WorldWideScience

Sample records for field induced orderings

  1. MAGNETIC FIELD INDUCED FIRST-ORDER TRANSITIONS IN DYSPROSIUM ORTHOFERRITE

    OpenAIRE

    Eremenko, V.; Gnatchenko, S.; Kharchenko, N.; Lebedev, P.; Piotrowski, K; Szymczak, H.; Szymczak, R.

    1988-01-01

    New type of magnetic first-order phase transition induced by external magnetic field applied in the ab-plane in DyFeO3 is investigated using different magnetooptic techniques. The phenomenological model of this transition is proposed. The phase diagram in H-T plane has been obtained for various H orientation in the ab-plane.

  2. Studies on magnetic-field-induced first-order transitions

    Indian Academy of Sciences (India)

    P Chaddah

    2006-07-01

    We shall discuss magnetization and transport measurements in materials exhibiting a broad first-order transition. The phase transitions would be caused by varying magnetic field as well as temperature, and we concentrate on ferro- to antiferromagnetic transitions in magnetic materials. We distinguish between metastable supercooled phases and metastable glassy phase.

  3. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Science.gov (United States)

    Noreen, Saima

    2013-01-01

    This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  4. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Directory of Open Access Journals (Sweden)

    Saima Noreen

    Full Text Available This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  5. Field-induced spin-density wave beyond hidden order in URu2Si2

    Science.gov (United States)

    Knafo, W.; Duc, F.; Bourdarot, F.; Kuwahara, K.; Nojiri, H.; Aoki, D.; Billette, J.; Frings, P.; Tonon, X.; Lelièvre-Berna, E.; Flouquet, J.; Regnault, L.-P.

    2016-10-01

    URu2Si2 is one of the most enigmatic strongly correlated electron systems and offers a fertile testing ground for new concepts in condensed matter science. In spite of >30 years of intense research, no consensus on the order parameter of its low-temperature hidden-order phase exists. A strong magnetic field transforms the hidden order into magnetically ordered phases, whose order parameter has also been defying experimental observation. Here, thanks to neutron diffraction under pulsed magnetic fields up to 40 T, we identify the field-induced phases of URu2Si2 as a spin-density-wave state. The transition to the spin-density wave represents a unique touchstone for understanding the hidden-order phase. An intimate relationship between this magnetic structure, the magnetic fluctuations and the Fermi surface is emphasized, calling for dedicated band-structure calculations.

  6. Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Mark, J. Abraham Hudson, E-mail: a.john.peter@gmail.com; Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, SSM Institute of Engineering and Technology, Dindigul-624002 (India)

    2014-04-24

    Third order susceptibility of third order harmonic generation is investigated in a Zn{sub 0.1}Mg{sub 0.9}Se/Zn{sub 0.8}Mg{sub 0.2}Se/Zn{sub 0.1}Mg{sub 0.9}Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

  7. Mixed Convection Peristaltic Flow of Third Order Nanofluid with an Induced Magnetic Field

    OpenAIRE

    Saima Noreen

    2013-01-01

    This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quant...

  8. Relativistic Néel-Order Fields Induced by Electrical Current in Antiferromagnets

    KAUST Repository

    Železný, J.

    2014-10-06

    We predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn2Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

  9. Magnetic field induced switching of the antiferromagnetic order parameter in thin films of magnetoelectric chromia

    Science.gov (United States)

    Fallarino, Lorenzo; Berger, Andreas; Binek, Christian

    2015-02-01

    A Landau-theoretical approach is utilized to model the magnetic field induced reversal of the antiferromagnetic order parameter in thin films of magnetoelectric antiferromagnets. A key ingredient of this peculiar switching phenomenon is the presence of a robust spin polarized state at the surface of the antiferromagnetic films. Surface or boundary magnetization is symmetry allowed in magnetoelectric antiferromagnets and experimentally established for chromia thin films. It couples rigidly to the antiferromagnetic order parameter and its Zeeman energy creates a pathway to switch the antiferromagnet via magnetic field application. In the framework of a minimalist Landau free energy expansion, the temperature dependence of the switching field and the field dependence of the transition width are derived. Least-squares fits to magnetometry data of (0001 ) textured chromia thin films strongly support this model of the magnetic reversal mechanism.

  10. Magnetic field induced 1st order transitions: Recent studies, and some new concepts

    Science.gov (United States)

    Chaddah, P.

    2015-05-01

    Phase transitions are caused by varying temperature, or pressure, or magnetic field. The observation of 1st order magneto-structural transitions has created application possibilities based on magnetoresistance, magnetocaloric effect, magnetic shape memory effect, and magneto-dielectric effect. Magnetic field induced transitions, and phase coexistence of competing magnetic phases down to the lowest temperature, gained prominence over a decade ago with theoretical models suggesting that the ground state is not homogeneous. Researchers at Indore pushed an alternative view that this phase coexistence could be due to glasslike "kinetic arrest" of a disorder-broadened first-order magnetic transition between two states with long-range magnetic order, resulting in phase coexistence down to the lowest temperatures. The CHUF (cooling and heating in unequal field) protocol created at Indore allows the observation of `devitrification', followed by `melting'. I show examples of measurements establishing kinetic arrest in various materials, emphasizing that glasslike arrest of 1st order magnetic transitions may be as ubiquitous as glass formation following the arrest of 1st order structural transitions.

  11. Boundary field induced first-order transition in the 2D Ising model: exact study

    Energy Technology Data Exchange (ETDEWEB)

    Clusel, Maxime [Institut Laue-Langevin, 6 rue Horowitz BP156 X, 38042 Grenoble Cedex (France); Fortin, Jean-Yves [Laboratoire Poncelet, 119002, Bolshoy Vlasyevskiy Pereulok 11, Moscow (Russian Federation)

    2006-02-03

    We present in this paper an exact study of a first-order transition induced by an inhomogeneous boundary magnetic field in the 2D Ising model. From a previous analysis of the interfacial free energy in the discrete case (Clusel and Fortin 2005 J. Phys. A: Math. Gen. 38 2849) we identify, using an asymptotic expansion in the thermodynamic limit, the line of transition that separates the regime where the interface is localized near the boundary from the one where it is propagating inside the bulk. In particular, the transition line has a strong dependence on the aspect ratio of the lattice.

  12. A boundary field induced first-order transition in the 2D Ising model: numerical study

    Energy Technology Data Exchange (ETDEWEB)

    Bittner, Elmar; Janke, Wolfhard [Institut fuer Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universitaet Leipzig, Postfach 100 920, D-04009 Leipzig (Germany)], E-mail: elmar.bittner@itp.uni-leipzig.de, E-mail: Wolfhard.janke@itp.uni-leipzig.de

    2008-10-03

    In a recent paper, Clusel and Fortin (2006 J. Phys. A: Math. Gen. 39 995) presented an analytical study of a first-order transition induced by an inhomogeneous boundary magnetic field in the two-dimensional Ising model. They identified the transition that separates the regime where the interface is localized near the boundary from that where it propagates inside the bulk. Inspired by these results, we measured the interface tension by using multimagnetic simulations combined with parallel tempering to determine the phase transition and the location of the interface. Our results are in very good agreement with the theoretical predictions. Furthermore, we studied the spin-spin correlation function for which no analytical results are available.

  13. Electric Field-Induced Second Order Nonlinear Optical Effects in Silicon Waveguides

    CERN Document Server

    Timurdogan, E; Watts, M R

    2016-01-01

    The demand for nonlinear effects within a silicon platform to support photonic circuits requiring phase-only modulation, frequency doubling, and/or difference frequency generation, is becoming increasingly clear. However, the symmetry of the silicon crystal inhibits second order optical nonlinear susceptibility, $\\chi^{(2)}$. Here, we show that the crystalline symmetry is broken when a DC field is present, inducing a $\\chi^{(2)}$ in a silicon waveguide that is proportional to the large $\\chi^{(3)}$ of silicon. First, Mach-Zehnder interferometers using the DC Kerr effect optical phase shifters in silicon ridge waveguides with p-i-n junctions are demonstrated with a $V_{\\pi}L$ of $2.4Vcm$ in telecom bands $({\\lambda}_{\\omega}=1.58{\\mu}m)$ without requiring to dope the silicon core. Second, the pump and second harmonic modes in silicon ridge waveguides are quasi-phase matched when the magnitude, spatial distribution of the DC field and $\\chi^{(2)}$ are controlled with p-i-n junctions. Using these waveguides, sec...

  14. NMR investigation of field-induced magnetic order in barium manganese oxide

    Science.gov (United States)

    Suh, Steve

    As early as 1956, Matsubara and Matsuda found an exact correspondence between a lattice gas model and a quantum antiferromagnet model[1]. They paved the way for the language of integer spin boson particles to be used interchangeably with quantum magnetic insulator systems in a general manner. For example, an analogy of density of bosons is found in magnetization, and analogy of chemical potential is found in external field. Just as there exist corresponding parameters between these two seemingly unrelated systems, quantum magnets can also exhibit consequences of Boson particle systems. In particular, spin-ordering transition in quantum magnets can be interpreted as Bose-Einstein condensate (BEC) transition in Boson particle framework. Direct observation of BEC in Boson particles has been realized in 4He's superfluid transition and in dilute atomic gas clouds cooled to very low temperatures[2]. In this thesis, we try to realize and analyze BEC transition through field-induced spin-ordering transition in the S = 1 antiferromagnetic dimer system, Ba3Mn2O8. We perform NMR measurements with 135,137Ba nucleus as a local probe. Although S = 1 spin properties of Ba 3Mn2O8 come from electronic spins on Mn atoms, hyperfine coupling between Mn electronic spins and Ba nuclear spins allow us to infer Mn electrons' spin information. Since there are 2 inequivalent Ba sites, Ba(1) and Ba(2), in Ba3Mn2O8, we essentially have two probes that provide a detailed picture of structure and nature of magnetism in this material. There are many antiferromagnetic BEC candidates, but there is a significant advantage of studying Ba3Mn 2O8. Unlike the other popular antiferromagnetic BEC candidates such as TlCuCl3[3] or BaCuSi2O6[4], we find no evidence of lattice deformation in Ba3Mn2O8 . This allows us an unprecedented clean look at magnetic properties. Aside from the aforementioned simple technical advantage, there are new physics that we can learn from Ba3Mn2O 8. The geometric frustration of

  15. A Sixth-order Image Approximation to the Ionic Solvent Induced Reaction Field.

    Science.gov (United States)

    Xiang, Ming; Deng, Shaozhong; Cai, Wei

    2009-12-01

    A recent article by Deng and Cai introduced fourth-order image approximations to the reaction field for a charge inside a dielectric sphere immersed in a solvent of low ionic strength. To represent such a reaction field, the image approximations employ a point charge at the classical Kelvin image point and two line charges that extend from the Kelvin image point along the radial direction to infinity. In this paper, a sixth-order image approximation is developed, using the same point charge with three different line charges. Procedures on how to discretize the line charges by point image charges and how to implement the resulting point image approximation in O(N) complexity for potential and force field calculations are included. Numerical results demonstrate the sixth-order convergence rate of the image approximation and the O(N) complexity of the fast implementation of the point image approximation.

  16. A Sixth-order Image Approximation to the Ionic Solvent Induced Reaction Field

    OpenAIRE

    Xiang, Ming; Deng, Shaozhong; Cai, Wei

    2009-01-01

    A recent article by Deng and Cai introduced fourth-order image approximations to the reaction field for a charge inside a dielectric sphere immersed in a solvent of low ionic strength. To represent such a reaction field, the image approximations employ a point charge at the classical Kelvin image point and two line charges that extend from the Kelvin image point along the radial direction to infinity. In this paper, a sixth-order image approximation is developed, using the same point charge w...

  17. Magnetic-Field-Induced Weak Order in Nematic Liquid Crystals Formed by Biaxial Molecules

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; ZHANG De-Xian; SUN Yu-Bao

    2000-01-01

    Nematic liquid crystal system of interacting biaxial particles via dispersion forces is studied. The molecular orienting potential form in a magnetic field is given for the first time. Weakly ordered isotropic phase is treated in the two-particle cluster approximation. Taking account of the molecular biaxiality, it is found that the ratio of the lowest supercooling temperature T* to the nematic-isotropic phase transition temperature TC approaches the observed value, and the validity of the mean field theory is clarified.

  18. Electric field induced orientational order of gold nanorods in dilute organic suspensions

    Science.gov (United States)

    Fontana, Jake; da Costa, Greice K. B.; Pereira, Joao M.; Naciri, Jawad; Ratna, Banahalli R.; Palffy-Muhoray, Peter; Carvalho, Isabel C. S.

    2016-02-01

    The electric field controlled alignment of gold nanorods offers a paradigm for anisotropic molecules with the potential for a wide variety of phases and structures. We experimentally study the optical absorption from gold nanorod suspensions aligned using external electric fields. We show that the absorption from these suspensions depends linearly on the orientational order parameter. We provide evidence that the critical electric field needed to orient the gold nanorods is proportional to the nanorod volume and depolarization anisotropy. Utilizing this critical field dependence, we demonstrate for suspensions with two different nanorod sizes that the alignment of each population can be controlled. We also develop a technique to determine the imaginary parts of the longitudinal and transverse electric susceptibilities of the nanorods. The ability to selectively address specific parts of the nanorod populations in a mixture using external fields may have significant potential for future display and optical filter applications.

  19. Studying the universality of field induced tunnel ionization times via high-order harmonic spectroscopy

    CERN Document Server

    Soifer, Hadas; Negro, Matteo; Devetta, Michele; Faccialà, Davide; Vozzi, Caterina; de Silvestri, Sandro; Stagira, Salvatore; Dudovich, Nirit

    2014-01-01

    High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and structure in atomic and molecular systems. This scheme, commonly described by the strong field approximation, requires a deep insight into the basic mechanism that leads to the harmonics generation. Recently, we have demonstrated the ability to resolve the first stage of the process -- field induced tunnel ionization -- by adding a weak perturbation to the strong fundamental field. Here we generalize this approach and show that the assumptions behind the strong field approximation are valid over a wide range of tunnel ionization conditions. Performing a systematic study -- modifying the fundamental wavelength, intensity and atomic system -- we observed a good agreement with quantum path analysis over a range of Keldysh parameters. The generality of this scheme opens new perspectives in high harmonics spectroscopy, holding the potential of probing large, complex molecular systems.

  20. Role of multipole moments in electric-field-induced order of dense molecular systems.

    Science.gov (United States)

    Acebal, Pablo; Carretero, Luis; Blaya, Salvador

    2010-07-12

    A new model is developed to describe the orientational order of dense molecular systems under an applied external electric field as a function of the n-particle distribution functions of a system under no external perturbation. From an approximation of this expression, the effects of several variables on this orientational order, such as the microscopic properties of the oriented molecules (the molecular geometry and multipole moments) and the solvent or matrix properties, are studied. The theoretical predictions show that, for a correct description of the orientational order, quadrupole and octupole moments must be included, as they play an important role in the orientational order achieved, depending on the molecular geometry. Furthermore, to verify the validity of the model, theoretical predictions are compared with experimental results, and show a good concordance.

  1. High-order harmonic generation in polyatomic molecules induced by a bicircular laser field

    CERN Document Server

    Odžak, Senad; Milošević, Dejan B

    2016-01-01

    High-order harmonic generation by a bicircular field, which consists of two coplanar counter-rotating circularly polarized fields of frequency $r\\omega$ and $s\\omega$ ($r$ and $s$ are integers), is investigated for a polyatomic molecule. This field possesses dynamical symmetry, which can be adjusted to the symmetry of the molecular Hamiltonian and used to investigate the molecular symmetry. For polyatomic molecules having the $C_{r+s}$ symmetry only the harmonics $n=q(r+s)\\pm r$, $q=1,2,\\ldots$, are emitted having the ellipticity $\\varepsilon_n=\\pm 1$. We illustrate this using the example of the planar molecules BH$_3$ and BF$_3$, which obey the $C_3$ symmetry. We show that for the BF$_3$ molecule, similarly to atoms with a $p$ ground state, there is a strong asymmetry in the emission of high harmonics with opposite helicities. This asymmetry depends on the molecular orientation.

  2. High-order harmonic generation in polyatomic molecules induced by a bicircular laser field

    Science.gov (United States)

    Odžak, S.; Hasović, E.; Milošević, D. B.

    2016-09-01

    High-order harmonic generation by a bicircular field, which consists of two coplanar counter-rotating circularly polarized fields of frequency r ω and s ω (r and s are integers), is investigated for a polyatomic molecule. This field possesses dynamical symmetry, which can be adjusted to the symmetry of the molecular Hamiltonian and used to investigate the molecular symmetry. For polyatomic molecules having the Cr +s symmetry, only the harmonics n =q (r +s )±r ,q =1 ,2 ,..., are emitted having the ellipticity ɛn=±1 . We illustrate this using the example of the planar molecules BH3 and BF3, which obey the C3 symmetry. We show that for the BF3 molecule, similarly to atoms with a p ground state, there is a strong asymmetry in the emission of high harmonics with opposite helicities. This asymmetry depends on the molecular orientation.

  3. Magnetic field-induced switching of magnetic ordering in SrFeO3- δ

    Science.gov (United States)

    Mohan Radheep, D.; Shanmugapriya, K.; Palanivel, Balan; Murugan, Ramaswamy

    2016-08-01

    The oxygen-deficient strontium iron oxide SrFeO3- δ (SFO) exhibits richness in the phase diagram over a broad range of temperatures and for other external parameters. Room-temperature X-ray diffraction and Raman spectrum reveals that the structure of synthesized SFO system consists of two mixed phases, i.e., major orthorhombic and minor tetragonal phases. The low-temperature Raman and vibrating sample magnetometer measurements indicated a structural transition below 253 K. The magnetic property of the synthesized SFO for various external magnetic field (up to 5 T) reveals possible variation in oxygen stoichiometry. Also, the application of external H increases Neel transition temperature ( T N), suppresses the hysteresis width ( W H), and thus weakens the first-order nature of the transition. Our analysis revealed the vanishing of hysteresis and the first-order antiferromagnetic transition becomes a crossover above a critical magnetic field H CR ≈ 5 T. Possible switching of magnetic ordering and oxidation state observed in same system enhances interest in related compounds which may be used in magnetic sensors and other magnetic switching devices.

  4. Magnetic field-induced switching of magnetic ordering in SrFeO{sub 3-δ}

    Energy Technology Data Exchange (ETDEWEB)

    Mohan Radheep, D.; Murugan, Ramaswamy [Pondicherry University, Department of Physics, Puducherry (India); Shanmugapriya, K.; Palanivel, Balan [Pondicherry Engineering College, Department of Physics, Puducherry (India)

    2016-08-15

    The oxygen-deficient strontium iron oxide SrFeO{sub 3-δ} (SFO) exhibits richness in the phase diagram over a broad range of temperatures and for other external parameters. Room-temperature X-ray diffraction and Raman spectrum reveals that the structure of synthesized SFO system consists of two mixed phases, i.e., major orthorhombic and minor tetragonal phases. The low-temperature Raman and vibrating sample magnetometer measurements indicated a structural transition below 253 K. The magnetic property of the synthesized SFO for various external magnetic field (up to 5 T) reveals possible variation in oxygen stoichiometry. Also, the application of external H increases Neel transition temperature (T{sub N}), suppresses the hysteresis width (W{sub H}), and thus weakens the first-order nature of the transition. Our analysis revealed the vanishing of hysteresis and the first-order antiferromagnetic transition becomes a crossover above a critical magnetic field H{sub CR} ∼ 5 T. Possible switching of magnetic ordering and oxidation state observed in same system enhances interest in related compounds which may be used in magnetic sensors and other magnetic switching devices. (orig.)

  5. Least-order torsion-gravity for chiral-spinor fields, induced self-interacting potentials and parity conservation

    Science.gov (United States)

    Fabbri, Luca

    2014-02-01

    We will consider the most general least-order derivative action for the torsional completion of gravitational backgrounds filled with left-handed and right-handed semi-spinorial fields, accounting for all parity-even as well as parity-odd contributions; we will proceed by performing the customary analysis, decomposing torsion and substituting it in terms of the semi-spinorial density currents, in order to obtain the effective action with the torsionally-induced self-interacting potentials among the chiral fermionic fields: we shall see that the resulting effective non-linear potentials will turn eventually out to be parity conserving after all.

  6. Magnetic-field-induced charge-stripe order in the high-temperature superconductor YBa2Cu3Oy.

    Science.gov (United States)

    Wu, Tao; Mayaffre, Hadrien; Krämer, Steffen; Horvatić, Mladen; Berthier, Claude; Hardy, W N; Liang, Ruixing; Bonn, D A; Julien, Marc-Henri

    2011-09-07

    Electronic charges introduced in copper-oxide (CuO(2)) planes generate high-transition-temperature (T(c)) superconductivity but, under special circumstances, they can also order into filaments called stripes. Whether an underlying tendency towards charge order is present in all copper oxides and whether this has any relationship with superconductivity are, however, two highly controversial issues. To uncover underlying electronic order, magnetic fields strong enough to destabilize superconductivity can be used. Such experiments, including quantum oscillations in YBa(2)Cu(3)O(y) (an extremely clean copper oxide in which charge order has not until now been observed) have suggested that superconductivity competes with spin, rather than charge, order. Here we report nuclear magnetic resonance measurements showing that high magnetic fields actually induce charge order, without spin order, in the CuO(2) planes of YBa(2)Cu(3)O(y). The observed static, unidirectional, modulation of the charge density breaks translational symmetry, thus explaining quantum oscillation results, and we argue that it is most probably the same 4a-periodic modulation as in stripe-ordered copper oxides. That it develops only when superconductivity fades away and near the same 1/8 hole doping as in La(2-x)Ba(x)CuO(4) (ref. 1) suggests that charge order, although visibly pinned by CuO chains in YBa(2)Cu(3)O(y), is an intrinsic propensity of the superconducting planes of high-T(c) copper oxides.

  7. Electric-field-induced fabrication of covalently linked second-order nonlinear optical multilayer films on nonconductive substrates.

    Science.gov (United States)

    Wang, Shiwei; Zhao, Lisha; Cui, Zhanchen

    2012-01-15

    A highly stable second-order nonlinear optical multilayer film was constructed on insulating substrates using the electric-field-induced layer-by-layer assembly technique. The substrates used in this method could be arbitrary. In another, the substrates could be modified with polyanion solution by spin coating as cladding layer. Then, the nonlinear optical multilayer films were assembled on the cladding layer directly by the electric-field-induced layer-by-layer assembly technique. The resulting cross-linked multilayer films fabricated by this method displayed high optical transparency, good thermal stability, and excellent nonlinear optical properties which can be made into waveguide devices directly. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. YbNiAl{sub 2}: A new Yb-based antiferromagnet with a field-induced ferromagnetic order

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, D.P., E-mail: rojasd@unican.e [Departamento CITIMAC, Av de los Castros S/N, Santander 39005 (Spain); Rodriguez Fernandez, J.; Espeso, J.I.; Gomez Sal, J.C. [Departamento CITIMAC, Av de los Castros S/N, Santander 39005 (Spain)

    2009-10-15

    We report measurements on the thermal and magnetic properties in the temperature range 2-300 K for the YbNiAl{sub 2} compound which crystallizes in the orthorhombic MgCuAl{sub 2}-type structure (space group Cmcm). At zero magnetic field, AC-magnetic susceptibility data show a peak in the real component consistent with an antiferromagnetic order below T{sub N}=4.8K. A field-induced ferromagnetic order is observed from the zero field cooled and field cooled curves of DC-magnetic susceptibility at different magnetic fields with a transition to a ferromagnetic state between 9 and 10 kOe. It is further confirmed by the isothermal magnetization curves as a function of the magnetic field at several temperatures, showing two metamagnetic transitions at H{sub 1}=8kOe and H{sub 2}=9.3kOe. The results are compared to those reported for other Yb-Ni-Al compounds.

  9. Spin state ordering of strongly correlating LaCoO3 induced at ultrahigh magnetic fields

    Science.gov (United States)

    Ikeda, Akihiko; Nomura, Toshihiro; Matsuda, Yasuhiro H.; Matsuo, Akira; Kindo, Koichi; Sato, Keisuke

    2016-06-01

    Magnetization measurements of LaCoO3 have been carried out up to 133 T, generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found at B >100 T and T >T*=32 ±5 K, which is characterized by its transition field increasing with increasing temperature. At T LaCoO3 at high magnetic fields.

  10. Exchange-bias field induced by surface inhomogeneities in ferromagnetic/charge-ordered bilayer structure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haiou, E-mail: wanghaiou@hdu.edu.cn [Institute of Materials Physics, Hangzhou Dianzi University, Hangzhou, 310018 (China); Key Laboratory of Soft Chemistry and Functional Materials, Ministry of Education, Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, 210094 (China); Yang, Weifeng; Su, Kunpeng [Institute of Materials Physics, Hangzhou Dianzi University, Hangzhou, 310018 (China); Huo, Dexuan, E-mail: dxhuo@hdu.edu.cn [Institute of Materials Physics, Hangzhou Dianzi University, Hangzhou, 310018 (China); Tan, Weishi [Key Laboratory of Soft Chemistry and Functional Materials, Ministry of Education, Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, 210094 (China)

    2015-11-05

    Epitaxial bilayer structure consisting of ferromagnetic metallic Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3} (PSMO) and charge-ordered insulator La{sub 0.5}Ca{sub 0.5}MnO{sub 3} (LCMO) was fabricated on (001) SrTiO{sub 3} substrate by pulsed laser deposition. High-resolution synchrotron X-ray diffraction showed high quality of epitaxial layer. However, besides diffraction peaks from PSMO layer, LCMO layer and SrTiO{sub 3} substrate, we observed an additional shoulder peak, which might stem from the inhomogeneities of composition in PSMO/LCMO. Further the atomic force microscopy measurement showed the presence of non-stoichiometric large particulates at surface, imparting an overall inhomogeneous composition to the film. This implied that the variation of crystalline structure of PSMO/LCMO occurred due to inhomogeneous composition. Moreover, studies on magnetic properties showed that surface inhomogeneities and ferromagnetic clusters at the PSMO/LCMO interface probably influenced the ferromagnetism of the bilayer film together, tuning exchange bias effect. - Highlights: • We report the epitaxial growth of Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}/La{sub 0.5}Ca{sub 0.5}MnO{sub 3} bilayer on SrTiO{sub 3}. • The non-stoichiometric particulates at surface impart inhomogeneous composition. • Inhomogeneities in the film lead to the variation of crystalline structure. • Surface inhomogeneities reduce ferromagnetism and enhance exchange bias effect.

  11. Chirality-driven intrinsic spin-glass ordering and field-induced ferromagnetism in Ni3Al nanoparticle aggregates

    Science.gov (United States)

    Kaul, S. N.; Messala, Umasankar

    2016-03-01

    Weak itinerant-electron ferromagnet Ni3Al is driven to magnetic instability (quantum critical point, QCP, where the long-range ferromagnetic order of the bulk ceases to exist) by reducing the average crystallite size to d=50 nm. 'Zero-field' (H=0) linear and nonlinear ac-susceptibilities, measured on Ni3Al nanoparticle aggregates, with d=50 nm (S1) and d=5 nm (S2), provide strong evidence for two spin glass (SG)-like thermodynamic phase transitions: one at Ti(H = 0) ≃ 30 K (Ti† (H = 0) ≃ 230 K) and the other at a lower temperature Tp(H = 0) ≃ 8 K (Th(H = 0) ≃ 52 K) in S1 (S2). 'In-field' (H ≠ 0) linear ac-susceptibility and dc magnetization demonstrate that the thermodynamic nature of these transitions is preserved in finite fields. The presently determined H-T phase diagrams for the samples S1 and S2 are compared with those predicted by the Kotliar-Sompolinsky and Gabay-Toulouse mean-field models and Monte Carlo simulations, based on the chirality-driven spin glass (SG) ordering scenario, for a three-dimensional nearest-neighbor Heisenberg SG system with or without weak random anisotropy. Such a detailed comparison permits us to unambiguously identify various 'zero-field' and 'in-field' SG phase transitions as: (i) the simultaneous paramagnetic (PM)-chiral glass (CG) and PM-SG phase transitions at Ti(H), (ii) the PM-CG transition at Ti† (H), (iii) the replica symmetry-breaking SG transition at Tp(H), and (iv) the continuous spin-rotation symmetry-breaking SG transition at Th(H). In the presence of random anisotropy, magnetization fails to saturate even at 90 kOe in S1 whereas negligibly small anisotropy allows even fields as weak as 1 kOe to saturate magnetization and induce ferromagnetism in S2. Due to the proximity to CG/SG-QCP, magnetization and susceptibility both exhibit non-Fermi liquid behavior over a wide range at low temperatures.

  12. Visualization and quantification of four steps in magnetic field induced two-dimensional ordering of superparamagnetic submicron particles

    DEFF Research Database (Denmark)

    Gajula, Gnana Prakash; Neves Petersen, Teresa; Petersen, Steffen B.

    2010-01-01

    We hereby report a methodology that permits a quantitative investigation of the temporal self-organization of superparamagnetic nanoparticles in the presence of an external magnetic field. The kinetics of field-induced self-organization into linear chains, time-dependent chain-size distribution...

  13. Order-to-disorder transition in the XY-like quantum magnet Cs2CoCl4 induced by noncommuting applied fields

    Science.gov (United States)

    Kenzelmann, M.; Coldea, R.; Tennant, D. A.; Visser, D.; Hofmann, M.; Smeibidl, P.; Tylczynski, Z.

    2002-04-01

    We explore the effects of noncommuting applied fields on the ground-state ordering of the quasi-one-dimensional spin-1/2 XY-like antiferromagnet Cs2CoCl4 using single-crystal neutron diffraction. In zero-field, interchain couplings cause long-range order below TN=217(5) mK with chains ordered antiferromagnetically along their length and moments confined to the (b,c) plane. Magnetic fields applied at an angle to the XY planes are found to initially stabilize the order by promoting a spin-flop phase with an increased perpendicular antiferromagnetic moment. In higher fields the antiferromagnetic order becomes unstable and a transition occurs to a phase with no long-range order in the (b,c) plane, proposed to be a spin-liquid phase that arises when the quantum fluctuations induced by the noncommuting field become strong enough to overcome ordering tendencies. Magnetization measurements confirm that saturation occurs at much higher fields and that the proposed spin-liquid state exists in the region 2.10HSL<2.52 T ||a. The observed phase diagram is discussed in terms of known results on XY-like chains in coexisting longitudinal and transverse fields.

  14. Magnetic-field-induced first-order phase transitions in Ca3(Ru1-xFex)2 O7 with unusual irreversible behaviors

    Science.gov (United States)

    Zhu, Mengze; Peng, Jin; Zou, Tao; Hong, Tao; Prokes, Karel; Mahanti, S. D.; Mao, Zhiqiang; Ke, Xianglin

    Neutron diffraction measurements reveal a magnetic-field-induced incommensurate-commensurate magnetic structure transition in a bilayer ruthenate Ca3(Ru1-xFex)2 O7 (x = 0.05). The transition is of first-order in nature, and exhibits intriguing irreversible behaviors at low temperature, i.e. the zero-field incommensurate state before and after field sweeping showing very distinct magnetic ordering wave vectors. The difference in the wavelength of magnetic ordering is strongly temperature-dependent, and disappears gradually as temperature raises. This unusual irreversibility in magnetic ordering vector is rarely observed, and in disagreement with phase coexistence phenomena that is commonly seen in other irreversible first-order phase transitions. Nevertheless, our results demonstrate that thermal fluctuations also play an essential role in this unusual behavior.

  15. Second-order nonlinear optical susceptibilities induced by built-in electric field in wurtzite nitride double quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L. [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China) and Department of Mechanism and Electron, Panyu Polytechnic, Panyu 511483 (China)]. E-mail: zhangli-gz@263.net; Chi Yuemeng [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China); Shi, J.-J. [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China)

    2007-06-25

    Based on the density matrix method and the iterative treatment, the second-harmonic generation (SHG) susceptibility of a wurtzite nitride coupling quantum well (CQW) with strong built-in electric fields have been theoretically investigated. The effect of the band non-parabolicity effect has been taken into account. A typical wurtzite GaN/In{sub x}Ga{sub 1-x}N CQW are chosen to perform numerical calculations. The localized properties of the electronic ground state and the low-excited states in the system are analyzed in detail. The calculated SHG coefficients reach the order of magnitude of 10{sup -7}m/V, which is two-order larger than the corresponding values in wurtzite single quantum wells. Moreover, it is confirmed that the SHG coefficients are not monotonic functions of the well width, barrier width and the doped concentration of the CQW systems, but have complicated dependent relations on them. The reasons resulting in these characteristics can be attributed to the intense competition between the strong built-in electric field effect and the quantum size effect for the electronic confined situation in the wurtzite CQWs. The calculated results also show that a strong SHG effect can be realized in the nitride CQW by choosing a group of optimized structural parameters and doped fraction.

  16. Third-Order Electric-Field-Induced Dipolar Resonances from Patterned Barium-Strontium-Titanate Thin-Films

    Science.gov (United States)

    Toonen, Ryan; Will Cole, Melanie; Ivill, Mathew; Hirsch, S.; Integrated Electromagnetic Materials Team Team

    2013-03-01

    Using microwave reflection spectroscopy, the complex permittivities of etch-defined, 240 nm thick, [Ba(0.6)Sr(0.4)]TiO(3), thin films were measured over the frequency range of (1 to 4) GHz. The observed electro-acoustic resonances were characterized as a function of extrinsic electric field magnitude, ambient temperature, and sample diameter. The real and imaginary parts of the measured permittivities were fit to frequency-dependent functions derived from the Lorentz oscillator model. From these functions, extracted static dielectric constants were found to display excellent agreement with a closed-form expression derived by calculating third-order nonlinear susceptibility from the Landau-Devonshire-Ginzberg model [R. C. Toonen and M. W. Cole, Appl. Phys. Lett. 100, 222908 (2012)]. By investigating the behavior of these loss mechanisms in response to external stimuli, we have gained insight with respect to how such effects can be reduced or even eliminated. It is also possible that these loss mechanisms could be exploited for the purpose of engineering micro-/nano-electro-mechanical resonators and super-compact high-quality-factor frequency-selective filters. Funding for these efforts was provided by an award from the ARL Director's Research Initiative (FY10-WMR-27).

  17. Pure quadratic or higher-order optical effects in anisotropic crystals induced by external dc fields and probed by a single low-intensity plane electromagnetic wave

    Science.gov (United States)

    Melnichuk, Mike; Wood, Lowell T.

    2017-07-01

    The determination of a clear theoretical demarcation between a true or a false quadratic or higher-order low-intensity optical effect induced by an externally applied static or quasistatic (dc) vector field in anisotropic crystals is the scope of the present work. A complete set of necessary and sufficient conditions required for the practical possibility of direct detection, measurement, and tabulation of only those pure optical contributions is finally obtained. The dc electro-optic effect stands out as the most representative of all of these low-power dc optical effects. However, although the dc Kerr effect remains the main topic of application of the analytical treatment developed in this work, the current theoretical formalism is extended to include other dc conventional crystal optics effects, such as electrogyration, electroabsorption, and externally induced ray or energy propagation. Even more, the theoretical conditions are further generalized to apply to any pure higher-order crystal optics effect induced by external dc fields. These can be electric, magnetic, force, and even temperature or concentration gradient fields. The current treatment does not extend to multiple-beam high-intensity nonlinear optics effects induced by optical (ac) fields. Compared to previously published expressions, a more general Fresnel equation is also provided here together with the most general Jones vectors describing the eigenpolarizations of the single probing beam of light. All the generalizations and extensions mentioned in this article are valid as long as the field-dependent coefficients of the particular optical effect under consideration satisfy the equation of a positive-definite complex Hermitian form.

  18. Dependence of third-order nonlinear susceptibility on strain induced piezoelectric field in InxGa1-xN/GaN quantum well

    Institute of Scientific and Technical Information of China (English)

    Yaochen Bai(白瑶晨); Jingliang Liu(刘景良); Duanzheng Yao(姚端正)

    2004-01-01

    The third-order susceptibility of InxGa1-xN/GaN quantum well (QW) has been investigated by taking into account the strain-induced piezoelectric (PZ) field, and the effective-mass SchrSdinger equation is solved numerically. It is shovn that the third-order susceptibility for third harmonic generation (THG)of InxGa1-x,N/GaN QW is related to indium content in QW and the intensity of the PZ field. The characteristics ofX(3)THG(-3ω,(3) ω, ω,ω) as the function of the wavelength of incident beam, well width and indium content, have been analyzed.

  19. Magnetic-field-induced stripe order and a 2D vortex glass phase in La1.905 Ba 0.095 CuO 4

    Science.gov (United States)

    Tranquada, John; Wen, Jinsheng; Jie, Qing; Han, Su Jung; Li, Qiang; Huecker, Markus; Xu, Zhijun; Zhang, Liyuan; Gu, Genda; Zimmermann, M. V.; Singh, D. K.

    2011-03-01

    We have measured the resistivity parallel and perpendicular to the Cu O2 planes in La 1.905 Ba 0.095 Cu O4 (Tc = 32 K) as a function of perpendicular magnetic field. We have discovered a significant regime of field and temperature where the perpendicular resistivity is finite (and large) but the parallel resistivity is zero. This regime appears to correspond to a quasi-two-dimensional vortex glass phase, a state that theory predicts cannot exist at finite temperature. It seems to be stabilized by field-induced charge and spin stripe order, which we have detected with x-ray and neutron diffraction, respectively. Supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC02-98CH10886.

  20. A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3.

    Science.gov (United States)

    Mohapatra, Niharika; Mukherjee, K; Iyer, Kartik K; Sampathkumaran, E V

    2011-12-14

    We present magnetic characterization of a binary rare-earth intermetallic compound Er(5)Si(3), crystallizing in Mn(5)Si(3)-type hexagonal structure, through magnetization, heat capacity, electrical resistivity and magnetoresistance measurements. Our investigations confirm that the compound exhibits two magnetic transitions with decreasing temperature, the first one at 35 K and the second one at 15 K. The present results reveal that the second magnetic transition is a disorder-broadened first-order transition, as shown by thermal hysteresis in the measured data. Another important finding is that, below 15 K, there is a magnetic-field-induced transition with a hysteretic effect with the electrical resistance getting unusually enhanced at this transition and the magnetoresistance is found to exhibit intriguing magnetic-field dependence, indicating novel magnetic phase coexistence phenomenon. It thus appears that this compound is characterized by interesting magnetic anomalies in the temperature-magnetic-field phase diagram.

  1. Colloidal Stability and Magnetic Field-Induced Ordering of Magnetorheological Fluids Studied with a Quartz Crystal Microbalance

    Directory of Open Access Journals (Sweden)

    Jaime Rodriguez-López

    2015-12-01

    Full Text Available This work proposes the use of quartz crystal microbalances (QCMs as a method to analyze and characterize magnetorheological (MR fluids. QCM devices are sensitive to changes in mass, surface interactions, and viscoelastic properties of the medium contacting its surface. These features make the QCM suitable to study MR fluids and their response to variable environmental conditions. MR fluids change their structure and viscoelastic properties under the action of an external magnetic field, this change being determined by the particle volume fraction, the magnetic field strength, and the presence of thixotropic agents among other factors. In this work, the measurement of the resonance parameters (resonance frequency and dissipation factor of a QCM are used to analyze the behavior of MR fluids in static conditions (that is, in the absence of external mechanical stresses. The influence of sedimentation under gravity and the application of magnetic fields on the shifts of resonance frequency and dissipation factor were measured and discussed in the frame of the coupled resonance produced by particles touching the QCM surface. Furthermore, the MR-fluid/QCM system has a great potential for the study of high-frequency contact mechanics because the translational and rotational stiffness of the link between the surface and the particles can be tuned by the magnetic field.

  2. Three order increase in scanning speed of space charge-controlled KTN deflector by eliminating electric field induced phase transition in nanodisordered KTN

    Science.gov (United States)

    Zhu, Wenbin; Chao, Ju-Hung; Chen, Chang-Jiang; Yin, Shizhuo; Hoffman, Robert C.

    2016-01-01

    In this paper, we report a three orders-of-magnitude increase in the speed of a space-charge-controlled KTN beam deflector achieved by eliminating the electric field-induced phase transition (EFIPT) in a nanodisordered KTN crystal. Previously, to maximize the electro-optic effect, a KTN beam deflector was operated at a temperature slightly above the Curie temperature. The electric field could cause the KTN to undergo a phase transition from the paraelectric phase to the ferroelectric phase at this temperature, which causes the deflector to operate in the linear electro-optic regime. Since the deflection angle of the deflector is proportional to the space charge distribution but not the magnitude of the applied electric field, the scanning speed of the beam deflector is limited by the electron mobility within the KTN crystal. To overcome this speed limitation caused by the EFIPT, we propose to operate the deflector at a temperature above the critical end point. This results in a significant increase in the scanning speed from the microsecond to nanosecond regime, which represents a major technological advance in the field of fast speed beam scanners. This can be highly beneficial for many applications including high-speed imaging, broadband optical communications, and ultrafast laser display and printing. PMID:27610923

  3. Three order increase in scanning speed of space charge-controlled KTN deflector by eliminating electric field induced phase transition in nanodisordered KTN

    Science.gov (United States)

    Zhu, Wenbin; Chao, Ju-Hung; Chen, Chang-Jiang; Yin, Shizhuo; Hoffman, Robert C.

    2016-09-01

    In this paper, we report a three orders-of-magnitude increase in the speed of a space-charge-controlled KTN beam deflector achieved by eliminating the electric field-induced phase transition (EFIPT) in a nanodisordered KTN crystal. Previously, to maximize the electro-optic effect, a KTN beam deflector was operated at a temperature slightly above the Curie temperature. The electric field could cause the KTN to undergo a phase transition from the paraelectric phase to the ferroelectric phase at this temperature, which causes the deflector to operate in the linear electro-optic regime. Since the deflection angle of the deflector is proportional to the space charge distribution but not the magnitude of the applied electric field, the scanning speed of the beam deflector is limited by the electron mobility within the KTN crystal. To overcome this speed limitation caused by the EFIPT, we propose to operate the deflector at a temperature above the critical end point. This results in a significant increase in the scanning speed from the microsecond to nanosecond regime, which represents a major technological advance in the field of fast speed beam scanners. This can be highly beneficial for many applications including high-speed imaging, broadband optical communications, and ultrafast laser display and printing.

  4. Terahertz field induced electromigration

    DEFF Research Database (Denmark)

    Strikwerda, Andrew; Zalkovskij, Maksim; Iwaszczuk, Krzysztof;

    We report the first observation of THz-field-induced electromigration in sub-wavelength metallic gap structures after exposure to intense single-cycle, sub-picosecond electric field transients of amplitude up to 400 kV/cm.......We report the first observation of THz-field-induced electromigration in sub-wavelength metallic gap structures after exposure to intense single-cycle, sub-picosecond electric field transients of amplitude up to 400 kV/cm....

  5. Fourth-order acoustic torque in intense sound fields

    Science.gov (United States)

    Wang, T. G.; Kanber, H.; Olli, E. E.

    1978-01-01

    The observation of a fourth-order acoustic torque in intense sound fields is reported. The torque was determined by measuring the acoustically induced angular deflection of a polished cylinder suspended by a torsion fiber. This torque was measured in a sound field of amplitude greater than that in which first-order acoustic torque has been observed.

  6. Geometric second order field equations for general tensor gauge fields

    Science.gov (United States)

    de Medeiros, Paul; Hull, Christopher M.

    2003-05-01

    Higher spin tensor gauge fields have natural gauge-invariant field equations written in terms of generalised curvatures, but these are typically of higher than second order in derivatives. We construct geometric second order field equations and actions for general higher spin boson fields, and first order ones for fermions, which are non-local but which become local on gauge-fixing, or on introducing auxiliary fields. This generalises the results of Francia and Sagnotti to all representations of the Lorentz group.

  7. Geometric Second Order Field Equations for General Tensor Gauge Fields

    CERN Document Server

    De Medeiros, P

    2003-01-01

    Higher spin tensor gauge fields have natural gauge-invariant field equations written in terms of generalised curvatures, but these are typically of higher than second order in derivatives. We construct geometric second order field equations and actions for general higher spin boson fields, and first order ones for fermions, which are non-local but which become local on gauge-fixing, or on introducing auxiliary fields. This generalises the results of Francia and Sagnotti to all representations of the Lorentz group.

  8. Finite-field Calculations of Molecular Polarizabilities Using Field-Induced Polarization Functions: Second- and Third-order Perturbation Correlation Corrections to the Coupled Hartree-Fock Polarizability of H2O

    Science.gov (United States)

    Langhoff, S. R.; Scott, W. R.; Suzuki, N.; Chong, D. P.

    1979-01-01

    Ordinary Rayleigh-Schroudinger perturbation theory with Moller-Plesset (RSMP) partitioning is used to calculate second- and third-order correlation corrections to the CHF polarizability and dipole moment of the water molecule by a finite-field procedure. Pade approximants are found to be useful in accelerating the convergence of the property perturbation expansions. Field-induced polarization functions suitable for polarizability calculations are determined. The average polarizability calculated, neglecting vibrational averaging, with Dunning's (9s5p/4s-4s2p/2s) contracted GTO basis set augmented by field-induced lslp2d/lp polarization functions is within 3 per cent of the experimental result. Correlation corrections to the dipole moment and polarizability of the water molecule calculated by the finite-field RSMP and single + double excitation CI(SDCI) methods for the same basis set are found to be in close agreement. The RSMP approach has the advantages of being size-consistent and of being capable of greater efficiency than the SCDI method. Comparative calculations carried out using Epstein-Nesbet partitioning show that through third order RSEN correlation perturbation expansions for the dipole moment and polarizability are less rapidly convergent than RSMP expansions. However, reasonable accord with RSMP results can be achieved by using Pade approximants to accelerate the convergence of RSEN energy perturbation expansions. The convergence of RSMP property correlation expansions based on the zeroth-order uncoupled-Hartree-Fock (UCHF) and coupled-Hartree-Fock (CHF) approximations are compared through third order. Whereas the CHF + RSMP expansions are for practical purposes fully converged, the UCHF + RSMP expansions are not adequately converged.

  9. Magnetic fields from second-order interactions

    CERN Document Server

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-free approach, but could be done in the standard covariant indexed-approach.

  10. Magnetic fields from second-order interactions

    OpenAIRE

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-fre...

  11. Degenerate second order mean field games systems

    OpenAIRE

    Tonon, Daniela; Cardaliaguet, Pierre; Graber, Philip,; Poretta, Alessio

    2014-01-01

    Parallel session; International audience; We consider degenerate second order mean field games systems with a local coupling. The starting point is the idea that mean field games systems can be understood as an optimality condition for optimal control of PDEs. Developing this strategy for the degenerate second order case, we discuss the existence and uniqueness of a weak solution as well as its stability (vanishing viscosity limit). Speaker: Daniela TONON

  12. A sixth order averaged vector field method

    OpenAIRE

    Li, Haochen; Wang, Yushun; Qin, Mengzhao

    2014-01-01

    In this paper, based on the theory of rooted trees and B-series, we propose the concrete formulas of the substitution law for the trees of order =5. With the help of the new substitution law, we derive a B-series integrator extending the averaged vector field (AVF) method to high order. The new integrator turns out to be of order six and exactly preserves energy for Hamiltonian systems. Numerical experiments are presented to demonstrate the accuracy and the energy-preserving property of the s...

  13. Kinetic arrest of field-temperature induced first order phase transition in quasi-one dimensional spin system Ca3Co2O6

    Science.gov (United States)

    De, Santanu; Kumar, Kranti; Banerjee, A.; Chaddah, P.

    2016-05-01

    We have found that the geometrically frustrated spin chain compound Ca3Co2O6 belonging to Ising like universality class with uniaxial anisotropy shows kinetic arrest of first order intermediate phase (IP) to ferrimagnetic (FIM) transition. In this system, dc magnetization measurements followed by different protocols suggest the coexistence of high temperature IP with equilibrium FIM phase in low temperature. Formation of metastable state due to hindered first order transition has also been probed through cooling and heating in unequal field (CHUF) protocol. Kinetically arrested high temperature IP appears to persist down to almost the spin freezing temperature in this system.

  14. Anomalous vortex dynamics in κ-[bis(ethylenedithio)tetrathiafulvalene]2Cu[N(CN)2]Br: Evidence for field-induced magnetic order and unconventional superconductivity

    Science.gov (United States)

    Lahaise, U. G.; Chen, Qun; de Long, L. E.; Brock, C. P.; Wang, H. H.; Carlson, K. D.; Schlueter, J. A.; Williams, J. M.

    1995-02-01

    Anisotropic superconducting flux-line behavior of single-crystal κ-[bis(ethylenedithio)tetrathiaful- valene]2Cu[N(CN)2]Br has been studied with dc magnetization and vibrating-reed (VR) techniques. A peak at T*(H) in the temperature dependence of the VR inverse quality factor 1/Q exhibits a shoulder for magnetic fields 0<μ0H<=0.5 T parallel to the conducting ac plane. The shoulder becomes unresolved near a kink in T*(H) at μ0H~=0.7 T. Discontinuities in 1/Q and the VR frequency shift occur for 0.1<=μ0H<=1.3 T applied perpendicular to the ac plane and temperatures T<=20 K, well into the normal state. These anomalies are preliminary evidence for a field-induced magnetic phase transition and unconventional superconductivity.

  15. Magnetic field-induced off-resonance third-order optical nonlinearity of iron oxide nanoparticles incorporated mesoporous silica thin films during heat treatment.

    Science.gov (United States)

    Cui, Fangming; Feng, Chude; Xie, Rongjun; Hua, Zile; Ohtsuka, Hideyuki; Sakka, Yoshio; Shi, Jianlin

    2010-02-01

    Highly dispersed and uniform Fe(2)O(3) nanoparticles (NPs) have been incorporated into the pore channels of SBA-15 mesoporous silica thin films (MSTFs). And such Fe(2)O(3) NPs incorporated MSTFs did not show detectable nonlinear optical (NLO) signals at off-resonance wavelength 1064 nm by Z-scan technique. However after a vacuum heat treatment at 800 degrees C for 1 h under 6 T magnetic field, the Fe(2)O(3) NPs incorporated MSTFs with very low Fe content (0.8 approximately 1.5 at.%) presented distinctive NLO signals with chi(3) value in an order of 10(-10) esu. We proposed the physical reason for the NLO property generation to be the magnetic domain orientation of the iron oxide NPs incorporated within the pore channels of the MSTFs by the magnetic field heat treatment.

  16. Field-induced transition of the magnetic ground state from A-type antiferromagnetic to ferromagnetic order in CsCo2Se2

    Science.gov (United States)

    von Rohr, Fabian; Krzton-Maziopa, Anna; Pomjakushin, Vladimir; Grundmann, Henrik; Guguchia, Zurab; Schnick, Wolfgang; Schilling, Andreas

    2016-07-01

    We report on the magnetic properties of CsCo2Se2 with ThCr2Si2 structure, which we have characterized through a series of magnetization and neutron diffraction measurements. We find that CsCo2Se2 undergoes a phase transition to an antiferromagnetically ordered state with a Néel temperature of {{T}\\text{N}}≈ 66 K. The nearest neighbour interactions are ferromagnetic as observed by the positive Curie-Weiss temperature of \\Theta≈ 51.0 K. We find that the magnetic structure of CsCo2Se2 consists of ferromagnetic sheets, which are stacked antiferromagnetically along the tetragonal c-axis, generally referred to as A-type antiferromagnetic order. The observed magnitude of the ordered magnetic moment at T  =  1.5 K is found to be only 0.20(1){μ\\text{Bohr}}  / Co. Already in comparably small magnetic fields of {μ0}H{{}\\text{MM}}(5~K)≈ 0.3 T, we observe a metamagnetic transition that can be attributed to spin-rearrangements of CsCo2Se2, with the moments fully ferromagnetically saturated in a magnetic field of {μ0}{{H}\\text{FM}}(5~K)≈ 6.4 T. We discuss the entire experimentally deduced magnetic phase diagram for CsCo2Se2 with respect to its unconventionally weak magnetic coupling. Our study characterizes CsCo2Se2, which is chemically and electronically posed closely to the A x Fe2-y Se2 superconductors, as a host of versatile magnetic interactions.

  17. Nuclear magnetic resonance study of the magnetic-field-induced ordered phase in the NiCl2-4 SC(NH2) 2 compound

    Science.gov (United States)

    Blinder, Rémi; Dupont, Maxime; Mukhopadhyay, Sutirtha; Grbić, Mihael S.; Laflorencie, Nicolas; Capponi, Sylvain; Mayaffre, Hadrien; Berthier, Claude; Paduan-Filho, Armando; Horvatić, Mladen

    2017-01-01

    Nuclear magnetic resonance study of the high magnetic field (H ) part of the Bose-Einstein condensed (BEC) phase of the quasi-one-dimensional (quasi-1D) antiferromagnetic quantum spin-chain compound NiCl2-4 SC (NH2)2 was performed. We precisely determined the phase boundary, Tc(H ) , down to 40 mK; the critical boson density, nc(Tc) ; and the absolute value of the BEC order parameter S⊥ at very low temperature (T =0.12 K ) . All results are accurately reproduced by numerical quantum Monte Carlo simulations of a realistic three-dimensional (3D) model Hamiltonian. Approximate analytical predictions based on the 1D Tomonaga-Luttinger liquid description are found to be precise for Tc(H ) , but less so for S⊥(H ) , which is more sensitive to the strength of 3D couplings, in particular close to the critical field. A mean-field treatment, based on the Hartree-Fock-Popov description, is found to be valid only up to nc≅4 % (T <0.3 K), while for higher nc boson interactions appear to modify the density of states.

  18. Second-order multisymplectic field theory: A variational approach to second-order multisymplectic field theory

    OpenAIRE

    Kouranbaeva, Shinar; Shkoller, Steve

    1999-01-01

    This paper presents a geometric-variational approach to continuous and discrete {\\it second-order} field theories following the methodology of \\cite{MPS}. Staying entirely in the Lagrangian framework and letting $Y$ denote the configuration fiber bundle, we show that both the multisymplectic structure on $J^3Y$ as well as the Noether theorem arise from the first variation of the action function. We generalize the multisymplectic form formula derived for first order field theories in \\cite{MPS...

  19. Magnetic-field-induced ordered phase in the chloro-bridged copper(II) dimer system [C u2(apyhist) 2C l2] (ClO4)2

    Science.gov (United States)

    Freitas, R. S.; Alves, W. A.; Paduan-Filho, A.

    2017-05-01

    Specific heat and magnetization measurements of the compound [C u2(apyhist) 2C l2] (ClO4)2 , where apyhist = (4-imidazolyl)ethylene-2-amino-1-ethylpyridine), were used to identify a magnetic-field-induced long-range antiferromagnetic ordered phase at low temperatures (T <0.36 K ) and magnetic fields (1.6 field-induced ordering behavior was analyzed using the mean-field approximation and Monte Carlo simulation results. The obtained physical properties of the system are consistent with the description of the ordered phase as a Bose-Einstein condensation (BEC) of magnetic excitations. We present the phase diagram of this compound, which shows one of the lowest critical magnetic field among all known members of the family of BEC quantum magnets.

  20. A Generalized Induced Ordered Weighted Geometric Operator

    Institute of Scientific and Technical Information of China (English)

    ZeshuiXu; DaiWu

    2004-01-01

    Yager presented the Ordered Weighted Averaging (OWA) operator to provide a method for aggregating information of decision-making. Yager and Filev further presented the Induced Ordered Weighted Averaging (IOWA) operator. In this paper, we propose a Generalized Induced Ordered Weighted Geometric (GIOWG) operator and establish a simple objective-programming model to learn the associated weighting vector from observational data. Each object processed by the GIOWG operator consists of three components, where the first component represents the importance degree or character of the second component, and the second component is used to induce an ordering, through the first component, over the third components which are then aggregated. The desirable properties, such as commutativity, idempotency and monotonicity, etc., associated wlth the GIOWG operator are studied in detail, and some numerical examples are given to show the practicality and effectiveness of the developed operator.

  1. Primordial magnetic fields from self-ordering scalar fields

    CERN Document Server

    Horiguchi, Kouichirou; Sekiguchi, Toyokazu; Sugiyama, Naoshi

    2015-01-01

    A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by $B\\sim{10^{-9}}{((1+z)/10^3)^{-2.5}}({v}/{m_{\\rm pl}})^2({k}/{\\rm Mpc^{-1}})^{3.5}/{\\sqrt{N}}$ Gauss in the radiation dominated era for $k\\lesssim 1$ Mpc$^{-1}$, with $v$ being the vacuum ...

  2. Charge Order Induced in an Orbital Density-Wave State

    Science.gov (United States)

    Singh, Dheeraj Kumar; Takimoto, Tetsuya

    2016-04-01

    Motivated by recent angle resolved photoemission measurements [D. V. Evtushinsky et al., Phys. Rev. Lett. 105, 147201 (2010)] and evidence of the density-wave state for the charge and orbital ordering [J. García et al., Phys. Rev. Lett. 109, 107202 (2012)] in La0.5Sr1.5MnO4, the issue of charge and orbital ordering in a two-orbital tight-binding model for layered manganite near half doping is revisited. We find that the charge order with the ordering wavevector 2{Q} = (π ,π ) is induced by the orbital order of d-/d+-type having B1g representation with a different ordering wavevector Q, where the orbital order as the primary order results from the strong Fermi-surface nesting. It is shown that the induced charge order parameter develops according to TCO - T by decreasing the temperature below the orbital ordering temperature TCO, in addition to the usual mean-field behavior of the orbital order parameter. Moreover, the same orbital order is found to stabilize the CE-type spin arrangement observed experimentally below TCE < TCO.

  3. Order by virtual crystal field fluctuations in pyrochlore XY antiferromagnets

    Science.gov (United States)

    Rau, Jeffrey G.; Petit, Sylvain; Gingras, Michel J. P.

    2016-05-01

    Conclusive evidence of order by disorder is scarce in real materials. Perhaps one of the strongest cases presented has been for the pyrochlore XY antiferromagnet Er2Ti2O7 , with the ground state selection proceeding by order by disorder induced through the effects of quantum fluctuations. This identification assumes the smallness of the effect of virtual crystal field fluctuations that could provide an alternative route to picking the ground state. Here we show that this order by virtual crystal field fluctuations is not only significant, but competitive with the effects of quantum fluctuations. Further, we argue that higher-multipolar interactions that are generically present in rare-earth magnets can dramatically enhance this effect. From a simplified bilinear-biquadratic model of these multipolar interactions, we show how the virtual crystal field fluctuations manifest in Er2Ti2O7 using a combination of strong-coupling perturbation theory and the random-phase approximation. We find that the experimentally observed ψ2 state is indeed selected and the experimentally measured excitation gap can be reproduced when the bilinear and biquadratic couplings are comparable while maintaining agreement with the entire experimental spin-wave excitation spectrum. Finally, we comment on possible tests of this scenario and discuss implications for other order-by-disorder candidates in rare-earth magnets.

  4. Nematic Ordering of Rigid Rods in a Gravitational Field

    CERN Document Server

    Baulin, V A; Baulin, Vladimir A.; Khokhlov, Alexei R.

    1999-01-01

    The isotropic-to-nematic transition in an athermal solution of long rigid rods subject to a gravitational (or centrifugal) field is theoretically considered in the Onsager approximation. The new feature emerging in the presence of gravity is a concentration gradient which coupled with the nematic ordering. For rodlike molecules this effect becomes noticeable at centrifugal acceleration g ~ 10^3--10^4 m/s^2, while for biological rodlike objects, such as tobacco mosaic virus, TMV, the effect is important even for normal gravitational acceleration conditions. Rods are concentrated near the bottom of the vessel which sometimes leads to gravity induced nematic ordering. The concentration range corresponding to phase separation increases with increasing g. In the region of phase separation the local rod concentration, as well as the order parameter, follow a step function with height.

  5. Disorder-Induced Order in Quantum XY Chains

    CERN Document Server

    Niederberger, Armand; Dziarmaga, Jacek; Cucchietti, Fernando M; Wehr, Jan; Lewenstein, Maciej

    2010-01-01

    We observe signatures of disorder-induced order in 1D XY spin chains with an external, site-dependent uni-axial random field within the XY plane. We numerically investigate signatures of a quantum phase transition at T=0, in particular an upsurge of the magnetization in the direction orthogonal to the external magnetic field, and the scaling of the block-entropy with the amplitude of this field. Also, we discuss possible realizations of this effect in ultra-cold atom experiments.

  6. Gravitational waves induced by spinor fields

    CERN Document Server

    Feng, Kaixi

    2015-01-01

    In realistic model-building, spinor fields with various masses are present. During inflation, spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of single massive spinor field to the power spectrum of primordial gravitational wave by using retarded Green propagator. We find that the correction is scale-invariant and of order $H^4/M_P^4$ for arbitrary spinor mass $m_{\\psi}$. Additionally, we also observe that when $m_\\psi \\gtrsim H$, the dependence of correction on $m_\\psi/H$ is nontrivial.

  7. Methods in Model Order Reduction (MOR) field

    Institute of Scientific and Technical Information of China (English)

    刘志超

    2014-01-01

    Nowadays, the modeling of systems may be quite large, even up to tens of thousands orders. In spite of the increasing computational powers, direct simulation of these large-scale systems may be impractical. Thus, to industry requirements, analytically tractable and computationally cheap models must be designed. This is the essence task of Model Order Reduction (MOR). This article describes the basics of MOR optimization, various way of designing MOR, and gives the conclusion about existing methods. In addition, it proposed some heuristic footpath.

  8. Mean field games systems of first order

    OpenAIRE

    Cardaliaguet, Pierre; Graber, Philip Jameson

    2014-01-01

    International audience; We consider a system of mean field games with local coupling in the deterministic limit. Under general structure conditions on the Hamiltonian and coupling, we prove existence and uniqueness of the weak solution, characterizing this solution as the minimizer of some optimal control of Hamilton-Jacobi and continuity equations. We also prove that this solution converges in the long time average to the solution of the associated ergodic problem.

  9. Magnetic order, field-induced phase transitions and magnetoresistance in the intercalated compound Fe0.5TiS2.

    Science.gov (United States)

    Baranov, N V; Sherokalova, E M; Selezneva, N V; Proshkin, A V; Gubkin, A F; Keller, L; Volegov, A S; Proskurina, E P

    2013-02-13

    Measurements of the magnetic susceptibility, magnetization, electrical resistivity and neutron diffraction have been performed for the compound Fe(0.5)TiS(2) in which Fe atoms are intercalated between S-Ti-S tri-layers. It has been shown that this compound with a monoclinic crystal structure exhibits an antiferromagnetic (AF) ground state below the Néel temperature T(N) ≈ 140 K. Small deviations from the stoichiometry and some disordering effects caused by the additional low-temperature heat treatment do not affect substantially the AF state in Fe(0.5)TiS(2). According to neutron diffraction data the magnetic structure at 2 K is described by the propagation vector k = (1/4,0,1/4). The Fe magnetic moments with a value of (2.9 ± 0.1) μ(B) are directed at an angle of (78.5 ± 1.8)° to the layers. Application of the magnetic field at T measurements. The magnetization reversal in the metastable F state is accompanied at low temperatures by substantial hysteresis (ΔH ~ 100 kOe) which is associated with the Ising character of Fe ions.

  10. Higher Order Equations and Constituent Fields

    Science.gov (United States)

    Barci, D. G.; Bollini, C. G.; Oxman, L. E.; Rocca, M.

    We consider a simple wave equation of fourth degree in the D'Alembertian operator. It contains the main ingredients of a general Lorentz-invariant higher order equation, namely, a normal bradyonic sector, a tachyonic state and a pair of complex conjugate modes. The propagators are respectively the Feynman causal function and three Wheeler-Green functions (half-advanced and half-retarded). The latter are Lorentz-invariant and consistent with the elimination of tachyons and complex modes from free asymptotic states. We also verify the absence of absorptive parts from convolutions involving Wheeler propagators.

  11. Variational principles for multisymplectic second-order classical field theories

    Science.gov (United States)

    Prieto-Martínez, Pedro Daniel; Román-Roy, Narciso

    2015-06-01

    We state a unified geometrical version of the variational principles for second-order classical field theories. The standard Lagrangian and Hamiltonian variational principles and the corresponding field equations are recovered from this unified framework.

  12. Variational principles for multisymplectic second-order classical field theories

    OpenAIRE

    Román Roy, Narciso; Prieto Martínez, Pedro Daniel

    2015-01-01

    We state a unified geometrical version of the variational principles for second-order classical field theories. The standard Lagrangian and Hamiltonian variational principles and the corresponding field equations are recovered from this unified framework. Peer Reviewed

  13. Towards a third-order topological invariant for magnetic fields

    CERN Document Server

    Hornig, G

    2002-01-01

    An expression for a third-order link integral of three magnetic fields is presented. It is a topological invariant and therefore an invariant of ideal magnetohydrodynamics. The integral generalizes existing expressions for third-order invariants which are obtained from the Massey triple product, where the three fields are restricted to isolated flux tubes. The derivation and interpretation of the invariant shows a close relationship with the well-known magnetic helicity, which is a second-order topological invariant. Using gauge fields with an SU(2) symmetry, helicity and the new third-order invariant originate from the same identity, an identity which relates the second Chern class and the Chern-Simons three-form. We present an explicit example of three magnetic fields with non-disjunct support. These fields, derived from a vacuum Yang-Mills field with a non-vanishing winding number, possess a third-order linkage detected by our invariant.

  14. High-order-harmonic generation from field-distorted orbitals

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Etches, Adam; Madsen, Lars Bojer

    2013-01-01

    We investigate the effect on high-order-harmonic generation of the distortion of molecular orbitals by the driving laser field. Calculations for high-order-harmonic generation including orbital distortion are performed for N2. Our results allow us to suggest that field distortion is the reason why...

  15. Lagrange Multipliers and Third Order Scalar-Tensor Field Theories

    CERN Document Server

    Horndeski, Gregory W

    2016-01-01

    In a space of 4-dimensions, I will examine constrained variational problems in which the Lagrangian, and constraint scalar density, are concomitants of a (pseudo-Riemannian) metric tensor and its first two derivatives. The Lagrange multiplier for these constrained extremal problems will be a scalar field. For suitable choices of the Lagrangian, and constraint, we can obtain Euler-Lagrange equations which are second order in the scalar field and third order in the metric tensor. The effect of disformal transformations on the constraint Lagrangians, and their generalizations, is examined. This will yield other second order scalar-tensor Lagrangians which yield field equations which are at most of third order. No attempt is made to construct all possible third order scalar-tensor Euler-Lagrange equations in a 4-space, although nine classes of such field equations are presented. Two of these classes admit subclasses which yield conformally invariant field equations. A few remarks on scalar-tensor-connection theor...

  16. Field strength scaling in quasi-phase-matching of high-order harmonic generation by low-intensity assisting fields

    CERN Document Server

    Balogh, Emeric

    2016-01-01

    High-order harmonic generation in gas targets is a widespread scheme used to produce extreme ultraviolet radiation, however, it has a limited microscopic efficiency. Macroscopic enhancement of the produced radiation relies on phase-matching, often only achievable in quasi-phase-matching arrangements. In the present work we numerically study quasi-phase-matching induced by low-intensity assisting fields. We investigate the required assisting field strength dependence on the wavelength and intensity of the driving field, harmonic order, trajectory class and period of the assisting field. We comment on the optimal spatial beam profile of the assisting field.

  17. Effect of Rashba Spin-Orbit Interaction on the Stability of Spin-Vortex-Induced Loop Current in Hole-Doped Cuprate Superconductors: A Scenario for the Appearance of Magnetic Field Enhanced Charge Order and Fermi Surface Reconstruction

    Science.gov (United States)

    Morisaki, Tsubasa; Wakaura, Hikaru; Koizumi, Hiroyasu

    2017-10-01

    Rashba type spin-orbit interaction is included in the model Hamiltonian for the spin-vortex-induced loop current (SVILC) mechanism of superconductivity for hole doped cuprate superconductors and its effects are investigated. We assume that a Rashba interaction appears around the small polarons formed by the doped holes in the bulk; its internal electric field is assumed to be in the direction perpendicular to the CuO2 plane and stabilizes the spin polarization lying in the CuO2 plane. We examine 4 × 4, 4 × 6, and 4 × 8 spin-vortex-quartet (SVQ) and perform Monte Carlo simulations to estimate the superconducting transition temperature Tc, where each SVQ is a n × m two dimensional region (in the units of the lattice constant) containing four holes, four spin-vortices, and four SVILCs. We find that the 4 × 6 SVQ is the most stable one among them with the highest Tc; in this case, the hole concentration per Cu atom is x = 0.167, which is close to the optimal doping value x = 0.170, suggesting that the optimal doping may be related to the stabilization of the superconducting state by the Rashba interaction. We also find that the 4 × 8 SVQ becomes more stable than the 4 × 6 SVQ in a current flowing situation; this indicates that the conversion from the 4 × 6 SVQs to 4 × 8 SVQs may occur upon the emergence of a macroscopic current by the application of a magnetic field. This conversion may explain the enhancement of the charge order around x = 0.125 and the Fermi surface reconstruction upon an application of a magnetic field.

  18. Unambiguous formalism for higher order Lagrangian field theories

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Cedric M; De Leon, Manuel; De Diego, David MartIn [Instituto de Ciencias Matematicas, CSIC-UAM-UC3M-UCM, Serrano 123, 28006 Madrid (Spain); Vankerschaver, Joris [Control and Dynamical Systems, California Institute of Technology, CA (United States)], E-mail: cedricmc@imaff.cfmac.csic.es, E-mail: mdeleon@imaff.cfmac.csic.es, E-mail: d.martin@imaff.cfmac.csic.es, E-mail: jv@caltech.edu

    2009-11-27

    The aim of this paper is to propose an unambiguous intrinsic formalism for higher order field theories which avoids the arbitrariness in the generalization of the conventional description of field theories, and implies the existence of different Cartan forms and Legendre transformations. We propose a differential-geometric setting for the dynamics of a higher order field theory, based on the Skinner and Rusk formalism for mechanics. This approach incorporates aspects of both the Lagrangian and the Hamiltonian description, since the field equations are formulated using the Lagrangian on a higher order jet bundle and the canonical multisymplectic form on its affine dual. As both of these objects are uniquely defined, the Skinner-Rusk approach has the advantage that it does not suffer from the arbitrariness in conventional descriptions. The result is that we obtain a unique and global intrinsic version of the Euler-Lagrange equations for higher order field theories. Several examples illustrate our construction.

  19. Field Method for Integrating the First Order Differential Equation

    Institute of Scientific and Technical Information of China (English)

    JIA Li-qun; ZHENG Shi-wang; ZHANG Yao-yu

    2007-01-01

    An important modern method in analytical mechanics for finding the integral, which is called the field-method, is used to research the solution of a differential equation of the first order. First, by introducing an intermediate variable, a more complicated differential equation of the first order can be expressed by two simple differential equations of the first order, then the field-method in analytical mechanics is introduced for solving the two differential equations of the first order. The conclusion shows that the field-method in analytical mechanics can be fully used to find the solutions of a differential equation of the first order, thus a new method for finding the solutions of the first order is provided.

  20. Lagrange Multipliers and Third Order Scalar-Tensor Field Theories

    OpenAIRE

    Horndeski, Gregory W.

    2016-01-01

    In a space of 4-dimensions, I will examine constrained variational problems in which the Lagrangian, and constraint scalar density, are concomitants of a (pseudo-Riemannian) metric tensor and its first two derivatives. The Lagrange multiplier for these constrained extremal problems will be a scalar field. For suitable choices of the Lagrangian, and constraint, we can obtain Euler-Lagrange equations which are second order in the scalar field and third order in the metric tensor. The effect of ...

  1. Modelling of the magnetic field effects in hydrodynamic codes using a second order tensorial diffusion scheme

    Energy Technology Data Exchange (ETDEWEB)

    Breil, J; Maire, P-H; Nicolai, P; Schurtz, G [CELIA, Universite Bordeaux I, CNRS, CEA, 351 cours de la Liberation, 33405 Talence (France)], E-mail: breil@celia.u-bordeaux1.fr

    2008-05-15

    In laser produced plasmas large self-generated magnetic fields have been measured. The classical formulas by Braginskii predict that magnetic fields induce a reduction of the magnitude of the heat flux and its rotation through the Righi-Leduc effect. In this paper a second order tensorial diffusion method used to correctly solve the Righi-Leduc effect in multidimensional code is presented.

  2. Second order higher-derivative corrections in Double Field Theory

    CERN Document Server

    Lescano, Eric

    2016-01-01

    HSZ Double Field Theory is a higher-derivative theory of gravity with exact and manifest T-duality symmetry. The first order corrections in the massless sector were shown to be governed solely by Chern-Simons deformations of the three-form field strength. We compute the full action with up to six derivatives ${\\cal O} (\\alpha'{}^2)$ for the universal sector containing the metric, two-form and dilaton fields. The Green-Schwarz transformation of the two-form field remains uncorrected to second order. In addition to the expected Chern-Simons-squared and Riemann-cubed terms the theory contains a cubic Gauss-Bonnet interaction, plus other six-derivative unambiguous terms involving the three-form field strength whose presence indicates that the theory must contain further higher-derivative corrections.

  3. Second order higher-derivative corrections in Double Field Theory

    Science.gov (United States)

    Lescano, Eric; Marqués, Diego

    2017-06-01

    HSZ Double Field Theory is a higher-derivative theory of gravity with exact and manifest T-duality symmetry. The first order corrections in the massless sector were shown to be governed solely by Chern-Simons deformations of the three-form field strength. We compute the full action with up to six derivatives O({α}^' 2}) for the universal sector containing the metric, two-form and dilaton fields. The Green-Schwarz transformation of the two-form field remains uncorrected to second order. In addition to the expected Chern-Simons-squared and Riemann-cubed terms the theory contains a cubic Gauss-Bonnet interaction, plus other six-derivative unambiguous terms involving the three-form field strength whose presence indicates that the theory must contain further higher-derivative corrections.

  4. Second order semiclassics with self-generated magnetic fields

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

    2012-01-01

    We consider the semiclassical asymptotics of the sum of negative eigenvalues of the three-dimensional Pauli operator with an external potential and a self-generated magnetic field $B$. We also add the field energy $\\beta \\int B^2$ and we minimize over all magnetic fields. The parameter $\\beta......$ effectively determines the strength of the field. We consider the weak field regime with $\\beta h^{2}\\ge {const}>0$, where $h$ is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order...... in the companion paper \\cite{EFS3} to prove the second order Scott correction to the ground state energy of large atoms and molecules....

  5. Self-Deflection of Dark Screening Spatial Solitons Based on Higher-Order Space Charge Field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-Yong; LIU Jin-Song; LIU Shi-Xiong; WANG Cheng; ZHANG Hui-Lan

    2007-01-01

    The effects of higher-order space charge field on the self-deflection of dark screening spatial solitons in biased photorefractive crystals are numerically investigated under steady-state conditions. The expression for an induced space-charge electric field including higher-order space-charge field terms is obtained. Numerical results indicate that dark solitons possess a self-deflection process during propagation, and the solitons always bend in the direction of the c axis of the crystal The self-deflection of dark solitons can experience considerable increase especially in the regime of high bias field strengths.

  6. Competing superconducting and magnetic order parameters and field-induced magnetism in electron doped Ba(Fe1-xCox)2As2

    DEFF Research Database (Denmark)

    Larsen, Jacob; Uranga, B. Mencia; Stieber, G.

    2015-01-01

    We have studied the magnetic and superconducting properties of Ba(Fe1-xCox)2As2 as a function of temperature and external magnetic field using neutron scattering and muon spin rotation. Below the superconducting transition temperature the magnetic and superconducting order parameters coexist...

  7. First-order framework for flat brane with auxiliary fields

    CERN Document Server

    Bazeia, D; Menezes, R

    2014-01-01

    This work deals with braneworld models in the presence of auxiliary fields. We investigate the case where Einstein's equation is modified with the inclusion of extra, non-dynamical terms. We show that the model supports first-order differential equations that solve the equations of motion, but the standard braneworld scenario changes under the presence of the parameter that controls the non-dynamical or auxiliary fields that modifies Einstein's equation.

  8. High-order harmonic generation from inhomogeneous fields

    CERN Document Server

    Ciappina, M F; Quidant, R; Lewenstein, M

    2011-01-01

    We present theoretical studies of high-order harmonic generation (HHG) produced by non-homogeneous fields as resulting from the illumination of plasmonic nanostructures with a short laser pulse. We show that the inhomogeneity of the local fields plays an important role in the HHG process and lead to the generation of even harmonics and a significantly increased cutoff, more pronounced for the longer wavelengths cases studied. In order to understand and characterize the new HHG features we employ two different approaches: the numerical solution of the time dependent Schr\\"odinger equation (TDSE) and the semiclassical approach known as Strong Field Approximation (SFA). Both approaches predict comparable results and show the new features, but using the semiclassical arguments behind the SFA, we are able to fully understand the reasons of the cutoff extension.

  9. Periodic Orbits in Rotating Second Degree and Order Gravity Fields

    Institute of Scientific and Technical Information of China (English)

    Wei-Duo Hu; Daniel J.Scheeres

    2008-01-01

    Periodic orbits in an arbitrary 2nd degree and order uniformly rotating gravity field are studied. We investigate the four equilibrium points in this gravity field. We see that close relation exists between the stability of these equilibria and the existence and stability of their nearby periodic orbits. We check the periodic orbits with non-zero periods. In our searching procedure for these periodic orbits, we remove the two unity eigenvalues from the state transition matrix to find a robust, non-singular linear map to solve for the periodic orbits. The algorithm converges well, especially for stable periodic orbits. Using the searching procedure, which is relatively automatic, we find five basic families of periodic orbits in the rotating second degree and order gravity field for planar motion, and discuss their existence and stability at different central body rotation rates.

  10. Geometry of Lagrangian First-order Classical Field Theories

    CERN Document Server

    Echeverría-Enríquez, A; Román-Roy, N; Echeverr\\'ia-Enr\\'iquez, Arturo; Muñoz-Lecanda, Miguel C.; Román-Roy, Narciso

    1996-01-01

    We construct a lagrangian geometric formulation for first-order field theories using the canonical structures of first-order jet bundles, which are taken as the phase spaces of the systems in consideration. First of all, we construct all the geometric structures associated with a first-order jet bundle and, using them, we develop the lagrangian formalism, defining the canonical forms associated with a lagrangian density and the density of lagrangian energy, obtaining the {\\sl Euler-Lagrange equations} in two equivalent ways: as the result of a variational problem and developing the {\\sl jet field formalism} (which is a formulation more similar to the case of mechanical systems). A statement and proof of Noether's theorem is also given, using the latter formalism. Finally, some classical examples are briefly studied.

  11. Fringing field correction of the second-order angular aberration in sector field electron energy analyzers

    Energy Technology Data Exchange (ETDEWEB)

    Yavor, M.I. [Institute for Analytical Instrumentation RAS, 190103 St. Petersburg (Russian Federation)], E-mail: mikhail.yavor@gmail.com; Belov, V.D.; Pomozov, T.V. [Institute for Analytical Instrumentation RAS, 190103 St. Petersburg (Russian Federation)

    2008-12-15

    A new way of correcting the second-order angular aberration in sector field and polar-toroidal electron energy analyzers with object and image located outside the field is proposed. Correction is performed by biasing the optic axis electrostatic potential inside the analyzer with respect to the potential of surrounding field-free space. The strength of the correcting aberration concentrated in the fringing field regions of the analyzer is calculated with the aid of the fringing field integral method. The described correction allows achieving second-order focusing and thus increasing the energy resolving power in sector field analyzers, in particular used for angle resolved energy measurements.

  12. Strong-field ionization via high-order Coulomb corrected strong-field approximation

    CERN Document Server

    Klaiber, Michael; Yakaboylu, Enderalp; Hatsagortsyan, Karen Z; Keitel, Christoph H

    2016-01-01

    Signatures of the Coulomb corrections in the photoelectron momentum distribution during laser-induced ionization of atoms or ions in tunneling and multiphoton regimes are investigated analytically in the case of an one-dimensional problem. High-order Coulomb corrected strong-field approximation is applied, where the exact continuum state in the S-matrix is approximated by the eikonal Coulomb-Volkov state including the second-order corrections to the eikonal. Although, without high-order corrections our theory coincides with the known analytical R-matrix (ARM) theory, we propose a simplified procedure for the matrix element derivation. Rather than matching the eikonal Coulomb-Volkov wave function with the bound state as in the ARM-theory to remove the Coulomb singularity, we calculate the matrix element via the saddle-point integration method as by time as well as by coordinate, and in this way avoiding the Coulomb singularity. The momentum shift in the photoelectron momentum distribution with respect to the A...

  13. Second order semiclassics with self-generated magnetic fields

    CERN Document Server

    Erdos, Laszlo; Solovej, Jan Philip

    2011-01-01

    We consider the semiclassical asymptotics of the sum of negative eigenvalues of the three-dimensional Pauli operator with an external potential and a self-generated magnetic field $B$. We also add the field energy $\\beta \\int B^2$ and we minimize over all magnetic fields. The parameter $\\beta$ effectively determines the strength of the field. We consider the weak field regime with $\\beta h^{2}\\ge {const}>0$, where $h$ is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order with an error bound that is smaller by a factor $h^{1+\\e}$, i.e. the subleading term vanishes. However, for potentials with a Coulomb singularity the subleading term does not vanish due to the non-semiclassical effect of the singularity. Combined with a multiscale technique, this refined estimate is used in the companion paper \\cite{EFS3} to prove the second order Scott correction to the ground state energy of large atoms an...

  14. Theory of field induced incommensurability: CsFeCl3

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1986-01-01

    Using correlation theory for the singlet-doublet magnet CsFeCl3 in a magnetic field, a field induced incommensurate ordering along K-M is predicted without invoking dipolar effects. A fully self-consistent RPA theory gives Hc=44 kG in agreement with experiments at T=1.3K. Correlation and dipolar ...

  15. First- and second-order statistics of optical near fields.

    Science.gov (United States)

    Apostol, Adela; Dogariu, Aristide

    2004-02-01

    The statistical properties of the intensity in close proximity to highly scattering, randomly inhomogeneous media are investigated. Whereas the intensity probability density function obeys the same law irrespective of the distance z from the interface, the second-order intensity correlation length changes for distances smaller than the wavelength. Contrary to predictions of the conventional coherence theory, the corresponding field correlation length can be smaller than the wavelength of light.

  16. The effect of induced multipoles on the fifth-order Raman response

    NARCIS (Netherlands)

    la Cour Jansen, T.; Duppen, K.; Snijders, J. G.

    2003-01-01

    In our previous work we developed the Finite Field method in order to calculate the fifth-order Raman response. The method was applied to calculate various polarization components of the two-dimensional response of liquid CS2. So far, all calculations relied on the dipole-induced dipole. Accurate ti

  17. Modulation field induces universe rotation

    CERN Document Server

    Chen, Chien Yu

    2008-01-01

    Noncommutative field theory is a theory concerning a background field on the string world sheet. Whole of the universe is survived on background field situation. In this paper, we consider a module field on spacetime expansion without modifying commutative relation, and omit the deformed effects by $\\star$ production. Lorentz symmetry is conserved on module and unmodule coordinate, the violation point is under the translation between each others by module expansion. However, considering a background field on spacetime geodesic we could understand that even magnetic force could not be generated by putting a module $Poincar\\check{e}$ boost due to CPT conservation. Which phenomenon, each particle field will be rotated and expanded. Assembling the commutative and anti-commutative null vector by putting an operated coefficients on three orthogonal states. Spacetime is homogeneous but anisotropic, since the energy fluid is not uniformed by a distribution of modulation field. Therefore, concentrating on which signif...

  18. Overlay control methodology comparison: field-by-field and high-order methods

    Science.gov (United States)

    Huang, Chun-Yen; Chiu, Chui-Fu; Wu, Wen-Bin; Shih, Chiang-Lin; Huang, Chin-Chou Kevin; Huang, Healthy; Choi, DongSub; Pierson, Bill; Robinson, John C.

    2012-03-01

    Overlay control in advanced integrated circuit (IC) manufacturing is becoming one of the leading lithographic challenges in the 3x and 2x nm process nodes. Production overlay control can no longer meet the stringent emerging requirements based on linear composite wafer and field models with sampling of 10 to 20 fields and 4 to 5 sites per field, which was the industry standard for many years. Methods that have emerged include overlay metrology in many or all fields, including the high order field model method called high order control (HOC), and field by field control (FxFc) methods also called correction per exposure. The HOC and FxFc methods were initially introduced as relatively infrequent scanner qualification activities meant to supplement linear production schemes. More recently, however, it is clear that production control is also requiring intense sampling, similar high order and FxFc methods. The added control benefits of high order and FxFc overlay methods need to be balanced with the increased metrology requirements, however, without putting material at risk. Of critical importance is the proper control of edge fields, which requires intensive sampling in order to minimize signatures. In this study we compare various methods of overlay control including the performance levels that can be achieved.

  19. Chiral effective field theory on the lattice at next-to-leading order

    CERN Document Server

    Borasoy, Bugra; Krebs, Hermann; Lee, Dean; Meißner, Ulf-G

    2007-01-01

    We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a hard spherical wall in the center-of-mass frame. At fixed lattice spacing we test model independence of the low-energy effective theory by computing next-to-leading-order corrections for two different leading-order lattice actions. The first leading-order action includes instantaneous one-pion exchange and same-site contact interactions. The second leading-order action includes instantaneous one-pion exchange and Gaussian-smeared interactions. We find that in each case the results at next-to-leading order are accurate up to corrections expected at higher order.

  20. A Study of Thermocurrent Induced Magnetic Fields in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Anthony C. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, Victoria [Univ. of Wisconsin, Madison, WI (United States)

    2014-03-31

    The case of axisymmetric ILC-type cavities with titanium helium vessels is investigated. A first-order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.

  1. A Study of Thermocurrent Induced Magnetic Fields in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Anthony C. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, Victoria [Univ. of Wisconsin, Madison, WI (United States)

    2014-03-31

    The case of axisymmetric ILC type cavities with titanium helium vessels is investigated. A first order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.

  2. Orientation ordering in J = 1 solid hydrogens at crystal fields

    CERN Document Server

    Antsygina, T N; Freimann, Y A; Hemley, R J

    2003-01-01

    A system of quantum linear rotators with a rotational quantum number J 1 is considered at a crystal field. An equation for orientation order parameter is derived, and the critical parameters, the phase separation curve and the lines of overheating and overcooling points are obtained. It is shown that in terms of the thermodynamics the behavior of the above linear rotators in the classical case and in the extremely quantum (J = 1) one is identical. For positive values of the crystal field there also exist parallels between orientation phase transitions in a system of rotators with J = 1 and phase transitions in a liquid-vapor system. It is shown that the consideration of J > 1 states results in a radical change of the phase transition behavior in a system of rotators: instead of the sole critical point typical for the J = 1 system, there appears a line of critical points.

  3. Thermal field theory to all orders in gradient expansion

    CERN Document Server

    Millington, Peter

    2013-01-01

    We present a new perturbative formulation of non-equilibrium thermal field theory, based upon non-homogeneous free propagators and time-dependent vertices. The resulting time-dependent diagrammatic perturbation series are free of pinch singularities without the need for quasi-particle approximation or effective resummation of finite widths. After arriving at a physically meaningful definition of particle number densities, we derive master time evolution equations for statistical distribution functions, which are valid to all orders in perturbation theory and all orders in a gradient expansion. For a scalar model, we make a loopwise truncation of these evolution equations, whilst still capturing fast transient behaviour, which is found to be dominated by energy-violating processes, leading to non-Markovian evolution of memory effects.

  4. Slowly rotating scalar field wormholes: the second order approximation

    CERN Document Server

    Kashargin, P E

    2008-01-01

    We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the non-rotating one, and the NEC violation in the rotating wormhole spacetime is weaker than that in the non-rotating one.

  5. Linearly first- and second-order, unconditionally energy stable schemes for the phase field crystal model

    Science.gov (United States)

    Yang, Xiaofeng; Han, Daozhi

    2017-02-01

    In this paper, we develop a series of linear, unconditionally energy stable numerical schemes for solving the classical phase field crystal model. The temporal discretizations are based on the first order Euler method, the second order backward differentiation formulas (BDF2) and the second order Crank-Nicolson method, respectively. The schemes lead to linear elliptic equations to be solved at each time step, and the induced linear systems are symmetric positive definite. We prove that all three schemes are unconditionally energy stable rigorously. Various classical numerical experiments in 2D and 3D are performed to validate the accuracy and efficiency of the proposed schemes.

  6. Field enhancement induced laser ablation

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    Sub-diffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures...

  7. Errors of first-order probe correction for higher-order probes in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Nielsen, Jeppe Majlund; Pivnenko, Sergiy

    2004-01-01

    An investigation is performed to study the error of the far-field pattern determined from a spherical near-field antenna measurement in the case where a first-order (mu=+-1) probe correction scheme is applied to the near-field signal measured by a higher-order probe....

  8. A time correlation function theory describing static field enhanced third order optical effects at interfaces.

    Science.gov (United States)

    Neipert, Christine; Space, Brian

    2006-12-14

    Sum vibrational frequency spectroscopy, a second order optical process, is interface specific in the dipole approximation. At charged interfaces, there exists a static field, and as a direct consequence, the experimentally detected signal is a combination of enhanced second and static field induced third order contributions. There is significant evidence in the literature of the importance/relative magnitude of this third order contribution, but no previous molecularly detailed approach existed to separately calculate the second and third order contributions. Thus, for the first time, a molecularly detailed time correlation function theory is derived here that allows for the second and third order contributions to sum frequency vibrational spectra to be individually determined. Further, a practical, molecular dynamics based, implementation procedure for the derived correlation functions that describe the third order phenomenon is also presented. This approach includes a novel generalization of point atomic polarizability models to calculate the hyperpolarizability of a molecular system. The full system hyperpolarizability appears in the time correlation functions responsible for third order contributions in the presence of a static field.

  9. The Weak Field Limit of Higher Order Gravity

    CERN Document Server

    Stabile, Arturo

    2008-01-01

    The Higher Order Theories of Gravity - $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta})$ - theory, where $R$ is the Ricci scalar, $R_{\\alpha\\beta}$ is the Ricci tensor and $f$ is any analytic function - have recently attracted a lot of interest as alternative candidates to explain the observed cosmic acceleration, the flatness of the rotation curves of spiral galaxies and other relevant astrophysical phenomena. It is a crucial point testing these alternative theories in the so called weak field and newtonian limit of a $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta})$ - theory. With this "perturbation technique" it is possible to find spherically symmetric solutions and compare them with the ones of General Relativity. On both approaches we found a modification of General Relativity: the behaviour of gravitational potential presents a modification Yukawa - like in the newtonian case and a massive propagation in the weak field case. When the modification of the theory is removed (i.e. $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta}) = R$, Hil...

  10. Total Field and Scattered Field Technique for Fourth-Order Symplectic Finite Difference Time Domain Method

    Institute of Scientific and Technical Information of China (English)

    SHA Wei; HUANG Zhi-Xiang; WU Xian-Liang; CHEN Ming-Sheng

    2006-01-01

    Using symplectic integrator propagator, a three-dimensional fourth-order symplectic finite difference time domain (SFDTD) method is studied, which is of the fourth order in both the time and space domains. The method is nondissipative and can save more memory compared with the traditional FDTD method. The total field and scattered field (TF-SF) technique is derived for the SFDTD method to provide the incident wave source conditions. The bistatic radar cross section (RCS) of a dielectric sphere is computed by using the SFDTD method for the first time. Numerical results suggest that the SFDTD algorithm acquires better stability and accuracy compared with the traditional FDTD method.

  11. High-order harmonic generation from Rydberg atoms driven by plasmonic-enhanced laser fields

    CERN Document Server

    Tikman, Y; Ciappina, M F; Chacon, A; Altun, Z; Lewenstein, M

    2015-01-01

    We theoretically investigate high-order harmonic generation (HHG) in Rydberg atoms driven by spatially inhomogeneous laser fields, induced, for instance, by plasmonic enhancement. It is well known that the laser intensity should to exceed certain threshold in order to generate HHG, when noble gas atoms in their ground state are used as an active medium. One way to enhance the coherent light coming from a conventional laser oscillator is to take advantage of the amplification obtained by the so-called surface plasmon polaritons, created when a low intensity laser field is focused onto a metallic nanostructure. The main limitation of this scheme is the low damage threshold of the materials employed in the nanostructures engineering. In this work we propose to use Rydberg atoms, driven by spatially inhomogeneous, plasmonic-enhanced laser fields, for HHG. We exhaustively discuss the behaviour and efficiency of these systems in the generation of coherent harmonic emission. To this aim we numerically solve the time...

  12. Weak lensing from self-ordering scalar fields

    Science.gov (United States)

    Saga, Shohei; Horiguchi, Kouichirou; Ichiki, Kiyotomo

    2017-06-01

    Cosmological defects result from cosmological phase transitions in the early Universe and the dynamics reflects their symmetry-breaking mechanisms. These cosmological defects may be probed through weak lensing effects because they interact with ordinary matters only through the gravitational force. In this paper, we investigate global textures by using weak lensing curl and B modes. Nontopological textures are modeled by the nonlinear sigma model (NLSM) and induce not only the scalar perturbation but also vector and tensor perturbations in the primordial plasma due to the nonlinearity in the anisotropic stress of scalar fields. We show angular power spectra of curl and B modes from both vector and tensor modes based on the NLSM. Furthermore, we give the analytic estimations for curl and B-mode power spectra. The amplitude of weak lensing signals depends on a combined parameter ɛv2=N-1(v/mpl) 4 where N and v are the number of the scalar fields and the vacuum expectation value, respectively. We discuss the detectability of the curl and B modes with several observation specifications. In the case of the CMB lensing observation without including the instrumental noise, we can reach ɛv≈2.7 ×10-6 . This constraint is about 10 times stronger than the current one determined from the Planck. For the cosmic shear observation, we find that the signal-to-noise ratio depends on the mean redshift and the observing number of galaxies as ∝zm0.7 and ∝Ng0.2, respectively. In the study of textures using cosmic shear observations, the mean redshift would be one of the key design parameters.

  13. Electric Field Effect on the Magnetic Order in Multiferroic LuMnO3

    Science.gov (United States)

    Duan, Chunruo; Yang, Junjie; Harriger, Leland; Louca, Despina

    LuMnO3 belongs to the family of hexagonal multiferroics in which ferroelectric and magnetic orders coexist and compete. The Mn3+ ions reside on a triangular lattice that is geometrically frustrated but undergoes a Neel transition at TN ~90 K. Neutron experiments under electric field were carried out on a single crystal of LuMnO3 at SPINS to investigate the coupling of the electric field to the magnetic order. The elastic and inelastic scattering around the commensurate (101) magnetic peak and the Mn trimerization induced (100) peak with and without electric field were investigated. When applying an E-field of 13.3 kV/cm along the (001) direction on an unpoled sample, an increase in (101) peak as well as a shift of the inelastic excitation near (100) to higher ΔE have been observed. Once the sample is polarized, these effects exist without the field. On the other hand, an E-field along (110) direction shows almost no effect. The spin arrangement of the magnetic order is within the ab-plane, thus the Dzyaloshinskii-Moriya interaction explains why a polarization perpendicular to the magnetic moment gives a larger effect. The implication will be discussed.

  14. Cosmic string interactions induced by gauge and scalar fields

    CERN Document Server

    Kabat, Daniel

    2012-01-01

    We study the interaction between two parallel cosmic strings induced by gauge fields and by scalar fields with non-minimal couplings to curvature. For small deficit angles the gauge field behaves like a collection of non-minimal scalars with a specific value for the non-minimal coupling. We check this equivalence by computing the interaction energy between strings at first order in the deficit angles. This result provides another physical context for the "contact terms" which play an important role in the renormalization of black hole entropy due to a spin-1 field.

  15. Evidence of stress-induced hydrogen ordering in zirconium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Steuwer, A. [FaME38 at the ESRF-ILL, 6 rue J Horowitz, 38042 Grenoble (France); ESS Scandinavia, University of Lund, Stora Algatan 4, 22350 Lund (Sweden)], E-mail: steuwer@ill.fr; Santisteban, J.R. [Centro Atomico Bariloche, CNEA, San Carlos de Bariloche (Argentina); Preuss, M. [University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Peel, M.J.; Buslaps, T. [European Synchrotron Radiation Facility, 6 rue J Horowitz, 38042 Grenoble (France); Harada, M. [R and D Section, Chofu-Kita Plant, Kobe Special Tube Co, Shimonoseki 752-0953 (Japan)

    2009-01-15

    The formation of hydrides in zirconium alloys significantly affects their mechanical properties and is considered to play a critical role in their failure mechanisms, yet relatively little is known about the micromechanical behavior of hydrides in the bulk. This paper presents the result of in situ uniaxial mechanical tensioning experiments on hydrided zircaloy-2 and zircaloy-4 specimens using energy-dispersive synchrotron X-ray diffraction, which suggests that a stress-induced transformation of the {delta}-hydride to {gamma}-hydride via ordering of the hydrogen atoms occurs, akin to a Snoek-type relaxation. Subsequent annealing was found to reverse the ordering phenomenon.

  16. Complexity Induced Lifshitz Ordering with Multifractal Antiscreening/Screening (CILOMAS)

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Tom T.S., E-mail: tom.tschang@gmail.com

    2016-04-08

    We demonstrate that renormalization-group effects of scale-running propagator-coupling constants due to classical fluctuations can induce antiscreening/screening and multifractal symmetry breakings among various helical and other ordered states of generalized Lifshitz character leading to novel phase-transition associated complexities in condensed matter physics and gravitational evolution. Such phenomenon can exhibit the sporadic and localized appearance of virtual particles and in the context of cosmological evolution, the coarse-grained scale-running of the gravitational constant G due to classical fluctuations may provide a partial explanation to the dark matter mystery. - Highlights: • An innovative theory in phase transitions related to complex helical orderings. • The phenomenon is induced by the “running” of the propagator-coupling constant. • The calculations are based on the exact renormalization group. • An example of gravitational evolution is described. • CILOMAS discusses Lifshitz points and virtual particles such as dark matter.

  17. Phase-field-crystal model for fcc ordering.

    Science.gov (United States)

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to and reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  18. Recovery of Topological Order Induced by Random Perturbations

    CERN Document Server

    Tsomokos, D I; Castelnovo, C

    2010-01-01

    We analyze the toric code model in presence of quenched disorder, which is introduced via different types of random magnetic fields. Remarkably, we find that topological order can be robust against arbitrarily strong disorder. In general, close to a quantum phase transition between a spin polarized phase and a topologically ordered one, increasing the amount of disorder favors the topological phase. For some realizations of disorder, a quantum spin glass phase borders the topological phase, thus leading to a peculiar transition between two quantum spin liquids, which differ purely by nonlocal properties.

  19. Order parameter and its critical exponent for some binary mixtures showing induced nematic phase

    Science.gov (United States)

    Sarkar, Sudipta Kumar; Das, Malay Kumar

    2016-09-01

    Refractive index measurements as a function of temperature have been performed for an induced nematic binary system by means of thin prism technique. The temperature dependence of the birefringence (Δn) has been assessed from the measured refractive index data. A direct extrapolation method has been employed to determine the orientational order parameter for the investigated mixtures and the order parameter so obtained has also been compared with the mean field values. The Haller type fitting expression results in a relatively lower value of the order parameter critical exponent (β) compared to the theoretically predicted values. Therefore, a four-parameter power law expression, consistent with the mean field theory as well as the first-order character of the nematic-isotropic (N-I) phase transition have been used to explore the critical behavior of the order parameter near the N-I transition.

  20. Induced magnetic ordering transition in RCo{sub 5} type materials

    Energy Technology Data Exchange (ETDEWEB)

    Rivin, Oleg, E-mail: drorivin@gmail.com [Department of Physics, Nuclear Research Center – Negev, P.O. Box 9001, Beer Sheva 84190 (Israel); Department of Physics, Ben-Gurion University, P.O. Box 653, Beer Sheva 84105 (Israel); Shaked, Hagai [Department of Physics, Ben-Gurion University, P.O. Box 653, Beer Sheva 84105 (Israel); Caspi, El’ad N. [Department of Physics, Nuclear Research Center – Negev, P.O. Box 9001, Beer Sheva 84190 (Israel)

    2015-09-15

    The magnetism in several materials of the RCo{sub 5} type is studied. A numerical calculation scheme, based on an induced magnetic ordering transition, is set up. Using this scheme, and previously reported crystalline electric and magnetic exchange fields parameters, the magnetic structure in R{sub 1−y}Y{sub y}Co{sub 3}B{sub 2} and R(Co{sub 1−x}Ni{sub x}){sub 5} materials (R=Tb and Ho), and its temperature evolution, is calculated, and compared with the corresponding observed results. It is proposed that the magnetic order in the materials of the RCO{sub 5} type, with R{sup 3+} of integral J, is driven by an induced transition. - Highlights: • A numerical calculations scheme, that simulates induced transition magnetic ordering in R{sub 1−y}YyCo{sub 3}B{sub 2} and R(Co{sub 1−x}Ni{sub x}){sub 5} type materials, is set up. • The observed ordered magnetic moment of the R sub-lattice, as function of the magnetic exchange field, and as function of temperature, is shown to agree with induced transition theory, and not with Curie–Weiss theory. • In R{sub 1−y}Y{sub y}Co{sub 3}B{sub 2}, the relative magnitudes of the crystalline electric field and the magnetic exchange field are just above the critical threshold for induced transition ordering, making them the best experimental ‘realization’ found so far.

  1. Electric field effect on the second-order nonlinear optical properties in semiparabolic quantum wells

    Science.gov (United States)

    Yuan, Jian-Hui; Chen, Ni; Zhang, Yan; Mo, Hua; Zhang, Zhi-Hai

    2016-03-01

    Electric field effect on the second-order nonlinear optical properties in semiparabolic quantum wells are studied theoretically. Both the second-harmonic generation susceptibility and nonlinear optical rectification depend dramatically on the direction and the strength of the electric field. Numerical results show that both the second-harmonic generation susceptibility and nonlinear optical rectification are always weakened as the electric field increases where the direction of the electric field is along the growth direction of the quantum wells, which is in contrast to the conventional case. However, the second-harmonic generation susceptibility is weakened, but the nonlinear optical rectification is strengthened as the electric field increases where the direction of the electric field is against the growth direction of the quantum wells. Also it is the blue (or red) shift of the resonance that is induced by increasing of the electric field when the direction of the electric field is along (or against) the growth direction of the quantum wells. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.

  2. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    Science.gov (United States)

    Jang, H.; Lee, W.-S.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Nie, L.; Maharaj, A. V.; Gerber, S.; Liu, Y.-J.; Mehta, A.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Burns, C. A.; Islam, Z.; Song, S.; Hastings, J.; Devereaux, T. P.; Shen, Z.-X.; Kivelson, S. A.; Kao, C.-C.; Zhu, D.; Lee, J.-S.

    2016-12-01

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.

  3. Three-Dimensional Charge Density Wave Order in YBa2Cu3O6.67 at High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, S.; Jang, H.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Bonn, D. A.; Liang, R.; Hardy, W.; Islam, Z.; Lee, W. -S.; Zhu, D.; Lee, J. -S.

    2015-11-20

    Charge density wave (CDW) correlations have been shown to universally exist in cuprate superconductors. However, their nature at high fields inferred from nuclear magnetic resonance is distinct from that measured by x-ray scattering at zero and low fields. Here we combine a pulsed magnet with an x-ray free electron laser to characterize the CDW in YBa2Cu3O6.67 via x-ray scattering in fields up to 28 Tesla. While the zero-field CDW order, which develops below T ~ 150 K, is essentially two-dimensional, at lower temperature and beyond 15 Tesla, another three-dimensionally ordered CDW emerges. The field-induced CDW onsets around the zero-field superconducting transition temperature, yet the incommensurate inplane ordering vector is field-independent. This implies that the two forms of CDW and hightemperature superconductivity are intimately linked.

  4. Near-field measurements of the even-order harmonics undetectable in far-field measurements

    Science.gov (United States)

    Moiseyev, Nimrod

    2016-12-01

    Even-order harmonics (EOHs) are generated for oriented molecules and for atoms under specific conditions. Here, we focus on the most common situations where EOHs are not observed in far-field measurements. We propose an experiment to show that the EOHs are produced close to the nucleus but are not detected in the far-field measurements due to destructive interferences of the propagated EOHs of the emitted radiation. However, Rydberg gas atoms (e.g., rubidium), which are out of the focus of the laser beam, are expected to be ionized due to their weak interaction with a specific EOH of helium, which is not observed by the far-field detector. The ionization energy of the Rydberg gas atoms should be in resonance with the single-photon energy of a specific EOH.

  5. Electromagnetic currents induced by color fields

    CERN Document Server

    Tanji, Naoto

    2015-01-01

    The quark production in classical color fields is investigated with a focus on the induction of an electromagnetic current by produced quarks. We show that the SU(2) and the SU(3) theories lead significantly different results for the electromagnetic current. In uniform SU(2) color fields, the net electromagnetic current is not generated, while for SU(3) the net current is induced depending on the color direction of background fields. Also the numerical study of the quark production in inhomogeneous color fields is done. Motivated by gauge field configurations provided by the color glass condensate framework, we introduce an ensemble of randomly distributed color electric fluxtubes. The spectrum of photons emitted from the quarks by a classical process is shown.

  6. Magnetic field induced optical vortex beam rotation

    CERN Document Server

    Shi, Shuai; Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen

    2015-01-01

    Light with orbital angular momentum (OAM) has drawn a great deal of attention for its important applications in the fields of precise optical measurements and high capacity optical communications. Here we adopt a method to study the rotation of a light beam, which is based on magnetic field induced circular birefringence in warm 87Rb atomic vapor. The dependence of the rotation angle to the intensity of the magnetic field makes it appropriate for weak magnetic field measurement. We derive a detail theoretical description that is in well agreement with the experimental observations. The experiment shows here provides a new method for precise measurement of magnetic field intensity and expands the application of OAM-carrying light.

  7. Electromagnetic field at finite temperature: A first order approach

    Science.gov (United States)

    Casana, R.; Pimentel, B. M.; Valverde, J. S.

    2006-10-01

    In this work we study the electromagnetic field at finite temperature via the massless DKP formalism. The constraint analysis is performed and the partition function for the theory is constructed and computed. When it is specialized to the spin 1 sector we obtain the well-known result for the thermodynamic equilibrium of the electromagnetic field.

  8. An empirical study to order citation statistics between subject fields

    CERN Document Server

    van Zyl, J Martin

    2012-01-01

    An empirical study is conducted to compare citations per publication, statistics and observed Hirsch indexes between subject fields using summary statistics of countries. No distributional assumptions are made and ratios are calculated. These ratios can be used to make approximate comparisons between researchers of different subject fields with respect to the Hirsch index.

  9. Fourth order phase-field model for local max-ent approximants applied to crack propagation

    OpenAIRE

    Amiri, Fatemeh; Millán, Daniel; Arroyo Balaguer, Marino; Silani, Mohammad; Rabczuk, Timon

    2016-01-01

    We apply a fourth order phase-field model for fracture based on local maximum entropy (LME) approximants. The higher order continuity of the meshfree LME approximants allows to directly solve the fourth order phase-field equations without splitting the fourth order differential equation into two second order differential equations. We will first show that the crack surface can be captured more accurately in the fourth order model. Furthermore, less nodes are needed for the fourth order model ...

  10. Van der Waals torque induced by external magnetic fields

    CERN Document Server

    Esquivel-Sirvent, R; Palomono-Ovando, M

    2010-01-01

    We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III-IV semiconductors such as $InSb$, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of $InSb$. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of $InSb$ increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.

  11. Van der Waals torque induced by external magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel-Sirvent, R.; Cocoletzi, G. H.; Palomino-Ovando, M.

    2010-01-01

    We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III–IV semiconductors such as InSb, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of InSb. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of InSb increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropicmaterials when the magnetic fields is close to 1 T.

  12. Electric field induced short range to long range structural ordering and its influence on the Eu{sup +3} photoluminescence in the lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kalaskar, Abhijeet; Rao, Badari Narayana; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science Bangalore, Bangalore 560012 (India); Thomas, Tiju, E-mail: tijuthomas@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu (India)

    2015-06-28

    Eu{sup +3} was incorporated into the lattice of a lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) as per the nominal formula Na{sub 0.5}Bi{sub 0.5−x}Eu{sub x}TiO{sub 3}. This system was investigated with regard to the Eu{sup +3} photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a long range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main {sup 5}D{sub 0}→{sup 7}F{sub 0} line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu{sup +3} luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.

  13. The second-order Klein-Gordon field equation

    OpenAIRE

    Gomes, D.; E. Capelas De Oliveira

    2004-01-01

    We introduce and discuss the generalized Klein-Gordon second-order partial differential equation in the Robertson-Walker space-time, using the Casimir second-order invariant operator written in hyperspherical coordinates. The de Sitter and anti-de Sitter space-times are recovered by means of a convenient choice of the parameter associated to the space-time curvature. As an application, we discuss a few properties of the solutions. We also discuss the case where we have positive frequency expo...

  14. Second order nonlinearity in Si by inhomogeneous strain and electric fields

    Science.gov (United States)

    Schilling, Jörg; Schriever, Clemens; Bianco, Federica; Cazzanelli, Massimo; Pavesi, Lorenzo

    2015-08-01

    The lack of a dipolar second order susceptibility (χ(2)) in silicon due to its centro-symmetric diamond lattice usually inhibits efficient second order nonlinear optical processes in the silicon bulk. Depositing stressed silicon nitride layers or growing a thermal oxide layer introduces an inhomogeneous strain into the silicon lattice and breaks the centro-symmetry of its crystal structure thereby creating a χ(2). This causes enhanced second harmonic generation and was observed in reflection and transmission measurements for wavelengths in the infrared. However strain is not the only means to break the structures symmetry. Fixed charges at the silicon nitride/silicon interface cause a high electric field close to the silicon interface which causes electric-field-induced-second-harmonic (EFISH) contributions too. The combination of both effects leads to χ(2) values which are estimated to be of the order as classic χ(2) materials like KDP or LiNiO3. This paves the way for the exploitation of other second order nonlinear processes in the area of silicon photonics and is an example how fundamental optical properties of materials can be altered by strain.

  15. Electromagnetic Field in Lyra Manifold: A First Order Approach

    Science.gov (United States)

    Casana, R.; de Melo, C. A. M.; Pimentel, B. M.

    2005-12-01

    We discuss the coupling of the electromagnetic field with a curved and torsioned Lyra manifold using the Duffin-Kemmer-Petiau theory. We will show how to obtain the equations of motion and energy-momentum and spin density tensors by means of the Schwinger Variational Principle.

  16. Electromagnetic Field in Lyra Manifold: A First Order Approach

    CERN Document Server

    Casana, R; Pimentel, B M

    2016-01-01

    We discuss the coupling of the electromagnetic field with a curved and torsioned Lyra manifold using the Duffin-Kemmer-Petiau theory. We will show how to obtain the equations of motion and energy-momentum and spin density tensors by means of the Schwinger Variational Principle.

  17. The Weak Field Limit of Fourth Order Gravity

    CERN Document Server

    Capozziello, Salvatore

    2010-01-01

    We discuss Newtonian and the post-Newtonian limits of Fourth Order Gravity Theories pointing out, in details, their resemblances and differences with respect to General Relativity. Particular emphasis is placed on the exact solutions and methods used to obtain them.

  18. The Weak Field Limit of Fourth Order Gravity

    OpenAIRE

    Capozziello, Salvatore; Stabile, Arturo

    2010-01-01

    We discuss Newtonian and the post-Newtonian limits of Fourth Order Gravity Theories pointing out, in details, their resemblances and differences with respect to General Relativity. Particular emphasis is placed on the exact solutions and methods used to obtain them.

  19. Role of high-order dispersion on strong-field laser-molecule interactions

    Science.gov (United States)

    Dantus, Marcos; Nairat, Muath

    2016-05-01

    Strong-field (1012- 1016 W/ cm2) laser-matter interactions are characterized by the extent of fragmentation and charge of the resulting ions as a function of peak intensity and pulse duration. Interactions are influenced by high-order dispersion, which is difficult to characterize and compress. Fourth-order dispersion (FOD) causes a time-symmetric pedestal, while third-order dispersion (TOD) causes a leading (negative) or following (positive) pedestal. Here, we report on strong-field interactions with pentane and toluene molecules, tracking the molecular ion and the doubly charged carbon ion C2+ yields as a function of TOD and FOD for otherwise transform-limited (TL) 35fs pulses. We find TL pulses enhance molecular ion yield and suppress C2+ yield, while FOD reverses this trend. Interestingly, the leading pedestal in negative TOD enhances C2+ yield compared to positive TOD. Pulse pedestals are of particular importance in strong-field science because target ionization or alignment can be induced well before the main pulse arrives. A pedestal following an intense laser pulse can cause sequential ionization or accelerate electrons causing cascaded ionization. Control of high-order dispersion allows us to provide strong-field measurements that can help address the mechanisms responsible for different product ions in the presence and absence of pedestals. Financial support of this work comes from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, DOE SISGR (DE-SC0002325)

  20. Closed Bosonic String Field Theory At Quartic Order

    OpenAIRE

    Moeller, Nicolas

    2004-01-01

    We give a complete numerical description of the geometry of the four-point contact interaction of closed bosonic string field theory. Namely, we compute the boundary of the relevant region of the moduli space of the four-punctured spheres, and everywhere in this region we give the local coordinates around each punctures in terms of a Strebel quadratic differential and mapping radii. The numerical methods are explained in details. And the results are translated into fits, which can in principl...

  1. Field-controlled magnetic order in the quantum spin-ladder system (Hpip)2CuBr4

    DEFF Research Database (Denmark)

    Thielemann, B.; Rüegg, C.; Kiefer, K.

    2009-01-01

    Neutron diffraction is used to investigate the field-induced, antiferromagnetically ordered state in the two-leg spin-ladder material (Hpip)(2)CuBr4. This "classical" phase, a consequence of weak interladder coupling, is nevertheless highly unconventional: its properties are influenced strongly b...

  2. All-Optical Field-Induced Second-Harmonic Generation

    CERN Document Server

    Davidson, Roderick B; Ziegler, Jed I; Avanesyan, Sergey M; Lawrie, Ben J; Haglund, Richard F

    2015-01-01

    Efficient frequency modulation techniques are crucial to the development of plasmonic metasurfaces for information processing and energy conversion. Nanoscale electric-field confinement in optically pumped plasmonic structures enables stronger nonlinear susceptibilities than are attainable in bulk materials. The interaction of three distinct electric fields in (chi)^3 optical processes allows for all-optical modulation of nonlinear signals. Here we demonstrate effcient third-order second harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients within a dielectric material. We utilize an ultrafast optical pump to control the plasmonically induced electric-fields and to generate bandwidth-limited ultrafast second-harmonic pulses driven by the control pulses. The combination of plasmonic metasurfaces with all-optical control and the freedom to choose the dielectric allow multiple generalizations of this concept and geometry to other four-wave mixing process...

  3. Zero-field NMR and NQR studies of magnetically ordered state in charge-ordered EuPtP

    Science.gov (United States)

    Koyama, T.; Maruyama, T.; Ueda, K.; Mito, T.; Mitsuda, A.; Umeda, M.; Sugishima, M.; Wada, H.

    2015-03-01

    EuPtP undergoes two valence transitions and has two kinds of valence states of Eu ions at low temperatures. In the charge-ordered state, this compound shows an antiferromagnetic order ascribed to magnetic divalent Eu ions. We investigated the antiferromagnetically ordered state of EuPtP by nuclear magnetic resonance (NMR) measurement and nuclear quadrupole resonance (NQR) measurement in a zero external magnetic field. The observed 153Eu NMR signals of a magnetic divalent state and Eu,153151 NQR signals of a nonmagnetic trivalent state clearly demonstrate that the spins order in the hexagonal basal plane and the internal magnetic field is not canceled out, even at the Eu3 + layers which are in the middle of magnetic Eu2 + layers. In addition, the observation of 31P and 195Pt NMR spectra allowed us to discuss a possible magnetic structure. We also evaluated the nuclear quadrupole frequencies for both Eu2 + and Eu3 + ion states.

  4. Partial Dissolution of Charge Order Phase Observed in β-(BEDT-TTF)2PF6 Single Crystal Field Effect Transistor.

    Science.gov (United States)

    Sakai, Masatoshi; Moritoshi, Norifumi; Kuniyoshi, Shigekazu; Yamauchi, Hiroshi; Kudo, Kazuhiro; Masu, Hyuma

    2016-04-01

    The effect of an applied gate electric field on the charge-order phase in β-(BEDT-TTF)2PF6 single-crystal field-effect transistor structure was observed at around room temperature by technical improvement with respect to sample preparation and electrical measurements. A relatively slight but systematic increase of the electrical conductance induced by the applied gate electric field and its temperature dependence was observed at around the metal-insulator transition temperature (TMI). The temperature dependence of the modulated electrical conductance demonstrated that TMI was shifted toward the lower side by application of a gate electric field, which corresponds to partial dissolution of the charge-order phase. The thickness of the partially dissolved charge order region was estimated to be several score times larger than the charge accumulation region.

  5. Third-order elastic solution of the stress field around a wellbore

    Energy Technology Data Exchange (ETDEWEB)

    Elata, D.

    1996-04-01

    Within a certain range of strain, consolidated granular materials may be characterized as nonlinear elastic solids. The nonlinearity can be easily observed by examining the effect of stress on the acoustical properties of the material. Ignoring damage evolution and failure that occur in higher strains and the hysteretic behavior due to intercyranular friction, the material can be modeled as a nonlinear hyperelastic solid. A simple example of such a model is formulating the strain energy as a third-order polynomial of the strain invariants. This model is limited in the sense that the material is assumed to be isotropic with respect to the stress free state, and that the mechanical response of the material is described by only five material constants. Nevertheless, this model is appealing because it naturally exhibits stress dependent stiffness and stress induced anisotropy, and it allows a different mechanical response to positive and negative volume changes. In this work, this model is used to calculate the stress field around a wellbore. Many well logging tools use acoustics (e.g., tube, surface, torsion, and flexural waves) to detect pore fluids and ore in the surrounding granular rock. By modeling the rock as an isotropic third-order elastic material the effects of the inhomogeneous stiffness and the stress induced anisotropy may be examined. Analysis of the tangential stress around a wellbore in an isotropic third-order elastic (TOE) material yields different results than the same analysis in the related isotropic linear elastic (LE) material (i.e., both materials have the same stiffness tensor at the stress free state). This difference modifies the far-field stress that is interpreted of from hydraulic fracturing data. The analysis in the present work is static and pore fluid effects are ignored.

  6. Reduction of static field equation of Faddeev model to first order PDE

    Energy Technology Data Exchange (ETDEWEB)

    Hirayama, Minoru [Department of Mathematics and Physics, Shanghai University of Electric Power, Pinglian road 2103, Shanghai 200090 (China); Shi Changguang [Department of Mathematics and Physics, Shanghai University of Electric Power, Pinglian road 2103, Shanghai 200090 (China)], E-mail: shichangguang@shiep.edu.cn

    2007-09-06

    A method to solve the static field equation of the Faddeev model is presented. For a special combination of the concerned field, we adopt a form which is compatible with the field equation and involves two arbitrary complex functions. As a result, the static field equation is reduced to a set of first order partial differential equations.

  7. Manipulating antiferromagnets with magnetic fields: Ratchet motion of multiple domain walls induced by asymmetric field pulses

    Science.gov (United States)

    Gomonay, O.; Kläui, M.; Sinova, J.

    2016-10-01

    Future applications of antiferromagnets (AFs) in many spintronics devices rely on the precise manipulation of domain walls. The conventional approach using static magnetic fields is inefficient due to the low susceptibility of AFs. Recently proposed electrical manipulation with spin-orbit torques is restricted to metals with a specific crystal structure. Here, we propose an alternative, broadly applicable approach: using asymmetric magnetic field pulses to induce controlled ratchet motion of AF domain walls. The efficiency of this approach is based on three peculiarities of AF dynamics. First, a time-dependent magnetic field couples with an AF order parameter stronger than a static magnetic field, which leads to higher mobility of the domain walls. Second, the rate of change of the magnetic field couples with the spatial variation of the AF order parameter inside the domain, and this enables a synchronous motion of multiple domain walls with the same structure. Third, tailored asymmetric field pulses in combination with static friction can prevent backward motion of domain walls and thus lead to the desired controlled ratchet effect. The proposed use of an external field, rather than internal spin-orbit torques, avoids any restrictions on size, conductivity, and crystal structure of the AF material. We believe that our approach paves a way for the development of AF-based devices based on the controlled motion of AF domain walls.

  8. Second-order spatial correlation in the far-field: Comparing entangled and classical light sources

    Science.gov (United States)

    Zhang, Erfeng; Liu, Weitao; Lin, Huizu; Chen, Pingxing

    2016-02-01

    We consider second-order spatial correlation with entangled and classical light in the far-field. The quantum theory of second-order spatial correlation is analyzed, and the role of photon statistics and detection mode in the second-order spatial correlation are discussed. Meanwhile, the difference of second-order spatial correlation with entangled and classical light sources is deduced.

  9. Gauge-invariant perturbations at second order: multiple scalar fields on large scales

    CERN Document Server

    Malik, K A

    2005-01-01

    We derive the governing equations for multiple scalar fields minimally coupled to gravity in a flat Friedmann-Robertson-Walker (FRW) background spacetime on large scales. We include scalar perturbations up to second order and write the equations in terms of physically transparent gauge-invariant variables at first and second order. This allows us to write the perturbed Klein-Gordon equation at second order solely in terms of the field fluctuations on flat slices at first and second order.

  10. Field-induced magnetic states in holmium tetraboride

    Science.gov (United States)

    Brunt, D.; Balakrishnan, G.; Wildes, A. R.; Ouladdiaf, B.; Qureshi, N.; Petrenko, O. A.

    2017-01-01

    A study of the zero field and field induced magnetic states of the frustrated rare earth tetraboride HoB4 has been carried out using single crystal neutron diffraction complemented by magnetization measurements. In zero field, HoB4 shows magnetic phase transitions at TN 1=7.1 K to an incommensurate state with a propagation vector (δ ,δ ,δ') , where δ =0.02 and δ'=0.43 and at TN 2=5.7 K to a noncollinear commensurate antiferromagnetic structure. Polarized neutron diffraction measurements in zero field have revealed that the incommensurate reflections, albeit much reduced in intensity, persist down to 1.5 K despite antiferromagnetic ordering at 5.7 K. At lower temperatures, application of a magnetic field along the c axis initially re-establishes the incommensurate phase as the dominant magnetic state in a narrow field range, just prior to HoB4 ordering with an up-up-down ferrimagnetic structure characterized by the (h k 1/3 ) -type reflections between 18 and 24 kOe. This field range is marked by the previously reported M /Msat=1/3 magnetization plateau, which we also see in our magnetization measurements. The region between 21 and 33 kOe is characterized by the increase in the intensity of the antiferromagnetic reflections, such as (100), the maximum of which coincides with the appearance of the narrow magnetization plateau with M /Msat≈3/5 . Further increase of the magnetic field results in the stabilization of a polarized state above 33 kOe, while the incommensurate reflections are clearly present in all fields up to 59 kOe. We propose the H -T phase diagram of HoB4 for the H ∥c containing both stationary and transitionary magnetic phases which overlap and show significant history dependence.

  11. A star role for stripes[Charge order in high-temperature superconductors in magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, John [Physics Department, Brookhaven National Laboratory (United States)

    2002-06-01

    New images of magnetic and charge order in copper-oxide compounds are providing important clues about the nature of high-temperature superconductors. Visual images can have a powerful impact on the viewer, and this is certainly the case when the images are atomic-scale pictures of the surface of a high-temperature copper-oxide superconductor. The unusual properties of these materials have vexed condensed-matter theorists for the last 15 years. Now a new flurry of theoretical papers has been stimulated by the latest images of a cuprate superconductor, which reveal that an applied magnetic field can induce 'stripes' of charge. The experimental results provide intriguing and important clues to the nature of these ever-surprising materials - although the theorists have still to agree on their meaning. (U.K.)

  12. Parahydrogen-induced polarization at zero magnetic field.

    Science.gov (United States)

    Butler, Mark C; Kervern, Gwendal; Theis, Thomas; Ledbetter, Micah P; Ganssle, Paul J; Blanchard, John W; Budker, Dmitry; Pines, Alexander

    2013-06-21

    We use symmetry arguments and simple model systems to describe the conversion of the singlet state of parahydrogen into an oscillating sample magnetization at zero magnetic field. During an initial period of free evolution governed by the scalar-coupling Hamiltonian HJ, the singlet state is converted into scalar spin order involving spins throughout the molecule. A short dc pulse along the z axis rotates the transverse spin components of nuclear species I and S through different angles, converting a portion of the scalar order into vector order. The development of vector order can be described analytically by means of single-transition operators, and it is found to be maximal when the transverse components of I are rotated by an angle of ±π∕2 relative to those of S. A period of free evolution follows the pulse, during which the vector order evolves as a set of oscillating coherences. The imaginary parts of the coherences represent spin order that is not directly detectable, while the real parts can be identified with oscillations in the z component of the molecular spin dipole. The dipole oscillations are due to a periodic exchange between Iz and Sz, which have different gyromagnetic ratios. The frequency components of the resulting spectrum are imaginary, since the pulse cannot directly induce magnetization in the sample; it is only during the evolution under HJ that the vector order present at the end of the pulse evolves into detectable magnetization.

  13. Parahydrogen-induced polarization at zero magnetic field

    Science.gov (United States)

    Butler, Mark C.; Kervern, Gwendal; Theis, Thomas; Ledbetter, Micah P.; Ganssle, Paul J.; Blanchard, John W.; Budker, Dmitry; Pines, Alexander

    2013-06-01

    We use symmetry arguments and simple model systems to describe the conversion of the singlet state of parahydrogen into an oscillating sample magnetization at zero magnetic field. During an initial period of free evolution governed by the scalar-coupling Hamiltonian HJ, the singlet state is converted into scalar spin order involving spins throughout the molecule. A short dc pulse along the z axis rotates the transverse spin components of nuclear species I and S through different angles, converting a portion of the scalar order into vector order. The development of vector order can be described analytically by means of single-transition operators, and it is found to be maximal when the transverse components of I are rotated by an angle of ±π/2 relative to those of S. A period of free evolution follows the pulse, during which the vector order evolves as a set of oscillating coherences. The imaginary parts of the coherences represent spin order that is not directly detectable, while the real parts can be identified with oscillations in the z component of the molecular spin dipole. The dipole oscillations are due to a periodic exchange between Iz and Sz, which have different gyromagnetic ratios. The frequency components of the resulting spectrum are imaginary, since the pulse cannot directly induce magnetization in the sample; it is only during the evolution under HJ that the vector order present at the end of the pulse evolves into detectable magnetization.

  14. Resistance switching induced by electric fields in manganite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Villafuerte, M [Facultad de Ciencias Exactas y TecnologIa, Universidad Nacional de Tucuman, S. M. de Tucuman (Argentina); Juarez, G [Facultad de Ciencias Exactas y TecnologIa, Universidad Nacional de Tucuman, S. M. de Tucuman (Argentina); Duhalde, S [Dpto de Fisica, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina); Golmar, F [Dpto de Fisica, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina); Degreef, C L [Dpto de Fisica, Facultad de IngenierIa, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina); Heluani, S P [Facultad de Ciencias Exactas y TecnologIa, Universidad Nacional de Tucuman, S. M. de Tucuman (Argentina)

    2007-04-15

    In this work, we investigate the polarity-dependent Electric Pulses Induced Resistive (EPIR) switching phenomenon in thin films driven by electric pulses. Thin films of {sub 0.5}Ca{sub 0.5}MnO{sub 3} (manganite) were deposited by PLD on Si substrate. The transport properties at the interface between the film and metallic electrode are characterized in order to study the resistance switching. Sample thermal treatment and electrical field history are important to be considered for get reproducible EPIR effect. Carriers trapping at the interfaces are considered as a possible explanation of our results.

  15. A perturbative method to solve fourth-order gravity field equations

    CERN Document Server

    Campanelli, M; Audretsch, J

    1994-01-01

    We develop a method for solving the field equations of a quadratic gravitational theory coupled to matter. The quadratic terms are written as a function of the matter stress tensor and its derivatives in such a way to have, order by order, a set of Einstein field equations with an effective $T_{\\mu\

  16. A Perturbative Method to solve fourth-order Gravity Field Equations

    OpenAIRE

    Campanelli, M.; Lousto, C. O.; Audretsch, J.

    1994-01-01

    We develop a method for solving the field equations of a quadratic gravitational theory coupled to matter. The quadratic terms are written as a function of the matter stress tensor and its derivatives in such a way to have, order by order, a set of Einstein field equations with an effective $T_{\\mu\

  17. Polarizable simulations with second order interaction model (POSSIM) force field: developing parameters for protein side-chain analogues.

    Science.gov (United States)

    Li, Xinbi; Ponomarev, Sergei Y; Sa, Qina; Sigalovsky, Daniel L; Kaminski, George A

    2013-05-30

    A previously introduced polarizable simulations with second-order interaction model (POSSIM) force field has been extended to include parameters for small molecules serving as models for peptide and protein side-chains. Parameters have been fitted to permit reproducing many-body energies, gas-phase dimerization energies, and geometries and liquid-phase heats of vaporization and densities. Quantum mechanical and experimental data have been used as the target for the fitting. The POSSIM framework combines accuracy of a polarizable force field and computational efficiency of the second-order approximation of the full-scale induced point dipole polarization formalism. The resulting parameters can be used for simulations of the parameterized molecules themselves or their analogues. In addition to this, these force field parameters are currently being used in further development of the POSSIM fast polarizable force field for proteins.

  18. Estimating the plasmonic field enhancement using high-order harmonic generation: The role of inhomogeneity of the fields

    CERN Document Server

    Shaaran, T; Lewenstein, M

    2012-01-01

    In strong field laser physics it is a common practice to use the high-order harmonic cutoff to estimate the laser intensity of the pulse that generates the harmonic radiation. Based on the semiclassical arguments it is possible to find a direct relationship between the maximum value of the photon energy and the laser intensity. This approach is only valid if the electric field driving HHG is spatially homogenous. In laser-matter processes driven by plasmonics fields, the enhanced fields present a spatial dependence that strongly modifies the electron motion and consequently the laser driven phenomena. As a result, this method should be revised in order to more realistically estimate the field. In this work, we demonstrate how the inhomogeneity of the fields will effect this estimation. Furthermore, by employing both quantum mechanical and classical calculations, we show how one can obtain a better estimation for the intensity of the enhanced field in plasmonic nanostructure.

  19. Evaporation induced orientational order in soft solid phases of clays

    Science.gov (United States)

    Lindbo Hansen, Elisabeth; Hemmen, Henrik; Dommersnes, Paul; Fossum, Jon Otto

    2012-02-01

    We demonstrate experimentally the possibility for promoting uniaxial orientational order in initially isotropic, soft solid dispersions of the synthetic clays Na-fluorohectorite and Laponite RD. We observe that strong orientational order can emerge from initially isotropic states when the samples are subjected to a slow concentration increase through evaporation of the dispersion water. During evaporation, there is a gradient in the order which, if evaporation is halted, slowly relaxes towards a uniform order throughout the samples. It is evident that the development of orientational order is not counterindicated by the viscoelastic nature of the samples, and that although the translational and likely also rotational diffusion of the particles is restricted in the soft solid state, the orientational degree of freedom can undergo a transition from a collectively random to an ordered state.

  20. Magnetic-field-induced shape recovery by reverse phase transformation.

    Science.gov (United States)

    Kainuma, R; Imano, Y; Ito, W; Sutou, Y; Morito, H; Okamoto, S; Kitakami, O; Oikawa, K; Fujita, A; Kanomata, T; Ishida, K

    2006-02-23

    Large magnetic-field-induced strains have been observed in Heusler alloys with a body-centred cubic ordered structure and have been explained by the rearrangement of martensite structural variants due to an external magnetic field. These materials have attracted considerable attention as potential magnetic actuator materials. Here we report the magnetic-field-induced shape recovery of a compressively deformed NiCoMnIn alloy. Stresses of over 100 MPa are generated in the material on the application of a magnetic field of 70 kOe; such stress levels are approximately 50 times larger than that generated in a previous ferromagnetic shape-memory alloy. We observed 3 per cent deformation and almost full recovery of the original shape of the alloy. We attribute this deformation behaviour to a reverse transformation from the antiferromagnetic (or paramagnetic) martensitic to the ferromagnetic parent phase at 298 K in the Ni45Co5Mn36.7In13.3 single crystal.

  1. Ordering of the three-dimensional Heisenberg spin glass in magnetic fields.

    Science.gov (United States)

    Kawamura, H; Imagawa, D

    2001-11-12

    Spin and chirality orderings of the three-dimensional Heisenberg spin glass are studied under magnetic fields in light of the recently developed spin-chirality decoupling-recoupling scenario. It is found by Monte Carlo simulations that the chiral-glass transition and the chiral-glass ordered state, which are essentially of the same character as their zero-field counterparts, occur under magnetic fields. The implication to the experimental phase diagram is discussed.

  2. First-order formalism for flat branes in generalized N-field models

    CERN Document Server

    Bazeia, D; Losano, L; Menezes, R

    2013-01-01

    This work deals with braneworld scenarios obtained from N real scalar fields, whose dynamics is generalized to include higher order power in the derivative of the fields. For the scalar fields being driven by nonstandard dynamics, we show how a first-order formalism can be obtained for flat brane in the presence of several fields. We then illustrate our findings investigating distinct potentials with one and two fields, obtaining stable standard and compact solutions in the braneworld theory. In particular, we have found different models describing the very same warp factor.

  3. On Second Order Gauge Invariant Perturbations in Multi-Field Inflationary Models

    CERN Document Server

    Rigopoulos, G I

    2002-01-01

    In a recent letter [1] Acquaviva et. al presented results from a second order calculation for a single field inflationary model. In this paper we elaborate on their approach. We present equations for the second order superhorizon perturbations of a generic multi field model. We utilise a change of coordinates in field space - first presented in [2] and given a more geometrical flavour here - to separate isocurvature and adiabatic perturbations and construct gauge invariant variables related to them to second order. Explicit relations are given for two scalar fields on a flat field manifold although the results can be generalised to curved field manifolds and an arbitrary number of fields. This is an outline of a possible procedure to study nonlinear and nongaussian effects during multifield inflation. For a more detailed discussion we refer to a future publication [12].

  4. Higher order asymptotic fields for mode Ⅰ crack in functionally gradient material

    Institute of Scientific and Technical Information of China (English)

    DAI Yao; YAN Xiu-fa

    2005-01-01

    Higher order stress fields for a mode Ⅰ crack perpendicular to the direction of property variation in a functionally gradient material(FGM), which has an exponential variation of elastic modulus along the gradient direction, were obtained through an asymptotic analysis. The Poisson's ratio of the FGMs was assumed to be constant throughout the analysis. The first five terms in the asymptotic expansions of crack tip stress fields were derived to bring out the influence of nonhomogeneity on the structure of the stress field explicitly. The analysis reveals that only the higher order terms in the expansion are influenced by the material nonhomogeneity. Moreover, it can be seen from expressions of higher order stress fields that at least three terms must be considered in the case of FGMs in order to explicitly account for the nonhomogeneity effects on the structure of crack tip stress fields.

  5. Complete Hamiltonian analysis of cosmological perturbations at all orders II: non-canonical scalar field

    Science.gov (United States)

    Nandi, Debottam; Shankaranarayanan, S.

    2016-10-01

    In this work, we present a consistent Hamiltonian analysis of cosmological perturbations for generalized non-canonical scalar fields. In order to do so, we introduce a new phase-space variable that is uniquely defined for different non-canonical scalar fields. We also show that this is the simplest and efficient way of expressing the Hamiltonian. We extend the Hamiltonian approach of [1] to non-canonical scalar field and obtain an unique expression of speed of sound in terms of phase-space variable. In order to invert generalized phase-space Hamilton's equations to Euler-Lagrange equations of motion, we prescribe a general inversion formulae and show that our approach for non-canonical scalar field is consistent. We also obtain the third and fourth order interaction Hamiltonian for generalized non-canonical scalar fields and briefly discuss the extension of our method to generalized Galilean scalar fields.

  6. Complete Hamiltonian analysis of cosmological perturbations at all orders II: Non-canonical scalar field

    CERN Document Server

    Nandi, Debottam

    2016-01-01

    In this work, we present a consistent Hamiltonian analysis of cosmological perturbations for generalized non-canonical scalar fields. In order to do so, we introduce a new phase-space variable that is uniquely defined for different non-canonical scalar fields. We also show that this is the simplest and efficient way of expressing the Hamiltonian. We extend the Hamiltonian approach of [arXiv:1512.02539] to non-canonical scalar field and obtain a new definition of speed of sound in phase-space. In order to invert generalized phase-space Hamilton's equations to Euler-Lagrange equations of motion, we prescribe a general inversion formulae and show that our approach for non-canonical scalar field is consistent. We also obtain the third and fourth order interaction Hamiltonian for generalized non-canonical scalar fields and briefly discuss the extension of our method to generalized Galilean scalar fields.

  7. Least-Order Torsion-Gravity for Fermion Fields, and the Non-Linear Potentials in the Standard Models

    CERN Document Server

    Fabbri, Luca

    2014-01-01

    We will consider least-order torsional completion of gravity for a spacetime filled with fermionic Dirac matter fields, and we study the effects of the background-induced non-linear potentials for the matter field themselves, in terms of their effects for both standard models of physics: from the one of cosmology to that of particles, we will discuss the mechanisms of generation of the cosmological constant and particles masses as well as the phenomenology of leptonic weak-like forces and neutrino oscillations, the problem of zero-point energy, how there can be neutral massive fields as candidates for dark matter, and gravitationally-induced singularity formation; we will show the way in which all these different effects can nevertheless be altogether described in terms of just a single model, which will be thoroughly discussed in the end.

  8. Induced Interval-Valued Intuitionistic Fuzzy Hybrid Aggregation Operators with TOPSIS Order-Inducing Variables

    Directory of Open Access Journals (Sweden)

    Jun-Ling Zhang

    2012-01-01

    Full Text Available Two induced aggregation operators with novelly designed TOPSIS order-inducing variables are proposed: Induced Interval-valued Intuitionistic Fuzzy Hybrid Averaging (I-IIFHA operator and Induced Interval-valued Intuitionistic Fuzzy Hybrid Geometric (I-IIFHG operator. The merit of two aggregation operators is that they can consider additional preference information of decision maker’s attitudinal characteristics besides argument-dependent information and argument-independent information. Some desirable properties of I-IIFHA and I-IIFHG are studied and theoretical analysis also shows that they can include a wide range of aggregation operators as special cases. Further, we extend these operators to form a novel group decision-making method for selecting the most desirable alternative in multiple attribute multi-interest group decision-making problems with attribute values and decision maker’s interest values taking the form of interval-valued intuitionistic fuzzy numbers, and application research to real estate purchase selection shows its practicality.

  9. Primordial magnetic fields from second-order cosmological perturbations:Tight coupling approximation

    CERN Document Server

    Maeda, Satoshi; Kobayashi, Tsutomu; Shiromizu, Tetsuya

    2008-01-01

    We explore the possibility of generating large-scale magnetic fields from second-order cosmological perturbations during the pre-recombination era. The key process for this is Thomson scattering between the photons and the charged particles within the cosmic plasma. To tame the multi-component interacting fluid system, we employ the tight coupling approximation. It is shown that the source term for the magnetic field is given by the product of the first order perturbations and so the intrinsically second-order quantities do not contribute to magnetogenesis. The magnetic fields generated by this process are estimated to be \\sim 10^{-26},Gauss on the horizon scale.

  10. Measurement, analysis and modification of the fifth-order fringe field components of magnetic quadrupole lenses

    Energy Technology Data Exchange (ETDEWEB)

    Moloney, G.R.; Jamieson, D.N.; Legge, G.J.F. (School of Physics, Univ. of Melbourne, Parkville (Australia))

    1991-03-01

    Extensive, quantitative measurements of magnetic quadrupole lens fringe fields have been conducted. The fringe field region of magnetic quadrupole lenses has been shown to contain significant contamination by higher-order multipole fields. These multipole components will contribute to the aberration coefficients of the lens. One of the largest components is the duodecapole component, which contributes to the fifth-order geometric aberrations of the lens. The measured multipole profiles in the fringe field region of the Melbourne quadrupoles are presented. We also present the results of an investigation into the effect of modifying the quadrupole pole tip profile at the pole ends. (orig.).

  11. First-order correction terms in the weak-field asymptotic theory of tunneling ionization

    DEFF Research Database (Denmark)

    Trinh, Vinh H.; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2013-01-01

    The weak-field asymptotic theory (WFAT) of tunneling ionization in a static electric field is developed to the next order in field. The first-order corrections to the ionization rate and transverse momentum distribution of the ionized electrons are derived. This extends the region of applicability...... of the WFAT at the quantitative level toward stronger fields, practically up to the boundary between tunneling and over-the-barrier regimes of ionization. The results apply to any atom or molecule treated in the single-active-electron and frozen-nuclei approximations. The theory is illustrated by calculations...... for hydrogen and noble-gas atoms....

  12. First-order correction terms in the weak-field asymptotic theory of tunneling ionization

    DEFF Research Database (Denmark)

    Trinh, Vinh H.; Tolstikhin, Oleg I.; Madsen, Lars Bojer;

    2013-01-01

    The weak-field asymptotic theory (WFAT) of tunneling ionization in a static electric field is developed to the next order in field. The first-order corrections to the ionization rate and transverse momentum distribution of the ionized electrons are derived. This extends the region of applicability...... of the WFAT at the quantitative level toward stronger fields, practically up to the boundary between tunneling and over-the-barrier regimes of ionization. The results apply to any atom or molecule treated in the single-active-electron and frozen-nuclei approximations. The theory is illustrated by calculations...

  13. On the maximum orders of an induced forest, an induced tree, and a stable set

    Directory of Open Access Journals (Sweden)

    Hertz Alain

    2014-01-01

    Full Text Available Let G be a connected graph, n the order of G, and f (resp. t the maximum order of an induced forest (resp. tree in G. We show that f - t is at most n - 2√n-1. In the special case where n is of the form a2 + 1 for some even integer a ≥ 4, f - t is at most n - 2√n-1-1. We also prove that these bounds are tight. In addition, letting α denote the stability number of G, we show that α - t is at most n + 1- 2√2n this bound is also tight.

  14. A higher order conditional random field model for simultaneous classification of land cover and land use

    Science.gov (United States)

    Albert, Lena; Rottensteiner, Franz; Heipke, Christian

    2017-08-01

    We propose a new approach for the simultaneous classification of land cover and land use considering spatial as well as semantic context. We apply a Conditional Random Fields (CRF) consisting of a land cover and a land use layer. In the land cover layer of the CRF, the nodes represent super-pixels; in the land use layer, the nodes correspond to objects from a geospatial database. Intra-layer edges of the CRF model spatial dependencies between neighbouring image sites. All spatially overlapping sites in both layers are connected by inter-layer edges, which leads to higher order cliques modelling the semantic relation between all land cover and land use sites in the clique. A generic formulation of the higher order potential is proposed. In order to enable efficient inference in the two-layer higher order CRF, we propose an iterative inference procedure in which the two classification tasks mutually influence each other. We integrate contextual relations between land cover and land use in the classification process by using contextual features describing the complex dependencies of all nodes in a higher order clique. These features are incorporated in a discriminative classifier, which approximates the higher order potentials during the inference procedure. The approach is designed for input data based on aerial images. Experiments are carried out on two test sites to evaluate the performance of the proposed method. The experiments show that the classification results are improved compared to the results of a non-contextual classifier. For land cover classification, the result is much more homogeneous and the delineation of land cover segments is improved. For the land use classification, an improvement is mainly achieved for land use objects showing non-typical characteristics or similarities to other land use classes. Furthermore, we have shown that the size of the super-pixels has an influence on the level of detail of the classification result, but also on the

  15. Influence of thermal annealing and magnetic field on first order magnetic transition in Pd substituted FeRh

    Energy Technology Data Exchange (ETDEWEB)

    Kushwaha, Pallavi; Lakhani, Archana; Rawat, R; Chaddah, P, E-mail: archnalakhani@csr.ernet.i [UGC-DAE Consortium for Scientific Research University Campus, Khandwa Road Indore-452001, M.P (India)

    2010-01-01

    Influence of successive thermal annealing and magnetic field on First order antiferro (AFM) to ferromagnetic (FM) transition in the Pd substituted FeRh has been studied. With successive thermal annealing CsCl type bcc phase increases at the expense of fct (pseudo fcc) phase. Resistivity measurements do not show any transition in as-cast sample in contrast to annealed samples. AFM to FM transition temperature (T{sub N}) is found to decrease with higher annealing temperature. With the application of magnetic field, T{sub N} shift to lower temperature. These measurements show anomalous thermomagnetic irreversibility besides showing giant magnetoresistance across magnetic field induced first order AFM to FM transition.

  16. Aspects of probe correction for odd-order probes in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey N.; Breinbjerg, Olav

    2004-01-01

    Probe correction aspects for the spherical near-field antenna measurements are investigated. First, the spherical mode analyses of the radiated fields of several antennas are performed. It is shown that many common antennas are essentially so-called odd-order antennas. Second, the errors caused...... by the use of the first-order probe correction [1] for a rectangular waveguide probe, that is an odd-order antenna, are demonstrated. Third, a recently developed probe correction technique for odd-order probes is applied for the rectangular waveguide probe and shown to provide accurate results....

  17. Models of second-order effects in metal-oxide-semiconductor field-effect transistors for computer applications

    Science.gov (United States)

    Benumof, Reuben; Zoutendyk, John; Coss, James

    1988-01-01

    Second-order effects in metal-oxide-semiconductor field-effect transistors (MOSFETs) are important for devices with dimensions of 2 microns or less. The short and narrow channel effects and drain-induced barrier lowering primarily affect threshold voltage, but formulas for drain current must also take these effects into account. In addition, the drain current is sensitive to channel length modulation due to pinch-off or velocity saturation and is diminished by electron mobility degradation due to normal and lateral electric fields in the channel. A model of a MOSFET including these considerations and emphasizing charge conservation is discussed.

  18. Simulations of flow induced ordering in viscoelastic fluids

    NARCIS (Netherlands)

    Santos de Oliveira, I.S.

    2012-01-01

    In this thesis we report on simulations of colloidal ordering phenomena in shearthinning viscoelastic fluids under shear flow. Depending on the characteristics of the fluid, the colloids are observed to align in the direction of the flow. These string-like structures remain stable as long as the she

  19. Second-order spatial correlation in the far-field: Comparing entangled and classical light sources

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Erfeng, E-mail: efzhang@163.com; Liu, Weitao; Lin, Huizu; Chen, Pingxing

    2016-02-15

    Highlights: • Second-order spatial correlation with entangled and classical light in the far-field is investigated. • The role of photon statistics and detection mode in the second-order spatial correlation are discussed. • The difference of second-order spatial correlation with entangled and classical light sources is deduced. - Abstract: We consider second-order spatial correlation with entangled and classical light in the far-field. The quantum theory of second-order spatial correlation is analyzed, and the role of photon statistics and detection mode in the second-order spatial correlation are discussed. Meanwhile, the difference of second-order spatial correlation with entangled and classical light sources is deduced.

  20. In-induced stable ordering of stepped Si(553) surface

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Amit Kumar Singh [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India); Department of Physics, JMI, New Delhi 110025 (India); Niazi, Asad; Nair, Lekha [Department of Physics, JMI, New Delhi 110025 (India); Gupta, Govind, E-mail: govind@nplindia.org [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India)

    2015-05-15

    Highlights: • Control growth of In on step Si(553) & thermal stability of novel superstructure. • Influence of temperature on growth modes (SK,VB) under different growth conditions. • In-induced superstructure: (8 × 2), (8 × 4), mixed (553)-7 × 1 + (111)√3 × √3R30° phases. - Abstract: The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 °C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski–Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 °C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual “cluster to layer” transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 °C with coverage 0.5 ML, (8 × 4) after annealing at 580 °C (∼1 ML coverage) and (553)-7 × 1 + (111)-√3 × √3-R30° at 0.3 ML (630 °C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for

  1. Local Field Distribution Function and High Order Field Moments for metal-dielectric composites.

    Science.gov (United States)

    Genov, Dentcho A.; Sarychev, Andrey K.; Shalaev, Vladimir M.

    2001-11-01

    In a span of two decades the physics of nonlinear optics saw vast improvement in our understanding of optical properties for various inhomogeneous mediums. One such medium is the metal-dielectric composite, where the metal inclusions have a surface coverage fraction of p, while the rest (1-p) is assumed to represent the dielectric host. The computations carried out by using different theoretical models and the experimental data show existence of giant local electric and magnetic field fluctuations. In this presentation we will introduce a new developed 2D model that determines exactly the Local Field Distribution Function (LFDF) and all other relevant parameters of the film. The LFDF for small filling factors will be shown to transform from lognormal distribution into a single-dipole distribution function. We also will confirm the predictions of the scaling theory for the high field moments, which have a power law dependence on the loss factor.

  2. Building a first order wave equation for the electromagnetic field: new perspectives on Dirac's equation

    CERN Document Server

    Duarte, Celso de Araujo

    2015-01-01

    Traditionally, the electromagnetic theory dictates the well-known second order differential equation for the components of the scalar and the vector potentials, or in other words, for the four-vector electromagnetic potential $\\phi^{\\mu}$. But the second order is not obligatory at least with respect to the electromagnetic radiation fields: actually, a heuristic first order differential equation can be constructed to describe the electromagnetic radiation, supported on the phenomenology of its electric and magnetic fields. Due to a formal similarity, such an equation suggests a direct comparative analysis with Dirac's equation for half spin fermions, conducting to the finding that the Dirac's spinor field $\\Psi$ for massive or massless fermions is equivalent to a set of two potential-like four vector fields $\\psi^{\\mu}$ and $\\chi^{\\mu}$. Under this point of view, striking similarities with the electromagnetic theory emerge with a category of "pseudo electric'' and "pseudo magnetic'' vector fermionic fields.

  3. High‐order numerical simulations of flow‐induced noise

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2011-01-01

    In this paper, the flow/acoustics splitting method for predicting flow‐generated noise is further developed by introducing high‐order finite difference schemes. The splitting method consists of dividing the acoustic problem into a viscous incompressible flow part and an inviscid acoustic part...... are used for the spatial discretizations. Applications and validations of the new acoustics solver are presented for benchmark aeroacoustic problems and for flow over an NACA 0012 airfoil. Copyright © 2010 John Wiley & Sons, Ltd....

  4. Comment on "Perturbative method to solve fourth-order gravity field equations"

    CERN Document Server

    Campanelli, M

    1995-01-01

    We reconsider the cosmic string perturbative solution to the classical fourth-order gravity field equations, obtained in Ref.\\cite{CLA94}, and we obtain that static, cylindricaly symmetric gauge cosmic strings, with constant energy density, can contain only \\beta-terms in the first order corrections to the interior gravitational field, while the exact exterior solution is a conical spacetime with deficit angle D=8\\pi\\mu.

  5. The period of fibonacci sequences over the finite field of order p2

    Directory of Open Access Journals (Sweden)

    YASEMİN TAŞYURDU

    2016-02-01

    Full Text Available In this paper , we obtain the period of Fibonacci sequence in the finite fields of order p^2 by using equality recursively defined by F(n+1=A(1F(n+A(0F(n-1, for n>0, where F(0=0, F(1=1 and A(0, A(1 are generators elements of these fields of order p^2.

  6. A New Class of Group Field Theories for 1st Order Discrete Quantum Gravity

    OpenAIRE

    Oriti, D; Tlas, T.

    2007-01-01

    Group Field Theories, a generalization of matrix models for 2d gravity, represent a 2nd quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of Group Field Theory models, for any choice of spacetime dimension and signature, whose Feynman amplitudes are given by path integrals for clearly identified discrete gravity actions, in 1st order variables. In the 3-dimensional case, the corresponding discrete action is that of 1st order Regg...

  7. Cooperative Ordering and Kinetics of Cellulose Nanocrystal Alignment in a Magnetic Field.

    Science.gov (United States)

    De France, Kevin J; Yager, Kevin G; Hoare, Todd; Cranston, Emily D

    2016-08-02

    Cellulose nanocrystals (CNCs) are emerging nanomaterials that form chiral nematic liquid crystals above a critical concentration (C*) and additionally orient within electromagnetic fields. The control over CNC alignment is significant for materials processing and end use; to date, magnetic alignment has been demonstrated using only strong fields over extended or arbitrary time scales. This work investigates the effects of comparatively weak magnetic fields (0-1.2 T) and CNC concentration (1.65-8.25 wt %) on the kinetics and degree of CNC ordering using small-angle X-ray scattering. Interparticle spacing, correlation length, and orientation order parameters (η and S) increased with time and field strength following a sigmoidal profile. In a 1.2 T magnetic field for CNC suspensions above C*, partial alignment occurred in under 2 min followed by slower cooperative ordering to achieve nearly perfect alignment in under 200 min (S = -0.499 where S = -0.5 indicates perfect antialignment). At 0.56 T, nearly perfect alignment was also achieved, yet the ordering was 36% slower. Outside of a magnetic field, the order parameter plateaued at 52% alignment (S = -0.26) after 5 h, showcasing the drastic effects of relatively weak magnetic fields on CNC alignment. For suspensions below C*, no magnetic alignment was detected.

  8. Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

    DEFF Research Database (Denmark)

    Haug, D.; Hinkov, V.; Suchaneck, A.

    2009-01-01

    We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

  9. Second-order magnetic critical points at finite magnetic fields: Revisiting Arrott plots

    Science.gov (United States)

    Bustingorry, S.; Pomiro, F.; Aurelio, G.; Curiale, J.

    2016-06-01

    The so-called Arrott plot, which consists in plotting H /M against M2, with H the applied magnetic field and M the magnetization, is used to extract valuable information in second-order magnetic phase transitions. Besides, it is widely accepted that a negative slope in the Arrott plot is indicative of a first-order magnetic transition. This is known as the Banerjee criterion. In consequence, the zero-field transition temperature T* is reported as the characteristic first-order transition temperature. By carefully analyzing the mean-field Landau model used for studying first-order magnetic transitions, we show in this work that T* corresponds in fact to a triple point where three first-order lines meet. More importantly, this analysis reveals the existence of two symmetrical second-order critical points at finite magnetic field (Tc,±Hc) . We then show that a modified Arrott plot can be used to obtain information about these second-order critical points. To support this idea we analyze experimental data on La2 /3Ca1 /3MnO3 and discuss an estimate for the location of the triple point and the second-order critical points.

  10. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissila, T.

    2010-01-01

    We present a derivation of the recently proposed eighth order phase field crystal model [Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase field crystal models. We find that among the phase field crystal models...

  11. Gravitational waves from the first order phase transition of the Higgs field at high energy scales

    Science.gov (United States)

    Jinno, Ryusuke; Nakayama, Kazunori; Takimoto, Masahiro

    2016-02-01

    In a wide class of new physics models, there exist scalar fields that obtain vacuum expectation values of high energy scales. We study the possibility that the standard model Higgs field has experienced first order phase transition at the high energy scale due to the couplings with these scalar fields. We estimate the amount of gravitational waves produced by the phase transition, and discuss observational consequences.

  12. Field Emission From Ordered Nano-array Structures Based on Porous Aluminum Oxide Templates

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ This thesis reports my research work of fabricating nanostructures by using nanoporous anodic aluminum oxide (AAO) templates and their field emission properties in the past few years. Some important results obtained are as follows: 1. We first proposed a new concept of fabricating field emitters with ordered nanostructures based on porous aluminum oxide templates such as AAO/Al, metal/AAO, PANI/AAO, CNTs/AAO, Si/AAO and did a lot of research in this field.

  13. Gravitational Waves from the First Order Phase Transition of the Higgs Field at High Energy Scales

    CERN Document Server

    Jinno, Ryusuke; Takimoto, Masahiro

    2015-01-01

    In a wide class of new physics models, there exist scalar fields which obtain vacuum expectation values of high energy scales. We study the possibility that the standard model Higgs field has experienced first-order phase transition at the high energy scale due to the couplings with these scalar fields.We estimate the amount of gravitational waves produced by the phase transition, and discuss observational consequences.

  14. Non-canonical two-field inflation to order $\\xi^2$

    CERN Document Server

    Wang, Yun-Chao

    2016-01-01

    In non-canonical two-field inflation models, deviations from the canonical model can be captured by a parameter $\\xi$. We show this parameter is usually one half of the slow-roll order and analytically calculate the primordial power spectra to the precision of order $\\xi^2$. The super-horizon perturbations are studied with an improved method, which gives a correction of order $\\xi$. Three typical examples demonstrate that our analytical formulae of power spectra fit well with numerical simulation.

  15. Practical aspects of spherical near-field antenna measurements using a high-order probe

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey; Nielsen, Jeppe Majlund

    2006-01-01

    Two practical aspects related to accurate antenna pattern characterization by probe-corrected spherical near-field antenna measurements with a high-order probe are examined. First, the requirements set by an arbitrary high-order probe on the scanning technique are pointed out. Secondly, a channel...... balance calibration procedure for a high-order dual-port probe with non-identical ports is presented, and the requirements set by this procedure for the probe are discussed....

  16. {mu} {sup +}SR study of zero-field magnetic ordering in CsC{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Cristofolini, L.; Lappas, A.; Vavekis, K.; Prassides, K.; DeRenzi, R.; Ricco, M.; Schenck, A.; Amato, A.; Gygax, F.N.; Kosaka, M.; Tanigaki, K. [Sch. of Chem. and Molecular Sci., Sussex Univ., Brighton (United Kingdom)

    1995-10-23

    We have measured the zero-field muon spin relaxation (ZF {mu} {sup +}SR) spectra of the quasi-one-dimensional fulleride conductor CsC{sub 60}. Static magnetic order of a random nature develops gradually below about 30 K. The local field distribution at the muon site has a Gaussian shape with a width of 48.3(7) G at 2.8 K. Muon spin rotation (TF {mu} {sup +}SR) measurements at an applied transverse field of 6 kG also show the onset of magnetic order in the same temperature range. (authors). Letter-to-the-editor.

  17. On the conservation of second-order cosmological perturbations in a scalar field dominated universe

    CERN Document Server

    Vernizzi, F

    2005-01-01

    We discuss second-order cosmological perturbations on super-Hubble scales, in a scalar field dominated universe, such as during single field inflation. In this contest we show that the gauge-invariant curvature perturbations defined on the uniform density and comoving hypersurfaces coincide and that perturbations are adiabatic in the large scale limit. Since it has been recently shown that the uniform curvature perturbation is conserved on large scales if perturbations are adiabatic, we conclude that both the uniform and comoving curvature perturbations at second-order in a scalar field dominated universe are conserved.

  18. First-Order Equations of Motion for Heterotic String Field Theory

    CERN Document Server

    Kunitomo, Hiroshi

    2014-01-01

    We consider the equations of motion of the full heterotic string field theory including both the Neveu-Schwarz and the Ramond sectors. It is shown that they can be formulated in the form of an infinite number of first-order equations for an infinite number of independent string fields. We prove that the conventional equations of motion are obtaned by solving the extra equations for the extra string fields with a certain assumptions at the linearized level. The conventional gauge transformations are also obtained from those in this first-order formulation, which is clarified by deriving some lower oder transformations explicitly.

  19. The Properties of Light Pressure Force with High Order in Laser Fields

    Institute of Scientific and Technical Information of China (English)

    陈险峰; 方建兴; 朱士群

    2002-01-01

    In this paper, the light pressure force in low and high intensity laser fields is derived. The exact numerical results of forces Fn∥(n=0,1,2,3,4,5,6…) through the matrix continued fraction method are presented. At low intensity field (G=1), the spatially averaged force F0∥ gives a cooling effect at the negative detuning. At high intensity (G=64), the effects of the forces with higher order (n≥2) appear and the contributes of the forces with odd or even order are opposite. It is great different from no high order force at low intensity.

  20. Protein-induced bilayer Perturbations: Lipid ordering and hydrophobic coupling

    DEFF Research Database (Denmark)

    Petersen, Frederic Nicolas Rønne; Laursen, Ib; Bohr, Henrik;

    2009-01-01

    The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction...... and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few Å results...... in up to 10-fold increased exchange rates as compared to the ‘optimal’ match situation pointing to the regulatory role of hydrophobic coupling in lipid–protein interactions....

  1. Euler-Heisenberg Lagrangian to all orders in the magnetic field and the Chiral Magnetic Effect

    CERN Document Server

    Mages, Simon Wolfgang; Schäfer, Andreas

    2010-01-01

    In high energy heavy ion collisions as well as in astrophysical objects like magnetars extreme magnetic field strengths are reached. Thus, there exists a need to calculate divers QED processes to all orders in the magnetic field. We calculate the vacuum polarization graph in second order of the electric field and all orders of the magnetic field resulting in a generalization of the Euler-Heisenberg Lagrangian. We perform the calculation in the effective Lagrangian approach of J. Schwinger as well as using modified Feynman rules. We find that both approaches give the same results provided that the different finite renormalization terms are taken into account. Our results imply that any quantitative explanation of the recently proposed Chiral Magnetic Effect has to take 'Strong QED' effects into account, because these corrections are huge.

  2. A new class of group field theories for first order discrete quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Oriti, D [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Utrecht 3584 TD (Netherlands); Tlas, T [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)], E-mail: d.oriti@phys.uu.nl, E-mail: t.tlas@damtp.cam.ac.uk

    2008-04-21

    Group field theories, a generalization of matrix models for 2D gravity, represent a second quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of group field theory models, for any choice of spacetime dimension and signature, whose Feynman amplitudes are given by path integrals for clearly identified discrete gravity actions, in first order variables. In the three-dimensional case, the corresponding discrete action is that of first order Regge calculus for gravity (generalized to include higher order corrections), while in higher dimensions, they correspond to a discrete BF theory (again, generalized to higher order) with an imposed orientation restriction on hinge volumes, similar to that characterizing discrete gravity. This new class of group field theories may represent a concrete unifying framework for loop quantum gravity and simplicial quantum gravity approaches.

  3. A New Class of Group Field Theories for 1st Order Discrete Quantum Gravity

    CERN Document Server

    Oriti, Daniele

    2007-01-01

    Group Field Theories, a generalization of matrix models for 2d gravity, represent a 2nd quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of Group Field Theory models, for any choice of spacetime dimension and signature, whose Feynman amplitudes are given by path integrals for clearly identified discrete gravity actions, in 1st order variables. In the 3-dimensional case, the corresponding discrete action is that of 1st order Regge calculus for gravity (generalized to include higher order corrections), while in higher dimensions, they correspond to a discrete BF-theory (again, generalized to higher order) with an imposed orientation restriction on hinge volumes, similar to that characterizing discrete gravity. The new models shed also light on the large distance or semi-classical approximation of spin foam models. This new class of group field theories may represent a concrete unifying framework for loop quantum gravity and simplicial quantum grav...

  4. Higher-order singletons, partially massless fields, and their boundary values in the ambient approach

    Energy Technology Data Exchange (ETDEWEB)

    Bekaert, Xavier [Laboratoire de Mathématiques et Physique Théorique, Unité Mixte de Recherche 7350 du CNRS, Fédération de Recherche 2964 Denis Poisson, Université François Rabelais, Parc de Grandmont, 37200 Tours (France); Grigoriev, Maxim, E-mail: grig@lpi.ru [Tamm Theory Department, Lebedev Physics Institute, Leninsky prospect 53, 119991 Moscow (Russian Federation)

    2013-11-11

    Using ambient space we develop a fully gauge and o(d,2)-covariant approach to boundary values of AdS{sub d+1} gauge fields. It is applied to the study of (partially) massless fields in the bulk and (higher-order) conformal scalars, i.e. singletons, as well as (higher-depth) conformal gauge fields on the boundary. In particular, we identify the corresponding generalized Fradkin–Tseytlin equations as obstructions to the extension of the off-shell boundary value to the bulk, generalizing the usual considerations for the holographic anomalies to the partially massless fields. We also relate the background fields for the higher-order singleton to the boundary values of partially massless fields and prove the appropriate generalization of the Flato–Fronsdal theorem, which is in agreement with the known structure of symmetries for the higher-order wave operator. All these facts support the following generalization of the higher-spin holographic duality: the O(N) model at a multicritical isotropic Lifshitz point should be dual to the theory of partially massless symmetric tensor fields described by the Vasiliev equations based on the higher-order singleton symmetry algebra.

  5. Calculation of induced modes of magnetic field in the geodynamo problem

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Yukiko; Yukutake, Takesi

    1989-01-01

    In the dynamo problem, the calculation of induced modes is of vital importance, because the interaction of fluid motions with the magnetic field induces specific types of fields which are, in many cases, different either from the type of velocity field or from the original magnetic field. This special induction relationship, known as 'selection rules', has so far been derived by calculating Adams-Gaunt integrals and Elsasser integrals. In this paper, we calculate the induced modes in a more direct way, expressing the magnetic fields and the velocity in a spherical harmonic series. By linearizing the product terms of spherical harmonic functions, which appear in interaction terms between the velocity and the magnetic field, into a simple spherical harmonic series, we have derived the induced magnetic modes in a simple general form. When the magnetic field and the velocity are expressed by toroidal and poloidal modes, four kinds of interaction are conceivable between the velocity and the magnetic field. By each interaction, two modes, the poloidal and toroidal, are induced, except in the interaction of the toroidal velocity with the toroidal magnetic field, which induces only the toroidal mode. In spite of the diversity of interaction processes, the induced modes have been found to be expressed simply by two types. For a velocity of degree l and order k interacting with a magnetic field of degree n and order m, one type is the mode with degree and order of n+l-2t, m+-k for an integer t, and the other with n+l-2t-1, m+-k . (author).

  6. Frequency modulation of high-order harmonic generation in an orthogonally polarized two-color laser field.

    Science.gov (United States)

    Li, Guicun; Zheng, Yinghui; Ge, Xiaochun; Zeng, Zhinan; Li, Ruxin

    2016-08-08

    We have experimentally investigated the frequency modulation of high-order harmonics in an orthogonally polarized two-color laser field consisting of a mid-infrared 1800nm fundamental pulse and its second harmonic pulse. It is demonstrated that the high harmonic spectra can be fine-tuned as we slightly change the relative delay of the two-color laser pulses. By analyzing the relative frequency shift of each harmonic at different two-color delays, the nonadiabatic spectral shift induced by the rapid variation of the intensity-dependent intrinsic dipole phase can be distinguished from the blueshift induced by the change of the refractive index during self-phase modulation (SPM). Our comprehensive analysis shows that the frequency modulation pattern is a reflection of the average emission time of high-order harmonic generation (HHG), thus offering a simple method to fine-tune the spectra of the harmonics on a sub-cycle time scale.

  7. Statistical Perturbation Theory of Cosmic Fields; 1, Basic Formalism and Second-order Theory

    CERN Document Server

    Matsubara, T

    2000-01-01

    We formulate a general method for perturbative evaluations of statistics of smoothed cosmic fields, which we call as ``Statistical Perturbation Theory''. The formalism is an extensive generalization of the method used by Matsubara (1994) who derived a weakly nonlinear formula of the genus statistic in a 3D density field. After describing the general method, we apply the formalism especially to analyses of more general genus statistics, level-crossing statistics, Minkowski functionals, and a density extrema statistic, regardless of the dimensions in which each statistic is defined. The relation between the Minkowski functionals and other geometrical statistics is clearly described. These examples are applied to some cosmic fields, including 3D density field, 3D velocity field, 2D projected density field, and 2D weak lensing field. The results are detailed for second order theory of the formalism. The reason why the genus curves etc. in CDM-like models exhibit smaller deviations from Gaussian predictions when t...

  8. Zero-field magnetic order in the boundary layers of /sup 3/He on Grafoil

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, L.J.; Thomson, A.L.; Gould, C.M.; Bozler, H.M.; Weichman, P.B.; Cross, M.C.

    1989-04-03

    The low-field NMR spectra of /sup 3/He boundary layers on exfoliated graphite show collective modes for T<1 mK. We measure the amplitude and frequency for these modes with the static H/sub 0/ field applied parallel to the graphite planes and varying continuously between 0 and 15 G. One of the modes extrapolates to a nonzero frequency and amplitude as the field is dropped to zero. We interpret these nonzero intercepts as an indication of zero-field magnetic order in the /sup 3/He boundary layers.

  9. Neutron induced degradation in nitrided pyrogenic field oxide MOS capacitors

    CERN Document Server

    Vaidya, S J; Shaikh, A M; Chandorkar, A N

    2002-01-01

    Neutron induced oxide charge trapping and generation of interface states in MOS capacitors with pyrogenic and nitrided pyrogenic field oxides have been studied. In order to assess the damage due to neutrons alone, it is necessary to account for the damage produced by the accompanying gamma rays from neutron radiation. This is done by measuring the intensity of gamma radiation accompanying neutrons at different neutron fluences at the irradiation position. MOS capacitor structures were subjected to neutron radiation in a swimming pool type of reactor. Other samples from the same batch were then subjected to an equivalent dose of gamma radiation from a Co sup 6 sup 0 source. The difference in the damage observed was used to characterize the damage caused by neutrons. It is observed that neutrons, though uncharged, are capable of causing ionization damage. This damage is found to be significant when the radiation is performed under biased conditions. Nitridation in different ambients is found to improve the radi...

  10. Ultranarrow absorptive spectral line induced by microwave field

    Institute of Scientific and Technical Information of China (English)

    Hu Zheng-Feng; Ma Yi-Sheng; Deng Jian-Liao; He Hui-Juan; Wang Yu-Zhu

    2009-01-01

    This paper investigates the absorptive spectral lines of four-level atomic system driven by a coupling, probe and microwave fields. Due to the perturbation of the microwave field, the original electromagnetically induced transparency is changed to electromagnetically induced absorption and the absorptive spectral line can be very narrow. This ultranarrow spectral line has potential applications to the microwave atomic frequency standard and the measurement of very weak magnetic field.

  11. Field induced phase segregation in ferrofluids

    NARCIS (Netherlands)

    Kooij, Ernst S.; Galca, A.C.; Poelsema, Bene

    2008-01-01

    We study the phase segregation in magnetite ferrofluids under the influence of an external magnetic field. A phase with lower nanoparticle density and corresponding higher optical transmission is formed in the bottom of a glass cell in the presence of only a very modest magnetic field gradient (smal

  12. Induced static magnetic field by a cellular phone

    Science.gov (United States)

    Einat, M.; Yahalom, A.

    2011-08-01

    Recent claims regarding the safety of cellular phones suggest that weak static magnetic fields are induced around the phone, and this field and its gradients may pose a health risk to the user. An experiment was conducted to measure the induced static magnetic field around a cellular phone. 65 μT variations and 18 μT/cm gradients were measured in the magnetic field at 6 cm from the phone. An analytical model is derived to explain the results. The influence that the measured magnetic fields may have on the user is beyond the scope of this research.

  13. Field-Induced Superconductivity in Electric Double Layer Transistors

    NARCIS (Netherlands)

    Ueno, Kazunori; Shimotani, Hidekazu; Yuan, Hongtao; Ye, Jianting; Kawasaki, Masashi; Iwasa, Yoshihiro

    2014-01-01

    Electric field tuning of superconductivity has been a long-standing issue in solid state physics since the invention of the field-effect transistor (FET) in 1960. Owing to limited available carrier density in conventional FET devices, electric-field-induced superconductivity was believed to be possi

  14. Oxygen vacancy induced by La and Fe into ZnO nanoparticles to modify ferromagnetic ordering

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Kuldeep Chand, E-mail: kuldeep0309@yahoo.co.in [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160 014 (India); Kotnala, R.K., E-mail: rkkotnala@gmail.com [CSIR-National Physical Laboratory, New Delhi 110012 (India)

    2016-05-15

    We reported long-range ferromagnetic interactions in La doped Zn{sub 0.95}Fe{sub 0.05}O nanoparticles that mediated through lattice defects or vacancies. Zn{sub 0.92}Fe{sub 0.05}La{sub 0.03}O (ZFLaO53) nanoparticles were synthesized by a sol–gel process. X-ray fluorescence spectrum of ZFLaO53 detects the weight percentage of Zn, Fe, La and O. X-ray diffraction shows the hexagonal Wurtzite ZnO phase. The Rietveld refinement has been used to calculate the lattice parameters and the position of Zn, Fe, La and O atoms in the Wurtzite unit cell. The average size of ZFLaO53 nanoparticles is 99 nm. The agglomeration type product due to OH ions with La results into ZnO nanoparticles than nanorods that found in pure ZnO and Zn{sub 0.95}Fe{sub 0.05}O sample. The effect of doping concentration to induce Wurtzite ZnO structure and lattice defects has been analyzed by Raman active vibrational modes. Photoluminescence spectra show an abnormal emission in both UV and visible region, and a blue shift at near band edge is formed with doping. The room temperature magnetic measurement result into weak ferromagnetism but pure ZnO is diamagnetic. However, the temperature dependent magnetic measurement using zero-field and field cooling at dc magnetizing field 500 Oe induces long-range ferromagnetic ordering. It results into antiferromagnetic Neel temperature of ZFLaO53 at around 42 K. The magnetic hysteresis is also measured at 200, 100, 50 and 10 K measurement that indicate enhancement in ferromagnetism at low temperature. Overall, the La doping into Zn{sub 0.95}Fe{sub 0.05}O results into enhanced antiferromagnetic interaction as well as lattice defects/vacancies. The role of the oxygen vacancy as the dominant defects in doped ZnO must form Bound magnetic polarons has been described. - Graphical abstract: The long-range ferromagnetic order in Zn{sub 0.92}Fe{sub 0.05}La{sub 0.03}O nanoparticles at low temperature measurements involves oxygen vacancy as the medium of magnetic

  15. Oxygen vacancy induced by La and Fe into ZnO nanoparticles to modify ferromagnetic ordering

    Science.gov (United States)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

    We reported long-range ferromagnetic interactions in La doped Zn0.95Fe0.05O nanoparticles that mediated through lattice defects or vacancies. Zn0.92Fe0.05La0.03O (ZFLaO53) nanoparticles were synthesized by a sol-gel process. X-ray fluorescence spectrum of ZFLaO53 detects the weight percentage of Zn, Fe, La and O. X-ray diffraction shows the hexagonal Wurtzite ZnO phase. The Rietveld refinement has been used to calculate the lattice parameters and the position of Zn, Fe, La and O atoms in the Wurtzite unit cell. The average size of ZFLaO53 nanoparticles is 99 nm. The agglomeration type product due to OH ions with La results into ZnO nanoparticles than nanorods that found in pure ZnO and Zn0.95Fe0.05O sample. The effect of doping concentration to induce Wurtzite ZnO structure and lattice defects has been analyzed by Raman active vibrational modes. Photoluminescence spectra show an abnormal emission in both UV and visible region, and a blue shift at near band edge is formed with doping. The room temperature magnetic measurement result into weak ferromagnetism but pure ZnO is diamagnetic. However, the temperature dependent magnetic measurement using zero-field and field cooling at dc magnetizing field 500 Oe induces long-range ferromagnetic ordering. It results into antiferromagnetic Neel temperature of ZFLaO53 at around 42 K. The magnetic hysteresis is also measured at 200, 100, 50 and 10 K measurement that indicate enhancement in ferromagnetism at low temperature. Overall, the La doping into Zn0.95Fe0.05O results into enhanced antiferromagnetic interaction as well as lattice defects/vacancies. The role of the oxygen vacancy as the dominant defects in doped ZnO must form Bound magnetic polarons has been described.

  16. Stripe order in La2-xBaxCuO4 in high magnetic fields

    Science.gov (United States)

    Huecker, M.; von Zimmermann, M.; Xu, Z. J.; Wen, J. S.; Gu, G. D.; Zaliznyak, I. A.; Chung, J.-H.; Choi, E. S.; Tranquada, J. M.

    2012-02-01

    The observation of enhanced spin stripe order in the vortex cores of La2-xSrxCuO4 has been a landmark experiment that revealed the intimate connection between superconductivity and incommensurate antiferromagnetism. Only recently we have observed a corresponding field dependence of the spin and, more importantly, of the charge stripe order in La2-xBaxCuO4. Here we present our recent results from neutron diffraction, x-ray diffraction, and torque measurements in high magnetic fields. These helped us to establish the field versus temperature and doping phase diagrams for spin and charge order, and to further corroborate the stripe model as the more appropriate description than for example spiral and vortex states.

  17. Second-order nonlinear susceptibility in quantum dot structure under applied electric field

    Science.gov (United States)

    Abdullah, M.; Noori, Farah T. Mohammed; Al-Khursan, Amin H.

    2015-06-01

    A model for quantum dot (QD) subbands, when the dots are in the form of quantum disks, under applied electric field was stated. Then, subbands of dots with different disk radii and heights were calculated under applied field. The competition between the shift due to confinement by field and the size was shown for subbands. Second-order nonlinear susceptibility in quantum dots (QDs) was derived using density matrix theory which is, then, simulated using the calculated subbands. Both interband (IB) and intersubband (ISB) transitions were discussed. High second-order susceptibility in QDs was predicted. The results show a reduction in the susceptibility with the applied field while the peak wavelength was mainly relates to energy difference between subbands. A good match between theory and laboratory experiments was observed. Laboratory experiments at terahertz region might be possible using valence intersubband which is important in many device applications.

  18. Anomaly induced effects in a magnetic field

    OpenAIRE

    Antoniadis, Ignatios; Boyarsky, Alexey; Ruchayskiy, Oleg

    2007-01-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light p...

  19. Stabilization of Néel order in frustrated magnets with increasing magnetic field

    Science.gov (United States)

    Schmidt, Burkhard; Siahatgar, Mohammad; Thalmeier, Peter

    2013-01-01

    For low-dimensional frustrated quantum magnets, the dependence of the staggered moment ms on a magnetic field is nonmonotonic: For small and intermediate fields, quantum fluctuations are gradually suppressed, leading to an increase of ms (H). For large applied magnetic fields however, the classically expected monotonous decrease is recovered. For the same reasons, the Néel ordering temperature TN of such compounds first increases and then exhibits a reentrant behavior as a function of the field strength. The quantitative analysis of this behavior is an excellent tool to determine the frustration parameter of a given compound. We have derived a general linear spin-wave (LSW) theory in the presence of a magnetic field. Based on our LSW theory, including a small interlayer coupling, we use a self-consistent approach determining TN by the condition of a vanishing total moment. We apply our findings to the recently measured field dependence of the magnetic ordering temperature TN of Cu(pz)2 (ClO4)2 in the framework of the S = 1/2 two-dimensional J1-J2 Heisenberg model. The observed increase with increasing field strength can be understood naturally using an intermediate frustration ratio J2/J1 ≈ 0.2, which is in accordance with the field dependence of the staggered moment.

  20. Imaging in scattering media via the second-order correlation of light field

    CERN Document Server

    Gong, Wenlin; Shen, Xia; Han, Shensheng

    2009-01-01

    Imaging with the second-order correlation of two light fields is a method to image an object by two-photon interference involving a joint detection of two photons at distant space-time points. We demonstrate for the first time that an image with high quality can still be obtained in the scattering media by applying the second-order correlation of illuminating light field. The scattering effect on the visibility of images is analyzed both theoretically and experimentally. Potential applications and the methods to further improve the visibility of the images in scattering media are also discussed.

  1. A note on second-order perturbations of non-canonical scalar fields

    CERN Document Server

    Appignani, Corrado; Shankaranarayanan, S

    2009-01-01

    We study second-order perturbations for a general non-canonical scalar field, minimally coupled to gravity, on the unperturbed FRW background, where metric fluctuations are neglected a priori. By employing different approaches to cosmological perturbation theory, we show that, even in this simplified set-up, there arise ambiguities in the expressions of physically relevant quantities, such as the effective speed of the perturbations, and the stress tensor and energy density display a potential instability which is not present at linear order. We also discuss the significance of our analysis in light of the possible linearization instability of these fields about the FRW background.

  2. Renormalization of an Abelian Tensor Group Field Theory: Solution at Leading Order

    CERN Document Server

    Lahoche, Vincent; Rivasseau, Vincent

    2015-01-01

    We study a just renormalizable tensorial group field theory of rank six with quartic melonic interactions and Abelian group U(1). We introduce the formalism of the intermediate field, which allows a precise characterization of the leading order Feynman graphs. We define the renormalization of the model, compute its (perturbative) renormalization group flow and write its expansion in terms of effective couplings. We then establish closed equations for the two point and four point functions at leading (melonic) order. Using the effective expansion and its uniform exponential bounds we prove that these equations admit a unique solution at small renormalized coupling.

  3. A Generalization of Gauge Symmetry, Fourth-Order Gauge Field Equations and Accelerated Cosmic-Expansion

    OpenAIRE

    2014-01-01

    A generalization of the usual gauge symmetry leads to fourth-order gauge field equations, which imply a new constant force independent of distances. The force associated with the new $U_1$ gauge symmetry is repulsive among baryons. Such a constant force based on baryon charge conservation gives a field-theoretic understanding of the accelerated cosmic-expansion in the observable portion of the universe dominated by baryon galaxies. In consistent with all conservation laws and known forces, a ...

  4. The third order helicity of magnetic fields via link maps II

    CERN Document Server

    Komendarczyk, R

    2009-01-01

    In this sequel we extend the derivation of the third order helicity to magnetic fields supported on unlinked domains in 3-space. The formula is expressed in terms of generators of the deRham cohomology of the configuration space of three points in $\\R^3$, which is a more practical domain from the perspective of applications. It also admits an ergodic interpretation as the asymptotic Milnor $\\bar{\\mu}_{123}$-invariant of orbits of the field.

  5. First-order formalism for twinlike models with several real scalar fields

    CERN Document Server

    Bazeia, D; Losano, L; Menezes, R

    2014-01-01

    We investigate the presence of twinlike models in theories described by several real scalar fields. We focus on the first-order formalism, and we show how to build distinct scalar field theories that support the same extended solution, with the same energy density and the very same linear stability. The results are valid for two distinct classes of generalized models, that include the standard model and cover a diversity of generalized models of current interest in high energy physics.

  6. A universal first order formula defining the ring of integers in a number field

    CERN Document Server

    Park, Jennifer

    2012-01-01

    We show that the complement of the ring of integers in a number field K is Diophantine. This means the set of ring of integers in K can be written as {t in K | for all x_1, ..., x_N in K, f(t,x_1, ..., x_N) is not 0}. We will use global class field theory and generalize the ideas originating from Koenigsmann's recent result giving a universal first order formula for Z in Q.

  7. Effective field theory calculation of conservative binary dynamics at third post-Newtonian order

    CERN Document Server

    Foffa, S

    2011-01-01

    We reproduce the two-body gravitational conservative dynamics at third post-Newtonian order for spin-less sources by using the effective field theory methods for the gravitationally bound two-body system, proposed by Goldberger and Rothstein. This result has been obtained by automatizing the computation of Feynman amplitudes within a Mathematica algorithm, paving the way for higher-order computations not yet performed by traditional methods.

  8. Electron-Helium Scattering in a Bichromatic Laser Field in the Second-Order Born Approximation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bin; LI Shu-Min

    2009-01-01

    @@ The elastic scattering of electrons in atomic helium assisted by a bichromatic laser field is investigated in the second order Born approximation. The target atom is approximated by a simple screening potential. The dependence of the differential cross section on the relative phase between the two laser components is calculated, and compared with the recent results of first order Born approximation [Sun J F, Liang M C and Zhu Z L 2007Chin. Phys. Lett. 24 2572].

  9. Computational estimation of magnetically induced electric fields in a rotating head.

    Science.gov (United States)

    Ilvonen, Sami; Laakso, Ilkka

    2009-01-21

    Change in a magnetic field, or similarly, movement in a strong static magnetic field induces electric fields in human tissues, which could potentially cause harmful effects. In this paper, the fields induced by different rotational movements of a head in a strong homogeneous magnetic field are computed numerically. Average field magnitudes near the retinas and inner ears are studied in order to gain insight into the causes of phosphenes and vertigo-like effects, which are associated with extremely low-frequency (ELF) magnetic fields. The induced electric fields are calculated in four different anatomically realistic head models using an efficient finite-element method (FEM) solver. The results are compared with basic restriction limits by IEEE and ICNIRP. Under rotational movement of the head, with a magnetic flux rate of change of 1 T s(-1), the maximum IEEE-averaged electric field and maximum ICNIRP-averaged current density were 337 mV m(-1) and 8.84 mA m(-2), respectively. The limits by IEEE seem significantly stricter than those by ICNIRP. The results show that a magnetic flux rate of change of 1 T s(-1) may induce electric field in the range of 50 mV m(-1) near retinas, and possibly even larger values near the inner ears. These results provide information for approximating the threshold electric field values of phosphenes and vertigo-like effects.

  10. Critical behavior in the presence of an order-parameter pinning field

    Science.gov (United States)

    Parisen Toldin, Francesco; Assaad, Fakher F.; Wessel, Stefan

    2017-01-01

    We apply a recently advocated simulation scheme that employs a local order-parameter pinning field to study quantum critical phenomena in the two-dimensional square-lattice bilayer quantum Heisenberg model. Using a world-line quantum Monte Carlo approach, we show that for this model, the pinning-field approach allows to locate the quantum critical point over a wide range of pinning-field strengths. However, the identification of the quantum critical scaling behavior is found to be hard since the pinning field introduces strong corrections to scaling. In order to further elucidate the scaling behavior in this situation, we also study an improved classical lattice model in the three-dimensional Ising universality class by means of Monte Carlo simulations on large lattice sizes, which allow us to employ refined finite-size scaling considerations. A renormalization group analysis exhibits the presence of an important crossover effect from the zero pinning-field to a critical adsorption fixed point. In line with field-theoretical results, we find that at the critical adsorption fixed point the short-distance expansion of the order-parameter profile exhibits a new universal critical exponent. This result also implies the presence of slowly decaying scaling corrections, which we analyze in detail.

  11. Generation of higher order nonclassical states via interaction of intense electromagnetic field with third order nonlinear medium

    CERN Document Server

    Pathak, A

    2006-01-01

    Interaction of intense laser beam with an inversion symmetric third order nonlinear medium is modeled as a quartic anharmonic oscillator. A first order operator solution of the model Hamiltonian is used to study the possibilities of generation of higher order nonclassical states. It is found that the higher order squeezed and higher order antibunched states can be produced by this interaction. It is also shown that the higher order nonclassical states may appear separately, i.e. a higher order antibunched state is not essentially higher order squeezed state and vice versa.

  12. Transverse flow induced by inhomogeneous magnetic fields in the Bjorken expansion

    CERN Document Server

    Pu, Shi

    2016-01-01

    We investigate the magnetohydrodynamics in the presence of an external magnetic field following the power-law decay in proper time and having spatial inhomogeneity characterized by a Gaussian distribution in one of transverse coordinates under the Bjorken expansion. The leading-order solution is obtained in the weak-field approximation, where both energy density and fluid velocity are modified. It is found that the spatial gradient of the magnetic field results in transverse flow, where the flow direction depends on the decay exponents of the magnetic field. We suggest that such a magnetic-field-induced effect might influence anisotropic flow in heavy ion collisions.

  13. Photoassociation dynamics driven by second- and third-order phase-modulated laser fields

    Science.gov (United States)

    Wang, Meng; Chen, Mao-Du; Hu, Xue-Jin; Li, Jing-Lun; Cong, Shu-Lin

    2016-05-01

    We investigate theoretically the photoassociation dynamics of ultracold 85Rb atoms driven by second- and third-order phase-modulated laser fields. The interplay between the second-order and third-order terms of the phase-modulated pulse has an obvious influence on photoassociation dynamics. The different combinations of the second-order and third-order phase coefficients lead to different pulse shapes. Most of the molecular population in the excited electronic state driven only by the third-order phase pulses can be distributed in a single vibrational level. The second-order term of the phase-modulated pulse can change the instantaneous frequency, and therefore the final population is distributed on several resonant vibrational levels, instead of concentrating on a single level. Although the second- and third-order phase-modulated pulse covers more resonant vibrational levels, the total population on the resonant vibrational levels is much smaller than that controlled only by the third-order phase pulse. In particular, the third-order term of the phase-modulated pulse can weaken the ‘multiple interaction’ to some degree.

  14. Electric field induced deformation of sessile drops

    Science.gov (United States)

    Corson, Lindsey; Tsakonas, Costas; Duffy, Brian; Mottram, Nigel; Brown, Carl; Wilson, Stephen

    2014-11-01

    The ability to control the shape of a drop with the application of an electric field has been exploited for many technological applications including measuring surface tension, producing an optical display device, and optimising the optical properties of microlenses. In this work we consider, both theoretically and experimentally, the deformation of pinned sessile drops with contact angles close to either 0° or 90° resting on the lower substrate inside a parallel plate capacitor due to an A.C. electric field. Using both asymptotic and numerical approaches we obtain predictive equations for the static and dynamic drop shape deformations as functions of the key experimental parameters (drop size, capacitor plate separation, electric field magnitude and contact angle). The asymptotic results agree well with the experimental results for a range of liquids. We gratefully acknowledge the financial support of EPSRC via research Grants EP/J009865 and EP/J009873.

  15. Anomaly induced effects in a magnetic field

    Science.gov (United States)

    Antoniadis, Ignatios; Boyarsky, Alexey; Ruchayskiy, Oleg

    2008-04-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light particles (including, for example, millicharged fermions). Due to the conservation of the gauge current, the production of the new vector field is suppressed at high energies. As a result, this theory can avoid both stellar bounds (which exist for axions) and the bounds from CMB considered recently, allowing for positive results in experiments like ALPS, LIPPS, OSQAR, PVLAS-2, BMV, Q&A, etc.

  16. Anomaly induced effects in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Antoniadis, Ignatios; Boyarsky, Alexey [Department of Physics, CERN, Theory Division, 1211 Geneva 23 (Switzerland); Ruchayskiy, Oleg [Ecole Polytechnique Federale de Lausanne, Institute of Theoretical Physics, FSB/ITP/LPPC, BSP 720, CH-1015 Lausanne (Switzerland)], E-mail: oleg.ruchayskiy@epfl.ch

    2008-04-11

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light particles (including, for example, millicharged fermions). Due to the conservation of the gauge current, the production of the new vector field is suppressed at high energies. As a result, this theory can avoid both stellar bounds (which exist for axions) and the bounds from CMB considered recently, allowing for positive results in experiments like ALPS, LIPPS, OSQAR, PVLAS-2, BMV, Q and A, etc.

  17. Anomaly induced effects in a magnetic field

    CERN Document Server

    Antoniadis, Ignatios; Ruchayskiy, O

    2008-01-01

    We consider a modification of electrodynamics by an additional light massive vector field, interacting with the photon via Chern-Simons-like coupling. This theory predicts observable effects for the experiments studying the propagation of light in an external magnetic field, very similar to those, predicted by theories of axion and axion-like particles. We discuss a possible microscopic origin of this theory from a theory with non-trivial gauge anomaly cancellation between massive and light particles (including, for example, millicharged fermions). Due to the conservation of the gauge current, the production of the new vector field is suppressed at high energies. As a result, this theory can avoid both stellar bounds (which exist for axions) and the bounds from CMB considered recently, allowing for positive results in experiments like ALPS, LIPPS, OSQAR, PVLAS-2, BMV, Q&A, etc.

  18. Explicit high-order symplectic integrators for charged particles in general electromagnetic fields

    CERN Document Server

    Tao, Molei

    2016-01-01

    This article considers non-relativistic charged particle dynamics in both static and non-static electromagnetic fields, which are governed by nonseparable, possibly time-dependent Hamiltonians. For the first time, explicit symplectic integrators of arbitrary high-orders are constructed for accurate and efficient simulations of such mechanical systems. Performances superior to the standard non-symplectic method of Runge-Kutta are demonstrated on two examples: the first is on the confined motion of a particle in a static toroidal magnetic field used in tokamak; the second is on how time-periodic perturbations to a magnetic field inject energy into a particle via parametric resonance at a specific frequency.

  19. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissilä, Tapio

    2010-01-01

    We present a derivation of the recently proposed eighth-order phase-field crystal model [A. Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two-dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase-field crystal models. We find that among the phase-field crystal mod...

  20. High order harmonic generation in noble gases using plasmonic field enhancement

    CERN Document Server

    Ciappina, M F; Lewenstein, M

    2012-01-01

    We present theoretical studies of high-order harmonic generation (HHG) in rare gases driven by plasmonic field enhancement. This kind of fields appears when plasmonic nanostructures are illuminated by an intense few-cycle laser and have a particular spatial dependency, depending on the geometrical shape of the nanostructure. We demonstrate that the strong nonhomogeneous character of the laser enhanced field plays an important role in the HHG process and significantly extends the harmonic cutoff. Our models are based on numerical solution of the time dependent Schroedinger equation (TDSE) and supported by classical and semiclassical calculations.

  1. Field Emission From Ordered Nano-array Structures Based on Porous Aluminum Oxide Templates

    Institute of Scientific and Technical Information of China (English)

    WANG; ChengWei

    2001-01-01

    This thesis reports my research work of fabricating nanostructures by using nanoporous anodic aluminum oxide (AAO) templates and their field emission properties in the past few years. Some important results obtained are as follows:  1. We first proposed a new concept of fabricating field emitters with ordered nanostructures based on porous aluminum oxide templates such as AAO/Al, metal/AAO, PANI/AAO, CNTs/AAO, Si/AAO and did a lot of research in this field.  ……

  2. Field-dependent tuning of the ferromagnetic ordering in CeAgSb{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Strydom, A.M. [Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006 (South Africa)], E-mail: amstrydom@uj.ac.za; Mhlungu, B.M. [Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006 (South Africa); South African Nuclear Energy Corporation, Pelindaba (South Africa); Thamizhavel, A. [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai (India)

    2008-07-15

    We report on the effects that different applied magnetic fields have on the electrical resistivity and the Hall coefficient in single crystals of the ferromagnetic Kondo lattice CeAgSb{sub 2}. The total measured Hall coefficient R{sub H} shows a large field-dependent anomaly at T{sub C}=9.5K. We resolved R{sub H} into its normal and anomalous components in order to address the question of the evolution of R{sub H} when T{sub C} is suppressed to zero by an applied magnetic field.

  3. Strong-field S -matrix theory with final-state Coulomb interaction in all orders

    Science.gov (United States)

    Faisal, F. H. M.

    2016-09-01

    During the last several decades the so-called Keldysh-Faisal-Reiss or strong-field approximation (SFA) has been highly useful for the analysis of atomic and molecular processes in intense laser fields. However, it is well known that SFA does not account for the final-state Coulomb interaction which is, however, unavoidable for the ubiquitous ionization process. In this Rapid Communication we solve this long-standing problem and give a complete strong-field S -matrix expansion that accounts for the final-state Coulomb interaction in all orders, explicitly.

  4. Interrupted Magnetic First Order Transitions and Kinetic Arrest probed with In-field Neutron Diffraction

    Science.gov (United States)

    Siruguri, V.; Kaushik, S. D.; Rayaprol, S.; Babu, P. D.; Chaddah, P.; Sampathkumaran, E. V.; Hoser, A.; Ritter, C.

    2016-09-01

    In-field neutron diffraction studies were carried out on two compounds that exhibit magnetic first order phase transitions (FOPT). It is shown that the FOPT can be interrupted by an external magnetic field, resulting in a coexistence of kinetically arrested metastable states and equilibrium phases. Use of a novel protocol CHUF (Cooling and Heating under Unequal Fields) helps to determine the coexisting phase fractions and also to observe the devitrification of the kinetically arrested phase into the equilibrium phase, in a manner similar to that found in structural glassy systems.

  5. Proton-Proton Fusion in Effective Field Theory to Fifth Order

    OpenAIRE

    Butler, Malcolm; Chen, Jiunn-Wei

    2001-01-01

    The proton-proton fusion process p p->d e^+ nu_e is calculated at threshold to fifth order in pionless effective field theory. There are two unknown two-body currents contributing at the second and fourth orders. Combined with the previous results for neutrino-deuteron and antineutrino-deuteron scattering, computed to third order in the same approach, we conclude that a 10% measurement of reactor antineutrino-deuteron scattering measurement could constrain the p p->d e^+ nu_e rate to ~7% whil...

  6. Proton-Proton Fusion in Effective Field Theory to Fifth Order

    CERN Document Server

    Butler, M; Butler, Malcolm; Chen, Jiunn-Wei

    2001-01-01

    The proton-proton fusion process p p->d e^+ nu_e is calculated at threshold to fifth order in pionless effective field theory. There are two unknown two-body currents contributing at the second and fourth orders. Combined with the previous results for neutrino-deuteron and antineutrino-deuteron scattering, computed to third order in the same approach, we conclude that a 10% measurement of reactor antineutrino-deuteron scattering measurement could constrain the p p->d e^+ nu_e rate to ~7% while a ~3% measurement of nu_e d-> e^- p p could constrain the pp rate to ~2%.

  7. Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

    Institute of Scientific and Technical Information of China (English)

    Y.J.Gu; Q.Yu; O.Klimo; T.Zh.Esirkepov; S.V.Bulanov; S.Weber; G.Korn

    2016-01-01

    Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.

  8. High magnetic field studies of the hidden order transition in URu2Si2.

    Science.gov (United States)

    Jaime, M; Kim, K H; Jorge, G; McCall, S; Mydosh, J A

    2002-12-31

    We studied in detail the low temperature/high magnetic field phases of URu2Si2 single crystals with specific heat, magnetocaloric effect, and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5 K, and extrapolated to T=0, show a suppression of the hidden-order phase at H0(0)=35.9+/-0.35 T and the appearance of a new phase for magnetic fields in excess of H1(0)=36.1+/-0.35 T observed only at temperatures lower than 6 K. In turn, complete suppression of this high field state is attained at a critical magnetic field H2(0)=39.7+/-0.35 T. No phase transitions are observed above 40 T. We discuss our results in the context of itinerant versus localized f electrons.

  9. Quantum-orbit analysis of high-order harmonic generation by resonant plasmon field enhancement

    CERN Document Server

    Shaaran, T; Lewenstein, M

    2012-01-01

    We perform a detailed analysis of high-order harmonic generation (HHG) in atoms within the strong field approximation (SFA) by considering spatially inhomogeneous monochromatic laser fields. We investigate how the individual pairs of quantum orbits contribute to the harmonic spectra. We show that in the case of inhomogeneous fields, the electron tunnels with two different canonical momenta. One of them leads to a higher cutoff and the other one develops a lower cutoff. Furthermore, we demonstrate that the quantum orbits have a very different behavior in comparison to the homogeneous field. We also conclude that in the case of the inhomogeneous fields, both odd and even harmonics are present in the HHG spectra. Within our model, we show that the HHG cutoff extends far beyond the semiclassical cutoff as a function of inhomogeneity strength. Our findings are in good agreement both with quantum mechanical and classical models.

  10. Electric Field Induced Surface Modification of Au

    Energy Technology Data Exchange (ETDEWEB)

    Erchak, A.A.; Franklin, G.F.; Houston, J.E.; Mayer, T.M.; Michalske, T.A.

    1999-02-15

    We discuss the role of localized high electric fields in the modification of Au surfaces with a W probe using the Interfacial Force Microscope. Upon bringing a probe close to a Au surface, we measure both the interfacial force and the field emission current as a function of separation with a constant potential of 100 V between tip and sample. The current initially increases exponentially as the separation decreases. However, at a distance of less than {approximately} 500{angstrom} the current rises sharply as the surface begins to distort and rapidly close the gap. Retraction of the tip before contact is made reveals the formation of a mound on the surface. We propose a simple model, in which the localized high electric field under the tip assists the production of mobile Au adatoms by detachment from surface steps, and a radial field gradient causes a net flux of atoms toward the tip by surface diffusion. These processes give rise to an unstable surface deformation which, if left unchecked, results in a destructive mechanical contact. We discuss our findings with respect to earlier work using voltage pulses in the STM as a means of nanofabrication.

  11. Fourth-order master equation for a charged harmonic oscillator coupled to an electromagnetic field

    Science.gov (United States)

    Kurt, Arzu; Eryigit, Resul

    Using Krylov averaging method, we have derived a fourth-order master equation for a charged harmonic oscillator weakly coupled to an electromagnetic field. Interaction is assumed to be of velocity coupling type which also takes into account the diagmagnetic term. Exact analytical expressions have been obtained for the second, the third and the fourth-order corrections to the diffusion and the drift terms of the master equation. We examined the validity range of the second order master equation in terms of the coupling constant and the bath cutoff frequency and found that for the most values of those parameters, the contribution from the third and the fourth order terms have opposite signs and cancel each other. Inclusion of the third and the fourth-order terms is found to not change the structure of the master equation. Bolu, Turkey.

  12. Magnetic field penetration into a 3D ordered Josephson medium and applicability of the bean model

    Science.gov (United States)

    Zelikman, M. A.

    2014-11-01

    The results of calculation of penetration of an external magnetic field into a 3D ordered Josephson medium, based on analysis of modification of the configuration in the direction of the decrease in its Gibbs potential, are reported. When the external field slightly exceeds the stability threshold, the Meissner configuration is transformed into a periodic sequence of linear vortices, which are parallel to the boundary of the medium and are located at a certain distance from it. There exists a critical value I C separating two possible regimes of penetration of the external magnetic field into the medium. For I > I C, for any value of the external field, a finite-length boundary current configuration appears, which completely compensates the external field in the bulk of the sample. At the sample boundary, the field decreases with increasing depth almost linearly. The values of the slope of the magnetic field dependence are rational fractions, which remain constant in finite intervals of I. When the value of I exceeds the upper boundary of such an interval, the slope increases and assumes the value of another rational fraction. If, however, I < I C, such a situation takes place only up to a certain value of external field H max. For higher values, the field penetrates into the medium to an infinite depth. These results lead to the conclusion that the Bean assumptions are violated and that Bean's model is inapplicable for analyzing the processes considered here.

  13. Native defect induced charge and ferromagnetic spin ordering and coexisting electronic phases in CoO epitaxial thin film

    Energy Technology Data Exchange (ETDEWEB)

    Negi, D. S., E-mail: devendranegi@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in; Loukya, B.; Datta, R., E-mail: devendranegi@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in [International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)

    2015-12-07

    We report on the observation of Co vacancy (V{sub Co}) induced charge ordering and ferromagnetism in CoO epitaxial thin film. The ordering is associated with the coexistence of commensurate, incommensurate, and discommensurate electronic phases. Density functional theory calculation indicates the origin of ordering in Co atoms undergoing high spin to low spin transition immediately surrounding the V{sub Co(16.6 at. %)}. Electron magnetic chiral dichroism experiment confirms the ferromagnetic signal at uncompensated Co spins. Such a native defects induced coexistence of different electronic phases at room temperature in a simple compound CoO is unique and adds to the richness of the field with the possibility of practical device application.

  14. Bifurcation of limit cycles in 3rd-order Z2 Hamiltonian planar vector fields with 3rd-order perturbations

    Science.gov (United States)

    Yu, Pei; Han, Maoan

    2013-04-01

    In this paper, we show that a Z2-equivariant 3rd-order Hamiltonian planar vector fields with 3rd-order symmetric perturbations can have at least 10 limit cycles. The method combines the general perturbation to the vector field and the perturbation to the Hamiltonian function. The Melnikov function is evaluated near the center of vector field, as well as near homoclinic and heteroclinic orbits.

  15. Control of high-order harmonic generation with two-colour laser field

    Institute of Scientific and Technical Information of China (English)

    Dai Jun; Zeng Zhi-Nan; Li Ru-Xin; Xu Zhi-Zhan

    2010-01-01

    We numerically investigate the high-order harmonic generation with two-colour optical field,taking into consideration the propagation effects.Some harmonics can be dramatically enhanced at a certain delay between the fundamental pulse and its second harmonics.Choice of the enhanced harmonics can be realised by changing the time delay between the two laser pulses.

  16. Explicit solutions of one-dimensional, first-order, stationary mean-field games with congestion

    KAUST Repository

    Gomes, Diogo A.

    2017-01-05

    Here, we consider one-dimensional first-order stationary mean-field games with congestion. These games arise when crowds face difficulty moving in high-density regions. We look at both monotone decreasing and increasing interactions and construct explicit solutions using the current formulation. We observe new phenomena such as discontinuities, unhappiness traps and the non-existence of solutions.

  17. Beam transport optics of dipole fringe field in the framework of third-order matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Sagalovsky, L. (Argonne National Lab. (USA))

    1990-12-01

    The paper describes analytical methods for studying the optical aberrations of charged particles' orbits in an extended fringing field of a dipole magnet. Solutions are obtained up to the third order in the formalism of the transfer matrix theory. (orig.).

  18. Two-Field Integrable Evolutionary Systems of the Third Order and Their Differential Substitutions

    Directory of Open Access Journals (Sweden)

    Maxim Ju. Balakhnev

    2008-02-01

    Full Text Available A list of forty third-order exactly integrable two-field evolutionary systems is presented. Differential substitutions connecting various systems from the list are found. It is proved that all the systems can be obtained from only two of them. Examples of zero curvature representations with 4 × 4 matrices are presented.

  19. Two-Field Integrable Evolutionary Systems of the Third Order and Their Differential Substitutions

    OpenAIRE

    Maxim Ju. Balakhnev; Anatoly G. Meshkov

    2008-01-01

    A list of forty third-order exactly integrable two-field evolutionary systems is presented. Differential substitutions connecting various systems from the list are found. It is proved that all the systems can be obtained from only two of them. Examples of zero curvature representations with $4 \\times 4$ matrices are presented.

  20. Generation of non-classical optical fields by a beam splitter with second-order nonlinearity

    CERN Document Server

    Prakash, Hari

    2016-01-01

    We propose quantum-mechanical model of a beam splitter with second-order nonlinearity and show that non-classical features such as squeezing and sub-Poissonian photon statistics of optical fields can be generated in output fundamental and second harmonic modes when we mix coherent light beams via such a nonlinear beam splitter.

  1. Modelling Distributed Shape Priors by Gibbs Random Fields of Second Order

    CERN Document Server

    Flach, Boris

    2011-01-01

    We analyse the potential of Gibbs Random Fields for shape prior modelling. We show that the expressive power of second order GRFs is already sufficient to express simple shapes and spatial relations between them simultaneously. This allows to model and recognise complex shapes as spatial compositions of simpler parts.

  2. Singularity-free static centrally symmetric solutions of some fourth order gravitational field equations

    Energy Technology Data Exchange (ETDEWEB)

    Fiedler, B.; Schimming, R.

    1983-01-01

    The fourth order field equations proposed by TREDER with a linear combination of BACH's tensor and EINSTEIN's tensor on the left-hand side admit static centrally symmetric solutions which are analytical and non-flat in some neighborhood of the centre of symmetry.

  3. Neutron matter instabilities induced by strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre, R. [Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata and IFLP-CCT-La Plata, CONICET (Argentina); Bauer, E., E-mail: bauer@fisica.unlp.edu.ar [Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata and IFLP-CCT-La Plata, CONICET (Argentina)

    2013-04-10

    We study some properties of spin-polarized neutron matter in the presence of a strong magnetic field at finite temperature. Using the Skyrme model together with the Hartree–Fock approximation we obtain an energy density functional that is employed to extract the spin polarization, the effective mass and the magnetic free energy of the system. In order to find the equilibrium state, we have analyzed different global spin configurations over a wide range of matter density (0field intensity (10{sup 14} G⩽B<10{sup 19} G) and temperature (T⩽80 MeV). The outcome is that the system can be either completely spin-down polarized or partially polarized. A change in any of the (n,T,B)-variables can induce a transition from one polarization state to the other. The transition takes place in a surface in the (n,T,B)-phase space, which represents an instability of the system. We have also found a discontinuity in the internal energy associated with this change in the state of magnetization.

  4. Field-induced crossover from phonon to field assisted hopping conductivity in organic materials

    Science.gov (United States)

    Bourbie, D.

    2011-01-01

    Recently the change in temperature dependence of conductivity observed in polythiophene field-effect transistors has been attributed to field-induced metal-insulator transition. Under a high source-drain voltage, the conductivity becomes independent from temperature and depends exponentially on the inverse of the square root of electric field. In this paper we present a theoretical interpretation of this behavior in the framework of hopping mechanism. The ingredient of this model, is the energy gained from the electrical field is always larger than the energy difference between the localized states involved into the charge transitions, which induces a crossover from phonon-assisted hopping to field-assisted hopping.

  5. Neutron Scattering Study of Magnetic Field Effect on the Stripe Order in LBCO

    Science.gov (United States)

    Xu, Zhijun; Wen, Jinsheng; Xu, Guangyong; Hücker, Markus; Tranquada, John; Gu, Genda

    2009-03-01

    We have been investigating the relationship of stripe order to high-temperature superconductivity in cuprates. In particular, our neutron scattering results indicate that spin-stripe order is present in La2-xBaxCuO4 (LBCO) over a substantial range of doping about x = 1/8, where the bulk superconductivity is anomalously suppressed. Focusing on the x = 1/8 composition, we have recently studied the impact on stripe order of a magnetic field applied along the c-axis [1]. Applying a field up to 7 T, we observed a small enhancement of the intensity of the incommensurate antiferromagnetic superlattice peaks and a slight increase in the ordering temperature. In measurements of the spin dynamics, the field had no significant impact on the small spin gap (˜ 0.5 meV) found in the ordered phase [2]. [1] Jinsheng Wen et al., arXiv:0810.4085. [2] J.M. Tranquada et al., arXiv:0809.0711. Work supported by Office of Science, U.S. DOE, under Contract No. DEAC02-98CH10886

  6. Interaction induced staggered spin-orbit order in two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Das, Tanmoy [Los Alamos National Laboratory

    2012-06-05

    Decoupling spin and charge transports in solids is among the many prerequisites for realizing spin electronics, spin caloritronics, and spin-Hall effect. Beyond the conventional method of generating and manipulating spin current via magnetic knob, recent advances have expanded the possibility to optical and electrical method which are controllable both internally and externally. Yet, due to the inevitable presence of charge excitations and electrical polarizibility in these methods, the separation between spin and charge degrees of freedom of electrons remains a challenge. Here we propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of matter. We show that when some form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly nested, a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states, with no active charge excitations. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or de-phasing time. BiAg2 surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin-splitting is decoupled from charge excitations.

  7. Lunar magnetic field - Permanent and induced dipole moments

    Science.gov (United States)

    Russell, C. T.; Coleman, P. J., Jr.; Schubert, G.

    1974-01-01

    Apollo 15 subsatellite magnetic field observations have been used to measure both the permanent and the induced lunar dipole moments. Although only an upper limit of 1.3 x 10 to the 18th gauss-cubic centimeters has been determined for the permanent dipole moment in the orbital plane, there is a significant induced dipole moment which opposes the applied field, indicating the existence of a weak lunar ionosphere.

  8. Lattice Simulations for Light Nuclei: Chiral Effective Field Theory at Leading Order

    CERN Document Server

    Borasoy, B; Krebs, H; Lee, D; Meißner, Ulf G; Borasoy, Bugra; Epelbaum, Evgeny; Krebs, Hermann; Lee, Dean; Mei{\\ss}ner, Ulf-G.

    2006-01-01

    We discuss lattice simulations of light nuclei at leading order in chiral effective field theory. Using lattice pion fields and auxiliary fields, we include the physics of instantaneous one-pion exchange and the leading-order S-wave contact interactions. We also consider higher-derivative contact interactions which adjust the S-wave scattering amplitude at higher momenta. By construction our lattice path integral is positive definite in the limit of exact Wigner SU(4) symmetry for any even number of nucleons. This SU(4) positivity and the approximate SU(4) symmetry of the low-energy interactions play an important role in suppressing sign and phase oscillations in Monte Carlo simulations. We assess the computational scaling of the lattice algorithm for light nuclei with up to eight nucleons and analyze in detail calculations of the deuteron, triton, and helium-4.

  9. Eighth-order phase-field-crystal model for two-dimensional crystallization

    Science.gov (United States)

    Jaatinen, A.; Ala-Nissila, T.

    2010-12-01

    We present a derivation of the recently proposed eighth-order phase-field crystal model [A. Jaatinen , Phys. Rev. E 80, 031602 (2009)10.1103/PhysRevE.80.031602] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two-dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase-field crystal models. We find that among the phase-field crystal models studied, the eighth-order fitting scheme gives results in good agreement with the density functional theory for both static and dynamic properties, suggesting it is an accurate and computationally efficient approximation to the density functional theory.

  10. Destruction of first-order phase transition in a random-field Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Crokidakis, Nuno; Nobre, Fernando D [Centro Brasileiro de Pesquisas Fisicas, Rua Xavier Sigaud 150, 22290-180, Rio de Janeiro-RJ (Brazil)], E-mail: nuno@if.uff.br, E-mail: fdnobre@cbpf.br

    2008-04-09

    The phase transitions that occur in an infinite-range-interaction Ising ferromagnet in the presence of a double Gaussian random magnetic field are analyzed. Such random fields are defined as a superposition of two Gaussian distributions, presenting the same width {sigma}. It is argued that this distribution is more appropriate for a theoretical description of real systems than other simpler cases, i.e. the bimodal ({sigma} = 0) and single Gaussian distributions. It is shown that a low-temperature first-order phase transition may be destroyed for increasing values of {sigma}, similarly to what happens in the compound Fe{sub x}Mg{sub 1-x}Cl{sub 2}, whose finite-temperature first-order phase transition is presumably destroyed by an increase in the field randomness.

  11. Theoretical analysis of the velocity field, stress field and vortex sheet of generalized second order fluid withfractional anomalous diffusion

    Institute of Scientific and Technical Information of China (English)

    徐明瑜; 谭文长

    2001-01-01

    The velocity field of generalized second order fluid with fractional anomalous diffusion caused by a plate moving impulsively in its own plane is investigated and the anomalous diffusion problems of the stress field and vortex sheet caused by this process are studied. Many previous and classical results can be considered as particular cases of this paper, such as the solutions of the fractional diffusion equations obtained by Wyss; the classical Rayleigh' s time-space similarity solution; the relationship between stress field and velocity field obtained by Bagley and co-worker and Podlubny' s results on the fractional motion equation of a plate. In addition, a lot of significant results also are obtained. For example, the necessary condition for causing the vortex sheet is that the time fractional diffusion index β must be greater than that of generalized second order fluid α; the establishment of the vorticity distribution function depends on the time history of the velocity profile at a given point, and the time history can be described by the fractional calculus.

  12. Divertor with a third-order null of the poloidal field

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D. D.; Umansky, M. V. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

    2013-09-15

    A concept and preliminary feasibility analysis of a divertor with the third-order poloidal field null is presented. The third-order null is the point where not only the field itself but also its first and second spatial derivatives are zero. In this case, the separatrix near the null-point has eight branches, and the number of strike-points increases from 2 (as in the standard divertor) to six. It is shown that this magnetic configuration can be created by a proper adjustment of the currents in a set of three divertor coils. If the currents are somewhat different from the required values, the configuration becomes that of three closely spaced first-order nulls. Analytic approach, suitable for a quick orientation in the problem, is used. Potential advantages and disadvantages of this configuration are briefly discussed.

  13. Ambiguities in second-order cosmological perturbations for non-canonical scalar fields

    CERN Document Server

    Appignani, Corrado; Shankaranarayanan, S

    2010-01-01

    Over the last few years, it was realised that non-canonical scalar fields can lead to the accelerated expansion in the early universe. The primordial spectrum in these scenarios not only shows near scale-invariance consistent with CMB observations,but also large primordial non-Gaussianity. Second-order perturbation theory is the primary theoretical tool to investigate such non-Gaussianity. However, it is still uncertain which quantities are gauge-invariant at second-order and their physical understanding therefore remains unclear. As an attempt to understand second order quantities, we consider a general non-canonical scalar field, minimally coupled to gravity, on the unperturbed FRW background where metric fluctuations are neglected a priori. In this simplified set-up, we show that there arise ambiguities in the expressions of physically relevant quantities, such as the effective speeds of the perturbations. Further, the stress tensor and energy density display a potential instability which is not present at...

  14. High-order harmonic generation and multi-photon ionization of Na2 in laser fields

    Institute of Scientific and Technical Information of China (English)

    Zhang Yan-Ping; Zhang Feng-Shou; Meng Ke-Lai; Xiao Guo-Qing

    2007-01-01

    In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.

  15. Direct three-dimensional ordering of quasi-one-dimensional quantum dimer system near critical fields

    Science.gov (United States)

    Matsushita, Taku; Hori, Nobuyoshi; Takata, Seiya; Wada, Nobuo; Amaya, Naoki; Hosokoshi, Yuko

    2017-01-01

    Dimensionalities of X X Z spin orderings or degenerate hard-core bosons in a quasi-one-dimensional (1D) dimer system are examined by the ac susceptibility and specific heat of antiferromagnetic bond-alternating chains in pentafluorophenyl nitronyl nitroxide (F5PNN ). At intermediate fields in the gapless region, the 1D short-range order (SRO) corresponding to the Tomonaga-Luttinger liquid and three-dimensional (3D) long-range order (LRO BEC) at lower temperatures are separately observed, as expected from the small interchain interaction. In contrast, a definite region around the critical field was established where 3D LRO occurs without the development of 1D SRO at higher temperatures.

  16. Triton charge radius to next-to-next-to-leading order in pionless effective field theory

    Science.gov (United States)

    Vanasse, Jared

    2017-02-01

    The triton point charge radius is calculated to next-to-next-to-leading order (NNLO) in pionless effective field theory ( EFT (π / )) , yielding a prediction of 1.14 ±0.19 fm (leading order), 1.59 ±0.08 fm (next-to leading order), and 1.62 ±0.03 fm (NNLO) in agreement with the current experimental extraction of 1.5978 ±0.040 fm [Angeli and Marinova, At. Data Nucl. Data Tables 99, 69 (2013)], 10.1016/j.adt.2011.12.006. The error at NNLO is due to cutoff variation (˜1 % ) within a reasonable range of calculated cutoffs and from a EFT (π / ) error estimate (˜1.5 % ). In addition new techniques are introduced to add perturbative corrections to bound- and scattering state calculations for short-range effective field theories, but with a focus on their use in EFT (π / ) .

  17. Oscillatory-shear-induced order in nonaqueous dispersions of charged colloidal spheres

    NARCIS (Netherlands)

    Yan, Y.D.; Dhont, J.K.G.; Smits, C.; Lekkerkerker, H.N.W.

    1994-01-01

    A light scattering study is presented of the nonequilibrium microstructure of nonaqueous dispersions of repulsive charged colloidal silica spheres subjected to an oscillatory shear flow. Two ordered structures are induced upon increasing the oscillation amplitude: alternating face-centred-cubic

  18. Stark-induced anapole magnetic fields in n=2 hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Robert R. [Department of Physics UM, Ann Arbor MI 48109 (United States); Gongora-T, A. [Instituto de Fisica UNAM, 01000 Mexico DF (Mexico)

    1998-08-28

    This paper presents results for the anapole magnetic field moment due to the mixing of states with opposite parity in the n=2 hydrogen atom in an external constant electric field. The evaluation of the current densities of the four n=2 states is carried out to first order in the field strength. These current densities and their associated magnetic fields are expanded in multipoles, including both the ordinary poloidal and the toroidal fields. The dominant contribution to the toroidal dipole (anapole) magnetic field comes from the strong mixing of the degenerate 2S, 2P states within the n=2 shell. A brief discussion is also presented of the electronic scattering from the anapole field of a Rydberg atom. The experimental conditions under which the atomic anapole field could be detected are critically considered, in particular, in terms of the quasi-resonant dependence of the anapole field on the applied electric field. (author)

  19. Physiologic and dosimetric considerations for limiting electric fields induced in the body by movement in a static magnetic field.

    Science.gov (United States)

    Jokela, Kari; Saunders, Richard D

    2011-06-01

    Movement in a strong static magnetic field induces electric fields in a human body, which may result in various sensory perceptions such as vertigo, nausea, magnetic phosphenes, and a metallic taste in the mouth. These sensory perceptions have been observed by patients and medical staff in the vicinity of modern diagnostic magnetic resonance (MR) equipment and may be distracting if they were to affect the balance and eye-hand coordination of, for example, a physician carrying out a medical operation during MR scanning. The stimulation of peripheral nerve tissue by a more intense induced electric field is also theoretically possible but has not been reported to result from such movement. The main objective of this study is to consider generic criteria for limiting the slowly varying broadband (magnetic field. In order to find a link between the static magnetic flux density and the time-varying induced electric field, the static magnetic field is converted to the homogeneous equivalent transient and sinusoidal magnetic fields exposing a stationary body. Two cases are considered: a human head moving in a non-uniform magnetic field and a head rotating in a homogeneous magnetic field. Then the electric field is derived from the magnetic flux rate (dB/dt) of the equivalent field by using computational dosimetric data published in the literature for various models of the human body. This conversion allows the plotting of the threshold electric field as a function of frequency for vertigo, phosphenes, and stimulation of peripheral nerves. The main conclusions of the study are: The basic restrictions for limiting exposure to extremely low frequency magnetic fields recommended by the International Commission on Non-Ionizing Radiation Protection ICNIRP in 1998 will prevent most cases of vertigo and other sensory perceptions that result from induced electric fields above 1 Hz, while limiting the static magnetic field below 2 T, as recently recommended by ICNIRP, provides

  20. Phase coexistence and electric-field control of toroidal order in oxide superlattices

    Science.gov (United States)

    Damodaran, A. R.; Clarkson, J. D.; Hong, Z.; Liu, H.; Yadav, A. K.; Nelson, C. T.; Hsu, S.-L.; McCarter, M. R.; Park, K.-D.; Kravtsov, V.; Farhan, A.; Dong, Y.; Cai, Z.; Zhou, H.; Aguado-Puente, P.; García-Fernández, P.; Íñiguez, J.; Junquera, J.; Scholl, A.; Raschke, M. B.; Chen, L.-Q.; Fong, D. D.; Ramesh, R.; Martin, L. W.

    2017-10-01

    Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO3/SrTiO3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a1/a2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.

  1. Implementation of fractional order integrator/differentiator on field programmable gate array

    Directory of Open Access Journals (Sweden)

    K.P.S. Rana

    2016-06-01

    Full Text Available Concept of fractional order calculus is as old as the regular calculus. With the advent of high speed and cost effective computing power, now it is possible to model the real world control and signal processing problems using fractional order calculus. For the past two decades, applications of fractional order calculus, in system modeling, control and signal processing, have grown rapidly. This paper presents a systematic procedure for hardware implementation of the basic operators of fractional calculus i.e. fractional integrator and derivative, using Grünwald–Letnikov definition, on field programmable gate array (FPGA in LabVIEW environment. The simulation and hardware implementation results for fractional order integrator and derivative of sinusoid and square waveform signals for some selected fractional orders have been presented. A close agreement between the simulated and the experimental results demonstrated the suitability of FPGA device in fractional order control and signal processing applications. LabVIEW being one of the finest tools for measurement and control, and signal processing applications the fractional order operator implementation is expected to further enhance the capability of the tool to cater to the needs of advanced experimental research employing fractional order operators.

  2. Induced Gravity I: Real Scalar Field

    CERN Document Server

    Einhorn, Martin B

    2016-01-01

    We show that classically scale invariant gravity coupled to a single scalar field can undergo dimensional transmutation and generate an effective Einstein-Hilbert action for gravity, coupled to a massive dilaton. The same theory has an ultraviolet fixed point for coupling constant ratios such that all couplings are asymptotically free. However the catchment basin of this fixed point does not include regions of coupling constant parameter space compatible with locally stable dimensional transmutation. We believe that the desirable outcome may obtain in more complicated theories with non-Abelian gauge interactions.

  3. Induced gravity I: real scalar field

    Energy Technology Data Exchange (ETDEWEB)

    Einhorn, Martin B. [Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106-4030 (United States); Jones, D.R. Timothy [Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106-4030 (United States); Department of Mathematical Sciences,University of Liverpool, Liverpool L69 3BX (United Kingdom)

    2016-01-05

    We show that classically scale invariant gravity coupled to a single scalar field can undergo dimensional transmutation and generate an effective Einstein-Hilbert action for gravity, coupled to a massive dilaton. The same theory has an ultraviolet fixed point for coupling constant ratios such that all couplings are asymptotically free. However the catchment basin of this fixed point does not include regions of coupling constant parameter space compatible with locally stable dimensional transmutation. In a companion paper, we will explore whether this more desirable outcome does obtain in more complicated theories with non-Abelian gauge interactions.

  4. Analysis of Slight Discrepancy Between Quantum Dynamics and Classical Statistical Dynamics For Second Order Field Theories

    CERN Document Server

    Werbos, P J

    2003-01-01

    Quantum Field Theory (QFT) makes predictions by combining two sets of assumptions: (1) quantum dynamics, such as a Schrodinger or Liouville equation; (2) quantum measurement, such as stochastic collapse to an eigenfunction of a measurement operator. A previous paper defined a classical density matrix R encoding the statistical moments of an ensemble of states of classical second-order Hamiltonian field theory. It proved Tr(RQ)=E(Q), etc., for the usual field operators as defined by Weinberg, and it proved that those observables of the classical system obey the usual Heisenberg dynamic equation. However, R itself obeys dynamics different from the usual Liouville equation! This paper derives those dynamics, and calculates the discrepancy between CFT and normal form QFT in predicting general observables g(Q,P). There is some preliminary evidence for the conjecture that the discrepancies disappear in equilibrium states (bound states and scattering states) for finite bosonic field theories. Even if not, they appea...

  5. Behaviour of the order parameter of the simple magnet in an external field

    Directory of Open Access Journals (Sweden)

    M.P.Kozlovskii

    2005-01-01

    Full Text Available The effect of a homogeneous external field on the three-dimensional uniaxial magnet behaviour near the critical point is investigated within the framework of the nonperturbative collective variables method using the ρ4 model. The research is carried out for the low-temperature region. The analytic explicit expressions for the free energy, average spin moment and susceptibility are obtained for weak and strong fields in comparison with the field value belonging to the pseudocritical line. The calculations are performed on the microscopic level without any adjusting parameters. It is established that the long-wave fluctuations of the order parameter play a crucial role in forming a crossover between the temperature-dependence and field-dependence critical behaviour of the system.

  6. Field-Induced CDW Phases in a Quasi-One-Dimensional Organic Conductor, HMTSF-TCNQ Under Pressure of 1 GPa in Magnetic Field of 31 T

    Science.gov (United States)

    Murata, K.; Kang, W.; Masuda, K.; Fukumoto, Y.; Graf, D.; Kiswandhi, A.; Choi, E. S.; Brooks, J. S.; Sasaki, T.; Yokogawa, K.; Yoshino, H.; Kato, R.

    2013-03-01

    HMTSF-TCNQ is a quasi-one-dimensional organic conductor which undergoes CDW(charge density wave) transition at 30 K at ambient pressure, where HMTSF-TCNQ is hexamethylenetetraselena fulvalene-tetracyano quino dimethane. This CDW is suppressed by the pressure of 1 GPa. At this pressure, we found field-induced successive hysteretic transitions in magnetoresistance. This reminds us of the successive field-induced SDW (spin density wave) phases in TMTSF2X salts. However, the field range of interest is 2-3 times higher than that of TMTSF2X salts. Therefore, we need really high field to examine these properties. It is very likely that the field induced phases are of field induced CDW (FICDW), where quantum Hall effect and many interesting phenomena are expected like in the case of FISDW. Together with the magnetoresistance study up to the field of 31 Tesla and at temperatures down to 0.4 K in various magnetic field angles respective to the crystal axes, we examined the angular dependence of magnetoresistance oscillations(AMRO). It turned out that AMRO demonstrates clearly the occurrence of field-induced phase rather than the magneto-resistance by field sweep. Since the Hall resistance, R xy in the field-induced phases showed stepwise plateau structure against the field sweep, and its strength was in the order of magnitude of h/ e 2 per molecular sheet, the Hall effect is very suggestive of quantum Hall effect.

  7. Second-order cosmological perturbations in two-field inflation and predictions for non-Gaussianity

    CERN Document Server

    Tzavara, Eleftheria

    2013-01-01

    Inflationary predictions for the power spectrum of the curvature perturbation have been verified to an excellent degree, leaving many models compatible with observations. In this thesis we studied third-order correlations, that might allow one to further distinguish between inflationary models. From all the possible extensions of the standard inflationary model, we chose to study two-field models with canonical kinetic terms and flat field space. The new feature is the presence of the so-called isocurvature perturbation. Its interplay with the adiabatic perturbation outside the horizon gives birth to non-linearities characteristic of multiple-field models. In this context, we established the second-order gauge-invariant form of the adiabatic and isocurvature perturbation and found the third-order action that describes their interactions. Furthermore, we built on and elaborated the long-wavelength formalism in order to acquire an expression for the parameter of non-Gaussianity fNL as a function of the potentia...

  8. Electromagnetic field induced biological effects in humans.

    Science.gov (United States)

    Kaszuba-Zwoińska, Jolanta; Gremba, Jerzy; Gałdzińska-Calik, Barbara; Wójcik-Piotrowicz, Karolina; Thor, Piotr J

    2015-01-01

    Exposure to artificial radio frequency electromagnetic fields (EMFs) has increased significantly in recent decades. Therefore, there is a growing scientific and social interest in its influence on health, even upon exposure significantly below the applicable standards. The intensity of electromagnetic radiation in human environment is increasing and currently reaches astronomical levels that had never before experienced on our planet. The most influential process of EMF impact on living organisms, is its direct tissue penetration. The current established standards of exposure to EMFs in Poland and in the rest of the world are based on the thermal effect. It is well known that weak EMF could cause all sorts of dramatic non-thermal effects in body cells, tissues and organs. The observed symptoms are hardly to assign to other environmental factors occurring simultaneously in the human environment. Although, there are still ongoing discussions on non-thermal effects of EMF influence, on May 31, 2011--International Agency for Research on Cancer (IARC)--Agenda of World Health Organization (WHO) has classified radio electromagnetic fields, to a category 2B as potentially carcinogenic. Electromagnetic fields can be dangerous not only because of the risk of cancer, but also other health problems, including electromagnetic hypersensitivity (EHS). Electromagnetic hypersensitivity (EHS) is a phenomenon characterized by the appearance of symptoms after exposure of people to electromagnetic fields, generated by EHS is characterized as a syndrome with a broad spectrum of non-specific multiple organ symptoms including both acute and chronic inflammatory processes located mainly in the skin and nervous systems, as well as in respiratory, cardiovascular systems, and musculoskeletal system. WHO does not consider the EHS as a disease-- defined on the basis of medical diagnosis and symptoms associated with any known syndrome. The symptoms may be associated with a single source of EMF

  9. Field-induced exciton condensation in LaCoO3

    Science.gov (United States)

    Sotnikov, A.; Kuneš, J.

    2016-07-01

    Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition can be induced by an external field, temperature dependencies of the critical field have opposite slopes. Based on this result we argue that the experimental observations select the exciton condensation scenario. We show that such condensation is possible due to high mobility of the intermediate spin excitations. The estimated width of the corresponding dispersion is large enough to overrule the order of atomic multiplets and to make the intermediate spin excitation propagating with a specific wave vector the lowest excitation of the system.

  10. Shear induced inactivation of a-amylase in a plain shear field

    NARCIS (Netherlands)

    Veen, van der M.E.; Iersel, van D.G.; Goot, van der A.J.; Boom, R.M.

    2004-01-01

    A newly developed shearing device was used to study shear-induced inactivation of thermostable alpha-amylase in a plain shear field, under conditions comparable to extrusion. The results show that the inactivation can be described well with a first-order process, in which the inactivation energy lar

  11. Shear induced inactivation of a-amylase in a plain shear field

    NARCIS (Netherlands)

    Veen, van der M.E.; Iersel, van D.G.; Goot, van der A.J.; Boom, R.M.

    2004-01-01

    A newly developed shearing device was used to study shear-induced inactivation of thermostable alpha-amylase in a plain shear field, under conditions comparable to extrusion. The results show that the inactivation can be described well with a first-order process, in which the inactivation energy

  12. Magnetic-field-induced polarization and magnetocapacitance in quantum paraelectric EuTiO3

    Science.gov (United States)

    Gong, S. J.; Jiang, Q.

    2004-11-01

    EuTiO3 is a quantum paraelectric as well as an antiferromagnet. The most attractive property for EuTiO3 is the magnetoelectric coupling effect. In the present work, we investigate the influence of the external fields on EuTiO3, including the electric field E and magnetic field h. The application of the electric field counteracts the quantum fluctuation and forces the system into an electrically ordered state. The applied magnetic field directly induces the fluctuation of the spin-pair correlation and indirectly influences the dielectric behaviors through the magnetoelectric coupling. In addition, we notice that the contribution of the magnetic field depends closely on the temperature condition and the electric field background. The (p, h, E, T) and (, h, T) diagrams are presented showing the temperature, magnetic and electric field dependence of the polarization and the dielectric capacitance.

  13. Higher-derivative scalar field theories as constrained second-order theories

    CERN Document Server

    Urries, F J

    1998-01-01

    As an alternative to the covariant Ostrogradski method, we show that higher-derivative relativistic Lagrangian field theories can be reduced to second differential-order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Notwithstanding the intrinsic non-covariance of the Dirac's procedure used to deal with the constraints, the Lorentz invariance is recovered at the end. We develope this new setting for a simple scalar model and then its applications to generalized electrodynamics and higher-derivative gravity are outlined. This method is better suited than Ostrogradski's for a generalization to 2n-derivative theories.

  14. BRST Quantization of a Sixth-Order Derivative Scalar Field Theory

    Science.gov (United States)

    Kim, Yong-Wan; Myung, Yun Soo; Park, Young-Jai

    2013-12-01

    We study a sixth-order derivative scalar field model in Minkowski spacetime as a toy model of higher-derivative critical gravity theories. This model is consistently quantized when using the Becchi-Rouet-Stora-Tyutin (BRST) quantization scheme even though it does not show gauge symmetry manifestly. Imposing a BRST quartet generated by two scalars and ghosts, there remains a nontrivial subspace with positive norm. This might be interpreted as a Minkowskian dual version of the unitary truncation in the logarithmic conformal field theory.

  15. BRST quantization of a sixth-order derivative scalar field theory

    CERN Document Server

    Kim, Yong-Wan; Park, Young-Jai

    2013-01-01

    We study a sixth order derivative scalar field model in Minkowski spacetime as a toy model of higher-derivative critical gravity theories. This model is consistently quantized when using the Becchi-Rouet-Stora-Tyutin (BRST) quantization scheme even though it does not show gauge symmetry manifestly. Imposing a BRST quartet generated by two scalars and ghosts, there remains a non-trivial subspace with positive norm. This might be interpreted as a Minkowskian dual version of the unitary truncation in the logarithmic conformal field theory.

  16. A generalization of gauge symmetry, fourth-order gauge field equations and accelerated cosmic expansion

    Science.gov (United States)

    Hsu, Jong-Ping

    2014-02-01

    A generalization of the usual gauge symmetry leads to fourth-order gauge field equations, which imply a new constant force independent of distances. The force associated with the new U1 gauge symmetry is repulsive among baryons. Such a constant force based on baryon charge conservation gives a field-theoretic understanding of the accelerated cosmic expansion in the observable portion of the universe dominated by baryon galaxies. In consistent with all conservation laws and known forces, a simple rotating "dumbbell model" of the universe is briefly discussed.

  17. A Generalization of Gauge Symmetry, Fourth-Order Gauge Field Equations and Accelerated Cosmic-Expansion

    CERN Document Server

    Hsu, Jong-Ping

    2014-01-01

    A generalization of the usual gauge symmetry leads to fourth-order gauge field equations, which imply a new constant force independent of distances. The force associated with the new $U_1$ gauge symmetry is repulsive among baryons. Such a constant force based on baryon charge conservation gives a field-theoretic understanding of the accelerated cosmic-expansion in the observable portion of the universe dominated by baryon galaxies. In consistent with all conservation laws and known forces, a simple rotating `dumbbell model' of the universe is briefly discussed.

  18. Second-order corrections to mean-field evolution of weakly interacting Bosons, II

    CERN Document Server

    Grillakis, M; Margetis, D

    2010-01-01

    We study the evolution of a N-body weakly interacting system of Bosons. Our work forms an extension of our previous paper I, in which we derived a second-order correction to a mean-field evolution law for coherent states in the presence of small interaction potential. Here, we remove the assumption of smallness of the interaction potential and prove global existence of solutions to the equation for the second-order correction. This implies an improved Fock-space estimate for our approximation of the N-body state.

  19. Superpositions of higher-order bessel beams and nondiffracting speckle fields

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2009-08-01

    Full Text Available present in certain types of resonators. In optical tweezing, beams which carry orbital angular momentum are used to rotate trapped particles. In the case of generating a superposition of two higher-order Bessel beams which possess equal orders... but of differing sign, the Proc. of SPIE Vol. 7430 74300A-6 produced field carries no orbital angular momentum. However, these beams are still able to trap a particle in its intensity distribution and cause it to rotate over a spiral path along the beam’s...

  20. Field induced rotational viscosity of ferrofluid: effect of capillary size and magnetic field direction.

    Science.gov (United States)

    Andhariya, Nidhi; Chudasama, Bhupendra; Patel, Rajesh; Upadhyay, R V; Mehta, R V

    2008-07-01

    In the present investigation we report the effect of capillary diameter and the direction of applied magnetic field on the rotational viscosity of water and kerosene based ferrofluids. We found that changes in the field induced rotational viscosity are larger in the case of water based magnetic fluid than that of kerosene based fluid. The field induced rotational viscosity is found to be inversely proportional to the capillary diameter and it falls exponentially as a function of the angle between the direction of field and vorticity of flow. Magnetophoretic mobility and hydrodynamic volume fraction of nanomagnetic particles are determined for above cases.

  1. Electric-field Induced Microdynamics of Charged Rods

    Directory of Open Access Journals (Sweden)

    Kyongok eKang

    2014-12-01

    Full Text Available Electric-field induced phase/state transitions are observed in AC electric fields with small amplitudes and low frequencies in suspensions of charged fibrous viruses (fd, which are model systems for highly charged rod-like colloids. Texture- and particle-dynamics in these field-induced states, and on crossing transition lines, are explored by image time-correlation and dynamic light scattering, respectively. At relatively low frequencies, starting from a system within the isotropic-nematic coexistence region, a transition from a nematic to a chiral nematic is observed, as well as a dynamical state where nematic domains melt and reform. These transitions are preliminary due to field-induced dissociation/association of condensed ions. At higher frequencies a uniform state is formed that is stabilized by hydrodynamic interactions through field-induced electro-osmotic flow where the rods align along the field direction. There is a point in the field-amplitude versus frequency plane where various transition lines meet. This point can be identified as a non-equilibrium critical point, in the sense that a length scale and a time scale diverge on approach of that point. The microscopic dynamics exhibits discontinuities on crossing transition lines that were identified independently by means of image and signal correlation spectroscopy.

  2. Methanol masers probing the ordered magnetic field of W75N

    Science.gov (United States)

    Surcis, G.; Vlemmings, W. H. T.; Dodson, R.; van Langevelde, H. J.

    2009-11-01

    Context: The role of magnetic fields during the protostellar phase of high-mass star-formation is a debated topic. In particular, it is still unclear how magnetic fields influence the formation and dynamic of disks and outflows. Most current information on magnetic fields close to high-mass protostars comes from H2O and OH maser observations. Recently, the first 6.7 GHz methanol maser polarization observations were made, and they reveal strong and ordered magnetic fields. Aims: The morphology of the magnetic field during high-mass star-formation needs to be investigated on small scales, which can only be done using very long baseline interferometry observations. The massive star-forming region W75N contains three radio sources and associated masers, while a large-scale molecular bipolar outflow is also present. Polarization observations of the 6.7 GHz methanol masers at high angular resolution probe the strength and structure of the magnetic field and determine its relation to the outflow. Methods: Eight of the European VLBI network antennas were used to measure the linear polarization and Zeeman-splitting of the 6.7 GHz methanol masers in the star-forming region W75N. Results: We detected 10 methanol maser features, 4 of which were undetected in previous work. All arise near the source VLA 1 of W75N. The linear polarization of the masers reveals a tightly ordered magnetic field over more than 2000 AU around VLA 1 that is exactly aligned with the large-scale molecular outflow. This is consistent with the twisted magnetic field model proposed for explaining dust polarization observations. The Zeeman-splitting measured on 3 of the maser features indicates a dynamically important magnetic field in the maser region of the order of 50 mG. We suggest VLA 1 is the powering sources of the bipolar outflow. Member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne.

  3. POSSIM: Parameterizing Complete Second-Order Polarizable Force Field for Proteins.

    Science.gov (United States)

    Li, Xinbi; Ponomarev, Sergei Y; Sigalovsky, Daniel L; Cvitkovic, John P; Kaminski, George A

    2014-11-11

    Previously, we reported development of a fast polarizable force field and software named POSSIM (POlarizable Simulations with Second order Interaction Model). The second-order approximation permits the speed up of the polarizable component of the calculations by ca. an order of magnitude. We have now expanded the POSSIM framework to include a complete polarizable force field for proteins. Most of the parameter fitting was done to high-level quantum mechanical data. Conformational geometries and energies for dipeptides have been reproduced within average errors of ca. 0.5 kcal/mol for energies of the conformers (for the electrostatically neutral residues) and 9.7° for key dihedral angles. We have also validated this force field by running Monte Carlo simulations of collagen-like proteins in water. The resulting geometries were within 0.94 Å root-mean-square deviation (RMSD) from the experimental data. We have performed additional validation by studying conformational properties of three oligopeptides relevant in the context of N-glycoprotein secondary structure. These systems have been previously studied with combined experimental and computational methods, and both POSSIM and benchmark OPLS-AA simulations that we carried out produced geometries within ca. 0.9 Å RMSD of the literature structures. Thus, the performance of POSSIM in reproducing the structures is comparable with that of the widely used OPLS-AA force field. Furthermore, our fitting of the force field parameters for peptides and proteins has been streamlined compared with the previous generation of the complete polarizable force field and relied more on transferability of parameters for nonbonded interactions (including the electrostatic component). The resulting deviations from the quantum mechanical data are similar to those achieved with the previous generation; thus, the technique is robust, and the parameters are transferable. At the same time, the number of parameters used in this work was

  4. Tailoring high-order harmonic generation with nonhomogeneous fields and electron confinement

    CERN Document Server

    Ciappina, M F; Shaaran, T; Biegert, J; Quidant, R; Lewenstein, M

    2012-01-01

    We study high-order harmonic generation (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse. We show that both the inhomogeneities of the local electric field and the confinement of the electron motion play an important role in the HHG process and lead to a significant increase of the harmonic cutoff. In order to understand and characterize this feature, we combine the numerical solution of the time dependent Schroedinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and to explain the extended harmonic spectra. Our findings have the potential to boost up the utilization of HHG as coherent extreme ultraviolet (XUV) sources.

  5. On the Polarization of non-Guassian optical quantum field: higher-order optical-polarization

    CERN Document Server

    Singh, Ravi S

    2013-01-01

    Polarization of light signifies transversal, anisotropic and asymmetrical statistical property of electromagnetic radiation about direction of propagation. Traditionally, optical-polarization is characterized by Stokes theory susceptible to be insufficient in assessing polarization structure of optical quantum fields and, also, does not decipher twin characteristic polarization parameters (ratio of real amplitudes and difference in phases). An alternative way, in spirit of classical description of optical-polarization, is introduced which can be generalized to deal higher-order polarization of quantum light, particularly, prepared in non-Guassian Schrodinger Cat or Cat-like states and entangled bi-modal coherent states. On account of pseudo mono-modal or multi-modal nature of such optical quantum field, higher-order polarization is seen to be highly sensitive to the basis of description.

  6. Surface-induced ordering and disordering in face-centered-cubic alloys: A Monte Carlo study

    Science.gov (United States)

    Schweika, W.; Landau, D. P.; Binder, K.

    1996-04-01

    Using extensive Monte Carlo simulations we have studied phase transitions in a fcc model with antiferromagnetic nearest-neighbor couplings J in the presence of different free surfaces which lead either to surface-induced order or to surface-induced disorder. Our model is a prototype for CuAu-type ordering alloys and shows a strong first-order bulk transition at a temperature kTcb/||J||=1.738 005(50). For free (100) surfaces, we find a continuous surface transition at a temperature Tcs>~Tcb exhibiting critical exponents of the two-dimensional Ising model. Surface-induced ordering occurs as the temperature approaches Tcb and the surface excess order and surface excess energy diverges logarithmically. For a free (111) surface, the surface order vanishes continuously at Tcb accompanied by surface-induced disorder (SID). In addition to a logarithmic divergence of the excess quantities of order and energy, we find further critical exponents which confirm the actual theory of SID and critical wetting and which can be understood in terms of rough interfaces. For both cases of free surfaces, the asymptotic behavior of the squared interfacial width shows the expected logarithmic divergence.

  7. The velocity field induced by a helical vortex tube

    DEFF Research Database (Denmark)

    Fukumoto, Y.; Okulov, Valery

    2005-01-01

    The influence of finite-core thickness on the velocity field around a vortex tube is addressed. An asymptotic expansion of the Biot-Savart law is made to a higher order in a small parameter, the ratio of core radius to curvature radius, which consists of the velocity field due to lines of monopoles...

  8. Fifth-Order Harmonic Generation using a Coherent Controlled Two-Pulsed Optical Field

    Institute of Scientific and Technical Information of China (English)

    刘婷婷; 王大威; 陆伟新; 孙泉; 杨宏; 蒋红兵; 龚旗煌

    2002-01-01

    We have experimentally studied the characteristics of fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase. The intensities of harmonic generation are found to increase vith the coherent degree. In one optical period, the temporal variation of harmonics exhibits an asymmetric characteristic, vhich is interpreted in terms of ionization theory and the deformation of the wave packets of fundamental field contribution to harmonic generation.

  9. Third order Lovelock black branes in the presence of a nonlinear electromagnetic field

    CERN Document Server

    Hendi, S H; Mohammadpour, H

    2015-01-01

    We consider third order Lovelock gravity coupled to an U(1) gauge field for which its Lagrangian is given by a power of Maxwell invariant. In this paper, we present a class of horizon flat rotating black branes and investigate their geometrical properties and the effect of nonlinearity on the solutions. We use some known formulas and methods to calculate thermodynamic and conserved quantities. Finally, we check the satisfaction of the first law of thermodynamics.

  10. Third order Lovelock black branes in the presence of a nonlinear electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hendi, S.H. [Shiraz University, Physics Department and Biruni Observatory, Shiraz (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM), P.O. Box 55134-441, Maragha (Iran, Islamic Republic of); Panahiyan, S.; Mohammadpour, H. [Shiraz University, Physics Department and Biruni Observatory, Shiraz (Iran, Islamic Republic of)

    2012-10-15

    We consider third order Lovelock gravity coupled to an U(1) gauge field for which its Lagrangian is given by a power of Maxwell invariant. In this paper, we present a class of horizon flat rotating black branes and investigate their geometrical properties and the effect of nonlinearity on the solutions. We use some known formulas and methods to calculate thermodynamic and conserved quantities. Finally, we check the satisfaction of the first law of thermodynamics. (orig.)

  11. BRST quantization of a sixth-order derivative scalar field theory

    OpenAIRE

    Kim, Yong-Wan; Myung, Yun Soo; Park, Young-Jai

    2013-01-01

    We study a sixth order derivative scalar field model in Minkowski spacetime as a toy model of higher-derivative critical gravity theories. This model is consistently quantized when using the Becchi-Rouet-Stora-Tyutin (BRST) quantization scheme even though it does not show gauge symmetry manifestly. Imposing a BRST quartet generated by two scalars and ghosts, there remains a non-trivial subspace with positive norm. This might be interpreted as a Minkowskian dual version of the unitary truncati...

  12. Classical field theories of first order and lagrangian submanifolds of premultisymplectic manifolds

    CERN Document Server

    Campos, Cédric M; Marrero, Juan Carlos

    2011-01-01

    A description of classical field theories of first order in terms of Lagrangian submanifolds of premultisymplectic manifolds is presented. For this purpose, a Tulczyjew's triple associated with a fibration is discussed. The triple is adapted to the extended Hamiltonian formalism. Using this triple, we prove that Euler-Lagrange and Hamilton-De Donder-Weyl equations are the local equations defining Lagrangian submanifolds of a premultisymplectic manifold.

  13. Enhanced solid-state order and field-effect hole mobility through control of nanoscale polymer aggregation

    KAUST Repository

    Chen, Mark S.

    2013-12-26

    Efficient charge carrier transport in organic field-effect transistors (OFETs) often requires thin films that display long-range order and close π-π packing that is oriented in-plane with the substrate. Although some polymers have achieved high field-effect mobility with such solid-state properties, there are currently few general strategies for controlling the orientation of π-stacking within polymer films. In order to probe structural effects on polymer-packing alignment, furan-containing diketopyrrolopyrrole (DPP) polymers with similar optoelectronic properties were synthesized with either linear hexadecyl or branched 2-butyloctyl side chains. Differences in polymer solubility were observed and attributed to variation in side-chain shape and polymer backbone curvature. Averaged field-effect hole mobilities of the polymers range from 0.19 to 1.82 cm2/V·s, where PDPP3F-C16 is the least soluble polymer and provides the highest maximum mobility of 2.25 cm2/V·s. Analysis of the films by AFM and GIXD reveal that less soluble polymers with linear side chains exhibit larger crystalline domains, pack considerably more closely, and align with a greater preference for in-plane π-π packing. Characterization of the polymer solutions prior to spin-coating shows a correlation between early onset nanoscale aggregation and the formation of films with highly oriented in-plane π-stacking. This effect is further observed when nonsolvent is added to PDPP3F-BO solutions to induce aggregation, which results in films with increased nanostructural order, in-plane π-π orientation, and field-effect hole mobilities. Since nearly all π-conjugated materials may be coaxed to aggregate, this strategy for enhancing solid-state properties and OFET performance has applicability to a wide variety of organic electronic materials. © 2013 American Chemical Society.

  14. Magnetic Fields Induced in the Solid Earth and Oceans

    DEFF Research Database (Denmark)

    Kuvshinov, Alexei; Olsen, Nils

    Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced...... in the oceans by two different sources: by time varying external magnetic fields, and by motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in the accurate and detailed prediction of magnetic fields induced by these sources has been achieved during the last years......, utilizing realistic 3-D conductivity models of the oceans, crust and mantle. In addition to these improvements in the prediction of 3-D induction effects, much attention has been paid to identifying magnetic signals of oceanic origin in observatory and satellite data. During the talk we will present...

  15. Electric field-induced softening of alkali silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    McLaren, C.; Heffner, W.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Tessarollo, R.; Raj, R. [Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309 (United States)

    2015-11-02

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  16. Electric field-induced softening of alkali silicate glasses

    Science.gov (United States)

    McLaren, C.; Heffner, W.; Tessarollo, R.; Raj, R.; Jain, H.

    2015-11-01

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  17. Magnetic Fields Induced in the Solid Earth and Oceans

    DEFF Research Database (Denmark)

    Kuvshinov, Alexei; Olsen, Nils

    Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced...... ocean circulation. Finally, we will discuss how the results of 3-D predictions can be utilized in geomagnetic field modeling and in a recovery of deep conductivity structures.......Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced...... in the oceans by two different sources: by time varying external magnetic fields, and by motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in the accurate and detailed prediction of magnetic fields induced by these sources has been achieved during the last years...

  18. Neutron star deformation due to arbitrary-order multipolar magnetic fields

    CERN Document Server

    Mastrano, Alpha; Melatos, Andrew

    2013-01-01

    Certain multi-wavelength observations of neutron stars, such as intermittent radio emissions from rotation-powered pulsars beyond the pair-cascade death line, the pulse profile of the magnetar SGR 1900+14 after its 1998 August 27 giant flare, and X-ray spectral features of PSR J0821-4300 and SGR 0418+5729, suggest that the magnetic fields of non-accreting neutron stars are not purely dipolar and may contain higher-order multipoles. Here, we calculate the ellipticity of a non-barotropic neutron star with (i) a quadrupole poloidal-toroidal field, and (ii) a purely poloidal field containing arbitrary multipoles, deriving the relation between the ellipticity and the multipole amplitudes. We present, as a worked example, a purely poloidal field comprising dipole, quadrupole, and octupole components. We show the correlation between field energy and ellipticity for each multipole, that the l=4 multipole has the lowest energy, and that l=5 has the lowest ellipticity. We show how a mixed multipolar field creates an ob...

  19. Double-electron recombination in high-order-harmonic generation driven by spatially inhomogeneous fields

    Science.gov (United States)

    Chacón, Alexis; Ciappina, Marcelo F.; Lewenstein, Maciej

    2016-10-01

    We present theoretical studies of high-order harmonic generation (HHG) driven by plasmonic fields in two-electron atomic systems. Comparing the single- and two-electron active approximation models of the hydrogen negative ion, we provide strong evidence that a nonsequential double-electron recombination mechanism appears to be mainly responsible for the HHG cutoff extension. Our analysis is carried out by means of a reduced one-dimensional numerical integration of the two-electron time-dependent Schrödinger equation, and on investigations of the classical electron trajectories, resulting from the Newton's equation of motion. Additional comparisons between the hydrogen negative ion and the helium atom suggest that the double recombination process depends distinctly on the atomic target. Our research paves the way to the understanding of strong field processes in multielectronic systems driven by spatially inhomogeneous fields.

  20. Higher-Derivative Boson Field Theories and Constrained Second-Order Theories

    CERN Document Server

    D'Urríes, F J; Villaseñor, E J S; Villase\\~nor, Eduardo J.S.

    2001-01-01

    As an alternative to the covariant Ostrogradski method, we show that higher-derivative relativistic Lagrangian field theories can be reduced to second differential-order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Despite the intrinsic non-covariance of the Dirac's procedure used to deal with the constraints, the explicit Lorentz invariance is recovered at the end. We develop this new setting on the grounds of a simple scalar model and then its applications to generalized electrodynamics and higher-derivative gravity are worked out. For a wide class of field theories this method is better suited than Ostrogradski's for a generalization to 2n-derivative theories

  1. Higher-derivative boson field theories and constrained second-order theories

    Energy Technology Data Exchange (ETDEWEB)

    Urries, F.J. de [Departamento de Fisica, Universidad de Alcala de Henares, Madrid (Spain) and IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (Spain)]. E-mail: fernando.urries@uah.es; Julve, J. [IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (Spain)]. E-mail: julve@imaff.cfmac.csic.es; Sanchez, E.J. [IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (ES) and Departamento de Matematica, Universidad Europea, Madrid (Spain)]. E-mail: ejesus.sanchez@mat.ind.uem.es

    2001-10-26

    As an alternative to the covariant Ostrogradski method, we show that higher-derivative (HD) relativistic Lagrangian field theories can be reduced to second differential order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Despite the intrinsic non-covariance of the Dirac procedure used to deal with the constraints, the explicit Lorentz invariance is recovered at the end. We develop this new setting on the basis of a simple scalar model and then its applications to generalized electrodynamics and HD gravity are worked out. For a wide class of field theories this method is better suited than Ostrogradski's for a generalization to 2n-derivative theories. (author)

  2. High order harmonic generation in noble gases using plasmonic field enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Ciappina, Marcelo F.; Shaaran, Tahir [ICFO-Institut de Ciences Fotoniques, Castelldefels (Barcelona) (Spain); Lewenstein, Maciej [ICFO-Institut de Ciences Fotoniques, Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, Barcelona (Spain)

    2013-02-15

    Theoretical studies of high-order harmonic generation (HHG) in rare gases driven by plasmonic field enhancement are presented. This kind of fields appears when plasmonic nanostructures are illuminated by an intense few-cycle laser and have a particular spatial dependency, depending on the geometrical shape of the nanostructure. It is demonstrated that the strong nonhomogeneous character of the laser enhanced field plays an important role in the HHG process and significantly extends the harmonic cutoff. The models are based on numerical solution of the time dependent Schroedinger equation (TDSE) and supported by classical and semiclassical calculations. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. High-order harmonic generation by enhanced plasmonic near-fields in metal nanoparticules

    CERN Document Server

    Shaaran, T; Guichard, R; Pérez-Hernández, J A; Arnold, M; Siegel, T; Zaïr, A; Lewenstein, M

    2013-01-01

    We present theoretical investigations of high-order harmonic generation (HHG) resulting from the interaction of noble gases with localized surface plasmons. These plasmonic fields are produced when a metal nanoparticle is subject to a few-cycle laser pulse. The enhanced field, which largely depends on the geometrical shape of the metallic structure, has a strong spatial dependency. We demonstrate that the strong non-homogeneity of this laser field plays an important role in the HHG process and leads to a significant increase of the harmonic cut-off energy. In order to understand and characterize this new feature, we include the functional form of the laser electric field obtained from recent attosecond streaking experiments [F. S{\\"u}{\\ss}mann and M. F. Kling, Proc. of SPIE, {\\bf Vol. 8096}, 80961C (2011)] in the time dependent Schr\\"odinger equation (TDSE). By performing classical simulations of the HHG process we show consistency between them and the quantum mechanical predictions. These allow us to underst...

  4. Collisional effects on Rayleigh-Taylor-induced magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Manuel, M. J.-E. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Flaig, M.; Plewa, T. [Florida State University, Tallahassee, Florida 32306 (United States); Li, C. K.; Séguin, F. H.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hu, S. X.; Betti, R.; Hager, J.; Meyerhofer, D. D.; Smalyuk, V. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

    2015-05-15

    Magnetic-field generation from the Rayleigh-Taylor (RT) instability was predicted more than 30 years ago, though experimental measurements of this phenomenon have only occurred in the past few years. These pioneering observations demonstrated that collisional effects are important to B-field evolution. To produce fields of a measurable strength, high-intensity lasers irradiate solid targets to generate the nonaligned temperature and density gradients required for B-field generation. The ablation process naturally generates an unstable system where RT-induced magnetic fields form. Field strengths inferred from monoenergetic-proton radiographs indicate that in the ablation region diffusive effects caused by finite plasma resistivity are not negligible. Results from the first proof-of-existence experiments are reviewed and the role of collisional effects on B-field evolution is discussed in detail.

  5. Electromagnetically induced transparency induced by a 100% amplitude-modulated coupling field

    Institute of Scientific and Technical Information of China (English)

    李晓莉; 张连水; 杨丽君; 冯晓敏; 赵敏

    2009-01-01

    We present a study of electromagnetically induced transparency(EIT) under the excitation of a 100% amplitude-modulated(AM) coupling field.The EIT feature is associated with a Λ type three-level configuration where a coupling and probe field couples two separate optical transitions and it is well-known that the spectrum of the swept probe field gives a simple single transparency feature induced by the single mode coupling field.It is shown that when a 100% AM coupling field is applied,there is an EIT doublet...

  6. Field-induced magnetic phases and electric polarization in LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius; Christensen, Niels Bech; Kenzelmann, M.

    2009-01-01

    Neutron diffraction is used to probe the (H,T) phase diagram of magnetoelectric (ME) LiNiPO4 for magnetic fields along the c axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors k(C)=(0,0,0); the other one...... is incommensurate (IC) with k(IC)=(0,q,0). At low temperatures the C order collapses above mu H-0=12 T and adopts an IC structure with modulation vector parallel to k(IC). We show that C order is required for the ME effect and establish how electric polarization results from a field-induced reduction in the total...

  7. DeepCNF-D: Predicting Protein Order/Disorder Regions by Weighted Deep Convolutional Neural Fields

    Directory of Open Access Journals (Sweden)

    Sheng Wang

    2015-07-01

    Full Text Available Intrinsically disordered proteins or protein regions are involved in key biological processes including regulation of transcription, signal transduction, and alternative splicing. Accurately predicting order/disorder regions ab initio from the protein sequence is a prerequisite step for further analysis of functions and mechanisms for these disordered regions. This work presents a learning method, weighted DeepCNF (Deep Convolutional Neural Fields, to improve the accuracy of order/disorder prediction by exploiting the long-range sequential information and the interdependency between adjacent order/disorder labels and by assigning different weights for each label during training and prediction to solve the label imbalance issue. Evaluated by the CASP9 and CASP10 targets, our method obtains 0.855 and 0.898 AUC values, which are higher than the state-of-the-art single ab initio predictors.

  8. Gauge-invariant perturbations at second order in two-field inflation

    Energy Technology Data Exchange (ETDEWEB)

    Tzavara, Eleftheria; Tent, Bartjan van, E-mail: Eleftheria.Tzavara@th.u-psud.fr, E-mail: Bartjan.Van-Tent@th.u-psud.fr [Laboratoire de Physique Théorique, Université Paris-Sud 11 and CNRS, Bâtiment 210, 91405 Orsay Cedex (France)

    2012-08-01

    We study the second-order gauge-invariant adiabatic and isocurvature perturbations in terms of the scalar fields present during inflation, along with the related fully non-linear space gradient of these quantities. We discuss the relation with other perturbation quantities defined in the literature. We also construct the exact cubic action of the second-order perturbations (beyond any slow-roll or super-horizon approximations and including tensor perturbations), both in the uniform energy-density gauge and the flat gauge in order to settle various gauge-related issues. We thus provide the tool to calculate the exact non-Gaussianity beyond slow-roll and at any scale.

  9. Gauge-invariant perturbations at second order in two-field inflation

    CERN Document Server

    Tzavara, Eleftheria

    2011-01-01

    We study the second-order gauge-invariant adiabatic and isocurvature perturbations in terms of the scalar fields present during inflation, along with the related fully non-linear space gradient of these quantities. We discuss the relation with other perturbation quantities defined in the literature. We also construct the exact cubic action of the second-order perturbations (beyond any slow-roll or super-horizon approximations and including tensor perturbations), both in the uniform energy density gauge and the flat gauge in order to settle various gauge-related issues. We thus provide the tool to calculate the exact non-Gaussianity beyond slow-roll and at any scale.

  10. Out-of-time-ordered correlators and purity in rational conformal field theories

    Science.gov (United States)

    Caputa, Paweł; Numasawa, Tokiro; Veliz-Osorio, Alvaro

    2016-11-01

    In this paper we investigate measures of chaos and entanglement in rational conformal field theories in 1 + 1 dimensions. First, we derive a formula for the late time value of the out-of-time-ordered correlators for this class of theories. Our universal result can be expressed as a particular combination of the modular S-matrix elements known as anyon monodromy scalar. Next, in the explicit setup of an SUN Wess-Zumino-Witten model, we compare the late time behavior of the out-of-time-ordered correlators and the purity. Interestingly, in the large-c limit, the purity grows logarithmically as in holographic theories; in contrast, the out-of-time-ordered correlators remain, in general, nonvanishing.

  11. Generalized Galileons: All scalar models whose curved background extensions maintain second-order field equations and stress-tensors

    CERN Document Server

    Deffayet, C; Esposito-Farèse, G

    2009-01-01

    We extend to curved backgrounds all flat-space scalar field models that obey purely second-order equations, while maintaining their second-order dependence on both field and metric. This extension simultaneously restores to second order the, originally higher derivative, stress-tensors as well. The process is transparent and uniform for all dimensions.

  12. Effects of coil orientation on the electric field induced by TMS over the hand motor area.

    Science.gov (United States)

    Laakso, Ilkka; Hirata, Akimasa; Ugawa, Yoshikazu

    2014-01-01

    Responses elicited by transcranial magnetic stimulation (TMS) over the hand motor area depend on the position and orientation of the stimulating coil. In this work, we computationally investigate the induced electric field for multiple coil orientations and locations in order to determine which parts of the brain are affected and how the sensitivity of motor cortical activation depends on the direction of the electric field. The finite element method is used for calculating the electric field induced by TMS in two individual anatomical models of the head and brain. The orientation of the coil affects both the strength and depth of penetration of the electric field, and the field strongly depends on the direction of the sulcus, where the target neurons are located. The coil position that gives the strongest electric field in the target cortical region may deviate from the closest scalp location by a distance on the order of 1 cm. Together with previous experimental data, the results support the hypothesis that the cortex is most sensitive to fields oriented perpendicular to the cortical layers, while it is relatively insensitive to fields parallel to them. This has important implications for targeting of TMS. To determine the most effective coil position and orientation, it is essential to consider both biological (the direction of the targeted axons) and physical factors (the strength and direction of the electric field).

  13. Investigation of Fano resonances induced by higher order plasmon modes on a circular nano-disk with an elongated cavity

    KAUST Repository

    Amin, Muhammad Ruhul

    2012-08-10

    In this paper, a planar metallic nanostructure design, which supports two distinct Fano resonances in its extinction cross-section spectrum under normally incident and linearly polarized electromagnetic field, is proposed. The proposed design involves a circular disk embedding an elongated cavity; shifting and rotating the cavity break the symmetry of the structure with respect to the incident field and induce higher order plasmon modes. As a result, Fano resonances are generated in the visible spectrum due to the destructive interference between the sub-radiant higher order modes and super-radiant the dipolar mode. The Fano resonances can be tuned by varying the cavity\\'s width and the rotation angle. An RLC circuit, which is mathematically equivalent to a mass-spring oscillator, is proposed to model the optical response of the nanostructure design.

  14. Superdirective narrowband first-order probe versus wideband higher-order probe for spherical near-field antenna measurements at P-band

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Breinbjerg, Olav

    2013-01-01

    A comparative study of the wideband 400-1200 MHz higher-order probe and the narrowband 431 MHz first-order probe, in terms of their advantages and disadvantages for spherical near-field antenna measurements at P-band, is presented. The comparison is based on the experimental data and focused...

  15. Numerical evaluation of E-fields induced by body motion near high-field MRI scanner.

    Science.gov (United States)

    Crozier, S; Liu, F

    2004-01-01

    In modern magnetic resonance imaging (MRI), both patients and radiologists are exposed to strong, nonuniform static magnetic fields inside or outside of the scanner, in which the body movement may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced E-fields in the human model when moving at various positions around the magnet. The numerical calculations are based on an efficient, quasistatic, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively-shielded 4 T magnet system are used and the body model projected through the field profile with normalized velocity. The simulation shows that it is possible to induce E-fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are easy to extrapolate to very high field strengths for the safety evaluation at a variety of field strengths and motion velocities.

  16. Mapping and correcting respiration-induced field changes in the brain using fluorine field probes

    DEFF Research Database (Denmark)

    Andersen, Mads; Madsen, Kristoffer H; Hanson, L.G.

    Purpose. Breathing induced dynamic B0 field perturbations in the head can lead to artefacts in ultra-high field MR by causing line broadening in spectroscopy and signal dropout, ghosting, displacement artifacts and blurring in imaging. It has recently been proposed to continuously stabilize...

  17. Mapping and correcting respiration-induced field changes in the brain using fluorine field probes

    DEFF Research Database (Denmark)

    Andersen, Mads; Madsen, Kristoffer; Hanson, Lars G.

    2014-01-01

    Purpose. Breathing induced dynamic B0 field perturbations in the head can lead to artefacts in ultra-high field MR by causing line broadening in spectroscopy and signal dropout, ghosting, displacement artifacts and blurring in imaging. It has recently been proposed to continuously stabilize...

  18. Photon-induced near-field electron microscopy.

    Science.gov (United States)

    Barwick, Brett; Flannigan, David J; Zewail, Ahmed H

    2009-12-17

    In materials science and biology, optical near-field microscopies enable spatial resolutions beyond the diffraction limit, but they cannot provide the atomic-scale imaging capabilities of electron microscopy. Given the nature of interactions between electrons and photons, and considering their connections through nanostructures, it should be possible to achieve imaging of evanescent electromagnetic fields with electron pulses when such fields are resolved in both space (nanometre and below) and time (femtosecond). Here we report the development of photon-induced near-field electron microscopy (PINEM), and the associated phenomena. We show that the precise spatiotemporal overlap of femtosecond single-electron packets with intense optical pulses at a nanostructure (individual carbon nanotube or silver nanowire in this instance) results in the direct absorption of integer multiples of photon quanta (nhomega) by the relativistic electrons accelerated to 200 keV. By energy-filtering only those electrons resulting from this absorption, it is possible to image directly in space the near-field electric field distribution, obtain the temporal behaviour of the field on the femtosecond timescale, and map its spatial polarization dependence. We believe that the observation of the photon-induced near-field effect in ultrafast electron microscopy demonstrates the potential for many applications, including those of direct space-time imaging of localized fields at interfaces and visualization of phenomena related to photonics, plasmonics and nanostructures.

  19. Near-field optical study of 3rd order nonlinear properties of amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yun Jin; Park, J.H.; Kim, M.R.; Jhe, Won Ho [Seoul National University, Seoul (Korea, Republic of); Rhee, B.K. [Sogang University, Seoul (Korea, Republic of)

    1999-07-01

    The 3rd order nonlinear properties show optical bleaching (Saturation) and Reverse saturation in absorption aspect, whereas self-focusing and self-defocusing in refraction aspect. Optical bleaching and self-focusing phenomena of those properties in particular can be useful to make the optical beam spot size smaller for application on the higher optical storage density. In this experiment, amorphous silicon layer is used to investigate the effect of 3rd order nonlinear material(1) on the spot size. The amorphous silicon (A-Si) layer is deposited by the method of PECVD on the corning 1737 fusion glass and its thickness is 300 nm. Two experiments are carried out in this work. One is the far-field Z-Scan and the other is the near-field Z-scan where the laser beam spot is scanned by NSOM in the near field region of the material. The former is for investigating the general 3rd order nonlinear properties of amorphous silicon and the latter is for measuring the change of the beam spot size directly. The far-field Z-scan shows Reverse saturation (Im{chi}{sup (3)} {approx} 8 X 10{sup -3} esu) and self-focusing (Re{chi}{sup (3)} {approx} 2 X 10{sup -2} esu) properties for the A-Si layer. In the second experiment, we present the change the beam spot size as a function of the input beam intensity for the A-Si layer. As a result, we find that the stronger the input beam intensity is, the smaller a beam spot size is obtained for A-Si layer. (author)

  20. Electric field-induced acoustic emission phenomena in ferroelectric and related ceramics

    Science.gov (United States)

    Aburatani, Hideaki

    Field induced AE phenomena in bulk ferroelectric and related ceramics as well as multilayer ceramic actuators were investigated in this work. Concerning the field induced AE measurement technique, it was shown that commonly used voltage application units can excite sample vibrations electromechanically through their voltage stabilization processes and generate extrinsic AE signals. In order to detect intrinsic AE signals from within piezoelectric samples, a modified voltage application unit with a long time constant tau was proposed. For the study of origins of field induced AE, a ferroelectric lead zirconate titanate (PZT-5A), an electrostrictive lead magnesium niobate-lead titanate (0.9PMN-0.1PT) and a field-enhanced ferroelectric type lead lanthanum zirconate titanate (PLZT(9/65/35)) ceramics were selected. Pre-applied maximum field dependence on the AE generation were observed for ferroelectric PZT-5A and electrostrictive 0.9PMN-0.1PT ceramics. The study showed that there are two origins for the field induced AE of the ferroelectric PZT-5A: deformation related to domain reorientation processes and piezoelectric deformation unrelated to domain reorientation processes. The stress induction/relaxation process simply caused by the electrostrictive deformation was found to be the origin of AE in the electrostrictive 0.9PMN-0.1PT ceramics. The electric field induced non-ferroelectric to ferroelectric transition, reorientation process of the induced ferroelectric domains and induced internal stress were found to be the origins of AE in the field-enhanced ferroelectric PLZT (9/65/35). The potential use of the AE method in production was explored using a Multilayer Ceramic Actuator (MCA) fabricated by a tape casting method.

  1. Effect of the induced field memory on the bunch lengthening

    Energy Technology Data Exchange (ETDEWEB)

    Pestrikov, D.V., E-mail: pestrikov@inp.nsk.su

    2015-02-11

    We study the variations of the solutions to the Haissinski equation versus the duration of the memory of the longitudinal induced fields. For simplicity, we assume that a single bunch in a storage ring interacts with surrounding electrodes, which electromagnetically are equivalent to a parallel LR-circuit. For this particular case, we have found out that controlling the decay time of the bunch induced fields we can substantially affect the length of the bunch as well as the features of Landau damping of coherent oscillations of the bunch.

  2. A new ordering principle in quantum field theory and its consequences

    CERN Document Server

    Greben, Jan M

    2016-01-01

    The ad-hoc imposition of normal ordering on the Lagrangian, energy-momentum tensor and currents is a standard tool in quantum field theory (QFT) to eliminate infinite vacuum expectation values (v.e.v.) However, for fermionic expressions these infinite terms are due to anti-particles only. This exposes an asymmetry in standard QFT, which can be traced back to a bias towards particles in the Dirac bra-ket notation. To counter this bias a new ordering principle (called the $\\mathbb{R}$-product) is required which restores the symmetry (or rather duality) between particles and anti-particles and eliminates the infinite v.e.v. While this $\\mathbb{R}$-product was already used in a bound-state application, this paper aims to give it a more general foundation and analyze its overall impact in QFT. For boson fields the particle bias is hidden and the fields must first be expanded into bilinear particle-anti-particle fermion operators. This new representation also leads to vanishing v.e.v.'s and avoids some common techn...

  3. First order mean field games - explicit solutions, perturbations and connection with classical mechanics

    KAUST Repository

    Gomes, Diogo A.

    2016-01-06

    We present recent developments in the theory of first-order mean-field games (MFGs). A standard assumption in MFGs is that the cost function of the agents is monotone in the density of the distribution. This assumption leads to a comprehensive existence theory and to the uniqueness of smooth solutions. Here, our goals are to understand the role of local monotonicity in the small perturbation regime and the properties of solutions for problems without monotonicity. Under a local monotonicity assumption, we show that small perturbations of MFGs have unique smooth solutions. In addition, we explore the connection between first-order MFGs and classical mechanics and KAM theory. Next, for non-monotone problems, we construct non-unique explicit solutions for a broad class of first-order mean-field games. We provide an alternative formulation of MFGs in terms of a new current variable. These examples illustrate two new phenomena: the non-uniqueness of solutions and the breakdown of regularity.

  4. Pressure-induced magnetic order in FeSe: A muon spin rotation study

    Science.gov (United States)

    Khasanov, Rustem; Guguchia, Zurab; Amato, Alex; Morenzoni, Elvezio; Dong, Xiaoli; Zhou, Fang; Zhao, Zhongxian

    2017-05-01

    The magnetic order induced by the pressure was studied in FeSe by means of muon spin rotation (μ SR ) technique. By following the evolution of the oscillatory part of the μ SR signal as a function of angle between the initial muon spin polarization and 101 axis of the studied FeSe sample, it was found that the pressure-induced magnetic order in FeSe corresponds either to the collinear (single-stripe) antiferromagnetic order as observed in parent compounds of various FeAs-based superconductors or to the bi-collinear order as obtained in the FeTe system, but with the Fe spins turned by 45o within the a b plane. The value of the magnetic moment per Fe atom was estimated to be ≃0.13 -0.14 μB at p ≃1.9 GPa.

  5. Effect of stacking order on device performance of bilayer black phosphorene-field-effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, A., E-mail: arnabm.electinstru@gmail.com; Banerjee, L.; Sengupta, A.; Rahaman, H. [School of VLSI Technology, IIEST, Shibpur, Howrah 711103 (India)

    2015-12-14

    We investigate the effect of stacking order of bilayer black phosphorene on the device properties of p-MOSFET and n-MOSFET. Two layers of black phosphorus are stacked in three different orders and are used as channel material in both n-MOSFET and p-MOSFET devices. The effects of different stacking orders on electron and hole effective masses and output characteristics of MOSFETs, such as ON currents, ON/OFF ratio, and transconductance are analyzed. Our results show that about 1.37 times and 1.49 times increase in ON current is possible along armchair and zigzag directions, respectively, 55.11% variation in transconductance is possible along armchair direction, by changing stacking orders (AA, AB, and AC) and about 8 times increase in ON current is achievable by changing channel orientation (armchair or zigzag) in p-MOSFET. About 14.8 mV/V drain induced barrier lowering is observed for both p-MOSFET and n-MOSFET, which signifies good immunity to short channel effects.

  6. Chemical ordering in magnetic FePd/Pd (001) epitaxial thin films induced by annealing

    Science.gov (United States)

    Halley, D.; Gilles, B.; Bayle-Guillemaud, P.; Arenal, R.; Marty, A.; Patrat, G.; Samson, Y.

    2004-11-01

    Chemically disordered FePd epitaxial layers are grown at room temperature by molecular beam epitaxy on a Pd(001) buffer layer and then annealed in order to induce the chemically ordered L 10 (AuCu I) structure. Contrary to what is observed in the case of ordering during growth above room temperature, the ordered structure appears here with the three possible variants of the L 10 phase. The ratio of the three different variant volumes is set by the residual epitaxial strain in the layer before annealing. It thus explains that for long annealing times, the long-range order parameter associated with the L 10 variant with c along the (100) growth direction saturates at a value close to 0.65, and never reaches unity. Magnetic consequences of the ordering are studied.

  7. Conducting state of GeTe by defect-induced topological insulating order

    Science.gov (United States)

    Kim, Jinwoong; Jhi, Seung-Hoon

    2012-02-01

    Topological insulating order protected by time-reversal symmetry is robust under structural disorder. Interestingly, recent studies on phase change materials like GeSbTe showed that their topological insulating order is sensitive to atomic stacking sequences. It was also shown that their structural phase transition is correlated with topological insulating order. GeTe, a well-known phase change material, is trivial insulator in its equilibrium structure. In this study, we discuss how atomic defects such as Ge tetrahedral defect observed in amorphous GeTe can change its topological insulating order based on first-principles calculations and model Hamiltonian. We also investigated the critical density of such tetrahedral defects to induce topological insulating order in GeTe. Our study will help explore hidden orders in GeTe.

  8. High-Order Temporal Corrected Fields of Ultra-Short Laser Pulses and Laser-Driven Acceleration

    Institute of Scientific and Technical Information of China (English)

    XIE Yong-Jie; HUO Yu-Kun; KONG Qing; WANG Ping-Xiao; CHEN Zhao; LIU Jing-Ru

    2006-01-01

    @@ Up to third-order temporal correction in terms of a small dimensionless temporal parameter ε = 1/(ω0t0) (ω0 =ck0 the central oscillatory frequency, t0 the pulse duration of half period), the field expressions of ultra-short focused laser pulses are explicitly presented. To evaluate the correction efficacy, electric amplitudes of zeroth-order and higher-order corrected fields are compared for different pulse durations. Furthermore, electron interaction with ultra-short laser pulses is simulated using both the zeroth-order and higher-order corrected field equations.

  9. Spacetimes with Longitudinal and Angular Magnetic Fields in Third Order Lovelock Gravity

    CERN Document Server

    Dehghani, M H

    2006-01-01

    We obtain two new classes of magnetic brane solutions in third order Lovelock gravity. The first class of solutions yields an $(n+1)$-dimensional spacetime with a longitudinal magnetic field generated by a static source. We generalize this class of solutions to the case of spinning magnetic branes with one or more rotation parameters. These solutions have no curvature singularity and no horizons, but have a conic geometry. For the spinning brane, when one or more rotation parameters are nonzero, the brane has a net electric charge which is proportional to the magnitude of the rotation parameters, while the static brane has no net electric charge. The second class of solutions yields a pacetime with an angular magnetic field. These solutions have no curvature singularity, no horizon, and no conical singularity. Although the second class of solutions may be made electrically charged by a boost transformation, the transformed solutions do not present new spacetimes. Finally, we use the counterterm method in thir...

  10. On p -form theories with gauge invariant second order field equations

    Science.gov (United States)

    Deffayet, Cédric; Mukohyama, Shinji; Sivanesan, Vishagan

    2016-04-01

    We explore field theories of a single p -form with equations of motions of order strictly equal to 2 and gauge invariance. We give a general method for the classification of such theories which are extensions to the p -forms of the Galileon models for scalars. Our classification scheme allows us to compute an upper bound on the number of different such theories depending on p and on the space-time dimension. We are also able to build a nontrivial Galileon-like theory for a 3-form with gauge invariance and an action which is polynomial into the derivatives of the form. This theory has gauge invariant field equations but an action which is not, like a Chern-Simons theory. Hence the recently discovered no-go theorem stating that there are no nontrivial gauge invariant vector Galileons (which we are also able here to confirm with our method) does not extend to other odd-p cases.

  11. Long-wavelength properties of phase-field-crystal models with second-order dynamics

    Science.gov (United States)

    Heinonen, V.; Achim, C. V.; Ala-Nissila, T.

    2016-05-01

    The phase-field-crystal (PFC) approach extends the notion of phase-field models by describing the topology of the microscopic structure of a crystalline material. One of the consequences is that local variation of the interatomic distance creates an elastic excitation. The dynamics of these excitations poses a challenge: pure diffusive dynamics cannot describe relaxation of elastic stresses that happen through phonon emission. To this end, several different models with fast dynamics have been proposed. In this article we use the amplitude expansion of the PFC model to compare the recently proposed hydrodynamic PFC amplitude model with two simpler models with fast dynamics. We compare these different models analytically and numerically. The results suggest that in order to have proper relaxation of elastic excitations, the full hydrodynamical description of the PFC amplitudes is required.

  12. On p-form theories with gauge invariant second order field equations

    CERN Document Server

    Deffayet, Cédric; Sivanesan, Vishagan

    2016-01-01

    We explore field theories of a single p-form with equations of motions of order strictly equal to two and gauge invariance. We give a general method for the classification of such theories which are extensions to the p-forms of the Galileon models for scalars. Our classification scheme allows to compute an upper bound on the number of different such theories depending on p and on the space-time dimension. We are also able to build a non trivial Galileon like theory for a 3-form with gauge invariance and an action which is polynomial into the derivatives of the form. This theory has gauge invariant field equations but an action which is not, like a Chern-Simons theory. Hence the recently discovered no-go theorem stating that there are no non trivial gauge invariant vector Galileons (which we are also able here to confirm with our method) does not extend to other odd p cases.

  13. The Renormalization Group, Entropy, Thermodynamic Phase Transitions and Order in Quantum Field Theory

    CERN Document Server

    Pérez-Mercader, J

    1993-01-01

    We define an entropy for a quantum field theory by combining quantum fluctuations, scaling and the maximum entropy concept. This entropy has different behavior in asymptotically free and non--asymptotically free theories. We find that the transition between the two regimes (from the asymptotically free to the non--asymptotically free) takes place via a continuous phase transition. For asymptotically free theories there exist regimes where the ``temperatures" are negative. In asymptotically free theories there exist maser--like states mostly in the infrared; furthermore, as one goes into the ultraviolet and more matter states contribute to quantum processes, the quantum field system can shed entropy and cause the formation of thermodynamically stable {\\it entropy--ordered} states. It is shown how the known heavier quarks can be thus described.

  14. Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

    CERN Document Server

    Degrande, Celine; Mawatari, Kentarou; Mimasu, Ken; Sanz, Veronica

    2016-01-01

    We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results.

  15. Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

    CERN Document Server

    Degrande, Celine; Mawatari, Kentarou; Mimasu, Ken; Sanz, Veronica

    2017-04-25

    We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results.

  16. Dissipation in the effective field theory for hydrodynamics: First order effects

    CERN Document Server

    Endlich, Solomon; Porto, Rafael A; Wang, Junpu

    2013-01-01

    We introduce dissipative effects in the effective field theory of hydrodynamics. We do this in a model-independent fashion by coupling the long-distance degrees of freedom explicitly kept in the effective field theory to a generic sector that "lives in the fluid", which corresponds physically to the microscopic constituents of the fluid. At linear order in perturbations, the symmetries, the derivative expansion, and the assumption that this microscopic sector is thermalized, allow us to characterize the leading dissipative effects at low frequencies via three parameters only, which correspond to bulk viscosity, shear viscosity, and--in the presence of a conserved charge--heat conduction. Using our methods we re-derive the Kubo relations for these transport coefficients.

  17. Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

    Energy Technology Data Exchange (ETDEWEB)

    Degrande, Celine [CERN, Theory Division, Geneva 23 (Switzerland); Fuks, Benjamin [Sorbonne Universites, UPMC Univ. Paris 06, Paris (France); CNRS, Paris (France); Mawatari, Kentarou [Universite Grenoble-Alpes, Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); Vrije Universiteit Brussel, Theoretische Natuurkunde and IIHE/ELEM, International Solvay Institutes, Brussels (Belgium); Mimasu, Ken [University of Sussex, Department of Physics and Astronomy, Brighton (United Kingdom); Universite catholique de Louvain, Centre for Cosmology, Particle Physics and Phenomenology (CP3), Louvain-la-Neuve (Belgium); Sanz, Veronica [University of Sussex, Department of Physics and Astronomy, Brighton (United Kingdom)

    2017-04-15

    We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results. (orig.)

  18. Going Beyond a Mean-field Model for the Learning Cortex: Second-Order Statistics

    Science.gov (United States)

    Steyn-Ross, Moira L.; Steyn-Ross, D. A.; Sleigh, J. W.

    2008-01-01

    Mean-field models of the cortex have been used successfully to interpret the origin of features on the electroencephalogram under situations such as sleep, anesthesia, and seizures. In a mean-field scheme, dynamic changes in synaptic weights can be considered through fluctuation-based Hebbian learning rules. However, because such implementations deal with population-averaged properties, they are not well suited to memory and learning applications where individual synaptic weights can be important. We demonstrate that, through an extended system of equations, the mean-field models can be developed further to look at higher-order statistics, in particular, the distribution of synaptic weights within a cortical column. This allows us to make some general conclusions on memory through a mean-field scheme. Specifically, we expect large changes in the standard deviation of the distribution of synaptic weights when fluctuation in the mean soma potentials are large, such as during the transitions between the “up” and “down” states of slow-wave sleep. Moreover, a cortex that has low structure in its neuronal connections is most likely to decrease its standard deviation in the weights of excitatory to excitatory synapses, relative to the square of the mean, whereas a cortex with strongly patterned connections is most likely to increase this measure. This suggests that fluctuations are used to condense the coding of strong (presumably useful) memories into fewer, but dynamic, neuron connections, while at the same time removing weaker (less useful) memories. PMID:19669541

  19. Magnetic Fields at First Order Phase Transition: A Threat to Electroweak Baryogenesis

    CERN Document Server

    De Simone, Andrea; Quiros, Mariano; Riotto, Antonio

    2011-01-01

    The generation of the observed baryon asymmetry may have taken place during the electroweak phase transition, thus involving physics testable at LHC, a scenario dubbed electroweak baryogenesis. In this paper we point out that the magnetic field which is produced in the bubbles of a first order phase transition endangers the baryon asymmetry produced in the bubble walls. The reason being that the produced magnetic field couples to the sphaleron magnetic moment and lowers the sphaleron energy; this strengthens the sphaleron transitions inside the bubbles and triggers a more effective wash out of the baryon asymmetry. We apply this scenario to the Minimal Supersymmetric extension of the Standard Model (MSSM) where, in the absence of a magnetic field, successful electroweak baryogenesis requires the lightest CP-even Higgs and the right-handed stop masses to be lighter than about 127 GeV and 120 GeV, respectively. We show that even for moderate values of the magnetic field, the Higgs mass required to preserve the ...

  20. Theoretical third-order hyperpolarizability of paratellurite from the finite field perturbation method.

    Science.gov (United States)

    Yahia, Mouna Ben; Orhan, Emmanuelle; Beltrán, Armando; Masson, Olivier; Merle-Méjean, Thérèse; Mirgorodski, Andreï; Thomas, Philippe

    2008-09-04

    Density functional theory was used to estimate the third-order hypersusceptibility chi (3) of the alpha-TeO2 paratellurite (as a model structure for TeO2 glass) and the same value for alpha-SiO2 cristobalite (as a model structure for glassy silica). The attempt was made to gain a physical insight into the nature of the extraordinarily high hypersusceptibility of TeO2 glass. A finite field perturbation method implemented in the CRYSTAL code with the "sawtooth" approach was employed. The chi (3) values calculated for alpha-TeO2 were found to be of the same order as that measured for TeO2 glass and much higher than the values computed for alpha-SiO2 which, in turn, were close to that of glassy silica.

  1. Second-Order Perturbation Theory for Generalized Active Space Self-Consistent-Field Wave Functions.

    Science.gov (United States)

    Ma, Dongxia; Li Manni, Giovanni; Olsen, Jeppe; Gagliardi, Laura

    2016-07-12

    A multireference second-order perturbation theory approach based on the generalized active space self-consistent-field (GASSCF) wave function is presented. Compared with the complete active space (CAS) and restricted active space (RAS) wave functions, GAS wave functions are more flexible and can employ larger active spaces and/or different truncations of the configuration interaction expansion. With GASSCF, one can explore chemical systems that are not affordable with either CASSCF or RASSCF. Perturbation theory to second order on top of GAS wave functions (GASPT2) has been implemented to recover the remaining electron correlation. The method has been benchmarked by computing the chromium dimer ground-state potential energy curve. These calculations show that GASPT2 gives results similar to CASPT2 even with a configuration interaction expansion much smaller than the corresponding CAS expansion.

  2. The Standard Model Effective Field Theory and Next to Leading Order

    CERN Document Server

    Passarino, Giampiero

    2016-01-01

    We review the status of calculations in the Standard Model Effective Field Theory (SMEFT) beyond leading order (LO). Improving the SMEFT beyond LO allows theoretical errors to be characterized and reduced when considering SMEFT interpretations of the data, which is essential considering the improving experimental precision at LHC. Next to leading order results also allow a more consistent analysis of measurements with different effective scales in the SMEFT. Going beyond LO is clearly important in the event that deviations from the SM are large enough that experimental indications of physics beyond the SM emerge. We discuss a consistent and well defined approach to LO in the SMEFT, so that the improvement to NLO is straightforward. We discuss the basic issues involved in improving calculations to NLO in the SMEFT, and review the advances in this direction that have been achieved to date.

  3. Perturbative Non-Equilibrium Thermal Field Theory to all Orders in Gradient Expansion

    CERN Document Server

    Millington, Peter

    2013-01-01

    We present a new perturbative formulation of non-equilibrium thermal field theory, based upon non-homogeneous free propagators and time-dependent vertices. The resulting time-dependent diagrammatic perturbation series are free of pinch singularities without the need for quasi-particle approximation or effective resummation of finite widths. After arriving at a physically meaningful definition of particle number densities, we derive master time evolution equations for statistical distribution functions, which are valid to all orders in perturbation theory and to all orders in a gradient expansion. For a scalar model, we perform a loopwise truncation of these evolution equations, whilst still capturing fast transient behaviour, which is found to be dominated by energy-violating processes, leading to the non-Markovian evolution of memory effects.

  4. Second-Order Self-Consistent-Field Density-Matrix Renormalization Group.

    Science.gov (United States)

    Ma, Yingjin; Knecht, Stefan; Keller, Sebastian; Reiher, Markus

    2017-06-13

    We present a matrix-product state (MPS)-based quadratically convergent density-matrix renormalization group self-consistent-field (DMRG-SCF) approach. Following a proposal by Werner and Knowles (J. Chem. Phys. 1985, 82, 5053), our DMRG-SCF algorithm is based on a direct minimization of an energy expression which is correct to second order with respect to changes in the molecular orbital basis. We exploit a simultaneous optimization of the MPS wave function and molecular orbitals in order to achieve quadratic convergence. In contrast to previously reported (augmented Hessian) Newton-Raphson and superconfiguration-interaction algorithms for DMRG-SCF, energy convergence beyond a quadratic scaling is possible in our ansatz. Discarding the set of redundant active-active orbital rotations, the DMRG-SCF energy converges typically within two to four cycles of the self-consistent procedure.

  5. Second-Order Self-Consistent-Field Density-Matrix Renormalization Group

    CERN Document Server

    Ma, Yingjin; Keller, Sebastian; Reiher, Markus

    2016-01-01

    We present a matrix-product state (MPS)-based quadratically convergent density-matrix renormalization group self-consistent-field (DMRG-SCF) approach. Following a proposal by Werner and Knowles (JCP 82, 5053, (1985)), our DMRG-SCF algorithm is based on a direct minimization of an energy expression which is correct to second-order with respect to changes in the molecular orbital basis. We exploit a simultaneous optimization of the MPS wave function and molecular orbitals in order to achieve quadratic convergence. In contrast to previously reported (augmented Hessian) Newton-Raphson and super-configuration-interaction algorithms for DMRG-SCF, energy convergence beyond a quadratic scaling is possible in our ansatz. Discarding the set of redundant active-active orbital rotations, the DMRG-SCF energy converges typically within two to four cycles of the self-consistent procedure

  6. Double Quarter Wave Crab Cavity Field Profile Analysis and Higher Order Mode Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Carlos [Brookhaven National Lab. (BNL), Upton, NY (United States). Accelerator R and D Div.; Stony Brook Univ., NY (United States). Physics and Astronomy Dept.; Xiao, B. P. [Brookhaven National Lab. (BNL), Upton, NY (United States). Accelerator R and D Div.; Belomestnykh, S. [Brookhaven National Lab. (BNL), Upton, NY (United States). Accelerator R and D Div.; Stony Brook Univ., NY (United States). Physics and Astronomy Dept.

    2014-06-01

    The Large Hadron Collider (LHC) is underway for a major upgrade to increase its luminosity by an order of magnitude beyond its original design specifications. This novel machine configuration known as the High Luminosity LHC (HL-LHC) will rely on various innovative technologies including very compact and ultra-precise superconducting crab cavities for beam rotation. A double quarter wave crab cavity (DQWCC) has been designed at Brookhaven National Laboratory for the HL-LHC. This cavity as well as the structural support components were fabricated and assembled at Niowave. The field profile of the crabbing mode for the DQWCC was investigated using a phase shift bead pulling technique and compared with simulated results to ensure proper operation or discover discrepancies from modeled results and/or variation in fabrication tolerances. Higher-Order Mode (HOM) characterization was also performed and correlated with simulations.

  7. Secular Motion in a 2nd Degree and Order-Gravity Field with no Rotation

    Science.gov (United States)

    Scheeres, D. J.; Hu, W.

    2001-03-01

    The motion of a particle about a non-rotating 2nd degree and order-gravity field is investigated. Averaging conditions are applied to the particle motion and a qualitative analysis which reveals the general character of motion in this system is given. It is shown that the orbit plane will either be stationary or precess about the body's axis of minimum or maximum moment of inertia. It is also shown that the secular equations for this system can be integrated in terms of trigonometric, hyperbolic or elliptic functions. The explicit solutions are derived in all cases of interest.

  8. Focus conditioning effects on molecular field-free alignment observed with high-order harmonic generation

    Institute of Scientific and Technical Information of China (English)

    吴家骏; 尉鹏飞

    2012-01-01

    We investigate the focus conditioning effects on molecular field-free alignment observed with high-order harmonic generation (HHG) from CO2 molecules.We also experimentally demonstrate that both the spectral shape and alignment signal of HHG significantly vary with changing focus position.A maximal alignment signal is achieved at a given focus position because of the optimal intensity of the driving laser.This intensity is related to the ionization potential of the molecules.These results indicate that a unique focus position provides an optimal alignment signal for practical applications.

  9. Numerical simulations with a first order BSSN formulation of Einstein's field equations

    CERN Document Server

    Brown, J David; Field, Scott E; Hesthaven, Jan S; Herrmann, Frank; Mroué, Abdul H; Schnetter, Erik; Tiglio, Manuel; Wagman, Michael

    2012-01-01

    We present a new fully first order strongly hyperbolic representation of the BSSN formulation of Einstein's equations with optional constraint damping terms. We describe the characteristic fields of the system, discuss its hyperbolicity properties, and present two numerical implementations and simulations: one using finite differences, adaptive mesh refinement and in particular binary black holes, and another one using the discontinuous Galerkin method in spherical symmetry. The results of this paper constitute a first step in an effort to combine the robustness of BSSN evolutions with very high accuracy numerical techniques, such as spectral collocation multi-domain or discontinuous Galerkin methods.

  10. Direct observations of field-induced assemblies in magnetite ferrofluids

    Science.gov (United States)

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  11. Direct observations of field-induced assemblies in magnetite ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi, N. S. Susan [Mechanical Engineering Department, Polytechnic School of Engineering, New York University, 6 Metrotech Center, Brooklyn, New York 11201 (United States); Khapli, Sachin D. [New York University Abu Dhabi, Saadiyat Island, PO Box 129 188, Abu Dhabi (United Arab Emirates); Kumar, Sunil [Mechanical Engineering Department, Polytechnic School of Engineering, New York University, 6 Metrotech Center, Brooklyn, New York 11201 (United States); New York University Abu Dhabi, Saadiyat Island, PO Box 129 188, Abu Dhabi (United Arab Emirates)

    2015-03-14

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  12. Field-induced layer formation in dipolar nanofilms.

    Science.gov (United States)

    Jordanovic, Jelena; Klapp, Sabine H L

    2008-07-18

    Using molecular dynamics simulations, we demonstrate that the layering of confined colloidal particles with dipolar interactions, such as ferrofluids, in slablike geometries can be controlled by homogeneous external fields. For suitable surface separations, strong fields directed perpendicular to the film plane do not only align the particles but create additional layers in the system. The reverse effect occurs with an in-plane field which can induce a collapse of layers. Both effects are accompanied by pronounced particle rearrangements in lateral directions. Our simulation results are consistent with recent experiments of ferrofluids at surfaces.

  13. Ultracold Fermions in a Cavity-Induced Artificial Magnetic Field

    Science.gov (United States)

    Kollath, Corinna; Sheikhan, Ameneh; Wolff, Stefan; Brennecke, Ferdinand

    2016-02-01

    We propose how a fermionic quantum gas confined to an optical lattice and coupled to an optical cavity can self-organize into a state where the spontaneously emerging cavity field amplitude induces an artificial magnetic field. The fermions form either a chiral insulator or a chiral liquid carrying chiral currents. The feedback mechanism via the dynamical cavity field enables robust and fast switching in time of the chiral phases, and the cavity output can be employed for a direct nondestructive measurement of the chiral current.

  14. Placement of field probes for stabilization of breathing-induced B0-fluctuations in the brain

    DEFF Research Database (Denmark)

    Andersen, Mads; Madsen, Kristoffer H.; Hanson, Lars G.;

    ). It is a fundamental challenge, however, that the B0 measurements are spatially sparse (e.g. 16 probes), and performed outside the brain. Typically, the field is modelled by a linear combination of the spatial shim fields that the scanner can produce (such as spherical harmonics up to 3rd order), and the coefficients......Introduction: B0-fluctuations induced by breathing and body motion lead to artifacts for certain brain imaging sequences at ultra-high field (7T). A promising solution is to monitor the B0-fluctuations during the scan using external field probes, and update the shim currents in real-time (1...... for these spatial terms are determined by least square fitting to the field probe measurements. The probes must be placed carefully to ensure that the spherical harmonics can be distinguished using these few samples, and they must be placed close to the head so that the spatial field model is valid and to have good...

  15. Electric Field-Induced Fluid Velocity Field Distribution in DNA Solution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ling-Yun; WANG Peng-Ye

    2008-01-01

    We present an analytical solution for fluid velocity field distribution of polyelectrolyte DNA. Both the electric field force and the viscous force in the DNA solution are considered under a suitable boundary condition. The solution of electric potential is analytically obtained by using the linearized Poisson-Boltzmann equation. The fluid velocity along the electric field is dependent on the cylindrical radius and concentration. It is shown that the electric field-induced fluid velocity will be increased with the increasing cylindrical radius, whose distribution also varies with the concentration

  16. Metal-induced fluorescence properties of three-dimensionally ordered macroporous silver inverse opal platforms

    Science.gov (United States)

    Chae, Weon-Sik; Lee, Myung-Jin; Kim, Kisun; Hyun, Jerome K.; Jeon, Seokwoo

    2016-02-01

    This study examined the metal-induced fluorescence properties of three-dimensionally ordered macroporous silver inverse opal (IO) films. Electrochemically synthesized silver IO films with a micrometer cavity exhibited notable fluorescence enhancement at the silver frame, and a decrease in fluorescence lifetime. Numerical calculations supported the observations of a higher fluorescence efficiency at the frame than in the cavity.

  17. Field induced spin chirality and chirality switching in magnetic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tartakovskaya, Elena V., E-mail: elena_tartakovskaya@yahoo.com [Institute of Magnetism NAS of Ukraine, Vernadsky blvd 36b, 03142 Kiev (Ukraine); Institute of High Technologies, Taras Shevchenko National University of Kiev, 03022 Kiev (Ukraine)

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman–Kittel–Kasuya–Yosida and the Dsyaloshinsky–Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness. - Highlights: • Field-induced spin chirality in magnetic multilayers is explained. • The roles of the RKKY, the DM and the Zeeman interactions are clarified. • Theoretical analysis of the chirality factor is in agreement with experimental data.

  18. High Degree and Order Gravity Fields of the Moon Derived from GRAIL Data

    Science.gov (United States)

    Lemoine, F. G.; Goossens, S. J.; Sabaka, T. J.; Nicholas, J. B.; Mazarico, E.; Rowlands, D. D.; Loomis, B. D.; Chinn, D. S.; Caprette, D. S.; McCarthy, J. J.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.

    2012-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) spacecraft conducted the mapping of the gravity field of the Moon from March 1, 2012 to May 29, 2012. The twin spacecraft acquired highly precise K Band range-rate (KBRR) intersatellite ranging data and Deep Space Network (DSN) data during this prime mission phase from altitudes of 15 to 75 km above the lunar surface over three lunar months. We have processed these data using the NASA GSFC GEODYN orbit determination and geodetic parameter estimation program, and we have determined gravity fields up to degree and order 420 in spherical harmonics. The new gravity solutions show improved correlations with LOLA-derived topography to high degree and order and resolve many lunar features in the geopotential with a resolution of less than 30 km, including for example the central peak of the crater Tycho. We discuss the methodology used for the processing of the GRAIL data, the quality of the orbit determination on the GRAIL satellites and the derivation of the solutions, and their evaluation with independent data, including Lunar Prospector. We show that with these new GRAIL gravity solutions, we can now fit the low altitude, extended mission Lunar Prospector tracking data better than with any previous gravity model that included the LP data.

  19. Reheating signature in the gravitational wave spectrum from self-ordering scalar fields

    CERN Document Server

    Kuroyanagi, Sachiko; Yokoyama, Jun'ichi

    2015-01-01

    We investigate the imprint of reheating on the gravitational wave spectrum produced by self-ordering of multi-component scalar fields after a global phase transition. The equation of state of the Universe during reheating, which usually has different behaviour from that of a radiation-dominated Universe, affects the evolution of gravitational waves through the Hubble expansion term in the equations of motion. This gives rise to a different power-law behavior of frequency in the gravitational wave spectrum. The reheating history is therefore imprinted in the shape of the spectrum. We perform $512^3$ lattice simulations to investigate how the ordering scalar field reacts to the change of the Hubble expansion and how the reheating effect arises in the spectrum. We also compare the result with inflation-produced gravitational waves, which has a similar spectral shape, and discuss whether it is possible to distinguish the origin between inflation and global phase transition by detecting the shape with future direc...

  20. Longitudinal Conductivity in Strong Magnetic Field in Perturbative QCD: Complete Leading Order

    CERN Document Server

    Hattori, Koichi; Satow, Daisuke; Yee, Ho-Ung

    2016-01-01

    We compute the longitudinal electrical conductivity in the presence of strong background magnetic field in complete leading order of perturbative QCD, based on the assumed hierarchy of scales $\\alpha_s eB\\ll (m_q^2,T^2)\\ll eB$. We formulate an effective kinetic theory of lowest Landau level quarks with the leading order QCD collision term arising from 1-to-2 processes that become possible due to 1+1 dimensional Landau level kinematics. In small $m_q/T\\ll 1$ regime, the longitudinal conductivity behaves as $\\sigma_{zz}\\sim e^2(eB)T/(\\alpha_s m_q^2\\log(m_q/T))$, where the quark mass dependence can be understood from the chiral anomaly with the axial charge relaxation provided by a finite quark mass $m_q$. We also present parametric estimates for the longitudinal and transverse "color conductivities" in the presence of strong magnetic field, by computing dominant damping rates for quarks and gluons that are responsible for color charge transportation. We observe that the longitudinal color conductivity is enhanc...

  1. Low-order statistics of effective permittivity and electric field fluctuations in two-phase heterostructures

    Science.gov (United States)

    Shamoon, D.; Lasquellec, S.; Brosseau, C.

    2017-07-01

    Understanding the collective, low-frequency dielectric properties of heterostructures is a major goal in condensed matter. In 1935, Bruggeman [Ann. Phys. Lpz. 24, 636 (1935)] conceived the concept of an effective medium approximation (EMA) involving a decoupling between the low-order statistics of the electric field fluctuations and the characteristic length scales. We report on and characterize, via finite element studies, the low-order statistics effective permittivity of two-phase 2D and 3D random and deterministic heterostructures as geometry, phase permittivity contrast, and inclusion content are varied. Since EMA analytical expressions become cumbersome even for simple shapes and arrangements, numerical approaches are more suitable for studying heterostructures with complex shapes and topologies. Our numerical study verifies the EMA analytic predictions when the scales are well-separated. Our numerical study compares two approaches for calculating effective permittivity by explicit calculations of local average fields and energy as geometry, phase permittivity contrast, and inclusion content are varied. We study the conditions under which these approaches give a reliable estimate of permittivity by comparing with 2D/3D EMA analytical models and duality relation. By considering 2D checkerboards which consist of a multitude of contiguous N × N square cells, the influence of the internal length scale (i.e., N) on permittivity is discussed.

  2. Shiga toxin induces membrane reorganization and formation of long range lipid order

    DEFF Research Database (Denmark)

    Solovyeva, Vita; Johannes, Ludger; Simonsen, Adam Cohen

    2015-01-01

    microscopy. A content of 1% of glycosphingolipid globotriaosylceramide (Gb3) receptor lipids in a bilayer was used to bind the Shiga toxin B-subunit to the surface of gel domains. Binding of the Shiga toxin B-subunit to lipids led to the modulation of orientational membrane texture in gel domains and induced...... membrane reordering. When Shiga toxin was added above the lipid chain melting temperature, the toxin interaction with the membrane induced rearrangement and clustering of Gb3 lipids that resulted in the long range order and alignment of lipids in gel domains. The toxin induced redistribution of Gb3 lipids...... inside gel domains is governed by the temperature at which Shiga toxin was added to the membrane: above or below the phase transition. The temperature is thus one of the critical factors controlling lipid organization and texture in the presence of Shiga toxin. Lipid chain ordering imposed by Shiga toxin...

  3. Light-induced gauge fields for ultracold atoms.

    Science.gov (United States)

    Goldman, N; Juzeliūnas, G; Öhberg, P; Spielman, I B

    2014-12-01

    Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle-the graviton-that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms 'feeling' laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials-both Abelian and non-Abelian-in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

  4. Light-induced gauge fields for ultracold atoms

    Science.gov (United States)

    Goldman, N.; Juzeliūnas, G.; Öhberg, P.; Spielman, I. B.

    2014-12-01

    Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle—the graviton—that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms ‘feeling’ laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials—both Abelian and non-Abelian—in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

  5. Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

    Science.gov (United States)

    Woodall, Christopher H.; Craig, Gavin A.; Prescimone, Alessandro; Misek, Martin; Cano, Joan; Faus, Juan; Probert, Michael R.; Parsons, Simon; Moggach, Stephen; Martínez-Lillo, José; Murrie, Mark; Kamenev, Konstantin V.; Brechin, Euan K.

    2016-12-01

    Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the `transformation' from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with Tc controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, `squeezing' the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of Tc with pressure.

  6. Temperature and magnetic field induced multiple magnetic transitions in DyAg(2).

    Science.gov (United States)

    Arora, Parul; Chattopadhyay, M K; Sharath Chandra, L S; Sharma, V K; Roy, S B

    2011-02-09

    The magnetic properties of the rare-earth intermetallic compound DyAg(2) are studied in detail with the help of magnetization and heat capacity measurements. It is shown that the multiple magnetic phase transitions can be induced in DyAg(2) both by temperature and magnetic field. The detailed magnetic phase diagram of DyAg(2) is determined experimentally. It was already known that DyAg(2) undergoes an incommensurate to commensurate antiferromagnetic phase transition close to 10 K. The present experimental results highlight the first order nature of this phase transition, and show that this transition can be induced by magnetic field as well. It is further shown that another isothermal magnetic field induced transition or metamagnetic transition exhibited by DyAg(2) at still lower temperatures is also of first order nature. The multiple magnetic phase transitions in DyAg(2) give rise to large peaks in the temperature dependence of the heat capacity below 17 K, which indicates its potential as a magnetic regenerator material for cryocooler related applications. In addition it is found that because of the presence of the temperature and field induced magnetic phase transitions, and because of short range magnetic correlations deep inside the paramagnetic regime, DyAg(2) exhibits a fairly large magnetocaloric effect over a wide temperature window, e.g., between 10 and 60 K.

  7. Field-induced quantum criticality in CeCu{sub 6-x}Au{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Grube, Kai; Eilers, Felix; Zocco, Diego; Schaefer, Roland [Karlsruher Institut fuer Technologie, Institut fuer Festkoerperphysik, 76021 Karlsruhe (Germany); Zaum, Sebastian; Loehneysen, Hilbert von [Karlsruher Institut fuer Technologie, Institut fuer Festkoerperphysik, 76021 Karlsruhe (Germany); Karlsruher Institut fuer Technologie, Physikalisches Institut, Karlsruhe (Germany); Fritsch, Veronika [Karlsruher Institut fuer Technologie, Physikalisches Institut, Karlsruhe (Germany); Stockert, Oliver [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, 01187 Dresden (Germany)

    2013-07-01

    The heavy-fermion system CeCu{sub 6-x}Au{sub x} is an archetype for pressure-induced quantum criticality at the onset of antiferromagnetic order. Up to now, investigations focused mainly on the behavior close to the critical concentration x{sub c}∼0.1. The antiferromagnetic order of samples with higher Au content can, however, be also suppressed by magnetic fields. We studied the field-induced quantum critical behavior of samples with Au contents x=0.3, 0.5 and 1.0 in fields applied along the magnetic easy axis by using thermal expansion and magnetostriction measurements. Due to their high sensitivities these measurements are especially suited to expose deviations from Fermi-liquid behavior. The measurements have been performed for temperatures ranging between 20 mK and 10 K, and in magnetic fields up to 14 T. With increasing Au content and critical field B{sub c} they show strongly varying critical behavior. We discuss our results taking into account the field-dependent Zeeman splitting of the CEF ground-state doublet, which manifests itself as a Schottky-like anomaly at low temperatures and fields larger than B{sub c}.

  8. Order-disorder phase transition and stress-induced diffusion in Au-Cu

    Science.gov (United States)

    Hennig, John; Mari, Daniele; Schaller, Robert

    2009-04-01

    Isothermal mechanical spectroscopy by means of a forced torsion pendulum (measuring internal friction/mechanical loss) was used to study the interplay of long-range atomic order and stress-induced diffusion (Zener relaxation) in Au57%Cu43% . Our results show that the relaxation strength of stress-induced diffusion exhibits the typical Curie-Weiss-type behavior in the disordered solid solution and then gradually goes to zero below the critical temperature marking the phase transition to the long-range-ordered AuCu II phase. The breakdown of the relaxation peak reflects the kinetics of the ordering process. The diffusion data were used to establish the transformation time vs temperature (TTT) diagram of the phase transformation.

  9. Weak arrest-like and field-driven first order magnetic phase transitions of itinerant Fe3Ga4 revealed by magnetization and magnetoresistance isotherms

    Science.gov (United States)

    Samatham, S. Shanmukharao; Suresh, K. G.

    2017-01-01

    The detailed magnetic study of complex 3d-electron based Fe3Ga4 is reported. It undergoes paramagnetic to antiferromagnetic (TN) and antiferromagnetic to ferromagnetic (TC) transitions respectively around 380 and 70 K. The thermal hysteresis of field-cooled cooling (FCC) and field-cooled warming (FCW) hints at first order phase transition below Curie temperature. A weak phase coexistence of ferro and antiferromagnetic phases is suggested by exploring the arrest-like first-order phenomenon. In the intermediate temperature range, field-driven metamagnetic transition from antiferro to ferromagnetic phase is confirmed. Further bringing the system very near to TN, field-induced transitions disappear and above TN predominant paramagnetic contribution is evident. The magnetic H-T phase diagram distinguishing different magnetic phases of Fe3Ga4 is obtained.

  10. The Effect of Magnetic Field and Initial Stress on Fractional Order Generalized Thermoelastic Half-Space

    Directory of Open Access Journals (Sweden)

    Sunita Deswal

    2013-01-01

    Full Text Available The aim of this paper is to study magneto-thermoelastic interactions in an initially stressed isotropic homogeneous half-space in the context of fractional order theory of generalized thermoelasticity. State space formulation with the Laplace transform technique is used to obtain the general solution, and the resulting formulation is applied to the ramp type increase in thermal load and zero stress. Solutions of the problem in the physical domain are obtained by using a numerical method of the Laplace inverse transform based on the Fourier expansion technique, and the expressions for the displacement, temperature, and stress inside the half-space are obtained. Numerical computations are carried out for a particular material for illustrating the results. Results obtained for the field variables are displayed graphically. Some comparisons have been shown in figures to present the effect of fractional parameter, ramp parameter, magnetic field, and initial stress on the field variables. Some particular cases of special interest have been deduced from the present investigation.

  11. Strong-Field S-Matrix Theory With Coulomb-Volkov Final State in All Orders

    CERN Document Server

    Faisal, F H M

    2016-01-01

    Despite its long standing usefulness for the analysis of various processes in intense laser fields, it is well-known that the so-called strong-field KFR or SFA ansatz does not account for the final-state Coulomb interaction. Due to its importance for the ubiquitous ionisation process, numerous heuristic attempts have been made during the last several decades to account for the final state Coulomb interaction with in the SFA. Also to this end an ad hoc model with the so-called Coulomb-Volkov final state was introduced a long time ago. However, till now, no systematic strong-field S-matrix expansion using the Coulomb-Volkov final state could be found. Here we solve this long standing problem by determining the Coulomb-Volkov Hamiltonian, identifying the rest-interaction in the final state, and explicitly constructng the Coulomb-Volkov propagator (or Green's function). We employ them to derive the complete S-matrix series for the ionisation amplitude governed by the Coulomb-Volkov final state in all orders. The ...

  12. Cosmic magnetization: from spontaneously emitted aperiodic turbulent to ordered equipartition fields.

    Science.gov (United States)

    Schlickeiser, R

    2012-12-28

    It is shown that an unmagnetized nonrelativistic thermal electron-proton plasma spontaneously emits aperiodic turbulent magnetic field fluctuations of strength |δB|=3.5β(e)g(1/3)W(e)(1/2)  G, where β(e) is the normalized thermal electron temperature, W(e) the thermal plasma energy density, and g the plasma parameter. For the unmagnetized intergalactic medium, immediately after the reionization onset, the field strengths from this mechanism are about 2×10(-16)  G in cosmic voids and 2×10(-10)  G in protogalaxies, both too weak to affect the dynamics of the plasma. Accounting for simultaneous viscous damping reduces these estimates to 2×10(-21)  G in cosmic voids and 2×10(-12)  G in protogalaxies. The shear and/or compression of the intergalactic and protogalactic medium exerted by the first supernova explosions locally amplify these seed fields and make them anisotropic, until the magnetic restoring forces affect the gas dynamics at ordered plasma betas near unity.

  13. Effect of a weak external electric field on the kinetics of the ordering of ferroelectrics upon first-order phase transitions

    Science.gov (United States)

    Mazur, O. Yu.; Stefanovich, L. I.; Yurchenko, V. M.

    2016-08-01

    The kinetics of the formation and growth of 180° domains in a weak quasi-stationary external electric field has been considered in the framework of the phenomenological Ginzburg-Landau model using the example of sodium nitrite (NaNO2) crystals that undergo a first-order ferroelectric phase transition of the order-disorder type. The influence of the rate and temperature of quenching, as well as the strength of an external electric field, on the subsequent evolution of the system toward the thermodynamic equilibrium state has been analyzed. It has been shown that, by varying a weak external electric field applied to the ferroelectric crystal after quenching, it is possible to obtain both single-domain and multi-domain ordered structures. It has been established that the formation of nonequilibrium ("virtual") multi-domain structures of the asymmetric type is possible for particular strengths of the electric field applied to the ferroelectric after quenching. A similar effect can be achieved by varying the depth of quenching of the sample. It has been found that, if the size of the order parameter inhomogeneities formed at the stage of quenching does not exceed a critical value, they can be reoriented partially or completely into domains of opposite sign. For this purpose, the relaxation after quenching should be performed in an external electric field of the appropriate sign.

  14. Reduced Order Modeling of Bubble Cloud Dynamics in a Focused Ultrasound Field

    Science.gov (United States)

    Maeda, Kazuki; Colonius, Tim

    2016-11-01

    In order to characterize the cloud cavitation in burst wave lithotripsy, reduced order modeling of the dynamics of a spherical bubble cloud of a radius O (1) mm interacting with traveling ultrasound waves of an amplitude O(1) MPa in water is presented. Bubbles are treated as spherical, radially oscillating cavities dispersed in continuous liquid phase. The volume of Lagrangian point bubbles is mapped with a regularization kernel as void fraction onto three-dimensional Cartesian grids that define the Eulerian liquid phase. The flow field is solved using a WENO-based compressible flow solver. The initial size and number density of the bubbles are critical for their coherent dynamics in the cloud, yet three-dimensional simulations of clouds with various parameters are computationally demanding. For further reduced-order modeling, a new kernel is introduce into the model to regularize bubbles onto two-dimensional, axisymmetric grids. The evolution of the void fraction and the maximum pressure in the cloud simulated using the model agree with results of three-dimensional simulations, while the reduction in computational cost is a factor of O (100) . Finally, the model is applied to a parametric study of the coherent dynamics of bubbles.

  15. Phase field crystal modelling of the order-to-disordered atomistic structure transition of metallic glasses

    Science.gov (United States)

    Zhang, W.; Mi, J.

    2016-03-01

    Bulk metallic glass composites are a new class of metallic alloy systems that have very high tensile strength, ductility and fracture toughness. This unique combination of mechanical properties is largely determined by the presence of crystalline phases uniformly distributed within the glassy matrix. However, there have been very limited reports on how the crystalline phases are nucleated in the super-cooled liquid and their growth dynamics, especially lack of information on the order-to-disordered atomistic structure transition across the crystalline-amorphous interface. In this paper, we use phase field crystal (PFC) method to study the nucleation and growth of the crystalline phases and the glass formation of the super cooled liquid of a binary alloy. The study is focused on understanding the order-to-disordered transition of atomistic configuration across the interface between the crystalline phases and amorphous matrix of different chemical compositions at different thermal conditions. The capability of using PFC to simulate the order-to-disorder atomistic transition in the bulk material or across the interface is discussed in details.

  16. General principles of describing second- and higher-order null points of a potential magnetic field in 3D

    Science.gov (United States)

    Lukashenko, A. T.; Veselovsky, I. S.

    2015-12-01

    General principles of describing secondand higher-order null points of a potential magnetic field are formulated. The potential near a second-order null of the general form can be specified by a linear combination of four basic functions, the list of which is presented. Near secondand higher-order null points, field line equations often cannot be integrated analytically; however, in some cases, it is possible to present a qualitative description of the geometry of null vicinities with consideration of the behavior of field lines near rays outgoing from null, at which the field is radial or equals zero.

  17. Anomaly-induced dynamical refringence in strong-field QED

    CERN Document Server

    Mueller, Niklas; Berges, Jürgen

    2016-01-01

    We investigate the impact of the Adler-Bell-Jackiw anomaly on the nonequilibrium evolution of strong-field quantum electrodynamics (QED) using real-time lattice gauge theory techniques. For field strengths exceeding the Schwinger limit for pair production, we encounter a highly absorptive medium with anomaly-induced dynamical refractive properties. In contrast to earlier expectations based on equilibrium properties, where net anomalous effects vanish because of the trivial vacuum structure, we find that out-of-equilibrium conditions can have dramatic consequences for the presence of quantum currents with distinctive macroscopic signatures. We observe an intriguing tracking behavior, where the system spends longest times near collinear field configurations with maximum anomalous current. Apart from the potential relevance of our findings for future laser experiments, similar phenomena related to the chiral magnetic effect are expected to play an important role for strong QED fields during initial stages of hea...

  18. A First/Third-Order Probe Correction Technique for Spherical Near-Field Antenna Measurements Using Three Probe Orientations

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Breinbjerg, Olav

    2008-01-01

    A probe correction technique is described for spherical near-field antenna measurements based on sampling the near field for three probe orientations in each measurement direction. The technique applies to odd-order probes whose radiated field contains (significant) power only in the first (µ=±1)...

  19. Nature of unusual spontaneous and field-induced phase transitions in multiferroics RMn 2O 5

    Science.gov (United States)

    Pyatakov, A. P.; Kadomtseva, A. M.; Vorob'ev, G. P.; Popov, Yu. F.; Krotov, S. S.; Zvezdin, A. K.; Lukina, M. M.

    2009-04-01

    Complex magnetic, magnetoelectric and magnetoelastic studies of spontaneous and field-induced phase transitions in TmMn 2O 5 were carried out. In the vicinity of spontaneous phase transition temperatures (35 and 25 K) the magnetoelectric and magnetoelastic dependences demonstrated the jumps of polarization and magnetostriction induced by the field ˜150 kOe. These anomalies can be attributed to the influence of magnetic field on the conditions of incommensurate-commensurate phase transition at 35 K and the reverse one at 25 K. In b-axis dependences the magnetic field-induced spin-reorientation phase transition was also observed below 20 K. Finally the magnetoelectric anomaly associated with metamagnetic transition is observed below the temperature of rare-earth subsystem ordering at relatively small critical fields of 5 kOe. This variety of spontaneous and induced phase transitions in RMn 2O 5 stems from the interplay of three magnetic subsystems: Mn 3+, Mn 4+, R 3+. The comparison with YMn 2O 5 highlights the role of rare earth in low-temperature region (metamagnetic and spin-reorientation phase transitions), while the phase transition at higher temperatures between incommensurate and commensurate phases should be ascribed to the different temperature dependences of Mn 3+ and Mn 4+ ions. The strong correlation of magnetoelastic and magnetoelectric properties observed in the whole class of RMn 2O 5 highlights their multiferroic nature.

  20. Graphene-based field effect transistors for radiation-induced field sensing

    Energy Technology Data Exchange (ETDEWEB)

    Di Gaspare, Alessandra, E-mail: alessandra.digaspare@lnf.infn.it [INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); Valletta, Antonio [CNR-Istituto per la Microelettronica e i Microsistemi, TorVergata, Rome (Italy); Fortunato, Guglielmo [CNR-Istituto per la Microelettronica e i Microsistemi, TorVergata, Rome (Italy); INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); Larciprete, Rosanna [CNR-Istituto di Sistemi Complessi, TorVergata, Rome (Italy); INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); Mariucci, Luigi [CNR-Istituto per la Microelettronica e i Microsistemi, TorVergata, Rome (Italy); INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); Notargiacomo, Andrea [CNR-Istituto di Fotonica e Nanotecnologie, Rome (Italy); INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); Cimino, Roberto [INFN-Laboratori Nazionali Frascati, Frascati, Rome (Italy); CERN, Geneva (Switzerland)

    2016-07-11

    We propose the implementation of graphene-based field effect transistor (FET) as radiation sensor. In the proposed detector, graphene obtained via chemical vapor deposition is integrated into a Si-based field effect device as the gate readout electrode, able to sense any change in the field distribution induced by ionization in the underneath absorber, because of the strong variation in the graphene conductivity close to the charge neutrality point. Different 2-dimensional layered materials can be envisaged in this kind of device.

  1. NMR studies of field induced magnetism in CeCoIn5

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Matthias [Los Alamos National Laboratory; Curro, Nicholas J [UC/DAVIS; Young, Ben - Li [NATIONAL CHIAO TUNG UNIV; Urbano, Ricardo R [FLORIDA STATE UNIV

    2009-01-01

    Recent Nuclear Magnetic Resonance and elastic neutron scattering experiments have revealed conclusively the presence of static incommensurate magnetism in the field-induced B phase of CeCoIns, We analyze the NMR data assuming the hyperfine coupling to the 1n(2) nuclei is anisotropic and simulate the spectra for several different magnetic structures, The NMR data are consistent with ordered Ce moments along the [001] direction, but are relatively insensitive to the direction of the incommensurate wavevector.

  2. Oscillation quenching in third order phase locked loop coupled by mean field diffusive coupling

    Science.gov (United States)

    Chakraborty, S.; Dandapathak, M.; Sarkar, B. C.

    2016-11-01

    We explored analytically the oscillation quenching phenomena (amplitude death and parameter dependent inhomogeneous steady state) in a coupled third order phase locked loop (PLL) both in periodic and chaotic mode. The phase locked loops were coupled through mean field diffusive coupling. The lower and upper limits of the quenched state were identified in the parameter space of the coupled PLL using the Routh-Hurwitz technique. We further observed that the ability of convergence to the quenched state of coupled PLLs depends on the design parameters. For identical systems, both the systems converge to the homogeneous steady state, whereas for non-identical parameter values they converge to an inhomogeneous steady state. It was also observed that for identical systems, the quenched state is wider than the non-identical case. When the system parameters are so chosen that each isolated loop is chaotic in nature, we observe narrowing down of the quenched state. All these phenomena were also demonstrated through numerical simulations.

  3. First and second order operator splitting methods for the phase field crystal equation

    Science.gov (United States)

    Lee, Hyun Geun; Shin, Jaemin; Lee, June-Yub

    2015-10-01

    In this paper, we present operator splitting methods for solving the phase field crystal equation which is a model for the microstructural evolution of two-phase systems on atomic length and diffusive time scales. A core idea of the methods is to decompose the original equation into linear and nonlinear subequations, in which the linear subequation has a closed-form solution in the Fourier space. We apply a nonlinear Newton-type iterative method to solve the nonlinear subequation at the implicit time level and thus a considerably large time step can be used. By combining these subequations, we achieve the first- and second-order accuracy in time. We present numerical experiments to show the accuracy and efficiency of the proposed methods.

  4. General second order complete active space self-consistent-field solver for large-scale systems

    CERN Document Server

    Sun, Qiming

    2016-01-01

    One challenge of the complete active space self-consistent field (CASSCF) program is to solve the transition metal complexes which are typically medium or large-size molecular systems with large active space. We present an AO-driven second order CASSCF solver to efficiently handle systems which have a large number of AO functions and many active orbitals. This solver allows user to replace the active space Full CI solver with any multiconfigurational solver without breaking the quadratic convergence feature. We demonstrate the capability of the CASSCF solver with the study of Fe(ii)-porphine ground state using DMRG-CASSCF method for 22 electrons in 27 active orbitals and 3000 basis functions.

  5. First and second order operator splitting methods for the phase field crystal equation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Geun; Shin, Jaemin [Institute of Mathematical Sciences, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Lee, June-Yub, E-mail: jyllee@ewha.ac.kr [Department of Mathematics, Ewha Womans University, Seoul 120-750 (Korea, Republic of)

    2015-10-15

    In this paper, we present operator splitting methods for solving the phase field crystal equation which is a model for the microstructural evolution of two-phase systems on atomic length and diffusive time scales. A core idea of the methods is to decompose the original equation into linear and nonlinear subequations, in which the linear subequation has a closed-form solution in the Fourier space. We apply a nonlinear Newton-type iterative method to solve the nonlinear subequation at the implicit time level and thus a considerably large time step can be used. By combining these subequations, we achieve the first- and second-order accuracy in time. We present numerical experiments to show the accuracy and efficiency of the proposed methods.

  6. Second-order corrections to mean field evolution for weakly interacting Bosons. I

    CERN Document Server

    Grillakis, Manoussos G; Margetis, Dionisios

    2009-01-01

    Inspired by the works of Rodnianski and Schlein and Wu, we derive a new nonlinear Schr\\"odinger equation that describes a second-order correction to the usual tensor product (mean-field) approximation for the Hamiltonian evolution of a many-particle system in Bose-Einstein condensation. We show that our new equation, if it has solutions with appropriate smoothness and decay properties, implies a new Fock space estimate. We also show that for an interaction potential $v(x)= \\epsilon \\chi(x) |x|^{-1}$, where $\\epsilon$ is sufficiently small and $\\chi \\in C_0^{\\infty}$, our program can be easily implemented locally in time. We leave global in time issues, more singular potentials and sophisticated estimates for a subsequent part (part II) of this paper.

  7. Strong-field-approximation theory of high-order harmonic generation by polyatomic molecules

    Science.gov (United States)

    Odžak, S.; Hasović, E.; Milošević, D. B.

    2016-04-01

    A theory of high-order harmonic generation by arbitrary polyatomic molecules is introduced. A polyatomic molecule is modeled by an (N +1 ) -particle system, which consists of N heavy atomic (ionic) centers and an electron. After the separation of the center-of-mass coordinate, the dynamics of this system is reduced to the relative electronic and nuclear coordinates. Various versions (with or without the dressing of the initial and/or final molecular state) of the molecular strong-field approximation are introduced. For neutral polyatomic molecules the derived expression for the T -matrix element takes a simple form. The interference minima in the harmonic spectrum are explained as a multiple-slit type of interference. This is illustrated by numerical examples for the ozone (O3) and carbon dioxide (CO2) molecules.

  8. Mean-Field Theory of Intra-Molecular Charge Ordering in (TTM--TTP)I3

    Science.gov (United States)

    Omori, Yukiko; Tsuchiizu, Masahisa; Suzumura, Yoshikazu

    2011-02-01

    We examine an intra-molecular charge-ordered (ICO) state in the multi-orbital molecular compound (TTM--TTP)I3 on the basis of an effective two-orbital model derived from ab initio calculations. Representing the model in terms of the fragment molecular-orbital (MO) picture, the ICO state is described as the charge disproportionation on the left and right fragment MOs. By applying the mean-field theory, the phase diagram of the ground state is obtained as a function of the inter-molecular Coulomb repulsion and the intra-molecular transfer integral. The ICO state is stabilized by large inter-fragment Coulomb interactions, and the small intra-molecular transfer energy between two fragment MOs. Furthermore, we examine the finite-temperature phase diagram. The relevance to the experimental observations in the molecular compound of (TTM--TTP)I3 is also discussed.

  9. On the covariant formalism of the effective field theory of gravity and leading order corrections

    DEFF Research Database (Denmark)

    Codello, Alessandro; Jain, Rajeev Kumar

    2016-01-01

    We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well...... as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology...... on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime....

  10. On the covariant formalism of the effective field theory of gravity and leading order corrections

    Science.gov (United States)

    Codello, Alessandro; Jain, Rajeev Kumar

    2016-11-01

    We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime.

  11. Entanglement of Three Atoms Induced by a Coherent Field

    Institute of Scientific and Technical Information of China (English)

    WANG Xiu-Wu; CAI Jin-Fang

    2006-01-01

    We calculate the concurrence and spin squeezing parameter of three atoms induced by a coherent field.It shows that when the mean numbers of photon of the field is very small, concurrence exhibits a certain kind of approximative periodic vibration. With the increase of the mean numbers of photon, its periodicity will be interrupted.As for the relationship between the concurrence and spin squeezing, numeric result shows that under Dick model, spin squeezing serves as a sufficient but not necessary condition for concurrence.

  12. Field induced spin chirality and chirality switching in magnetic multilayers

    Science.gov (United States)

    Tartakovskaya, Elena V.

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.

  13. Calibration of aero-structural reduced order models using full-field experimental measurements

    Science.gov (United States)

    Perez, R.; Bartram, G.; Beberniss, T.; Wiebe, R.; Spottswood, S. M.

    2017-03-01

    The structural response of hypersonic aircraft panels is a multi-disciplinary problem, where the nonlinear structural dynamics, aerodynamics, and heat transfer models are coupled. A clear understanding of the impact of high-speed flow effects on the structural response, and the potential influence of the structure on the local environment, is needed in order to prevent the design of overly-conservative structures, a common problem in past hypersonic programs. The current work investigates these challenges from a structures perspective. To this end, the first part of this investigation looks at the modeling of the response of a rectangular panel to an external heating source (thermo-structural coupling) where the temperature effect on the structure is obtained from forward looking infrared (FLIR) measurements and the displacement via 3D-digital image correlation (DIC). The second part of the study uses data from a previous series of wind-tunnel experiments, performed to investigate the response of a compliant panel to the effects of high-speed flow, to train a pressure surrogate model. In this case, the panel aero-loading is obtained from fast-response pressure sensitive paint (PSP) measurements, both directly and from the pressure surrogate model. The result of this investigation is the use of full-field experimental measurements to update the structural model and train a computational efficient model of the loading environment. The use of reduced order models, informed by these full-field physical measurements, is a significant step toward the development of accurate simulation models of complex structures that are computationally tractable.

  14. Surface induced ordering of micelles at the solid-liquid interface

    DEFF Research Database (Denmark)

    Gerstenberg, M.C.; Pedersen, J.S.; Smith, G.S.

    1998-01-01

    The surface induced ordering of triblock copolymer micelles in aqueous solution was measured with neutron reflectivity far above the critical micelle concentration. The scattering length density profiles showed a clear indication of ordered layers of micelles perpendicular to a quartz surface....... The structure and interactions of the micelles were modeled in detail. The convolution of the center distribution of the micelles, obtained from Monte Carlo simulations of hard spheres at a hard wall, and the projected density of the micelle showed excellent agreement with the experimental profiles. [S1063-651X...

  15. Electromagnetic superconductivity of vacuum induced by strong magnetic field

    CERN Document Server

    Chernodub, M N

    2012-01-01

    The quantum vacuum may become an electromagnetic superconductor in the presence of a strong external magnetic field of the order of 10^{16} Tesla. The magnetic field of the required strength (and even stronger) is expected to be generated for a short time in ultraperipheral collisions of heavy ions at the Large Hadron Collider. The superconducting properties of the new phase appear as a result of a magnetic-field-assisted condensation of quark-antiquark pairs with quantum numbers of electrically charged rho mesons. We discuss similarities and differences between the suggested superconducting state of the quantum vacuum, a conventional superconductivity and the Schwinger pair creation. We argue qualitatively and quantitatively why the superconducting state should be a natural ground state of the vacuum at the sufficiently strong magnetic field. We demonstrate the existence of the superconducting phase using both the Nambu-Jona-Lasinio model and an effective bosonic model based on the vector meson dominance (th...

  16. Blast-induced electromagnetic fields in the brain from bone piezoelectricity.

    Science.gov (United States)

    Lee, Ka Yan Karen; Nyein, Michelle K; Moore, David F; Joannopoulos, J D; Socrate, Simona; Imholt, Timothy; Radovitzky, Raul; Johnson, Steven G

    2011-01-01

    In this paper, we show that bone piezoelectricity-a phenomenon in which bone polarizes electrically in response to an applied mechanical stress and produces a short-range electric field-may be a source of intense blast-induced electric fields in the brain, with magnitudes and timescales comparable to fields with known neurological effects. We compute the induced charge density in the skull from stress data on the skull from a finite-element full-head model simulation of a typical IED-scale blast wave incident on an unhelmeted human head as well as a human head protected by a kevlar helmet, and estimate the resulting electric fields in the brain in both cases to be on the order of 10 V/m in millisecond pulses. These fields are more than 10 times stronger than the IEEE safety guidelines for controlled environments (IEEE Standards Coordinating Committee 28, 2002) and comparable in strength and timescale to fields from repetitive Transcranial Magnetic Stimulation (rTMS) that are designed to induce neurological effects (Wagner et al., 2006a). They can be easily measured by RF antennas, and may provide the means to design a diagnostic tool that records a quantitative measure of the head's exposure to blast insult.

  17. Induced electric fields and plasmonic interactions between a metallic nanotube and a thin metallic film

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We have numerically simulated the induced electric fields and the plasmonic interactions of a metallic nanotube near a thin metallic film. Our study shows that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube as well as the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. The enhancement of the induced electric field of this system reaches as high as 10 4 orders of magnitude and its field distribution is characterized by waveguide-mode resonance. The report proposes that these phenomena can be applied to designing surface enhanced spectroscopies such as surface enhanced Raman spectroscopy for efficient chemical and biological sensing.

  18. Impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors

    Science.gov (United States)

    Guo, Yao-Wu; Li, Wei; Chen, Yan

    2017-10-01

    Both impurity- and magnetic-field-induced quasiparticle states in chiral p-wave superconductors are investigated theoretically by solving the Bogoliubov-de Gennes equations self-consistently. At the strong scattering limit, we find that a universal state bound to the impurity can be induced for both a single nonmagnetic impurity and a single magnetic impurity. Furthermore, we find that different chiral order parameters and the corresponding supercurrents have uniform distributions around linear impurities. Calculations of the local density of states in the presence of an external magnetic field show that the intensity peak of the zero-energy Majorana mode in the vortex core can be enhanced dramatically by tuning the strength of the external magnetic field or pairing interaction.

  19. Adjoint based data assimilation for phase field model using second order information of a posterior distribution

    Science.gov (United States)

    Ito, Shin-Ichi; Nagao, Hiromichi; Yamanaka, Akinori; Tsukada, Yuhki; Koyama, Toshiyuki; Inoue, Junya

    Phase field (PF) method, which phenomenologically describes dynamics of microstructure evolutions during solidification and phase transformation, has progressed in the fields of hydromechanics and materials engineering. How to determine, based on observation data, an initial state and model parameters involved in a PF model is one of important issues since previous estimation methods require too much computational cost. We propose data assimilation (DA), which enables us to estimate the parameters and states by integrating the PF model and observation data on the basis of the Bayesian statistics. The adjoint method implemented on DA not only finds an optimum solution by maximizing a posterior distribution but also evaluates the uncertainty in the estimations by utilizing the second order information of the posterior distribution. We carried out an estimation test using synthetic data generated by the two-dimensional Kobayashi's PF model. The proposed method is confirmed to reproduce the true initial state and model parameters we assume in advance, and simultaneously estimate their uncertainties due to quality and quantity of the data. This result indicates that the proposed method is capable of suggesting the experimental design to achieve the required accuracy.

  20. Invariant domain watermarking using heaviside function of order alpha and fractional Gaussian field.

    Science.gov (United States)

    Abbasi, Almas; Woo, Chaw Seng; Ibrahim, Rabha Waell; Islam, Saeed

    2015-01-01

    Digital image watermarking is an important technique for the authentication of multimedia content and copyright protection. Conventional digital image watermarking techniques are often vulnerable to geometric distortions such as Rotation, Scaling, and Translation (RST). These distortions desynchronize the watermark information embedded in an image and thus disable watermark detection. To solve this problem, we propose an RST invariant domain watermarking technique based on fractional calculus. We have constructed a domain using Heaviside function of order alpha (HFOA). The HFOA models the signal as a polynomial for watermark embedding. The watermark is embedded in all the coefficients of the image. We have also constructed a fractional variance formula using fractional Gaussian field. A cross correlation method based on the fractional Gaussian field is used for watermark detection. Furthermore the proposed method enables blind watermark detection where the original image is not required during the watermark detection thereby making it more practical than non-blind watermarking techniques. Experimental results confirmed that the proposed technique has a high level of robustness.

  1. A field methodology for quantifying phosphorus transfer and delivery to streams in first order agricultural catchments

    Science.gov (United States)

    Deasy, C.; Heathwaite, A. L.; Brazier, R. E.

    2008-02-01

    SummaryAn understanding of the relative importance of different hydrological pathways in phosphorus delivery from land to water is currently constrained by a lack of appropriate methods available to quantify the delivery process. New monitoring tools are needed which will provide a framework for understanding phosphorus (P) transfer and delivery at a range of scales in agricultural catchments. A field methodology incorporating the techniques of event-based, on-site observation and sampling within a flexible, non-plot based structure is described and applied to a first order stream catchment in Southern England, UK. The results show that P transfers to the stream reach monitored were dominated by inputs from one field drain, and that overland flow inputs, despite being directly connected to the stream and containing higher P concentrations (maximum 3708 μg l -1), contributed less to the stream P flux. The processes of P transfer and delivery to the stream were complex, changing both within flow pathways and temporally over an event.

  2. Fifth-order field aberration coefficients for an optical surface of rotational symmetry.

    Science.gov (United States)

    Gaj, M

    1971-07-01

    The approximate formulas for the principal ray parameters, such as directional cosines and heights of incidence, as well as for the paraxial sagittal quantities h(s) and H (s) have been expressed by paraxial quantities and Seidel aberrations to fifth-order accuracy. On the basis of these relations an expression for the sagittal radius of curvature r(s), (for a given y ) has been obtained. These quantities are used to derive fifth-order field aberration coefficients for arbitrary surfaces of rotational symmetry by using the wave aberration formula for sagittal focus {M. Gaj, Opt. Spectrosk. 21, 373 (1966) [Opt. Spectrosc. 21, 209 (1966)]}. The resulting expression has four terms. The first one depends only on asphericity and tends to equal zero when the surface becomes spherical. The second is a disturbance term and disappears in the Seidel region. The third and fourth terms may be treated as a generalization of the Petzval curvature and of the Seidel astigmatism, respectively. The limits of the terms, when h tends to zero, has been examined.

  3. Nuclear matter fourth-order symmetry energy in relativistic mean field models

    CERN Document Server

    Cai, Bao-Jun

    2011-01-01

    Within the nonlinear relativistic mean field model, we derive the analytical expression of the nuclear matter fourth-order symmetry energy $E_{4}(\\rho)$. Our results show that the value of $E_{4}(\\rho)$ at normal nuclear matter density $\\rho_{0}$ is generally less than 1 MeV, confirming the empirical parabolic approximation to the equation of state for asymmetric nuclear matter at $\\rho_{0}$. On the other hand, we find that the $E_{4}(\\rho)$ may become nonnegligible at high densities. Furthermore, the analytical form of the $E_{4}(\\rho)$ provides the possibility to study the higher-order effects on the isobaric incompressibility of asymmetric nuclear matter, i.e., $K_{\\mathrm{sat}}(\\delta)=K_{0}+K_{\\mathrm{{sat},2}}\\delta ^{2}+K_{\\mathrm{{sat},4}}\\delta ^{4}+\\mathcal{O}(\\delta ^{6})$ where $\\delta =(\\rho_{n}-\\rho_{p})/\\rho $ is the isospin asymmetry, and we find that the value of $K_{\\mathrm{{sat},4}}$ is generally comparable with that of the $K_{\\mathrm{{sat},2}}$. In addition, we study the effects of the $E...

  4. Properties of Lithium-11 and Carbon-22 at leading order in halo effective field theory

    Directory of Open Access Journals (Sweden)

    Acharya Bijaya

    2016-01-01

    Full Text Available We study the 11Li and 22C nuclei at leading order (LO in halo effective field theory (Halo EFT. Using the value of the 22C rms matter radius deduced in Ref. [1] as an input in a LO calculation, we simultaneously constrain the values of the two-neutron (2n separation energy of 22C and the virtual-state energy of the 20C−neutron system (hereafter denoted 21C. The 1−σ uncertainty of the input rms matter radius datum, along with the theory error estimated from the anticipated size of the higher-order terms in the Halo EFT expansion, gives an upper bound of about 100 keV for the 2n separation energy. We also study the electric dipole excitation of 2n halo nuclei to a continuum state of two neutrons and the core at LO in Halo EFT. We first compare our results with the 11Li data from a Coulomb dissociation experiment and obtain good agreement within the theoretical uncertainty of a LO calculation. We then obtain the low-energy spectrum of B(E1 of this transition at several different values of the 2n separation energy of 22C and the virtual-state energy of 21C. Our predictions can be compared to the outcome of an ongoing experiment on the Coulomb dissociation of 22C to obtain tighter constraints on the two- and three-body energies in the 22C system.

  5. Field-induced stacking transition of biofunctionalized trilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Masato Nakano, C. [Flintridge Preparatory School, La Canada, California 91011 (United States); Sajib, Md Symon Jahan; Samieegohar, Mohammadreza; Wei, Tao [Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710 (United States)

    2016-02-01

    Trilayer graphene (TLG) is attracting a lot of attention as their stacking structures (i.e., rhombohedral vs. Bernal) drastically affect electronic and optical properties. Based on full-atom molecular dynamics simulations, we here predict electric field-induced rhombohedral-to-Bernal transition of TLG tethered with proteins. Furthermore, our simulations show that protein's electrophoretic mobility and diffusivity are enhanced on TLG surface. This phenomenon of controllable TLG stacking transition will contribute to various applications including biosensing.

  6. Chemically induced electric field: flat band potential engineering

    Science.gov (United States)

    Bak, T.; Guo, Z.; Li, W.; Atanacio, A. J.; Nowotny, J.

    2012-10-01

    The present work considers engineering of the flat band potential, FBP, of metal oxides in a controlled manner. The aim is to minimise the energy losses related to recombination. The related experimental approaches include imposition of a chemically-induced electric field using the phenomena of segregation, diffusion and the formation of multilayer systems. This paper considers several basic phenomena that allow the modification of the surface charge and the space charge at the gas/solid and solid/liquid interfaces.

  7. Induced Unbalanced Linguistic Ordered Weighted Average and Its Application in Multiperson Decision Making

    Directory of Open Access Journals (Sweden)

    Lucas Marin

    2014-01-01

    Full Text Available Linguistic variables are very useful to evaluate alternatives in decision making problems because they provide a vocabulary in natural language rather than numbers. Some aggregation operators for linguistic variables force the use of a symmetric and uniformly distributed set of terms. The need to relax these conditions has recently been posited. This paper presents the induced unbalanced linguistic ordered weighted average (IULOWA operator. This operator can deal with a set of unbalanced linguistic terms that are represented using fuzzy sets. We propose a new order-inducing criterion based on the specificity and fuzziness of the linguistic terms. Different relevancies are given to the fuzzy values according to their uncertainty degree. To illustrate the behaviour of the precision-based IULOWA operator, we present an environmental assessment case study in which a multiperson multicriteria decision making model is applied.

  8. Inducing Order from Disordered Copolymers: On Demand Generation of Triblock Morphologies Including Networks

    Energy Technology Data Exchange (ETDEWEB)

    Tureau, Maëva S.; Kuan, Wei-Fan; Rong, Lixia; Hsiao, Benjamin S.; Epps, III, Thomas H. (Delaware); (Buffalo)

    2015-10-15

    Disordered block copolymers are generally impractical in nanopatterning applications due to their inability to self-assemble into well-defined nanostructures. However, inducing order in low molecular weight disordered systems permits the design of periodic structures with smaller characteristic sizes. Here, we have induced nanoscale phase separation from disordered triblock copolymer melts to form well-ordered lamellae, hexagonally packed cylinders, and a triply periodic gyroid network structure, using a copolymer/homopolymer blending approach, which incorporates constituent homopolymers into selective block domains. This versatile blending approach allows one to precisely target multiple nanostructures from a single disordered material and can be applied to a wide variety of triblock copolymer systems for nanotemplating and nanoscale separation applications requiring nanoscale feature sizes and/or high areal feature densities.

  9. Magnetic Order in Ce0.95Nd0.05CoIn5: The Q-Phase at Zero Magnetic Field

    Science.gov (United States)

    Raymond, Stéphane; Ramos, Scheilla M.; Aoki, Dai; Knebel, Georg; Mineev, Vladimir P.; Lapertot, Gérard

    2014-01-01

    We report neutron scattering experiment results revealing the nature of the magnetic order occurring in the heavy fermion superconductor Ce0.95Nd0.05CoIn5. In this system, an antiferromagnetic state is stabilized at a temperature below the superconducting transition one. We evidence that it is an incommensurate order and its propagation vector is found to be identical to that of the magnetic field induced antiferromagnetic order occurring in the stoichiometric superconductor CeCoIn5, the so-called Q-phase. The commonality between these two cases suggests that d-wave superconductivity is playing a key role for the formation of this kind of magnetic order. The proposed mechanism is the enhancement of the nesting condition by an order parameter with nodes in the nesting area.

  10. High-order squeezing of the quantum electromagnetic field and the generalized uncertainty relations in two-mode squeezed states

    Science.gov (United States)

    Li, Xi-Zeng; Su, Bao-Xia

    1994-01-01

    It is found that two-mode output quantum electromagnetic field in two-mode squeezed states exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations are also presented for the first time. The concept of higher-order squeezing of the single-mode quantum electromagnetic field was first introduced and applied to several processes by Hong and Mandel in 1985. Lately Li Xizeng and Shan Ying have calculated the higher-order squeezing in the process of degenerate four-wave mixing and presented the higher-order uncertainty relations of the fields in single-mode squeezed states. In this paper we generalize the above work to the higher-order squeezing in two-mode squeezed states. The generalized uncertainty relations are also presented for the first time.

  11. Validation and application of an high-order spectral difference method for flow induced noise simulation

    KAUST Repository

    Parsani, Matteo

    2011-09-01

    The main goal of this paper is to develop an efficient numerical algorithm to compute the radiated far field noise provided by an unsteady flow field from bodies in arbitrary motion. The method computes a turbulent flow field in the near fields using a high-order spectral difference method coupled with large-eddy simulation approach. The unsteady equations are solved by advancing in time using a second-order backward difference formulae scheme. The nonlinear algebraic system arising from the time discretization is solved with the nonlinear lowerupper symmetric GaussSeidel algorithm. In the second step, the method calculates the far field sound pressure based on the acoustic source information provided by the first step simulation. The method is based on the Ffowcs WilliamsHawkings approach, which provides noise contributions for monopole, dipole and quadrupole acoustic sources. This paper will focus on the validation and assessment of this hybrid approach using different test cases. The test cases used are: a laminar flow over a two-dimensional (2D) open cavity at Re = 1.5 × 10 3 and M = 0.15 and a laminar flow past a 2D square cylinder at Re = 200 and M = 0.5. In order to show the application of the numerical method in industrial cases and to assess its capability for sound field simulation, a three-dimensional turbulent flow in a muffler at Re = 4.665 × 10 4 and M = 0.05 has been chosen as a third test case. The flow results show good agreement with numerical and experimental reference solutions. Comparison of the computed noise results with those of reference solutions also shows that the numerical approach predicts noise accurately. © 2011 IMACS.

  12. H2 O2-induced higher order chromatin degradation: A novel mechanism of oxidative genotoxicity

    Indian Academy of Sciences (India)

    Gregory W Konat

    2003-02-01

    The genotoxicity of reactive oxygen species (ROS) is well established. The underlying mechanism involves oxidation of DNA by ROS. However, we have recently shown that hydrogen peroxide (H2O2), the major mediator of oxidative stress, can also cause genomic damage indirectly. Thus, H2O2 at pathologically relevant concentrations rapidly induces higher order chromatin degradation (HOCD), i.e. enzymatic excision of chromatin loops and their oligomers at matrix-attachment regions. The activation of endonuclease that catalyzes HOCD is a signalling event triggered specifically by H2O2. The activation is not mediated by an influx of calcium ions, but resting concentrations of intracellular calcium ions are required for the maintenance of the endonuclease in an active form. Although H2O2-induced HOCD can efficiently dismantle the genome leading to cell death, under sublethal oxidative stress conditions H2O2-induced HOCD may be the major source of somatic mutations.

  13. 二阶张量场可视化研究%The Research on Visualization of Second Order Tensor Fields

    Institute of Scientific and Technical Information of China (English)

    李海生; 杨钦; 陈其明

    2003-01-01

    Second-order tensors are widely existed in engineering,physical science and biomechanics. Examples arestresses and strains in solids and velocity gradients in fluid flows. This paper takes the Boussinesq' s problem as an ex-ample which is typical in Elasticity Mechanics ,and visualizes the second-order real symmetric tensor fields by ellipsoidicons and hyperStreamlines. The results are reasonable. The visualization methods adopted in this paper are also suit-able for other second-order symmetric tensor fields such as electromagnetic field.

  14. Cascade of magnetic field induced spin transitions in LaCoO3.

    Science.gov (United States)

    Altarawneh, M M; Chern, G-W; Harrison, N; Batista, C D; Uchida, A; Jaime, M; Rickel, D G; Crooker, S A; Mielke, C H; Betts, J B; Mitchell, J F; Hoch, M J R

    2012-07-20

    We present magnetization and magnetostriction studies of LaCoO3 in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co3+ ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co3+ ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.

  15. Plasma transport induced by the stochastic magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Tetsuyuki [Interdisciplinary Graduate School of Engineering Sciences, Kyushu Univ., Kasuga, Fukuoka (Japan); Itoh, Sanae-I.; Yagi, Masatoshi

    1998-10-01

    The anomalous plasma transport induced by the stochastic magnetic field is studied to understand the disruption phenomena in the tokamak plasma. At first, the transport matrix which indicate the plasma transport in the stochastic magnetic field is formulated. For the formulation, the quasi-linear approximation for the diffusivity of the stochastic magnetic field is used and the shifted Maxwellian is assumed to the particle distribution. Using this transport matrix the radial electric field formation, which is generated by the ambipolar condition, and the associated temperature profile is obtained. The temperature profile in the stochastic magnetic field becomes flat because of the rapid temperature diffusion. Next the temperature crash, i.e., the sawtooth oscillation and the giant ELM, is analyzed using the turbulence-turbulence transition model, which describes the transition between the state of the electrostatic turbulence and that of the electromagnetic turbulence. This transition has a hysteresis characteristics. When the state changes to the electromagnetic mode, the stochastic magnetic field appears and the temperature transport is enhanced. This transition model is included in the 1-D transport equation. To calculate this transport equation numerically the crash of the temperature profile and the propagation of the crash front (avalanche) are realized by this model. The collapse without a precursor oscillation is revealed. (author)

  16. Solar wind induced magnetic field around the unmagnetized Earth

    CERN Document Server

    Birk, G T; Konz, C

    2004-01-01

    The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth's surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These polarity reversals correspond to drastic breakdowns of the dynamo action. The question arises what the consequences for the Earth's atmosphere, climate, and, in particular, biosphere are. It is shown by kinematic estimates and three-dimensional plasma-neutral gas simulations that the solar wind can induce very fast a magnetic field in the previously completely unmagnetized Earth's ionosphere that is strong enough to protect Earth from cosmic radiations comparable to the case of an intact magnetic dynamo.

  17. Field induced phase transition in the few photon regime

    CERN Document Server

    Panferov, A D; Titov, A I; Kaempfer, B; Otto, A; Blaschke, D B; Juchnowski, L

    2016-01-01

    Some features of the field induced phase transition accompanied by the vacuum creation of an electron-positron plasma (EPP) in strong time-dependent electric fields have been discussed in the work [1] in the domain of the tunneling mechanism ($\\omega \\ll m$, where $\\omega$ is the characteristic frequency of the external field and $m$ is the electron mass). In the present contribution the features of the this process will be considered in the few photon domain where $\\omega \\sim m$. We observe a narrowing of the transient domain of the fast oscillations and, mainly, a considerable growth of the effectiveness of the EPP production. Under these circumstances, we see an increase of the effectiveness of the EPP creation in the particular case of a bifrequent excitation, where both mechanisms (tunneling and few photon) act simultaneously [2,3].

  18. Field induced heliconical structure of cholesteric liquid crystal

    Science.gov (United States)

    Lavrentovich, Oleg D.; Shiyanovsii, Sergij V.; Xiang, Jie; Kim, Young-Ki

    2017-06-27

    A diffraction grating comprises a liquid crystal (LC) cell configured to apply an electric field through a cholesteric LC material that induces the cholesteric LC material into a heliconical state with an oblique helicoid director. The applied electric field produces diffracted light from the cholesteric LC material within the visible, infrared or ultraviolet. The axis of the heliconical state is in the plane of the liquid crystal cell or perpendicular to the plane, depending on the application. A color tuning device operates with a similar heliconical state liquid crystal material but with the heliconical director axis oriented perpendicular to the plane of the cell. A power generator varies the strength of the applied electric field to adjust the wavelength of light reflected from the cholesteric liquid crystal material within the visible, infrared or ultraviolet.

  19. The most general second-order field equations of bi-scalar-tensor theory in four dimensions

    Science.gov (United States)

    Ohashi, Seiju; Tanahashi, Norihiro; Kobayashi, Tsutomu; Yamaguchi, Masahide

    2015-07-01

    The Horndeski theory is known as the most general scalar-tensor theory with second-order field equations. In this paper, we explore the bi-scalar extension of the Horndeski theory. Following Horndeski's approach, we determine all the possible terms appearing in the second-order field equations of the bi-scalar-tensor theory. We compare the field equations with those of the generalized multi-Galileons, and confirm that our theory contains new terms that are not included in the latter theory. We also discuss the construction of the Lagrangian leading to our most general field equations.

  20. The most general second-order field equations of bi-scalar-tensor theory in four dimensions

    CERN Document Server

    Ohashi, Seiju; Kobayashi, Tsutomu; Yamaguchi, Masahide

    2015-01-01

    The Horndeski theory is known as the most general scalar-tensor theory with second-order field equations. In this paper, we explore the bi-scalar extension of the Horndeski theory. Following Horndeski's approach, we determine all the possible terms appearing in the second-order field equations of the bi-scalar-tensor theory. We compare the field equations with those of the generalized multi-Galileons, and confirm that our theory contains new terms that are not included in the latter theory. We also discuss the construction of the Lagrangian leading to our most general field equations.

  1. First-order Freedericksz transition at the threshold point for weak anchoring nematic liquid crystal cell under external electric and magnetic fields

    Institute of Scientific and Technical Information of China (English)

    关荣华; 杨国琛

    2003-01-01

    Based on the modified formula of Rapini-Papoular, the equilibrium equation and boundary condition of the director have been obtained and the behaviour of the Freedericksz transition at the threshold point has been studied for weak-anchoring nematic liquid crystal cells under external electric and magnetic fields with the methods of analytical derivation and numerical calculation. The results show that, except for the usual second-order transition, the first-order Freedericksz transition can also be induced by a suitable surface anchoring technique for the liquid crystal cell given in the paper. The conditions for the existence of the first-order Freedericksz transition are obtained. They are related to the material elastic coefficient k11, k33 the thickness of the liquid crystal cell, the external electric field and the strength of surface anchoring, etc.

  2. Third-order transfer matrices calculated for an electrostatic toroidal sector condenser including fringing-field effects

    Energy Technology Data Exchange (ETDEWEB)

    Mordik, S.N. E-mail: iapuas@gluk.apc.org; Ponomarev, A.G

    2002-03-21

    The third-order transfer matrices are calculated for an electrostatic toroidal sector condenser using a rigorously conserved matrix method that implies the conservation of the beam phase volume at each step in the calculations. The transfer matrices (matrizants) obtained, include the fringing-field effect due to the stray fields. In the case of a rectangular distribution of the field components along the optical axis, the analytical expressions for all aberration coefficients, including the dispersion ones, are derived accurate to the third-order terms. In simulations of real fields with the stray field width other than zero, a smooth distribution of the field components is used for which similar aberration coefficients were calculated by means of the conserved numerical method . It has been found that for a smooth model, as the stray field width tends to zero, the aberration coefficients approach the corresponding aberration values in the rectangular model.

  3. Third-order transfer matrices calculated for an electrostatic toroidal sector condenser including fringing-field effects

    CERN Document Server

    Mordik, S N

    2002-01-01

    The third-order transfer matrices are calculated for an electrostatic toroidal sector condenser using a rigorously conserved matrix method that implies the conservation of the beam phase volume at each step in the calculations. The transfer matrices (matrizants) obtained, include the fringing-field effect due to the stray fields. In the case of a rectangular distribution of the field components along the optical axis, the analytical expressions for all aberration coefficients, including the dispersion ones, are derived accurate to the third-order terms. In simulations of real fields with the stray field width other than zero, a smooth distribution of the field components is used for which similar aberration coefficients were calculated by means of the conserved numerical method . It has been found that for a smooth model, as the stray field width tends to zero, the aberration coefficients approach the corresponding aberration values in the rectangular model.

  4. Inhomogeneous field induced magnetoelectric effect in Mott insulators

    Energy Technology Data Exchange (ETDEWEB)

    Boulaevskii, Lev N [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

    2008-01-01

    We consider a Mott insulator like HoMnO{sub 3} whose magnetic lattice is geometrically frustrated and comprises a 3D array of triangular layers with magnetic moments ordered in a 120{sup o} structure. We show that the effect of a uniform magnetic field gradient, {gradient}H, is to redistribute the electronic charge of the magnetically ordered phase leading to a unfirom electric field gradient. The resulting voltage difference between the crystal edges is proportional to the square of the crystal thickness, or inter-edge distance, L. It can reach values of several volts for |{gradient}H| {approx} 0.01 T/cm and L {approx_equal} 1mm, as long as the crystal is free of antiferromagnetic domain walls.

  5. Curvature-induced cross-hatched order in two-dimensional semiflexible polymer networks

    CERN Document Server

    Vrusch, Cyril

    2015-01-01

    A recurring motif in the organization of biological tissues are networks of long, fibrillar protein strands effectively confined to cylindrical surfaces. Often, the fibers in such curved, quasi-2D geometries adopt a characteristic order: the fibers wrap around the central axis at an angle which varies with radius and, in several cases, is strongly bimodally distributed. In this Letter, we investigate the general problem of a 2D crosslinked network of semiflexible fibers confined to a cylindrical substrate, and demonstrate that in such systems the trade-off between bending and stretching energies, very generically, gives rise to cross-hatched order. We discuss its general dependency on the radius of the confining cylinder, and present an intuitive model that illustrates the basic physical principle of curvature-induced order. Our findings shed new light on the potential origin of some curiously universal fiber orientational distributions in tissue biology, and suggests novel ways in which synthetic polymeric s...

  6. Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

    Science.gov (United States)

    Huang, Haihong; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng

    2016-10-01

    Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, Hp(y), induced by applied magnetic fields with different intensities measured through the tensile tests. The Hp(y), its slope coefficient KS and maximum gradient Kmax changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of Hp(y) and its slope coefficient KS increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, Hp(y) and KS reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of Hp(y) instead of changing the signal curve‧s profile; and the magnitude of Hp(y), KS, Kmax and the change rate of KS increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials.

  7. Coupling-induced ferromagnetic transitions in ferroelectromagnets of weak antiferromagnetic order

    Institute of Scientific and Technical Information of China (English)

    LI Qichang; LIU Junming

    2006-01-01

    A Monte-Carlo simulation on phase transitions in ferroelectromagnets (FEMs) in which a weak antiferromagnetic ordering occurs at the Neel point TN far below the ferroelectric ordering point TE was performed. It is revealed that an intrinsic coupling between spins and electric-dipoles ( mp -coupling) does result in a weak ferromagnetic transition from the paramagnetic state at a temperature far above TN, as long as the coupling is strong enough. The magnetoelectric properties as a function of temperature, mp -coupling strength and external electric and magnetic fields were investigated. A mean-field calculation based on the Heisenberg model was performed and a rough consistency between the simulated and calculated ferromagnetic transitions was shown.

  8. Misalignment Induced Aberrations of JWST: Isolating Low Order Primary Figure Residuals from Misalignment

    Science.gov (United States)

    2010-06-07

    7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Iris AO, Inc. 2680 Bancroft Way Berkeley, CA 04704 8...aberration theory. 15. SUBJECT TERMS Nodal Aberration Theory, James Webb Space Telescope, Misalignment, Segmented , Mirror, Adaptive Optics, Coma...NOT field quadratic K. P. Thompson, “Description of the third-order optical aberrations of near-circular pupil optical systems without symmetry,” J

  9. Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Haihong, E-mail: huanghaihong@hfut.edu.cn; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng

    2016-10-15

    Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H{sub p}(y), induced by applied magnetic fields with different intensities measured through the tensile tests. The H{sub p}(y), its slope coefficient K{sub S} and maximum gradient K{sub max} changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H{sub p}(y) and its slope coefficient K{sub S} increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H{sub p}(y) and K{sub S} reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H{sub p}(y) instead of changing the signal curve′s profile; and the magnitude of H{sub p}(y), K{sub S}, K{sub max} and the change rate of K{sub S} increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials. - Highlights: • We investigated how applied magnetic field and tensile stress impact H{sub p}(y) signals. • Magnitude of H{sub p}(y), K{sub S} and K{sub max} increase with the increase of applied magnetic field. • Both applied magnetic field and tensile stress impact material magnetic permeability. • Applied magnetic field can help to evaluate the stress distribution of components.

  10. Enhancement of Bichromatic High-Order Harmonic Generation by a Strong Laser Field and Its Third Harmonic

    Institute of Scientific and Technical Information of China (English)

    PI Liang-Wen; SHI Ting-Yun; QIAO Hao-Xue

    2006-01-01

    We investigate high-order harmonic generation (HUG) in a linearly polarized bichromatic field composed of a fundamental laser Geld with frequencyωand an additional laser field with frequency 3ω. The numerical results show that it is possible to enhance the intensity of most high harmonics in orders of magnitude. A most striking feature in the enhancement is that the intensity of several special high harmonics is practically impaired as compared with that in the monochromatic case. The qualitative explanation to the great enhancement is that the additional high-frequency field can provide new transition paths for electrons to reach the continuum. The relative phase between the fundamental field and its third harmonic field also affects the intensity of high-order harmonics near the cutoff efficiently.

  11. Pressure-induced superconductivity in a ferromagnet, UGe sub 2 : resistivity measurements in a magnetic field

    CERN Document Server

    Kobayashi, T C; Tateiwa, N; Amaya, K; Haga, Y; Settai, R; Onuki, Y

    2002-01-01

    Electrical resistivity measurements in a magnetic field are carried out on UGe sub 2 which exhibits pressure-induced superconductivity. The superconductivity is observed from 1.06 to 1.44 GPa. In the temperature and field dependences of the resistivity at P > P sub C where the ferromagnetic ordering disappears, it is observed that the application of an external field along the a-axis increases the coefficient A of the Fermi-liquid behaviour (propor to AT sup 2) abruptly - corresponding to the metamagnetic transition. The characteristic enhancement of H sub C sub 2 is reconfirmed for H || a-axis. The upper critical field of H sub C sub 2 is anisotropic: H sub C sub 2 (T) exhibits positive curvature for H || b-axis and H || c-axis.

  12. Unusual dc electric fields induced by a high frequency alternating current in superconducting Nb films under a perpendicular magnetic field

    Science.gov (United States)

    Aliev, F. G.; Levanyuk, A. P.; Villar, R.; Sierra, J. F.; Pryadun, V. V.; Awad, A.; Moshchalkov, V. V.

    2009-06-01

    We report a systematic study of dc electric fields produced by sinusoidal high frequency ac currents in Nb superconducting films subject to a constant magnetic field perpendicular to the film plane. At frequencies in the 100 kHz to MHz range appears a new rectification effect which has not been previously observed at lower frequencies. We have observed the dc electric field generated in this regime in films without intentionally created anisotropic pinning centres, i.e. plain films, both in strip geometry as in cross-shape geometry, and also in films with symmetric periodic pinning centres. The electric field appears in both directions along and transverse to the alternating current and is essentially different at opposite film sides. It depends strongly on the intensity of the magnetic field and may exceed by nearly an order of magnitude the rectified electric fields recently reported at lower frequencies (few kHz) in systems with artificially induced anisotropic vortex pinning. The effect has a non-monotonic dependence on the drive current frequency, being maximum around a few 100 kHz to MHz, and shows a complicated temperature dependence. It is found to be different in long strips and cross shape samples. In the case of films with symmetric periodic pinning centres the rectified voltage shows a lower magnitude than in plain films, and shows an interesting structure when the applied magnetic field crosses the matching fields. We are only able to put forward tentative ideas to explain this phenomenon, which irrespective of its explanation should be taken into account in experimental studies of rectification effects in superconductors.

  13. The particle motion through the fringing field of a toroidal condenser in a third-order approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, B. [Giessen Univ. (Germany). 2. Physikalisches Inst.; Wollnik, H. [Giessen Univ. (Germany). 2. Physikalisches Inst.

    1995-09-01

    The ion trajectories through the extended fringing field of a toroidal condenser are calculated including the effects of curved field boundaries. The optical fringing-field effects are expressed by analytical formulas including fringing-field integrals using the transfer matrix method. These formulas describe in an effective third-order approximation all effects in the plane of deflection as well as in the perpendicular surface to this plane. The obtained expressions are compared to precise numerical ray-tracing calculations through typical field distributions. (orig.).

  14. Higher-Order Squeezing of Quantum Field and the Generalized Uncertainty Relations in Non-Degenerate Four-Wave Mixing

    Science.gov (United States)

    Li, Xi-Zeng; Su, Bao-Xia

    1996-01-01

    It is found that the field of the combined mode of the probe wave and the phase-conjugate wave in the process of non-degenerate four-wave mixing exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations in this process are also presented.

  15. Robust conversion of singlet spin order in coupled spin-1/2 pairs by adiabatically switched RF-fields

    CERN Document Server

    Pravdivtsev, Andrey N; Yurkovskaya, Alexandra V; Vieth, Hans-Martin; Ivanov, Konstantin L

    2016-01-01

    We propose a robust and highly efficient NMR technique to create singlet spin order from longitudinal spin magnetization in coupled spin-1/2 pairs and to perform backward conversion (singlet order)$\\to$magnetization. In this method we exploit adiabatic switching of an RF-field in order to drive transitions between the singlet state and the $T_\\pm$ triplet states of a spin pair under study. We demonstrate that the method works perfectly for both strongly and weakly coupled spin pairs, providing a conversion efficiency between the singlet spin order and magnetization, which is equal to the theoretical maximum. We anticipate that the proposed technique is useful for generating long-lived singlet order, for preserving spin hyperpolarization and for assessing singlet spin order in nearly equivalent spin pairs in specially designed molecules and in low-field NMR studies.

  16. Analysis of pulse broadening induced by the second-order PMD

    Institute of Scientific and Technical Information of China (English)

    Fu Song-Nian; Wu Chong-Qing; Shum Ping

    2005-01-01

    We propose a new conception of depolarization vector to describe the effect of depolarization induced by the second-order polarization mode dispersion (PMD). Deriving the formula of pulse broadening induced by the secondorder PMD, we find that the polarization-dependent chromatic dispersion (PCD) always enhances the pulse broadening.However the depolarization vector decreases the pulse broadening. The pulse broadening is correlated with the bit-rate of a transmission system. By adjusting the directions of the Stokes vector of initial state of polarization, initial firstorder polarization dispersion vector and depolarization vector to be parallel to each other, one can obtain an optimum dispersion compensation.But when the PCD is not equal to zero, the optimum dispersion cannot achieve a complete compensation, and the minimum pulse broadening is equal to σ = ( 2/4) (DCF/T0).

  17. Induced Coherence, Vacuum Fields, and Complementarity in Biphoton Generation

    Science.gov (United States)

    Heuer, A.; Menzel, R.; Milonni, P. W.

    2015-02-01

    It is well established that spontaneous parametric down-conversion with induced coherence across two coupled interferometers results in high-visibility single-photon interference. We describe experiments in which additional photon channels are introduced such that "which-path" information is made possible and the fringe visibility in single-photon interference is reduced in accordance with basic notions of complementarity. However, these additional pathways result in nearly perfect visibility when photons are counted in coincidence. A simplified theoretical model accounts for these observations and attributes them directly to the vacuum fields at the different crystals.

  18. Coherent Population Trapping Induced by Phase Modulated and Fluctuating Fields

    Institute of Scientific and Technical Information of China (English)

    WANG Jian; HU Xiang-Ming

    2007-01-01

    We examine the effects of cross correlated phase fluctuations on the coherent population trapping (CPT) induced by a pair of phase-modulated fields with equal modulation frequencies in a three-level A system. The maximal coherence of -0.5, which appears when CPT occurs for equal modulation indices, is preserved in the presence of the critically cross-correlated fluctuations. Unexpectedly, the non-maximal coherence, which is established when CPT is obtained for different modulation indices, is significantly enhanced due to the critically cross-correlated fluctuations.

  19. Regional cosmic ray induced ionization and geomagnetic field changes

    Directory of Open Access Journals (Sweden)

    G. A. Kovaltsov

    2007-08-01

    Full Text Available Cosmic ray induced ionization (CRII is an important factor of outer space influences on atmospheric properties. Variations of CRII are caused by two different processes – solar activity variations, which modulate the cosmic ray flux in interplanetary space, and changes of the geomagnetic field, which affects the cosmic ray access to Earth. Migration of the geomagnetic dipole axis may greatly alter CRII in some regions on a time scale of centuries and longer. Here we present a study of CRII regional effects of the geomagnetic field changes during the last millennium for two regions: Europe and the Far East. We show that regional effects of the migration of the geomagnetic dipole axis may overcome global changes due to solar activity variations.

  20. Optomechanically induced stochastic resonance and chaos transfer between optical fields

    Science.gov (United States)

    Monifi, Faraz; Zhang, Jing; Özdemir, Şahin Kaya; Peng, Bo; Liu, Yu-Xi; Bo, Fang; Nori, Franco; Yang, Lan

    2016-06-01

    Chaotic dynamics has been reported in many physical systems and has affected almost every field of science. Chaos involves hypersensitivity to the initial conditions of a system and introduces unpredictability into its output. Thus, it is often unwanted. Interestingly, the very same features make chaos a powerful tool to suppress decoherence, achieve secure communication and replace background noise in stochastic resonance—a counterintuitive concept that a system's ability to transfer information can be coherently amplified by adding noise. Here, we report the first demonstration of chaos-induced stochastic resonance in an optomechanical system, as well as the optomechanically mediated chaos transfer between two optical fields such that they follow the same route to chaos. These results will contribute to the understanding of nonlinear phenomena and chaos in optomechanical systems, and may find applications in the chaotic transfer of information and for improving the detection of otherwise undetectable signals in optomechanical systems.

  1. Transformation and Field-Induced Strains in as-Cast Ni-Mn-Ga Alloy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wei-ren; LI Jian-liang; QI Yan; ZHANG Yang-huan; WANG Xin-lin; YU Yuan-jun

    2004-01-01

    The characteristics of the strains induced by transformation and magnetic field in as-cast Ni-Mn-Ga alloy were systematically investigated. It is found that internal stress and texture introduced during casting bring the anisotropy of temperature-induced strains. However, no anisotropy of field-induced strains is induced, and the internal stress and the texture modulate only the temperature dependence of field-induced strains. Large retardance of field-induced strains was observed, which indicates the rearrangement of martensitic variants as a competition process between the stress energy and Zeeman energy. The non-continuous field dependence of strain indicates the unstable microstructure during martensitic transformation.

  2. Non-equilibrium simulations of thermally induced electric fields in water

    CERN Document Server

    Wirnsberger, Peter; Šarić, Anđela; Neumann, Martin; Dellago, Christoph; Frenkel, Daan

    2016-01-01

    Using non-equilibrium molecular dynamics simulations, Bresme and co-workers recently demonstrated that water molecules align in response to an imposed temperature gradient. Employing the Wolf method to truncate the electrostatic interactions, they reported electric fields as high as $3.7\\times10^8~\\text{V/m}$ for a gradient of about $5.2~\\text{K/\\AA}$ [J. Chem. Phys. 139, 014504 (2013)]. Recently, however, Bresme and co-workers [J. Chem. Phys. 143, 036101 (2015)] advocated that the Wolf method overestimates the induced electric field by an order of magnitude. In this work, we investigate how thermally induced fields depend on the underlying treatment of long-ranged interactions. Our key findings are: Firstly, under identical conditions we find the peak field strength to be $2.8\\times 10^7~\\text{V/m}$ and $2.2\\times 10^7~\\text{V/m}$ for Ewald summation and the Wolf method, respectively. Our value for the short-ranged method is therefore an order of magnitude lower than the original value reported by Bresme and...

  3. Influence of thermal agitation on the electric field induced precessional magnetization reversal with perpendicular easy axis

    Directory of Open Access Journals (Sweden)

    Hongguang Cheng

    2013-12-01

    Full Text Available We investigated the influence of thermal agitation on the electric field induced precessional magnetization switching probability with perpendicular easy axis by solving the Fokker-Planck equation numerically with finite difference method. The calculated results show that the thermal agitation during the reversal process crucially influences the switching probability. The switching probability can be achieved is only determined by the thermal stability factor Δ of the free layer, it is independent on the device dimension, which is important for the high density device application. Ultra-low error rate down to the order of 10−9 can be achieved for the device of thermal stability factor Δ of 40. Low damping factor α material should be used for the free layer for high reliability device applications. These results exhibit potential of electric field induced precessional magnetization switching with perpendicular easy axis for ultra-low power, high speed and high density magnetic random access memory (MRAM applications.

  4. Influence of thermal agitation on the electric field induced precessional magnetization reversal with perpendicular easy axis

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Hongguang, E-mail: chenghg7932@gmail.com; Deng, Ning [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

    2013-12-15

    We investigated the influence of thermal agitation on the electric field induced precessional magnetization switching probability with perpendicular easy axis by solving the Fokker-Planck equation numerically with finite difference method. The calculated results show that the thermal agitation during the reversal process crucially influences the switching probability. The switching probability can be achieved is only determined by the thermal stability factor Δ of the free layer, it is independent on the device dimension, which is important for the high density device application. Ultra-low error rate down to the order of 10{sup −9} can be achieved for the device of thermal stability factor Δ of 40. Low damping factor α material should be used for the free layer for high reliability device applications. These results exhibit potential of electric field induced precessional magnetization switching with perpendicular easy axis for ultra-low power, high speed and high density magnetic random access memory (MRAM) applications.

  5. Dispersion of Electric-Field-Induced Faraday Effect in Magnetoelectric Cr2O3

    Science.gov (United States)

    Wang, Junlei; Binek, Christian

    2016-03-01

    The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η . The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η . The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3 + crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a tabletop setup. The voltage-specific Faraday rotation is independent of the sample thickness, making the method scalable and versatile down to the limit of dielectric breakdown.

  6. Mechanisms of two-color laser-induced field-free molecular orientation.

    Science.gov (United States)

    Spanner, Michael; Patchkovskii, Serguei; Frumker, Eugene; Corkum, Paul

    2012-09-14

    Two mechanisms of two-color (ω+2ω) laser-induced field-free molecular orientation, based on the hyperpolarizability and ionization depletion, are explored and compared. The CO molecule is used as a computational example. While the hyperpolarizability mechanism generates small amounts of orientation at intensities below the ionization threshold, ionization depletion quickly becomes the dominant mechanism as soon as ionizing intensities are reached. Only the ionization mechanism leads to substantial orientation (e.g., on the order of ≳0.1). For intensities typical of laser-induced molecular alignment and orientation experiments, the two mechanisms lead to robust, characteristic timings of the field-free orientation wave-packet revivals relative to the alignment revivals and the revival time. The revival timings can be used to detect the active orientation mechanism experimentally.

  7. Some remarks on real numbers induced by first-order spectra

    DEFF Research Database (Denmark)

    Jakobsen, Sune; Simonsen, Jakob Grue

    2016-01-01

    The spectrum of a first-order sentence is the set of natural numbers occurring as the cardinalities of finite models of the sentence. In a recent survey, Durand et al. introduce a new class of real numbers, the spectral reals, induced by spectra and pose two open problems associated to this class...... may occur, and (iv) every right-computable real number between 0 and 1 occurs as the subword entropy of a spectral real. In addition, Durand et al. note that the set of spectral reals is not closed under addition or multiplication. We extend this result by showing that the class of spectral reals...

  8. Laser-induced micron and submicron ordering effects in quasi-percolated nanostructured silver thin films

    Energy Technology Data Exchange (ETDEWEB)

    Haro-Poniatowski, E; Alonso-Huitron, J C; Acosta-Zepeda, C [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa, Avenida San Rafael Atlixco No. 186 Colonia Vicentina, CP 09340 Mexico DF (Mexico); Acosta-Garcia, M C; Batina, N, E-mail: haro@xanum.uam.m [Departamento de Quimica, Universidad Autonoma Metropolitana Iztapalapa, Avenida San Rafael Atlixco No. 186 Colonia Vicentina, CP 09340 Mexico DF (Mexico)

    2009-09-02

    Quasi-percolated nanostructured silver thin films are used as the starting morphology for inducing simultaneously changes in shape and ordering effects by laser irradiation. The complex fingered nanostructures are transformed into nanospheres which in turn are arranged in micro-circular patterns when irradiated through a pinhole. These transformations are characterized by transmission electron microscopy and atomic force microscopy. The observed effects are explained using Fresnel diffraction theory. Good agreement with the experimental results is obtained. These results suggest that precise patterning engineering can be achieved through control of the spatial parameters such as the pinhole diameter and the distance from the mask to the sample.

  9. Benzene at 1 GHz. Magnetic field-induced fine structure

    Science.gov (United States)

    Heist, L. M.; Poon, C.-D.; Samulski, E. T.; Photinos, D. J.; Jokisaari, J.; Vaara, J.; Emsley, J. W.; Mamone, S.; Lelli, M.

    2015-09-01

    The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1 GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the 13C satellite doublets Δν‧. This difference, Δ(Δν) = Δν‧ - Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the 13C and 2H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.

  10. Enhanced charge stripe order of superconducting La2-xBaxCuO4 in a magnetic field

    Science.gov (United States)

    Hücker, M.; v. Zimmermann, M.; Xu, Z. J.; Wen, J. S.; Gu, G. D.; Tranquada, J. M.

    2013-01-01

    The effect of a magnetic field on the charge stripe order in La2-xBaxCuO4 has been studied by means of high-energy (100 keV) x-ray diffraction for charge carrier concentrations ranging from strongly underdoped to optimally doped. We find that charge stripe order can be significantly enhanced by a magnetic field applied along the c axis, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x=(1)/(8) compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of a magnetic field. The results for La2-xBaxCuO4 resemble recent observations in YBa2Cu3O6+δ and, independent of potential differences in the microscopic origin of charge order in these two compounds, imply a very similar competition with three-dimensionally coherent superconductivity.

  11. Enhanced charge stripe order in superconducting La2-xBaxCuO4 in high magnetic fields

    Science.gov (United States)

    Huecker, M.; Zimmermann, M. V.; Xu, Z. J.; Wen, J. S.; Gu, G. D.; Tranquada, J. M.

    2013-03-01

    There is mounting evidence for a proximity of the superconducting ground state in the cuprates to competing states with static spin and/or charge density modulations. One such competing state is the spin and charge stripe phase in La2-xBaxCuO4. By means of high energy (100 keV) x-ray diffraction we have studied the effect of a high magnetic field (H||c) on the charge stripe order in a broad range of doping (0.095 <= x <= 0.155). We find that the field can significantly enhance the charge stripe order, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x =1/8 compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of the field. The results imply that static stripe order and three-dimensionally coherent superconductivity are competing ground states. The work at Brookhaven was supported by the Office of Basic Energy Sciences, Division of Materials Science and Engineering, U.S. Department of Energy (DOE), under Contract No. DE-AC02-98CH10886.

  12. Vacuum Particle-Antiparticle Creation in Strong Fields as a Field-Induced Phase Transition

    Science.gov (United States)

    Smolyansky, S. A.; Panferov, A. D.; Blaschke, D. B.; Juchnowski, L.; Kämpfer, B.; Otto, A.

    2017-03-01

    We study the special features of vacuum particle creation in an external classical field for two simple external field models in standard QED. Our investigation is based on a kinetic equation that is a nonperturbative consequence of the fundamental QED equations of motion. We identify the special features of system evolution that apply qualitatively also for other systems and are therefore rather general. The common basis for a description of these systems is formed by kinetic equations for vacuum particle creation belonging to the class of integro-differential equations of non-Markovian type with fastly oscillating kernel. This allows us to characterize the processes of this type as belonging to the class of field-induced phase transitions. Examples range from condensed matter physics to cosmology.

  13. Vacuum particle-antiparticle creation in strong fields as a field induced phase transition

    CERN Document Server

    Smolyansky, S A; Blaschke, D B; Juchnowski, L; Kaempfer, B; Otto, A

    2016-01-01

    The features of vacuum particle creation in an external classical field are studied for simplest external field models in $3 + 1$ dimensional QED. The investigation is based on a kinetic equation that is a nonperturbative consequence of the fundamental equations of motion of QED. The observed features of the evolution of the system apply on the qualitative level also for systems of other nature and therefore are rather general. Examples from cosmology and condensed matter physics illustrate this statement. The common basis for the description of these systems are kinetic equations for vacuum particle creation belonging to the class of integro-differential equations of non-Markovian type with fastly oscillating kernel. This allows to characterize processes of this type as belonging to the class of field induced phase transitions.

  14. First and second order numerical methods based on a new convex splitting for phase-field crystal equation

    Science.gov (United States)

    Shin, Jaemin; Lee, Hyun Geun; Lee, June-Yub

    2016-12-01

    The phase-field crystal equation derived from the Swift-Hohenberg energy functional is a sixth order nonlinear equation. We propose numerical methods based on a new convex splitting for the phase-field crystal equation. The first order convex splitting method based on the proposed splitting is unconditionally gradient stable, which means that the discrete energy is non-increasing for any time step. The second order scheme is unconditionally weakly energy stable, which means that the discrete energy is bounded by its initial value for any time step. We prove mass conservation, unique solvability, energy stability, and the order of truncation error for the proposed methods. Numerical experiments are presented to show the accuracy and stability of the proposed splitting methods compared to the existing other splitting methods. Numerical tests indicate that the proposed convex splitting is a good choice for numerical methods of the phase-field crystal equation.

  15. Third-order particle motion through the fringing field of a homogeneous bending magnet

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, B. (2. Physikalisches Inst. der Justus-Liebig-Univ., Giessen (Germany)); Wollnik, H. (2. Physikalisches Inst. der Justus-Liebig-Univ., Giessen (Germany))

    1994-05-01

    The ion trajectories through the extended fringing field of a homogeneous magnet are approximated by analytic formulas including the effects of inclined and curved field boundaries. The results are expressed by transfer matrices. All expressions are compared to numerical integrations through typical field distributions. (orig.)

  16. A convective divertor utilizing a 2nd-order magnetic field null

    Science.gov (United States)

    Rognlien, Thomas

    2014-10-01

    New results motivate a detailed study of a magnetic divertor concept characterized by strong plasma convection near a poloidal magnetic field (Bp) null region. The configuration is that of a near-2nd-order Bp null (Bp ~ Δ r2) , as in a snowflake divertor. The concept has 2 key features: (A) Convection spreads the heat flux between multiple divertor legs and further broadens the heat-flux profile within each leg, thereby greatly reducing target-plate heat loads. (B) The heat flux is further reduced by line radiation in each leg in detachment-like ionization zones. Theory indicates that convective turbulence arises when the poloidal plasma beta, βp = 2μ0nT/B p 2 >> 1 . Measurements in TCV now more fully quantify earlier NSTX and TCV observations of plasma mixing, and related modeling of TCV indicates that strongly enhanced null-region transport is present. Convective mixing provides a stabilizing mechanism to prevent the ionization fronts (hydrogenic and impurity) from collapsing to a highly radiating core MARFE. Also, the radiating zone maps to a very small region at the midplane owing to the very weak Bp in the convective region, thus minimizing its impact on the core plasma. Detailed calculations are reported that combine features A and B noted above. The plasma mixing mechanisms are described together with the corresponding transport model implemented in the 2D UEDGE edge transport code. UEDGE calculations are presented that quantify the roles of mixing, impurity radiation, and detachment stability for a realistic snowflake configuration. Work in collaboration with D.D. Ryutov, S.I. Krasheninnikov, and M.V. Umansky. Performed for the U.S. DoE by LLNS, LLC, LLNL, under Contract DE-AC52-07NA27344.

  17. Ritual orders and ritologiques: a terminological quest for some neglected fields of study

    Directory of Open Access Journals (Sweden)

    Michael Stausberg

    2003-01-01

    Full Text Available The topic presented in this paper lies at the crossroads between ritual studies and ritual theory. In order to get an idea of the field of study, it may be useful to distinguish between the following general approaches to the study of ritual. To begin with, ritual theory in the strict sense, i.e. with explanatory ambitions etc., tends to focus on RITUAL as such: what IT is, what IT does, how IT works ("functions", and why IT is as it is.Softer varieties of ritual theory, e.g. approaches that wish to foster a better "understanding" of what goes on when rituals are being performed, may focus on RITUALS in a semi-empirical and semi-theoretical fashion. As a matter of fact, to a large extent ritual "theory" seems to be the result of theoretical reflections on matters of empirical research. Apart from that, we find studies of this and that phenomenon (e.g. time, space, violence, aesthetics, media, etc. in relation to rituals ("ritual and time", "ritual and space", etc.. Then, of course, we have a good dose of studies on different "types", "classes", or "groups" of rituals. Most popular, (in the absence of any statistical evidence, are studies of "sacrifice", "rites of passage", and "initiations", with "healing rituals" and "pilgrimages" as ever more successful runner-ups. Correspondingly, there is a number of studies about any variety of any class of rituals among the so-and-so people ("initiation among the NN". Moreover, there are plenty of books about the rituals of this and that religion or people — in colonial times often published under such titles as "The customs and ceremonies of the NN". Last but not least, there is an overwhelming amount of studies devoted to the presentation or analysis of single rituals.

  18. Spiral magnetic order and pressure-induced superconductivity in transition metal compounds

    Science.gov (United States)

    Wang, Yishu; Feng, Yejun; Cheng, J.-G.; Wu, W.; Luo, J. L.; Rosenbaum, T. F.

    2016-10-01

    Magnetic and superconducting ground states can compete, cooperate and coexist. MnP provides a compelling and potentially generalizable example of a material where superconductivity and magnetism may be intertwined. Using a synchrotron-based non-resonant X-ray magnetic diffraction technique, we reveal a spiral spin order in MnP and trace its pressure evolution towards superconducting order via measurements in a diamond anvil cell. Judging from the magnetostriction, ordered moments vanish at the quantum phase transition as pressure increases the electron kinetic energy. Spins remain local in the disordered phase, and the promotion of superconductivity is likely to emerge from an enhanced coupling to residual spiral spin fluctuations and their concomitant suppression of phonon-mediated superconductivity. As the pitch of the spiral order varies across the 3d transition metal compounds in the MnP family, the magnetic ground state switches between antiferromagnet and ferromagnet, providing an additional tuning parameter in probing spin-fluctuation-induced superconductivity.

  19. Spiral magnetic order and pressure-induced superconductivity in transition metal compounds

    Science.gov (United States)

    Wang, Yishu; Feng, Yejun; Cheng, J.-G.; Wu, W.; Luo, J. L.; Rosenbaum, T. F.

    2016-01-01

    Magnetic and superconducting ground states can compete, cooperate and coexist. MnP provides a compelling and potentially generalizable example of a material where superconductivity and magnetism may be intertwined. Using a synchrotron-based non-resonant X-ray magnetic diffraction technique, we reveal a spiral spin order in MnP and trace its pressure evolution towards superconducting order via measurements in a diamond anvil cell. Judging from the magnetostriction, ordered moments vanish at the quantum phase transition as pressure increases the electron kinetic energy. Spins remain local in the disordered phase, and the promotion of superconductivity is likely to emerge from an enhanced coupling to residual spiral spin fluctuations and their concomitant suppression of phonon-mediated superconductivity. As the pitch of the spiral order varies across the 3d transition metal compounds in the MnP family, the magnetic ground state switches between antiferromagnet and ferromagnet, providing an additional tuning parameter in probing spin-fluctuation-induced superconductivity. PMID:27708255

  20. AC electric field induced vortex in laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan

    2014-09-22

    Experiments were performed by applying sub-critical high-voltage alternating current (AC) to the nozzle of laminar propane coflow diffusion flames. Light scattering, laser-induced incandescence and laser-induced fluorescence techniques were used to identify the soot zone, and the structures of OH and polycyclic aromatic hydrocarbons (PAHs). Particle image velocimetry was adopted to quantify the velocity field. Under certain AC conditions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. The onset conditions for the vortex formation supported the role of an electromagnetic force acting on charged particles in the flame zone. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  1. The Phase Transition of Syndiotactic Polystrene Induced by Electrostatic Field

    Institute of Scientific and Technical Information of China (English)

    肖学山; 莫志深; 等

    2002-01-01

    The crystal structure and morphology of syndiotactic polystryene(sPS)melt-crystallized in various electrostatic fields have been investigated by using wide angle X-ray diffraction(WAXD),differential scanning calorimeter(DSC) and scanning electron microscope(SEM).WAXD and DSC analyses show that SPS is gradually transformed from a phase to β phase with increase of electrostatic intensity.The SEM observations indicate that the morphology of sPS micro-crystals is strongly dependent on electrostatic intensity applied to the sample during solidification.The variation of the micro-crystals orientation from disordered lamellae to ordered lamellare have been observed with increase of electrostatic intensity.

  2. Determination of imidacloprid in water samples via photochemically induced fluorescence and second-order multivariate calibration.

    Science.gov (United States)

    Fuentes, Edwar; Cid, Camila; Báez, María E

    2015-03-01

    This paper presents a new method for the determination of imidacloprid in water samples; one of the most widely used neonicotinoid pesticides in the farming industry. The method is based on the measurement of excitation-emission spectra of photo-induced fluorescence (PIF-EEMs) associated with second-order multivariate calibration with a parallel factor analysis (PARAFAC) and unfolded partial least squares coupled to residual bilinearization (U-PLS/RBL). The second order advantage permitted the determination of imidacloprid in the presence of potential interferences, which also shows photo-induced fluorescence (other pesticides and/or unexpected compounds of the real samples). The photoreaction was performed in 100-μl disposable micropipettes. As a preliminary step, solid phase extraction on C18 (SPE-C18) was applied to concentrate the analyte and diminish the limit of detection. The LOD was approximately 1 ng mL(-1), which is suitable for detecting imidacloprid in water according to the guidelines established in North America and Europe. The PIF-EEMs coupled to PARAFAC or U-PLS/RBL was successfully applied for the determination of imidacloprid in different real water samples, with an average recovery of 101±10%.

  3. Task Order 22 – Engineering and Technical Support, Deep Borehole Field Test. AREVA Summary Review Report

    Energy Technology Data Exchange (ETDEWEB)

    Denton, Mark A. [AREVA Federal Services, Charlotte, NC (United States)

    2016-01-19

    Under Task Order 22 of the industry Advisory and Assistance Services (A&AS) Contract to the Department of Energy (DOE) DE-NE0000291, AREVA has been tasked with providing assistance with engineering, analysis, cost estimating, and design support of a system for disposal of radioactive wastes in deep boreholes (without the use of radioactive waste). As part of this task order, AREVA was requested, through a letter of technical direction, to evaluate Sandia National Laboratory’s (SNL’s) waste package borehole emplacement system concept recommendation using input from DOE and SNL. This summary review report (SRR) documents this evaluation, with its focus on the primary input document titled: “Deep Borehole Field Test Specifications/M2FT-15SN0817091” Rev. 1 [1], hereafter referred to as the “M2 report.” The M2 report focuses on the conceptual design development for the Deep Borehole Field Test (DBFT), mainly the test waste packages (WPs) and the system for demonstrating emplacement and retrieval of those packages in the Field Test Borehole (FTB). This SRR follows the same outline as the M2 report, which allows for easy correlation between AREVA’s review comments, discussion, potential proposed alternatives, and path forward with information established in the M2 report. AREVA’s assessment focused on three primary elements of the M2 report: the conceptual design of the WPs proposed for deep borehole disposal (DBD), the mode of emplacement of the WP into DBD, and the conceptual design of the DBFT. AREVA concurs with the M2 report’s selection of the wireline emplacement mode specifically over the drill-string emplacement mode and generically over alternative emplacement modes. Table 5-1 of this SRR compares the pros and cons of each emplacement mode considered viable for DBD. The primary positive characteristics of the wireline emplacement mode include: (1) considered a mature technology; (2) operations are relatively simple; (3) probability of a

  4. Task Order 22 – Engineering and Technical Support, Deep Borehole Field Test. AREVA Summary Review Report

    Energy Technology Data Exchange (ETDEWEB)

    Denton, Mark A. [AREVA Federal Services, Charlotte, NC (United States)

    2016-01-19

    Under Task Order 22 of the industry Advisory and Assistance Services (A&AS) Contract to the Department of Energy (DOE) DE-NE0000291, AREVA has been tasked with providing assistance with engineering, analysis, cost estimating, and design support of a system for disposal of radioactive wastes in deep boreholes (without the use of radioactive waste). As part of this task order, AREVA was requested, through a letter of technical direction, to evaluate Sandia National Laboratory’s (SNL’s) waste package borehole emplacement system concept recommendation using input from DOE and SNL. This summary review report (SRR) documents this evaluation, with its focus on the primary input document titled: “Deep Borehole Field Test Specifications/M2FT-15SN0817091” Rev. 1 [1], hereafter referred to as the “M2 report.” The M2 report focuses on the conceptual design development for the Deep Borehole Field Test (DBFT), mainly the test waste packages (WPs) and the system for demonstrating emplacement and retrieval of those packages in the Field Test Borehole (FTB). This SRR follows the same outline as the M2 report, which allows for easy correlation between AREVA’s review comments, discussion, potential proposed alternatives, and path forward with information established in the M2 report. AREVA’s assessment focused on three primary elements of the M2 report: the conceptual design of the WPs proposed for deep borehole disposal (DBD), the mode of emplacement of the WP into DBD, and the conceptual design of the DBFT. AREVA concurs with the M2 report’s selection of the wireline emplacement mode specifically over the drill-string emplacement mode and generically over alternative emplacement modes. Table 5-1 of this SRR compares the pros and cons of each emplacement mode considered viable for DBD. The primary positive characteristics of the wireline emplacement mode include: (1) considered a mature technology; (2) operations are relatively simple; (3) probability of a

  5. Magnetic field induced strain assisted by stress in Ni-Fe-GaCo single crystals

    Directory of Open Access Journals (Sweden)

    Chumlyakov Y.

    2010-06-01

    Full Text Available Ferromagnetic shape memory alloys (FSMA have the possibility to induced a strain by applying a magnetic field. The main advantage of the FSMA is that the strain cycling frequency is two orders of magnitude higher than coventional shape memory alloys. The best alloy showing this effect is the Ni-Mn-Ga system, with a high mobility of its martensite variants and high magnetocrystalline anisotropy constant. Nevertheless, due to the high brittleness of this alloy, other systems (Ni-Fe-Ga, Co-Ni-Al, Co-Ni-Ga, ... are being investigated as an alternative to Ni-Mn-Ga. In the current work, Ni-Fe-Ga-Co single crystals have been studied. In spite of the formation of L10 martensite (low mobility of the variants, the [001] crystals exhibited magnetic-field-induced strains (in tension larger than 2%, under an assisting tensile stress around 16 MPa and fields below 15 kOe. In martensitic samples previously compressed, application of a constant tensile stress along the same axis together with a perpendicular magnetic field produces the elongation of the sample by variant reorientation, as one of the variants rotates its c axis from the field direction to the stress-axis direction. An estimated magnetostress of ~0.8 MPa is in good agreement with the theoretical value given by the ratio of magnetocrystalline anisotropy constant and twinning shear.

  6. Electric field control of magnon-induced magnetization dynamics in multiferroics

    Science.gov (United States)

    Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

    2016-01-01

    We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves. PMID:27554064

  7. A telluric method for natural field induced polarization studies

    Science.gov (United States)

    Zorin, Nikita; Epishkin, Dmitrii; Yakovlev, Andrey

    2016-12-01

    Natural field induced polarization (NFIP) is a branch of low-frequency electromagnetics designed for detection of buried polarizable objects from magnetotelluric (MT) data. The conventional approach to the method deals with normalized MT apparent resistivity. We show that it is more favorable to extract the IP effect from solely electric (telluric) transfer functions instead. For lateral localization of polarizable bodies it is convenient to work with the telluric tensor determinant, which does not depend on the rotation of the receiving electric dipoles. Applicability of the new method was verified in the course of a large-scale field research. The field work was conducted in a well-explored area in East Kazakhstan known for the presence of various IP sources such as graphite, magnetite, and sulfide mineralization. A new multichannel processing approach allowed the determination of the telluric tensor components with very good accuracy. This holds out a hope that in some cases NFIP data may be used not only for detection of polarizable objects, but also for a rough estimation of their spectral IP characteristics.

  8. Radiation-induced solidification of ionic liquid under extreme electric field

    Science.gov (United States)

    Terhune, Kurt J.; King, Lyon B.; He, Kai; Cumings, John

    2016-09-01

    An extreme electric field on the order of 1010 V m-1 was applied to the free surface of an ionic liquid to cause electric-field-induced evaporation of molecular ions from the liquid. The point of ion emission was observed in situ using a TEM. The resulting electrospray emission process was observed to create nanoscale high-aspect-ratio dendritic features that were aligned with the direction of the electric field. Upon removal of the stressing field the features were seen to remain, indicating that the ionic liquid residue was solidified or gelled. Similar electrospray experiments performed in a field-emission scanning electron microscope revealed that the features are created when the high-energy electron beam damages the molecular structure of the ionic liquid. While the electric field does not play a direct role in the fluid modification, the electric stress was critical in detecting the liquid property change. It is only because the electric stress mechanically elongated the fluid during the electrospray process and these obviously non-liquid structures persisted when the field was removed that the damage was evident. This evidence of ionic liquid radiation damage may have significant bearing on electrospray devices where it is possible to produce high-energy secondary electrons through surface impacts of emitted ions downstream of the emitter. Any such impacts that are in close proximity could see reflected secondary electrons impact the emitter causing gelling of the ionic liquid.

  9. Pressure-induced frustration in charge ordered spinel AlV2O4

    Science.gov (United States)

    Kalavathi, S.; Vennila Raju, Selva; Williams, Quentin; Sahu, P. Ch; Sastry, V. S.; Sahu, H. K.

    2013-07-01

    AlV2O4 is the only spinel compound so far known that exists in the charge ordered state at room temperature. It is known to transform to a charge frustrated cubic spinel structure above 427 ° C. The presence of multivalent V ions in the pyrochlore lattice of the cubic spinel phase brings about the charge frustration that is relieved in the room temperature rhombohedral phase by the clustering of vanadium into a heptamer molecular unit along with a lone V atom. The present work is the first demonstration of pressure-induced frustration in the charge ordered state of AlV2O4. Synchrotron powder x-ray diffraction studies carried out at room temperature on AlV2O4 subjected to high pressure in a diamond anvil cell show that the charge ordered rhombohedral phase becomes unstable under the application of pressure and transforms to the frustrated cubic spinel structure. The frustration is found to be present even after pressure recovery. The possible role of pressure on vanadium t2g orbitals in understanding these observations is discussed.

  10. Probing higher order correlations of the photon field with photon number resolving avalanche photodiodes.

    Science.gov (United States)

    Dynes, J F; Yuan, Z L; Sharpe, A W; Thomas, O; Shields, A J

    2011-07-04

    We demonstrate the use of two high speed avalanche photodiodes in exploring higher order photon correlations. By employing the photon number resolving capability of the photodiodes the response to higher order photon coincidences can be measured. As an example we show experimentally the sensitivity to higher order correlations for three types of photon sources with distinct photon statistics. This higher order correlation technique could be used as a low cost and compact tool for quantifying the degree of correlation of photon sources employed in quantum information science.

  11. Fourth-order master equation for a charged harmonic oscillator interacting with the electromagnetic field

    Science.gov (United States)

    Kurt, Arzu; Eryigit, Resul

    2015-12-01

    The master equation for a charged harmonic oscillator coupled to an electromagnetic reservoir is investigated up to fourth order in the interaction strength by using Krylov averaging method. The interaction is in the velocity-coupling form and includes a diamagnetic term. Exact analytical expressions for the second-, the third-, and the fourth-order contributions to mass renormalization, decay constant, normal and anomalous diffusion coefficients are obtained for the blackbody type environment. It is found that, generally, the third- and the fourth-order contributions have opposite signs when their magnitudes are comparable to that of the second-order one.

  12. Ground state energy of dilute neutron matter at next-to-leading order in lattice chiral effective field theory

    CERN Document Server

    Epelbaum, Evgeny; Lee, Dean; Meißner, Ulf-G

    2008-01-01

    We present lattice calculations for the ground state energy of dilute neutron matter at next-to-leading order in chiral effective field theory. This study follows a series of recent papers on low-energy nuclear physics using chiral effective field theory on the lattice. In this work we introduce an improved spin- and isospin-projected leading-order action which allows for a perturbative treatment of corrections at next-to-leading order and smaller estimated errors. Using auxiliary fields and Euclidean-time projection Monte Carlo, we compute the ground state of 8, 12, and 16 neutrons in a periodic cube, covering a density range from 2% to 10% of normal nuclear density.

  13. A new class of group field theories for 1st order discrete quantum gravity

    NARCIS (Netherlands)

    Oriti, D.; Tlas, T.

    2008-01-01

    Group Field Theories, a generalization of matrix models for 2d gravity, represent a 2nd quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of Group Field Theory models, for any choice of spacetime dimension and signature, whose Feynman

  14. A new class of group field theories for 1st order discrete quantum gravity

    NARCIS (Netherlands)

    Oriti, D.; Tlas, T.

    2008-01-01

    Group Field Theories, a generalization of matrix models for 2d gravity, represent a 2nd quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of Group Field Theory models, for any choice of spacetime dimension and signature, whose Feynman a

  15. A new class of group field theories for 1st order discrete quantum gravity

    NARCIS (Netherlands)

    Oriti, D.; Tlas, T.

    2008-01-01

    Group Field Theories, a generalization of matrix models for 2d gravity, represent a 2nd quantization of both loop quantum gravity and simplicial quantum gravity. In this paper, we construct a new class of Group Field Theory models, for any choice of spacetime dimension and signature, whose Feynman a

  16. The electric field induced by transcranial magnetic stimulation: A comparison between analytic and fem solutions

    Directory of Open Access Journals (Sweden)

    Porzig Konstantin

    2014-01-01

    Full Text Available The induced electric field profiles in a homogeneous isotropic sphere, were calculated and compared between an analytic and a finite-element method in the framework of transcranial magnetic stimulation (TMS. This model can also be applied for concentric spheres in the framework of magnetic induction tomography (MIT, non destructive testing (NDT or to calculate the lead field in magnetoencephalography (MEG. The calculations were performed using Eaton’s method as well as the finite-element program Comsol Multiphysics 4.2a (COMSOL Inc., Burlington, USA. A circular- and a figure-of-8 coil were used to operate as the sources of excitation. In our study the spherical volume conductor represents the human head consisting of grey matter. In order to quantify the differences between both methods an intense parameter study was performed. A comparison between both methods show a higher conformity than reported in previous studies. Regarding Eaton’s method, the influence of the maximum order of approximation L and the number of elements per winding K was investigated. The maximum relative difference was approximately 0.3% for L = 20 and K > 16. Furthermore the relative efficiency of the algorithm was calculated to save computational time. With the presented results it is possible to use Eaton’s method efficiently to compute the induced electric field profiles very quickly for example while searching for specific coil arrangements around the humans head, as in the case of deep brain transcranial magnetic stimulation (dTMS.

  17. Resonance in Interacting Induced-Dipole Polarizing Force Fields: Application to Force-Field Derivatives

    Directory of Open Access Journals (Sweden)

    Francisco Torrens

    2009-03-01

    Full Text Available The Silberstein model of the molecular polarizability of diatomic molecules, generalized by Applequist et al. for polyatomic molecules, is analyzed. The atoms are regarded as isotropically polarizable points located at their nuclei, interacting via the fields of their induced dipoles. The use of additive values for atom polarizabilities gives poor results, in some cases leading to artificial predictions of absorption bands. The molecular polarizability of methane and its derivative are computed. The agreement with experimental mean molecular polarizabilities is within 1–5%. A hypothesis is indispensable for a suitable representation of polarizability derivative.

  18. INFLUENCE OF THE HIGHER ORDER DERIVATIVES ON THE PLANET PERIHELION PRECESSION IN THE EINSTEIN FIELD EQUATIONS FOR VACUUM CONDITION

    Directory of Open Access Journals (Sweden)

    Teguh Budi Prayitno

    2011-04-01

    Full Text Available This paper studies the effect of higher order derivative tensor in the Einstein field equations for vacuum condition on the planet perihelion precession. This tensor was initially proposed as the space-time curvature tensor by Deser and Tekin on discussions about the energy effects caused by this tensor. However, they include this tensor to Einstein field equations as a new model in general relativity theory. This is very interesting since there are some questions in cosmology and astrophysics that have no answers. Thus, they hoped this model could solve those problems by finding analytical or perturbative solution and interpreting it. In this case, the perturbative solution was used to find the Schwarzschild solution and it was also applied to consider the planetary motion in the solar gravitational field. Furthermore, it was proven that the tensor is divergence-free in order to keep the Einstein field equations remain valid.

  19. Electric Field Effects on the Hidden Order of Microstructured URu2Si2

    Energy Technology Data Exchange (ETDEWEB)

    Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moll, P.J.W. [Max Planck Society, Dresden (Germany); Shekhter, A. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Ramshaw, B.J. [Cornell Univ., Ithaca, NY (United States); Bauer, Eric Dietzgen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    Despite being studied for over 30 years there is still continual interest in they heavy-fermion URu2Si2 due largely in part to the still disagreed upon origin of the so-called hidden-order (HO) state that arises below THO = 17.5 K. While both the application of pressure and high magnetic fields have been shown to suppress the HO state, one mechanism that has yet to be explored is the application of an electric field, most likely due to the difficulty of measuring such an effect in a metal. To overcome this challenge we have used focused ion beam (FIB) lithography to obtain the necessary sample geometry to create an electric field across a small section of the sample by applying a voltage. Our results suggest that at low temperatures the application of an electric field is able to suppress the hidden order state.

  20. Fourth-order master equation for a charged harmonic oscillator interacting with the electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kurt, Arzu; Eryigit, Resul, E-mail: resul@ibu.edu.tr

    2015-12-18

    The master equation for a charged harmonic oscillator coupled to an electromagnetic reservoir is investigated up to fourth order in the interaction strength by using Krylov averaging method. The interaction is in the velocity-coupling form and includes a diamagnetic term. Exact analytical expressions for the second-, the third-, and the fourth-order contributions to mass renormalization, decay constant, normal and anomalous diffusion coefficients are obtained for the blackbody type environment. It is found that, generally, the third- and the fourth-order contributions have opposite signs when their magnitudes are comparable to that of the second-order one. - Highlights: • Exact analytical expressions for up to the fourth-order master equation are obtained. • High and low temperature limits of anomalous diffusion coefficients are elucidated. • Convergence range of the oscillator and the bath parameters discussed.