant topology optimization  

Microsoft Academic Search

In this paper we present an extension of the topology optimization method to include uncertainties during the fabrication\\u000a of macro, micro and nano structures. More specifically, we consider devices that are manufactured using processes which may\\u000a result in (uniformly) too thin (eroded) or too thick (dilated) structures compared to the intended topology. Examples are\\u000a MEMS devices manufactured using etching processes,

Ole Sigmund

2009-01-01

167

Definitely Life but not Definitively  

Microsoft Academic Search

Although there have been attempts at a definition of life from many disciplines, none is accepted by all as definitive. Some\\u000a people believe that it is impossible to define ‘life’ adequately at the moment. We agree with this point of view on linguistic\\u000a grounds, examining the different types of definition, the contexts in which they are used and their relative

Joan D. Oliver; Randall S. Perry

2006-01-01

168

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

169

Geometry of complex networks and topological centrality  

NASA Astrophysics Data System (ADS)

We explore the geometry of complex networks in terms of an n-dimensional Euclidean embedding represented by the Moore–Penrose pseudo-inverse of the graph Laplacian (L). The squared distance of a node i to the origin in this n-dimensional space (lii+), yields a topological centrality index, defined as C?(i)=1/lii+. In turn, the sum of reciprocals of individual node centralities, ?i1/C?(i)=?ilii+, or the trace of L, yields the well-known Kirchhoff index (K), an overall structural descriptor for the network. To put into context this geometric definition of centrality, we provide alternative interpretations of the proposed indices that connect them to meaningful topological characteristics — first, as forced detour overheads and frequency of recurrences in random walks that has an interesting analogy to voltage distributions in the equivalent electrical network; and then as the average connectedness of i in all the bi-partitions of the graph. These interpretations respectively help establish the topological centrality (C?(i)) of node i as a measure of its overall position as well as its overall connectedness in the network; thus reflecting the robustness of i to random multiple edge failures. Through empirical evaluations using synthetic and real world networks, we demonstrate how the topological centrality is better able to distinguish nodes in terms of their structural roles in the network and, along with Kirchhoff index, is appropriately sensitive to perturbations/re-wirings in the network.

Ranjan, Gyan; Zhang, Zhi-Li

2013-09-01

170

Dislocations as ideal metallic quantum wires in topological insulators  

NASA Astrophysics Data System (ADS)

Topological insulators are novel states of matter that have been realized in the recently discovered systems such as Bi0.9Sb0.1. What happens if a topological defect is present in such a material? In this talk I will show that strikingly, dislocation lines in a topological insulator can be metallic - i.e. associated with one dimensional fermionic excitations. The condition for the appearance of these modes is derived, and only found to depend on the ``weak'' topological indices. In contrast to electrons in a regular quantum wire, these modes are topologically protected, and not scattered by disorder. Our results provide a novel route to creating a potentially ideal quantum wire in a bulk solid. Since dislocations are ubiquitous in real materials, they could dominate spin and charge transport in topological insulators. Experimental signatures of such dislocation hosted 1D metals are discussed. The existence of these metallic modes has important consequences for the classification of topological band structures in the presence of lattice order. We also report new results for lattice topological superconductors in three dimensions, where both the two and one dimensional indices appear. (Ref: Ying Ran, Yi Zhang and Ashvin Vishwanath, Nature Physics 5, 298, 2009)

Ran, Ying

2010-03-01

171

Interaction effects and quantum phase transitions in topological insulators  

SciTech Connect

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

172

Topology preserving tissue classification with fast marching and topology templates.  

PubMed

This paper presents a novel approach for object segmentation in medical images that respects the topological relationships of multiple structures as given by a template. The algorithm combines advantages of tissue classification, digital topology, and level-set evolution into a topology-invariant multiple-object fast marching method. The technique can handle any given topology and enforces object-level relationships with little constraint over the geometry. Applied to brain segmentation, it sucessfully extracts gray matter and white matter structures with the correct spherical topology without topology correction or editing of the subcortical structures. PMID:17354699

Bazin, Pierre-Louis; Pham, Dzung L

2005-01-01

173

Electrically Detected Interferometry of Majorana Fermions in a Topological Insulator  

NASA Astrophysics Data System (ADS)

Majorana fermions are zero-energy quasiparticles that may exist in superconducting vortices and interfaces, but their detection is problematic since they have no charge. This is an obstacle to the realization of topological quantum computation, which relies on Majorana fermions to store qubits in a way which is insensitive to decoherence. We show how a pair of neutral Majorana fermions can be converted reversibly into a charged Dirac fermion. These two types of fermions are predicted to exist on the metallic surface of a topological insulator (such as Bi2Se3). Our Dirac-Majorana fermion converter enables electrical detection of a qubit by an interferometric measurement.

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

2009-05-01

174

The Formulation and Justification of Mathematical Definitions Illustrated By Deterministic Chaos  

Microsoft Academic Search

\\u000a The general theme of this article is the actual practice of how definitions are justified and formulated in mathematics. The\\u000a theoretical insights of this article are based on a case study of topological definitions of chaos. After introducing this\\u000a case study, I identify the three kinds of justification which are important for topological definitions of chaos: natural-world-justification,\\u000a condition-justification and redundancy-justification.

Charlotte Werndl

175

Wormhole effect in a strong topological insulator  

NASA Astrophysics Data System (ADS)

When the surface of a strong topological insulator (STI) is coated by a ferromagnetic film the surface state acquires a gap and becomes a quantum Hall liquid with the Hall conductance (n+1/2)e^2/h, n integer. Applying the Laughlin flux-insertion argument to such a surface implies the existence of quasiparticles with fractional charge ±e/2. This result however contradicts the microscopic theory of the surface state, given by a simple massive Dirac Hamiltonian with odd number of fermion species, which only has excitations with integral charge. The paradox is resolved by noticing that an infinitesimally thin flux tube employed in the Laughlin argument is not innocuous inside a STI; we show that when the flux is equal to hc/2e the flux tube carries topologically protected one-dimensional gapless modes that form a conducting `wormhole' through the STI bulk. The wormhole allows the excess charge to escape to the other side of the STI and, in the end, no fractional charge is accumulated at the surface.

Franz, M.; Rosenberg, G.; Guo, H.-M.

2010-03-01

176

Preliminary measurement of time-dependent B{sub d}{sup 0}-B{sub d}{sup 0} mixing using topology and charge selected semi-leptonic B decays  

SciTech Connect

The time dependence of B{sub d}{sup 0}-B{sub d}{sup 0} mixing has 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 identifies the semileptonic decays of B mesons with high (p, p{sub t}) leptons and reconstructs the B meson decay length and charge by vertexing the lepton with a partially reconstructed D meson. Vertex charge is used to enrich the selection of neutral over charged B mesons. This method results in a sample of 581 neutral decays with high charge purity. The B candidate is tagged at production with a combined tag that exploits the large polarized b forward-backward asymmetry in conjunction with the opposite hemisphere b jet charge. The final state is tagged by the sign of the high (p, p{sub t}) lepton. From their preliminary analysis the authors find a mass difference between the two B{sub d}{sup 0} mass eigenstates of, {Delta}m{sub d} = 0.452 {+-} 0.074(stat) {+-} 0.049(syst) ps{sup {minus}1}.

NONE

1996-07-01

177

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.Translated AbstractTopologie und FermikondensatEs wird der Einfluß einer Raum-Zeittopologie auf die Bildung des Fermikondensats in einem Modell mit Vierfermionenwechselwirkung ()2 untersucht. Für eine Raum-Zeit mit der Topologie R1 × R2 × S1 werden die Parameter gegeben. Weiterhin wird die Relation der Größe des Fermikondensats zu einer periodischen Länge untersucht. In diesem Zusammenhang wird die Verbindung des topologischen Depots zur Struktur der Hadronen diskutiert.

Kulikov, I.; Pronin, P.

178

Topological Anderson insulator.  

PubMed

Disorder plays an important role in two dimensions, and is responsible for striking phenomena such as metal-insulator transition and the integral and fractional quantum Hall effects. In this Letter, we investigate the role of disorder in the context of the recently discovered topological insulator, which possesses a pair of helical edge states with opposing spins moving in opposite directions and exhibits the phenomenon of quantum spin Hall effect. We predict an unexpected and nontrivial quantum phase termed "topological Anderson insulator," which is obtained by introducing impurities in a two-dimensional metal; here disorder not only causes metal-insulator transition, as anticipated, but is fundamentally responsible for creating extended edge states. We determine the phase diagram of the topological Anderson insulator and outline its experimental consequences. PMID:19392389

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

2009-04-01

179

Witten effect in a crystalline topological insulator  

SciTech Connect

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

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

2010-07-15

180

Topology Preserving Tissue Classification with Fast Marching and Topology Templates  

Microsoft Academic Search

This paper presents a novel approach for object segmentation in med- ical images that respects the topological relationships of multiple structures as given by a template. The algorithm combines advantages of tissue classification, digital topology, and level-set evolution into a topology-invariant multiple-object fast marching method. The technique can handle any given topology and enforces object-level relationships with little constraint over

Pierre-louis Bazin; Dzung L. Pham

2005-01-01

181

Topological Mott Insulators  

SciTech Connect

We consider extended Hubbard models with repulsive interactions on a honeycomb lattice, and the transitions from the semimetal to Mott insulating phases at half-filling. Because of the frustrated nature of the second-neighbor interactions, topological Mott phases displaying the quantum Hall and the quantum spin Hall effects are found for spinless and spin fermion models, respectively. The mean-field phase diagram is presented and the fluctuations are treated within the random phase approximation. Renormalization group analysis shows that these states can be favored over the topologically trivial Mott insulating states.

Raghu, S.

2010-03-02

182

Topological insulators: Chemists join in  

NASA Astrophysics Data System (ADS)

Topological insulators have generated much interest in condensed-matter physics. The synthesis and characterization of Bi14Rh3I9, a so-called weak topological insulator, demonstrates that chemists also have much to offer to the field.

Cava, Robert J.

2013-05-01

183

Andreev magnetointerferometry in topological hybrid junctions  

NASA Astrophysics Data System (ADS)

We investigate the fate of topological edge states in the quantum Hall (QH) regime when they experience tunneling processes through a narrow superconducting (S) strip. By computing the charge conductance flowing through a graphene-based QH/S/QH junction, the S strip is shown to act as an Andreev interferometer, giving rise to spectacular conductance oscillations as a function of the Landau level filling factor. We provide a semiclassical analysis allowing for a natural interpretation of these oscillations in terms of interferences between electron and hole trajectories propagating along the QH/S interfaces. Our results suggest that nontrivial junctions between topologically distinct phases could offer a highly tunable means of partitioning the flow of edge states.

Carmier, Pierre

2013-10-01

184

TOPPER: topology prediction of transmembrane protein based on evidential reasoning.  

PubMed

The topology prediction of transmembrane protein is a hot research field in bioinformatics and molecular biology. It is a typical pattern recognition problem. Various prediction algorithms are developed to predict the transmembrane protein topology since the experimental techniques have been restricted by many stringent conditions. Usually, these individual prediction algorithms depend on various principles such as the hydrophobicity or charges of residues. In this paper, an evidential topology prediction method for transmembrane protein is proposed based on evidential reasoning, which is called TOPPER (topology prediction of transmembrane protein based on evidential reasoning). In the proposed method, the prediction results of multiple individual prediction algorithms can be transformed into BPAs (basic probability assignments) according to the confusion matrix. Then, the final prediction result can be obtained by the combination of each individual prediction base on Dempster's rule of combination. The experimental results show that the proposed method is superior to the individual prediction algorithms, which illustrates the effectiveness of the proposed method. PMID:23401665

Deng, Xinyang; Liu, Qi; Hu, Yong; Deng, Yong

2013-01-17

185

Symmetry Protected Josephson Supercurrents in Three-Dimensional Topological Insulators  

NASA Astrophysics Data System (ADS)

Coupling the surface state of a topological insulator (TI) to an s-wave superconductor is predicted to produce the long-sought Majorana quasiparticle excitations. However, superconductivity has not been measured in surface states when the bulk charge carriers are fully depleted, i.e., in the true topological regime relevant for investigating Majorana modes. Here, we report measurements of DC Josephson effects in TI-superconductor junctions as the chemical potential is moved through the true topological regime characterized by the presence of only surface currents. We compare our results to 3D quantum transport simulations, and determine the effects of bulk/surface mixing, disorder, and magnetic field; in particular, we show that the supercurrent is largely carried by surface states, due to the inherent topology of the bands, and that it is robust against disorder. Our results thus clarify key open issues regarding the nature of supercurrents in TIs.

Cho, Sungjae; Dellabetta, Brian; Yang, Alina; Schneeloch, John; Xu, Zhijun; Valla, Tonica; Gu, Genda; Gilbert, Matthew; Mason, Nadya

2013-03-01

186

Topological Open Membranes  

Microsoft Academic Search

We study topological open membranes of BF type in a manifest BV formalism. Our main interest is the effect of the bulk deformations on the algebra of boundary operators. This forms a homotopy Lie algebra, which can be understood in terms of a closed string field theory. The simplest models are associated to quasi-Lie bialgebras and are of Chern-Simons type.

Christiaan Hofman; Jae-Suk Park

2002-01-01

187

Distended Topologically Massive Electrodynamics  

Microsoft Academic Search

We extend topologically massive electrodynamics, both by adding a higher derivative action to cast the entire three-term model in Chern-Simons (CS) form, and by embedding it in an AdS background. It can then be written as the sum of two CS terms, one of which vanishes at the \\

S. Deser

2008-01-01

188

Topological Geometrodynamics: Three Visions  

Microsoft Academic Search

In this article I will discuss three basic visions about quantum Topological Geometrody- namics (TGD). It is somewhat matter of taste which idea one should call a vision and the selection of these three in a special role is what I feel natural just now. 1. The rst vision is generalization of Einstein's geometrization program based on the idea that

M. Pitkanen

189

Topological quantum field theory  

Microsoft Academic Search

A twisted version of four dimensional supersymmetric gauge theory is formulated. The model, which refines a nonrelativistic treatment by Atiyah, appears to underlie many recent developments in topology of low dimensional manifolds; the Donaldson polynomial invariants of four manifolds and the Floer groups of three manifolds appear naturally. The model may also be interesting from a physical viewpoint; it is

Edward Witten

1988-01-01

190

Measuring shape with topology  

NASA Astrophysics Data System (ADS)

We propose a measure of shape which is appropriate for the study of a complicated geometric structure, defined using the topology of neighborhoods of the structure. One aspect of this measure gives a new notion of fractal dimension. We demonstrate the utility and computability of this measure by applying it to branched polymers, Brownian trees, and self-avoiding random walks.

MacPherson, Robert; Schweinhart, Benjamin

2012-07-01

191

Holographic fractional topological insulators  

SciTech Connect

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

192

Topological field theory and physics  

Microsoft Academic Search

Topological Yang - Mills theory with the Belavin - Polyakov - Schwarz - Tyupkin SU(2) instanton is solved completely, revealing an underlying multi-link intersection theory. Link invariants are also shown to survive the coupling to a certain kind of matter (hyperinstantons). The physical relevance of topological field theory and its invariants is discussed. By embedding topological Yang - Mills theory

Damiano Anselmi

1997-01-01

193

Dynamics of topological magnetic solitons  

Microsoft Academic Search

A direct link between the topological complexity of magnetic media and their dynamics is established through the construction of unambiguous conservation laws for the linear and angular momenta as moments of a topological vorticity. As a consequence, the dynamics of topological magnetic solitons is shown to exhibit the characteristic features of the Hall effect of electrodynamics or the Magnus effect

N. Papanicolaou

1997-01-01

194

Dynamics of topological light states in spiraling structures  

NASA Astrophysics Data System (ADS)

We expose a mechanism for the dynamical generation and control of light states with diverse topologies in spiraling guiding structures. Specifically, we show that spiraling shallow refractive index landscapes induce coupling and periodic energy exchange between states with different topological charges. Such a resonant effect enables excitation of optical vortices by vortex-free inputs and allows the output topological charge of the beam to be controlled. The presence of nonlinearity results in a strong asymmetrization of the resonant curves and a shift of the resonant frequencies. Resonant vortex dynamic generation, including revivals, is shown to be possible not only in waveguides mediated by total internal reflection but also in Bragg-guiding hollow-core geometries.

Kartashov, Yaroslav V.; Vysloukh, Victor A.; Torner, Lluis

2013-09-01

195

32 CFR 220.14 - Definitions.  

Code of Federal Regulations, 2013 CFR

...PARTY PAYERS OF REASONABLE CHARGES FOR HEALTHCARE SERVICES § 220.14 Definitions...beneficiaries. Covered beneficiaries are all healthcare beneficiaries under chapter 55 of...Facilitiesâ or âUSTFsâ). Healthcare services. Healthcare services...

2013-07-01

196

Topological Modeling of Metamict Zircon  

NASA Astrophysics Data System (ADS)

Zircon (ZrSiO4) is the most studied metamict mineral and a leading model for candidate ceramic hosts designed to encapsulate highly radioactive nuclear waste and excess plutonium. It is also emblematic of compound oxide ceramics with a potential to phase separate in the amorphized state. Several groups have carried out ab initio or molecular dynamics (MD) simulations of melt-quenched or radiation-disordered zircon. A tendency for silica tetrahedra to polymerize, implying incipient phase separation, has been noted, but adequate descriptors of the amorphous state capable of distinguishing between different disordered arrangements have not been available. This contribution details critical modifications made to empirical potentials used in MD simulations and useful improvements in modeling efficiency that have facilitated constant pressure simulations of quenched and displacement cascade-amorphized zircon. The simulated end- states have been subjected to topological assessment algorithms for enumerating coordinations, bond lengths and bond angles; counting primitive rings and identifying structure-defining local primitive-ring clusters; and assessing degree of coordination-unit polymerization. The topologies of simulated melt, melt-quenched and cascade-amorphized disordered arrangements have been found to be different and distinguishable. A two-body Born-Mayer empirical potential with ZBL short-range repulsive term was fit to major structural, elastic, thermal and dielectric properties of crystalline zircon, but it was noted that the best crystalline fit, with non-stoichiometric partial ion charges, led to unrealistic coordinations in amorphized arrangements and uncontrolled expansions in constant pressure simulations because of silica polymerization. Therefore, stoichiometrically charge-balanced partial charges were instead chosen and optimized; the optimal choice of O-1.2, Si+2.4, Zr+2.4 led to realistic coordinations (Zr 7, Si 4) and well-behaved constant-pressure simulations of amorphous zircon that notably differed from constant volume simulations using unbalanced changes and imposed volume swellings. Compact cascade simulations (up to 14,112 atoms) were made possible by using heat removal at simulation cell periodic boundaries and simulation cell shape optimized to cascade geometry for Zr and U primary-knock-on atom (PKA) with energies 1-10 keV (collisional). Ring count distributions and primitive ring size averages for Zr and Si local clusters proved different and distinguishable for melt (Zr 11.57, Si 11.47), quenched (Zr 9.81, Si 9.80) and cascade-amorphized (Zr 9.74, Si 9.36) structures, and larger than for crystalline zircon (Zr 7.66, Si 7.76). Topological signatures, devised to distinguish locally-crystalline from locally-amorphized zircon, established unambiguously that zircon amorphized within the first PKA cascade. Sub-cascades were observed for 10-keV Zr, but not U PKAs. In quenched zircon, 93% of Si atoms were connected to another Si atom through bridging O atoms (i.e. polymerized), with the average number Q of bridging O per Si found to be 1.95.

Hobbs, L. W.; Zhang, Y.; Yuan, X.

2006-05-01

197

Thermodynamical Properties of Topological Born-Infeld Black Holes  

Microsoft Academic Search

We examine the (n + 1)-dimensional (n >= 3) action in which gravity is coupled to the Born-Infeld nonlinear electrodynamic and a dilaton field. We construct a new (n + 1)-dimensional analytic solution of this theory in the presence of Liouville-type dilaton potentials. These solutions, which describe charged topological dilaton black holes with nonlinear electrodynamics, have unusual asymptotics. They are

Ahmad Sheykhi

2009-01-01

198

Z2 Topological Order and the Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum spin Hall (QSH) phase is a time reversal invariant electronic state with a bulk electronic band gap that supports the transport of charge and spin in gapless edge states. We show that this phase is associated with a novel Z2 topological invariant, which distinguishes it from an ordinary insulator. The Z2 classification, which is defined for time reversal

C. L. Kane; E. J. Mele

2005-01-01

199

Topology improves phylogenetic motif functional site predictions.  

PubMed

Prediction of protein functional sites from sequence-derived data remains an open bioinformatics problem. We have developed a phylogenetic motif (PM) functional site prediction approach that identifies functional sites from alignment fragments that parallel the evolutionary patterns of the family. In our approach, PMs are identified by comparing tree topologies of each alignment fragment to that of the complete phylogeny. Herein, we bypass the phylogenetic reconstruction step and identify PMs directly from distance matrix comparisons. In order to optimize the new algorithm, we consider three different distance matrices and 13 different matrix similarity scores. We assess the performance of the various approaches on a structurally nonredundant data set that includes three types of functional site definitions. Without exception, the predictive power of the original approach outperforms the distance matrix variants. While the distance matrix methods fail to improve upon the original approach, our results are important because they clearly demonstrate that the improved predictive power is based on the topological comparisons. Meaning that phylogenetic trees are a straightforward, yet powerful way to improve functional site prediction accuracy. While complementary studies have shown that topology improves predictions of protein-protein interactions, this report represents the first demonstration that trees improve functional site predictions as well. PMID:21071810

Kc, Dukka B; Livesay, Dennis R

200

Topology Preserving SOM with Transductive Confidence Machine  

NASA Astrophysics Data System (ADS)

We propose a novel topology preserving self-organized map (SOM) classifier with transductive confidence machine (TPSOM-TCM). Typically, SOM acts as a dimension reduction tool for mapping training samples from a high-dimensional input space onto a neuron grid. However, current SOM-based classifiers can not provide degrees of classification reliability for new unlabeled samples so that they are difficult to be used in risk-sensitive applications where incorrect predictions may result in serious consequences. Our method extends a typical SOM classifier to allow it to supply such reliability degrees. To achieve this objective, we define a nonconformity measurement with which a randomness test can predict how nonconforming a new unlabeled sample is with respect to the training samples. In addition, we notice that the definition of nonconformity measurement is more dependent on the quality of topology preservation than that of quantization error reduction. We thus incorporate the grey relation coefficient (GRC) into the calculation of neighborhood radii to improve the topology preservation without increasing the quantization error. Our method is able to improve the time efficiency of a previous method kNN-TCM, when the number of samples is large. Extensive experiments on both the UCI and KDDCUP 99 data sets show the effectiveness of our method.

Tong, Bin; Qin, Zhiguang; Suzuki, Einoshin

201

Topology maps of bond descriptors based on the kinetic energy density and the essence of chemical bonding.  

PubMed

Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are intuitively linked to familiar concepts of chemical bonding. The function ?(r), termed localized-orbital locator and based on the positive-definite kinetic energy density ?+, is employed to characterize classes of covalent bonds in terms of its full topology of all critical points of rank three. Not only does ?(r) reveal patterns in chemical bonding, it also discloses features and the influence of extended electronic cores. Gradient paths define the extension of the valence space around an atomic centre; they separate various core level regions from bonding domains, and partition molecules in sensible bonded subunits. Location and ?(r)-values of critical points add a quantitative aspect to the bond characterization; profiles of unconventional chemical linkages such as charge-shift bonds emerge in a natural way. PMID:23450168

Jacobsen, Heiko

2013-04-14

202

Changing topology by topological defects in three-dimensional topologically ordered phases  

NASA Astrophysics Data System (ADS)

A hallmark feature of topologically ordered states of matter is the dependence of ground-state degeneracy (GSD) on the topology of the manifold determined by the global shape of the system. Although the topology of a physical system is practically hard to manipulate, recently, it was shown that in certain topologically ordered phases, topological defects can introduce extra topological GSD. Here the topological defects can be viewed as effectively changing the topology of the physical system. Previous studies have been focusing on two spatial dimensions with pointlike topological defects. In three dimensions, linelike topological defects can appear. They are closed loops in the bulk that can be linked and knotted, effectively leading to complex three-dimensional manifolds in certain topologically ordered states. This paper studies the properties of such line defects in a particular context: the lattice dislocations. We give an analytical construction, together with support from exact numerical calculations, for the dependence of the GSD on dislocations of certain doubled versions of the exactly solvable Kitaev's toric code models in both two and three dimensions. We find that the GSD of the 3D model depends only on the total number of dislocation loops, no matter how they are linked or knotted. The results are extended to Zn generalizations of the model. Additionally, we consider the phases in which the crystalline orders are destroyed through proliferation of double dislocations. The resulting phases are shown to host topological orders described by non-Abelian gauge theories.

Mesaros, Andrej; Kim, Yong Baek; Ran, Ying

2013-07-01

203

Aharonov-Casher Effect Without Line Charge  

NASA Astrophysics Data System (ADS)

It is shown that the case considered by Casella, which has no path-enclosed charge and was claimed to have different topology from the original Aharonov-Casher case of line charge, is actually equivalent to the Aharonov-Casher case.

Lee, Taeyeon

204

Seeing the magnetic monopole through the mirror of topological surface states  

SciTech Connect

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

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

2010-03-25

205

12 CFR 508.2 - Definitions.  

Code of Federal Regulations, 2013 CFR

... Banks and Banking 6 2013-01-01 2012-01-01 true Definitions. 508.2 Section 508.2 Banks and Banking...TREASURY REMOVALS, SUSPENSIONS, AND PROHIBITIONS WHERE A CRIME IS CHARGED OR PROVEN § 508.2 Definitions. As used...

2013-01-01

206

CHARGE syndrome: an update.  

PubMed

CHARGE syndrome is a rare, usually sporadic autosomal dominant disorder due in 2/3 of cases to mutations within the CHD7 gene. The clinical definition has evolved with time. The 3C triad (Coloboma-Choanal atresia-abnormal semicircular Canals), arhinencephaly and rhombencephalic dysfunctions are now considered the most important and constant clues to the diagnosis. We will discuss here recent aspects of the phenotypic delineation of CHARGE syndrome and highlight the role of CHD7 in its pathogeny. We review available data on its molecular pathology as well as cytogenetic and molecular evidences for genetic heterogeneity within CHARGE syndrome. PMID:17299439

Sanlaville, Damien; Verloes, Alain

2007-02-14

207

Topological parameters in gravity  

NASA Astrophysics Data System (ADS)

We present the Hamiltonian analysis of the theory of gravity based on a Lagrangian density containing the Hilbert-Palatini term along with three topological densities, Nieh-Yan, Pontryagin and Euler. The addition of these topological terms modifies the symplectic structure nontrivially. The resulting canonical theory develops a dependence on three parameters which are coefficients of these terms. In the time gauge, we obtain a real SU(2) gauge theoretic description with a set of seven first-class constraints corresponding to three SU(2) rotations, three spatial diffeomorphisms and one to evolution in a timelike direction. The inverse of the coefficient of the Nieh-Yan term, identified as the Barbero-Immirzi parameter, acts as the coupling constant of the gauge theory.

Kaul, Romesh K.; Sengupta, Sandipan

2012-01-01

208

Topological confinement and superconductivity  

SciTech Connect

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

209

Modulated Floquet topological insulators.  

PubMed

The application of spatially uniform light on conventional insulators can induce Floquet spectra with characteristics akin to those of topological insulators. We demonstrate that spatial modulation of light allows for remarkable control of the properties in these systems. We provide configurations to generate one-dimensional bulk modes, photoinduced currents, as well as fractionalized excitations. We show a close analogy to p-wave superconductors and use this analogy to explain our results. PMID:23383821

Katan, Yaniv Tenenbaum; Podolsky, Daniel

2013-01-02

210

Modulated Floquet Topological Insulators  

NASA Astrophysics Data System (ADS)

The application of spatially uniform light on conventional insulators can induce Floquet spectra with characteristics akin to those of topological insulators. We demonstrate that spatial modulation of light allows for remarkable control of the properties in these systems. We provide configurations to generate one-dimensional bulk modes, photoinduced currents, as well as fractionalized excitations. We show a close analogy to p-wave superconductors and use this analogy to explain our results.

Katan, Yaniv Tenenbaum; Podolsky, Daniel

2013-01-01

211

Topological quantum computation  

Microsoft Academic Search

The theory of quantum computation can be constructed from the abstract study\\u000aof anyonic systems. In mathematical terms, these are unitary topological\\u000amodular functors. They underlie the Jones polynomial and arise in\\u000aWitten-Chern-Simons theory. The braiding and fusion of anyonic excitations in\\u000aquantum Hall electron liquids and 2D-magnets are modeled by modular functors,\\u000aopening a new possibility for the realization

Michael H. Freedman; Alexei Kitaev; Michael J. Larsen; Zhenghan Wang; L. D. Landau; Michael H. Freedman

2002-01-01

212

Electrostatic repulsion of positively charged vesicles and negatively charged objects  

PubMed

A positively charged, mixed bilayer vesicle in the presence of negatively charged surfaces (for example, colloidal particles) can spontaneously partition into an adhesion zone of definite area and another zone that repels additional negative objects. Although the membrane itself has nonnegative charge in the repulsive zone, negative counterions on the interior of the vesicle spontaneously aggregate there and present a net negative charge to the exterior. Beyond the fundamental result that oppositely charged objects can repel, this mechanism helps to explain recent experiments on surfactant vesicles. PMID:10411499

Aranda-Espinoza; Chen; Dan; Lubensky; Nelson; Ramos; Weitz

1999-07-16

213

Multiple Dirac fermions from a topological insulator and graphene superlattice  

NASA Astrophysics Data System (ADS)

Graphene and three-dimensional topological insulators are well-known Dirac materials whose bulk and surface states are governed by Dirac equations. They not only show good transport properties but also carry various quanta related to the geometrical phase such as charge, spin, and valley Hall conductances. Therefore, it is a great challenge to combine the two Dirac materials together, realizing multiple Dirac fermions. By using first-principles density-functional-theory calculations, we demonstrate such a system built from topological insulator-band insulator-graphene superlattice structures. Hexagonal boron nitride is proposed as an ideal band-insulating material in gluing graphene and topological insulators, providing a good substrate for graphene and a sharp interface with a topological insulator. The power factors for p-type doping are largely enhanced due to the charge-conducting channels through multiple Dirac cones. The systems characterized by the coexistence of the topologically protected interfacial and graphene Dirac cones can pave the way for developing integrated devices for electronics, spintronics and valleytronics applications.

Jin, Hosub; Im, Jino; Song, Jung-Hwan; Freeman, Arthur J.

2012-01-01

214

Topological aspects of fermions on hyperdiamond  

SciTech Connect

Motivated by recent results on the index of the Dirac operator D={gamma}{sup {mu}}D{sub {mu}} of QCD on lattice and also by results on topological features of electrons and holes of two-dimensional graphene, we compute in this paper the index of D for fermions living on a family of even-dimensional lattices denoted as L{sub 2N} and describing the 2N-dimensional generalization of the graphene honeycomb. The calculation of this topological index is done by using the direct method based on solving explicitly the gauged Dirac equation and also by using specific properties of the lattices L{sub 2N}, which are shown to be intimately linked with the weight lattices of SU(2N+ 1). The index associated with the two leading N= 1 and N= 2 elements of this family describe precisely the chiral anomalies of graphene and QCD{sub 4}. Comments on the method using the spectral flow approach as well as the computation of the topological charges on 2-cycles of 2N-dimensional compact supercell in L{sub 2N} and applications to QCD{sub 4} are also given.

Saidi, E. H. [Hassan II Academy of Science and Technology, Avenue Mohammed VI, KM 4, Souissi, Rabat (Morocco); Lab Of High Energy Physics, Modeling and Simulations, Faculty of Science, University Mohammed V-Agdal, Rabat (Morocco); Fassi-Fehri, O.; Bousmina, M. [Hassan II Academy of Science and Technology, Avenue Mohammed VI, KM 4, Souissi, Rabat (Morocco)

2012-07-15

215

On the completeness of topological rings in maximal topologies  

NASA Astrophysics Data System (ADS)

The article studies rings that are direct sums of an infinite family of subrings. The question of the completeness of these rings in maximal ring topologies is investigated for various classes of ring topologies. In particular it is shown that if the continuum hypothesis is assumed, then both complete and non-complete maximal ring topologies exist on a ring that is an infinite direct sum of copies of the same finite field.

Arnautov, V. I.

1996-02-01

216

Topological indices based on topological distances in molecular graphs  

Microsoft Academic Search

Abstract,— Three ,,distance—based,topological,indices,are,described; two,of them, D and D1 (mean distance topological indices, for any graphs, and for acyclic graphs, respectively) have a modest discrimi- nating,ability but may be useful for correlations, e. g. with octane numbers.,The third index, J (average distance sum connectivity) is the,least,degenerate,single,topological,index,proposed,till,now.,The properties,of this,promising,index,J are discussed,in more,detail.

T. Balaban

1988-01-01

217

Fractional topological phase in one-dimensional flat bands with nontrivial topology  

NASA Astrophysics Data System (ADS)

We consider a topologically nontrivial flat-band structure in one spatial dimension in the presence of nearest- and next-nearest-neighbor Hubbard interaction. The noninteracting band structure is characterized by a symmetry-protected topologically quantized Berry phase. At certain fractional fillings, a gapped phase with a filling-dependent ground-state degeneracy and fractionally charged quasiparticles emerges. At filling (1)/(3), the ground states carry a fractional Berry phase in the momentum basis. These features at first glance suggest a certain analogy to the fractional quantum Hall scenario in two dimensions. We solve the interacting model analytically in the physically relevant limit of a large band gap in the underlying band structure, the analog of a lowest Landau level projection. Our solution affords a simple physical understanding of the properties of the gapped interacting phase. We pinpoint crucial differences to the fractional quantum Hall case by studying the Berry phase and the entanglement entropy associated with the degenerate ground states. In particular, we conclude that the “fractional topological phase in one-dimensional flat bands” is not a one-dimensional analog of the two-dimensional fractional quantum Hall states, but rather a charge density wave with a nontrivial Berry phase. Finally, the symmetry-protected nature of the Berry phase of the interacting phase is demonstrated by explicitly constructing a gapped interpolation to a state with a trivial Berry phase.

Budich, Jan Carl; Ardonne, Eddy

2013-07-01

218

FONO: A difficult case for theory. The ELF and ELI-D topological studies on the chemical bonding using correlated wavefunctions  

NASA Astrophysics Data System (ADS)

The complicated nature of the chemical bonding in cis and trans isomers of F-O-N=O is discussed based on the results obtained from the topological analysis of electron localization function (?) (ELF), electron localizability index (YD?), and electron density (?). The calculations have been performed for correlated wavefunctions using the CCSD and CASSCF methods. The F-O1 bond with non-bonding basins, V(F) and V'(O1), belongs to the protocovalent type (?,YD?) and its total population ranges between 0.2 and 0.4e. The central N-O1 bond in the cis form is protocovalent (?, YD?) with two basins, V(N) and V(O1). The total population oscillates between 0.7 and 0.9e. In the trans isomer, topology of ELF depends on used method. At the CCSD level only one non-bonding basin, V(N), is observed (?). Its population is about 0.5e. According to the definition of a heteronuclear charge-shift (CS) bond, only N-O1 bond in trans-FONO belongs to the CS class. A relation between ?- and ?-topology and N-O1 bond length is discussed.

Berski, Slawomir; Gordon, Agnieszka J.; Latajka, Zdzislaw

2013-04-01

219

FONO: a difficult case for theory. The ELF and ELI-D topological studies on the chemical bonding using correlated wavefunctions.  

PubMed

The complicated nature of the chemical bonding in cis and trans isomers of F-O-N=O is discussed based on the results obtained from the topological analysis of electron localization function (?) (ELF), electron localizability index (Y(D)(?)), and electron density (?). The calculations have been performed for correlated wavefunctions using the CCSD and CASSCF methods. The F-O1 bond with non-bonding basins, V(F) and V(')(O1), belongs to the protocovalent type (?,Y(D)(?)) and its total population ranges between 0.2 and 0.4e. The central N-O1 bond in the cis form is protocovalent (?, Y(D)(?)) with two basins, V(N) and V(O1). The total population oscillates between 0.7 and 0.9e. In the trans isomer, topology of ELF depends on used method. At the CCSD level only one non-bonding basin, V(N), is observed (?). Its population is about 0.5e. According to the definition of a heteronuclear charge-shift (CS) bond, only N-O1 bond in trans-FONO belongs to the CS class. A relation between ?- and ?-topology and N-O1 bond length is discussed. PMID:23574233

Berski, Slawomir; Gordon, Agnieszka J; Latajka, Zdzislaw

2013-04-01

220

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

221

Battery charger and state of charge indicator. Final report  

SciTech Connect

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

222

Continuous-variable topological codes  

NASA Astrophysics Data System (ADS)

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

Morimae, Tomoyuki

2013-10-01

223

Measuring ISP topologies with rocketfuel  

Microsoft Academic Search

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

224

Measuring ISP topologies with rocketfuel  

Microsoft Academic Search

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

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

2004-01-01

225

Topology optimization of compressor bracket  

Microsoft Academic Search

Topology optimization is very useful engineering technique especially at the concept design stage. It is common habit to design\\u000a depending on the designer’s experience at the early stage of product development. Structural analysis methodology of compressor\\u000a bracket was verified on the static and dynamic loading condition with 2 bracket samples for the topology optimization base\\u000a model. Topology optimization is able

Jeong Woo Chang; Young Shin Lee

2008-01-01

226

Communication: An approximation to Bader's topological atom  

NASA Astrophysics Data System (ADS)

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.

Salvador, Pedro; Ramos-Cordoba, Eloy

2013-08-01

227

Classifying Topological Defects in Insulators and Superconductors  

NASA Astrophysics Data System (ADS)

We develop a unified framework to classify topological defects in insulators and superconductors described by spatially modulated Bloch and Bogoliubov de Gennes Hamiltonians. We consider a Hamiltonian H(k,r) that varies slowly with adiabatic parameters r away from the defect. Band theories are grouped into ten classes according to the presence or absence of anti-unitary symmetries, time reversal 2?=±1 and/or particle-hole 2?=±1. Both send k-k and rr. Stable classification of topological band theories are characterized by a unified set of integral formulae for all the symmetry classes in any dimensions. Examples that fall into this framework include edge and surface states along an interface, 1D chiral, helical and Majorana modes along a line defect, bound charge and Majorana zero mode at a point defect. This approach also applies to time dependent phenomena, such as the Thouless charge pumb, the Z2 spin pumb and the exchange statistics of Majorana bound states in three dimensions.

Teo, Jeffrey C. Y.; Kane, C. L.

2010-03-01

228

Topological Structure of the Magnetic Solar Corona  

NASA Astrophysics Data System (ADS)

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

Maclean, R. C.

2007-12-01

229

Topological nodal semimetals  

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

230

Intelligent Topology Analyzer for Improved Plant Operation  

Microsoft Academic Search

Almost all process engineering practices are tightly linked with process topology. In order to support plant life cycle activities, it is essential to provide intelligent topology analyzer that can intelligently partition plant topology and define topology areas for the different plant operation tasks and activities. This paper presents design of intelligent plant topology analyzer which is integrated with plant automation

Hossam A. Gabbar

2006-01-01

231

Topological Confinement and Superconductivity  

NASA Astrophysics Data System (ADS)

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 con?nement 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 a 1D-system. [1] K. A. Al-Hassanieh, C. D. Batista, P. Sengupta, and A. E. Feiguin, preprint arXiv:0808.3735.

Al-Hassanieh, Khaled; Batista, Cristian; Sengupta, Pinaki; Feiguin, Adrian

2009-03-01

232

Generalization of topological indices  

NASA Astrophysics Data System (ADS)

A generalized (molecular) graph-theoretical matrix is introduced in such a way that the adjacency and distance matrices of (molecular) graphs are particular cases of it. By using this matrix, two new molecular graph-theoretical vectors and a vector-matrix-vector multiplication procedure, a generalized invariant is introduced. This invariant permits a generalization of some of the classical topological indices (TIs). Thus, Wiener W index, Zagreb M1 and M2 indices, Balaban J index, Harary H number, Randic ? index and valence connectivity index ?v resulted as particular cases of an infinite set of molecular descriptors that can be derived from the same invariant.

Estrada, Ernesto

2001-03-01

233

Meshless approximation combined with implicit topology description for optimization of continua  

Microsoft Academic Search

The implicit topology description function method is integrated into Reproducing Kernel Particle Method and presents a new\\u000a implementation of topology optimization of continua. The structural response analysis and the sensitivity analysis are carried\\u000a out by using the meshless reproducing kernel approximations. Compared with mesh-based methods, the construction of an explicit\\u000a mesh and the definition of nodal connectivity are avoided. The

J. X. Zhou; W. Zou

2008-01-01

234

Casimir Charge and AN Explanation for C Violation  

NASA Astrophysics Data System (ADS)

In this paper, the concept of Casimir charge is introduced, which is defined to be the characteristic quantity that describes an elementary particle. From the viewpoint of Casimir charge, the definition of charge conjugation is analyzed. As a result we find that the definition is not self-consistent, perhaps this is responsible for C violation.

Gao, Li; Peng, Guang-Xiong

2013-09-01

235

Topological censorship and the topology of black holes  

Microsoft Academic Search

A new result on topological censorship is presented. Roughly speaking, the result shows that, under suitable conditions, the topology of space outside the event horizon must eventually be simple. In particular, cross sections of the event horizon must eventually be spherical. This latter consequence of the main result generalizes in many respects the classical theorem of Hawking (1972) that black

S. F. Browdy; G. J. Galloway

1995-01-01

236

Topological censorship and the topology of black holes  

Microsoft Academic Search

A new result on topological censorship is presented. Roughly speaking, the result shows that, under suitable conditions, the topology of space outside the event horizon must eventually be simple. In particular, cross sections of the event horizon must eventually be spherical. This latter consequence of the main result generalizes in many respects the classical theorem of Hawking that black hole

Steven F. Browdy; Gregory J. Galloway

1995-01-01

237

Universal topological phase of two-dimensional stabilizer codes  

NASA Astrophysics Data System (ADS)

Topological phases can be defined in terms of local equivalence: two systems are in the same topological phase if it is possible to transform one into the other by a local reorganization of its degrees of freedom. The classification of topological phases therefore amounts to the classification of long-range entanglement. Such local transformation could result, for instance, from the adiabatic continuation of one system's Hamiltonian to the other. Here, we use this definition to study the topological phase of translationally invariant stabilizer codes in two spatial dimensions, and show that they all belong to one universal phase. We do this by constructing an explicit mapping from any such code to a number of copies of Kitaev's code. Some of our results extend to some two-dimensional (2D) subsystem codes, including topological subsystem codes. Error correction benefits from the corresponding local mappings. In particular, it enables us to use decoding algorithm developed for Kitaev's code to decode any 2D stabilizer code and subsystem code.

Bombin, H.; Duclos-Cianci, Guillaume; Poulin, David

2012-07-01

238

Topological implications of inhomogeneity  

NASA Astrophysics Data System (ADS)

The approximate homogeneity of spatial sections of the Universe is well supported observationally, but the inhomogeneity of the spatial sections is even better supported. Here, we consider the implications of inhomogeneity in dust models for the connectedness of spatial sections at early times. We consider a nonglobal Lemaître-Tolman-Bondi (LTB) model designed to match observations, a more general, heuristic model motivated by the former, and two specific, global LTB models. We propose that the generic class of solutions of the Einstein equations projected back in time from the spatial section at the present epoch includes subclasses in which the spatial section evolves (with increasing time) smoothly (i) from being disconnected to being connected, or (ii) from being simply connected to being multiply connected, where the coordinate system is comoving and synchronous. We show that (i) and (ii) each contain at least one exact solution. These subclasses exist because the Einstein equations allow nonsimultaneous big bang times. The two types of topology evolution occur over time slices that include significantly postquantum epochs if the bang time varies by much more than a Planck time. In this sense, it is possible for cosmic topology evolution to be “mostly” classical.

Roukema, Boudewijn F.; Blanlœil, Vincent; Ostrowski, Jan J.

2013-02-01

239

The quantum spin Hall effect and the topological magneto-electric effect  

NASA Astrophysics Data System (ADS)

Search for topologically non-trivial states of matter has become a important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. I shall review the theoretical prediction[1] of the QSH state in HgTe/CdTe semiconductor quantum wells, and its recent experimental observation [2]. The QSH effect can be generalized to three dimensions as the topological magneto-electric effect (TME) of the topological insulators [4]. I shall also present realistic experimental proposals to observe fractional charge [3], spin-charge separation and the deconfinement of the magnetic monopoles in these novel topological states of matter. [4pt] [1] A. Bernevig, T. Hughes and S. C. Zhang, Science, 314, 1757, (2006) [0pt] [2] M. Koenig et al, Science 318, 766, (2007) [0pt] [3] X. Qi, T. Hughes and S. C. Zhang, Nature Physics, 4, 273 (2008) [0pt] [4] Xiao-Liang Qi, Taylor Hughes and Shou-Cheng Zhang, ``Topological Field Theory of Time-Reversal Invariant Insulators", Phys. Rev B. 78, 195424 (2008)

Zhang, Shoucheng

2009-03-01

240

Topological hypercovers and 1 -realizations  

Microsoft Academic Search

We show that if U * is a hypercover of a topological space X then the natural map hocolim U * ? X is a weak equivalence. This fact is used to construct topological realization functors for the 1-homotopy theory of schemes over real and complex fields. In an appendix, we also prove a theorem about computing homotopy colimits of

Daniel Dugger; Daniel C. Isaksen

2004-01-01

241

Topological Insulator Nanoribbons and Nanocrystals  

NASA Astrophysics Data System (ADS)

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

Cui, Yi

2010-03-01

242

Visualizing Nonlinear Vector Field Topology  

Microsoft Academic Search

Abstract| We present our results on the visualization of non-linear vector eld topology. The underlying mathemat- ics is done in Cliord algebra, a system describing geometry by extending the usual vector space by a multiplication of vectors. We started with the observation that all known algorithms for vector eld topology are based on piecewise linear or bilinear approximation and that

Gerik Scheuermann; Heinz Krüger; Martin Menzel; Alyn P. Rockwood

1998-01-01

243

Electromagnetic topology - Junction characterization methods  

Microsoft Academic Search

The electrical characterization of topological network junctions using a formalism in accordance with electromagnetic topology is discussed. It is shown how the characteristic impedance of the network in which the junction is located can be chosen to treat several physical cable connection and termination configurations. Junctions which represent the separation of a conductor into other conductors are used as an

J. P. Parmantier; G. Labaume; J. C. Alliot; P. Degauque

1990-01-01

244

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

245

Radiating Charge  

NSDL National Science Digital Library

The electric field lines from a point charge evolve in time as the charge moves. Watch radiation propagate outward at the speed of light as you wiggle the charge. Stop a moving charge to see bremsstrahlung (braking) radiation. Explore the radiation patterns as the charge moves with sinusoidal, circular, or linear motion. You can move the charge any way you like, as long as you donât exceed the speed of light.

Simulations, Phet I.; Dubson, Michael; Paul, Ariel

2013-02-01

246

Dense topological spaces and dense continuity  

NASA Astrophysics Data System (ADS)

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

Aldwoah, Khaled A.

2013-09-01

247

Detectability of nontrivial topologies  

SciTech Connect

We study how the uncertainty in the cosmological parameters impacts on the detection of topological signals, focussing on three cubic torus universes and using three tests: the information content, the S/N statistic, and the Bayesian evidence. We find, within the concordance cosmological model, that 3D torus universes with a size of {approx}29 Gpc{sup 3} or larger cannot be detected. For the toroidal models that can be detected, the detection significance is primarily influenced by {omega}{sub {lambda}}, which enters both in the noise amplitude due to the Integrated Sachs-Wolfe effect and in the size of the causal horizon which limits the accessible fundamental domain. On large angular scales l<40, only {omega}{sub {lambda}} significantly alters the detection for all three estimators considered here.

Kunz, M. [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneva 4 (Switzerland); Aghanim, N. [IAS, CNRS and Univ. Paris-Sud, Bat. 121, F-91405, Orsay Cedex (France); Riazuelo, A. [Institut d'Astrophysique de Paris, UMR7095 CNRS, Universite Pierre and Marie Curie, 98 bis boulevard Arago, 75014 Paris (France); Forni, O. [CESR, 9 Avenue du Colonel Roche, B.P. 44346, F-31028 Toulouse, Cedex 4 (France)

2008-01-15

248

Topology in chaotic scattering  

NASA Astrophysics Data System (ADS)

In chaotic scattering, an initially freely moving orbit (such as that of an atom or a star) enters a scattering region and evolves chaotically for a period of time before it escapes and returns to free motion. We have looked at cases in which escape can occur in three or more distinct ways. Using a laboratory model, we demonstrate experimentally that the regions of state space (called basins) corresponding to different ways of escaping can have an interesting topological property that we call the Wada property, by which we mean that these regions of state space might be so convoluted that every point on the boundary of a basin is on the boundary of all basins,.

Sweet, David; Ott, Edward; Yorke, James A.

1999-05-01

249

Disordered Floquet Topological Insulators  

NASA Astrophysics Data System (ADS)

We study the problem of localization in the recently proposed two-dimensional Floquet topological insulators in semiconductor quantum wells. We compute the single particle Green's function for the system using a real-time simulation. The phase diagram obtained indicates that at weak disorder the system remains delocalized. The edge-states are protected and only destroyed when the disorder closes the gap in the Floquet spectrum. The system localizes only at disorder strength which is much larger than the gap in the Floquet spectrum, long after this gap has been closed due to disorder. Analytically we compare these results with the results obtained using disorder averaged Floquet Green's functions in the Born approximation.

Bhattacharjee, Paraj; Lindner, Netanel; Refael, Gil

2013-03-01

250

Charge transport in pn and npn junctions of silicene  

NASA Astrophysics Data System (ADS)

We investigate charge transport of pn and npn junctions made from silicene, a Si analogue of graphene. The conductance shows the distinct gate-voltage dependencies peculiar to the topological and nontopological phases, where the topological phase transition is caused by external electric field. Namely, the conductance is (not) suppressed in the np (nn) regime when both sides are topological, and in the nn (np) regime when one side is topological and the other side is nontopological. Furthermore, we find that the conductance is almost quantized to be 0, 1, and 2. Our findings will open a new way to nanoelectronics based on silicene.

Yamakage, Ai; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

2013-08-01

251

Models of three-dimensional fractional topological insulators  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

252

Interface currents in topological superconductor-ferromagnet heterostructures  

NASA Astrophysics Data System (ADS)

We propose the existence of a substantial charge current parallel to the interface between a noncentrosymmetric superconductor and a metallic ferromagnet. Our analysis focuses upon two complementary orbital-angular-momentum pairing states of the superconductor, exemplifying topologically nontrivial states which are gapped and gapless in the bulk, respectively. Utilizing a quasiclassical scattering theory, we derive an expression for the interface current in terms of Andreev reflection coefficients. Performing a systematic study of the current, we find stark qualitative differences between the gapped and gapless superconductors, which reflect the very different underlying topological properties. For the fully gapped superconductor, there is a sharp drop in the zero-temperature current as the system is tuned from a topologically nontrivial to a trivial phase. We explain this in terms of the sudden disappearance of the contribution to the current from the subgap edge states at the topological transition. The current in the gapless superconductor is characterized by a dramatic enhancement at low temperatures, and exhibits a singular dependence on the exchange-field strength in the ferromagnetic metal at zero temperature. This is caused by the energy shift of the strongly spin-polarized nondegenerate zero-energy flat bands due to their coupling to the exchange field. We argue that the interface current provides a novel test of the topology of the superconductor, and discuss prospects for the experimental verification of our predictions.

Brydon, P. M. R.; Timm, Carsten; Schnyder, Andreas P.

2013-04-01

253

Z2 anomaly and boundaries of topological insulators  

NASA Astrophysics Data System (ADS)

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

Ringel, Zohar; Stern, Ady

2013-09-01

254

The Ehrenfest force topology: a physically intuitive approach for analyzing chemical interactions.  

PubMed

Modified ANO-RCC basis sets are used to determine twelve molecular graphs of the Ehrenfest force for H2, CH4, CH2O, CH3NO, C2H2, C2H4, C3H3NO, N4H4, H2O, (H2O)2, (H2O)4 and (H2O)6. The molecular graphs include all types of topological critical points and a mix of bonding types is chosen to include sigma-, ?- and hydrogen-bonding. We then compare a wide range of point properties: charge density, trace of the Hessian, eigenvalues, ellipticity, stiffness, total local energy and the eigenvectors are calculated at the bond critical points (BCPs) and compared for the Ehrenfest, QTAIM and stress tensor schemes. QTAIM is found to be the only partitioning scheme that can differentiate between shared- and closed-shell chemical bond types. Only the results from the Ehrenfest force partitioning, however, are demonstrated to be physically intuitive. This is demonstrated for the water molecule, the water-dimer and the water clusters (H2O)4 and (H2O)6. In particular, both the stiffness and the trace of the Hessians of the appropriate quantities of the sigma-bond BCPs for the water clusters are found to depend on the quantum topology dimension of the molecular graph. The behavior of all the stress tensor point properties is found to be erratic. This is explained by the ambiguity in the theoretical definition of the stress tensor. As a complementary approach the Ehrenfest force provides a new indicator of the mixed chemical character of the hydrogen-bond BCP, which arises from the collinear donor sigma-bond donating a degree of covalent character to the hydrogen-bond. This indicator takes the form of the relative orientation of the shallowest direction of the Ehrenfest potential of the hydrogen-bond BCPs and the corresponding direction for the collinear sigma-bond BCP. PMID:24045853

Maza, Julio R; Jenkins, Samantha; Kirk, Steven R; Anderson, James S M; Ayers, Paul W

2013-10-01

255

CHARGE syndrome: an update  

Microsoft Academic Search

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

Damien Sanlaville; Alain Verloes

2007-01-01

256

Fractional Topological Insulators of Cooper Pairs Induced by the Proximity Effect  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

257

Topological Insulators at Room Temperature  

Microsoft Academic Search

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 $Sb_2Te_3$, $Sb_2Se_3$, $Bi_2Te_3$ and $Bi_2Se_3$ crystals. Our calculations predict that $Sb_2Te_3$, $Bi_2Te_3$ and $Bi_2Se_3$ are topological insulators, while $Sb_2Se_3$ is not. In particular, $Bi_2Se_3$ has a topologically non-trivial energy gap of $0.3 eV$, suitable

Haijun Zhang; Chao-Xing Liu; Xiao-Liang Qi; Xi Dai; Zhong Fang; Shou-Cheng Zhang

2008-01-01

258

Topological Insulators at Room Temperature  

Microsoft Academic Search

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 SbTe, SbSe, BiTe and BiSe crystals. Our calculations predict that SbTe, BiT e and BiSe are topological insulators, while SbSe is not. In particular, BiSe has a topologically non-trivial energy gap of 0.3eV ,

Haijun Zhang; Chao-Xing Liu; Xiao-Liang Qi; Xi Dai; Zhong Fang; Shou-Cheng Zhang

2010-01-01

259

Gauge dynamics and topological insulators  

NASA Astrophysics Data System (ADS)

A non-abelian magnetic field in Yang-Mills theory induces the formation of a "W-boson" vortex lattice. We study the propagation of fundamental fermions in the presence of this lattice in 2+1 dimensions. We show that the spectrum for massless fermions contains four topologically-protected Dirac points with non-zero Bloch momentum. For massive fermions, we compute topological invariants of the band structure and show that it is possible to realise a topological insulator within Yang-Mills theory.

Béri, Benjamin; Tong, David; Wong, Kenny

2013-09-01

260

Z_{2} Topological Order and the Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum spin Hall (QSH) phase is a time reversal invariant electronic\\u000astate with a bulk electronic band gap that supports the transport of charge and\\u000aspin in gapless edge states. We show that this phase is associated with a novel\\u000a$Z_2$ topological invariant, which distinguishes it from an ordinary insulator.\\u000aThe $Z_2$ classification, which is defined for time reversal

C. L. Kane; E. J. Mele

2005-01-01

261

An Integral Representation for a Class of Positive Definite Functions.  

National Technical Information Service (NTIS)

Let G be a locally compact topological group with a closed subgroup K and let alpha be a character of K. A continuous positive definite function phi on G is said to be bi-invariant with respect to (K, alpha) if phi(KxK') = alpha(KK')phi(x) for all K,K' ep...

B. J. McCabe

1969-01-01

262

Analytic estimates and topological properties of the weak stability boundary  

NASA Astrophysics Data System (ADS)

The weak stability boundary (WSB) is the transition region of the phase space where the change from gravitational escape to ballistic capture occurs. Studies on this complicated region of chaotic motion aim to investigate its unique, fuel saving properties to enlarge the frontiers of low energy transfers. This "fuzzy stability" region is characterized by highly sensitive motion, and any analysis of it has been carried out almost exclusively using numerical methods. On the contrary this paper presents, for the planar circular restricted 3-body problem, (1) an analytic definition of the WSB which is coherent with the known algorithmic definitions; (2) a precise description of the topology of the WSB; (3) analytic estimates on the "stable region" (nearby the smaller primary) whose boundary is, by definition, the WSB.

Ceccaroni, Marta; Biggs, James; Biasco, Luca

2012-10-01

263

Quantum topological geometrodynamics  

SciTech Connect

The description of 3-space as a spacelike 3-surface X of the space H = M/sup 4/ x CP/sub 2/ (Product of Minkowski space and two-dimensional complex projective space CP/sub 2/) and the idea that particles correspond to 3-surfaces of finite size in H are the basic ingredients of topological geometrodynamics (TGD), an attempt at a geometry-based unification of the fundamental interactions. The observations that the Schrodinger equation can be derived from a variational principle and that existence of a unitary S-matrix follows from the phase symmetry of this action lead to the idea that quantum TGD should be derivable from a quadratic phase-symmetric variational principle for some kind of superfield (describing both fermions and bosons) in the configuration space consisting of the spacelike 3-surfaces of H. This idea as such has not led to a calculable theory. The reason is the wrong realization of the general coordinate invariance. The crucial observation is that the space Map(X,H), the space of maps from an abstract 3-manifold X to H, inherits a coset space structure from H and can be given a Kahler geometry invariant under the local M/sup 4/ x SU(3) an under the group Diff of X diffeomorphisms. The space Map(X,H) is taken as a basic geometric object and general coordinate invariance is realized by requiring that superfields defined in Map(X,H) are diffeo-invariant, so that they can be regarded as fields in Map(X,H)/Diff, the space of surfaces with given manifold topology. Superd'Alembert equations are found to reduce to a simple algebraic condition due to the constant curvature and Kahler properties of Map(X,H). The construction of physical states leads by local M/sup 4/ x SU(3) invariance to a formalism closely resembling the quantization of strings. The pointlike limit of the theory is discussed. Finally, a formal expression for the S-matrix of the theory is derived and general properties of the S-matrix are discussed.

Pitkaenen, M.

1986-09-01

264

Topologically induced local P and CP violation in hot QCD  

SciTech Connect

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

265

Towards a general theory of topological maps  

Microsoft Academic Search

We present a general theory of topological maps whereby sensory input, topological and local metrical information are combined to define the topological maps explaining such information. Topological maps correspond to the minimal models of an axiomatic theory describing the relationships between the different sources of information explained by a map. We use a circumscriptive theory to specify the minimal models

Emilio Remolina; Benjamin Kuipers

2004-01-01

266

Visualizing vector field topology in fluid flows  

Microsoft Academic Search

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

267

Evolving Neural Networks through Augmenting Topologies  

Microsoft Academic Search

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

268

Manipulating surface states in topological insulator nanoribbons.  

PubMed

Topological insulators display unique properties, such as the quantum spin Hall effect, because time-reversal symmetry allows charges and spins to propagate along the edge or surface of the topological insulator without scattering. However, the direct manipulation of these edge/surface states is difficult because they are significantly outnumbered by bulk carriers. Here, we report experimental evidence for the modulation of these surface states by using a gate voltage to control quantum oscillations in Bi(2)Te(3) nanoribbons. Surface conduction can be significantly enhanced by the gate voltage, with the mobility and Fermi velocity reaching values as high as ~5,800 cm(2) V(-1) s(-1) and ~3.7 × 10(5) m s(-1), respectively, with up to ~51% of the total conductance being due to the surface states. We also report the first observation of h/2e periodic oscillations, suggesting the presence of time-reversed paths with the same relative zero phase at the interference point. The high surface conduction and ability to manipulate the surface states demonstrated here could lead to new applications in nanoelectronics and spintronics. PMID:21317891

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

2011-02-13

269

Role of sequence bias in the topology of the multidrug transporter EmrE.  

PubMed

EmrE is the prototype of small multidrug resistance transporters and has emerged as a model of membrane protein evolution. Analysis of the distances separating symmetry-related site-specific spin labels, correlation of topological sequence bias to C-terminal orientation, to membrane insertion efficiency, and to resistance to ethidium bromide collectively demonstrate that EmrE monomers adopt a parallel topology in the functional dimer. We propose a coupled insertion and assembly model for EmrE in which the favorable energetics of the parallel dimer interface override topological constraints arising from weak asymmetry in positive charge distribution. PMID:18616286

McHaourab, Hassane S; Mishra, Sanjay; Koteiche, Hanane A; Amadi, Sepan H

2008-07-11

270

Interface-Induced Topological Insulator Transition in GaAs/Ge/GaAs Quantum Wells.  

PubMed

We demonstrate theoretically that interface engineering can drive germanium, one of the most commonly used semiconductors, into a topological insulating phase. Utilizing giant electric fields generated by charge accumulation at GaAs/Ge/GaAs opposite semiconductor interfaces and band folding, the new design can reduce the sizable gap in Ge and induce large spin-orbit interaction, which leads to a topological insulator transition. Our work provides a new method to realize topological insulators in commonly used semiconductors and suggests a promising approach to integrate it in well-developed semiconductor electronic devices. PMID:24160616

Zhang, Dong; Lou, Wenkai; Miao, Maosheng; Zhang, Shou-Cheng; Chang, Kai

2013-10-11

271

Interface-Induced Topological Insulator Transition in GaAs/Ge/GaAs Quantum Wells  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically that interface engineering can drive germanium, one of the most commonly used semiconductors, into a topological insulating phase. Utilizing giant electric fields generated by charge accumulation at GaAs/Ge/GaAs opposite semiconductor interfaces and band folding, the new design can reduce the sizable gap in Ge and induce large spin-orbit interaction, which leads to a topological insulator transition. Our work provides a new method to realize topological insulators in commonly used semiconductors and suggests a promising approach to integrate it in well-developed semiconductor electronic devices.

Zhang, Dong; Lou, Wenkai; Miao, Maosheng; Zhang, Shou-cheng; Chang, Kai

2013-10-01

272

Classification of engineered topological superconductors  

NASA Astrophysics Data System (ADS)

I perform a complete classification of two-dimensional, quasi-one-dimensional (1D) and 1D topological superconductors which originate from the suitable combination of inhomogeneous Rashba spin–orbit coupling, magnetism and superconductivity. My analysis reveals alternative types of topological superconducting platforms for which Majorana fermions are accessible. Specifically, I observe that for quasi-1D systems with Rashba spin–orbit coupling and time-reversal violating superconductivity, such as for instance due to a finite Josephson current flow, Majorana fermions can emerge even in the absence of magnetism. Furthermore, for the classification I also consider situations where additional ‘hidden’ symmetries emerge, with a significant impact on the topological properties of the system. The latter generally originate from a combination of space group and complex conjugation operations that separately do not leave the Hamiltonian invariant. Finally, I suggest alternative directions in topological quantum computing for systems with additional unitary symmetries.

Kotetes, Panagiotis

2013-10-01

273

Nematic colloids, topology and photonics.  

PubMed

We review and discuss recent progress in the field of nematic colloids, with an emphasis on possible future applications in photonics. The role of the topology is described, based on experimental manipulations of the topological defects in nematic colloids. The topology of the ordering field in nematics provides the forces between colloidal particles that are unique to these materials. We also discuss recent progress in the new field of active microphotonic devices based on liquid crystals (LCs), where chiral nematic microlasers and tuneable nematic microresonators are just two of the recently discovered examples. We conclude that the combination of topology and microphotonic devices based on LCs provides an interesting platform for future progress in the field of LCs. PMID:23459967

Musevic, I

2013-03-04

274

Topological Entropy and Secondary Folding  

NASA Astrophysics Data System (ADS)

A convenient measure of a map or flow's chaotic action is the topological entropy. In many cases, the entropy has a homological origin: it is forced by the topology of the space. For example, in simple toral maps, the topological entropy is exactly equal to the growth induced by the map on the fundamental group of the torus. However, in many situations the numerically computed topological entropy is greater than the bound implied by this action. We associate this gap between the bound and the true entropy with `secondary folding': material lines undergo folding which is not homologically forced. We examine this phenomenon both for physical rod stirring devices and toral linked twist maps, and show rigorously that for the latter secondary folds occur.

Tumasz, Sarah; Thiffeault, Jean-Luc

2013-06-01

275

Cyclic foam topological field theories  

NASA Astrophysics Data System (ADS)

This paper proposes an axiomatic form for cyclic foam topological field theories, that is, topological field theories corresponding to string theories where particles are arbitrary graphs. World surfaces in this case are 2-manifolds with one-dimensional singularities. I prove that cyclic foam topological field theories are in one-to-one correspondence with graph-Cardy-Frobenius algebras that are families (A,B?,?) where A={As|s?S} are families of commutative associative Frobenius algebras, B?=?B? is an associative algebra of Frobenius type graduated by graphs, and ?={??s:As?End(B?)|s?S,???} is a family of special representations. Examples of cyclic foam topological field theories and graph-Cardy-Frobenius algebras are constructed.

Natanzon, Sergey M.

2010-06-01

276

Topological Dynamics. An International Symposium.  

National Technical Information Service (NTIS)

In August 1967, a symposium on topological dynamics was held at Colorado State University. Over seventy mathematicians from the United States and several foreign countries - England, France, Germany, Israel, Italy, Mexico - participated. This volume consi...

J. Auslander W. H. Gottschalk

1968-01-01

277

Magnetic topology of blinkers  

NASA Astrophysics Data System (ADS)

Context: Co-spatial and co-temporal spectroscopic, imaging and magnetogram data enable us to better understand various solar transient phenomena. Here, we study brightening events in the transition region of the quiet Sun, also called “blinkers”. Aims: We aim to investigate the physical mechanism responsible for blinkers. Methods: An automated blinker identification procedure (BLIP) is used to identify blinker events in SoHO/CDS data. The 3D magnetic topology of the magnetic field in the blinker region is reconstructed based on SoHO/MDI magnetogram data. Results: During 3 h of SoHO/CDS observations on 2006 January 18, 66 blinkers were identified in the O v 629 Å emission line. Out of them, a group comprising of 16 events were modelled here. They were found to be associated with the emergence of magnetic flux which gave rise to the appearance of, and multiple magnetic reconnection events across, an upper atmosphere (coronal) magnetic null point, along with a loop structure as observed with TRACE. Conclusions: This blinker group results from the release of energy that was accumulated during flux emergence, although whether all blinkers follow the same formation scenario requires further investigation using additional multi-instrument/multi-mission studies. 2 movies are only available in electronic form at http://star.arm.ac.uk/preprints/ and http://www.aanda.org

Subramanian, S.; Madjarska, M. S.; Maclean, R. C.; Doyle, J. G.; Bewsher, D.

2008-09-01

278

Electric-Magnetic Duality and Topological Insulators  

SciTech Connect

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

279

Refining the shifted topological vertex  

SciTech Connect

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

280

High Spin Topologically Massive Gravity  

NASA Astrophysics Data System (ADS)

We study the high spin fields coupled to topologically massive gravity in AdS3, paying special attention to the nature of the theory at the critical point. We propose an action incorporating the high spin AdS3 gravity and the topological Chern-Simons term for high spin fields. We discuss the fluctuation spectrum around the AdS3 vacuum and find that besides the usual massless modes there are local massive modes.

Chen, Bin

2012-12-01

281

Algebraic topology and modular forms  

Microsoft Academic Search

Modular forms appear in many facets of mathematics, and have played important\\u000aroles in geometry, mathematical physics, number theory, representation theory,\\u000atopology, and other areas. Around 1994, motivated by technical issues in\\u000ahomotopy theory, Mark Mahowald, Haynes Miller and I constructed a topological\\u000arefinement of modular forms, which we call {\\\\em topological modular forms}. At\\u000athe Zurich ICM I sketched

Michael J. Hopkins

2002-01-01

282

The Category of Topological Thermodynamics  

NASA Astrophysics Data System (ADS)

The Category theory of Topological Thermodynamics and Continuous Topological Evolution can be used as an abstract, but universal, foundation for understanding, among other things, scale invariance, chaos, emergence, self-similarity, dynamical systems, irreversible processes, and other non-linear, and even statistical, phenomena. The abstract Category theory, as an exterior differential system, has solutions which can be put into correspondence with numerous physical experiments in different disciplines.

Kiehn, R. M.

2012-12-01

283

Z2 Topological Anderson Insulator  

NASA Astrophysics Data System (ADS)

Effects of disorder on a two-dimensional Z2 topological insulator are studied numerically. We propose and study the phase diagram of a variant of Bernevig-Hughes-Zhang model, which takes account of the sz non-conserving spin-orbit coupling. Using scaling analyses, we determine the phase boundary and the critical exponent characterizing the transition between metallic and the topologically insulating phases.

Yamakage, Ai; Nomura, Kentaro; Imura, Ken-Ichiro; Kuramoto, Yoshio

2012-12-01

284

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

285

Abelian Hopfions of the CPn model on R and a fractionally powered topological lower bound  

NASA Astrophysics Data System (ADS)

Regarding the Skyrme–Faddeev model on R3 as a CP1 sigma model, we propose CPn sigma models on R as generalisations which may support finite energy Hopfion solutions in these dimensions. The topological charge stabilising these field configurations is the Chern–Simons charge, namely the volume integral of the Chern–Simons density which has a local expression in terms of the composite connection and curvature of the CPn field. It turns out that subject to the sigma model constraint, this density is a total divergence. We prove the existence of a topological lower bound on the energy, which, as in the Vakulenko–Kapitansky case in R3, is a fractional power of the topological charge, depending on n. The numerical construction of the simplest ring shaped un-knot Hopfion on R5 is also discussed.

Radu, Eugen; Tchrakian, D. H.; Yang, Yisong

2013-10-01

286

The finite thermodynamic topology of photons  

NASA Astrophysics Data System (ADS)

All physical measurements are based on finite intervals of space and time. It follows that the appropriate topologies of measurement must be finite. However, there are only two types of finite power set topologies: T0 topologies and Not-T0 topologies. All singlet subsets of T0 (Kolmogorov) topologies are topologically distinguishable. Therefor it is natural that such topologies should be called Particle-like topologies. On the otherhand, some, if not all, singlet subsets of Not-T0 topologies are indistinguishable. Hence such topologies will be called Statistical, Wave-like, or Photon topologies. This article starts with a short review of the topological properties of Kolomogorov T0 particle topologies using processes that generate homotopic evolution of those exterior differential 1-forms chosed to describe thermodynamic states. Not-T0 topologies can use homotopic evolution of N-form densities to generate systems of partial differential equations that describe both reversible and irreversible dynamics. Numerous examples will be presented to demonstrate continuous topological evolution of complex exterior differential form densities in terms of Cartan's homotopic magic formula.

Kiehn, R. M.

2013-10-01

287

D-brane charges in Gepner models  

NASA Astrophysics Data System (ADS)

We construct Gepner models in terms of coset conformal field theories and compute their twisted equivariant K-theories. These classify the D-brane charges on the associated geometric backgrounds and therefore agree with the topological K-theories. We show this agreement for various cases, in particular the Fermat quintic.

Braun, Volker; Schäfer-Nameki, Sakura

2006-09-01

288

Conserved charges in 3D gravity  

SciTech Connect

The covariant canonical expression for the conserved charges, proposed by Nester, is tested on several solutions in three-dimensional gravity with or without torsion and topologically massive gravity. In each of these cases, the calculated values of energy momentum and angular momentum are found to satisfy the first law of black hole thermodynamics.

Blagojevic, M.; Cvetkovic, B. [University of Belgrade, Institute of Physics, P. O. Box 57, 11001 Belgrade (Serbia)

2010-06-15

289

Classification of chemical bonds based on topological analysis of electron localization functions  

Microsoft Academic Search

THE definitions currently used to classify chemical bonds (in terms of bond order, covalency versus ionicity and so forth) are derived from approximate theories1 3 and are often imprecise. Here we outline a first step towards a more rigorous means of classification based on topological analysis of local quantum-mechanical functions related to the Pauli exclusion principle. The local maxima of

B. Silvi; A. Savin

1994-01-01

290

Take Charge!  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

291

A simple topological factor determining the allowance of pericyclic reactions  

NASA Astrophysics Data System (ADS)

The study is aimed at revealing the possible manifestation of the overlap topology of AOs at early stages of pericyclic reactions. To this end, formation of an evenmembered cycle of carbon atoms is considered as a unified model, wherein relatively strong (C?C) bonds alternate with weak onesE A direct perturbative method is applied to derive algebraic expressions for energy and bond order corrections due to cyclization. To represent the overlap topology of 2pz AOs over the cycle, a new concept of the roundabout interaction is introduced. The relevant definition contains a product of resonance parameters (or overlap integrals) between orbitals of all neighboring pairs of C?C bonds and a certain N-dependent parity factor, where N coincides with the total number of these bonds. The principal result of the study consists in demonstration of proportionality of both energy and bond order corrections to the roundabout interaction of the given cycle and thereby of a direct dependence between these corrections and the overlap topology of AOs. Moreover, the sign of the roundabout interaction is shown to determine the allowance of the given way of the process, viz. cycles described by positive (negative) roundabout interactions refer to allowed (forbidden) ways. Thus, an analog of the famous Woodward-Hoffmann rule is obtained, wherein the overlap topology of AOs stands instead of symmetry of molecular orbitals. Along with stabilization of the cycle vs. the initial open chain, the allowed processes also are necessarily characterized by growing uniformity of all bond orders over the cycle, while the forbidden ones are accompanied by both destabilization and an increasing distinction between strong and weak bonds. The results obtained also yield a new definition of the concerted nature of pericyclic processes. The general conclusions of the study are illustrated by consideration of specific examples including the electrocyclic closure of polyene chains.0

Gineityte, V.

292

Symmetries, topological phases, and bound states in the one-dimensional quantum walk  

NASA Astrophysics Data System (ADS)

Discrete-time quantum walks have been shown to simulate all known topological phases in one and two dimensions. Being periodically driven quantum systems, their topological description, however, is more complex than that of closed Hamiltonian systems. We map out the topological phases of the particle-hole symmetric one-dimensional discrete-time quantum walk. We find that there is no chiral symmetry in this system: its topology arises from the particle-hole symmetry alone. We calculate the Z2×Z2 topological invariant in a simple way that is consistent with a general definition for one-dimensional periodically driven quantum systems. These results allow for a transparent interpretation of the edge states on a finite lattice via the the bulk-boundary correspondence. We find that the bulk Floquet operator does not contain all the information needed for the topological invariant. As an illustration to this statement, we show that in the split-step quantum walk, the edges between two bulks with the same Floquet operator can host topologically protected edge states.

Asbóth, J. K.

2012-11-01

293

Entanglement Spectrum of Topological Insulators  

NASA Astrophysics Data System (ADS)

Topological order in electronic systems leads to striking features in the ``entanglement spectrum'' which characterizes quantum entanglement between two halves of a system (FDMH, PRL 101,101504 (2008)). If the system is divided along a translationally-invariant boundary, the spectrum can be labeled by momentum parallel to it, and is gapless if topological order is present. The gapless spectrum is related to gapless edge states that appear at free edges of such systems. Topological insulators have non-trivial one-electron band structure properties; the entanglement spectrum of a non-interacting electron Slater determinant state is itself a non-interacting fermionic spectrum. This spectrum is gapped for ``trivial'' ordinary insulating band structures, but exhbits characteristic spectral flow and gapless modes when the band structure is topologically non-trivial. As a case study, the entanglement spectrum of the ``Haldane model'' of a Bloch electron band structure with a zero-field quantum Hall effect will be described in detail, and generalizations to spin-orbit-coupled topological insulators discussed.

Haldane, F. D. M.

2009-03-01

294

Characterization of heterocyclic rings through quantum chemical topology.  

PubMed

Five-membered rings are found in a myriad of molecules important in a wide range of areas such as catalysis, nutrition, and drug and agrochemical design. Systematic insight into their largely unexplored chemical space benefits from first principle calculations presented here. This study comprehensively investigates a grand total of 764 different rings, all geometry optimized at the B3LYP/6-311+G(2d,p) level, from the perspective of Quantum Chemical Topology (QCT). For the first time, a 3D space of local topological properties was introduced, in order to characterize rings compactly. This space is called RCP space, after the so-called ring critical point. This space is analogous to BCP space, named after the bond critical point, which compactly and successfully characterizes a chemical bond. The relative positions of the rings in RCP space are determined by the nature of the ring scaffold, such as the heteroatoms within the ring or the number of ?-bonds. The summed atomic QCT charges of the five ring atoms revealed five features (number and type of heteroatom, number of ?-bonds, substituent and substitution site) that dictate a ring's net charge. Each feature independently contributes toward a ring's net charge. Each substituent has its own distinct and systematic effect on the ring's net charge, irrespective of the ring scaffold. Therefore, this work proves the possibility of designing a ring with specific properties by fine-tuning it through manipulation of these five features. PMID:23795608

Griffiths, Mark Z; Popelier, Paul L A

2013-07-03

295

Topological exploration of subterranean environments  

SciTech Connect

The need for reliable maps of subterranean spaces too hazardous for humans to occupy has motivated the development of robotic mapping tools suited to these domains. As such, this work describes a system developed for autonomous topological exploration of mine environments to facilitate the process of mapping. The exploration framework is based upon the interaction of three main components: Node detection, node matching, and edge exploration. Node detection robustly identifies mine corridor intersections from sensor data and uses these features as the building blocks of a topological map. Node matching compares newly observed intersections to those stored in the map, providing global localization during exploration. Edge exploration translates topological exploration objectives into locomotion along mine corridors. This article describes both the robotic platform and the algorithms developed for exploration, and presents results from experiments conducted at a research coal mine near Pittsburgh, PA.

Silver, D.; Ferguson, D.; Morris, A.; Thayer, S. [Carnegie Mellon University, Pittsburgh, PA (United States)

2006-06-15

296

Quantum capacitance in topological insulators.  

PubMed

Topological insulators show unique properties resulting from massless, Dirac-like surface states that are protected by time-reversal symmetry. Theory predicts that the surface states exhibit a quantum spin Hall effect with counter-propagating electrons carrying opposite spins in the absence of an external magnetic field. However, to date, the revelation of these states through conventional transport measurements remains a significant challenge owing to the predominance of bulk carriers. Here, we report on an experimental observation of Shubnikov-de Haas oscillations in quantum capacitance measurements, which originate from topological helical states. Unlike the traditional transport approach, the quantum capacitance measurements are remarkably alleviated from bulk interference at high excitation frequencies, thus enabling a distinction between the surface and bulk. We also demonstrate easy access to the surface states at relatively high temperatures up to 60 K. Our approach may eventually facilitate an exciting exploration of exotic topological properties at room temperature. PMID:22993694

Xiu, Faxian; Meyer, Nicholas; Kou, Xufeng; He, Liang; Lang, Murong; Wang, Yong; Yu, Xinxin; Fedorov, Alexei V; Zou, Jin; Wang, Kang L

2012-09-18

297

Nearly Flatbands with Nontrivial Topology  

SciTech Connect

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

298

5 CFR 2502.11 - Definitions.  

Code of Federal Regulations, 2013 CFR

...Act, 5 U.S.C. 552 Charges for Search and Reproduction § 2502.11 Definitions...records are stored. (d) The term search includes all time spent looking for...should not engage in a line-by-line search when merely duplicating an entire...

2013-01-01

299

5 CFR 1303.30 - Definitions.  

Code of Federal Regulations, 2013 CFR

...ADMINISTRATIVE PROCEDURES ACT Charges for Search and Reproduction § 1303.30 Definitions...records are stored. (d) The term search means the process of looking for...should not engage in line-by-line search when merely duplicating an entire...

2013-01-01

300

Topological Quantum Field Theories from Compact Lie Groups  

Microsoft Academic Search

It is a long-standing question to extend the definition of 3-dimensional\\u000aChern-Simons theory to one which associates values to 1-manifolds with boundary\\u000aand to 0-manifolds. We provide a solution in case the gauge group is a torus.\\u000aWe also develop from different points of view an associated 4-dimensional\\u000ainvertible topological field theory which encodes the anomaly of Chern-Simons.\\u000aFinite gauge

Daniel S. Freed; Michael J. Hopkins; Jacob Lurie; Constantin Teleman

2009-01-01

301

Photogalvanic effects in topological insulators  

NASA Astrophysics Data System (ADS)

We discuss optical absorption in topological insulators and study possible photoelectric effects theoretically. We found that absorption of circularly polarized electromagnetic waves in two-dimensional topological insulators results in electric current in the conducting 1D edge channels, the direction of the current being determined by the light polarization. We suggest two ways of inducing such a current: due to magnetic dipole electron transitions stimulated by irradiation of frequency below the bulk energy gap, and due to electric dipole transitions in the bulk at frequencies larger than the energy gap with subsequent capture of the photogenerated carriers on conducting edge states.

Artemenko, S. N.; Kaladzhyan, V. O.

2013-03-01

302

Entanglement renormalization and topological order.  

PubMed

The multiscale entanglement renormalization ansatz (MERA) is argued to provide a natural description for topological states of matter. The case of Kitaev's toric code is analyzed in detail and shown to possess a remarkably simple MERA description leading to distillation of the topological degrees of freedom at the top of the tensor network. Kitaev states on an infinite lattice are also shown to be a fixed point of the renormalization group flow associated with entanglement renormalization. All of these results generalize to arbitrary quantum double models. PMID:18352529

Aguado, Miguel; Vidal, Guifré

2008-02-21

303

Center vortex model for the infrared sector of SU(3) Yang-Mills theory: Topological susceptibility  

SciTech Connect

The topological susceptibility of the SU(3) random vortex world-surface ensemble, an effective model of infrared Yang-Mills dynamics, is investigated. The model is implemented by composing vortex world surfaces of elementary squares on a hypercubic lattice, supplemented by an appropriate specification of vortex color structure on the world surfaces. Topological charge is generated in this picture by writhe and self-intersection of the vortex world surfaces. Systematic uncertainties in the evaluation of the topological charge, engendered by the hypercubic construction, are discussed. Results for the topological susceptibility are reported as a function of temperature and compared to corresponding measurements in SU(3) lattice Yang-Mills theory. In the confined phase, the topological susceptibility of the random vortex world-surface ensemble appears quantitatively consistent with Yang-Mills theory. As the temperature is raised into the deconfined regime, the topological susceptibility falls off rapidly, but significantly less so than in SU(3) lattice Yang-Mills theory. Possible causes of this deviation, ranging from artefacts of the hypercubic description to more physical sources, such as the adopted vortex dynamics, are discussed.

Engelhardt, M. [Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003 (United States)

2011-01-15

304

EDITORIAL: Progress in topological insulators Progress in topological insulators  

NASA Astrophysics Data System (ADS)

One of the most remarkable discoveries of the last few years in condensed matter physics is that the established distinction of crystalline solids in metals and insulators—which relies on the material band-structure—is incomplete. During the last several decades, the band structure of an uncountable variety of compounds of increasing complexity have been computed, and yet it has been overlooked that in the presence of sufficiently strong spin-orbit interaction, a new class of materials can be realized, that intrinsically behaves as insulators in their bulk and as metals at their surface. The discovery of this new class of materials was made only recently by Kane and Mele, during their theoretical studies of graphene in the presence of a sufficiently strong intrinsic spin-orbit interaction. Although the strength of the spin-orbit interaction in graphene is not sufficient to make the topological insulating state visible experimentally under currently reachable conditions, the validity and the originality of the concept were fully appreciated. Predictions for the occurrence of a two-dimensional topological insulating state in HgTe/CdTe heterostructures were made by Bernevig, Hughes and Zhang, and were followed by the experimental verification at Würzburg, in the Molenkamp group. Within a couple of years, this work brought the concept of topological insulator from an abstract theoretical discovery to an experimental reality, which stimulated further work. The concept of topological insulators was extended to the case of three-dimensional systems, for which an ideal experimental probe is angle-resolved photo-emission spectroscopy. Using this technique, specific theoretical predictions that had been made regarding the topological insulating character of different materials (e.g., for Bi-based compounds such as BiSb, Bi2Se3 or Bi2Te3), were verified experimentally through the direct observation of the Dirac surface fermions. This research was sufficient to put on solid theoretical and experimental grounds the notion of topological insulators, but, clearly, the excitement associated with this new concept goes well beyond the initial predictions and verifications. Theoretically, it is interesting to extend the concept of topological insulating states to interacting systems, to investigate the interplay of this new state of matter with other phenomena, such as superconductivity or magnetism, and to analyze all possible different experimental manifestations of the topologically insulating state. Furthermore, it is interesting to classify topological insulators and topological superconductors in both the absence and the presence of Coulomb interactions. Experimentally, the angle-resolved experimental measurements are only a first step, and what one would really like to do is, for instance, to realize nano-electronic devices with this new class of materials, much in the same way as is being done for graphene. It is in these new directions that current work is focusing, trying to solve experimental difficulties which are often present due to the limited material control of these systems that we currently have. The articles that are published in this issue provide an excellent demonstration of the spectrum of activities that is being pursued, as well as an introduction to some of the most established achievements in the field. As such, they will serve as a useful guideline for the interested reader to different important aspects in the field, from its start to the present.

Morpurgo, Alberto; Trauzettel, Björn

2012-12-01

305

Organic topological insulators in organometallic lattices.  

PubMed

Topological insulators are a recently discovered class of materials having insulating bulk electronic states but conducting boundary states distinguished by nontrivial topology. So far, several generations of topological insulators have been theoretically predicted and experimentally confirmed, all based on inorganic materials. Here, based on first-principles calculations, we predict a family of two-dimensional organic topological insulators made of organometallic lattices. Designed by assembling molecular building blocks of triphenyl-metal compounds with strong spin-orbit coupling into a hexagonal lattice, this new classes of organic topological insulators are shown to exhibit nontrivial topological edge states that are robust against significant lattice strain. We envision that organic topological insulators will greatly broaden the scientific and technological impact of topological insulators. PMID:23403572

Wang, Z F; Liu, Zheng; Liu, Feng

2013-01-01

306

Unifying Derivation of Switching DC-DC Converter Topologies.  

National Technical Information Service (NTIS)

A canonical switching cell is proposed from which the three basic dc-dc converter topologies can be derived. In addition, it is possible to perform topological transformations which yield apparently new topologies. Upon examination, however, these topolog...

E. E. Landsman

1979-01-01

307

Quantized anomalous Hall effect in magnetic topological insulators.  

PubMed

The anomalous Hall effect is a fundamental transport process in solids arising from the spin-orbit coupling. In a quantum anomalous Hall insulator, spontaneous magnetic moments and spin-orbit coupling combine to give rise to a topologically nontrivial electronic structure, leading to the quantized Hall effect without an external magnetic field. Based on first-principles calculations, we predict that the tetradymite semiconductors Bi2Te3, Bi2Se3, and Sb2Te3 form magnetically ordered insulators when doped with transition metal elements (Cr or Fe), in contrast to conventional dilute magnetic semiconductors where free carriers are necessary to mediate the magnetic coupling. In two-dimensional thin films, this magnetic order gives rise to a topological electronic structure characterized by a finite Chern number, with the Hall conductance quantized in units of e2/h (where e is the charge of an electron and h is Planck's constant). PMID:20522741

Yu, Rui; Zhang, Wei; Zhang, Hai-Jun; Zhang, Shou-Cheng; Dai, Xi; Fang, Zhong

2010-06-03

308

Structural topology optimization for crashworthiness  

Microsoft Academic Search

This paper presents a method to obtain optimum topologies of structures subject to impact loads that produce geometric and material nonlinear behavior, surface contact, friction, and other phenomena in shell and three-dimensional structures. The main feature of this method is an algorithm that does not use sensitivity (gradient) information and does not require large number of iterations. A criterion called

C. A. Soto

2004-01-01

309

Crystallographic topology and its applications  

SciTech Connect

Geometric topology and structural crystallography concepts are combined to define a new area we call Structural Crystallographic Topology, which may be of interest to both crystallographers and mathematicians. In this paper, we represent crystallographic symmetry groups by orbifolds and crystal structures by Morse - functions. The Morse function uses mildly overlapping Gaussian thermal-motion probability density functions centered on atomic sites to form a critical net with peak, pass, pale, and pit critical points joined into a graph by density gradient-flow separatrices. Critical net crystal structure drawings can be made with the ORTEP-III graphics pro- An orbifold consists of an underlying topological space with an embedded singular set that represents the Wyckoff sites of the crystallographic group. An orbifold for a point group, plane group, or space group is derived by gluing together equivalent edges or faces of a crystallographic asymmetric unit. The critical-net-on-orbifold model incorporates the classical invariant lattice complexes of crystallography and allows concise quotient-space topological illustrations to be drawn without the repetition that is characteristic of normal crystal structure drawings.

Johnson, C.K.; Burnett, M.N. [Oak Ridge National Lab., TN (United States); Dunbar, W.D. [Simon`s Rock Coll., Great Barrington, MA (United States). Div. of Natural Sciences and Mathematics

1996-10-01

310

Geometry, Topology and String Theory.  

National Technical Information Service (NTIS)

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 problems of a given classical space-time se...

U. Varadarajan

2003-01-01

311

Topological methods in combinatorial geometry  

NASA Astrophysics Data System (ADS)

This survey is devoted to some results in the area of combinatorial and convex geometry, from classical theorems up to the latest contemporary results, mainly those results whose proofs make essential use of the methods of algebraic topology. Various generalizations of the Borsuk-Ulam theorem for a (Z_p)^k-action are explained in detail, along with applications to Knaster's problem about levels of a function on a sphere, and applications are discussed to the Lyusternik-Shnirel'man theory for estimating the number of critical points of a smooth function. An overview is given of the topological methods for estimating the chromatic number of graphs and hypergraphs, in theorems of Tverberg and van Kampen-Flores type. The author's results on the `dual' analogues of the central point theorem and Tverberg's theorem are described. Results are considered on the existence of inscribed and circumscribed polytopes of special form for convex bodies and on the existence of billiard trajectories in a convex body. Results on partition of measures by hyperplanes and other partitions of Euclidean space are presented. For theorems of Helly type a brief overview is given of topological approaches connected with the nerve of a family of convex sets in Euclidean space. Also surveyed are theorems of Helly type for common flat transversals, and results using the topology of the Grassmann manifold and of the canonical vector bundle over it are considered in detail.

Karasev, Roman N.

2008-12-01

312

Characterization of topological keystone species  

Microsoft Academic Search

An important question in the network representation of ecological systems is to determine how direct and indirect interactions between species determine the positional importance of species in the ecosystem. Here we present a quantitative analysis of the similarities and differences of six different topological centrality measures as indicators of keystone species in 17 food webs. These indicators account for local,

Ernesto Estrada

2007-01-01

313

A versatile zero ripple topology  

NASA Astrophysics Data System (ADS)

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.

Capel, A.; Spruyt, H.; Weinberg, A.; O'Sullivan, D.; Crausaz, A.

314

Topological protection of Majorana qubits  

NASA Astrophysics Data System (ADS)

We study the stability of the topological quantum computation proposals involving Majorana fermions against thermal fluctuations. We use a minimal realistic model of a spinless px+ipy superconductor and consider the effect of excited midgap states localized in the vortex core as well as of transitions above the bulk superconducting gap on the quasiparticle braiding, interferometry-based qubit readout schemes, and quantum coherence of the topological qubits. We find that thermal occupation of the midgap states does not affect adiabatic braiding operations but leads to a reduction in the visibility of the interferometry measurements. We also consider quantum decoherence of topological qubits at finite temperatures and calculate their decay rate which is associated with the change of the fermion parity and, as such, is exponentially suppressed at temperatures well below the bulk excitation gap. Our conclusion is that the Majorana-based topological quantum computing schemes are indeed protected by virtue of the quantum nonlocality of the stored information and the presence of the bulk superconducting gap.

Cheng, Meng; Lutchyn, Roman M.; Das Sarma, S.

2012-04-01

315

Topological Methods in Automorphic Forms.  

National Technical Information Service (NTIS)

The work supported by this grant resulted in the solution by Michael Hill, Michael Hopkins and Doug Ravenel of the 'Kervaire Invariant' problem. The Kervaire invariant problem was one of the longest standing open problems in algebraic topology, and its so...

M. J. Hopkins

2011-01-01

316

Planarity Criteria in Electromagnetic Topology.  

National Technical Information Service (NTIS)

The principal tool of the electromagnetic topologist is the interaction sequence diagram (ISD), which is the dual graph of the electromagnetic topology (EMT) of a system. One of the problems of working with the ISD is its complex appearance, in part due t...

R. S. Noss

1984-01-01

317

Planarity criteria in electromagnetic topology  

Microsoft Academic Search

The principal tool of the electromagnetic topologist is the interaction sequence diagram (ISD), which is the dual graph of the electromagnetic topology (EMT) of a system. One of the problems of working with the ISD is its complex appearance, in part due to multiple crossings of edges. This report presents some necessary and sufficient conditions for a graph to be

R. S. Noss

1984-01-01

318

Topological states of quantum matter  

Microsoft Academic Search

Electrons in graphene can be described by the relativistic Dirac equation for massless fermions and exhibit a host of unusual properties. The surfaces of certain band insulators---called topological insulators---can be described in a similar way, leading to an exotic metallic surface on an otherwise ``ordinary'' insulator.

Shou-Cheng Zhang

2008-01-01

319

Theory and applications of fluctuating-charge models  

NASA Astrophysics Data System (ADS)

Fluctuating-charge models are computationally efficient methods of treating polarization and charge-transfer phenomena in molecular mechanics and classical molecular dynamics simulations. They are also theoretically appealing as they are minimally parameterized, with parameters corresponding to the chemically important concepts of electronegativities and chemical hardness. However, they are known to overestimate charge transfer for widely separated atoms, leading to qualitative errors in the predicted charge distribution and exaggerated electrostatic properties. We present the charge transfer with polarization current equilibration (QTPIE) model, which solves this problem by introducing distance-dependent electronegativities. A graph-theoretic analysis of the topology of charge transfer allows us to relate the fundamental quantities of charge transfer back to the more familiar variables that represent atomic partial charges. This allows us to formulate a unified theoretical framework for fluctuating-charge models and topological charge descriptors. We also demonstrate the important role of charge screening effects in obtaining correct size extensivity in electrostatic properties. Analyzing the spatial symmetries of these properties allows us to shed light on the role of charge conservation in the electronegativity equalization process. Finally, we develop a water model for use in classical molecular dynamics simulations that is capable of treating both polarization and charge transfer phenomena.

Chen, Jiahao

320

Chern-Simons Theory and Topological Strings  

Microsoft Academic Search

We review the relation between Chern-Simons gauge theory and topological string theory on noncompact Calabi-Yau spaces. This relation has made possible to give an exact solution of topological string theory on these spaces to all orders in the string coupling constant. We focus on the construction of this solution, which is encoded in the topological vertex, and we emphasize the

Marcos Marino

2004-01-01

321

Topology on locally finite metric spaces  

Microsoft Academic Search

The necessity of a theory of General Topology and, most of all, of Algebraic Topology on locally finite metric spaces comes from many areas of research in both Applied and Pure Mathematics: Molecular Biology, Mathematical Chemistry, Computer Science, Topological Graph Theory and Metric Geometry. In this paper we propose the basic notions of such a theory and some applications: we

Valerio Capraro

2011-01-01

322

Robust Energy-Efficient Adder Topologies  

Microsoft Academic Search

In this paper we explore the relationship between adder topology and energy efficiency. We compare the energy-delay tradeoff curves of selected 32-bit adder topologies, to determine how architectural features and design techniques affect energy efficiency. Optimizing different adders for the supply and threshold voltages, and transistor sizing, we show that topologies with the least number of logic stages having an

Dinesh Patil; Omid Azizi; Mark Horowitz; Ron Ho; Rajesh Ananthraman

2007-01-01

323

Quantum Network Models and Topological Insulators  

NASA Astrophysics Data System (ADS)

We develop quantum network models for Anderson localization on the surface of weak topological insulators and topological crystalline insulators. These models represent systems in which delocalized helical electrons travel along contours that separate topologically distinct states. We perform numerical studies on random network systems to study the localization-delocalization transition in these materials.

Pate, Monica; Fu, Liang

2013-03-01

324

Evolving Neural Networks through Augmenting Topologies  

Microsoft Academic Search

An important question in neuroevolution is how to gain an advantage from evolving neural network topologies along with weights. We present a method, NeuroEvolu- tion 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 differ-

Kenneth O. Stanley; Risto Miikkulainen

2001-01-01

325

TOPOLOGY FOR 3D SPATIAL OBJECTS  

Microsoft Academic Search

Topology is one of the mechanisms to describe relationships between spatial objects and thus the basics for many spatial operations. In this paper, we present models that are built on the topological properties of the spatial objects. They are usually called topological models and are considered by many the best suited for complex spatial analysis (i.e. shortest path, line of

Siyka Zlatanova; Alias Abdul Rahman; Wenzhong Shi

326

Topological constraints on basic PWM converters  

NASA Astrophysics Data System (ADS)

A modeling and synthesis technique is introduced for single-ended ladder-structured dc-dc converter topologies. Topological constraints are derived that enhance the understanding of structural properties of converter circuits and clarify the roles of inductors and capacitors in various converters using magnetic or capacitive energy storage/transfer mechanisms. The exact duality relationships among the basic converter topologies are established.

Liu, Kwang-Hwa; Lee, Fred C.

327

An overview of the electromagnetic topology  

Microsoft Academic Search

A general description of the electromagnetic topology method is presented with emphasis on the topological diagram and interaction graph. Quantitative treatment of electromagnetic interactions is considered, and for a general case, a model physically representing the propagation channels of electromagnetic signals and their scattering in topological volumes is derived. A multiconductor transmission line network is analyzed, and simplifications and approximations

J. P. Parmantier; X. Ferrieres; J. P. Aparicio; J. C. Alliot

1991-01-01

328

Aspects of topological string theory  

NASA Astrophysics Data System (ADS)

Two aspects of the topological string and its applications are considered in this thesis. Firstly, non-perturbative contributions to the OSV conjecture relating four-dimensional extremal black holes and the closed topological string partition function are studied. A new technique is formulated for encapsulating these contributions for the case of a Calabi-Yau manifold constructed by fibering two line bundle over a torus, with the unexpected property that the resulting non-perturbative completion of the topological string partition function is such that the black hole partition function is equal to a product of a chiral and an anti-chiral function. This new approach is considered both in the context of the requirement of background independence for the topological string, and for more general Calabi-Yau manifolds. Secondly, this thesis provides a microscopic derivation of the open topological string holomorphic anomaly equations proposed by Walcher in arXiv:0705.4098 under the assumption that open string moduli do not contribute. In doing so, however, new anomalies are found for compact Calabi-Yau manifolds when the disk one-point functions (string to boundary amplitudes) are non-zero. These new anomalies introduce coupling to wrong moduli (complex structure moduli in A-model and Kahler moduli in B-model), and spoil the recursive structure of the holomorphic anomaly equations. For vanishing disk one-point functions, the open string holomorphic anomaly equations can be integrated to solve for amplitudes recursively, using a Feynman diagram approach, for which a proof is presented.

Cook, Paul L. H.

329

Clinical definitions of melioidosis.  

PubMed

Clinical definitions of melioidosis and inhalation-acquired melioidosis (Burkholderia pseudomallei infection) are described together with the evidence used to develop these definitions. Such definitions support accurate public health reporting, preparedness planning for deliberate B. pseudomallei release, design of experimental models, and categorization of naturally acquired melioidosis. PMID:23468355

Cheng, Allen C; Currie, Bart J; Dance, David A B; Funnell, Simon G P; Limmathurotsakul, Direk; Simpson, Andrew J H; Peacock, Sharon J

2013-03-01

330

Charging machine  

DOEpatents

A charging machine for loading fuel slugs into the process tubes of a nuclear reactor includes a tubular housing connected to the process tube, a charging trough connected to the other end of the tubular housing, a device for loading the charging trough with a group of fuel slugs, means for equalizing the coolant pressure in the charging trough with the pressure in the process tubes, means for pushing the group of fuel slugs into the process tube and a latch and a seal engaging the last object in the group of fuel slugs to prevent the fuel slugs from being ejected from the process tube when the pusher is removed and to prevent pressure liquid from entering the charging machine.

Medlin, John B. (Newark, DE)

1976-05-25

331

Holographic Wilson loops, dielectric interfaces, and topological insulators  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

332

Skyrmion quantum numbers and quantized pumping in two dimensional topological chiral magnets  

Microsoft Academic Search

We investigate the general conditions to achieve the adiabatic charge and spin polarizations and quantized pumping in 2D magnetic insulators possessing inhomogeneous spin structures. In particular, we focus on the chiral ferrimagnetic insulators which are generated via spontaneous symmetry breaking from correlated two dimensional topological insulators. Adiabatic deformation of the inhomogeneous spin structure generates the spin gauge flux, which induces

Bohm-Jung Yang; Naoto Nagaosa

2011-01-01

333

Half quantum spin Hall effect on the surface of weak topological insulators  

Microsoft Academic Search

We investigate interaction effects in three dimensional weak topological insulators (TI) with an even number of Dirac cones on the surface. We find that the surface states can be gapped by a surface charge density wave (CDW) order without breaking the time-reversal symmetry. In this sense, time reversal symmetry alone can not robustly protect the weak TI state in the

Chao-Xing Liu; Xiao-Liang Qi; Shou-Cheng Zhang

2011-01-01

334

40 CFR 98.430 - Definition of the source category.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

335

Chemistry explained by topology: an alternative approach.  

PubMed

Molecular topology can be considered an application of graph theory in which the molecular structure is characterized through a set of graph-theoretical descriptors called topological indices. Molecular topology has found applications in many different fields, particularly in biology, chemistry, and pharmacology. The first topological index was introduced by H. Wiener in 1947 [1]. Although its very first application was the prediction of the boiling points of the alkanes, the Wiener index has demonstrated since then a predictive capability far beyond that. Along with the Wiener index, in this paper we focus on a few pioneering topological indices, just to illustrate the connection between physicochemical properties and molecular connectivity. PMID:21375503

Galvez, Jorge; Villar, Vincent M; Galvez-Llompart, Maria; Amigó, José M

2011-05-01

336

Topological order following a quantum quench  

SciTech Connect

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

337

Role of dipole charges in black hole thermodynamics  

SciTech Connect

Modern derivations of the first law of black holes appear to show that the only charges that arise are monopole charges that can be obtained by surface integrals at infinity. However, the recently discovered five dimensional black ring solutions empirically satisfy a first law in which dipole charges appear. We resolve this contradiction and derive a general form of the first law for black rings. Dipole charges do appear together with a corresponding potential. We also include theories with Chern-Simons terms and generalize the first law to other horizon topologies and more generic local charges.

Copsey, Keith; Horowitz, Gary T. [Department of Physics, UCSB, Santa Barbara, California 93106 (United States)

2006-01-15

338

Majorana Single-Charge Transistor  

NASA Astrophysics Data System (ADS)

We study transport through a Coulomb blockaded topologically nontrivial superconducting wire (with Majorana end states) contacted by metallic leads. An exact formula for the current through this interacting Majorana single-charge transistor is derived in terms of wire spectral functions. A comprehensive picture follows from three different approaches. We find Coulomb oscillations with universal halving of the finite-temperature peak conductance under strong blockade conditions, where the valley conductance mainly comes from elastic cotunneling. The nonlinear conductance exhibits finite-voltage sidebands due to anomalous tunneling involving Cooper pair splitting.

Hützen, R.; Zazunov, A.; Braunecker, B.; Yeyati, A. Levy; Egger, R.

2012-10-01

339

Formation of a topological non-Fermi liquid in MnSi.  

PubMed

Fermi liquid theory provides a remarkably powerful framework for the description of the conduction electrons in metals and their ordering phenomena, such as superconductivity, ferromagnetism, and spin- and charge-density-wave order. A different class of ordering phenomena of great interest concerns spin configurations that are topologically protected, that is, their topology can be destroyed only by forcing the average magnetization locally to zero. Examples of such configurations are hedgehogs (points at which all spins are either pointing inwards or outwards) and vortices. A central question concerns the nature of the metallic state in the presence of such topologically distinct spin textures. Here we report a high-pressure study of the metallic state at the border of the skyrmion lattice in MnSi, which represents a new form of magnetic order composed of topologically non-trivial vortices. When long-range magnetic order is suppressed under pressure, the key characteristic of the skyrmion lattice--that is, the topological Hall signal due to the emergent magnetic flux associated with the topological winding--is unaffected in sign or magnitude and becomes an important characteristic of the metallic state. The regime of the topological Hall signal in temperature, pressure and magnetic field coincides thereby with the exceptionally extended regime of a pronounced non-Fermi-liquid resistivity. The observation of this topological Hall signal in the regime of the NFL resistivity suggests empirically that spin correlations with non-trivial topological character may drive a breakdown of Fermi liquid theory in pure metals. PMID:23636328

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

2013-05-01

340

Search for Gauge-Mediated SUSY Breaking Topologies at $\\\\sqrt{s}\\\\sim{189}$ GeV  

Microsoft Academic Search

Searches for topologies characteristic of Gauge Mediated SUSY Breaking models (GMSB) are performed by analysing 173.6 pb^-1 of data collected at Ecm = 188.6~GeV with the ALEPH detector.These topologies include acoplanar photons, non-pointing single photon, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and four leptons plus missing energy final states.No evidence for these

R Barate; D Décamp; P Ghez; C Goy; S Jézéquel; J P Lees; F Martin; E Merle; M N Minard; B Pietrzyk; R Alemany; S Bravo; M P Casado; M Chmeissani; J M Crespo; E Fernández; M Fernández-Bosman; L Garrido; E Graugès-Pous; A Juste; M Martínez; G Merino; R Miquel; L M Mir; P Morawitz; A Pacheco; I Riu; H Ruiz; A Colaleo; D Creanza; 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; G Boix; O L Buchmüller; M Cattaneo; F Cerutti; V Ciulli; G Davies; G Dissertori; H Drevermann; Roger W Forty; M Frank; F Gianotti; T C Greening; A W Halley; J B Hansen; J Harvey; P Janot; B Jost; M Kado; O Leroy; P Maley; P Mato; Adolf G Minten; A Moutoussi; F Ranjard; Luigi Rolandi; W D Schlatter; M Schmitt; O Schneider; P Spagnolo; W Tejessy; F Teubert; E Tournefier; Andrea Valassi; A E Wright; Ziad J Ajaltouni; F Badaud; G Chazelle; O Deschamps; S Dessagne; A Falvard; C Ferdi; P Gay; C Guicheney; P Henrard; J Jousset; B Michel; S Monteil; J C Montret; D Pallin; J M Pascolo; P Perret; F Podlyski; J D Hansen; J R Hansen; P H Hansen; B S Nilsson; B Rensch; A Wäänänen; G Daskalakis; A Kyriakis; C Markou; Errietta Simopoulou; Anna Vayaki; A Blondel; J C Brient; F P Machefert; A Rougé; M Swynghedauw; R Tanaka; H L Videau; E Focardi; G Parrini; K Zachariadou; M Corden; C H Georgiopoulos; A Antonelli; G Bencivenni; G Bologna; F Bossi; P Campana; G Capon; V Chiarella; P Laurelli; G Mannocchi; F Murtas; G P Murtas; L Passalacqua; M Pepé-Altarelli; M Chalmers; J Kennedy; J G Lynch; P Negus; V O'Shea; B Räven; D Smith; P Teixeira-Dias; A S Thompson; J J Ward; R J Cavanaugh; S Dhamotharan; C Geweniger; P Hanke; V Hepp; E E Kluge; G Leibenguth; A Putzer; K Tittel; S Werner; M Wunsch; R Beuselinck; David M Binnie; W Cameron; Peter J Dornan; M Girone; S M Goodsir; N Marinelli; E B Martin; J Nash; J Nowell; H Przysiezniak; A Sciabà; J K Sedgbeer; J C Thompson; E Thomson; M D Williams; V M Ghete; P Girtler; E Kneringer; D Kuhn; G Rudolph; C K Bowdery; P G Buck; G Ellis; A J Finch; F Foster; G Hughes; R W L Jones; N A Robertson; M Smizanska; M I Williams; I Giehl; F Hölldorfer; K Jakobs; K Kleinknecht; M Kröcker; A S Müller; H A Nürnberger; G Quast; B Renk; E Rohne; H G Sander; S Schmeling; H W Wachsmuth; C Zeitnitz; T Ziegler; A Bonissent; J Carr; P Coyle; A Ealet; D Fouchez; A Tilquin; M Aleppo; M Antonelli; S S Gilardoni; F Ragusa; V Büscher; H Dietl; G Ganis; K Hüttmann; G Lütjens; C Mannert; W Männer; H G Moser; S Schael; Ronald Settles; H C J Seywerd; H Stenzel; W Wiedenmann; G Wolf; P Azzurri; J Boucrot; O Callot; S Chen; M Davier; L Duflot; J F Grivaz; P Heusse; A Jacholkowska; J Lefrançois; L Serin; J J Veillet; I Videau; J B De Vivie de Régie; D Zerwas; G Bagliesi; T Boccali; C Bozzi; G Calderini; R Dell'Orso; I Ferrante; A Giassi; A Gregorio; F Ligabue; P S Marrocchesi; A Messineo; Fabrizio Palla; G Rizzo; G Sanguinetti; G Sguazzoni; Roberto Tenchini; A Venturi; P G Verdini; G A Blair; J Coles; G D Cowan; M G Green; D E Hutchcroft; L T Jones; T Medcalf; J A Strong; David R Botterill; R W Clifft; T R Edgecock; P R Norton; I R Tomalin; B Bloch-Devaux; P Colas; B Fabbro; G Faïf; E Lançon; M C Lemaire; E Locci; P Pérez; J Rander; J F Renardy; A Rosowsky; P Seager; A Trabelsi; B Tuchming; B Vallage; S N Black; J H Dann; C Loomis; H Y Kim; N P Konstantinidis; A M Litke; M A McNeil; 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 Misiejuk; G Prange; U Sieler; C Borean; G Giannini; B Gobbo; J Pütz; J E Rothberg; S R Wasserbaech; R W Williams; S R Armstrong; P Elmer; D P S Ferguson; Y Gao; S González; O J Hayes; H Hu; S Jin; J Kile; P A McNamara; J Nielsen; W Orejudos; Y B Pan; Y Saadi; I J Scott; J Walsh; J H Von Wimmersperg-Töller; Wu Sau Lan; X Wu; G Zobernig

1999-01-01

341

Topological interactions in spacetimes with thick line defects  

NASA Astrophysics Data System (ADS)

In this work we study the topologically induced electric self-energy and self-force on a long, straight, wire in two distinct, but similar, spacetimes: (i) the Gott-Hiscock thick cosmic string spacetime, and (ii) the spacetime of a continuous distribution of infinitely thin cosmic strings over a disk of finite radius. In each case we obtain the electric self-energy and self-force both in the internal and external regions of the defect distribution. The self-force is always repulsive, independently of the sign of the charge, and is maximum on the string’s surface, in both cases.

Moraes, Fernando; Carvalho, A. M.; Costa, Ismael V.; Oliveira, F. A.; Furtado, Claudio

2003-08-01

342

Topological Strings and Quantum Curves  

NASA Astrophysics Data System (ADS)

This thesis presents several new insights on the interface between mathematics and theoretical physics, with a central role for fermions on Riemann surfaces. First of all, the duality between Vafa-Witten theory and WZW models is embedded into string theory. Secondly, this model is generalized to a web of dualities connecting topological string theory and N=2 supersymmetric gauge theories to a configuration of D-branes that intersect over a Riemann surface. This description yields a new perspective on topological string theory in terms of a KP integrable system based on a quantum curve. Thirdly, this thesis describes a geometric analysis of wall-crossing in N=4 string theory. And lastly, it offers a novel approach to construct metastable vacua in type IIB string theory.

Hollands, Lotte

2009-11-01

343

Constraining topology in harmonic space  

SciTech Connect

We consider several ways to test for topology directly in harmonic space by comparing the measured a{sub lm} with the expected correlation matrices. Two tests are of a frequentist nature while we compute the Bayesian evidence as the third test. Using correlation matrices for cubic and slab-space tori, we study how these tests behave as a function of the minimal scale probed and as a function of the size of the Universe. We also apply them to different first-year Wilkinson microwave anisotropy probe CMB maps and confirm that the Universe is compatible with being infinitely big for the cases considered. We argue that there is an information theoretical limit (given by the Kullback-Leibler divergence) on the size of the topologies that can be detected.

Kunz, M. [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneva 4 (Switzerland); Astronomy Centre, SciTech, University of Sussex, Brighton BN1 9QJ (United Kingdom); Aghanim, N.; Forni, O. [Institut d'Astrophysique Spatiale (IAS), Batiment 121, F-91405, Orsay (France); Universite Paris-Sud 11 et CNRS, UMR 8617 (France); Cayon, L. [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, Indiana 47907-2036 (United States); Riazuelo, A.; Uzan, J. P. [Institut d'Astrophysique de Paris, Universite Pierre et Marie Curie, Paris VI, 98 bis bd Arago, 75014 Paris (France)

2006-01-15

344

Universe as a topological defect  

SciTech Connect

Four-dimensional Einstein's general relativity is shown to arise from a gauge theory for the conformal group, SO(4,2). The theory is constructed from a topological dimensional reduction of the six-dimensional Euler density integrated over a manifold with a four-dimensional topological defect. The resulting action is a four-dimensional theory defined by a gauged Wess-Zumino-Witten term. An ansatz is found which reduces the full set of field equations to those of Einstein's general relativity. When the same ansatz is replaced in the action, the gauged WZW term reduces to the Einstein-Hilbert action. Furthermore, the unique coupling constant in the action can be shown to take integer values if the fields are allowed to be analytically continued to complex values.

Anabalon, Andres [Centro de Estudios Cientificos (CECS), Casilla 1469 Valdivia (Chile); Departmento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Willison, Steven; Zanelli, Jorge [Centro de Estudios Cientificos (CECS), Casilla 1469 Valdivia (Chile)

2008-02-15

345

Topological structure of fractal squares  

NASA Astrophysics Data System (ADS)

Given an integer $n\\geq 2$ and a digit set ${\\mathcal D}\\subsetneq {0,1,...,n-1}^2$, there is a self-similar set $F \\subset {\\Bbb R}^2$ satisfying the set equation: $F=(F+{\\mathcal D})/n$. We call such $F$ a fractal square. By studying a periodic extension $H= F+ {\\mathbb Z}^2$, we classify $F$ into three types according to their topological properties. We also provide some simple criteria for such classification.

Lau, Ka–Sing; Luo, Jun Jason; Rao, Hui

2013-07-01

346

Topological strings on noncommutative manifolds  

Microsoft Academic Search

We identify a deformation of the N=2 supersymmetric sigma model on a Calabi-Yau manifold X which has the same effect on B-branes as a noncommutative deformation of X. We show that for hyperkahler X such deformations allow one to interpolate continuously between the A-model and the B-model. For generic values of the noncommutativity and the B-field, properties of the topologically

Anton Kapustin

2003-01-01

347

On topological F-theory  

Microsoft Academic Search

We consider the construction of a topological version of F-theory on a particular Spin(7) 8-manifold which is a Calabi-Yau 3-fold times a 2-torus. We write an action for this theory in eight dimensions and reduce it to lower dimensions using Hitchin's gradient flow method. A symmetry of the eight-dimensional theory which follows from modular transformations of the torus induces duality

Lilia Anguelova; Paul de Medeiros; Annamaria Sinkovics

2005-01-01

348

Topological Derivatives in Plane Elasticity  

Microsoft Academic Search

We present a method for construction of the topological derivatives in plane elasticity. It is assumed that a hole is created\\u000a in the subdomain of the elastic body which is filled out with isotropic material. The asymptotic analysis of elliptic boundary\\u000a value problems in singularly perturbed geometrical domains is used in order to derive the asymptotics of the shape functionals

Jan Sokolowski; Antoni Zochowski

2007-01-01

349

Dynamics, Spectral Geometry and Topology  

NASA Astrophysics Data System (ADS)

The paper is an informal report on joint work with Stefan Haller on Dynamics in relation with Topology and Spectral Geometry. By dynamics one means a smooth vector field on a closed smooth manifold; the elements of dynamics of concern are the rest points, instantons and closed trajectories. One discusses their counting in the case of a generic vector field which has some additional properties satisfied by a still very large class of vector fields.

Burghelea, Dan

2011-02-01

350

Dynamics, Spectral Geometry and Topology  

SciTech Connect

The paper is an informal report on joint work with Stefan Haller on Dynamics in relation with Topology and Spectral Geometry. By dynamics one means a smooth vector field on a closed smooth manifold; the elements of dynamics of concern are the rest points, instantons and closed trajectories. One discusses their counting in the case of a generic vector field which has some additional properties satisfied by a still very large class of vector fields.

Burghelea, Dan [Department of Mathematics, Ohio State University, 231 West 18th Avenue, Columbus, OH 43210 (United States)

2011-02-10

351

Topological coordinates for deformed nanotubes  

NASA Astrophysics Data System (ADS)

Starting from the topological arrangement of carbon atoms an algorithm is given for the construction of nanotube Cartesian coordinates. The final relaxed structures were obtained by a molecular mechanics calculation where the carbon-carbon interactions were supposed only between neighboring atoms of the initial tiling. In a given tiling we obtained toroidal or helical structures depending on the special position of the super cell parallelogram.

László, István; Rassat, André

2003-10-01

352

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

353

Charge Challenge  

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

354

A new class of (2 + 1)-dimensional topological superconductors with {Z}_8 topological classification  

NASA Astrophysics Data System (ADS)

The classification of topological states of matter depends on spatial dimension and symmetry class. For non-interacting topological insulators and superconductors, the topological classification is obtained systematically and non-trivial topological insulators are classified by either integer or Z2. The classification of interacting topological states of matter is much more complicated and only special cases are understood. In this paper we study a new class of topological superconductors in (2 + 1) dimensions which has time-reversal symmetry and a {Z}_2 spin conservation symmetry. We demonstrate that the superconductors in this class are classified by {Z}_8 when electron interaction is considered, while the classification is {Z} without interaction.

Qi, Xiao-Liang

2013-06-01

355

Topological patterns in metazoan evolution and development.  

PubMed

Topological patterns in the development and evolution of metazoa, from sponges to chordates, are considered by means of previously elaborated methodology, with the genus of the surface used as a topological invariant. By this means metazoan morphogenesis may be represented as topological modification(s) of the epithelial surfaces of an animal body. The animal body surface is an interface between an organism and its environment, and topological transformations of the body surface during metazoan development and evolution results in better distribution of flows to and from the external medium, regarded as the source of nutrients and oxygen and the sink of excreta, so ensuring greater metabolic intensity. In sponges and some Cnidaria, the increase of this genus up to high values and the shaping of topologically complicated fractal-like systems are evident. In most Bilateria, a stable topological pattern with a through digestive tube is formed, and the subsequent topological complications of other systems can also appear. The present paper provides a topological interpretation of some developmental events through the use of well-known mathematical concepts and theorems; the relationship between local and global orders in metazoan development, i.e., between local morphogenetic processes and integral developmental patterns, is established. Thus, this methodology reveals a "topological imperative": A certain set of topological rules that constrains and directs biological morphogenesis. PMID:16850353

Isaeva, Valeria; Presnov, Eugene; Chernyshev, Alexey

2006-07-19

356

Braiding statistics approach to symmetry-protected topological phases  

NASA Astrophysics Data System (ADS)

Symmetry-protected topological (SPT) phases can be thought of as generalizations of topological insulators. Just as topological insulators have robust gapless boundary modes protected by time reversal and charge conservation symmetry, SPT phases have boundary modes protected by more general symmetries. In this talk, I will describe a method for analyzing 2D SPT phases using braiding statistics. I will present this approach in the context of a simple example: a 2D Ising paramagnet with gapless edge modes protected by Ising symmetry. First, I will show that if the paramagnet is coupled to a Z2 gauge field, the resulting ?-flux excitations have different braiding statistics from that of a usual Ising paramagnet. This result provides a simple proof that the spin model belongs to a distinct quantum phase from a conventional paramagnet. Second, I will show that the ?-flux braiding statistics directly imply the existence of protected edge modes. I will argue that this analysis can be generalized to any 2D SPT phase with unitary symmetries.[4pt] [1] M. Levin and Z.-C. Gu, Phys. Rev. B 86, 115109 (2012)

Levin, Michael

2013-03-01

357

Finite temperature current densities and Bose-Einstein condensation in topologically nontrivial spaces  

NASA Astrophysics Data System (ADS)

We investigate the finite temperature expectation values of the charge and current densities for a complex scalar field with nonzero chemical potential in the background of a flat spacetime with spatial topology Rp×(S1)q. Along compact dimensions quasiperiodicity conditions with general phases are imposed on the field. In addition, we assume the presence of a constant gauge field which, due to the nontrivial topology of background space, leads to Aharonov-Bohm-like effects on the expectation values. By using the Abel-Plana-type summation formula and zeta function techniques, two different representations are provided for both the current and charge densities. The current density has nonzero components along the compact dimensions only and, in the absence of a gauge field, it vanishes for special cases of twisted and untwisted scalar fields. In the high-temperature limit, the current density and the topological part in the charge density are linear functions of the temperature. The Bose-Einstein condensation for a fixed value of the charge is discussed. The expression for the chemical potential is given in terms of the lengths of compact dimensions, temperature, and gauge field. It is shown that the parameters of the phase transition can be controlled by tuning the gauge field. The separate contributions to the charge and current densities coming from the Bose-Einstein condensate and from excited states are also investigated.

Bezerra de Mello, E. R.; Saharian, A. A.

2013-02-01

358

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

359

Soliton growth-signal transduction in topologically quantized T cells  

NASA Astrophysics Data System (ADS)

A model for growth-signal transduction of the T cell and its growth factor, interleukin-2, is presented. It is obtained as a generalization of the usual rate equation and is founded on the observation that a definite number of receptor occupations must take place in order to promote transition to the S phase and subsequent DNA replication. The generalized rate equation is identified as the equation of motion of a Lagrangian field theory of Ginzburg-Landau (Goldstone) type. However it is not an ad hoc model but is a microscopic theory of the interaction of interleukin-2 and its receptor. The topological quantum number of the model is related to the observed definite number of receptor occupations required to elicit growth-signal transduction. Individual receptor quanta, up to this limit, are subjected to a type of Bose condensation. This collective excitation constitutes the growth signal in the form of a topological kink soliton which is then launched by the next potential receptor occupation that makes the interaction repulsive. The model provides a possible long-absent explanation of the triggering mechanism for growth-signal transduction by means of the ambivalent interaction, which switches sign after a definite number of receptor occupations. Moreover, it offers an explanation of how Nature screens out fractional signals in the growth-signal-transduction process of T cells. Although the model is derived for assumed point-like cells and certain other restrictions, the obtained dose-response curves are in striking agreement with proliferation data from studies of both the leukemic T cell line MLA-144 from gibbon ape and normal human T cells in, and without, the presence of monoclonal anti-Tac antibodies.

Matsson, Leif

1993-09-01

360

Topological string theory from D-brane bound states  

NASA Astrophysics Data System (ADS)

We investigate several examples of BPS bound states of branes and their associated topological field theories, providing a window on the nonperturbative behavior of the topological string. First, we demonstrate the existence of a large N phase transition with respect to the 't Hooft coupling in q-deformed Yang-Mills theory on S2. The Ooguri-Strominger-Vafa [62] relation of this theory to topological strings on a local Calabi-Yau [7], motivates us to investigate the phase structure of the trivial chiral block at small Kahler moduli. Second, we develop means of computing exact degeneracies of BPS black holes on certain toric Calabi-Yau manifolds. We show that the gauge theory on the D4 branes wrapping ample divisors reduces to 2D q-deformed Yang-Mills theory on necklaces of P1's. At large N the D-brane partition function factorizes as a sum over squares of chiral blocks, the leading one of which is the topological closed string amplitude on the Calabi-Yau, in agreement with the conjecture of [62]. Third, we complete the analysis of the index of BPS bound states of D4, D2 and D0 branes in IIA theory compactified on toric Calabi-Yau, demonstrating that they are encoded in the combinatoric counting of restricted three dimensional partitions. We obtain a geometric realization of the torus invariant configurations as a crystal associated to the bound states of 0-branes at the singular points of a single D4 brane wrapping a high degree equivariant surface that carries the total D4 charge. The crystal picture provides a direct realization of the OSV relation to the square of the topological string partition function, which in toric Calabi-Yau is also equivalent to a theory of three dimensional partitions. Finally, we apply the techniques of the quiver representation of the derived category of coherent sheaves to discover a topological matrix model for the index of BPS states of D2 and D0 branes bound to a 6-brane. This enables us to examine the quantum foam [37] description of the A-model by embedding it in the full string theory.

Jafferis, Daniel Louis

361

High-definition television  

SciTech Connect

According to this report, high-definition television is the next generation in video technology. By increasing the number of scanning lines from 525 to over 1,000 high-definition television transmits an image that is wider than and twice as sharp as current television. This fact sheet contains information on 14 applications of high- definition television. Defense, medical, space exploration, and other uses are discussed. The report also presents the opinions of key industry officials on the effect that a high- definition television standard would have on potential applications of this technology.

Not Available

1990-01-01

362

Scattering theory of topological insulators and superconductors  

NASA Astrophysics Data System (ADS)

The topological invariant of a topological insulator (or superconductor) is given by the number of symmetry-protected edge states present at the Fermi level. Despite this fact, established expressions for the topological invariant require knowledge of all states below the Fermi energy. Here we propose a way to calculate the topological invariant employing solely its scattering matrix at the Fermi level without knowledge of the full spectrum. Since the approach based on scattering matrices requires much less information than the Hamiltonian-based approaches (surface versus bulk), it is numerically more efficient. In particular, is better suited for studying disordered systems. Moreover, it directly connects the topological invariant to transport properties potentially providing a new way to probe topological phases.

Fulga, I. C.; Hassler, F.; Akhmerov, A. R.

2012-04-01

363

Topological Crystalline Insulators in Transition Metal Oxides  

NASA Astrophysics Data System (ADS)

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 Pb1-xSnxTe, 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.

Kargarian, Mehdi; Fiete, Gregory A.

2013-04-01

364

Generalized quantization condition for topological insulators  

NASA Astrophysics Data System (ADS)

The topological magnetoelectric effect (TME) is the fundamental quantization effect for topological insulators in units of the fine structure constant, ?. In a recent study [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.166803 105, 166803 (2010)], a topological quantization condition of the TME was given under orthogonal incidence of the optical beam, in which the wavelength of the light or the thickness of the topological insulator film must be tuned to some commensurate values. This fine tuning is difficult to realize experimentally. In this article, we give manifestly SL(2,Z) covariant expressions for Kerr and Faraday angles at oblique incidence in a topological insulator thick film. We obtain a generalized quantization condition independent of material details, and propose a more easily realizable optical experiment, in which only the incidence angle is tuned to directly measure the topological quantization associated with the TME.

Lan, Yuanpei; Wan, Shaolong; Zhang, Shou-Cheng

2011-05-01

365

Topological Raman band in the carbon nanohorn.  

PubMed

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

2013-09-10

366

Topological Raman Band in the Carbon Nanohorn  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

367

Topological phase transitions in frustrated magnets  

NASA Astrophysics Data System (ADS)

The role of topological excitations in frustrated Heisenberg antiferromagnets between two and three spatial dimensions is considered. In particular, the antiferromagnetic Heisenberg model on a stacked triangular geometry with a finite number of layers is studied using Monte Carlo methods. A phase transition that is purely topological in nature occurs at a finite temperature for all film thicknesses. The results indicate that topological excitations are important for a complete understanding of the critical properties of the model between two and three dimensions.

Southern, B. W.; Peles, A.

2006-06-01

368

Topological indices for structure-activity correlations  

Microsoft Academic Search

This chapter deals with the description of the main topological indices and of related indicatros for molecular constitution\\u000a used in structure-activity relationships (QSAR). The topological indices are numerical quantities based on various invariants\\u000a or characteristics of molecular graphs. For the convenience of the discussion, these indices are classified according to their\\u000a logical derivation from topological invariants, rather than according to

Alexandru T. Balaban; Ioan Motoc; Danail Bonchev; Ovanes Mekenyan

369

Proximity effects in topological insulator heterostructures  

NASA Astrophysics Data System (ADS)

Topological insulators (TIs) are bulk insulators that possess robust helical conducting states along their interfaces with conventional insulators. A tremendous research effort has recently been devoted to Tl-based heterostructures, in which conventional proximity effects give rise to a series of exotic physical phenomena. This paper reviews our recent studies on the potential existence of topological proximity effects at the interface between a topological insulator and a normal insulator or other topologically trivial systems. Using first-principles approaches, we have realized the tunability of the vertical location of the topological helical state via intriguing dual-proximity effects. To further elucidate the control parameters of this effect, we have used the graphene-based heterostructures as prototypical systems to reveal a more complete phase diagram. On the application side of the topological helical states, we have presented a catalysis example, where the topological helical state plays an essential role in facilitating surface reactions by serving as an effective electron bath. These discoveries lay the foundation for accurate manipulation of the real space properties of the topological helical state in TI-based heterostructures and pave the way for realization of the salient functionality of topological insulators in future device applications.

Li, Xiao-Guang; Zhang, Gu-Feng; Wu, Guang-Fen; Chen, Hua; Dimitrie, Culcer; Zhang, Zhen-Yu

2013-09-01

370

Characterizing topological order in superconducting systems  

SciTech Connect

Two established frameworks account for the onset of a gap in a superconducting system: one is based on spontaneous symmetry breaking via the Anderson-Higgs-Kibble mechanism and the other is based on the recently developed paradigm of topological order. We show that, on manifolds with non trivial topology, both mechanisms yield a degeneracy of the ground state arising only from the incompressibility induced by the presence of a gap. We compute the topological entanglement entropy of a topological superconductor and argue that its measure allows to distinguish between the two mechanisms of generating a superconducting gap.

Diamantini, M. Cristina; Sodano, Pasquale [Dipartimento di Fisica, University of Perugia, via A. Pascoli, I-06123 Perugia (Italy) and Sezione INFN, Perugia (Italy)

2010-10-01

371

The Largest Topologically Cartesian Closed Categories of Domains as Topological Spaces  

Microsoft Academic Search

\\u000a A subcategory of the category CONT of continuous dcpos is called topologically cartesian closed(tcc for short) if it is closed with respect to finite topological products and function spaces equipped with the Isbell topology.\\u000a We prove that a full subcategory of CONT is tcc if and only if it is cartesian closed (by means of category) and the Isbell topology

Hui Kou; Maokang Luo

372

46 CFR 167.05-30 - Officer in Charge, Marine Inspection.  

Code of Federal Regulations, 2011 CFR

...2012-10-01 false Officer in Charge, Marine Inspection...GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Definitions § 167.05-30 Officer in Charge, Marine...

2012-10-01

373

46 CFR 50.10-10 - Officer in Charge, Marine Inspection, (OCMI).  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Officer in Charge, Marine Inspection, (OCMI). 50...HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING GENERAL PROVISIONS Definition...10-10 Officer in Charge, Marine Inspection, (OCMI). The...

2012-10-01

374

Thermodynamic optimization under topological constraints  

NASA Astrophysics Data System (ADS)

Computational thermodynamics is a powerful tool for solving practically important problems including the design of new materials and the analysis of their internal and external stability. This thesis contributes to computational thermodynamics by proposing several practical solutions to eliminate the so-called thermodynamic artifacts rather frequently found in thermodynamic assessments. First, a method is developed to eliminate the artifacts such as inverted miscibility gaps in the liquid phase at high-temperatures and reappearance of the liquid phase at low-temperatures or reappearance of a solid phase at elevated temperatures. This method is based on introducing a sufficiently dense mesh of knots (not related to experimental points utilized in the optimization) and ensuring that specific inequality conditions (topological constraints) governing the appearance of the phase diagram are satisfied in these knots. A feasibility of the approach proposed is exemplified by carrying out a re-optimization of the Mg-Sb system. Generally re-optimization of a system would take months to get the optimized results. Hence, to minimize time needed to get rid of artifacts, two different quick correction methods are developed to eliminate the unrealistic inverted miscibility gap in the liquid phase at elevated temperatures. Both methods employ optimization under topological constraints via controlling the sign of the second derivative of the Gibbs energy. Their applicability is exemplified on the Sn-Zr system. Also, a theoretical study was done on undulate phase boundaries. Usually, an inflection point on a phase boundary is considered as an unambiguous indication that one of the phases participating in the equilibrium is internally unstable, i.e., that it is prone to phase separation. It has been generally assumed that an inflection point may occur only if the thermodynamic model of this phase contains an excess Gibbs energy term. It is shown that in contrast to this assumption, inflection points on a phase boundary may appear when a pure solid component or a stoichiometric binary phase is in equilibrium with the ideal binary solution, which is internally stable. Finally, in addition to the theoretical analysis on undulate phase boundaries, a thermodynamic optimization is done on an imaginary A-B binary system subjected to topological constraints. Since, Thermo-Calc does not have the necessary tools to implement such topological constraints as d 2T/dx2>0 or d2T/dx2<0. A Fortran 90 program was developed to make use of these constraints.

Balakumar, Thevika

375

Geometry, topology, and string theory  

SciTech Connect

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

376

Topological deformation of isolated horizons  

SciTech Connect

We show that the Gauss-Bonnet term can have physical effects in four dimensions. Specifically, the entropy of a black hole acquires a correction term that is proportional to the Euler characteristic of the cross sections of the horizon. While this term is constant for a single black hole, it will be a nontrivial function for a system with dynamical topologies such as black-hole mergers: it is shown that for certain values of the Gauss-Bonnet parameter, the second law of black-hole mechanics can be violated.

Liko, Tomas [Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X7 (Canada)

2008-03-15

377

Entanglement Spectrum In Topological Phasess  

NASA Astrophysics Data System (ADS)

I will review the information that entanglement spectra give for a wide range of systems in condensed matter physics, such as fractional quantum hall effect, quantum spin chains, topological insulators, and disordered systems. I will also show how the entanglement spectrum is a unique tool to examine previously unknown many-body wavefunctions such as the ground-states of Fractional Chern Insulators (the results are based on a series of works performed in collaboration with N. Regnault, M. Hermanns, B. Estienne, Yangle Wu, Aris Alexandadinata, R. Thomale, A Sterdyniak, Z. Papic, T.L. Hughes, E. Prodan, D.P. Arovas, P. Bonderson)

Bernevig, B. Andrei

2012-02-01

378

Critical charge calculations for a bipolar SRAM array  

Microsoft Academic Search

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

379

Seclusion: Definitional interpretations  

Microsoft Academic Search

Seclusion of psychiatric patients means different things to different people and different organizations. Without a clear definitional framework misunderstanding can occur and comparative analyses are made difficult. In an attempt to establish universal themes 166 international articles and books on seclusion were reviewed and their definitional interpretations evaluated. The results highlight a wide disparity between studies and there is little

Tom Mason

1992-01-01

380

TEDS Report Definitions.  

National Technical Information Service (NTIS)

This report provides definitions for terms used in The TEDS Report, which presents findings from the Treatment Episode Data Set (TEDS). These definitions will also be available on the OAS website. In the future, The TEDS Report will refer readers to this ...

2008-01-01

381

Inland Wetland Definitions  

Microsoft Academic Search

This work is the result of a year-long study of the definitions of inland wetlands in which definitions from geology, hydrogeology, hydrology, pedology, biology, systems ecology, sociology, economics, political sciences, public health and law were considered. Of these, geology, hydrogeology, hydrology, biology, systems ecology and economics are discussed in detail in this report and used in writing a final theoretical

Michael W Lefor; William C Kennard

1977-01-01

382

Gravitational instantons as models for charged particle systems  

NASA Astrophysics Data System (ADS)

In this paper we propose ALF gravitational instantons of types A k and D k as models for charged particle systems. We calculate the charges of the two families. These are -( k + 1) for A k , which is proposed as a model for k + 1 electrons, and 2 - k for D k , which is proposed as a model for either a particle of charge +2 and k electrons or a proton and k - 1 electrons. Making use of preferred topological and metrical structures of the manifolds, namely metrically preferred representatives of middle dimension homology classes, we construct two different energy functionals which reproduce the Coulomb interaction energy for a system of charged particles.

Franchetti, Guido; Manton, Nicholas S.

2013-03-01

383

Topological structure of dictionary graphs  

NASA Astrophysics Data System (ADS)

We investigate the topological structure of the subgraphs of dictionary graphs constructed from WordNet and Moby thesaurus data. In the process of learning a foreign language, the learner knows only a subset of all words of the language, corresponding to a subgraph of a dictionary graph. When this subgraph grows with time, its topological properties change. We introduce the notion of the pseudocore and argue that the growth of the vocabulary roughly follows decreasing pseudocore numbers—that is, one first learns words with a high pseudocore number followed by smaller pseudocores. We also propose an alternative strategy for vocabulary growth, involving decreasing core numbers as opposed to pseudocore numbers. We find that as the core or pseudocore grows in size, the clustering coefficient first decreases, then reaches a minimum and starts increasing again. The minimum occurs when the vocabulary reaches a size between 103 and 104. A simple model exhibiting similar behavior is proposed. The model is based on a generalized geometric random graph. Possible implications for language learning are discussed.

Fuk?, Henryk; Krzemi?ski, Mark

2009-09-01

384

Topological determinants of protein folding  

NASA Astrophysics Data System (ADS)

The folding of many small proteins is kinetically a two-state process that represents overcoming the major free-energy barrier. A kinetic characteristic of a conformation, its probability to descend to the native state domain in the amount of time that represents a small fraction of total folding time, has been introduced to determine to which side of the free-energy barrier a conformation belongs. However, which features make a protein conformation on the folding pathway become committed to rapidly descending to the native state has been a mystery. Using two small, well characterized proteins, CI2 and C-Src SH3, we show how topological properties of protein conformations determine their kinetic ability to fold. We use a macroscopic measure of the protein contact network topology, the average graph connectivity, by constructing graphs that are based on the geometry of protein conformations. We find that the average connectivity is higher for conformations with a high folding probability than for those with a high probability to unfold. Other macroscopic measures of protein structural and energetic properties such as radius of gyration, rms distance, solvent-accessible surface area, contact order, and potential energy fail to serve as predictors of the probability of a given conformation to fold.

Dokholyan, Nikolay V.; Li, Lewyn; Ding, Feng; Shakhnovich, Eugene I.

2002-06-01

385

Photo-induced Chiral Edge Current in the 3D Topological Insulator Bi2Se3  

NASA Astrophysics Data System (ADS)

We perform scanning photocurrent (PC) microscopy measurements on the 3D topological insulator Bi2Se3, and observe spatially separated PC peaks of opposite sign, localized along the sample edges. The physics origin of this experimentally observed two-way PC is attributed to the chiral nature of the TI surface states. We show that the coupling between the optical field and the topological surface states yields a spin population imbalance along the edges of the surface, leading to the first order chiral edge charge current observed in the experiment. Further experimental observations of the weak polarization and strong temperature dependence of the PC agree with the theoretical predications. The PC fades away at a low temperature indicating a mean-free path of ˜ 3 ?m for topologically protected surface spins.

Roy, Ricky; Li, Mao; Aivazian, Grant; Yao, Wang; Cobden, David; Zhang, Chuanwei; Xu, Xiaodong

2012-02-01

386

Quantum analysis of Jackiw and Teitelboim's model for (1 + 1)D gravity and topological gauge theory  

NASA Astrophysics Data System (ADS)

We study the BRST quantization of the (1 + 1)-dimensional gravity model proposed by Jackiw and Teitelboim and also the topological gauge model which is equivalent to the gravity model at least classically. The gravity model quantized in the light-cone gauge is found to be a free theory with a nilpotent BRST charge. We show also that there exist twisted N = 2 superconformal algebras in the Jackiw-Teitelboim model as well as in the topological gauge model. We discuss the quantum equivalence between the gravity theory and the topological gauge theory. It is shown that these theories are indeed equivalent to each other in the light-cone gauge. Research supported in part by Sasakawa Scientific Research Grants of the Japan Science Society.

Terao, Haruhiko

1993-05-01

387

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

SciTech Connect

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, Yulin

2011-05-20

388

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

389

Network topologies: inference, modeling, and generation  

Microsoft Academic Search

Abstract, Accurate measurement, inference and mod-elling techniques are fundamental to Internet topology re-search. Spatial analysis of the Internet is needed to develop network planning, optimal routing algorithms and failure detection measures. A first step towards achieving such goals is the availability of network topologies at different levels of granularity, facilitating realistic simulations of new Internet systems.

Hamed Haddadi; Miguel Rio; Gianluca Iannaccone; ANDREW MOORE; Richard Mortier

2008-01-01

390

TOPOLOGICAL ELECTROMAGNETISM FOR QUARKS AND LEPTONS  

SciTech Connect

As outgrowth of a topological bootstrap theory of strong interactions and precursor to a corresponding theory of weak interactions, we propose a representation of electromagnetic interactions for "elementary" hadrons and leptons through combinatorial topology. The representation supports the prediction of four lepton doublets.

Chew, G.F.; Poenaru, V.

1980-04-01

391

TOPOLOGICAL THEORY OF HADRONS II: BARYONS  

SciTech Connect

The first paper of this series described a method for incorporating spin into the meson sector of the topological theory of hadrons. This second paper extends the theory to all hadrons. It also incorporates into the covariant S-matrix topological framework the group-theoretic properties of the constituent quark model.

Stapp, Henry P.

1981-10-01

392

Topological theory of hadrons. II. Baryons  

SciTech Connect

The first paper of this series described a method for incorporating spin into the meson sector of the topological theory of hadrons. This second paper extends the theory to all hadrons. It also incorporates into the covariant S-matrix topological framework the group-theoretic properties of the constituent-quark model.

Stapp, H.P.

1983-05-15

393

A topological theory of the electromagnetic field  

Microsoft Academic Search

It is shown that Maxwell equations in vacuum derive from an underlying topological structure given by a scalar field ? which represents a map S3×R?S2 and determines the electromagnetic field through a certain transformation, which also linearizes the highly nonlinear field equations to the Maxwell equations. As a consequence, Maxwell equations in vacuum have topological solutions, characterized by a Hopf

Antonio F. Rañada

1989-01-01

394

A topological theory of the electromagnetic field  

Microsoft Academic Search

It is shown that Maxwell equations in vacuum derive from an underlying topological structure given by a scalar field varphi which represents a map S 3× R--> S 2 and determines the electromagnetic field through a certain transformation, which also linearizes the highly nonlinear field equations to the Maxwell equations. As a consequence, Maxwell equations in vacuum have topological solutions,

Antonio F. Rañada

1989-01-01

395

Topological Analysis of Network Attack Vulnerability  

Microsoft Academic Search

To understand overall vulnerability to network attack, one must consider attacker exploits not just in isolation, but also in combination. That is, one must analyze how low-level vulnerabilities can be combined to achieve high-level attack goals. In this chapter, we describe a tool that implements an integrated, topological approach to network vulnerability analysis. Our Topological Vulnerability Analysis (TVA) tool automates

Sushil Jajodia; Steven Noel; Brian O’Berry

396

From Contour Similarity to Motivic Topologies  

Microsoft Academic Search

This paper is devoted to a qualitative and quantitative study of topological spaces built on premotif collections of musical scores. These motivic topologies are related to similarity concepts in the American music set theory. Through shapes, imitations and gestalts, and similarity relations between any two shapes, we obtain a motivic hierarchy of a score. This model of motivic analysis is

Chantal Buteau; Guerino Mazzola

2000-01-01

397

QCD as a topologically ordered system  

NASA Astrophysics Data System (ADS)

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 problem where the would be ?? 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 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.

Zhitnitsky, Ariel R.

2013-09-01

398

Topologies on the Algebra of Test Functions.  

National Technical Information Service (NTIS)

The algebraical structure of deltasub(THETA) (tensor algebra over the Schwartz space) defines two topologies, tausub(P)tausub(THETA). Some properties are studied of the locally convex topologies situated between tausub(P) and tausub(THETA). A lot of topol...

G. Hofmann

1977-01-01

399

Two Examples in Linear Topological Spaces.  

National Technical Information Service (NTIS)

This note first gives examples of B-complete linear topological spaces, and shows that neither the closed graph theorem nor the open mapping theorem holds for linear mappings from such a space to itself. It then looks at Hausdorff linear topological space...

S. O. Iyahen

1985-01-01

400

Topological insulators and superconductors from string theory  

Microsoft Academic Search

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,

Tadashi Takayanagi; Shinsei Ryu

2010-01-01

401

Topological amplitudes in heterotic superstring theory.  

National Technical Information Service (NTIS)

We show that certain heterotic string amplitudes are given in terms of correlators of the twisted topological (2,0) SCFT, corresponding to the internal sector of the N = 1 spacetime supersymmetric background. The genus g topological partition function F(s...

I. Antoniadis T. R. Taylor E. Gava K. S. Narain

1996-01-01

402

Visualizing Non-Linear Vector Field Topology  

Microsoft Academic Search

We present our results on the visualization of non-linear vector eld topology. The underlying mathemat- ics is done in Cliord algebra, a system describing geometry by extending the usual vector space by a multiplication of vectors. We started with the observation that all known algorithms for vector eld topology are based on piecewise linear or bilinear approximation and that these

Gerik Scheuermann; Heinz Kr; Martin Menzel; Alyn P. Rockwood

403

New topology for Class E amplifiers  

Microsoft Academic Search

A Class E RF amplifier, which can operate into any load conditions without need for other additional circuitry to protect transistors, is introduced. This is provided by the new topology, which is called an inductive clamp. Our topology incorporates inductive clamp circuitry to the basic Class E amplifier circuit and it has all the benefits of Class E amplifiers. Additionally,

A. Eroglu; D. Lincoln; A. Radomski; Y. Chawla

2007-01-01

404

A general circuit topology of multilevel inverter  

Microsoft Academic Search

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

405

Robust optical delay lines with topological protection  

Microsoft Academic Search

Phenomena associated with the topological properties of physical systems can be naturally robust against perturbations. This robustness is exemplified by quantized conductance and edge state transport in the quantum Hall and quantum spin Hall effects. Here we show how exploiting topological properties of optical systems can be used to improve photonic devices. We demonstrate how quantum spin Hall Hamiltonians can

Eugene A. Demler; Mikhail D. Lukin; Jacob M. Taylor; Mohammad Hafezi

2011-01-01

406

T-snakes: Topology adaptive snakes  

Microsoft Academic Search

We present a new class of deformable contours (snakes) and apply them to the segmentation of medical images. Our snakes are defined in terms of an affine cell image decomposition (ACID). The 'snakes in ACID' framework significantly extends conventional snakes, enabling topological flexibility among other features. The resulting topology adaptive snakes, or 'T-snakes', can be used to segment some of

Tim McInerney; Demetri Terzopoulos

1999-01-01

407

Medical image segmentation using topologically adaptable surfaces  

Microsoft Academic Search

. Efficient and powerful topologically adaptable deformablesurfaces can be created by embedding and defining discrete deformablesurface models in terms of an Affine Cell Decomposition (ACD) framework.The ACD framework, combined with a novel and original reparameterizationalgorithm, creates a simple but elegant mechanism formultiresolution deformable curve, surface, and solid models to "flow" or"grow" into objects with complex geometries and topologies, and adapttheir

Tim Mcinerney; Demetri Terzopoulos

1997-01-01

408

License plate recognition using topology structure features  

Microsoft Academic Search

License plate recognition (LPR) has been widely used for intelligent transportation systems. In this paper, we present a novel license plate recognition method using characters' topology structure and feature-weighted template matching. As the topology skeleton feature is the most radical and intrinsic characteristics, our proposed algorithm is robust against license tilt and noise influence. First, detect license and correct skew

Lu Liu; Hongjiang Yu; Kehe Cai; Jia Wang

2011-01-01

409

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

410

Topological Proximity Effects in Graphene Nanoribbon Heterostructures  

NASA Astrophysics Data System (ADS)

Topological insulators (TI) are bulk insulators that possess robust chiral conducting states along their interfaces with normal insulators. A tremendous research effort has recently been devoted to TI-based heterostructures, in which conventional proximity effects give rise to many exotic physical phenomena. Here we establish the potential existence of ``topological proximity effect'' at the interface of a topological graphene nanoribbon (GNR) and a normal GNR. Specifically, we show that the location of the topological edge states exhibits versatile tunability as a function of the interface orientation, as well as the strengths of the interface coupling and spin-orbit coupling in the normal GNR. For zigzag and bearded GNRs, the topological edge state can be tuned to be either at the interface or outer edge of the normal ribbon. For armchair GNR, the potential location of the topological edge state can be further enriched to be at the edge of or within the normal ribbon, at the interface, or diving into the topological GNR. We also discuss potential experimental realization of the predicted topological proximity effects, which may pave the way for integrating the salient functionality of TI and graphene in future device applications.

Zhang, Gufeng; Li, Xiaoguang; Wu, Guangfen; Wang, Jie; Culcer, Dimitrie; Kaxiras, Efthimios; Zhang, Zhenyu

2013-03-01

411

Electromagnetic topology: Characterization of internal electromagnetic coupling  

Microsoft Academic Search

The main principles are presented of a method dealing with the resolution of electromagnetic internal problems: Electromagnetic Topology. A very interesting way is to generalize the multiconductor transmission line network theory to the basic equation of the Electromagnetic Topology: the BLT equation. This generalization is illustrated by the treatment of an aperture as a four port junction. Analytical and experimental

J. P. Parmantier; J. P. Aparicio; F. Faure

1991-01-01

412

Electromagnetic topology - Characterization of internal electromagnetic coupling  

Microsoft Academic Search

This paper presents the main principles of a method dealing with the resolution of electromagnetic internal problems: electromagnetic topology. A very interesting way is to generalize the multiconductor transmission line network theory to the basic equation of electromagnetic topology. This generalization is illustrated by the treatment of an aperture as a four port junction. Analytical and experimental derivations of the

J. P. Parmantier; J. P. Aparicio; F. Faure

1991-01-01

413

On compactness of induced I( L)-fuzzy topological spaces  

Microsoft Academic Search

The induced I(L)-fuzzy topological spaces for L-fuzzy topological spaces introduced by Wang Geping is a kind of important fuzzy topological space. In this paper, the author studies the fuzzy compactness of induced I(L)-fuzzy topological spaces. Some available relations between molecular nets of an L-fuzzy topological space and that of its induced I(L)-fuzzy topological space are firstly presented. By using these

Yixiang Chen

1997-01-01

414

Topological Rényi Entropy after a Quantum Quench  

NASA Astrophysics Data System (ADS)

We present an analytical study on the resilience of topological order after a quantum quench. The system is initially prepared in the ground state of the toric-code model, and then quenched by switching on an external magnetic field. During the subsequent time evolution, the variation in topological order is detected via the topological Rényi entropy of order 2. We consider two different quenches: the first one has an exact solution, while the second one requires perturbation theory. In both cases, we find that the long-term time average of the topological Rényi entropy in the thermodynamic limit is the same as its initial value. Based on our results, we argue that topological order is resilient against a wide range of quenches.

Halász, Gábor B.; Hamma, Alioscia

2013-04-01

415

Topological Models for Protein-DNA Interaction  

NASA Astrophysics Data System (ADS)

Cellular DNA is a long, thread-like molecule with remarkably complex topology. Enzymes which manipulate the geometry and topology of cellular DNA perform many important cellular processes (including segregation of daughter chromosomes, gene regulation, DNA repair, and generation of antibody diversity). Some enzymes pass DNA through itself via enzyme-bridged transient breaks in the DNA; other enzymes break the DNA apart and reconnect it to different ends. In the topological approach to enzymology, circular DNA is incubated with an enzyme, producing an enzyme signature in the form of DNA knots and links. By observing the changes in DNA geometry (supercoiling) and topology (knotting and linking) due to enzyme action, the enzyme binding and mechanism can often be characterized. This lecture will discuss topological models for DNA strand passage and exchange.

Witt Sumners, De

2003-03-01

416

Optical properties for topological insulators with metamaterials  

NASA Astrophysics Data System (ADS)

The two fields of topological insulators and metamaterials are independent. In this Letter, we firstly investigate the Fresnel coefficients for the reflected and refracted electromagnetic waves across the interface between topological insulators and left-handed metamaterials. Then, we derive the exact analytic expressions for Kerr and Faraday rotations. By way of multiple reflections method, we demonstrate that perfect lens with left-handed metamaterials slab and topological insulators can be designed. On the other hand, the processes of reflection and refraction are investigated in the case of topological insulator and chiral metamaterial. Then, we give the reflection and transmission coefficients of topological insulator with a chiral medium slab. Lastly, the potential applications of these results are discussed.

Zuo, Zheng-Wei; Ling, Dong-Bo; Sheng, L.; Xing, D. Y.

2013-11-01

417

Topological constraints in nucleic acid hybridization kinetics  

PubMed Central

A theoretical examination of kinetic mechanisms for forming knots and links in nucleic acid structures suggests that molecules involving base pairs between loops are likely to become topologically trapped in persistent frustrated states through the mechanism of ‘helix-driven wrapping’. Augmentation of the state space to include both secondary structure and topology in describing the free energy landscape illustrates the potential for topological effects to influence the kinetics and function of nucleic acid strands. An experimental study of metastable complementary ‘kissing hairpins’ demonstrates that the topological constraint of zero linking number between the loops effectively prevents conversion to the minimum free energy helical state. Introduction of short catalyst strands that break the topological constraint causes rapid conversion to full duplex.

Bois, Justin S.; Venkataraman, Suvir; Choi, Harry M. T.; Spakowitz, Andrew J.; Wang, Zhen-Gang; Pierce, Niles A.

2005-01-01

418

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

419

The topology of asymptotically locally flat gravitational instantons  

NASA Astrophysics Data System (ADS)

In this Letter we demonstrate that the intersection form of the Hausel Hunsicker Mazzeo compactification of a four-dimensional ALF gravitational instanton is definite and diagonalizable over the integers if one of the Kähler forms of the hyper-Kähler gravitational instanton metric is exact. This leads to their topological classification. The proof exploits the relationship between L cohomology and U(1) anti-instantons over gravitational instantons recognized by Hitchin. We then interprete these as reducible points in a singular SU(2) anti-instanton moduli space over the compactification leading to the identification of its intersection form. This observation on the intersection form might be a useful tool in the full geometric classification of various asymptotically locally flat gravitational instantons.

Etesi, Gábor

2006-10-01

420

Digital topology of multicolor images  

NASA Astrophysics Data System (ADS)

In this paper a solution is presented which guarantees we avoid the connectivity paradoxes related to the Jordan Curve Theorem for all multicolor images. Only one connectedness relation is used for the entire digital image. We use only 4-connectedness (which is equivalent to 8-connectedness) for every component of every color. The idea is not to allow a certain `critical configuration' which can be detected locally to occur in digital pictures; such pictures are called `well-composed.' Well-composed images have very nice topological properties. For example, the Jordan Curve Theorem holds and the Euler characteristic is locally computable. This implies that properties of algorithms used in computer vision can be stated and proved in a clear way, and that the algorithms themselves become simpler and faster.

Latecki, Longin

1994-10-01

421

Cycloid crystals by topology change  

NASA Astrophysics Data System (ADS)

A cycloid, formerly known as a roulette, is a curve arising from a point on a circumference that rolls on its plane over a fixed straight line, and the cycloid shape is observed in many natural objects formed under a constraint. Here we report the discovery of cycloid-shaped crystals of TaSe3 obtained via the “topology-change surgery” of thin ring-shaped crystals. We cut the ring-shaped crystals with a focused ion beam. After being cut, they formed a cycloidal shape similar to Cyclotron trajectories of electrons under magnetic and electric fields. We conclude that the inhomogeneous curvature distribution minimizes the bending energy and shear modulation, which corresponds to our shear-less model.

Matsuura, T.; Matsuyama, T.; Tanda, S.

2013-05-01

422

Definition of the Mesoscale  

NSDL National Science Digital Library

This module provides a working definition of mesoscale meteorology. The module briefly touches on many topics crucial to forecasting mesoscale weather phenomena, such as non-hydrostatic processes, the importance of terrain, NWP model resolution, and impact on sensible weather.

Spangler, Tim

1999-05-01

423

1 Purpose and Definitions  

Center for Food Safety and Applied Nutrition (CFSAN)

Text Version... This Code establishes definitions; sets standards for ... (b) A FOOD ingredient that contains protein derived from a ... (1) Any domesticated bird (chickens ... More results from www.fda.gov/downloads/food/guidanceregulation

424

Genomic definition of species  

SciTech Connect

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

Crkvenjakov, R.; Drmanac, R.

1991-07-01

425

Force-Momentum Radiation from Relativistic Charged Particles  

NASA Astrophysics Data System (ADS)

Two alternative definitions of density of angular momentum of electromagnetic field by Ivanenko-Sokolov and by Teitelboim et al. are discussed. It is shown that both definitions give identical integral characteristics of radiation for an arbitrary moving relativistic charge. The total powers of orbital angular momentum and spin momentum of radiation are deduced and the exactly physical interpretation obtained.

Bordovitsyn, V. A.; Nemchenko, E. A.

2011-10-01

426

Life without definitions  

Microsoft Academic Search

The question ‘what is life?’ has long been a source of philosophical debate and in recent years has taken on increasing scientific\\u000a importance. The most popular approach among both philosophers and scientists for answering this question is to provide a “definition”\\u000a of life. In this article I explore a variety of different definitional approaches, both traditional and non-traditional, that\\u000a have

Carol E. Cleland

427

Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3  

NASA Astrophysics Data System (ADS)

The three dimensional strong topological insulator (STI) is a new phase of electronic matter which is distinct from ordinary insulators in that it supports on its surface a conducting two-dimensional surface state whose existence is guaranteed by topology. I will discuss experiments on the STI material Bi2Se3, which has a bulk bandgap of 300 meV, much greater than room temperature, and a single topological surface state with a massless Dirac dispersion. Field effect transistors consisting of thin (3-20 nm) Bi2Se3 are fabricated from mechanically exfoliated from single crystals, and electrochemical and/or chemical gating methods are used to move the Fermi energy into the bulk bandgap, revealing the ambipolar gapless nature of transport in the Bi2Se3 surface states. The minimum conductivity of the topological surface state is understood within the self-consistent theory of Dirac electrons in the presence of charged impurities. The intrinsic finite-temperature resistivity of the topological surface state due to electron-acoustic phonon scattering is measured to be ˜60 times larger than that of graphene largely due to the smaller Fermi and sound velocities in Bi2Se3, which will have implications for topological electronic devices operating at room temperature. As samples are made thinner, coherent coupling of the top and bottom topological surfaces is observed through the magnitude of the weak anti-localization correction to the conductivity, and, in the thinnest Bi2Se3 samples (˜ 3 nm), in thermally-activated conductivity reflecting the opening of a bandgap.

Fuhrer, Michael

2013-03-01

428

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

SciTech Connect

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

429

Simplified topological invariants for interacting insulators and superconductors  

NASA Astrophysics Data System (ADS)

Topological invariants are precise mathematical tools characterizing the topological properties of topological insulators and superconductors. While many simple and powerful topological invariants for noninteracting insulators and superconductors have been well established, the topological invariants for interacting systems are much less investigated, despite of their great importance in studies of topological states in interacting systems. In this talk I will report some recent progress in the search of topological invariants for interacting systems. I will show that topological invariants defined in terms of zero frequency Green's function are precise and convenient tools for interacting topological insulators and superconductors. They have much simpler forms compared to earlier interacting topological invariants, and have the potential to facilitate discoveries of new topological insulators with strong electron-electron interaction.

Wang, Zhong

2013-03-01

430

Topological Fractionation of Resting-State Networks  

PubMed Central

Exploring topological properties of human brain network has become an exciting topic in neuroscience research. Large-scale structural and functional brain networks both exhibit a small-world topology, which is evidence for global and local parallel information processing. Meanwhile, resting state networks (RSNs) underlying specific biological functions have provided insights into how intrinsic functional architecture influences cognitive and perceptual information processing. However, topological properties of single RSNs remain poorly understood. Here, we have two hypotheses: i) each RSN also has optimized small-world architecture; ii) topological properties of RSNs related to perceptual and higher cognitive processes are different. To test these hypotheses, we investigated the topological properties of the default-mode, dorsal attention, central-executive, somato-motor, visual and auditory networks derived from resting-state functional magnetic resonance imaging (fMRI). We found small-world topology in each RSN. Furthermore, small-world properties of cognitive networks were higher than those of perceptual networks. Our findings are the first to demonstrate a topological fractionation between perceptual and higher cognitive networks. Our approach may be useful for clinical research, especially for diseases that show selective abnormal connectivity in specific brain networks.

Zhang, Zhiqiang; Mantini, Dante; Xu, Qiang; Wu, Guo-Rong; Lu, Guangming; Chen, Huafu

2011-01-01

431

Global topological dominance in the left hemisphere  

PubMed Central

A series of experiments with right-handers demonstrated that the left hemisphere (LH) is reliably and consistently superior to the right hemisphere (RH) for global topological perception. These experiments generalized the topological account of lateralization to different kinds of topological properties (including holes, inside/outside relation, and “presence vs. absence”) in comparison with a broad spectrum of geometric properties, including orientation, distance, size, mirror-symmetry, parallelism, collinearity, etc. The stimuli and paradigms used were also designed to prevent subjects from using various nontopological properties in performing the tasks of topological discrimination. Furthermore, task factors commonly considered in the study of hemispheric asymmetry, such as response latency vs. accuracy, vertical vs. horizontal presentation, detection vs. recognition, and simultaneous vs. sequential judgment, were manipulated to not be confounding factors. Moreover, left-handed subjects were tested and showed the right lateralization of topological perception, in the opposite direction of lateralization compared with right-handers. In addition, the functional magnetic resonance imaging measure revealed that only a region in the left temporal gyrus was consistently more activated across subjects in the task of topological discrimination, consistent with the behavioral results. In summary, the global topological dominance in the LH is well supported by the converging evidence from the variety of paradigms and techniques, and it suggests a unified solution to the current major controversies on visual lateralization.

Wang, Bo; Zhou, Tian Gang; Zhuo, Yan; Chen, Lin

2007-01-01

432

Topological phases: An expedition off lattice  

SciTech Connect

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

433

Topological signatures in CMB temperature anisotropy maps  

SciTech Connect

We propose an alternative formalism to simulate cosmic microwave background (CMB) temperature maps in {lambda}CDM universes with nontrivial spatial topologies. This formalism avoids the need to explicitly compute the eigenmodes of the Laplacian operator in the spatial sections. Instead, the covariance matrix of the coefficients of the spherical harmonic decomposition of the temperature anisotropies is expressed in terms of the elements of the covering group of the space. We obtain a decomposition of the correlation matrix that isolates the topological contribution to the CMB temperature anisotropies out of the simply connected contribution. A further decomposition of the topological signature of the correlation matrix for an arbitrary topology allows us to compute it in terms of correlation matrices corresponding to simpler topologies, for which closed quadrature formulas might be derived. We also use this decomposition to show that CMB temperature maps of (not too large) multiply connected universes must show ''patterns of alignment,'' and propose a method to look for these patterns, thus opening the door to the development of new methods for detecting the topology of our Universe even when the injectivity radius of space is slightly larger than the radius of the last scattering surface. We illustrate all these features with the simplest examples, those of flat homogeneous manifolds, i.e., tori, with special attention given to the cylinder, i.e., T{sup 1} topology.

Hipolito-Ricaldi, W.S.; Gomero, G.I. [Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Pamplona 145 Sao Paulo, SP 01405-900 (Brazil)

2005-11-15

434

Get Charged!  

NSDL National Science Digital Library

Students are introduced to the idea of electrical energy. They learn about the relationships between charge, voltage, current and resistance. They discover that electrical energy is the form of energy that powers most of their household appliances and toys. In the associated activities, students learn how a circuit works and test materials to see if they conduct electricity. Building upon a general understanding of electrical energy, they design their own potato power experiment. In two literacy activities, students learn about the electrical power grid and blackouts.

Integrated Teaching And Learning Program

435

TRW CHARGED DROPLET SCRUBBER CORROSION STUDIES  

EPA Science Inventory

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

436

The biHermitian topological sigma model  

NASA Astrophysics Data System (ADS)

BiHermitian geometry, discovered long ago by Gates, Hull and Rocek, is the most general sigma model target space geometry allowing for (2,2) world sheet supersymmetry. By using the twisting procedure proposed by Kapustin and Li, we work out the type A and B topological sigma models for a general biHermtian target space, we write down the explicit expression of the sigma model's action and BRST transformations and present a computation of the topological gauge fermion and the topological action.

Zucchini, Roberto

2006-12-01

437

Does the topology of space fluctuate?  

NASA Astrophysics Data System (ADS)

Evidence is presented that the singularities induced in causal Lorentzian spacetimes by changes in 3-space topology give rise to infinite particle and energy production under reasonable laws of quantum field propagation. In the case of the gravitational field, if 3-space is compact the total energy must vanish. A topological transition therefore induces a violent collapse that effectively aborts the transition, since the collapse mode is the only mode carrying the negative energy needed to compensate the associated infinite energy production. The existence of the Hamiltonian constraint of general relativity suggests that topological stability is a local property of the quantum theory that is maintained even when 3-space is noncompact.

Anderson, Arlen; Dewitt, Bryce

1986-02-01

438

Interacting topological phases and modular invariance  

NASA Astrophysics Data System (ADS)

We discuss (2+1)-dimensional topological superconductors with Nf left- and right-moving Majorana edge modes and a Z2×Z2 symmetry. In the absence of interactions, these phases are distinguished by an integral topological invariant Nf. With interactions, the edge state in the case of Nf=8 is unstable against interactions, and a Z2×Z2 invariant mass gap can be generated dynamically. We show that this phenomenon is closely related to the modular invariance of type II superstring theory. More generally, we show that the global gravitational anomaly of the nonchiral Majorana edge states is the physical manifestation of the bulk topological superconductors classified by Z8.

Ryu, Shinsei; Zhang, Shou-Cheng

2012-06-01

439

Charged Particle Environment Definition for NGST: Model Development.  

National Technical Information Service (NTIS)

NGST will operate in a halo orbit about the L2 point, 1.5 million km from the Earth, where the spacecraft will periodically travel through the magnetotail region. There are a number of tools available to calculate the high energy, ionizing radiation parti...

W. C. Blackwell J. I. Minow S. W. Evans D. M. Hardage R. M. Suggs

2000-01-01

440

Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator  

Microsoft Academic Search

Breaking the time-reversal symmetry of a topological insulator (TI) by ferromagnetism can induce exotic magnetoelectric phenomena such as quantized anomalous Hall (QAH) effect. Experimental observation of QAH effect in a magnetically doped TI requires ferromagnetism not relying on the charge carriers. We have realized the ferromagnetism independent of both polarity and density of carriers in Cr-doped BixSb2-xTe3 thin films grown

Cui-Zu Chang; Jin-Song Zhang; Min-Hao Liu; Zuo-Cheng Zhang; Xiao Feng; Kang Li; Li-Li Wang; Xi Chen; Xi Dai; Zhong Fang; Xiao-Liang Qi; Shou-Cheng Zhang; Yayu Wang; Ke He; Xu-Cun Ma; Qi-Kun Xue

2011-01-01

441

Tunable multifunctional topological insulators in ternary Heusler compounds.  

PubMed

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

2010-05-30

442

Testing atypical depression definitions.  

PubMed

The evidence supporting the DSM-IV definition of atypical depression (AD) is weak. This study aimed to test different definitions of AD. Major depressive disorder (MDD) patients (N = 254) and bipolar-II (BP-II) outpatients (N = 348) were interviewed consecutively, during major depressive episodes, with the Structured Clinical Interview for DSM-IV. DSM-IV criteria for AD were followed. AD validators were female gender, young onset, BP-II, axis I comorbidity, bipolar family history. Frequency of DSM-IV AD was 43.0%. AD, versus non-AD, was significantly associated with all AD validators, apart from comorbidity when controlling for age and sex. Factor analysis of atypical symptoms found factor 1 including oversleeping, overeating and weight gain (leaden paralysis at trend correlation), and factor 2 including interpersonal sensitivity, mood reactivity, and leaden paralysis. Multiple logistic regression of factor 1 versus AD validators found significant associations with several validators (including bipolar family history), whereas factor 2 had no significant associations. Findings may support a new definition of AD based on the state-dependent features oversleeping and overeating (plus perhaps leaden paralysis) versus the current AD definition based on a combination of state and trait features. Pharmacological studies are required to support any new definition of AD, as the current concept of AD is based on different response to TCA antidepressants versus non-AD. PMID:16175877

Benazzi, Franco

2005-01-01

443

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

SciTech Connect

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

444

Charge resistance in a Majorana RC circuit  

NASA Astrophysics Data System (ADS)

We investigate the dynamical charge response in a “Majorana Coulomb box” realized by two Majorana bound states hosted at the ends of a mesoscopic topological superconductor. One side of the wire is coupled to a normal lead and low frequency gate voltage is applied to the system. There is no dc current; the system can be considered as an RC quantum circuit. We calculate the effective capacitance and charge relaxation resistance. The latter is in agreement with the Korringa-Shiba formula where, however, the charge relaxation resistance is equal to h/2e2. This value corresponds to the strong Coulomb blockade limit described by a resonant model formulated by Fu [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.056402 104, 056402 (2010)]. We also performed direct calculations using the latter model and defined its parameters by direct comparison with our perturbation theory results.

Golub, Anatoly; Grosfeld, Eytan

2012-12-01

445

Ecotourism: The Evolving Contemporary Definition  

Microsoft Academic Search

A rise in the popularity of ecotourism has coincided with voluminous definitional discourse. Amongst stakeholders, confusion has resulted from the disparate nature of these definitions. In the absence of a common definition or set of key tenets the challenge has been to ensure operational ecotourism that adheres to the theoretical underpinnings of the concept. Without some semblance of definitional consensus,

Holly M. Donohoe; Roger D. Needham

2006-01-01

446

Statute Definitions of Elder Abuse  

Microsoft Academic Search

Differences in elder abuse definitions hinder the comparison of research and state elder abuse data (Jogerst, Daly, Brinig et al., in press). The purposes of this paper are to describe and summarize the elder abuse definitions in the state statutes and present current definitions used in practice, education, and research. The definitions of elder abuse for the 50 state and

Jeanette M. Daly; Gerald Jogerst

2003-01-01

447

Structured Analysis for Requirements Definition  

Microsoft Academic Search

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

Douglas T. Ross; Kenneth E. Schoman Jr.

1977-01-01

448

Theoretical study of carrier transport and screening in topological insulator Bi2Se3  

NASA Astrophysics Data System (ADS)

This theoretical work is motivated by two recent experiments on Bi2Se3 examining the charge inhomogeneity [1-2] close to the topologically protected crossing point of surface bands in these bulk topological insulators. Reminiscent of graphene close to charge neutrality [3-4], the energy landscape becomes highly inhomogeneous, forming a sea of electron and hole puddles, which determine the properties at low carrier density. Here, we show that the induced carrier density fluctuations are of order 1 % of the impurity density, providing a small-parameter with which we can perform a controlled perturbation theory. Analytic results are obtained for the minimum conductivity and puddle auto-correlation length. We also find that the band asymmetry between electron and holes states is a necessary ingredient to understand the aforementioned experiments. References: [1] H. Beidenkopf et al, ``Spatial fluctuations of helical Dirac fermions on the surface of topological insulators,'' Nat. Phys. online publ., (2011) [2] D. Kim et al., ``Minimum conductivity and charge inhomogeneity in Bi2Se3,'' arXiv:1105.1410. [3] S. Adam et al., ``A self-consistent theory for graphene transport,'' PNAS 104, 18392 (2007). [4] S. Das Sarma et al., ``Electronic transport in 2D graphene,'' Rev. Mod. Phys. 83, 407 (2011).

Adam, Shaffique; Hwang, E. H.; Stiles, M. D.; Das Sarma, S.

2012-02-01

449

Topologically induced local PandCP violation in QCD x QED  

SciTech Connect

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

450

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

451

The weakest m-convex topology stronger than an A-convex topology need not exist  

Microsoft Academic Search

It is known that every locally A-convex algebra (E, ?) can be endowed with, at least, one locally m-convex topology stronger than?. In this note, we answer several questions concerning such locally m-convex topologies. In particular, we show that, unlike\\u000a what is asserted in several previous papers, the collection of all such topologies does not have any weakest element in

L. Oubbi

2005-01-01

452

Entanglement and topological entropy of the toric code at finite temperature  

SciTech Connect

We calculate exactly the von Neumann and topological entropies of the toric code as a function of system size and temperature. We do so for systems with infinite energy scale separation between magnetic and electric excitations, so that the magnetic closed loop structure is fully preserved while the electric loop structure is tampered with by thermally excited electric charges. We find that the entanglement entropy is a singular function of temperature and system size, and that the limit of zero temperature and the limit of infinite system size do not commute. The two orders of limit differ by a term that does not depend on the size of the boundary between the partitions of the system, but instead depends on the topology of the bipartition. From the entanglement entropy we obtain the topological entropy, which is shown to drop to half its zero-temperature value for any infinitesimal temperature in the thermodynamic limit, and remains constant as the temperature is further increased. Such discontinuous behavior is replaced by a smooth decreasing function in finite-size systems. If the separation of energy scales in the system is large but finite, we argue that our results hold at small enough temperature and finite system size, and a second drop in the topological entropy should occur as the temperature is raised so as to disrupt the magnetic loop structure by allowing the appearance of free magnetic charges. We discuss the scaling of these entropies as a function of system size, and how the quantum topological entropy is shaved off in this two-step process as a function of temperature and system size. We interpret our results as an indication that the underlying magnetic and electric closed loop structures contribute equally to the topological entropy (and therefore to the topological order) in the system. Since each loop structure per se is a classical object, we interpret the quantum topological order in our system as arising from the ability of the two structures to be superimposed and appear simultaneously.

Castelnovo, Claudio [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, OX1 3NP (United Kingdom); Chamon, Claudio [Physics Department, Boston University, Boston, Massachusetts 02215 (United States)

2007-11-01

453

Proceedings of the workshop on Quantum Gravity and Topology  

NASA Astrophysics Data System (ADS)

The workshop on Quantum Gravity and Topology was held at INS on February 21-23, 1991. Several introductory lectures and more than 15 talks were delivered for about 100 participants. The main subjects discussed were: (1) topological quantum field theories and topological gravity; (2) low dimensional and four dimensional gravity; (3) topology change; and (4) superstring theories etc.

Oda, Ichiro

1991-10-01

454

The topology of symmetric, second-order tensor fields  

Microsoft Academic Search

We study the topology of symmetric, second-order tensor fields. The goal is to represent their complex structure by a simple set of carefully chosen points and lines analogous to vector field topology. We extract topological skeletons of the eigenvector fields, and we track their evolution over time. We study tensor topological transitions and correlate tensor and vector data.The basic constituents

Thierry Delmarcelle; Lambertus Hesselink

1994-01-01

455

Editing the topology of 3D models by sketching  

Microsoft Academic Search

We present a method for modifying the topology of a 3D model with user control. The heart of our method is a guided topology editing algorithm. Given a source model and a user-provided target shape, the algorithm modifies the source so that the resulting model is topologically consistent with the target. Our algorithm permits removing or adding various topological features

Tao Ju; Qian-yi Zhou; Shi-min Hu

2007-01-01

456

Design of Logical Topologies for Wavelength-Routed Optical Networks  

Microsoft Academic Search

This paper studies the problem of designing a logical topology over a wavelengthroutedall-optical network physical topology. The physical topology consists of the nodesand fiber links in the network. On an all-optical network physical topology, we can setup lightpaths between pairs of nodes, where a lightpath represents a direct opticalconnection without any intermediate electronics. The set of lightpaths along with thenodes

Rajiv Ramaswami; Kumar N. Sivarajan

1996-01-01

457

Topological Insulators and the Quantum Spin Hall Effect  

Microsoft Academic Search

A topological insulator is a material with a bulk excitation gap generated by the spin orbit interaction that is topologically distinct from an ordinary insulator. This distinction, characterized by a Z2 topological invariant, necessitates the existence of gapless electronic states on the sample boundary, which have important implications for electronic transport. In two dimensions, the topological insulator is a quantum

C. L. Kane

2009-01-01

458

Things Fall Apart: Topology Change From Winding Tachyons  

SciTech Connect

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

459

Instanton and spectral flow in topological conformal field theories  

NASA Astrophysics Data System (ADS)

A class of two-dimensional topological conformal field theories (TCFTs) is studied within the framework of gauged WZW models in order to obtain some insights on the global geometrical nature of TCFTs. The BRST quantizations of topological G/H gauged WZW models (the twisted versions of supersymmetric gauged WZW models) are given under fixed background gauge fields. The BRST cohomology of the system is investigated, and then the correlation functions among these physical observables are considered under the instanton backgrounds. As a consequences, two-dimensional BF gauge theoretical aspects of TCFTs are revealed. Especially, it is shown that two correlatation functions under the different instanton backgrounds can change into each other. This process of transmutation is described by the spectral flow. The flow is formulated as a ``singular'' gauge transformation which creates an appropriate background charge on the physical vacuum of the system. The field identification problem of the system is also discussed from the above point of view. A Fellow of the Japan Society for the Promotion for Japanese Junior Scientists. Partly supported by the Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture (No. 05-3531).

Nakatsu, Toshio; Sugawara, Yuji

1993-09-01

460

Correlated effects in topological phase transitions  

NASA Astrophysics Data System (ADS)

Correlation effects in topological phases have been a central topic of interest, yet elusive in experiment. In this talk, we present the results of a numerical study beyond mean-field theory of a phase transition between a two-dimensional Z2 topological insulator phase and a trivial insulator that is driven by correlation effects. In addition to the Z2 invariant, we find that certain features of the single-particle Green's functions (simpler to compute than the full Z2 invariant) carry important information that are strongly indicative of a non-trivial Z2 topological character. We observe that the fluctuations originating from correlations tend to move the topological phase transition boundary to larger values of interactions.

Hung, Hsiang-Hsuan; Wang, Lei; Gu, Zheng-Cheng; Fiete, Gregory A.

2013-03-01

461

Information and topology in attractor neural networks.  

PubMed

A wide range of networks, including those with small-world topology, can be modeled by the connectivity ratio and randomness of the links. Both learning and attractor abilities of a neural network can be measured by the mutual information (MI) as a function of the load and the overlap between patterns and retrieval states. In this letter, we use MI to search for the optimal topology with regard to the storage and attractor properties of the network in an Amari-Hopfield model. We find that while an optimal storage implies an extremely diluted topology, a large basin of attraction leads to moderate levels of connectivity. This optimal topology is related to the clustering and path length of the network. We also build a diagram for the dynamical phases with random or local initial overlap and show that very diluted networks lose their attractor ability. PMID:17348769

Dominguez, D; Koroutchev, K; Serrano, E; Rodríguez, F B

2007-04-01

462

Shielding and Grounding Topology for Interference Control.  

National Technical Information Service (NTIS)

The topological approach to shielding and grounding is a rational and systematic method of providing the high degree of isolation required between external conductors exposed to lightning or other harsh environments and small-signal circuits susceptible t...

E. F. Vance

1977-01-01

463

Molecular beam epitaxial growth of topological insulators.  

PubMed

With the molecular beam epitaxy technique, layer-by-layer growth of atomically flat topological insulator Bi(2) Te(3) and Bi(2) Se(3) thin films has been realized on Si(111) and graphene substrates, respectively. The growth criteria by which intrinsic topological insulators can readily be obtained is established. By using in situ angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements, the band structure and surface morphology of Bi(2) Te(3) and Bi(2) Se(3) thin films of different thickness can be studied. Molecular beam epitaxy technique was shown to not only provide an excellent method to prepare high quality topological insulators but show possibilities of engineering their electronic and spin structures as well, which is of significant importance for potential applications of topological insulators based on well-developed Si technology. PMID:21360770

Chen, Xi; Ma, Xu-Cun; He, Ke; Jia, Jin-Feng; Xue, Qi-Kun

2011-03-01

464

Modeling the Internet's large-scale topology.  

PubMed

Network generators that capture the Internet's large-scale topology are crucial for the development of efficient routing protocols and modeling Internet traffic. Our ability to design realistic generators is limited by the incomplete understanding of the fundamental driving forces that affect the Internet's evolution. By combining several independent databases capturing the time evolution, topology, and physical layout of the Internet, we identify the universal mechanisms that shape the Internet's router and autonomous system level topology. We find that the physical layout of nodes form a fractal set, determined by population density patterns around the globe. The placement of links is driven by competition between preferential attachment and linear distance dependence, a marked departure from the currently used exponential laws. The universal parameters that we extract significantly restrict the class of potentially correct Internet models and indicate that the networks created by all available topology generators are fundamentally different from the current Internet. PMID:12368484

Yook, Soon-Hyung; Jeong, Hawoong; Barabasi, Albert-Laszlo

2002-10-04

465

Topological Pumping in the Lower Overshoot Layer  

NASA Astrophysics Data System (ADS)

Problems associated with topological pumping in the lower overshoot layer suggest a strongly turbulent and strongly differentially rotating upper radiative zone as the seat of the dynamo and as flux reservoir.

Petrovay, Kristóf

466

Electromagnetic coupling on complex systems - Topological approach  

Microsoft Academic Search

The principles of electromagnetic topology, developed by Baum, are reviewed. The method involves breaking a comp