WorldWideScience

Sample records for hcp lattices

  1. Lattice distortion in hcp rare gas solids

    Science.gov (United States)

    Grechnev, A.; Tretyak, S. M.; Freiman, Yu. A.

    2010-04-01

    The lattice distortion parameter δ ≡c/a-√8/3 has been calculated as a function of molar volume for the hcp phases of He, Ar, Kr, and Xe. Results from both semi-empirical potentials and density functional theory are presented. Our study shows that δ is negative for helium in the entire pressure range. For Ar, Kr, and Xe δ changes sign from negative to positive as the pressure increases, growing rapidly in magnitude at higher pressures.

  2. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

    International Nuclear Information System (INIS)

    Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M; Ekholm, M; Abrikosov, I A; Vitos, L

    2010-01-01

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  3. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Ekholm, M; Abrikosov, I A [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, SE-581 83 Linkoeping (Sweden); Vitos, L, E-mail: gebhardt@mch.rwth-aachen.d [Department of Materials Science and Engineering, Applied Materials Physics, oyal Institute of Technology, SE-10044 Stockholm (Sweden)

    2010-07-28

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  4. Lattice dynamics and thermophysical properties of h.c.p. Os and Ru from the quasi-harmonic approximation.

    Science.gov (United States)

    Palumbo, Mauro; Dal Corso, Andrea

    2017-10-04

    We report first-principles phonon frequencies and anharmonic thermodynamic properties of h.c.p. Os and Ru calculated within the quasi-harmonic approximation, including Grüneisen parameters, temperature-dependent lattice parameters, thermal expansion, and isobaric heat capacity. We discuss the differences between a full treatment of anisotropy and a simplified approach with a constant [Formula: see text] ratio. The results are systematically compared with the available theoretical and experimental data and an overall satisfactory agreement is obtained.

  5. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, T; Music, D; Schneider, J M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Ekholm, M; Abrikosov, I A [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, SE-58183 Linkoeping (Sweden); Vitos, L [Department of Materials and Engineering, Applied Materials Physics, Royal Institute of Technology (KTH), SE-10044 Stockholm (Sweden); Dick, A; Hickel, T; Neugebauer, J, E-mail: gebhardt@mch.rwth-aachen.de [Department of Computational Materials Design, Max-Planck-Institut fuer Eisenforschung GmbH, D-40237 Duesseldorf (Germany)

    2011-06-22

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Neel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  6. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys

    International Nuclear Information System (INIS)

    Gebhardt, T; Music, D; Schneider, J M; Ekholm, M; Abrikosov, I A; Vitos, L; Dick, A; Hickel, T; Neugebauer, J

    2011-01-01

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Neel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  7. Thermodynamics of dilute 3He-4He solid solutions with hcp structure

    Science.gov (United States)

    Chishko, K. A.

    2018-02-01

    To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ˜ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.

  8. The mechanism of bcc α′ nucleation in single hcp ε laths in the fcc γ → hcp ε → bcc α′ martensitic phase transformation

    International Nuclear Information System (INIS)

    Yang, Xu-Sheng; Sun, Sheng; Zhang, Tong-Yi

    2015-01-01

    High Resolution Transmission Electron Microscopy (HRTEM) and Molecular Dynamics (MD) simulations were conducted here to study the plastic deformation induced γ (fcc) → ε (hcp) → α′ (bcc) martensitic transformation in 304 stainless steels for the α′ nucleation from single hcp-ε laths. Results elucidate that the underlying microscopic mechanism for the α′ nucleation from single hcp-ε laths obeys the Bogers–Burgers–Olson–Cohen “3T/8–T/3” model. In particular, the atomic-scale observations clearly show the Kurdyumov–Sachs (K–S) lattice orientation relation (OR) and Pitsch OR at the γ/α′ interfaces, the lattice rotation inside an α′ martensitic inclusion, the transition lattice and the reverse shear-shuffling induced continuous lattice elastic deformation at the diffuse ε/α′ interface, which caters the 3T/8 and T/3 shears and sheds atomic process insight into the mechanism of the martensitic transformation

  9. Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition.

    Science.gov (United States)

    Glazyrin, K; Pourovskii, L V; Dubrovinsky, L; Narygina, O; McCammon, C; Hewener, B; Schünemann, V; Wolny, J; Muffler, K; Chumakov, A I; Crichton, W; Hanfland, M; Prakapenka, V B; Tasnádi, F; Ekholm, M; Aichhorn, M; Vildosola, V; Ruban, A V; Katsnelson, M I; Abrikosov, I A

    2013-03-15

    We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

  10. Defect accumulation behaviour in hcp metals and alloys

    International Nuclear Information System (INIS)

    Woo, C.H.

    2000-01-01

    The effects of displacement damage on the physical and mechanical properties of metals and alloys, caused by the bombardment of energetic particles, have been investigated for several decades. Besides the obvious technical and industrial implications, an important motive of such investigations is to understand the factors that differentiate the response of different metals under different irradiation conditions. Recently, much interest is shown in the possible effects of the crystal lattice structure on variations in the damage accumulation behaviour of metals and alloys. In this paper we focus on the case of metals and alloys that crystallize in the hexagonal close pack (hcp) structure, and describe recent understanding of the damage production, accumulation and its consequences in these metals

  11. Calculated temperature dependence of elastic constants and phonon dispersion of hcp and bcc beryllium

    Science.gov (United States)

    Hahn, Steven; Arapan, Sergiu; Harmon, Bruce; Eriksson, Olle

    2011-03-01

    Conventional first principle methods for calculating lattice dynamics are unable to calculate high temperature thermophysical properties of materials containing modes that are entropically stabilized. In this presentation we use a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD) to study the hcp to bcc transition (1530 K) in beryllium. The SCAILD method goes beyond the harmonic approximation to include phonon-phonon interactions and produces a temperature-dependent phonon dispersion. In the high temperature bcc structure, phonon-phonon interactions dynamically stabilize the N-point phonon. Fits to the calculated phonon dispersion were used to determine the temperature dependence of the elastic constants in the hcp and bcc phases. Work at the Ames Laboratory was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  12. Premelting hcp to bcc Transition in Beryllium

    Science.gov (United States)

    Lu, Y.; Sun, T.; Zhang, Ping; Zhang, P.; Zhang, D.-B.; Wentzcovitch, R. M.

    2017-04-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to x-ray equipment. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp → bcc transition occurs near the melting curve at 0 materials.

  13. A metastable HCP intermetallic phase in Cu-Al bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Limei

    2006-07-01

    For the present study, three kinds of layered Cu/Al films have been fabricated. The first kind of samples were multilayered Cu/Al films deposited by sputtering on (001)Si. The individual layer thicknesses were 100 nm, 200 nm and 400 nm, while the total film thickness of 800 nm was kept constant, thus leading to multilayer systems with 8, 4 and 2 layers, respectively. The second type of samples were Cu/Al bilayer films grown on (0001) sapphire by sputtering, with individual layer thicknesses of 400 nm. The third type of samples were bilayer films (100 nm Cu and 100 nm Al) deposited on (0001)sapphire by MBE at room temperature. Applying conventional transmission electron microscopy and X-ray diffraction, different epitaxial growth behaviors were found in these films. All multilayer films from the first type were polycrystalline. The second type of films show a (111) FCC texture and possess intermetallic phases at the interfaces. HRTEM investigations displayed that along [111]FCC, the atomic structure of the interlayer has an ABAB stacking sequence, which is identical with a hexagonal close-packed (HCP) structure in [0001] direction, but not with the ABCABC stacking sequence of Cu and Al in [111]FCC. The lattice parameters of the HCP structure at the interlayer were determined from a model which gave the best agreement between the experimental and simulated images. The parameters are: a=b=0.256 nm, c=0.419 nm, ?=120 , with the space group of P6m2. Furthermore, lattice distortion analysis revealed that the lattice parameters of the HCP phase are increasing from the near-Cu-side to the near-Al-side. The chemical composition of the interlayer was investigated by energy dispersive X-ray spectroscopy (EDS). EDS linescans were performed from pure Al to pure Cu layers. In order to examine the stability of this HCP phase, in-situ heating experiments were performed in the HRTEM at {proportional_to}600 C. Ex-situ heating experiments were performed at different temperatures to

  14. Energetics of dislocation transformations in hcp metals

    International Nuclear Information System (INIS)

    Wu, Zhaoxuan; Yin, Binglun; Curtin, W.A.

    2016-01-01

    Dislocation core structures of hcp metals are highly complex and differ significantly among the hcp family. Some dislocations undergo unconventional transformations that have significant effects on the material plastic flow. Here, the energetics of dislocation dissociations are analyzed in a general anisotropic linear elastic theory framework for transformations in which changes in the partial Burgers vectors are small. Quantitative analyses on various transformations are made using DFT-computed stacking fault energies and partial Burgers vectors. Specifically, possible transformations of the mixed, edge, and screw 〈c+a〉 and screw 〈a〉 dislocations in 6 hcp metals (Mg, Ti, Zr, Re, Zn, Cd) are studied. Climb dissociation of mixed or edge 〈c+a〉 dislocations to the Basal plane is energetically favorable in all 6 metals and thus only limited by thermal activation. The 〈c+a〉 screw dislocation is energetically preferable on Pyramidal I for Ti, Zr, and Re, and on Pyramidal II for Zn and Cd. In Mg, the energy difference between screw 〈c+a〉 on Pyramidal I and II planes is small, suggesting relatively easy cross-slip. For the screw 〈a〉, Basal dissociation is energetically favorable in Mg, Re, Zn and Cd, while Prism dissociation is strongly favorable in Ti and Zr. Only Ti, Zr and Re show a metastable state for dissociation on the Prism plane, and the energy difference between screw 〈a〉 on the Prism and Pyramidal I planes is relatively small in all systems, suggesting relatively easy cross-slip of 〈a〉 in Ti and Zr. The elastic analysis thus provides a single framework able to capture the controlling energetics for different dissociations and slip systems in hcp metals. When the calculated energy differences are very small, the results point to the need for detailed modeling of the atomistic core structure. Moreover, the analyses rationalize broad experimental observations on dominant slip systems and dislocation behaviours, and provide

  15. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  16. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 {sup 0}C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc{sub r}eases in the film. The Ni film prepared at 100 {sup 0}C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  17. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 0 C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc r eases in the film. The Ni film prepared at 100 0 C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  18. Electronic structure of hcp transition metals

    DEFF Research Database (Denmark)

    Jepsen, O.; Andersen, O. Krogh; Mackintosh, A. R.

    1975-01-01

    Using the linear muffin-tin-orbital method described in the previous paper, we have calculated the electronic structures of the hcp transition metals, Zr, Hf, Ru, and Os. We show how the band structures of these metals may be synthesized from the sp and d bands, and illustrate the effects...... of hybridization, relativistic band shifts, and spin-orbit coupling by the example of Os. By making use of parameters derived from the muffin-tin potential, we discuss trends in the positions and widths of the energy bands, especially the d bands, as a function of the location in the periodic table. The densities...... of states of the four metals are presented, and the calculated heat capacities compared with experiment. The Fermi surfaces of both Ru and Os are found to be in excellent quantitative agreement with de Haas-van Alphen measurements, indicating that the calculated d-band position is misplaced by less than 10...

  19. Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa.

    Science.gov (United States)

    Osipiuk, Jerzy; Xu, Xiaohui; Cui, Hong; Savchenko, Alexei; Edwards, Aled; Joachimiak, Andrzej

    2011-03-01

    The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in vitro. Two Hcp1 paralogues have been identified in the P. aeruginosa genome, Hsp2 and Hcp3. Here, we present the structure of the Hcp3 protein from P. aeruginosa. The overall structure of the monomer resembles Hcp1 despite the lack of amino-acid sequence similarity between the two proteins. The monomers assemble into hexamers similar to Hcp1. However, instead of forming nanotubes in head-to-tail mode like Hcp1, Hcp3 stacks its rings in head-to-head mode forming double-ring structures.

  20. Calculation of the surface energy of hcp-metals with the empirical electron theory

    International Nuclear Information System (INIS)

    Fu Baoqin; Liu Wei; Li Zhilin

    2009-01-01

    A brief introduction of the surface model based on the empirical electron theory (EET) and the dangling bond analysis method (DBAM) is presented in this paper. The anisotropy of spatial distribution of covalent bonds of hexagonal close-packed (hcp) metals such as Be, Mg, Sc, Ti, Co, Zn, Y, Zr, Tc, Cd, Hf, and Re, has been analyzed. And under the first-order approximation, the calculated surface energy values for low index surfaces of these hcp-metals are in agreement with experimental and other theoretical values. Correlated analysis showed that the anisotropy of surface energy of hcp-metals was related with the ratio of lattice constants (c/a). The calculation method for the research of surface energy provides a good basis for models of surface science phenomena, and the model may be extended to the surface energy estimation of more metals, alloys, ceramics, and so on, since abundant information about the valence electronic structure (VES) is generated from EET.

  1. Allotropic transformation bcc in equilibrium hcp in zirconium

    International Nuclear Information System (INIS)

    Akhtar, A.

    1976-01-01

    The allotropic transformation hcp(α) in equilibrium bcc(β) was examined in crystal bar zirconium. The β → α transformation is massive type in melt grown crystals of β--Zr. Upon thermal cycling through α → β → α the bcc → hcp transformation occurs frequently through a shear process and less frequently through a massive transformation. The presence of α → β transformation substructure may favor the operation of the shear mode. The hcp → bcc phase change occurs through a massive transformation. A lack of transformation memory is associated with the process of thermal cycling. 11 fig., 3 tables

  2. NMR-ON on 60CoCo(fcc, hcp, thin film), 52MnCo(fcc), and 90NbCo(fcc)

    International Nuclear Information System (INIS)

    Zech, E.; Hagn, E.; Ernst, H.; Eska, G.

    1978-01-01

    With the NMR-ON method the magnetic hyperfine splitting constant of dilute impurities in a ferromagnetic host material (Fe, Ni, Co) can be determined with high accuracy (10 -3 ...10 -4 ). Only few NMR-ON experiments with Co as host lattice have been performed up to now. In constrast to Fe and Ni, two stable modifications exist for Co (fcc and hcp). In the hcp case the magnetic hyperfine field is expected to be anisotropic. Due to the electric field gradient, which is present in this case, a (small) guadrupole interaction is superimposed to the magnetic hyperfine interaction. For 60 CoCo measurements were done on a fcc foil, a hcp single crystal, and on thin films, which were prepared by evaporating Co into glass. For 52 MnCo and 90 NbCo measurements were performed for fcc Co. (Auth.)

  3. Structural and magnetic properties of hcp and fcc Ni nanoparticles

    International Nuclear Information System (INIS)

    Gong, J.; Wang, L.L.; Liu, Y.; Yang, J.H.; Zong, Z.G.

    2008-01-01

    The face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Ni nanoparticles were synthesized with citrate by sol-gel method and heat-treating technique. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Our XRD and TEM results suggested that hcp Ni nanoparticles were successfully synthesized when the heating temperature reaches 300 deg. C. With a further increase in temperature to 400 deg. C, a temperature-induced phase transformation of hcp to fcc was observed. Moreover, the VSM results demonstrated the existence of ferromagnetic behavior in the synthesized fcc and hcp Ni nanoparticles. Nevertheless, the magnetic measurement suggested that the magnetic properties in hcp nanoparticles is probably the sum of two contributions: superparamagnetic and ferromagnetic one. The unsaturated magnetization is much smaller than 47.6 emu/g for the fcc nanoparticles obtained at 400 deg. C and 55 emu/g for the bulk material. It was also found that changes of the stress, grain size and crystal structure during heat-treating have significant influences on the magnetic properties of the Ni nanoparticles

  4. Ab-initio approach to the effect of Fe on the diffusion in hcp Zr

    International Nuclear Information System (INIS)

    Perez, Rodolfo Ariel; Weissmann, Mariana

    2008-01-01

    The role of Fe in the hcp Zr diffusion process is analyzed, given its ultra-fast diffusion (up to nine orders of magnitude higher than the self-diffusion in the temperature range 779-1128 K) and the enhancement observed in the self and substitutional diffusion induced by its unavoidable presence as impurity. Ab-initio calculations using SIESTA and WIEN2K codes were performed in order to find the actual Fe minimum energy configuration within the hcp Zr matrix and its interaction with vacancies. Several off-centre quasi-interstitial positions with energies similar to substitutional Fe were encountered. The comparison with diffusion coefficient measurements and Moessbauer experiments allows us to discard the substitutional position of the Fe atom as well as to affirm that its presence creates a considerable lattice distortion together with an increment in the number of vacancies. The above effects could be responsible for the enhancement in the self and substitutional diffusion, whereas the large amount of quasi-interstitial positions for Fe could be, at least partially, responsible for the ultra-fast Fe diffusion

  5. Diffraction evidence for an FCC in equilibrium HCP transformation in ytterbium

    International Nuclear Information System (INIS)

    Kayser, F.X.

    1971-04-01

    X-ray powder patterns obtained from polycrystalline wires of high-purity Yb in several heat treated conditions have demonstrated (i) the existence of a martensitic transformation, β-Yb (fcc) reversible α-Yb(hcp) and (ii) that the hexagonal close-packed structure is the thermodynamically stable form of Yb at temperatures below approximately 270 0 K. Precision lattice parameters determined for both polymorphs at room temperature indicate the fractional volume change on the transformation to be 0.0091, a magnitude that is consistent with the belief that α-Yb is divalent. This can be regarded as a stacking fault transformation, and one wherein the preponderance of the volume change is accommodated by displacements normal to the habit plane

  6. High precision measurement of the hyperfine fields of substitutional and defect associated Cd in single crystalline hcp cobalt

    CERN Document Server

    Correia, J G; Melo, A A; Soares, J C

    1996-01-01

    The hyperfine fields of Cd in single crystalline hcp Co were measured after simultaneous implantation of 111mCd and 111In. High statistics measurements could be done separately for each parent isotope combining the e--g and g-g PAC techniques. The hyperfine coupling constants wL(CdCo)=422.8(1) Mrad/s and w0(CdCo)=6.14(11) Mrad/s are determined for Cd probes in undisturbed substitutional sites. Several defect associated sites in the hcp Co lattice are clearly seen in the data. Most of the radiation damage created by the ion implantation anneals out at temperatures below 503 K, with only one dominating component surviving at this temperature. This defect is assigned as a probe atom in an interstitial site, surrounded by a vacancy tetrahedron. The corresponding magnetic field and electric field gradient are collinear with the c-axis of the Co lattice, and the respective coupling constants are wL(defect)= 216.7(2) Mrad/s and w0(defect)= 45.3(6) Mrad/s.

  7. Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa

    OpenAIRE

    Osipiuk, Jerzy; Xu, Xiaohui; Cui, Hong; Savchenko, Alexei; Edwards, Aled; Joachimiak, Andrzej

    2011-01-01

    The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in...

  8. Pre-melting hcp to bcc Transition in Beryllium

    OpenAIRE

    Lu, Y.; Sun, T.; Zhang, Ping.; Zhang, P.; Zhang, D. -B.; Wentzcovitch, R. M.

    2017-01-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  9. Micromechanical modeling of the deformation of HCP metals

    Energy Technology Data Exchange (ETDEWEB)

    Graff, S. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung

    2008-12-04

    Nowadays, intense research is conducted to understand the relation between microstructural features and mechanical properties of hexagonal close-packed (hcp) metals. Due to their hexagonal structure, hcp metals exhibit mechanical properties such as strong anisotropy, which is more pronounced than for construction metals with cubic crystal structure, and tension/compression asymmetry. Deformation mechanisms in hcp metals, dislocation motion on specific slip systems and activation of twinning, are not yet completely understood. The purpose of this work is to link the physical mechanisms developing during deformation of magnesium (Mg) on the microscale with the macroscopic yielding properties of texture Mg samples. It will be shown that the mechanical behavior of hcp metals may be understood and reproduced with the help of a visco-plastic model for crystal plasticity and a phenomenological yield criterion with appropriate hardening behavior. The study of single crystal specimens subjected to channel die compression tests reveals the active slip systems and twinning systems of the material considered. The material anisotropy at mesoscale is reproduced by using adequate critical resolved shear stresses (CRSS) for the considered deformation mechanisms. In order to describe the macroscopic behavior, texture is incorporated into polycrystalline Representative Volume Elements (RVEs) and various mechanical properties of extruded bars and rolled plates can be predicted. For RVEs exhibiting the texture of rolled plates the numerical results reveal the plate's anisotropic yielding and hardening behavior on a mesoscale. In order to extend the modeling possibilities to process simulations and to allow for time-saving simulations of structural behavior, a phenomenological yield surface accounting for anisotropy and tension/compression asymmetry has been established and implemented in a finite element code. Its numerous model parameters are calibrated by an optimization

  10. Genetic analysis of the spindle checkpoint genes san-1, mdf-2, bub-3 and the CENP-F homologues hcp-1 and hcp-2 in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Moore Landon L

    2008-02-01

    Full Text Available Abstract Background The spindle checkpoint delays the onset of anaphase until all sister chromatids are aligned properly at the metaphase plate. To investigate the role san-1, the MAD3 homologue, has in Caenorhabditis elegans embryos we used RNA interference (RNAi to identify genes synthetic lethal with the viable san-1(ok1580 deletion mutant. Results The san-1(ok1580 animal has low penetrating phenotypes including an increased incidence of males, larvae arrest, slow growth, protruding vulva, and defects in vulva morphogenesis. We found that the viability of san-1(ok1580 embryos is significantly reduced when HCP-1 (CENP-F homologue, MDF-1 (MAD-1 homologue, MDF-2 (MAD-2 homologue or BUB-3 (predicted BUB-3 homologue are reduced by RNAi. Interestingly, the viability of san-1(ok1580 embryos is not significantly reduced when the paralog of HCP-1, HCP-2, is reduced. The phenotype of san-1(ok1580;hcp-1(RNAi embryos includes embryonic and larval lethality, abnormal organ development, and an increase in abnormal chromosome segregation (aberrant mitotic nuclei, anaphase bridging. Several of the san-1(ok1580;hcp-1(RNAi animals displayed abnormal kinetochore (detected by MPM-2 and microtubule structure. The survival of mdf-2(RNAi;hcp-1(RNAi embryos but not bub-3(RNAi;hcp-1(RNAi embryos was also compromised. Finally, we found that san-1(ok1580 and bub-3(RNAi, but not hcp-1(RNAi embryos, were sensitive to anoxia, suggesting that like SAN-1, BUB-3 has a functional role as a spindle checkpoint protein. Conclusion Together, these data suggest that in the C. elegans embryo, HCP-1 interacts with a subset of the spindle checkpoint pathway. Furthermore, the fact that san-1(ok1580;hcp-1(RNAi animals had a severe viability defect whereas in the san-1(ok1580;hcp-2(RNAi and san-1(ok1580;hcp-2(ok1757 animals the viability defect was not as severe suggesting that hcp-1 and hcp-2 are not completely redundant.

  11. Measurements of electric quadrupole moments of neutron-deficient Au, Pt, and Ir nuclei with NMR-ON in hcp-Co

    CERN Multimedia

    Smolic, E; Hagn, E; Zech, E; Seewald, G

    2002-01-01

    The aim of the experiments is the measurement of $\\,$i) nuclear magnetic moments and electric quadrupole moments of neutron-deficient isotopes in the region Os-Ir-Pt-Au with the methods of quadrupole-interaction-resolved NMR on oriented nuclei " QI-NMR-ON " and modulated adiabatic passage on oriented nuclei " MAPON " and $\\,$ii) the magnetic hyperfine field, electric field gradient (EFG), and spin-lattice relaxation of 5d elements in ferromagnetic Fe, Ni, fcc-Co and hcp-Co.\\\\ The measurements on Au isotopes have been finished successfully. The quadrupole moments of $^{186}$Au, $^{193m}$Au, $^{195}$Au, $^{195m}$Au, $^{197m}$Au, $^{198}$Au and $^{199}$Au were determined with high precision.\\\\ For neutron-deficient Ir isotopes QI-NMR-ON measurements were performed after implantation of Hg precursors. The EFG of Ir in hcp-Co has been calibrated. Thus precise values for the spectroscopic quadrupole mo...

  12. Electron microscopy and plastic deformation of HCP metals and alloys

    International Nuclear Information System (INIS)

    Poirier, J.-P.; Le Hazif, Roger

    1976-01-01

    The recent literature on the slip systems of the h.c.p. metals is reviewed and the contribution of transmission electron microscopy assessed. It is now clear that the stress-strain curves and the dislocation configurations in the slip plane are very similar, whether the principal slip system is basal or prismatic. The important problem of the relative ease of slip systems is linked to the ease of splitting of dislocations in the slip planes and to the electronic band structure of the metal [fr

  13. HCP, grid and data infrastructures for astrophysics: an integrated view

    International Nuclear Information System (INIS)

    Pasian, F.

    2009-01-01

    Also in the case of astrophysics, the capability of performing Big Science requires the availability of large Hcp facilities. But computational resources alone are far from being enough for the community: as a matter of fact, the whole set of e-infrastructures (network, computing nodes, data repositories, applications) need to work in an inter operable way. This implies the development of common (or at least compatible) user interfaces to computing resources, transparent access to observations and numerical simulations through the Virtual Observatory, integrated data processing pipelines, data mining and semantic web applications. Achieving this inter operability goal is a must to build a real Knowledge Infrastructure in the astrophysical domain.

  14. Stacking faults and mechanisms strain-induced transformations of hcp metals (Ti, Mg) during mechanical activation in liquid hydrocarbons

    Science.gov (United States)

    Lubnin, A. N.; Dorofeev, G. A.; Nikonova, R. M.; Mukhgalin, V. V.; Lad'yanov, V. I.

    2017-11-01

    The evolution of the structure and substructure of metals Ti and Mg with hexagonal close-packed (hcp) lattice is studied during their mechanical activation in a planetary ball mill in liquid hydrocarbons (toluene, n-heptane) and with additions of carbon materials (graphite, fullerite, nanotubes) by X-ray diffraction, scanning electron microscopy, and chemical analysis. The temperature behavior and hydrogen-accumulating properties of mechanocomposites are studied. During mechanical activation of Ti and Mg, liquid hydrocarbons decay, metastable nanocrystalline titanium carbohydride Ti(C,H) x and magnesium hydride β-MgH2 are formed, respectively. The Ti(C,H) x and MgH2 formation mechanisms during mechanical activation are deformation ones and are associated with stacking faults accumulation, and the formation of face-centered cubic (fcc) packing of atoms. Metastable Ti(C,H)x decays at a temperature of 550°C, the partial reverse transformation fcc → hcp occurs. The crystalline defect accumulation (nanograin boundaries, stacking faults), hydrocarbon destruction, and mechanocomposite formation leads to the enhancement of subsequent magnesium hydrogenation in the Sieverts reactor.

  15. Lattice QCD

    International Nuclear Information System (INIS)

    Hasenfratz, P.

    1983-01-01

    The author presents a general introduction to lattice gauge theories and discusses non-perturbative methods in the gauge sector. He then shows how the lattice works in obtaining the string tension in SU(2). Lattice QCD at finite physical temperature is discussed. Universality tests in SU(2) lattice QCD are presented. SU(3) pure gauge theory is briefly dealt with. Finally, fermions on the lattice are considered. (Auth.)

  16. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Jumpei, E-mail: higuchi@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Ohtake, Mitsuru; Sato, Yoichi [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    NiFe epitaxial films are prepared on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  17. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    International Nuclear Information System (INIS)

    Higuchi, Jumpei; Ohtake, Mitsuru; Sato, Yoichi; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    NiFe epitaxial films are prepared on Cr(211) bcc and Cr(100) bcc underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211) bcc and Cr(100) bcc underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  18. Ultrahigh pressure deformation of polycrystaline hcp-cobalt

    Science.gov (United States)

    Merkel, S.; Antonangeli, D.; Fiquet, G.; Yagi, T.

    2003-12-01

    During the past few years, a novel set of methods has been developed allowing direct measurements on elasticity and rheology under static ultrahigh pressures using synchrotron x-ray diffraction and the diamond anvil cell. In particular, the analysis on the development of texture and uniaxial stress in a polycrystalline sample under ultrahigh pressure and non-hydrostatic conditions yielded to very interesting results on the microscopic deformation mechanisms and strength of MgO, silicate perovskite or ɛ -Fe [eg. Merkel et al. 2002, Merkel et al. 2003]. However, our understanding of the properties of the ɛ phase of iron remains poor. There are considerable uncertainties and disagreement on the results of various experiments or first-principles calculations. In particular, the results of the radial diffraction measurement on ɛ -Fe [Mao et al. 1998] have been highly controversial. In order to address this issue, we performed investigations on polycrystalline hcp-cobalt. Its properties such as the bulk modulus and thermal expansion are very close to those of ɛ -Fe and it is readily available under ambient conditions. Thus, it is a well known material and results from the high pressure radial diffraction experiments can be compared with those from well-established techniques. In the present analysis, we performed a new set a measurements between 0 and 20 GPa under ambient temperature conditions at the ESRF synchrotron source using amorphous boron gasket, monochromatic x-ray beam, and imaging plate techniques. From such an experiment, we are able to extract information on non-hydrostatic stress, elasticity, and preferred orientations of the sample in-situ under high pressure and compare them with results obtained previously on ɛ -Fe. Documenting the evolution of stress, elasticity and texture in hcp metals is of great interest for our understanding of the bulk properties and seismic anisotropy of the Earth's inner core. S. Merkel et al., J. Geophys. Res. 107 (2002

  19. Improving the Accuracy of a Heliocentric Potential (HCP Prediction Model for the Aviation Radiation Dose

    Directory of Open Access Journals (Sweden)

    Junga Hwang

    2016-12-01

    Full Text Available The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs, flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA. However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015. In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1 real-time daily sunspot assessments, (2 predictions of the daily HCP by our prediction algorithm, and (3 calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

  20. Absence of lattice strain anomalies at the electronic topological transition in zinc at high pressure

    International Nuclear Information System (INIS)

    Steinle-Neumann, Gerd; Stixrude, Lars; Cohen, Ronald E.

    2001-01-01

    High-pressure structural distortions of the hexagonal close-packed (hcp) element zinc have been a subject of controversy. Earlier experimental results and theory showed a large anomaly in lattice strain with compression in zinc at about 10 GPa which was explained theoretically by a change in Fermi surface topology. Later hydrostatic experiments showed no such anomaly, resulting in a discrepancy between theory and experiment. We have computed the compression and lattice strain of hcp zinc over a wide range of compressions using the linearized augmented plane-wave method paying special attention to k-point convergence. We find that the behavior of the lattice strain is strongly dependent on k-point sampling, and with large k-point sets the previously computed anomaly in lattice parameters under compression disappears, in agreement with recent experiments

  1. Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

    Directory of Open Access Journals (Sweden)

    Santiago Sempere

    2018-01-01

    Full Text Available We study the structural and mobility properties of edge dislocations in rare-gas crystals with the hexagonal close-packed (hcp structure by using classical simulation techniques. Our results are discussed in the light of recent experimental and theoretical studies on hcp 4 He, an archetypal quantum crystal. According to our simulations classical hcp rare-gas crystals present a strong tendency towards dislocation dissociation into Shockley partials in the basal plane, similarly to what is observed in solid helium. This is due to the presence of a low-energy metastable stacking fault, of the order of 0.1 mJ/m 2 , that can get further reduced by quantum nuclear effects. We compute the minimum shear stress that induces glide of dislocations within the hcp basal plane at zero temperature, namely, the Peierls stress, and find a characteristic value of the order of 1 MPa. This threshold value is similar to the Peierls stress reported for metallic hcp solids (Zr and Cd but orders of magnitude larger than the one estimated for solid helium. We find, however, that in contrast to classical hcp metals but in analogy to solid helium, glide of edge dislocations can be thermally activated at very low temperatures, T∼10 K, in the absence of any applied shear stress.

  2. Void lattices

    International Nuclear Information System (INIS)

    Chadderton, L.T.; Johnson, E.; Wohlenberg, T.

    1976-01-01

    Void lattices in metals apparently owe their stability to elastically anisotropic interactions. An ordered array of voids on the anion sublattice in fluorite does not fit so neatly into this scheme of things. Crowdions may play a part in the formation of the void lattice, and stability may derive from other sources. (Auth.)

  3. Lattice fermions

    International Nuclear Information System (INIS)

    Randjbar-Daemi, S.

    1995-12-01

    The so-called doubling problem in the lattice description of fermions led to a proof that under certain circumstances chiral gauge theories cannot be defined on the lattice. This is called the no-go theorem. It implies that if Γ/sub/A is defined on a lattice then its infrared limit, which should correspond to the quantum description of the classical action for the slowly varying fields on lattice scale, is inevitably a vector like theory. In particular, if not circumvented, the no-go theorem implies that there is no lattice formulation of the Standard Weinberg-Salam theory or SU(5) GUT, even though the fermions belong to anomaly-free representations of the gauge group. This talk aims to explain one possible attempt at bypassing the no-go theorem. 20 refs

  4. Lattice fermions

    Energy Technology Data Exchange (ETDEWEB)

    Randjbar-Daemi, S

    1995-12-01

    The so-called doubling problem in the lattice description of fermions led to a proof that under certain circumstances chiral gauge theories cannot be defined on the lattice. This is called the no-go theorem. It implies that if {Gamma}/sub/A is defined on a lattice then its infrared limit, which should correspond to the quantum description of the classical action for the slowly varying fields on lattice scale, is inevitably a vector like theory. In particular, if not circumvented, the no-go theorem implies that there is no lattice formulation of the Standard Weinberg-Salam theory or SU(5) GUT, even though the fermions belong to anomaly-free representations of the gauge group. This talk aims to explain one possible attempt at bypassing the no-go theorem. 20 refs.

  5. Lattice strings

    International Nuclear Information System (INIS)

    Thorn, C.B.

    1988-01-01

    The possibility of studying non-perturbative effects in string theory using a world sheet lattice is discussed. The light-cone lattice string model of Giles and Thorn is studied numerically to assess the accuracy of ''coarse lattice'' approximations. For free strings a 5 by 15 lattice seems sufficient to obtain better than 10% accuracy for the bosonic string tachyon mass squared. In addition a crude lattice model simulating string like interactions is studied to find out how easily a coarse lattice calculation can pick out effects such as bound states which would qualitatively alter the spectrum of the free theory. The role of the critical dimension in obtaining a finite continuum limit is discussed. Instead of the ''gaussian'' lattice model one could use one of the vertex models, whose continuum limit is the same as a gaussian model on a torus of any radius. Indeed, any critical 2 dimensional statistical system will have a stringy continuum limit in the absence of string interactions. 8 refs., 1 fig. , 9 tabs

  6. ISABELLE lattice

    International Nuclear Information System (INIS)

    Smith, L.

    1975-01-01

    An analysis is given of a number of variants of the basic lattice of the planned ISABELLE storage rings. The variants were formed by removing cells from the normal part of the lattice and juggling the lengths of magnets, cells, and insertions in order to maintain a rational relation of circumference to that of the AGS and approximately the same dispersion. Special insertions, correction windings, and the working line with nonlinear resonances are discussed

  7. Calculation of the electronic and magnetic structures of 3d impurities in the Hcp Fe matrix

    International Nuclear Information System (INIS)

    Franca, Fernando

    1995-01-01

    In this work we investigate the local magnetic properties and the electronic structure of HCP Fe, as well introducing transition metals atoms 3d (Cs, Ti, Cr, Mn, Co, Ni, Cu, Zn) in HCP iron matrix. We employed the discrete variational method (DVM), which is an orbital molecular method which incorporate the Hartree-Fock-Slater theory and the linear combination of atomic orbitals (LCAO), in the self-consistent charge approximation and the local density approximation of Von Barth and Hedin to the exchange-correlation potential. We used the embedded cluster model to investigate the electronic structure and the local magnetic properties for the central atom of a cluster of 27 atoms immersed in the microcrystal representing the HCP Fe. (author)

  8. Mechanism and energetics of dislocation cross-slip in hcp metals

    Science.gov (United States)

    Wu, Zhaoxuan; Curtin, W. A.

    2016-10-01

    Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

  9. Influence of the intermediate bcc phase on the evolution of superfluid inclusions in hcp matrix 3He-4He

    International Nuclear Information System (INIS)

    Birchenko, A.P.; Mikhin, N.P.; Neoneta, A.S.; Rudavskij, Eh.Ya.; Fisun, Ya.Yu.

    2016-01-01

    The evolution of liquid inclusions which are formed in the hcp matrix by rapid cooling of the 3 He- 4 He solution containing 1.05% 3 He was studied by pulse NMR. The diffusion coefficient of 3 He in the liquid was measured by two-pulses spin-echo method during evolution of the inclusions. Measurements were carried out at 1.67 K which corresponds to the bcc phase existence in the phase diagram, as well as at 1.38 K, where the bcc phase is absent. It is found that in the process of the evolution, in both cases the size of the liquid inclusions is less than diffusion length and so the diffusion is restricted. The measured restricted dif-fusion coefficient allowed to find the characteristic size of the inclusions. In the first case, during the evolution of liquid inclusions, dendrites of intermediate bcc phase is forming and the inclusions are separating into a lot of smaller droplets. Due to the rapid growth of the bcc dendrites, the droplet size decreases rapidly, and the process comes to disappearance of bcc phase and an amorphous state appearance. The results obtained by measuring the diffusion coefficient, correlated with the behavior of the spin-lattice relaxation time in such a system. In the second case at a lower temperature bcc phase is not formed, and the size of the liquid inclusions decreases very slow until the completion of their solidification.

  10. Observation of mass flux through hcp 4He off the melting curve

    International Nuclear Information System (INIS)

    Ray, M W; Hallock, R B

    2009-01-01

    Solid hcp 4 He has been created off the melting curve using two growth techniques. In an effort to observe the flow of 4 He through the solid, rather than squeezing the solid directly, the experimental apparatus allows injection of 4 He atoms from superfluid in porous Vycor directly into the solid. We will describe the apparatus and our observations. Evidence for the transport of mass through a sample cell filled with hcp solid 4 He off the melting curve is found. The temperature and pressure dependence of this behavior will be presented.

  11. Electronic properties of iron impurity in hcp metals from Moessbauer studies

    International Nuclear Information System (INIS)

    Janot, C.; Delcroix, P.

    1975-01-01

    Moessbauer spectroscopy was used in quantitative investigating the electronic properties of iron impurities in hexagonal close-packed metals. Beryllium of the highest commercially obtainable purity containing about 300 ppm residual impurities was used as a host element. Experimental evidence is given for the existence of localized electronic states which have non-spherical distribution and obviously contribute especially to the electric field gradient. Iron impurity seems to retain the same electronic behaviour as long as the host hcp metal is a normal one (Mg, Cd, Zn), but the localized electronic states seem to disappear when the host is a transition hcp metal (Co, Ti, Sc, Zr, etc.). (Z.S.)

  12. Supersymmetric lattices

    International Nuclear Information System (INIS)

    Catterall, Simon

    2013-01-01

    Discretization of supersymmetric theories is an old problem in lattice field theory. It has resisted solution until quite recently when new ideas drawn from orbifold constructions and topological field theory have been brought to bear on the question. The result has been the creation of a new class of lattice gauge theory in which the lattice action is invariant under one or more supersymmetries. The resultant theories are local and free of doublers and in the case of Yang-Mills theories also possess exact gauge invariance. In principle they form the basis for a truly non-perturbative definition of the continuum supersymmetric field theory. In this talk these ideas are reviewed with particular emphasis being placed on N = 4 super Yang-Mills theory.

  13. First-principles calculations of the structural and thermodynamic properties of bcc, fcc and hcp solid solutions in the Al-TM (TM = Ti, Zr and Hf) systems: A comparison of cluster expansion and supercell methods

    International Nuclear Information System (INIS)

    Ghosh, G.; Walle, A. van de; Asta, M.

    2008-01-01

    The thermodynamic properties of solid solutions with body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed (hcp) structures in the Al-TM (TM = Ti, Zr and Hf) systems are calculated from first-principles using cluster expansion (CE), Monte-Carlo simulation and supercell methods. The 32-atom special quasirandom structure (SQS) supercells are employed to compute properties at 25, 50 and 75 at.% TM compositions, and 64-atom supercells have been employed to compute properties of alloys in the dilute concentration limit (one solute and 63 solvent atoms). In general, the energy of mixing (Δ m E) calculated by CE and dilute supercells agree very well. In the concentrated region, the Δ m E values calculated by CE and SQS methods also agree well in many cases; however, noteworthy discrepancies are found in some cases, which we argue originate from inherent elastic and dynamic instabilities of the relevant parent lattice structures. The importance of short-range order on the calculated values of Δ m E for hcp Al-Ti alloys is demonstrated. We also present calculated results for the composition dependence of the atomic volumes in random solid solutions with bcc, fcc and hcp structures. The properties of solid solutions reported here may be integrated within the CALPHAD formalism to develop reliable thermodynamic databases in order to facilitate: (i) calculations of stable and metastable phase diagrams of binary and multicomponent systems, (ii) alloy design, and (iii) processing of Al-TM-based alloys

  14. Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in ?-Ti alloys

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.; Sietsma, J.; Van der Zwaag, S.

    2006-01-01

    The formation mechanisms of two hcp ? phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary ? forms predominantly on prior bcc ? grain

  15. Search for anisotropy in the Debye-Waller factor of HCP solid 4He

    Science.gov (United States)

    Barnes, Ashleigh L.; Hinde, Robert J.

    2016-02-01

    The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

  16. Lattice overview

    International Nuclear Information System (INIS)

    Creutz, M.

    1984-01-01

    After reviewing some recent developments in supercomputer access, the author discusses a few areas where perturbation theory and lattice gauge simulations make contact. The author concludes with a brief discussion of a deterministic dynamics for the Ising model. This may be useful for numerical studies of nonequilibrium phenomena. 13 references

  17. Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

    Science.gov (United States)

    Rosa, A. D.; Garbarino, G.; Briggs, R.; Svitlyk, V.; Morard, G.; Bouhifd, M. A.; Jacobs, J.; Irifune, T.; Mathon, O.; Pascarelli, S.

    2018-03-01

    Solid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc) to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducing important modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailed in situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compression behavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformation was observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, the maximum investigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening and splitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuous nucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stacking faults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin. The apparent small Gibbs free-energy differences between the two structures that decrease upon compression may explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. We observe a clear anomaly in the equation of state of the fcc solid at ˜20 GPa when the proportion of the hcp form reaches ˜20 % . We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcp phases and propose two distinct equation of states for the low and high-pressure regimes.

  18. Synthesis and characterization of branched fcc/hcp ruthenium nanostructures and their catalytic activity in ammonia borane hydrolysis

    KAUST Repository

    AlYami, Noktan

    2018-01-30

    Several systems have shown the ability to stabilize uncommon crystal structures during the synthesis of metallic nanoparticles. By tailoring the nanoparticle crystal structure, the physical and chemical properties of the particles can also be controlled. Herein, we first synthesized branched nanoparticles of mixed hcp/fcc ruthenium, which were formed using tungsten carbonyl [W(CO)6] as both a reducing agent and a source of carbon monoxide. The branched particles were formed from multiple particulates off a central core. High-resolution transmission electron microscopy (HRTEM) clearly showed that the branched structures consisted of aligned hcp crystal domains, a mixture of fcc and hcp crystal domains with several defects and misalignments, and particles that contained multiple cores and branches. Branched particles were also formed with molybdenum carbonyl [Mo(CO)6], and faceted particles of hcp and fcc particles were formed with Re2(CO)10 as a carbon monoxide source. Without metal carbonyls, small particles of spherical hcp ruthenium were produced, and their size could be controlled by the selection of the precursor. The ruthenium nanoparticles were tested for ammonia borane hydrolysis; the branched nanoparticles were more reactive for catalytic hydrogen evolution than the faceted hcp/fcc nanoparticles or the spherical hcp nanoparticles. This work showcases the potential of crystal phase engineering of transition metal nanoparticles by different carbon monoxide precursors for tailoring their catalytic reactivity.

  19. Lattice QCD on fine lattices

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing

    2016-11-01

    These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.

  20. Effect of stacking faults on the magnetocrystalline anisotropy of hcp Co: a first-principles study.

    Science.gov (United States)

    Aas, C J; Szunyogh, L; Evans, R F L; Chantrell, R W

    2013-07-24

    In terms of the fully relativistic screened Korringa-Kohn-Rostoker method we investigate the effect of stacking faults on the magnetic properties of hexagonal close-packed (hcp) cobalt. In particular, we consider the formation energy and the effect on the magnetocrystalline anisotropy energy (MAE) of four different stacking faults in hcp cobalt-an intrinsic growth fault, an intrinsic deformation fault, an extrinsic fault and a twin-like fault. We find that the intrinsic growth fault has the lowest formation energy, in good agreement with previous first-principles calculations. With the exception of the intrinsic deformation fault which has a positive impact on the MAE, we find that the presence of a stacking fault generally reduces the MAE of bulk Co. Finally, we consider a pair of intrinsic growth faults and find that their effect on the MAE is not additive, but synergic.

  1. Comprehensive first-principles study of stable stacking faults in hcp metals

    International Nuclear Information System (INIS)

    Yin, Binglun; Wu, Zhaoxuan; Curtin, W.A.

    2017-01-01

    The plastic deformation in hcp metals is complex, with the associated dislocation core structures and properties not well understood on many slip planes in most hcp metals. A first step in establishing the dislocation properties is to examine the stable stacking fault energy and its structure on relevant slip planes. However, this has been perplexing in the hcp structure due to additional in-plane displacements on both sides of the slip plane. Here, density functional theory guided by crystal symmetry analysis is used to study all relevant stable stacking faults in 6 hcp metals (Mg, Ti, Zr, Re, Zn, Cd). Specially, the stable stacking fault energy, position, and structure on the Basal, Prism I and II, Pyramidal I and II planes are determined using all-periodic supercells with full atomic relaxation. All metals show similar stacking fault position and structure as dictated by crystal symmetry, but the associated stacking fault energy, being governed by the atomic bonding, differs significantly among them. Stacking faults on all the slip planes except the Basal plane show substantial out-of-plane displacements while stacking faults on the Prism II, Pyramidal I and II planes show additional in-plane displacements, all extending to multiple atom layers. The in-plane displacements are not captured in the standard computational approach for stacking faults, and significant differences are shown in the energies of such stacking faults between the standard approach and fully-relaxed case. The existence of well-defined stable stacking fault on the Pyramidal planes suggests zonal dislocations are unlikely. Calculations on the equilibrium partial separation further suggests 〈c + a〉 dissociation into three partials on the Pyramidal I plane is unlikely and 〈c〉 dissociation on Prism planes is unlikely to be stable against climb-dissociation onto the Basal planes in these metals.

  2. Superparamagnetism and coercivity in HCP-Co nanoparticles dispersed in silica matrix

    Energy Technology Data Exchange (ETDEWEB)

    Julian Fernandez, C. de E-mail: dejulian@padova.infm.it; Mattei, G.; Sangregorio, C.; Battaglin, C.; Gatteschi, D.; Mazzoldi, P

    2004-05-01

    The magnetic properties of Co HCP nanoparticles dispersed in a silica matrix with sizes between 2{+-}0.7 and 5{+-}2.2 nm were investigated. The temperature dependence of zero-field cooled and field cooled magnetizations and of the coercive field were analyzed considering the thermal activated demagnetization process. Enhanced anisotropy was observed for the 2 nm nanoparticles, while the demagnetization process of the larger ones is dominated by interparticle interactions.

  3. Superparamagnetism and coercivity in HCP-Co nanoparticles dispersed in silica matrix

    International Nuclear Information System (INIS)

    Julian Fernandez, C. de; Mattei, G.; Sangregorio, C.; Battaglin, C.; Gatteschi, D.; Mazzoldi, P.

    2004-01-01

    The magnetic properties of Co HCP nanoparticles dispersed in a silica matrix with sizes between 2±0.7 and 5±2.2 nm were investigated. The temperature dependence of zero-field cooled and field cooled magnetizations and of the coercive field were analyzed considering the thermal activated demagnetization process. Enhanced anisotropy was observed for the 2 nm nanoparticles, while the demagnetization process of the larger ones is dominated by interparticle interactions

  4. Synthesis, multi-nonlinear dielectric resonance and electromagnetic absorption properties of hcp-cobalt particles

    International Nuclear Information System (INIS)

    Wen, Shulai; Liu, Ying; Zhao, Xiuchen; Cheng, Jingwei; Li, Hong

    2014-01-01

    Hcp-cobalt particles were successfully prepared by a liquid phase reduction method, and the microstructure, static magnetic properties, electromagnetic and microwave absorption properties of the cobalt particles with irregular shape were investigated in detail. The measured results indicate that the saturation magnetization was less than that of hcp-Co single crystals, and the coercivity was larger than that of bulk cobalt crystal. The permittivity presents multi-nonlinear dielectric resonance, which may result from the irregular shape containing parts of cutting angle of dodecahedron of cobalt particles. The real part of permeability decreases with the frequency, and the imaginary part has a wide resonant peak. The paraffin-based composite containing 70 wt% cobalt particles possessed strong absorption characteristics with a minimum RL of −38.97 dB at 10.81 GHz and an absorption band with RL under −10 dB from 8.72 to 13.26 GHz when the thickness is 1.8 mm, which exhibits excellent microwave absorption in middle and high frequency. The architectural design of material morphologies is important for improving microwave absorption properties toward future application. - Highlights: • Hcp-cobalt particles were prepared by a liquid phase reduction method. • The saturation magnetization was less than that of hcp-Co single crystals. • The permittivity presents multi-nonlinear dielectric resonance. • The real part of permeability decreases with frequency, and the imaginary part presents a wide resonant peak. • The paraffin-based composite possessed a minimum RL of −38.97 dB at 10.81 GHz

  5. Crystal Structure of Hcp from Acinetobacter baumannii: A Component of the Type VI Secretion System.

    Directory of Open Access Journals (Sweden)

    Federico M Ruiz

    Full Text Available The type VI secretion system (T6SS is a bacterial macromolecular machine widely distributed in Gram-negative bacteria, which transports effector proteins into eukaryotic host cells or other bacteria. Membrane complexes and a central tubular structure, which resembles the tail of contractile bacteriophages, compose the T6SS. One of the proteins forming this tube is the hemolysin co-regulated protein (Hcp, which acts as virulence factor, as transporter of effectors and as a chaperone. In this study, we present the structure of Hcp from Acinetobacter baumannii, together with functional and oligomerization studies. The structure of this protein exhibits a tight β barrel formed by two β sheets and flanked at one side by a short α-helix. Six Hcp molecules associate to form a donut-shaped hexamer, as observed in both the crystal structure and solution. These results emphasize the importance of this oligomerization state in this family of proteins, despite the low similarity of sequence among them. The structure presented in this study is the first one for a protein forming part of a functional T6SS from A. baumannii. These results will help us to understand the mechanism and function of this secretion system in this opportunistic nosocomial pathogen.

  6. Ab initio study of stability and migration of H and He in hcp-Sc

    International Nuclear Information System (INIS)

    Yang, L; Zu, X T; Peng, S M; Long, X G; Gao, F; Heinisch, H L; Kurtz, R J

    2011-01-01

    Ab initio calculations based on density functional theory have been performed to determine the relative stabilities and migration of H and He atoms in hcp-Sc. The results show that the formation energy of an interstitial H or He atom is smaller than that of a corresponding substitutional atom. The tetrahedral (T) interstitial position is more stable than an octahedral (O) position for both He and H interstitials. The nudged elastic band method has been used to study the migration of interstitial H and He atoms in hcp-Sc. It is found that the migration energy barriers for H interstitials in hcp-Sc are significantly different from those for He interstitials, but their migration mechanisms are similar. In addition, the formation energies of five different configurations of a H-H pair were determined, revealing that the most stable configuration consists of two H atoms located at the second-neighbor tetrahedral interstitial sites along the hexagonal direction. The formation and relative stabilities of some small He clusters have also been investigated.

  7. Area of Lattice Polygons

    Science.gov (United States)

    Scott, Paul

    2006-01-01

    A lattice is a (rectangular) grid of points, usually pictured as occurring at the intersections of two orthogonal sets of parallel, equally spaced lines. Polygons that have lattice points as vertices are called lattice polygons. It is clear that lattice polygons come in various shapes and sizes. A very small lattice triangle may cover just 3…

  8. LATTICE: an interactive lattice computer code

    International Nuclear Information System (INIS)

    Staples, J.

    1976-10-01

    LATTICE is a computer code which enables an interactive user to calculate the functions of a synchrotron lattice. This program satisfies the requirements at LBL for a simple interactive lattice program by borrowing ideas from both TRANSPORT and SYNCH. A fitting routine is included

  9. Axial ratio dependence of the stability of self-interstitials in HCP structures

    International Nuclear Information System (INIS)

    Peng, Qing; Ji, Wei; Huang, Hanchen; De, Suvranu

    2013-01-01

    We investigate the effect of the axial ratio (c/a) on the stability of self-interstitial atoms (SIAs) in hexagonal close-packed crystal structures, using hcp-zirconium as a prototype, through density functional theory based ab initio calculations. The axial ratio is found to dominate the relative stability of SIAs over volumetric strains. We observe that below the ideal value of 1.633, the basal octahedral configuration is the most stable. Above the ideal value, the off-plane SIAs are more stable than in-plane ones

  10. Self-interstitials structure in the hcp metals: A further perspective from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pasianot, Roberto C., E-mail: pasianot@cnea.gov.ar [Gerencia Materiales, CAC-CNEA, Avda. Gral. Paz 1499, 1650 San Martín (Argentina); CONICET, Godoy Cruz 2290, 1425 Buenos Aires (Argentina); Instituto Sabato, UNSAM/CNEA, Avda. Gral. Paz 1499, 1650 San Martín (Argentina)

    2016-12-01

    We study the structure of several standard and non-standard self-interstitial configurations in a series of hcp metals, by using Density Functional Theory as embodied in the computer codes SIESTA and WIEN2k. The considered metals include Be, Mg, Ti, Zr, Co, Zn, and Cd, thus spanning the whole range of experimental c/a ratios, different kinds of bonding, and even magnetism (Co). The results show the importance of low symmetry configurations, closely related to the non-basal crowdion, in order to rationalize the experimental data on self-interstitial structure and migration.

  11. Calculation of the electronic and magnetic structures of 3d impurities in the Hcp Fe matrix; Calculo da estrutura eletronica e magnetica de impurezas 3d na matriz do Fe HCP

    Energy Technology Data Exchange (ETDEWEB)

    Franca, Fernando

    1995-12-31

    In this work we investigate the local magnetic properties and the electronic structure of HCP Fe, as well introducing transition metals atoms 3d (Cs, Ti, Cr, Mn, Co, Ni, Cu, Zn) in HCP iron matrix. We employed the discrete variational method (DVM), which is an orbital molecular method which incorporate the Hartree-Fock-Slater theory and the linear combination of atomic orbitals (LCAO), in the self-consistent charge approximation and the local density approximation of Von Barth and Hedin to the exchange-correlation potential. We used the embedded cluster model to investigate the electronic structure and the local magnetic properties for the central atom of a cluster of 27 atoms immersed in the microcrystal representing the HCP Fe. (author) 32 refs., 19 figs., 2 tabs.

  12. Lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1982-01-01

    After a description of a pure Yang-Mills theory on a lattice, the author considers a three-dimensional pure U(1) lattice gauge theory. Thereafter he discusses the exact relation between lattice gauge theories with the gauge groups SU(2) and SO(3). Finally he presents Monte Carlo data on phase transitions in SU(2) and SO(3) lattice gauge models. (HSI)

  13. Atomistic properties of helium in hcp titanium: A first-principles study

    International Nuclear Information System (INIS)

    Wang Yongli; Liu, Shi; Rong Lijian; Wang Yuanming

    2010-01-01

    First-principles calculations based on density functional theory have been performed to investigate the behaviors of He in hcp-type Ti. The most favorable interstitial site for He is not an ordinary octahedral or tetrahedral site, but a novel interstitial site (called FC) with a formation energy as low as 2.67 eV, locating the center of the face shared by two adjacent octahedrons. The origin was further analyzed by composition of formation energy of interstitial He defects and charge density of defect-free hcp Ti. It has also been found that an interstitial He atom can easily migrate along direction with an activation energy of 0.34 eV and be trapped by another interstitial He atom with a high binding energy of 0.66 eV. In addition, the small He clusters with/without Ti vacancy have been compared in details and the formation energies of He n V clusters with a pre-existing Ti vacancy are even higher than those of He n clusters until n ≥ 3.

  14. bcc-to-hcp transformation pathways for iron versus hydrostatic pressure: Coupled shuffle and shear modes

    Science.gov (United States)

    Liu, J. B.; Johnson, D. D.

    2009-04-01

    Using density-functional theory, we calculate the potential-energy surface (PES), minimum-energy pathway (MEP), and transition state (TS) versus hydrostatic pressure σhyd for the reconstructive transformation in Fe from body-centered cubic (bcc) to hexagonal closed-packed (hcp). At fixed σhyd , the PES is described by coupled shear (γ) and shuffle (η) modes and is determined from structurally minimized hcp-bcc energy differences at a set of (η,γ) . We fit the PES using symmetry-adapted polynomials, permitting the MEP to be found analytically. The MEP is continuous and fully explains the transformation and its associated magnetization and volume discontinuity at TS. We show that σhyd (while not able to induce shear) dramatically alters the MEP to drive reconstruction by a shuffle-only mode at ≤30GPa , as observed. Finally, we relate our polynomial-based results to Landau and nudge-elastic-band approaches and show they yield incorrect MEP in general.

  15. Momentum density of hcp and liquid helium-4 by inelastic neutron scattering

    International Nuclear Information System (INIS)

    Hilleke, R.O.

    1983-01-01

    A measurement of the momentum density in hcp and liquid 4 He by inelastic neutron scattering is reported. Using the Low Resolution Medium Energy Chopper Spectrometer at the Intense Pulsed Neutron Source at Argonne National Laboratory, momentum transfers in the range 12 to 22.5 A -1 were attained. At these momentum transfers, the momentum density of the sample is related to the dynamic structure factor by the impulse approximation. The measured momentum distribution is Gaussian and the kinetic energy is larger than proposed by existing theories. Data were taken on two solid samples, the first was a 19.45 cm 3 /mole hcp solid, the second was 18.20 cm 3 /mole; both solid samples were maintained at 1.70 K during data collection. Data were also taken on a liquid sample with a molar volume of 18.20 cm 3 /mole at 4.00 K. At 1.70 K the two solid samples are essentially in their ground states so that the measurement is of the ground state momentum density. The liquid sample was included to see if the difference between the liquid and solid momentum density at the same molar volume was observable

  16. Extended solubility and martensitic hcp nickel formation in antimony implanted nickel

    International Nuclear Information System (INIS)

    Johnson, E.; Sarholt-Kristensen, L.; Johansen, A.

    1982-01-01

    Radiation damage microstructure and associated disorder have been investigated in antimony implanted nickel crystals using combined RBS and TEM analyses. In crystals implanted at and below room temperature with 80 keV Sb + ions to a fluence of 5x10 20 m -2 , the retained antimony concentration in the implantation zone is approaching 15 at.%, with nearly all the antimony located substitutionally. The associated disorder as seen in the RBS analysis is insignificant. Annealing up to 600 0 C has little influence on the antimony distribution, whilst the dechanneling level is reduced. TEM and diffraction analysis of room temperature implanted samples show that the radiation damage consists of dense distributions of dislocation clusters and tangles, superimposed on a rather homogeneous background of new phase particles, identified as hcp nickel. The particles have a size 0.1-0.2 μm. The high substitutional antimony concentration at and below room temperature, which exceeds the solubility limit, indicates that its formation is thermally diffusionless and rather an effect of radiation enhanced solubility. The diffusionless nature of the microstructure is also indicated from the presence of martensitic hcp nickel, believed to form due to relief of radiation induced internal stress. (Auth.)

  17. Modeling the effect of neighboring grains on twin growth in HCP polycrystals

    Science.gov (United States)

    Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

    2017-09-01

    In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

  18. Remanence coercivity of dot arrays of hcp-CoPt perpendicular films

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuzuka, K; Shimatsu, T; Aoi, H [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan); Kikuchi, N; Okamoto, S; Kitakami, O, E-mail: shimatsu@riec.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The remanence coercivity, H{sub r}, of hcp-CoPt dot arrays with various dot thicknesses, {delta}, (3 and 10 nm) and Pt content (20-30at%) were experimentally investigated as a function of the dot diameter, D(30-400 nm). All dot arrays showed a single domain state, even after removal of an applied field equal to H{sub r}. The angular dependence of H{sub r} for the dot arrays indicated coherent rotation of the magnetization during nucleation. H{sub r} increased as Ddecreased in all series of dot arrays with various {delta} and Pt content. Assuming that the nucleation field of a dot is determined by the switching field of a grain having the smallest switching field, we calculated the value of nucleation field H{sub n}{sup cal} taking account of the c-axis distribution and the distribution of the demagnetizing field in the dot. The values of H{sub r} obtained experimentally are in good agreement with those of H{sub n}{sup cal}, taking account of thermal agitation of magnetization. This result suggested that the reversal process of hcp-CoPt dot arrays starts from a nucleation at the center of the dot followed by a propagation process.

  19. Lattices with unique complements

    CERN Document Server

    Saliĭ, V N

    1988-01-01

    The class of uniquely complemented lattices properly contains all Boolean lattices. However, no explicit example of a non-Boolean lattice of this class has been found. In addition, the question of whether this class contains any complete non-Boolean lattices remains unanswered. This book focuses on these classical problems of lattice theory and the various attempts to solve them. Requiring no specialized knowledge, the book is directed at researchers and students interested in general algebra and mathematical logic.

  20. The hamster cheek pouch (HCP) as an experimental model of oral cancer for BNCT: biodistribution and pharmacokinetics of BPA

    International Nuclear Information System (INIS)

    Kreimann, E.; Itoiz, M.E.; Dagrosa, A.; Garavaglia, R.; Farias, S.; Batistoni, D.; Schwint, A.E.

    2000-01-01

    We propose and validate the HCP model of oral cancer for BNCT studies. This model serves to explore new applications of the technique, study the biology of BNCT and assess Boron uptake in clinically relevant oral tissues. Tumors are induced by a process that mimics spontaneous malignant transformation instead of by the growth of implanted tumor cells. Syrian hamsters were submitted to tumor induction with a chemical carcinogenesis protocol and then used for biodistribution and pharmacokinetic studies of BPA. The data reveal selective uptake by tumor and, to a lesser degree, by precancerous tissue. Boron concentration in oral tissues and skin was higher than in blood, an issue of clinical relevance given that these tissues may be dose-limiting. Absolute and relative values of Boron concentration would be potentially therapeutic. Boron concentration exhibited a linear relationship with percentage of viable tissue in HCP tumors. The HCP model would provide a novel, contributory approach to BNCT research. (author)

  1. Deformed lattice states in a Zn{sub 0.9}V{sub 0.1}Se cubic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, V. I., E-mail: kokailo@rambler.ru; Dubinin, S. F.; Surkova, T. P.; Parkhomenko, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

    2016-01-15

    Neutron scattering patterns have been recorded for a bulk Zn{sub 0.9}V{sub 0.1}Se cubic crystal at room temperature; they are indicative of macroscopic deformation in the material and its significant inhomogeneity. Specific features of the previously found state, preceding the fcc ↔ hcp structural transformation of the sphalerite lattice upon strong destabilization induced by vanadium ions in the doped ZnSe matrix, are discussed taking into account the data obtained.

  2. Constraining Phosphorus Chemistry in Carbon- and Oxygen-Rich Circumstellar Envelopes: Observations of PN, HCP, and CP

    Science.gov (United States)

    Milam, S. N.; Halfen, D. T.; Tenenbaum, E. D.; Apponi, A. J.; Woolf, N. J.; Ziurys, L. M.

    2008-09-01

    Millimeter-wave observations of PN, CP, and HCP have been carried out toward circumstellar envelopes of evolved stars using the Arizona Radio Observatory (ARO). HCP and PN have been identified in the carbon-rich source CRL 2688 via observations at 1 mm using the Submillimeter Telescope (SMT) and 2-3 mm with the Kitt Peak 12 m. An identical set of measurements were carried out toward IRC +10216, as well as observations of CP at 1 mm. PN was also observed toward VY Canis Majoris (VY CMa), an oxygen-rich supergiant star. The PN and HCP line profiles in CRL 2688 and IRC +10216 are roughly flat topped, indicating unresolved, optically thin emission; CP, in contrast, has a distinct "U" shape in IRC +10216. Modeling of the line profiles suggests abundances, relative to H2, of f(PN) ~ (3-5) × 10-9 and f(HCP) ~ 2 × 10-7 in CRL 2688, about an order of magnitude higher than in IRC +10216. In VY CMa, f(PN) is ~4 × 10-8. The data in CRL 2688 and IRC +10216 are consistent with LTE formation of HCP and PN in the inner envelope, as predicted by theoretical calculations, with CP a photodissociation product at larger radii. The observed abundance of PN in VY CMa is a factor of 100 higher than LTE predictions. In IRC +10216, the chemistry of HCP/CP mimics that of HCN/CN and suggests an N2 abundance of f ~ 1 × 10-7. The chemistry of phosphorus appears active in both carbon- and oxygen-rich envelopes of evolved stars.

  3. Dielectric matrix, dynamical matrix and phonon dispersion in hcp transition metal scandium

    International Nuclear Information System (INIS)

    Singh, Joginder; Singh, Natthi; Prakash, S.

    1976-01-01

    Complete dielectric matrix is evaluated for hcp transition metal scandium using the non-interacting s- and d-band model. The local field corrections which are consequence of the non-diagonal part of the dielectric matrix are calculated explicitly. The free electron approximation is used for the s-electrons and the simple tight-binding approximation is used for the d-electrons. The theory developed by Singh and others is used to invert the dielectric matrix and the explicit expressions for the dynamical matrix are obtained. The phonon dispersion relations are investigated by using the renormalized Animalu transition metal model potential (TMMP) for bare ion potential. The contribution due to non-central forces which arise due to local fields is found to be 20%. The results are found in resonably good agreement with the experimental values. (author)

  4. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Aliou Hamady [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Laboratoire Chimie des Matériaux, Département de Chimie, Faculté des Sciences et Technique, Université de Nouakchott (Mauritania, Islamic Republic of); Dirras, Guy, E-mail: dirras@unv-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France)

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  5. About the choice of Gibbs' potential for modelling of FCC ↔ HCP transformation in FeMnSi-based shape memory alloys

    Science.gov (United States)

    Evard, Margarita E.; Volkov, Aleksandr E.; Belyaev, Fedor S.; Ignatova, Anna D.

    2018-05-01

    The choice of Gibbs' potential for microstructural modeling of FCC ↔ HCP martensitic transformation in FeMn-based shape memory alloys is discussed. Threefold symmetry of the HCP phase is taken into account on specifying internal variables characterizing volume fractions of martensite variants. Constraints imposed on model constants by thermodynamic equilibrium conditions are formulated.

  6. New integrable lattice hierarchies

    International Nuclear Information System (INIS)

    Pickering, Andrew; Zhu Zuonong

    2006-01-01

    In this Letter we give a new integrable four-field lattice hierarchy, associated to a new discrete spectral problem. We obtain our hierarchy as the compatibility condition of this spectral problem and an associated equation, constructed herein, for the time-evolution of eigenfunctions. We consider reductions of our hierarchy, which also of course admit discrete zero curvature representations, in detail. We find that our hierarchy includes many well-known integrable hierarchies as special cases, including the Toda lattice hierarchy, the modified Toda lattice hierarchy, the relativistic Toda lattice hierarchy, and the Volterra lattice hierarchy. We also obtain here a new integrable two-field lattice hierarchy, to which we give the name of Suris lattice hierarchy, since the first equation of this hierarchy has previously been given by Suris. The Hamiltonian structure of the Suris lattice hierarchy is obtained by means of a trace identity formula

  7. Impact of polymorphisms in the HCP5 and HLA-C, and ZNRD1 genes on HIV viral load

    DEFF Research Database (Denmark)

    Thørner, Lise Wegner; Erikstrup, Christian; Harritshøj, Lene Holm

    2016-01-01

    AIMS: Single nucleotide polymorphisms (SNPs) in the human leucocyte antigen (HLA) complex P5 (HCP5), HLA-C, and near the zinc ribbon domain containing 1 (ZNRD1) have been shown to influence viral load (VL) set point in HIV-infected individuals with a known seroconversion onset. We aimed to determ...

  8. First Results for Fluid Dynamics, Neutronics and Fission Product Behaviour in HTR applying the HTR Code Package (HCP) Prototype

    International Nuclear Information System (INIS)

    Allelein, H.-J.; Kasselmann, S.; Xhonneux, A.; Lambertz, D.

    2014-01-01

    To simulate the different aspects of High Temperature Reactor (HTR) cores, a variety of specialized computer codes have been developed at Forschungszentrum Jülich (IEK-6) and Aachen University (LRST) in the last decades. In order to preserve knowledge, to overcome present limitations and to make these codes applicable to modern computer clusters, these individual programs are being integrated into a consistent code package. The so-called HTR code package (HCP) couples the related and recently applied physics models in a highly integrated manner and therefore allows to simulate phenomena with higher precision in space and time while at the same time applying state-of-the-art programming techniques and standards. This paper provides an overview of the status of the HCP and reports about first benchmark results for an HCP prototype which couples the fluid dynamics and time dependent neutronics code MGT-3D, the burn up code TNT and the fission product release code STACY. Due to the coupling of MGT-3D and TNT, a first step towards a new reactor operation and accident simulation code was made, where nuclide concentrations calculated by TNT are fed back into a new spectrum code of the HCP. Selected operation scenarios of the HTR-Module 200 concept plant and the HTTR were chosen to be simulated with the HCP prototype. The fission product release during normal operation conditions will be calculated with STACY based on a core status derived from SERPENT and MGT–3D. Comparisons will be shown against data generated by the legacy codes VSOP99/11, NAKURE and FRESCO-II. (author)

  9. Electrostatic instability of some jellium model lattices of high symmetry to their plane cleavage

    International Nuclear Information System (INIS)

    Kholopov, Eugene V; Kalashnikova, Vita V

    2007-01-01

    Jellium model structures composed of regular lattices of equal point charges immersed in a neutralizing uniform background are considered. The symmetric description eliminating the effect of potentials without transverse structural modulation is extended to the events specified by alternating distances between point-charge planes. Based on modulated potentials typical of plane-wise lattice summation, the energy of interaction between two semi-infinite hemi-crystals divided by a plane is obtained for cubic and hexagonal crystals, where all the characteristic orientations of the cleavage plane are taken into account. We found that simple cubic and hexagonal lattices, as well as cubic and hexagonal diamond structures, turn out to be unstable for certain cleavage planes. The most favourable cleavage planes for the bcc, fcc and hcp structures are also emphasized

  10. Generalized isothermic lattices

    International Nuclear Information System (INIS)

    Doliwa, Adam

    2007-01-01

    We study multi-dimensional quadrilateral lattices satisfying simultaneously two integrable constraints: a quadratic constraint and the projective Moutard constraint. When the lattice is two dimensional and the quadric under consideration is the Moebius sphere one obtains, after the stereographic projection, the discrete isothermic surfaces defined by Bobenko and Pinkall by an algebraic constraint imposed on the (complex) cross-ratio of the circular lattice. We derive the analogous condition for our generalized isothermic lattices using Steiner's projective structure of conics, and we present basic geometric constructions which encode integrability of the lattice. In particular, we introduce the Darboux transformation of the generalized isothermic lattice and we derive the corresponding Bianchi permutability principle. Finally, we study two-dimensional generalized isothermic lattices, in particular geometry of their initial boundary value problem

  11. Threefold symmetric magnetic two-ion coupling in hcp rare-earth metals

    International Nuclear Information System (INIS)

    Jensen, J.

    1997-01-01

    The heavy rare earths crystallize in the hcp structure. Most of magnetic couplings between two ions in these metals are independent of the two different orientations of the hexagonal layers. However, trigonal anisotropy terms may occur, reflecting that c-axis is only threefold axis. In the presence of a trigonal coupling the symmetry is reduced, and the double-zone representation in the c-direction ceases to be valid. The strong interaction between the transverse optical phonons and the acoustic spin waves propagating in the c-direction of Yb detected more than twenty years ago, was the first example of a trigonal coupling found in these systems. A few years ago a careful neutron-diffraction study of the c-axis modulated magnetic structures in Er showed the presence of higher harmonics at positions along the c-axis translated by odd multiple of 2φ/c. This indicates distortions of the structures due to trigonal couplings, and the same characteristic phenomenon has now been also observed in Ho. Additionally, mean field calculations show that a trigonal coupling in Ho is required, in order to explain the increase in the commensurable effects observed for the 8 and 10 layered periodic structures, when a field is applied along the c-axis. (author)

  12. Modelling the motion of {112-bar 2} twinning dislocations in the HCP metals

    International Nuclear Information System (INIS)

    Serra, A.; Bacon, D.J.

    2005-01-01

    Deformation twinning is important for plasticity of the hcp metals, but little is known about the dynamics of the mechanisms that control twin boundary motion. With the exception of the {112-bar 1} twin, atomic shuffles are required for glide of twinning dislocations and hence boundary movement is temperature-dependent. A computer method has been developed to simulate a step with dislocation character in a boundary with full periodicity in the boundary plane, i.e. along both the direction of the line of the defect and its direction of motion. It may be used to investigate the properties of such interfaces as the defects in them move over large distances. We explain the nature of the method and apply it to study the motion of twinning dislocations in the {112-bar 2} boundary as a function of applied stress and temperature. A new reaction at the boundary leading to the creation of a (c+a) crystal dislocation and a {112-bar 1} micro-twin is described

  13. Atomic vibration amplitudes in fcc and hcp 4He through x-ray diffraction measurements

    International Nuclear Information System (INIS)

    Venkataraman, C.T.; Simmons, R.O.

    2003-01-01

    Atomic vibration amplitudes in dense fcc and hcp 4 He crystals have been measured using synchrotron x rays from the dependence of integrated Bragg intensities up to wave vectors of 91 nm -1 . Observed raw Bragg x-ray integrated intensities cover an extraordinary range, greater than 10 5 , due to the combined effect of the Debye-Waller factor and electronic form factor. From analysis of these intensities mean-square atomic vibration amplitudes Q 2 > and Lindemann ratios are determined. Path-integral Monte Carlo (PIMC) computations of Draeger and Ceperley, extrapolated to the thermodynamic limit, provide excellent agreement with these experimental results. For both present measurements and the PIMC results, one finds both a predominantly Gaussian distribution in Q 2 > and an extraordinarily large Lindemann ratio. In contrast, these directly measured x-ray values are significantly larger than published values inferred from Born-von Karman fitting to phonon dispersion measured by neutron scattering. Mildly anharmonic neon, which is fairly well described by self-consistent phonon theories, is contrasted with present results on fcc 4 He at corresponding densities

  14. Positron lifetime studies of the hcp to fcc transformation induced by mechanical attrition of elemental titanium

    International Nuclear Information System (INIS)

    Manna, I.; Chattopadhyay, P.P.; Nandi, P.; Nambissan, P.M.G.

    2004-01-01

    Nanocrystallisation by planetary ball-milling of high purity elemental titanium (Ti) revealed a polymorphic transformation from its normal hexagonal close packed (hcp) structure to a face-centered cubic (fcc) phase. Positron lifetime measurements were carried out on samples collected after different hours of milling to characterize the defect structures at grain surfaces. With increasing hours of milling, the nanocrystalline grain size decreased and the positron lifetimes--one related to the annihilation at the grain surfaces and the other to that at the intergranular open volume domains--increased significantly due to the increased free volume at the trapping vacancy sites. However, between 5 to 10 hours of milling, the two lifetimes decreased before resuming increasing once again. This marked deviation from an otherwise expected continuous increase of positron lifetime coincided with structural rearrangement within the system bringing in an enhancement in the density of electrons. The repacking of atoms along the [0001] crystallographic direction could be a possibility for this observation. Positron radiation effects on the migration and agglomeration of nanoparticles are also discussed

  15. Nucleation size of hcp-CoPt dot arrays characterized by time dependence of coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, N; Kitakami, O [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan); Mitsuzuka, K; Shimatsu, T; Aoi, H, E-mail: kikuchin@tagen.tohoku.ac.j [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The magnetization reversal process for dot arrays is likely to start from a nucleation followed by propagation process. In this study, we estimated the nucleation diameter D{sub n} for dot arrays made from thin hcp-CoPt perpendicular films (thickness {delta}=3 nm) and Co/Pt multilayered films ({delta}=9 nm), respectively. The dot diameter, D, was varied from 30 to 200 nm for CoPt dot arrays, and from 40 to 80 nm for Co/Pt dot arrays. The remanence coercivity was measured at measurement times t' = 10{sup 3} s and 10{sup -5} s (pulse field), and defined as H{sub r} and H{sub r}{sup P}. The energy barrier {Delta}E was evaluated by fitting H{sub r} and H{sub r}{sup P} to Sharrock's equation. The value of D{sub n} was estimated from {Delta}E, {delta} and the effective magnetic anisotropy of dot arrays including the demagnetizing energy due to the dot shape K{sub u}{sup eff}. D{sub n} was independent of Din both series of dot arrays, and about 17 nm for CoPt dot arrays and about 11 nm for Co/Pt dot arrays. These values were close to both the grain size and the exchange length of these films.

  16. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  17. Lattice theory for nonspecialists

    International Nuclear Information System (INIS)

    Hari Dass, N.D.

    1984-01-01

    These lectures were delivered as part of the academic training programme at the NIKHEF-H. These lectures were intended primarily for experimentalists, and theorists not specializing in lattice methods. The goal was to present the essential spirit behind the lattice approach and consequently the author has concentrated mostly on issues of principle rather than on presenting a large amount of detail. In particular, the author emphasizes the deep theoretical infra-structure that has made lattice studies meaningful. At the same time, he has avoided the use of heavy formalisms as they tend to obscure the basic issues for people trying to approach this subject for the first time. The essential ideas are illustrated with elementary soluble examples not involving complicated mathematics. The following subjects are discussed: three ways of solving the harmonic oscillator problem; latticization; gauge fields on a lattice; QCD observables; how to solve lattice theories. (Auth.)

  18. Lattice gauge theories

    International Nuclear Information System (INIS)

    Creutz, M.

    1983-04-01

    In the last few years lattice gauge theory has become the primary tool for the study of nonperturbative phenomena in gauge theories. The lattice serves as an ultraviolet cutoff, rendering the theory well defined and amenable to numerical and analytical work. Of course, as with any cutoff, at the end of a calculation one must consider the limit of vanishing lattice spacing in order to draw conclusions on the physical continuum limit theory. The lattice has the advantage over other regulators that it is not tied to the Feynman expansion. This opens the possibility of other approximation schemes than conventional perturbation theory. Thus Wilson used a high temperature expansion to demonstrate confinement in the strong coupling limit. Monte Carlo simulations have dominated the research in lattice gauge theory for the last four years, giving first principle calculations of nonperturbative parameters characterizing the continuum limit. Some of the recent results with lattice calculations are reviewed

  19. Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium.

    Energy Technology Data Exchange (ETDEWEB)

    Shulenburger, Luke [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mattsson, Thomas Kjell Rene [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Desjarlais, Michael Paul [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Motivated by the disagreement between recent diffusion Monte Carlo calculations of the phase transition pressure between the ambient and beta-Sn phases of silicon and experiments, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an opportunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation and after removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

  20. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    International Nuclear Information System (INIS)

    Gao, Lei; Ding, Xiangdong; Sun, Jun; Lookman, Turab; Salje, E. K. H.

    2016-01-01

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  1. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Lei; Ding, Xiangdong, E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Salje, E. K. H., E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom)

    2016-07-18

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  2. On Traveling Waves in Lattices: The Case of Riccati Lattices

    Science.gov (United States)

    Dimitrova, Zlatinka

    2012-09-01

    The method of simplest equation is applied for analysis of a class of lattices described by differential-difference equations that admit traveling-wave solutions constructed on the basis of the solution of the Riccati equation. We denote such lattices as Riccati lattices. We search for Riccati lattices within two classes of lattices: generalized Lotka-Volterra lattices and generalized Holling lattices. We show that from the class of generalized Lotka-Volterra lattices only the Wadati lattice belongs to the class of Riccati lattices. Opposite to this many lattices from the Holling class are Riccati lattices. We construct exact traveling wave solutions on the basis of the solution of Riccati equation for three members of the class of generalized Holling lattices.

  3. Lattice degeneracies of fermions

    International Nuclear Information System (INIS)

    Raszillier, H.

    1983-10-01

    We present a detailed description of the minimal degeneracies of geometric (Kaehler) fermions on all the lattices of maximal symmetries in n = 1, ..., 4 dimensions. We also determine the isolated orbits of the maximal symmetry groups, which are related to the minimal numbers of ''naive'' fermions on the reciprocals of these lattices. It turns out that on the self-reciprocal lattices the minimal numbers of naive fermions are equal to the minimal numbers of degrees of freedom of geometric fermions. The description we give relies on the close connection of the maximal lattice symmetry groups with (affine) Weyl groups of root systems of (semi-) simple Lie algebras. (orig.)

  4. Twisted mass lattice QCD

    International Nuclear Information System (INIS)

    Shindler, A.

    2007-07-01

    I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)

  5. Twisted mass lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2007-07-15

    I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)

  6. Pre-melting hcp to bcc Transition in Beryllium: A Study by First-Principles Phonon Quasiparticle Approach

    Science.gov (United States)

    Zhang, D. B., Sr.

    2017-12-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  7. High temperature series expansions with a multiple-exchange Hamiltonian for the bcc and hcp phases of solid 3He

    International Nuclear Information System (INIS)

    Roger, M.; Suaudeau, E.; Bernier, M.E.R.

    1987-08-01

    High temperature series expansions with a multiple-exchange Hamiltonian are performed to fourth order in arbitrary magnetic field for both phases of solid 3 He. The susceptibility series are analysed with Pade approximants and compared with recent experimental results. For the hcp phase we estimate the ferromagnetic ordering temperature from susceptibility series and discuss the influence of four-particle exchange in lowering the transition

  8. First results for fluid dynamics, neutronics and fission product behavior in HTR applying the HTR code package (HCP) prototype

    Energy Technology Data Exchange (ETDEWEB)

    Allelein, H.-J., E-mail: h.j.allelein@fz-juelich.de [Forschungszentrum Jülich, 52425 Jülich (Germany); Institute for Reactor Safety and Reactor Technology, RWTH Aachen University, 52064 Aachen (Germany); Kasselmann, S.; Xhonneux, A.; Tantillo, F.; Trabadela, A.; Lambertz, D. [Forschungszentrum Jülich, 52425 Jülich (Germany)

    2016-09-15

    To simulate the different aspects of High Temperature Reactor (HTR) cores, a variety of specialized computer codes have been developed at Forschungszentrum Jülich (IEK-6) and Aachen University (LRST) in the last decades. In order to preserve knowledge, to overcome present limitations and to make these codes applicable to modern computer clusters, these individual programs are being integrated into a consistent code package. The so-called HTR code package (HCP) couples the related and recently applied physics models in a highly integrated manner and therefore allows to simulate phenomena with higher precision in space and time while at the same time applying state-of-the-art programming techniques and standards. This paper provides an overview of the status of the HCP and reports about first benchmark results for an HCP prototype which couples the fluid dynamics and time dependent neutronics code MGT-3D, the burn up code TNT and the fission product release code STACY. Due to the coupling of MGT-3D and TNT, a first step towards a new reactor operation and accident simulation code was made, where nuclide concentrations calculated by TNT lead to new cross sections, which are fed back into MGT-3D. Selected operation scenarios of the HTR-Module 200 concept plant and the HTTR were chosen to be simulated with the HCP prototype. The fission product release during normal operation conditions will be calculated with STACY based on a core status derived from SERPENT and MGT-3D. Comparisons will be shown against data generated by SERPENT and the legacy codes VSOP99/11, NAKURE and FRESCO-II.

  9. Nuclear lattice simulations

    Directory of Open Access Journals (Sweden)

    Epelbaum E.

    2010-04-01

    Full Text Available We review recent progress on nuclear lattice simulations using chiral effective field theory. We discuss lattice results for dilute neutron matter at next-to-leading order, three-body forces at next-to-next-toleading order, isospin-breaking and Coulomb effects, and the binding energy of light nuclei.

  10. Lattice Higgs models

    International Nuclear Information System (INIS)

    Jersak, J.

    1986-01-01

    This year has brought a sudden interest in lattice Higgs models. After five years of only modest activity we now have many new results obtained both by analytic and Monte Carlo methods. This talk is a review of the present state of lattice Higgs models with particular emphasis on the recent development

  11. HCP to FCT + precipitate transformations in lamellar gamma-titanium aluminide alloys

    Science.gov (United States)

    Karadge, Mallikarjun Baburao

    Fully lamellar gamma-TiAl [alpha2(HCP) + gamma(FCT)] based alloys are potential structural materials for aerospace engine applications. Lamellar structure stabilization and additional strengthening mechanisms are major issues in the ongoing development of titanium aluminides due to the microstructural instability resulting from decomposition of the strengthening alpha 2 phase. This work addresses characterization of multi-component TiAl systems to identify the mechanism of lamellar structure refinement and assess the effects of light element additions (C and Si) on creep deformation behavior. Transmission electron microscopy studies directly confirmed for the first time that, fine lamellar structure is formed by the nucleation and growth of a large number of basal stacking faults on the 1/6 dislocations cross slipping repeatedly into and out of basal planes. This lamellar structure can be tailored by modifying jog heights through chemistry and thermal processing. alpha 2 → gamma transformation during heating (investigated by differential scanning calorimetry and X-ray diffraction) is a two step process involving the formation of a novel disordered FCC gamma' TiAl [with a(gamma') = c(gamma)] as an intermediate phase followed by ordering. Addition of carbon and silicon induced Ti2AlC H-type carbide precipitation inside the alpha2 lath and Ti 5(Al,Si)3 zeta-type silicide precipitation at the alpha 2/gamma interface. The H-carbides preserve alpha2/gamma type interfaces, while zeta-silicide precipitates restrict ledge growth and interfacial sliding enabling strong resistance to creep deformation.

  12. On singularities of lattice varieties

    OpenAIRE

    Mukherjee, Himadri

    2013-01-01

    Toric varieties associated with distributive lattices arise as a fibre of a flat degeneration of a Schubert variety in a minuscule. The singular locus of these varieties has been studied by various authors. In this article we prove that the number of diamonds incident on a lattice point $\\a$ in a product of chain lattices is more than or equal to the codimension of the lattice. Using this we also show that the lattice varieties associated with product of chain lattices is smooth.

  13. MEETING: Lattice 88

    International Nuclear Information System (INIS)

    Mackenzie, Paul

    1989-01-01

    The forty-year dream of understanding the properties of the strongly interacting particles from first principles is now approaching reality. Quantum chromodynamics (QCD - the field theory of the quark and gluon constituents of strongly interacting particles) was initially handicapped by the severe limitations of the conventional (perturbation) approach in this picture, but Ken Wilson's inventions of lattice gauge theory and renormalization group methods opened new doors, making calculations of masses and other particle properties possible. Lattice gauge theory became a major industry around 1980, when Monte Carlo methods were introduced, and the first prototype calculations yielded qualitatively reasonable results. The promising developments over the past year were highlighted at the 1988 Symposium on Lattice Field Theory - Lattice 88 - held at Fermilab

  14. Angles in hyperbolic lattices

    DEFF Research Database (Denmark)

    Risager, Morten S.; Södergren, Carl Anders

    2017-01-01

    It is well known that the angles in a lattice acting on hyperbolic n -space become equidistributed. In this paper we determine a formula for the pair correlation density for angles in such hyperbolic lattices. Using this formula we determine, among other things, the asymptotic behavior of the den......It is well known that the angles in a lattice acting on hyperbolic n -space become equidistributed. In this paper we determine a formula for the pair correlation density for angles in such hyperbolic lattices. Using this formula we determine, among other things, the asymptotic behavior...... of the density function in both the small and large variable limits. This extends earlier results by Boca, Pasol, Popa and Zaharescu and Kelmer and Kontorovich in dimension 2 to general dimension n . Our proofs use the decay of matrix coefficients together with a number of careful estimates, and lead...

  15. Reactor lattice codes

    International Nuclear Information System (INIS)

    Kulikowska, T.

    1999-01-01

    The present lecture has a main goal to show how the transport lattice calculations are realised in a standard computer code. This is illustrated on the example of the WIMSD code, belonging to the most popular tools for reactor calculations. Most of the approaches discussed here can be easily modified to any other lattice code. The description of the code assumes the basic knowledge of reactor lattice, on the level given in the lecture on 'Reactor lattice transport calculations'. For more advanced explanation of the WIMSD code the reader is directed to the detailed descriptions of the code cited in References. The discussion of the methods and models included in the code is followed by the generally used homogenisation procedure and several numerical examples of discrepancies in calculated multiplication factors based on different sources of library data. (author)

  16. MEETING: Lattice 88

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, Paul

    1989-03-15

    The forty-year dream of understanding the properties of the strongly interacting particles from first principles is now approaching reality. Quantum chromodynamics (QCD - the field theory of the quark and gluon constituents of strongly interacting particles) was initially handicapped by the severe limitations of the conventional (perturbation) approach in this picture, but Ken Wilson's inventions of lattice gauge theory and renormalization group methods opened new doors, making calculations of masses and other particle properties possible. Lattice gauge theory became a major industry around 1980, when Monte Carlo methods were introduced, and the first prototype calculations yielded qualitatively reasonable results. The promising developments over the past year were highlighted at the 1988 Symposium on Lattice Field Theory - Lattice 88 - held at Fermilab.

  17. Computers for Lattice QCD

    International Nuclear Information System (INIS)

    Christ, Norman H

    2000-01-01

    The architecture and capabilities of the computers currently in use for large-scale lattice QCD calculations are described and compared. Based on this present experience, possible future directions are discussed

  18. Reactor lattice codes

    International Nuclear Information System (INIS)

    Kulikowska, T.

    2001-01-01

    The description of reactor lattice codes is carried out on the example of the WIMSD-5B code. The WIMS code in its various version is the most recognised lattice code. It is used in all parts of the world for calculations of research and power reactors. The version WIMSD-5B is distributed free of charge by NEA Data Bank. The description of its main features given in the present lecture follows the aspects defined previously for lattice calculations in the lecture on Reactor Lattice Transport Calculations. The spatial models are described, and the approach to the energy treatment is given. Finally the specific algorithm applied in fuel depletion calculations is outlined. (author)

  19. Lattice gauge theories

    International Nuclear Information System (INIS)

    Petronzio, R.

    1992-01-01

    Lattice gauge theories are about fifteen years old and I will report on the present status of the field without making the elementary introduction that can be found in the proceedings of the last two conferences. The talk covers briefly the following subjects: the determination of α s , the status of spectroscopy, heavy quark physics and in particular the calculation of their hadronic weak matrix elements, high temperature QCD, non perturbative Higgs bounds, chiral theories on the lattice and induced theories

  20. Permutohedral Lattice CNNs

    OpenAIRE

    Kiefel, Martin; Jampani, Varun; Gehler, Peter V.

    2014-01-01

    This paper presents a convolutional layer that is able to process sparse input features. As an example, for image recognition problems this allows an efficient filtering of signals that do not lie on a dense grid (like pixel position), but of more general features (such as color values). The presented algorithm makes use of the permutohedral lattice data structure. The permutohedral lattice was introduced to efficiently implement a bilateral filter, a commonly used image processing operation....

  1. Ab initio study of vibronic transitions between x2π and 12Σ+ electronic states of HCP+ ion

    Directory of Open Access Journals (Sweden)

    Stojanović Ljiljana

    2013-01-01

    Full Text Available The ground and low-lying excited doublet electronic states of the HCP+ ion were studied by means of multireference configuration interaction method. Vibronic energy levels of the X2Π state of Σ, Π, Δ, and Φ symmetry, up to the 2500 cm-1, have been calculated variationally, employing previously developed ab initio methods which take into account vibronic and spin-orbit interactions. Obtained vibronic wave functions were used to estimate transition moments between vibronic energy levels of the X2Π and 12Σ+ electronic states. Results were compared to available experimental and theoretical data. [Projekat Ministarstva nauke Republike Srbije, br. 172040

  2. Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

    International Nuclear Information System (INIS)

    Mattei, G.; Maurizio, C.; Fernandez, C Julian de; Mazzoldi, P.; Battaglin, G.; Canton, P.; Cattaruzza, E.; Scian, C.

    2006-01-01

    In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 deg. C) when nanoclusters are considered. Starting from Co:SiO 2 composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 deg. C and 900 deg. C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented

  3. Additive lattice kirigami.

    Science.gov (United States)

    Castle, Toen; Sussman, Daniel M; Tanis, Michael; Kamien, Randall D

    2016-09-01

    Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes.

  4. Lattice regularized chiral perturbation theory

    International Nuclear Information System (INIS)

    Borasoy, Bugra; Lewis, Randy; Ouimet, Pierre-Philippe A.

    2004-01-01

    Chiral perturbation theory can be defined and regularized on a spacetime lattice. A few motivations are discussed here, and an explicit lattice Lagrangian is reviewed. A particular aspect of the connection between lattice chiral perturbation theory and lattice QCD is explored through a study of the Wess-Zumino-Witten term

  5. Vortex lattices in layered superconductors

    International Nuclear Information System (INIS)

    Prokic, V.; Davidovic, D.; Dobrosavljevic-Grujic, L.

    1995-01-01

    We study vortex lattices in a superconductor--normal-metal superlattice in a parallel magnetic field. Distorted lattices, resulting from the shear deformations along the layers, are found to be unstable. Under field variation, nonequilibrium configurations undergo an infinite sequence of continuous transitions, typical for soft lattices. The equilibrium vortex arrangement is always a lattice of isocell triangles, without shear

  6. Deformation-induced crystallographic-preferred orientation of hcp-iron: An experimental study using a deformation-DIA apparatus

    Science.gov (United States)

    Nishihara, Yu; Ohuchi, Tomohiro; Kawazoe, Takaaki; Seto, Yusuke; Maruyama, Genta; Higo, Yuji; Funakoshi, Ken-ichi; Tange, Yoshinori; Irifune, Tetsuo

    2018-05-01

    Shear and uniaxial deformation experiments on hexagonal close-packed iron (hcp-Fe) was conducted using a deformation-DIA apparatus at a pressure of 13-17 GPa and a temperature of 723 K to determine its deformation-induced crystallographic-preferred orientation (CPO). Development of the CPO in the deforming sample is determined in-situ based on two-dimensional X-ray diffraction using monochromatic synchrotron X-rays. In the shear deformation geometry, the and axes gradually align to be sub-parallel to the shear plane normal and shear direction, respectively, from the initial random texture. In the uniaxial compression and tensile geometry, the and axes, respectively, gradually align along the direction of the uniaxial deformation axis. These results suggest that basal slip (0001) is the dominant slip system in hcp-Fe under the studied deformation conditions. The P-wave anisotropy for a shear deformed sample was calculated using elastic constants at the inner core condition by recent ab-initio calculations. Strength of the calculated anisotropy was comparable to or higher than axisymmetric anisotropy in Earth's inner core.

  7. Size effects of nano-spaced basal stacking faults on the strength and deformation mechanisms of nanocrystalline pure hcp metals

    Science.gov (United States)

    Wang, Wen; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei

    2018-05-01

    The size effects of nano-spaced basal stacking faults (SFs) on the tensile strength and deformation mechanisms of nanocrystalline pure cobalt and magnesium have been investigated by a series of large-scale 2D columnar and 3D molecular dynamics simulations. Unlike the strengthening effect of basal SFs on Mg alloys, the nano-spaced basal SFs are observed to have no strengthening effect on the nanocrystalline pure cobalt and magnesium from MD simulations. These observations could be attributed to the following two reasons: (i) Lots of new basal SFs are formed before (for cobalt) or simultaneously with (for magnesium) the other deformation mechanisms (i.e. the formation of twins and the edge dislocations) during the tensile deformation; (ii) In hcp alloys, the segregation of alloy elements and impurities at typical interfaces, such as SFs, can stablilise them for enhancing the interactions with dislocation and thus elevating the strength. Without such segregation in pure hcp metals, the edge dislocations can cut through the basal SFs although the interactions between the dislocations and the pre-existing SFs/newly formed SFs are observed. The nano-spaced basal SFs are also found to have no restriction effect on the formation of deformation twins.

  8. Gibbs energy modelling of the driving forces and calculation of the fcc/hcp martensitic transformation temperatures in Fe-Mn and Fe-Mn-Si alloys

    International Nuclear Information System (INIS)

    Cotes, S.; Fernandez Guillermet, A.; Sade, M.

    1999-01-01

    Very recent, accurate dilatometric measurements of the fcc hcp martensitic transformation (MT) temperatures are used to develop a new thermodynamic description of the fcc and hcp phases in the Fe-Mn-Si system, based on phenomenological models for the Gibbs energy function. The composition dependence of the driving forces for the fcc→hcp and the hcp→fcc MTs is established. Detailed calculations of the MT temperatures are reported, which are used to investigate the systematic effects of Si additions upon the MT temperatures of Fe-Mn alloys. A critical comparison with one of the most recent thermodynamic analyses of the Fe-Mn-Si system, which is due to Forsberg and Agren, is also presented. (orig.)

  9. Dynamical lattice theory

    International Nuclear Information System (INIS)

    Chodos, A.

    1978-01-01

    A version of lattice gauge theory is presented in which the shape of the lattice is not assumed at the outset but is a consequence of the dynamics. Other related features which are not specified a priori include the internal and space-time symmetry groups and the dimensionality of space-time. The theory possesses a much larger invariance group than the usual gauge group on a lattice, and has associated with it an integer k 0 analogous to the topological quantum numer of quantum chromodynamics. Families of semiclassical solutions are found which are labeled by k 0 and a second integer x, but the analysis is not carried far enough to determine which space-time and internal symmetry groups characterize the lowest-lying states of the theory

  10. Graphene antidot lattice waveguides

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Gunst, Tue; Markussen, Troels

    2012-01-01

    We introduce graphene antidot lattice waveguides: nanostructured graphene where a region of pristine graphene is sandwiched between regions of graphene antidot lattices. The band gaps in the surrounding antidot lattices enable localized states to emerge in the central waveguide region. We model...... the waveguides via a position-dependent mass term in the Dirac approximation of graphene and arrive at analytical results for the dispersion relation and spinor eigenstates of the localized waveguide modes. To include atomistic details we also use a tight-binding model, which is in excellent agreement...... with the analytical results. The waveguides resemble graphene nanoribbons, but without the particular properties of ribbons that emerge due to the details of the edge. We show that electrons can be guided through kinks without additional resistance and that transport through the waveguides is robust against...

  11. Exact Lattice Supersymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Catterall, Simon; Kaplan, David B.; Unsal, Mithat

    2009-03-31

    We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.

  12. Quarks, gluons and lattices

    International Nuclear Information System (INIS)

    Krojts, M.

    1987-01-01

    The book by the known american physicist-theoretist M.Kreuts represents the first monography in world literature, where a new perspective direction in elementary particle physics and quantum field theory - lattice formulation of gauge theories is stated systematically. Practically all main ideas of this direction are given. Material is stated in systematic and understandable form

  13. Phenomenology Using Lattice QCD

    Science.gov (United States)

    Gupta, R.

    2005-08-01

    This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.

  14. Baryons on the lattice

    International Nuclear Information System (INIS)

    Bali, G.S.

    2005-01-01

    I comment on progress of lattice QCD techniques and calculations. Recent results on pentaquark masses as well as of the spectrum of excited baryons are summarized and interpreted. The present state of calculations of quantities related to the nucleon structure and of electromagnetic transition form factors is surveyed

  15. Finite lattice extrapolation algorithms

    International Nuclear Information System (INIS)

    Henkel, M.; Schuetz, G.

    1987-08-01

    Two algorithms for sequence extrapolation, due to von den Broeck and Schwartz and Bulirsch and Stoer are reviewed and critically compared. Applications to three states and six states quantum chains and to the (2+1)D Ising model show that the algorithm of Bulirsch and Stoer is superior, in particular if only very few finite lattice data are available. (orig.)

  16. Lattice Multiverse Models

    OpenAIRE

    Williamson, S. Gill

    2010-01-01

    Will the cosmological multiverse, when described mathematically, have easily stated properties that are impossible to prove or disprove using mathematical physics? We explore this question by constructing lattice multiverses which exhibit such behavior even though they are much simpler mathematically than any likely cosmological multiverse.

  17. Quantum lattice problems

    NARCIS (Netherlands)

    de Raedt, Hans; von der Linden, W.; Binder, K

    1995-01-01

    In this chapter we review methods currently used to perform Monte Carlo calculations for quantum lattice models. A detailed exposition is given of the formalism underlying the construction of the simulation algorithms. We discuss the fundamental and technical difficulties that are encountered and

  18. Convex Lattice Polygons

    Science.gov (United States)

    Scott, Paul

    2006-01-01

    A "convex" polygon is one with no re-entrant angles. Alternatively one can use the standard convexity definition, asserting that for any two points of the convex polygon, the line segment joining them is contained completely within the polygon. In this article, the author provides a solution to a problem involving convex lattice polygons.

  19. Lattices for antiproton rings

    International Nuclear Information System (INIS)

    Autin, B.

    1984-01-01

    After a description of the constraints imposed by the cooling of Antiprotons on the lattice of the rings, the reasons which motivate the shape and the structure of these machines are surveyed. Linear and non-linear beam optics properties are treated with a special amplification to the Antiproton Accumulator. (orig.)

  20. Unquenched lattice upsilon spectroscopy

    International Nuclear Information System (INIS)

    Marcantonio, L.M.

    2001-03-01

    A non-relativistic effective theory of QCD (NRQCD) is used in calculations of the upsilon spectrum. Simultaneous multi-correlation fitting routines are used to yield lattice channel energies and amplitudes. The lattice configurations used were both dynamical, with two flavours of sea quarks included in the action; and quenched, with no sea quarks. These configurations were generated by the UKQCD collaboration. The dynamical configurations used were ''matched'', having the same lattice spacing, but differing in the sea quark mass. Thus, it was possible to analyse trends of observables with sea quark mass, in the certainty that the trend isn't partially due to varying lattice spacing. The lattice spacing used for spectroscopy was derived from the lattice 1 1 P 1 - 1 3 S 1 splitting. On each set of configurations two lattice bare b quark masses were used, giving kinetic masses bracketing the physical Υ mass. The only quantity showing a strong dependence on these masses was the hyperfine splitting, so it was interpolated to the real Υ mass. The radial and orbital splittings gave good agreement with experiment. The hyperfine splitting results showed a clear signal for unquenching and the dynamical hyperfine splitting results were extrapolated to a physical sea quark mass. This result, combined with the quenched result yielded a value for the hyperfine splitting at n f = 3, predicting an η b mass of 9.517(4) GeV. The NRQCD technique for obtaining a value of the strong coupling constant in the M-barS-bar scheme was followed. Using quenched and dynamical results a value was extrapolated to n f = 3. Employing a three loop beta function to run the coupling, with suitable matching conditions at heavy quark thresholds, the final result was obtained for n f = 5 at a scale equal to the Z boson mass. This result was α(5)/MS(Mz)=0.110(4). Two methods for finding the mass of the b quark in the MS scheme were employed. The results of both methods agree within error but the

  1. Superspace approach to lattice supersymmetry

    International Nuclear Information System (INIS)

    Kostelecky, V.A.; Rabin, J.M.

    1984-01-01

    We construct a cubic lattice of discrete points in superspace, as well as a discrete subgroup of the supersymmetry group which maps this ''superlattice'' into itself. We discuss the connection between this structure and previous versions of lattice supersymmetry. Our approach clarifies the mathematical problems of formulating supersymmetric lattice field theories and suggests new methods for attacking them

  2. Basis reduction for layered lattices

    NARCIS (Netherlands)

    Torreão Dassen, Erwin

    2011-01-01

    We develop the theory of layered Euclidean spaces and layered lattices. We present algorithms to compute both Gram-Schmidt and reduced bases in this generalized setting. A layered lattice can be seen as lattices where certain directions have infinite weight. It can also be

  3. An overview of lattice QCD

    International Nuclear Information System (INIS)

    Woloshyn, R.M.

    1988-03-01

    The basic concepts of the Lagrangian formulation of lattice field theory are discussed. The Wilson and staggered schemes for dealing with fermions on the lattice are described. Some recent results for hadron masses and vector and axial vector current matrix elements in lattice QCD are reviewed. (Author) (118 refs., 16 figs.)

  4. Basis reduction for layered lattices

    NARCIS (Netherlands)

    E.L. Torreão Dassen (Erwin)

    2011-01-01

    htmlabstractWe develop the theory of layered Euclidean spaces and layered lattices. With this new theory certain problems that usually are solved by using classical lattices with a "weighting" gain a new, more natural form. Using the layered lattice basis reduction algorithms introduced here these

  5. Datagrids for lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Buechner, O. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Ernst, M. [Deutsches Elektronen-Synchrotron DESY, 22603 Hamburg (Germany); Jansen, K. [John von Neumann-Institut fuer Computing NIC/DESY, 15738 Zeuthen (Germany); Lippert, Th. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Melkumyan, D. [Deutsches Elektronen-Synchrotron DESY, 15738 Zeuthen (Germany); Orth, B. [Zentralinstitut fuer Angewandte Mathematik ZAM, 52425 Juelich (Germany); Pleiter, D. [John von Neumann-Institut fuer Computing NIC/DESY, 15738 Zeuthen (Germany)]. E-mail: dirk.pleiter@desy.de; Stueben, H. [Konrad-Zuse-Institut fuer Informationstechnik ZIB, 14195 Berlin (Germany); Wegner, P. [Deutsches Elektronen-Synchrotron DESY, 15738 Zeuthen (Germany); Wollny, S. [Konrad-Zuse-Institut fuer Informationstechnik ZIB, 14195 Berlin (Germany)

    2006-04-01

    As the need for computing resources to carry out numerical simulations of Quantum Chromodynamics (QCD) formulated on a lattice has increased significantly, efficient use of the generated data has become a major concern. To improve on this, groups plan to share their configurations on a worldwide level within the International Lattice DataGrid (ILDG). Doing so requires standardized description of the configurations, standards on binary file formats and common middleware interfaces. We describe the requirements and problems, and discuss solutions. Furthermore, an overview is given on the implementation of the LatFor DataGrid [http://www-zeuthen.desy.de/latfor/ldg], a France/German/Italian grid that will be one of the regional grids within the ILDG grid-of-grids concept.

  6. Lattice QCD for cosmology

    International Nuclear Information System (INIS)

    Borsanyi, Sz.; Kampert, K.H.; Fodor, Z.; Forschungszentrum Juelich; Eoetvoes Univ., Budapest

    2016-06-01

    We present a full result for the equation of state (EoS) in 2+1+1 (up/down, strange and charm quarks are present) flavour lattice QCD. We extend this analysis and give the equation of state in 2+1+1+1 flavour QCD. In order to describe the evolution of the universe from temperatures several hundreds of GeV to the MeV scale we also include the known effects of the electroweak theory and give the effective degree of freedoms. As another application of lattice QCD we calculate the topological susceptibility (χ) up to the few GeV temperature region. These two results, EoS and χ, can be used to predict the dark matter axion's mass in the post-inflation scenario and/or give the relationship between the axion's mass and the universal axionic angle, which acts as a initial condition of our universe.

  7. Lattice vibration spectra. 16

    International Nuclear Information System (INIS)

    Lutz, H.D.; Willich, P.

    1977-01-01

    The FIR absorption spectra of pyrite type compounds RuS 2 , RuSsub(2-x)Sesub(x), RuSe 2 , RuTe 2 , OsS 2 , OsSe 2 , and PtP 2 as well as loellingite type phosphides FeP 2 , RuP 2 , and OsP 2 are reported. For RuS 2 , RuSe 2 , RuTe 2 , OsS 2 , and PtP 2 all of the five infrared allowed modes (k = 0) are observed. As a first result of a numerical normal coordinate treatment vibration forms of pyrite structure are communicated. The spectra show that lattice forces of corresponding sulfides, tellurides, and phosphides are about the same strength, but increase strongly by substitution of iron by ruthenium and especially of ruthenium by osmium. The lattice constants of the RuSsub(2-x)Sesub(x) solid solution obey Vegard's rule. (author)

  8. Lattice Wigner equation

    Science.gov (United States)

    Solórzano, S.; Mendoza, M.; Succi, S.; Herrmann, H. J.

    2018-01-01

    We present a numerical scheme to solve the Wigner equation, based on a lattice discretization of momentum space. The moments of the Wigner function are recovered exactly, up to the desired order given by the number of discrete momenta retained in the discretization, which also determines the accuracy of the method. The Wigner equation is equipped with an additional collision operator, designed in such a way as to ensure numerical stability without affecting the evolution of the relevant moments of the Wigner function. The lattice Wigner scheme is validated for the case of quantum harmonic and anharmonic potentials, showing good agreement with theoretical results. It is further applied to the study of the transport properties of one- and two-dimensional open quantum systems with potential barriers. Finally, the computational viability of the scheme for the case of three-dimensional open systems is also illustrated.

  9. Lattice Quantum Chromodynamics

    CERN Document Server

    Sachrajda, C T

    2016-01-01

    I review the the application of the lattice formulation of QCD and large-scale numerical simulations to the evaluation of non-perturbative hadronic effects in Standard Model Phenomenology. I present an introduction to the elements of the calculations and discuss the limitations both in the range of quantities which can be studied and in the precision of the results. I focus particularly on the extraction of the QCD parameters, i.e. the quark masses and the strong coupling constant, and on important quantities in flavour physics. Lattice QCD is playing a central role in quantifying the hadronic effects necessary for the development of precision flavour physics and its use in exploring the limits of the Standard Model and in searches for inconsistencies which would signal the presence of new physics.

  10. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  11. Lattice gauge theories

    International Nuclear Information System (INIS)

    Hasenfratz, A.; Hasenfratz, P.

    1985-01-01

    This paper deals almost exclusively with applications in QCD. Presumably QCD will remain in the center of lattice calculations in the near future. The existing techniques and the available computer resources should be able to produce trustworthy results in pure SU(3) gauge theory and in quenched hadron spectroscopy. Going beyond the quenched approximation might require some technical breakthrough or exceptional computer resources, or both. Computational physics has entered high-energy physics. From this point of view, lattice QCD is only one (although the most important, at present) of the research fields. Increasing attention is devoted to the study of other QFTs. It is certain that the investigation of nonasymptotically free theories, the Higgs phenomenon, or field theories that are not perturbatively renormalizable will be important research areas in the future

  12. Lattice degeneracies of geometric fermions

    International Nuclear Information System (INIS)

    Raszillier, H.

    1983-05-01

    We give the minimal numbers of degrees of freedom carried by geometric fermions on all lattices of maximal symmetries in d = 2, 3, and 4 dimensions. These numbers are lattice dependent, but in the (free) continuum limit, part of the degrees of freedom have to escape to infinity by a Wilson mechanism built in, and 2sup(d) survive for any lattice. On self-reciprocal lattices we compare the minimal numbers of degrees of freedom of geometric fermions with the minimal numbers of naive fermions on these lattices and argue that these numbers are equal. (orig.)

  13. Light water lattices

    International Nuclear Information System (INIS)

    1962-01-01

    The panel was attended by prominent physicists from most of the well-known laboratories in the field of light-water lattices, who exchanged the latest information on the status of work in their countries and discussed both the theoretical and the experimental aspects of the subjects. The supporting papers covered most problems, including criticality, resonance absorption, thermal utilization, spectrum calculations and the physics of plutonium bearing systems. Refs, figs and tabs

  14. Diffusion in heterogeneous lattices

    Czech Academy of Sciences Publication Activity Database

    Tarasenko, Alexander; Jastrabík, Lubomír

    2010-01-01

    Roč. 256, č. 17 (2010), s. 5137-5144 ISSN 0169-4332 R&D Projects: GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : lattice- gas systems * diffusion * Monte Carlo simulations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.795, year: 2010

  15. Automated lattice data generation

    Directory of Open Access Journals (Sweden)

    Ayyar Venkitesh

    2018-01-01

    Full Text Available The process of generating ensembles of gauge configurations (and measuring various observables over them can be tedious and error-prone when done “by hand”. In practice, most of this procedure can be automated with the use of a workflow manager. We discuss how this automation can be accomplished using Taxi, a minimal Python-based workflow manager built for generating lattice data. We present a case study demonstrating this technology.

  16. Automated lattice data generation

    Science.gov (United States)

    Ayyar, Venkitesh; Hackett, Daniel C.; Jay, William I.; Neil, Ethan T.

    2018-03-01

    The process of generating ensembles of gauge configurations (and measuring various observables over them) can be tedious and error-prone when done "by hand". In practice, most of this procedure can be automated with the use of a workflow manager. We discuss how this automation can be accomplished using Taxi, a minimal Python-based workflow manager built for generating lattice data. We present a case study demonstrating this technology.

  17. Lattice dynamics of thorium

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, J [Agra Coll. (India). Dept. of Physics

    1977-03-01

    In the present work, a local model pseudopotential has been proposed to study the lattice dynamics of thorium. The model potential depends on the core and ionic radii, and accounts for the s-d-f hybridization effects in a phenomenological way. When this form of potential is applied to derive the photon dispersion curves of Th, sufficiently good agreement is found between the computed and experimental results.

  18. Computing: Lattice work

    International Nuclear Information System (INIS)

    Bowler, Ken

    1990-01-01

    One of the major recent developments in particle theory has been the use of very high performance computers to obtain approximate numerical solutions of quantum field theories by formulating them on a finite space-time lattice. The great virtue of this new technique is that it avoids the straitjacket of perturbation theory and can thus attack new, but very fundamental problems, such as the calculation of hadron masses in quark-gluon field theory (quantum chromodynamics - QCD)

  19. Robots and lattice automata

    CERN Document Server

    Adamatzky, Andrew

    2015-01-01

    The book gives a comprehensive overview of the state-of-the-art research and engineering in theory and application of Lattice Automata in design and control of autonomous Robots. Automata and robots share the same notional meaning. Automata (originated from the latinization of the Greek word “αυτόματον”) as self-operating autonomous machines invented from ancient years can be easily considered the first steps of robotic-like efforts. Automata are mathematical models of Robots and also they are integral parts of robotic control systems. A Lattice Automaton is a regular array or a collective of finite state machines, or automata. The Automata update their states by the same rules depending on states of their immediate neighbours. In the context of this book, Lattice Automata are used in developing modular reconfigurable robotic systems, path planning and map exploration for robots, as robot controllers, synchronisation of robot collectives, robot vision, parallel robotic actuators. All chapters are...

  20. Digital lattice gauge theories

    Science.gov (United States)

    Zohar, Erez; Farace, Alessandro; Reznik, Benni; Cirac, J. Ignacio

    2017-02-01

    We propose a general scheme for a digital construction of lattice gauge theories with dynamical fermions. In this method, the four-body interactions arising in models with 2 +1 dimensions and higher are obtained stroboscopically, through a sequence of two-body interactions with ancillary degrees of freedom. This yields stronger interactions than the ones obtained through perturbative methods, as typically done in previous proposals, and removes an important bottleneck in the road towards experimental realizations. The scheme applies to generic gauge theories with Lie or finite symmetry groups, both Abelian and non-Abelian. As a concrete example, we present the construction of a digital quantum simulator for a Z3 lattice gauge theory with dynamical fermionic matter in 2 +1 dimensions, using ultracold atoms in optical lattices, involving three atomic species, representing the matter, gauge, and auxiliary degrees of freedom, that are separated in three different layers. By moving the ancilla atoms with a proper sequence of steps, we show how we can obtain the desired evolution in a clean, controlled way.

  1. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1983-06-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)epsilong that are attached to the links b = (x+esub(μ),x) of the lattice and take their values in the linear space g which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)osub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportionalosub(i)osub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson loop expectation values show an area law decay, if the Euclidean action has certain qualitative features which imply that PHI = 0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  2. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1984-01-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)element ofG that are attached to the links b = (x+esub(μ), x) of the lattice and take their values in the linear space G which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)sigmasub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportional sigmasub(i)sigmasub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder-Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson-loop expectation values show an area law decay, if the euclidean action has certain qualitative features which imply that PHI=0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  3. Toward lattice fractional vector calculus

    Science.gov (United States)

    Tarasov, Vasily E.

    2014-09-01

    An analog of fractional vector calculus for physical lattice models is suggested. We use an approach based on the models of three-dimensional lattices with long-range inter-particle interactions. The lattice analogs of fractional partial derivatives are represented by kernels of lattice long-range interactions, where the Fourier series transformations of these kernels have a power-law form with respect to wave vector components. In the continuum limit, these lattice partial derivatives give derivatives of non-integer order with respect to coordinates. In the three-dimensional description of the non-local continuum, the fractional differential operators have the form of fractional partial derivatives of the Riesz type. As examples of the applications of the suggested lattice fractional vector calculus, we give lattice models with long-range interactions for the fractional Maxwell equations of non-local continuous media and for the fractional generalization of the Mindlin and Aifantis continuum models of gradient elasticity.

  4. Two-extremum electrostatic potential of metal-lattice plasma and the work function of an electron

    Directory of Open Access Journals (Sweden)

    Surma S.A.

    2015-06-01

    Full Text Available Metal-lattice plasma is treated as a neutral two-component two-phase system of 2D surface and 3D bulk. Free electron density and bulk chemical potential are used as intensive parameters of the system with the phase boundary position determined in the crystalline lattice. A semiempirical expression for the electron screened electrostatic potential is constructed using the lattice-plasma polarization concept. It comprises an image term and three repulsion/attraction terms of second and fourth orders. The novel curve has two extremes and agrees with certain theoretical forms of potential. A practical formula for the electron work function of metals and a simplified schema of electronic structure at the metal/vacuum interface are proposed. This yields 10.44 eV for the Fermi energy of free electron gas; -5.817 eV for the Fermi energy level; 4.509 eV for the average work function of bcc tungsten. Selected data are also given for fcc Cu and hcp Re. For harmonic frequencies ~ 10E16 per s of the self-excited metal-lattice plasma, energy gaps of 14.54 and 8.02 eV are found, which correspond to the bulk and surface plasmons, respectively. Further extension of this thermodynamics and metal-lattice theory based approach may contribute to a better understanding of theoretical models which are employed in chemical physics, catalysis and materials science of nanostructures.

  5. Lattice-induced nonadiabatic frequency shifts in optical lattice clocks

    International Nuclear Information System (INIS)

    Beloy, K.

    2010-01-01

    We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10 -18 and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

  6. Lattice topology dictates photon statistics.

    Science.gov (United States)

    Kondakci, H Esat; Abouraddy, Ayman F; Saleh, Bahaa E A

    2017-08-21

    Propagation of coherent light through a disordered network is accompanied by randomization and possible conversion into thermal light. Here, we show that network topology plays a decisive role in determining the statistics of the emerging field if the underlying lattice is endowed with chiral symmetry. In such lattices, eigenmode pairs come in skew-symmetric pairs with oppositely signed eigenvalues. By examining one-dimensional arrays of randomly coupled waveguides arranged on linear and ring topologies, we are led to a remarkable prediction: the field circularity and the photon statistics in ring lattices are dictated by its parity while the same quantities are insensitive to the parity of a linear lattice. For a ring lattice, adding or subtracting a single lattice site can switch the photon statistics from super-thermal to sub-thermal, or vice versa. This behavior is understood by examining the real and imaginary fields on a lattice exhibiting chiral symmetry, which form two strands that interleave along the lattice sites. These strands can be fully braided around an even-sited ring lattice thereby producing super-thermal photon statistics, while an odd-sited lattice is incommensurate with such an arrangement and the statistics become sub-thermal.

  7. A cornucopia of lattices

    International Nuclear Information System (INIS)

    Kilcup, G.

    1986-01-01

    A progress report on a lattice project at Los Alamos is presented. The projects are basically of two sorts: approaching the continuum (determination of MCRG flows under the blocking transformation, and beta-function along Wilson and improved action lines); and arriving at the continuum (hadron spectrum, coupling constants, and matrix elements). Since the ultimate goal is to determine matrix elements for which chiral symmetry is very relevant, the authors choose the formalism whose chiral properties are easier to understand, i.e., staggered fermions

  8. Lattice of quantum predictions

    Science.gov (United States)

    Drieschner, Michael

    1993-10-01

    What is the structure of reality? Physics is supposed to answer this question, but a purely empiristic view is not sufficient to explain its ability to do so. Quantum mechanics has forced us to think more deeply about what a physical theory is. There are preconditions every physical theory must fulfill. It has to contain, e.g., rules for empirically testable predictions. Those preconditions give physics a structure that is “a priori” in the Kantian sense. An example is given how the lattice structure of quantum mechanics can be understood along these lines.

  9. Lattice Vibrations in Chlorobenzenes:

    DEFF Research Database (Denmark)

    Reynolds, P. A.; Kjems, Jørgen; White, J. W.

    1974-01-01

    Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...

  10. Diamond lattice Heisenberg antiferromagnet

    Science.gov (United States)

    Oitmaa, J.

    2018-04-01

    We investigate ground-state and high-temperature properties of the nearest-neighbour Heisenberg antiferromagnet on the three-dimensional diamond lattice, using series expansion methods. The ground-state energy and magnetization, as well as the magnon spectrum, are calculated and found to be in good agreement with first-order spin-wave theory, with a quantum renormalization factor of about 1.13. High-temperature series are derived for the free energy, and physical and staggered susceptibilities for spin S  =  1/2, 1 and 3/2, and analysed to obtain the corresponding Curie and Néel temperatures.

  11. Lattice cell burnup calculation

    International Nuclear Information System (INIS)

    Pop-Jordanov, J.

    1977-01-01

    Accurate burnup prediction is a key item for design and operation of a power reactor. It should supply information on isotopic changes at each point in the reactor core and the consequences of these changes on the reactivity, power distribution, kinetic characters, control rod patterns, fuel cycles and operating strategy. A basic stage in the burnup prediction is the lattice cell burnup calculation. This series of lectures attempts to give a review of the general principles and calculational methods developed and applied in this area of burnup physics

  12. Renormalons on the lattice

    CERN Document Server

    Crisafulli, M.; Martinelli, G.; Sachrajda, Christopher T.; Crisafulli, M; Gimenez, V; Martinelli, G; Sachrajda, C T

    1994-01-01

    We present the first lattice calculation of the B-meson binding energy \\labar and of the kinetic energy \\lambda_1/2 m_Q of the heavy-quark inside the pseudoscalar B-meson. In order to cancel the ambiguities due to the ultraviolet renormalons present in the operator matrix elements, this calculation has required the non-perturbative subtraction of the power divergences present in the Lagrangian operator \\energy and in the kinetic energy operator \\kkinetic. The non-perturbative renormalization of the relevant operators has been implemented by imposing suitable renormalization conditions on quark matrix elements in the Landau gauge.

  13. Study of Gd lattices

    International Nuclear Information System (INIS)

    Vidovsky, I.; Kereszturi, A.

    1991-11-01

    The results of experiments and calculations on Gd lattices are presented, and a comparison of experimental and calculational data is given. This latter can be divided into four groups. The first belongs to the comparison of criticality parameters, the second group is related with the comparison of 2D distributions, the third one relates the comparison of intra-macrocell distributions, whereas the fourth group is devoted for the comparison of spectral parameters. For comparison, the computer code RFIT based on strict statistical criteria has been used. The calculated and measured results agree, in most cases, sufficiently. (R.P.) 11 refs.; 13 figs.; 9 tabs

  14. Lattice Transparency of Graphene.

    Science.gov (United States)

    Chae, Sieun; Jang, Seunghun; Choi, Won Jin; Kim, Youn Sang; Chang, Hyunju; Lee, Tae Il; Lee, Jeong-O

    2017-03-08

    Here, we demonstrated the transparency of graphene to the atomic arrangement of a substrate surface, i.e., the "lattice transparency" of graphene, by using hydrothermally grown ZnO nanorods as a model system. The growth behaviors of ZnO nanocrystals on graphene-coated and uncoated substrates with various crystal structures were investigated. The atomic arrangements of the nucleating ZnO nanocrystals exhibited a close match with those of the respective substrates despite the substrates being bound to the other side of the graphene. By using first-principles calculations based on density functional theory, we confirmed the energetic favorability of the nucleating phase following the atomic arrangement of the substrate even with the graphene layer present in between. In addition to transmitting information about the atomic lattice of the substrate, graphene also protected its surface. This dual role enabled the hydrothermal growth of ZnO nanorods on a Cu substrate, which otherwise dissolved in the reaction conditions when graphene was absent.

  15. Introduction to lattice gauge theories

    International Nuclear Information System (INIS)

    La Cock, P.

    1988-03-01

    A general introduction to Lattice Gauge Theory (LGT) is given. The theory is discussed from first principles to facilitate an understanding of the techniques used in LGT. These include lattice formalism, gauge invariance, fermions on the lattice, group theory and integration, strong coupling methods and mean field techniques. A review of quantum chromodynamics on the lattice at finite temperature and density is also given. Monte Carlo results and analytical methods are discussed. An attempt has been made to include most relevant data up to the end of 1987, and to update some earlier reviews existing on the subject. 224 refs., 33 figs., 14 tabs

  16. Hadron structure from lattice QCD

    International Nuclear Information System (INIS)

    Schaefer, Andreas

    2008-01-01

    Some elements and current developments of lattice QCD are reviewed, with special emphasis on hadron structure observables. In principle, high precision experimental and lattice data provide nowadays a very detailled picture of the internal structure of hadrons. However, to relate both, a very good controle of perturbative QCD is needed in many cases. Finally chiral perturbation theory is extremely helpful to boost the precision of lattice calculations. The mutual need and benefit of all four elements: experiment, lattice QCD, perturbative QCD and chiral perturbation theory is the main topic of this review

  17. Lattice formulations of reggeon interactions

    International Nuclear Information System (INIS)

    Brower, R.C.; Ellis, J.; Savit, R.; Zinn-Justin, J.

    1976-01-01

    A class of lattice analogues to reggeon field theory is examined. First the transition from a continuum to a lattice field theory is discussed, emphasizing the necessity of a Wick rotation and the consideration of symmetry properties. Next the theory is transformed to a discrete system with two spins at each lattice site, and the problems of the triple-reggeon interaction and the reggeon energy gap are discussed. It is pointed out that transferring the theory from the continuum to a lattice necesarily introduces new relevant operators not normally present in reggeon field theory. (Auth.)

  18. Neutron and PIMC determination of the longitudinal momentum distribution of HCP, BCC and normal liquid 4He

    International Nuclear Information System (INIS)

    Blasdell, R.C.; Ceperley, D.M.; Simmons, R.O.

    1993-07-01

    Deep inelastic neutron scattering has been used to measure the neutron Compton profile (NCP) of a series of condensed 4 He samples at densities from 28.8 atoms/nm 3 (essentially the minimum possible density in the solid phase) up to 39.8 atoms/nm 3 using a chopper spectrometer at the Argonne National Laboratory Intense Pulsed Neutron Source. At the lowest density, the NCP was measured along an isochore through the hcp, bcc, and normal liquid phases. Average atomic kinetic energies are extracted from each of the data sets and are compared to both published and new path integral Monte-Carlo (PIMC) calculations as well as other theoretical predictions. In this preliminary analysis of the data, account is taken of the effects of instrumental resolution, multiple scattering, and final-state interactions. Both our measurements and the PIMC theory show that there are only small differences in the kinetic energy and longitudinal momentum distribution of isochoric helium samples, regardless of their phase or crystal structure

  19. A multi-scale homogenization model for fine-grained porous viscoplastic polycrystals: II - Applications to FCC and HCP materials

    Science.gov (United States)

    Song, Dawei; Ponte Castañeda, P.

    2018-06-01

    In Part I of this work (Song and Ponte Castañeda, 2018a), a new homogenization model was developed for the macroscopic behavior of three-scale porous polycrystals consisting of random distributions of large pores in a fine-grained polycrystalline matrix. In this second part, the model is used to investigate both the instantaneous effective behavior and the finite-strain macroscopic response of porous FCC and HCP polycrystals for axisymmetric loading conditions. The stress triaxiality and Lode parameter are found to have significant effects on the evolution of the substructure, which in turn have important implications for the overall hardening/softening behavior of the porous polycrystal. The intrinsic effect of the texture evolution of the polycrystalline matrix is inferred by appropriate comparisons with corresponding results for porous isotropic materials, and found to be significant, especially at low triaxialities. In particular, the predictions of the model identify, for the first time, two disparate regimes for the macroscopic response of porous polycrystals: a porosity-controlled regime at high triaxialities, and a texture-controlled regime at low triaxialities. The transition between these two regimes is found to be quite sharp, taking place between triaxialities of 1 and 2.

  20. Convection-diffusion lattice Boltzmann scheme for irregular lattices

    NARCIS (Netherlands)

    Sman, van der R.G.M.; Ernst, M.H.

    2000-01-01

    In this paper, a lattice Boltzmann (LB) scheme for convection diffusion on irregular lattices is presented, which is free of any interpolation or coarse graining step. The scheme is derived using the axioma that the velocity moments of the equilibrium distribution equal those of the

  1. Elimination of spurious lattice fermion solutions and noncompact lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T.D.

    1997-09-22

    It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.

  2. Dynamics of the HCP/BCC phase transition and of the diffusion in zirconium: a model based on a tight-binding potential

    International Nuclear Information System (INIS)

    Willaime, F.

    1991-09-01

    We have developed an N-body interatomic potential, based on the second moment approximation of the tight-binding scheme, by fitting its four adjustable parameters to the cohesive energy, atomic volume, and elastic constants of hcp-Zr. We then showed that various properties of this potential compare favorably with those of zirconium in both the low temperatures hcp phase and the high temperature bcc phase. Such is the case in particular for the elastic constants, the phonon dispersion curves, the thermal expansion, and the melting temperature. We reproduced by molecular dynamics (MD) simulations on this potential the hcp/bcc phase transformation in both ways. It indeed occurs following the mechanism predicted by Burgers. We find a vibrational entropy of transformation equal to 0.13 k B . Our calculations suggest that in real zirconium the electronic contribution to the transformation entropy is important. We show that some interatomic potential lead to a higher value of the vibrational entropy in the hcp phase than in the bcc phase. We specified the dynamics of the vacancy migration in the bcc phase. The atomic jumps are almost exclusively nearest neighbour ones. The walk of the vacancy becomes strongly correlated at high temperatures. The vacancy jump frequency is very large and has a perfectly arrhenian behaviour. There is no evicence of a dynamical lowering of the vacancy migration barrier: the static and dynamic values of the vacancy migration energy are almost equal, both being unusually small (0.3 eV). The self diffusion coefficent of our model for the vacancy mechanism reproduces an anomalous fast diffusion close to that measured experimentally in bcc-Zr. In our model at high temperatures the time interval between successive jumps is almost equal to the time of flight. The migration events will therefore influence the formation of the vacancies [fr

  3. Lattice quantum chromodynamics

    International Nuclear Information System (INIS)

    Hassenfratz, P.

    1983-01-01

    It is generally accepted that relativistic field theory is relevant in high energy physics. It is also recognized that even in QCD, which is asymptotically free, the scope of perturbation theory is very limited. Despite the tremendous theoretical and experimental effort to study scaling, scaling violations, e + e - , lepton pair creation, jets, etc., the answer to the question whether and to what extent is QCD the theory of strong interactions is vague. At present-day energies it is difficult to disentangle perturbative and non-perturbative effects. The author states that QCD must be understood and that quantitative non-perturbative methods are needed. He states that the lattice formulation of field theories is a promising approach to meeting this need and discusses the formulation in detail in this paper

  4. Geometry of lattice field theory

    International Nuclear Information System (INIS)

    Honan, T.J.

    1986-01-01

    Using some tools of algebraic topology, a general formalism for lattice field theory is presented. The lattice is taken to be a simplicial complex that is also a manifold and is referred to as a simplicial manifold. The fields on this lattice are cochains, that are called lattice forms to emphasize the connections with differential forms in the continuum. This connection provides a new bridge between lattice and continuum field theory. A metric can be put onto this simplicial manifold by assigning lengths to every link or I-simplex of the lattice. Regge calculus is a way of defining general relativity on this lattice. A geometric discussion of Regge calculus is presented. The Regge action, which is a discrete form of the Hilbert action, is derived from the Hilbert action using distribution valued forms. This is a new derivation that emphasizes the underlying geometry. Kramers-Wannier duality in statistical mechanics is discussed in this general setting. Nonlinear field theories, which include gauge theories and nonlinear sigma models are discussed in the continuum and then are put onto a lattice. The main new result here is the generalization to curved spacetime, which consists of making the theory compatible with Regge calculus

  5. Homogenization theory in reactor lattices

    International Nuclear Information System (INIS)

    Benoist, P.

    1986-02-01

    The purpose of the theory of homogenization of reactor lattices is to determine, by the mean of transport theory, the constants of a homogeneous medium equivalent to a given lattice, which allows to treat the reactor as a whole by diffusion theory. In this note, the problem is presented by laying emphasis on simplicity, as far as possible [fr

  6. Remarks on lattice gauge models

    International Nuclear Information System (INIS)

    Grosse, H.

    1981-01-01

    The author reports a study of the phase structure of lattice gauge models where one takes as a gauge group a non-abelian discrete subgroup of SU(3). In addition he comments on a lattice action proposed recently by Manton and observes that it violates a positivity property. (Auth.)

  7. Remarks on lattice gauge models

    International Nuclear Information System (INIS)

    Grosse, H.

    1981-01-01

    The author reports on a study of the phase structure of lattice gauge models where one takes as a gauge group a non-abelian discrete subgroup of SU(3). In addition he comments on a lattice action proposed recently by Manton (1980) and observes that it violates a positivity property. (Auth.)

  8. Lattices, supersymmetry and Kaehler fermions

    International Nuclear Information System (INIS)

    Scott, D.M.

    1984-01-01

    It is shown that a graded extension of the space group of a (generalised) simple cubic lattice exists in any space dimension, D. The fermionic variables which arise admit a Kaehlerian interpretation. Each graded space group is a subgroup of a graded extension of the appropriate Euclidean group, E(D). The relevance of this to the construction of lattice theories is discussed. (author)

  9. Lattice polytopes in coding theory

    Directory of Open Access Journals (Sweden)

    Ivan Soprunov

    2015-05-01

    Full Text Available In this paper we discuss combinatorial questions about lattice polytopes motivated by recent results on minimum distance estimation for toric codes. We also include a new inductive bound for the minimum distance of generalized toric codes. As an application, we give new formulas for the minimum distance of generalized toric codes for special lattice point configurations.

  10. Computing the writhe on lattices

    International Nuclear Information System (INIS)

    Laing, C; Sumners, D W

    2006-01-01

    Given a polygonal closed curve on a lattice or space group, we describe a method for computing the writhe of the curve as the average of weighted projected writhing numbers of the polygon in a few directions. These directions are determined by the lattice geometry, the weights are determined by areas of regions on the unit 2-sphere, and the regions are formed by the tangent indicatrix to the polygonal curve. We give a new formula for the writhe of polygons on the face centred cubic lattice and prove that the writhe of polygons on the body centred cubic lattice, the hexagonal simple lattice, and the diamond space group is always a rational number, and discuss applications to ring polymers

  11. Epitaxial growth of Co(0 0 0 1)hcp/Fe(1 1 0)bcc magnetic bi-layer films on SrTiO3(1 1 1) substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2008-01-01

    Co(0 0 0 1) hcp /Fe(1 1 0) bcc epitaxial magnetic bi-layer films were successfully prepared on SrTiO 3 (1 1 1) substrates. The crystallographic properties of Co/Fe epitaxial magnetic bi-layer films were investigated. Fe(1 1 0) bcc soft magnetic layer grew epitaxially on SrTiO 3 (1 1 1) substrate with two type variants, Nishiyama-Wasserman and Kurdjumov-Sachs relationships. An hcp-Co single-crystal layer is obtained on Ru(0 0 0 1) hcp interlayer, while hcp-Co layer formed on Au(1 1 1) fcc or Ag(1 1 1) fcc interlayer is strained and may involve fcc-Co phase. It has been shown possible to prepare Co/Fe epitaxial magnetic bi-layer films which can be usable for patterned media application

  12. Lattice gas cellular automata and lattice Boltzmann models an introduction

    CERN Document Server

    Wolf-Gladrow, Dieter A

    2000-01-01

    Lattice-gas cellular automata (LGCA) and lattice Boltzmann models (LBM) are relatively new and promising methods for the numerical solution of nonlinear partial differential equations. The book provides an introduction for graduate students and researchers. Working knowledge of calculus is required and experience in PDEs and fluid dynamics is recommended. Some peculiarities of cellular automata are outlined in Chapter 2. The properties of various LGCA and special coding techniques are discussed in Chapter 3. Concepts from statistical mechanics (Chapter 4) provide the necessary theoretical background for LGCA and LBM. The properties of lattice Boltzmann models and a method for their construction are presented in Chapter 5.

  13. Validation of a 15-item care-related regret coping scale for health-care professionals (RCS-HCP).

    Science.gov (United States)

    Courvoisier, Delphine Sophie; Cullati, Stephane; Ouchi, Rieko; Schmidt, Ralph Eric; Haller, Guy; Chopard, Pierre; Agoritsas, Thomas; Perneger, Thomas V

    2014-01-01

    Coping with difficult care-related situations is a common challenge for health-care professionals. How these professionals deal with the regrets they may experience following one of the many decisions and interventions they must make every day can have an impact on their own health and quality of life, and also on their patient care practices. To identify professionals most at need for extra support, development and validation of a tool measuring coping style are needed. We performed a survey of physicians and nurses of a French-speaking University hospital; 469 health-care professionals responded to the survey, and 175 responded to the same survey one-month later. Regret was assessed with the regret coping scale developed for this study, self-report questions on the frequency of regretted situations and the intensity of regret. Construct validity was assessed using measures of health-care professionals' quality of life (including job and life satisfaction, and self-reported health) as well as sleep problems and depression. Based on factor analysis and item response analysis, the initial 31-item scale was shortened to 15 items, which measured three types of strategies: problem-focused strategies (i.e., trying to find solutions, talking to colleagues) and two types of emotion-focused strategies, A (i.e., self-blame, rumination) and B (e.g., acceptance, emotional distance). All subscales showed high internal consistency (α >0.85). Overall, as expected, problem-focused and emotion-focused B strategies correlated with higher quality of life, fewer sleep problems and less depression, and emotion-focused A strategies showed the opposite pattern. The regret coping scale (RCS-HCP) is a valid and reliable measure of coping abilities of hospital-based health-care professionals.

  14. HCP track calculations in Lif:Mg,Ti: 3D modeling of the ''track – escape'' parameter

    International Nuclear Information System (INIS)

    Sattinger, D.; Sharon, A.; Horowitz, Y.S.

    2011-01-01

    The conceptual framework of the track interaction model (TIM) was conceived in the 1970s and mathematically formulated in the 1980s to describe heavy charged particle TL fluence response supralinearity. The extended track interaction model (ETIM) was developed to include saturation effects due to overlapping tracks and has been applied to both proton and alpha particle TL fluence response. One of the parameters of major importance in the TIM is the ''track – escape'' parameter, defined by N e /N w , where N e represents the number of electrons which escape the parent track during heating, and N w is the number of electrons which recombine within the parent track to produce a TL photon. Recently a first attempt was carried out to theoretically model escape parameters calculated in 2D geometry as a function of particle type and energy using trapping center (TC), luminescent center (LC) and competitive center (CC) occupation probabilities calculated from track segment radial dose distributions and optical absorption (OA) dose response. In this study, the calculations are extended to 3D geometry using a Monte Carlo approach which samples the point of creation of the charge carriers according to the TC occupation probabilities and then estimates N w by sampling the chord length to the track exterior. Charge carriers which escape the irradiated track volume contribute to N e . This more sophisticated 3D calculation of N e /N w is expected to increase the reliability of the modeling of heavy charged particle TL fluence response in the framework of the ETIM and enhance our understanding of “track effects” in Heavy Charged Particle (HCP) induced TL.

  15. Martensitic transformation, fcc and hcp relative phase stability, and thermal cycling effects in Fe-Mn and Fe-Mn-X Alloys (X = Si, Co)

    International Nuclear Information System (INIS)

    Baruj, Alberto

    1999-01-01

    In this Thesis we present a study of the fcc and hcp relative phase stability in the Fe-Mn and Fe-Mn-Co systems. In particular, we have investigated the effect of two main factors affecting the relative phase stability: changes in the chemical composition of the alloys and changes in the density of crystalline defects in the microstructure.In order to analyse the effect of chemical composition, we have performed an experimental study of the fcc/hcp martensitic transformation temperatures in Fe-Mn-Co alloys in the composition range lying between 15% and 34% Mn, and between 1% and 16% Co.We have measured the martensitic transformation temperatures by means of dilatometry and electrical resistivity.We have combined this information with measurements of the fcc/hcp martensitic transformation temperatures in Co-rich alloys to perform a modelling of the Gibbs energy function for the hcp phase in the Fe-Mn-Co and Fe-Co systems.We found that, for alloys in the Mn range between 17% and 25%, Co additions tend to stabilise slightly the fcc phase.In the alloys with Mn contents below that range, increasing the amount of Co stabilise the bcc phase. In alloys with Mn contents above 25% the Neel temperature is depressed by the addition of Co, which stabilise the hcp phase.In order to investigate the effect of changes in the density of crystalline defects, we have performed thermal cycling experiments through the fcc/hcp martensitic transformation in Fe-Mn, Fe-Mn-Co and Fe-Mn-Si alloys.We have applied the thermodynamic description obtained before in order to analyse these experiments.We found in the thermal cycling experiments a first stage where the martensitic transformation is promoted.This stage occurs in all the studied alloys during the first cycle or the two first cycles.Increasing the number of thermal cycles, the promotion stage is replaced by an inhibition of the transformation stage.We propose a possible microstructural interpretation of these phenomena where the plastic

  16. Irreversible stochastic processes on lattices

    International Nuclear Information System (INIS)

    Nord, R.S.

    1986-01-01

    Models for irreversible random or cooperative filling of lattices are required to describe many processes in chemistry and physics. Since the filling is assumed to be irreversible, even the stationary, saturation state is not in equilibrium. The kinetics and statistics of these processes are described by recasting the master equations in infinite hierarchical form. Solutions can be obtained by implementing various techniques: refinements in these solution techniques are presented. Programs considered include random dimer, trimer, and tetramer filling of 2D lattices, random dimer filling of a cubic lattice, competitive filling of two or more species, and the effect of a random distribution of inactive sites on the filling. Also considered is monomer filling of a linear lattice with nearest neighbor cooperative effects and solve for the exact cluster-size distribution for cluster sizes up to the asymptotic regime. Additionally, a technique is developed to directly determine the asymptotic properties of the cluster size distribution. Finally cluster growth is considered via irreversible aggregation involving random walkers. In particular, explicit results are provided for the large-lattice-size asymptotic behavior of trapping probabilities and average walk lengths for a single walker on a lattice with multiple traps. Procedures for exact calculation of these quantities on finite lattices are also developed

  17. Toward lattice fractional vector calculus

    International Nuclear Information System (INIS)

    Tarasov, Vasily E

    2014-01-01

    An analog of fractional vector calculus for physical lattice models is suggested. We use an approach based on the models of three-dimensional lattices with long-range inter-particle interactions. The lattice analogs of fractional partial derivatives are represented by kernels of lattice long-range interactions, where the Fourier series transformations of these kernels have a power-law form with respect to wave vector components. In the continuum limit, these lattice partial derivatives give derivatives of non-integer order with respect to coordinates. In the three-dimensional description of the non-local continuum, the fractional differential operators have the form of fractional partial derivatives of the Riesz type. As examples of the applications of the suggested lattice fractional vector calculus, we give lattice models with long-range interactions for the fractional Maxwell equations of non-local continuous media and for the fractional generalization of the Mindlin and Aifantis continuum models of gradient elasticity. (papers)

  18. Introduction to lattice gauge theory

    International Nuclear Information System (INIS)

    Gupta, R.

    1987-01-01

    The lattice formulation of Quantum Field Theory (QFT) can be exploited in many ways. We can derive the lattice Feynman rules and carry out weak coupling perturbation expansions. The lattice then serves as a manifestly gauge invariant regularization scheme, albeit one that is more complicated than standard continuum schemes. Strong coupling expansions: these give us useful qualitative information, but unfortunately no hard numbers. The lattice theory is amenable to numerical simulations by which one calculates the long distance properties of a strongly interacting theory from first principles. The observables are measured as a function of the bare coupling g and a gauge invariant cut-off ≅ 1/α, where α is the lattice spacing. The continuum (physical) behavior is recovered in the limit α → 0, at which point the lattice artifacts go to zero. This is the more powerful use of lattice formulation, so in these lectures the author focuses on setting up the theory for the purpose of numerical simulations to get hard numbers. The numerical techniques used in Lattice Gauge Theories have their roots in statistical mechanics, so it is important to develop an intuition for the interconnection between quantum mechanics and statistical mechanics. This will be the emphasis of the first lecture. In the second lecture, the author reviews the essential ingredients of formulating QCD on the lattice and discusses scaling and the continuum limit. In the last lecture the author summarizes the status of some of the main results. He also mentions the bottlenecks and possible directions for research. 88 refs

  19. Lattice Methods for Quantum Chromodynamics

    CERN Document Server

    DeGrand, Thomas

    2006-01-01

    Numerical simulation of lattice-regulated QCD has become an important source of information about strong interactions. In the last few years there has been an explosion of techniques for performing ever more accurate studies on the properties of strongly interacting particles. Lattice predictions directly impact many areas of particle and nuclear physics theory and phenomenology. This book provides a thorough introduction to the specialized techniques needed to carry out numerical simulations of QCD: a description of lattice discretizations of fermions and gauge fields, methods for actually do

  20. Localized structures in Kagome lattices

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Avadh B [Los Alamos National Laboratory; Bishop, Alan R [Los Alamos National Laboratory; Law, K J H [UNIV OF MASSACHUSETTS; Kevrekidis, P G [UNIV OF MASSACHUSETTS

    2009-01-01

    We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.

  1. Lattice QCD: Status and Prospect

    International Nuclear Information System (INIS)

    Ukawa, Akira

    2006-01-01

    A brief review is given of the current status and near-future prospect of lattice QCD studies of the Standard Model. After summarizing a bit of history, we describe current attempts toward inclusion of dynamical up, down and strange quarks. Recent results on the light hadron mass spectrum as well as those on the heavy quark quantities are described. Recent work on lattice pentaquark search is summarized. We touch upon the PACS-CS Project for building our next machine for lattice QCD, and conclude with a summary of computer situation and the physics possibilities over the next several years

  2. Lattice sums then and now

    CERN Document Server

    Borwein, J M; McPhedran, R C

    2013-01-01

    The study of lattice sums began when early investigators wanted to go from mechanical properties of crystals to the properties of the atoms and ions from which they were built (the literature of Madelung's constant). A parallel literature was built around the optical properties of regular lattices of atoms (initiated by Lord Rayleigh, Lorentz and Lorenz). For over a century many famous scientists and mathematicians have delved into the properties of lattices, sometimes unwittingly duplicating the work of their predecessors. Here, at last, is a comprehensive overview of the substantial body of

  3. Non-Abelian vortex lattices

    Science.gov (United States)

    Tallarita, Gianni; Peterson, Adam

    2018-04-01

    We perform a numerical study of the phase diagram of the model proposed in [M. Shifman, Phys. Rev. D 87, 025025 (2013)., 10.1103/PhysRevD.87.025025], which is a simple model containing non-Abelian vortices. As per the case of Abrikosov vortices, we map out a region of parameter space in which the system prefers the formation of vortices in ordered lattice structures. These are generalizations of Abrikosov vortex lattices with extra orientational moduli in the vortex cores. At sufficiently large lattice spacing the low energy theory is described by a sum of C P (1 ) theories, each located on a vortex site. As the lattice spacing becomes smaller, when the self-interaction of the orientational field becomes relevant, only an overall rotation in internal space survives.

  4. Lattice Studies of Hyperon Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Richards, David G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-04-01

    I describe recent progress at studying the spectrum of hadrons containing the strange quark through lattice QCD calculations. I emphasise in particular the richness of the spectrum revealed by lattice studies, with a spectrum of states at least as rich as that of the quark model. I conclude by prospects for future calculations, including in particular the determination of the decay amplitudes for the excited states.

  5. Harmonic oscillator on a lattice

    International Nuclear Information System (INIS)

    Ader, J.P.; Bonnier, B.; Hontebeyrie, M.; Meyers, C.

    1983-01-01

    The continuum limit of the ground state energy for the harmonic oscillator with discrete time is derived for all possible choices of the lattice derivative. The occurrence of unphysical values is shown to arise whenever the lattice laplacian is not strictly positive on its Brillouin zone. These undesirable limits can either be finite and arbitrary (multiple spectrum) or infinite (overlapping sublattices with multiple spectrum). (orig.)

  6. Lattice gauge theory for QCD

    International Nuclear Information System (INIS)

    DeGrand, T.

    1997-01-01

    These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and α s (M z ), and B-anti B mixing. 67 refs., 36 figs

  7. Wigner Functions on a Lattice

    OpenAIRE

    Takami, A.; Hashimoto, T.; Horibe, M.; Hayashi, A.

    2000-01-01

    The Wigner functions on the one dimensional lattice are studied. Contrary to the previous claim in literature, Wigner functions exist on the lattice with any number of sites, whether it is even or odd. There are infinitely many solutions satisfying the conditions which reasonable Wigner functions should respect. After presenting a heuristic method to obtain Wigner functions, we give the general form of the solutions. Quantum mechanical expectation values in terms of Wigner functions are also ...

  8. Lattice gauge theory for QCD

    Energy Technology Data Exchange (ETDEWEB)

    DeGrand, T. [Univ. of Colorado, Boulder, CO (United States). Dept. of Physics

    1997-06-01

    These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.

  9. Racetrack lattices for the TRIUMF KAON factory

    International Nuclear Information System (INIS)

    Servranckx, R.V.; Wienands, U.; Craddock, M.K.; Rees, G.H.

    1989-03-01

    Separated-function racetrack lattices have been developed for the KAON Factory accelerators that have more flexibility than the old circular lattices. Straight sections with zero dispersion are provided for rf cavities and fast injection and extraction, and with controlled dispersion for H - injection and slow extraction. In addition the new lattices have fewer depolarizing resonances than the old circular lattices

  10. Lattice gauge theory using parallel processors

    International Nuclear Information System (INIS)

    Lee, T.D.; Chou, K.C.; Zichichi, A.

    1987-01-01

    The book's contents include: Lattice Gauge Theory Lectures: Introduction and Current Fermion Simulations; Monte Carlo Algorithms for Lattice Gauge Theory; Specialized Computers for Lattice Gauge Theory; Lattice Gauge Theory at Finite Temperature: A Monte Carlo Study; Computational Method - An Elementary Introduction to the Langevin Equation, Present Status of Numerical Quantum Chromodynamics; Random Lattice Field Theory; The GF11 Processor and Compiler; and The APE Computer and First Physics Results; Columbia Supercomputer Project: Parallel Supercomputer for Lattice QCD; Statistical and Systematic Errors in Numerical Simulations; Monte Carlo Simulation for LGT and Programming Techniques on the Columbia Supercomputer; Food for Thought: Five Lectures on Lattice Gauge Theory

  11. The future of host cell protein (HCP) identification during process development and manufacturing linked to a risk-based management for their control.

    Science.gov (United States)

    Bracewell, Daniel G; Francis, Richard; Smales, C Mark

    2015-09-01

    The use of biological systems to synthesize complex therapeutic products has been a remarkable success. However, during product development, great attention must be devoted to defining acceptable levels of impurities that derive from that biological system, heading this list are host cell proteins (HCPs). Recent advances in proteomic analytics have shown how diverse this class of impurities is; as such knowledge and capability grows inevitable questions have arisen about how thorough current approaches to measuring HCPs are. The fundamental issue is how to adequately measure (and in turn monitor and control) such a large number of protein species (potentially thousands of components) to ensure safe and efficacious products. A rather elegant solution is to use an immunoassay (enzyme-linked immunosorbent assay [ELISA]) based on polyclonal antibodies raised to the host cell (biological system) used to synthesize a particular therapeutic product. However, the measurement is entirely dependent on the antibody serum used, which dictates the sensitivity of the assay and the degree of coverage of the HCP spectrum. It provides one summed analog value for HCP amount; a positive if all HCP components can be considered equal, a negative in the more likely event one associates greater risk with certain components of the HCP proteome. In a thorough risk-based approach, one would wish to be able to account for this. These issues have led to the investigation of orthogonal analytical methods; most prominently mass spectrometry. These techniques can potentially both identify and quantify HCPs. The ability to measure and monitor thousands of proteins proportionally increases the amount of data acquired. Significant benefits exist if the information can be used to determine critical HCPs and thereby create an improved basis for risk management. We describe a nascent approach to risk assessment of HCPs based upon such data, drawing attention to timeliness in relation to biosimilar

  12. The future of host cell protein (HCP) identification during process development and manufacturing linked to a risk‐based management for their control

    Science.gov (United States)

    Francis, Richard; Smales, C. Mark

    2015-01-01

    ABSTRACT The use of biological systems to synthesize complex therapeutic products has been a remarkable success. However, during product development, great attention must be devoted to defining acceptable levels of impurities that derive from that biological system, heading this list are host cell proteins (HCPs). Recent advances in proteomic analytics have shown how diverse this class of impurities is; as such knowledge and capability grows inevitable questions have arisen about how thorough current approaches to measuring HCPs are. The fundamental issue is how to adequately measure (and in turn monitor and control) such a large number of protein species (potentially thousands of components) to ensure safe and efficacious products. A rather elegant solution is to use an immunoassay (enzyme‐linked immunosorbent assay [ELISA]) based on polyclonal antibodies raised to the host cell (biological system) used to synthesize a particular therapeutic product. However, the measurement is entirely dependent on the antibody serum used, which dictates the sensitivity of the assay and the degree of coverage of the HCP spectrum. It provides one summed analog value for HCP amount; a positive if all HCP components can be considered equal, a negative in the more likely event one associates greater risk with certain components of the HCP proteome. In a thorough risk‐based approach, one would wish to be able to account for this. These issues have led to the investigation of orthogonal analytical methods; most prominently mass spectrometry. These techniques can potentially both identify and quantify HCPs. The ability to measure and monitor thousands of proteins proportionally increases the amount of data acquired. Significant benefits exist if the information can be used to determine critical HCPs and thereby create an improved basis for risk management. We describe a nascent approach to risk assessment of HCPs based upon such data, drawing attention to timeliness in relation to

  13. Embedded Lattice and Properties of Gram Matrix

    Directory of Open Access Journals (Sweden)

    Futa Yuichi

    2017-03-01

    Full Text Available In this article, we formalize in Mizar [14] the definition of embedding of lattice and its properties. We formally define an inner product on an embedded module. We also formalize properties of Gram matrix. We formally prove that an inverse of Gram matrix for a rational lattice exists. Lattice of Z-module is necessary for lattice problems, LLL (Lenstra, Lenstra and Lov´asz base reduction algorithm [16] and cryptographic systems with lattice [17].

  14. Finite-lattice-spacing corrections to masses and g factors on a lattice

    International Nuclear Information System (INIS)

    Roskies, R.; Wu, J.C.

    1986-01-01

    We suggest an alternative method for extracting masses and g factors from lattice calculations. Our method takes account of more of the infrared and ultraviolet lattice effects. It leads to more reasonable results in simulations of QED on a lattice

  15. Quantum lattice model solver HΦ

    Science.gov (United States)

    Kawamura, Mitsuaki; Yoshimi, Kazuyoshi; Misawa, Takahiro; Yamaji, Youhei; Todo, Synge; Kawashima, Naoki

    2017-08-01

    HΦ [aitch-phi ] is a program package based on the Lanczos-type eigenvalue solution applicable to a broad range of quantum lattice models, i.e., arbitrary quantum lattice models with two-body interactions, including the Heisenberg model, the Kitaev model, the Hubbard model and the Kondo-lattice model. While it works well on PCs and PC-clusters, HΦ also runs efficiently on massively parallel computers, which considerably extends the tractable range of the system size. In addition, unlike most existing packages, HΦ supports finite-temperature calculations through the method of thermal pure quantum (TPQ) states. In this paper, we explain theoretical background and user-interface of HΦ. We also show the benchmark results of HΦ on supercomputers such as the K computer at RIKEN Advanced Institute for Computational Science (AICS) and SGI ICE XA (Sekirei) at the Institute for the Solid State Physics (ISSP).

  16. Frustrated lattices of Ising chains

    International Nuclear Information System (INIS)

    Kudasov, Yurii B; Korshunov, Aleksei S; Pavlov, V N; Maslov, Dmitrii A

    2012-01-01

    The magnetic structure and magnetization dynamics of systems of plane frustrated Ising chain lattices are reviewed for three groups of compounds: Ca 3 Co 2 O 6 , CsCoCl 3 , and Sr 5 Rh 4 O 12 . The available experimental data are analyzed and compared in detail. It is shown that a high-temperature magnetic phase on a triangle lattice is normally and universally a partially disordered antiferromagnetic (PDA) structure. The diversity of low-temperature phases results from weak interactions that lift the degeneracy of a 2D antiferromagnetic Ising model on the triangle lattice. Mean-field models, Monte Carlo simulation results on the static magnetization curve, and results on slow magnetization dynamics obtained with Glauber's theory are discussed in detail. (reviews of topical problems)

  17. Lattice QCD for nuclear physics

    CERN Document Server

    Meyer, Harvey

    2015-01-01

    With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun, and many new observables will be calculated at the new computational facilities.  The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems, and in particular to nuclear physics.  A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spect...

  18. Nucleon structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Dinter, Simon

    2012-11-13

    In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.

  19. Nucleon structure from lattice QCD

    International Nuclear Information System (INIS)

    Dinter, Simon

    2012-01-01

    In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a 2 ) discretization effects.

  20. Kondo length in bosonic lattices

    Science.gov (United States)

    Giuliano, Domenico; Sodano, Pasquale; Trombettoni, Andrea

    2017-09-01

    Motivated by the fact that the low-energy properties of the Kondo model can be effectively simulated in spin chains, we study the realization of the effect with bond impurities in ultracold bosonic lattices at half filling. After presenting a discussion of the effective theory and of the mapping of the bosonic chain onto a lattice spin Hamiltonian, we provide estimates for the Kondo length as a function of the parameters of the bosonic model. We point out that the Kondo length can be extracted from the integrated real-space correlation functions, which are experimentally accessible quantities in experiments with cold atoms.

  1. Supersymmetry on the noncommutative lattice

    International Nuclear Information System (INIS)

    Nishimura, Jun; Rey, Soo-Jong; Sugino, Fumihiko

    2003-01-01

    Built upon the proposal of Kaplan et al. (heplat{0206109}), we construct noncommutative lattice gauge theory with manifest supersymmetry. We show that such theory is naturally implementable via orbifold conditions generalizing those used by Kaplan et al. We present the prescription in detail and illustrate it for noncommutative gauge theories latticized partially in two dimensions. We point out a deformation freedom in the defining theory by a complex-parameter, reminiscent of discrete torsion in string theory. We show that, in the continuum limit, the supersymmetry is enhanced only at a particular value of the deformation parameter, determined solely by the size of the noncommutativity. (author)

  2. Machines for lattice gauge theory

    International Nuclear Information System (INIS)

    Mackenzie, P.B.

    1989-05-01

    The most promising approach to the solution of the theory of strong interactions is large scale numerical simulation using the techniques of lattice gauge theory. At the present time, computing requirements for convincing calculations of the properties of hadrons exceed the capabilities of even the most powerful commercial supercomputers. This has led to the development of massively parallel computers dedicated to lattice gauge theory. This talk will discuss the computing requirements behind these machines, and general features of the components and architectures of the half dozen major projects now in existence. 20 refs., 1 fig

  3. Graphene on graphene antidot lattices

    DEFF Research Database (Denmark)

    Gregersen, Søren Schou; Pedersen, Jesper Goor; Power, Stephen

    2015-01-01

    Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure......, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing...

  4. Unconventional superconductivity in honeycomb lattice

    Directory of Open Access Journals (Sweden)

    P Sahebsara

    2013-03-01

    Full Text Available   ‎ The possibility of symmetrical s-wave superconductivity in the honeycomb lattice is studied within a strongly correlated regime, using the Hubbard model. The superconducting order parameter is defined by introducing the Green function, which is obtained by calculating the density of the electrons ‎ . In this study showed that the superconducting order parameter appears in doping interval between 0 and 0.5, and x=0.25 is the optimum doping for the s-wave superconductivity in honeycomb lattice.

  5. [Lattice degeneration of the retina].

    Science.gov (United States)

    Boĭko, E V; Suetov, A A; Mal'tsev, D S

    2014-01-01

    Lattice degeneration of the retina is a clinically important type of peripheral retinal dystrophies due to its participation in the pathogenesis of rhegmatogenous retinal detachment. In spite of extensive epidemiological, morphological, and clinical data, the question on causes of this particular type of retinal dystrophies currently remains debatable. Existing hypotheses on pathogenesis of retinal structural changes in lattice degeneration explain it to a certain extent. In clinical ophthalmology it is necessary to pay close attention to this kind of degenerations and distinguish between cases requiring preventive treatment and those requiring monitoring.

  6. Lattice calculations in gauge theory

    International Nuclear Information System (INIS)

    Rebbi, C.

    1985-01-01

    The lattice formulation of quantum gauge theories is discussed as a viable technique for quantitative studies of nonperturbative effects in QCD. Evidence is presented to ascertain that whole classes of lattice actions produce a universal continuum limit. Discrepancies between numerical results from Monto Carlo simulations for the pure gauge system and for the system with gauge and quark fields are discussed. Numerical calculations for QCD require very substantial computational resources. The use of powerful vector processors of special purpose machines, in extending the scope and magnitude or the calculations is considered, and one may reasonably expect that in the near future good quantitative predictions will be obtained for QCD

  7. Chiral symmetry on the lattice

    International Nuclear Information System (INIS)

    Creutz, M.

    1994-11-01

    The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model

  8. Nuclear Physics from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage

    2011-01-01

    We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.

  9. Representation theory of lattice current algebras

    International Nuclear Information System (INIS)

    Alekseev, A.Yu.; Eidgenoessische Technische Hochschule, Zurich; Faddeev, L.D.; Froehlich, L.D.; Schomerus, V.; Kyoto Univ.

    1996-04-01

    Lattice current algebras were introduced as a regularization of the left-and right moving degrees of freedom in the WZNW model. They provide examples of lattice theories with a local quantum symmetry U q (G). Their representation theory is studied in detail. In particular, we construct all irreducible representations along with a lattice analogue of the fusion product for representations of the lattice current algebra. It is shown that for an arbitrary number of lattice sites, the representation categories of the lattice current algebras agree with their continuum counterparts. (orig.)

  10. Comparative genomics of the type VI secretion systems of Pantoea and Erwinia species reveals the presence of putative effector islands that may be translocated by the VgrG and Hcp proteins

    Directory of Open Access Journals (Sweden)

    De Maayer Pieter

    2011-11-01

    Full Text Available Abstract Background The Type VI secretion apparatus is assembled by a conserved set of proteins encoded within a distinct locus. The putative effector proteins Hcp and VgrG are also encoded within these loci. We have identified numerous distinct Type VI secretion system (T6SS loci in the genomes of several ecologically diverse Pantoea and Erwinia species and detected the presence of putative effector islands associated with the hcp and vgrG genes. Results Between two and four T6SS loci occur among the Pantoea and Erwinia species. While two of the loci (T6SS-1 and T6SS-2 are well conserved among the various strains, the third (T6SS-3 locus is not universally distributed. Additional orthologous loci are present in Pantoea sp. aB-valens and Erwinia billingiae Eb661. Comparative analysis of the T6SS-1 and T6SS-3 loci showed non-conserved islands associated with the vgrG and hcp, and vgrG genes, respectively. These regions had a G+C content far lower than the conserved portions of the loci. Many of the proteins encoded within the hcp and vgrG islands carry conserved domains, which suggests they may serve as effector proteins for the T6SS. A number of the proteins also show homology to the C-terminal extensions of evolved VgrG proteins. Conclusions Extensive diversity was observed in the number and content of the T6SS loci among the Pantoea and Erwinia species. Genomic islands could be observed within some of T6SS loci, which are associated with the hcp and vgrG proteins and carry putative effector domain proteins. We propose new hypotheses concerning a role for these islands in the acquisition of T6SS effectors and the development of novel evolved VgrG and Hcp proteins.

  11. High-pressure high-temperature stability of hcp-IrxOs1-x (x = 0.50 and 0.55) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yusenko, Kirill V.; Bykova, Elena; Bykov, Maxim; Gromilov, Sergey A.; Kurnosov, Alexander V.; Prescher, Clemens; Prakapenka, Vitali B.; Crichton, Wilson A.; Hanfland, Michael; Margadonna, Serena; Dubrovinsky, Leonid S.

    2016-12-23

    Hcp-Ir0.55Os0.45 and hcp-Ir0.50Os0.50 alloys were synthesised by thermal decomposition of single-source precursors in hydrogen atmosphere. Both alloys correspond to a miscibility gap in the Ir–Os binary phase diagram and therefore are metastable at ambient conditions. An in situ powder X-ray diffraction has been used for a monitoring a formation of hcp-Ir0.55Os0.45 alloy from (NH4)2[Ir0.55Os0.45Cl6] precursor. A crystalline intermediate compound and nanodimentional metallic particles with a large concentration of defects has been found as key intermediates in the thermal decomposition process in hydrogen flow. High-temperature stability of titled hcp-structured alloys has been investigated upon compression up to 11 GPa using a multi-anvil press and up to 80 GPa using laser-heated diamond-anvil cells to obtain a phase separation into fcc + hcp mixture. Compressibility curves at room temperature as well as thermal expansion at ambient pressure and under compression up to 80 GPa were collected to obtain thermal expansion coefficients and bulk moduli. hcp-Ir0.55Os0.45 alloy shows bulk moduli B0 = 395 GPa. Thermal expansion coefficients were estimated as α = 1.6·10-5 K-1 at ambient pressure and α = 0.3·10-5 K-1 at 80 GPa. Obtained high-pressure high-temperature data allowed us to construct the first model for pressure-dependent Ir–Os phase diagram.

  12. Computers for lattice field theories

    International Nuclear Information System (INIS)

    Iwasaki, Y.

    1994-01-01

    Parallel computers dedicated to lattice field theories are reviewed with emphasis on the three recent projects, the Teraflops project in the US, the CP-PACS project in Japan and the 0.5-Teraflops project in the US. Some new commercial parallel computers are also discussed. Recent development of semiconductor technologies is briefly surveyed in relation to possible approaches toward Teraflops computers. (orig.)

  13. Synthesis of spatially variant lattices.

    Science.gov (United States)

    Rumpf, Raymond C; Pazos, Javier

    2012-07-02

    It is often desired to functionally grade and/or spatially vary a periodic structure like a photonic crystal or metamaterial, yet no general method for doing this has been offered in the literature. A straightforward procedure is described here that allows many properties of the lattice to be spatially varied at the same time while producing a final lattice that is still smooth and continuous. Properties include unit cell orientation, lattice spacing, fill fraction, and more. This adds many degrees of freedom to a design such as spatially varying the orientation to exploit directional phenomena. The method is not a coordinate transformation technique so it can more easily produce complicated and arbitrary spatial variance. To demonstrate, the algorithm is used to synthesize a spatially variant self-collimating photonic crystal to flow a Gaussian beam around a 90° bend. The performance of the structure was confirmed through simulation and it showed virtually no scattering around the bend that would have arisen if the lattice had defects or discontinuities.

  14. From lattice gases to polymers

    NARCIS (Netherlands)

    Frenkel, D.

    1990-01-01

    The modification of a technique that was developed to study time correlations in lattice-gas cellular automata to facilitate the numerical simulation of chain molecules is described. As an example, the calculation of the excess chemical potential of an ideal polymer in a dense colloidal

  15. Flavor extrapolation in lattice QCD

    International Nuclear Information System (INIS)

    Duffy, W.C.

    1984-01-01

    Explicit calculation of the effect of virtual quark-antiquark pairs in lattice QCD has eluded researchers. To include their effect explicitly one must calculate the determinant of the fermion-fermion coupling matrix. Owing to the large number of sites in a continuum limit size lattice, direct evaluation of this term requires an unrealistic amount of computer time. The effect of the virtual pairs can be approximated by ignoring this term and adjusting lattice couplings to reproduce experimental results. This procedure is called the valence approximation since it ignores all but the minimal number of quarks needed to describe hadrons. In this work the effect of the quark-antiquark pairs has been incorporated in a theory with an effective negative number of quark flavors contributing to the closed loops. Various particle masses and decay constants have been calculated for this theory and for one with no virtual pairs. The author attempts to extrapolate results towards positive numbers of quark flavors. The results show approximate agreement with experimental measurements and demonstrate the smoothness of lattice expectations in the number of quark flavors

  16. Nuclear physics on the lattice?

    International Nuclear Information System (INIS)

    Koonin, S.E.

    1985-01-01

    The goal of the paper is to try to adapt lattice gauge theory to build in some biases in order for being applicable to nuclear physics. In so doing the calculations are made more precise, and the author can address questions like the size of the nucleon, the nucleon-nucleon potential, the modifications of the nucleon in the nuclear medium, etc. (Auth.)

  17. Differential geometry of group lattices

    International Nuclear Information System (INIS)

    Dimakis, Aristophanes; Mueller-Hoissen, Folkert

    2003-01-01

    In a series of publications we developed ''differential geometry'' on discrete sets based on concepts of noncommutative geometry. In particular, it turned out that first-order differential calculi (over the algebra of functions) on a discrete set are in bijective correspondence with digraph structures where the vertices are given by the elements of the set. A particular class of digraphs are Cayley graphs, also known as group lattices. They are determined by a discrete group G and a finite subset S. There is a distinguished subclass of ''bicovariant'' Cayley graphs with the property ad(S)S subset of S. We explore the properties of differential calculi which arise from Cayley graphs via the above correspondence. The first-order calculi extend to higher orders and then allow us to introduce further differential geometric structures. Furthermore, we explore the properties of ''discrete'' vector fields which describe deterministic flows on group lattices. A Lie derivative with respect to a discrete vector field and an inner product with forms is defined. The Lie-Cartan identity then holds on all forms for a certain subclass of discrete vector fields. We develop elements of gauge theory and construct an analog of the lattice gauge theory (Yang-Mills) action on an arbitrary group lattice. Also linear connections are considered and a simple geometric interpretation of the torsion is established. By taking a quotient with respect to some subgroup of the discrete group, generalized differential calculi associated with so-called Schreier diagrams are obtained

  18. Lattice dynamics of lithium oxide

    Indian Academy of Sciences (India)

    Abstract. Li2O finds several important technological applications, as it is used in solid- state batteries, can be used as a blanket breeding material in nuclear fusion reactors, etc. Li2O exhibits a fast ion phase, characterized by a thermally induced dynamic disorder in the anionic sub-lattice of Li+, at elevated temperatures ...

  19. Lattice fields and strong interactions

    International Nuclear Information System (INIS)

    Creutz, M.

    1989-06-01

    I review the lattice formulation of gauge theories and the use of numerical methods to investigate nonperturbative phenomena. These methods are directly applicable to studying hadronic matter at high temperatures. Considerable recent progress has been made in numerical algorithms for including dynamical fermions in such calculations. Dealing with a nonvanishing baryon density adds new unsolved challenges. 33 refs

  20. Mean-field lattice trees

    NARCIS (Netherlands)

    Borgs, C.; Chayes, J.T.; Hofstad, van der R.W.; Slade, G.

    1999-01-01

    We introduce a mean-field model of lattice trees based on embeddings into d of abstract trees having a critical Poisson offspring distribution. This model provides a combinatorial interpretation for the self-consistent mean-field model introduced previously by Derbez and Slade [9], and provides an

  1. Lattice quantum chromodynamics: Some topics

    Indian Academy of Sciences (India)

    I will begin with a lightning quick overview of the basic lattice gauge theory and then go on to .... The Monte Carlo technique to evaluate C(t), or the expectation value of any other observable ... x }occurs with a probability proportional to. 890.

  2. Lattice continuum and diffusional creep.

    Science.gov (United States)

    Mesarovic, Sinisa Dj

    2016-04-01

    Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro-Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro-Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate.

  3. Fields on a random lattice

    International Nuclear Information System (INIS)

    Itzykson, C.

    1983-10-01

    We review the formulation of field theory and statistical mechanics on a Poissonian random lattice. Topics discussed include random geometry, the construction of field equations for arbitrary spin, the free field spectrum and the question of localization illustrated in the one dimensional case

  4. Disconnected Diagrams in Lattice QCD

    Science.gov (United States)

    Gambhir, Arjun Singh

    In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called "disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements

  5. Disconnected Diagrams in Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gambhir, Arjun [College of William and Mary, Williamsburg, VA (United States)

    2017-08-01

    In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called \\disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements

  6. Statistical hydrodynamics of lattice-gas automata

    OpenAIRE

    Grosfils, Patrick; Boon, Jean-Pierre; Brito López, Ricardo; Ernst, M. H.

    1993-01-01

    We investigate the space and time behavior of spontaneous thermohydrodynamic fluctuations in a simple fluid modeled by a lattice-gas automaton and develop the statistical-mechanical theory of thermal lattice gases to compute the dynamical structure factor, i.e., the power spectrum of the density correlation function. A comparative analysis of the theoretical predictions with our lattice gas simulations is presented. The main results are (i) the spectral function of the lattice-gas fluctuation...

  7. Lattice QCD. A critical status report

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Karl

    2008-10-15

    The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)

  8. Lattice QCD. A critical status report

    International Nuclear Information System (INIS)

    Jansen, Karl

    2008-10-01

    The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)

  9. Gauge theories on a small lattice

    International Nuclear Information System (INIS)

    Robson, D.; Webber, D.M.

    1980-01-01

    We present exact solutions to U(1), SU(2), and SU(3) lattice gauge theories on a Kogut-Susskind lattice consisting of a single plaquette. We demonstrate precise equivalence between the U(1) theory and the harmonic oscillator on an infinite one-dimensional lattice, and between the SU(N) theory and an N-fermion Schroedinger equation. (orig.)

  10. Spatiotemporal complexity in coupled map lattices

    International Nuclear Information System (INIS)

    Kaneko, Kunihiko

    1986-01-01

    Some spatiotemporal patterns of couple map lattices are presented. The chaotic kink-like motions are shown for the phase motion of the coupled circle lattices. An extension of the couple map lattice approach to Hamiltonian dynamics is briefly reported. An attempt to characterize the high-dimensional attractor by the extension of the correlation dimension is discussed. (author)

  11. Clar sextets in square graphene antidot lattices

    DEFF Research Database (Denmark)

    Petersen, Rene; Pedersen, Thomas Garm; Jauho, Antti-Pekka

    2011-01-01

    A periodic array of holes transforms graphene from a semimetal into a semiconductor with a band gap tuneable by varying the parameters of the lattice. In earlier work only hexagonal lattices have been treated. Using atomistic models we here investigate the size of the band gap of a square lattice...

  12. Spatial classification with fuzzy lattice reasoning

    NARCIS (Netherlands)

    Mavridis, Constantinos; Athanasiadis, I.N.

    2017-01-01

    This work extends the Fuzzy Lattice Reasoning (FLR) Classifier to manage spatial attributes, and spatial relationships. Specifically, we concentrate on spatial entities, as countries, cities, or states. Lattice Theory requires the elements of a Lattice to be partially ordered. To match such

  13. Inexpensive chirality on the lattice

    International Nuclear Information System (INIS)

    Kamleh, W.; Williams, A.G.; Adams, D.

    2000-01-01

    Full text: Implementing lattice fermions that resemble as closely as possible continuum fermions is one of the main goals of the theoretical physics community. Aside from a lack of infinitely powerful computers, one of the main impediments to this is the Nielsen-Ninomiya No-Go theorem for chirality on the lattice. One of the consequences of this theorem is that exact chiral symmetry and a lack of fermion doublers cannot be simultaneously satisfied for fermions on the lattice. In the commonly used Wilson fermion formulation, chiral symmetry is explicitly sacrificed on the lattice to avoid fermion doubling. Recently, an alternative has come forward, namely, the Ginsparg-Wilson relation and one of its solutions, the Overlap fermion. The Ginsparg-Wilson relation is a statement of lattice-deformed chirality. The Overlap-Dirac operator is a member of the family of solutions of the Ginsparg-Wilson relation. In recent times, Overlap fermions have been of great interest to the community due to their excellent chiral properties. However, they are significantly more expensive to implement than Wilson fermions. This expense is primarily due to the fact that the Overlap implementation requires an evaluation of the sign function for the Wilson-Dirac operator. The sign function is approximated by a high order rational polynomial function, but this approximation is poor close to the origin. The less near-zero modes that the Wilson- Dirac operator possesses, the cheaper the Overlap operator will be to implement. A means of improving the eigenvalue properties of the Wilson-Dirac operator by the addition of a so-called 'Clover' term is put forward. Numerical results are given that demonstrate this improvement. The Nielsen-Ninomiya no-go theorem and chirality on the lattice are reviewed. The general form of solutions of the Ginsparg-Wilson relation are given, and the Overlap solution is discussed. Properties of the Overlap-Dirac operator are given, including locality and analytic

  14. ''Cube-on-hexagon'' orientation relationship for Fe on GaN(0001): The missing link in bcc/hcp epitaxy

    International Nuclear Information System (INIS)

    Gao Cunxu; Brandt, Oliver; Laehnemann, Jonas; Jahn, Uwe; Jenichen, Bernd; Schoenherr, Hans-Peter; Erwin, Steven C.

    2010-01-01

    We investigate, experimentally and theoretically, the epitaxy of body-centered-cubic Fe on hexagonal GaN. For growth on the Ga-polar GaN(0001) surface we find the well-known Pitsch-Schrader orientation relationship between Fe and GaN. On the N-polar GaN(0001) surface we observe coexistence between the familiar Burgers orientation and a new orientation in which the Fe(001) plane is parallel to GaN(0001). This 'cube-on-hexagon' orientation constitutes the high-symmetry link required for constructing a symmetry diagram for bcc/hcp systems in which all orientation relationships are connected by simple rotations.

  15. Chiral fermions on the lattice

    International Nuclear Information System (INIS)

    Randjbar Daemi, S.; Strathdee, J.

    1995-01-01

    The overlap approach to chiral gauge theories on arbitrary D-dimensional lattices is studied. The doubling problem and its relation to chiral anomalies for D = 2 and 4 is examined. In each case it is shown that the doublers can be eliminated and the well known perturbative results for chiral anomalies can be recovered. We also consider the multi-flavour case and give the general criteria for the construction of anomaly free chiral gauge theories on arbitrary lattices. We calculate the second order terms in a continuum approximation to the overlap formula in D dimensions and show that they coincide with the bilinear part of the effective action of D-dimensional Weyl fermions coupled to a background gauge field. Finally, using the same formalism we reproduce the correct Lorentz, diffeomorphism and gauge anomalies in the coupling of a Weyl fermion to 2-dimensional gravitation and Maxwell fields. (author). 15 refs

  16. Entropy favours open colloidal lattices

    Science.gov (United States)

    Mao, Xiaoming; Chen, Qian; Granick, Steve

    2013-03-01

    Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.

  17. Electroweak interactions on the lattice

    International Nuclear Information System (INIS)

    Kieu, T.D.

    1994-07-01

    It is shown that the lattice fermion doubling phenomenon is connected to the chiral anomaly which is unique to the electroweak interactions. The chiral anomaly is the breaking of chiral gauge symmetry at the quantum level due to the quantum fluctuations. Such breaking, however, is undesirable and to be avoided. The preservation of gauge symmetry imposes stringent constraints on acceptable chiral gauge theory. It is argued that the constraints are unnecessary because the conventional quantization of chiral gauge theory has missed out some crucial contributions of the chiral interactions. The corrected quantization yields consistent theory in which there is no gauge anomaly and in which various mass terms can be introduced with neither the loss of gauge invariance nor the need for the Higgs mechanism. The new quantization also provide a solution to the difficulty of how to model the electroweak interactions on the lattice. 9 refs. 1 fig

  18. Entanglement scaling in lattice systems

    Energy Technology Data Exchange (ETDEWEB)

    Audenaert, K M R [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Cramer, M [QOLS, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Eisert, J [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom); Plenio, M B [Institute for Mathematical Sciences, Imperial College London, 53 Prince' s Gate, Exhibition Road, London SW7 2PG (United Kingdom)

    2007-05-15

    We review some recent rigorous results on scaling laws of entanglement properties in quantum many body systems. More specifically, we study the entanglement of a region with its surrounding and determine its scaling behaviour with its size for systems in the ground and thermal states of bosonic and fermionic lattice systems. A theorem connecting entanglement between a region and the rest of the lattice with the surface area of the boundary between the two regions is presented for non-critical systems in arbitrary spatial dimensions. The entanglement scaling in the field limit exhibits a peculiar difference between fermionic and bosonic systems. In one-spatial dimension a logarithmic divergence is recovered for both bosonic and fermionic systems. In two spatial dimensions in the setting of half-spaces however we observe strict area scaling for bosonic systems and a multiplicative logarithmic correction to such an area scaling in fermionic systems. Similar questions may be posed and answered in classical systems.

  19. Transitionless lattices for LAMPF II

    International Nuclear Information System (INIS)

    Franczak, B.J.

    1984-10-01

    Some techniques are described for the design of synchrotron lattices that have zero dispersion in the straight sections and/or imaginary transition energy (negative momentum-compaction factor) but no excessive amplitudes of the dispersion function. Included as an application is a single-stage synchrotron, with variable optics, that has different ion-optical properties at injection and extraction but requires a complex way of programming the quadrupoles. In addition, a two-stage facility consisting of a 45-GeV synchrotron of 1100-m circumference and a 9-GeV booster of half that size is presented. As alternates to these separated-function lattices, some combined-function modules are given that can be used to construct a synchrotron with similar properties

  20. Graphene antidot lattice transport measurements

    DEFF Research Database (Denmark)

    Mackenzie, David; Cagliani, Alberto; Gammelgaard, Lene

    2017-01-01

    We investigate graphene devices patterned with a narrow band of holes perpendicular to the current flow, a few-row graphene antidot lattice (FR-GAL). Theoretical reports suggest that a FR-GAL can have a bandgap with a relatively small reduction of the transmission compared to what is typical...... for antidot arrays devices. Graphene devices were fabricated using 100 keV electron beam lithography (EBL) for nanopatterning as well as for defining electrical contacts. Patterns with hole diameter and neck widths of order 30 nm were produced, which is the highest reported pattern density of antidot lattices...... in graphene reported defined by EBL. Electrical measurements showed that devices with one and five rows exhibited field effect mobility of ∼100 cm2/Vs, while a larger number of rows, around 40, led to a significant reduction of field effect mobility (

  1. Cellular automata in cytoskeletal lattices

    Energy Technology Data Exchange (ETDEWEB)

    Smith, S A; Watt, R C; Hameroff, S R

    1984-01-01

    Cellular automata (CA) activities could mediate biological regulation and information processing via nonlinear electrodynamic effects in cytoskeletal lattice arrays. Frohlich coherent oscillations and other nonlinear mechanisms may effect discrete 10/sup -10/ to 10/sup -11/ s interval events which result in dynamic patterns in biolattices such as cylindrical protein polymers: microtubules (MT). Structural geometry and electrostatic forces of MT subunit dipole oscillations suggest neighbor rules among the hexagonally packed protein subunits. Computer simulations using these suggested rules and MT structural geometry demonstrate CA activities including dynamical and stable self-organizing patterns, oscillators, and traveling gliders. CA activities in MT and other cytoskeletal lattices may have important biological regulatory functions. 23 references, 6 figures, 1 table.

  2. Innovations in lattice QCD algorithms

    International Nuclear Information System (INIS)

    Orginos, Konstantinos

    2006-01-01

    Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today

  3. Baryon structure from lattice QCD

    International Nuclear Information System (INIS)

    Alexandrou, C.

    2009-01-01

    We present recent lattice results on the baryon spectrum, nucleon electromagnetic and axial form factors, nucleon to Δ transition form factors as well as the Δ electromagnetic form factors. The masses of the low lying baryons and the nucleon form factors are calculated using two degenerate flavors of twisted mass fermions down to pion mass of about 270 MeV. We compare to the results of other collaborations. The nucleon to Δ transition and Δ form factors are calculated in a hybrid scheme, which uses staggered sea quarks and domain wall valence quarks. The dominant magnetic dipole nucleon to Δ transition form factor is also evaluated using dynamical domain wall fermions. The transverse density distributions of the Δ in the infinite momentum frame are extracted using the form factors determined from lattice QCD. (author)

  4. Multigrid for Staggered Lattice Fermions

    Energy Technology Data Exchange (ETDEWEB)

    Brower, Richard C. [Boston U.; Clark, M. A. [Unlisted, US; Strelchenko, Alexei [Fermilab; Weinberg, Evan [Boston U.

    2018-01-23

    Critical slowing down in Krylov methods for the Dirac operator presents a major obstacle to further advances in lattice field theory as it approaches the continuum solution. Here we formulate a multi-grid algorithm for the Kogut-Susskind (or staggered) fermion discretization which has proven difficult relative to Wilson multigrid due to its first-order anti-Hermitian structure. The solution is to introduce a novel spectral transformation by the K\\"ahler-Dirac spin structure prior to the Galerkin projection. We present numerical results for the two-dimensional, two-flavor Schwinger model, however, the general formalism is agnostic to dimension and is directly applicable to four-dimensional lattice QCD.

  5. Computing nucleon EDM on a lattice

    Science.gov (United States)

    Abramczyk, Michael; Aoki, Sinya; Blum, Tom; Izubuchi, Taku; Ohki, Hiroshi; Syritsyn, Sergey

    2018-03-01

    I will discuss briefly recent changes in the methodology of computing the baryon EDM on a lattice. The associated correction substantially reduces presently existing lattice values for the proton and neutron theta-induced EDMs, so that even the most precise previous lattice results become consistent with zero. On one hand, this change removes previous disagreements between these lattice results and the phenomenological estimates of the nucleon EDM. On the other hand, the nucleon EDM becomes much harder to compute on a lattice. In addition, I will review the progress in computing quark chromo-EDM-induced nucleon EDM using chiral quark action.

  6. Heavy water critical experiments on plutonium lattice

    International Nuclear Information System (INIS)

    Miyawaki, Yoshio; Shiba, Kiminori

    1975-06-01

    This report is the summary of physics study on plutonium lattice made in Heavy Water Critical Experiment Section of PNC. By using Deuterium Critical Assembly, physics study on plutonium lattice has been carried out since 1972. Experiments on following items were performed in a core having 22.5 cm square lattice pitch. (1) Material buckling (2) Lattice parameters (3) Local power distribution factor (4) Gross flux distribution in two region core (5) Control rod worth. Experimental results were compared with theoretical ones calculated by METHUSELAH II code. It is concluded from this study that calculation by METHUSELAH II code has acceptable accuracy in the prediction on plutonium lattice. (author)

  7. Computing nucleon EDM on a lattice

    Energy Technology Data Exchange (ETDEWEB)

    Abramczyk, Michael; Izubuchi, Taku

    2017-06-18

    I will discuss briefly recent changes in the methodology of computing the baryon EDM on a lattice. The associated correction substantially reduces presently existing lattice values for the proton and neutron theta-induced EDMs, so that even the most precise previous lattice results become consistent with zero. On one hand, this change removes previous disagreements between these lattice results and the phenomenological estimates of the nucleon EDM. On the other hand, the nucleon EDM becomes much harder to compute on a lattice. In addition, I will review the progress in computing quark chromo-EDM-induced nucleon EDM using chiral quark action.

  8. Aliasing modes in the lattice Schwinger model

    International Nuclear Information System (INIS)

    Campos, Rafael G.; Tututi, Eduardo S.

    2007-01-01

    We study the Schwinger model on a lattice consisting of zeros of the Hermite polynomials that incorporates a lattice derivative and a discrete Fourier transform with many properties. Such a lattice produces a Klein-Gordon equation for the boson field and the exact value of the mass in the asymptotic limit if the boundaries are not taken into account. On the contrary, if the lattice is considered with boundaries new modes appear due to aliasing effects. In the continuum limit, however, this lattice yields also a Klein-Gordon equation with a reduced mass

  9. Scale setting in lattice QCD

    International Nuclear Information System (INIS)

    Sommer, Rainer

    2014-02-01

    The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.

  10. Apiary B Factory lattice design

    International Nuclear Information System (INIS)

    Donald, M.H.R.; Garren, A.A.

    1991-04-01

    The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper will present the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent. 8 figs. 1 tab

  11. BROOKHAVEN: Lattice gauge theory symposium

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1986-12-15

    Originally introduced by Kenneth Wilson in the early 70s, the lattice formulation of a quantum gauge theory became a hot topic of investigation after Mike Creutz, Laurence Jacobs and Claudio Rebbi demonstrated in 1979 the feasibility of meaningful computer simulations. The initial enthusiasm led gradually to a mature research effort, with continual attempts to improve upon previous results, to develop better computational techniques and to find new domains of application.

  12. Harmonic Lattice Dynamics of Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Nelin, G

    1974-07-01

    The phonon dispersion relations of the DELTA-, LAMBDA-, and SIGMA-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field.

  13. Screening in graphene antidot lattices

    DEFF Research Database (Denmark)

    Schultz, Marco Haller; Jauho, A. P.; Pedersen, T. G.

    2011-01-01

    We compute the dynamical polarization function for a graphene antidot lattice in the random-phase approximation. The computed polarization functions display a much more complicated structure than what is found for pristine graphene (even when evaluated beyond the Dirac-cone approximation...... the plasmon dispersion law and find an approximate square-root dependence with a suppressed plasmon frequency as compared to doped graphene. The plasmon dispersion is nearly isotropic and the developed approximation schemes agree well with the full calculation....

  14. Symplectic maps for accelerator lattices

    International Nuclear Information System (INIS)

    Warnock, R.L.; Ruth, R.; Gabella, W.

    1988-05-01

    We describe a method for numerical construction of a symplectic map for particle propagation in a general accelerator lattice. The generating function of the map is obtained by integrating the Hamilton-Jacobi equation as an initial-value problem on a finite time interval. Given the generating function, the map is put in explicit form by means of a Fourier inversion technique. We give an example which suggests that the method has promise. 9 refs., 9 figs

  15. Harmonic Lattice Dynamics of Germanium

    International Nuclear Information System (INIS)

    Nelin, G.

    1974-01-01

    The phonon dispersion relations of the Δ-, Λ-, and Σ-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field

  16. Scale setting in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, Rainer [DESY, Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2014-02-15

    The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.

  17. Wave transmission in nonlinear lattices

    International Nuclear Information System (INIS)

    Hennig, D.; Tsironis, G.P.

    1999-01-01

    The interplay of nonlinearity with lattice discreteness leads to phenomena and propagation properties quite distinct from those appearing in continuous nonlinear systems. For a large variety of condensed matter and optics applications the continuous wave approximation is not appropriate. In the present review we discuss wave transmission properties in one dimensional nonlinear lattices. Our paradigmatic equations are discrete nonlinear Schroedinger equations and their study is done through a dynamical systems approach. We focus on stationary wave properties and utilize well known results from the theory of dynamical systems to investigate various aspects of wave transmission and wave localization. We analyze in detail the more general dynamical system corresponding to the equation that interpolates between the non-integrable discrete nonlinear Schroedinger equation and the integrable Albowitz-Ladik equation. We utilize this analysis in a nonlinear Kronig-Penney model and investigate transmission and band modification properties. We discuss the modifications that are effected through an electric field and the nonlinear Wannier-Stark localization effects that are induced. Several applications are described, such as polarons in one dimensional lattices, semiconductor superlattices and one dimensional nonlinear photonic band gap systems. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  18. Spin lattices of walking droplets

    Science.gov (United States)

    Saenz, Pedro; Pucci, Giuseppe; Goujon, Alexis; Dunkel, Jorn; Bush, John

    2017-11-01

    We present the results of an experimental investigation of the spontaneous emergence of collective behavior in spin lattice of droplets walking on a vibrating fluid bath. The bottom topography consists of relatively deep circular wells that encourage the walking droplets to follow circular trajectories centered at the lattice sites, in one direction or the other. Wave-mediated interactions between neighboring drops are enabled through a thin fluid layer between the wells. The sense of rotation of the walking droplets may thus become globally coupled. When the coupling is sufficiently strong, interactions with neighboring droplets may result in switches in spin that lead to preferred global arrangements, including correlated (all drops rotating in the same direction) or anti-correlated (neighboring drops rotating in opposite directions) states. Analogies with ferromagnetism and anti-ferromagnetism are drawn. Different spatial arrangements are presented in 1D and 2D lattices to illustrate the effects of topological frustration. This work was supported by the US National Science Foundation through Grants CMMI-1333242 and DMS-1614043.

  19. Calculational methods for lattice cells

    International Nuclear Information System (INIS)

    Askew, J.R.

    1980-01-01

    At the current stage of development, direct simulation of all the processes involved in the reactor to the degree of accuracy required is not an economic proposition, and this is achieved by progressive synthesis of models for parts of the full space/angle/energy neutron behaviour. The split between reactor and lattice calculations is one such simplification. Most reactors are constructed of repetitions of similar geometric units, the fuel elements, having broadly similar properties. Thus the provision of detailed predictions of their behaviour is an important step towards overall modelling. We shall be dealing with these lattice methods in this series of lectures, but will refer back from time to time to their relationship with overall reactor calculation The lattice cell is itself composed of somewhat similar sub-units, the fuel pins, and will itself often rely upon a further break down of modelling. Construction of a good model depends upon the identification, on physical and mathematical grounds, of the most helpful division of the calculation at this level

  20. Topological magnon bands in ferromagnetic star lattice

    International Nuclear Information System (INIS)

    Owerre, S A

    2017-01-01

    The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1–3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii–Moriya (DM) spin–orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases. (paper)

  1. Topological magnon bands in ferromagnetic star lattice.

    Science.gov (United States)

    Owerre, S A

    2017-05-10

    The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1-3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii-Moriya (DM) spin-orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases.

  2. Lattice dynamics and lattice thermal conductivity of thorium dicarbide

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Zongmeng [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Qiu, Wujie [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Ke, Xuezhi, E-mail: xzke@phy.ecnu.edu.cn [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); Zhang, Wenqing [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhu, Zhiyuan [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2014-11-15

    The elastic and thermodynamic properties of ThC{sub 2} with a monoclinic symmetry have been studied by means of density functional theory and direct force-constant method. The calculated properties including the thermal expansion, the heat capacity and the elastic constants are in a good agreement with experiment. Our results show that the vibrational property of the C{sub 2} dimer in ThC{sub 2} is similar to that of a free standing C{sub 2} dimer. This indicates that the C{sub 2} dimer in ThC{sub 2} is not strongly bonded to Th atoms. The lattice thermal conductivity for ThC{sub 2} was calculated by means of the Debye–Callaway model. As a comparison, the conductivity of ThC was also calculated. Our results show that the ThC and ThC{sub 2} contributions of the lattice thermal conductivity to the total conductivity are 29% and 17%, respectively.

  3. First principles analysis of lattice dynamics for Fe-based superconductors and entropically-stabilized phases

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Steven [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Modern calculations are becoming an essential, complementary tool to inelastic x-ray scattering studies, where x-rays are scattered inelastically to resolve meV phonons. Calculations of the inelastic structure factor for any value of Q assist in both planning the experiment and analyzing the results. Moreover, differences between the measured data and theoretical calculations help identify important new physics driving the properties of novel correlated systems. We have used such calculations to better and more e ciently measure the phonon dispersion and elastic constants of several iron pnictide superconductors. This dissertation describes calculations and measurements at room temperature in the tetragonal phase of CaFe{sub 2}As{sub 2} and LaFeAsO. In both cases, spin-polarized calculations imposing the antiferromagnetic order present in the low-temperature orthorhombic phase dramatically improves the agreement between theory and experiment. This is discussed in terms of the strong antiferromagnetic correlations that are known to persist in the tetragonal phase. In addition, we discuss a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD), which goes beyond the harmonic approximation to include phonon-phonon interactions and produce a temperature-dependent phonon dispersion. We used this technique to study the HCP to BCC transition in beryllium.

  4. Nucleon deformation from lattice QCD

    International Nuclear Information System (INIS)

    Tsapalis, A.

    2008-01-01

    The issue of nucleon and Delta(1232) deformation is discussed through the evaluation of the N to Delta electromagnetic transition and Delta electromagnetic form factors in Lattice QCD. The momentum dependence of the form factors is studied using 2+1 staggered dynamical flavors at pion masses as low as 350 MeV and compared to results obtained in the Wilson quenched and two-flavor dynamical theory at similar pion masses. The measurement of small non-zero quadrupole amplitudes, in agreement to recent experiments, establishes the existence of deformation in the N and Delta states. (author)

  5. Nucleon Structure from Lattice QCD

    International Nuclear Information System (INIS)

    Zanotti, J. M.

    2011-01-01

    Lattice simulations of hadronic structure are now reaching a level where they are able to not only complement, but also provide guidance to current and forthcoming experimental programmes.By considering new simulations at low quark masses and on large volumes, we review the recent progress that has been made in this area by the QCDSF/UKQCD collaboration. In particular, results obtained close to the physical point for several quantities, including electromagnetic form factors and moments of parton distribution functions, show some indication of approaching their phenomenological values.

  6. GLAD: a generic lattice debugger

    International Nuclear Information System (INIS)

    Lee, M.J.

    1992-01-01

    Today, numerous simulation and analysis codes exist for the design, commission, and operation of accelerator beam lines. There is a need to develop a common user interface and database link to run these codes interactively. This paper will describe a proposed system, GLAD (Generic LAttice Debugger), to fulfill this need. Specifically, GLAD can be used to find errors in beam lines during commissioning, control beam parameters during operation, and design beam line optics and error correction systems for the next generation of linear accelerators and storage rings. (author)

  7. Lattice dynamics of ionic crystals

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1990-01-01

    The theory of lattice dynamics for ionic and rare-gas crystals is derived in the harmonic approximation. We start from a Hamiltonian and average over electron coordinates in order to obtain an effective interaction between ion displacements. We assume that electronic excitations are localized on a single ion, which limits the theory to ionic crystals. The deformation-dipole model and the indirect-ionic-interaction model are derived. These two contributions are closely linked, and together provide an accurate description of short-range forces

  8. Degeneración Lattice

    OpenAIRE

    Rojas Bocanegra, Alberto

    2004-01-01

    Objetivo: Determinar la prevalencia de degeneración periférica de retina Lattice y su relación con estados refractivos y rupturas retinales. Metodología: Estudio de corte transversal con exploración de asociación, mediante análisis de casos y controles. Se examinaron 680 ojos en el Instituto de Investigaciones Optométricas e Instituto de Córnea. El estado refractivo se determinó mediante técnica estática y el estado retinal mediante oftalmoscopia indirecta con indentación escleral. Resultados...

  9. Lattice degeneration of the retina.

    Science.gov (United States)

    Byer, N E

    1979-01-01

    Lattice degeneration of the retina is the most important of all clinically distinct entities that effect the peripheral fundus and are related to retinal detachment. The purpose of this review is to survey the extensive literature, to evaluate the many diverse opinions on this subject, and to correlate and summarize all the known facts regarding this disease entity. The disease is fully defined and described, both clinically and histologically. Some aspects of the disease are still poorly understood, and some remain controversial, especially in the area of management. For this reason, the indications for treatment are discussed under eight subsections, with a view toward providing practical guidelines for recommendations in management.

  10. The lattice dynamics of imidazole

    International Nuclear Information System (INIS)

    Link, K.H.

    1983-05-01

    The lattice dynamics of imidazole have been investigated. To this end dispersion curves have been determined at 10 K by inelastic coherent neutron scattering. RAMAN measurements have been done to investigate identical gamma - point modes. The combination of extinction rules for RAMAN - and neutron scattering leads to the symmetry assignment of identical gamma - point modes. The experiment yields a force constant of the streching vibration of the hydrogen bond of 0.33 mdyn/A. A force model has been developed to describe the intermolecular atom - atom Interactions in imidazole. (orig./BHO)

  11. Working Group Report: Lattice Field Theory

    Energy Technology Data Exchange (ETDEWEB)

    Blum, T.; et al.,

    2013-10-22

    This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.

  12. Lattice vibrations in α-boron

    International Nuclear Information System (INIS)

    Richter, W.

    1976-01-01

    α-rhombohedral boron is the simplest boron modification, with only 12 atoms per unit cell. The boron atoms are arranged in B 12 icosahedra, which are centered at the lattice points of a primitive rhombohedral lattice. The icosahedra are slightly deformed, as the five-fold symmetry of the ideal icosahedron is incompatible with any crystal structure. The lattice dynamics of α-boron are discussed in terms of the model developed by Weber and Thorpe. (Auth.)

  13. Experimental generation of optical coherence lattices

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yahong; Cai, Yangjian, E-mail: serpo@dal.ca, E-mail: yangjiancai@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Ponomarenko, Sergey A., E-mail: serpo@dal.ca, E-mail: yangjiancai@suda.edu.cn [Department of Electrical and Computer Engineering, Dalhousie University, Halifax, Nova Scotia B3J 2X4 (Canada)

    2016-08-08

    We report experimental generation and measurement of recently introduced optical coherence lattices. The presented optical coherence lattice realization technique hinges on a superposition of mutually uncorrelated partially coherent Schell-model beams with tailored coherence properties. We show theoretically that information can be encoded into and, in principle, recovered from the lattice degree of coherence. Our results can find applications to image transmission and optical encryption.

  14. Introduction to Vortex Lattice Theory

    Directory of Open Access Journals (Sweden)

    Santiago Pinzón

    2015-10-01

    Full Text Available Panel methods have been widely used in industry and are well established since the 1970s for aerodynamic analysis and computation. The Vortex Lattice Panel Method presented in this study comes across a sophisticated method that provides a quick solution time, allows rapid changes in geometry and suits well for aerodynamic analysis. The aerospace industry is highly competitive in design efficiency, and perhaps one of the most important factors on airplane design and engineering today is multidisciplinary optimization.  Any cost reduction method in the design cycle of a product becomes vital in the success of its outcome. The subsequent sections of this article will further explain in depth the theory behind the vortex lattice method, and the reason behind its selection as the method for aerodynamic analysis during preliminary design work and computation within the aerospace industry. This article is analytic in nature, and its main objective is to present a mathematical summary of this widely used computational method in aerodynamics.

  15. Coherent lattice vibrations in superconductors

    International Nuclear Information System (INIS)

    Kadin, Alan M.

    2008-01-01

    A recent analysis has shown that the pair wavefunction within the BCS theory may be represented in real-space as a spherical electronic orbital (on the scale of the coherence length ξ 0 ) coupled to a standing-wave lattice vibration with wavevector 2k F and a near-resonant phonon frequency. The present paper extends this picture to a coherent pattern of phonon standing-waves on the macroscopic scale, with electrons forming Bloch waves and an energy gap much like those in the classic band theory of crystals. These parallel planes form a diffractive waveguide permitting electron waves to traveling parallel to the planes, corresponding to lossless supercurrent. A similar picture may be extended to unconventional superconductors such as the cuprates, with an array of standing spin waves rather than phonons. Such coherent lattice vibrations should be universal indicators of the superconducting state, and should be observable below T c using X-ray and neutron diffraction techniques. Further implications of this picture are discussed

  16. Lattice dynamics in solid oxygen

    International Nuclear Information System (INIS)

    Kobashi, K.; Klein, M.L.; Chandrasekharan, V.

    1979-01-01

    Lattice dynamical calculations for the bulk α, β, and γ phases of solid O 2 and for the monolayer α and β phases have been made in the harmonic approximation. In the α and β phases, atom-atom 6-12 potentials are employed. In the γ phase, effective potentials are used between molecular centers and only the translational lattice vibrations are calculated. It is found that Laufer and Leroi's potential parameters give two k=O frequencies at 42.7 and 43.6 cm -1 in the bulk α-O 2 , and at 40.7 cm -1 for the degenerate k=0 modes in the β phase. The observed Raman lines for α-O 2 at 43 and 79 cm -1 , which are both known to exhibit isotope shifts, are thus tentatively assigned to an accidentally degenerate line and a two-phonon band, respectively, In view of the possible contribution from anharmonic effects, the agreement of the calculation with experiment (48-51 cm -1 ) in β-O 2 may be better than it seems. For the bulk γ-O 2 , a discrepancy is observed between the calculated elastic constants and those derived from Brillouin scattering experiments. This discrepancy may be due to the neglect of translation-rotation coupling. In the monolayer O 2 , Raman active modes at 28.3 and 40.6 cm -1 for the α phase, and 31.9 cm -1 for the β phase are predicted

  17. Polarization response of RHIC electron lens lattices

    International Nuclear Information System (INIS)

    Ranjbar, V. H.; Méot, F.; Bai, M.; Abell, D. T.; Meiser, D.

    2016-01-01

    Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. Particularly, we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. Furthermore, these results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. We then consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.

  18. Advancements in simulations of lattice quantum chromodynamics

    International Nuclear Information System (INIS)

    Lippert, T.

    2008-01-01

    An introduction to lattice QCD with emphasis on advanced fermion formulations and their simulation is given. In particular, overlap fermions will be presented, a quite novel fermionic discretization scheme that is able to exactly preserve chiral symmetry on the lattice. I will discuss efficiencies of state-of-the-art algorithms on highly scalable supercomputers and I will show that, due to many algorithmic improvements, overlap simulations will soon become feasible for realistic physical lattice sizes. Finally I am going to sketch the status of some current large scale lattice QCD simulations. (author)

  19. On diffeomorphism invariance for lattice theories

    International Nuclear Information System (INIS)

    Corichi, A.; Zapata, J.

    1997-01-01

    We consider the role of the diffeomorphism constraint in the quantization of lattice formulations of diffeomorphism invariant theories of connections. It has been argued that in working with abstract lattices one automatically takes care of the diffeomorphism constraint in the quantum theory. We use two systems in order to show that imposing the diffeomorphism constraint is imperative to obtain a physically acceptable quantum theory. First, we consider 2+1 gravity where an exact lattice formulation is available. Next, general theories of connections for compact gauge groups are treated, where the quantum theories are known - for both the continuum and the lattice - and can be compared. (orig.)

  20. Elastic lattice in an incommensurate background

    International Nuclear Information System (INIS)

    Dickman, R.; Chudnovsky, E.M.

    1995-01-01

    We study a harmonic triangular lattice, which relaxes in the presence of an incommensurate short-wavelength potential. Monte Carlo simulations reveal that the elastic lattice exhibits only short-ranged translational correlations, despite the absence of defects in either lattice. Extended orientational order, however, persists in the presence of the background. Translational correlation lengths exhibit approximate power-law dependence upon cooling rate and background strength. Our results may be relevant to Wigner crystals, atomic monolayers on crystals surfaces, and flux-line and magnetic bubble lattices

  1. Anomalous diffusion in a dynamical optical lattice

    Science.gov (United States)

    Zheng, Wei; Cooper, Nigel R.

    2018-02-01

    Motivated by experimental progress in strongly coupled atom-photon systems in optical cavities, we study theoretically the quantum dynamics of atoms coupled to a one-dimensional dynamical optical lattice. The dynamical lattice is chosen to have a period that is incommensurate with that of an underlying static lattice, leading to a dynamical version of the Aubry-André model which can cause localization of single-particle wave functions. We show that atomic wave packets in this dynamical lattice generically spread via anomalous diffusion, which can be tuned between superdiffusive and subdiffusive regimes. This anomalous diffusion arises from an interplay between Anderson localization and quantum fluctuations of the cavity field.

  2. Polarization response of RHIC electron lens lattices

    Directory of Open Access Journals (Sweden)

    V. H. Ranjbar

    2016-10-01

    Full Text Available Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.

  3. Internal space decimation for lattice gauge theories

    International Nuclear Information System (INIS)

    Flyvbjerg, H.

    1984-01-01

    By a systematic decimation of internal space lattice gauge theories with continuous symmetry groups are mapped into effective lattice gauge theories with finite symmetry groups. The decimation of internal space makes a larger lattice tractable with the same computational resources. In this sense the method is an alternative to Wilson's and Symanzik's programs of improved actions. As an illustrative test of the method U(1) is decimated to Z(N) and the results compared with Monte Carlo data for Z(4)- and Z(5)-invariant lattice gauge theories. The result of decimating SU(3) to its 1080-element crystal-group-like subgroup is given and discussed. (orig.)

  4. Transmission Electron Microscope Measures Lattice Parameters

    Science.gov (United States)

    Pike, William T.

    1996-01-01

    Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

  5. Testing the holographic principle using lattice simulations

    Directory of Open Access Journals (Sweden)

    Jha Raghav G.

    2018-01-01

    Full Text Available The lattice studies of maximally supersymmetric Yang-Mills (MSYM theory at strong coupling and large N is important for verifying gauge/gravity duality. Due to the progress made in the last decade, based on ideas from topological twisting and orbifolding, it is now possible to study these theories on the lattice while preserving an exact supersymmetry on the lattice. We present some results from the lattice studies of two-dimensional MSYM which is related to Type II supergravity. Our results agree with the thermodynamics of different black hole phases on the gravity side and the phase transition (Gregory–Laflamme between them.

  6. Hadron physics from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Andreas [Regensburg Univ. (Germany). Inst. for Theoretical Physics

    2016-11-01

    Particle physics experiments at modern high luminosity particle accelerators achieve orders of magnitude higher count rates than what was possible ten or twenty years ago. This extremely large statistics allows to draw far reaching conclusions even from minute signals, provided that these signals are well understood by theory. This is, however, ever more difficult to achieve. Presently, technical and scientific progress in general and experimental progress in particle physics in particular, shows typically an exponential growth rate. For example, data acquisition and analysis are, among many other factor, driven by the development of ever more efficient computers and thus by Moore's law. Theory has to keep up with this development by also achieving an exponential increase in precision, which is only possible using powerful computers. This is true for both types of calculations, analytic ones as, e.g., in quantum field perturbation theory, and purely numerical ones as in Lattice QCD. As stated above such calculations are absolutely indispensable to make best use of the extremely costly large particle physics experiments. Thus, it is economically reasonable to invest a certain percentage of the cost of accelerators and experiments in related theory efforts. The basic ideas behind Lattice QCD simulations are the following: Because quarks and gluons can never be observed individually but are always ''confined'' into colorless hadrons, like the proton, all quark-gluon states can be expressed in two different systems of basis states, namely in a quark-gluon basis and the basis of hadron states. The proton, e.g., is an eigenstate of the latter, a specific quark-gluon configuration is part of the former. In the quark-gluon basis a physical hadron, like a proton, is given by an extremely complicated multi-particle wave function containing all effects of quantum fluctuations. This state is so complicated that it is basically impossible to model it

  7. Lattices for laymen: a non-specialist's introduction to lattice gauge theory

    International Nuclear Information System (INIS)

    Callaway, D.J.E.

    1985-01-01

    The review on lattice gauge theory is based upon a series of lectures given to the Materials Science and Technology Division at Argonne National Laboratory. Firstly the structure of gauge theories in the continuum is discussed. Then the lattice formulation of these theories is presented, including quantum electrodynamics and non-abelian lattice gauge theories. (U.K.)

  8. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    International Nuclear Information System (INIS)

    Jahangir, Vafa; Riahifar, Reza; Sahba Yaghmaee, Maziar

    2016-01-01

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  9. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jahangir, Vafa, E-mail: vafa.jahangir@yahoo.com; Riahifar, Reza, E-mail: reza_rfr@yahoo.com; Sahba Yaghmaee, Maziar, E-mail: fkmsahba@uni-miskolc.hu

    2016-03-31

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  10. Pion structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Javadi Motaghi, Narjes

    2015-05-12

    In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.

  11. Computer programs for lattice calculations

    International Nuclear Information System (INIS)

    Keil, E.; Reich, K.H.

    1984-01-01

    The aim of the workshop was to find out whether some standardisation could be achieved for future work in this field. A certain amount of useful information was unearthed, and desirable features of a ''standard'' program emerged. Progress is not expected to be breathtaking, although participants (practically from all interested US, Canadian and European accelerator laboratories) agreed that the mathematics of the existing programs is more or less the same. Apart from the NIH (not invented here) effect, there is a - to quite some extent understandable - tendency to stay with a program one knows and to add to it if unavoidable rather than to start using a new one. Users of the well supported program TRANSPORT (designed for beam line calculations) would prefer to have it fully extended for lattice calculations (to some extent already possible now), while SYNCH users wish to see that program provided with a user-friendly input, rather than spending time and effort for mastering a new program

  12. Monte Carlo lattice program KIM

    International Nuclear Information System (INIS)

    Cupini, E.; De Matteis, A.; Simonini, R.

    1980-01-01

    The Monte Carlo program KIM solves the steady-state linear neutron transport equation for a fixed-source problem or, by successive fixed-source runs, for the eigenvalue problem, in a two-dimensional thermal reactor lattice. Fluxes and reaction rates are the main quantities computed by the program, from which power distribution and few-group averaged cross sections are derived. The simulation ranges from 10 MeV to zero and includes anisotropic and inelastic scattering in the fast energy region, the epithermal Doppler broadening of the resonances of some nuclides, and the thermalization phenomenon by taking into account the thermal velocity distribution of some molecules. Besides the well known combinatorial geometry, the program allows complex configurations to be represented by a discrete set of points, an approach greatly improving calculation speed

  13. Particle states of lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Kapoyannis, A.S.; Panagiotou, A.D. [University of Athens, Nuclear and Particle Physics Section, Faculty of Physics, Athens (Greece)

    2017-11-15

    We determine the degeneracy factor and the average particle mass of particles that produce the lattice QCD pressure and specific entropy at zero baryon chemical potential. The number of states of the gluons and the quarks are found to converge above T = 230 MeV to almost constant values, close to the number of states of an ideal quark-gluon phase, while their assigned masses retain high values. The number of states and the average mass of a system containing quarks in interaction with gluons are found to decrease steeply with increase of temperature between T ∝ 150 and 160 MeV, a region contained within the region of the chiral transition. The minimum value of the number of states within this temperature interval indicates that the states are of hadronic nature. (orig.)

  14. Fermion determinants in lattice QCD

    International Nuclear Information System (INIS)

    Johnson, Christopher Andrew

    2001-01-01

    The main topic of this thesis concerns efficient algorithms for the calculation of determinants of the kind of matrix typically encountered in lattice QCD. In particular an efficient method for calculating the fermion determinant is described. Such a calculation is useful to illustrate the effects of light dynamical (virtual) quarks. The methods employed in this thesis are stochastic methods, based on the Lanczos algorithm, which is used for the solution of large, sparse matrix problems via a partial tridiagonalisation of the matrix. Here an implementation is explored which requires less exhaustive treatment of the matrix than previous Lanczos methods. This technique exploits the analogy between the Lanczos tridiagonalisation algorithm and Gaussian quadrature in order to calculate the fermion determinant. A technique for determining a number of the eigenvalues of the matrix is also presented. A demonstration is then given of how one can improve upon this estimate considerably using variance reduction techniques, reducing the variance by a factor of order 100 with a further, equal amount of work. The variance reduction method is a two-stage process, involving a Chebyshev approximation to the quantity in question and then the subtraction of traceless operators. The method is applied to the fermion determinant for non-perturbatively improved Wilson fermions on a 16 3 x 32 lattice. It is also applicable to a wider class of matrix operators. Finally we discuss how dynamical quark effects may be simulated in a Monte Carlo process with an effective partitioning of low and high eigenmodes. This may be done via selective updating of a trial configuration which highlights the physically relevant effects of light quark modes. (author)

  15. An Application of Linear Algebra over Lattices

    Directory of Open Access Journals (Sweden)

    M. Hosseinyazdi

    2008-03-01

    Full Text Available In this paper, first we consider L n as a semimodule over a complete bounded distributive lattice L. Then we define the basic concepts of module theory for L n. After that, we proved many similar theorems in linear algebra for the space L n. An application of linear algebra over lattices for solving linear systems, was given

  16. An Application of Linear Algebra over Lattices

    OpenAIRE

    M. Hosseinyazdi

    2008-01-01

    In this paper, first we consider L n as a semimodule over a complete bounded distributive lattice L. Then we define the basic concepts of module theory for L n. After that, we proved many similar theorems in linear algebra for the space L n. An application of linear algebra over lattices for solving linear systems, was given

  17. Compact lattice QED with Wilson fermions

    International Nuclear Information System (INIS)

    Hoferichter, A.

    1994-08-01

    We study the phase structure and the chiral limit of 4d compact lattice QED with Wilson fermions (both dynamical and quenched). We use the standard Wilson gauge action and also a modified one suppressing lattice artifacts. Different techniques and observables to locate the chiral limit are discussed. (orig.)

  18. Chimera states in Gaussian coupled map lattices

    Science.gov (United States)

    Li, Xiao-Wen; Bi, Ran; Sun, Yue-Xiang; Zhang, Shuo; Song, Qian-Qian

    2018-04-01

    We study chimera states in one-dimensional and two-dimensional Gaussian coupled map lattices through simulations and experiments. Similar to the case of global coupling oscillators, individual lattices can be regarded as being controlled by a common mean field. A space-dependent order parameter is derived from a self-consistency condition in order to represent the collective state.

  19. Dark Solitons in FPU Lattice Chain

    Science.gov (United States)

    Wang, Deng-Long; Yang, Ru-Shu; Yang, You-Tian

    2007-11-01

    Based on multiple scales method, we study the nonlinear properties of a new Fermi-Pasta-Ulam lattice model analytically. It is found that the lattice chain exhibits a novel nonlinear elementary excitation, i.e. a dark soliton. Moreover, the modulation depth of dark soliton is increasing as the anharmonic parameter increases.

  20. Dark Solitons in FPU Lattice Chain

    International Nuclear Information System (INIS)

    Wang Denglong; Yang Youtian; Yang Rushu

    2007-01-01

    Based on multiple scales method, we study the nonlinear properties of a new Fermi-Pasta-Ulam lattice model analytically. It is found that the lattice chain exhibits a novel nonlinear elementary excitation, i.e. a dark soliton. Moreover, the modulation depth of dark soliton is increasing as the anharmonic parameter increases.

  1. Lattice-Valued Possibilistic Entropy Measure

    Czech Academy of Sciences Publication Activity Database

    Kramosil, Ivan

    2008-01-01

    Roč. 16, č. 6 (2008), s. 829-846 ISSN 0218-4885 R&D Projects: GA AV ČR IAA100300503 Institutional research plan: CEZ:AV0Z10300504 Keywords : complete lattice * lattice-valued possibilistic distribution * entropy measure * product of possibilistic distribution Subject RIV: BA - General Mathematics Impact factor: 1.000, year: 2008

  2. Unorthodox lattice fermion derivatives and their shortcomings

    International Nuclear Information System (INIS)

    Bodwin, G.T.; Kovacs, E.V.

    1987-01-01

    We discuss the DWY (Lagrangian), Quinn-Weinstein, and Rebbi proposals for incorporating fermions into lattice gauge theory and analyze them in the context of weak coupling perturbation theory. We find that none of these proposals leads to a completely satisfactory lattice transcription of fully-interacting gauge theory

  3. Gauge field theories on a || lattice

    International Nuclear Information System (INIS)

    Burkardt, Matthias

    1999-01-01

    In these notes, the transverse || lattice approach is presented as a means to control the k + →0 divergences in light-front QCD. Technical difficulties of both the canonical compact formulation as well as the non-compact formulation of the || lattice motivate the color-dielectric formulation, where the link fields are linearized

  4. Selective nanoscale growth of lattice mismatched materials

    Science.gov (United States)

    Lee, Seung-Chang; Brueck, Steven R. J.

    2017-06-20

    Exemplary embodiments provide materials and methods of forming high-quality semiconductor devices using lattice-mismatched materials. In one embodiment, a composite film including one or more substantially-single-particle-thick nanoparticle layers can be deposited over a substrate as a nanoscale selective growth mask for epitaxially growing lattice-mismatched materials over the substrate.

  5. Spectral Gaps in Graphene Antidot Lattices

    DEFF Research Database (Denmark)

    Barbaroux, Jean-Marie; Cornean, Decebal Horia; Stockmeyer, Edgardo

    2017-01-01

    We consider the gap creation problem in an antidot graphene lattice, i.e. a sheet of graphene with periodically distributed obstacles. We prove several spectral results concerning the size of the gap and its dependence on different natural parameters related to the antidot lattice....

  6. Cold collisions in dissipative optical lattices

    International Nuclear Information System (INIS)

    Piilo, J; Suominen, K-A

    2005-01-01

    The invention of laser cooling methods for neutral atoms allows optical and magnetic trapping of cold atomic clouds in the temperature regime below 1 mK. In the past, light-assisted cold collisions between laser cooled atoms have been widely studied in magneto-optical atom traps (MOTs). We describe here theoretical studies of dynamical interactions, specifically cold collisions, between atoms trapped in near-resonant, dissipative optical lattices. The extension of collision studies to the regime of optical lattices introduces several complicating factors. For the lattice studies, one has to account for the internal substates of atoms, position-dependent matter-light coupling, and position-dependent couplings between the atoms, in addition to the spontaneous decay of electronically excited atomic states. The developed one-dimensional quantum-mechanical model combines atomic cooling and collision dynamics in a single framework. The model is based on Monte Carlo wavefunction simulations and is applied when the lattice-creating lasers have frequencies both below (red-detuned lattice) and above (blue-detuned lattice) the atomic resonance frequency. It turns out that the radiative heating mechanism affects the dynamics of atomic cloud in a red-detuned lattice in a way that is not directly expected from the MOT studies. The optical lattice and position-dependent light-matter coupling introduces selectivity of collision partners. The atoms which are most mobile and energetic are strongly favoured to participate in collisions, and are more often ejected from the lattice, than the slow ones in the laser parameter region selected for study. Consequently, the atoms remaining in the lattice have a smaller average kinetic energy per atom than in the case of non-interacting atoms. For blue-detuned lattices, we study how optical shielding emerges as a natural part of the lattice and look for ways to optimize the effect. We find that the cooling and shielding dynamics do not mix

  7. Quantum transport in d -dimensional lattices

    International Nuclear Information System (INIS)

    Manzano, Daniel; Chuang, Chern; Cao, Jianshu

    2016-01-01

    We show that both fermionic and bosonic uniform d -dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. We then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour of uniform spin lattices is a consequence of the interaction between different excitations. (paper)

  8. A lattice approach to spinorial quantum gravity

    Science.gov (United States)

    Renteln, Paul; Smolin, Lee

    1989-01-01

    A new lattice regularization of quantum general relativity based on Ashtekar's reformulation of Hamiltonian general relativity is presented. In this form, quantum states of the gravitational field are represented within the physical Hilbert space of a Kogut-Susskind lattice gauge theory. The gauge field of the theory is a complexified SU(2) connection which is the gravitational connection for left-handed spinor fields. The physical states of the gravitational field are those which are annihilated by additional constraints which correspond to the four constraints of general relativity. Lattice versions of these constraints are constructed. Those corresponding to the three-dimensional diffeomorphism generators move states associated with Wilson loops around on the lattice. The lattice Hamiltonian constraint has a simple form, and a correspondingly simple interpretation: it is an operator which cuts and joins Wilson loops at points of intersection.

  9. Design of the SPEAR 3 magnet lattice

    International Nuclear Information System (INIS)

    Corbett, J.; Limborg, C.; Nosochkov, Y.; Safranek, J.

    1998-01-01

    The SPEAR 3 Upgrade Project seeks to replace the present 160 nm-rad FODO lattice with an 18 nm-rad double bend achromat (DBA) lattice. The new lattice must conform to the layout of the SPEAR racetrack tunnel and service the existing photon beamlines. Working within these constraints, the authors designed a lattice with 18 achromatic cells and 3 GeV beam energy. This paper reports on design of the main DBA cells, design of the matching cells leading into the 6.5 m racetrack straights, and simulation of the dynamic aperture. The new lattice has gradient dipoles, conventional quadrupoles, and provides horizontal dynamic aperture to ± 20 mm with conservative magnetic multipole errors

  10. Light Hadron Spectroscopy on course lattices with

    CERN Document Server

    Lee, F

    1999-01-01

    The masses and dispersions of light hadrons are calculated in lattice QCD using an O(a sup 2) tadpole-improved gluon action and an O(a sup 2) tadpole-improved next-nearest-neighbor fermion action originally proposed by Hamber and Wu. Two lattices of constant volume with lattice spacings of approximately 0.40 fm and 0.24 fm are considered. The results reveal some scaling violations at the coarser lattice spacing on the order of 5%. At the finer lattice spacing, the nucleon to rho mass ratio reproduces state-of-the-art results using unimproved actions. Good dispersion and rotational invariance up to momenta of pa approx = 1 are also found. The relative merit of alternative choices for improvement operators is assessed through close comparisons with other plaquette-based tadpole-improved actions.

  11. Supersymmetry on a space-time lattice

    Energy Technology Data Exchange (ETDEWEB)

    Kaestner, Tobias

    2008-10-28

    In this thesis the WZ model in one and two dimensions has been thoroughly investigated. With the help of the Nicolai map it was possible to construct supersymmetrically improved lattice actions that preserve one of several supersymmetries. For the WZ model in one dimension SLAC fermions were utilized for the first time leading to a near-perfect elimination of lattice artifacts. In addition the lattice superpotential does not get modified which in two dimensions becomes important when further (discrete) symmetries of the continuum action are considered. For Wilson fermions two new improvements have been suggested and were shown to yield far better results than standard Wilson fermions concerning lattice artifacts. In the one-dimensional theory Ward Identities were studied.However, supersymmetry violations due to broken supersymmetry could only be detected at coarse lattices and very strong couplings. For the two-dimensional models a detailed analysis of supersymmetric improvement terms was given, both for Wilson and SLAC fermions. (orig.)

  12. Lattices for the TRIUMF KAON factory

    International Nuclear Information System (INIS)

    Servranckx, R.V.; Craddock, M.K.

    1989-09-01

    Separated-function racetrack lattices have been developed for the KAON Factory accelerators that have more flexibility than the old circular lattices. The arcs of the large rings have a regular FODO structure with a superimposed six-fold symmetric modulation of the betafunction in order to raise γ t to infinity. Straight sections with zero dispersion are provided for rf cavities and fast injection and extraction, and with controlled dispersion for H - injection and slow extraction. For the small rings, sixfold symmetric circular lattices with high γ t are retained. In the Accumulator lattice, a straight section with double waist and controlled η function allows for H - injection and phase-space painting. The ion-optical properties of the lattices and the results from tracking studies are discussed

  13. Ising antiferromagnet on the Archimedean lattices

    Science.gov (United States)

    Yu, Unjong

    2015-06-01

    Geometric frustration effects were studied systematically with the Ising antiferromagnet on the 11 Archimedean lattices using the Monte Carlo methods. The Wang-Landau algorithm for static properties (specific heat and residual entropy) and the Metropolis algorithm for a freezing order parameter were adopted. The exact residual entropy was also found. Based on the degree of frustration and dynamic properties, ground states of them were determined. The Shastry-Sutherland lattice and the trellis lattice are weakly frustrated and have two- and one-dimensional long-range-ordered ground states, respectively. The bounce, maple-leaf, and star lattices have the spin ice phase. The spin liquid phase appears in the triangular and kagome lattices.

  14. Synthesizing lattice structures in phase space

    International Nuclear Information System (INIS)

    Guo, Lingzhen; Marthaler, Michael

    2016-01-01

    In one dimensional systems, it is possible to create periodic structures in phase space through driving, which is called phase space crystals (Guo et al 2013 Phys. Rev. Lett. 111 205303). This is possible even if for particles trapped in a potential without periodicity. In this paper we discuss ultracold atoms in a driven optical lattice, which is a realization of such a phase space crystals. The corresponding lattice structure in phase space is complex and contains rich physics. A phase space lattice differs fundamentally from a lattice in real space, because its coordinate system, i.e., phase space, has a noncommutative geometry, which naturally provides an artificial gauge (magnetic) field. We study the behavior of the quasienergy band structure and investigate the dissipative dynamics. Synthesizing lattice structures in phase space provides a new platform to simulate the condensed matter phenomena and study the intriguing phenomena of driven systems far away from equilibrium. (paper)

  15. Supersymmetry on a space-time lattice

    International Nuclear Information System (INIS)

    Kaestner, Tobias

    2008-01-01

    In this thesis the WZ model in one and two dimensions has been thoroughly investigated. With the help of the Nicolai map it was possible to construct supersymmetrically improved lattice actions that preserve one of several supersymmetries. For the WZ model in one dimension SLAC fermions were utilized for the first time leading to a near-perfect elimination of lattice artifacts. In addition the lattice superpotential does not get modified which in two dimensions becomes important when further (discrete) symmetries of the continuum action are considered. For Wilson fermions two new improvements have been suggested and were shown to yield far better results than standard Wilson fermions concerning lattice artifacts. In the one-dimensional theory Ward Identities were studied.However, supersymmetry violations due to broken supersymmetry could only be detected at coarse lattices and very strong couplings. For the two-dimensional models a detailed analysis of supersymmetric improvement terms was given, both for Wilson and SLAC fermions. (orig.)

  16. Lattice gravity near the continuum limit

    International Nuclear Information System (INIS)

    Feinberg, G.; Friedberg, R.; Lee, T.D.; Ren, H.C.

    1984-01-01

    We prove that the lattice gravity always approaches the usual continuum limit when the link length l -> 0, provided that certain general boundary conditions are satisfied. This result holds for any lattice, regular or irregular. Furthermore, for a given lattice, the deviation from its continuum limit can be expressed as a power series in l 2 . General formulas for such a perturbative calculation are given, together with a number of illustrative examples, including the graviton propagator. The lattice gravity satisfies all the invariance properties of Einstein's theory of general relativity. In addition, it is symmetric under a new class of transformations that are absent in the usual continuum theory. The possibility that the lattice theory (with a nonzero l) may be more fundamental is discussed. (orig.)

  17. Synthetic magnetic fluxes on the honeycomb lattice

    Energy Technology Data Exchange (ETDEWEB)

    Gorecka, Agnieszka [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Gremaud, Benoit [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Laboratoire Kastler Brossel, Ecole Normale Superieure, CNRS, UPMC, 4 Place Jussieu, FR-75005 Paris (France); Miniatura, Christian [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institut Non Lineaire de Nice, UMR 6618, UNS, CNRS, 1361 Route des Lucioles, FR-06560 Valbonne (France); Institute of Advanced Studies, Nanyang Technological university, 60 Nanyang View, Singapore 639673 (Singapore)

    2011-08-15

    We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.

  18. Interstructure Lattices and Types of Peano Arithmetic

    Science.gov (United States)

    Abdul-Quader, Athar

    The collection of elementary substructures of a model of PA forms a lattice, and is referred to as the substructure lattice of the model. In this thesis, we study substructure and interstructure lattices of models of PA. We apply techniques used in studying these lattices to other problems in the model theory of PA. In Chapter 2, we study a problem that had its origin in Simpson ([Sim74]), who used arithmetic forcing to show that every countable model of PA has an expansion to PA* that is pointwise definable. Enayat ([Ena88]) later showed that there are 2N0 models with the property that every expansion to PA* is pointwise definable. In this Chapter, we use techniques involved in representations of lattices to show that there is a model of PA with this property which contains an infinite descending chain of elementary cuts. In Chapter 3, we study the question of when subsets can be coded in elementary end extensions with prescribed interstructure lattices. This problem originated in Gaifman [Gai76], who showed that every model of PA has a conservative, minimal elementary end extension. That is, every model of PA has a minimal elementary end extension which codes only definable sets. Kossak and Paris [KP92] showed that if a model is countable and a subset X can be coded in any elementary end extension, then it can be coded in a minimal extension. Schmerl ([Sch14] and [Sch15]) extended this work by considering which collections of sets can be the sets coded in a minimal elementary end extension. In this Chapter, we extend this work to other lattices. We study two questions: given a countable model M, which sets can be coded in an elementary end extension such that the interstructure lattice is some prescribed finite distributive lattice; and, given an arbitrary model M, which sets can be coded in an elementary end extension whose interstructure lattice is a finite Boolean algebra?

  19. Bidirectional Fano Algorithm for Lattice Coded MIMO Channels

    KAUST Repository

    Al-Quwaiee, Hessa

    2013-01-01

    channel model. Channel codes based on lattices are preferred due to three facts: lattice codes have simple structure, the code can achieve the limits of the channel, and they can be decoded efficiently using lattice decoders which can be considered

  20. Manipulation and quantification of microtubule lattice integrity

    Directory of Open Access Journals (Sweden)

    Taylor A. Reid

    2017-08-01

    Full Text Available Microtubules are structural polymers that participate in a wide range of cellular functions. The addition and loss of tubulin subunits allows the microtubule to grow and shorten, as well as to develop and repair defects and gaps in its cylindrical lattice. These lattice defects act to modulate the interactions of microtubules with molecular motors and other microtubule-associated proteins. Therefore, tools to control and measure microtubule lattice structure will be invaluable for developing a quantitative understanding of how the structural state of the microtubule lattice may regulate its interactions with other proteins. In this work, we manipulated the lattice integrity of in vitro microtubules to create pools of microtubules with common nucleotide states, but with variations in structural states. We then developed a series of novel semi-automated analysis tools for both fluorescence and electron microscopy experiments to quantify the type and severity of alterations in microtubule lattice integrity. These techniques will enable new investigations that explore the role of microtubule lattice structure in interactions with microtubule-associated proteins.

  1. Commensurability effects in holographic homogeneous lattices

    International Nuclear Information System (INIS)

    Andrade, Tomas; Krikun, Alexander

    2016-01-01

    An interesting application of the gauge/gravity duality to condensed matter physics is the description of a lattice via breaking translational invariance on the gravity side. By making use of global symmetries, it is possible to do so without scarifying homogeneity of the pertinent bulk solutions, which we thus term as “homogeneous holographic lattices.' Due to their technical simplicity, these configurations have received a great deal of attention in the last few years and have been shown to correctly describe momentum relaxation and hence (finite) DC conductivities. However, it is not clear whether they are able to capture other lattice effects which are of interest in condensed matter. In this paper we investigate this question focusing our attention on the phenomenon of commensurability, which arises when the lattice scale is tuned to be equal to (an integer multiple of) another momentum scale in the system. We do so by studying the formation of spatially modulated phases in various models of homogeneous holographic lattices. Our results indicate that the onset of the instability is controlled by the near horizon geometry, which for insulating solutions does carry information about the lattice. However, we observe no sharp connection between the characteristic momentum of the broken phase and the lattice pitch, which calls into question the applicability of these models to the physics of commensurability.

  2. Lattice-Based Revocable Certificateless Signature

    Directory of Open Access Journals (Sweden)

    Ying-Hao Hung

    2017-10-01

    Full Text Available Certificateless signatures (CLS are noticeable because they may resolve the key escrow problem in ID-based signatures and break away the management problem regarding certificate in conventional signatures. However, the security of the mostly previous CLS schemes relies on the difficulty of solving discrete logarithm or large integer factorization problems. These two problems would be solved by quantum computers in the future so that the signature schemes based on them will also become insecure. For post-quantum cryptography, lattice-based cryptography is significant due to its efficiency and security. However, no study on addressing the revocation problem in the existing lattice-based CLS schemes is presented. In this paper, we focus on the revocation issue and present the first revocable CLS (RCLS scheme over lattices. Based on the short integer solution (SIS assumption over lattices, the proposed lattice-based RCLS scheme is shown to be existential unforgeability against adaptive chosen message attacks. By performance analysis and comparisons, the proposed lattice-based RCLS scheme is better than the previously proposed lattice-based CLS scheme, in terms of private key size, signature length and the revocation mechanism.

  3. Status and future of lattice gauge theory

    International Nuclear Information System (INIS)

    Hoek, J.

    1989-07-01

    The current status of lattice Quantum Chromo Dynamics (QCD) calculations, the computer requirements to obtain physical results and the direction computing is taking are described. First of all, there is a lot of evidence that QCD is the correct theory of strong interactions. Since it is an asymptotically free theory we can use perturbation theory to solve it in the regime of very hard collisions. However even in the case of very hard parton collisions the end-results of the collisions are bound states of quarks and perturbation theory is not sufficient to calculate these final stages. The way to solve the theory in this regime was opened by Wilson. He contemplated replacing the space-time continuum by a discrete lattice, with a lattice spacing a. Continuum physics is then recovered in the limit where the correlation length of the theory, say ξ. is large with respect to the lattice spacing. This will be true if the lattice spacing becomes very small, which for asymptotically free theories also implies that the coupling g becomes small. The lattice approach to QCD is in many respects analogous to the use of finite element methods to solve classical field theories. These finite element methods are easy to apply in 2-dimensional simulations but are computationally demanding in the 3-dimensional case. Therefore it is not unexpected that the 4-dimensional simulations needed for lattice gauge theories have led to an explosion in demand for computing power by theorists. (author)

  4. 3D Metallic Lattices for Accelerator Applications

    CERN Document Server

    Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J

    2005-01-01

    We present the results of research on 3D metallic lattices operating at microwave frequencies for application in (1) accelerator structures with higher order mode suppression, (2) Smith-Purcell radiation beam diagnostics, and (3) polaritonic materials for laser acceleration. Electromagnetic waves in a 3D simple cubic lattice formed by metal wires are calculated using HFSS. The bulk modes in the lattice are determined using single cell calculations with different phase advances in all three directions. The Brillouin diagram for the bulk modes is presented and indicates the absence of band gaps in simple lattices except the band below the cutoff. Lattices with thin wires as well as with thick wires have been analyzed. The Brillouin diagram also indicates the presence of low frequency 3D plasmon mode as well as the two degenerate photon modes analogous to those in a 2D lattice. Surface modes for a semi-infinite cubic lattice are modeled as a stack of cells with different phase advances in the two directions alon...

  5. Lattice solitons in Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Efremidis, Nikolaos K.; Christodoulides, Demetrios N.

    2003-01-01

    We systematically study the properties of lattice solitons in Bose-Einstein condensates with either attractive or repulsive atom interactions. This is done, by exactly solving the mean-field Gross-Pitaevskii equation in the presence of a periodic potential. We find new families of lattice soliton solutions that are characterized by the position of the energy eigenvalue within the associated band structure. These include lattice solitons in condensates with either attractive or repulsive atom interactions that exist in finite or semi-infinite gaps, as well as nonlinear modes that exhibit atomic population cutoffs

  6. Supersymmetric quiver gauge theories on the lattice

    International Nuclear Information System (INIS)

    Joseph, Anosh

    2013-12-01

    In this paper we detail the lattice constructions of several classes of supersymmetric quiver gauge theories in two and three Euclidean spacetime dimensions possessing exact supersymmetry at finite lattice spacing. Such constructions are obtained through the methods of topological twisting and geometric discretization of Euclidean Yang-Mills theories with eight and sixteen supercharges in two and three dimensions. We detail the lattice constructions of two-dimensional quiver gauge theories possessing four and eight supercharges and three-dimensional quiver gauge theories possessing eight supercharges.

  7. Construction of Capacity Achieving Lattice Gaussian Codes

    KAUST Repository

    Alghamdi, Wael

    2016-04-01

    We propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3].

  8. Dynamical Regge calculus as lattice gravity

    International Nuclear Information System (INIS)

    Hagura, Hiroyuki

    2001-01-01

    We propose a hybrid approach to lattice quantum gravity by combining simultaneously the dynamical triangulation with the Regge calculus, called the dynamical Regge calculus (DRC). In this approach lattice diffeomorphism is realized as an exact symmetry by some hybrid (k, l) moves on the simplicial lattice. Numerical study of 3D pure gravity shows that an entropy of the DRC is not exponetially bounded if we adopt the uniform measure Π i dl i . On the other hand, using the scale-invariant measure Π i dl i /l i , we can calculate observables and observe a large hysteresis between two phases that indicates the first-order nature of the phase transition

  9. Calculating luminosity for a coupled Tevatron lattice

    International Nuclear Information System (INIS)

    Holt, J.A.; Martens, M.A.; Michelotti, L.; Goderre, G.

    1995-05-01

    The traditional formula for calculating luminosity assumes an uncoupled lattice and makes use of one-degree-of-freedom lattice functions, β H and β v , for relating transverse beam widths to emittances. Strong coupling requires changing this approach. It is simplest to employ directly the linear normal form coordinates of the one turn map. An equilibrium distribution in phase space is expressed as a function of the Jacobian's eigenvectors and beam size parameters or emittances. Using the equilibrium distributions an expression for the luminosity was derived and applied to the Tevatron lattice, which was coupled due to a quadrupole roll

  10. Optical lattice on an atom chip

    DEFF Research Database (Denmark)

    Gallego, D.; Hofferberth, S.; Schumm, Thorsten

    2009-01-01

    Optical dipole traps and atom chips are two very powerful tools for the quantum manipulation of neutral atoms. We demonstrate that both methods can be combined by creating an optical lattice potential on an atom chip. A red-detuned laser beam is retroreflected using the atom chip surface as a high......-quality mirror, generating a vertical array of purely optical oblate traps. We transfer thermal atoms from the chip into the lattice and observe cooling into the two-dimensional regime. Using a chip-generated Bose-Einstein condensate, we demonstrate coherent Bloch oscillations in the lattice....

  11. Continuum gauge fields from lattice gauge fields

    International Nuclear Information System (INIS)

    Goeckeler, M.; Kronfeld, A.S.; Schierholz, G.; Wiese, U.J.

    1993-01-01

    On the lattice some of the salient features of pure gauge theories and of gauge theories with fermions in complex representations of the gauge group seem to be lost. These features can be recovered by considering part of the theory in the continuum. The prerequisite for that is the construction of continuum gauge fields from lattice gauge fields. Such a construction, which is gauge covariant and complies with geometrical constructions of the topological charge on the lattice, is given in this paper. The procedure is explicitly carried out in the U(1) theory in two dimensions, where it leads to simple results. (orig.)

  12. The η' meson from lattice QCD

    International Nuclear Information System (INIS)

    Jansen, K.; Michael, C.; Urbach, C.

    2008-04-01

    We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. With N f =2 flavours of light quark, this is the so-called η 2 meson and we discuss the phenomenological status of this. Using maximally twisted-mass lattice QCD, we extract the mass of the η 2 meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses. (orig.)

  13. Racetrack lattices for the TRIUMF KAON factory

    International Nuclear Information System (INIS)

    Servranckx, R.V.; Craddock, M.K.

    1989-05-01

    Separated-function racetrack lattices have been developed for the KAON Factory accelerators that have more flexibility than the old circular lattices. The arcs of the large rings have a regular FODO structure with a superimposed six-fold symmetric modulation of the betafunction in order to raise γ t to infinity. In the small rings, γ t is kept high enough by choosing a sufficiently large phase advance in the arcs. Straight sections with zero dispersion are provided for rf cavities and fast injection and extraction, and with controlled dispersion for H - injection and slow extraction. The ion-optical properties of the lattices and the results from tracking studies are discussed

  14. More on random-lattice fermions

    International Nuclear Information System (INIS)

    Kieu, T.D.; Institute for Advanced Study, Princeton, NJ; Markham, J.F.; Paranavitane, C.B.

    1995-01-01

    The lattice fermion determinants, in a given background gauge field, are evaluated for two different kinds of random lattices and compared to those of naive and wilson fermions in the continuum limit. While the fermion doubling is confirmed on one kind of lattices, there is positive evidence that it may be absent for the other, at least for vector interactions in two dimensions. Combined with previous studies, arbitrary randomness by itself is shown to be not a sufficient condition to remove the fermion doublers. 8 refs., 3 figs

  15. Vortex-Peierls States in Optical Lattices

    International Nuclear Information System (INIS)

    Burkov, A.A.; Demler, Eugene

    2006-01-01

    We show that vortices, induced in cold atom superfluids in optical lattices, may order in a novel vortex-Peierls ground state. In such a state vortices do not form a simple lattice but arrange themselves in clusters, within which the vortices are partially delocalized, tunneling between classically degenerate configurations. We demonstrate that this exotic quantum many-body state is selected by an order-from-disorder mechanism for a special combination of the vortex filling and lattice geometry that has a macroscopic number of classically degenerate ground states

  16. Lattice-Like Total Perfect Codes

    Directory of Open Access Journals (Sweden)

    Araujo Carlos

    2014-02-01

    Full Text Available A contribution is made to the classification of lattice-like total perfect codes in integer lattices Λn via pairs (G, Φ formed by abelian groups G and homomorphisms Φ: Zn → G. A conjecture is posed that the cited contribution covers all possible cases. A related conjecture on the unfinished work on open problems on lattice-like perfect dominating sets in Λn with induced components that are parallel paths of length > 1 is posed as well.

  17. Electronic properties of graphene antidot lattices

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Pedersen, Jesper Goor; Flindt, C.

    2009-01-01

    Graphene antidot lattices constitute a novel class of nano-engineered graphene devices with controllable electronic and optical properties. An antidot lattice consists of a periodic array of holes that causes a band gap to open up around the Fermi level, turning graphene from a semimetal...... into a semiconductor. We calculate the electronic band structure of graphene antidot lattices using three numerical approaches with different levels of computational complexity, efficiency and accuracy. Fast finite-element solutions of the Dirac equation capture qualitative features of the band structure, while full...

  18. How to Share a Lattice Trapdoor

    DEFF Research Database (Denmark)

    Bendlin, Rikke; Peikert, Chris; Krehbiel, Sara

    2013-01-01

    We develop secure threshold protocols for two important operations in lattice cryptography, namely, generating a hard lattice Λ together with a "strong" trapdoor, and sampling from a discrete Gaussian distribution over a desired coset of Λ using the trapdoor. These are the central operations...... delegation, which is used in lattice-based hierarchical IBE schemes. Our work therefore directly transfers all these systems to the threshold setting. Our protocols provide information-theoretic (i.e., statistical) security against adaptive corruptions in the UC framework, and they are robust against up to ℓ...

  19. Group theory and lattice gauge fields

    International Nuclear Information System (INIS)

    Creutz, M.

    1988-09-01

    Lattice gauge theory, formulated in terms of invariant integrals over group elements on lattice bonds, benefits from many group theoretical notions. Gauge invariance provides an enormous symmetry and powerful constraints on expectation values. Strong coupling expansions require invariant integrals over polynomials in group elements, all of which can be evaluated by symmetry considerations. Numerical simulations involve random walks over the group. These walks automatically generate the invariant group measure, avoiding explicit parameterization. A recently proposed overrelaxation algorithm is particularly efficient at exploring the group manifold. These and other applications of group theory to lattice gauge fields are reviewed in this talk. 17 refs

  20. Lattice Dynamics of Gallium Phosphide

    International Nuclear Information System (INIS)

    Yarnell, J.L.; Warren, J.L.; Wenzel, R.G.; Dean, P.J.

    1968-01-01

    Dispersion curves for phonons propagating in the [100], [110], and [111] directions in gallium phosphide have been measured using a triple-axis neutron diffraction spectrometer operating in the constant-Q mode. The sample was a pseudo-single crystal which was prepared by gluing together 36 single crystal plates of gallium phosphide 1 to 2.5 cm in diameter and ∼0.07 cm thick. The plates were grown epitaxially on substrates of gallium arsenide or gallium phosphide, and aligned individually by neutron diffraction. Rocking curves for eight reflections symmetrically distributed in the plane of the experiment had full widths at half maximum in the range 0.52° - 0.58° and were approximately Gaussian in shape. Gallium phosphide crystallizes in the zinc blende structure. A group theoretic analysis of the lattice dynamics of this structure and a shell model fit to the measured dispersion curves are presented. Various optical properties of gallium phosphide are discussed in terms of the phonon dispersion curves. In particular, the phonons which assist indirect electronic transitions are identified as those at the zone boundary in the [100] direction (symmetry point X) in agreement with theoretical and experimental indications that the extrema of the conduction and valence bands are at X and Γ (center of the zone), respectively. The LO branches lie above the TO branches throughout the Brillouin zone in contradiction to the predictions of Keyes and Mitra. The shell model fit indicates that the charge on the gallium atom is negative. (author)

  1. Lattice dynamics of alpha uranium

    International Nuclear Information System (INIS)

    Crummett, W.P.

    1978-01-01

    Inelastic neutron scattering measurements of the phonon dispersion curves along the three-principal high-symmetry directions have been performed to investigate the lattice dynamics of α-U. The dispersion curves along the [0 zeta 0] and [00 zeta] directions are not too unusual. However, dips and depressions are observed in the [zeta 00] branches similar to those observed in high-T/sub c/ superconductors. Standard group theoretical techniques have been employed to discern the symmetry properties of the phonon branches and to block diagonalize the dynamical matrix of the various phenomenological models that have been applied to α-U. These phenomenological models include: a four neighbor Born-von Karman general tensor model, a twelve neighbor axially symmetric model, and a shell model. None of these models was able to satisfactorily fit the [zeta 00] data. However, a modified form of the shell model which included axially symmetric interactions to six neighbors was found to reproduce most of the dispersion curves well, including the [zeta 00] branches. A simple pseudopotential model was less successful. To obtain all real frequencies from this model it was necessary to include a Born-von Karman short range contribution. These measurements and calculations have implied that the bonding properties of α-U are particularly dependent upon the details of the electronic system

  2. Anderson localization in bipartite lattices

    International Nuclear Information System (INIS)

    Fabrizio, Michele; Castellani, Claudio

    2000-01-01

    We study the localization properties of a disordered tight-binding Hamiltonian on a generic bipartite lattice close to the band center. By means of a fermionic replica trick method, we derive the effective non-linear σ-model describing the diffusive modes, which we analyse by using the Wilson-Polyakov renormalization group. In addition to the standard parameters which define the non-linear σ-model, namely, the conductance and the external frequency, a new parameter enters, which may be related to the fluctuations of the staggered density of states. We find that, when both the regular hopping and the disorder only couple one sublattice to the other, the quantum corrections to the Kubo conductivity vanish at the band center, thus implying the existence of delocalized states. In two dimensions, the RG equations predict that the conductance flows to a finite value, while both the density of states and the staggered density of states fluctuations diverge. In three dimensions, we find that, sufficiently close to the band center, all states are extended, independently of the disorder strength. We also discuss the role of various symmetry breaking terms, as a regular hopping between same sublattices, or an on-site disorder

  3. Essentially Entropic Lattice Boltzmann Model

    Science.gov (United States)

    Atif, Mohammad; Kolluru, Praveen Kumar; Thantanapally, Chakradhar; Ansumali, Santosh

    2017-12-01

    The entropic lattice Boltzmann model (ELBM), a discrete space-time kinetic theory for hydrodynamics, ensures nonlinear stability via the discrete time version of the second law of thermodynamics (the H theorem). Compliance with the H theorem is numerically enforced in this methodology and involves a search for the maximal discrete path length corresponding to the zero dissipation state by iteratively solving a nonlinear equation. We demonstrate that an exact solution for the path length can be obtained by assuming a natural criterion of negative entropy change, thereby reducing the problem to solving an inequality. This inequality is solved by creating a new framework for construction of Padé approximants via quadrature on appropriate convex function. This exact solution also resolves the issue of indeterminacy in case of nonexistence of the entropic involution step. Since our formulation is devoid of complex mathematical library functions, the computational cost is drastically reduced. To illustrate this, we have simulated a model setup of flow over the NACA-0012 airfoil at a Reynolds number of 2.88 ×106.

  4. Infinitesimal diffeomorfisms on the lattice

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    The energy-momentum tensor and local translation Ward identities constitute the essential toolkit to probe the response of a QFT to an infinitesimal change of geometry. This is relevant in a number of contexts. For instance in order to get the thermodynamical equation of state, one wants to study the response of a Euclidean QFT in a finite box to a change in the size of the box. The lattice formulation of QFTs is a prime tool to study their dynamics beyond perturbation theory. However Poincaré invariance is explicitly broken, and is supposed to be recovered only in the continuum limit. Approximate local Ward identities for translations can be defined, by they require some care for two reasons: 1) the energy-momentum tensor needs to be properly defined through a renormalization procedure; 2) the action of infinitesimal local translations (i.e. infinitesimal diffeomorfisms) is ill-defined on local observables. In this talk I will review the issues related to the renormalization of the energy-momentum tensor ...

  5. Anderson localization in bipartite lattices

    International Nuclear Information System (INIS)

    Fabrizio, M.; Castellani, C.

    2000-04-01

    We study the localization properties of a disordered tight-binding Hamiltonian on a generic bipartite lattice close to the band center. By means of a fermionic replica trick method, we derive the effective non-linear σ-model describing the diffusive modes, which we analyse by using the Wilson-Polyakov renormalization group. In addition to the standard parameters which define the non-linear σ-model, namely the conductance and the external frequency, a new parameter enters, which may be related to the fluctuations of the staggered density of states. We find that, when both the regular hopping and the disorder only couple one sublattice to the other, the quantum corrections to the Kubo conductivity vanish at the band center, thus implying the existence of delocalized states. In two dimensions, the RG equations predict that the conductance flows to a finite value, while both the density of states and the staggered density of states fluctuations diverge. In three dimensions, we find that, sufficiently close to the band center, all states are extended, independently of the disorder strength. We also discuss the role of various symmetry breaking terms, as a regular hopping between same sublattices, or an on-site disorder. (author)

  6. A new lattice for PEP

    International Nuclear Information System (INIS)

    Rees, J.; Wiedemann, H.

    1976-01-01

    A new low-beta configuration has been proposed for PEP which has a reduced β/sub y/* and is capable of delivering design luminosity with lower circulating beam currents that those required in the standard configuration described in the Conceptual Design Report of February, 1976. A feasibility study has been carried out and it is reported in PTM-65, September 8, 1976, by Lee, Morton and Wiedemann. The beam-stay-clear region is specified in PTM-66, September 3, 1976 by H. Wiedemann. The principal advantages of the new lattice are that the lower beam currents lead to lower higher-order-mode power and permit reduction of the total rf power required which in turn reduces both capital cost and operating cost. Its disadvantages stem primarily from the relatively high maximum beta values which occur in the interaction-region quadrupoles. These produce high chromaticities which require a generally stronger sextupole system for their compensation. The advantages outweigh the disadvantages and the new 11-cm-beta configuration has been adopted as the design configuration for energies of 15-GeV and lower. In the remainder of this report we shall discuss the implications of this new configuration for the various systems of PEP. 1 fig., 3 tabs

  7. Lattice Dynamics of fcc Ca

    DEFF Research Database (Denmark)

    Stassis, C.; Zaretsky, J.; Misemer, D. K.;

    1983-01-01

    A large single crystal of FCC Ca was grown and was used to study the lattice dynamics of this divalent metal by coherent inelastic neutron scattering. The phonon dispersion curves were measured, at room temperature, along the [ξ00], [ξξ0], [ξξξ], and [0ξ1] symmetry directions. The dispersion curves...... to the propagation of elastic waves. The frequencies of the T1[ξξ0] branch for ξ between approximately 0.5 and 0.8 are slightly above the velocity-of-sound line determined from the low-frequency measurements. Since a similar effect has been observed in FCC Yb, it is natural to assume that the anomalous dispersion...... bear a striking resemblance to those of FCC Yb, which is also a divalent metal with an electronic band structure similar to that of Ca. In particular, the shear moduli c44 and (c11-c 12)/2 differ by a factor of 3.4, which implies that FCC Ca (like FCC Yb) is very anisotropic with regard...

  8. Neutron diffraction and lattice defects

    International Nuclear Information System (INIS)

    Hamaguchi, Yoshikazu

    1974-01-01

    Study on lattice defects by neutron diffraction technique is described. Wave length of neutron wave is longer than that of X-ray, and absorption cross-section is small. Number of defects observed by ESR is up to several defects, and the number studied with electron microscopes is more than 100. Information obtained by neutron diffraction concerns the number of defects between these two ranges. For practical analysis, several probable models are selected from the data of ESR or electron microscopes, and most probable one is determined by calculation. Then, defect concentration is obtained from scattering cross section. It is possible to measure elastic scattering exclusively by neutron diffraction. Minimum detectable concentration estimated is about 0.5% and 10 20 - 10 21 defects per unit volume. A chopper and a time of flight system are used as a measuring system. Cold neutrons are obtained from the neutron sources inserted into reactors. Examples of measurements by using similar equipments to PTNS-I system of Japan Atomic Energy Research Institute are presented. Interstitial concentration in the graphite irradiated by fast neutrons is shown. Defects in irradiated MgO were also investigated by measuring scattering cross section. Study of defects in Ge was made by measuring total cross section, and model analysis was performed in comparison with various models. (Kato, T.)

  9. Halo Mitigation Using Nonlinear Lattices

    CERN Document Server

    Sonnad, Kiran G

    2005-01-01

    This work shows that halos in beams with space charge effects can be controlled by combining nonlinear focusing and collimation. The study relies on Particle-in-Cell (PIC) simulations for a one dimensional, continuous focusing model. The PIC simulation results show that nonlinear focusing leads to damping of the beam oscillations thereby reducing the mismatch. It is well established that reduced mismatch leads to reduced halo formation. However, the nonlinear damping is accompanied by emittance growth causing the beam to spread in phase space. As a result, inducing nonlinear damping alone cannot help mitigate the halo. To compensate for this expansion in phase space, the beam is collimated in the simulation and further evolution of the beam shows that the halo is not regenerated. The focusing model used in the PIC is analysed using the Lie Transform perturbation theory showing that by averaging over a lattice period, one can reuduce the focusing force to a form that is identical to that used in the PIC simula...

  10. The Lattice-Valued Turing Machines and the Lattice-Valued Type 0 Grammars

    Directory of Open Access Journals (Sweden)

    Juan Tang

    2014-01-01

    Full Text Available Purpose. The purpose of this paper is to study a class of the natural languages called the lattice-valued phrase structure languages, which can be generated by the lattice-valued type 0 grammars and recognized by the lattice-valued Turing machines. Design/Methodology/Approach. From the characteristic of natural language, this paper puts forward a new concept of the l-valued Turing machine. It can be used to characterize recognition, natural language processing, and dynamic characteristics. Findings. The mechanisms of both the generation of grammars for the lattice-valued type 0 grammar and the dynamic transformation of the lattice-valued Turing machines were given. Originality/Value. This paper gives a new approach to study a class of natural languages by using lattice-valued logic theory.

  11. Strange Baryon Physics in Full Lattice QCD

    International Nuclear Information System (INIS)

    Huey-Wen Lin

    2007-01-01

    Strange baryon spectra and form factors are key probes to study excited nuclear matter. The use of lattice QCD allows us to test the strength of the Standard Model by calculating strange baryon quantities from first principles

  12. Topology optimization and lattice Boltzmann methods

    DEFF Research Database (Denmark)

    Nørgaard, Sebastian Arlund

    This thesis demonstrates the application of the lattice Boltzmann method for topology optimization problems. Specifically, the focus is on problems in which time-dependent flow dynamics have significant impact on the performance of the devices to be optimized. The thesis introduces new topology...... a discrete adjoint approach. To handle the complexity of the discrete adjoint approach more easily, a method for computing it based on automatic differentiation is introduced, which can be adapted to any lattice Boltzmann type method. For example, while it is derived in the context of an isothermal lattice...... Boltzmann model, it is shown that the method can be easily extended to a thermal model as well. Finally, the predicted behavior of an optimized design is compared to the equiva-lent prediction from a commercial finite element solver. It is found that the weakly compressible nature of the lattice Boltzmann...

  13. Optical properties of graphene antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Flindt, Christian; Pedersen, Jesper Goor

    2008-01-01

    Undoped graphene is semimetallic and thus not suitable for many electronic and optoelectronic applications requiring gapped semiconductor materials. However, a periodic array of holes (antidot lattice) renders graphene semiconducting with a controllable band gap. Using atomistic modeling, we demo...

  14. Thermoelectric properties of finite graphene antidot lattices

    DEFF Research Database (Denmark)

    Gunst, Tue; Markussen, Troels; Jauho, Antti-Pekka

    2011-01-01

    We present calculations of the electronic and thermal transport properties of graphene antidot lattices with a finite length along the transport direction. The calculations are based on the π-tight-binding model and the Brenner potential. We show that both electronic and thermal transport...... properties converge fast toward the bulk limit with increasing length of the lattice: only a few repetitions (≃6) of the fundamental unit cell are required to recover the electronic band gap of the infinite lattice as a transport gap for the finite lattice. We investigate how different antidot shapes...... and sizes affect the thermoelectric properties. The resulting thermoelectric figure of merit, ZT, can exceed 0.25, and it is highly sensitive to the atomic arrangement of the antidot edges. Specifically, hexagonal holes with pure armchair edges lead to an order-of-magnitude larger ZT as compared to pure...

  15. Lattice Waves, Spin Waves, and Neutron Scattering

    Science.gov (United States)

    Brockhouse, Bertram N.

    1962-03-01

    Use of neutron inelastic scattering to study the forces between atoms in solids is treated. One-phonon processes and lattice vibrations are discussed, and experiments that verified the existence of the quantum of lattice vibrations, the phonon, are reviewed. Dispersion curves, phonon frequencies and absorption, and models for dispersion calculations are discussed. Experiments on the crystal dynamics of metals are examined. Dispersion curves are presented and analyzed; theory of lattice dynamics is considered; effects of Fermi surfaces on dispersion curves; electron-phonon interactions, electronic structure influence on lattice vibrations, and phonon lifetimes are explored. The dispersion relation of spin waves in crystals and experiments in which dispersion curves for spin waves in Co-Fe alloy and magnons in magnetite were obtained and the reality of the magnon was demonstrated are discussed. (D.C.W)

  16. Breatherlike impurity modes in discrete nonlinear lattices

    DEFF Research Database (Denmark)

    Hennig, D.; Rasmussen, Kim; Tsironis, G. P.

    1995-01-01

    We investigate the properties of a disordered generalized discrete nonlinear Schrodinger equation, containing both diagonal and nondiagonal nonlinear terms. The equation models a Linear host lattice doped with nonlinear impurities. We find different types of impurity states that form itinerant...

  17. Exact vacuum energy of orbifold lattice theories

    International Nuclear Information System (INIS)

    Matsuura, So

    2007-01-01

    We investigate the orbifold lattice theories constructed from supersymmetric Yang-Mills matrix theories (mother theories) with four and eight supercharges. We show that the vacuum energy of these theories does not receive any quantum correction perturbatively

  18. Tinkering at the main-ring lattice

    Energy Technology Data Exchange (ETDEWEB)

    Ohnuma, S.

    1982-08-23

    To improve production of usable antiprotons using the proton beam from the main ring and the lossless injection of cooled antiprotons into the main ring, modifications of the main ring lattice are recommended.

  19. Simulation of diffusion in concentrated lattice gases

    International Nuclear Information System (INIS)

    Kehr, K.W.

    1986-01-01

    Recently the diffusion of particles in lattice gases was studied extensively by theoretical methods and numerical simulations. This paper reviews work on collective and, in particular, on tracer diffusion. The diffusion of tagged particles is characterized by a correlation factor whose behavior as a function of concentration is now well understood. Also the detailed kinetics of the tracer transitions was investigated. A special case is the one-dimensional lattice gas where the tracer diffusion coefficient vanishes. An interesting extension is the case of tagged atoms with a different transition rate. This model allows to study various physical situations, including impurity diffusion, percolation, and diffusion in partially blocked lattices. Finally some recent work on diffusion in lattice gases under the influence of a drift field will be reported. (author)

  20. Nucleon electromagnetic form factors from lattice QCD

    International Nuclear Information System (INIS)

    Alexandrou, C.; Koutsou, G.; Negele, J. W.; Tsapalis, A.

    2006-01-01

    We evaluate the isovector nucleon electromagnetic form factors in quenched and unquenched QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at β=6.0 enabling us to reach low momentum transfers and a lowest pion mass of about 400 MeV. In the unquenched theory we use two degenerate flavors of dynamical Wilson fermions on a lattice of spatial size 1.9 fm at β=5.6 and lowest pion mass of about 380 MeV enabling comparison with the results obtained in the quenched theory. that unquenching effects are small for the pion masses considered in this work. We compare our lattice results to the isovector part of the experimentally measured form factors

  1. Benchmarking computer platforms for lattice QCD applications

    International Nuclear Information System (INIS)

    Hasenbusch, M.; Jansen, K.; Pleiter, D.; Wegner, P.; Wettig, T.

    2003-09-01

    We define a benchmark suite for lattice QCD and report on benchmark results from several computer platforms. The platforms considered are apeNEXT, CRAY T3E, Hitachi SR8000, IBM p690, PC-Clusters, and QCDOC. (orig.)

  2. Benchmarking computer platforms for lattice QCD applications

    International Nuclear Information System (INIS)

    Hasenbusch, M.; Jansen, K.; Pleiter, D.; Stueben, H.; Wegner, P.; Wettig, T.; Wittig, H.

    2004-01-01

    We define a benchmark suite for lattice QCD and report on benchmark results from several computer platforms. The platforms considered are apeNEXT, CRAY T3E; Hitachi SR8000, IBM p690, PC-Clusters, and QCDOC

  3. Extended Josephson Relation and Abrikosov lattice deformation

    International Nuclear Information System (INIS)

    Matlock, Peter

    2012-01-01

    From the point of view of time-dependent Ginzburg Landau (TDGL) theory, a Josephson-like relation is derived for an Abrikosov vortex lattice accelerated and deformed by applied fields. Beginning with a review of the Josephson Relation derived from the two ingredients of a lattice-kinematics assumption in TDGL theory and gauge invariance, we extend the construction to accommodate a time-dependent applied magnetic field, a Floating-Kernel formulation of normal current, and finally lattice deformation due to the electric field and inertial effects of vortex-lattice motion. The resulting Josephson-like relation, which we call an Extended Josephson Relation, applies to a much wider set of experimental conditions than the original Josephson Relation, and is explicitly compatible with the considerations of TDGL theory.

  4. Arbitrary spin fermions on the lattice

    International Nuclear Information System (INIS)

    Bullinaria, J.A.

    1985-01-01

    Lattice actions are constructed for free Dirac and Majorana fermions of arbitrary (half-integer) spin various extensions of the spin 1/2 Kogut-Susskind, Kaehler and Wilson formalisms. In each case, the spectrum degeneracy and preservation of gauge invariance is analysed, and the equivalence or non-equivalence to previously constructed actions is determined. The Kogut-Susskind and lattice Kaehler actions are then written explicitly in terms of spinors to demonstrate how the degenerate fermions couple on the lattice and how the original spinorial actions are recovered (or to recovered) in the continuum limit. Both degenerate and non-degenerate mass terms are dealt with and the various U(1) invariances of the lattice actions are pointed out

  5. Renormalization transformation of periodic and aperiodic lattices

    International Nuclear Information System (INIS)

    Macia, Enrique; Rodriguez-Oliveros, Rogelio

    2006-01-01

    In this work we introduce a similarity transformation acting on transfer matrices describing the propagation of elementary excitations through either periodic or Fibonacci lattices. The proposed transformation can act at two different scale lengths. At the atomic scale the transformation allows one to express the systems' global transfer matrix in terms of an equivalent on-site model one. Correlation effects among different hopping terms are described by a series of local phase factors in that case. When acting on larger scale lengths, corresponding to short segments of the original lattice, the similarity transformation can be properly regarded as describing an effective renormalization of the chain. The nature of the resulting renormalized lattice significantly depends on the kind of order (i.e., periodic or quasiperiodic) of the original lattice, expressing a delicate balance between chemical complexity and topological order as a consequence of the renormalization process

  6. Quantum chromodynamics on the lattice

    International Nuclear Information System (INIS)

    Kovacs, T.G.; Pittler, F.

    2012-01-01

    Complete text of publication follows. Quantum chromodynamics (QCD) is the generally accepted theory of the strong interactions that bind quarks into hadrons like the proton and the neutron. The only systematic way of computing low-energy observables starting from the theory is to discretize it on a space-time lattice and perform large-scale Monte Carlo numerical simulations. In the past years lattice QCD did not only provide more and more precise numerical data to be compared to experimental data but also contributed to a better intuitive understanding of the phenomena occurring in strongly interacting systems. One of the most interesting of these phenomena is the transition of ordinary strongly interacting matter to the so called quark-gluon plasma phase occurring at high temperature and already observed in heavy ion collisions. Quarks that are all confined into hadrons at low temperature become liberated above the critical temperature characterizing the transition. At the same time the chiral symmetry that is spontaneously broken at low temperatures also gets restored. Chiral symmetry is intimately connected to the density of low-lying quark states. At low temperature these states are known to follow Wigner-Dyson random matrix statistics. This has been successfully exploited to compute the parameters of the effective chiral Lagrangian describing strongly interacting systems in the low energy limit. In contrast, up to a few years ago there was no generally accepted understanding of the statistical properties of lowlying quark states above the critical temperature. We showed that in simplified models of QCD the low quark eigenmodes obey Poisson statistics that gradually crosses over to Wigner-Dyson statistics higher up in the spectrum. This also implies that the low modes are highly localized which can have significant physical consequences. In this year, for the first time we could verify Poisson statistics for the low quark modes in full dynamical QCD without any

  7. Lattice Boltzmann approach for complex nonequilibrium flows.

    Science.gov (United States)

    Montessori, A; Prestininzi, P; La Rocca, M; Succi, S

    2015-10-01

    We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion.

  8. Lattice quantum chromodynamics with approximately chiral fermions

    Energy Technology Data Exchange (ETDEWEB)

    Hierl, Dieter

    2008-05-15

    In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the {theta}{sup +} pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)

  9. The world according to lattice QCD

    International Nuclear Information System (INIS)

    Sharpe, S.R.

    1988-12-01

    A non-technical introduction to lattice calculations is given. The successes and problems of current calculations are emphasized. A summary of lattice results on non-exotic meson and baryon masses indicates that while calculations in the quenched approximation are becoming reliable, the results differ in systematic ways from the physical values. Results for exotic mesons (glueballs and hybrids) are then presented. The future prospects are discussed. 23 refs., 4 figs

  10. Lattice and Phase Diagram in QCD

    International Nuclear Information System (INIS)

    Lombardo, Maria Paola

    2008-01-01

    Model calculations have produced a number of very interesting expectations for the QCD Phase Diagram, and the task of a lattice calculations is to put these studies on a quantitative grounds. I will give an overview of the current status of the lattice analysis of the QCD phase diagram, from the quantitative results of mature calculations at zero and small baryochemical potential, to the exploratory studies of the colder, denser phase.

  11. Lattice models and conformal field theories

    International Nuclear Information System (INIS)

    Saleur, H.

    1988-01-01

    Theoretical studies concerning the connection between critical physical systems and the conformal theories are reviewed. The conformal theory associated to a critical (integrable) lattice model is derived. The obtention of the central charge, critical exponents and torus partition function, using renormalization group arguments, is shown. The quantum group structure, in the integrable lattice models, and the theory of Visaro algebra representations are discussed. The relations between off-critical integrable models and conformal theories, in finite geometries, are studied

  12. Soliton solutions in a diatomic lattice system

    International Nuclear Information System (INIS)

    Yajima, Nobuo; Satsuma, Junkichi.

    1979-04-01

    A continuum limit is considered for a diatomic lattice system with a cubic nonlinearity. A long wave equation describing the interaction of acoustic and optical modes is obtained. It reduces, in certain approximations, to equations having coupled wave solutions. The solutions exhibit trapping of an optical mode by an acoustic soliton. The form of the trapped optical wave depends on the mass ratio of adjacent particles in the diatomic lattice. (author)

  13. Matching fields and lattice points of simplices

    OpenAIRE

    Loho, Georg; Smith, Ben

    2018-01-01

    We show that the Chow covectors of a linkage matching field define a bijection of lattice points and we demonstrate how one can recover the linkage matching field from this bijection. This resolves two open questions from Sturmfels & Zelevinsky (1993) on linkage matching fields. For this, we give an explicit construction that associates a bipartite incidence graph of an ordered partition of a common set to all lattice points in a dilated simplex. Given a triangulation of a product of two simp...

  14. Status of the Fermilab lattice supercomputer project

    International Nuclear Information System (INIS)

    Mackenzie, P.; Eichten, E.; Hockney, G.

    1988-10-01

    Fermilab has completed construction of a sixteen node (320 megaflop peak speed) parallel computer for lattice gauge theory calculations. The architecture was designed to provide the highest possible cost effectiveness while maintaining a high level of programmability and constraining as little as possible the types of lattice problems which can be done on it. The machine is programmed in C. It is a prototype for a 256 node (5 gigaflop peak speed) computer which will be assembled this winter. 6 refs

  15. Lattice results for heavy light matrix elements

    International Nuclear Information System (INIS)

    Soni, A.

    1994-09-01

    Lattice results for heavy light matrix elements are reviewed and some of their implications are very briefly discussed. Despite the fact that in most cases the lattice results for weak matrix elements at the moment have only a modest accuracy of about 20--30% they already have important phenomenological repercussions; e.g. for V td /V ts , x s /x d and B → K*γ

  16. Finite size scaling and lattice gauge theory

    International Nuclear Information System (INIS)

    Berg, B.A.

    1986-01-01

    Finite size (Fisher) scaling is investigated for four dimensional SU(2) and SU(3) lattice gauge theories without quarks. It allows to disentangle violations of (asymptotic) scaling and finite volume corrections. Mass spectrum, string tension, deconfinement temperature and lattice β-function are considered. For appropriate volumes, Monte Carlo investigations seem to be able to control the finite volume continuum limit. Contact is made with Luescher's small volume expansion and possibly also with the asymptotic large volume behavior. 41 refs., 19 figs

  17. Lattice quantum chromodynamics with approximately chiral fermions

    International Nuclear Information System (INIS)

    Hierl, Dieter

    2008-05-01

    In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the Θ + pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)

  18. Chiral Schwinger model and lattice fermionic regularizations

    International Nuclear Information System (INIS)

    Kieu, T.D.; Sen, D.; Xue, S.

    1988-01-01

    The chiral Schwinger model is studied on the lattice with use of Wilson fermions. The arbitrary mass term for the gauge boson is shown to originate from the arbitrariness of the Wilson parameter, which is required to avoid the doubling phenomenon on the lattice. The necessity for such a term is thus demonstrated in contrast to the mere admissibility as indicated by previous continuum calculations

  19. A lattice hierarchy and its continuous limits

    International Nuclear Information System (INIS)

    Fan Engui

    2008-01-01

    By introducing a discrete spectral problem, we derive a lattice hierarchy which is integrable in Liouville's sense and possesses a multi-Hamiltonian structure. It is show that the discrete spectral problem converges to the well-known AKNS spectral problem under a certain continuous limit. In particular, we construct a sequence of equations in the lattice hierarchy which approximates the AKNS hierarchy as a continuous limit

  20. Improved lattice fermion action for heavy quarks

    International Nuclear Information System (INIS)

    Cho, Yong-Gwi; Hashimoto, Shoji; Jüttner, Andreas; Kaneko, Takashi; Marinkovic, Marina; Noaki, Jun-Ichi; Tsang, Justus Tobias

    2015-01-01

    We develop an improved lattice action for heavy quarks based on Brillouin-type fermions, that have excellent energy-momentum dispersion relation. The leading discretization errors of O(a) and O(a"2) are eliminated at tree-level. We carry out a scaling study of this improved Brillouin fermion action on quenched lattices by calculating the charmonium energy-momentum dispersion relation and hyperfine splitting. We present a comparison to standard Wilson fermions and domain-wall fermions.

  1. Lattice Paths and the Constant Term

    International Nuclear Information System (INIS)

    Brak, R; Essam, J; Osborn, J; Owczarek, A L; Rechnitzer, A

    2006-01-01

    We firstly review the constant term method (CTM), illustrating its combinatorial connections and show how it can be used to solve a certain class of lattice path problems. We show the connection between the CTM, the transfer matrix method (eigenvectors and eigenvalues), partial difference equations, the Bethe Ansatz and orthogonal polynomials. Secondly, we solve a lattice path problem first posed in 1971. The model stated in 1971 was only solved for a special case - we solve the full model

  2. Superfluidity of bosons on a deformable lattice

    International Nuclear Information System (INIS)

    Jackeli, G.; Ranninger, J.

    2001-01-01

    We study the superfluid properties of a system of interacting bosons on a lattice, which, moreover, are coupled to the vibrational modes of this lattice, treated here in terms of Einstein phonon modes. The ground state corresponds to two correlated condensates: that of the bosons and that of the phonons. Two competing effects determine the common collective sound-wave-like mode with sound velocity v, arising from gauge symmetry breaking. (i) The sound velocity v 0 (corresponding to a weakly interacting Bose system on a rigid lattice) in the lowest-order approximation is reduced due to reduction of the repulsive boson-boson interaction, arising from the attractive part of the phonon-mediated interaction in the static limit. (ii) The second-order correction to the sound velocity is enhanced as compared to that of bosons on a rigid lattice when the boson-phonon interaction is switched on due to the retarded nature of the phonon-mediated interaction. The overall effect is that the sound velocity is essentially unaffected by the coupling with phonons, indicating the robustness of the superfluid state. The induction of a coherent state in the phonon system driven by the condensation of the bosons could be of experimental significance, permitting spectroscopic detection of superfluid properties of bosons. Our results are based on an extension of the Beliaev-Popov formalism for a weakly interacting Bose gas on a rigid lattice to one on a deformable lattice with which it interacts

  3. Lattice calculation of nonleptonic charm decays

    International Nuclear Information System (INIS)

    Simone, J.N.

    1991-11-01

    The decays of charmed mesons into two body nonleptonic final states are investigated. Weak interaction amplitudes of interest in these decays are extracted from lattice four-point correlation functions using a effective weak Hamiltonian including effects to order G f in the weak interactions yet containing effects to all orders in the strong interactions. The lattice calculation allows a quantitative examination of non-spectator processes in charm decays helping to elucidate the role of effects such as color coherence, final state interactions and the importance of the so called weak annihilation process. For D → Kπ, we find that the non-spectator weak annihilation diagram is not small, and we interpret this as evidence for large final state interactions. Moreover, there is indications of a resonance in the isospin 1/2 channel to which the weak annihilation process contributes exclusively. Findings from the lattice calculation are compared to results from the continuum vacuum saturation approximation and amplitudes are examined within the framework of the 1/N expansion. Factorization and the vacuum saturation approximation are tested for lattice amplitudes by comparing amplitudes extracted from lattice four-point functions with the same amplitude extracted from products of two-point and three-point lattice correlation functions arising out of factorization and vacuum saturation

  4. Vitreous in lattice degeneration of retina.

    Science.gov (United States)

    Foos, R Y; Simons, K B

    1984-05-01

    A localized pocket of missing vitreous invariably overlies lattice degeneration of the retina. Subjects with lattice also have a higher rate of rhegmatogenous retinal detachment, which is usually a complication of retinal tears. The latter are in turn a result of alterations in the central vitreous--that is, synchysis senilis leading to posterior vitreous detachment. In order to determine if there is either an association or a deleterious interaction between the local and central lesions of the vitreous in eyes with lattice, a comparison was made in autopsy eyes with and without lattice the degree of synchysis and rate of vitreous detachment. Results show no association between the local and central vitreous lesions, indicating that a higher rate of vitreous detachment is not the basis for the higher rate of retinal detachment in eyes with lattice. Also, there was no suggestion of deleterious interaction between the local and central vitreous lesions, either through vitreodonesis as a basis for precocious vitreous detachment, or through a greater degree of synchysis as a basis for interconnection of local and central lacunae (which could extend the localized retinal detachment in eyes with holes in lattice degeneration).

  5. Matter-wave bright solitons in effective bichromatic lattice potentials

    Indian Academy of Sciences (India)

    Matter-wave bright solitons in bichromatic lattice potentials are considered and their dynamics for different lattice environments are studied. Bichromatic potentials are created from superpositions of (i) two linear optical lattices and (ii) a linear and a nonlinear optical lattice. Effective potentials are found for the solitons in both ...

  6. Instantons and topological charge in lattice gauge theory

    International Nuclear Information System (INIS)

    Iwasaki, Y.; Yoshie, T.

    1983-01-01

    The existence of instantons on the lattice in SU(2) lattice gauge theory is investigated for various lattice actions with loops of up to six lattice spacings. Instantons exist only for the actions where short range fluctuations are suppressed. A formula for topological properties of the solutions are examined. (orig.)

  7. An approach to the isoperimetric problem on some lattices

    International Nuclear Information System (INIS)

    Duarte, J.A.M.S.

    1979-01-01

    In this paper it is shown how elements of convex-set theory and lattice symmetry requirements can be combined to determine the areas, symmetry point groups and lattice constants of all isoperimetric solutions for regular lattices. The technique is also applied to one semi-regular lattice, where it assists in obtaining the exact expansion for polygonal closures. (author)

  8. Hyper-lattice algebraic model for data warehousing

    CERN Document Server

    Sen, Soumya; Chaki, Nabendu

    2016-01-01

    This book presents Hyper-lattice, a new algebraic model for partially ordered sets, and an alternative to lattice. The authors analyze some of the shortcomings of conventional lattice structure and propose a novel algebraic structure in the form of Hyper-lattice to overcome problems with lattice. They establish how Hyper-lattice supports dynamic insertion of elements in a partial order set with a partial hierarchy between the set members. The authors present the characteristics and the different properties, showing how propositions and lemmas formalize Hyper-lattice as a new algebraic structure.

  9. On the performance of 1-level LDPC lattices

    OpenAIRE

    Sadeghi, Mohammad-Reza; Sakzad, Amin

    2013-01-01

    The low-density parity-check (LDPC) lattices perform very well in high dimensions under generalized min-sum iterative decoding algorithm. In this work we focus on 1-level LDPC lattices. We show that these lattices are the same as lattices constructed based on Construction A and low-density lattice-code (LDLC) lattices. In spite of having slightly lower coding gain, 1-level regular LDPC lattices have remarkable performances. The lower complexity nature of the decoding algorithm for these type ...

  10. Strong dynamics and lattice gauge theory

    Science.gov (United States)

    Schaich, David

    In this dissertation I use lattice gauge theory to study models of electroweak symmetry breaking that involve new strong dynamics. Electroweak symmetry breaking (EWSB) is the process by which elementary particles acquire mass. First proposed in the 1960s, this process has been clearly established by experiments, and can now be considered a law of nature. However, the physics underlying EWSB is still unknown, and understanding it remains a central challenge in particle physics today. A natural possibility is that EWSB is driven by the dynamics of some new, strongly-interacting force. Strong interactions invalidate the standard analytical approach of perturbation theory, making these models difficult to study. Lattice gauge theory is the premier method for obtaining quantitatively-reliable, nonperturbative predictions from strongly-interacting theories. In this approach, we replace spacetime by a regular, finite grid of discrete sites connected by links. The fields and interactions described by the theory are likewise discretized, and defined on the lattice so that we recover the original theory in continuous spacetime on an infinitely large lattice with sites infinitesimally close together. The finite number of degrees of freedom in the discretized system lets us simulate the lattice theory using high-performance computing. Lattice gauge theory has long been applied to quantum chromodynamics, the theory of strong nuclear interactions. Using lattice gauge theory to study dynamical EWSB, as I do in this dissertation, is a new and exciting application of these methods. Of particular interest is non-perturbative lattice calculation of the electroweak S parameter. Experimentally S ≈ -0.15(10), which tightly constrains dynamical EWSB. On the lattice, I extract S from the momentum-dependence of vector and axial-vector current correlators. I created and applied computer programs to calculate these correlators and analyze them to determine S. I also calculated the masses

  11. Symmetry of semi-reduced lattices.

    Science.gov (United States)

    Stróż, Kazimierz

    2015-05-01

    The main result of this work is extension of the famous characterization of Bravais lattices according to their metrical, algebraic and geometric properties onto a wide class of primitive lattices (including Buerger-reduced, nearly Buerger-reduced and a substantial part of Delaunay-reduced) related to low-restricted semi-reduced descriptions (s.r.d.'s). While the `geometric' operations in Bravais lattices map the basis vectors into themselves, the `arithmetic' operators in s.r.d. transform the basis vectors into cell vectors (basis vectors, face or space diagonals) and are represented by matrices from the set {\\bb V} of all 960 matrices with the determinant ±1 and elements {0, ±1} of the matrix powers. A lattice is in s.r.d. if the moduli of off-diagonal elements in both the metric tensors M and M(-1) are smaller than corresponding diagonal elements sharing the same column or row. Such lattices are split into 379 s.r.d. types relative to the arithmetic holohedries. Metrical criteria for each type do not need to be explicitly given but may be modelled as linear derivatives {\\bb M}(p,q,r), where {\\bb M} denotes the set of 39 highest-symmetry metric tensors, and p,q,r describe changes of appropriate interplanar distances. A sole filtering of {\\bb V} according to an experimental s.r.d. metric and subsequent geometric interpretation of the filtered matrices lead to mathematically stable and rich information on the Bravais-lattice symmetry and deviations from the exact symmetry. The emphasis on the crystallographic features of lattices was obtained by shifting the focus (i) from analysis of a lattice metric to analysis of symmetry matrices [Himes & Mighell (1987). Acta Cryst. A43, 375-384], (ii) from the isometric approach and invariant subspaces to the orthogonality concept {some ideas in Le Page [J. Appl. Cryst. (1982), 15, 255-259]} and splitting indices [Stróż (2011). Acta Cryst. A67, 421-429] and (iii) from fixed cell transformations to transformations

  12. Few quantum particles on one dimensional lattices

    International Nuclear Information System (INIS)

    Valiente Cifuentes, Manuel

    2010-01-01

    There is currently a great interest in the physics of degenerate quantum gases and low-energy few-body scattering due to the recent experimental advances in manipulation of ultracold atoms by light. In particular, almost perfect periodic potentials, called optical lattices, can be generated. The lattice spacing is fixed by the wavelength of the laser field employed and the angle betwen the pair of laser beams; the lattice depth, defining the magnitude of the different band gaps, is tunable within a large interval of values. This flexibility permits the exploration of different regimes, ranging from the ''free-electron'' picture, modified by the effective mass for shallow optical lattices, to the tight-binding regime of a very deep periodic potential. In the latter case, effective single-band theories, widely used in condensed matter physics, can be implemented with unprecedent accuracy. The tunability of the lattice depth is nowadays complemented by the use of magnetic Feshbach resonances which, at very low temperatures, can vary the relevant atom-atom scattering properties at will. Moreover, optical lattices loaded with gases of effectively reduced dimensionality are experimentally accessible. This is especially important for one spatial dimension, since most of the exactly solvable models in many-body quantum mechanics deal with particles on a line; therefore, experiments with one-dimensional gases serve as a testing ground for many old and new theories which were regarded as purely academic not so long ago. The physics of few quantum particles on a one-dimensional lattice is the topic of this thesis. Most of the results are obtained in the tight-binding approximation, which is amenable to exact numerical or analytical treatment. For the two-body problem, theoretical methods for calculating the stationary scattering and bound states are developed. These are used to obtain, in closed form, the two-particle solutions of both the Hubbard and extended Hubbard models

  13. Few quantum particles on one dimensional lattices

    Energy Technology Data Exchange (ETDEWEB)

    Valiente Cifuentes, Manuel

    2010-06-18

    There is currently a great interest in the physics of degenerate quantum gases and low-energy few-body scattering due to the recent experimental advances in manipulation of ultracold atoms by light. In particular, almost perfect periodic potentials, called optical lattices, can be generated. The lattice spacing is fixed by the wavelength of the laser field employed and the angle betwen the pair of laser beams; the lattice depth, defining the magnitude of the different band gaps, is tunable within a large interval of values. This flexibility permits the exploration of different regimes, ranging from the ''free-electron'' picture, modified by the effective mass for shallow optical lattices, to the tight-binding regime of a very deep periodic potential. In the latter case, effective single-band theories, widely used in condensed matter physics, can be implemented with unprecedent accuracy. The tunability of the lattice depth is nowadays complemented by the use of magnetic Feshbach resonances which, at very low temperatures, can vary the relevant atom-atom scattering properties at will. Moreover, optical lattices loaded with gases of effectively reduced dimensionality are experimentally accessible. This is especially important for one spatial dimension, since most of the exactly solvable models in many-body quantum mechanics deal with particles on a line; therefore, experiments with one-dimensional gases serve as a testing ground for many old and new theories which were regarded as purely academic not so long ago. The physics of few quantum particles on a one-dimensional lattice is the topic of this thesis. Most of the results are obtained in the tight-binding approximation, which is amenable to exact numerical or analytical treatment. For the two-body problem, theoretical methods for calculating the stationary scattering and bound states are developed. These are used to obtain, in closed form, the two-particle solutions of both the Hubbard and

  14. SSC lattice database and graphical interface

    International Nuclear Information System (INIS)

    Trahern, C.G.; Zhou, J.

    1991-11-01

    When completed the Superconducting Super Collider will be the world's largest accelerator complex. In order to build this system on schedule, the use of database technologies will be essential. In this paper we discuss one of the database efforts underway at the SSC, the lattice database. The SSC lattice database provides a centralized source for the design of each major component of the accelerator complex. This includes the two collider rings, the High Energy Booster, Medium Energy Booster, Low Energy Booster, and the LINAC as well as transfer and test beam lines. These designs have been created using a menagerie of programs such as SYNCH, DIMAD, MAD, TRANSPORT, MAGIC, TRACE3D AND TEAPOT. However, once a design has been completed, it is entered into a uniform database schema in the database system. In this paper we discuss the reasons for creating the lattice database and its implementation via the commercial database system SYBASE. Each lattice in the lattice database is composed of a set of tables whose data structure can describe any of the SSC accelerator lattices. In order to allow the user community access to the databases, a programmatic interface known as dbsf (for database to several formats) has been written. Dbsf creates ascii input files appropriate to the above mentioned accelerator design programs. In addition it has a binary dataset output using the Self Describing Standard data discipline provided with the Integrated Scientific Tool Kit software tools. Finally we discuss the graphical interfaces to the lattice database. The primary interface, known as OZ, is a simulation environment as well as a database browser

  15. Galilean invariant lattice Boltzmann scheme for natural convection on square and rectangular lattices

    NARCIS (Netherlands)

    Sman, van der R.G.M.

    2006-01-01

    In this paper we present lattice Boltzmann (LB) schemes for convection diffusion coupled to fluid flow on two-dimensional rectangular lattices. Via inverse Chapman-Enskog analysis of LB schemes including source terms, we show that for consistency with physics it is required that the moments of the

  16. The lattice distortion around the divacancy in cubic metals using the method of lattice statics

    International Nuclear Information System (INIS)

    Yoshioki, S.

    1976-01-01

    The lattice distortion produced by a divacancy in FCC metals (Al, Cu, Ag and Au) and in BCC metals (Fe, Mo and V) has been calculated using the method of lattice statics. The model assumes non-equilibrium pairwise interactions extending out to second nearest neighbours. Roughly speaking, the relaxation volumes associated with the divacancy are twice the values for the isolated vacancy. (author)

  17. On techniques of ATR lattice computation

    International Nuclear Information System (INIS)

    1997-08-01

    Lattice computation is to compute the average nuclear constants of unit fuel lattice which are required for computing core nuclear characteristics such as core power distribution and reactivity characteristics. The main nuclear constants are infinite multiplying rate, neutron movement area, cross section for diffusion computation, local power distribution and isotope composition. As for the lattice computation code, WIMS-ATR is used, which is based on the WIMS-D code developed in U.K., and for the purpose of heightening the accuracy of analysis, which was improved by adding heavy water scattering cross section considering the temperature dependence by Honeck model. For the computation of the neutron absorption by control rods, LOIEL BLUE code is used. The extrapolation distance of neutron flux on control rod surfaces is computed by using THERMOS and DTF codes, and the lattice constants of adjoining lattices are computed by using the WIMS-ATR code. As for the WIMS-ATR code, the computation flow and nuclear data library, and as for the LOIEL BLUE code, the computation flow are explained. The local power distribution in fuel assemblies determined by the WIMS-ATR code was verified with the measured data, and the results are reported. (K.I.)

  18. Full CKM matrix with lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Masataka; /Fermilab

    2004-12-01

    The authors show that it is now possible to fully determine the CKM matrix, for the first time, using lattice QCD. |V{sub cd}|, |V{sub cs}|, |V{sub ub}|, |V{sub cb}| and |V{sub us}| are, respectively, directly determined with the lattice results for form factors of semileptonic D {yields} {pi}lv, D {yields} Klv, B {yields} {pi}lv, B {yields} Dlv and K {yields} {pi}lv decays. The error from the quenched approximation is removed by using the MILC unquenced lattice gauge configurations, where the effect of u, d and s quarks is included. The error from the ''chiral'' extrapolation (m{sub l} {yields} m{sub ud}) is greatly reduced by using improved staggered quarks. The accuracy is comparable to that of the Particle Data Group averages. In addition, |V{sub ud}|, |V{sub ts}|, |V{sub ts}| and |V{sub td}| are determined by using unitarity of the CKM matrix and the experimental result for sin (2{beta}). In this way, they obtain all 9 CKM matrix elements, where the only theoretical input is lattice QCD. They also obtain all the Wolfenstein parameters, for the first time, using lattice QCD.

  19. Minimal knotted polygons in cubic lattices

    International Nuclear Information System (INIS)

    Van Rensburg, E J Janse; Rechnitzer, A

    2011-01-01

    In this paper we examine numerically the properties of minimal length knotted lattice polygons in the simple cubic, face-centered cubic, and body-centered cubic lattices by sieving minimal length polygons from a data stream of a Monte Carlo algorithm, implemented as described in Aragão de Carvalho and Caracciolo (1983 Phys. Rev. B 27 1635), Aragão de Carvalho et al (1983 Nucl. Phys. B 215 209) and Berg and Foester (1981 Phys. Lett. B 106 323). The entropy, mean writhe, and mean curvature of minimal length polygons are computed (in some cases exactly). While the minimal length and mean curvature are found to be lattice dependent, the mean writhe is found to be only weakly dependent on the lattice type. Comparison of our results to numerical results for the writhe obtained elsewhere (see Janse van Rensburg et al 1999 Contributed to Ideal Knots (Series on Knots and Everything vol 19) ed Stasiak, Katritch and Kauffman (Singapore: World Scientific), Portillo et al 2011 J. Phys. A: Math. Theor. 44 275004) shows that the mean writhe is also insensitive to the length of a knotted polygon. Thus, while these results for the mean writhe and mean absolute writhe at minimal length are not universal, our results demonstrate that these values are quite close the those of long polygons regardless of the underlying lattice and length

  20. Techniques for transparent lattice measurement and correction

    Science.gov (United States)

    Cheng, Weixing; Li, Yongjun; Ha, Kiman

    2017-07-01

    A novel method has been successfully demonstrated at NSLS-II to characterize the lattice parameters with gated BPM turn-by-turn (TbT) capability. This method can be used at high current operation. Conventional lattice characterization and tuning are carried out at low current in dedicated machine studies which include beam-based measurement/correction of orbit, tune, dispersion, beta-beat, phase advance, coupling etc. At the NSLS-II storage ring, we observed lattice drifting during beam accumulation in user operation. Coupling and lifetime change while insertion device (ID) gaps are moved. With the new method, dynamical lattice correction is possible to achieve reliable and productive operations. A bunch-by-bunch feedback system excites a small fraction (∼1%) of bunches and gated BPMs are aligned to see those bunch motions. The gated TbT position data are used to characterize the lattice hence correction can be applied. As there are ∼1% of total charges disturbed for a short period of time (several ms), this method is transparent to general user operation. We demonstrated the effectiveness of these tools during high current user operation.

  1. Lattice Gauge Theories Have Gravitational Duals

    International Nuclear Information System (INIS)

    Hellerman, Simeon

    2002-01-01

    In this paper we examine a certain threebrane solution of type IIB string theory whose long-wavelength dynamics are those of a supersymmetric gauge theory in 2+1 continuous and 1 discrete dimension, all of infinite extent. Low-energy processes in this background are described by dimensional deconstruction, a strict limit in which gravity decouples but the lattice spacing stays finite. Relating this limit to the near-horizon limit of our solution we obtain an exact, continuum gravitational dual of a lattice gauge theory with nonzero lattice spacing. H-flux in this translationally invariant background encodes the spatial discreteness of the gauge theory, and we relate the cutoff on allowed momenta to a giant graviton effect in the bulk

  2. Chiral perturbation theory for lattice QCD

    International Nuclear Information System (INIS)

    Baer, Oliver

    2010-01-01

    The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)

  3. Lattice sigma models with exact supersymmetry

    International Nuclear Information System (INIS)

    Simon Catterall; Sofiane Ghadab

    2004-01-01

    We show how to construct lattice sigma models in one, two and four dimensions which exhibit an exact fermionic symmetry. These models are discretized and twisted versions of conventional supersymmetric sigma models with N=2 supersymmetry. The fermionic symmetry corresponds to a scalar BRST charge built from the original supercharges. The lattice theories possess local actions and exhibit no fermion doubling. In the two and four dimensional theories we show that these lattice theories are invariant under additional discrete symmetries. We argue that the presence of these exact symmetries ensures that no fine tuning is required to achieve N=2 supersymmetry in the continuum limit. As a concrete example we show preliminary numerical results from a simulation of the O(3) supersymmetric sigma model in two dimensions. (author)

  4. Multisite Interactions in Lattice-Gas Models

    Science.gov (United States)

    Einstein, T. L.; Sathiyanarayanan, R.

    For detailed applications of lattice-gas models to surface systems, multisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We recall that trio (3-adatom, non-pairwise) interactions do not inevitably create phase boundary asymmetries about half coverage. We discuss a sophisticated application to an experimental system and describe refinements in extracting lattice-gas energies from calculations of total energies of several different ordered overlayers. We describe how lateral relaxations complicate matters when there is direct interaction between the adatoms, an issue that is important when examining the angular dependence of step line tensions. We discuss the connector model as an alternative viewpoint and close with a brief account of recent work on organic molecule overlayers.

  5. Chiral perturbation theory for lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Baer, Oliver

    2010-07-21

    The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)

  6. Making sense of nanocrystal lattice fringes

    International Nuclear Information System (INIS)

    Fraundorf, P.; Qin Wentao; Moeck, Peter; Mandell, Eric

    2005-01-01

    The orientation dependence of thin-crystal lattice fringes can be gracefully quantified using fringe-visibility maps, a direct-space analog of Kikuchi maps [Nishikawa and Kikuchi, Nature (London) 121, 1019 (1928)]. As in navigation of reciprocal space with the aid of Kikuchi lines, fringe-visibility maps facilitate acquisition of crystallographic information from lattice images. In particular, these maps can help researchers to determine the three-dimensional lattice of individual nanocrystals, to 'fringe-fingerprint' collections of randomly oriented particles, and to measure local specimen thickness with only a modest tilt. Since the number of fringes in an image increases with maximum spatial-frequency squared, these strategies (with help from more precise goniometers) will be more useful as aberration correction moves resolutions into the subangstrom range

  7. Exotic meson decay widths using lattice QCD

    International Nuclear Information System (INIS)

    Cook, M. S.; Fiebig, H. R.

    2006-01-01

    A decay width calculation for a hybrid exotic meson h, with J PC =1 -+ , is presented for the channel h→πa 1 . This quenched lattice QCD simulation employs Luescher's finite box method. Operators coupling to the h and πa 1 states are used at various levels of smearing and fuzzing, and at four quark masses. Eigenvalues of the corresponding correlation matrices yield energy spectra that determine scattering phase shifts for a discrete set of relative πa 1 momenta. Although the phase shift data is sparse, fits to a Breit-Wigner model are attempted, resulting in a decay width of about 60 MeV when averaged over two lattice sizes having a lattice spacing of 0.07 fm

  8. A lattice formulation of chiral gauge theories

    International Nuclear Information System (INIS)

    Bodwin, G.T.

    1995-12-01

    The authors present a method for formulating gauge theories of chiral fermions in lattice field theory. The method makes use of a Wilson mass to remove doublers. Gauge invariance is then restored by modifying the theory in two ways: the magnitude of the fermion determinant is replaced with the square root of the determinant for a fermion with vector-like couplings to the gauge field; a double limit is taken in which the lattice spacing associated with the fermion field is taken to zero before the lattice spacing associated with the gauge field. The method applies only to theories whose fermions are in an anomaly-free representation of the gauge group. They also present a related technique for computing matrix elements of operators involving fermion fields. Although the analyses of these methods are couched in weak-coupling perturbation theory, it is argued that computational prescriptions are gauge invariant in the presence of a nonperturbative gauge-field configuration

  9. Condensate oscillations in a Penrose tiling lattice

    Science.gov (United States)

    Akdeniz, Z.; Vignolo, P.

    2017-07-01

    We study the dynamics of a Bose-Einstein condensate subject to a particular Penrose tiling lattice. In such a lattice, the potential energy at each site depends on the neighbour sites, accordingly to the model introduced by Sutherland [16]. The Bose-Einstein wavepacket, initially at rest at the lattice symmetry center, is released. We observe a very complex time-evolution that strongly depends on the symmetry center (two choices are possible), on the potential energy landscape dispersion, and on the interaction strength. The condensate-width oscillates at different frequencies and we can identify large-frequency reshaping oscillations and low-frequency rescaling oscillations. We discuss in which conditions these oscillations are spatially bounded, denoting a self-trapping dynamics.

  10. Symmetry and fermion degeneracy on a lattice

    International Nuclear Information System (INIS)

    Raszillier, H.

    1982-03-01

    In this paper we consider the general form of finite difference approximation to the Dirac (Weyl) Hamiltonian on a lattice and investigate systematically the dependence on symmetry of the number of particles described by it. Our result is, that to a symmetry - expressed by a crystallographic space group - there corresponds a minimal number of particles, which are associated to prescribed points of momentum space (the unit cell of the reciprocal lattice). For convenience of the reader we show, using the existing detailed descriptions of space groups, how these results look for all the relevant (symmorphic) symmetry groups. Only for lattice Hamiltonians with a momentum dependent mass term can this degeneracy be reduced and even eliminated without reducing the symmetry. (orig./HSI)

  11. Lattice Boltzmann model for numerical relativity.

    Science.gov (United States)

    Ilseven, E; Mendoza, M

    2016-02-01

    In the Z4 formulation, Einstein equations are written as a set of flux conservative first-order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for numerical relativity and validate it with well-established tests, also known as "apples with apples." Furthermore, we find that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improve. Finally, in order to show the potential of our approach, a linear scaling law for parallelization with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems.

  12. Updated lattice results for parton distributions

    International Nuclear Information System (INIS)

    Alexandrou, Constantia; Cichy, Krzysztof; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian

    2017-07-01

    We provide an analysis of the x-dependence of the bare unpolarized, helicity and transversity iso-vector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The x-dependence of the calculated PDFs resembles the one of the phenomenological parameterizations, a feature that makes this approach very promising. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum, which is essential for the prospects of a reliable extraction of the PDFs in the future.

  13. Updated lattice results for parton distributions

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrou, Constantia [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Poznan Univ. (Poland). Faculty of Physics; Constantinou, Martha [Temple Univ., Philadelphia, PA (United States); Hadjiyiannakou, Kyriakos [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Jansen, Karl; Steffens, Fernanda; Wiese, Christian [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2017-07-15

    We provide an analysis of the x-dependence of the bare unpolarized, helicity and transversity iso-vector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The x-dependence of the calculated PDFs resembles the one of the phenomenological parameterizations, a feature that makes this approach very promising. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum, which is essential for the prospects of a reliable extraction of the PDFs in the future.

  14. Low-energy scattering on the lattice

    International Nuclear Information System (INIS)

    Bour Bour, Shahin

    2014-01-01

    In this thesis we present precision benchmark calculations for two-component fermions in the unitarity limit using an ab initio method, namely Hamiltonian lattice formalism. We calculate the ground state energy for unpolarized four particles (Fermi gas) in a periodic cube as a fraction of the ground state energy of the non-interacting system for two independent representations of the lattice Hamiltonians. We obtain the values 0.211(2) and 0.210(2). These results are in full agreement with the Euclidean lattice and fixed-node diffusion Monte Carlo calculations. We also give an expression for the energy corrections to the binding energy of a bound state in a moving frame. These corrections contain information about the mass and number of the constituents and are topological in origin and will have a broad applications to the lattice calculations of nucleons, nuclei, hadronic molecules and cold atoms. As one of its applications we use this expression and determine the low-energy parameters for the fermion dimer elastic scattering in shallow binding limit. For our lattice calculations we use Luescher's finite volume method. From the lattice calculations we find κa fd =1.174(9) and κr fd =-0.029(13), where κ represents the binding momentum of dimer and a fd (r fd ) denotes the scattering length (effective-range). These results are confirmed by the continuum calculations using the Skorniakov-Ter-Martirosian integral equation which gives 1.17907(1) and -0.0383(3) for the scattering length and effective range, respectively.

  15. Lattice gauge theory approach to quantum chromodynamics

    International Nuclear Information System (INIS)

    Kogut, J.B.

    1983-01-01

    The author reviews in a pedagogical fashion some of the recent developments in lattice quantum chromodynamics. This review emphasizes explicit examples and illustrations rather than general proofs and analyses. It begins with a discussion of the heavy-quark potential in continuum quantum chromodynamics. Asymptotic freedom and renormalization-group improved perturbation theory are discussed. A simple dielectric model of confinement is considered as an intuitive guide to the vacuum of non-Abelian gauge theories. Next, the Euclidean form of lattice gauge theory is introduced, and an assortment of calculational methods are reviewed. These include high-temperature expansions, duality, Monte Carlo computer simulations, and weak coupling expansions. A #betta#-parameter calculation for asymptotically free-spin models is presented. The Hamiltonian formulation of lattice gauge theory is presented and is illustrated in the context of flux tube dynamics. Roughening transitions, Casimir forces, and the restoration of rotational symmetry are discussed. Mechanisms of confinement in lattice theories are illustrated in the two-dimensional electrodynamics of the planar model and the U(1) gauge theory in four dimensions. Generalized actions for SU(2) gauge theories and the relevance of monopoles and strings to crossover phenomena are considered. A brief discussion of the continuity of fields and topologial charge in asymptotically free lattice models is presented. The final major topic of this review concerns lattice fermions. The species doubling problem and its relation to chiral symmetry are illustrated. Staggered Euclidean fermion methods are discussed in detail, with an emphasis on species counting, remnants of chiral symmetry, Block spin variables, and the axial anomaly. Numerical methods for including fermions in computer simulations are considered. Jacobi and Gauss-Siedel inversion methods to obtain the fermion propagator in a background gauge field are reviewed

  16. Experience with split transition lattices at RHIC

    International Nuclear Information System (INIS)

    Montag, C.; Tepikian, S.; Blaskiewicz, M.; Brennan, J.M.

    2010-01-01

    During the acceleration process, heavy ion beams in RHIC cross the transition energy. When RHIC was colliding deuterons and gold ions during Run-8, lattices with different integer tunes were used for the two rings. This resulted in the two rings crossing transition at different times, which proved beneficial for the 'Yellow' ring, the RF system of which is slaved to the 'Blue' ring. For the symmetric gold-gold run in FY2010, lattices with different transition energies but equal tunes were implemented. We report the optics design concept as well as operational experience with this configuration.

  17. Automated generation of lattice QCD Feynman rules

    Energy Technology Data Exchange (ETDEWEB)

    Hart, A.; Mueller, E.H. [Edinburgh Univ. (United Kingdom). SUPA School of Physics and Astronomy; von Hippel, G.M. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Horgan, R.R. [Cambridge Univ. (United Kingdom). DAMTP, CMS

    2009-04-15

    The derivation of the Feynman rules for lattice perturbation theory from actions and operators is complicated, especially for highly improved actions such as HISQ. This task is, however, both important and particularly suitable for automation. We describe a suite of software to generate and evaluate Feynman rules for a wide range of lattice field theories with gluons and (relativistic and/or heavy) quarks. Our programs are capable of dealing with actions as complicated as (m)NRQCD and HISQ. Automated differentiation methods are used to calculate also the derivatives of Feynman diagrams. (orig.)

  18. YANG-MILLS FIELDS AND THE LATTICE.

    Energy Technology Data Exchange (ETDEWEB)

    CREUTZ,M.

    2004-05-18

    The Yang-Mills theory lies at the heart of our understanding of elementary particle interactions. For the strong nuclear forces, we must understand this theory in the strong coupling regime. The primary technique for this is the lattice. While basically an ultraviolet regulator, the lattice avoids the use of a perturbative expansion. I discuss some of the historical circumstances that drove us to this approach, which has had immense success, convincingly demonstrating quark confinement and obtaining crucial properties of the strong interactions from first principles.

  19. Response of Kondo lattice systems to pressure

    International Nuclear Information System (INIS)

    Thompson, J.D.; Borges, H.A.; Fisk, Z.; Horn, S.; Parks, R.D.; Wells, G.L.

    1987-01-01

    Yb-based Kondo lattice systems (YbAgCu 4 , YbCu 2 Si 2 , YbRh 2 Si 2 ) represent an interesting class of materials in which it is possible to study systematically the development of heavy electron behavior through the application of pressure. Certainly, additional experiments are required to determine to what extent Yb compounds are mirror images of their Ce counterparts. Finally, pressure reveals the presence of competing interactions for which a simple model exists that qualitatively accounts for the pressure response observed in a large number of Ce, U and Yb-based Kondo lattice systems

  20. London limit for lattice model of superconductor

    International Nuclear Information System (INIS)

    Ktitorov, S.A.

    2004-01-01

    The phenomenological approach to the strong-bond superconductor, which is based on the Ginzburg-Landau equation in the London limit, is considered. The effect of the crystalline lattice discreteness on the superconductors electromagnetic properties is studied. The classic problems on the critical current and magnetic field penetration are studied within the frames of the lattice model for thin superconducting films. The dependence of the superconducting current on the thin film order parameter is obtained. The critical current dependence on the degree of deviation from the continual approximation is calculated [ru

  1. Deflation acceleration of lattice QCD simulations

    International Nuclear Information System (INIS)

    Luescher, Martin

    2007-01-01

    Close to the chiral limit, many calculations in numerical lattice QCD can potentially be accelerated using low-mode deflation techniques. In this paper it is shown that the recently introduced domain-decomposed deflation subspaces can be propagated along the field trajectories generated by the Hybrid Monte Carlo (HMC) algorithm with a modest effort. The quark forces that drive the simulation may then be computed using a deflation-accelerated solver for the lattice Dirac equation. As a consequence, the computer time required for the simulations is significantly reduced and an improved scaling behaviour of the simulation algorithm with respect to the quark mass is achieved

  2. Deflation acceleration of lattice QCD simulations

    CERN Document Server

    Lüscher, Martin

    2007-01-01

    Close to the chiral limit, many calculations in numerical lattice QCD can potentially be accelerated using low-mode deflation techniques. In this paper it is shown that the recently introduced domain-decomposed deflation subspaces can be propagated along the field trajectories generated by the Hybrid Monte Carlo (HMC) algorithm with a modest effort. The quark forces that drive the simulation may then be computed using a deflation-accelerated solver for the lattice Dirac equation. As a consequence, the computer time required for the simulations is significantly reduced and an improved scaling behaviour of the simulation algorithm with respect to the quark mass is achieved.

  3. Rydberg dressing of atoms in optical lattices

    Science.gov (United States)

    Macrı, T.; Pohl, T.

    2014-01-01

    We study atoms in optical lattices whose electronic ground state is off-resonantly coupled to a highly excited state with strong binary interactions. We present a time-dependent treatment of the resulting quantum dynamics, which—contrary to recent predictions [36 Li, Ates, and Lesanovsky, Phys. Rev. Lett. 110, 213005 (2013), 10.1103/PhysRevLett.110.213005]—proves that the strong repulsion between the weakly admixed Rydberg states does not lead to atomic trap loss. This finding provides an important basis for creating and manipulating coherent long-range interactions in optical lattice experiments.

  4. Statistical Transmutation in Floquet Driven Optical Lattices.

    Science.gov (United States)

    Sedrakyan, Tigran A; Galitski, Victor M; Kamenev, Alex

    2015-11-06

    We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state.

  5. Two Dimensional Super QCD on a Lattice

    Energy Technology Data Exchange (ETDEWEB)

    Catterall, Simon [Syracuse U.; Veernala, Aarti [Fermilab

    2017-10-04

    We construct a lattice theory with one exact supersymmetry which consists of fields transforming in both the adjoint and fundamental representations of a U(Nc) gauge group. In addition to gluons and gluinos, the theory contains Nf flavors of fermion in the fundamental representation along with their scalar partners and is invariant under a global U(Nf) flavor symmetry. The lattice action contains an additional Fayet-Iliopoulos term which can be used to generate a scalar potential. We perform numerical simulations that corroborate the theoretical expectation that supersymmetry is spontaneously broken for Nf

  6. Topology in dynamical lattice QCD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, Florian

    2012-08-20

    Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.

  7. Spectral tunneling of lattice nonlocal solitons

    International Nuclear Information System (INIS)

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

    2010-01-01

    We address spectral tunneling of walking spatial solitons in photorefractive media with nonlocal diffusion component of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where solitons traveling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending, solitons survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.

  8. Automated generation of lattice QCD Feynman rules

    International Nuclear Information System (INIS)

    Hart, A.; Mueller, E.H.; Horgan, R.R.

    2009-04-01

    The derivation of the Feynman rules for lattice perturbation theory from actions and operators is complicated, especially for highly improved actions such as HISQ. This task is, however, both important and particularly suitable for automation. We describe a suite of software to generate and evaluate Feynman rules for a wide range of lattice field theories with gluons and (relativistic and/or heavy) quarks. Our programs are capable of dealing with actions as complicated as (m)NRQCD and HISQ. Automated differentiation methods are used to calculate also the derivatives of Feynman diagrams. (orig.)

  9. Perturbative and nonperturbative renormalization in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [University of Edinburgh (United Kingdom). School of Physics and Astronomy; Perlt, H. [Leipzig Univ. (DE). Institut fuer Theoretische Physik] (and others)

    2010-03-15

    We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular with recent two-loop calculations. (orig.)

  10. Ultracold Dipolar Gases in Optical Lattices

    OpenAIRE

    Trefzger, C.; Menotti, C.; Capogrosso-Sansone, B.; Lewenstein, M.

    2011-01-01

    This tutorial is a theoretical work, in which we study the physics of ultra-cold dipolar bosonic gases in optical lattices. Such gases consist of bosonic atoms or molecules that interact via dipolar forces, and that are cooled below the quantum degeneracy temperature, typically in the nK range. When such a degenerate quantum gas is loaded into an optical lattice produced by standing waves of laser light, new kinds of physical phenomena occur. These systems realize then extended Hubbard-type m...

  11. Topology in dynamical lattice QCD simulations

    International Nuclear Information System (INIS)

    Gruber, Florian

    2012-01-01

    Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.

  12. The Lanczos method in lattice gauge theories

    International Nuclear Information System (INIS)

    Barbour, I.M.; Behilil, N.E.; Gibbs, P.E.; Teper, M.; Schierholz, G.

    1984-09-01

    We present a modified version of the Lanczos algorithm as a computational method for tridiagonalising large sparse matrices, which avoids the requirement for large amounts of storage space. It can be applied as a first step in calculating eigenvalues and eigenvectors or for obtaining the inverse of a matrix row by row. Here we describe the method and apply it to various problems in lattice gauge theories. We have found it to have excellent convergence properties. In particular it enables us to do lattice calculations at small and even zero quark mass. (orig.)

  13. A Lattice Calculation of Parton Distributions

    International Nuclear Information System (INIS)

    Alexandrou, Constantia; Cichy, Krzysztof; Poznan Univ.; Drach, Vincent; Univ. of Southern Denmark, Odense; Garcia-Ramos, Elena; Humboldt-Universitaet, Berlin; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian

    2015-04-01

    We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using N f =2+1+1 twisted mass fermions with a pion mass of about 370 MeV. The focus of this work is a detailed description of the computation, including the lattice calculation, the matching to an infinite momentum and the nucleon mass correction. In addition, we test the effect of gauge link smearing in the operator to estimate the influence of the Wilson line renormalization, which is yet to be done.

  14. Axial nucleon form factors from lattice QCD

    International Nuclear Information System (INIS)

    Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Constantinou, M.; Guichon, P.; Jansen, K.; Korzec, T.

    2011-01-01

    We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.

  15. Bottomonium above Deconfinement in Lattice Nonrelativistic QCD

    International Nuclear Information System (INIS)

    Aarts, G.; Kim, S.; Lombardo, M. P.; Oktay, M. B.; Ryan, S. M.; Sinclair, D. K.; Skullerud, J.-I.

    2011-01-01

    We study the temperature dependence of bottomonium for temperatures in the range 0.4T c c , using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for N f =2 light flavors on a highly anisotropic lattice. We find that the Υ is insensitive to the temperature in this range, while the χ b propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly free dynamics at T≅2T c .

  16. Late complications following cryotherapy of lattice degeneration.

    Science.gov (United States)

    Benson, W E; Morse, P H; Nantawan, P

    1977-10-01

    We observed 341 patients who had received cryotherapy for lattice degeneration in order to identify possible late complications. Sequelae such as retinal tears posterior to an operculum or flap tears within treated areas showed that treatment did not necessarily prevent subsequent vitreous traction. Moreover, the newly created flap tears may extend beyond the treated area and can cause retinal detachment. Even scleral buckling did not necesserily prevent further traction. Therefore, we concluded that when cryotherapy is used to treat lattice degeneration, an adequate margin of surrounding retina should be treated and the treatment should extend to the ora serrata.

  17. Genetics of lattice degeneration of the retina.

    Science.gov (United States)

    Murakami, F; Ohba, N

    1982-01-01

    First-degree relatives of proband patients with lattice degeneration of the retina revealed a significantly higher prevalence of the disease than the prevalence in the general population: the former had the disease about three times as frequently as the latter. The observed data were analyzed in terms of their accordance with recognized genetic models. The inheritance pattern did not fit well to a monogenic mode of inheritance, and it was hypothesized that a polygenic or multifactorial mode of inheritance is the most likely for lattice degeneration of the retina.

  18. Mobile localization in nonlinear Schroedinger lattices

    International Nuclear Information System (INIS)

    Gomez-Gardenes, J.; Falo, F.; Floria, L.M.

    2004-01-01

    Using continuation methods from the integrable Ablowitz-Ladik lattice, we have studied the structure of numerically exact mobile discrete breathers in the standard discrete nonlinear Schroedinger equation. We show that, away from that integrable limit, the mobile pulse is dressed by a background of resonant plane waves with wavevectors given by a certain selection rule. This background is seen to be essential for supporting mobile localization in the absence of integrability. We show how the variations of the localized pulse energy during its motion are balanced by the interaction with this background, allowing the localization mobility along the lattice

  19. Lattice BGK simulation of natural convection

    International Nuclear Information System (INIS)

    Chen, Yu; Ohashi, Hirotada; Akiyama, Mamoru

    1995-01-01

    Recently a new thermal lattice Bhatnagar-Gross-Krook fluid model was suggested by the authors. In this study, this new model was applied into the numerical simulation of natural convection, namely the Rayleigh Benard flow. The critical number for the onset of convective phenomenon was numerically measured and compared with that of theoretical prediction. A gravity dependent deviation was found in the numerical simulation, which is explained as an unavoidable consequence of the incorporation of gravity force in the lattice BGK system. (author)

  20. Neutron transmission bands in one dimensional lattices

    International Nuclear Information System (INIS)

    Monsivais, G.; Moshinsky, M.

    1999-01-01

    The original Kronig-Penney lattice, which had delta function interactions at the end of each of the equal segments, seems a good model for the motion of neutrons in a linear lattice if the strength b of the δ functions depends of the energy of the neutrons, i.e., b(E). We derive the equation for the transmission bands and consider the relations of b(E) with the R(E) function discussed in a previous paper. We note the great difference in the behavior of the bands when b(E) is constant and when it is related with a single resonance of the R function. (Author)

  1. Neutron Electric Dipole Moment on the Lattice

    Science.gov (United States)

    Yoon, Boram; Bhattacharya, Tanmoy; Gupta, Rajan

    2018-03-01

    For the neutron to have an electric dipole moment (EDM), the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.

  2. Neutron Electric Dipole Moment on the Lattice

    Directory of Open Access Journals (Sweden)

    Yoon Boram

    2018-01-01

    Full Text Available For the neutron to have an electric dipole moment (EDM, the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.

  3. Natural uranium lattice in heavy water

    International Nuclear Information System (INIS)

    Girard, Y.; Koechlin, J.C.; Moreau, J.; Naudet, R.

    1959-01-01

    A group of Laplacian determinations have been made under critical running conditions in a heavy water pile specially constructed to this end using either complete lattices or samples of lattices employing a two-zone method. The experimental equipment is briefly described: it has been devised to allow rapid modifications of the charge. The methods of measurement employed are also summarily described one operates either by flux charts in the case of lattices which are then used as references, or by progressive replacement of the bars by concentric rings and measurements of the reactivity. In this case, one attempts to obtain the difference between the material laplacian of the central unknown lattice and that of the reference lattice. The method has been specially develop ped to give precision. Results of Laplacian measurements for all these lattice types are presented, allowing the construction of a set of curves as a function of the separation. Various other effects have also been measured: the equivalent reactivity of a mm of water - anisotropy - temperature effect, etc. However in this first attack on the problem, the measurement of a large variety of Laplacian has been carried out, rather than careful measurements in particular cases. It is in this spirit that the interpretation of the results has been made. As a large number of very complex phenomena still escape the possibilities of the calculation, it is considered that a certain number of adjustments are necessary; now these can only give the desired efficiency in forecasting results if they refer to a sufficiently great number of experimental data. It is necessary then to connect the measurements closely on with the other whilst, at the same time, subdividing them according to logically deduced formulae. The principal source of trouble has been that of coherence. The rules governing the calculations employed in the interpretation of the data are given. In the first instance simple formula are used: first of

  4. The Developement of A Lattice Structured Database

    DEFF Research Database (Denmark)

    Bruun, Hans

    In this project we have investigated the possibilities to make a system based on the concept algebra described in [3], [4] and [5]. The concept algebra is used for ontology specification and knowledge representation. It is a distributive lattice extended with attribution operations. One of the main...... ideas in this work is to use Birkhoff's representation theorem, so we represent distributive lattices using its dual representation: the partial order of join irreducibles. We show how to construct a concept algebra satisfying a given set of equations. The universal/initial algebra is usually too big...

  5. END FIELD EFFECTS IN BEND ONLY COOLING LATTICES

    International Nuclear Information System (INIS)

    BEERG, J.S.; KIRK, H.; GARREN, A.

    2003-01-01

    Cooling lattices consisting only of bends (using either rotated pole faces or gradient dipoles to achieve focusing) often require large apertures and short magnets. One expects the effect of end fields to be significant in this case. In this paper we explore the effect of adding end fields to a working lattice design that originally lacked them. The paper describes the process of correcting the lattice design for the added end fields so as to maintain desirable lattice characteristics. It then compares the properties of the lattice with end fields relative to the lattice without them

  6. Lattice formulation of a two-dimensional topological field theory

    International Nuclear Information System (INIS)

    Ohta, Kazutoshi; Takimi, Tomohisa

    2007-01-01

    We investigate an integrable property and the observables of 2-dimensional N=(4,4) topological field theory defined on a discrete lattice by using the 'orbifolding' and 'deconstruction' methods. We show that our lattice model is integrable and, for this reason, the partition function reduces to matrix integrals of scalar fields on the lattice sites. We elucidate meaningful differences between a discrete lattice and a differentiable manifold. This is important for studying topological quantities on a lattice. We also propose a new construction of N=(2,2) supersymmetric lattice theory, which is realized through a suitable truncation of scalar fields from the N=(4,4) theory. (author)

  7. On the hierarchical lattices approximation of Bravais lattices: Specific heat and correlation length

    International Nuclear Information System (INIS)

    Tsallis, C.

    1984-01-01

    Certain types of real-space renormalization groups (which essentially approximate Bravais lattices through hierarchical ones) do not preserve standard thermodynamic convexity properties. It is pointed out that this serious defect is not intrinsic to any real-space renormalization. It can be avoided if form-invariance (under uniform translation of the energy scale) of the equation connecting the Bravais lattice (which is intended to study) to the hierarchical one (which approximates it) is demanded. In addition to that expressions for the critical exponentes ν and α corresponding to hierarchical lattices are analysed; these are consistent with Melrose recent analysis of the fractal intrinsic dimensionality. (Author) [pt

  8. Efficient LBM visual simulation on face-centered cubic lattices.

    Science.gov (United States)

    Petkov, Kaloian; Qiu, Feng; Fan, Zhe; Kaufman, Arie E; Mueller, Klaus

    2009-01-01

    The Lattice Boltzmann method (LBM) for visual simulation of fluid flow generally employs cubic Cartesian (CC) lattices such as the D3Q13 and D3Q19 lattices for the particle transport. However, the CC lattices lead to suboptimal representation of the simulation space. We introduce the face-centered cubic (FCC) lattice, fD3Q13, for LBM simulations. Compared to the CC lattices, the fD3Q13 lattice creates a more isotropic sampling of the simulation domain and its single lattice speed (i.e., link length) simplifies the computations and data storage. Furthermore, the fD3Q13 lattice can be decomposed into two independent interleaved lattices, one of which can be discarded, which doubles the simulation speed. The resulting LBM simulation can be efficiently mapped to the GPU, further increasing the computational performance. We show the numerical advantages of the FCC lattice on channeled flow in 2D and the flow-past-a-sphere benchmark in 3D. In both cases, the comparison is against the corresponding CC lattices using the analytical solutions for the systems as well as velocity field visualizations. We also demonstrate the performance advantages of the fD3Q13 lattice for interactive simulation and rendering of hot smoke in an urban environment using thermal LBM.

  9. Fuel lattice design using heuristics and new strategies

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz S, J. J.; Castillo M, J. A.; Torres V, M.; Perusquia del Cueto, R. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Pelta, D. A. [ETS Ingenieria Informatica y Telecomunicaciones, Universidad de Granada, Daniel Saucedo Aranda s/n, 18071 Granada (Spain); Campos S, Y., E-mail: juanjose.ortiz@inin.gob.m [IPN, Escuela Superior de Fisica y Matematicas, Unidad Profesional Adolfo Lopez Mateos, Edif. 9, 07738 Mexico D. F. (Mexico)

    2010-10-15

    This work show some results of the fuel lattice design in BWRs when some allocation pin rod rules are not taking into account. Heuristics techniques like Path Re linking and Greedy to design fuel lattices were used. The scope of this work is to search about how do classical rules in design fuel lattices affect the heuristics techniques results and the fuel lattice quality. The fuel lattices quality is measured by Power Peaking Factor and Infinite Multiplication Factor at the beginning of the fuel lattice life. CASMO-4 code to calculate these parameters was used. The analyzed rules are the following: pin rods with lowest uranium enrichment are only allocated in the fuel lattice corner, and pin rods with gadolinium cannot allocated in the fuel lattice edge. Fuel lattices with and without gadolinium in the main diagonal were studied. Some fuel lattices were simulated in an equilibrium cycle fuel reload, using Simulate-3 to verify their performance. So, the effective multiplication factor and thermal limits can be verified. The obtained results show a good performance in some fuel lattices designed, even thought, the knowing rules were not implemented. A fuel lattice performance and fuel lattice design characteristics analysis was made. To the realized tests, a dell workstation was used, under Li nux platform. (Author)

  10. Fuel lattice design using heuristics and new strategies

    International Nuclear Information System (INIS)

    Ortiz S, J. J.; Castillo M, J. A.; Torres V, M.; Perusquia del Cueto, R.; Pelta, D. A.; Campos S, Y.

    2010-10-01

    This work show some results of the fuel lattice design in BWRs when some allocation pin rod rules are not taking into account. Heuristics techniques like Path Re linking and Greedy to design fuel lattices were used. The scope of this work is to search about how do classical rules in design fuel lattices affect the heuristics techniques results and the fuel lattice quality. The fuel lattices quality is measured by Power Peaking Factor and Infinite Multiplication Factor at the beginning of the fuel lattice life. CASMO-4 code to calculate these parameters was used. The analyzed rules are the following: pin rods with lowest uranium enrichment are only allocated in the fuel lattice corner, and pin rods with gadolinium cannot allocated in the fuel lattice edge. Fuel lattices with and without gadolinium in the main diagonal were studied. Some fuel lattices were simulated in an equilibrium cycle fuel reload, using Simulate-3 to verify their performance. So, the effective multiplication factor and thermal limits can be verified. The obtained results show a good performance in some fuel lattices designed, even thought, the knowing rules were not implemented. A fuel lattice performance and fuel lattice design characteristics analysis was made. To the realized tests, a dell workstation was used, under Li nux platform. (Author)

  11. Dynamical fermions in lattice quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Szabo, Kalman

    2007-07-01

    The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)

  12. Dynamical fermions in lattice quantum chromodynamics

    International Nuclear Information System (INIS)

    Szabo, Kalman

    2007-01-01

    The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)

  13. Physical correlation effects in the lattice gas

    International Nuclear Information System (INIS)

    Murch, G.E.; Thorn, R.J.

    1979-01-01

    The circumstances of the existence of the physical correlation factor in the Nernst--Einstein relation are discussed. Use is then made of the linear phenomenological equations of irreversible thermodynamics to show that the physical correlation factor must also be present in the Darken equation. Computer simulation results in the nearest neighbor interacting lattice gas are then presented to verify this finding

  14. First multi-bend achromat lattice consideration

    Energy Technology Data Exchange (ETDEWEB)

    Einfeld, Dieter, E-mail: dieter.einfeld@maxlab.lu.se [Lund University, PO Box 118, Lund SE-221 00 (Sweden); Plesko, Mark [COSYLAB, Teslova ulica 30, Ljubljana SI-1000 (Slovakia); Schaper, Joachim [HAWK University of Applied Sciences and Arts, Hohnsen 4, D-31134 Hildesheim (Germany)

    2014-08-27

    The first proposed lattice for a ‘diffraction-limited light source’ is reported. This approach has now more or less been used for the MAX IV project. By the beginning of 1990, three third-generation synchrotron light sources had been successfully commissioned in Grenoble, Berkeley and Trieste (ESRF, ALS and ELETTRA). Each of these new machines reached their target specifications without any significant problems. In parallel, already at that time discussions were underway regarding the next generation, the ‘diffraction-limited light source (DLSR)’, which featured sub-nm rad electron beam emittance, photon beam brilliance exceeding 10{sup 22} and the potential to emit coherent radiation. Also, at about that time, a first design for a 3 GeV DLSR was developed, based on a modified multiple-bend achromat (MBA) design leading to a lattice with normalized emittance of ∊{sub x} = 0.5 nm rad. The novel feature of the MBA lattice was the use of seven vertically focusing bend magnets with different bending angles throughout the achromat cell to keep the radiation integrals and resulting beam emittance low. The baseline design called for a 400 m ring circumference with 12 straight sections of 6 m length. The dynamic aperture behaviour of the DLSR lattice was estimated to produce > 5 h beam lifetime at 100 mA stored beam current.

  15. Canonical sampling of a lattice gas

    International Nuclear Information System (INIS)

    Mueller, W.F.

    1997-01-01

    It is shown that a sampling algorithm, recently proposed in conjunction with a lattice-gas model of nuclear fragmentation, samples the canonical ensemble only in an approximate fashion. A residual weight factor has to be taken into account to calculate correct thermodynamic averages. Then, however, the algorithm is numerically inefficient. copyright 1997 The American Physical Society

  16. Lattice for FPGAs using logarithmic arithmetic

    Czech Academy of Sciences Publication Activity Database

    Kadlec, Jiří; Matoušek, Rudolf; Heřmánek, Antonín; Líčko, Miroslav; Tichý, Milan

    2002-01-01

    Roč. 74, č. 906 (2002), s. 53-56 ISSN 0013-4902 Grant - others: ESPRIT (XE) 33544 Institutional research plan: CEZ:AV0Z1075907 Keywords : lattice Rls algorithm * FPGA * logarithmic arithmetic Subject RIV: JC - Computer Hardware ; Software Impact factor: 0.039, year: 2002

  17. Electronic properties of disordered graphene antidot lattices

    DEFF Research Database (Denmark)

    Yuan, Shengjun; Roldán, Rafael; Jauho, Antti-Pekka

    2013-01-01

    Regular nanoscale perforations in graphene (graphene antidot lattices, GALs) are known to lead to a gap in the energy spectrum, thereby paving a possible way towards many applications. This theoretical prediction relies on a perfect placement of identical perforations, a situation not likely to o...

  18. Vector fields and gravity on the lattice

    International Nuclear Information System (INIS)

    Khatsymovsky, V.M.

    1988-01-01

    The problem of discretization of vector field on Regge lattice is considered. Our approach is based on geometrical interpretation of the vector field as the field of infinitesimal coordinate transformation. A discrete version of the vector field action is obtained as a particular case of the continuum action, and it is shown to have the true continuum limit

  19. Radiative Transitions in Charmonium from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek; Robert Edwards; David Richards

    2006-01-17

    Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the {eta}{sub c}, J/{psi} and {chi}{sub c0}. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched approximation. With an anisotropy {xi} = 3 at a{sub s} {approx} 0.1 fm we find a reasonable gross spectrum and a hyperfine splitting {approx}90 MeV, which compares favorably with other improved actions. In general, after extrapolation of lattice data at non-zero Q{sup 2} to the photopoint, our results agree within errors with all well measured experimental values. Furthermore, results are compared with the expectations of simple quark models where we find that many features are in agreement; beyond this we propose the possibility of constraining such models using our extracted values of physically unobservable quantities such as the J/{psi} quadrupole moment. We conclude that our methods are successful and propose to apply them to the problem of radiative transitions involving hybrid mesons, with the eventual goal of predicting hybrid meson photoproduction rates at the GlueX experiment.

  20. Shaking the entropy out of a lattice

    DEFF Research Database (Denmark)

    C. Tichy, Malte; Mølmer, Klaus; F. Sherson, Jacob

    2012-01-01

    , for which we implement a protocol that circumvents the constraints of unitarity. The preparation of large regions with precisely one atom per lattice site is discussed for both bosons and fermions. The resulting low-entropy Mott-insulating states may serve as high-fidelity register states for quantum...

  1. Soft covariant gauges on the lattice

    Energy Technology Data Exchange (ETDEWEB)

    Henty, D.S.; Oliveira, O.; Parrinello, C.; Ryan, S. [Department of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (UKQCD Collaboration)

    1996-12-01

    We present an exploratory study of a one-parameter family of covariant, nonperturbative lattice gauge-fixing conditions that can be implemented through a simple Monte Carlo algorithm. We demonstrate that at the numerical level the procedure is feasible, and as a first application we examine the gauge dependence of the gluon propagator. {copyright} {ital 1996 The American Physical Society.}

  2. Scattering processes and resonances from lattice QCD

    Science.gov (United States)

    Briceño, Raúl A.; Dudek, Jozef J.; Young, Ross D.

    2018-04-01

    The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This article reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.

  3. Probabilistic representation of fermionic lattice systems

    International Nuclear Information System (INIS)

    Beccaria, Matteo; Presilla, Carlo; De Angelis, Gian Fabrizio; Jona-Lasinio, Giovanni

    2000-01-01

    We describe an exact Feynman-Kac type formula to represent the dynamics of fermionic lattice systems. In this approach the real time or Euclidean time dynamics is expressed in terms of the stochastic evolution of a collection of Poisson processes. From this formula we derive a family of algorithms for Monte Carlo simulations, parametrized by the jump rates of the Poisson processes

  4. Lattice effects in YVO3 single crystal

    NARCIS (Netherlands)

    Marquina, C; Sikora, M; Ibarra, MR; Nugroho, AA; Palstra, TTM

    In this paper we report on the lattice effects in the Mott insulator yttrium orthovanadate (YVO3). Linear thermal expansion and magnetostriction experiments have been performed on a single crystal, in the temperature range from 5 K to room temperature. The YVO3 orders antiferromagnetically at T-N =

  5. Heavy water lattices: Second panel report

    Energy Technology Data Exchange (ETDEWEB)

    1963-09-15

    The panel was attended by prominent physicists from most of the laboratories engaged in the field of heavy water lattices throughout the world. The participants presented written contributions and status reports describing the past history and plans for further development of heavy-water reactors. Valuable discussions took place, during which recommendations for future work were formulated. Refs, figs, tabs.

  6. Heavy water lattices: Second panel report

    International Nuclear Information System (INIS)

    1963-01-01

    The panel was attended by prominent physicists from most of the laboratories engaged in the field of heavy water lattices throughout the world. The participants presented written contributions and status reports describing the past history and plans for further development of heavy-water reactors. Valuable discussions took place, during which recommendations for future work were formulated. Refs, figs, tabs

  7. A lattice model for influenza spreading.

    Directory of Open Access Journals (Sweden)

    Antonella Liccardo

    Full Text Available We construct a stochastic SIR model for influenza spreading on a D-dimensional lattice, which represents the dynamic contact network of individuals. An age distributed population is placed on the lattice and moves on it. The displacement from a site to a nearest neighbor empty site, allows individuals to change the number and identities of their contacts. The dynamics on the lattice is governed by an attractive interaction between individuals belonging to the same age-class. The parameters, which regulate the pattern dynamics, are fixed fitting the data on the age-dependent daily contact numbers, furnished by the Polymod survey. A simple SIR transmission model with a nearest neighbors interaction and some very basic adaptive mobility restrictions complete the model. The model is validated against the age-distributed Italian epidemiological data for the influenza A(H1N1 during the [Formula: see text] season, with sensible predictions for the epidemiological parameters. For an appropriate topology of the lattice, we find that, whenever the accordance between the contact patterns of the model and the Polymod data is satisfactory, there is a good agreement between the numerical and the experimental epidemiological data. This result shows how rich is the information encoded in the average contact patterns of individuals, with respect to the analysis of the epidemic spreading of an infectious disease.

  8. Extension theorems for homogenization on lattice structures

    Science.gov (United States)

    Miller, Robert E.

    1992-01-01

    When applying homogenization techniques to problems involving lattice structures, it is necessary to extend certain functions defined on a perforated domain to a simply connected domain. This paper provides general extension operators which preserve bounds on derivatives of order l. Only the special case of honeycomb structures is considered.

  9. Renormalization of Supersymmetric QCD on the Lattice

    Science.gov (United States)

    Costa, Marios; Panagopoulos, Haralambos

    2018-03-01

    We perform a pilot study of the perturbative renormalization of a Supersymmetric gauge theory with matter fields on the lattice. As a specific example, we consider Supersymmetric N=1 QCD (SQCD). We study the self-energies of all particles which appear in this theory, as well as the renormalization of the coupling constant. To this end we compute, perturbatively to one-loop, the relevant two-point and three-point Green's functions using both dimensional and lattice regularizations. Our lattice formulation involves theWilson discretization for the gluino and quark fields; for gluons we employ the Wilson gauge action; for scalar fields (squarks) we use naive discretization. The gauge group that we consider is SU(Nc), while the number of colors, Nc, the number of flavors, Nf, and the gauge parameter, α, are left unspecified. We obtain analytic expressions for the renormalization factors of the coupling constant (Zg) and of the quark (ZΨ), gluon (Zu), gluino (Zλ), squark (ZA±), and ghost (Zc) fields on the lattice. We also compute the critical values of the gluino, quark and squark masses. Finally, we address the mixing which occurs among squark degrees of freedom beyond tree level: we calculate the corresponding mixing matrix which is necessary in order to disentangle the components of the squark field via an additional finite renormalization.

  10. Spontaneous CP violation on the lattice

    CERN Document Server

    Laine, Mikko

    2000-01-01

    At finite temperatures around the electroweak phase transition, the thermodynamics of the MSSM can be described by a three-dimensional two Higgs doublet effective theory. This effective theory has a phase where CP is spontaneously violated. We study spontaneous CP violation with non-perturbative lattice simulations, and analyse whether one could end up in this phase for any physical MSSM parameter values.

  11. Extracting physics from the lattice higgs model

    International Nuclear Information System (INIS)

    Neuberger, H.

    1988-05-01

    The relevance and usefulness of lattice /phi/ 4 for particle physics is discussed from older and newer points of view. The talk will start with a review of the main ideas and suggestions in my work in the past with Dashen and will proceed to present newer developments both on the conceptual and the practical level. 12 refs

  12. Supersymmetry and the lattice: A reconciliation?

    International Nuclear Information System (INIS)

    Curci, G.

    1987-01-01

    Contrary to common prejudice, we claim that supersymmetric gauge theories can be studied non-perturbatively on the lattice (by using known ideas and techniques). We discuss in detail super-Yang-Mills theory and propose some explicit measurements which are both physically interesting and within present or near-future computer capabilities. (orig.)

  13. Proof of Nishida's Conjecture on Anharmonic Lattices

    Science.gov (United States)

    Rink, Bob

    2006-02-01

    We prove Nishida's 1971 conjecture stating that almost all low-energetic motions of the anharmonic Fermi-Pasta-Ulam lattice with fixed endpoints are quasi-periodic. The proof is based on the formal computations of Nishida, the KAM theorem, discrete symmetry considerations and an algebraic trick that considerably simplifies earlier results.

  14. Cutoff dependence in lattice phi44 theory

    International Nuclear Information System (INIS)

    Symanzik, K.

    1979-11-01

    The author discusses corrections to the high temperature expansion of the lattice phi 4 4 theory in 4 + epsilon dimensions using the renormalization group. He works with vertex functions, whose expansion is derived from an effective Lagrangian for large-cutoff behaviour. He concludes that the numerical phi 4 4 results offer a test of the idea of asymptotic freedom. (HSI)

  15. Lattice Model for Production of Gas

    KAUST Repository

    Marder, M.; Eftekhari, Behzad; Patzek, Tadeusz

    2017-01-01

    We define a lattice model for rock, absorbers, and gas that makes it possible to examine the flow of gas to a complicated absorbing boundary over long periods of time. The motivation is to deduce the geometry of the boundary from the time history

  16. Spin-2 NΩ dibaryon from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Etminan, Faisal [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Department of Physics, Faculty of Sciences, University of Birjand, Birjand 97175-615 (Iran, Islamic Republic of); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Nemura, Hidekatsu [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Aoki, Sinya [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Doi, Takumi [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Hatsuda, Tetsuo [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Kavli IPMU (WPI), The University of Tokyo, Chiba 277-8583 (Japan); Ikeda, Yoichi [Theoretical Research Division, Nishina Center, RIKEN, Saitama 351-0198 (Japan); Inoue, Takashi [Nihon University, College of Bioresource Sciences, Kanagawa 252-0880 (Japan); Ishii, Noriyoshi [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan); Murano, Keiko [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Sasaki, Kenji [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8571 (Japan)

    2014-08-15

    We investigate properties of the N(nucleon)–Ω(Omega) interaction in lattice QCD to seek for possible dibaryon states in the strangeness −3 channel. We calculate the NΩ potential through the equal-time Nambu–Bethe–Salpeter wave function in 2+1 flavor lattice QCD with the renormalization group improved Iwasaki gauge action and the nonperturbatively O(a) improved Wilson quark action at the lattice spacing a≃0.12 fm on a (1.9 fm){sup 3}× 3.8 fm lattice. The ud and s quark masses in our study correspond to m{sub π}=875(1) MeV and m{sub K}=916(1) MeV. At these parameter values, the central potential in the S-wave with the spin 2 shows attractions at all distances. By solving the Schrödinger equation with this potential, we find one bound state whose binding energy is 18.9(5.0)({sup +12.1}{sub −1.8}) MeV, where the first error is the statistical one, while the second represents the systematic error.

  17. Entanglement complexity of semiflexible lattice polygons

    International Nuclear Information System (INIS)

    Orlandini, E; Tesi, M C; Whittington, S G

    2005-01-01

    We use Monte Carlo methods to study knotting in polygons on the simple cubic lattice with a stiffness fugacity. We investigate how the knot probability depends on stiffness and how the relative frequency of trefoils and figure eight knots changes as the stiffness changes. In addition, we examine the effect of stiffness on the writhe of the polygons. (letter to the editor)

  18. Classical solutions in lattice gauge theories

    International Nuclear Information System (INIS)

    Mitrjushkin, V.K.

    1996-08-01

    The solutions of the classical equations of motion on a periodic lattice are found which correspond to abelian single and double Dirac sheets. These solutions exist also in non-abelian theories. Possible applications of these solutions to the calculation of gauge dependent and gauge invariant observables are discussed. (orig.)

  19. Lattice QCD simulation of meson exchange forces

    International Nuclear Information System (INIS)

    Richards, D.G.; Sinclair, D.K.; Sivers, D.

    1990-01-01

    We present the formalism for investigating the bar Qq bar Qq system in lattice QCD. This system serves as a model for describing exchange forces between heavy, static hadrons. We use this formalism to calculate the exchange potential from gauge configurations which incorporate the effects of dynamical quarks. Our data can be interpreted as giving preliminary results on the range of the nuclear force

  20. Numerical techniques for lattice gauge theories

    International Nuclear Information System (INIS)

    Creutz, M.

    1981-01-01

    The motivation for formulating gauge theories on a lattice is reviewed. Monte Carlo simulation techniques are then discussed for these systems. Finally, the Monte Carlo methods are combined with renormalization group analysis to give strong numerical evidence for confinement of quarks by non-Abelian gauge fields