WorldWideScience

Sample records for pseudo-zero-mode landau levels

  1. Landau levels on a torus

    OpenAIRE

    Enrico OnofriDipartimento di Fisica, Universita` di Parma, and INFN, Gruppo Collegato di Parma, Parma, Italy

    2015-01-01

    Landau levels have represented a very rich field of research, which has gained widespread attention after their application to quantum Hall effect. In a particular gauge, the holomorphic gauge, they give a physical implementation of Bargmann's Hilbert space of entire functions. They have also been recognized as a natural bridge between Feynman's path integral and Geometric Quantization. We discuss here some mathematical subtleties involved in the formulation of the problem when one tries to s...

  2. The lowest Landau level in QCD

    Directory of Open Access Journals (Sweden)

    Bruckmann Falk

    2017-01-01

    Full Text Available The thermodynamics of Quantum Chromodynamics (QCD in external (electro-magnetic fields shows some unexpected features like inverse magnetic catalysis, which have been revealed mainly through lattice studies. Many effective descriptions, on the other hand, use Landau levels or approximate the system by just the lowest Landau level (LLL. Analyzing lattice configurations we ask whether such a picture is justified. We find the LLL to be separated from the rest by a spectral gap in the two-dimensional Dirac operator and analyze the corresponding LLL signature in four dimensions. We determine to what extent the quark condensate is LLL dominated at strong magnetic fields.

  3. Infrared spectroscopy of Landau levels of graphene.

    Science.gov (United States)

    Jiang, Z; Henriksen, E A; Tung, L C; Wang, Y-J; Schwartz, M E; Han, M Y; Kim, P; Stormer, H L

    2007-05-11

    We report infrared studies of the Landau level (LL) transitions in single layer graphene. Our specimens are density tunable and show in situ half-integer quantum Hall plateaus. Infrared transmission is measured in magnetic fields up to B=18 T at selected LL fillings. Resonances between hole LLs and electron LLs, as well as resonances between hole and electron LLs, are resolved. Their transition energies are proportional to sqrt[B], and the deduced band velocity is (-)c approximately equal to 1.1 x 10(6) m/s. The lack of precise scaling between different LL transitions indicates considerable contributions of many-particle effects to the infrared transition energies.

  4. Anti-levitation of Landau levels in vanishing magnetic fields

    Science.gov (United States)

    Pan, W.; Baldwin, K. W.; West, K. W.; Pfeiffer, L. N.; Tsui, D. C.

    Soon after the discovery of the quantum Hall effects in two-dimensional electron systems, the question on the fate of the extended states in a Landau level in vanishing magnetic (B) field arose. Many theoretical models have since been proposed, and experimental results remain inconclusive. In this talk, we report experimental observation of anti-levitation behavior of Landau levels in vanishing B fields (down to as low as B 58 mT) in a high quality heterojunction insulated-gated field-effect transistor (HIGFET). We observed that, in the Landau fan diagram of electron density versus magnetic field, the positions of the magneto-resistance minima at Landau level fillings ν = 4, 5, 6 move below the ``traditional'' Landau level line to lower electron densities. This clearly differs from what was observed in the earlier experiments where in the same Landau fan plot the density moved up. Our result strongly supports the anti-levitation behavior predicted recently. Moreover, the even and odd Landau level filling states show quantitatively different behaviors in anti-levitation, suggesting that the exchange interactions, which are important at odd fillings, may play a role. SNL is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energys National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Excited Landau levels, orbital angular momentum and axial anomaly

    International Nuclear Information System (INIS)

    Teryaev, O.V.

    1993-01-01

    The IR cutoff via the exclusion of the high orbital momentum components for the excited Landau levels leads to the physical interpretation of the cancellation between the explicity and anomalous chiral symmetry breaking. 21 refs

  6. Electrically pumped graphene-based Landau-level laser

    Science.gov (United States)

    Brem, Samuel; Wendler, Florian; Winnerl, Stephan; Malic, Ermin

    2018-03-01

    Graphene exhibits a nonequidistant Landau quantization with tunable Landau-level (LL) transitions in the technologically desired terahertz spectral range. Here, we present a strategy for an electrically driven terahertz laser based on Landau-quantized graphene as the gain medium. Performing microscopic modeling of the coupled electron, phonon, and photon dynamics in such a laser, we reveal that an inter-LL population inversion can be achieved resulting in the emission of coherent terahertz radiation. The presented paper provides a concrete recipe for the experimental realization of tunable graphene-based terahertz laser systems.

  7. A novel method of including Landau level mixing in numerical studies of the quantum Hall effect

    International Nuclear Information System (INIS)

    Wooten, Rachel; Quinn, John; Macek, Joseph

    2013-01-01

    Landau level mixing should influence the quantum Hall effect for all except the strongest applied magnetic fields. We propose a simple method for examining the effects of Landau level mixing by incorporating multiple Landau levels into the Haldane pseudopotentials through exact numerical diagonalization. Some of the resulting pseudopotentials for the lowest and first excited Landau levels will be presented

  8. Landau Levels of Majorana Fermions in a Spin Liquid.

    Science.gov (United States)

    Rachel, Stephan; Fritz, Lars; Vojta, Matthias

    2016-04-22

    Majorana fermions, originally proposed as elementary particles acting as their own antiparticles, can be realized in condensed-matter systems as emergent quasiparticles, a situation often accompanied by topological order. Here we propose a physical system which realizes Landau levels-highly degenerate single-particle states usually resulting from an orbital magnetic field acting on charged particles-for Majorana fermions. This is achieved in a variant of a quantum spin system due to Kitaev which is distorted by triaxial strain. This strained Kitaev model displays a spin-liquid phase with charge-neutral Majorana-fermion excitations whose spectrum corresponds to that of Landau levels, here arising from a tailored pseudomagnetic field. We show that measuring the dynamic spin susceptibility reveals the Landau-level structure by a remarkable mechanism of probe-induced bound-state formation.

  9. Relativistic Landau levels in the rotating cosmic string spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, M.S. [Universidade Estadual do Ceara, Grupo de Fisica Teorica (GFT), Fortaleza, CE (Brazil); Muniz, C.R. [Universidade Estadual do Ceara, Faculdade de Educacao, Ciencias e Letras de Iguatu, Iguatu, CE (Brazil); Christiansen, H.R. [Instituto Federal de Ciencia, Educacao e Tecnologia, IFCE Departamento de Fisica, Sobral (Brazil); Bezerra, V.B. [Universidade Federal da Paraiba-UFPB, Departamento de Fisica, Caixa Postal 5008, Joao Pessoa, PB (Brazil)

    2016-09-15

    In the spacetime induced by a rotating cosmic string we compute the energy levels of a massive spinless particle coupled covariantly to a homogeneous magnetic field parallel to the string. Afterwards, we consider the addition of a scalar potential with a Coulomb-type and a linear confining term and completely solve the Klein-Gordon equations for each configuration. Finally, assuming rigid-wall boundary conditions, we find the Landau levels when the linear defect is itself magnetized. Remarkably, our analysis reveals that the Landau quantization occurs even in the absence of gauge fields provided the string is endowed with spin. (orig.)

  10. Bargmann representation for Landau levels in two dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Rohringer, Nina [Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Vienna (Austria); Burgdoerfer, Joachim [Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Vienna (Austria); Macris, Nicolas [Institut de Physique Theorique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    2003-04-11

    We present a formulation of the quantum mechanics of an electron gas confined to two dimensions in a strong magnetic field within the framework of the Hilbert space of analytic functions (Bargmann's space). Our approach extends the representation introduced by Girvin and Jach for the ground state to arbitrary Landau levels and to the regime of coupling between Landau levels. By projecting out the rapid cyclotron motion, the quantum mechanics of the slow guiding centre motion is converted into a system of coupled-channel equations describing the coupling between Landau levels due to the (disorder) potentials. In the limit of strong fields, the coupled-channel equations can be solved perturbatively. For the single-channel case we derive a WKB-like quantization condition for the one-dimensional motion along equipotential lines for arbitrary Landau levels. Two applications of this formalism are discussed: the weak-levitation problem in quantum Hall systems and a two-electron quantum dot in a strong magnetic field.

  11. Bargmann representation for Landau levels in two dimensions

    International Nuclear Information System (INIS)

    Rohringer, Nina; Burgdoerfer, Joachim; Macris, Nicolas

    2003-01-01

    We present a formulation of the quantum mechanics of an electron gas confined to two dimensions in a strong magnetic field within the framework of the Hilbert space of analytic functions (Bargmann's space). Our approach extends the representation introduced by Girvin and Jach for the ground state to arbitrary Landau levels and to the regime of coupling between Landau levels. By projecting out the rapid cyclotron motion, the quantum mechanics of the slow guiding centre motion is converted into a system of coupled-channel equations describing the coupling between Landau levels due to the (disorder) potentials. In the limit of strong fields, the coupled-channel equations can be solved perturbatively. For the single-channel case we derive a WKB-like quantization condition for the one-dimensional motion along equipotential lines for arbitrary Landau levels. Two applications of this formalism are discussed: the weak-levitation problem in quantum Hall systems and a two-electron quantum dot in a strong magnetic field

  12. Bargmann representation for Landau levels in two dimensions

    CERN Document Server

    Rohringer, N; Macris, N

    2003-01-01

    We present a formulation of the quantum mechanics of an electron gas confined to two dimensions in a strong magnetic field within the framework of the Hilbert space of analytic functions (Bargmann's space). Our approach extends the representation introduced by Girvin and Jach for the ground state to arbitrary Landau levels and to the regime of coupling between Landau levels. By projecting out the rapid cyclotron motion, the quantum mechanics of the slow guiding centre motion is converted into a system of coupled-channel equations describing the coupling between Landau levels due to the (disorder) potentials. In the limit of strong fields, the coupled-channel equations can be solved perturbatively. For the single-channel case we derive a WKB-like quantization condition for the one-dimensional motion along equipotential lines for arbitrary Landau levels. Two applications of this formalism are discussed: the weak-levitation problem in quantum Hall systems and a two-electron quantum dot in a strong magnetic field...

  13. Three-body interactions and the Landau levels using Nikiforov

    Indian Academy of Sciences (India)

    In this article, the eigenvalues for the three-body interactions on the line and the Landau levels in the presence of topological defects have been regenerated by the Nikiforov–Uvarov (NU) method. Two exhaustive lists of such exactly solvable potentials are given.

  14. Three-body interactions and the Landau levels using Nikiforov ...

    Indian Academy of Sciences (India)

    In this article, the eigenvalues for the three-body interactions on the line and the Landau levels in the presence of topological defects have been regenerated by the Nikiforov–Uvarov (NU) method. Two exhaustive lists of such exactly solvable potentials are given. Keywords. Nikiforov–Uvarov (NU) method; three-body ...

  15. Tuning of graphene nanoribbon Landau levels by a nanotube

    International Nuclear Information System (INIS)

    Li, T S; Chang, S C; Lin, M F

    2009-01-01

    We investigate theoretically the effects of a nanotube on the graphene nanoribbon Landau level spectrum utilizing the tight-binding model. The addition of a nanotube changes the original dispersionless Landau subbands into distorted parabolic ones, creates additional band-edge states, and modifies the subband spacings. Moreover, the dispersion relations rely sensitively on the nanotube location. The nanotube-ribbon couplings disrupt the Landau wavefunctions and lift their spatial symmetry, which will change the selection rule of optical transitions. The numbers, frequencies and heights of the density of states (DOS) peaks are found to be strongly dependent on the magnetic flux density and the nanotube location. The evolution of the DOS peak with the magnetic flux density is explored. The graphene nanoribbon Landau levels are shown to be modified in an unexpected fashion by the nanotube-ribbon interactions. These predictions can be validated by measuring the spectra of scanning tunneling experiments or magneto-optical experiments, and they are most observable by placing the nanotube at the electron wavefunction localization sites.

  16. Pulsar kicks with modified Urca and electrons in Landau levels

    International Nuclear Information System (INIS)

    Henley, Ernest M.; Johnson, Mikkel B.; Kisslinger, Leonard S.

    2007-01-01

    We derive the energy asymmetry given the protoneutron star during the time when the neutrino sphere is near the surface of the protoneutron star, using the modified Urca process. The electrons produced with the antineutrinos are in Landau levels due to the strong magnetic field, and this leads to asymmetry in the neutrino momentum, and a pulsar kick. The magnetic field must be strong enough for a large fraction of the electrons to be in the lowest Landau level; however, there is no direct dependence of our pulsar velocity on the strength of the magnetic field. Our main prediction is that the large pulsar kicks start at about 10 s and last for about 10 s, with the corresponding neutrinos correlated with the direction of the magnetic field. We predict a pulsar velocity of 1.03x10 -4 (T/10 10 K) 7 km/s, which reaches 1000 km/s if T≅10 11 K

  17. Raise and collapse of pseudo Landau levels in graphene

    Science.gov (United States)

    Castro, Eduardo V.; Cazalilla, Miguel A.; Vozmediano, María A. H.

    2017-12-01

    Lattice deformations couple to the low-energy electronic excitations of graphene as vector fields similar to the electromagnetic potential. The observation of strain-induced pseudo Landau levels with scanning tunnel microscopy experiments has been one of the most exciting events in the history of graphene. Nevertheless, the experimental observation presents some ambiguities. Similar strain patterns show different images that are sometimes difficult to interpret. In this Rapid Communication, we show that, for some strain configurations, the deformation potential acts as a parallel electric field able to destabilize the Landau level structure via a mechanism identical to that occurring for real electromagnetic fields. This effect also alters the estimations of the value of the pseudomagnetic field, which can be significantly bigger. The mechanism applies equally if the electric field has an external origin, which opens the door to an electric control of giant pseudomagnetic fields in graphene.

  18. Zero-field magnetic response functions in Landau levels

    Science.gov (United States)

    Gao, Yang; Niu, Qian

    2017-07-01

    We present a fresh perspective on the Landau level quantization rule; that is, by successively including zero-field magnetic response functions at zero temperature, such as zero-field magnetization and susceptibility, the Onsager’s rule can be corrected order by order. Such a perspective is further reinterpreted as a quantization of the semiclassical electron density in solids. Our theory not only reproduces Onsager’s rule at zeroth order and the Berry phase and magnetic moment correction at first order but also explains the nature of higher-order corrections in a universal way. In applications, those higher-order corrections are expected to curve the linear relation between the level index and the inverse of the magnetic field, as already observed in experiments. Our theory then provides a way to extract the correct value of Berry phase as well as the magnetic susceptibility at zero temperature from Landau level fan diagrams in experiments. Moreover, it can be used theoretically to calculate Landau levels up to second-order accuracy for realistic models.

  19. Landau levels and magneto-transport property of monolayer phosphorene

    Science.gov (United States)

    Zhou, X. Y.; Zhang, R.; Sun, J. P.; Zou, Y. L.; Zhang, D.; Lou, W. K.; Cheng, F.; Zhou, G. H.; Zhai, F.; Chang, Kai

    2015-01-01

    We investigate theoretically the Landau levels (LLs) and magneto-transport properties of phosphorene under a perpendicular magnetic field within the framework of the effective k·p Hamiltonian and tight-binding (TB) model. At low field regime, we find that the LLs linearly depend both on the LL index n and magnetic field B, which is similar with that of conventional semiconductor two-dimensional electron gas. The Landau splittings of conduction and valence band are different and the wavefunctions corresponding to the LLs are strongly anisotropic due to the different anisotropic effective masses. An analytical expression for the LLs in low energy regime is obtained via solving the decoupled Hamiltonian, which agrees well with the numerical calculations. At high magnetic regime, a self-similar Hofstadter butterfly (HB) spectrum is obtained by using the TB model. The HB spectrum is consistent with the LL fan calculated from the effective k·p theory in a wide regime of magnetic fields. We find the LLs of phosphorene nanoribbon depend strongly on the ribbon orientation due to the anisotropic hopping parameters. The Hall and the longitudinal conductances (resistances) clearly reveal the structure of LLs. PMID:26159856

  20. Pseudo Landau levels and quantum oscillations in strained Weyl semimetals

    Science.gov (United States)

    Alisultanov, Z. Z.

    2018-05-01

    The crystal lattice deformation in Weyl materials where the two chiralities are separated in momentum space leads to the appearance of gauge pseudo-fields. We investigated the pseudo-magnetic field induced quantum oscillations in strained Weyl semimetal (WSM). In contrast to all previous works on this problem, we use here a more general tilted Hamiltonian. Such Hamiltonian, seems to be is more suitable for a strained WSMs. We have shown that a pseudo-magnetic field induced magnetization of strained WSM is nonzero due to the fact that electric field (gradient of the deformation potential) is induced simultaneously with the pseudo-magnetic field. This related with fact that the pseudo Landau levels (LLs) in strained WSM are differ in vicinities of different WPs due to the presence of tilt in spectrum. Such violation of the equivalence between Weyl points (WPs) leads to modulation of quantum oscillations. We also showed that magnetization magnitude can be changed by application of an external electric field. In particular, it can be reduced to zero. The possibility of controlling of the magnetization by an electric field is interesting both from a fundamental point of view (a new type of magneto-electric effect) and application point of view (additional possibility to control diamagnetism of deformed WSMs). Finally, a coexistence of type-I and type-II Weyl fermions is possible in the system under investigation. Such phase is absolutely new for physics of topological systems.

  1. Observation of roton density of states in two-dimensional Landau-level excitations

    International Nuclear Information System (INIS)

    Pinczuk, A.; Valladares, J.P.; Heiman, D.; Gossard, A.C.; English, J.H.; Tu, C.W.; Pfeiffer, L.; West, K.

    1988-01-01

    Inelastic light scattering by inter-Landau-level excitations of the 2D electron gas in high-mobility GaAs structures in a perpendicular magnetic field was observed at the energies of the critical points in the mode dispersions. For Landau-level filling factors /nu//ge/, structure in the spectra indicates the excitonic binding and roton behavior predicted by the Hartree-Fock approximation. The large critical-point wave vectors, qapprox. >((h/2/pi/)c/eB)/sup -1/2/approx. >10/sup 6/ cm/sup -1/, are probably accessible in resonant light scattering through the residual disorder that broadens the Landau levels

  2. Competing Quantum Hall Phases in the Second Landau Level in Low Density Limit

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Wei [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Serafin, A. [Univ. of Florida, Gainesville, FL (United States). National High Magnetic Field Lab. (MagLab); Xia, J. S. [Univ. of Florida, Gainesville, FL (United States). National High Magnetic Field Lab. (MagLab); Liang, Y. [Univ. of Florida, Gainesville, FL (United States). National High Magnetic Field Lab. (MagLab); Sullivan, N. S. [Univ. of Florida, Gainesville, FL (United States). National High Magnetic Field Lab. (MagLab); Baldwin, K. W. [Princeton Univ., NJ (United States); West, K. W. [Princeton Univ., NJ (United States); Pfeiffer, L. N. [Princeton Univ., NJ (United States); Tsui, D. C. [Princeton Univ., NJ (United States)

    2015-01-01

    Up to date, studies of the fractional quantum Hall effect (FQHE) states in the second Landau level have mainly been carried out in the high electron density regime, where the electron mobility is the highest. Only recently, with the advance of high quality low density MBE growth, experiments have been pushed to the low density regime [1], where the electron-electron interactions are strong and the Landau level mixing parameter, defined by κ = e2/εIB/ℏωe, is large. Here, lB = (ℏe/B)1/2 is the magnetic length and ωc = eB/m the cyclotron frequency. All other parameters have their normal meanings. It has been shown that a large Landau level mixing effect strongly affects the electron physics in the second Landau level [2].

  3. STS Observations of Landau Levels at Graphite Surfaces

    OpenAIRE

    Matsui, T.; Kambara, H.; Niimi, Y.; Tagami, K.; Tsukada, M.; Fukuyama, Hiroshi

    2004-01-01

    Scanning tunneling spectroscopy measurements were made on surfaces of two different kinds of graphite samples, Kish graphite and highly oriented pyrolytic graphite (HOPG), at very low temperatures and in high magnetic fields. We observed a series of peaks in the tunnel spectra, which grow with increasing field, both at positive and negative bias voltages. These are associated with Landau quantization of the quasi two-dimensional electrons and holes in graphite in magnetic fields perpendicular...

  4. Impact of Many-Body Effects on Landau Levels in Graphene

    Science.gov (United States)

    Sonntag, J.; Reichardt, S.; Wirtz, L.; Beschoten, B.; Katsnelson, M. I.; Libisch, F.; Stampfer, C.

    2018-05-01

    We present magneto-Raman spectroscopy measurements on suspended graphene to investigate the charge carrier density-dependent electron-electron interaction in the presence of Landau levels. Utilizing gate-tunable magnetophonon resonances, we extract the charge carrier density dependence of the Landau level transition energies and the associated effective Fermi velocity vF. In contrast to the logarithmic divergence of vF at zero magnetic field, we find a piecewise linear scaling of vF as a function of the charge carrier density, due to a magnetic-field-induced suppression of the long-range Coulomb interaction. We quantitatively confirm our experimental findings by performing tight-binding calculations on the level of the Hartree-Fock approximation, which also allow us to estimate an excitonic binding energy of ≈6 meV contained in the experimentally extracted Landau level transitions energies.

  5. Terahertz imaging of Landau levels in HgTe-based topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Kadykov, Aleksandr M.; Krishtopenko, Sergey S. [Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS–Université de Montpellier, Montpellier (France); Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation); Torres, Jeremie [Institut d' Electronique et des Systèmes (IES), UMR 5214 CNRS–Université de Montpellier, Montpellier (France); Consejo, Christophe; Ruffenach, Sandra; Marcinkiewicz, Michal; But, Dmytro; Teppe, Frederic, E-mail: frederic.teppe@umontpellier.fr [Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS–Université de Montpellier, Montpellier (France); Knap, Wojciech [Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS–Université de Montpellier, Montpellier (France); Institute of High Pressure Institute Physics, Polish Academy of Sciences, 01-447 Warsaw (Poland); Morozov, Sergey V.; Gavrilenko, Vladimir I. [Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Mikhailov, Nikolai N. [Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent' eva 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Dvoretsky, Sergey A. [Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent' eva 13, 630090 Novosibirsk (Russian Federation)

    2016-06-27

    We report on sub-terahertz photoconductivity under the magnetic field of a two dimensional topological insulator based on HgTe quantum wells. We perform a detailed visualization of Landau levels by means of photoconductivity measured at different gate voltages. This technique allows one to determine a critical magnetic field, corresponding to topological phase transition from inverted to normal band structure, even in almost gapless samples. The comparison with realistic calculations of Landau levels reveals a smaller role of bulk inversion asymmetry in HgTe quantum wells than it was assumed previously.

  6. Tuning the effects of Landau level mixing on anisotropic transport in quantum Hall systems

    International Nuclear Information System (INIS)

    Smith, Peter M; Kennett, Malcolm P

    2012-01-01

    Electron-electron interactions in half-filled high Landau levels in two-dimensional electron gases in a strong perpendicular magnetic field can lead to states with anisotropic longitudinal resistance. This longitudinal resistance is generally believed to arise from broken rotational invariance, which is indicated by charge density wave order in Hartree-Fock calculations. We use the Hartree-Fock approximation to study the influence of externally tuned Landau level mixing on the formation of interaction-induced states that break rotational invariance in two-dimensional electron and hole systems. We focus on the situation when there are two non-interacting states in the vicinity of the Fermi level and construct a Landau theory to study coupled charge density wave order that can occur as interactions are tuned and the filling or mixing are varied. We consider numerically a specific example where mixing is tuned externally through Rashba spin-orbit coupling. We calculate the phase diagram and find the possibility of ordering involving coupled striped or triangular charge density waves in the two levels. Our results may be relevant to recent transport experiments on quantum Hall nematics in which Landau level mixing plays an important role. (paper)

  7. Degeneracy of the lowest Landau level and suq(2) on the Poincare half plane

    International Nuclear Information System (INIS)

    Jellal, A.

    2000-01-01

    It is shown that the presence of the quantum group symmetry su q (2) in the quantum Hall effect on the Poincare upper half plane the degeneracy of the lowest Landau level. It is also shown that the relation between the degeneracy and the cyclic representation of su q (2) appears in accordance with q being a kth root of unity. (Authors)

  8. Fine structure of the lowest Landau level in suspended trilayer graphene

    NARCIS (Netherlands)

    van Elferen, H. J.; Veligura, A.; Tombros, N.; Kurganova, E. V.; van Wees, B. J.; Maan, J. C.; Zeitler, U.

    2013-01-01

    Magnetotransport experiments on ABC-stacked suspended trilayer graphene reveal a complete splitting of the 12-fold degenerated lowest Landau level, and, in particular, the opening of an exchange-driven gap at the charge neutrality point. A quantitative analysis of distinctness of the quantum Hall

  9. Quantum transport in graphene in presence of strain-induced pseudo-Landau levels

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Leconte, Nicolas; Barrios-Vargas, Jose E.

    2016-01-01

    We report on mesoscopic transport fingerprints in disordered graphene caused by strain-field induced pseudomagnetic Landau levels (pLLs). Efficient numerical real space calculations of the Kubo formula are performed for an ordered network of nanobubbles in graphene, creating pseudomagnetic fields...

  10. Landau and modern physics

    International Nuclear Information System (INIS)

    Pokrovsky, Valery L

    2009-01-01

    This article describes the history of the creation and further development of Landau's famous works on phase transitions, diamagnetism of electron gas (Landau levels), and quantum transitions at a level crossing (the Landau-Zener phenomenon), and its role in modern physics. (methodological notes)

  11. The effect of exchange interaction on quasiparticle Landau levels in narrow-gap quantum well heterostructures.

    Science.gov (United States)

    Krishtopenko, S S; Gavrilenko, V I; Goiran, M

    2012-04-04

    Using the 'screened' Hartree-Fock approximation based on the eight-band k·p Hamiltonian, we have extended our previous work (Krishtopenko et al 2011 J. Phys.: Condens. Matter 23 385601) on exchange enhancement of the g-factor in narrow-gap quantum well heterostructures by calculating the exchange renormalization of quasiparticle energies, the density of states at the Fermi level and the quasiparticle g-factor for different Landau levels overlapping. We demonstrate that exchange interaction yields more pronounced Zeeman splitting of the density of states at the Fermi level and leads to the appearance of peak-shaped features in the dependence of the Landau level energies on the magnetic field at integer filling factors. We also find that the quasiparticle g-factor does not reach the maximum value at odd filling factors in the presence of large overlapping of spin-split Landau levels. We advance an argument that the behavior of the quasiparticle g-factor in weak magnetic fields is defined by a random potential of impurities in narrow-gap heterostructures. © 2012 IOP Publishing Ltd

  12. On the landau levels on the hyperbolic plane

    International Nuclear Information System (INIS)

    Comtet, A.

    1986-04-01

    The classical and quantum mechanics of a charged particle moving on the hyperbolic plane in a constant magnetic field is discussed. The underlying SL(2,R) symmetry leads to a general description of various possible trajectories. In contrast with the flat case, it is shown that closed orbits only arise for sufficiently strong fields. At the quantum level a group theoretical approach including both bound and continuum states is presented. It is shown that the semiclassical approximation leads to the exact bound state spectrum. The resolvent and its flat space limit are constructed in closed form

  13. Dynamic nuclear polarization at high Landau levels in a quantum point contact

    Science.gov (United States)

    Fauzi, M. H.; Noorhidayati, A.; Sahdan, M. F.; Sato, K.; Nagase, K.; Hirayama, Y.

    2018-05-01

    We demonstrate a way to polarize and detect nuclear spin in a gate-defined quantum point contact operating at high Landau levels. Resistively detected nuclear magnetic resonance (RDNMR) can be achieved up to the fifth Landau level and at a magnetic field lower than 1 T. We are able to retain the RDNMR signals in a condition where the spin degeneracy of the first one-dimensional (1D) subband is still preserved. Furthermore, the effects of orbital motion on the first 1D subband can be made smaller than those due to electrostatic confinement. This developed RDNMR technique is a promising means to study electronic states in a quantum point contact near zero magnetic field.

  14. Analysis of generalized negative binomial distributions attached to hyperbolic Landau levels

    International Nuclear Information System (INIS)

    Chhaiba, Hassan; Demni, Nizar; Mouayn, Zouhair

    2016-01-01

    To each hyperbolic Landau level of the Poincaré disc is attached a generalized negative binomial distribution. In this paper, we compute the moment generating function of this distribution and supply its atomic decomposition as a perturbation of the negative binomial distribution by a finitely supported measure. Using the Mandel parameter, we also discuss the nonclassical nature of the associated coherent states. Next, we derive a Lévy-Khintchine-type representation of its characteristic function when the latter does not vanish and deduce that it is quasi-infinitely divisible except for the lowest hyperbolic Landau level corresponding to the negative binomial distribution. By considering the total variation of the obtained quasi-Lévy measure, we introduce a new infinitely divisible distribution for which we derive the characteristic function.

  15. Analysis of generalized negative binomial distributions attached to hyperbolic Landau levels

    Energy Technology Data Exchange (ETDEWEB)

    Chhaiba, Hassan, E-mail: chhaiba.hassan@gmail.com [Department of Mathematics, Faculty of Sciences, Ibn Tofail University, P.O. Box 133, Kénitra (Morocco); Demni, Nizar, E-mail: nizar.demni@univ-rennes1.fr [IRMAR, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Mouayn, Zouhair, E-mail: mouayn@fstbm.ac.ma [Department of Mathematics, Faculty of Sciences and Technics (M’Ghila), Sultan Moulay Slimane, P.O. Box 523, Béni Mellal (Morocco)

    2016-07-15

    To each hyperbolic Landau level of the Poincaré disc is attached a generalized negative binomial distribution. In this paper, we compute the moment generating function of this distribution and supply its atomic decomposition as a perturbation of the negative binomial distribution by a finitely supported measure. Using the Mandel parameter, we also discuss the nonclassical nature of the associated coherent states. Next, we derive a Lévy-Khintchine-type representation of its characteristic function when the latter does not vanish and deduce that it is quasi-infinitely divisible except for the lowest hyperbolic Landau level corresponding to the negative binomial distribution. By considering the total variation of the obtained quasi-Lévy measure, we introduce a new infinitely divisible distribution for which we derive the characteristic function.

  16. Partially filled Landau level at even denominators: A vortex metal with a Berry phase

    Science.gov (United States)

    You, Yizhi

    2018-04-01

    We develop a vortex metal theory for a partially filled Landau level at ν =1/2 n whose ground state contains a composite Fermi surface formed by the vortex of electrons. In the projected Landau-level limit, the composite Fermi surface contains a -π/n Berry phase. Such a fractional Berry phase is a consequence of Landau-level projection which produces the Girvin-MacDonald-Platzman [S. M. Girvin, A. H. MacDonald, and P. M. Platzman, Phys. Rev. B 33, 2481 (1986), 10.1103/PhysRevB.33.2481] guiding center algebra and embellishes an anomalous velocity to the equation of motion for the vortex metal. Further, we investigate a particle-hole symmetric bilayer system with ν1=1/2 n and ν2=1 -1/2 n at each layer, and demonstrate that the -π/n Berry phase on the composite Fermi surface leads to the suppression of 2 kf backscattering between the particle-hole partner bilayer, which could be a smoking gun to detect the fractional Berry phase. We also mention various instabilities and competing orders in such bilayer systems, including a Z4 n topological order phase driven by quantum criticality.

  17. Fractional charge and inter-Landau-level states at points of singular curvature.

    Science.gov (United States)

    Biswas, Rudro R; Son, Dam Thanh

    2016-08-02

    The quest for universal properties of topological phases is fundamentally important because these signatures are robust to variations in system-specific details. Aspects of the response of quantum Hall states to smooth spatial curvature are well-studied, but challenging to observe experimentally. Here we go beyond this prevailing paradigm and obtain general results for the response of quantum Hall states to points of singular curvature in real space; such points may be readily experimentally actualized. We find, using continuum analytical methods, that the point of curvature binds an excess fractional charge and sequences of quantum states split away, energetically, from the degenerate bulk Landau levels. Importantly, these inter-Landau-level states are bound to the topological singularity and have energies that are universal functions of bulk parameters and the curvature. Our exact diagonalization of lattice tight-binding models on closed manifolds demonstrates that these results continue to hold even when lattice effects are significant. An important technological implication of these results is that these inter-Landau-level states, being both energetically and spatially isolated quantum states, are promising candidates for constructing qubits for quantum computation.

  18. Chern-Simons field theory of two-dimensional electrons in the lowest Landau level

    International Nuclear Information System (INIS)

    Zhang, L.

    1996-01-01

    We propose a fermion Chern-Simons field theory describing two-dimensional electrons in the lowest Landau level. This theory is constructed with a complete set of states, and the lowest-Landau-level constraint is enforced through a δ functional described by an auxiliary field λ. Unlike the field theory constructed directly with the states in the lowest Landau level, this theory allows one, utilizing the physical picture of open-quote open-quote composite fermion,close-quote close-quote to study the fractional quantum Hall states by mapping them onto certain integer quantum Hall states; but, unlike its application in the unconstrained theory, such a mapping is sensible only when interactions between electrons are present. An open-quote open-quote effective mass,close-quote close-quote which characterizes the scale of low energy excitations in the fractional quantum Hall systems, emerges naturally from our theory. We study a Gaussian effective theory and interpret physically the dressed stationary point equation for λ as an equation for the open-quote open-quote mass renormalization close-quote close-quote of composite fermions. copyright 1996 The American Physical Society

  19. Validity of the lowest-Landau-level approximation for rotating Bose gases

    International Nuclear Information System (INIS)

    Morris, Alexis G.; Feder, David L.

    2006-01-01

    The energy spectrum for an ultracold rotating Bose gas in a harmonic trap is calculated exactly for small systems, allowing the atoms to occupy several Landau levels. Two vortexlike states and two strongly correlated states (the Pfaffian and Laughlin) are considered in detail. In particular, their critical rotation frequencies and energy gaps are determined as a function of particle number, interaction strength, and the number of Landau levels occupied (up to three). For the vortexlike states, the lowest-Landau-level (LLL) approximation is justified only if the interaction strength decreases with the number of particles; nevertheless, the constant of proportionality increases rapidly with the angular momentum per particle. For the strongly correlated states, however, the interaction strength can increase with particle number without violating the LLL condition. The results suggest that, in large systems, the Pfaffian and Laughlin states might be stabilized at rotation frequencies below the centrifugal limit for sufficiently large interaction strengths, with energy gaps a significant fraction of the trap energy

  20. Magneto-transport in the zero-energy Landau level of single-layer and bilayer graphene

    International Nuclear Information System (INIS)

    Zeitler, U; Giesbers, A J M; Elferen, H J van; Kurganova, E V; McCollam, A; Maan, J C

    2011-01-01

    We present recent low-temperature magnetotransport experiments on single-layer and bilayer graphene in high magnetic field up to 33 T. In single layer graphene the fourfold degeneracy of the zero-energy Landau level is lifted by a gap opening at filling factor ν = 0. In bilayer graphene, we observe a partial lifting of the degeneracy of the eightfold degenerate zero-energy Landau level.

  1. Electric-field induced spin accumulation in the Landau level states of topological insulator thin films

    Science.gov (United States)

    Siu, Zhuo Bin; Chowdhury, Debashree; Basu, Banasri; Jalil, Mansoor B. A.

    2017-08-01

    A topological insulator (TI) thin film differs from the more typically studied thick TI system in that the former has both a top and a bottom surface where the states localized at both surfaces can couple to one other across the finite thickness. An out-of-plane magnetic field leads to the formation of discrete Landau level states in the system, whereas an in-plane magnetization breaks the angular momentum symmetry of the system. In this work, we study the spin accumulation induced by the application of an in-plane electric field to the TI thin film system where the Landau level states and inter-surface coupling are simultaneously present. We show, via Kubo formula calculations, that the in-plane spin accumulation perpendicular to the magnetization due to the electric field vanishes for a TI thin film with symmetric top and bottom surfaces. A finite in-plane spin accumulation perpendicular to both the electric field and magnetization emerges upon applying either a differential magnetization coupling or a potential difference between the two film surfaces. This spin accumulation results from the breaking of the antisymmetry of the spin accumulation around the k-space equal-energy contours.

  2. Investigation of Landau level spin reversal in (110) oriented p-type GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Isik, Nebile

    2009-09-01

    In this thesis, the Landau level crossing or anticrossing of hole levels has been investigated in p-type GaAs 400 Aa wide quantum wells. In magneto-transport measurements, this is evidenced with the presence of an anomalous peak in the longitudinal resistance measurements at {nu}=1. In the transversal resistance measurements, no signature of this anomalous peak is observed. By increasing the hole density in the quantum well by applying a top gate voltage, the position of the anomalous peak shifts to higher magnetic fields. At very high densities, anomalous peak disappears. By applying a back gate voltage, the electric field in the quantum well is tuned. A consequence is that the geometry of the quantum well is tuned from square to triangular. The anomalous peak position is shown to depend also on the back gate voltage applied. Temperature dependence of the peak height is consistent with thermal activation energy gap ({delta}/2= 135 {mu}eV). The activation energy gap as a function of the magnetic field has a parabolic like dependence, with the minimum of 135 {mu}eV at 4 T. The peak magnitude is observed to decrease with increasing temperature. An additional peak is observed at {nu}=2 minimum. This additional peak at {nu}=2 might be due to the higher Landau level crossing. The p-type quantum wells have been investigated by photoluminescence spectroscopy, as a function of the magnetic field. The polarization of the emitted light has been analyzed in order to distinguish between the transitions related to spin of electron {+-} 1/2 and spin of hole -+ 3/2. The transition energies of the lowest electron Landau levels with spin {+-} 1/2 and hole Landau levels with spin -+ 3/2 versus magnetic field show crossing at 4 T. The heavy hole Landau levels with spins {+-} 3/2 are obtained by the substraction of transition energies from the sum of lowest electron Landau level energy and the energy gap of GaAs. The heavy hole Landau levels show a crossing at 4 T. However, due to the

  3. Stability of zero-mode Landau levels in bilayer graphene against disorder in the presence of the trigonal warping

    International Nuclear Information System (INIS)

    Kawarabayashi, Tohru; Hasugai, Yasuhiro; Aoki, Hideo

    2013-01-01

    The stability of the zero-energy Landau levels in bilayer graphene against the chiral symmetric disorder is examined in the presence of the trigonal warping. Based on the tight-binding lattice model with a bond disorder correlated over several lattice constants, it is shown that among the four Landau levels per spin and per valley, two Landau levels exhibit the anomalous sharpness as in the absence of the trigonal warping, while the other two are broadened, yielding split peaks in the density of states. This can be attributed to the fact that the total chirality in each valley is ±2, which is protected topologically even in the presence of an intra-valley scattering due to disorder

  4. Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole.

    Science.gov (United States)

    Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

    2018-03-30

    We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s-wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

  5. Quantum driving protocols for a two-level system: From generalized Landau-Zener sweeps to transitionless control

    DEFF Research Database (Denmark)

    Malossi, Nicola; Bason, Mark George; Viteau, Matthieu

    2013-01-01

    We present experimental results on the preparation of a desired quantum state in a two-level system with the maximum possible fidelity using driving protocols ranging from generalizations of the linear Landau-Zener protocol to transitionless driving protocols that ensure perfect following of the ...

  6. Thermoelectric Transport Signatures of Dirac Composite Fermions in the Half-Filled Landau Level

    Science.gov (United States)

    Potter, Andrew C.; Serbyn, Maksym; Vishwanath, Ashvin

    2016-07-01

    The half-filled Landau level is expected to be approximately particle-hole symmetric, which requires an extension of the Halperin-Lee-Read (HLR) theory of the compressible state observed at this filling. Recent work indicates that, when particle-hole symmetry is preserved, the composite fermions experience a quantized π -Berry phase upon winding around the composite Fermi surface, analogous to Dirac fermions at the surface of a 3D topological insulator. In contrast, the effective low-energy theory of the composite fermion liquid originally proposed by HLR lacks particle-hole symmetry and has vanishing Berry phase. In this paper, we explain how thermoelectric transport measurements can be used to test the Dirac nature of the composite fermions by quantitatively extracting this Berry phase. First, we point out that longitudinal thermopower (Seebeck effect) is nonvanishing because of the unusual nature of particle-hole symmetry in this context and is not sensitive to the Berry phase. In contrast, we find that off-diagonal thermopower (Nernst effect) is directly related to the topological structure of the composite Fermi surface, vanishing for zero Berry phase and taking its maximal value for π Berry phase. In contrast, in purely electrical transport signatures, the Berry phase contributions appear as small corrections to a large background signal, making the Nernst effect a promising diagnostic of the Dirac nature of composite fermions.

  7. Composite Fermi surface in the half-filled Landau level with anisotropic electron mass

    Science.gov (United States)

    Ippoliti, Matteo; Geraedts, Scott; Bhatt, Ravindra

    We study the problem of interacting electrons in the lowest Landau level at half filling in the quantum Hall regime, when the electron dispersion is given by an anisotropic mass tensor. Based on experimental observations and theoretical arguments, the ground state of the system is expected to consist of composite Fermions filling an elliptical Fermi sea, with the anisotropy of the ellipse determined by the competing effects of the isotropic Coulomb interaction and anisotropic electron mass tensor. We test this idea quantitatively by using a numerical density matrix renormalization group method for quantum Hall systems on an infinitely long cylinder. Singularities in the structure factor allow us to map the Fermi surface of the composite Fermions. We compute the composite Fermi surface anisotropy for several values of the electron mass anisotropy which allow us to deduce the functional dependence of the former on the latter. This research was supported by Department of Energy Office of Basic Energy Sciences through Grant No. DE-SC0002140.

  8. Landau levels in biased graphene structures with monolayer-bilayer interfaces

    Science.gov (United States)

    Mirzakhani, M.; Zarenia, M.; Vasilopoulos, P.; Ketabi, S. A.; Peeters, F. M.

    2017-09-01

    The electron energy spectrum in monolayer-bilayer-monolayer and in bilayer-monolayer-bilayer graphene structures is investigated and the effects of a perpendicular magnetic field and electric bias are studied. Different types of monolayer-bilayer interfaces are considered as zigzag (ZZ) or armchair (AC) junctions which modify considerably the bulk Landau levels (LLs) when the spectra are plotted as a function of the center coordinate of the cyclotron orbit. Far away from the two interfaces, one obtains the well-known LLs for extended monolayer or bilayer graphene. The LL structure changes significantly at the two interfaces or junctions where the valley degeneracy is lifted for both types of junctions, especially when the distance between them is approximately equal to the magnetic length. Varying the nonuniform bias and the width of this junction-to-junction region in either structure strongly influence the resulting spectra. Significant differences exist between ZZ and AC junctions in both structures. The densities of states (DOSs) for unbiased structures are symmetric in energy whereas those for biased structures are asymmetric. An external bias creates interface LLs in the gaps between the LLs of the unbiased system in which the DOS can be quite small. Such a pattern of LLs can be probed by scanning tunneling microscopy.

  9. Weiss oscillations and particle-hole symmetry at the half-filled Landau level

    Science.gov (United States)

    Cheung, Alfred K. C.; Raghu, S.; Mulligan, Michael

    2017-06-01

    Particle-hole symmetry in the lowest Landau level of the two-dimensional electron gas requires the electrical Hall conductivity to equal ±e2/2 h at half filling. We study the consequences of weakly broken particle-hole symmetry for magnetoresistance oscillations about half filling in the presence of an applied periodic one-dimensional electrostatic potential using the Dirac composite fermion theory proposed by Son [Son, Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027]. At fixed electron density, the oscillation minima are asymmetrically biased towards higher magnetic fields, while at fixed magnetic field the oscillations occur symmetrically as the electron density is varied about half filling. We find an approximate "sum rule" obeyed for all pairs of oscillation minima that can be tested in experiment. The locations of the magnetoresistance oscillation minima for the composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole conjugate agree exactly. Within the current experimental resolution, the locations of the oscillation minima produced by the Dirac composite fermion coincide with those of HLR. These results may indicate that all three composite fermion theories describe the same long-wavelength physics.

  10. Landau-level spectroscopy of massive Dirac fermions in single-crystalline ZrTe5 thin flakes

    Science.gov (United States)

    Jiang, Y.; Dun, Z. L.; Zhou, H. D.; Lu, Z.; Chen, K.-W.; Moon, S.; Besara, T.; Siegrist, T. M.; Baumbach, R. E.; Smirnov, D.; Jiang, Z.

    2017-07-01

    We report infrared magnetospectroscopy studies on thin crystals of an emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure of the Landau-level transitions and zero-field infrared absorption indicate a two-dimensional Dirac-like electronic structure, similar to that in graphene but with a small relativistic mass corresponding to a 9.4-meV energy gap. Measurements with circularly polarized light reveal a significant electron-hole asymmetry, which leads to splitting of the Landau-level transitions at high magnetic fields. Our model, based on the Bernevig-Hughes-Zhang effective Hamiltonian, quantitatively explains all observed transitions, determining the values of the Fermi velocity, Dirac mass (or gap), electron-hole asymmetry, and electron and hole g factors.

  11. Unusual interlayer quantum transport behavior caused by the zeroth Landau level in YbMnBi2.

    Science.gov (United States)

    Liu, J Y; Hu, J; Graf, D; Zou, T; Zhu, M; Shi, Y; Che, S; Radmanesh, S M A; Lau, C N; Spinu, L; Cao, H B; Ke, X; Mao, Z Q

    2017-09-21

    Relativistic fermions in topological quantum materials are characterized by linear energy-momentum dispersion near band crossing points. Under magnetic fields, relativistic fermions acquire Berry phase of π in cyclotron motion, leading to a zeroth Landau level (LL) at the crossing point, a signature unique to relativistic fermions. Here we report the unusual interlayer quantum transport behavior resulting from the zeroth LL mode observed in the time reversal symmetry breaking type II Weyl semimetal YbMnBi 2 . The interlayer magnetoresistivity and Hall conductivity of this material are found to exhibit surprising angular dependences under high fields, which can be well fitted by a model, which considers the interlayer quantum tunneling transport of the zeroth LL's Weyl fermions. Our results shed light on the unusual role of zeroth LLl mode in transport.The transport behavior of the carriers residing in the lowest Landau level is hard to observe in most topological materials. Here, Liu et al. report a surprising angular dependence of the interlayer magnetoresistivity and Hall conductivity arising from the lowest Landau level under high magnetic field in type II Weyl semimetal YbMnBi 2 .

  12. Splitting of the zero-energy Landau level and universal dissipative conductivity at critical points in disordered graphene.

    Science.gov (United States)

    Ortmann, Frank; Roche, Stephan

    2013-02-22

    We report on robust features of the longitudinal conductivity (σ(xx)) of the graphene zero-energy Landau level in the presence of disorder and varying magnetic fields. By mixing an Anderson disorder potential with a low density of sublattice impurities, the transition from metallic to insulating states is theoretically explored as a function of Landau-level splitting, using highly efficient real-space methods to compute the Kubo conductivities (both σ(xx) and Hall σ(xy)). As long as valley degeneracy is maintained, the obtained critical conductivity σ(xx) =/~ 1.4e(2)/h is robust upon an increase in disorder (by almost 1 order of magnitude) and magnetic fields ranging from about 2 to 200 T. When the sublattice symmetry is broken, σ(xx) eventually vanishes at the Dirac point owing to localization effects, whereas the critical conductivities of pseudospin-split states (dictating the width of a σ(xy) = 0 plateau) change to σ(xx) =/~ e(2)/h, regardless of the splitting strength, superimposed disorder, or magnetic strength. These findings point towards the nondissipative nature of the quantum Hall effect in disordered graphene in the presence of Landau level splitting.

  13. Landau levels from neutral Bogoliubov particles in two-dimensional nodal superconductors under strain and doping gradients

    Science.gov (United States)

    Nica, Emilian M.; Franz, Marcel

    2018-02-01

    Motivated by recent work on strain-induced pseudomagnetic fields in Dirac and Weyl semimetals, we analyze the possibility of analogous fields in two-dimensional nodal superconductors. We consider the prototypical case of a d -wave superconductor, a representative of the cuprate family, and find that the presence of weak, spatially varying strain leads to pseudomagnetic fields and Landau quantization of Bogoliubov quasiparticles in the low-energy sector. A similar effect is induced by the presence of generic, weak doping gradients. In contrast to genuine magnetic fields in superconductors, the strain- and doping-gradient-induced pseudomagnetic fields couple in a way that preserves time-reversal symmetry and is not subject to the screening associated with the Meissner effect. These effects can be probed by tuning weak applied supercurrents which lead to shifts in the energies of the Landau levels and hence to quantum oscillations in thermodynamic and transport quantities.

  14. The Interplay of Rashba Spin-Orbit Interaction and Landau Level Broadening on a Two-Dimensional Electron Gas Under a Tilted Magnetic Field

    International Nuclear Information System (INIS)

    Gammag, Rayda; Villagonzalo, Cristine

    2012-01-01

    A two-dimensional electron gas in a tilted magnetic field with Rashba spin-orbit interaction (RSOI) was studied. The RSOI is accredited to the asymmetry of the heterostructure where the two-dimensional electron gas is found. The effects of the disorder-attributed Landau level broadening and the RSOI on the spin splitting were identified by simulating the density of states which was assumed to take a Gaussian shape. Increased Landau level broadening obscures the spin splitting and increases the overlap between spin states resulting to stout Gaussian peaks. On the other hand, stronger RSOI amplifies the splitting and lessens the overlap between spin states of the Landau levels. The splitting, however, results to stouter peaks. The similarity in the RSOI and Landau level broadening effects can be explained by recognizing that the asymmetry of the heterostructure is in itself a form of structural disorder.

  15. Inhomogeneous Weyl and Dirac Semimetals: Transport in Axial Magnetic Fields and Fermi Arc Surface States from Pseudo-Landau Levels

    Science.gov (United States)

    Grushin, Adolfo G.; Venderbos, Jörn W. F.; Vishwanath, Ashvin; Ilan, Roni

    2016-10-01

    Topological Dirac and Weyl semimetals have an energy spectrum that hosts Weyl nodes appearing in pairs of opposite chirality. Topological stability is ensured when the nodes are separated in momentum space and unique spectral and transport properties follow. In this work, we study the effect of a space-dependent Weyl node separation, which we interpret as an emergent background axial-vector potential, on the electromagnetic response and the energy spectrum of Weyl and Dirac semimetals. This situation can arise in the solid state either from inhomogeneous strain or nonuniform magnetization and can also be engineered in cold atomic systems. Using a semiclassical approach, we show that the resulting axial magnetic field B5 is observable through an enhancement of the conductivity as σ ˜B52 due to an underlying chiral pseudomagnetic effect. We then use two lattice models to analyze the effect of B5 on the spectral properties of topological semimetals. We describe the emergent pseudo-Landau-level structure for different spatial profiles of B5, revealing that (i) the celebrated surface states of Weyl semimetals, the Fermi arcs, can be reinterpreted as n =0 pseudo-Landau levels resulting from a B5 confined to the surface, (ii) as a consequence of position-momentum locking, a bulk B5 creates pseudo-Landau levels interpolating in real space between Fermi arcs at opposite surfaces, and (iii) there are equilibrium bound currents proportional to B5 that average to zero over the sample, which are the analogs of bound currents in magnetic materials. We conclude by discussing how our findings can be probed experimentally.

  16. The constraint for the lowest Landau level and the effective field theory approach for the fractional quantum hall system

    International Nuclear Information System (INIS)

    Ma Zhongshui; Su Zhaobin.

    1992-09-01

    By applying the Dirac quantization method, we build the constraint that all electrons are in the lowest Landau level into the Chern-Simons field theory approach for the fractional quantum Hall system and show that the constraint can be transmuted from hierarchy to hierarchy. For a finite system, we derive that the action for each hierarchy can be split into two parts: a surface part provides the action for the edge excitations while the remaining part is precisely the bulk action for the next hierarchy. An the action for the edge could be decoupled from the bulk only at the hierarchy filling. (author). 16 refs

  17. The "Forgotten" Pseudomomenta and Gauge Changes in Generalized Landau Level Problems: Spatially Nonuniform Magnetic and Temporally Varying Electric Fields

    Science.gov (United States)

    Konstantinou, Georgios; Moulopoulos, Konstantinos

    2017-05-01

    By perceiving gauge invariance as an analytical tool in order to get insight into the states of the "generalized Landau problem" (a charged quantum particle moving inside a magnetic, and possibly electric field), and motivated by an early article that correctly warns against a naive use of gauge transformation procedures in the usual Landau problem (i.e. with the magnetic field being static and uniform), we first show how to bypass the complications pointed out in that article by solving the problem in full generality through gauge transformation techniques in a more appropriate manner. Our solution provides in simple and closed analytical forms all Landau Level-wavefunctions without the need to specify a particular vector potential. This we do by proper handling of the so-called pseudomomentum ěc {{K}} (or of a quantity that we term pseudo-angular momentum L z ), a method that is crucially different from the old warning argument, but also from standard treatments in textbooks and in research literature (where the usual Landau-wavefunctions are employed - labeled with canonical momenta quantum numbers). Most importantly, we go further by showing that a similar procedure can be followed in the more difficult case of spatially-nonuniform magnetic fields: in such case we define ěc {{K}} and L z as plausible generalizations of the previous ordinary case, namely as appropriate line integrals of the inhomogeneous magnetic field - our method providing closed analytical expressions for all stationary state wavefunctions in an easy manner and in a broad set of geometries and gauges. It can thus be viewed as complementary to the few existing works on inhomogeneous magnetic fields, that have so far mostly focused on determining the energy eigenvalues rather than the corresponding eigenkets (on which they have claimed that, even in the simplest cases, it is not possible to obtain in closed form the associated wavefunctions). The analytical forms derived here for these

  18. Topological approach to quantum Hall effects and its important applications: higher Landau levels, graphene and its bilayer

    Science.gov (United States)

    Jacak, Janusz; Łydżba, Patrycja; Jacak, Lucjan

    2017-05-01

    In this paper the topological approach to quantum Hall effects is carefully described. Commensurability conditions together with proposed generators of a system braid group are employed to establish the fractional quantum Hall effect hierarchies of conventional semiconductors, monolayer and bilayer graphene structures. Obtained filling factors are compared with experimental data and a very good agreement is achieved. Preliminary constructions of ground-state wave functions in the lowest Landau level are put forward. Furthermore, this work explains why pyramids of fillings from higher bands are not counterparts of the well-known composite-fermion hierarchy - it provides with the cause for an intriguing robustness of ν = 7/3 , 8/3 and 5/2 states (also in graphene). The argumentation why paired states can be developed in two-subband systems (wide quantum wells) only when the Fermi energy lies in the first Landau level is specified. Finally, the paper also clarifies how an additional surface in bilayer systems contributes to an observation of the fractional quantum Hall effect near half-filling, ν = 1/2 .

  19. Vortex lattices in a rotating Fermi superfluid in the BCS–BEC crossover with many Landau levels

    International Nuclear Information System (INIS)

    Song, Tie-ling; Ma, C.R.; Ma, Yong-li

    2012-01-01

    We present an explicit analytical analysis of the ground state of vortex lattice structure, based on a minimization of the generalized Gross–Pitaevskii energy functional in a trapped rotating Fermi superfluid gas. By a Bogoliubov-like transformation we find that the coarse-grained average of the atomic density varies as inverted parabola in three dimensional cases; the Fermi superfluid in the BEC regime enters into the lowest Landau level at fast rotation, in which the vortices form an almost regular triangular lattice over a central region and the vortex lattice is expanded along the radial direction in the outer region; the fluid in the unitarity and BCS regimes occupies many low-lying Landau levels, in which a trapped gas with a triangular vortex lattice has a superfluid core surrounded by a normal gas. The calculation is qualitatively consistent with recent numerical and experimental data both in the vortex lattice structure and vortex numbers and in the density profiles versus the stirring frequency in the whole BCS–BEC crossover. - Highlights: ► We present an analysis of vortex lattice in an interacting trapped rotating Fermi superfluid gas. ► Decomposing the vortex from the condensate, we can explain the vortex lattice. ► The calculation is consistent with numerical and experimental data. ► It can characterize experimentally properties in different regimes of the BCS–BEC crossover.

  20. Landau levels and shallow donor states in GaAs/AlGaAs multiple quantum wells at megagauss magnetic fields

    Science.gov (United States)

    Zybert, M.; Marchewka, M.; Sheregii, E. M.; Rickel, D. G.; Betts, J. B.; Balakirev, F. F.; Gordon, M.; Stier, A. V.; Mielke, C. H.; Pfeffer, P.; Zawadzki, W.

    2017-03-01

    Landau levels and shallow donor states in multiple GaAs/AlGaAs quantum wells (MQWs) are investigated by means of the cyclotron resonance at megagauss magnetic fields. Measurements of magneto-optical transitions were performed in pulsed fields up to 140 T and temperatures from 6-300 K. The 14 ×14 P.p band model for GaAs is used to interpret free-electron transitions in a magnetic field. Temperature behavior of the observed resonant structure indicates, in addition to the free-electron Landau states, contributions of magnetodonor states in the GaAs wells and possibly in the AlGaAs barriers. The magnetodonor energies are calculated using a variational procedure suitable for high magnetic fields and accounting for conduction band nonparabolicity in GaAs. It is shown that the above states, including their spin splitting, allow one to interpret the observed magneto-optical transitions in MQWs in the middle infrared region. Our experimental and theoretical results at very high magnetic fields are consistent with the picture used previously for GaAs/AlGaAs MQWs at lower magnetic fields.

  1. Electric Conductivity of Hot and Dense Quark Matter in a Magnetic Field with Landau Level Resummation via Kinetic Equations

    Science.gov (United States)

    Fukushima, Kenji; Hidaka, Yoshimasa

    2018-04-01

    We compute the electric conductivity of quark matter at finite temperature T and a quark chemical potential μ under a magnetic field B beyond the lowest Landau level approximation. The electric conductivity transverse to B is dominated by the Hall conductivity σH. For the longitudinal conductivity σ∥, we need to solve kinetic equations. Then, we numerically find that σ∥ has only a mild dependence on μ and the quark mass mq. Moreover, σ∥ first decreases and then linearly increases as a function of B , leading to an intermediate B region that looks consistent with the experimental signature for the chiral magnetic effect. We also point out that σ∥ at a nonzero B remains within the range of the lattice-QCD estimate at B =0 .

  2. Exact Quantization of the Even-Denominator Fractional Quantum Hall State at ν =5/2 Landau Level Filling Factor

    International Nuclear Information System (INIS)

    Pan, W.; Tsui, D.C.; Pan, W.; Xia, J.; Shvarts, V.; Adams, D.E.; Xia, J.; Shvarts, V.; Adams, D.E.; Stormer, H.L.; Stormer, H.L.; Pfeiffer, L.N.; Baldwin, K.W.; West, K.W.

    1999-01-01

    We report ultralow temperature experiments on the obscure fractional quantum Hall effect at Landau level filling factor ν=5/2 in a very high-mobility specimen of μ=1.7x10 7 cm 2 /V s . We achieve an electron temperature as low as ∼4 mK , where we observe vanishing R xx and, for the first time, a quantized Hall resistance, R xy =h/(5/2)e 2 to within 2ppm. R xy at the neighboring odd-denominator states ν=7/3 and 8/3 is also quantized. The temperature dependences of the R xx minima at these fractional fillings yield activation energy gaps Δ 5/2 =0.11 , Δ 7/3 =0.10 , and Δ 8/3 =0.055 K . copyright 1999 The American Physical Society

  3. Emergence of liquid crystalline order in the lowest Landau level of a quantum Hall system with internal anisotropy

    Science.gov (United States)

    Ciftja, Orion

    2018-05-01

    It has now become evident that interplay between internal anisotropy parameters (such as electron mass anisotropy and/or anisotropic coupling of electrons to the substrate) and electron-electron correlation effects can create a rich variety of possibilities especially in quantum Hall systems. The electron mass anisotropy or material substrate effects (for example, the piezoelectric effect in GaAs) can lead to an effective anisotropic interaction potential between electrons. For lack of knowledge of realistic ab-initio potentials that may describe such effects, we adopt a phenomenological approach and assume that an anisotropic Coulomb interaction potential mimics the internal anisotropy of the system. In this work we investigate the emergence of liquid crystalline order at filling factor ν = 1/6 of the lowest Landau level, a state very close to the point where a transition from the liquid to the Wigner solid happens. We consider small finite systems of electrons interacting with an anisotropic Coulomb interaction potential and study the energy stability of an anisotropic liquid crystalline state relative to its isotropic Fermi-liquid counterpart. Quantum Monte Carlo simulation results in disk geometry show stabilization of liquid crystalline order driven by an anisotropic Coulomb interaction potential at all values of the interaction anisotropy parameter studied.

  4. Landau level broadening without disorder, non-integer plateaus without interactions- an alternative model of the quantum Hall effect

    International Nuclear Information System (INIS)

    Kramer, T.

    2006-01-01

    I review some aspects of an alternative model of the quantum Hall effect, which is not based on the presence of disorder potentials. Instead, a quantization of the electronic drift current in the presence of crossed electric and magnetic fields is employed to construct a non-linear transport theory. Another important ingredient of the alternative theory is the coupling of the two-dimensional electron gas to the leads and the applied voltages. By working in a picture where the external voltages fix the chemical potential in the 2D subsystem, the experimentally observed linear relation between the voltage and the location of the quantum Hall plateaus finds an natural explanation. Also, the classical Hall effect emerges as a natural limit of the quantum Hall effect. For low temperatures (or high currents), a non-integer substructure splits higher Landau levels into sublevels. The appearance of substructure and non-integer plateaus in the resistivity is not linked to electron-electron interactions, but caused by the presence of a (linear) electric field. Some of the resulting fractions correspond exactly to half-integer plateaus. (Author)

  5. From Mahan excitons to Landau levels at high magnetic fields: 2DFT spectroscopy reveals hidden quantum correlations (Conference Presentation)

    Science.gov (United States)

    Karaiskaj, Denis

    2017-02-01

    Two-dimensional electron gases have been the subject of research for decades. Modulation doped GaAs quantum wells in the absence of magnetic fields exhibit interesting many-body physics such as the Fermi edge singularity or Mahan exciton and can be regarded as a collective excitation of the system. Under high magnetic fields Landau levels form which have been studied using transport and optical measurements. Nonlinear coherent two-dimensional Fourier transform (2DFT) spectroscopy however provides new insights into these systems. We present the 2DFT spectra of Mahan Excitons associated with the heavy-hole and light-hole resonances observed in a modulation doped GaAs/AlGaAs single quantum well [1]. These resonances are observed to be strongly coupled through many-body interactions. The 2DFT spectra were measured using co-linear, cross-linear, and co-circular polarizations and reveal striking differences. Furthermore, 2DFT spectra at high magnetic fields performed at the National High Magnetic Field Lab (NHMFL) in Tallahassee, Florida will be discussed. The spectra exhibit new features and peculiar line shapes suggesting interesting underlying physics. [1] J. Paul, C. E. Stevens, C. Liu, P. Dey, C. McIntyre, V. Turkowski, J. L. Reno, D. J. Hilton, and D. Karaiskaj, Phys. Rev. Lett.116, 157401 (2016).

  6. Generators of dynamical symmetries and the correct gauge transformation in the Landau level problem: use of pseudomomentum and pseudo-angular momentum

    Science.gov (United States)

    Konstantinou, Georgios; Moulopoulos, Konstantinos

    2016-11-01

    Due to the importance of gauge symmetry in all fields of physics, and motivated by an article written almost three decades ago that warns against a naive handling of gauge transformations in the Landau level problem (a quantum electron moving in a spatially uniform magnetic field), we point out a proper use of the generators of dynamical symmetries combined with gauge transformation methods to easily obtain exact analytical solutions for all Landau level-wavefunctions in arbitrary gauge. Our method is different from the old argument and provides solutions in an easier manner and in a broader set of geometries and gauges; in so doing, it eliminates the need for extra procedures (i.e. a change of basis) pointed out as a necessary step in the old literature, and gives back the standard simple result, provided that an appropriate use is made of the dynamical symmetries of the system and their generators. In this way the present work will at least be useful for university-level education, i.e. in advanced classes in quantum mechanics and condensed matter physics. In addition, it clarifies the actual role of the gauge in the Landau level problem, which often appears confusing in the usual derivations provided in textbooks. Finally, we go further by showing that a similar methodology can be made to apply to the more difficult case of a spatially non-uniform magnetic field (where closed analytical results are rare), in which case the various generators (pseudomomentum and pseudo-angular momentum) appear as line integrals of the inhomogeneous magnetic field; we give closed analytical solutions for all cases, and show how the old and rather forgotten Bawin-Burnel gauge shows up naturally as a ‘reference gauge’ in all solutions.

  7. Phase Diagram of the ν=5/2 Fractional Quantum Hall Effect: Effects of Landau-Level Mixing and Nonzero Width

    Directory of Open Access Journals (Sweden)

    Kiryl Pakrouski

    2015-04-01

    Full Text Available Interesting non-Abelian states, e.g., the Moore-Read Pfaffian and the anti-Pfaffian, offer candidate descriptions of the ν=5/2 fractional quantum Hall state. But, the significant controversy surrounding the nature of the ν=5/2 state has been hampered by the fact that the competition between these and other states is affected by small parameter changes. To study the phase diagram of the ν=5/2 state, we numerically diagonalize a comprehensive effective Hamiltonian describing the fractional quantum Hall effect of electrons under realistic conditions in GaAs semiconductors. The effective Hamiltonian takes Landau-level mixing into account to lowest order perturbatively in κ, the ratio of the Coulomb energy scale to the cyclotron gap. We also incorporate the nonzero width w of the quantum-well and subband mixing. We find the ground state in both the torus and spherical geometries as a function of κ and w. To sort out the nontrivial competition between candidate ground states, we analyze the following four criteria: its overlap with trial wave functions, the magnitude of energy gaps, the sign of the expectation value of an order parameter for particle-hole symmetry breaking, and the entanglement spectrum. We conclude that the ground state is in the universality class of the Moore-Read Pfaffian state, rather than the anti-Pfaffian, for κ<κ_{c}(w, where κ_{c}(w is a w-dependent critical value 0.6≲κ_{c}(w≲1. We observe that both Landau-level mixing and nonzero width suppress the excitation gap, but Landau-level mixing has a larger effect in this regard. Our findings have important implications for the identification of non-Abelian fractional quantum Hall states.

  8. Exact Landau levels in two-dimensional electron systems with Rashba and Dresselhaus spin-orbit interactions in a perpendicular magnetic field

    International Nuclear Information System (INIS)

    Zhang Degang

    2006-01-01

    We study a two-dimensional electron system in the presence of both Rashba and Dresselhaus spin-orbit interactions in a perpendicular magnetic field. Defining two suitable boson operators and using the unitary transformations we are able to obtain the exact Landau levels in the range of all the parameters. When the strengths of the Rashba and Dresselhaus spin-orbit interactions are equal, a new analytical solution for the vanishing Zeeman energy is found, where the orbital and spin wavefunctions of the electron are separated. It is also shown that in this case the Zeeman and spin-orbit splittings are independent of the Landau level index n. Due to the Zeeman energy, new crossing between the eigenstates vertical bar n, k, s = 1, σ) and vertical bar n + 1, k, s' = -1, σ') is produced at a certain magnetic field for larger Rashba spin-orbit coupling. This degeneracy leads to a resonant spin Hall conductance if it happens at the Fermi level. (letter to the editor)

  9. Landau levels and shallow donor states in GaAs/AlGaAs multiple quantum wells at mega-gauss magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Zybert, M. [Univ. of Rzeszow, Pigonia (Poland); Marchweka, M. [Univ. of Rzeszow, Pigonia (Poland); Sheregii, E. M. [Center for Microelectronics and Nanotechnology, University of Rzeszow; Rickel, Dwight Gene [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Betts, Jonathan Bobby [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Balakirev, Fedor Fedorovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gordon, Michael Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stier, Andreas V. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mielke, Charles H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pfeffer, P. [Polish Academy of Sciences (PAS), Warsaw (Poland); Zawadski, W. [Polish Academy of Sciences (PAS), Warsaw (Poland)

    2017-03-06

    Landau levels and shallow donor states in multiple GaAs/AlGaAs quantum wells (MQWs) are investigated by means of the cyclotron resonance at mega-gauss magnetic fields. Measurements of magneto-optical transitions were performed in pulsed fields up to 140 T and temperatures from 6 to 300 K. The 14 x 14 P.p band model for GaAs is used to interpret free-electron transitions in a magnetic field. Temperature behavior of the observed resonant structure indicates, in addition to the free-electron Landau states, contributions of magneto-donor states in the GaAs wells and possibly in the AlGaAs barriers. The magneto-donor energies are calculated using a variational procedure suitable for high magnetic fields and accounting for conduction band nonparabolicity in GaAs. It is shown that the above states, including their spin splitting, allow one to interpret the observed mengeto-optical transitions in MQWs in the middle infrared region. Our experimental and theoretical results at very high magnetic fields are consistent with the picture used previously for GaAs/AlGaAs MQWs at lower magnetic fields.

  10. Strongly Anisotropic Electronic Transport at Landau Level Filling Factor ν =9/2 and ν =5/2 under a Tilted Magnetic Field

    International Nuclear Information System (INIS)

    Pan, W.; Tsui, D.C.; Pan, W.; Du, R.R.; Du, R.R.; Stormer, H.L.; Pfeiffer, L.N.; Baldwin, K.W.; West, K.W.; Stormer, H.L.; Stormer, H.L.

    1999-01-01

    We have investigated the influence of an increasing in-plane magnetic field on the states of half filling of Landau levels (ν=11/2, 9/2, 7/2, thinspandthinsp 5/2) of a two-dimensional electron system. In the electrically anisotropic phase at ν=9/2 and 11/2 an in-plane magnetic field of ∼1 - 2 T overcomes its initial pinning to the crystal lattice and reorients this phase. In the initially isotropic phases at ν=5/2 and 7/2 an in-plane magnetic field induces a strong electrical anisotropy. In all cases, for high in-plane fields the high-resistance axis is parallel to the direction of the in-plane field. copyright 1999 The American Physical Society

  11. Landau Damping Revisited

    International Nuclear Information System (INIS)

    Rees, John; Chao, Alexander

    2008-01-01

    Landau damping, as the term is used in accelerator science, is a physical process in which an ensemble of harmonic oscillators--an accelerator beam, for example--that would otherwise be unstable is stabilized by a spread in the natural frequencies of the oscillators. This is a study of the most basic aspects of that process. It has two main goals: to gain a deeper insight into the mechanism of Landau damping and to find the coherent motion of the ensemble and thus the dependence of the total damping rate on the frequency spread

  12. Decoherence and Landau-Damping

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K.Y.; /Fermilab

    2005-12-01

    The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.

  13. Rapid characterization of microscopic two-level systems using Landau-Zener transitions in a superconducting qubit

    International Nuclear Information System (INIS)

    Tan, Xinsheng; Yu, Haifeng; Yu, Yang; Han, Siyuan

    2015-01-01

    We demonstrate a fast method to detect microscopic two-level systems in a superconducting phase qubit. By monitoring the population leak after sweeping the qubit bias flux, we are able to measure the two-level systems that are coupled with the qubit. Compared with the traditional method that detects two-level systems by energy spectroscopy, our method is faster and more sensitive. This method supplies a useful tool to investigate two-level systems in solid-state qubits

  14. Landau-Ginzburg skeletons

    Energy Technology Data Exchange (ETDEWEB)

    Davenport, Ian C.; Melnikov, Ilarion V. [Department of Physics and Astronomy, James Madison University,Harrisonburg, VA 22807 (United States)

    2017-05-10

    We study the class of indecomposable two-dimensional Landau-Ginzburg theories with (2,2) supersymmetry and central charge c < 6 with the aim of classifying all such theories up to marginal deformations. Our results include cases overlooked in previous classifications. The results are rigorous for three or fewer fields and more generally are rigorous if we assume an extra bound. Numerics suggest that we have the complete set of indecomposable Landau-Ginzburg families with c < 6. This set consists of 38 infinite families and a finite list of 418 sporadic cases. The basic tools are classic results of Kreuzer and Skarke on quasi-homogeneous isolated singularities and solutions to certain feasibility integer programming problems.

  15. Landau-Zener-Stueckelberg interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Shevchenko, S.N., E-mail: sshevchenko@ilt.kharkov.u [B.Verkin Institute for Low Temperature Physics and Engineering, Kharkov (Ukraine); RIKEN Advanced Science Institute, Wako-shi, Saitama (Japan); Ashhab, S.; Nori, Franco [RIKEN Advanced Science Institute, Wako-shi, Saitama (Japan); Department of Physics, The University of Michigan, Ann Arbor, MI (United States)

    2010-07-15

    A transition between energy levels at an avoided crossing is known as a Landau-Zener transition. When a two-level system (TLS) is subject to periodic driving with sufficiently large amplitude, a sequence of transitions occurs. The phase accumulated between transitions (commonly known as the Stueckelberg phase) may result in constructive or destructive interference. Accordingly, the physical observables of the system exhibit periodic dependence on the various system parameters. This phenomenon is often referred to as Landau-Zener-Stueckelberg (LZS) interferometry. Phenomena related to LZS interferometry occur in a variety of physical systems. In particular, recent experiments on LZS interferometry in superconducting TLSs (qubits) have demonstrated the potential for using this kind of interferometry as an effective tool for obtaining the parameters characterizing the TLS as well as its interaction with the control fields and with the environment. Furthermore, strong driving could allow for fast and reliable control of the quantum system. Here we review recent experimental results on LZS interferometry, and we present related theory.

  16. Landau-Zener-Stueckelberg interferometry

    International Nuclear Information System (INIS)

    Shevchenko, S.N.; Ashhab, S.; Nori, Franco

    2010-01-01

    A transition between energy levels at an avoided crossing is known as a Landau-Zener transition. When a two-level system (TLS) is subject to periodic driving with sufficiently large amplitude, a sequence of transitions occurs. The phase accumulated between transitions (commonly known as the Stueckelberg phase) may result in constructive or destructive interference. Accordingly, the physical observables of the system exhibit periodic dependence on the various system parameters. This phenomenon is often referred to as Landau-Zener-Stueckelberg (LZS) interferometry. Phenomena related to LZS interferometry occur in a variety of physical systems. In particular, recent experiments on LZS interferometry in superconducting TLSs (qubits) have demonstrated the potential for using this kind of interferometry as an effective tool for obtaining the parameters characterizing the TLS as well as its interaction with the control fields and with the environment. Furthermore, strong driving could allow for fast and reliable control of the quantum system. Here we review recent experimental results on LZS interferometry, and we present related theory.

  17. Dynamics of a Landau-Zener transitions in a two-level system driven by a dissipative environment

    Science.gov (United States)

    Ateuafack, M. E.; Diffo, J. T.; Fai, L. C.

    2016-02-01

    The paper investigates the effects of a two-level quantum system coupled to transversal and longitudinal dissipative environment. The time-dependent phase accumulation, LZ transition probability and entropy in the presence of fast-ohmic, sub-ohmic and super-ohmic quantum noise are derived. Analytical results are obtained in terms of temperature, dissipation strength, LZ parameter and bath cutoff frequency. The bath is observed to modify the standard occupation difference by a decaying random phase factor and also produces dephasing during the transfer of population. The dephasing characteristics or the initial non-zero decoherence rate are observed to increase in time with the bath temperature and depend on the system-bath coupling strength and cutoff frequency. These parameters are found to strongly affect the memory and thus tailor the coherence process of the system.

  18. On Landau damping

    KAUST Repository

    Mouhot, Clément

    2011-09-01

    Going beyond the linearized study has been a longstanding problem in the theory of Landau damping. In this paper we establish exponential Landau damping in analytic regularity. The damping phenomenon is reinterpreted in terms of transfer of regularity between kinetic and spatial variables, rather than exchanges of energy; phase mixing is the driving mechanism. The analysis involves new families of analytic norms, measuring regularity by comparison with solutions of the free transport equation; new functional inequalities; a control of non-linear echoes; sharp "deflection" estimates; and a Newton approximation scheme. Our results hold for any potential no more singular than Coulomb or Newton interaction; the limit cases are included with specific technical effort. As a side result, the stability of homogeneous equilibria of the non-linear Vlasov equation is established under sharp assumptions. We point out the strong analogy with the KAM theory, and discuss physical implications. Finally, we extend these results to some Gevrey (non-analytic) distribution functions. © 2011 Institut Mittag-Leffler.

  19. Gyrotropic Zener tunneling and nonlinear IV curves in the zero-energy Landau level of graphene in a strong magnetic field.

    Science.gov (United States)

    Laitinen, Antti; Kumar, Manohar; Hakonen, Pertti; Sonin, Edouard

    2018-01-12

    We have investigated tunneling current through a suspended graphene Corbino disk in high magnetic fields at the Dirac point, i.e. at filling factor ν = 0. At the onset of the dielectric breakdown the current through the disk grows exponentially before ohmic behaviour, but in a manner distinct from thermal activation. We find that Zener tunneling between Landau sublevels dominates, facilitated by tilting of the source-drain bias potential. According to our analytic modelling, the Zener tunneling is strongly affected by the gyrotropic force (Lorentz force) due to the high magnetic field.

  20. Ginzburg-Landau vortices

    CERN Document Server

    Bethuel, Fabrice; Helein, Frederic

    2017-01-01

    This book is concerned with the study in two dimensions of stationary solutions of uɛ of a complex valued Ginzburg-Landau equation involving a small parameter ɛ. Such problems are related to questions occurring in physics, e.g., phase transition phenomena in superconductors and superfluids. The parameter ɛ has a dimension of a length which is usually small.  Thus, it is of great interest to study the asymptotics as ɛ tends to zero. One of the main results asserts that the limit u-star of minimizers uɛ exists. Moreover, u-star is smooth except at a finite number of points called defects or vortices in physics. The number of these defects is exactly the Brouwer degree – or winding number – of the boundary condition. Each singularity has degree one – or as physicists would say, vortices are quantized. The singularities have infinite energy, but after removing the core energy we are lead to a concept of finite renormalized energy.  The location of the singularities is completely determined by minimiz...

  1. Landau quantization of Dirac fermions in graphene and its multilayers

    Science.gov (United States)

    Yin, Long-Jing; Bai, Ke-Ke; Wang, Wen-Xiao; Li, Si-Yu; Zhang, Yu; He, Lin

    2017-08-01

    When electrons are confined in a two-dimensional (2D) system, typical quantum-mechanical phenomena such as Landau quantization can be detected. Graphene systems, including the single atomic layer and few-layer stacked crystals, are ideal 2D materials for studying a variety of quantum-mechanical problems. In this article, we review the experimental progress in the unusual Landau quantized behaviors of Dirac fermions in monolayer and multilayer graphene by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Through STS measurement of the strong magnetic fields, distinct Landau-level spectra and rich level-splitting phenomena are observed in different graphene layers. These unique properties provide an effective method for identifying the number of layers, as well as the stacking orders, and investigating the fundamentally physical phenomena of graphene. Moreover, in the presence of a strain and charged defects, the Landau quantization of graphene can be significantly modified, leading to unusual spectroscopic and electronic properties.

  2. The Landau theory of phase transitions

    Indian Academy of Sciences (India)

    2 Department of Computer Sci- ence, Indian ... in plasma physics, the Landau pole in quantum electro-. Keywords ... with Vitalyn Ginzburg, Landau made a milestone con- tribution to ..... This work was supported by the Physics Olympiad Pro-.

  3. Rotating effects on the Landau quantization for an atom with a magnetic quadrupole moment

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, I. C.; Bakke, K., E-mail: kbakke@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, João Pessoa, PB 58051-970 (Brazil)

    2016-01-07

    Based on the single particle approximation [Dmitriev et al., Phys. Rev. C 50, 2358 (1994) and C.-C. Chen, Phys. Rev. A 51, 2611 (1995)], the Landau quantization associated with an atom with a magnetic quadrupole moment is introduced, and then, rotating effects on this analogue of the Landau quantization is investigated. It is shown that rotating effects can modify the cyclotron frequency and breaks the degeneracy of the analogue of the Landau levels.

  4. Rotating effects on the Landau quantization for an atom with a magnetic quadrupole moment

    Science.gov (United States)

    Fonseca, I. C.; Bakke, K.

    2016-01-01

    Based on the single particle approximation [Dmitriev et al., Phys. Rev. C 50, 2358 (1994) and C.-C. Chen, Phys. Rev. A 51, 2611 (1995)], the Landau quantization associated with an atom with a magnetic quadrupole moment is introduced, and then, rotating effects on this analogue of the Landau quantization is investigated. It is shown that rotating effects can modify the cyclotron frequency and breaks the degeneracy of the analogue of the Landau levels.

  5. Rotating effects on the Landau quantization for an atom with a magnetic quadrupole moment

    International Nuclear Information System (INIS)

    Fonseca, I. C.; Bakke, K.

    2016-01-01

    Based on the single particle approximation [Dmitriev et al., Phys. Rev. C 50, 2358 (1994) and C.-C. Chen, Phys. Rev. A 51, 2611 (1995)], the Landau quantization associated with an atom with a magnetic quadrupole moment is introduced, and then, rotating effects on this analogue of the Landau quantization is investigated. It is shown that rotating effects can modify the cyclotron frequency and breaks the degeneracy of the analogue of the Landau levels

  6. Landau parameters for finite range density dependent nuclear interactions

    International Nuclear Information System (INIS)

    Farine, M.

    1997-01-01

    The Landau parameters represent the effective particle-hole interaction at Fermi level. Since between the physical observables and the Landau parameters there is a direct relation their derivation from an effective interaction is of great interest. The parameter F 0 determines the incompressibility K of the system. The parameter F 1 determines the effective mass (which controls the level density at the Fermi level). In addition, F 0 ' determines the symmetry energy, G 0 the magnetic susceptibility, and G 0 ' the pion condensation threshold in nuclear matter. This paper is devoted to a general derivation of Landau parameters for an interaction with density dependent finite range terms. Particular carefulness is devoted to the inclusion of rearrangement terms. This report is part of a larger project which aims at defining a new nuclear interaction improving the well-known D1 force of Gogny et al. for describing the average nuclear properties and exotic nuclei and satisfying, in addition, the sum rules

  7. Revisiting the Landau fluid closure.

    Science.gov (United States)

    Hunana, P.; Zank, G. P.; Webb, G. M.; Adhikari, L.

    2017-12-01

    Advanced fluid models that are much closer to the full kinetic description than the usual magnetohydrodynamic description are a very useful tool for studying astrophysical plasmas and for interpreting solar wind observational data. The development of advanced fluid models that contain certain kinetic effects is complicated and has attracted much attention over the past years. Here we focus on fluid models that incorporate the simplest possible forms of Landau damping, derived from linear kinetic theory expanded about a leading-order (gyrotropic) bi-Maxwellian distribution function f_0, under the approximation that the perturbed distribution function f_1 is gyrotropic as well. Specifically, we focus on various Pade approximants to the usual plasma response function (and to the plasma dispersion function) and examine possibilities that lead to a closure of the linear kinetic hierarchy of fluid moments. We present re-examination of the simplest Landau fluid closures.

  8. Multiparticle phenomena and Landau damping

    International Nuclear Information System (INIS)

    Talman, R.

    1987-01-01

    The purpose of this paper is to survey various methods of studying multiparticle phenomena in accelerators. Both experimental and theoretical methods are described. An effort has been made to emphasize the intuitive and qualitative aspects rather than the detailed mathematics. Some of the terms or concepts to be explained are coherent and incoherent tunes, normal modes, Landau damping, beam-transfer functions, and feedback. These are all of daily importance in the interpretation of colliding-beam observations and the control of performance

  9. Landau - Great scientist and teacher

    International Nuclear Information System (INIS)

    1968-01-01

    In 1962 a feeling of deep sadness was experienced by the whole scientific world when it was learned that L.D. Landau, one of the most distinguished physicists and teachers of the USSR, has been seriously injured in a road accident. All the resources of his own country and ready assistance from many others combined to save his life, but early this year the long fight to recover his faculties ended with his death. (author)

  10. Gyrokinetic linearized Landau collision operator

    DEFF Research Database (Denmark)

    Madsen, Jens

    2013-01-01

    , which is important in multiple ion-species plasmas. Second, the equilibrium operator describes drag and diffusion of the magnetic field aligned component of the vorticity associated with the E×B drift. Therefore, a correct description of collisional effects in turbulent plasmas requires the equilibrium......The full gyrokinetic electrostatic linearized Landau collision operator is calculated including the equilibrium operator, which represents the effect of collisions between gyrokinetic Maxwellian particles. First, the equilibrium operator describes energy exchange between different plasma species...... operator, even for like-particle collisions....

  11. Explosions in Landau Vlasov dynamics

    International Nuclear Information System (INIS)

    Suraud, E.; Cussol, D.; Gregoire, C.; Boilley, D.; Pi, M.; Schuck, P.; Remaud, B.; Sebille, F.

    1988-01-01

    A microscopic study of the quasi-fusion/explosion transition is presented in the framework of Landau-Vlasov simulations of intermediate energy heavy-ion collisions (bombarding energies between 10 and 100 MeV/A). A detailed analysis in terms of the Equation of State of the system is performed. In agreement with schematic models we find that the composite nuclear system formed in the collision does explode when it stays long enough in the mechanically unstable region (spinodal region). Quantitative estimates of the explosion threshold are given for central symmetric reactions (Ca+Ca and Ar+Ti). The effect of the nuclear matter compressibility modulus is discussed

  12. Landau

    Directory of Open Access Journals (Sweden)

    José Abdalla Helayël-Neto

    2013-10-01

    Full Text Available https://dx.doi.org/2175-7941.2013v30n3p656 Resenha do livro “Landau”, da autoria de José Maria Filardo Bassalo e Francisco Caruso Editora Livraria da Física, São Paulo, 2013, 1a edição ISBN: 9788578612009

  13. Parametric Landau damping of space charge modes

    Energy Technology Data Exchange (ETDEWEB)

    Macridin, Alexandru [Fermilab; Burov, Alexey [Fermilab; Stern, Eric [Fermilab; Amundson, James [Fermilab; Spentzouris, Panagiotis [Fermilab

    2016-09-23

    Landau damping is the mechanism of plasma and beam stabilization; it arises through energy transfer from collective modes to the incoherent motion of resonant particles. Normally this resonance requires the resonant particle's frequency to match the collective mode frequency. We have identified an important new damping mechanism, parametric Landau damping, which is driven by the modulation of the mode-particle interaction. This opens new possibilities for stability control through manipulation of both particle and mode-particle coupling spectra. We demonstrate the existence of parametric Landau damping in a simulation of transverse coherent modes of bunched accelerator beams with space charge.

  14. Landau levels on the hyperbolic plane

    International Nuclear Information System (INIS)

    Fakhri, H; Shariati, M

    2004-01-01

    The quantum states of a spinless charged particle on a hyperbolic plane in the presence of a uniform magnetic field with a generalized quantization condition are proved to be the bases of the irreducible Hilbert representation spaces of the Lie algebra u(1, 1). The dynamical symmetry group U(1, 1) with the explicit form of the Lie algebra generators is extracted. It is also shown that the energy has an infinite-fold degeneracy in each of the representation spaces which are allocated to the different values of the magnetic field strength. Based on the simultaneous shift of two parameters, it is also noted that the quantum states realize the representations of Lie algebra u(2) by shifting the magnetic field strength. (letter to the editor)

  15. Landau levels on the hyperbolic plane

    Energy Technology Data Exchange (ETDEWEB)

    Fakhri, H [Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran 19395-5531 (Iran, Islamic Republic of); Shariati, M [Department of Physics, Khajeh Nassir-Al-Deen Toosi University of Technology, Tehran 15418 (Iran, Islamic Republic of)

    2004-11-05

    The quantum states of a spinless charged particle on a hyperbolic plane in the presence of a uniform magnetic field with a generalized quantization condition are proved to be the bases of the irreducible Hilbert representation spaces of the Lie algebra u(1, 1). The dynamical symmetry group U(1, 1) with the explicit form of the Lie algebra generators is extracted. It is also shown that the energy has an infinite-fold degeneracy in each of the representation spaces which are allocated to the different values of the magnetic field strength. Based on the simultaneous shift of two parameters, it is also noted that the quantum states realize the representations of Lie algebra u(2) by shifting the magnetic field strength. (letter to the editor)

  16. Simplified Model of Nonlinear Landau Damping

    International Nuclear Information System (INIS)

    Yampolsky, N.A.; Fisch, N.J.

    2009-01-01

    The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.

  17. Holography with a Landau pole

    Energy Technology Data Exchange (ETDEWEB)

    Faedo, Antón F. [Departament de Física Quántica i Astrofísica and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Martí i Franquès 1, ES-08028, Barcelona (Spain); Mateos, David [Departament de Física Quántica i Astrofísica and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Martí i Franquès 1, ES-08028, Barcelona (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, ES-08010, Barcelona (Spain); Pantelidou, Christiana [Departament de Física Quántica i Astrofísica and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Martí i Franquès 1, ES-08028, Barcelona (Spain); Tarrío, Javier [Physique Théorique et Mathématique, Université Libre de Bruxelles (ULB), and International Solvay Institutes, Campus de la Plaine CP 231, B-1050, Brussels (Belgium)

    2017-02-08

    Holography for UV-incomplete gauge theories is important but poorly understood. A paradigmatic example is d=4, N=4 super Yang-Mills coupled to N{sub f} quark flavors, which possesses a Landau pole at a UV scale Λ{sub LP}. The dual gravity solution exhibits a UV singularity at a finite proper distance along the holographic direction. Despite this, holographic renormalization can be fully implemented via analytic continuation to an AdS solution. The presence of a UV cut-off manifests itself in several interesting ways. At energies E≪Λ{sub LP} no pathologies appear, as expected from effective field theory. In contrast, at scales E≲Λ{sub LP} the gravitational potential becomes repulsive, and at temperatures T≲Λ{sub LP} the specific heat becomes negative. Although we focus on N=4 super Yang-Mills with flavor, our qualitative results apply to a much more general class of theories, since they only depend on the fact that the metric near the UV singularity is a hyper-scaling violating metric with exponent θ>d−1.

  18. Holography with a Landau pole

    International Nuclear Information System (INIS)

    Faedo, Antón F.; Mateos, David; Pantelidou, Christiana; Tarrío, Javier

    2017-01-01

    Holography for UV-incomplete gauge theories is important but poorly understood. A paradigmatic example is d=4, N=4 super Yang-Mills coupled to N f quark flavors, which possesses a Landau pole at a UV scale Λ LP . The dual gravity solution exhibits a UV singularity at a finite proper distance along the holographic direction. Despite this, holographic renormalization can be fully implemented via analytic continuation to an AdS solution. The presence of a UV cut-off manifests itself in several interesting ways. At energies E≪Λ LP no pathologies appear, as expected from effective field theory. In contrast, at scales E≲Λ LP the gravitational potential becomes repulsive, and at temperatures T≲Λ LP the specific heat becomes negative. Although we focus on N=4 super Yang-Mills with flavor, our qualitative results apply to a much more general class of theories, since they only depend on the fact that the metric near the UV singularity is a hyper-scaling violating metric with exponent θ>d−1.

  19. Generalized Landau-Pollak uncertainty relation

    International Nuclear Information System (INIS)

    Miyadera, Takayuki; Imai, Hideki

    2007-01-01

    The Landau-Pollak uncertainty relation treats a pair of rank one projection valued measures and imposes a restriction on their probability distributions. It gives a nontrivial bound for summation of their maximum values. We give a generalization of this bound (weak version of the Landau-Pollak uncertainty relation). Our generalization covers a pair of positive operator valued measures. A nontrivial but slightly weak inequality that can treat an arbitrary number of positive operator valued measures is also presented. A possible application to the problem of separability criterion is also suggested

  20. Modulated Langmuir waves and nonlinear Landau damping

    International Nuclear Information System (INIS)

    Yajima, Nobuo; Oikawa, Masayuki; Satsuma, Junkichi; Namba, Chusei.

    1975-01-01

    The nonlinear Schroedinger euqation with an integral term, iusub(t)+P/2.usub(xx)+Q/u/ 2 u+RP∫sub(-infinity)sup(infinity)[/u(x',t)/ 2 /(x-x')]dx'u=0, which describes modulated Langmuir waves with the nonlinear Landau damping effect, is solved by numerical calculations. Especially, the effects of nonlinear Landau damping on solitary wave solutions are studied. For both cases, PQ>0 and PQ<0, the results show that the solitary waves deform in an asymmetric way changing its velocity. (auth.)

  1. Effects of periodic modulation on the Landau-Zener transition

    International Nuclear Information System (INIS)

    Duan Suqing; Fu Libin; Liu Jie; Zhao Xiangeng

    2005-01-01

    We study the quantum tunnelling of a two-level crossing system which extends the standard Landau-Zener model with applying a periodic modulation on its energy sweep. By directly integrating the time evolution operator we obtain the analytic expressions of tunnelling probability in the cases of high and low modulation frequency limit as well as in weak inter-level coupling limit. Our formula clarify the conditions for resonance occurrence, with the help of it we can readily manipulate the system in a desired way, say, to enhance or suppress the tunnelling probability effectively through adjusting the modulation properly

  2. Improved Landau gauge fixing and discretisation errors

    International Nuclear Information System (INIS)

    Bonnet, F.D.R.; Bowman, P.O.; Leinweber, D.B.; Richards, D.G.; Williams, A.G.

    2000-01-01

    Lattice discretisation errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which O(a 2 ) errors are removed is presented. O(a 2 ) improvement of the gauge fixing condition displays the secondary benefit of reducing the size of higher-order errors. These results emphasise the importance of implementing an improved gauge fixing condition

  3. Critical Landau Velocity in Helium Nanodroplets

    NARCIS (Netherlands)

    Brauer, N.B.; Smolarek, S.; Loginov, E.; Mateo, D.; Hernando, A.; Pi, M.; Barranco, M.; Buma, W.J.; Drabbels, M.

    2013-01-01

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective

  4. Viscosity effect in Landau's hydrodynamical model

    International Nuclear Information System (INIS)

    Hoang, T.F.; Phua, K.K.; Nanyang Univ., Singapore

    1979-01-01

    The Bose-Einstein distribution is used to investigate Landau's hydrodynamical model with viscosity. In case the viscosity dependence on the temperature is T 3 , the correction to the multiplicity behaves like I/E and is found to be negligible for the pp data. A discussion is presented on a possibility of reconciling E 1 / 2 and logE dependence of the multiplicity law. (orig.)

  5. Bose-Einstein correlation in Landau's model

    International Nuclear Information System (INIS)

    Hama, Y.; Padula, S.S.

    1986-01-01

    Bose-Einstein correlation is studied by taking an expanding fluid given by Landau's model as the source, where each space-time point is considered as an independent and chaotic emitting center with Planck's spectral distribution. As expected, the correlation depends on the relative angular positions as well as on the overall localization of the measuring system and it turns out that the average dimension of the source increases with the multiplicity N/sub ch/

  6. Possibility of Landau damping of gravitational waves

    International Nuclear Information System (INIS)

    Gayer, S.; Kennel, C.F.

    1979-01-01

    There is considerable uncertainty in the literature concerning whether or not transverse traceless gravitational waves can Landau damp. Physically, the issue is whether particles of nonzero mass can comove with surfaces of constant wave phase, and therefore, loosely, whether gravitational waves can have phase speeds less than that of light. We approach the question of Landau damping in various ways. We consider first the propagation of small-amplitude gravitational waves in an ideal fluid-filled Robertson-Walker universe of zero spatial curvature. We argue that the principle of equivalence requires those modes to be lightlike. We show that a freely moving particle interacting only with the collective fields cannot comove with such waves if it has nonzero mass. The equation for gravitational waves in collisionless kinetic gases differs from that for fluid media only by terms so small that deviations from lightlike propagation are unmeasurable. Thus, we conclude that Landau damping of small-amplitude, transverse traceless gravitational waves is not possible

  7. Aspects of Landau condensation in atomic physics

    International Nuclear Information System (INIS)

    Gay, J.C.

    1980-01-01

    Some aspects of Landau condensation in atomic physics are reviewed both as regards current work on Rydberg states under laboratory conditions and from the viewpoint of the prospects of spontaneous decay of neutral vacuum with superheavy elements. The characteristics of the hydrogen-atom spectrum in a strong magnetic field are presented and discussed using essentially semiclassical arguments. Some schematic attempt at a global interpretation of the Rydberg spectrum near the ionization limit is also given. Then the action of an electric field on the quasi-Landau spectrum is discussed. The conditions for spontaneous production of positrons from neutral vacuum decay with superheavy elements are reconsidered for the case when the system experiences ultrastrong magnetic fields, as in pulsars and white dwarfs. It is shown that spontaneous decay of neutral vacuum may occur at lower Z values than 169. The possible importance of such effects during heavy-ion collisions is briefly discussed. We deal with some qualitative trends of the problem of an atom in a magnetic field with particular emphasis on diamagnetic effects. In the last few years, we have had the capability of making accurate experimental investigations of Rydberg atoms, and perhaps in the future we will develop fundamentally new means of studying heavy-ion collisions. Accordingly it seems of interest to make qualitative remarks regarding the present state of the problem and the possible importance of Landau condensation in various domains of atomic physics now under active development. (author)

  8. Tunable Landau-Zener transitions using continuous- and chirped-pulse-laser couplings

    Science.gov (United States)

    Sarreshtedari, Farrokh; Hosseini, Mehdi

    2017-03-01

    The laser coupled Landau-Zener avoided crossing has been investigated with an aim towards obtaining the laser source parameters for precise controlling of the state dynamics in a two-level quantum system. The conventional Landau-Zener equation is modified for including the interaction of the system with a laser field during a bias energy sweep and the obtained Hamiltonian is numerically solved for the investigation of the two-state occupation probabilities. We have shown that in the Landau-Zener process, using an additional laser source with controlled amplitude, frequency, and phase, the system dynamics could be arbitrarily engineered. This is while, by synchronous frequency sweeping of a chirped-pulse laser, the system could be guided into a resonance condition, which again gives the remarkable possibility for precise tuning and controlling of the quantum system dynamics.

  9. Integrable time-dependent Hamiltonians, solvable Landau-Zener models and Gaudin magnets

    Science.gov (United States)

    Yuzbashyan, Emil A.

    2018-05-01

    We solve the non-stationary Schrödinger equation for several time-dependent Hamiltonians, such as the BCS Hamiltonian with an interaction strength inversely proportional to time, periodically driven BCS and linearly driven inhomogeneous Dicke models as well as various multi-level Landau-Zener tunneling models. The latter are Demkov-Osherov, bow-tie, and generalized bow-tie models. We show that these Landau-Zener problems and their certain interacting many-body generalizations map to Gaudin magnets in a magnetic field. Moreover, we demonstrate that the time-dependent Schrödinger equation for the above models has a similar structure and is integrable with a similar technique as Knizhnik-Zamolodchikov equations. We also discuss applications of our results to the problem of molecular production in an atomic Fermi gas swept through a Feshbach resonance and to the evaluation of the Landau-Zener transition probabilities.

  10. Ginzburg-Landau vortices driven by the Landau-Lifshitz-Gilbert equation

    Energy Technology Data Exchange (ETDEWEB)

    Kurzke, Matthias; Melcher, Christof; Moser, Roger; Spirn, Daniel

    2009-06-15

    A simplified model for the energy of the magnetization of a thin ferromagnetic film gives rise to a version of the theory of Ginzburg-Landau vortices for sphere-valued maps. In particular we have the development of vortices as a certain parameter tends to 0. The dynamics of the magnetization is ruled by the Landau-Lifshitz-Gilbert equation, which combines characteristic properties of a nonlinear Schroedinger equation and a gradient flow. This paper studies the motion of the vortex centers under this evolution equation. (orig.)

  11. Ginzburg-Landau vortices driven by the Landau-Lifshitz-Gilbert equation

    International Nuclear Information System (INIS)

    Kurzke, Matthias; Melcher, Christof; Moser, Roger; Spirn, Daniel

    2009-01-01

    A simplified model for the energy of the magnetization of a thin ferromagnetic film gives rise to a version of the theory of Ginzburg-Landau vortices for sphere-valued maps. In particular we have the development of vortices as a certain parameter tends to 0. The dynamics of the magnetization is ruled by the Landau-Lifshitz-Gilbert equation, which combines characteristic properties of a nonlinear Schroedinger equation and a gradient flow. This paper studies the motion of the vortex centers under this evolution equation. (orig.)

  12. Metriplectic Gyrokinetics and Discretization Methods for the Landau Collision Integral

    Science.gov (United States)

    Hirvijoki, Eero; Burby, Joshua W.; Kraus, Michael

    2017-10-01

    We present two important results for the kinetic theory and numerical simulation of warm plasmas: 1) We provide a metriplectic formulation of collisional electrostatic gyrokinetics that is fully consistent with the First and Second Laws of Thermodynamics. 2) We provide a metriplectic temporal and velocity-space discretization for the particle phase-space Landau collision integral that satisfies the conservation of energy, momentum, and particle densities to machine precision, as well as guarantees the existence of numerical H-theorem. The properties are demonstrated algebraically. These two result have important implications: 1) Numerical methods addressing the Vlasov-Maxwell-Landau system of equations, or its reduced gyrokinetic versions, should start from a metriplectic formulation to preserve the fundamental physical principles also at the discrete level. 2) The plasma physics community should search for a metriplectic reduction theory that would serve a similar purpose as the existing Lagrangian and Hamiltonian reduction theories do in gyrokinetics. The discovery of metriplectic formulation of collisional electrostatic gyrokinetics is strong evidence in favor of such theory and, if uncovered, the theory would be invaluable in constructing reduced plasma models. Supported by U.S. DOE Contract Nos. DE-AC02-09-CH11466 (EH) and DE-AC05-06OR23100 (JWB) and by European Union's Horizon 2020 research and innovation Grant No. 708124 (MK).

  13. Chiral algebras in Landau-Ginzburg models

    Science.gov (United States)

    Dedushenko, Mykola

    2018-03-01

    Chiral algebras in the cohomology of the {\\overline{Q}}+ supercharge of two-dimensional N=(0,2) theories on flat spacetime are discussed. Using the supercurrent multiplet, we show that the answer is renormalization group invariant for theories with an R-symmetry. For N=(0,2) Landau-Ginzburg models, the chiral algebra is determined by the operator equations of motion, which preserve their classical form, and quantum renormalization of composite operators. We study these theories and then specialize to the N=(2,2) models and consider some examples.

  14. Landau fluid models of collisionless magnetohydrodynamics

    International Nuclear Information System (INIS)

    Snyder, P.B.; Hammett, G.W.; Dorland, W.

    1997-01-01

    A closed set of fluid moment equations including models of kinetic Landau damping is developed which describes the evolution of collisionless plasmas in the magnetohydrodynamic parameter regime. The model is fully electromagnetic and describes the dynamics of both compressional and shear Alfven waves, as well as ion acoustic waves. The model allows for separate parallel and perpendicular pressures p parallel and p perpendicular , and, unlike previous models such as Chew-Goldberger-Low theory, correctly predicts the instability threshold for the mirror instability. Both a simple 3 + 1 moment model and a more accurate 4 + 2 moment model are developed, and both could be useful for numerical simulations of astrophysical and fusion plasmas

  15. The Wang-Landau Sampling Algorithm

    Science.gov (United States)

    Landau, David P.

    2003-03-01

    Over the past several decades Monte Carlo simulations[1] have evolved into a powerful tool for the study of wide-ranging problems in statistical/condensed matter physics. Standard methods sample the probability distribution for the states of the system, usually in the canonical ensemble, and enormous improvements have been made in performance through the implementation of novel algorithms. Nonetheless, difficulties arise near phase transitions, either due to critical slowing down near 2nd order transitions or to metastability near 1st order transitions, thus limiting the applicability of the method. We shall describe a new and different Monte Carlo approach [2] that uses a random walk in energy space to determine the density of states directly. Once the density of states is estimated, all thermodynamic properties can be calculated at all temperatures. This approach can be extended to multi-dimensional parameter spaces and has already found use in classical models of interacting particles including systems with complex energy landscapes, e.g., spin glasses, protein folding models, etc., as well as for quantum models. 1. A Guide to Monte Carlo Simulations in Statistical Physics, D. P. Landau and K. Binder (Cambridge U. Press, Cambridge, 2000). 2. Fugao Wang and D. P. Landau, Phys. Rev. Lett. 86, 2050 (2001); Phys. Rev. E64, 056101-1 (2001).

  16. Landau damping in trapped Bose condensed gases

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, B; Zaremba, E [Department of Physics, Queen' s University, Kingston, ON K7L 3N6 (Canada)

    2003-07-01

    We study Landau damping in dilute Bose-Einstein condensed gases in both spherical and prolate ellipsoidal harmonic traps. We solve the Bogoliubov equations for the mode spectrum in both of these cases, and calculate the damping by summing over transitions between excited quasiparticle states. The results for the spherical case are compared to those obtained in the Hartree-Fock (HF) approximation, where the excitations take on a single-particle character, and excellent agreement between the two approaches is found. We have also taken the semiclassical limit of the HF approximation and obtain a novel expression for the Landau damping rate involving the time-dependent self-diffusion function of the thermal cloud. As a final approach, we study the decay of a condensate mode by making use of dynamical simulations in which both the condensate and thermal cloud are evolved explicitly as a function of time. A detailed comparison of all these methods over a wide range of sample sizes and trap geometries is presented.

  17. Breaking the hidden symmetry in the Ginzburg-Landau equation

    NARCIS (Netherlands)

    Doelman, A.

    1996-01-01

    In this paper we study localised, traveling, solutions to a Ginzburg-Landau equation to which we have added a small, O(e), 0 < e << 1, quintic term. We consider this term as a model for the higher order nonlinearities which appear in the derivation of the Ginzburg-Landau equation. By a combination

  18. Breaking the hidden symmetry in the Ginzburg-Landau equation

    NARCIS (Netherlands)

    Doelman, A.

    1997-01-01

    In this paper we study localised, traveling, solutions to a Ginzburg-Landau equation to which we have added a small, O ( " ), 0 < "? 1, quintic term. We consider this term as a model for the higher order nonlinearities which appear in the derivation of the Ginzburg-Landau equation. By a combination

  19. Landau degeneracy and black hole entropy

    International Nuclear Information System (INIS)

    Costa, M.S.; Perry, M.J.

    1998-01-01

    We consider the supergravity solution describing a configuration of intersecting D4-branes with non-vanishing world-volume gauge fields. The entropy of such a black hole is calculated in terms of the D-branes quantised charges. The non-extreme solution is also considered and the corresponding thermodynamical quantities are calculated in terms of a D-brane/anti-D-brane system. To perform the quantum mechanical D-brane analysis we study open strings with their ends on branes with a magnetic condensate. Applying the results to our D-brane system we manage to have a perfect agreement between the D-brane entropy counting and the corresponding semi-classical result. The Landau degeneracy of the open string states describing the excitations of the D-brane system enters in a crucial way. We also derive the near-extreme results which agree with the semi-classical calculations. (orig.)

  20. Transversal expansion study in the Landau hydrodynamic

    International Nuclear Information System (INIS)

    Pottag, F.W.

    1984-01-01

    The system of equations in the frame of Landau's hydrodynamical model for multiparticle production at high energies is studied. Taking as a first approximation the one-dimensional exact due to Khalatnikov, and a special set of curvilinear coordinates, the radial part is separated from the longitudinal one in the equations of motion, and a system of partial differential equations (non-linear, hyperbolic) is obtained for the radial part. These equations are solved numerically by the method of caracteristics. The hydrodynamical variables are obtained over all the three-dimensional-flow region as well as its variation with the mass of the initially expanding system. Both, the transverse rapidity distribution of the fluid and the inclusive particle distribution at 90 0 in the center of mass system, are calculated. The last one is compared with recent experimental data. (author) [pt

  1. Landau-Zener transitions and Dykhne formula in a simple continuum model

    Science.gov (United States)

    Dunham, Yujin; Garmon, Savannah

    The Landau-Zener model describing the interaction between two linearly driven discrete levels is useful in describing many simple dynamical systems; however, no system is completely isolated from the surrounding environment. Here we examine a generalizations of the original Landau-Zener model to study simple environmental influences. We consider a model in which one of the discrete levels is replaced with a energy continuum, in which we find that the survival probability for the initially occupied diabatic level is unaffected by the presence of the continuum. This result can be predicted by assuming that each step in the evolution for the diabatic state evolves independently according to the Landau-Zener formula, even in the continuum limit. We also show that, at least for the simplest model, this result can also be predicted with the natural generalization of the Dykhne formula for open systems. We also observe dissipation as the non-escape probability from the discrete levels is no longer equal to one.

  2. The Rubber Band Revisited: Wang-Landau Simulation

    OpenAIRE

    Ferreira, Lucas S.; Caparica, Alvaro A.; Neto, Minos A.; Galiceanu, Mircea D.

    2012-01-01

    In this work we apply Wang-Landau simulations to a simple model which has exact solutions both in the microcanonical and canonical formalisms. The simulations were carried out by using an updated version of the Wang-Landau sampling. We consider a homopolymer chain consisting of $N$ monomers units which may assume any configuration on the two-dimensional lattice. By imposing constraints to the moves of the polymers we obtain three different models. Our results show that updating the density of...

  3. Discretisation errors in Landau gauge on the lattice

    International Nuclear Information System (INIS)

    Bonnet DR, Frederic; Bowman O, Patrick; Leinweber B, Derek; Williams G, Anthony; Richards G, David G.

    1999-01-01

    Lattice discretization errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which O(a 2 ) errors are removed is presented. O(a 2 ) improvement of the gauge fixing condition improves comparison with continuum Landau gauge in two ways: (1) through the elimination of O(a 2 ) errors and (2) through a secondary effect of reducing the size of higher-order errors. These results emphasize the importance of implementing an improved gauge fixing condition

  4. Landau damping of dust acoustic solitary waves in nonthermal plasmas

    Science.gov (United States)

    Ghai, Yashika; Saini, N. S.; Eliasson, B.

    2018-01-01

    Dust acoustic (DA) solitary and shock structures have been investigated under the influence of Landau damping in a dusty plasma containing two temperature nonthermal ions. Motivated by the observations of Geotail spacecraft that reported two-temperature ion population in the Earth's magnetosphere, we have investigated the effect of resonant wave-particle interactions on DA nonlinear structures. The Korteweg-de Vries (KdV) equation with an additional Landau damping term is derived and its analytical solution is presented. The solution has the form of a soliton whose amplitude decreases with time. Further, we have illustrated the influence of Landau damping and nonthermality of the ions on DA shock structures by a numerical solution of the Landau damping modified KdV equation. The study of the time evolution of shock waves suggests that an initial shock-like pulse forms an oscillatory shock at later times due to the balance of nonlinearity, dispersion, and dissipation due to Landau damping. The findings of the present investigation may be useful in understanding the properties of nonlinear structures in the presence of Landau damping in dusty plasmas containing two temperature ions obeying nonthermal distribution such as in the Earth's magnetotail.

  5. Lev Landau and the concept of neutron stars

    International Nuclear Information System (INIS)

    Yakovlev, Dmitrii G; Haensel, Pawel; Baym, Gordon; Pethick, Christopher

    2013-01-01

    We review Lev Landau's role in the history of neutron star physics in the 1930s. According to the recollections of Rosenfeld (Proc. 16th Solvay Conference on Physics, 1974, p. 174), Landau improvised the concept of neutron stars in a discussion with Bohr and Rosenfeld just after the news of the discovery of the neutron reached Copenhagen in February 1932. We present arguments that the discussion must have taken place in March 1931, before the discovery of the neutron, and that they, in fact, discussed the paper written by Landau in Zurich in February 1931 but not published until February 1932 (Phys. Z. Sowjetunion 1, 285). In this paper, Landau mentioned the possible existence of dense stars that look like one giant nucleus; this could be regarded as an early theoretical prediction or anticipation of neutron stars, albeit prior to the discovery of the neutron. The coincidence of the dates of the neutron discovery and the publication of the paper has led to an erroneous association of Landau's paper with the discovery of the neutron. In passing, we outline Landau's contribution to the theory of white dwarfs and to the hypothesis of stars with neutron cores. (from the history of physics)

  6. Landau-Zener-Stueckelberg interferometry with low- and high-frequency driving

    Science.gov (United States)

    Shevchenko, Sergey; Ashhab, Sahel; Nori, Franco

    2010-03-01

    The problem of a periodically driven two-level system cannot be solved exactly. The rotating-wave approximation (RWA) is the most common approximation used to analyze this problem. I will discuss an alternative approximation that applies in the case of very strong driving, where the RWA is generally invalid. The dynamics is approximated by a sequence of Landau-Zener transitions that can interfere constructively or destructively, depending on the Stueckelberg phase accumulated between transitions. It turns out that the resonance conditions are qualitatively different for the cases of low- and high-frequency driving. I will discuss the two respective limits. I will also show that our theoretical results describe recent experiments on Landau-Zener-Stuckelberg interferometry with superconducting qubits [S.N. Shevchenko, S. Ashhab, and F. Nori, arXiv:0911.1917].

  7. Landau-Zener-Stückelberg Interferometry of a Single Electronic Spin in a Noisy Environment

    Directory of Open Access Journals (Sweden)

    Pu Huang

    2011-08-01

    Full Text Available We demonstrate quantum coherent control of single electronic spins in a nitron-vacancy center in diamond by exploiting and implementing the general concept of Landau-Zener-Stückelberg interferometry at room temperature. The interferometry manipulates an effective two-level system of electronic spins which are coupled to the nearby ^{14}N nuclear spin in the nitron-vacancy center as well as the nuclear spin bath in the diamond. With a microwave field to control the energy gap between the two levels and an AC field as the time-dependent driving field in Landau-Zener-Stückelberg interferometry, the interference pattern can be generated and controlled by controlling a number of parameters in the fields, corresponding to coherent control of the state of the electronic spins. In particular, the interference pattern is observed oscillating as a function of the frequency of the microwave field. Decays in the visibility of the interference pattern are also observed and well explained by numerical simulation which takes into account the thermal fluctuations arising from the nuclear bath. Therefore, our work also demonstrates that Landau-Zener-Stückelberg interferometry can be used for probing decoherence processes of electronic spins.

  8. Moving boundary - Oxygen diffusion. Two algorithms using Landau transformation

    International Nuclear Information System (INIS)

    Moyano, E.A.

    1991-01-01

    A description is made of two algorithms which solve a mathematical model destinated for the study of one-dimensional problems with moving boundaries and implicit boundary conditions. The Landau transformation is used in both methods for each temporal level so as to work all through with the same amount of nodes. Thus, it is necessary to deal with a partial differential equation whose diffusive and convective terms are accompanied by variable coefficients. The partial differential equation is made discrete implicitly, using the Laasonen scheme -which is always stable- instead of the Crank-Nicholson scheme, as performed by Ferris and Hill (5), in the fixed time passing method. The second method employs the tridiagonal algorithm. The first algorithm uses fixed time passing and iterates with variable interface positions, that is to say, it varies δs until it satisfies the boundary condition. The mathematical model describes oxygen diffusion in live tissues. Its numerical solution is obtained by finite differences. An important application of this method could be the estimation of the radiation dose in cancerous tumor treatment. (Author) [es

  9. Energy spread in SLC linac with Landau damping

    International Nuclear Information System (INIS)

    Seeman, J.

    1984-01-01

    The possibility of using Landau damping to reduce the growth of the beam size due to transverse wake fields has been known for some time. Recently K. Bane has calculated the effects of Landau damping for the SLC. The energy spread is then slowly removed so that at the end of the linac it has returned to the SLC specification of less than +0.5%. The purpose of the energy spread is to reduce the resonant driving of the tail of the bunch by the head. In this note the expected energy spreads within the beam are tabulated at various positions along the linac for use by those people designing momentum dependent equipment and for those interested in Landau damping

  10. Geometric singularities and spectra of Landau-Ginzburg models

    International Nuclear Information System (INIS)

    Greene, B.R.; Roan, S.S.; Yau, S.T.

    1991-01-01

    Some mathematical and physical aspects of superconformal string compactification in weighted projective space are discussed. In particular, we recast the path integral argument establishing the connection between Landau-Ginsburg conformal theories and Calabi-Yau string compactification in a geometric framework. We then prove that the naive expression for the vanishing of the first Chern class for a complete intersection (adopted from the smooth case) is sufficient to ensure that the resulting variety, which is generically singular, can be resolved to a smooth Calabi-Yau space. This justifies much analysis which has recently been expended on the study of Landau-Ginzburg models. Furthermore, we derive some simple formulae for the determination of the Witten index in these theories which are complementary to those derived using semiclassical reasoning by Vafa. Finally, we also comment on the possible geometrical significance of unorbifolded Landau-Ginzburg theories. (orig.)

  11. The rubber band revisited: Wang–Landau simulation

    International Nuclear Information System (INIS)

    Ferreira, Lucas S; Caparica, Álvaro A; Neto, Minos A; Galiceanu, Mircea D

    2012-01-01

    In this work we apply Wang–Landau simulations to a simple model which has exact solutions both in the microcanonical and canonical formalisms. The simulations were carried out by using an updated version of the Wang–Landau sampling. We consider a homopolymer chain consisting of N monomers units which may assume any configuration on the two-dimensional lattice. By imposing constraints to the moves of the polymers we obtain three different models. Our results show that updating the density of states only after every N monomer moves leads to a better precision. We obtain the specific heat and the end-to-end distance per monomer and test the precision of our simulations by comparing the location of the maximum of the specific heat with the exact results and conventional Wang–Landau simulations for the three types of walk. (paper)

  12. Landau damping dynamic aperture and octupole in LHC

    CERN Document Server

    Gareyte, Jacques; Ruggiero, F

    1997-01-01

    Maximization of the dynamic aperture and Landau damping of the collective instabilities are partly conflicting requirements. On the one hand, the non-linearities of the lattice must be minimized at large oscillation amplitude to guarantee the stability of the single particle motion. On the other hand, a spread of the betatron frequencies is necessary to guarantee the stability of the collective motion of bunches of particles; this requires the introduction of non-linearities effective at small amplitudes. We show in this note that the `natural' spread of betatron tunes due to the field imperfections is inadequate or Landau damping. An octupole scheme is required to provide collective stability at high energy. At low energy it may be used to find the optimum between the correction of the octupolar field imperfections and Landau damping. The solution of the stability problem taking into account the two degrees of freedom of the transverse motion allows a significant saving in octupole strength: 144 octupoles wi...

  13. Oscillating Sign of Drag in High Landau Levels

    International Nuclear Information System (INIS)

    von Oppen, Felix; Simon, Steven H.; Stern, Ady

    2001-01-01

    Motivated by experiments, we study the sign of the Coulomb drag voltage in a double layer system in a strong magnetic field. We show that the commonly used Fermi golden rule approach implicitly assumes a linear dependence of intralayer conductivity on density, and is thus inadequate in strong magnetic fields. Going beyond this approach, we show that the drag voltage commonly changes sign with density difference between the layers. We find that, in the quantum Hall regime, the Hall and longitudinal drag resistivities may be comparable. Our results are also relevant for pumping and acoustoelectric experiments

  14. Landau levels of Majorana fermions in a spin liquid

    NARCIS (Netherlands)

    Rachel, Stephan; Fritz, Lars; Vojta, Matthias

    2016-01-01

    Majorana fermions were originally proposed as elementary particles acting as their own antiparticles. In recent years, it has become clear that Majorana fermions can instead be realized in condensed-matter systems as emergent quasiparticles, a situation often accompanied by topological order. Here

  15. Landau-Ginzburg Orbifolds, Mirror Symmetry and the Elliptic Genus

    OpenAIRE

    Berglund, P.; Henningson, M.

    1994-01-01

    We compute the elliptic genus for arbitrary two dimensional $N=2$ Landau-Ginzburg orbifolds. This is used to search for possible mirror pairs of such models. We show that if two Landau-Ginzburg models are conjugate to each other in a certain sense, then to every orbifold of the first theory corresponds an orbifold of the second theory with the same elliptic genus (up to a sign) and with the roles of the chiral and anti-chiral rings interchanged. These orbifolds thus constitute a possible mirr...

  16. Thirty years of the Landau Institute selected papers

    CERN Document Server

    Khalatnikov, I M

    1996-01-01

    The Landau Institute for Theoretical Physics was created in 1965 by a group of LD Landau's pupils. Very soon, it was widely recognized as one of the world's leading centers in theoretical physics. According to Science Magazine, the Institute in the eighties had the highest citation index among all the scientific organizations in the former Soviet Union. This collection of the best papers of the Institute reflects the development of the many directions in the exact sciences during the last 30 years. The reader can find the original formulations of well-known notions in condensed matter theory,

  17. Evolutionary algorithms applied to Landau-gauge fixing

    International Nuclear Information System (INIS)

    Markham, J.F.

    1998-01-01

    Current algorithms used to put a lattice gauge configuration into Landau gauge either suffer from the problem of critical slowing-down or involve an additions computational expense to overcome it. Evolutionary Algorithms (EAs), which have been widely applied to other global optimisation problems, may be of use in gauge fixing. Also, being global, they should not suffer from critical slowing-down as do local gradient based algorithms. We apply EA'S and also a Steepest Descent (SD) based method to the problem of Landau Gauge Fixing and compare their performance. (authors)

  18. Discretisation errors in Landau gauge on the lattice

    International Nuclear Information System (INIS)

    Bonnet, F.D.R.; Bowmen, P.O.; Leinweber, D.B.

    1999-01-01

    Lattice discretisation errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which O(a 2 ) errors are removed is presented. O(a 2 ) improvement of the gauge fixing condition improves comparison with the continuum Landau gauge in two ways: (1) through the elimination of O(a 2 ) errors and (2) through a secondary effect of reducing the size of higher-order errors. These results emphasise the importance of implementing an improved gauge fixing condition. Copyright (1999) CSIRO Australia

  19. On the Ginzburg-Landau critical field in three dimensions

    DEFF Research Database (Denmark)

    Fournais, Søren; Helffer, Bernard

    2009-01-01

    We study the three-dimensional Ginzburg-Landau model of superconductivity. Several natural definitions of the (third) critical field, HC3, governing the transition from the superconducting state to the normal state, are considered. We analyze the relation between these fields and give conditions ...

  20. The Landau-Placzek ratio for multicomponent fluids

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Laidlaw, W.G.

    1972-01-01

    Under the assumption that the coupling between the sound modes and modes associated with heat and mass diffusion can be neglected, an expression for the Landau-Placzek ratio for multicomponent fluids is derived using thermodynamic fluctuation theory. Applications of the general formula to ternary

  1. Ginzburg-Landau-type theory of nonpolarized spin superconductivity

    Science.gov (United States)

    Lv, Peng; Bao, Zhi-qiang; Guo, Ai-Min; Xie, X. C.; Sun, Qing-Feng

    2017-01-01

    Since the concept of spin superconductor was proposed, all the related studies concentrate on the spin-polarized case. Here, we generalize the study to the spin-non-polarized case. The free energy of nonpolarized spin superconductor is obtained, and Ginzburg-Landau-type equations are derived by using the variational method. These Ginzburg-Landau-type equations can be reduced to the spin-polarized case when the spin direction is fixed. Moreover, the expressions of super linear and angular spin currents inside the superconductor are derived. We demonstrate that the electric field induced by the super spin current is equal to the one induced by an equivalent charge obtained from the second Ginzburg-Landau-type equation, which shows self-consistency of our theory. By applying these Ginzburg-Landau-type equations, the effect of electric field on the superconductor is also studied. These results will help us get a better understanding of the spin superconductor and related topics such as the Bose-Einstein condensate of magnons and spin superfluidity.

  2. Drift of Spiral Waves in Complex Ginzburg-Landau Equation

    International Nuclear Information System (INIS)

    Yang Junzhong; Zhang Mei

    2006-01-01

    The spontaneous drift of the spiral wave in a finite domain in the complex Ginzburg-Landau equation is investigated numerically. By using the interactions between the spiral wave and its images, we propose a phenomenological theory to explain the observations.

  3. Exact solutions of generalized Zakharov and Ginzburg-Landau equations

    International Nuclear Information System (INIS)

    Zhang Jinliang; Wang Mingliang; Gao Kequan

    2007-01-01

    By using the homogeneous balance principle, the exact solutions of the generalized Zakharov equations and generalized Ginzburg-Landau equation are obtained with the aid of a set of subsidiary higher-order ordinary differential equations (sub-equations for short)

  4. The energy density of a Landau damped plasma wave

    NARCIS (Netherlands)

    Best, R. W. B.

    1999-01-01

    In this paper some theories about the energy of a Landau damped plasma wave are discussed and new initial conditions are proposed. Analysis of a wave packet, rather than an infinite wave, gives a clear picture of the energy transport from field to particles. Initial conditions are found which excite

  5. Quantum corrections to nonlinear ion acoustic wave with Landau damping

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Abhik; Janaki, M. S. [Saha Institute of Nuclear Physics, Calcutta (India); Bose, Anirban [Serampore College, West Bengal (India)

    2014-07-15

    Quantum corrections to nonlinear ion acoustic wave with Landau damping have been computed using Wigner equation approach. The dynamical equation governing the time development of nonlinear ion acoustic wave with semiclassical quantum corrections is shown to have the form of higher KdV equation which has higher order nonlinear terms coming from quantum corrections, with the usual classical and quantum corrected Landau damping integral terms. The conservation of total number of ions is shown from the evolution equation. The decay rate of KdV solitary wave amplitude due to the presence of Landau damping terms has been calculated assuming the Landau damping parameter α{sub 1}=√(m{sub e}/m{sub i}) to be of the same order of the quantum parameter Q=ℏ{sup 2}/(24m{sup 2}c{sub s}{sup 2}L{sup 2}). The amplitude is shown to decay very slowly with time as determined by the quantum factor Q.

  6. Microscopic Derivation of the Ginzburg-Landau Model

    DEFF Research Database (Denmark)

    Frank, Rupert; Hainzl, Christian; Seiringer, Robert

    2014-01-01

    We present a summary of our recent rigorous derivation of the celebrated Ginzburg-Landau (GL) theory, starting from the microscopic Bardeen-Cooper-Schrieffer (BCS) model. Close to the critical temperature, GL arises as an effective theory on the macroscopic scale. The relevant scaling limit...

  7. On the effects on a Landau-type system for an atom with no permanent electric dipole moment due to a Coulomb-type potential

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Abinael B.; Bakke, Knut, E-mail: kbakke@fisica.ufpb.br

    2016-02-15

    We analyse the bound states for a Landau-type system for an atom with no permanent electric dipole moment subject to a Coulomb-type potential. By comparing the energy levels for bound states of the system with the Landau quantization for an atom with no permanent electric dipole moment (Furtado et al., 2006), we show that the energy levels of the Landau-type system are modified, where the degeneracy of the energy levels is broken. Another quantum effect investigated is a dependence of the angular frequency of the system on the quantum numbers associated with the radial modes and the angular momentum. As examples, we obtain the angular frequency and the energy levels associated with the ground state and the first excited state of the system.

  8. On the effects on a Landau-type system for an atom with no permanent electric dipole moment due to a Coulomb-type potential

    International Nuclear Information System (INIS)

    Oliveira, Abinael B.; Bakke, Knut

    2016-01-01

    We analyse the bound states for a Landau-type system for an atom with no permanent electric dipole moment subject to a Coulomb-type potential. By comparing the energy levels for bound states of the system with the Landau quantization for an atom with no permanent electric dipole moment (Furtado et al., 2006), we show that the energy levels of the Landau-type system are modified, where the degeneracy of the energy levels is broken. Another quantum effect investigated is a dependence of the angular frequency of the system on the quantum numbers associated with the radial modes and the angular momentum. As examples, we obtain the angular frequency and the energy levels associated with the ground state and the first excited state of the system.

  9. Bounce-harmonic Landau Damping of Plasma Waves

    Science.gov (United States)

    Anderegg, Francois

    2015-11-01

    We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v vph / 5 . The measurements are conducted in trapped pure ion plasmas contained in Penning-Malmberg trap, with wave-coherent LIF diagnostics of particle velocities. Our focus is on bounce harmonics damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

  10. Axion production from Landau quantization in the strong magnetic field of magnetars

    Science.gov (United States)

    Maruyama, Tomoyuki; Balantekin, A. Baha; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.

    2018-04-01

    We utilize an exact quantum calculation to explore axion emission from electrons and protons in the presence of the strong magnetic field of magnetars. The axion is emitted via transitions between the Landau levels generated by the strong magnetic field. The luminosity of axions emitted by protons is shown to be much larger than that of electrons and becomes stronger with increasing matter density. Cooling by axion emission is shown to be much larger than neutrino cooling by the Urca processes. Consequently, axion emission in the crust may significantly contribute to the cooling of magnetars. In the high-density core, however, it may cause heating of the magnetar.

  11. Hamiltonian formalism of Whitham-type hierarchies and topological Landau-Ginsburg models

    International Nuclear Information System (INIS)

    Dubrovin, B.A.

    1992-01-01

    We show that the bi-hamiltonian structure of the averaged Gelfand-Dikii hierarchy is involved in the Landau-Ginsburg topological models (for A n -Series): The Casimirs for the first P.B. give the correct coupling parameters for the perturbed topological minimal model; the correspondence {coupling parameters}→{primary fields} is determined by the second P.B. The partition function (at the tree level) and the chiral algebra for LG minimal models are calculated for any genus g. (orig.)

  12. Gyro-Landau fluid model of tokamak core fluctuations

    International Nuclear Information System (INIS)

    Leboeuf, J.N.; Carreras, B.A.; Dominguez, N.; Hedrick, C.L.; Sidikman, K.L.; Lynch, V.E.; Drake, J.B.; Walker, D.W.

    1992-01-01

    Dissipative trapped electron modes (DTEM) may be one of the causes of deterioration of confinement in tokamak and stellatator plasmas. We have implemented a fluid model to study DTEM turbulence in slab geometry. The electron dynamics include in addition to the adiabatic part, a non-adiabatic piece modeled with an i-delta-type response. The ion dynamics include Landau damping and FLR corrections through Landau fluid approximate techniques and Pade approximants for Γ 0 (b)=I 0 (b)e -b . The model follows from the gyrokinetic equation. Evolution equations, which closely resemble those used in standard reduced MHD, are presented since these are better suited to non-linear calculations. The numerical results of radially resolved calculations will be discussed. A recently developed hybrid model, which consists of a gyrokinetic implementation for the ions using particles and the same description for the electron dynamics as in the fluid model, will also be presented

  13. Reversible dissipative processes, conformal motions and Landau damping

    International Nuclear Information System (INIS)

    Herrera, L.; Di Prisco, A.; Ibáñez, J.

    2012-01-01

    The existence of a dissipative flux vector is known to be compatible with reversible processes, provided a timelike conformal Killing vector (CKV) χ α =(V α )/T (where V α and T denote the four-velocity and temperature respectively) is admitted by the spacetime. Here we show that if a constitutive transport equation, either within the context of standard irreversible thermodynamics or the causal Israel–Stewart theory, is adopted, then such a compatibility also requires vanishing dissipative fluxes. Therefore, in this later case the vanishing of entropy production generated by the existence of such CKV is not actually associated to an imperfect fluid, but to a non-dissipative one. We discuss also about Landau damping. -- Highlights: ► We review the problem of compatibility of dissipation with reversibility. ► We show that the additional assumption of a transport equation renders such a compatibility trivial. ► We discuss about Landau damping.

  14. Ensemble inequivalence: Landau theory and the ABC model

    International Nuclear Information System (INIS)

    Cohen, O; Mukamel, D

    2012-01-01

    It is well known that systems with long-range interactions may exhibit different phase diagrams when studied within two different ensembles. In many of the previously studied examples of ensemble inequivalence, the phase diagrams differ only when the transition in one of the ensembles is first order. By contrast, in a recent study of a generalized ABC model, the canonical and grand-canonical ensembles of the model were shown to differ even when they both exhibit a continuous transition. Here we show that the order of the transition where ensemble inequivalence may occur is related to the symmetry properties of the order parameter associated with the transition. This is done by analyzing the Landau expansion of a generic model with long-range interactions. The conclusions drawn from the generic analysis are demonstrated for the ABC model by explicit calculation of its Landau expansion. (paper)

  15. Nonlinear damping of oblique whistler mode waves through Landau resonance

    Science.gov (United States)

    Hsieh, Y.; Omura, Y.

    2017-12-01

    Nonlinear trapping of electrons through Landau resonance is a characteristic dynamics in oblique whistler-mode wave particle interactions. The resonance velocity of the Landau resonance at quasi-parallel propagation becomes very close to the parallel group velocity of whistler-mode wave at frequency around 0.5 Ωe, causing a long distance of resonant interaction and strong acceleration of resonant electrons [1]. We demonstrate these effective accelerations for electrons with high equatorial pitch angle ( > 60°) by test particle simulations with parameters for the Earth's inner magnetosphere at L=5. In the simulations, we focus on slightly oblique whistler mode waves with wave normal angle 10.1002/2016JA023255.

  16. Generalized Landau-Lifshitz models on the interval

    International Nuclear Information System (INIS)

    Doikou, Anastasia; Karaiskos, Nikos

    2011-01-01

    We study the classical generalized gl n Landau-Lifshitz (L-L) model with special boundary conditions that preserve integrability. We explicitly derive the first non-trivial local integral of motion, which corresponds to the boundary Hamiltonian for the sl 2 L-L model. Novel expressions of the modified Lax pairs associated to the integrals of motion are also extracted. The relevant equations of motion with the corresponding boundary conditions are determined. Dynamical integrable boundary conditions are also examined within this spirit. Then the generalized isotropic and anisotropic gl n Landau-Lifshitz models are considered, and novel expressions of the boundary Hamiltonians and the relevant equations of motion and boundary conditions are derived.

  17. Irreducible diagrams in Landau-Ginzburg field theory

    Energy Technology Data Exchange (ETDEWEB)

    Witten, Jr, T A [Michigan Univ., Ann Arbor (USA). Dept. of Psychology

    1981-10-19

    It is shown that the free energy W of a Landau-Ginzburg-Wilson field theory with O(n) symmetry may be written in terms of the generating function V of diagrams irreducible in both propagator and interaction lines. This generalizes and simplifies a recent result of Des Cloizeaux. The functions W and V are related by a type of Legendre transformation on the bare mass variable.

  18. Landau-Darrieus instability in an ablation front

    International Nuclear Information System (INIS)

    Piriz, A.R.; Portugues, R.F.

    2003-01-01

    An analytical model that shows the conditions for the existence of the Landau-Darrieus instability of an ablation front is presented. The model seems to agree with recently claimed simulation results [L. Masse et al., Proceedings of the 1st International Conference on Inertial Fusion Sciences and Applications (Elsevier, Paris, 2000), p. 220]. The model shows that the ablation front can be unstable in absence of gravity when the thermal flux is inhibited within the supercritical region of the corona

  19. Landau fluid model for weakly nonlinear dispersive magnetohydrodynamics

    International Nuclear Information System (INIS)

    Passot, T.; Sulem, P. L.

    2005-01-01

    In may astrophysical plasmas such as the solar wind, the terrestrial magnetosphere, or in the interstellar medium at small enough scales, collisions are negligible. When interested in the large-scale dynamics, a hydrodynamic approach is advantageous not only because its numerical simulations is easier than of the full Vlasov-Maxwell equations, but also because it provides a deep understanding of cross-scale nonlinear couplings. It is thus of great interest to construct fluid models that extended the classical magnetohydrodynamic (MHD) equations to collisionless situations. Two ingredients need to be included in such a model to capture the main kinetic effects: finite Larmor radius (FLR) corrections and Landau damping, the only fluid-particle resonance that can affect large scales and can be modeled in a relatively simple way. The Modelization of Landau damping in a fluid formalism is hardly possible in the framework of a systematic asymptotic expansion and was addressed mainly by means of parameter fitting in a linearized setting. We introduced a similar Landau fluid model but, that has the advantage of taking dispersive effects into account. This model properly describes dispersive MHD waves in quasi-parallel propagation. Since, by construction, the system correctly reproduces their linear dynamics, appropriate tests should address the nonlinear regime. In a first case, we show analytically that the weakly nonlinear modulational dynamics of quasi-parallel propagating Alfven waves is well captured. As a second test we consider the parametric decay instability of parallel Alfven waves and show that numerical simulations of the dispersive Landau fluid model lead to results that closely match the outcome of hybrid simulations. (Author)

  20. Boundary condition for Ginzburg-Landau theory of superconducting layers

    Czech Academy of Sciences Publication Activity Database

    Koláček, Jan; Lipavský, Pavel; Morawetz, K.; Brandt, E. H.

    2009-01-01

    Roč. 79, č. 17 (2009), 174510/1-174510/6 ISSN 1098-0121 R&D Projects: GA ČR GA202/08/0326; GA AV ČR IAA100100712 Institutional research plan: CEZ:AV0Z10100521 Keywords : superconductivity * Ginzburg-Landau theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  1. Gauges for the Ginzburg-Landau equations of superconductivity

    International Nuclear Information System (INIS)

    Fleckinger-Pelle, J.; Kaper, H.G.

    1995-01-01

    This note is concerned with gauge choices for the time-dependent Ginzburg-Landau equations of superconductivity. The requiations model the state of a superconducting sample in a magnetic field near the critical tempeature. Any two solutions related through a ''gauge transformation'' describe the same state and are physically indistinquishable. This ''gauge invariance'' can be exploited for analtyical and numerical purposes. A new gauge is proposed, which reduces the equations to a particularly attractive form

  2. Numerical Analysis of Ginzburg-Landau Models for Superconductivity.

    Science.gov (United States)

    Coskun, Erhan

    Thin film conventional, as well as High T _{c} superconductors of various geometric shapes placed under both uniform and variable strength magnetic field are studied using the universially accepted macroscopic Ginzburg-Landau model. A series of new theoretical results concerning the properties of solution is presented using the semi -discrete time-dependent Ginzburg-Landau equations, staggered grid setup and natural boundary conditions. Efficient serial algorithms including a novel adaptive algorithm is developed and successfully implemented for solving the governing highly nonlinear parabolic system of equations. Refinement technique used in the adaptive algorithm is based on modified forward Euler method which was also developed by us to ease the restriction on time step size for stability considerations. Stability and convergence properties of forward and modified forward Euler schemes are studied. Numerical simulations of various recent physical experiments of technological importance such as vortes motion and pinning are performed. The numerical code for solving time-dependent Ginzburg-Landau equations is parallelized using BlockComm -Chameleon and PCN. The parallel code was run on the distributed memory multiprocessors intel iPSC/860, IBM-SP1 and cluster of Sun Sparc workstations, all located at Mathematics and Computer Science Division, Argonne National Laboratory.

  3. Avoidance of a Landau pole by flat contributions in QED

    Energy Technology Data Exchange (ETDEWEB)

    Klaczynski, Lutz, E-mail: lutz.klaczynski@gmx.de [Department of Physics, Humboldt University Berlin, 12489 Berlin (Germany); Kreimer, Dirk, E-mail: kreimer@mathematik.hu-berlin.de [Alexander von Humboldt Chair in Mathematical Physics, Humboldt University, Berlin 12489 (Germany)

    2014-05-15

    We consider massless Quantum Electrodynamics in the momentum scheme and carry forward an approach based on Dyson–Schwinger equations to approximate both the β-function and the renormalized photon self-energy (Yeats, 2011). Starting from the Callan–Symanzik equation, we derive a renormalization group (RG) recursion identity which implies a non-linear ODE for the anomalous dimension and extract a sufficient but not necessary criterion for the existence of a Landau pole. This criterion implies a necessary condition for QED to have no such pole. Solving the differential equation exactly for a toy model case, we integrate the corresponding RG equation for the running coupling and find that even though the β-function entails a Landau pole it exhibits a flat contribution capable of decreasing its growth, in other cases possibly to the extent that such a pole is avoided altogether. Finally, by applying the recursion identity, we compute the photon propagator and investigate the effect of flat contributions on both spacelike and timelike photons. -- Highlights: •We present an approach to approximate both the β-function and the photon self-energy. •We find a sufficient criterion for the self-energy to entail the existence of a Landau pole. •We study non-perturbative ‘flat’ contributions that emerge within the context of our approach. •We discuss a toy model and how it is affected by flat contributions.

  4. Electron Landau damping of ion Bernstein waves in tokamak plasmas

    International Nuclear Information System (INIS)

    Brambilla, M.

    1998-01-01

    Absorption of ion Bernstein (IB) waves by electrons is investigated. These waves are excited by linear mode conversion in tokamak plasmas during fast wave (FW) heating and current drive experiments in the ion cyclotron range of frequencies. Near mode conversion, electromagnetic corrections to the local dispersion relation largely suppress electron Landau damping of these waves, which becomes important again, however, when their wavelength is comparable to the ion Larmor radius or shorter. The small Larmor radius wave equations solved by most numerical codes do not correctly describe the onset of electron Landau damping at very short wavelengths, and these codes, therefore, predict very little damping of IB waves, in contrast to what one would expect from the local dispersion relation. We present a heuristic, but quantitatively accurate, model which allows account to be taken of electron Landau damping of IB waves in such codes, without affecting the damping of the compressional wave or the efficiency of mode conversion. The possibilities and limitations of this approach are discussed on the basis of a few examples, obtained by implementing this model in the toroidal axisymmetric full wave code TORIC. (author)

  5. A Landau fluid model for dissipative trapped electron modes

    International Nuclear Information System (INIS)

    Hedrick, C.L.; Leboeuf, J.N.; Sidikman, K.L.

    1995-09-01

    A Landau fluid model for dissipative trapped electron modes is developed which focuses on an improved description of the ion dynamics. The model is simple enough to allow nonlinear calculations with many harmonics for the times necessary to reach saturation. The model is motivated by a discussion that starts with the gyro-kinetic equation and emphasizes the importance of simultaneously including particular features of magnetic drift resonance, shear, and Landau effects. To ensure that these features are simultaneously incorporated in a Landau fluid model with only two evolution equations, a new approach to determining the closure coefficients is employed. The effect of this technique is to reduce the matching of fluid and kinetic responses to a single variable, rather than two, and to allow focusing on essential features of the fluctuations in question, rather than features that are only important for other types of fluctuations. Radially resolved nonlinear calculations of this model, advanced in time to reach saturation, are presented to partially illustrate its intended use. These calculations have a large number of poloidal and toroidal harmonics to represent the nonlinear dynamics in a converged steady state which includes cascading of energy to both short and long wavelengths

  6. Study of Landau spectrum for a two-dimensional random magnetic field; Etude du spectre de Landau pour un champ magnetique aleatoire en dimension deux

    Energy Technology Data Exchange (ETDEWEB)

    Furtlehner, C. [Paris-6 Univ., 75 (France)

    1997-09-24

    This thesis deals with the two-dimensional problem of a charged particle coupled to a random magnetic field. Various situations are considered, according to the relative importance of the mean value of field and random component. The last one is conceived as a distribution of magnetic impurities (punctual vortex), having various statistical properties (local or non-local correlations, Poisson distribution, etc). The study of this system has led to two distinct situations: - the case of the charged particle feeling the influence of mean field that manifests its presence in the spectrum of broadened Landau levels; - the disordered situation in which the spectrum can be distinguished from the free one only by a low energy Lifshits behaviour. Additional properties are occurring in the limit of `strong` mean field, namely a non-conventional low energy behaviour (in contrast to Lifshits behaviour) which was interpreted in terms of localized states. (author) 78 refs.

  7. Landau-Kleffner syndrome: study of four cases Síndrome de Landau-Kleffner: estudo de quatro casos

    Directory of Open Access Journals (Sweden)

    Lúcia H. Coutinho dos Santos

    2002-06-01

    Full Text Available We describe four patients with clinical features of Landau-Kleffner syndrome and discuss electroencephalographic features, treatment and prognosis. Anticonvulsants and prednisone were used for treatment with good control of seizures in all cases and a less effect response in acquired aphasia. Further studies are necessary to elucidate the causes and management of this syndrome.Descrevemos quatro pacientes com achados clínicos de síndrome de Landau Kleffner . São discutidos os aspectos relacionados aos achados eletrencefalográficos, tratamento e prognóstico. Anticonvulsivantes e prednisona foram os principais métodos terapêuticos utilizados com controle das crises convulsivas em todos os casos e resposta variável quanto a afasia adquirida. Mais estudos são necessários para elucidar as causas e o manejo desta síndrome

  8. Approximate solution of generalized Ginzburg-Landau-Higgs system via homotopy perturbation method

    Energy Technology Data Exchange (ETDEWEB)

    Lu Juhong [School of Physics and Electromechanical Engineering, Shaoguan Univ., Guangdong (China); Dept. of Information Engineering, Coll. of Lishui Professional Tech., Zhejiang (China); Zheng Chunlong [School of Physics and Electromechanical Engineering, Shaoguan Univ., Guangdong (China); Shanghai Inst. of Applied Mathematics and Mechanics, Shanghai Univ., SH (China)

    2010-04-15

    Using the homotopy perturbation method, a class of nonlinear generalized Ginzburg-Landau-Higgs systems (GGLH) is considered. Firstly, by introducing a homotopic transformation, the nonlinear problem is changed into a system of linear equations. Secondly, by selecting a suitable initial approximation, the approximate solution with arbitrary degree accuracy to the generalized Ginzburg-Landau-Higgs system is derived. Finally, another type of homotopic transformation to the generalized Ginzburg-Landau-Higgs system reported in previous literature is briefly discussed. (orig.)

  9. Landau damping due to tune spreads in betatron amplitude and momentum

    International Nuclear Information System (INIS)

    Lee, S.Y.; Tran, P.; Weng, W.T.

    1989-01-01

    Due to the large space charge transverse impedance in a low energy synchrotron, the coherent tune shift causes the Landau damping to be ineffective in damping the transverse coherent motion. We analyze the effect of Landau damping that is caused by the tune spreads of the betatron amplitude (space charge and/or octupole) and momentum. We find that the Landau damping becomes more significant in our two dimensional analysis. 5 refs

  10. Chiral correlators in Landau-Ginsburg theories and N=2 superconformal models

    International Nuclear Information System (INIS)

    Howe, P.S.; West, P.C.

    1989-01-01

    Chiral correlation functions are computed in N=2 Landau-Ginsburg models using the ε-expansion and the superconformal Ward identities for the Landau-Ginsburg effective action. They are also computed directly using superconformal model techniques. The same results are obtained yielding further confirmation of the identification of superconformal minimal models with Landau-Ginsburg models evaluated at their fixed points. The formulae for the chiral commutators that we compute are extremely simple when expressed in terms of effective actions. (orig.)

  11. Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

    Energy Technology Data Exchange (ETDEWEB)

    Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia [Department of Physics, Brown University,Providence RI 02912 (United States)

    2016-03-14

    We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

  12. Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

    International Nuclear Information System (INIS)

    Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia

    2016-01-01

    We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

  13. Design of an rf quadrupole for Landau damping

    Science.gov (United States)

    Papke, K.; Grudiev, A.

    2017-08-01

    The recently proposed superconducting quadrupole resonator for Landau damping in accelerators is subjected to a detailed design study. The optimization process of two different cavity types is presented following the requirements of the High Luminosity Large Hadron Collider (HL-LHC) with the main focus on quadrupolar strength, surface peak fields, and impedance. The lower order and higher order mode (LOM and HOM) spectrum of the optimized cavities is investigated and different approaches for their damping are proposed. On the basis of an example the first two higher order multipole errors are calculated. Likewise on this example the required rf power and optimal external quality factor for the input coupler is derived.

  14. Periods for Calabi-Yau and Landau-Ginzburg vacua

    CERN Document Server

    Berglund, P; De la Ossa, X C; Font, A; Hübsch, T; Jancic, D; Quevedo, Fernando; Berglund, Per; Candelas, Philip; Ossa, Xenia de la; Font, Anamaria; Hubsch, Tristan; Jancic, Dubravka; Quevedo, Fernando

    1994-01-01

    The complete structure of the moduli space of \\cys\\ and the associated Landau-Ginzburg theories, and hence also of the corresponding low-energy effective theory that results from (2,2) superstring compactification, may be determined in terms of certain holomorphic functions called periods. These periods are shown to be readily calculable for a great many such models. We illustrate this by computing the periods explicitly for a number of classes of \\cys. We also point out that it is possible to read off from the periods certain important information relating to the mirror manifolds.

  15. Collisional width of giant resonances and interplay with Landau damping

    International Nuclear Information System (INIS)

    Bonasera, A.; Burgio, G.F.; Di Toro, M.; Wolter, H.H.

    1989-01-01

    We present a semiclassical method to calculate the widths of giant resonances. We solve a mean-field kinetic equation (Vlasov equation) with collision terms treated within the relaxation time approximation to construct a damped strength distribution for collective motions. The relaxation time is evaluated from the time evolution of distortions in the nucleon momentum distribution using a test-particle approach. The importance of an energy dependent nucleon-nucleon cross section is stressed. Results are shown for isoscalar giant quadrupole and octupole motions. A quite important interplay between self-consistent (Landau) and collisional damping is revealed

  16. Landau fluid equations for electromagnetic and electrostatic fluctuations

    International Nuclear Information System (INIS)

    Hedrick, C.L.; Leboeuf, J.

    1992-01-01

    Closure relations are developed to allow approximate treatment of Landau damping and growth using fluid equations for both electrostatic and electromagnetic modes. The coefficients in these closure relations are related to approximations of the plasma dispersion function by ratios of polynomials. Thirteen different numerical sets of coefficients are given and explicitly related to previous fits to the plasma dispersion function. The application of the techniques presented in this paper is illustrated with the specific example of resistive g modes. Comparisons of full kinetic and approximate results are made for the solutions to the dispersion relation, radially resolved modes in sheared magnetic geometry, and the plasma dispersion function itself

  17. Fluid moments of the nonlinear Landau collision operator

    Energy Technology Data Exchange (ETDEWEB)

    Hirvijoki, E.; Pfefferlé, D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lingam, M.; Bhattacharjee, A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Comisso, L. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Candy, J. [General Atomics, San Diego, California 92186 (United States)

    2016-08-15

    An important problem in plasma physics is the lack of an accurate and complete description of Coulomb collisions in associated fluid models. To shed light on the problem, this Letter introduces an integral identity involving the multivariate Hermite tensor polynomials and presents a method for computing exact expressions for the fluid moments of the nonlinear Landau collision operator. The proposed methodology provides a systematic and rigorous means of extending the validity of fluid models that have an underlying inverse-square force particle dynamics to arbitrary collisionality and flow.

  18. About Ginzburg-Landau, and a bit on others

    International Nuclear Information System (INIS)

    Maksimov, Evgenii G

    2011-01-01

    This note is a brief history of how the theory of Ginzburg and Landau came to be. Early publications on the macroscopic theory of superconductivity are reviewed in detail. Discussions that the two co-authors had with their colleagues and between themselves are described. The 1952 review by V L Ginzburg is discussed, in which a number of well-defined requirements on the yet-to-be-developed microscopic theory of superconductivity were formulated, constituting what J Bardeen called the 'Ginzburg energy gap model'. (from the history of physics)

  19. Reversible dissipative processes, conformal motions and Landau damping

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, L., E-mail: laherrera@cantv.net.ve [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain); Di Prisco, A., E-mail: adiprisc@fisica.ciens.ucv.ve [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain); Ibáñez, J., E-mail: j.ibanez@ehu.es [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain)

    2012-02-06

    The existence of a dissipative flux vector is known to be compatible with reversible processes, provided a timelike conformal Killing vector (CKV) χ{sup α}=(V{sup α})/T (where V{sup α} and T denote the four-velocity and temperature respectively) is admitted by the spacetime. Here we show that if a constitutive transport equation, either within the context of standard irreversible thermodynamics or the causal Israel–Stewart theory, is adopted, then such a compatibility also requires vanishing dissipative fluxes. Therefore, in this later case the vanishing of entropy production generated by the existence of such CKV is not actually associated to an imperfect fluid, but to a non-dissipative one. We discuss also about Landau damping. -- Highlights: ► We review the problem of compatibility of dissipation with reversibility. ► We show that the additional assumption of a transport equation renders such a compatibility trivial. ► We discuss about Landau damping.

  20. Fourier acceleration in lattice gauge theories. I. Landau gauge fixing

    International Nuclear Information System (INIS)

    Davies, C.T.H.; Batrouni, G.G.; Katz, G.R.; Kronfeld, A.S.; Lepage, G.P.; Wilson, K.G.; Rossi, P.; Svetitsky, B.

    1988-01-01

    Fourier acceleration is a useful technique which can be applied to many different numerical algorithms in order to alleviate the problem of critical slowing down. Here we describe its application to an optimization problem in the simulation of lattice gauge theories, that of gauge fixing a configuration of link fields to the Landau gauge (partial/sub μ/A/sup μ/ = 0). We find that a steepest-descents method of gauge fixing link fields at β = 5.8 on an 8 4 lattice can be made 5 times faster using Fourier acceleration. This factor will grow as the volume of the lattice is increased. We also discuss other gauges that are useful to lattice-gauge-theory simulations, among them one that is a combination of the axial and Landau gauges. This seems to be the optimal gauge to impose for the Fourier acceleration of two other important algorithms, the inversion of the fermion matrix and the updating of gauge field configurations

  1. The Landau-Lifshitz equation of the ferromagnetic spin chain and harmonic maps

    International Nuclear Information System (INIS)

    Guo Boling; Hong Minchun.

    1992-05-01

    We prove a global existence of solutions for the Landau-Lifshitz equation of the ferromagnetic spin chain from an m-dimensional manifold M into the unit sphere S 2 of R 3 and establish some new links between harmonic maps and the solutions of the Landau-Lifshitz equation. (author). 25 refs

  2. Solution Theory of Ginzburg-Landau Theory on BCS-BEC Crossover

    Directory of Open Access Journals (Sweden)

    Shuhong Chen

    2014-01-01

    Full Text Available We establish strong solution theory of time-dependent Ginzburg-Landau (TDGL systems on BCS-BEC crossover. By the properties of Besov, Sobolev spaces, and Fourier functions and the method of bootstrapping argument, we deduce that the global existence of strong solutions to time-dependent Ginzburg-Landau systems on BCS-BEC crossover in various spatial dimensions.

  3. Integral definition of transition time in the Landau-Zener model

    International Nuclear Information System (INIS)

    Yan Yue; Wu Biao

    2010-01-01

    We give a general definition for the transition time in the Landau-Zener model. This definition allows us to compute numerically the Landau-Zener transition time at any sweeping rate without ambiguity in both diabatic and adiabatic bases. With this new definition, analytical results are obtained in both the adiabatic limit and the sudden limit.

  4. Noise-sustained structure, Intermittency, and the Ginzburg--Landau equation

    International Nuclear Information System (INIS)

    Deissler, R.J.

    1985-01-01

    The time-dependent generalized Ginzburg--Landau equation is an equation that is related to many physical systems. Solutions of this equation in the presence of low-level external noise are studied. Numerical solutions of this equation in the stationary frame of refernce and with nonzero group velocity that is greater than a critical velocity exhibit a selective spatial amplification of noise resulting in spatially growing waves. These waves in turn result in the formation of a dynamic structure. It is found that the microscopic noise plays an importuant role in the macroscopic dynamics of the system. For certain parameter values the system exhibits intermittent turbulent behavior in which the random nature of the external noise plays a crucial role. A mechanism which may be responsible for the intermittent turbulence occurring in some fluid systems is suggested

  5. Fine structure of the isoscalar giant quadrupole resonance in 40Ca due to Landau damping?

    International Nuclear Information System (INIS)

    Usman, I.; Buthelezi, Z.; Carter, J.; Cooper, G.R.J.; Fearick, R.W.; Foertsch, S.V.; Fujita, H.; Fujita, Y.; Kalmykov, Y.; Neumann-Cosel, P. von; Neveling, R.; Papakonstantinou, P.; Richter, A.; Roth, R.; Shevchenko, A.; Sideras-Haddad, E.; Smit, F.D.

    2011-01-01

    The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40 Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at E p =200 MeV. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon-nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40 Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle-two-hole (2p-2h) states.

  6. Study of Landau spectrum for a two-dimensional random magnetic field

    International Nuclear Information System (INIS)

    Furtlehner, C.

    1997-01-01

    This thesis deals with the two-dimensional problem of a charged particle coupled to a random magnetic field. Various situations are considered, according to the relative importance of the mean value of field and random component. The last one is conceived as a distribution of magnetic impurities (punctual vortex), having various statistical properties (local or non-local correlations, Poisson distribution, etc). The study of this system has led to two distinct situations: - the case of the charged particle feeling the influence of mean field that manifests its presence in the spectrum of broadened Landau levels; - the disordered situation in which the spectrum can be distinguished from the free one only by a low energy Lifshits behaviour. Additional properties are occurring in the limit of 'strong' mean field, namely a non-conventional low energy behaviour (in contrast to Lifshits behaviour) which was interpreted in terms of localized states. (author)

  7. The damping of spin motions in ultrathin films: Is the Landau-Lifschitz-Gilbert phenomenology applicable?

    International Nuclear Information System (INIS)

    Mills, D.L.; Arias, Rodrigo

    2006-01-01

    The Landau-Lifschitz-Gilbert (LLG) equation is used widely in device design to describe spin motions in magnetic nanoscale structures. The damping term in this equation plays an essential role in the description of the magnetization dynamics. The form of this term is simple and appealing, but it is derived through use of elementary phenomenological considerations. An important question is whether or not it provides a proper description of the damping of the magnetization in real materials. Recently, it was predicted that a mechanism called two magnon damping should contribute importantly to linewidths and consequently spin damping in ultrathin ferromagnetic films. This process yields ferromagnetic resonance (FMR) linewidths whose frequency dependence is incompatible with the linear variation expected from the Landau-Lifschitz equation. This prediction has now been confirmed experimentally. Furthermore, subsequent experimental and theoretical studies have demonstrated that the damping rate depends strongly on wave vector as well. It is thus clear that for many samples, the LLG equation fails to account for the systematics of the damping of the magnetization in ultrathin ferromagnets, at the linear response level. The paper will review the recent literature on this topic relevant to this issue. One must then inquire into the nature of a proper phenomenology to describe these materials. At the linear response level, the theory of the two magnon mechanism is sufficiently complete that one can describe the response of these systems without resort to LLG phenomenology. However, currently there is very great interest in the large amplitude response of the magnetization in magnetic nanostructures. In the view of the authors, it is difficult to envision a generally applicable extension of linear response theory into the large amplitude regime

  8. Dual Ginzburg-Landau theory and quark nuclear physics

    International Nuclear Information System (INIS)

    Toki, Hiroshi

    1999-01-01

    The elementary building blocks of matter are quarks. Hence, it is fundamental to describe hadrons and nuclei in terms of quarks and gluons, the subject of which is called Quark Nuclear Physics. The quark-dynamics is described by Quantum Chromodynamics (QCD). Our interest is the non-perturbative aspect of QCD as confinement, chiral symmetry breaking, hadronization etc. We introduce the dual Ginzburg-Landau theory (DGL), where the color monopole fields and their condensation is the QCD vacuum, play essential roles in describing these non-perturbative phenomena. We emphasize its connection to QCD through the use of the Abelian gauge. We apply the DGL theory to various observables. We discuss then the connection of the monopole fields with instantons, which are the classical solutions of the non-Abelian gauge theory and connect through the tunneling process QCD vacuum with different winding numbers. (author)

  9. Ginsburg-Landau equation around the superconductor-insulator transition

    International Nuclear Information System (INIS)

    Ng, T.K.

    1991-01-01

    Based on the scaling theory of localization, we construct a Ginsburg-Landau (GL) equation for superconductors in an arbitrary strength of disordered potential. Using this GL equation, we reexamine the criteria for the superconductor-insulator transition and find that the transition to a localized superconductor can happen on both sides of the (normal) metal-insulator transition, in contrast to a previous prediction by Ma and Lee [Phys. Rev. B 32, 5658 (1985)] that the transition can only be on the insulator side. Furthermore, by comparing our theory with a recent scaling theory of dirty bosons by Fisher et al. [Phys. Rev. Lett. 64, 587 (1990)], we conclude that nontrivial crossover behavior in transport properties may occur in the vicinity of the superconductor-insulator transition

  10. Geometry of (0,2) Landau-Ginzburg orbifolds

    International Nuclear Information System (INIS)

    Kawai, Toshiya; Mohri, Kenji

    1994-01-01

    Several aspects of (0,2) Landau-Ginzburg orbifolds are investigated. Especially the elliptic genera are computed in general and, for a class of models recently invented by Distler and Kachru, they are compared with the ones from (0,2) sigma models. Our formalism gives an easy way to calculate the generation numbers for lots of Distler-Kachru models even if they are based on singular Calabi-Yau spaces. We also make some general remarks on the Born-Oppenheimer calculation of the ground states elucidating its mathematical meaning in the untwisted sector. For Distler-Kachru models based on non-singular Calabi-Yau spaces we show that there exist ''residue'' type formulas of the elliptic genera as well. ((orig.))

  11. Asymmetric Landau bands due to spin–orbit coupling

    International Nuclear Information System (INIS)

    Erlingsson, Sigurdur I; Manolescu, Andrei; Marinescu, D C

    2015-01-01

    We show that the Landau bands obtained in a two-dimensional lateral semiconductor superlattice with spin–orbit coupling (SOC) of the Rashba/Dresselhaus type, linear in the electron momentum, placed in a tilted magnetic field, do not follow the symmetry of the spatial modulation. Moreover, this phenomenology is found to depend on the relative tilt of magnetic field and on the SOC type: (a) when only Rashba SOC exists and the magnetic field is tilted in the direction of the superlattice (b) Dresselhaus SOC exists and the magnetic field is tilted in the direction perpendicular to the superlattice. Consequently, measurable properties of the modulated system become anisotropic in a tilted magnetic field when the field is conically rotated around the z axis, at a fixed polar angle, as we demonstrate by calculating the resistivity and the magnetization. (paper)

  12. Generalized Landau-Lifshitz-Gilbert equation for uniformly magnetized bodies

    Energy Technology Data Exchange (ETDEWEB)

    Serpico, C. [Dipartimento di Ingegneria Elettrica, Universita di Napoli ' FedericoII' , Via Claudio 21, I-80125 Naples (Italy)], E-mail: serpico@unina.it; Mayergoyz, I.D. [ECE Department and UMIACS, University of Maryland, College Park, MD 20742 (United States); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica (INRiM), I-10135 Turin (Italy); D' Aquino, M. [Dipartimento per le Tecnologie, University of Napoli ' Parthenope' , I-80133 Naples (Italy); Bonin, R. [Istituto Nazionale di Ricerca Metrologica (INRiM), I-10135 Turin (Italy)

    2008-02-01

    We consider generalized Landau-Lifshitz-Gilbert (LLG) deterministic dynamics in uniformly magnetized bodies. The dynamics take place on the unit sphere {sigma}, and are characterized by a vector field v tangential to {sigma}. By using Helmholtz decomposition on {sigma}, it is proven that v is uniquely defined by two potentials {chi} and {psi}. Potential {chi} can be identified with the free energy of the system, while {psi} describes non-conservative interactions of the system with the environment. The presence of {psi} modifies the usual energy balance of LLG dynamics. Instead of purely relaxation dynamics we may have steady injection of energy through non-conservative interactions. The implications of the new form of the energy balance are discussed in detail.

  13. Quenching oscillating behaviors in fractional coupled Stuart-Landau oscillators

    Science.gov (United States)

    Sun, Zhongkui; Xiao, Rui; Yang, Xiaoli; Xu, Wei

    2018-03-01

    Oscillation quenching has been widely studied during the past several decades in fields ranging from natural sciences to engineering, but investigations have so far been restricted to oscillators with an integer-order derivative. Here, we report the first study of amplitude death (AD) in fractional coupled Stuart-Landau oscillators with partial and/or complete conjugate couplings to explore oscillation quenching patterns and dynamics. It has been found that the fractional-order derivative impacts the AD state crucially. The area of the AD state increases along with the decrease of the fractional-order derivative. Furthermore, by introducing and adjusting a limiting feedback factor in coupling links, the AD state can be well tamed in fractional coupled oscillators. Hence, it provides one an effective approach to analyze and control the oscillating behaviors in fractional coupled oscillators.

  14. Design of an rf quadrupole for Landau damping

    Directory of Open Access Journals (Sweden)

    K. Papke

    2017-08-01

    Full Text Available The recently proposed superconducting quadrupole resonator for Landau damping in accelerators is subjected to a detailed design study. The optimization process of two different cavity types is presented following the requirements of the High Luminosity Large Hadron Collider (HL-LHC with the main focus on quadrupolar strength, surface peak fields, and impedance. The lower order and higher order mode (LOM and HOM spectrum of the optimized cavities is investigated and different approaches for their damping are proposed. On the basis of an example the first two higher order multipole errors are calculated. Likewise on this example the required rf power and optimal external quality factor for the input coupler is derived.

  15. Landau Damping of Beam Instabilities by Electron Lenses

    Energy Technology Data Exchange (ETDEWEB)

    Shiltsev, V. [Fermilab; Alexahin, Yuri; Burov, A. [Fermilab; Valishev, A. [Fermilab

    2017-06-26

    Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, a magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.

  16. Dual Ginzburg-Landau theory and quark nuclear physics

    International Nuclear Information System (INIS)

    Toki, H.; Suganuma, H.; Ichie, H.; Monden, H.; Umisedo, S.

    1998-01-01

    In quark nuclear physics (QNP), where hadrons and nuclei are described in terms of quarks and gluons, confinement and chiral symmetry breaking are the most fundamental phenomena. The dual Ginzburg-Landau (DGL) theory, which contains monopole fields as the most essential degrees of freedom and their condensation in the vacuum, is able to describe both phenomena. We discuss also the recovery of the chiral symmetry and the deconfinement phase transition at finite temperature in the DGL theory. As for the connection to QCD, we study the instanton configurations in the abelian gauge a la 't Hooft. We find a close connection between instantons and QCD monopoles. We demonstrate also the signature of confinement as the appearance of long monopole trajectories in the MA gauge for the case of dense instanton configurations. (orig.)

  17. Multiple Walkers in the Wang-Landau Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Brown, G

    2005-12-28

    The mean cost for converging an estimated density of states using the Wang-Landau algorithm is measured for the Ising and Heisenberg models. The cost increases in a power-law fashion with the number of spins, with an exponent near 3 for one-dimensional models, and closer to 2.4 for two-dimensional models. The effect of multiple, simultaneous walkers on the cost is also measured. For the one-dimensional Ising model the cost can increase with the number of walkers for large systems. For both the Ising and Heisenberg models in two-dimensions, no adverse impact on the cost is observed. Thus multiple walkers is a strategy that should scale well in a parallel computing environment for many models of magnetic materials.

  18. Landau damping: the mechanics model and its ultimate entropy gain

    International Nuclear Information System (INIS)

    Hannay, J H; Kluge, Michel

    2011-01-01

    Classical mechanics has only been invoked to account for Landau damping in a rather half-hearted way, alongside plasma perturbation theory. In particular this invocation is essential for the study of the saturation, or post-linear (or 'nonlinear') regime of the damping initiated by Dawson and O'Neill. By embracing mechanics wholeheartedly here, with its attendant phase space, one can access results, old and new, cleanly and directly, and with one fewer numerical integration for the post-linear regime. By using a summation technique familiar in semiclassical quantum mechanics (Poisson summation), the one remaining numerical integration can be much improved in accuracy. Also accessible from mechanics is the ultimate entropy gain. Though zero for any finite time (in the absence of coarse graining), the entropy gain is ultimately non-zero (at infinite time the required coarse graining is zero). It is calculated analytically by using the appropriate asymptotics, hitherto not fully exploited.

  19. Berry phases for Landau Hamiltonians on deformed tori

    Science.gov (United States)

    Lévay, Péter

    1995-06-01

    Parametrized families of Landau Hamiltonians are introduced, where the parameter space is the Teichmüller space (topologically the complex upper half plane) corresponding to deformations of tori. The underlying SO(2,1) symmetry of the families enables an explicit calculation of the Berry phases picked up by the eigenstates when the torus is slowly deformed. It is also shown that apart from these phases that are local in origin, there are global non-Abelian ones too, related to the hidden discrete symmetry group Γϑ (the theta group, which is a subgroup of the modular group) of the families. The induced Riemannian structure on the parameter space is the usual Poincare metric on the upper half plane of constant negative curvature. Due to the discrete symmetry Γϑ the geodesic motion restricted to the fundamental domain of this group is chaotic.

  20. Weak coupling polaron and Landau-Zener scenario: Qubits modeling

    Science.gov (United States)

    Jipdi, M. N.; Tchoffo, M.; Fokou, I. F.; Fai, L. C.; Ateuafack, M. E.

    2017-06-01

    The paper presents a weak coupling polaron in a spherical dot with magnetic impurities and investigates conditions for which the system mimics a qubit. Particularly, the work focuses on the Landau-Zener (LZ) scenario undergone by the polaron and derives transition coefficients (transition probabilities) as well as selection rules for polaron's transitions. It is proven that, the magnetic impurities drive the polaron to a two-state superposition leading to a qubit structure. We also showed that the symmetry deficiency induced by the magnetic impurities (strong magnetic field) yields to the banishment of transition coefficients with non-stacking states. However, the transition coefficients revived for large confinement frequency (or weak magnetic field) with the orbital quantum numbers escorting transitions. The polaron is then shown to map a qubit independently of the number of relevant states with the transition coefficients lifted as LZ probabilities and given as a function of the electron-phonon coupling constant (Fröhlich constant).

  1. Spatially Localized Particle Energization by Landau Damping in Current Sheets

    Science.gov (United States)

    Howes, G. G.; Klein, K. G.; McCubbin, A. J.

    2017-12-01

    Understanding the mechanisms of particle energization through the removal of energy from turbulent fluctuations in heliospheric plasmas is a grand challenge problem in heliophysics. Under the weakly collisional conditions typical of heliospheric plasma, kinetic mechanisms must be responsible for this energization, but the nature of those mechanisms remains elusive. In recent years, the spatial localization of plasma heating near current sheets in the solar wind and numerical simulations has gained much attention. Here we show, using the innovative and new field-particle correlation technique, that the spatially localized particle energization occurring in a nonlinear gyrokinetic simulation has the velocity space signature of Landau damping, suggesting that this well-known collisionless damping mechanism indeed actively leads to spatially localized heating in the vicinity of current sheets.

  2. Transit-Time Damping, Landau Damping, and Perturbed Orbits

    Science.gov (United States)

    Simon, A.; Short, R. W.

    1997-11-01

    Transit-time damping(G.J. Morales and Y.C. Lee, Phys. Rev. Lett. 33), 1534 (1974).*^,*(P.A. Robinson, Phys. Fluids B 3), 545 (1991).** has traditionally been obtained by calculating the net energy gain of transiting electrons, of velocity v, to order E^2* in the amplitude of a localized electric field. This necessarily requires inclusion of the perturbed orbits in the equation of motion. A similar method has been used by others(D.R. Nicholson, Introduction to Plasma Theory) (Wiley, 1983).*^,*(E.M. Lifshitz and L.P. Pitaevskifi, Physical Kinetics) (Pergamon, 1981).** to obtain a ``physical'' picture of Landau damping in a nonlocalized field. The use of perturbed orbits seems odd since the original derivation of Landau (and that of Dawson) never went beyond a linear picture of the dynamics. We introduce a novel method that takes advantage of the time-reversal invariance of the Vlasov equation and requires only the unperturbed orbits to obtain the result. Obviously, there is much reduction in complexity. Application to finite slab geometry yields a simple expression for the damping rate. Equivalence to much more complicated results^2* is demonstrated. This method allows us to calculate damping in more complicated geometries and more complex electric fields, such as occur in SRS in filaments. See accompanying talk.(R.W. Short and A. Simon, this conference.) This work was supported by the U.S. DOE Office of Inertial Confinement Fusion under Co-op Agreement No. DE-FC03-92SF19460.

  3. Ginzburg-Landau equation and vortex liquid phase of Fermi liquid superconductors

    International Nuclear Information System (INIS)

    Ng, T-K; Tse, W-T

    2007-01-01

    In this paper we study the Ginzburg-Landau (GL) equation for Fermi liquid superconductors with strong Landau interactions F 0s and F 1s . We show that Landau interactions renormalize two parameters entering the GL equation, leading to the renormalization of the compressibility and superfluid density. The renormalization of the superfluid density in turn leads to an unconventional (2D) Berezinskii-Kosterlitz-Thouless (BKT) transition and vortex liquid phase. Application of the GL equation to describe underdoped high-T c cuprates is discussed

  4. Multiphonon generation during photodissociation of slow Landau-Pekar polarons

    International Nuclear Information System (INIS)

    Myasnikov, E. N.; Myasnikova, A. E.; Mastropas, Z. P.

    2006-01-01

    The spectra of the low-temperature photodissociation (photoionization) of Landau-Pekar polarons are calculated using the theory of quantum-coherent states and a new method of variation with respect to the parameters of phonon vacuum deformation. It is shown that the final polaron states upon photodissociation may have different numbers of phonons produced in a single dissociation event and different momenta of charge carriers. The spectrum of optical absorption related to the photodissociation of polarons exhibits a superposition of bands corresponding to various numbers of phonons formed as a result of dissociation of a single polaron. Due to a large width of the energy region corresponding to the final states of charge carriers, the halfwidth of each band is on the order of the energy of polaron coupling and is much greater than the phonon energy. For this reason, the individual phonon bands exhibit strong overlap. The very broad and, probably, structureless band formed as a result of the superposition of all these components begins at an energy equal to the sum of the polaron coupling energy (E p ) and the phonon energy. This band has a maximum at a frequency of about 5.6E p /ℎ and a halfwidth on the order of 5.6E p /ℎ at a unit effective mass (m* = m e ) of band electrons. For an effective charge carrier mass within m* = (1-3)m e , the energy of the polaron band maximum can be estimated as 5E p with an error of about 10%, and the halfwidth falls within 3.4E p 1/2 p . The multiphonon character of this band is related to a decay of the phonon condensate after the escape of charge carrier from a polaron. Such polarons are likely to be observed in the spectra of complex metal oxides, including high-temperature superconductors. Examples of such polaron bands in the reported absorption and photoconductivity spectra of nonstoichiometric cuprates, manganites, nickelates, and titanates are presented. A theory of the formation of Landau-Pekar polarons with the

  5. Electron Landau damping of lower hybrid waves from a finite length antenna

    International Nuclear Information System (INIS)

    Brambilla, M.

    1977-01-01

    Launching and propagation of Lower Hybrid Waves to heat large plasmas by Electron Landau Damping is discussed. Conditions on the appropriate frequency and on the antenna location in the plasma density profile are derived

  6. Symmetry of Uniaxial Global Landau--de Gennes Minimizers in the Theory of Nematic Liquid Crystals

    KAUST Repository

    Henao, Duvan; Majumdar, Apala

    2012-01-01

    We extend the recent radial symmetry results by Pisante [J. Funct. Anal., 260 (2011), pp. 892-905] and Millot and Pisante [J. Eur. Math. Soc. (JEMS), 12 (2010), pp. 1069- 1096] (who show that the equivariant solutions are the only entire solutions of the three-dimensional Ginzburg-Landau equations in superconductivity theory) to the Landau-de Gennes framework in the theory of nematic liquid crystals. In the low temperature limit, we obtain a characterization of global Landau-de Gennes minimizers, in the restricted class of uniaxial tensors, in terms of the well-known radial-hedgehog solution. We use this characterization to prove that global Landau-de Gennes minimizers cannot be purely uniaxial for sufficiently low temperatures. Copyright © by SIAM.

  7. Surface Acoustic Analog of Bloch Oscillations, Wannier-Stark Ladders and Landau-Zener Tunneling

    Science.gov (United States)

    de Lima, M. M.; Kosevich, Yu. A.; Santos, P. V.; Cantarero, A.

    2011-12-01

    In this contribution, we discuss the recent experimental demonstration of Wannier-Stark ladders, Bloch Oscillations and Landau Zener tunneling in a solid by means of surface acoustic waves propagating through perturbed grating structures.

  8. Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

    Science.gov (United States)

    Lee, Myoung-Jae; Jung, Young-Dae

    2018-04-01

    The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

  9. Dispersion relation and Landau damping of waves in high-energy density plasmas

    International Nuclear Information System (INIS)

    Zhu Jun; Ji Peiyong

    2012-01-01

    We present a theoretical investigation on the propagation of electromagnetic waves and electron plasma waves in high energy density plasmas using the covariant Wigner function approach. Based on the covariant Wigner function and Dirac equation, a relativistic quantum kinetic model is established to describe the physical processes in high-energy density plasmas. With the zero-temperature Fermi–Dirac distribution, the dispersion relation and Landau damping of waves containing the relativistic quantum corrected terms are derived. The relativistic quantum corrections to the dispersion relation and Landau damping are analyzed by comparing our results with those obtained in classical and non-relativistic quantum plasmas. We provide a detailed discussion on the Landau damping obtained in classical plasmas, non-relativistic Fermi plasmas and relativistic Fermi plasmas. The contributions of the Bohm potential, the Fermi statistics pressure and relativistic effects to the dispersion relation and Landau damping of waves are quantitatively calculated with real plasma parameters. (paper)

  10. Landau-Ginzburg orbifolds and symmetries of K3 CFTs

    International Nuclear Information System (INIS)

    Cheng, Miranda C. N.; Ferrari, Francesca; Harrison, Sarah M.; Paquette, Natalie M.

    2017-01-01

    Recent developments in the study of the moonshine phenomenon, including umbral and Conway moonshine, suggest that it may play an important role in encoding the action of finite symmetry groups on the BPS spectrum of K 3 string theory. To test and clarify these proposed K 3 -moonshine connections, we study Landau-Ginzburg orbifolds that flow to conformal field theories in the moduli space of K 3 sigma models. We compute K 3 elliptic genera twined by discrete symmetries that are manifest in the UV description, though often inaccessible in the IR. We obtain various twining functions coinciding with moonshine predictions that have not been observed in physical theories before. These include twining functions arising from Mathieu moonshine, other cases of umbral moonshine, and Conway moonshine. For instance, all functions arising from M 11 c 2.M 12 moonshine appear as explicit twining genera in the LG models, which moreover admit a uniform description in terms of its natural 12-dimensional representation. Finally, our results provide strong evidence for the relevance of umbral moonshine for K 3 symmetries, as well as new hints for its eventual explanation.

  11. Landau-Ginzburg orbifolds and symmetries of K3 CFTs

    Science.gov (United States)

    Cheng, Miranda C. N.; Ferrari, Francesca; Harrison, Sarah M.; Paquette, Natalie M.

    2017-01-01

    Recent developments in the study of the moonshine phenomenon, including umbral and Conway moonshine, suggest that it may play an important role in encoding the action of finite symmetry groups on the BPS spectrum of K3 string theory. To test and clarify these proposed K3-moonshine connections, we study Landau-Ginzburg orbifolds that flow to conformal field theories in the moduli space of K3 sigma models. We compute K3ellipticgeneratwinedbydiscretesymmetriesthataremanifestintheUVdescription, though often inaccessible in the IR. We obtain various twining functions coinciding with moonshine predictions that have not been observed in physical theories before. These include twining functions arising from Mathieu moonshine, other cases of umbral moonshine, and Conway moonshine. For instance, all functions arising from M 11 ⊂ 2 .M 12 moonshine appear as explicit twining genera in the LG models, which moreover admit a uniform description in terms of its natural 12-dimensional representation. Our results provide strong evidence for the relevance of umbral moonshine for K3 symmetries, as well as new hints for its eventual explanation.

  12. On Landau Scenario of Chaotization for Beam Distribution

    International Nuclear Information System (INIS)

    Parsa, Z.; Zadorozhny, V.

    1999-01-01

    We examine a problem in nonlinear dynamics in which both regular and chaotic motions are possible. Thus we deal with some of the fundamental theoretical problem of accelerator physics, mathematics theory of dynamical systems, and other fields of physics. The focus is on the appearance of chaos in a beam distribution. A study of the problem is based on two observations. The First observation is that using Lyapunov method and its extension we obtain solutions of partial differential equations. Using this approach we discuss the problem of finding a solution of Vlasov-Poisson equation, i.e., some stationary solution where we consider magnetic field as some disturbance with a small parameter. Thus the solution of Vlasov equation yields an asymptotic series such that the solution of Vlasov-Poisson equation is the basis solution for one. The second observation is that physical chaos is weakly limit of, well known, the Landau bifurcation's. This fact we have proved using ideas on the Nature of Turbulence

  13. Attractive Hubbard model: Homogeneous Ginzburg–Landau expansion and disorder

    International Nuclear Information System (INIS)

    Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.

    2016-01-01

    We derive a Ginzburg–Landau (GL) expansion in the disordered attractive Hubbard model within the combined Nozieres–Schmitt-Rink and DMFT+Σ approximation. Restricting ourselves to the homogeneous expansion, we analyze the disorder dependence of GL expansion coefficients for a wide range of attractive potentials U, from the weak BCS coupling region to the strong-coupling limit, where superconductivity is described by Bose–Einstein condensation (BEC) of preformed Cooper pairs. We show that for the a semielliptic “bare” density of states of the conduction band, the disorder influence on the GL coefficients A and B before quadratic and quartic terms of the order parameter, as well as on the specific heat discontinuity at the superconducting transition, is of a universal nature at any strength of the attractive interaction and is related only to the general widening of the conduction band by disorder. In general, disorder growth increases the values of the coefficients A and B, leading either to a suppression of the specific heat discontinuity (in the weak-coupling limit), or to its significant growth (in the strong-coupling region). However, this behavior actually confirms the validity of the generalized Anderson theorem, because the disorder dependence of the superconducting transition temperature T c , is also controlled only by disorder widening of the conduction band (density of states).

  14. MD 1407 - Landau Damping: Beam Transfer Functions and diffusion mechanisms

    CERN Document Server

    Tambasco, Claudia; Boccardi, Andrea; Buffat, Xavier; Gasior, Marek; Lefevre, Thibaut; Levens, Tom; Pojer, Mirko; Salvachua Ferrando, Belen Maria; Solfaroli Camillocci, Matteo; Pieloni, Tatiana; Crouch, Matthew Paul; CERN. Geneva. ATS Department

    2017-01-01

    In the 2012, 2015 and 2016 run several instabilities were developing at flat-top, during and at the end of the betatron squeeze where beam-beam interactions are present. The tune spread in the beams is therefore modified by the beam-beam long-range interactions and by other sources of spread. Studies of the stability area computed by evaluating the dispersion integral for different tune spreads couldn’t explain the observed instabilities during the squeeze and stable beams. The size of the stability area given by the computed dispersion integral depends on the transverse tune spread but its shape is defined by the particle distribution in the beams. Therefore any change of the particle distribution can lead to a deterioration of the Landau stability area. The Beam Transfer Functions (BTF) are direct measurements of the Stability Diagrams (SD). They are sensitive to particle distributions and contain information about the transverse tune spread in the beams. In this note are summarized the results of the BTF...

  15. Non perturbative analysis of an N=2 Landau-Ginsburg model

    International Nuclear Information System (INIS)

    Leaf Herrmann, W.A.

    1993-01-01

    We analyze the topological sector of an N=2 Landau-Ginsburg model using nonperturbative methods. In particular, we study the renormalization group flow between two superconformal minimal models, numerically compute the correlation functions along this trajectory, and compare the results to semi-classical calculations. We also study some aspects of arbitrary supersymmetric perturbations of the Landau-Ginsburg model. 20 refs, 4 figs

  16. Landau Damping of the Weak Head-Tail Instability at Tevatron

    CERN Document Server

    Ivanov, Petr M; Annala, Jerry; Lebedev, Valeri; Shiltsev, Vladimir

    2005-01-01

    Landau damping of the head-tail modes in Tevatron beam with the help of octupole-generated betatron tune spreads permits to reduce chromaticity from 15-20 units to zero thus significantly improving the beam lifetime. The octupole strengths have been experimentally optimized at different stages of the Tevatron operation, from proton injection to collision. Predictions of the analytical Landau damping model are compared with the experimental results.

  17. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    International Nuclear Information System (INIS)

    Hwa-Min, Kim; Young-Dae, Jung

    2007-01-01

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle θ L = π/4. (authors)

  18. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hwa-Min, Kim [Daegu Univ. Catholic, Dept. of Electronics Engineering (Korea, Republic of); Young-Dae, Jung [Hanyang Univ., Dept. of Applied Physics, Seoul (Korea, Republic of)

    2007-07-15

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle {theta}{sub L} = {pi}/4. (authors)

  19. On the quantum Landau collision operator and electron collisions in dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Daligault, Jérôme, E-mail: daligaul@lanl.gov [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-03-15

    The quantum Landau collision operator, which extends the widely used Landau/Fokker-Planck collision operator to include quantum statistical effects, is discussed. The quantum extension can serve as a reference model for including electron collisions in non-equilibrium dense plasmas, in which the quantum nature of electrons cannot be neglected. In this paper, the properties of the Landau collision operator that have been useful in traditional plasma kinetic theory and plasma transport theory are extended to the quantum case. We outline basic properties in connection with the conservation laws, the H-theorem, and the global and local equilibrium distributions. We discuss the Fokker-Planck form of the operator in terms of three potentials that extend the usual two Rosenbluth potentials. We establish practical closed-form expressions for these potentials under local thermal equilibrium conditions in terms of Fermi-Dirac and Bose-Einstein integrals. We study the properties of linearized quantum Landau operator, and extend two popular approximations used in plasma physics to include collisions in kinetic simulations. We apply the quantum Landau operator to the classic test-particle problem to illustrate the physical effects embodied in the quantum extension. We present useful closed-form expressions for the electron-ion momentum and energy transfer rates. Throughout the paper, similarities and differences between the quantum and classical Landau collision operators are emphasized.

  20. On the quantum Landau collision operator and electron collisions in dense plasmas

    Science.gov (United States)

    Daligault, Jérôme

    2016-03-01

    The quantum Landau collision operator, which extends the widely used Landau/Fokker-Planck collision operator to include quantum statistical effects, is discussed. The quantum extension can serve as a reference model for including electron collisions in non-equilibrium dense plasmas, in which the quantum nature of electrons cannot be neglected. In this paper, the properties of the Landau collision operator that have been useful in traditional plasma kinetic theory and plasma transport theory are extended to the quantum case. We outline basic properties in connection with the conservation laws, the H-theorem, and the global and local equilibrium distributions. We discuss the Fokker-Planck form of the operator in terms of three potentials that extend the usual two Rosenbluth potentials. We establish practical closed-form expressions for these potentials under local thermal equilibrium conditions in terms of Fermi-Dirac and Bose-Einstein integrals. We study the properties of linearized quantum Landau operator, and extend two popular approximations used in plasma physics to include collisions in kinetic simulations. We apply the quantum Landau operator to the classic test-particle problem to illustrate the physical effects embodied in the quantum extension. We present useful closed-form expressions for the electron-ion momentum and energy transfer rates. Throughout the paper, similarities and differences between the quantum and classical Landau collision operators are emphasized.

  1. Combined study of the gluon and ghost condensates μ2> and abccbcc> in Euclidean SU(2) Yang-Mills theory in the Landau gauge

    International Nuclear Information System (INIS)

    Capri, M.A.L.; Lemes, V.E.R.; Sobreiro, R.F.; Sorella, S.P.; Dudal, D.; Verschelde, H.; Gracey, J.A.

    2006-01-01

    The ghost condensate abc c b c c > is considered together with the gluon condensate μ 2 > in SU(2) Euclidean Yang-Mills theories quantized in the Landau gauge. The vacuum polarization ceases to be transverse due to the nonvanishing condensate abc c b c c >. The gluon propagator itself remains transverse. By polarization effects, this ghost condensate induces then a splitting in the gluon mass parameter, which is dynamically generated through μ 2 >. The obtained effective masses are real when μ 2 > is included in the analysis. In the absence of μ 2 >, the already known result that the ghost condensate induces effective tachyonic masses is recovered. At the one-loop level, we find that the effective diagonal mass becomes smaller than the off-diagonal one. This might serve as an indication for some kind of Abelian dominance in the Landau gauge, similar to what happens in the maximal Abelian gauge

  2. Localization in nonuniform media: Exponential decay of the late-time Ginzburg-Landau impulse response

    International Nuclear Information System (INIS)

    Smith, E.

    1998-01-01

    Instanton methods have been used, in the context of a classical Ginzburg-Landau field theory, to compute the averaged density of states and probability Green close-quote s function for electrons scattered by statistically uniform site energy perturbations. At tree level, all states below some critical energy appear localized, and all states above extended. The same methods are applied here to macroscopically nonuniform systems, for which it is shown that localized and extended states can be coupled through a tunneling barrier created by the instanton background. Both electronic and acoustic systems are considered. An incoherent exponential decay is predicted for the late-time impulse response in both cases, valid for long-wavelength nonuniformity, and scaling relations are derived for the decay time constant as a function of energy or frequency and spatial dimension. The acoustic results are found to lie within a range of scaling relations obtained empirically from measurements of seismic coda, suggesting a connection between the universal properties of localization and the robustness of the observed scaling. The relation of instantons to the acoustic coherent-potential approximation is demonstrated in the recovery of the uniform limit. copyright 1998 The American Physical Society

  3. Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

    Science.gov (United States)

    Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

    2018-06-01

    A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

  4. Landau quantization and quasiparticle interference in the three-dimensional Dirac semimetal Cd₃As₂.

    Science.gov (United States)

    Jeon, Sangjun; Zhou, Brian B; Gyenis, Andras; Feldman, Benjamin E; Kimchi, Itamar; Potter, Andrew C; Gibson, Quinn D; Cava, Robert J; Vishwanath, Ashvin; Yazdani, Ali

    2014-09-01

    Condensed-matter systems provide a rich setting to realize Dirac and Majorana fermionic excitations as well as the possibility to manipulate them for potential applications. It has recently been proposed that chiral, massless particles known as Weyl fermions can emerge in certain bulk materials or in topological insulator multilayers and give rise to unusual transport properties, such as charge pumping driven by a chiral anomaly. A pair of Weyl fermions protected by crystalline symmetry effectively forming a massless Dirac fermion has been predicted to appear as low-energy excitations in a number of materials termed three-dimensional Dirac semimetals. Here we report scanning tunnelling microscopy measurements at sub-kelvin temperatures and high magnetic fields on the II-V semiconductor Cd3As2. We probe this system down to atomic length scales, and show that defects mostly influence the valence band, consistent with the observation of ultrahigh-mobility carriers in the conduction band. By combining Landau level spectroscopy and quasiparticle interference, we distinguish a large spin-splitting of the conduction band in a magnetic field and its extended Dirac-like dispersion above the expected regime. A model band structure consistent with our experimental findings suggests that for a magnetic field applied along the axis of the Dirac points, Weyl fermions are the low-energy excitations in Cd3As2.

  5. Nonlinear stability of source defects in the complex Ginzburg–Landau equation

    International Nuclear Information System (INIS)

    Beck, Margaret; Nguyen, Toan T; Sandstede, Björn; Zumbrun, Kevin

    2014-01-01

    In an appropriate moving coordinate frame, source defects are time-periodic solutions to reaction–diffusion equations that are spatially asymptotic to spatially periodic wave trains whose group velocities point away from the core of the defect. In this paper, we rigorously establish nonlinear stability of spectrally stable source defects in the complex Ginzburg–Landau equation. Due to the outward transport at the far field, localized perturbations may lead to a highly non-localized response even on the linear level. To overcome this, we first investigate in detail the dynamics of the solution to the linearized equation. This allows us to determine an approximate solution that satisfies the full equation up to and including quadratic terms in the nonlinearity. This approximation utilizes the fact that the non-localized phase response, resulting from the embedded zero eigenvalues, can be captured, to leading order, by the nonlinear Burgers equation. The analysis is completed by obtaining detailed estimates for the resolvent kernel and pointwise estimates for Green's function, which allow one to close a nonlinear iteration scheme. (paper)

  6. Renormalization group equations and the Lifshitz point in noncommutative Landau-Ginsburg theory

    International Nuclear Information System (INIS)

    Chen, G.-H.; Wu, Y.-S.

    2002-01-01

    A one-loop renormalization group (RG) analysis is performed for noncommutative Landau-Ginsburg theory in an arbitrary dimension. We adopt a modern version of the Wilsonian RG approach, in which a shell integration in momentum space bypasses the potential IR singularities due to UV-IR mixing. The momentum-dependent trigonometric factors in interaction vertices, characteristic of noncommutative geometry, are marginal under RG transformations, and their marginality is preserved at one loop. A negative Θ-dependent anomalous dimension is discovered as a novel effect of the UV-IR mixing. We also found a noncommutative Wilson-Fisher (NCWF) fixed point in less than four dimensions. At large noncommutativity, a momentum space instability is induced by quantum fluctuations, and a consequential first-order phase transition is identified together with a Lifshitz point in the phase diagram. In the vicinity of the Lifshitz point, we introduce two critical exponents ν m and β k , whose values are determined to be 1/4 and 1/2, respectively, at mean-field level

  7. From the atomic bomb to the Landau Institute autobiography top non-secret

    CERN Document Server

    Khalatnikov, Isaak M

    2012-01-01

    The book is an expanded autobiography of the famous theoretical physicist Isaak Khalatnikov. He worked together with L.D. Landau at the Institute for Physical Problems lead by P.L. Kapitza. He is the co-author of L.D. Landau in a number of important works. They worked together in the frame of the so-called Nuclear Bomb Project. After the death of L.D. Landau, I.M. Khalatnikov initiated the establishment of the Institute for Theoretical Physics, named in honour of L.D. Landau, within the USSR Academy of Sciences. He headed this institute from the beginning as its Director. The institute inherited almost all traditions of the Landau scientific school and played a prominent role in the development of theoretical physics. So, this is a story about how the institute was created, how it worked, and about the life of the physicists in the "golden age" of the Soviet science. A separate chapter is devoted to today´s life of the institute and the young generation of physicists working now in science. It is an historic...

  8. Landau retardation on the occurrence scattering time in quantum electron–hole plasmas

    International Nuclear Information System (INIS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2016-01-01

    The Landau damping effects on the occurrence scattering time in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Shukla–Stenflo–Bingham effective potential model is employed to obtain the occurrence scattering time in a quantum electron–hole plasma. The result shows that the influence of Landau damping produces the imaginary term in the scattering amplitude. It is then found that the Landau damping generates the retardation effect on the occurrence scattering time. It is found that the occurrence scattering time increases in forward scattering domains and decreases in backward scattering domains with an increase of the Landau parameter. It is also found that the occurrence scattering time decreases with increasing collision energy. In addition, it is found that the quantum shielding effect enhances the occurrence scattering time in the forward scattering and, however, suppresses the occurrence scattering time in the backward scattering. - Highlights: • The Landau damping effects on the occurrence scattering time are investigated in a quantum electron–hole plasma. • The Shukla–Stenflo–Bingham potential model is employed to obtain the occurrence scattering time in quantum plasmas. • The influence of quantum shielding on the occurrence scattering time is discussed.

  9. The Landau-de Gennes theory of nematic liquid crystals: Uniaxiality versus Biaxiality

    KAUST Repository

    Majumdar, Apala

    2011-12-01

    We study small energy solutions within the Landau-de Gennes theory for nematic liquid crystals, subject to Dirichlet boundary conditions. We consider two-dimensional and three-dimensional domains separately. In the two-dimensional case, we establish the equivalence of the Landau-de Gennes and Ginzburg-Landau theory. In the three-dimensional case, we give a new definition of the defect set based on the normalized energy. In the threedimensional uniaxial case, we demonstrate the equivalence between the defect set and the isotropic set and prove the C 1,α-convergence of uniaxial small energy solutions to a limiting harmonic map, away from the defect set, for some 0 < a < 1, in the vanishing core limit. Generalizations for biaxial small energy solutions are also discussed, which include physically relevant estimates for the solution and its scalar order parameters. This work is motivated by the study of defects in liquid crystalline systems and their applications.

  10. On translational superfluidity and the Landau criterion for Bose gases in the Gross-Pitaevski limit

    International Nuclear Information System (INIS)

    Wreszinski, Walter F

    2008-01-01

    The two-fluid and Landau criteria for superfluidity are compared for trapped Bose gases. While the two-fluid criterion predicts translational superfluidity, it is suggested, on the basis of the homogeneous Gross-Pitaevski limit, that a necessary part of Landau's criterion, adequate for non-translationally invariant systems, does not hold for trapped Bose gases in the GP limit. As a consequence, if the compressibility is detected to be very large (infinite by experimental standards), the two-fluid criterion is seen to be the relevant one in case the system is a translational superfluid, while the Landau criterion is the relevant one if translational superfluidity is absent. (fast track communication)

  11. Estimating the Partition Function Zeros by Using the Wang-Landau Monte Carlo Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung-Yeon [Korea National University of Transportation, Chungju (Korea, Republic of)

    2017-03-15

    The concept of the partition function zeros is one of the most efficient methods for investigating the phase transitions and the critical phenomena in various physical systems. Estimating the partition function zeros requires information on the density of states Ω(E) as a function of the energy E. Currently, the Wang-Landau Monte Carlo algorithm is one of the best methods for calculating Ω(E). The partition function zeros in the complex temperature plane of the Ising model on an L × L square lattice (L = 10 ∼ 80) with a periodic boundary condition have been estimated by using the Wang-Landau Monte Carlo algorithm. The efficiency of the Wang-Landau Monte Carlo algorithm and the accuracies of the partition function zeros have been evaluated for three different, 5%, 10%, and 20%, flatness criteria for the histogram H(E).

  12. Isoscalar giant resonances and Landau parameters with density-dependent effective interactions

    International Nuclear Information System (INIS)

    Kohno, Michio; Ando, Kazuhiko

    1979-01-01

    Discussion is given on the relations between the Landau parameters and the isoscalar giant (quadrupole- and monopole-) resonance energies by using general density-dependent interactions. In the limit of infinite nuclear matter, the isoscalar giant quadrupole energy is shown to depend not only on the effective mass but also on the Landau parameter F 2 . Collective energies of the isoscalar giant resonances are calculated for 16 O and 40 Ca with four different effective interactions, G-0, B1, SII and SV, by using the scaling- and constrained Hartree-Fock-methods. It is shown that the dependence of the collective energies on the effective interactions is essentially determined by the Landau parameters. The G-0 force is found to be most successful in reproducing the giant resonance energies. Validity of the RPA-moment theorems is examined for the case of local density-dependent interactions. (author)

  13. Magnetic field-induced Landau Fermi liquid in high-T{sub c} metals

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M.Ya.; Shaginyan, V.R

    2003-08-25

    We consider the behavior of strongly correlated electron liquid in high-temperature superconductors within the framework of the fermion condensation model. We show that at low temperatures the normal state recovered by the application of a magnetic field larger than the critical field can be viewed as the Landau Fermi liquid induced by the magnetic field. In this state, the Wiedemann-Franz law and the Korringa law are held and the elementary excitations are the Landau Fermi liquid quasiparticles. Contrary to what might be expected from the Landau theory, the effective mass of quasiparticles depends on the magnetic field. The recent experimental verifications of the Wiedemann-Franz law in heavily hole-overdoped, overdoped and optimally doped cuprates and the verification of the Korringa law in the electron-doped copper oxide superconductor strongly support the existence of fermion condensate in high-T{sub c} metals.

  14. Landau-Lifshitz sigma-models, fermions and the AdS/CFT correspondence

    OpenAIRE

    Stefanski Jr, B.

    2007-01-01

    We define Landau-Lifshitz sigma models on general coset space $G/H$, with $H$ a maximal stability sub-group of $G$. These are non-relativistic models that have $G$-valued N\\"other charges, local $H$ invariance and are classically integrable. Using this definition, we construct the $PSU(2,2|4)/PS(U(2|2)^2)$ Landau-Lifshitz sigma-model. This sigma model describes the thermodynamic limit of the spin-chain Hamiltonian obtained from the complete one-loop dilatation operator of the N=4 super Yang-M...

  15. Verifying the Kugo-Ojima Confinement Criterion in Landau Gauge Yang-Mills Theory

    International Nuclear Information System (INIS)

    Watson, Peter; Alkofer, Reinhard

    2001-01-01

    Expanding the Landau gauge gluon and ghost two-point functions in a power series we investigate their infrared behavior. The corresponding powers are constrained through the ghost Dyson-Schwinger equation by exploiting multiplicative renormalizability. Without recourse to any specific truncation we demonstrate that the infrared powers of the gluon and ghost propagators are uniquely related to each other. Constraints for these powers are derived, and the resulting infrared enhancement of the ghost propagator signals that the Kugo-Ojima confinement criterion is fulfilled in Landau gauge Yang-Mills theory

  16. Exact results for survival probability in the multistate Landau-Zener model

    International Nuclear Information System (INIS)

    Volkov, M V; Ostrovsky, V N

    2004-01-01

    An exact formula is derived for survival probability in the multistate Landau-Zener model in the special case where the initially populated state corresponds to the extremal (maximum or minimum) slope of a linear diabatic potential curve. The formula was originally guessed by S Brundobler and V Elzer (1993 J. Phys. A: Math. Gen. 26 1211) based on numerical calculations. It is a simple generalization of the expression for the probability of diabatic passage in the famous two-state Landau-Zener model. Our result is obtained via analysis and summation of the entire perturbation theory series

  17. Spatial Landau-Zener-Stueckelberg interference in spinor Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Zhang, J.-N.; Sun, C.-P.; Yi, S.; Nori, Franco

    2011-01-01

    We investigate the Stueckelberg oscillations of a spin-1 Bose-Einstein condensate subject to a spatially inhomogeneous transverse magnetic field and a periodic longitudinal field. We show that the time-domain Stueckelberg oscillations result in modulations in the density profiles of all spin components due to the spatial inhomogeneity of the transverse field. This phenomenon represents the Landau-Zener-Stueckelberg interference in the space domain. Since the magnetic dipole-dipole interaction between spin-1 atoms induces an inhomogeneous effective magnetic field, interference fringes also appear if a dipolar spinor condensate is driven periodically. We also point out some potential applications of this spatial Landau-Zener-Stuekelberg interference.

  18. Integrability and structural stability of solutions to the Ginzburg-Landau equation

    Science.gov (United States)

    Keefe, Laurence R.

    1986-01-01

    The integrability of the Ginzburg-Landau equation is studied to investigate if the existence of chaotic solutions found numerically could have been predicted a priori. The equation is shown not to possess the Painleveproperty, except for a special case of the coefficients that corresponds to the integrable, nonlinear Schroedinger (NLS) equation. Regarding the Ginzburg-Landau equation as a dissipative perturbation of the NLS, numerical experiments show all but one of a family of two-tori solutions, possessed by the NLS under particular conditions, to disappear under real perturbations to the NLS coefficients of O(10 to the -6th).

  19. Under the spell of Landau when theoretical physics was shaping destinies

    CERN Document Server

    2013-01-01

    This invaluable collection of memoirs and reviews on scientific activities of the most prominent theoretical physicists belonging to the Landau School - Landau, Anselm, Gribov, Zeldovich, Kirzhnits, Migdal, Ter-Martirosyan and Larkin - are being published in English for the first time. The main goal is to acquaint readers with the life and work of outstanding Soviet physicists who, to a large extent, shaped theoretical physics in the 1950s - 70s. Many intriguing details have remained unknown beyond the "Iron Curtain" which was dismantled only with the fall of the USSR.

  20. Quantum resonances of Landau damping in the electromagnetic response of metallic nanoslabs.

    Science.gov (United States)

    Castillo-López, S G; Makarov, N M; Pérez-Rodríguez, F

    2018-05-15

    The resonant quantization of Landau damping in far-infrared absorption spectra of metal nano-thin films is predicted within the Kubo formalism. Specifically, it is found that the discretization of the electromagnetic and electron wave numbers inside a metal nanoslab produces quantum nonlocal resonances well-resolved at slab thicknesses smaller than the electromagnetic skin depth. Landau damping manifests itself precisely as such resonances, tracing the spectral curve obtained within the semiclassical Boltzmann approach. For slab thicknesses much greater than the skin depth, the classical regime emerges. Here the results of the quantum model and the Boltzmann approach coincide. Our analytical study is in perfect agreement with corresponding numerical simulations.

  1. From Landau's hydrodynamical model to field theory model to field theory models of multiparticle production: a tribute to Peter

    International Nuclear Information System (INIS)

    Cooper, F.

    1996-01-01

    We review the assumptions and domain of applicability of Landau's Hydrodynamical Model. By considering two models of particle production, pair production from strong electric fields and particle production in the linear σ model, we demonstrate that many of Landau's ideas are verified in explicit field theory calculations

  2. The effect of boundaries on the asymptotic wavenumber of spiral wave solutions of the complex Ginzburg–Landau equation

    KAUST Repository

    Aguareles, M.

    2014-01-01

    In this paper we consider an oscillatory medium whose dynamics are modeled by the complex Ginzburg-Landau equation. In particular, we focus on n-armed spiral wave solutions of the complex Ginzburg-Landau equation in a disk of radius d

  3. Remarks on the Landau-Ginzburg potential and RG-flow for SU(2)-coset models

    International Nuclear Information System (INIS)

    Marzban, C.

    1989-09-01

    The existence of a Landau-Ginzburg (LG)-field for the SU(2)-coset models is motivated and conjectured. The general form of the LG potential for the A-series is found, and the RG-flow pattern suggested by this is shown to agree with that found by other authors, thereby further supporting the conjecture. (author). 17 refs

  4. Three-dimensional Ginzburg–Landau simulation of a vortex line ...

    Indian Academy of Sciences (India)

    pp. 295–304. Three-dimensional Ginzburg–Landau simulation of a vortex line displaced by a zigzag of pinning spheres. MAURO M DORIA1,∗, ANTONIO R de C ROMAGUERA1 and WELLES A M MORGADO2. 1Instituto de Fısica, Universidade Federal do Rio de Janeiro, C.P. 68528,. 21941-972, Rio de Janeiro RJ, Brazil.

  5. Strongly enhanced flow effect from Landau-Vlasov versus Vlasov-Uehling-Uhlenbeck approach

    International Nuclear Information System (INIS)

    Gregoire, C.; Remaud, B.; Sebille, F.; Schuck, P.

    1988-01-01

    The simulation of the collision integral in the Landau-Vlasov approach for heavy ion collisions is examined. It turns out that quantities like the nucleon mean free path can be compared with parallel ensemble models. Convergency of results with time step and sampling is clearly established. Quadratic quantities, like the internal pressure, are found to be strongly underestimated in parallel ensemble models

  6. Self-consistent Ginzburg-Landau theory for transport currents in superconductors

    DEFF Research Database (Denmark)

    Ögren, Magnus; Sørensen, Mads Peter; Pedersen, Niels Falsig

    2012-01-01

    We elaborate on boundary conditions for Ginzburg-Landau (GL) theory in the case of external currents. We implement a self-consistent theory within the finite element method (FEM) and present numerical results for a two-dimensional rectangular geometry. We emphasize that our approach can in princi...... in principle also be used for general geometries in three-dimensional superconductors....

  7. Homotopy classification of minimizers of the Ginzburg-Landau energy and the existence of permanent currents

    International Nuclear Information System (INIS)

    Rubinstein, J.

    1996-01-01

    Our objective is to explain the phenomenon of permanent currents within the context of the Ginzburg-Landau model for superconductors. Using variational techniques we make a connection between the formation of permanent currents and the topology of the superconducting sample. (orig.)

  8. Evidence for the existence of Gribov copies in Landau gauge lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Marinari, E.; Ricci, R. (Rome-2 Univ. (Italy). Dipt. di Fisica INFN, Rome (Italy)); Parrinello, C. (New York Univ., NY (USA). Physics Dept.)

    1991-09-16

    We unambiguously show the existence of Gribov copies in a pure SU(3) gauge lattice model, with Wilson action. We show that the usual steepest-descent algorithms used for implementing the lattice Landau gauge lead to ambiguities, which are related to the existence of Gribov copies in the model. (orig.).

  9. Time-dependent Ginzburg-Landau equations for rotating and accelerating superconductors

    Czech Academy of Sciences Publication Activity Database

    Lipavský, P.; Bok, J.; Koláček, Jan

    2013-01-01

    Roč. 492, Sept (2013), 144-151 ISSN 0921-4534 R&D Projects: GA ČR(CZ) GAP204/11/0015 Institutional support: RVO:68378271 Keywords : superconductivity * Ginzburg-Landau theory * London field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.110, year: 2013

  10. Gradient corrections to the time-dependent Ginzburg-Landau eqzation for anisotropic perturbations of quasiparticles

    Czech Academy of Sciences Publication Activity Database

    Lin, P.-J.; Lipavský, Pavel

    2008-01-01

    Roč. 77, č. 14 (2008), 144505/1-144505/16 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : non-equilibrium superconductivity * Ginzburg-Landau theory Subject RIV: BE - Theoretical Physics Impact factor: 3.322, year: 2008

  11. Magnetic vortices for a Ginzburg-Landau type energy with discontinuous constraint

    DEFF Research Database (Denmark)

    Kachmar, Ayman

    2010-01-01

    This paper is devoted to an analysis of vortex-nucleation for a Ginzburg-Landau functional with discontinuous constraint. This functional has been proposed as a model for vortex-pinning, and usually accounts for the energy resulting from the interface of two superconductors. The critical applied ...

  12. Domain Walls and Textured Vortices in a Two-Component Ginzburg-Landau Model

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Gaididei, Yu. B.; Christiansen, Peter Leth

    2005-01-01

    coupling between the two order parameters a ''textured vortex'' is found by analytical and numerical solution of the Ginzburg-Landau equations. With a Josephson type coupling between the two order parameters we find the system to split up in two domains separated by a domain wall, where the order parameter...... is depressed to zero....

  13. Derivation of Ginzburg-Landau theory for a one-dimensional system with contact interaction

    DEFF Research Database (Denmark)

    Frank, Rupert; Hanizl, Christian; Seiringer, Robert

    2013-01-01

    In a recent paper we give the first rigorous derivation of the celebrated Ginzburg-Landau (GL) theory, starting from the microscopic Bardeen-Cooper-Schrieffer (BCS) model. Here we present our results in the simplified case of a one-dimensional system of particles interacting via a delta-potential....

  14. Two-dimensional quantisation of the quasi-Landau hydrogenic spectrum

    International Nuclear Information System (INIS)

    Gallas, J.A.C.; O'Connell, R.F.

    1982-01-01

    Based on the two-dimensional WKB model, an equation is derived from which the non-relativistic quasi-Landau energy spectrum of hydrogen-like atoms may be easily obtained. In addition, the solution of radial equations in the WKB approximation and its relation with models recently used to fit experimental data are discussed. (author)

  15. Quantum Hall conductivity in a Landau type model with a realistic geometry

    International Nuclear Information System (INIS)

    Chandelier, F.; Georgelin, Y.; Masson, T.; Wallet, J.-C.

    2003-01-01

    In this paper, we revisit some quantum mechanical aspects related to the quantum Hall effect. We consider a Landau type model, paying a special attention to the experimental and geometrical features of quantum Hall experiments. The resulting formalism is then used to compute explicitly the Hall conductivity from a Kubo formula

  16. Variational principles for Ginzburg-Landau equation by He's semi-inverse method

    International Nuclear Information System (INIS)

    Liu, W.Y.; Yu, Y.J.; Chen, L.D.

    2007-01-01

    Via the semi-inverse method of establishing variational principles proposed by He, a generalized variational principle is established for Ginzburg-Landau equation. The present theory provides a quite straightforward tool to the search for various variational principles for physical problems. This paper aims at providing a more complete theoretical basis for applications using finite element and other direct variational methods

  17. Boundary conditions in Ginsburg Landau theory and critical temperature of high-T superconductors

    Science.gov (United States)

    Lykov, A. N.

    2008-06-01

    New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature ( T) of high- T superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T of cuprate superconductors.

  18. N=2 superconformal models, Landau-Ginsburg Hamiltonians and the ε expansion

    International Nuclear Information System (INIS)

    Howe, P.S.; West, P.C.

    1989-01-01

    The anomalous dimensions of a class of operators, operator product expansions and the central change, c, are calculated in a family of N=2 supersymmetric two-dimensional Landau-Ginsburg models. The results allow the identification of these theories with N=2 minimal superconformal models. A key role is placed by the N=2 non-renormalization theorem. (orig.)

  19. Boundary conditions in Ginsburg-Landau theory and critical temperature of high-Tc superconductors

    International Nuclear Information System (INIS)

    Lykov, A.N.

    2008-01-01

    New mixed boundary conditions to the Ginsburg-Landau equations are found to limit the critical temperature (T c ) of high-T c superconductors. Moreover, the value of the pseudogap in these superconductors can be explained by using the method. As a result, the macroscopic approach is proposed to increase T c of cuprate superconductors

  20. Landau-Ginsburg models with N=2 supersymmetry as conventional conformal theories

    International Nuclear Information System (INIS)

    Marshakov, A.

    1990-01-01

    The conformal Landau-Ginsburg (LG) models are identified with the Toda-like two-dimensional field theories. At least in the N=2 supersymmetric case they possess a simple free-field representation, related to the Nicolai map. (orig.)

  1. A Study of the Nonlinear Landau Damping in the Fourier Transformed VelocitySpace

    Czech Academy of Sciences Publication Activity Database

    Sedláček, Zdeněk

    2002-01-01

    Roč. 34, 1-2 (2002), s. 63-87 ISSN 0041-1450 Institutional research plan: CEZ:AV0Z2043910 Keywords : Landau damping * Van Kampen-Case eigenmodes * BGK modes * free streaming Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.453, year: 2002

  2. Ginzburg-Landau theory of the superheating field anisotropy of layered superconductors

    Science.gov (United States)

    Liarte, Danilo B.; Transtrum, Mark K.; Sethna, James P.

    2016-10-01

    We investigate the effects of material anisotropy on the superheating field of layered superconductors. We provide an intuitive argument both for the existence of a superheating field, and its dependence on anisotropy, for κ =λ /ξ (the ratio of magnetic to superconducting healing lengths) both large and small. On the one hand, the combination of our estimates with published results using a two-gap model for MgB2 suggests high anisotropy of the superheating field near zero temperature. On the other hand, within Ginzburg-Landau theory for a single gap, we see that the superheating field shows significant anisotropy only when the crystal anisotropy is large and the Ginzburg-Landau parameter κ is small. We then conclude that only small anisotropies in the superheating field are expected for typical unconventional superconductors near the critical temperature. Using a generalized form of Ginzburg Landau theory, we do a quantitative calculation for the anisotropic superheating field by mapping the problem to the isotropic case, and present a phase diagram in terms of anisotropy and κ , showing type I, type II, or mixed behavior (within Ginzburg-Landau theory), and regions where each asymptotic solution is expected. We estimate anisotropies for a number of different materials, and discuss the importance of these results for radio-frequency cavities for particle accelerators.

  3. New Wang-Landau approach to obtain phase diagrams for multicomponent alloys

    Science.gov (United States)

    Takeuchi, Kazuhito; Tanaka, Ryohei; Yuge, Koretaka

    2017-10-01

    We develop an approach to apply the Wang-Landau algorithm to multicomponent alloys in a semi-grand-canonical ensemble. Although the Wang-Landau algorithm has great advantages over conventional sampling methods, there are few applications to alloys. This is because calculating compositions in a semi-grand-canonical ensemble via the Wang-Landau algorithm requires a multidimensional density of states in terms of total energy and compositions, and constructing it is difficult from the viewpoints of both implementation and computational cost. In this study, we develop a simple approach to calculate the alloy phase diagram based on the Wang-Landau algorithm, and show that a number of one-dimensional densities of states could lead to compositions in a semi-grand-canonical ensemble as a multidimensional density of states could. Finally, we apply the present method to Cu-Au and Pd-Rh alloys and confirm that the present method successfully describes the phase diagram with high efficiency, validity, and accuracy.

  4. Definite evidence of the Landau-Zener transition in nucleus-nucleus collisions

    International Nuclear Information System (INIS)

    Imanishi, B.; Oertzen, W. von; Voit, H.

    1986-05-01

    It is shown that the Landau-Zener transition mechanism due to the formation of molecular orbitals of the active neutron exists in the inelastic scattering 13 C( 12 C, 12 C) 13 C* (3.086 MeV, 1/2 + ). The evidence stems from characteristic changes of the angular distributions observed as function of the incident energy. (author)

  5. Statistical mechanics of low-dimensional Ginzburg-Landau fields. Some new results

    International Nuclear Information System (INIS)

    Barsan, V.

    1987-08-01

    The Ginzburg-Landau theory for low-dimensional systems is approached using the transfer matrix method. Analitical formulae for the thermodynamical quantities of interest are obtained in the one-dimensional case. An exact expression for the free energy of of a planar array of linear chains is deduced. A good agrement with numerical and experimental data is found.(authors)

  6. Landau-Kleffner Syndrome: An Exploration of Parent Experience of the Diagnostic Process

    Science.gov (United States)

    Lemard-Reid, Daunette

    2014-01-01

    Landau-Kleffner syndrome (LKS) is a rare childhood disorder that is often misdiagnosed as autism or childhood psychosis because of overlapping symptom presentation. Favorable prognoses in LKS depend on early diagnosis and treatment. While much is known about the clinical basis for LKS diagnosis, little is known about parents' lived experience with…

  7. Symmetry breaking in Landau gauge. A comment to a paper by T. Kennedy and C. King

    International Nuclear Information System (INIS)

    Borgs, C.; Nill, F.

    1986-01-01

    The authors generalize the result of T. Kennedy and C. King (Princeton preprint, 1985) on the non-compact abelian lattice Higgs model in Landau gauge in order to show that there are states parameterized by an angle such that the expectation value of the Higgs field is described by a phase factor and a value which is uniformly bounded away from zero. (HSI)

  8. Landau-Kleffner Syndrome, Electrical Status Epilepticus in Slow Wave Sleep, and Language Regression in Children

    Science.gov (United States)

    McVicar, Kathryn A.; Shinnar, Shlomo

    2004-01-01

    The Landau-Kleffner syndrome (LKS) and electrical status epilepticus in slow wave sleep (ESES) are rare childhood-onset epileptic encephalopathies in which loss of language skills occurs in the context of an epileptiform EEG activated in sleep. Although in LKS the loss of function is limited to language, in ESES there is a wider spectrum of…

  9. Asymptotic Bethe ansatz S-matrix and Landau-Lifshitz-type effective 2d actions

    International Nuclear Information System (INIS)

    Roiban, R; Tirziu, A; Tseytlin, A A

    2006-01-01

    Motivated by the desire to relate Bethe ansatz equations for anomalous dimensions found on the gauge-theory side of the AdS/CFT correspondence to superstring theory on AdS 5 x S 5 we explore a connection between the asymptotic S-matrix that enters the Bethe ansatz and an effective two-dimensional quantum field theory. The latter generalizes the standard 'non-relativistic' Landau-Lifshitz (LL) model describing low-energy modes of ferromagnetic Heisenberg spin chain and should be related to a limit of superstring effective action. We find the exact form of the quartic interaction terms in the generalized LL-type action whose quantum S-matrix matches the low-energy limit of the asymptotic S-matrix of the spin chain of Beisert, Dippel and Staudacher (BDS). This generalizes to all orders in the 't Hooft coupling λ an earlier computation of Klose and Zarembo of the S-matrix of the standard LL model. We also consider a generalization to the case when the spin-chain S-matrix contains an extra 'string' phase and determine the exact form of the LL 4-vertex corresponding to the low-energy limit of the ansatz of Arutyunov, Frolov and Staudacher (AFS). We explain the relation between the resulting 'non-relativistic' non-local action and the second-derivative string sigma model. We comment on modifications introduced by strong-coupling corrections to the AFS phase. We mostly discuss the SU(2) sector but also present generalizations to the SL(2) and SU(1|1) sectors, confirming universality of the dressing phase contribution by matching the low-energy limit of the AFS-type spin-chain S-matrix with tree-level string-theory S-matrix

  10. Surface Acoustic Bloch Oscillations, the Wannier-Stark Ladder, and Landau-Zener Tunneling in a Solid

    Science.gov (United States)

    de Lima, M. M., Jr.; Kosevich, Yu. A.; Santos, P. V.; Cantarero, A.

    2010-04-01

    We present the experimental observation of Bloch oscillations, the Wannier-Stark ladder, and Landau-Zener tunneling of surface acoustic waves in perturbed grating structures on a solid substrate. A model providing a quantitative description of our experimental observations, including multiple Landau-Zener transitions of the anticrossed surface acoustic Wannier-Stark states, is developed. The use of a planar geometry for the realization of the Bloch oscillations and Landau-Zener tunneling allows a direct access to the elastic field distribution. The vertical surface displacement has been measured by interferometry.

  11. Effects of periodic scattering potential on Landau quantization and ballistic transport of electrons in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Gumbs, Godfrey [Department of Physics and Astronomy, Hunter College, CUNY, 695 Park Avenue, New York, NY 10065, USA and Donostia International Physics Center (DIPC), P de Manuel Lardizabal, 4, 20018 San Sebastian, Basque Country (Spain); Iurov, Andrii [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10065 (United States); Huang, Danhong [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, NM 87117 (United States); Fekete, Paula [West Point Military Academy, West Point, NY (United States); Zhemchuzhna, Liubov [Department of Physics, North Carolina Central University, Durham, North Carolina 27707 (United States)

    2014-03-31

    A two-dimensional periodic array of scatterers has been introduced to a single layer of graphene in the presence of an external magnetic field perpendicular to the graphene layer. The eigenvalue equation for such a system has been solved numerically to display the structure of split Landau subbands as functions of both wave number and magnetic flux. The effects of pseudo-spin coupling and Landau subbands mixing by a strong scattering potential have been demonstrated. Additionally, we investigated the square barrier tunneling problem when magnetic field is present, as well as demonstrate the crucial difference in the modulated band structure between graphene and the two-dimensional electron gas. The low-magnetic field regime is particularly interesting for Dirac fermions and has been discussed. Tunneling of Dirac electrons through a magnetic potential barrier has been investigated to complement the reported results on electrostatic potential scattering in the presence of an ambient magnetic field.

  12. Thermodynamic properties of and Nuclei using modified Ginzburg-Landau theory

    Directory of Open Access Journals (Sweden)

    V Dehghani

    2016-09-01

    Full Text Available In this paper, formulation of Modified Ginsberg – Landau theory of second grade phase transitions has been expressed. Using this theory, termodynamic properties, such as heat capacity, energy, entropy and order parameters ofandnuclei has been investigated. In the heat capacity curve, calculated according to tempreture, a smooth peak is observed which is assumed to be a signature of transition from the paired phase to the normal phase of the nuclei. The same pattern is also observed in the experimental data of the heat capacity of the studied nuclei. Calculations of this model shows that, by increasing tempreture, expectation value of the order parameter tends to zero with smoother slip, comparing with Ginsberg – Landau theory. This indicates  that the pairing effect exists between nucleons even at high temperatures. The experimental data obtained confirms the results of the model qualitatively.

  13. Dyson-Schwinger equations and N = 4 SYM in Landau gauge

    Energy Technology Data Exchange (ETDEWEB)

    Maas, Axel; Zitz, Stefan [University of Graz, Institute of Physics, NAWI Graz, Graz (Austria)

    2016-03-15

    N = 4 Super Yang-Mills theory is a highly constrained theory, and therefore a valuable tool to test the understanding of less constrained Yang-Mills theories. Our aim is to use it to test our understanding of both the Landau gauge beyond perturbation theory and the truncations of Dyson-Schwinger equations in ordinary Yang-Mills theories. We derive the corresponding equations within the usual one-loop truncation for the propagators after imposing the Landau gauge. We find a conformal solution in this approximation, which surprisingly resembles many aspects of ordinary Yang-Mills theories. We furthermore discuss which role the Gribov-Singer ambiguity in this context could play, should it exist in this theory. (orig.)

  14. Landau quantization and spin-momentum locking in topological Kondo insulators

    Directory of Open Access Journals (Sweden)

    P. Schlottmann

    2016-05-01

    Full Text Available SmB6 has been predicted to be a strong topological Kondo insulator and experimentally it has been confirmed that at low temperatures the electrical conductivity only takes place at the surfaces of the crystal. Quantum oscillations and ARPES measurements revealed several Dirac cones on the (001 and (101 surfaces of the crystal. We considered three types of surface Dirac cones with an additional parabolic dispersion and studied their Landau quantization and the expectation value of the spin of the electrons. The Landau quantization is quite similar in all three cases and would give rise to very similar de Haas-van Alphen oscillations. The spin-momentum locking, on the other hand, differs dramatically. Without the additional parabolic dispersion the spins are locked in the plane of the surface. The parabolic dispersion, however, produces a gradual canting of the spins out of the surface plane.

  15. Wang-Landau Reaction Ensemble Method: Simulation of Weak Polyelectrolytes and General Acid-Base Reactions.

    Science.gov (United States)

    Landsgesell, Jonas; Holm, Christian; Smiatek, Jens

    2017-02-14

    We present a novel method for the study of weak polyelectrolytes and general acid-base reactions in molecular dynamics and Monte Carlo simulations. The approach combines the advantages of the reaction ensemble and the Wang-Landau sampling method. Deprotonation and protonation reactions are simulated explicitly with the help of the reaction ensemble method, while the accurate sampling of the corresponding phase space is achieved by the Wang-Landau approach. The combination of both techniques provides a sufficient statistical accuracy such that meaningful estimates for the density of states and the partition sum can be obtained. With regard to these estimates, several thermodynamic observables like the heat capacity or reaction free energies can be calculated. We demonstrate that the computation times for the calculation of titration curves with a high statistical accuracy can be significantly decreased when compared to the original reaction ensemble method. The applicability of our approach is validated by the study of weak polyelectrolytes and their thermodynamic properties.

  16. Episodic epileptic verbal auditory agnosia in Landau Kleffner syndrome treated with combination diazepam and corticosteroids.

    Science.gov (United States)

    Devinsky, Orrin; Goldberg, Rina; Miles, Daniel; Bojko, Aviva; Riviello, James

    2014-10-01

    We report 2 pediatric patients who presented initially with seizures followed by subacute language regression characterized by a verbal auditory agnosia. These previously normal children had no evidence of expressive aphasia during their symptomatic periods. Further, in both cases, auditory agnosia was associated with sleep-activated electroencephalographic (EEG) epileptiform activity, consistent with Landau-Kleffner syndrome. However, both cases are unique since the episodic auditory agnosia and sleep-activated EEG epileptiform activity rapidly responded to combination therapy with pulse benzodiazepine and corticosteroids. Further, in each case, recurrences were characterized by similar symptoms, EEG findings, and beneficial responses to the pulse benzodiazepine and corticosteroid therapy. These observations suggest that pulse combination high-dose corticosteroid and benzodiazepine therapy may be especially effective in Landau-Kleffner syndrome. © The Author(s) 2014.

  17. Direct path from microscopic mechanics to Debye shielding, Landau damping and wave-particle interaction

    International Nuclear Information System (INIS)

    Escande, D F; Elskens, Yves; Doveil, F

    2015-01-01

    The derivation of Debye shielding and Landau damping from the N-body description of plasmas is performed directly by using Newton’s second law for the N-body system. This is done in a few steps with elementary calculations using standard tools of calculus and no probabilistic setting. Unexpectedly, Debye shielding is encountered together with Landau damping. This approach is shown to be justified in the one-dimensional case when the number of particles in a Debye sphere becomes large. The theory is extended to accommodate a correct description of trapping and chaos due to Langmuir waves. On top of their well-known production of collisional transport, the repulsive deflections of electrons are shown to produce shielding, in such a way that each particle is shielded by all other ones, while keeping in uninterrupted motion. (paper)

  18. Landau-Placzek ratio for heat density dynamics and its application to heat capacity of liquids.

    Science.gov (United States)

    Bryk, Taras; Ruocco, Giancarlo; Scopigno, Tullio

    2013-01-21

    Exact relation for contributions to heat capacity of liquids is obtained from hydrodynamic theory. It is shown from analysis of the long-wavelength limit of heat density autocorrelation functions that the heat capacity of simple liquids is represented as a sum of two contributions due to "phonon-like" collective excitations and heat relaxation. The ratio of both contributions being the analogy of Landau-Placzek ratio for heat processes depends on the specific heats ratio. The theory of heat density autocorrelation functions in liquids is verified by computer simulations. Molecular dynamics simulations for six liquids having the ratio of specific heats γ in the range 1.1-2.3, were used for evaluation of the heat density autocorrelation functions and predicted Landau-Placzek ratio for heat processes. The dependence of contributions from collective excitations and heat relaxation process to specific heat on γ is shown to be in excellent agreement with the theory.

  19. Anisotropic harmonic oscillator, non-commutative Landau problem and exotic Newton-Hooke symmetry

    International Nuclear Information System (INIS)

    Alvarez, Pedro D.; Gomis, Joaquim; Kamimura, Kiyoshi; Plyushchay, Mikhail S.

    2008-01-01

    We investigate the planar anisotropic harmonic oscillator with explicit rotational symmetry as a particle model with non-commutative coordinates. It includes the exotic Newton-Hooke particle and the non-commutative Landau problem as special, isotropic and maximally anisotropic, cases. The system is described by the same (2+1)-dimensional exotic Newton-Hooke symmetry as in the isotropic case, and develops three different phases depending on the values of the two central charges. The special cases of the exotic Newton-Hooke particle and non-commutative Landau problem are shown to be characterized by additional, so(3) or so(2,1) Lie symmetry, which reflects their peculiar spectral properties

  20. Landau damping of dust acoustic waves in the presence of hybrid nonthermal nonextensive electrons

    Science.gov (United States)

    El-Taibany, W. F.; Zedan, N. A.; Taha, R. M.

    2018-06-01

    Based on the kinetic theory, Landau damping of dust acoustic waves (DAWs) propagating in a dusty plasma composed of hybrid nonthermal nonextensive distributed electrons, Maxwellian distributed ions and negatively charged dust grains is investigated using Vlasov-Poisson's equations. The characteristics of the DAWs Landau damping are discussed. It is found that the wave frequency increases by decreasing (increasing) the value of nonextensive (nonthermal) parameter, q (α ). It is recognized that α plays a significant role in observing damping or growing DAW oscillations. For small values of α , damping modes have been observed until reaching a certain value of α at which ω i vanishes, then a growing mode appears in the case of superextensive electrons. However, only damping DAW modes are observed in case of subextensive electrons. The present study is useful in the space situations where such distribution exists.

  1. Relativistic electron beam acceleration by cascading nonlinear Landau damping of electromagnetic waves in a plasma

    International Nuclear Information System (INIS)

    Sugaya, R.; Ue, A.; Maehara, T.; Sugawa, M.

    1996-01-01

    Acceleration and heating of a relativistic electron beam by cascading nonlinear Landau damping involving three or four intense electromagnetic waves in a plasma are studied theoretically based on kinetic wave equations and transport equations derived from relativistic Vlasov endash Maxwell equations. Three or four electromagnetic waves excite successively two or three nonresonant beat-wave-driven relativistic electron plasma waves with a phase velocity near the speed of light [v p =c(1-γ -2 p ) 1/2 , γ p =ω/ω pe ]. Three beat waves interact nonlinearly with the electron beam and accelerate it to a highly relativistic energy γ p m e c 2 more effectively than by the usual nonlinear Landau damping of two electromagnetic waves. It is proved that the electron beam can be accelerated to more highly relativistic energy in the plasma whose electron density decreases temporally with an appropriate rate because of the temporal increase of γ p . copyright 1996 American Institute of Physics

  2. Exact solutions of the one-dimensional generalized modified complex Ginzburg-Landau equation

    International Nuclear Information System (INIS)

    Yomba, Emmanuel; Kofane, Timoleon Crepin

    2003-01-01

    The one-dimensional (1D) generalized modified complex Ginzburg-Landau (MCGL) equation for the traveling wave systems is analytically studied. Exact solutions of this equation are obtained using a method which combines the Painleve test for integrability in the formalism of Weiss-Tabor-Carnevale and Hirota technique of bilinearization. We show that pulses, fronts, periodic unbounded waves, sources, sinks and solution as collision between two fronts are the important coherent structures that organize much of the dynamical properties of these traveling wave systems. The degeneracies of the 1D generalized MCGL equation are examined as well as several of their solutions. These degeneracies include two important equations: the 1D generalized modified Schroedinger equation and the 1D generalized real modified Ginzburg-Landau equation. We obtain that the one parameter family of traveling localized source solutions called 'Nozaki-Bekki holes' become a subfamily of the dark soliton solutions in the 1D generalized modified Schroedinger limit

  3. Inertia and ion Landau damping of low-frequency magnetohydrodynamical modes in tokamaks

    International Nuclear Information System (INIS)

    Bondeson, A.; Chu, M.S.

    1996-01-01

    The inertia and Landau damping of low-frequency magnetohydrodynamical modes are investigated using the drift-kinetic energy principle for the motion along the magnetic field. Toroidal trapping of the ions decreases the Landau damping and increases the inertia for frequencies below (r/R) 1/2 v thi /qR. The theory is applied to toroidicity-induced Alfvacute en eigenmodes and to resistive wall modes in rotating plasmas. An explanation of the beta-induced Alfvacute en eigenmode is given in terms of the Pfirsch endash Schlueter-like enhancement of inertia at low frequency. The toroidal inertia enhancement also increases the effects of plasma rotation on resistive wall modes. copyright 1996 American Institute of Physics

  4. Magnetization plateaus of the frustrated Ising Shastry–Sutherland system: Wang–Landau simulation

    International Nuclear Information System (INIS)

    Lin, W.S.; Yang, T.H.; Wang, Y.; Qin, M.H.; Liu, J.-M.; Ren, Zhifeng

    2014-01-01

    The Wang–Landau algorithm is used to study the magnetic properties of the Ising model on the Shastry–Sutherland lattice in order to understand the interesting magnetization plateaus observed in TmB 4 . The simulated results demonstrate that the equilibrium state of the model produces only the 1/3 and 1/2 magnetization plateaus at low temperatures even when the random-exchange term or the long-range interactions are taken into account. This confirms our earlier conclusion (Huang et al., 2013) [20] that those fractional plateaus observed in experiments may be due to the magnetization dynamics. - Highlights: • The magnetic behaviors of TmB 4 are investigated using the Wang–Landau method. • The equilibrium state only produces the 1/3 and 1/2 magnetization plateaus. • Those fractional plateaus must arise from the non-equilibrium magnetization

  5. Magnetization plateaus of the frustrated Ising Shastry–Sutherland system: Wang–Landau simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W.S.; Yang, T.H.; Wang, Y. [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Qin, M.H., E-mail: qinmh@scnu.edu.cn [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Department of Physics and TcSUH, University of Houston, Houston, TX 77204 (United States); Liu, J.-M. [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Ren, Zhifeng, E-mail: zren@uh.edu [Department of Physics and TcSUH, University of Houston, Houston, TX 77204 (United States)

    2014-07-04

    The Wang–Landau algorithm is used to study the magnetic properties of the Ising model on the Shastry–Sutherland lattice in order to understand the interesting magnetization plateaus observed in TmB{sub 4}. The simulated results demonstrate that the equilibrium state of the model produces only the 1/3 and 1/2 magnetization plateaus at low temperatures even when the random-exchange term or the long-range interactions are taken into account. This confirms our earlier conclusion (Huang et al., 2013) [20] that those fractional plateaus observed in experiments may be due to the magnetization dynamics. - Highlights: • The magnetic behaviors of TmB{sub 4} are investigated using the Wang–Landau method. • The equilibrium state only produces the 1/3 and 1/2 magnetization plateaus. • Those fractional plateaus must arise from the non-equilibrium magnetization.

  6. Effects of periodic scattering potential on Landau quantization and ballistic transport of electrons in graphene

    International Nuclear Information System (INIS)

    Gumbs, Godfrey; Iurov, Andrii; Huang, Danhong; Fekete, Paula; Zhemchuzhna, Liubov

    2014-01-01

    A two-dimensional periodic array of scatterers has been introduced to a single layer of graphene in the presence of an external magnetic field perpendicular to the graphene layer. The eigenvalue equation for such a system has been solved numerically to display the structure of split Landau subbands as functions of both wave number and magnetic flux. The effects of pseudo-spin coupling and Landau subbands mixing by a strong scattering potential have been demonstrated. Additionally, we investigated the square barrier tunneling problem when magnetic field is present, as well as demonstrate the crucial difference in the modulated band structure between graphene and the two-dimensional electron gas. The low-magnetic field regime is particularly interesting for Dirac fermions and has been discussed. Tunneling of Dirac electrons through a magnetic potential barrier has been investigated to complement the reported results on electrostatic potential scattering in the presence of an ambient magnetic field

  7. The finite dimensional behaviour of the global attractors for the generalized Landau-Lifshitz equation on compact manifolds

    International Nuclear Information System (INIS)

    Guo Boling

    1994-01-01

    We prove the existence of the global attractors for the generalized Landau-Lifshitz equation on compact manifold M, and give the upper and lower estimates of their Hausdorff and fractal dimensions. (author). 18 refs

  8. Fractional Quantum Hall Effect in n = 0 Landau Band of Graphene with Chern Number Matrix

    Science.gov (United States)

    Kudo, Koji; Hatsugai, Yasuhiro

    2018-06-01

    Fully taking into account the honeycomb lattice structure, fractional quantum Hall states of graphene are considered by a pseudopotential projected into the n = 0 Landau band. By using chirality as an internal degree of freedom, the Chern number matrices are defined and evaluated numerically. Quantum phase transition induced by changing a range of the interaction is demonstrated that is associated with chirality ferromagnetism. The chirality-unpolarized ground state is consistent with the Halperin 331 state of the bilayer quantum Hall system.

  9. The infrared behaviour of the running coupling in Landau gauge QCD

    International Nuclear Information System (INIS)

    Alkofer, R.; Fischer, C.S.; Smekal, L. von.

    2002-01-01

    Approximate solutions for the gluon and ghost propagators as well as the running coupling in Landau gauge Yang-Mills theories are presented. These propagators obtained from the corresponding Dyson-Schwinger equations are in remarkable agreement with those of recent lattice calculations. The resulting running coupling possesses an infrared fixed point, α s (0) = 8.92/N for all gauge SU(N). Above one GeV the running coupling rapidly approaches its perturbative form (Authors)

  10. Robust control problems of vortex dynamics in superconducting films with Ginzburg-Landau complex systems

    OpenAIRE

    Belmiloudi, Aziz

    2006-01-01

    We formulate and study robust control problems for a two-dimensional time-dependent Ginzburg-Landau model with Robin boundary conditions on phase-field parameter, which describes the phase transitions taking place in superconductor films with variable thickness. The objective of such study is to control the motion of vortices in the superconductor films by taking into account the influence of noises in data. Firstly, we introduce the perturbation problem of the nonlinear ...

  11. Dirac mechanics and Landau two-fluid model in /sup 4/HeII

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Gomez, J [Instituto Universitario Pedagogico de Caracas (Venezuela). Dept. de Matematica y Fisica

    1980-07-01

    This paper is devoted to the development of the Dirac formalism for singular systems when applied to the Landau two-fluid model in superfluid helium. Notably, the Hamiltonian density is weakly zero (in the sense of Dirac). We obtain the physical and gauge variables and show that all the constraints are of first class and hence that the Dirac bracket coincides with the Poisson bracket. The quantization of this system is left for a future paper.

  12. Global a priori estimates for the inhomogeneous Landau equation with moderately soft potentials

    Science.gov (United States)

    Cameron, Stephen; Silvestre, Luis; Snelson, Stanley

    2018-05-01

    We establish a priori upper bounds for solutions to the spatially inhomogeneous Landau equation in the case of moderately soft potentials, with arbitrary initial data, under the assumption that mass, energy and entropy densities stay under control. Our pointwise estimates decay polynomially in the velocity variable. We also show that if the initial data satisfies a Gaussian upper bound, this bound is propagated for all positive times.

  13. Solutions without phase-slip for the Ginsburg-Landau equation

    International Nuclear Information System (INIS)

    Collet, P.; Eckmann, J.P.

    1992-01-01

    We consider the Ginsburg-Landau equation for a complex scalar field in one dimension and consider initial data which have two different stationary solutions as their limits in space as x→±∞. If these solutions are not very different, then we show that the initial data will evolve to a stationary solution by a 'phase melting' process which avoids 'phase slips,' i.e., which does not go through zero amplitude. (orig.)

  14. Modeling of superconductors based on the timedependent Ginsburg-Landau equations

    Science.gov (United States)

    Grishakov, K. S.; Degtyarenko, P. N.; Degtyarenko, N. N.; Elesin, V. F.; Kruglov, V. S.

    2009-11-01

    Results of modeling of superconductor magnetization process based on a numerical solution of the timedependent Ginsburg-Landau equations are presented. Methods of grid approximation of the equations and method of finite elements are used. Two-dimensional patterns of changes in the order parameter and supercurrent distribution in superconductors are calculated and visualized. The main results are in agreement with the well-known representations for type I and II superconductors.

  15. A fast non-Fourier method for Landau-fluid operators

    Energy Technology Data Exchange (ETDEWEB)

    Dimits, A. M., E-mail: dimits1@llnl.gov; Joseph, I.; Umansky, M. V. [Lawrence Livermore National Laboratory, L-637, P.O. Box 808, Livermore, California 94511-0808 (United States)

    2014-05-15

    An efficient and versatile non-Fourier method for the computation of Landau-fluid (LF) closure operators [Hammett and Perkins, Phys. Rev. Lett. 64, 3019 (1990)] is presented, based on an approximation by a sum of modified-Helmholtz-equation solves (SMHS) in configuration space. This method can yield fast-Fourier-like scaling of the computational time requirements and also provides a very compact data representation of these operators, even for plasmas with large spatial nonuniformity. As a result, the method can give significant savings compared with direct application of “delocalization kernels” [e.g., Schurtz et al., Phys. Plasmas 7, 4238 (2000)], both in terms of computational cost and memory requirements. The method is of interest for the implementation of Landau-fluid models in situations where the spatial nonuniformity, particular geometry, or boundary conditions render a Fourier implementation difficult or impossible. Systematic procedures have been developed to optimize the resulting operators for accuracy and computational cost. The four-moment Landau-fluid model of Hammett and Perkins has been implemented in the BOUT++ code using the SMHS method for LF closure. Excellent agreement has been obtained for the one-dimensional plasma density response function between driven initial-value calculations using this BOUT++ implementation and matrix eigenvalue calculations using both Fourier and SMHS non-Fourier implementations of the LF closures. The SMHS method also forms the basis for the implementation, which has been carried out in the BOUT++ code, of the parallel and toroidal drift-resonance LF closures. The method is a key enabling tool for the extension of gyro-Landau-fluid models [e.g., Beer and Hammett, Phys. Plasmas 3, 4046 (1996)] to codes that treat regions with strong profile variation, such as the tokamak edge and scrapeoff-layer.

  16. Pattern selection and spatio-temporal transition to chaos in Ginzburg-Landau equation

    Energy Technology Data Exchange (ETDEWEB)

    Nozaki, K; Bekki, N

    1983-07-01

    It is shown that a modulationally unstable pattern is selected and propagates into an initially unstable motionless state in the 1-D generalized Ginzburg-Landau equation. A further spatio-temporal transition occurs with a sharp interface from the selected unstable pattern to a stabilized pattern or a chaotic state. The distinct transition makes a coherent structure to coexist with a chaotic state. 12 refs., 4 figs.

  17. Electrostatic field in superconductors IV: theory of Ginzburg-Landau type

    Czech Academy of Sciences Publication Activity Database

    Lipavský, Pavel; Koláček, Jan

    2009-01-01

    Roč. 23, 20-21 (2009), s. 4505-4511 ISSN 0217-9792 R&D Projects: GA ČR GA202/04/0585; GA ČR GA202/05/0173; GA AV ČR IAA1010312 Institutional research plan: CEZ:AV0Z10100521 Keywords : superconductivity * Ginzburg-Landau theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.408, year: 2009

  18. A rigorous proof of the Landau-Peierls formula and much more

    DEFF Research Database (Denmark)

    Briet, Philippe; Cornean, Horia; Savoie, Baptiste

    2012-01-01

    We present a rigorous mathematical treatment of the zero-field orbital magnetic susceptibility of a non-interacting Bloch electron gas, at fixed temperature and density, for both metals and semiconductors/insulators. In particular, we obtain the Landau-Peierls formula in the low temperature and d...... and density limit as conjectured by Kjeldaas and Kohn (Phys Rev 105:806–813, 1957)....

  19. Critical opalescence in fluids: 1.5-Scattering effects and the Landau-Placzek ratio

    OpenAIRE

    Sushko, M. Ya.

    2010-01-01

    We adduce new arguments for the significance of so-called 1.5- (or sesquialteral) molecular light scattering in one-component fluids. For this purpose, we analyze its effect on the Landau-Placzek ratio for the critical opalescence spectrum. The results obtained are used to reveal experimental data which can be interpreted as evidence for its existence and to evaluate both the relative magnitude and the sign of the 1.5-scattering contribution.

  20. Real-time relaxation and kinetics in hot scalar QED: Landau damping

    International Nuclear Information System (INIS)

    Boyanovsky, D.; Vega, H.J. de; Holman, R.; Kumar, S.P.; Pisarski, R.D.

    1998-01-01

    The real time evolution of non-equilibrium expectation values with soft length scales ∼k -1 >(eT) -1 is solved in hot scalar electrodynamics, with a view towards understanding relaxational phenomena in the QGP and the electroweak plasma. We find that the gauge invariant non-equilibrium expectation values relax via power laws to asymptotic amplitudes that are determined by the quasiparticle poles. The long time relaxational dynamics and relevant time scales are determined by the behavior of the retarded self-energy not at the small frequencies, but at the Landau damping thresholds. This explains the presence of power laws and not of exponential decay. In the process we rederive the HTL effective action using non-equilibrium field theory. Furthermore we obtain the influence functional, the Langevin equation and the fluctuation-dissipation theorem for the soft modes, identifying the correlators that emerge in the classical limit. We show that a Markovian approximation fails to describe the dynamics both at short and long times. We find that the distribution function for soft quasiparticles relaxes with a power law through Landau damping. We also introduce a novel kinetic approach that goes beyond the standard Boltzmann equation by incorporating off-shell processes and find that the distribution function for soft quasiparticles relaxes with a power law through Landau damping. We find an unusual dressing dynamics of bare particles and anomalous (logarithmic) relaxation of hard quasiparticles. copyright 1998 The American Physical Society

  1. Effective Ginzburg–Landau free energy functional for multi-band isotropic superconductors

    International Nuclear Information System (INIS)

    Grigorishin, Konstantin V.

    2016-01-01

    Highlights: • The intergradient coupling of order parameters in a two-band superconductor plays important role and cannot be neglected. • A two-band superconductor must be characterized with a single coherence length and a single Ginzburg–Landau parameter. • Type-1.5 superconductors are impossible. • The free energy functional for a multi-band superconductor can be reduced to the effective single-band Ginzburg–Landau functional. - Abstract: It has been shown that interband mixing of gradients of two order parameters (drag effect) in an isotropic bulk two-band superconductor plays important role – such a quantity of the intergradients coupling exists that the two-band superconductor is characterized with a single coherence length and a single Ginzburg–Landau (GL) parameter. Other quantities or neglecting of the drag effect lead to existence of two coherence lengths and dynamical instability due to violation of the phase relations between the order parameters. Thus so-called type-1.5 superconductors are impossible. An approximate method for solving of set of GL equations for a multi-band superconductor has been developed: using the result about the drag effect it has been shown that the free-energy functional for a multi-band superconductor can be reduced to the GL functional for an effective single-band superconductor.

  2. Towards a generalized Landau theory of quasi-particles for hot dense matter

    International Nuclear Information System (INIS)

    Leermakers, R.

    1985-01-01

    In this thesis it is tried to construct a Landau quasi-particle theory for relativistic systems, using field-theoretical methods. It includes a perturbative calculation of the pressure of a quark-gluon plasma. It reports the existence of a hitherto unnoticed plasmon contribution of the order g 3 due to transverse quasi-gluons. A new and Lorentz covariant formulation of the Landau theory is being developed, for a general relativistic system. A detailed calculation is presented of the observables of a quantum electrodynamical (QED) plasma, in lowest orders of perturbation theory. A transverse plasmon effect is discovered, both analytically and numerically. In addition, the analysis shows quasi-electrons and positrons to be stable excitations at any temperature. This is proven in all orders of perturbation theory. Along with a Landau theory for quark-gluon matter, a linearized kinetic equation is derived for the singlet quark distribution function, with a collision term for soft encounters between quasi-quarks. (Auth.)

  3. Nucleation of the lamellar phase from the disordered phase of the renormalized Landau-Brazovskii model

    Science.gov (United States)

    Carilli, Michael F.; Delaney, Kris T.; Fredrickson, Glenn H.

    2018-02-01

    Using the zero-temperature string method, we investigate nucleation of a stable lamellar phase from a metastable disordered phase of the renormalized Landau-Brazovskii model at parameters explicitly connected to those of an experimentally accessible diblock copolymer melt. We find anisotropic critical nuclei in qualitative agreement with previous experimental and analytic predictions; we also find good quantitative agreement with the predictions of a single-mode analysis. We conduct a thorough search for critical nuclei containing various predicted and experimentally observed defect structures. The predictions of the renormalized model are assessed by simulating the bare Landau-Brazovskii model with fluctuations. We find that the renormalized model makes reasonable predictions for several important quantities, including the order-disorder transition (ODT). However, the critical nucleus size depends sharply on proximity to the ODT, so even small errors in the ODT predicted by the renormalized model lead to large errors in the predicted critical nucleus size. We conclude that the renormalized model is a poor tool to study nucleation in the fluctuating Landau-Brazovskii model, and recommend that future studies work with the fluctuating bare model directly, using well-chosen collective variables to investigate kinetic pathways in the disorder → lamellar transition.

  4. Exact solutions to the Mo-Papas and Landau-Lifshitz equations

    Science.gov (United States)

    Rivera, R.; Villarroel, D.

    2002-10-01

    Two exact solutions of the Mo-Papas and Landau-Lifshitz equations for a point charge in classical electrodynamics are presented here. Both equations admit as an exact solution the motion of a charge rotating with constant speed in a circular orbit. These equations also admit as an exact solution the motion of two identical charges rotating with constant speed at the opposite ends of a diameter. These exact solutions allow one to obtain, starting from the equation of motion, a definite formula for the rate of radiation. In both cases the rate of radiation can also be obtained, with independence of the equation of motion, from the well known fields of a point charge, that is, from the Maxwell equations. The rate of radiation obtained from the Mo-Papas equation in the one-charge case coincides with the rate of radiation that comes from the Maxwell equations; but in the two-charge case the results do not coincide. On the other hand, the rate of radiation obtained from the Landau-Lifshitz equation differs from the one that follows from the Maxwell equations in both the one-charge and two-charge cases. This last result does not support a recent statement by Rohrlich in favor of considering the Landau-Lifshitz equation as the correct and exact equation of motion for a point charge in classical electrodynamics.

  5. Exact solutions to the Mo-Papas and Landau-Lifshitz equations

    International Nuclear Information System (INIS)

    Rivera, R.; Villarroel, D.

    2002-01-01

    Two exact solutions of the Mo-Papas and Landau-Lifshitz equations for a point charge in classical electrodynamics are presented here. Both equations admit as an exact solution the motion of a charge rotating with constant speed in a circular orbit. These equations also admit as an exact solution the motion of two identical charges rotating with constant speed at the opposite ends of a diameter. These exact solutions allow one to obtain, starting from the equation of motion, a definite formula for the rate of radiation. In both cases the rate of radiation can also be obtained, with independence of the equation of motion, from the well known fields of a point charge, that is, from the Maxwell equations. The rate of radiation obtained from the Mo-Papas equation in the one-charge case coincides with the rate of radiation that comes from the Maxwell equations; but in the two-charge case the results do not coincide. On the other hand, the rate of radiation obtained from the Landau-Lifshitz equation differs from the one that follows from the Maxwell equations in both the one-charge and two-charge cases. This last result does not support a recent statement by Rohrlich in favor of considering the Landau-Lifshitz equation as the correct and exact equation of motion for a point charge in classical electrodynamics

  6. Ginzburg-Landau equation as a heuristic model for generating rogue waves

    Science.gov (United States)

    Lechuga, Antonio

    2016-04-01

    Envelope equations have many applications in the study of physical systems. Particularly interesting is the case 0f surface water waves. In steady conditions, laboratory experiments are carried out for multiple purposes either for researches or for practical problems. In both cases envelope equations are useful for understanding qualitative and quantitative results. The Ginzburg-Landau equation provides an excellent model for systems of that kind with remarkable patterns. Taking into account the above paragraph the main aim of our work is to generate waves in a water tank with almost a symmetric spectrum according to Akhmediev (2011) and thus, to produce a succession of rogue waves. The envelope of these waves gives us some patterns whose model is a type of Ginzburg-Landau equation, Danilov et al (1988). From a heuristic point of view the link between the experiment and the model is achieved. Further, the next step consists of changing generating parameters on the water tank and also the coefficients of the Ginzburg-Landau equation, Lechuga (2013) in order to reach a sufficient good approach.

  7. ABOUT SOME APPROXIMATIONS TO THE CLOSED SET OF NOT TRIVIAL SOLUTIONS OF THE EQUATIONS OF GINZBURG - LANDAU

    Directory of Open Access Journals (Sweden)

    A. A. Fonarev

    2014-01-01

    Full Text Available Possibility of use of a projective iterative method for search of approximations to the closed set of not trivial generalised solutions of a boundary value problem for Ginzburg - Landau's equations of the phenomenological theory of superconduction is investigated. The projective iterative method combines a projective method and iterative process. The generalised solutions of a boundary value problem for Ginzburg - Landau's equations are critical points of a functional of a superconductor free energy.

  8. Stability and activation gaps of the parafermionic Hall states in the second Landau level

    International Nuclear Information System (INIS)

    Georgiev, L.S.

    2002-01-01

    Analyzing the effective conformal field theory for the parafermionic Hall states, corresponding to filling fractions ν k =2+k/(kM+2), k=2,3,..., M odd, we show that the even k plateaux are expected to be more stable than their odd k neighbors. The reason is that the parafermion chiral algebra can be locally extended for k even. This reconciles the theoretical implication, that the bigger the k the less stable the fluid, with the experimental fact that, for M=1, the k=2 and k=4 plateaux are already observed at electron temperature T e ≅8 mK, while the Hall resistance for k=3 is not precisely quantized at that temperature in the sample of Pan et al. Using a heuristic gap ansatz we estimate the activation energy gap for ν 3 =13/5 to be approximately 0.015 K, which implies that the quantization of the Hall conductance could be observed for temperature below 1 mK in the same sample. We also find an appealing exact relation between the fractional electric charge and fractional statistics of the quasiholes. Finally, we argue that besides the Moore-Read phase for the ν 2 =5/2 state there is another relevant phase, in which the fundamental quasiholes obey abelian statistics and carry half-integer electric charge

  9. The half-filled Landau level: The case for Dirac composite fermions

    Science.gov (United States)

    Geraedts, Scott D.; Zaletel, Michael P.; Mong, Roger S. K.; Metlitski, Max A.; Vishwanath, Ashvin; Motrunich, Olexei I.

    2016-04-01

    In a two-dimensional electron gas under a strong magnetic field, correlations generate emergent excitations distinct from electrons. It has been predicted that “composite fermions”—bound states of an electron with two magnetic flux quanta—can experience zero net magnetic field and form a Fermi sea. Using infinite-cylinder density matrix renormalization group numerical simulations, we verify the existence of this exotic Fermi sea, but find that the phase exhibits particle-hole symmetry. This is self-consistent only if composite fermions are massless Dirac particles, similar to the surface of a topological insulator. Exploiting this analogy, we observe the suppression of 2kF backscattering, a characteristic of Dirac particles. Thus, the phenomenology of Dirac fermions is also relevant to two-dimensional electron gases in the quantum Hall regime.

  10. Onset of Darrieus-Landau Instability in Expanding Flames

    Science.gov (United States)

    Mohan, Shikhar; Matalon, Moshe

    2017-11-01

    The effect of small amplitude perturbations on the propagation of circular flames in unconfined domains is investigated, computationally and analytically, within the context of the hydrodynamic theory. The flame, treated as a surface of density discontinuity separating fresh combustible mixture from the burnt gas, propagates at a speed dependent upon local curvature and hydrodynamic strain. For mixtures with Lewis numbers above criticality, thermodiffusive effects have stabilizing influences which largely affect the flame at small radii. The amplitude of these disturbances initially decay and only begin to grow once a critical radius is reached. This instability is hydrodynamic in nature and is a consequence of thermal expansion. Through linear stability analysis, predictions of critical flame radius at the onset of instability are obtained as functions of Markstein length and thermal expansion coefficients. The flame evolution is also examined numerically where the motion of the interface is tracked via a level-set method. Consistent with linear stability results, simulations show the flame initially remaining stable and the existence of a particular mode that will be first to grow and later determine the cellular structure observed experimentally at the onset of instability.

  11. ENERGY DISSIPATION AND LANDAU DAMPING IN TWO- AND THREE-DIMENSIONAL PLASMA TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tak Chu; Howes, Gregory G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Klein, Kristopher G. [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); TenBarge, Jason M. [IREAP, University of Maryland, College Park, MD 20742 (United States)

    2016-12-01

    Plasma turbulence is ubiquitous in space and astrophysical plasmas, playing an important role in plasma energization, but the physical mechanisms leading to dissipation of the turbulent energy remain to be definitively identified. Kinetic simulations in two dimensions (2D) have been extensively used to study the dissipation process. How the limitation to 2D affects energy dissipation remains unclear. This work provides a model of comparison between two- and three-dimensional (3D) plasma turbulence using gyrokinetic simulations; it also explores the dynamics of distribution functions during the dissipation process. It is found that both 2D and 3D nonlinear gyrokinetic simulations of a low-beta plasma generate electron velocity-space structures with the same characteristics as that of the linear Landau damping of Alfvén waves in a 3D linear simulation. The continual occurrence of the velocity-space structures throughout the turbulence simulations suggests that the action of Landau damping may be responsible for the turbulent energy transfer to electrons in both 2D and 3D, and makes possible the subsequent irreversible heating of the plasma through collisional smoothing of the velocity-space fluctuations. Although, in the 2D case where variation along the equilibrium magnetic field is absent, it may be expected that Landau damping is not possible, a common trigonometric factor appears in the 2D resonant denominator, leaving the resonance condition unchanged from the 3D case. The evolution of the 2D and 3D cases is qualitatively similar. However, quantitatively, the nonlinear energy cascade and subsequent dissipation is significantly slower in the 2D case.

  12. Landau-Zener evolution under weak measurement: manifestation of the Zeno effect under diabatic and adiabatic measurement protocols

    Science.gov (United States)

    Novelli, Anna; Belzig, Wolfgang; Nitzan, Abraham

    2015-01-01

    The time evolution and the asymptotic outcome of a Landau-Zener-Stueckelberg-Majorana (LZ) process under continuous weak non-selective measurement is analyzed. We compare two measurement protocols in which the populations of either the adiabatic or the non-adiabatic levels are (continuously and weakly) monitored. The weak measurement formalism, described using a Gaussian Kraus operator, leads to a time evolution characterized by a Markovian dephasing process, which, in the non-adiabatic measurement protocol is similar to earlier studies of LZ dynamics in a dephasing environment. Casting the problem in the language of measurement theory makes it possible for us to compare diabatic and adiabatic measurement scenarios, to consider engineered dephasing as a control device and to examine the manifestation of the Zeno effect under the different measurement protocols. In particular, under measurement of the non-adiabatic populations, the Zeno effect is manifested not as a freezing of the measured system in its initial state, but rather as an approach to equal asymptotic populations of the two diabatic states. This behavior can be traced to the way by which the weak measurement formalism behaves in the strong measurement limit, with a built-in relationship between measurement time and strength.

  13. Construction of the dual Ginzburg-Landau theory from the lattice QCD

    International Nuclear Information System (INIS)

    Suganuma, H.; Amemiya, K.; Ichie, H.; Koma, Y.

    2002-01-01

    We roughly review the QCD physics and then introduce recent topics on the confinement physics. In the maximally abelian (MA) gauge, the low-energy QCD is abelianized owing to the effective off-diagonal gluon mass M off ≅ 1.2 GeV induced by the MA gauge fixing. We demonstrate the construction of the dual Ginzburg-Landau (DGL) theory from the low-energy QCD in the MA gauge in terms of the lattice QCD evidences on infrared abelian dominance and infrared monopole condensation. (author)

  14. Strong-coupling study of the Gribov ambiguity in lattice Landau gauge

    International Nuclear Information System (INIS)

    Maas, Axel; Pawlowski, Jan M.; Spielmann, Daniel; Sternbeck, Andre; Smekal, Lorenz von

    2010-01-01

    We study the strong-coupling limit β=0 of lattice SU(2) Landau gauge Yang-Mills theory. In this limit the lattice spacing is infinite, and thus all momenta in physical units are infinitesimally small. Hence, the infrared behavior can be assessed at sufficiently large lattice momenta. Our results show that at the lattice volumes used here, the Gribov ambiguity has an enormous effect on the ghost propagator in all dimensions. This underlines the severity of the Gribov problem and calls for refined studies also at finite β. In turn, the gluon propagator only mildly depends on the Gribov ambiguity. (orig.)

  15. On the Possibility of Using Nonlinear Elements for Landau Damping in High-Intensity Beams

    Energy Technology Data Exchange (ETDEWEB)

    Alexahin, Y. [Fermilab; Gianfelice-Wendt, E. [Fermilab; Lebedev, V. [Fermilab; Valishev, A. [Fermilab

    2016-09-30

    Direct space-charge force shifts incoherent tunes downwards from the coherent ones breaking the Landau mechanism of coherent oscillations damping at high beam intensity. To restore it nonlinear elements can be employed which move back tunes of large amplitude particles. In the present report we consider the possibility of creating a “nonlinear integrable optics” insertion in the Fermilab Recycler to host either octupoles or hollow electron lens for this purpose. For comparison we also consider the classic scheme with distributed octupole families. It is shown that for the Proton Improvement Plan II (PIP II) parameters the required nonlinear tune shift can be created without destroying the dynamic aperture.

  16. Inverse Landau-Zener-Stuckelberg interferometry for the measurement of a resonator's state using a qubit

    Science.gov (United States)

    Shevchenko, Sergey; Ashhab, Sahel; Nori, Franco

    2013-03-01

    We consider theoretically a superconducting qubit - nanomechanical resonator system, which was realized recently by LaHaye et al. [Nature 459, 960 (2009)]. We formulate and solve the inverse Landau-Zener-Stuckelberg problem, where we assume the driven qubit's state to be known (i.e. measured by some other device) and aim to find the parameters of the qubit's Hamiltonian. In particular, for our system the qubit's bias is defined by the nanomechanical resonator's displacement. This may provide a tool for monitoring the nanomechanical resonator 's position. [S. N. Shevchenko, S. Ashhab, and F. Nori, Phys. Rev. B 85, 094502 (2012).

  17. Martensitic phase transformations in Ni–Ti-based shape memory alloys: The Landau theory

    International Nuclear Information System (INIS)

    Shchyglo, Oleg; Salman, Umut; Finel, Alphonse

    2012-01-01

    We present a simple Landau free energy functional for cubic-to-orthorhombic and cubic-to-monoclinic martensitic phase transformations. The functional is derived following group–subgroup relations between different martensitic phases – tetragonal, trigonal, orthorhombic and monoclinic – in order to fully capture the symmetry properties of the free energy of the austenite and martensite phases. The derived free energy functional is fitted to the elastic and thermodynamic properties of NiTi and NiTiCu shape memory alloys which exhibit cubic-to-monoclinic and cubic-to-orthorhombic martensitic phase transformations, respectively.

  18. Transient analysis of scattering from ferromagnetic objects using Landau-Lifshitz-Gilbert and volume integral equations

    KAUST Repository

    Sayed, Sadeed Bin

    2016-11-02

    An explicit marching on-in-time scheme for analyzing transient electromagnetic wave interactions on ferromagnetic scatterers is described. The proposed method solves a coupled system of time domain magnetic field volume integral and Landau-Lifshitz-Gilbert (LLG) equations. The unknown fluxes and fields are discretized using full and half Schaubert-Wilton-Glisson functions in space and bandlimited temporal interpolation functions in time. The coupled system is cast in the form of an ordinary differential equation and integrated in time using a PE(CE)m type linear multistep method to obtain the unknown expansion coefficients. Numerical results demonstrating the stability and accuracy of the proposed scheme are presented.

  19. Spectrum of the linearized operator for the Ginzburg-Landau equation

    Directory of Open Access Journals (Sweden)

    Tai-Chia Lin

    2000-06-01

    Full Text Available We study the spectrum of the linearized operator for the Ginzburg-Landau equation about a symmetric vortex solution with degree one. We show that the smallest eigenvalue of the linearized operator has multiplicity two, and then we describe its behavior as a small parameter approaches zero. We also find a positive lower bound for all the other eigenvalues, and find estimates of the first eigenfunction. Then using these results, we give partial results on the dynamics of vortices in the nonlinear heat and Schrodinger equations.

  20. Infrared Behavior of Gluon and Ghost Propagators in Landau Gauge QCD

    International Nuclear Information System (INIS)

    von Smekal, L.; Hauck, A.; Alkofer, R.

    1997-01-01

    A truncation scheme for the Dyson-Schwinger equations of Euclidean QCD in Landau gauge is presented. It implements the Slavnov-Taylor identities for the three-gluon and ghost-gluon vertices, whereas irreducible four-gluon couplings as well as the gluon-ghost and ghost-ghost scattering kernels are neglected. The infrared behavior of gluon and ghost propagators is obtained analytically: The gluon propagator vanishes for small momenta, whereas the ghost propagator diverges strongly. The numerical solutions are compared with recent lattice results. The running coupling approaches a fixed point, α c ≅9.5 , in the infrared. copyright 1997 The American Physical Society

  1. Specific heat of Ginzburg-Landau fields in the n-1 expansion

    International Nuclear Information System (INIS)

    Bray, A.J.

    1975-01-01

    The n -1 expansion for the specific heat C/subv/ of the n-component Ginzburg-Landau model is discussed in terms of an n -1 expansion for the irreducible polarization. In the low-temperature limit, each successive term of the latter expansion diverges more strongly than the last, invalidating a truncation of this series at any finite order in 1/n. The most divergent terms in each order are identified and summed. The results provide justification for the usual truncated expansions for C/subv/

  2. The buckling transition of two-dimensional elastic honeycombs: numerical simulation and Landau theory

    International Nuclear Information System (INIS)

    Jagla, E A

    2004-01-01

    I study the buckling transition under compression of a two-dimensional, hexagonal, regular elastic honeycomb. Under isotropic compression, the system buckles to a configuration consisting of a unit cell containing four of the original hexagons. This buckling pattern preserves the sixfold rotational symmetry of the original lattice but is chiral, and can be described as a combination of three different elemental distortions in directions rotated by 2π/3 from each other. Non-isotropic compression may induce patterns consisting of a single elemental distortion or a superposition of two of them. The numerical results compare very well with the outcome of a Landau theory of second-order phase transitions

  3. Ginsburg-Landau theory of two antagonistic order parameters: magnetism and superconductivity

    International Nuclear Information System (INIS)

    Suhl, H.

    1978-01-01

    An attempt is made to construct a Ginsburg-Landau theory of so-called magnetic superconductors. Two order parameters, the magnetization field and the gap function, are introduced in such a way as to inhibit each others growth. It is found that the non-local character of the superconducting order parameter must be taken into account in any evaluation of effects of the critical magnetic fluctuations. Some predictions are made within the limits of Ornstein-Zoernicke-like fluctuation theory and some comparison is made with available data. (Auth.)

  4. Transient analysis of scattering from ferromagnetic objects using Landau-Lifshitz-Gilbert and volume integral equations

    KAUST Repository

    Sayed, Sadeed Bin; Ulku, Huseyin Arda; Bagci, Hakan

    2016-01-01

    An explicit marching on-in-time scheme for analyzing transient electromagnetic wave interactions on ferromagnetic scatterers is described. The proposed method solves a coupled system of time domain magnetic field volume integral and Landau-Lifshitz-Gilbert (LLG) equations. The unknown fluxes and fields are discretized using full and half Schaubert-Wilton-Glisson functions in space and bandlimited temporal interpolation functions in time. The coupled system is cast in the form of an ordinary differential equation and integrated in time using a PE(CE)m type linear multistep method to obtain the unknown expansion coefficients. Numerical results demonstrating the stability and accuracy of the proposed scheme are presented.

  5. Sum rules for nuclear excitations with the Skyrme-Landau interaction

    International Nuclear Information System (INIS)

    Liu Kehfei; Luo Hongde; Ma Zhongyu; Feng Man; Shen Qingbiao

    1991-01-01

    The energy-weighted sum rules for electric, magnetic, Fermi and Gamow-Teller transitions with the Skyrme-Landau interaction are derived from the double commutators and numerically calculated in a HF + RPA formalism. As a numerical check of the Thouless theorem, our self-consistent calculations show that the calculated RPA strengths exhaust more than 85% of the sum rules in most cases. The well known non-energy-weighted sum rules for Fermi and Gamow-Teller transitions are also checked numerically. The sum rules are exhausted by more than 94% in these cases. (orig.)

  6. First-principles-based Landau-Devonshire potential for BiFeO.sub.3./sub.

    Czech Academy of Sciences Publication Activity Database

    Márton, Pavel; Klíč, Antonín; Pasciak, Marek; Hlinka, Jiří

    2017-01-01

    Roč. 96, č. 17 (2017), s. 1-5, č. článku 174110. ISSN 2469-9950 R&D Projects: GA ČR GA15-04121S Grant - others:GA MŠk(CZ) LM2015042 Institutional support: RVO:68378271 Keywords : Landau-Devonshire potential * first-principles calculations * BiFeO3 * Energy-sampling technique Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  7. Hc2 of anisotropy two-band superconductors by Ginzburg-Landau approach

    International Nuclear Information System (INIS)

    Udomsamuthirun, P.; Changjan, A.; Kumvongsa, C.; Yoksan, S.

    2006-01-01

    The purpose of this research is to study the upper critical field H c2 of two-band superconductors by two-band Ginzburg-Landau approach. The analytical formula of H c2 included anisotropy of order parameter and anisotropy of effective-mass are found. The parameters of the upper critical field in ab-plane (H c2 - bar ab ) and c-axis (H c2 - bar c ) can be found by fitting to the experimental data. Finally, we can find the ratio of upper critical field that temperature dependent in the range of experimental result

  8. Sindrome de Landau Kleffner aspectos clinicos, eletrencefalograficos e psicossociais : estudo de seguimento a longo prazo

    OpenAIRE

    Marcos Henrique Coelho Duran

    2008-01-01

    Resumo: Objetivos: A Síndrome de Landau-Kleffner (SLK) é uma entidade rara, caracterizada por epilepsia e afasia. Ocorre em crianças com aquisição normal da linguagem, geralmente, entre 3 e 7 anos de idade. A evolução a longo prazo é controversa e pouco estudada. O presente estudo tem como objetivo verificar a evolução em uma série de sujeitos com diagnóstico de SLK, enfocando os aspectos clínicos, eletrencefalográficos, psicossociais e da qualidade de vida. Métodos: Trata-se de um estudo tra...

  9. Electron collisions in the trapped gyro-Landau fluid transport model

    International Nuclear Information System (INIS)

    Staebler, G. M.; Kinsey, J. E.

    2010-01-01

    Accurately modeling electron collisions in the trapped gyro-Landau fluid (TGLF) equations has been a major challenge. Insights gained from numerically solving the gyrokinetic equation have lead to a significant improvement of the low order TGLF model. The theoretical motivation and verification of this model with the velocity-space gyrokinetic code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] will be presented. The improvement in the fidelity of TGLF to GYRO is shown to also lead to better prediction of experimental temperature profiles by TGLF for a dedicated collision frequency scan.

  10. Use of riser tube rotation equipment in the Emlichheim and Landau petroleum mines of Wintershall AG Erdoelwerke; Einsatz von Steigrohrdrehvorrichtungen in den Erdoelfoerderbetrieben Emlichheim und Landau der Wintershall AG Erdoelwerke

    Energy Technology Data Exchange (ETDEWEB)

    Caspari, R. [Wintershall AG Erdoelwerke, Emlichheim (Germany)

    1998-12-31

    Riser tube rotation equipment has been in use in the Emlichheim and Landau petroleum wells since 1994 in order to ensure longer life of the riser tubes. (orig.) [Deutsch] In den von Wintershall operierten Erdoelfoerderbetrieben Emlichheim und Landau werden ca. 90% der Bohrungen mit Gestaengetiefpumpen gefoerdert. Aufgrund der lagerstaettentechnischen Gegebenheiten, der Thermalmassnahmen in Emlichheim und der Infrastruktur der Betriebe koennen andere Foerderhilfsmittel wie Tauchkreiselpumpe, Excenterschneckenpumpe oder Gasliften nur bedingt zum Einsatz kommen. Ein wesentlicher Faktor fuer den wirtschaftlichen Betrieb dieser Bohrungen sind die Aufwaeltigungen zur Beseitigung von Schaeden an der Tiefpumpe, dem Pumpgestaenge und den Steigrohren. Waehrend die Einsatzdauer der Tiefpumpen und des Pumpgestaenges durch hoeherwertige Materialguete und geeignete Optimierungsmassnahmen erhoeht werden konnten, sind die Standzeiten der Steigrohre nahezu unveraendert geblieben. Um diese zu erhoehen, werden in den Erdoelfoerderbetrieben Emlichheim und Landau seit April 1994 Steigrohrdrehvorrichtungen eingesetzt. (orig.)

  11. El síndrome de Landau-Kleffner: Presentación de dos casos Landau-Kleffner's syndrome: Reports of two cases

    Directory of Open Access Journals (Sweden)

    Albia J. Pozo Alonso

    2005-06-01

    Full Text Available Se presentan dos niños que reúnen los criterios clínicos y electroencefalográficos del síndrome de Landau-Kleffner. En uno de los pacientes las dificultades para comprender el lenguaje y para la expresión oral espontánea comenzaron a manifestarse a los 6 años, y en el otro caso a los 6 años y 9 meses. Uno de los niños no ha presentado crisis epilépticas hasta el momento actual. En este paciente la tomografía computadorizada por emisión de positrón único (SPECT cerebral mostró una ligera hipoperfusión temporoparietal posterior bilateral. En el niño que presenta crisis epilépticas; éstas se iniciaron a la edad de 2 años y 6 meses y eran focales simples motoras que se generalizaron secundariamente. Desde hace un año no presenta crisis. Desde el punto de vista clínico y electroencefalográfico, ambos pacientes tuvieron una respuesta favorable al tratamiento con prednisona. En un niño, aunque ha mejorado, persisten las dificultades para la comprensión y la expresión orales. Se concluye que son muy importantes para el diagnóstico de este síndrome la existencia de una afasia adquirida y las descargas observadas en el electroencefalogramaTwo children with the clinical and electroencephalographic criteria of Landau-Kleffner's syndrome are presented. In one of the patients, the difficulties for understanding the language and for the spontaneous oral expression started at 6 years old. In the other case, they were manifested at 6 years and 9 months old. One of the children has not had epileptic seizures so far. In this patient, the single positron emission computerized tomography (brain SPECT showed a mild bilateral posterior temporoparietal hypoperfusion. The epileptic seizures in the other child started when he was 2 years and 6 months old and were focal , simple, motor and secondarily generalized. He has not had seizures for a year. Both patients had a favorable response to prednisone from the clinical and

  12. Variations on the planar Landau problem: canonical transformations, a purely linear potential and the half-plane

    International Nuclear Information System (INIS)

    Govaerts, Jan; Hounkonnou, M Norbert; Mweene, Habatwa V

    2009-01-01

    The ordinary Landau problem of a charged particle in a plane subjected to a perpendicular homogeneous and static magnetic field is reconsidered from different points of view. The role of phase space canonical transformations and their relation to a choice of gauge in the solution of the problem is addressed. The Landau problem is then extended to different contexts, in particular the singular situation of a purely linear potential term being added as an interaction, for which a complete purely algebraic solution is presented. This solution is then exploited to solve this same singular Landau problem in the half-plane, with as motivation the potential relevance of such a geometry for quantum Hall measurements in the presence of an electric field or a gravitational quantum well.

  13. Fractional generalization of the Ginzburg–Landau equation: an unconventional approach to critical phenomena in complex media

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2005-01-01

    Equations built on fractional derivatives prove to be a powerful tool in the description of complex systems when the effects of singularity, fractal supports, and long-range dependence play a role. In this Letter, we advocate an application of the fractional derivative formalism to a fairly general...... class of critical phenomena when the organization of the system near the phase transition point is influenced by a competing nonlocal ordering. Fractional modifications of the free energy functional at criticality and of the widely known Ginzburg-Landau equation central to the classical Landau theory...... of second-type phase transitions are discussed in some detail. An implication of the fractional Ginzburg-Landau equation is a renormalization of the transition temperature owing to the nonlocality present. (c) 2005 Elsevier B.V. All rights reserved....

  14. Variations on the planar Landau problem: canonical transformations, a purely linear potential and the half-plane

    Energy Technology Data Exchange (ETDEWEB)

    Govaerts, Jan [Center for Particle Physics and Phenomenology (CP3), Institut de Physique Nucleaire, Universite catholique de Louvain (UCL), 2, Chemin du Cyclotron, B-1348 Louvain-la Neuve (Belgium); Hounkonnou, M Norbert [International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), University of Abomey-Calavi, 072 BP 50, Cotonou (Benin); Mweene, Habatwa V [Physics Department, University of Zambia, PO Box 32379, Lusaka (Zambia)], E-mail: Jan.Govaerts@uclouvain.be, E-mail: hounkonnou@yahoo.fr, E-mail: norbert.hounkonnou@cipma.uac.bj, E-mail: habatwamweene@yahoo.com, E-mail: hmweene@unza.zm

    2009-12-04

    The ordinary Landau problem of a charged particle in a plane subjected to a perpendicular homogeneous and static magnetic field is reconsidered from different points of view. The role of phase space canonical transformations and their relation to a choice of gauge in the solution of the problem is addressed. The Landau problem is then extended to different contexts, in particular the singular situation of a purely linear potential term being added as an interaction, for which a complete purely algebraic solution is presented. This solution is then exploited to solve this same singular Landau problem in the half-plane, with as motivation the potential relevance of such a geometry for quantum Hall measurements in the presence of an electric field or a gravitational quantum well.

  15. Quasi-linear landau kinetic equations for magnetized plasmas: compact propagator formalism, rotation matrices and interaction

    International Nuclear Information System (INIS)

    Misguich, J.H.

    2004-04-01

    As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation

  16. The dispersion-managed Ginzburg–Landau equation and its application to femtosecond lasers

    International Nuclear Information System (INIS)

    Biondini, Gino

    2008-01-01

    The complex Ginzburg–Landau equation has been used extensively to describe various nonequilibrium phenomena. In the context of lasers, it models the dynamics by averaging over the effects that take place inside the cavity. Pulses produced by Ti : sapphire femtosecond lasers, however, undergo significant changes in different parts of the cavity during each round-trip. The dynamics of such pulses is therefore not adequately described by an average model that does not take such changes into account. The purpose of this work is severalfold. We introduce the dispersion-managed Ginzburg–Landau equation (DMGLE) as an average model that describes the long-term dynamics of systems characterized by rapid variations of dispersion, nonlinearity and gain in a general setting, and we study the properties of the equation. We then explain how in particular the DMGLE arises for Ti : sapphire femtosecond lasers and we characterize its solutions. In particular, we show that, for moderate values of the gain/loss parameters, the solutions of the DMGLE are well approximated by those of the dispersion-managed nonlinear Schrödinger equation (DMNLSE), and the main effect of gain and loss dynamics is simply to select one among the one-parameter family of solutions of the DMNLSE

  17. Dromion-like structures and stability analysis in the variable coefficients complex Ginzburg–Landau equation

    International Nuclear Information System (INIS)

    Wong, Pring; Pang, Li-Hui; Huang, Long-Gang; Li, Yan-Qing; Lei, Ming; Liu, Wen-Jun

    2015-01-01

    The study of the complex Ginzburg–Landau equation, which can describe the fiber laser system, is of significance for ultra-fast laser. In this paper, dromion-like structures for the complex Ginzburg–Landau equation are considered due to their abundant nonlinear dynamics. Via the modified Hirota method and simplified assumption, the analytic dromion-like solution is obtained. The partial asymmetry of structure is particularly discussed, which arises from asymmetry of nonlinear and dispersion terms. Furthermore, the stability of dromion-like structures is analyzed. Oscillation structure emerges to exhibit strong interference when the dispersion loss is perturbed. Through the appropriate modulation of modified exponent parameter, the oscillation structure is transformed into two dromion-like structures. It indicates that the dromion-like structure is unstable, and the coherence intensity is affected by the modified exponent parameter. Results in this paper may be useful in accounting for some nonlinear phenomena in fiber laser systems, and understanding the essential role of modified Hirota method

  18. MD 2722: Investigation of Landau damping by means of BTF measurements

    CERN Document Server

    Tambasco, Claudia; Barranco Garcia, Javier; Boccardi, Andrea; Buffat, Xavier; Bruce, Roderik; Gasior, Marek; Hostettler, Michi; Lefevre, Thibaut; Levens, Tom; Louro Alves, Diogo Miguel; Metral, Elias; Pieloni, Tatiana; Pojer, Mirko; Salvachua Ferrando, Belen Maria; Solfaroli Camillocci, Matteo; CERN. Geneva. ATS Department

    2018-01-01

    Stability diagrams quantify the LHC stability thresholds due to the beam coupling impedance. Beam Transfer Function (BTF) measurements are a direct measurements of the stability diagram and therefore of the Landau damping of proton beams. Some coherent instabilities at the LHC are still not fully understood, especially when in the presence of beam-beam long range interactions at the end of the betatron squeeze. The beam-beam excited resonances can cause diffusive mechanisms and particle distribution changes that can lead to a different stability w.r.t. expectations for a Gaussian particle distribution. To investigate limitations of the models, a BTF system has been installed in the LHC in the 2015 in order to measure the Landau damping. During past MDs several configurations have been investigated: tune shifts and tune spread of the beams have been measured as a function of the octupole currents, tunes and beam-beam long range interactions. Some measurements artifacts were observed and mitigated, however the...

  19. Quasi-linear landau kinetic equations for magnetized plasmas: compact propagator formalism, rotation matrices and interaction

    Energy Technology Data Exchange (ETDEWEB)

    Misguich, J.H

    2004-04-01

    As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation.

  20. Dynamics of perturbed wavetrain solutions to the Ginzburg-Landau equation

    International Nuclear Information System (INIS)

    Keefe, L.R.

    1984-01-01

    The bifurcation structure of even, spatially periodic solutions to the time-dependent Ginzburg-Landau equation is investigated analytically and numerically. A rich variety of behavior, including limit cycles, two-tori, period-doubling sequences, and strange attractors are found to exist in the phase space of the solutions constructed from spatial Fourier modes. Beginning with unstable perturbations to the spatially homogeneous Stokes solution, changes in solution behavior are examined as the perturbing wavenumber q is varied in the range 0.6 to 1.3. Solution bifurcations as q changes are often found to be associated with symmetry making or breaking changes in the structure of attractors in phase space. Two distinct mirror image attractors are found to coexist for many values of q. Chaotic motion is found for two ranges of q Lyapunov exponents of the solutions and the Lyapunov dimension of the corresponding attractors are calculated for the larger of these regions. Poincare sections of the attractors within this chaotic range are consistent with the dimension calculation and also reveal a bifurcation structure within the chaos which broadly resembles that found in one-dimensional quadratic maps. The integrability of the Ginzburg-Landau equation is also examined. It is demonstrated that the equation does not possess the Painleve property, except for a special case of the coefficients which corresponds to the integrable non-linear Schroedinger (NLS) equation

  1. Landau quantized dynamics and spectra for group-VI dichalcogenides, including a model quantum wire

    Science.gov (United States)

    Horing, Norman J. M.

    2017-06-01

    This work is concerned with the derivation of the Green's function for Landau-quantized carriers in the Group-VI dichalcogenides. In the spatially homogeneous case, the Green's function is separated into a Peierls phase factor and a translationally invariant part which is determined in a closed form integral representation involving only elementary functions. The latter is expanded in an eigenfunction series of Laguerre polynomials. These results for the retarded Green's function are presented in both position and momentum representations, and yet another closed form representation is derived in circular coordinates in terms of the Bessel wave function of the second kind (not to be confused with the Bessel function). The case of a quantum wire is also addressed, representing the quantum wire in terms of a model one-dimensional δ (x ) -potential profile. This retarded Green's function for propagation directly along the wire is determined exactly in terms of the corresponding Green's function for the system without the δ (x ) -potential, and the Landau quantized eigenenergy dispersion relation is examined. The thermodynamic Green's function for the dichalcogenide carriers in a normal magnetic field is formulated here in terms of its spectral weight, and its solution is presented in a momentum/integral representation involving only elementary functions, which is subsequently expanded in Laguerre eigenfunctions and presented in both momentum and position representations.

  2. Landau quantized dynamics and spectra for group-VI dichalcogenides, including a model quantum wire

    Directory of Open Access Journals (Sweden)

    Norman J. M. Horing

    2017-06-01

    Full Text Available This work is concerned with the derivation of the Green’s function for Landau-quantized carriers in the Group-VI dichalcogenides. In the spatially homogeneous case, the Green’s function is separated into a Peierls phase factor and a translationally invariant part which is determined in a closed form integral representation involving only elementary functions. The latter is expanded in an eigenfunction series of Laguerre polynomials. These results for the retarded Green’s function are presented in both position and momentum representations, and yet another closed form representation is derived in circular coordinates in terms of the Bessel wave function of the second kind (not to be confused with the Bessel function. The case of a quantum wire is also addressed, representing the quantum wire in terms of a model one-dimensional δ(x-potential profile. This retarded Green’s function for propagation directly along the wire is determined exactly in terms of the corresponding Green’s function for the system without the δ(x-potential, and the Landau quantized eigenenergy dispersion relation is examined. The thermodynamic Green’s function for the dichalcogenide carriers in a normal magnetic field is formulated here in terms of its spectral weight, and its solution is presented in a momentum/integral representation involving only elementary functions, which is subsequently expanded in Laguerre eigenfunctions and presented in both momentum and position representations.

  3. Efficient solution of 3D Ginzburg-Landau problem for mesoscopic superconductors

    International Nuclear Information System (INIS)

    Pereira, Paulo J; Moshchalkov, Victor V; Chibotaru, Liviu F

    2014-01-01

    The recently proposed approach for the solution of Ginzburg-Landau (GL) problem for 2D samples of arbitrary shape is, in this article, extended over 3D samples having the shape of (i) a prism with arbitrary base and (ii) a solid of revolution with arbitrary profile. Starting from the set of Laplace operator eigenfunctions of a 2D object, we construct an approximation to or the exact eigenfunctions of the Laplace operator of a 3D structure by applying an extrusion or revolution to these solutions. This set of functions is used as the basis to construct the solutions of the linearized GL equation. These solutions are then used as basis for the non-linear GL equation much like the famous LCAO method. To solve the non-linear equation, we used the Newton-Raphson method starting from the solution of the linear equation, i.e., the nucleation distribution of superconducting condensate. The vector potential approximations typically used in 2D cases, i.e., considering it as corresponding to applied constant field, are in the 3D case harder to justify. For that reason, we use a locally corrected Nystrom method to solve the second Ginzburg-Landau equation. The complete solution of GL problem is then achieved by solving self-consistently both equations

  4. Low-frequency Landau-Zener-Stuckelberg interference in dissipative superconducting qubits

    International Nuclear Information System (INIS)

    Du-lingjie; Lan- Dong; Yu-Yang

    2013-01-01

    Landau-Zener-Stuckelberg (LZS) interference of continuously driven superconducting qubits is studied. Going beyond the second order perturbation expansion, we find a time dependent stationary population evolution as well as unsymmetrical microwave driven Landau-Zener transitions, resulting from the nonresonant terms which are neglected in rotating-wave approximation. For the low-frequency driving, the qubit population at equilibrium is a periodical function of time, owing to the contribution of the nonresonant terms. In order to obtain the average population, it is found that the average approximation based on the perturbation approach can be applied to the low-frequency region. For the extremely low frequency which is much smaller than the decoherence rate, we develop noncoherence approximation by dividing the evolution into discrete time steps during which the coherence is lost totally. These approximations present comprehensive analytical descriptions of LZS interference in most of parameter space of frequency and decoherence rate, agreeing well with those of the numerical simulations and providing a simple but integrated understanding to system dynamics. The application of our models to microwave cooling can obtain the minimal frequency to realize effective microwave cooling.

  5. Landau-Ginzburg Limit of Black Hole's Quantum Portrait: Self Similarity and Critical Exponent

    CERN Document Server

    Dvali, Gia

    2012-01-01

    Recently we have suggested that the microscopic quantum description of a black hole is an overpacked self-sustained Bose-condensate of N weakly-interacting soft gravitons, which obeys the rules of 't Hooft's large-N physics. In this note we derive an effective Landau-Ginzburg Lagrangian for the condensate and show that it becomes an exact description in a semi-classical limit that serves as the black hole analog of 't Hooft's planar limit. The role of a weakly-coupled Landau-Ginzburg order parameter is played by N. This description consistently reproduces the known properties of black holes in semi-classical limit. Hawking radiation, as the quantum depletion of the condensate, is described by the slow-roll of the field N. In the semiclassical limit, where black holes of arbitrarily small size are allowed, the equation of depletion is self similar leading to a scaling law for the black hole size with critical exponent 1/3.

  6. Ginzburg–Landau theory of mesoscopic multi-band Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Romeo, F.; De Luca, R., E-mail: rdeluca@unisa.it

    2017-05-15

    Highlights: • We generalize, in the realm of the Ginzburg–Landau theory, the de Gennes matching-matrix method for the interface order parameters to describe the superconducting properties of multi-band mesoscopic Josephson junctions. • The results are in agreement with a microscopic treatment of nanobridge junctions. • Thermal stability of the nanobridge junction is discussed in connection with recent experiments on iron-based grain-boundary junctions. - Abstract: A Ginzburg–Landau theory for multi-band mesoscopic Josephson junctions has been developed. The theory, obtained by generalizing the de Gennes matching-matrix method for the interface order parameters, allows the study of the phase dynamics of various types of mesoscopic Josephson junctions. As a relevant application, we studied mesoscopic double-band junctions also in the presence of a superconducting nanobridge interstitial layer. The results are in agreement with a microscopic treatment of the same system. Furthermore, thermal stability of the nanobridge junction is discussed in connection with recent experiments on iron-based grain-boundary junctions.

  7. The Simplest Quantum Model Supporting the Kibble-Zurek Mechanism of Topological Defect Production: Landau-Zener Transitions from a New Perspective

    International Nuclear Information System (INIS)

    Damski, Bogdan

    2005-01-01

    It can be shown that the dynamics of the Landau-Zener model can be accurately described in terms of the Kibble-Zurek theory of the topological defect production in nonequilibrium phase transitions. The simplest quantum model exhibiting the Kibble-Zurek mechanism is presented. A new intuitive description of Landau-Zener dynamics is found

  8. Effects on a Landau-type system for a neutral particle with no permanent electric dipole moment subject to the Kratzer potential in a rotating frame.

    Science.gov (United States)

    Oliveira, Abinael B; Bakke, Knut

    2016-06-01

    The behaviour of a neutral particle (atom, molecule) with an induced electric dipole moment in a region with a uniform effective magnetic field under the influence of the Kratzer potential (Kratzer 1920 Z. Phys. 3 , 289-307. (doi:10.1007/BF01327754)), and rotating effects is analysed. It is shown that the degeneracy of the Landau-type levels is broken and the angular frequency of the system acquires a new contribution that stems from the rotation effects. Moreover, in the search for bound state solutions, it is shown that the possible values of this angular frequency of the system are determined by the quantum numbers associated with the radial modes and the angular momentum, the angular velocity of the rotating frame and by the parameters associated with the Kratzer potential.

  9. Cyclotron Acceleration of Relativistic Electrons through Landau Resonance with Obliquely Propagating Whistler Mode Chorus Emissions

    Science.gov (United States)

    Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.

    2017-12-01

    A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear

  10. Conformational landscape of an amyloid intra-cellular domain and Landau-Ginzburg-Wilson paradigm in protein dynamics

    International Nuclear Information System (INIS)

    Dai, Jin; He, Jianfeng; Niemi, Antti J.

    2016-01-01

    The Landau-Ginzburg-Wilson paradigm is proposed as a framework, to investigate the conformational landscape of intrinsically unstructured proteins. A universal Cα-trace Landau free energy is deduced from general symmetry considerations, with the ensuing all-atom structure modeled using publicly available reconstruction programs Pulchra and Scwrl. As an example, the conformational stability of an amyloid precursor protein intra-cellular domain (AICD) is inspected; the reference conformation is the crystallographic structure with code 3DXC in Protein Data Bank (PDB) that describes a heterodimer of AICD and a nuclear multi-domain adaptor protein Fe65. Those conformations of AICD that correspond to local or near-local minima of the Landau free energy are identified. For this, the response of the original 3DXC conformation to variations in the ambient temperature is investigated, using the Glauber algorithm. The conclusion is that in isolation the AICD conformation in 3DXC must be unstable. A family of degenerate conformations that minimise the Landau free energy is identified, and it is proposed that the native state of an isolated AICD is a superposition of these conformations. The results are fully in line with the presumed intrinsically unstructured character of isolated AICD and should provide a basis for a systematic analysis of AICD structure in future NMR experiments.

  11. Conformational landscape of an amyloid intra-cellular domain and Landau-Ginzburg-Wilson paradigm in protein dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jin; He, Jianfeng, E-mail: Antti.Niemi@physics.uu.se, E-mail: hjf@bit.edu.cn [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se, E-mail: hjf@bit.edu.cn [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108 Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200 Tours (France)

    2016-07-28

    The Landau-Ginzburg-Wilson paradigm is proposed as a framework, to investigate the conformational landscape of intrinsically unstructured proteins. A universal Cα-trace Landau free energy is deduced from general symmetry considerations, with the ensuing all-atom structure modeled using publicly available reconstruction programs Pulchra and Scwrl. As an example, the conformational stability of an amyloid precursor protein intra-cellular domain (AICD) is inspected; the reference conformation is the crystallographic structure with code 3DXC in Protein Data Bank (PDB) that describes a heterodimer of AICD and a nuclear multi-domain adaptor protein Fe65. Those conformations of AICD that correspond to local or near-local minima of the Landau free energy are identified. For this, the response of the original 3DXC conformation to variations in the ambient temperature is investigated, using the Glauber algorithm. The conclusion is that in isolation the AICD conformation in 3DXC must be unstable. A family of degenerate conformations that minimise the Landau free energy is identified, and it is proposed that the native state of an isolated AICD is a superposition of these conformations. The results are fully in line with the presumed intrinsically unstructured character of isolated AICD and should provide a basis for a systematic analysis of AICD structure in future NMR experiments.

  12. Landau-Devonshire Parameters for the Tunable Paraelectric Material BaTi.9(Sc,Ta).05O3

    National Research Council Canada - National Science Library

    Miller, Virginia; Crowne, Frank

    2008-01-01

    ...).05O3 are used to deduce the thermodynamic Landau-Devonshire parameters of the material, which are found to differ strongly from those of the parent material BaTiO3, despite the small amount of added Sc and Ta...

  13. In memory of Alois Apfelbeck: An Interconnection between Cayley-Eisenstein-Pólya and Landau Probability Distributions

    Directory of Open Access Journals (Sweden)

    Vladimír Vojta

    2013-01-01

    Full Text Available The interconnection between the Cayley-Eisenstein-Pólya distribution and the Landau distribution is studied, and possibly new transform pairs for the Laplace and Mellin transform and integral expressions for the Lambert W function have been found.

  14. Understanding the Planck blackbody spectrum and Landau diamagnetism within classical electromagnetism

    International Nuclear Information System (INIS)

    Boyer, Timothy H

    2016-01-01

    Electromagnetism is a relativistic theory, and one must exercise care in coupling this theory with nonrelativistic classical mechanics and with nonrelativistic classical statistical mechanics. Indeed historically, both the blackbody radiation spectrum and diamagnetism within classical theory have been misunderstood because of two crucial failures: (1) the neglect of classical electromagnetic zero-point radiation, and (2) the use of erroneous combinations of nonrelativistic mechanics with relativistic electrodynamics. Here we review the treatment of classical blackbody radiation, and show that the presence of Lorentz-invariant classical electromagnetic zero-point radiation can explain both the Planck blackbody spectrum and Landau diamagnetism at thermal equilibrium within classical electromagnetic theory. The analysis requires that relativistic electromagnetism is joined appropriately with simple nonrelativistic mechanical systems which can be regarded as the zero-velocity limits of relativistic systems, and that nonrelativistic classical statistical mechanics is applied only in the low-frequency limit when zero-point energy makes no contribution. (paper)

  15. Coarse graining from variationally enhanced sampling applied to the Ginzburg–Landau model

    Science.gov (United States)

    Invernizzi, Michele; Valsson, Omar; Parrinello, Michele

    2017-01-01

    A powerful way to deal with a complex system is to build a coarse-grained model capable of catching its main physical features, while being computationally affordable. Inevitably, such coarse-grained models introduce a set of phenomenological parameters, which are often not easily deducible from the underlying atomistic system. We present a unique approach to the calculation of these parameters, based on the recently introduced variationally enhanced sampling method. It allows us to obtain the parameters from atomistic simulations, providing thus a direct connection between the microscopic and the mesoscopic scale. The coarse-grained model we consider is that of Ginzburg–Landau, valid around a second-order critical point. In particular, we use it to describe a Lennard–Jones fluid in the region close to the liquid–vapor critical point. The procedure is general and can be adapted to other coarse-grained models. PMID:28292890

  16. Coarse graining from variationally enhanced sampling applied to the Ginzburg-Landau model

    Science.gov (United States)

    Invernizzi, Michele; Valsson, Omar; Parrinello, Michele

    2017-03-01

    A powerful way to deal with a complex system is to build a coarse-grained model capable of catching its main physical features, while being computationally affordable. Inevitably, such coarse-grained models introduce a set of phenomenological parameters, which are often not easily deducible from the underlying atomistic system. We present a unique approach to the calculation of these parameters, based on the recently introduced variationally enhanced sampling method. It allows us to obtain the parameters from atomistic simulations, providing thus a direct connection between the microscopic and the mesoscopic scale. The coarse-grained model we consider is that of Ginzburg-Landau, valid around a second-order critical point. In particular, we use it to describe a Lennard-Jones fluid in the region close to the liquid-vapor critical point. The procedure is general and can be adapted to other coarse-grained models.

  17. Child with Landau Kleffner Syndrome Misdiagnosed as Autism: A Case Report

    Directory of Open Access Journals (Sweden)

    Mohsen Jekan

    2013-10-01

    Full Text Available Objectives:The aim of this single case study is to describe a child with Landau Kleffner Syndrome who misdiagnosed as a child with autism spectrum disorder. We also explore occupational therapy`s role in correct process for diagnosis and treatment. Methods:Three times measurement with Autism Treatment Evaluation Checklist was performed to measure severity of symptoms and compare treatment outcomes. Results: The outcome showed great improvements after pharmacotherapy. Discussion: Results of this study indicated that correct diagnosis, early detection and early intervention in this disorder are essential to reach a proper treatment. Of course, therapeutic team work is crucial as well. Occupational and speech therapy interventions can also been recommended as a helpful treatment to improve social and sensory-motor and communicative skills. Parent`s consultation should not be ignored to decrease parental stress.

  18. Laser light triggers increased Raman amplification in the regime of nonlinear Landau damping

    International Nuclear Information System (INIS)

    Depierreux, S.; Goyon, C.; Masson-Laborde, P.E.; Yahia, V.; Loisel, G.; Labaune, C.

    2014-01-01

    Stimulated Raman backscattering (SRS) has many unwanted effects in megajoule-scale inertially confined fusion (ICF) plasmas. Moreover, attempts to harness SRS to amplify short laser pulses through backward Raman amplification have achieved limited success. In high temperature fusion plasmas, SRS usually occurs in a kinetic regime where the nonlinear response of the Langmuir wave to the laser drive and its host of complicating factors make it difficult to predict the degree of amplification that can be achieved under given experimental conditions. Here we present experimental evidence of reduced Landau damping with increasing Langmuir wave amplitude and determine its effects on Raman amplification. The threshold for trapping effects to influence the amplification is shown to be very low. Above threshold, the complex SRS dynamics results in increased amplification factors, which partly explains previous ICF experiments. These insights could aid the development of more efficient backward Raman amplification schemes in this regime. (authors)

  19. Loss of Landau Damping for Inductive Impedance in a Double RF System

    CERN Document Server

    Argyropoulos, T; Burov, A

    2013-01-01

    In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. A high harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven necessary to stabilize the bunch. These results, confirmed also by particle simulations, now are able to explain observations during the pp operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.

  20. Transport of energy and momentum due to spatial Landau damping and growth of electrostatic waves

    International Nuclear Information System (INIS)

    Lacina, J.

    1994-01-01

    It is shown that Landau damping in space (LDS), occuring for time-periodic electrostatic waves, does not lead to any deposition of energy in plasmas. A steady-state balance and a steady-state transport of energy, momentum and particles take place both for damped and growing waves. Because of the phase interference of coherent free and forced particle oscillations, the oscillatory energy of particles increases in the direction of wave propagation; the time-averaged flow of plasma kinetic energy being constant in space for these waves, the LDS must take place for a Maxwellian plasma in order to compensate for the growth of the particle oscillatory energy in space. (Author)

  1. Energie du type Ginzburg-Landau avec un terme de chevillage

    OpenAIRE

    AMARI, Nassima

    2010-01-01

    L’objectif de ce travail est l’étude d’un modèle bidimensionnel de Ginzburg-Landau avec un problème de l’ancrage (pinning) des vortex. La principale difficulté en réitérant l’approche faite par F. Béthuel, H. Brézis et F. Hélein, résulte du fait que la construction de mauvais disques ne soit pas évidente. Pour surmonter cette difficulté,on remplace le minimiseur u epsilon par v epsilon U epsilon. Cette substitution nous conduit à l'étude d'une énergie classique (qui correspond à p=1). ...

  2. Surface adsorption of lattice HP proteins: Thermodynamics and structural transitions using Wang-Landau sampling

    International Nuclear Information System (INIS)

    Li Yingwai; Landau, David P; Wüst, Thomas

    2012-01-01

    Wang-Landau sampling has been applied to investigate the thermodynamics and structural properties of a lattice hydrophobic-polar heteropolymer (the HP protein model) interacting with an attractive substrate. For simplicity, we consider a short HP sequence consisting of only 36 monomers interacting with a substrate which attracts all monomers in the sequence. The conformational “phase transitions” have been identified by a canonical analysis of the specific heat and suitable structural observables. Three major “transitions”, namely, adsorption, hydrophobic core formation and “flattening” of adsorbed structures, are observed. Depending on the surface attractive strength relative to the intra-protein attraction among the H monomers, these processes take place in different sequences upon cooling.

  3. Analytic solutions to a family of boundary-value problems for Ginsburg-Landau type equations

    Science.gov (United States)

    Vassilev, V. M.; Dantchev, D. M.; Djondjorov, P. A.

    2017-10-01

    We consider a two-parameter family of nonlinear ordinary differential equations describing the behavior of a critical thermodynamic system, e.g., a binary liquid mixture, of film geometry within the framework of the Ginzburg-Landau theory by means of the order-parameter. We focus on the case in which the confining surfaces are strongly adsorbing but prefer different components of the mixture, i.e., the order-parameter tends to infinity at one of the boundaries and to minus infinity at the other one. We assume that the boundaries of the system are positioned at a finite distance from each other and give analytic solutions to the corresponding boundary-value problems in terms of Weierstrass and Jacobi elliptic functions.

  4. Evolution of nonconformal Landau-Levich-Bretherton films of partially wetting liquids

    Science.gov (United States)

    Kreutzer, Michiel T.; Shah, Maulik S.; Parthiban, Pravien; Khan, Saif A.

    2018-01-01

    We experimentally and theoretically describe the dynamics of evolution and eventual rupture of Landau-Levich-Bretherton films of partially wetting liquids in microchannels in terms of nonplanar interface curvatures and disjoining pressure. While both the early-stage dynamics of film evolution and near-collapse dynamics of rupture are understood, we match these regimes and find theoretically that the dimensionless rupture time, Tr, scales with κ-10 /7. Here, κ is the dimensionless curvature given by the ratio of the Laplace-pressure discontinuity that initiates film thinning to the initial strength of the disjoining pressure that drives the rupture. We experimentally verify the rupture times and highlight the crucial consequences of early film rupture in digital microfluidic contexts: pressure drop in segmented flow and isolation of droplets from the walls.

  5. GPU-advanced 3D electromagnetic simulations of superconductors in the Ginzburg–Landau formalism

    Energy Technology Data Exchange (ETDEWEB)

    Stošić, Darko; Stošić, Dušan; Ludermir, Teresa [Centro de Informática, Universidade Federal de Pernambuco, Av. Luiz Freire s/n, 50670-901, Recife, PE (Brazil); Stošić, Borko [Departamento de Estatística e Informática, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Dois Irmãos, 52171-900 Recife, PE (Brazil); Milošević, Milorad V., E-mail: milorad.milosevic@uantwerpen.be [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

    2016-10-01

    Ginzburg–Landau theory is one of the most powerful phenomenological theories in physics, with particular predictive value in superconductivity. The formalism solves coupled nonlinear differential equations for both the electronic and magnetic responsiveness of a given superconductor to external electromagnetic excitations. With order parameter varying on the short scale of the coherence length, and the magnetic field being long-range, the numerical handling of 3D simulations becomes extremely challenging and time-consuming for realistic samples. Here we show precisely how one can employ graphics-processing units (GPUs) for this type of calculations, and obtain physics answers of interest in a reasonable time-frame – with speedup of over 100× compared to best available CPU implementations of the theory on a 256{sup 3} grid.

  6. Disordered λ φ4+ρ φ6 Landau-Ginzburg model

    Science.gov (United States)

    Diaz, R. Acosta; Svaiter, N. F.; Krein, G.; Zarro, C. A. D.

    2018-03-01

    We discuss a disordered λ φ4+ρ φ6 Landau-Ginzburg model defined in a d -dimensional space. First we adopt the standard procedure of averaging the disorder-dependent free energy of the model. The dominant contribution to this quantity is represented by a series of the replica partition functions of the system. Next, using the replica-symmetry ansatz in the saddle-point equations, we prove that the average free energy represents a system with multiple ground states with different order parameters. For low temperatures we show the presence of metastable equilibrium states for some replica fields for a range of values of the physical parameters. Finally, going beyond the mean-field approximation, the one-loop renormalization of this model is performed, in the leading-order replica partition function.

  7. Two-dimensional massless quantum electrodynamics in the Landau-gauge formalism and the Higgs mechanism

    International Nuclear Information System (INIS)

    Ito, K.R.

    1975-01-01

    The Schwinger model is considered in the Landau-gauge formalism of quantum electrodynamics. This model can be solved exactly on the assumption of no radiative corrections to the anomaly. It is found that the photon obtains a non-zero mass through the Higgs mechanism. In this case, the would-be Nambu-Goldstone boson is an associated boson which is constructed from a pair of two-component massless fermions. This would-be Nambu-Goldstone boson appears as a result of the spontaneous breaking of the gauge invariance of the first kind, and it becomes unphysical through the Higgs mechanism. However, as all the fermions themselves decouple from photons, they cannot appear as real particles in our world. (author)

  8. Multi-flux-tube system in the dual Ginzburg-Landau theory

    International Nuclear Information System (INIS)

    Ichie, H.; Suganuma, H.; Toki, H.

    1996-01-01

    We study the multi-flux-tube system in terms of the dual Ginzburg-Landau theory. We consider two periodic cases, where the directions of all the flux tubes are the same in one case and alternating in the other case for neighboring flux tubes. We formulate the multi-flux-tube system by regarding it as the system of two flux tubes penetrating through a two-dimensional spherical surface. We find the multi-flux-tube configuration becomes uniform above some critical flux-tube number density ρ c =1.3 endash 1.7 fm -2 . On the other hand, the inhomogeneity of the color electric distribution appears when the flux-tube density is smaller than ρ c . We study the inhomogeneity on the color electric distribution in relation with the flux-tube number density, and discuss the quark-gluon plasma formation process in ultrarelativistic heavy-ion collisions. copyright 1996 The American Physical Society

  9. Landau-de Gennes theory of surface-enhanced ordering in smectic films.

    Science.gov (United States)

    Shalaginov, A N; Sullivan, D E

    2001-03-01

    A Landau theory for surface-enhanced ordering in smectic-A free-standing films is described, based on a generalization of de Gennes' model for a "presmectic" fluid confined between two walls. According to the theory, smectic ordering in free-standing films heated above the bulk smectic melting temperature is due to an intrinsic surface contribution rather than an external field. The theory yields a persistent finite-size effect, in that the film melting temperatures do not tend to the bulk transition temperature in the limit of infinite film thickness. It also predicts that a continuous transition from (N+1)- to N-layer films is impossible without an external field. The theory closely fits existing experimental data on layer-thinning transitions in compounds which exhibit a bulk smectic-A to nematic phase transition. Possible origins of the intrinsic surface contribution are discussed.

  10. Landau damping of transverse quadrupole oscillations of an elongated Bose-Einstein condensate

    International Nuclear Information System (INIS)

    Guilleumas, M.; Pitaevskii, L.P.

    2003-01-01

    We have studied the interaction between the low-lying transverse collective oscillations and the thermal excitations of an elongated Bose-Einstein condensate by means of perturbation theory. We consider a cylindrical trapped condensate and calculate the transverse elementary excitations at zero temperature by solving the linearized Gross-Pitaevskii equations in two dimensions (2D). We use them to calculate the matrix elements between the thermal excited states and the quasi-2D collective modes. The Landau damping of transverse collective modes is studied as a function of temperature. At low temperatures, the corresponding damping rate is in agreement with the experimental data for the decay of the transverse quadrupole mode, but it is too small to explain the observed slow decay of the transverse breathing mode. The reason for this discrepancy is discussed

  11. Topological Landau-Ginzburg theory with a rational potential and the dispersionless KP hierarchy

    International Nuclear Information System (INIS)

    Aoyama, S.; Kodama, Y.

    1996-01-01

    Based on the dispersionless KP (dKP) theory, we study a topological Landau-Ginzburg (LG) theory characterized by a rational potential. Writing the dKP hierarchy in a general form treating all the primaries in an equal basis, we find that the hierarchy naturally includes the dispersionless (continuous) limit of Toda hierarchy and its generalizations having a finite number of primaries. Several flat solutions of the topological LG theory are obtained in this formulation, and are identified with those discussed by Dubrovin. We explicitly construct gravitational descendants for all the primary fields. Giving a residue formula for the 3-point functions of the fields, we show that these 3-point functions satisfy the topological recursion relation. The string equation is obtained as the generalized hodograph solutions of the dKP hierarchy, which show that all the gravitational effects to the constitutive equations (2-point functions) can be renormalized into the coupling constants in the small phase space. (orig.)

  12. Critical initial-slip scaling for the noisy complex Ginzburg–Landau equation

    International Nuclear Information System (INIS)

    Liu, Weigang; Täuber, Uwe C

    2016-01-01

    We employ the perturbative fieldtheoretic renormalization group method to investigate the universal critical behavior near the continuous non-equilibrium phase transition in the complex Ginzburg–Landau equation with additive white noise. This stochastic partial differential describes a remarkably wide range of physical systems: coupled nonlinear oscillators subject to external noise near a Hopf bifurcation instability; spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations; and driven-dissipative Bose–Einstein condensation, realized in open systems on the interface of quantum optics and many-body physics, such as cold atomic gases and exciton-polaritons in pumped semiconductor quantum wells in optical cavities. Our starting point is a noisy, dissipative Gross–Pitaevski or nonlinear Schrödinger equation, or equivalently purely relaxational kinetics originating from a complex-valued Landau–Ginzburg functional, which generalizes the standard equilibrium model A critical dynamics of a non-conserved complex order parameter field. We study the universal critical behavior of this system in the early stages of its relaxation from a Gaussian-weighted fully randomized initial state. In this critical aging regime, time translation invariance is broken, and the dynamics is characterized by the stationary static and dynamic critical exponents, as well as an independent ‘initial-slip’ exponent. We show that to first order in the dimensional expansion about the upper critical dimension, this initial-slip exponent in the complex Ginzburg–Landau equation is identical to its equilibrium model A counterpart. We furthermore employ the renormalization group flow equations as well as construct a suitable complex spherical model extension to argue that this conclusion likely remains true to all orders in the perturbation expansion. (paper)

  13. An Approach to Quad Meshing Based On Cross Valued Maps and the Ginzburg-Landau Theory

    Energy Technology Data Exchange (ETDEWEB)

    Viertel, Ryan [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Mathematics; Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Osting, Braxton [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Mathematics

    2017-08-01

    A generalization of vector fields, referred to as N-direction fields or cross fields when N=4, has been recently introduced and studied for geometry processing, with applications in quadrilateral (quad) meshing, texture mapping, and parameterization. We make the observation that cross field design for two-dimensional quad meshing is related to the well-known Ginzburg-Landau problem from mathematical physics. This identification yields a variety of theoretical tools for efficiently computing boundary-aligned quad meshes, with provable guarantees on the resulting mesh, for example, the number of mesh defects and bounds on the defect locations. The procedure for generating the quad mesh is to (i) find a complex-valued "representation" field that minimizes the Dirichlet energy subject to a boundary constraint, (ii) convert the representation field into a boundary-aligned, smooth cross field, (iii) use separatrices of the cross field to partition the domain into four sided regions, and (iv) mesh each of these four-sided regions using standard techniques. Under certain assumptions on the geometry of the domain, we prove that this procedure can be used to produce a cross field whose separatrices partition the domain into four sided regions. To solve the energy minimization problem for the representation field, we use an extension of the Merriman-Bence-Osher (MBO) threshold dynamics method, originally conceived as an algorithm to simulate motion by mean curvature, to minimize the Ginzburg-Landau energy for the optimal representation field. Lastly, we demonstrate the method on a variety of test domains.

  14. Serial auditory-evoked potentials in the diagnosis and monitoring of a child with Landau-Kleffner syndrome.

    Science.gov (United States)

    Plyler, Erin; Harkrider, Ashley W

    2013-01-01

    A boy, aged 2 1/2 yr, experienced sudden deterioration of speech and language abilities. He saw multiple medical professionals across 2 yr. By almost 5 yr, his vocabulary diminished from 50 words to 4, and he was referred to our speech and hearing center. The purpose of this study was to heighten awareness of Landau-Kleffner syndrome (LKS) and emphasize the importance of an objective test battery that includes serial auditory-evoked potentials (AEPs) to audiologists who often are on the front lines of diagnosis and treatment delivery when faced with a child experiencing unexplained loss of the use of speech and language. Clinical report. Interview revealed a family history of seizure disorder. Normal social behaviors were observed. Acoustic reflexes and otoacoustic emissions were consistent with normal peripheral auditory function. The child could not complete behavioral audiometric testing or auditory processing tests, so serial AEPs were used to examine central nervous system function. Normal auditory brainstem responses, a replicable Na and absent Pa of the middle latency responses, and abnormal slow cortical potentials suggested dysfunction of auditory processing at the cortical level. The child was referred to a neurologist, who confirmed LKS. At age 7 1/2 yr, after 2 1/2 yr of antiepileptic medications, electroencephalographic (EEG) and audiometric measures normalized. Presently, the child communicates manually with limited use of oral information. Audiologists often are one of the first professionals to assess children with loss of speech and language of unknown origin. Objective, noninvasive, serial AEPs are a simple and valuable addition to the central audiometric test battery when evaluating a child with speech and language regression. The inclusion of these tests will markedly increase the chance for early and accurate referral, diagnosis, and monitoring of a child with LKS which is imperative for a positive prognosis. American Academy of Audiology.

  15. Mean-field dynamics of a Bose-Einstein condensate in a time-dependent triple-well trap: Nonlinear eigenstates, Landau-Zener models, and stimulated Raman adiabatic passage

    International Nuclear Information System (INIS)

    Graefe, E. M.; Korsch, H. J.; Witthaut, D.

    2006-01-01

    We investigate the dynamics of a Bose-Einstein condensate in a triple-well trap in a three-level approximation. The interatomic interactions are taken into account in a mean-field approximation (Gross-Pitaevskii equation), leading to a nonlinear three-level model. Additional eigenstates emerge due to the nonlinearity, depending on the system parameters. Adiabaticity breaks down if such a nonlinear eigenstate disappears when the parameters are varied. The dynamical implications of this loss of adiabaticity are analyzed for two important special cases: A three-level Landau-Zener model and the stimulated Raman adiabatic passage (STIRAP) scheme. We discuss the emergence of looped levels for an equal-slope Landau-Zener model. The Zener tunneling probability does not tend to zero in the adiabatic limit and shows pronounced oscillations as a function of the velocity of the parameter variation. Furthermore we generalize the STIRAP scheme for adiabatic coherent population transfer between atomic states to the nonlinear case. It is shown that STIRAP breaks down if the nonlinearity exceeds the detuning

  16. Effect of colored noise on the critical dynamics of the Time-Dependent Landau-Ginzburg Model A

    International Nuclear Information System (INIS)

    Korutcheva, E.; Rubia, J. de la

    1999-08-01

    By using the dynamical renormalization-group method, we show that the introduction of an additive colored noise with weak long-range correlations in the Time-Dependent Landau-Ginzburg Model A, does not give perturbative corrections for the dynamical critical exponent at least up to order O(ε 2 ). This result differs for a system with random quenched impurities, where a similar type of impurity correlation leads to corrections even of order O(ε). (author)

  17. Nuclear magnetism of liquid 3He: new determination of the Landau parameter F0a

    International Nuclear Information System (INIS)

    Goudon, V.

    2006-10-01

    He 3 is a liquid Fermi model, isotropic, with an attainable Fermi temperature and the interaction between atoms can be controlled by changing the pressure of the liquid. In this document, we present accurate NMR measurements of the nuclear magnetic susceptibility of liquid He 3 as a function of temperature and pressure. The emphasis has been placed on reliable thermometry and on He 3 pressure measurements directly in the cell to increase the measuring range until solidification, and an accurate characterization of the NMR spectrometer. Our measurements give an effective Fermi temperature 5% lower than former results. The Landau parameter F 0 a depends on the effective mass, which is determined by specific heat measurements, and consequently on the temperature scale. The re-analysis of the specific heat measurements with the PLTS-2000 temperature scale yields an effective mass increase of 4.5%. In this document, F 0 a is determined for 2 temperature scales (PLTS-2000 and Greywall). Contrarily to former measurements, the F 0 a density dependence does not show any saturation at high pressures. (author)

  18. Manipulation of the spin in single molecule magnets via Landau-Zener transitions

    Science.gov (United States)

    Palii, Andrew; Tsukerblat, Boris; Clemente-Juan, Juan M.; Gaita-Ariño, Alejandro; Coronado, Eugenio

    2011-11-01

    We theoretically investigate the effects of a magnetic pulse on a single-molecule magnet (SMM) initially magnetized by a dc field along the easy axis of magnetization. In the Landau-Zener (LZ) scheme, it is shown that the final spin state is a function of the shape and duration of the pulse, conditioned by the decoherence time of the SMM. In the case of coherent tunneling, the asymmetric pulses are shown to reverse the direction of the magnetization, while the symmetric pulses can only decrease the value of the initial magnetization. It is also demonstrated that the application of an external variable dc field in the hard plane of magnetization provides the possibility to tune the resulting magnetization due to quantum interference effects. The results and the conditions for the observation of the pulse-triggered LZ transitions are illustrated by the application of the proposed scheme to the well-studied single-molecule magnet Fe8. To put the results into perspective, some potential applications of SMMs experiencing pulse-induced LZ transitions, such as switching devices and qubits, are discussed.

  19. Stable amplitude chimera states in a network of locally coupled Stuart-Landau oscillators

    Science.gov (United States)

    Premalatha, K.; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.

    2018-03-01

    We investigate the occurrence of collective dynamical states such as transient amplitude chimera, stable amplitude chimera, and imperfect breathing chimera states in a locally coupled network of Stuart-Landau oscillators. In an imperfect breathing chimera state, the synchronized group of oscillators exhibits oscillations with large amplitudes, while the desynchronized group of oscillators oscillates with small amplitudes, and this behavior of coexistence of synchronized and desynchronized oscillations fluctuates with time. Then, we analyze the stability of the amplitude chimera states under various circumstances, including variations in system parameters and coupling strength, and perturbations in the initial states of the oscillators. For an increase in the value of the system parameter, namely, the nonisochronicity parameter, the transient chimera state becomes a stable chimera state for a sufficiently large value of coupling strength. In addition, we also analyze the stability of these states by perturbing the initial states of the oscillators. We find that while a small perturbation allows one to perturb a large number of oscillators resulting in a stable amplitude chimera state, a large perturbation allows one to perturb a small number of oscillators to get a stable amplitude chimera state. We also find the stability of the transient and stable amplitude chimera states and traveling wave states for an appropriate number of oscillators using Floquet theory. In addition, we also find the stability of the incoherent oscillation death states.

  20. Large spin limits of AdS/CFT and generalized Landau-Lifshitz equations

    International Nuclear Information System (INIS)

    Stefanski, B. Jr.; Tseytlin, A.A.

    2004-01-01

    We consider AdS 5 x S 5 string states with several large angular momenta along AdS 5 and S 5 directions which are dual to single-trace Super-Yang-Mills (SYM) operators built out of chiral combinations of scalars and covariant derivatives. In particular, we focus on the SU(3) sector (with three spins in S 5 ) and the SL(2) sector (with one spin in AdS 5 and one in S 5 ), generalizing recent work hep-th/0311203 and hep-th/0403120 on the SU(2) sector with two spins in S 5 . We show that, in the large spin limit and at the leading order in the effective coupling expansion, the string sigma model equations of motion reduce to matrix Landau-Lifshitz equations. We then demonstrate that the coherent-state expectation value of the one-loop SYM dilatation operator restricted to the corresponding sector of single trace operators is also effectively described by the same equations. This implies a universal leading order equivalence between string energies and SYM anomalous dimensions, as well as a matching of integrable structures. We also discuss the more general 5-spin sector and comment on SO(6) states dual to non-chiral scalar operators. (author)

  1. Advances in the simulation of toroidal gyro Landau fluid model turbulence

    International Nuclear Information System (INIS)

    Waltz, R.E.; Kerbel, G.D.; Milovich, J.; Hammett, G.W.

    1994-12-01

    The gyro-Landau fluid (GLF) model equations for toroidal geometry have been recently applied to the study ion temperature gradient (ITG) mode turbulence using the 3D nonlinear ballooning mode representation (BMR). The present paper extends this work by treating some unresolved issues conceming ITG turbulence with adiabatic electrons. Although eddies are highly elongated in the radial direction long time radial correlation lengths are short and comparable to poloidal lengths. Although transport at vanishing shear is not particularly large, transport at reverse global shear, is significantly less. Electrostatic transport at moderate shear is not much effected by inclusion of local shear and average favorable curvature. Transport is suppressed when critical ExB rotational shear is comparable to the maximum linear growth rate with only a weak dependence on magnetic shear. Self consistent turbulent transport of toroidal momentum can result in a transport bifurcation at suffciently large r/(Rq). However the main thrust of the new formulation in the paper deals with advances in the development of finite beta GLF models with trapped electron and BMR numerical methods for treating the fast parallel field motion of the untrapped electrons

  2. Correlation of the ghost and the quark in the lattice Landau gauge QCD

    International Nuclear Information System (INIS)

    Furui, Sadataka; Nakajima, Hideo

    2007-01-01

    Effects of the quark field on the ghost propagator of the lattice Landau gauge are investigated by using the unquenched SU(3) configurations produced by the MILC collaboration and compared with quenched gauge configurations of SU(2) first copy of the over relaxation gauge fixing, the parallel tempering (PT) gauge fixing and quenched SU(3) 56 4 configurations. We measure the color symmetric and the color antisymmetric ghost propagator and the Binder cumulant of the l 1 norm and the l 2 norm of color antisymmetric ghost propagators and investigate deviation from those of Gaussian distributions. In the first copy samples of quenched SU(2) we observe a large fluctuation in the Binder cumulant at the lowest momentum point. This fluctuation is reduced in the P T gauge fixed samples. The color anti-symmetric ghost propagator of quenched SU(3) configurations depends on the lattice size and is small as compared to the symmetric one in the large lattice of 56 4 . The Binder cumulant of the quenched SU(2) and the N f = 2 + 1 unquenched SU(3) are almost consistent with 3-d and 8-d Gaussian distribution, respectively. A comparison of the SU(3) unquenched configurations and quenched configurations indicates that the dynamical quarks have the effect of making color antisymmetric ghost propagator closer to the Gaussian distribution and the Kugo-Ojima color confinement parameter c closer to 1. (author)

  3. Localization and traces in open-closed topological Landau-Ginzburg models

    International Nuclear Information System (INIS)

    Herbst, Manfred; Lazaroiu, Calin-Iuliu

    2005-01-01

    We reconsider the issue of localization in open-closed B-twisted Landau-Ginzburg models with arbitrary Calabi-Yau target. Through careful analysis of zero-mode reduction, we show that the closed model allows for a one-parameter family of localization pictures, which generalize the standard residue representation. The parameter λ which indexes these pictures measures the area of worldsheets with S 2 topology, with the residue representation obtained in the limit of small area. In the boundary sector, we find a double family of such pictures, depending on parameters λ and μ which measure the area and boundary length of worldsheets with disk topology. We show that setting μ = 0 and varying λ interpolates between the localization picture of the B-model with a noncompact target space and a certain residue representation proposed recently. This gives a complete derivation of the boundary residue formula, starting from the explicit construction of the boundary coupling. We also show that the various localization pictures are related by a semigroup of homotopy equivalences

  4. Plain and oscillatory solitons of the cubic complex Ginzburg-Landau equation with nonlinear gradient terms

    Science.gov (United States)

    Facão, M.; Carvalho, M. I.

    2017-10-01

    In this work, we present parameter regions for the existence of stable plain solitons of the cubic complex Ginzburg-Landau equation (CGLE) with higher-order terms associated with a fourth-order expansion. Using a perturbation approach around the nonlinear Schrödinger equation soliton and a full numerical analysis that solves an ordinary differential equation for the soliton profiles and using the Evans method in the search for unstable eigenvalues, we have found that the minimum equation allowing these stable solitons is the cubic CGLE plus a term known in optics as Raman-delayed response, which is responsible for the redshift of the spectrum. The other favorable term for the occurrence of stable solitons is a term that represents the increase of nonlinear gain with higher frequencies. At the stability boundary, a bifurcation occurs giving rise to stable oscillatory solitons for higher values of the nonlinear gain. These oscillations can have very high amplitudes, with the pulse energy changing more than two orders of magnitude in a period, and they can even exhibit more complex dynamics such as period-doubling.

  5. Landau-Pomeranchuk-Migdal Effect for High-Energy Electrons Observed with Emulsion Chambers

    CERN Document Server

    Yoshida, Kenji; Yanagisawa, K; Kobayashi, T; Sato, Y; Nishimura, J

    We have performed high-energy electron observations using balloon-borne emulsion chambers, and derived the cosmic-ray electron spectrum in the energy range from 30 GeV to 3 TeV. For the calibration of the emulsion chambers, we have also carried out beam tests of 50 GeV, 200 GeV, and 250 GeV electrons at CERN-SPS. The Landau-Pomeranchuk-Migdal (LPM) effect predicts the reduction of amplitude for bremsstrahlung photon emission. It affects to the depth of the first electron-positron pair of the electron-induced shower, the so-called shower starting point. In the emulsion chambers, we can measure the shower starting points for high- energy electrons with the position resolution of 1 m m. From the observations of accelerator-beam electrons of 200 GeV and 250 GeV, and cosmic-ray electrons above 400 GeV, we found the direct evidence of suppression of the bremsstrahlung cross sections due to the LPM effect.

  6. Finding equilibrium in the spatiotemporal chaos of the complex Ginzburg-Landau equation

    Science.gov (United States)

    Ballard, Christopher C.; Esty, C. Clark; Egolf, David A.

    2016-11-01

    Equilibrium statistical mechanics allows the prediction of collective behaviors of large numbers of interacting objects from just a few system-wide properties; however, a similar theory does not exist for far-from-equilibrium systems exhibiting complex spatial and temporal behavior. We propose a method for predicting behaviors in a broad class of such systems and apply these ideas to an archetypal example, the spatiotemporal chaotic 1D complex Ginzburg-Landau equation in the defect chaos regime. Building on the ideas of Ruelle and of Cross and Hohenberg that a spatiotemporal chaotic system can be considered a collection of weakly interacting dynamical units of a characteristic size, the chaotic length scale, we identify underlying, mesoscale, chaotic units and effective interaction potentials between them. We find that the resulting equilibrium Takahashi model accurately predicts distributions of particle numbers. These results suggest the intriguing possibility that a class of far-from-equilibrium systems may be well described at coarse-grained scales by the well-established theory of equilibrium statistical mechanics.

  7. Landau quantization effects on hole-acoustic instability in semiconductor plasmas

    Science.gov (United States)

    Sumera, P.; Rasheed, A.; Jamil, M.; Siddique, M.; Areeb, F.

    2017-12-01

    The growth rate of the hole acoustic waves (HAWs) exciting in magnetized semiconductor quantum plasma pumped by the electron beam has been investigated. The instability of the waves contains quantum effects including the exchange and correlation potential, Bohm potential, Fermi-degenerate pressure, and the magnetic quantization of semiconductor plasma species. The effects of various plasma parameters, which include relative concentration of plasma particles, beam electron temperature, beam speed, plasma temperature (temperature of electrons/holes), and Landau electron orbital magnetic quantization parameter η, on the growth rate of HAWs, have been discussed. The numerical study of our model of acoustic waves has been applied, as an example, to the GaAs semiconductor exposed to electron beam in the magnetic field environment. An increment in either the concentration of the semiconductor electrons or the speed of beam electrons, in the presence of magnetic quantization of fermion orbital motion, enhances remarkably the growth rate of the HAWs. Although the growth rate of the waves reduces with a rise in the thermal temperature of plasma species, at a particular temperature, we receive a higher instability due to the contribution of magnetic quantization of fermions to it.

  8. Infrared exponents and the strong-coupling limit in lattice Landau gauge

    International Nuclear Information System (INIS)

    Sternbeck, Andre; Smekal, Lorenz von

    2010-01-01

    We study the gluon and ghost propagators of lattice Landau gauge in the strong-coupling limit β=0 in pure SU(2) lattice gauge theory to find evidence of the conformal infrared behavior of these propagators as predicted by a variety of functional continuum methods for asymptotically small momenta q 2 QCD 2 . In the strong-coupling limit, this same behavior is obtained for the larger values of a 2 q 2 (in units of the lattice spacing a), where it is otherwise swamped by the gauge-field dynamics. Deviations for a 2 q 2 <1 are well parameterized by a transverse gluon mass ∝1/a. Perhaps unexpectedly, these deviations are thus no finite-volume effect but persist in the infinite-volume limit. They furthermore depend on the definition of gauge fields on the lattice, while the asymptotic conformal behavior does not. We also comment on a misinterpretation of our results by Cucchieri and Mendes (Phys. Rev. D 81:016005, 2010). (orig.)

  9. Spin Singlet Quantum Hall Effect and nonabelian Landau-Ginzburg theory

    International Nuclear Information System (INIS)

    Balatsky, A.

    1991-01-01

    In this paper we present a theory of Singlet Quantum Hall Effect (SQHE). We show that the Halperin-Haldane SQHE wave function can be written in the form of a product of a wave function for charged semions in a magnetic field and a wave function for the Chiral Spin Liquid of neutral spin-1/2 semions. We introduce field-theoretic model in which the electron operators are factorized in terms of charged spinless semions (holons) and neutral spin-1/2 semions (spinons). Broken time reversal symmetry and short ranged spin correlations lead to Su(2) κ=1 Chern-Simons term in Landau-Ginzburg action for SQHE phase. We construct appropriate coherent states for SQHE phase and show the existence of SU(2) valued gauge potential. This potential appears as a result of ''spin rigidity'' of the ground state against any displacements of nodes of wave function from positions of the particles and reflects the nontrivial monodromy in the presence of these displacenmants. We argue that topological structure of Su(2) κ=1 Chern-Simons theory unambiguously dictates semion statistics of spinons. 19 refs

  10. Molecular orientational re-ordering and the transformation of a Landau second order phase transition to first order in a nematic liquid crystal

    International Nuclear Information System (INIS)

    Ponce, T.C.

    1988-08-01

    We consider the nature of the nematic to isotropic phase transition in terms of the molecular orientational re-ordering, expressed by the variation of the order parameter, s, in the light of Landau's theory of second order phase transition. Then, we show how the de Gennes modification to the Landau thermodynamic potential converts the transition to first order which is in better agreement with the experimental observations. (author). 9 refs, 2 figs, 1 tab

  11. The Coulomb law and atomic levels in a superstrong B

    Directory of Open Access Journals (Sweden)

    Vysotsky M.I.

    2014-04-01

    Full Text Available The spectrum of atomic levels of hydrogen-like ions originating from the lowest Landau level in an external homogeneous superstrong magnetic field is obtained. The influence of the screening of the Coulomb potential on the values of critical nuclear charges is studied.

  12. Effects of the quark field on the ghost propagator of lattice Landau gauge QCD

    International Nuclear Information System (INIS)

    Furui, Sadataka; Nakajima, Hideo

    2006-01-01

    Infrared features of the ghost propagator of color-diagonal and color antisymmetric ghost propagator of quenched SU(2) and quenched SU(3) are compared with those of unquenched Kogut-Susskind fermion SU(3) lattice Landau gauge. We compare (i) the fluctuation of the ghost propagator (ii) the ghost condensate parameter v of the local composite operator (LCO) approach, and (iii) the Binder cumulant of color antisymmetric ghost propagator between quenched and unquenched configurations. The color-diagonal SU(3) ghost dressing function of unquenched configurations has weaker singularity than the quenched configurations. In both cases fluctuations become large in q c configuration samples is ∼0.002-0.04 GeV 2 while that of the SU(2) parallel tempering samples is consistent with 0. The Binder cumulant defined as U(q)=1-(1/3)( 4 >/( 2 >) 2 ), where φ-vector(q) is the color antisymmetric ghost propagator measured by the sample average of gauge fixed configurations via parallel tempering method, becomes ∼4/9 in all the momentum region. The Binder cumulant of the color antisymmetric ghost propagator of quenched SU(2) can be explained by the 3D Gaussian distribution, but that of the unquenched MILC c deviates slightly from that of the eight-dimensional Gaussian distribution. The stronger singularity and large fluctuation in the quenched configuration could be the cause of the deviation of the Kugo-Ojima confinement parameter c from 1, and the presence of ordering in the ghost propagator of unquenched configurations makes it closer to 1

  13. Ginzburg-Landau theory and the superconducting transition in thin, amorphous bismuth films

    International Nuclear Information System (INIS)

    Van Vechten, D.

    1979-01-01

    The Aslamasov-Larkin (AL) theory can be derived from a classical treatment of the conductivity due to short-lived statistical fluctuations into the superconducting state if one truncates the Ginzburg-Landau free energy density expression to read F[psi] = α 0 vertical barpsi vertical bar 2 + c 0 vertical bar del psi vertical bar 2 , where psi is the superconducting order parameter. The next largest term in the GL free energy is (b/2) (vertical bar psi vertical bar 2 ) 2 and is conventionally interpreted as representing the energy associated with interactions between the fluctuations. My dissertation consists of the calculation of the effect of this term on the fluctuation conductivity in three different approximations and the comparison of my predictions to the data of R.E. Glover III and M.K. Chien on thin amorphous bismuth films. The first approximation calculates the contribution to the fluctuations' self energy of the ''tadpole'' diagrams. This approximation yields a 4 parameter equation. Its fits were particularly outstanding for the films deposited on quartz or roughened glass substrates and only for two smooth glass substrates were there non-isolated data points that were not fit at the lowest temperatures measured. (The equation runs into trouble for these films at approximately R(T)/R/sub o/ =.08.) The values of the theoretical equation's fitting parameters were determined by a least squares method and turns out to depend on film thickness in the manner predicted by the theory. The next calculation improves the self energy approximation by including all the ''ring'' diagrams

  14. Stochasticity of bacterial attachment and its predictability by the extended derjaguin-landau-verwey-overbeek theory.

    Science.gov (United States)

    Chia, Teck Wah R; Nguyen, Vu Tuan; McMeekin, Thomas; Fegan, Narelle; Dykes, Gary A

    2011-06-01

    Bacterial attachment onto materials has been suggested to be stochastic by some authors but nonstochastic and based on surface properties by others. We investigated this by attaching pairwise combinations of two Salmonella enterica serovar Sofia (S. Sofia) strains (with different physicochemical and attachment properties) with one strain each of S. enterica serovar Typhimurium, S. enterica serovar Infantis, or S. enterica serovar Virchow (all with similar physicochemical and attachment abilities) in ratios of 0.428, 1, and 2.333 onto glass, stainless steel, Teflon, and polysulfone. Attached bacterial cells were recovered and counted. If the ratio of attached cells of each Salmonella serovar pair recovered was the same as the initial inoculum ratio, the attachment process was deemed stochastic. Experimental outcomes from the study were compared to those predicted by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Significant differences (P attached ratios for serovar pairs containing S. Sofia S1296a for all different ratios were apparent for all materials. For S. Sofia S1635-containing pairs, 7 out of 12 combinations of serovar pairs and materials had attachment ratios not significantly different (P > 0.05) from the initial ratio of 0.428. Five out of 12 and 10 out of 12 samples had attachment ratios not significantly different (P > 0.05) from the initial ratios of 1 and 2.333, respectively. These results demonstrate that bacterial attachment to different materials is likely to be nonstochastic only when the key physicochemical properties of the bacteria were significantly different (P theory could successfully predict the attachment of some individual isolates to particular materials but could not be used to predict the likelihood of stochasticity in pairwise attachment experiments.

  15. 1/J2 corrections to BMN energies from the quantum long range Landau-Lifshitz model

    International Nuclear Information System (INIS)

    Minahan, Joseph A.; Tirziu, Alin; Tseytlin, Arkady A.

    2005-01-01

    In a previous paper [hep-th/0509071], it was shown that quantum 1/J corrections to the BMN spectrum in an effective Landau-Lifshitz (LL) model match with the results from the one-loop gauge theory, provided one chooses an appropriate regularization. In this paper we continue this study for the conjectured Bethe ansatz for the long range spin chain representing perturbative large-N N = 4 Super Yang-Mills in the SU(2) sector, and the 'quantum string' Bethe ansatz for its string dual. The comparison is carried out for corrections to BMN energies up to order λ-tilde 3 in the effective expansion parameter λ-tilde = λ/J 2 . After determining the 'gauge-theory' LL action to order λ-tilde 3 , which is accomplished indirectly by fixing the coefficients in the LL action so that the energies of circular strings match with the energies found using the Bethe ansatz, we find perfect agreement. We interpret this as further support for an underlying integrability of the system. We then consider the 'string-theory' LL action which is a limit of the classical string action representing fast string motion on an S 3 subspace of S 5 and compare the resulting λ-tilde 3 /J 2 corrections to the prediction of the 'string' Bethe ansatz. As in the gauge case, we find precise matching. This indicates that the LL hamiltonian supplemented with a normal ordering prescription and ζ-function regularization reproduces the full superstring result for the 1/J 2 corrections, and also signifies that the string Bethe ansatz does describe the quantum BMN string spectrum to order 1/J 2 . We also comment on using the quantum LL approach to determine the non-analytic contributions in λ that are behind the strong to weak coupling interpolation between the string and gauge results

  16. Smoothed particle hydrodynamics model for Landau-Lifshitz-Navier-Stokes and advection-diffusion equations.

    Science.gov (United States)

    Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre

    2014-12-14

    We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called "giant fluctuations" of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power -4 of the wavenumber-except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.

  17. Avaliação audiológica e eletrofisiológica da audição na síndrome de Landau-Kleffner Audiologic and electrophysiologic evaluation in Landau-Kleffner syndrome

    Directory of Open Access Journals (Sweden)

    Carla Gentile Matas

    2007-06-01

    Full Text Available OBJETIVO: Descrever os resultados obtidos nas avaliações audiológica e eletrofisiológica da audição, verificando a ocorrência de alterações auditivas periféricas e/ou centrais, de indivíduos com síndrome de Landau-Kleffner. MÉTODOS: Foram submetidos à avaliação audiológica (inspeção do meato acústico externo, medidas de imitância acústica, audiometrias tonal e vocal e eletrofisiológica da audição (potenciais evocados auditivos de curta, média e longa latência, quatro indivíduos com diagnóstico de síndrome de Landau-Kleffner, na faixa etária de nove a 19 anos, encaminhados ao Laboratório de Investigação Fonoaudiológica em Potenciais Evocados Auditivos do Curso de Fonoaudiologia da Universidade de São Paulo. RESULTADOS: Os resultados mostraram que 100% dos indivíduos apresentaram alteração em pelo menos uma das avaliações realizadas, sendo que houve uma maior ocorrência de alterações no potencial evocado auditivo de média latência (100% dos indivíduos apresentaram alterações. CONCLUSÕES: Observou-se uma grande ocorrência de alterações nos resultados das avaliações audiológicas e eletrofisiológicas da audição em indivíduos com síndrome de Landau-Kleffner. Enfatiza-se a importância da investigação da função auditiva destes indivíduos a fim de verificar possíveis relações entre os déficits da comunicação e alterações auditivas que possam estar presentes nessa população.PURPOSE: To describe the audiological and electrophysiological results of individuals with Landau-Kleffner syndrome, verifying the occurrence of peripheral and/or central auditory disorders. METHODS: Four individuals with Landau-Kleffner syndrome with ages ranging from nine to 19 years old, referred to the Auditory Evoked Potentials Laboratory of the Speech and Language Pathology and Audiology Course of the University of São Paulo, were submitted to audiologic (otoscopy, immitance measurements, pure tone and

  18. Theory of a condensed charged-Bose, charged Fermi gas and Ginzburg--Landau studies of superfluid 3He

    International Nuclear Information System (INIS)

    Dahl, D.A.

    1976-01-01

    Two independent topics in the field of condensed matter physics are examined: the condensed charged-Bose, charged Fermi gas and superfluid 3 He. Green's function (field theoretic) methods are used to derive the low-temperature properties of a dense, neutral gas of condensed charged bosons and degenerate charged fermions. Restriction is made to the case where the fermion mass is much lighter than the boson mass. Linear response and the density-density correlation function are examined and shown to exhibit two collective modes: a plasmon branch and a phonon branch with speed equal to that of ionic sound in solids. Comparison with a possible astrophysical application (white dwarf stars) is made. The behavior near the superfluid transition temperature (Ginzburg--Landau regime) of 3 He is then studied. Gorkov equations are derived and studied in the weak-coupling limit. In this way the form and order of magnitude estimates of coefficients appearing in the Ginzburg--Landau theory are obtained. Weak-coupling particle and spin currents are derived. Various perturbations break the large degeneracy of the states and have experimental implications. The electric contribution to the Ginzburg--Landau free energy is studied for the proposed A and B phases. Imposition of an electric field orients the axial state, but does not give rise to shifts in the NMR resonances. Shifts and discontinuous jumps in the longitudinal and transverse signals are predicted for the Balian--Werthamer state, the details depending on the relative strengths of the fields, as well as the angle between them

  19. Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems.

    Science.gov (United States)

    Ogawa, Shun; Yamaguchi, Yoshiyuki Y

    2015-06-01

    An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.

  20. Lower hybrid heating data on the Wega experiment revisited using ion stochastic heating and electron Landau damping theories

    International Nuclear Information System (INIS)

    Gormezano, C.; Hess, W.; Ichtchenko, G.

    1980-07-01

    The already obtained data on the Wega Tokamak by lower hybrid heating (f=500 MHz - Psub(HF)=130 KW) are revisited in the light of recent theories on ion stochastic heating and quasi-linear electron Landau damping. It is possible to correctly estimate with these theories the fast ion mean energy, the H.F. power density coupled to the ions and that coupled to the electrons. The values of the parallel index of refraction, Nsub(//), which are necessary to obtain a good quantitative agreement between experiment and theoretical estimates, are the same for the ions and for the electrons, even though at higher values than expected

  1. Entropic sampling of simple polymer models within Wang-Landau algorithm

    International Nuclear Information System (INIS)

    Vorontsov-Velyaminov, P N; Volkov, N A; Yurchenko, A A

    2004-01-01

    In this paper we apply a new simulation technique proposed in Wang and Landau (WL) (2001 Phys. Rev. Lett. 86 2050) to sampling of three-dimensional lattice and continuous models of polymer chains. Distributions obtained by homogeneous (unconditional) random walks are compared with results of entropic sampling (ES) within the WL algorithm. While homogeneous sampling gives reliable results typically in the range of 4-5 orders of magnitude, the WL entropic sampling yields them in the range of 20-30 orders and even larger with comparable computer effort. A combination of homogeneous and WL sampling provides reliable data for events with probabilities down to 10 -35 . For the lattice model we consider both the athermal case (self-avoiding walks, SAWs) and the thermal case when an energy is attributed to each contact between nonbonded monomers in a self-avoiding walk. For short chains the simulation results are checked by comparison with the exact data. In WL calculations for chain lengths up to N = 300 scaling relations for SAWs are well reproduced. In the thermal case distribution over the number of contacts is obtained in the N-range up to N = 100 and the canonical averages - internal energy, heat capacity, excess canonical entropy, mean square end-to-end distance - are calculated as a result in a wide temperature range. The continuous model is studied in the athermal case. By sorting conformations of a continuous phantom freely joined N-bonded chain with a unit bond length over a stochastic variable, the minimum distance between nonbonded beads, we determine the probability distribution for the N-bonded chain with hard sphere monomer units over its diameter a in the complete diameter range, 0 ≤ a ≤ 2, within a single ES run. This distribution provides us with excess specific entropy for a set of diameters a in this range. Calculations were made for chain lengths up to N = 100 and results were extrapolated to N → ∞ for a in the range 0 ≤ a ≤ 1.25

  2. Effect of Landau damping on kinetic Alfven and ion-acoustic solitary waves in a magnetized nonthermal plasma with warm ions

    International Nuclear Information System (INIS)

    Bandyopadhyay, Anup; Das, K.P.

    2002-01-01

    The evolution equations describing both kinetic Alfven wave and ion-acoustic wave in a nonthermal magnetized plasma with warm ions including weak nonlinearity and weak dispersion with the effect of Landau damping have been derived. These equations reduce to two coupled equations constituting the KdV-ZK (Korteweg-de Vries-Zakharov-Kuznetsov) equation for both kinetic Alfven wave and ion-acoustic wave, including an extra term accounting for the effect of Landau damping. When the coefficient of the nonlinear term of the evolution equation for ion-acoustic wave vanishes, the nonlinear behavior of ion-acoustic wave, including the effect of Landau damping, is described by two coupled equations constituting the modified KdV-ZK (MKdV-ZK) equation, including an extra term accounting for the effect of Landau damping. It is found that there is no effect of Landau damping on the solitary structures of the kinetic Alfven wave. Both the macroscopic evolution equations for the ion-acoustic wave admits solitary wave solutions, the former having a sech 2 profile and the latter having a sech profile. In either case, it is found that the amplitude of the ion-acoustic solitary wave decreases slowly with time

  3. Effect of elastic compliances and higher order Landau coefficients on the phase diagram of single domain epitaxial Pb(Zr,TiO3 (PZT thin films

    Directory of Open Access Journals (Sweden)

    M. Mtebwa

    2014-12-01

    Full Text Available We report the qualitative study of the influence of both elastic compliances and higher order terms of Landau free energy potential on the phase diagram of Pb(Zr0.5Ti0.5O3 thin films by using a single domain Landau theory. Although the impact of elastic compliances and higher order terms of the Landau free energy potential on the phase diagram of ferroelectric thin films are known, the sensitivity of the phase diagram of PZT thin film on these parameters have not been reported. It is demonstrated that, while values of elastic compliances affect the positions of the phase boundaries including phase transition temperature of the cubic phase; higher order terms can potentially introduce an a1a2-phase previously predicted in PbTiO3 phase diagram.

  4. The effect of boundaries on the asymptotic wavenumber of spiral wave solutions of the complex Ginzburg–Landau equation

    KAUST Repository

    Aguareles, M.

    2014-06-01

    In this paper we consider an oscillatory medium whose dynamics are modeled by the complex Ginzburg-Landau equation. In particular, we focus on n-armed spiral wave solutions of the complex Ginzburg-Landau equation in a disk of radius d with homogeneous Neumann boundary conditions. It is well-known that such solutions exist for small enough values of the twist parameter q and large enough values of d. We investigate the effect of boundaries on the rotational frequency of the spirals, which is an unknown of the problem uniquely determined by the parameters d and q. We show that there is a threshold in the parameter space where the effect of the boundary on the rotational frequency switches from being algebraic to exponentially weak. We use the method of matched asymptotic expansions to obtain explicit expressions for the asymptotic wavenumber as a function of the twist parameter and the domain size for small values of q. © 2014 Elsevier B.V. All rights reserved.

  5. Macroscopically constrained Wang-Landau method for systems with multiple order parameters and its application to drawing complex phase diagrams

    Science.gov (United States)

    Chan, C. H.; Brown, G.; Rikvold, P. A.

    2017-05-01

    A generalized approach to Wang-Landau simulations, macroscopically constrained Wang-Landau, is proposed to simulate the density of states of a system with multiple macroscopic order parameters. The method breaks a multidimensional random-walk process in phase space into many separate, one-dimensional random-walk processes in well-defined subspaces. Each of these random walks is constrained to a different set of values of the macroscopic order parameters. When the multivariable density of states is obtained for one set of values of fieldlike model parameters, the density of states for any other values of these parameters can be obtained by a simple transformation of the total system energy. All thermodynamic quantities of the system can then be rapidly calculated at any point in the phase diagram. We demonstrate how to use the multivariable density of states to draw the phase diagram, as well as order-parameter probability distributions at specific phase points, for a model spin-crossover material: an antiferromagnetic Ising model with ferromagnetic long-range interactions. The fieldlike parameters in this model are an effective magnetic field and the strength of the long-range interaction.

  6. The dynamics of magnetic vortices in type II superconductors with pinning sites studied by the time dependent Ginzburg–Landau model

    Energy Technology Data Exchange (ETDEWEB)

    Sørensen, Mads Peter, E-mail: mpso@dtu.dk [Department of Applied Mathematics and Computer Science, Richard Petersens Plads, Bldg. 324, Technical University of Denmark, Kongens Lyngby DK-2800 (Denmark); Pedersen, Niels Falsig [Department of Applied Mathematics and Computer Science, Richard Petersens Plads, Bldg. 324, Technical University of Denmark, Kongens Lyngby DK-2800 (Denmark); Ögren, Magnus [School of Science and Technology, Örebro University, Örebro SE-70182 (Sweden)

    2017-02-15

    We investigate the dynamics of magnetic vortices in type II superconductors with normal state pinning sites using the Ginzburg–Landau equations. Simulation results demonstrate hopping of vortices between pinning sites, influenced by external magnetic fields and external currents. The system is highly nonlinear and the vortices show complex nonlinear dynamical behaviour.

  7. On the SL(2,R) symmetry in Yang-Mills theories in the Landau, Curci-Ferrari and maximal abelian gauge

    International Nuclear Information System (INIS)

    Dudal, David; Verschelde, Henri; Rodino Lemes, Vitor Emanuel; Sarandy, Marcelo S.; Sorella, Silvio Paolo; Picariello, Marco

    2002-01-01

    The existence of a SL(2;R) symmetry is discussed in SU(N) Yang-Mills in the maximal abelian gauge. This symmetry, also present in the Landau and Curci-Ferrari gauge, ensures the absence of tachyons in the maximal abelian gauge. In all these gauges, SL(2;R) turns out to be dynamically broken by ghost condensates. (author)

  8. Tune distributions and effective tune spread from beam-beam interactions and the consequences for Landau damping in the LHC

    CERN Document Server

    Herr, Werner

    2003-01-01

    We have calculated the tune distribution functions in the presence of beam-beam effects in order to evaluate the efect of Landau damping of instabilities driven by the impedance. The corresponding stability diagrams have been computed and the limits on the transverse impedance have be derived.

  9. Selective-field-ionization dynamics of a lithium m=2 Rydberg state: Landau-Zener model versus quantal approach

    International Nuclear Information System (INIS)

    Foerre, M.; Hansen, J.P.

    2003-01-01

    The selective-field-ionization (SFI) dynamics of a Rydberg state of lithium with magnetic quantum number m=2 is studied in detail based on two different theoretical models: (1) a close coupling integration of the Schroedinger equation and (2) the multichannel (incoherent) Landau-Zener (MLZ) model. The m=2 states are particularly interesting, since they define a border zone between fully adiabatic (m=0,1) and fully diabatic (m>2) ionization dynamics. Both sets of calculations are performed up to, and above, the classical ionization limit. It is found that the MLZ model is excellent in the description of the fully diabatic dynamics while certain discrepancies between the time dependent quantal amplitudes appear when the dynamics become involved. Thus, in this region, the analysis of experimental SFI spectra should be performed with care

  10. Running coupling from gluon and ghost propagators in the Landau gauge: Yang-Mills theories with adjoint fermions

    Science.gov (United States)

    Bergner, Georg; Piemonte, Stefano

    2018-04-01

    Non-Abelian gauge theories with fermions transforming in the adjoint representation of the gauge group (AdjQCD) are a fundamental ingredient of many models that describe the physics beyond the Standard Model. Two relevant examples are N =1 supersymmetric Yang-Mills (SYM) theory and minimal walking technicolor, which are gauge theories coupled to one adjoint Majorana and two adjoint Dirac fermions, respectively. While confinement is a property of N =1 SYM, minimal walking technicolor is expected to be infrared conformal. We study the propagators of ghost and gluon fields in the Landau gauge to compute the running coupling in the MiniMom scheme. We analyze several different ensembles of lattice Monte Carlo simulations for the SU(2) adjoint QCD with Nf=1 /2 ,1 ,3 /2 , and 2 Dirac fermions. We show how the running of the coupling changes as the number of interacting fermions is increased towards the conformal window.

  11. The Landau-Lifshitz equation describes the Ising spin correlation function in the free-fermion model

    CERN Document Server

    Rutkevich, S B

    1998-01-01

    We consider time and space dependence of the Ising spin correlation function in a continuous one-dimensional free-fermion model. By the Ising spin we imply the 'sign' variable, which takes alternating +-1 values in adjacent domains bounded by domain walls (fermionic world paths). The two-point correlation function is expressed in terms of the solution of the Cauchy problem for a nonlinear partial differential equation, which is proved to be equivalent to the exactly solvable Landau-Lifshitz equation. A new zero-curvature representation for this equation is presented. In turn, the initial condition for the Cauchy problem is given by the solution of a nonlinear ordinary differential equation, which has also been derived. In the Ising limit the above-mentioned partial and ordinary differential equations reduce to the sine-Gordon and Painleve III equations, respectively. (author)

  12. Verified Representations of Landau's "Grundlagen" in the lambda-delta Family and in the Calculus of Constructions

    Directory of Open Access Journals (Sweden)

    Ferruccio Guidi

    2016-01-01

    Full Text Available Landau's "Grundlagen der Analysis" formalized in the language Aut-QE, represents an early milestone in computer-checked mathematics and is the only non-trivial development finalized in the languages of the Automath family. Here we discuss an implemented procedure producing a faithful representation of the Grundlagen in the Calculus of Constructions, verified by the proof assistant Coq 8.4.3. The point at issue is distinguishing lambda-abstractions from pi-abstractions where the original text uses Automath unified binders, taking care of the cases in which a binder corresponds to both abstractions at one time. It is a fact that some binders can be disambiguated only by verifying the Grundlagen in a calculus accepting Aut-QE and the Calculus of Constructions. To this end, we rely on lambda-delta version 3, a system that the author is proposing here for the first time.

  13. Two-dimensional massless quantum electrodynamics in the Landau-gauge formalism and the Higgs mechanism. [Schwinger model

    Energy Technology Data Exchange (ETDEWEB)

    Ito, K R [Kyoto Univ. (Japan). Research Inst. for Mathematical Sciences

    1975-03-01

    The Schwinger model is considered in the Landau-gauge formalism of quantum electrodynamics. This model can be solved exactly on the assumption of no radiative corrections to the anomaly. It is found that the photon obtains a non-zero mass through the Higgs mechanism. In this case, the would-be Nambu-Goldstone boson is an associated boson which is constructed from a pair of two-component massless fermions. This would-be Nambu-Goldstone boson appears as a result of the spontaneous breaking of the gauge invariance of the first kind, and it becomes unphysical through the Higgs mechanism. However, as all the fermions themselves decouple from photons, they cannot appear as real particles in our world.

  14. Time-dependent occupation numbers in reduced-density-matrix-functional theory: Application to an interacting Landau-Zener model

    International Nuclear Information System (INIS)

    Requist, Ryan; Pankratov, Oleg

    2011-01-01

    We prove that if the two-body terms in the equation of motion for the one-body reduced density matrix are approximated by ground-state functionals, the eigenvalues of the one-body reduced density matrix (occupation numbers) remain constant in time. This deficiency is related to the inability of such an approximation to account for relative phases in the two-body reduced density matrix. We derive an exact differential equation giving the functional dependence of these phases in an interacting Landau-Zener model and study their behavior in short- and long-time regimes. The phases undergo resonances whenever the occupation numbers approach the boundaries of the interval [0,1]. In the long-time regime, the occupation numbers display correlation-induced oscillations and the memory dependence of the functionals assumes a simple form.

  15. Ultrashort optical solitons in the cubic-quintic complex Ginzburg-Landau equation with higher-order terms

    International Nuclear Information System (INIS)

    Fewo, Serge I.; Kofane, Timoleon C.; Ngabireng, Claude M.

    2008-01-01

    With the help of the Maxwell equations, a basic equation modeling the propagation of ultrashort optical solitons in optical fiber is derived, namely the higher-order complex Ginzburg-Landau equation (HCGLE). Considering this one-dimensional HCGLE, we obtain a set of differential equations characterizing the variation of the pulse parameters called collective variables (CVs), of a pulse propagating in dispersion-managed (DM) fiber optic-links. Equations obtained are investigated numerically in order to observe the behaviour of pulse parameters along the optical fiber. A fully numerical simulation of the one-dimensional HCGLE finally tests the results of the CV theory. A good agreement between both methods is observed. Among various behaviours, chaotic pulses, attenuate pulses and stable pulses can be obtained under certain parameter values. (author)

  16. Dynamics for the complex Ginzburg-Landau equation on non-cylindrical domains II: The monotone case

    Science.gov (United States)

    Zhou, Feng; Sun, Chunyou; Cheng, Jiaqi

    2018-02-01

    In this article, we continue the study of the dynamics of the following complex Ginzburg-Landau equation ∂tu - (λ + iα)Δu + (κ + iβ)|u|p-2u - γu = f(t) on non-cylindrical domains. We assume that the spatial domains are bounded and increase with time, which is different from the diffeomorphism case presented in Zhou and Sun [Discrete Contin. Dyn. Syst., Ser. B 21, 3767-3792 (2016)]. We develop a new penalty function to establish the existence and uniqueness of a variational solution satisfying energy equality as well as some energy inequalities and prove the existence of a D -pullback attractor for the non-autonomous dynamical system generated by this class of solutions.

  17. Thermal coupling effect on the vortex dynamics of superconducting thin films: time-dependent Ginzburg–Landau simulations

    Science.gov (United States)

    Jing, Ze; Yong, Huadong; Zhou, Youhe

    2018-05-01

    In this paper, vortex dynamics of superconducting thin films are numerically investigated by the generalized time-dependent Ginzburg–Landau (TDGL) theory. Interactions between vortex motion and the motion induced energy dissipation is considered by solving the coupled TDGL equation and the heat diffusion equation. It is found that thermal coupling has significant effects on the vortex dynamics of superconducting thin films. Branching in the vortex penetration path originates from the coupling between vortex motion and the motion induced energy dissipation. In addition, the environment temperature, the magnetic field ramp rate and the geometry of the superconducting film also greatly influence the vortex dynamic behaviors. Our results provide new insights into the dynamics of superconducting vortices, and give a mesoscopic understanding on the channeling and branching of vortex penetration paths during flux avalanches.

  18. Are the dressed gluon and ghost propagators in the Landau gauge presently determined in the confinement regime of QCD?

    International Nuclear Information System (INIS)

    Pennington, M. R.; Wilson, D. J.

    2011-01-01

    The gluon and ghost propagators in Landau gauge QCD are investigated using the Schwinger-Dyson equation approach. Working in Euclidean spacetime, we solve for these propagators using a selection of vertex inputs, initially for the ghost equation alone and then for both propagators simultaneously. The results are shown to be highly sensitive to the choices of vertices. We favor the infrared finite ghost solution from studying the ghost equation alone where we argue for a specific unique solution. In order to solve this simultaneously with the gluon using a dressed-one-loop truncation, we find that a nontrivial full ghost-gluon vertex is required in the vanishing gluon momentum limit. The self-consistent solutions we obtain correspond to having a masslike term in the gluon propagator dressing, in agreement with similar studies supporting the long-held proposal of Cornwall.

  19. Induced scattering due to nonlinear Landau and cyclotron damping of electromagnetic and electrostatic waves in a magnetized plasma

    International Nuclear Information System (INIS)

    Sugaya, Reiji

    1989-01-01

    General expressions of the matrix elements for nonlinear wave-particle scattering (nonlinear Landau and cyclotron damping) of electromagnetic and electrostatic waves in a homogeneous magnetized plasma are derived from the Vlasov-Maxwell equations. The kinetic wave equations obtained for electromagnetic waves are expressed by four-order tensors in the rotating and cartesian coordinates. No restrictions are imposed on the propagation angle to a uniform magnetic field, the Larmor radius, the frequencies, or the wave numbers. By electrostatic approximation of the dielectric tensor and the matrix elements the kinetic wave equations can be applied to the case in which two scattering waves are electrostatic or they are partially electrostatic. Further, the matrix elements in the limit of parallel or perpendicular propagation to the magnetic field are given. (author)

  20. The issue of gauge choice in the Landau problem and the physics of canonical and mechanical orbital angular momenta

    Science.gov (United States)

    Wakamatsu, M.; Kitadono, Y.; Zhang, P.-M.

    2018-05-01

    One intriguing issue in the nucleon spin decomposition problem is the existence of two types of decompositions, which are representably characterized by two different orbital angular momenta (OAMs) of quarks. The one is the mechanical OAM, while the other is the so-called gauge-invariant canonical (g.i.c.) OAM, the concept of which was introduced by Chen et al. An especially delicate quantity is the g.i.c. OAM, which must be distinguished from the ordinary (gauge-variant) canonical OAM. We find that, owing to its analytically solvable nature, the famous Landau problem offers an ideal tool to understand the difference and the physical meaning of the above three OAMs, i.e. the standard canonical OAM, g.i.c. OAM, and the mechanical OAM. We analyze these three OAMs in two different formulations of the Landau problem, first in the standard (gauge-fixed) formulation and second in the gauge-invariant (but path-dependent) formulation of DeWitt. Especially interesting is the latter formalism. It is shown that the choice of path has an intimate connection with the choice of gauge, but they are not necessarily equivalent. Then, we answer the question about what is the consequence of a particular choice of path in DeWitt's formalism. This analysis also clarifies the implication of the gauge symmetry hidden in the concept of g.i.c. OAM. Finally, we show that the finding above offers a clear understanding about the uniqueness or non-uniqueness problem of the nucleon spin decomposition, which arises from the arbitrariness in the definition of the so-called physical component of the gauge field.

  1. Benchmark studies of the gyro-Landau-fluid code and gyro-kinetic codes on kinetic ballooning modes

    Energy Technology Data Exchange (ETDEWEB)

    Tang, T. F. [Dalian University of Technology, Dalian 116024 (China); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Xu, X. Q. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Ma, C. H. [Fusion Simulation Center, School of Physics, Peking University, Beijing (China); Bass, E. M.; Candy, J. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Holland, C. [University of California San Diego, La Jolla, California 92093-0429 (United States)

    2016-03-15

    A Gyro-Landau-Fluid (GLF) 3 + 1 model has been recently implemented in BOUT++ framework, which contains full Finite-Larmor-Radius effects, Landau damping, and toroidal resonance [Ma et al., Phys. Plasmas 22, 055903 (2015)]. A linear global beta scan has been conducted using the JET-like circular equilibria (cbm18 series), showing that the unstable modes are kinetic ballooning modes (KBMs). In this work, we use the GYRO code, which is a gyrokinetic continuum code widely used for simulation of the plasma microturbulence, to benchmark with GLF 3 + 1 code on KBMs. To verify our code on the KBM case, we first perform the beta scan based on “Cyclone base case parameter set.” We find that the growth rate is almost the same for two codes, and the KBM mode is further destabilized as beta increases. For JET-like global circular equilibria, as the modes localize in peak pressure gradient region, a linear local beta scan using the same set of equilibria has been performed at this position for comparison. With the drift kinetic electron module in the GYRO code by including small electron-electron collision to damp electron modes, GYRO generated mode structures and parity suggest that they are kinetic ballooning modes, and the growth rate is comparable to the GLF results. However, a radial scan of the pedestal for a particular set of cbm18 equilibria, using GYRO code, shows different trends for the low-n and high-n modes. The low-n modes show that the linear growth rate peaks at peak pressure gradient position as GLF results. However, for high-n modes, the growth rate of the most unstable mode shifts outward to the bottom of pedestal and the real frequency of what was originally the KBMs in ion diamagnetic drift direction steadily approaches and crosses over to the electron diamagnetic drift direction.

  2. Study of the heavy ions (Au+Au at 150 AMeV) collisions with the FOPI detector. Comparison with the Landau-Vlasov model; Etude des collisions d`ions lourds AU+AU a 150 A.MeV avec le detecteur FOPI. Comparaison avec le modele de Landau-Vlasov

    Energy Technology Data Exchange (ETDEWEB)

    Boussange, S

    1995-09-15

    In this thesis, heavy ions (Au+Au) collisions experiments are made at 150 AMeV.In the first part, a general study of the nuclear matter equation is presented. Then the used Landau-Vlasov theoretical model is describe. The third part presents the FOPI experience and the details of how to obtain this theoretical predictions (filter, cuts, corrections, possible centrality selections).At the end, experimental results and comparisons with the Landau-Vlasov model are presented. (TEC). 105 refs., 96 figs., 14 tabs.

  3. Síndrome de Landau-Kleffner e regressão autística: a importância do diagnóstico diferencial Landau-Kleffner and autistic regression: the importance of differential diagnosis

    Directory of Open Access Journals (Sweden)

    Karla M.N. Ribeiro

    2002-09-01

    Full Text Available Algumas doenças neurológicas podem apresentar sinais e sintomas psiquiátricos, portanto a exploração do diagnóstico etiológico é crucial. O objetivo deste estudo é relatar o caso de um paciente com um distúrbio neurológico, diagnosticado durante internação psiquiátrica. Um menino com desenvolvimento neuropsicomotor normal até 3 anos, quando começou a apresentar crises epilépticas, seguidas por distúrbio de comportamento e deterioração da linguagem. Durante o acompanhamento neurológico, o paciente foi encaminhado ao Departamento de Psiquiatria com a suspeita de autismo, regressão autística (RA. Durante internação, o diagnóstico de síndrome de Landau-Kleffner (SLK foi estabelecido em bases clínicas e eletrencefalográficas. A SLK é caracterizada por afasia adquirida, epilepsia, anormalidades eletrencefalográficas e distúrbios de comportamento, incluindo traços autísticos. A regressão da linguagem é observada na SLK e na RA. Enfatizamos as principais diferenças entre estas entidades, pois o diagnóstico errôneo adia a intervenção precoce e benefícios, como observado em nosso caso.Some neurological disorders may present psychiatric signs and symptoms, therefore the search for an etiological diagnosis is crucial. The aim of this study is to report the case of a patient with a neurological disorder, diagnosed during a psychiatric admission. A boy with normal neuropsychomotor development until the age of 3 years, started presenting epileptic seizures, followed by behavioral disorder and language deterioration. During neurologic follow-up, the patient was referred to the Psychiatry Department with a diagnosis of autism, in this case an autistic regression (AR. During his admission, diagnosis of Landau-Kleffner syndrome (LKS was established on clinical and EEG grounds. LKS is characterized by acquired aphasia, epilepsy, EEG abnormalities and behavioral changes, including autistic traits. Language regression is

  4. On the Landau-de Gennes Elastic Energy of a Q-Tensor Model for Soft Biaxial Nematics

    Science.gov (United States)

    Mucci, Domenico; Nicolodi, Lorenzo

    2017-12-01

    In the Landau-de Gennes theory of liquid crystals, the propensities for alignments of molecules are represented at each point of the fluid by an element Q of the vector space S_0 of 3× 3 real symmetric traceless matrices, or Q-tensors. According to Longa and Trebin (1989), a biaxial nematic system is called soft biaxial if the tensor order parameter Q satisfies the constraint tr(Q^2) = {const}. After the introduction of a Q-tensor model for soft biaxial nematic systems and the description of its geometric structure, we address the question of coercivity for the most common four-elastic-constant form of the Landau-de Gennes elastic free-energy (Iyer et al. 2015) in this model. For a soft biaxial nematic system, the tensor field Q takes values in a four-dimensional sphere S^4_ρ of radius ρ ≤ √{2/3} in the five-dimensional space S_0 with inner product = tr(QP). The rotation group it{SO}(3) acts orthogonally on S_0 by conjugation and hence induces an action on S^4_ρ \\subset {S}_0. This action has generic orbits of codimension one that are diffeomorphic to an eightfold quotient S^3/H of the unit three-sphere S^3, where H={± 1, ± i, ± j, ± k} is the quaternion group, and has two degenerate orbits of codimension two that are diffeomorphic to the projective plane RP^2. Each generic orbit can be interpreted as the order parameter space of a constrained biaxial nematic system and each singular orbit as the order parameter space of a constrained uniaxial nematic system. It turns out that S^4_ρ is a cohomogeneity one manifold, i.e., a manifold with a group action whose orbit space is one-dimensional. Another important geometric feature of the model is that the set Σ _ρ of diagonal Q-tensors of fixed norm ρ is a (geodesic) great circle in S^4_ρ which meets every orbit of S^4_ρ orthogonally and is then a section for S^4_ρ in the sense of the general theory of canonical forms. We compute necessary and sufficient coercivity conditions for the elastic energy by

  5. On the Aharonov-Casher system and the Landau-Aharonov-Casher system confined to a two-dimensional quantum ring

    International Nuclear Information System (INIS)

    Bakke, K.; Furtado, C.

    2012-01-01

    We study the quantum dynamics of a neutral particle in the Aharonov-Casher system and in the Landau-Aharonov-Casher system confined to a two-dimensional quantum ring, a quantum dot, and a quantum anti-dot potentials described by the Tan-Inkson model [W.-C. Tan and J. C. Inkson, Semicond. Sci. Technol. 11, 1635 (1996)]. We show, in the Aharonov-Casher system, that bound states can be achieved when the neutral particle is confined to the two-dimensional quantum ring and the quantum dot and discuss the appearance of persistent currents. In the Landau-Aharonov-Casher system, we show that bound states can be achieved when the neutral particle is confined to the quantum anti-dot, quantum dot, and the two-dimensional quantum ring, but there are no persistent currents.

  6. Domain walls of BaTiO.sub.3./sub. and PbTiO.sub.3./sub. within Ginzburg-Landau-Devonshire model

    Czech Academy of Sciences Publication Activity Database

    Hlinka, Jiří

    2008-01-01

    Roč. 375, č. 1 (2008), 132-137 ISSN 0015-0193 R&D Projects: GA ČR GA202/06/0411 Institutional research plan: CEZ:AV0Z10100520 Keywords : domain walls * Landau- Ginsburg theory * ferroelectricity * BaTiO 3 * PbTiO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.562, year: 2008

  7. Fast and high-order numerical algorithms for the solution of multidimensional nonlinear fractional Ginzburg-Landau equation

    Science.gov (United States)

    Mohebbi, Akbar

    2018-02-01

    In this paper we propose two fast and accurate numerical methods for the solution of multidimensional space fractional Ginzburg-Landau equation (FGLE). In the presented methods, to avoid solving a nonlinear system of algebraic equations and to increase the accuracy and efficiency of method, we split the complex problem into simpler sub-problems using the split-step idea. For a homogeneous FGLE, we propose a method which has fourth-order of accuracy in time component and spectral accuracy in space variable and for nonhomogeneous one, we introduce another scheme based on the Crank-Nicolson approach which has second-order of accuracy in time variable. Due to using the Fourier spectral method for fractional Laplacian operator, the resulting schemes are fully diagonal and easy to code. Numerical results are reported in terms of accuracy, computational order and CPU time to demonstrate the accuracy and efficiency of the proposed methods and to compare the results with the analytical solutions. The results show that the present methods are accurate and require low CPU time. It is illustrated that the numerical results are in good agreement with the theoretical ones.

  8. Scattering of a two skyrmion configuration on potential holes or barriers in a model Landau-Lifshitz equation

    International Nuclear Information System (INIS)

    Collins, J C; Zakrzewski, W J

    2009-01-01

    The dynamics of a baby-skyrmion configuration, in a model Landau-Lifshitz equation, was studied in the presence of various potential obstructions. The baby-skyrmion configuration was constructed from two Q = 1 hedgehog solutions to the baby-skyrme model in (2+1) dimensions. The potential obstructions were created by introducing a new term into the Lagrangian which resulted in a localized inhomogeneity in the potential terms' coefficient. In the barrier system, the normal circular path was deformed as the skyrmions traversed the barrier. During the same period, it was seen that the skyrmions sped up as they went over the barrier. For critical values of the barrier height and width, the skyrmions were no longer bound and were free to separate. In the case of a potential hole, the baby skyrmions no longer formed a bound state and moved asymptotically along the axis of the hole. It is shown how to modify the definition of the angular momentum to include the effects of the obstructions, so that it is conserved

  9. A new approach to the theory of Cherenkov radiation based on relativistic generalization of the Landau criterion

    International Nuclear Information System (INIS)

    Chefranov, S.G.

    2004-01-01

    Relativistic generalization of the Landau criterion is obtained which, in contrast to the classical Tamm-Frank and Ginzburg theories, determines the primary energy mechanism of emission of nonbremsstrahlung Cherenkov radiation. It is shown that Cherenkov radiation may correspond to a threshold energetically favorable conversion of the condensate (ultimately long-wavelength) elementary Bose perturbations of a medium into transverse Cherenkov photons emitted by the medium proper during its interaction with a sufficiently fast charged particle. The threshold conditions of emission are determined for a medium with an arbitrary refractive index n, including the case of isotropic plasma with n < 1 for which the classical theory of Cherenkov radiation prohibits such direct and effective nonbremsstrahlung emission of these particular transverse high-frequency electromagnetic waves. It is established that these conditions of emission agree with the data of well-known experiments on the threshold for observation of Cherenkov radiation, whereas the classical theory only corresponds to the conditions of observation of the interference maximum of this radiation. The possibility of direct effective emission of nonbremsstrahlung Cherenkov radiation, not taken into account in the classical theory, is considered for many observed astrophysical phenomena (type III solar radio bursts, particle acceleration by radiation, etc.)

  10. Ginzburg-Landau equations for a d-wave superconductor with applications to vortex structure and surface problems

    International Nuclear Information System (INIS)

    Xu, J.; Ren, Y.; Ting, C.S.

    1995-01-01

    The properties of a d x 2 -y 2 -wave superconductor in an external magnetic field are investigated on the basis of Gorkov's theory of weakly coupled superconductors. The Ginzburg-Landau (GL) equations, which govern the spatial variations of the order parameter and the supercurrent, are microscopically derived. The single vortex structure and surface problems in such a superconductor are studied using these equations. It is shown that the d-wave vortex structure is very different from the conventional s-wave vortex: the s-wave and d-wave components, with the opposite winding numbers, are found to coexist in the region near the vortex core. The supercurrent and local magnetic field around the vortex are calculated. Far away from the vortex core, both of them exhibit a fourfold symmetry, in contrast to an s-wave superconductor. The surface problem in a d-wave superconductor is also studied by solving the GL equations. The total order parameter near the surface is always a real combination of s- and d-wave components, which means that the proximity effect cannot induce a time-reversal symmetry-breaking state at the surface

  11. All-atom simulation study of protein PTH(1-34) by using the Wang-Landau sampling method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung-Yeon [Korea National University of Transportation, Chungju (Korea, Republic of); Kwak, Woo-Seop [Chosun University, Gwangju (Korea, Republic of)

    2014-12-15

    We perform simulations of the N-terminal 34-residue protein fragment PTH(1-34), consisting of 581 atoms, of the 84-residue human parathyroid hormone by using the all-atom ECEPP/3 force field and the Wang-Landau sampling method. Through a massive high-performance computation, the density of states and the partition function Z(T), as a continuous function of T, are obtained for PTH(1-34). From the continuous partition function Z(T), the partition function zeros of PTH(1-34) are evaluated for the first time. From both the specific heat and the partition function zeros, two characteristic transition temperatures are obtained for the all-atom protein PTH(1-34). The higher transition temperature T{sub 1} and the lower transition temperature T{sub 2} of PTH(1-34) can be interpreted as the collapse temperature T{sub θ} and the folding temperature T{sub f} , respectively.

  12. Application of the Landau-Zener-Stückelberg-Majorana dynamics to the electrically driven flip of a hole spin

    Science.gov (United States)

    Pasek, W. J.; Maialle, M. Z.; Degani, M. H.

    2018-03-01

    An idea of employing the Landau-Zener-Stückelberg-Majorana dynamics to flip a spin of a single ground state hole is introduced and explored by a time-dependent simulation. This configuration interaction study considers a hole confined in a quantum molecule formed in an InSb 〈111 〉 quantum wire by application of an electrostatic potential. An up-down spin-mixing avoided crossing is formed by nonaxial terms in the Kohn-Luttinger Hamiltonian and the Dresselhaus spin-orbit one. Manipulation of the system is possible by the dynamic change of an external vertical electric field, which enables the consecutive driving of the hole through two anticrossings. Moreover, a simple model of the power-law-type noise that impedes precise electric control of the system is included in the form of random telegraph noise to estimate the limitations of the working conditions. We show that in principle the process is possible, but it requires precise control of the parameters of the driving impulse.

  13. A Fokker-Planck-Landau collision equation solver on two-dimensional velocity grid and its application to particle-in-cell simulation

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, E. S.; Chang, C. S., E-mail: cschang@pppl.gov [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Korea Advanced Institute of Science and Technology, Yuseong-gu, DaeJeon 305-701 (Korea, Republic of)

    2014-03-15

    An approximate two-dimensional solver of the nonlinear Fokker-Planck-Landau collision operator has been developed using the assumption that the particle probability distribution function is independent of gyroangle in the limit of strong magnetic field. The isotropic one-dimensional scheme developed for nonlinear Fokker-Planck-Landau equation by Buet and Cordier [J. Comput. Phys. 179, 43 (2002)] and for linear Fokker-Planck-Landau equation by Chang and Cooper [J. Comput. Phys. 6, 1 (1970)] have been modified and extended to two-dimensional nonlinear equation. In addition, a method is suggested to apply the new velocity-grid based collision solver to Lagrangian particle-in-cell simulation by adjusting the weights of marker particles and is applied to a five dimensional particle-in-cell code to calculate the neoclassical ion thermal conductivity in a tokamak plasma. Error verifications show practical aspects of the present scheme for both grid-based and particle-based kinetic codes.

  14. MD 2197: Experimental studies of Landau damping by means of Beam Transfer Function measurements in the presence of beam-beam interactions and diffusive mechanisms

    CERN Document Server

    Tambasco, Claudia; Barranco Garcia, Javier; Boccardi, Andrea; Buffat, Xavier; Bruce, Roderik; Gasior, Marek; Hostettler, Michi; Lefevre, Thibaut; Louro Alves, Diogo Miguel; Metral, Elias; Persson, Tobias Hakan Bjorn; Pieloni, Tatiana; Pojer, Mirko; Salvachua Ferrando, Belen Maria; Solfaroli Camillocci, Matteo; CERN. Geneva. ATS Department

    2018-01-01

    Beam Transfer Function (BTF) measurements are direct measurement of the stability diagrams that define the stability threshold of coherent beam instabilities driven by the impedance. At the LHC, some coherent instabilities at flat top energy are still not fully understood and the BTF measurements provide a method to experimentally probe the Landau damping of the proton beams. The BTF response is sensitive to the particle distribution changes and contain information about the transverse tune spread in the beams. The BTF system has been installed in the LHC in the 2015 in order to investigate the Landau damping at different stages of the operational cycle, machine configurations (different octupole currents, crossing angles, tunes etc...) and in presence of beam-beam excited resonances that may provoke diffusion mechanisms with a consequence change of Landau damping. Past MDs showed some difficulties for the reconstruction of the stability diagram from BTF measurements and several improvements on the BTF sy...

  15. Non-radially symmetric solutions to the Ginzburg-Landau equation

    CERN Document Server

    Ovchinnikov, Yu N

    2000-01-01

    We study an atom with finitely many energy levels in contact with a heat bath consisting of photons (black body radiation) at a temperature $T >0$. The dynamics of this system is described by a Liouville operator, or thermal Hamiltonian, which is the sum of an atomic Liouville operator, of a Liouville operator describing the dynamics of a free, massless Bose field, and a local operator describing the interactions between the atom and the heat bath. We show that an arbitrary initial state which is normal with respect to the equilibrium state of the uncoupled system at temperature $T$ converges to an equilibrium state of the coupled system at the same temperature, as time tends to $+ \\infty$

  16. Criticality and novel quantum liquid phases in Ginzburg-Landau theories with compact and non-compact gauge fields

    Energy Technology Data Exchange (ETDEWEB)

    Smiseth, Jo

    2005-07-01

    The critical properties of three-dimensional U(1)-symmetric lattice gauge theories have been studied. The models apply to various physical systems such as insulating phases of strongly correlated electron systems as well as superconducting and superfluid states of liquid metallic hydrogen under extreme pressures. The thesis contains an introductory part and a collection of research papers of which seven are published works and one is submitted for publication. The outline of this thesis is as follows. In Chapter 2 the theory of phase transitions is discussed with emphasis on continuous phase transitions, critical phenomena and phase transitions in gauge theories. In the next chapter the phases of the abelian Higgs model are presented, and the critical phenomena are discussed. Furthermore, the multicomponent Ginzburg-Landau theory and the applications to liquid metallic hydrogen are presented. Chapter 4 contains an overview of the Monte Carlo integration scheme, including the Metropolis algorithm, error estimates, and re weighting techniques. This chapter is followed by the papers I-VIII. Paper I: Criticality in the (2+1)-Dimensional Compact Higgs Model and Fractionalized Insulators. Paper II: Phase structure of (2+1)-dimensional compact lattice gauge theories and the transition from Mott insulator to fractionalized insulator. Paper III: Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials. Paper IV: Phase structure of Abelian Chern-Simons gauge theories. Paper V: Critical Properties of the N-Color London Model. Paper VI: Field- and temperature induced topological phase transitions in the three-dimensional N-component London superconductor. Paper VII: Vortex Sublattice Melting in a Two-Component Superconductor. Paper VIII: Observation of a metallic superfluid in a numerical experiment (ml)

  17. Dynamical transitions in large systems of mean field-coupled Landau-Stuart oscillators: Extensive chaos and cluster states.

    Science.gov (United States)

    Ku, Wai Lim; Girvan, Michelle; Ott, Edward

    2015-12-01

    In this paper, we study dynamical systems in which a large number N of identical Landau-Stuart oscillators are globally coupled via a mean-field. Previously, it has been observed that this type of system can exhibit a variety of different dynamical behaviors. These behaviors include time periodic cluster states in which each oscillator is in one of a small number of groups for which all oscillators in each group have the same state which is different from group to group, as well as a behavior in which all oscillators have different states and the macroscopic dynamics of the mean field is chaotic. We argue that this second type of behavior is "extensive" in the sense that the chaotic attractor in the full phase space of the system has a fractal dimension that scales linearly with N and that the number of positive Lyapunov exponents of the attractor also scales linearly with N. An important focus of this paper is the transition between cluster states and extensive chaos as the system is subjected to slow adiabatic parameter change. We observe discontinuous transitions between the cluster states (which correspond to low dimensional dynamics) and the extensively chaotic states. Furthermore, examining the cluster state, as the system approaches the discontinuous transition to extensive chaos, we find that the oscillator population distribution between the clusters continually evolves so that the cluster state is always marginally stable. This behavior is used to reveal the mechanism of the discontinuous transition. We also apply the Kaplan-Yorke formula to study the fractal structure of the extensively chaotic attractors.

  18. The infrared behavior of lattice QCD Green's functions. A numerical study of lattice QCD in Landau gauge

    Energy Technology Data Exchange (ETDEWEB)

    Sternbeck, A.

    2006-07-18

    Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator. (orig.)

  19. The infrared behavior of lattice QCD Green's functions. A numerical study of lattice QCD in Landau gauge

    International Nuclear Information System (INIS)

    Sternbeck, A.

    2006-01-01

    Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator. (orig.)

  20. Thermally activated vapor bubble nucleation: The Landau-Lifshitz-Van der Waals approach

    Science.gov (United States)

    Gallo, Mirko; Magaletti, Francesco; Casciola, Carlo Massimo

    2018-05-01

    Vapor bubbles are formed in liquids by two mechanisms: evaporation (temperature above the boiling threshold) and cavitation (pressure below the vapor pressure). The liquid resists in these metastable (overheating and tensile, respectively) states for a long time since bubble nucleation is an activated process that needs to surmount the free energy barrier separating the liquid and the vapor states. The bubble nucleation rate is difficult to assess and, typically, only for extremely small systems treated at an atomistic level of detail. In this work a powerful approach, based on a continuum diffuse interface modeling of the two-phase fluid embedded with thermal fluctuations (fluctuating hydrodynamics), is exploited to study the nucleation process in homogeneous conditions, evaluating the bubble nucleation rates and following the long-term dynamics of the metastable system, up to the bubble coalescence and expansion stages. In comparison with more classical approaches, this methodology allows us on the one hand to deal with much larger systems observed for a much longer time than possible with even the most advanced atomistic models. On the other, it extends continuum formulations to thermally activated processes, impossible to deal with in a purely determinist setting.

  1. Group theoretical arguments on the Landau theory of second-order phase transitions applied to the phase transitions in some liquid crystals

    International Nuclear Information System (INIS)

    Rosciszewski, K.

    1979-01-01

    The phase transitions between liquids and several of the simplest liquid crystalline phases (nematic, cholesteric, and the simplest types of smectic A and smectic C) were studied from the point of view of the group-theoretical arguments of Landau theory. It was shown that the only possible candidates for second-order phase transitions are those between nematic and smectic A, between centrosymmetric nematic and smectic C and between centrosymmetric smectic A and smectic C. Simple types of density functions for liquid crystalline phases are proposed. (author)

  2. Birth–death process of local structures in defect turbulence described by the one-dimensional complex Ginzburg–Landau equation

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Yusuke, E-mail: r1230160@risk.tsukuba.ac.jp; Konno, Hidetoshi

    2014-04-01

    Defect turbulence described by the one-dimensional complex Ginzburg–Landau equation is investigated and analyzed via a birth–death process of the local structures composed of defects, holes, and modulated amplitude waves (MAWs). All the number statistics of each local structure, in its stationary state, are subjected to Poisson statistics. In addition, the probability density functions of interarrival times of defects, lifetimes of holes, and MAWs show the existence of long-memory and some characteristic time scales caused by zigzag motions of oscillating traveling holes. The corresponding stochastic process for these observations is fully described by a non-Markovian master equation.

  3. Nuclear Landau-Zener phenomena and the fusion cross sections in the system 13C + 16O → 12C + 17O

    International Nuclear Information System (INIS)

    Imanishi, B.; Oertzen, W. von.

    1990-07-01

    Reaction mechanism of the system 13 C+ 16 O- 12 C+ 17 O is investigated with the use of the nucleon molecular-orbital model in the framework of the orthogonalized coupled-reaction-channel (OCRC) theory. The adiabatic potentials obtained are quite different from the diagonal potentials of the original OCRC basis. The Landau-Zener radial coupling explains the backward enhancement of measured differential cross sections of the transfer reaction 13 C( 16 O, 17 O) 12 C. In the OCRC calculation the fusion cross sections of the channel 13 C+ 16 O is enhanced at low bombarding energies, in agreement with the experimental data. (author)

  4. On Landau damping

    KAUST Repository

    Mouhot, Clé ment; Villani, Cé dric

    2011-01-01

    of regularity between kinetic and spatial variables, rather than exchanges of energy; phase mixing is the driving mechanism. The analysis involves new families of analytic norms, measuring regularity by comparison with solutions of the free transport equation

  5. On Pseudorapidity Distribution and Speed of Sound in High Energy Heavy Ion Collisions Based on a New Revised Landau Hydrodynamic Model

    Directory of Open Access Journals (Sweden)

    Li-Na Gao

    2015-01-01

    Full Text Available We propose a new revised Landau hydrodynamic model to study systematically the pseudorapidity distributions of charged particles produced in heavy ion collisions over an energy range from a few GeV to a few TeV per nucleon pair. The interacting system is divided into three sources, namely, the central, target, and projectile sources, respectively. The large central source is described by the Landau hydrodynamic model and further revised by the contributions of the small target/projectile sources. The modeling results are in agreement with the available experimental data at relativistic heavy ion collider, large hadron collider, and other energies for different centralities. The value of square speed of sound parameter in different collisions has been extracted by us from the widths of rapidity distributions. Our results show that, in heavy ion collisions at energies of the two colliders, the central source undergoes a phase transition from hadronic gas to quark-gluon plasma liquid phase; meanwhile, the target/projectile sources remain in the state of hadronic gas. The present work confirms that the quark-gluon plasma is of liquid type rather than being of a gas type.

  6. c-T phase diagram and Landau free energies of (AgAu)55 nanoalloy via neural-network molecular dynamic simulations.

    Science.gov (United States)

    Chiriki, Siva; Jindal, Shweta; Bulusu, Satya S

    2017-10-21

    For understanding the structure, dynamics, and thermal stability of (AgAu) 55 nanoalloys, knowledge of the composition-temperature (c-T) phase diagram is essential due to the explicit dependence of properties on composition and temperature. Experimentally, generating the phase diagrams is very challenging, and therefore theoretical insight is necessary. We use an artificial neural network potential for (AgAu) 55 nanoalloys. Predicted global minimum structures for pure gold and gold rich compositions are lower in energy compared to previous reports by density functional theory. The present work based on c-T phase diagram, surface area, surface charge, probability of isomers, and Landau free energies supports the enhancement of catalytic property of Ag-Au nanoalloys by incorporation of Ag up to 24% by composition in Au nanoparticles as found experimentally. The phase diagram shows that there is a coexistence temperature range of 70 K for Ag 28 Au 27 compared to all other compositions. We propose the power spectrum coefficients derived from spherical harmonics as an order parameter to calculate Landau free energies.

  7. Spatiotemporal structure of pulsating solitons in the cubic-quintic Ginzburg-Landau equation: A novel variational formulation

    Energy Technology Data Exchange (ETDEWEB)

    Mancas, Stefan C. [Department of Mathematics, University of Central Florida, Orlando, FL 32816-1364 (United States)], E-mail: smancas@mail.ucf.edu; Roy Choudhury, S. [Department of Mathematics, University of Central Florida, Orlando, FL 32816-1364 (United States)], E-mail: choudhur@longwood.cs.ucf.edu

    2009-04-15

    Comprehensive numerical simulations (reviewed in Dissipative Solitons, Akhmediev and Ankiewicz (Eds.), Springer, Berlin, 2005) of pulse solutions of the cubic-quintic Ginzburg-Landau Equation (CGLE), a canonical equation governing the weakly nonlinear behavior of dissipative systems in a wide variety of disciplines, reveal various intriguing and entirely novel classes of solutions. In particular, there are five new classes of pulse or solitary waves solutions, viz. pulsating, creeping, snake, erupting, and chaotic solitons. In contrast to the regular solitary waves investigated in numerous integrable and non-integrable systems over the last three decades, these dissipative solitons are not stationary in time. Rather, they are spatially confined pulse-type structures whose envelopes exhibit complicated temporal dynamics. The numerical simulations also reveal very interesting bifurcations sequences of these pulses as the parameters of the CGLE are varied. In this paper, we address the issues of central interest in the area, i.e., the conditions for the occurrence of the five categories of dissipative solitons, as well the dependence of both their shape and their stability on the various parameters of the CGLE, viz. the nonlinearity, dispersion, linear and nonlinear gain, loss and spectral filtering parameters. Our predictions on the variation of the soliton amplitudes, widths and periods with the CGLE parameters agree with simulation results. First, we elucidate the Hopf bifurcation mechanism responsible for the various pulsating solitary waves, as well as its absence in Hamiltonian and integrable systems where such structures are absent. Next, we develop and discuss a variational formalism within which to explore the various classes of dissipative solitons. Given the complex dynamics of the various dissipative solutions, this formulation is, of necessity, significantly generalized over all earlier approaches in several crucial ways. Firstly, the starting formulation

  8. In-plane magnetic field-induced anisotropy and orientation energy of stripe phases at half-filled high Landau levels

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; MacDonald, A. H.; Smrčka, Ludvík; Girvin, S. M.

    2000-01-01

    Roč. 6, - (2000), s. 43-46 ISSN 1386-9477 R&D Projects: GA ČR GA202/98/0085 Institutional research plan: CEZ:AV0Z1010914 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.878, year: 2000

  9. Bäcklund transformation, analytic soliton solutions and numerical simulation for a (2+1)-dimensional complex Ginzburg-Landau equation in a nonlinear fiber

    Science.gov (United States)

    Yu, Ming-Xiao; Tian, Bo; Chai, Jun; Yin, Hui-Min; Du, Zhong

    2017-10-01

    In this paper, we investigate a nonlinear fiber described by a (2+1)-dimensional complex Ginzburg-Landau equation with the chromatic dispersion, optical filtering, nonlinear and linear gain. Bäcklund transformation in the bilinear form is constructed. With the modified bilinear method, analytic soliton solutions are obtained. For the soliton, the amplitude can decrease or increase when the absolute value of the nonlinear or linear gain is enlarged, and the width can be compressed or amplified when the absolute value of the chromatic dispersion or optical filtering is enhanced. We study the stability of the numerical solutions numerically by applying the increasing amplitude, embedding the white noise and adding the Gaussian pulse to the initial values based on the analytic solutions, which shows that the numerical solutions are stable, not influenced by the finite initial perturbations.

  10. A collective variable approach and stabilization for dispersion-managed optical solitons in the quintic complex Ginzburg-Landau equation as perturbations of the nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Fewo, S I; Kenfack-Jiotsa, A; Kofane, T C

    2006-01-01

    With the help of the one-dimensional quintic complex Ginzburg-Landau equation (CGLE) as perturbations of the nonlinear Schroedinger equation (NLSE), we derive the equations of motion of pulse parameters called collective variables (CVs), of a pulse propagating in dispersion-managed (DM) fibre optic links. The equations obtained are investigated numerically in order to view the evolution of pulse parameters along the propagation distance, and also to analyse effects of initial amplitude and width on the propagating pulse. Nonlinear gain is shown to be beneficial in stabilizing DM solitons. A fully numerical simulation of the one-dimensional quintic CGLE as perturbations of NLSE finally tests the results of the CV theory. A good agreement is observed between both methods

  11. Regional Cerebral Blood-Flow with 99mTc-ECD Brain Perfusion SPECT in Landau-Kleffner Syndrome: Report of Two Cases

    Directory of Open Access Journals (Sweden)

    Reza Nemati

    2014-01-01

    Full Text Available Landau-Kleffner syndrome (LKS is a rare childhood disorder characterized by acquired aphasia and epilepsy. 99mTc-ECD SPECT imaging was performed in two right-handed children with LKS. A relative decrease in perfusion was found in the left frontal-temporal cortices of both patients as well as in the left and right parietal cortices of one patient with aphasia, without clinical epilepsy. The degree of regional cerebral perfusion impairment did not correlate with the severity of the clinical and EEG abnormalities, but the area of hypoperfusion was compatible with the speech area of the brain. Overall, although asymmetrical temporoparietal perfusion appears as a common finding in LKS, SPECT findings in LKS alone cannot elucidate the pathogenic features of the disorder in the brain. Here, we present two cases of LKS in which we investigated SPECT perfusion scans.

  12. Size effect on the dielectric properties of BaTiO3 nanoceramics in a modified Ginsburg-Landau-Devonshire thermodynamic theory

    Science.gov (United States)

    Lin, Shan; Lü, Tianquan; Jin, Changqing; Wang, Xiaohui

    2006-10-01

    Grain size effects on the dielectric properties of BaTiO3 nanoceramics have been studied by using the modified Ginsburg-Landau-Devonshire (GLD) thermodynamic theory. Considering the existence of internal stresses, it is found that with decreasing grain size the transition temperature of cubic-tetragonal phase decreases, while those of tetragonal-orthorhombic and orthorhombic-rhombohedral phases increase. With further reducing grain size, our model predicts that the two ferroelectric structures of orthorhombic and tetragonal phases will become unstable and disappear at a critical size, leaving only one stable ferroelectric phase of rhombohedral structure. Consequently, a theoretical phase diagram of the transition temperature versus grain size is established wherein two triple points and a reentrance behavior are indicated. The results are compared with experimental data.

  13. Pulsating Hydrodynamic Instability and Thermal Coupling in an Extended Landau/Levich Model of Liquid-Propellant Combustion -- I. Inviscid Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Stephen B. Margolis; Forman A. Williams

    1999-03-01

    Hydrodynamic (Landau) instability in combustion is typically associated with the onset of wrinkling of a flame surface, corresponding to the formation of steady cellular structures as the stability threshold is crossed. In the context of liquid-propellant combustion, such instability has recently been shown to occur for critical values of the pressure sensitivity of the burning rate and the disturbance wavenumber, significantly generalizing previous classical results for this problem that assumed a constant normal burning rate. Additionally, however, a pulsating form of hydrodynamic instability has been shown to occur as well, corresponding to the onset of temporal oscillations in the location of the liquid/gas interface. In the present work, we consider the realistic influence of a nonzero temperature sensitivity in the local burning rate on both types of stability thresholds. It is found that for sufficiently small values of this parameter, there exists a stable range of pressure sensitivities for steady, planar burning such that the classical cellular form of hydrodynamic instability and the more recent pulsating form of hydrodynamic instability can each occur as the corresponding stability threshold is crossed. For larger thermal sensitivities, however, the pulsating stability boundary evolves into a C-shaped curve in the (disturbance-wavenumber, pressure-sensitivity) plane, indicating loss of stability to pulsating perturbations for all sufficiently large disturbance wavelengths. It is thus concluded, based on characteristic parameter values, that an equally likely form of hydrodynamic instability in liquid-propellant combustion is of a nonsteady, long-wave nature, distinct from the steady, cellular form originally predicted by Landau.

  14. Remarks on the three-level topological string theories

    International Nuclear Information System (INIS)

    Budzynski, R.J.

    1997-01-01

    A few observations concerning topological string theories at the string-tree level are presented: (1) The tree-level, large phase space solution of an arbitrary model is expressed in terms of a variational problem, with an ''action'' equal, at the solution, to the one-point function of the puncture operator, and found by solving equations of Gauss-Manin type; (2) For A k Landau-Ginzburg models, an extension to large phase space of the usual residue formula for three-point functions is given. (author)

  15. About positive, energy conservative and equilibrium state preserving schemes for the isotropic Fokker-Planck-Landau equation; Sur les schemas positifs, conservant l'energie et les etats d'equilibre pour l'equation de Fokker-Planck-Landau isotrope

    Energy Technology Data Exchange (ETDEWEB)

    Buet, Ch. [CEA Bruyeres-le-Chatel, Dept. des Sciences de la Simulation et de l' Information, 91 (France); Le Thanh, K.C. [CEA Bruyeres-le-Chatel, Dept. de Physique Theorique et Appliquee, 91 (France)

    2006-07-01

    The aim of this paper is to describe the discretization of the Fokker-Planck-Landau (FPL) collision term in the isotropic case which models the self collision for the electrons when they are totally isotropized by heavy particles background such as ions. The discussion focus on schemes which could preserve positivity, mass, energy and Maxwellian equilibrium. First, we analyze in detail the popular Chang and Cooper method for this non-linear collision term: derivation, conservation and positivity properties. We show that some variants of this method, based on the drift-diffusion form of the FPL operator, could not be positive or could not conserve the energy. We present a new variant of the Chang and Cooper method derived from the Landau form that is both positive and conservative. We also propose two new alternatives and simpler schemes for the FPL operator which show that the Chang and Cooper method is not the only way to construct positive, energy conservative and equilibrium state preserving schemes for this operator. For all these schemes, we explain clearly the properties of conservation of the density and the energy, the positivity of the solution and the conservation of the equilibrium states, or their lack. The case of Maxwellian and Coulombian potentials are emphasized. (authors)

  16. Data-adaptive harmonic analysis and prediction of sea level change in North Atlantic region

    Science.gov (United States)

    Kondrashov, D. A.; Chekroun, M.

    2017-12-01

    This study aims to characterize North Atlantic sea level variability across the temporal and spatial scales. We apply recently developed data-adaptive Harmonic Decomposition (DAH) and Multilayer Stuart-Landau Models (MSLM) stochastic modeling techniques [Chekroun and Kondrashov, 2017] to monthly 1993-2017 dataset of Combined TOPEX/Poseidon, Jason-1 and Jason-2/OSTM altimetry fields over North Atlantic region. The key numerical feature of the DAH relies on the eigendecomposition of a matrix constructed from time-lagged spatial cross-correlations. In particular, eigenmodes form an orthogonal set of oscillating data-adaptive harmonic modes (DAHMs) that come in pairs and in exact phase quadrature for a given temporal frequency. Furthermore, the pairs of data-adaptive harmonic coefficients (DAHCs), obtained by projecting the dataset onto associated DAHMs, can be very efficiently modeled by a universal parametric family of simple nonlinear stochastic models - coupled Stuart-Landau oscillators stacked per frequency, and synchronized across different frequencies by the stochastic forcing. Despite the short record of altimetry dataset, developed DAH-MSLM model provides for skillful prediction of key dynamical and statistical features of sea level variability. References M. D. Chekroun and D. Kondrashov, Data-adaptive harmonic spectra and multilayer Stuart-Landau models. HAL preprint, 2017, https://hal.archives-ouvertes.fr/hal-01537797

  17. Fully non-linear multi-species Fokker-Planck-Landau collisions for gyrokinetic particle-in-cell simulations of fusion plasma

    Science.gov (United States)

    Hager, Robert; Yoon, E. S.; Ku, S.; D'Azevedo, E. F.; Worley, P. H.; Chang, C. S.

    2015-11-01

    We describe the implementation, and application of a time-dependent, fully nonlinear multi-species Fokker-Planck-Landau collision operator based on the single-species work of Yoon and Chang [Phys. Plasmas 21, 032503 (2014)] in the full-function gyrokinetic particle-in-cell codes XGC1 [Ku et al., Nucl. Fusion 49, 115021 (2009)] and XGCa. XGC simulations include the pedestal and scrape-off layer, where significant deviations of the particle distribution function from a Maxwellian can occur. Thus, in order to describe collisional effects on neoclassical and turbulence physics accurately, the use of a non-linear collision operator is a necessity. Our collision operator is based on a finite volume method using the velocity-space distribution functions sampled from the marker particles. Since the same fine configuration space mesh is used for collisions and the Poisson solver, the workload due to collisions can be comparable to or larger than the workload due to particle motion. We demonstrate that computing time spent on collisions can be kept affordable by applying advanced parallelization strategies while conserving mass, momentum, and energy to reasonable accuracy. We also show results of production scale XGCa simulations in the H-mode pedestal and compare to conventional theory. Work supported by US DOE OFES and OASCR.

  18. Acquired auditory agnosia in childhood and normal sleep electroencephalography subsequently diagnosed as Landau-Kleffner syndrome: a report of three cases.

    Science.gov (United States)

    van Bogaert, Patrick; King, Mary D; Paquier, Philippe; Wetzburger, Catherine; Labasse, Catherine; Dubru, Jean-Marie; Deonna, Thierry

    2013-06-01

      We report three cases of Landau-Kleffner syndrome (LKS) in children (two females, one male) in whom diagnosis was delayed because the sleep electroencephalography (EEG) was initially normal.   Case histories including EEG, positron emission tomography findings, and long-term outcome were reviewed.   Auditory agnosia occurred between the age of 2 years and 3 years 6 months, after a period of normal language development. Initial awake and sleep EEG, recorded weeks to months after the onset of language regression, during a nap period in two cases and during a full night of sleep in the third case, was normal. Repeat EEG between 2 months and 2 years later showed epileptiform discharges during wakefulness and strongly activated by sleep, with a pattern of continuous spike-waves during slow-wave sleep in two patients. Patients were diagnosed with LKS and treated with various antiepileptic regimens, including corticosteroids. One patient in whom EEG became normal on hydrocortisone is making significant recovery. The other two patients did not exhibit a sustained response to treatment and remained severely impaired.   Sleep EEG may be normal in the early phase of acquired auditory agnosia. EEG should be repeated frequently in individuals in whom a firm clinical diagnosis is made to facilitate early treatment. © The Authors. Developmental Medicine & Child Neurology © 2012 Mac Keith Press.

  19. The cubic-quintic-septic complex Ginzburg-Landau equation formulation of optical pulse propagation in 3D doped Kerr media with higher-order dispersions

    Science.gov (United States)

    Djoko, Martin; Kofane, T. C.

    2018-06-01

    We investigate the propagation characteristics and stabilization of generalized-Gaussian pulse in highly nonlinear homogeneous media with higher-order dispersion terms. The optical pulse propagation has been modeled by the higher-order (3+1)-dimensional cubic-quintic-septic complex Ginzburg-Landau [(3+1)D CQS-CGL] equation. We have used the variational method to find a set of differential equations characterizing the variation of the pulse parameters in fiber optic-links. The variational equations we obtained have been integrated numerically by the means of the fourth-order Runge-Kutta (RK4) method, which also allows us to investigate the evolution of the generalized-Gaussian beam and the pulse evolution along an optical doped fiber. Then, we have solved the original nonlinear (3+1)D CQS-CGL equation with the split-step Fourier method (SSFM), and compare the results with those obtained, using the variational approach. A good agreement between analytical and numerical methods is observed. The evolution of the generalized-Gaussian beam has shown oscillatory propagation, and bell-shaped dissipative optical bullets have been obtained under certain parameter values in both anomalous and normal chromatic dispersion regimes. Using the natural control parameter of the solution as it evolves, named the total energy Q, our numerical simulations reveal the existence of 3D stable vortex dissipative light bullets, 3D stable spatiotemporal optical soliton, stationary and pulsating optical bullets, depending on the used initial input condition (symmetric or elliptic).

  20. Quantitative analysis and prediction of experimental observations on quasi-static hysteretic metal–ferroelectric–metal–insulator–semiconductor FET and its dynamic behaviour based on Landau theory

    International Nuclear Information System (INIS)

    Li, Yang; Lian, Yong; Samudra, Ganesh S

    2015-01-01

    Due to internal voltage amplification induced by the negative capacitance of ferroelectrics, the metal–ferroelectric–metal–insulator–semiconductor (MFMIS) FET has been widely investigated to explore its potential application in low power devices. Based on Landau theory and stability criterion, a simulation program is implemented and MFMIS structure is quantitatively analyzed. The results show that it can be appropriately designed for both integrated circuits and memory devices by tuning capacitances contributed by MOSFET dielectric stack and ferroelectrics. Our simulation results on electrical characteristics of ferroelectric devices agree well with both quasi-static and dynamic experimental observations. The influence of the ferroelectric/dielectric layer thickness and area as well as temperature on hysteretic polarization-electric field characteristic of a ferroelectric are successfully explained. For a C–V loop sweeping over the gate voltage in MFMIS, possible asymmetry in the accessible negative capacitance region is also interpreted. Moreover, experimentally observed reduction in the equivalent capacitance of the ferroelectric–dielectric bilayer at high frequency is confirmed by Landau–Khalatnikov theory based simulation. Our work provides a more complete and explicit analytical treatment to understand the effect of negative capacitance of a ferroelectric on device performance. (paper)

  1. Predictions of the near edge transport shortfall in DIII-D L-mode plasmas using the trapped gyro-Landau-fluid model

    Energy Technology Data Exchange (ETDEWEB)

    Kinsey, J. E. [CompX, P.O. Box 2672, Del Mar, California 92014 (United States); Staebler, G. M.; Candy, J.; Petty, C. C.; Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Rhodes, T. L. [Physics Department and PSTI, University of California, Los Angeles, California 90095 (United States)

    2015-01-15

    Previous studies of DIII-D L-mode plasmas have shown that a transport shortfall exists in that our current models of turbulent transport can significantly underestimate the energy transport in the near edge region. In this paper, the Trapped Gyro-Landau-Fluid (TGLF) drift wave transport model is used to simulate the near edge transport in a DIII-D L-mode experiment designed to explore the impact of varying the safety factor on the shortfall. We find that the shortfall systematically increases with increasing safety factor and is more pronounced for the electrons than for the ions. Within the shortfall dataset, a single high current case has been found where no transport shortfall is predicted. Reduced neutral beam injection power has been identified as the key parameter separating this discharge from other discharges exhibiting a shortfall. Further analysis shows that the energy transport in the L-mode near edge region is not stiff according to TGLF. Unlike the H-mode core region, the predicted temperature profiles are relatively more responsive to changes in auxiliary heating power. In testing the fidelity of TGLF for the near edge region, we find that a recalibration of the collision model is warranted. A recalibration improves agreement between TGLF and nonlinear gyrokinetic simulations performed using the GYRO code with electron-ion collisions. The recalibration only slightly impacts the predicted shortfall.

  2. Pulsating hydrodynamic instability and thermal coupling in an extended Landau/Levich model of liquid-propellant combustion. 2. Viscous analysis

    Energy Technology Data Exchange (ETDEWEB)

    Stephen B. Margolis

    2000-01-01

    A pulsating form of hydrodynamic instability has recently been shown to arise during liquid-propellant deflagration in those parameter regimes where the pressure-dependent burning rate is characterized by a negative pressure sensitivity. This type of instability can coexist with the classical cellular, or Landau, form of hydrodynamic instability, with the occurrence of either dependent on whether the pressure sensitivity is sufficiently large or small in magnitude. For the inviscid problem, it has been shown that when the burning rate is realistically allowed to depend on temperature as well as pressure, that sufficiently large values of the temperature sensitivity relative to the pressure sensitivity causes the pulsating form of hydrodynamic instability to become dominant. In that regime, steady, planar burning becomes intrinsically unstable to pulsating disturbances whose wavenumbers are sufficiently small. In the present work, this analysis is extended to the fully viscous case, where it is shown that although viscosity is stabilizing for intermediate and larger wavenumber perturbations, the intrinsic pulsating instability for small wavenumbers remains. Under these conditions, liquid-propellant combustion is predicted to be characterized by large unsteady cells along the liquid/gas interface.

  3. Inhomogeneous ordered states and translational nature of the gauge group in the Landau continuum theory: II. Applications of the general theory

    International Nuclear Information System (INIS)

    Braginsky, A. Ya.

    2007-01-01

    A group theory approach to description of phase transitions to an inhomogeneous ordered state, proposed in the preceding paper, is applied to two problems. First, a theory of the state of a liquid-crystalline smectic type-A phase under the action of uniaxial pressure is developed. Second, a model of strengthening in quasicrystals is constructed. According to the proposed approach, the so-called elastic dislocations always appear during the phase transitions in an inhomogeneous deformed state in addition to static dislocations, which are caused by peculiarities of the crystal growth or by other features in the prehistory of a sample. The density of static dislocations weakly depends on the external factors, whereas the density of elastic dislocations depends on the state. An analogy between the proposed theory of the inhomogeneous ordered state and the quantum-field theory of interaction between material fields is considered. On this basis, the phenomenological Ginzburg-Landau equation for the superconducting state is derived using the principle of locality of the transformation properties of the superconducting order parameter with respect to temporal translations

  4. Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal of Mn4 single-molecule magnets

    Science.gov (United States)

    Wernsdorfer, W.; Bhaduri, S.; Vinslava, A.; Christou, G.

    2005-12-01

    A Mn4 single-molecule magnet (SMM), with a well-isolated spin ground state of S=9/2 , is used as a model system to study Landau-Zener (LZ) tunneling in the presence of weak intermolecular dipolar and exchange interactions. The anisotropy constants D and B are measured with minor hysteresis loops. A transverse field is used to tune the tunnel splitting over a large range. Using the LZ and inverse LZ method, it is shown that these interactions play an important role in the tunnel rates. Three regions are identified: (i) at small transverse fields, tunneling is dominated by single tunnel transitions, (ii) at intermediate transverse fields, the measured tunnel rates are governed by reshuffling of internal fields, and (iii) at larger transverse fields, the magnetization reversal starts to be influenced by the direct relaxation process, and many-body tunnel events may occur. The hole digging method is used to study the next-nearest-neighbor interactions. At small external fields, it is shown that magnetic ordering occurs which does not quench tunneling. An applied transverse field can increase the ordering rate. Spin-spin cross-relaxations, mediated by dipolar and weak exchange interactions, are proposed to explain additional quantum steps.

  5. Landau quantization, Aharonov–Bohm effect and two-dimensional pseudoharmonic quantum dot around a screw dislocation

    International Nuclear Information System (INIS)

    Filgueiras, Cleverson; Rojas, Moises; Aciole, Gilson; Silva, Edilberto O.

    2016-01-01

    Highlights: • We derive the Schrödinger equation for an electron around a screw dislocation in the presence of an external magnetic field. • We consider the electron confined on an interface. • Modifications due to the screw dislocation on the light interband absorption coefficient and absorption threshold frequency. - Abstract: We investigate the influence of a screw dislocation on the energy levels and the wavefunctions of an electron confined in a two-dimensional pseudoharmonic quantum dot under the influence of an external magnetic field inside a dot and Aharonov–Bohm field inside a pseudodot. The exact solutions for energy eigenvalues and wavefunctions are computed as functions of applied uniform magnetic field strength, Aharonov–Bohm flux, magnetic quantum number and the parameter characterizing the screw dislocation, the Burgers vector. We investigate the modifications due to the screw dislocation on the light interband absorption coefficient and absorption threshold frequency. Two scenarios are possible, depending on if singular effects either manifest or not. We found that as the Burgers vector increases, the curves of frequency are pushed up towards of the growth of it. One interesting aspect which we have observed is that the Aharonov–Bohm flux can be tuned in order to cancel the screw effect of the model.

  6. Landau quantization, Aharonov–Bohm effect and two-dimensional pseudoharmonic quantum dot around a screw dislocation

    Energy Technology Data Exchange (ETDEWEB)

    Filgueiras, Cleverson, E-mail: cleverson.filgueiras@dfi.ufla.br [Departamento de Física, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000, Lavras, MG (Brazil); Rojas, Moises, E-mail: moises.leyva@dfi.ufla.br [Departamento de Física, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000, Lavras, MG (Brazil); Aciole, Gilson [Unidade Acadêmica de Física, Universidade Federal de Campina Grande, POB 10071, 58109-970, Campina Grande, PB (Brazil); Silva, Edilberto O., E-mail: edilberto.silva@ufma.br [Departamento de Física, Universidade Federal do Maranhão, 65085-580, São Luís, MA (Brazil)

    2016-11-25

    Highlights: • We derive the Schrödinger equation for an electron around a screw dislocation in the presence of an external magnetic field. • We consider the electron confined on an interface. • Modifications due to the screw dislocation on the light interband absorption coefficient and absorption threshold frequency. - Abstract: We investigate the influence of a screw dislocation on the energy levels and the wavefunctions of an electron confined in a two-dimensional pseudoharmonic quantum dot under the influence of an external magnetic field inside a dot and Aharonov–Bohm field inside a pseudodot. The exact solutions for energy eigenvalues and wavefunctions are computed as functions of applied uniform magnetic field strength, Aharonov–Bohm flux, magnetic quantum number and the parameter characterizing the screw dislocation, the Burgers vector. We investigate the modifications due to the screw dislocation on the light interband absorption coefficient and absorption threshold frequency. Two scenarios are possible, depending on if singular effects either manifest or not. We found that as the Burgers vector increases, the curves of frequency are pushed up towards of the growth of it. One interesting aspect which we have observed is that the Aharonov–Bohm flux can be tuned in order to cancel the screw effect of the model.

  7. Exact analytic solutions for Mikheyev-Smirnov-Wolfenstein level crossings

    International Nuclear Information System (INIS)

    Noetzold, D.

    1987-01-01

    An exact formula for the transition probability in level-crossing phenomena is derived for a general case, ranging from adiabatic to sudden crossings. This is done in the context of neutrino flavor oscillations for the Mikheyev-Smirnov-Wolfenstein (MSW) effect, where hitherto only numerical or approximate solutions were obtained. The matter density or level splitting is assumed to be governed by a hyperbolic-tangent function which, however, can change arbitrarily fast between two constant values. For example, in context of the MSW effect this furnishes a nice fit to the solar density determining the level crossing of solar neutrinos. In the quasiadiabatic limit the exact Landau-Zener factor can be read off, correcting some expressions obtained so far. Even in the opposite limit of a sudden level crossing a conversion is found, which can have far-reaching consequences for neutrino detection on Earth

  8. Kastenhof - museum in Landau. Kastenhof - Museum in Landau

    Energy Technology Data Exchange (ETDEWEB)

    Anon,

    1991-08-01

    When modifying the box-type court to a subsidiary museum of the prehistoric national compilation of Munich with multiple-purpose hall and a little restaurant, a considerable expenditure with regard to the preservation of monuments had to be done in order to uncover and keep the old built volumes. A low-temperature heating system as well as low-temperature oil/gas boiler were applied as heating system. The heating is realized via floor heating, plate heat exchanger for avoiding corrossions, hot-air heating, heating units and fan convectors. For energy saving an air-to-water heat pump was applied which can be used alternatively for heating or cooling. In addition, energy distribution and system control are treated by means of flowsheets. (BWI).

  9. Level shifts induced by a short-range potential

    International Nuclear Information System (INIS)

    Karnakov, B.M.; Mur, V.D.

    1984-01-01

    Formulas are derived which express the shifts of levels with energies Esub(n)sup((0)) << rsub(c)sup(-2) in a field Vsub(f)(r) induced by a short-range potential U(r) of radius rsub(c) in terms of the low energy scattering parameters (scattering length and effective radius) with a moment l in the potential. If the interaction between the particle and center is nonresonant, the method developed is identical to perturbation theory on the scattering length. The theory is extended to systems with random degeneracy (Vsub(f) is the Coulomb potential). Formulas describing quasi-intersection of terms are obtained for the case of resonance interaction with the center in a partial wave with l not equal to 0 when energetically close levels are present in both U and Vsub(f). Some features of the level shift are mentioned for the case when the level possesses an anomalously small coupling energy and its coresponding wave function becomes delocalized with decrease of the coupling energy to zero. The problem is discussed of the level shift when the potential Vsub(f) is a potential well surrounded by a weaklyt penetrable barrier. Some applications of the theory to a particle in the field of two short-range potentials or in the field of a short-range and Coulomb centers are considered. Formulas are also obtained for the shifts and widths of the Landau levels and of the shallow level with an arbitrary moment which perturbs the Landau levels

  10. Quantum driving of a two level system: quantum speed limit and superadiabatic protocols – an experimental investigation

    International Nuclear Information System (INIS)

    Malossi, N; Arimondo, E; Ciampini, D; Mannella, R; Bason, M G; Viteau, M; Morsch, O

    2013-01-01

    A fundamental requirement in quantum information processing and in many other areas of science is the capability of precisely controlling a quantum system by preparing a quantum state with the highest fidelity and/or in the fastest possible way. Here we present an experimental investigation of a two level system, characterized by a time-dependent Landau-Zener Hamiltonian, aiming to test general and optimal high-fidelity control protocols. The experiment is based on a Bose-Einstein condensate (BEC) loaded into an optical lattice, then accelerated, which provides a high degree of control over the experimental parameters. We implement generalized Landau-Zener sweeps, comparing them with the well-known linear Landau-Zener sweep. We drive the system from an initial state to a final state with fidelity close to unity in the shortest possible time (quantum brachistochrone), thus reaching the ultimate speed limit imposed by quantum mechanics. On the opposite extreme of the quantum control spectrum, the aim is not to minimize the total transition time but to maximize the adiabaticity during the time-evolution, the system being constrained to the adiabatic ground state at any time. We implement such transitionless superadiabatic protocols by an appropriate transformation of the Hamiltonian parameters. This transformation is general and independent of the physical system.

  11. Measurements of the superconducting fluctuations in optimally doped BaFe2−xNixAs2 under high magnetic fields: probing the 3D-anisotropic Ginzburg–Landau approach

    International Nuclear Information System (INIS)

    Rey, R I; Ramos-Álvarez, A; Carballeira, C; Mosqueira, J; Vidal, F; Salem-Sugui, S Jr.; Alvarenga, A D; Zhang, Rui; Luo, Huiqian

    2014-01-01

    The superconducting fluctuations well inside the normal state of Fe-based superconductors were experimentally studied through the in-plane paraconductivity in several high-quality, optimally doped BaFe 2−x Ni x As 2 crystals. These measurements were performed in magnetic fields with amplitudes up to 14 T, and different orientations relative to the c-axis of the crystals (θ=0 ∘ , 53 ∘ , and 90 ∘ ). The results allowed a stringent check of the applicability of a recently proposed Ginzburg–Landau approach for the fluctuating electrical conductivity of three-dimensional (3D) anisotropic materials in the presence of finite applied magnetic fields. (papers)

  12. Calculation of strained BaTiO3 with different exchange correlation functionals examined with criterion by Ginzburg-Landau theory, uncovering expressions by crystallographic parameters

    Science.gov (United States)

    Watanabe, Yukio

    2018-05-01

    In the calculations of tetragonal BaTiO3, some exchange-correlation (XC) energy functionals such as local density approximation (LDA) have shown good agreement with experiments at room temperature (RT), e.g., spontaneous polarization (PS), and superiority compared with other XC functionals. This is due to the error compensation of the RT effect and, hence, will be ineffective in the heavily strained case such as domain boundaries. Here, ferroelectrics under large strain at RT are approximated as those at 0 K because the strain effect surpasses the RT effects. To find effective XC energy functionals for strained BaTiO3, we propose a new comparison, i.e., a criterion. This criterion is the properties at 0 K given by the Ginzburg-Landau (GL) theory because GL theory is a thermodynamic description of experiments working under the same symmetry-constraints as ab initio calculations. With this criterion, we examine LDA, generalized gradient approximations (GGA), meta-GGA, meta-GGA + local correlation potential (U), and hybrid functionals, which reveals the high accuracy of some XC functionals superior to XC functionals that have been regarded as accurate. This result is examined directly by the calculations of homogenously strained tetragonal BaTiO3, confirming the validity of the new criterion. In addition, the data points of theoretical PS vs. certain crystallographic parameters calculated with different XC functionals are found to lie on a single curve, despite their wide variations. Regarding these theoretical data points as corresponding to the experimental results, analytical expressions of the local PS using crystallographic parameters are uncovered. These expressions show the primary origin of BaTiO3 ferroelectricity as oxygen displacements. Elastic compliance and electrostrictive coefficients are estimated. For the comparison of strained results, we show that the effective critical temperature TC under strain 1000 K from an approximate method combining ab initio

  13. Topological phase transition in the two-dimensional anisotropic Heisenberg model: A study using the Replica Exchange Wang-Landau sampling

    Science.gov (United States)

    Figueiredo, T. P.; Rocha, J. C. S.; Costa, B. V.

    2017-12-01

    Although the topological Berezinskii-Kosterlitz-Thouless transition was for the first time described by 40 years ago, it is still a matter of discussion. It has been used to explain several experiments in the most diverse physical systems. In contrast with the ordinary continuous phase transitions the BKT-transition does not break any symmetry. However, in some contexts it can easily be confused with other continuous transitions, in general due to an insufficient data analysis. The two-dimensional XY (or sometimes called planar rotator) spin model is the fruit fly model describing the BKT transition. As demonstrated by Bramwell and Holdsworth (1993) the finite-size effects are more important in two-dimensions than in others due to the logarithmic system size dependence of the properties of the system. Closely related is the anisotropic two dimensional Heisenberg model (AH). Although they have the same Hamiltonian the spin variable in the former has only two degrees of freedom while the AH has three. Many works treat the AH model as undergoing a transition in the same universality class as the XY model. However, its characterization as being in the BKT class of universality deserve some investigation. This paper has two goals. First, we describe an analytical evidence showing that the AH model is in the BKT class of universality. Second, we make an extensive simulation, using the numerical Replica Exchange Wang-Landau method that corroborate our analytical calculations. From our simulation we obtain the BKT transition temperature as TBKT = 0 . 6980(10) by monitoring the susceptibility, the two point correlation function and the helicity modulus. We discuss the misuse of the fourth order Binder's cumulant to locate the transition temperature. The specific heat is shown to have a non-critical behavior as expected in the BKT transition. An analysis of the two point correlation function at low temperature, C(r) ∝r - η(T), shows that the exponent, η, is consistent

  14. Nuclear magnetism of liquid {sup 3}He: new determination of the Landau parameter F{sub 0}{sup a}; Magnetisme nucleaire de l'{sup 3}He liquide: nouvelle determination du parametre de Landau F{sup a}{sub 0}

    Energy Technology Data Exchange (ETDEWEB)

    Goudon, V

    2006-10-15

    He{sup 3} is a liquid Fermi model, isotropic, with an attainable Fermi temperature and the interaction between atoms can be controlled by changing the pressure of the liquid. In this document, we present accurate NMR measurements of the nuclear magnetic susceptibility of liquid He{sup 3} as a function of temperature and pressure. The emphasis has been placed on reliable thermometry and on He{sup 3} pressure measurements directly in the cell to increase the measuring range until solidification, and an accurate characterization of the NMR spectrometer. Our measurements give an effective Fermi temperature 5% lower than former results. The Landau parameter F{sub 0}{sup a} depends on the effective mass, which is determined by specific heat measurements, and consequently on the temperature scale. The re-analysis of the specific heat measurements with the PLTS-2000 temperature scale yields an effective mass increase of 4.5%. In this document, F{sub 0}{sup a} is determined for 2 temperature scales (PLTS-2000 and Greywall). Contrarily to former measurements, the F{sub 0}{sup a} density dependence does not show any saturation at high pressures. (author)

  15. Efficient positive, conservative, Maxwellian preserving and implicit difference schemes for the 1-D isotropic Fokker-Planck-Landau equation; Schemas positifs, implicites, conservant l'energie et les etats d'equilibre pour l'equation de Fokker-Planck-Landau isotrope

    Energy Technology Data Exchange (ETDEWEB)

    Buet, Ch. [CEA Bruyeres-le-Chatel, Dept. Sciences de la Simulation et de l' Information, Service Numerique Environnement et Constantes, 91 (France); Le Thanh, K.C. [CEA Bruyeres-le-Chatel, Service Physique des Plasmas et Electromagnetisme, 91 (France). Dept. de Physique Theorique et Appliquee

    2008-07-01

    The aim of this paper is to describe the discretization of the Fokker-Planck-Landau (FPL) collision term in the isotropic case, which models the self-collision for the electrons when they are totally isotropized by heavy particles background such as ions. The discussion focuses on schemes, which could preserve positivity, mass, energy and Maxwellian equilibrium. The Chang and Cooper method is widely used by plasma's physicists for the FPL equation (and for Fokker-Planck type equations). We present a new variant that is both positive and conservative contrary to the existing one's. We propose also a non Chang and Cooper 'type scheme on non-uniform grid, which is also both positive, conservative and equilibrium state preserving contrary to existing one's. The case of Coulombian potential is emphasized. We address also the problem of the time discretization. In particular we show how to recast some implicit methods to get band diagonal system and to solve it by direct method with a linear cost. (authors)

  16. On the questions of the nuclear level density and the E1 photon strength functions

    International Nuclear Information System (INIS)

    Mughabghab, S.F.; Dunford, C.L.

    1999-01-01

    New results were derived from average level spacings of neutron resonances for the spin dispersion parameter of the nuclear level density, which demonstrated the influence of shell effects, as well as the interplay of nucleon pairing correlations for nuclei in the mass range from 29 Si to 241 Pu. The volume and surface components of the nuclear level density parameter, as well as the shell-damping factor, were determined as, a v = 0.076 ± 0.009 MeV -1 , a s = 0.180 ± 0.047 MeV -1 , and y 0 = 0.047 ± 0.04 MeV±, respectively. The effective nucleon mass at the Fermi surface is derived as m*/m = 1.09 ± 0.13. New evidence is presented for a dipole-quadrupole interaction term in the primary E1 transitions of average resonance capture data. This evidence is obtained by testing a proposed generalized Landau Fermi liquid model for spherical and deformed nuclei, which includes the effect of the dipole-quadrupole interaction. The Landau-Migdal interaction constant and the effective nucleon mass, are determined as F 0 prime = 1.49 ± 0.08, and m*/m=1.04 ± 0.07, respectively

  17. Parallel solution of the time-dependent Ginzburg-Landau equations and other experiences using BlockComm-Chameleon and PCN on the IBM SP, Intel iPSC/860, and clusters of workstations

    International Nuclear Information System (INIS)

    Coskun, E.

    1995-09-01

    Time-dependent Ginzburg-Landau (TDGL) equations are considered for modeling a thin-film finite size superconductor placed under magnetic field. The problem then leads to the use of so-called natural boundary conditions. Computational domain is partitioned into subdomains and bond variables are used in obtaining the corresponding discrete system of equations. An efficient time-differencing method based on the Forward Euler method is developed. Finally, a variable strength magnetic field resulting in a vortex motion in Type II High T c superconducting films is introduced. The authors tackled the problem using two different state-of-the-art parallel computing tools: BlockComm/Chameleon and PCN. They had access to two high-performance distributed memory supercomputers: the Intel iPSC/860 and IBM SP1. They also tested the codes using, as a parallel computing environment, a cluster of Sun Sparc workstations

  18. Alteration of the ground state by external magnetic fields. [External field, coupling constant ratio, static tree level approximation

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, B J; Shepard, H K [New Hampshire Univ., Durham (USA). Dept. of Physics

    1976-03-22

    By fully exploiting the mathematical and physical analogy to the Ginzburg-Landau theory of superconductivity, a complete discussion of the ground state behavior of the four-dimensional Abelian Higgs model in the static tree level approximation is presented. It is shown that a sufficiently strong external magnetic field can alter the ground state of the theory by restoring a spontaneously broken symmetry, or by creating a qualitatively different 'vortex' state. The energetically favored ground state is explicitly determined as a function of the external field and the ratio between coupling constants of the theory.

  19. Solutions of the two-level problem in terms of biconfluent Heun functions

    Energy Technology Data Exchange (ETDEWEB)

    Ishkhanyan, Artur [Engineering Center of Armenian National Academy of Sciences, Ashtarak (Armenia)]. E-mail: artur@ec.sci.am; Suominen, Kalle-Antti [Helsinki Institute of Physics, Helsinki (Finland); Department of Applied Physics, University of Turku, Turku (Finland)

    2001-08-17

    Five four-parametric classes of quantum mechanical two-level models permitting solutions in terms of the biconfluent Heun function are derived. Three of these classes are generalizations of the well known classes of Landau-Zener, Nikitin and Crothers. It is shown that two other classes describe super- and sublinear and essentially nonlinear level crossings, as well as processes with three crossing points. In particular, these classes include two-level models where the field amplitude is constant and the detuning varies as {delta}{sub 0}t+{delta}{sub 2}t{sup 3} or {approx}t{sup 1/3}. For the essentially nonlinear cubic-crossing model, {delta}{sub t}{approx}{delta}{sub 2}t{sup 3}, the general solution of the two-level problem is shown to be expressed as series of confluent hypergeometric functions. (author)

  20. Lathe leveler

    Energy Technology Data Exchange (ETDEWEB)

    Lovelady, III, Michael W.J.

    2018-03-06

    A lathe leveler for centering a cutting tool in relation to a cylindrical work piece includes a first leveling arm having a first contact point disposed adjacent a distal end of the first leveling arm, a second leveling arm having a second contact point disposed adjacent a distal end of the second leveling arm, a leveling gage, and a leveling plate having a cutting tool receiving surface positioned parallel to a horizontal axis of the leveling gage and on a same plane as a midpoint of the first contact point and the second contact point. The leveling arms and leveling plate are dimensioned and configured such that the cutting tool receiving surface is centered in relation to the work piece when the first and second contact points are in contact with one of the inner surface and outer surface of the cylindrical work piece and the leveling gage is centered.

  1. Cortisol level

    Science.gov (United States)

    ... enable JavaScript. The cortisol blood test measures the level of cortisol in the blood. Cortisol is a ... in the morning. This is important, because cortisol level varies throughout the day. You may be asked ...

  2. Triglyceride level

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003493.htm Triglyceride level To use the sharing features on this page, please enable JavaScript. The triglyceride level is a blood test to measure the amount ...

  3. Level 1 - level 2 interface

    International Nuclear Information System (INIS)

    Boneham, P.

    2003-01-01

    The Plant Damage States (PDS) are the starting point for the level 2 analysis. A PDS is group of core damage sequences that are expected to have similar severe accident progressions. In this paper an overview of Level 1/Level 2 interface, example PDS parameters, example PDS definitions using codes and example Bridge Tree are presented. PDS frequency calculation (identification of sequences for each PDS in level 1,split some CD sequences which have different level 2 progressions), code calculations providing support for grouping decisions and timings as well as PDS frequencies and definitions input to level 2 are also discussed

  4. Estimation of the magnetic entropy change by means of Landau theory and phenomenological model in La0.6Ca0.2 Sr0.2MnO3/Sb2O3 ceramic composites

    Science.gov (United States)

    Nasri, M.; Dhahri, E.; Hlil, E. K.

    2018-06-01

    In this paper, magnetocaloric properties of La0.6Ca0.2Sr0.2MnO3/Sb2O3 oxides have been investigated. The composite samples were prepared using the conventional solid-state reaction method. The second-order phase transition can be testified with the positive slope in Arrott plots. An excellent agreement has been found between the -ΔSM values estimated by Landau theory and those obtained using the classical Maxwell relation. The field dependence of the magnetic entropy change analysis shows a power law dependence,|ΔSM|≈Hn , with n(TC) = 0.65. Moreover, the scaling analysis of magnetic entropy change exhibits that ΔSM(T) curves collapse into a single universal curve, indicating that the observed paramagnetic to ferromagnetic phase transition is an authentic second-order phase transition. The maximum value of magnetic entropy change of composites is found to decrease slightly with the further increasing of Sb2O3 concentration. A phenomenological model was used to predict magnetocaloric properties of La0.6Ca0.2Sr0.2MnO3/Sb2O3 composites. The theoretical calculations are compared with the available experimental data.

  5. Landau theory and giant room-temperature barocaloric effect in MF3 metal trifluorides

    Energy Technology Data Exchange (ETDEWEB)

    Corrales-Salazar, A. [Univ. of Costa Rica, San Jose (Costa Rica); Brierley, R. T. [Yale Univ., New Haven, CT (United States); Littlewood, P. B. [Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Guzmán-Verri, G. G. [Univ. of Costa Rica, San Jose (Costa Rica); Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-10-17

    The structural phase transitions of MF3 (M = Al, Cr, V, Fe, Ti, Sc) metal trifluorides are studied within a simple Landau theory consisting of tilts of rigid MF6 octahedra associated with soft antiferrodistortive optic modes that are coupled to long-wavelength strain generating acoustic phonons. We calculate the temperature and pressure dependence of several quantities such as the spontaneous distortions, volume expansion, and shear strains as well as T - P phase diagrams. By contrasting our model to experiments we quantify the deviations from mean-field behavior and find that the tilt fluctuations of the MF6 octahedra increase with metal cation size. We apply our model to predict giant barocaloric effects in Sc-substituted TiF3 of up to about 15 JK-1 kg-1 for modest hydrostatic compressions of 0.2GPa. The effect extends over a wide temperature range of over 140K (including room temperature) due to a large predicted rate, dTc/dP = 723K GPa-1, which exceeds those of typical barocaloric materials. Our results suggest that open lattice frameworks such as the trifluorides are an attractive platform to search for giant barocaloric effects.

  6. Level densities

    International Nuclear Information System (INIS)

    Ignatyuk, A.V.

    1998-01-01

    For any applications of the statistical theory of nuclear reactions it is very important to obtain the parameters of the level density description from the reliable experimental data. The cumulative numbers of low-lying levels and the average spacings between neutron resonances are usually used as such data. The level density parameters fitted to such data are compiled in the RIPL Starter File for the tree models most frequently used in practical calculations: i) For the Gilber-Cameron model the parameters of the Beijing group, based on a rather recent compilations of the neutron resonance and low-lying level densities and included into the beijing-gc.dat file, are chosen as recommended. As alternative versions the parameters provided by other groups are given into the files: jaeri-gc.dat, bombay-gc.dat, obninsk-gc.dat. Additionally the iljinov-gc.dat, and mengoni-gc.dat files include sets of the level density parameters that take into account the damping of shell effects at high energies. ii) For the backed-shifted Fermi gas model the beijing-bs.dat file is selected as the recommended one. Alternative parameters of the Obninsk group are given in the obninsk-bs.dat file and those of Bombay in bombay-bs.dat. iii) For the generalized superfluid model the Obninsk group parameters included into the obninsk-bcs.dat file are chosen as recommended ones and the beijing-bcs.dat file is included as an alternative set of parameters. iv) For the microscopic approach to the level densities the files are: obninsk-micro.for -FORTRAN 77 source for the microscopical statistical level density code developed in Obninsk by Ignatyuk and coworkers, moller-levels.gz - Moeller single-particle level and ground state deformation data base, moller-levels.for -retrieval code for Moeller single-particle level scheme. (author)

  7. Two-level systems driven by large-amplitude fields

    Science.gov (United States)

    Nori, F.; Ashhab, S.; Johansson, J. R.; Zagoskin, A. M.

    2009-03-01

    We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition, (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems. S. Ashhab, J.R. Johansson, A.M. Zagoskin, F. Nori, Two-level systems driven by large-amplitude fields, Phys. Rev. A 75, 063414 (2007). S. Ashhab et al, unpublished.

  8. Evolution of superpositions of quantum states through a level crossing

    International Nuclear Information System (INIS)

    Torosov, B. T.; Vitanov, N. V.

    2011-01-01

    The Landau-Zener-Stueckelberg-Majorana (LZSM) model is widely used for estimating transition probabilities in the presence of crossing energy levels in quantum physics. This model, however, makes the unphysical assumption of an infinitely long constant interaction, which introduces a divergent phase in the propagator. This divergence remains hidden when estimating output probabilities for a single input state insofar as the divergent phase cancels out. In this paper we show that, because of this divergent phase, the LZSM model is inadequate to describe the evolution of pure or mixed superposition states across a level crossing. The LZSM model can be used only if the system is initially in a single state or in a completely mixed superposition state. To this end, we show that the more realistic Demkov-Kunike model, which assumes a hyperbolic-tangent level crossing and a hyperbolic-secant interaction envelope, is free of divergences and is a much more adequate tool for describing the evolution through a level crossing for an arbitrary input state. For multiple crossing energies which are reducible to one or more effective two-state systems (e.g., by the Majorana and Morris-Shore decompositions), similar conclusions apply: the LZSM model does not produce definite values of the populations and the coherences, and one should use the Demkov-Kunike model instead.

  9. Whistlers, helicons, and lower hybrid waves: The physics of radio frequency wave propagation and absorption for current drive via Landau damping

    International Nuclear Information System (INIS)

    Pinsker, R. I.

    2015-01-01

    This introductory-level tutorial article describes the application of plasma waves in the lower hybrid range of frequencies (LHRF) for current drive in tokamaks. Wave damping mechanisms in a nearly collisionless hot magnetized plasma are briefly described, and the connections between the properties of the damping mechanisms and the optimal choices of wave properties (mode, frequency, wavelength) are explored. The two wave modes available for current drive in the LHRF are described and compared. The terms applied to these waves in different applications of plasma physics are elucidated. The character of the ray paths of these waves in the LHRF is illustrated in slab and toroidal geometries. Applications of these ideas to experiments in the DIII-D tokamak are discussed

  10. Two-level systems driven by large-amplitude fields

    International Nuclear Information System (INIS)

    Ashhab, S.; Johansson, J. R.; Zagoskin, A. M.; Nori, Franco

    2007-01-01

    We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems

  11. Microscopic description of dissipative dynamics of a level-crossing transition

    Energy Technology Data Exchange (ETDEWEB)

    Scala, M.; Militello, B.; Messina, A. [Dipartimento di Fisica dell' Universita di Palermo, Via Archirafi 36, I-90123 Palermo (Italy); Vitanov, N. V. [Department of Physics, Sofia University, 5 James Bourchier Boulevard, BG-1164 Sofia (Bulgaria)

    2011-08-15

    We analyze the effect of a dissipative bosonic environment on the Landau-Zener-Stueckelberg-Majorana (LZSM) level crossing model by using a microscopic approach to derive the relevant master equation. For an environment at zero temperature and weak dissipation, our microscopic approach confirms the independence of the survival probability on the decay rate that has been predicted earlier by the simple phenomenological LZSM model. For strong decay the microscopic approach predicts a notable increase of the survival probability, which signals dynamical decoupling of the initial state. Unlike the phenomenological model, our approach makes it possible to study the dependence of the system dynamics on the temperature of the environment. In the limit of very high temperature we find that the dynamics is characterized by a very strong dynamical decoupling of the initial state--the temperature-induced quantum Zeno effect.

  12. Level set method for optimal shape design of MRAM core. Micromagnetic approach

    International Nuclear Information System (INIS)

    Melicher, Valdemar; Cimrak, Ivan; Keer, Roger van

    2008-01-01

    We aim at optimizing the shape of the magnetic core in MRAM memories. The evolution of the magnetization during the writing process is described by the Landau-Lifshitz equation (LLE). The actual shape of the core in one cell is characterized by the coefficient γ. Cost functional f=f(γ) expresses the quality of the writing process having in mind the competition between the full-select and the half-select element. We derive an explicit form of the derivative F=∂f/∂γ which allows for the use of gradient-type methods for the actual computation of the optimized shape (e.g., steepest descend method). The level set method (LSM) is employed for the representation of the piecewise constant coefficient γ

  13. On Landau Vlasov simulations of giant resonances

    International Nuclear Information System (INIS)

    Pi, M.; Schuck, P.; Suraud, E.; Gregoire, C.; Remaud, B.; Sebille, F.

    1987-05-01

    We present VUU calculations of giant resonances obtained in energetic heavy ion collisions. Also is considered the case of the giant dipole in 40 Ca and the possibility of studying the effects of rotation on such collective modes

  14. Biohydrology research after Landau 2013 conference

    Czech Academy of Sciences Publication Activity Database

    Lichner, Ľ.; Cerdà, A.; Rajkai, K.; Tesař, Miroslav

    2014-01-01

    Roč. 62, č. 4 (2014), s. 253-257 ISSN 0042-790X Institutional support: RVO:67985874 Keywords : biohydrology * hydrological research * biological and hydrological systems * hydrological processes Subject RIV: DA - Hydrology ; Limnology Impact factor: 1.486, year: 2014

  15. Lev D. Landau: his life and work

    International Nuclear Information System (INIS)

    Janouch, F.

    1979-01-01

    A biographical portrait of the Soviet theoretical physicist as presented at a CERN Colloquium in June 1978. A selected list of 39 scientific papers, and 18 references to his work in books and articles, are appended. (Auth.)

  16. Landau-Migdal parameters and pion condensation

    Energy Technology Data Exchange (ETDEWEB)

    Tatsumi, Toshitaka [Department of Physics, Kyoto Univ., Kyoto (Japan)

    1999-08-01

    The possibility of pion condensation, one of the long-standing issues in nuclear physics, is reexamined in the light of the recent experimental data on the giant Gamow-Teller resonance. The experimental result tells that the coupling of nucleon particle-hole states with {delta} isobar-hole states in the spin-isospin channel should be weaker than that previously believed. It, in turn, implies that nuclear matter has the making of pion condensation at low densities. The possibility and implications of pion condensation in the heavy-ion collisions and neutron stars should be seriously reconsidered. (author)

  17. Landau superfluids as nonequilibrium stationary states

    International Nuclear Information System (INIS)

    Wreszinski, Walter F.

    2015-01-01

    We define a superfluid state to be a nonequilibrium stationary state (NESS), which, at zero temperature, satisfies certain metastability conditions, which physically express that there should be a sufficiently small energy-momentum transfer between the particles of the fluid and the surroundings (e.g., pipe). It is shown that two models, the Girardeau model and the Huang-Yang-Luttinger (HYL) model, describe superfluids in this sense and, moreover, that, in the case of the HYL model, the metastability condition is directly related to Nozières’ conjecture that, due to the repulsive interaction, the condensate does not suffer fragmentation into two (or more) parts, thereby assuring its quantum coherence. The models are rigorous examples of NESS in which the system is not finite, but rather a many-body system

  18. Yang--Mills vacua in Landau gauge

    International Nuclear Information System (INIS)

    Frampton, P.H.; Hagiwara, T.; Palmer, W.F.; Pinsky, S.S.

    1977-01-01

    A vacuum gauge field A/sub μ//sup a/ for Yang-Mills theory is constructed; this field is pure vacuum (A/sub μ//sup a/ = 0) at the origin, approaches at large distances, the Belavin-Polyakov-Schwartz-Tyupkin pseudo-particle, and satisfies delta/sub μ/A/sub μ//sup a/ = 0 everywhere. The net topological charge is zero, and there is a Dirac-like string terminating at the origin

  19. Birationality and Landau-Ginzburg Models

    Science.gov (United States)

    Clarke, Patrick

    2017-08-01

    We introduce a new technique for approaching birationality questions that arise in the mirror symmetry of complete intersections in toric varieties. As an application we answer affirmatively and conclusively the question of Batyrev-Nill (Integer points in polyhedra—geometry, number theory, representation theory, algebra, optimization, statistics, volume 452 of Contemporary mathematics. American Mathematical Society, Providence, pp 35-66, 2008) about the birationality of Calabi-Yau families associated to multiple mirror nef-partitions. This completes the progress in this direction made by Li's breakthrough (Li in Adv Math 299:71-107, 2016). In the process, we obtain results in the theory of Borisov's nef-partitions (Borisov in Towards the mirror symmetry for Calabi-Yau complete intersections in Gorenstein toric Fano varieties, 1993. arXiv:alg-geom/9310001 ) and provide new insight into the geometric content of the multiple mirror phenomenon.

  20. Plasmonic Landau damping in active environments

    Science.gov (United States)

    Thakkar, Niket; Montoni, Nicholas P.; Cherqui, Charles; Masiello, David J.

    2018-03-01

    Optical manipulation of charge on the nanoscale is of fundamental importance to an array of proposed technologies from selective photocatalysis to nanophotonics. Open plasmonic systems where collective electron oscillations release energy and charge to their environments offer a potential means to this end as plasmons can rapidly decay into energetic electron-hole pairs; however, isolating this decay from other plasmon-environment interactions remains a challenge. Here we present an analytic theory of noble-metal nanoparticles that quantitatively models plasmon decay into electron-hole pairs, demonstrates that this decay depends significantly on the nanoparticle's dielectric environment, and disentangles this effect from competing decay pathways. Using our approach to incorporate embedding material and substrate effects on plasmon-electron interaction, we show that predictions from the model agree with four separate experiments. Finally, examination of coupled nanoparticle-emitter systems further shows that the hybridized in-phase mode more efficiently decays to photons whereas the out-of-phase mode more efficiently decays to electron-hole pairs, offering a strategy to tailor open plasmonic systems for charge manipulation.