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Sample records for ising axis conversion

  1. The Conversational Framework and the ISE "Basketball Shot" Video Analysis Activity

    ERIC Educational Resources Information Center

    English, Vincent; Crotty, Yvonne; Farren, Margaret

    2015-01-01

    Inspiring Science Education (ISE) (http://www.inspiringscience.eu/) is an EU funded initiative that seeks to further the use of inquiry-based science learning (IBSL) through the medium of ICT in the classroom. The Basketball Shot is a scenario (lesson plan) that involves the use of video capture to help the student investigate the concepts of…

  2. The UTRC wind energy conversion system performance analysis for horizontal axis wind turbines (WECSPER)

    NASA Technical Reports Server (NTRS)

    Egolf, T. A.; Landgrebe, A. J.

    1981-01-01

    The theory for the UTRC Energy Conversion System Performance Analysis (WECSPER) for the prediction of horizontal axis wind turbine performance is presented. Major features of the analysis are the ability to: (1) treat the wind turbine blades as lifting lines with a prescribed wake model; (2) solve for the wake-induced inflow and blade circulation using real nonlinear airfoil data; and (3) iterate internally to obtain a compatible wake transport velocity and blade loading solution. This analysis also provides an approximate treatment of wake distortions due to tower shadow or wind shear profiles. Finally, selected results of internal UTRC application of the analysis to existing wind turbines and correlation with limited test data are described.

  3. ISE structural dynamic experiments

    NASA Technical Reports Server (NTRS)

    Lock, Malcolm H.; Clark, S. Y.

    1988-01-01

    The topics are presented in viewgraph form and include the following: directed energy systems - vibration issue; Neutral Particle Beam Integrated Space Experiment (NPB-ISE) opportunity/study objective; vibration sources/study plan; NPB-ISE spacecraft configuration; baseline slew analysis and results; modal contributions; fundamental pitch mode; vibration reduction approaches; peak residual vibration; NPB-ISE spacecraft slew experiment; goodbye ISE - hello Zenith Star Program.

  4. Horizontal Axis Wind Energy Conversion System with Aerodynamic Blade Pitch Control

    SciTech Connect

    Rossman, W. E.

    1983-12-27

    The horizontal axis wind turbine converts wind into electrical energy and includes a pitch control vane with a flyweight mechanism on each rotor blade to provide aerodynamic efficiency at operating wind velocities, near constant speed and zero lift pitch of the rotor blades when speeds exceed the design speed of the system. A gravity neutralization means composed of a bevel gear and pinions couples the blades together while a flyweight arrangement connected to the bevel gear acts to neutralize centrifugal torque on the blades.

  5. Vertical axis wind rotors: Status and potential. [energy conversion efficiency and aerodynamic characteristics

    NASA Technical Reports Server (NTRS)

    Vance, W.

    1973-01-01

    The design and application of a vertical axis wind rotor is reported that operates as a two stage turbine wherein the wind impinging on the concave side is circulated through the center of the rotor to the back of the convex side, thus decreasing what might otherwise be a high negative pressure region. Successful applications of this wind rotor to water pumps, ship propulsion, and building ventilators are reported. Also shown is the feasibility of using the energy in ocean waves to drive the rotor. An analysis of the impact of rotor aspect ratio on rotor acceleration shows that the amount of venting between rotor vanes has a very significant effect on rotor speed for a given wind speed.

  6. Safety and wind energy conversion systems with horizontal axis (HA WECS)

    NASA Astrophysics Data System (ADS)

    Eggwertz, S.; Carlsson, I.; Gustafsson, A.; Linde, M.; Lundemo, C.; Montgomerie, B.; Thor, S. E.

    1981-03-01

    Hazards imposed by a wind energy conversion system on the general public and on the operator personnel by complete collapse, by separation of fractured parts, or by pieces of ice (flying off) were calculated to provide a manual for safety evaluations. Land based large scale turbine systems with horizontal axes situated in areas with sparse population are considered. Blade material is assumed to be steel, aluminum alloy or fiber reinforced plastics; the tower being built of steel or reinforced concrete. Primary structure, function and failure modes are identified. Statistical information of loads and load combinations, strength properties of materials and geometry deviation are provided. A simplified method of risk analysis is described. The object and function of a safety system, both hardware and software, is reviewed, considering the effects of inspection and repair. The probability of being hit is evaluated, provided a fracture occurs and a risk zone is established.

  7. Off-axis holographic lens spectrum-splitting photovoltaic system for direct and diffuse solar energy conversion.

    PubMed

    Vorndran, Shelby D; Chrysler, Benjamin; Wheelwright, Brian; Angel, Roger; Holman, Zachary; Kostuk, Raymond

    2016-09-20

    This paper describes a high-efficiency, spectrum-splitting photovoltaic module that uses an off-axis volume holographic lens to focus and disperse incident solar illumination to a rectangular shaped high-bandgap indium gallium phosphide cell surrounded by strips of silicon cells. The holographic lens design allows efficient collection of both direct and diffuse illumination to maximize energy yield. We modeled the volume diffraction characteristics using rigorous coupled-wave analysis, and simulated system performance using nonsequential ray tracing and PV cell data from the literature. Under AM 1.5 illumination conditions the simulated module obtained a 30.6% conversion efficiency. This efficiency is a 19.7% relative improvement compared to the more efficient cell in the system (silicon). The module was also simulated under a typical meteorological year of direct and diffuse irradiance in Tucson, Arizona, and Seattle, Washington. Compared to a flat panel silicon module, the holographic spectrum splitting module obtained a relative improvement in energy yield of 17.1% in Tucson and 14.0% in Seattle. An experimental proof-of-concept volume holographic lens was also fabricated in dichromated gelatin to verify the main characteristics of the system. The lens obtained an average first-order diffraction efficiency of 85.4% across the aperture at 532 nm. PMID:27661578

  8. Off-axis holographic lens spectrum-splitting photovoltaic system for direct and diffuse solar energy conversion.

    PubMed

    Vorndran, Shelby D; Chrysler, Benjamin; Wheelwright, Brian; Angel, Roger; Holman, Zachary; Kostuk, Raymond

    2016-09-20

    This paper describes a high-efficiency, spectrum-splitting photovoltaic module that uses an off-axis volume holographic lens to focus and disperse incident solar illumination to a rectangular shaped high-bandgap indium gallium phosphide cell surrounded by strips of silicon cells. The holographic lens design allows efficient collection of both direct and diffuse illumination to maximize energy yield. We modeled the volume diffraction characteristics using rigorous coupled-wave analysis, and simulated system performance using nonsequential ray tracing and PV cell data from the literature. Under AM 1.5 illumination conditions the simulated module obtained a 30.6% conversion efficiency. This efficiency is a 19.7% relative improvement compared to the more efficient cell in the system (silicon). The module was also simulated under a typical meteorological year of direct and diffuse irradiance in Tucson, Arizona, and Seattle, Washington. Compared to a flat panel silicon module, the holographic spectrum splitting module obtained a relative improvement in energy yield of 17.1% in Tucson and 14.0% in Seattle. An experimental proof-of-concept volume holographic lens was also fabricated in dichromated gelatin to verify the main characteristics of the system. The lens obtained an average first-order diffraction efficiency of 85.4% across the aperture at 532 nm.

  9. Nagoya, Ise Bay, Japan

    NASA Technical Reports Server (NTRS)

    1982-01-01

    This view of Nagoya, Ise Bay and nearby Kyoto, on the main island of Honshu, Japan (35.0N, 137.0E) combines in a single photo both the political, cultural and educational centers of early Japan as well as one of the main educational and business centers of modern Japan. Besides being a business, cultural and educational center, Nagoya is near the geographic center of the Japanese home islands.

  10. Learning planar ising models

    SciTech Connect

    Johnson, Jason K; Chertkov, Michael; Netrapalli, Praneeth

    2010-11-12

    Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus our attention on the class of planar Ising models, for which inference is tractable using techniques of statistical physics [Kac and Ward; Kasteleyn]. Based on these techniques and recent methods for planarity testing and planar embedding [Chrobak and Payne], we propose a simple greedy algorithm for learning the best planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. We present the results of numerical experiments evaluating the performance of our algorithm.

  11. Properties of Ising Networks

    NASA Astrophysics Data System (ADS)

    Zhang, Guihua

    1992-08-01

    Inhomogeneous Ising networks are studied in this thesis. Profile equations for Ising systems with inhomogeneous external fields and short range interactions are presented for simply-connected, closed chain and ring-like networks. The existence of generating functionals has been proved; for some special cases, the corresponding generating functionals are written out explicitly. The profile equations for a simply-connected system turns out to be a local form, in terms of local quantities like magnetizations and local correlations of two site magnetizations. For nonsimply-connected systems, additional collective mode variables are found which regain the localities of the profile equations. The collective variables take care of all the global effects from all the feedback loops. They enable us to treat the local and global aspects simultaneously. The statistical mechanics of a nonuniform nearest -neighbor interaction with four states per site is carried out and converted to that of a two state second-neighbor gas. A mixed density-potential representation is presented and the appropriate generating functional is constructed. Application is made to the site representation of a hydrogenmolecule -water mixture. A one dimensional spin glass is studied by using the entropy functional method; the integral equations for the effective field are rederived. The corresponding integral equations in magnetization space are established. Extension to a Bethe lattice is made. The thermodynamics of a classical lattice gas in Ising form, with arbitrary interaction, is set up in entropy format, with multipoint magnetizations as control parameters. It is specialized to the case of one and two -point interactions on a simply connected lattice; both entropy and profile equations are written down explicitly. Linear response functions are expressed in Wertheim-Baxter factorization and used to derive the Jacobian of the transformation from couplings to magnetizations. An arbitrary spin

  12. Characterization of the Dilute Ising Antiferromagnet

    SciTech Connect

    Wiener, T.

    2000-09-12

    A spin glass is a magnetic ground state in which ferromagnetic and antiferromagnetic exchange interactions compete, thereby creating frustration and a multidegenerate state with no long range order. An Ising system is a system where the spins are constrained to lie parallel or antiparallel to a primary axis. There has been much theoretical interest in the past ten years in the effects of applying a magnetic field transverse to the primary axis in an Ising spin glass at low temperatures and thus study phase transitions at the T=0 limit. The focus of this study is to search for and characterize a new Ising spin glass system. This is accomplished by site diluting yttrium for terbium in the crystalline material TbNi{sub 2}Ge{sub 2}. The first part of this work gives a brief overview of the physics of rare earth magnetism and an overview of experimental characteristics of spin glasses. This is followed by the methodology used to manufacture the large single crystals used in this study, as well as the measurement techniques used. Next, a summary of the results of magnetic measurements on across the dilution series from pure terbium to pure yttrium is presented. This is followed by detailed measurements on particular dilutions which demonstrate spin glass behavior. Pure TbNi{sub 2}Ge{sub 2} is an Ising antiferromagnet with a several distinct metamagnetic states below 17 K. As the terbium is alloyed with yttrium, these magnetic states are weakened in a consistent manner, as is seen in measurements of the transition temperatures and analysis of Curie-Weiss behavior at high temperature. At low concentrations of terbium, below 35%, long range order is no longer present and a spin-glass-like state emerges. This state is studied through various measurements, dc and ac susceptibility, resistivity, and specific heat. This magnetic behavior was then compared to that of other well characterized spin glasses. It is concluded that there is a region of concentration s for which a spin

  13. Integrals of the Ising Class

    SciTech Connect

    Bailey, David H.; Borwein, Jonathan M.; Crandall, Richard E.

    2006-06-01

    From an experimental-mathematical perspective we analyze"Ising-class" integrals. Our experimental results involvedextreme-precision, multidimensional quadrature on intricate integrands;thus, highly parallel computation was required.

  14. Stable Degeneracies for Ising Models

    NASA Astrophysics Data System (ADS)

    Knauf, Andreas

    2016-10-01

    We introduce and consider the notion of stable degeneracies of translation invariant energy functions, taken at spin configurations of a finite Ising model. By this term we mean the lack of injectivity that cannot be lifted by changing the interaction. We show that besides the symmetry-induced degeneracies, related to spin flip, translation and reflection, there exist additional stable degeneracies, due to more subtle symmetries. One such symmetry is the one of the Singer group of a finite projective plane. Others are described by combinatorial relations akin to trace identities. Our results resemble traits of the length spectrum for closed geodesics on a Riemannian surface of constant negative curvature. There, stable degeneracy is defined w.r.t. Teichmüller space as parameter space.

  15. ISE: An Integrated Search Environment. The manual

    NASA Technical Reports Server (NTRS)

    Chu, Lon-Chan

    1992-01-01

    Integrated Search Environment (ISE), a software package that implements hierarchical searches with meta-control, is described in this manual. ISE is a collection of problem-independent routines to support solving searches. Mainly, these routines are core routines for solving a search problem and they handle the control of searches and maintain the statistics related to searches. By separating the problem-dependent and problem-independent components in ISE, new search methods based on a combination of existing methods can be developed by coding a single master control program. Further, new applications solved by searches can be developed by coding the problem-dependent parts and reusing the problem-independent parts already developed. Potential users of ISE are designers of new application solvers and new search algorithms, and users of experimental application solvers and search algorithms. The ISE is designed to be user-friendly and information rich. In this manual, the organization of ISE is described and several experiments carried out on ISE are also described.

  16. Ising formulations of many NP problems

    NASA Astrophysics Data System (ADS)

    Lucas, Andrew

    2014-02-01

    We provide Ising formulations for many NP-complete and NP-hard problems, including all of Karp's 21 NP-complete problems. This collects and extends mappings to the Ising model from partitioning, covering and satisfiability. In each case, the required number of spins is at most cubic in the size of the problem. This work may be useful in designing adiabatic quantum optimization algorithms.

  17. Applications of ISES for meteorology

    NASA Technical Reports Server (NTRS)

    Try, Paul D.

    1990-01-01

    The results are summarized from an initial assessment of the potential real-time meteorological requirements for the data from Eos systems. Eos research scientists associated with facility instruments, investigator instruments, and interdisciplinary groups with data related to meteorological support were contacted, along with those from the normal operational user and technique development groups. Two types of activities indicated the greatest need for real-time Eos data: technology transfer groups (e.g., NOAA's Forecasting System Laboratory and the DOD development laboratories), and field testing groups with airborne operations. A special concern was expressed by several non-U.S. participants who desire a direct downlink to be sure of rapid receipt of the data for their area of interest. Several potential experiments or demonstrations are recommended for ISES which include support for hurricane/typhoon forecasting, space shuttle reentry, severe weather forecasting (using microphysical cloud classification techniques), field testing, and quick reaction of instrumented aircraft to measure such events as polar stratospheric clouds and volcanic eruptions.

  18. Aneesur Rahman Prize: The Inverse Ising Problem

    NASA Astrophysics Data System (ADS)

    Swendsen, Robert

    2014-03-01

    Many methods are available for carrying out computer simulations of a model Hamiltonian to obtain thermodynamic information by generating a set of configurations. The inverse problem consists of recreating the parameters of the Hamiltonian, given a set of configurations. The problem arises in a variety of contexts, and there has been much interest recently in the inverse Ising problem, in which the configurations consist of Ising spins. I will discuss an efficient method for solving the problem and what it can tell us about the Sherrington-Kirkpatrick model.

  19. Estrogen/ERR-α signaling axis is associated with fiber-type conversion of upper airway muscles in patients with obstructive sleep apnea hypopnea syndrome

    PubMed Central

    Chen, H. H.; Lu, J.; Guan, Y. F.; Li, S. J.; Hu, T. T.; Xie, Z. S.; Wang, F.; Peng, X. H.; Liu, X.; Xu, X.; Zhao, F. P.; Yu, B. L.; Li, X. P.

    2016-01-01

    Estrogen is related with the low morbidity associated with obstructive sleep apnea hypopnea syndrome (OSAS) in women, but the underlying mechanisms remain largely unknown. In this study, we examined the relationship between OSAS and estrogen related receptor-α (ERR-α). We found that the expression levels of ERR-α and Myh7 were both downregulated in palatopharyngeal tissues from OSAS patients. In addition, we report that ERR-α is dynamically expressed during differentiation of C2C12 myoblasts. Knockdown of ERR-α via instant siRNA resulted in reduced expression of Myh7, but not Myh4. Furthermore, differentiation of C2C12 cells under 3% chronic intermittent hypoxia, a model resembling human OSAS, was impaired and accompanied by a obvious reduction in Myh7 expression levels. Moreover, activation of ERR-α with 17β-estradiol (E2) increased the expression of Myh7, whereas pretreatment with the ERR-α antagonist XCT790 reversed the E2-induced slow fiber-type switch. A rat ovariectomy model also demonstrated the switch to fast fiber type. Collectively, our findings suggest that ERR-α is involved in estrogen-mediated OSAS by regulating Myhc-slow expression. The present study illustrates an important role of the estrogen/ERR-α axis in the pathogenesis of OSAS, and may represent an attractive therapeutic target, especially in postmenopausal women. PMID:27250523

  20. ISEE/ICE plasma wave data analysis

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.

    1989-01-01

    The work performed for the period 1 Jan. 1985 to 30 Oct. 1989 is presented. The objective was to provide reduction and analysis of data from a scientific instrument designed to study solar wind and plasma wave phenomena on the International Sun Earth Explorer 3 (ISEE-3)/International Cometary Explorer (ICE) missions.

  1. Ising, Schelling and self-organising segregation

    NASA Astrophysics Data System (ADS)

    Stauffer, D.; Solomon, S.

    2007-06-01

    The similarities between phase separation in physics and residential segregation by preference in the Schelling model of 1971 are reviewed. Also, new computer simulations of asymmetric interactions different from the usual Ising model are presented, showing spontaneous magnetisation (=self-organising segregation) and in one case a sharp phase transition.

  2. Robustness of topological quantum codes: Ising perturbation

    NASA Astrophysics Data System (ADS)

    Zarei, Mohammad Hossein

    2015-02-01

    We study the phase transition from two different topological phases to the ferromagnetic phase by focusing on points of the phase transition. To this end, we present a detailed mapping from such models to the Ising model in a transverse field. Such a mapping is derived by rewriting the initial Hamiltonian in a new basis so that the final model in such a basis has a well-known approximated phase transition point. Specifically, we consider the toric codes and the color codes on various lattices with Ising perturbation. Our results provide a useful table to compare the robustness of the topological codes and to explicitly show that the robustness of the topological codes depends on triangulation of their underlying lattices.

  3. Transverse Ising model with multi-impurity

    NASA Astrophysics Data System (ADS)

    Huang, Xuchu; Yang, Zhihua

    2015-05-01

    We study the transverse Ising spin model with spin-1 impurities under the exact solution. We develop a universal method to deal with the multi-impurity problem by introducing a displacement quantity in the wave function and get a recursive formula to simplify the calculation of the partition function. This allows us to rigorously determine the impurity effects for a specific distribution of impurity in the thermodynamic limit. The low temperature behaviors are governed by the interplay between host and impurity excitations, and the quantum critical fluctuations around the critical point of the transverse Ising model are tuned by the transverse field and the concentration of impurity. However the impurity effects are limited, which depends on the host-impurity exchange interaction and the coupling strength of impurities.

  4. Ferrimagnetic behaviors in a transverse Ising nanoisland

    NASA Astrophysics Data System (ADS)

    Kaneyoshi, T.

    2016-05-01

    In this paper, the phase diagrams and magnetizations of a magnetic nanoisland described by the transverse Ising model (TIM) are investigated by the use of the effective-field theory (EFT) with correlations. A lot of characteristic behaviors observed in standard ferrimagnetic materials as well as novel phenomena have been obtained, although the system consists of two finite spin-1/2 layers coupled antiferromagnetically with a negative interlayer coupling.

  5. Dynamic phase transition in diluted Ising model

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Sourav; Gorai, Gopal; Santra, S. B.

    2015-06-01

    Dynamic phase transition in disordered Ising model in two dimensions has been studied in presence of external time dependent oscillating magnetic field applying Glauber Monte Carlo techniques. Dynamic phase transitions are identified estimating dynamic order parameter against temperature for different concentrations of disorder. For a given field strength and frequency for which there was no hysteresis, it is observed that disorder is able induce hysteresis in the system. Effect of increasing concentration of disorder on hysteresis loop area has also been studied.

  6. Complexity and Ability in Ising Games

    NASA Astrophysics Data System (ADS)

    Ramirez, Ayax; George, Michael

    2008-03-01

    In previous work [1, 2], we discussed various facets of designs in games, and considered the evolution [2] of Ising games. The traditional aspect of game theory, with its focus on rational decisions, was not considered in this work. Instead, there was a predominant interest in the time evolution of design toward a goal design, and resulting levels of frustration. There was also a concern with time- reversal properties. In the new work, our goal is to consider the molecular structureof the Ising model as it evolves, and to associate this molecular structure with feedback into the structure that can be understood in algorithmic terms. We develop an analogy with the famous Malthusian argument concerning exponential population increase, associating ability to cope with complexity, and algorithmic complexity, and discuss biological implications of the ideas associated with these games. [1] M. George, A nonequilibrium statistical model based on latin squares, paper presented at WorldComp'07, Las Vegas, Nevada, June 25-28, 2007. [2] M. George, Classical and quantum Ising games, paper presented at Fourth International Conference in Applied Mathematics and Computing, Plovdiv, Bulgaria, August, 2007.

  7. ICE/ISEE plasma wave data analysis

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.

    1992-01-01

    The interval reported on, from Jan. 1990 to Dec. 1991, has been one of continued processing and archiving of ICE plasma wave (pw) data and transition from analysis of ISEE 3 and ICE cometary data to ICE data taken along its cruise trajectory, where coronal mass ejections are the focus of attention. We have continued to examine with great interest the last year of ISEE 3's precomet phase, when it spent considerable time far downwind from Earth, recording conditions upstream, downstream, and across the very weak, distant flank bow shock. Among other motivations was the apparent similarity of some shock and post shock structures to the signatures of the bow wave surrounding comet Giacobini-Zinner, whose ICE-phase data was revisited. While pursuing detailed, second-order scientific inquiries still pending from the late ISEE 3 recordings, we have also sought to position ourselves for study of CME's by instituting a data processing format new to the ISEE 3/ICE pw detector. Processed detector output has always been summarized and archived in 24-hour segments, with all pw channels individually plotted and stacked one above the next down in frequency, with each channel calibrated separately to keep all data patterns equally visible in the plots, regardless of gross differences in energy content at the various frequencies. Since CME's, with their preceding and following solar wind plasmas, can take more than one day to pass by the spacecraft, a more condensed synoptic view of the pw data is required to identify, let alone assess, CME characteristics than has been afforded by the traditional routines. This requirement is addressed in a major new processing initiative in the past two years. Besides our own ongoing and fresh investigations, we have cooperated, within our resources, with studies conducted extramurally by distant colleagues irrespective of the phase of the ISEE 3/ICE mission under scrutiny. The remainder of this report summarizes our processing activities, our

  8. The 1983 tail-era series. Volume 1: ISEE 3 plasma

    NASA Astrophysics Data System (ADS)

    Fairfield, D. H.; Phillips, J. L.

    1991-04-01

    Observations from the ISEE 3 electron analyzer are presented in plots. Electrons were measured in 15 continuous energy levels between 8.5 and 1140 eV during individual 3-sec spacecraft spins. Times associated with each data point are the beginning time of the 3 sec data collection interval. Moments calculated from the measured distribution function are shown as density, temperature, velocity, and velocity azimuthal angle. Spacecraft ephemeris is shown at the bottom in GSE and GSM coordinates in units of Earth radii, with vertical ticks on the time axis corresponding to the printed positions.

  9. The 1983 tail-era series. Volume 1: ISEE 3 plasma

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Phillips, J. L.

    1991-01-01

    Observations from the ISEE 3 electron analyzer are presented in plots. Electrons were measured in 15 continuous energy levels between 8.5 and 1140 eV during individual 3-sec spacecraft spins. Times associated with each data point are the beginning time of the 3 sec data collection interval. Moments calculated from the measured distribution function are shown as density, temperature, velocity, and velocity azimuthal angle. Spacecraft ephemeris is shown at the bottom in GSE and GSM coordinates in units of Earth radii, with vertical ticks on the time axis corresponding to the printed positions.

  10. Nuclear and ionic charge distribution experiment on ISEE-1 and ISEE-3

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.

    1987-01-01

    The experimental work carried out under this contract is a continuation of that originally performed under Contracts NAS5-20062 and NAS5-26739. The data analyzed are from the Max-Planck Institut/Univ. of Maryland experiment on ISEE-1 and ISEE-3. Each spacecraft experiment consists of a nearly identical set of three sensors (designated the ULECA, ULEWAT, and ULEZEQ sensors) designed to measure the energy spectra and composition of suprathermal and energetic ions over a broad energy range (less than 3 keV/e to more than 20 MeV/nucleon). Since the launch of ISEE's 2 and 3, the MPI/Univ. of Maryland experiments have generally performed as expected except for a partial failure of the ULEWAT sensor on ISEE-1 in August 1978. A number of scientific studies have either been completed, initiated or are at various stages of completion. A brief summary of Primary Results is given, followed by a more detailed summary of the major accomplishments at the Univ. of Maryland.

  11. Three representations of the Ising model

    NASA Astrophysics Data System (ADS)

    Kruis, Joost; Maris, Gunter

    2016-10-01

    Statistical models that analyse (pairwise) relations between variables encompass assumptions about the underlying mechanism that generated the associations in the observed data. In the present paper we demonstrate that three Ising model representations exist that, although each proposes a distinct theoretical explanation for the observed associations, are mathematically equivalent. This equivalence allows the researcher to interpret the results of one model in three different ways. We illustrate the ramifications of this by discussing concepts that are conceived as problematic in their traditional explanation, yet when interpreted in the context of another explanation make immediate sense.

  12. Dynamical transitions of a driven Ising interface

    NASA Astrophysics Data System (ADS)

    Sahai, Manish K.; Sengupta, Surajit

    2008-03-01

    We study the structure of an interface in a three-dimensional Ising system created by an external nonuniform field H(r,t) . H changes sign over a two-dimensional plane of arbitrary orientation. When the field is pulled with velocity ve , [i.e., H(r,t)=H(r-vet) ], the interface undergoes several dynamical transitions. For low velocities it is pinned by the field profile and moves along with it, the distribution of local slopes undergoing a series of commensurate-incommensurate transitions. For large ve the interface depins and grows with Kardar-Parisi-Zhang exponents.

  13. Three representations of the Ising model

    PubMed Central

    Kruis, Joost; Maris, Gunter

    2016-01-01

    Statistical models that analyse (pairwise) relations between variables encompass assumptions about the underlying mechanism that generated the associations in the observed data. In the present paper we demonstrate that three Ising model representations exist that, although each proposes a distinct theoretical explanation for the observed associations, are mathematically equivalent. This equivalence allows the researcher to interpret the results of one model in three different ways. We illustrate the ramifications of this by discussing concepts that are conceived as problematic in their traditional explanation, yet when interpreted in the context of another explanation make immediate sense. PMID:27698356

  14. Topological phases of shaken quantum Ising lattices

    NASA Astrophysics Data System (ADS)

    Fernández-Lorenzo, Samuel; José García-Ripoll, Juan; Porras, Diego

    2016-02-01

    The quantum compass model consists of a two-dimensional square spin lattice where the orientation of the spin-spin interactions depends on the spatial direction of the bonds. It has remarkable symmetry properties and the ground state shows topological degeneracy. The implementation of the quantum compass model in quantum simulation setups like ultracold atoms and trapped ions is far from trivial, since spin interactions in those systems typically are independent of the spatial direction. Ising spin interactions, on the contrary, can be induced and controlled in atomic setups with state-of-the art experimental techniques. In this work, we show how the quantum compass model on a rectangular lattice can be simulated by the use of the photon-assisted tunneling induced by periodic drivings on a quantum Ising spin model. We describe a procedure to adiabatically prepare one of the doubly degenerate ground states of this model by adiabatically ramping down a transverse magnetic field, with surprising differences depending on the parity of the lattice size. Exact diagonalizations confirm the validity of this approach for small lattices. Specific implementations of this scheme are presented with ultracold atoms in optical lattices in the Mott insulator regime, as well as with Rydberg atoms.

  15. Inverse Ising inference with correlated samples

    NASA Astrophysics Data System (ADS)

    Obermayer, Benedikt; Levine, Erel

    2014-12-01

    Correlations between two variables of a high-dimensional system can be indicative of an underlying interaction, but can also result from indirect effects. Inverse Ising inference is a method to distinguish one from the other. Essentially, the parameters of the least constrained statistical model are learned from the observed correlations such that direct interactions can be separated from indirect correlations. Among many other applications, this approach has been helpful for protein structure prediction, because residues which interact in the 3D structure often show correlated substitutions in a multiple sequence alignment. In this context, samples used for inference are not independent but share an evolutionary history on a phylogenetic tree. Here, we discuss the effects of correlations between samples on global inference. Such correlations could arise due to phylogeny but also via other slow dynamical processes. We present a simple analytical model to address the resulting inference biases, and develop an exact method accounting for background correlations in alignment data by combining phylogenetic modeling with an adaptive cluster expansion algorithm. We find that popular reweighting schemes are only marginally effective at removing phylogenetic bias, suggest a rescaling strategy that yields better results, and provide evidence that our conclusions carry over to the frequently used mean-field approach to the inverse Ising problem.

  16. An Artificial Ising System with Phononic Excitations

    NASA Astrophysics Data System (ADS)

    Ghaffari, Hamed; Griffith, W. Ashley; Benson, Philip; Nasseri, M. H. B.; Young, R. Paul

    Many intractable systems and problems can be reduced to a system of interacting spins. Here, we report mapping collective phononic excitations from different sources of crystal vibrations to spin systems. The phononic excitations in our experiments are due to micro and nano cracking (yielding crackling noises due to lattice distortion). We develop real time mapping of the multi-array senores to a network-space and then mapping the excitation- networks to spin-like systems. We show that new mapped system satisfies the quench (impulsive) characteristics of the Ising model in 2D classical spin systems. In particular, we show that our artificial Ising system transits between two ground states and approaching the critical point accompanies with a very short time frozen regime, inducing formation of domains separated by kinks. For a cubic-test under a true triaxial test (3D case), we map the system to a 6-spin ring under a transversal-driving field where using functional multiplex networks, the vector components of the spin are inferred (i.e., XY model). By visualization of spin patterns of the ring per each event, we demonstrate that ``kinks'' (as defects) proliferate when system approach from above to its critical point. We support our observations with employing recorded acoustic excitations during distortion of crystal lattices in nano-indentation tests on different crystals (silicon and graphite), triaxial loading test on rock (poly-crystal) samples and a true 3D triaxial test.

  17. ICE/ISEE plasma wave data analysis

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.; Moses, S. L.

    1993-01-01

    This report is one of the final processing of ICE plasma wave (pw) data and analysis of late ISEE 3, ICE cometary, and ICE cruise trajectory data, where coronal mass ejections (CME's) were the first locus of attention. Interest in CME's inspired an effort to represent our pw data in a condensed spectrogram format that facilitated rapid digestion of interplanetary phenomena on long (greater than 1 day) time scales. The format serendipitously allowed us to also examine earth-orbiting data from a new perspective, invigorating older areas of investigation in Earth's immediate environment. We, therefore, continued to examine with great interest the last year of ISEE 3's precomet phase, when it spent considerable time far downwind from Earth, recording for days on end conditions upstream, downstream, and across the very weak, distant flank bow shock. Among other motivations has been the apparent similarity of some shock and post shock structures to the signatures of the bow wave surrounding comet Giacobini-Zinner, whose ICE-phase data we revisited.

  18. The Worm Process for the Ising Model is Rapidly Mixing

    NASA Astrophysics Data System (ADS)

    Collevecchio, Andrea; Garoni, Timothy M.; Hyndman, Timothy; Tokarev, Daniel

    2016-09-01

    We prove rapid mixing of the worm process for the zero-field ferromagnetic Ising model, on all finite connected graphs, and at all temperatures. As a corollary, we obtain a fully-polynomial randomized approximation scheme for the Ising susceptibility, and for a certain restriction of the two-point correlation function.

  19. One-Dimensional Ising Model with "k"-Spin Interactions

    ERIC Educational Resources Information Center

    Fan, Yale

    2011-01-01

    We examine a generalization of the one-dimensional Ising model involving interactions among neighbourhoods of "k" adjacent spins. The model is solved by exploiting a connection to an interesting computational problem that we call ""k"-SAT on a ring", and is shown to be equivalent to the nearest-neighbour Ising model in the absence of an external…

  20. Networked Ising-Sznajd AR-β Model

    NASA Astrophysics Data System (ADS)

    Nagao, Tomonori; Ohmiya, Mayumi

    2009-09-01

    The modified Ising-Sznajd model is studied to clarify the machanism of price formation in the stock market. The conventional Ising-Sznajd model is improved as a small world network with the rewireing probability β(t) which depends on the time. Numerical experiments show that phase transition, regarded as a economical crisis, is inevitable in this model.

  1. Ising superconductivity and Majorana fermions in transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Zhou, Benjamin T.; Yuan, Noah F. Q.; Jiang, Hong-Liang; Law, K. T.

    2016-05-01

    In monolayer transition-metal dichalcogenides (TMDs), electrons in opposite K valleys are subject to opposite effective Zeeman fields, which are referred to as Ising spin-orbit coupling (SOC) fields. The Ising SOC, originating from in-plane mirror symmetry breaking, pins the electron spins to the out-of-plane directions, and results in Ising superconducting states with strongly enhanced upper critical fields. Here, we show that the Ising SOC generates equal-spin-triplet Cooper pairs with spin polarized in the in-plane directions. Importantly, the spin-triplet Cooper pairs can induce superconducting pairings in a half-metal wire placed on top of the TMD and result in a topological superconductor with Majorana end states. Direct ways to detect equal-spin triplet Cooper pairs and the differences between Ising superconductors and Rashba superconductors are discussed.

  2. Ising antiferromagnet on the Archimedean lattices

    NASA Astrophysics Data System (ADS)

    Yu, Unjong

    2015-06-01

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

  3. Magnetocaloric effect in ferroelectric Ising chain magnet

    NASA Astrophysics Data System (ADS)

    Qi, Yan; Liu, Jia; Yu, Nai-sen; Du, An

    2016-05-01

    We investigate the magnetocaloric effect (MCE) in multiferroic chain system by adopting the elastic Ising-chain model. Based on the transfer-matrix method, the magnetothermal quantities of characterizing MCE behaviors including the entropy, entropy change and adiabatic cooling rate are rigorously determined. Combined with analysis of ground-state, we mainly discuss results in an antiferromagnetic regime associated with ferroelectric transition. Our results show that the entropy change is greatly enhanced near the saturation field as frustration parameter varies in this regime, and accompanied with remarkable inverse MCE, indicating the enormous potential of multiferroic system in low-temperature refrigeration. Meanwhile we also observe a prominent temperature variation in the isoentropy curves close to zero-temperature ferroelectric transition, but this enhancing MCE signal is very sensitive to the thermal fluctuations, and can be strongly suppressed even under a small temperature.

  4. The Ising Spin Glass in dimension four

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Campbell, I. A.

    2015-09-01

    The critical behaviors of the bimodal and Gaussian Ising spin glass (ISG) models in dimension four are studied through extensive numerical simulations, and from an analysis of high temperature series expansion (HTSE) data of Klein et al. (1991). The simulations include standard finite size scaling measurements, thermodynamic limit regime measurements, and analyses which provide estimates of critical exponents without any consideration of the critical temperature. The higher order HTSE series for the bimodal model provide accurate estimates of the critical temperature and critical exponents. These estimates are independent of and fully consistent with the simulation values. Comparisons between ISG models in dimension four show that the critical exponents and the critical constants for dimensionless observables depend on the form of the interaction distribution of the model.

  5. Spacecraft potential control on ISEE-1

    NASA Technical Reports Server (NTRS)

    Gonfalone, A.; Pedersen, A.; Fahleson, U. V.; Faelthammar, C. G.; Mozer, F. S.; Torbert, R. B.

    1979-01-01

    Active control of the potential of the ISEE-1 satellite by the use of electron guns is reviewed. The electron guns contain a special cathode capable of emitting an electron current selectable between 10 to the -8th power and 10 to the -3rd power at energies from approximately .6 to 41 eV. Results obtained during flight show that the satellite potential can be stabilized at a value more positive than the normally positive floating potential. The electron guns also reduce the spin modulation of the spacecraft potential which is due to the aspect dependent photoemission of the long booms. Plasma parameters like electron temperature and density can be deduced from the variation of the spacecraft potential as a function of the gun current. The effects of electron beam emission on other experiments are briefly mentioned.

  6. Ising antiferromagnet on the 2-uniform lattices.

    PubMed

    Yu, Unjong

    2016-08-01

    The antiferromagnetic Ising model is investigated on the twenty 2-uniform lattices using the Monte Carlo method based on the Wang-Landau algorithm and the Metropolis algorithm to study the geometric frustration effect systematically. Based on the specific heat, the residual entropy, and the Edwards-Anderson freezing order parameter, the ground states of them were determined. In addition to the long-range-ordered phase and the spin ice phase found in the Archimedean lattices, two more phases were found. The partial long-range order is long-range order with exceptional disordered sites, which give extensive residual entropy. In the partial spin ice phase, the partial freezing phenomenon appears: A majority of sites are frozen without long-range order, but the other sites are fluctuating even at zero temperature. The spin liquid ground state was not found in the 2-uniform lattices. PMID:27627251

  7. Ising antiferromagnet on the 2-uniform lattices

    NASA Astrophysics Data System (ADS)

    Yu, Unjong

    2016-08-01

    The antiferromagnetic Ising model is investigated on the twenty 2-uniform lattices using the Monte Carlo method based on the Wang-Landau algorithm and the Metropolis algorithm to study the geometric frustration effect systematically. Based on the specific heat, the residual entropy, and the Edwards-Anderson freezing order parameter, the ground states of them were determined. In addition to the long-range-ordered phase and the spin ice phase found in the Archimedean lattices, two more phases were found. The partial long-range order is long-range order with exceptional disordered sites, which give extensive residual entropy. In the partial spin ice phase, the partial freezing phenomenon appears: A majority of sites are frozen without long-range order, but the other sites are fluctuating even at zero temperature. The spin liquid ground state was not found in the 2-uniform lattices.

  8. Transient Loschmidt echo in quenched Ising chains

    NASA Astrophysics Data System (ADS)

    Lupo, Carla; Schiró, Marco

    2016-07-01

    We study the response to sudden local perturbations of highly excited quantum Ising spin chains. The key quantity encoding this response is the overlap between time-dependent wave functions, which we write as a transient Loschmidt Echo. Its asymptotics at long time differences contain crucial information about the structure of the highly excited nonequilibrium environment induced by the quench. We compute the echo perturbatively for a weak local quench but for arbitrarily large global quench, using a cumulant expansion. Our perturbative results suggest that the echo decays exponentially, rather than power law as in the low-energy orthogonality catastrophe, a further example of quench-induced decoherence already found in the case of quenched Luttinger liquids. The emerging decoherence scale is set by the strength of the local potential and the bulk excitation energy.

  9. Hypergeometric Forms for Ising-Class Integrals

    SciTech Connect

    Bailey, David H.; Borwein, David; Borwein, Jonathan M.; Crandall,Richard E.

    2006-07-01

    We apply experimental-mathematical principles to analyzecertain integrals relevant to the Ising theory of solid-state physics. Wefind representations of the these integrals in terms of MeijerG-functions and nested-Barnes integrals. Our investigations began bycomputing 500-digit numerical values of Cn,k,namely a 2-D array of Isingintegrals for all integers n, k where n is in [2,12]and k is in [0,25].We found that some Cn,k enjoy exact evaluations involving DirichletL-functions or the Riemann zeta function. In theprocess of analyzinghypergeometric representations, we found -- experimentally and strikingly-- that the Cn,k almost certainly satisfy certain inter-indicialrelations including discrete k-recursions. Using generating functions,differential theory, complex analysis, and Wilf-Zeilberger algorithms weare able to prove some central cases of these relations.

  10. Taxonomy of particles in Ising spin chains.

    PubMed

    Liu, Dan; Lu, Ping; Müller, Gerhard; Karbach, Michael

    2011-08-01

    The statistical mechanics of particles with shapes on a one-dimensional lattice is investigated in the context of the s=1 Ising chain with uniform nearest-neighbor coupling, quadratic single-site potential, and a magnetic field, which supports four distinct ground states: |↑↓↑↓⋯>, |∘∘⋯>, |↑↑⋯>, |↑∘↑∘⋯>. The complete spectrum is generated from each ground state by particles from a different set of six or seven species. Particles and elements of the pseudovacuum are characterized by motifs (patterns of several consecutive site variables). Particles are floating objects that can be placed into open slots on the lattice. Open slots are recognized as permissible links between motifs. The energy of a particle varies between species but is independent of where it is placed. Placement of one particle changes the open-slot configuration for particles of all species. This statistical interaction is encoded in a generalized Pauli principle, from which the multiplicity of states for a given particle combination is determined and used for the exact statistical mechanical analysis. Particles from all species belong to one of four categories: compacts, hosts, tags, or hybrids. Compacts and hosts find open slots in segments of pseudovacuum. Tags find open slots inside hosts. Hybrids are tags with hosting capability. In the taxonomy of particles proposed here, "species" is indicative of structure and "category" indicative of function. The hosting function splits the Pauli principle into exclusion and accommodation parts. Near phase boundaries, the state of the Ising chain at low temperature is akin to that of miscible or immiscible liquids with particles from one species acting as surfactant molecules.

  11. Simulating Ising spin glasses on a quantum computer

    NASA Astrophysics Data System (ADS)

    Lidar, Daniel A.; Biham, Ofer

    1997-09-01

    A linear-time algorithm is presented for the construction of the Gibbs distribution of configurations in the Ising model, on a quantum computer. The algorithm is designed so that each run provides one configuration with a quantum probability equal to the corresponding thermodynamic weight. The partition function is thus approximated efficiently. The algorithm neither suffers from critical slowing down nor gets stuck in local minima. The algorithm can be applied in any dimension, to a class of spin-glass Ising models with a finite portion of frustrated plaquettes, diluted Ising models, and models with a magnetic field.

  12. Upstream particle events close to the bow shock and 200 earth radii upstream - ISEE-1 and ISEE-3 observations

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Hovestadt, D.; Klecker, B.; Ipavich, F. M.; Gloeckler, G.

    1980-01-01

    Two energetic particle events (28 keV - 145 keV) upstream of the earth's bow shock have been investigated with two identical experiments of the Max-Planck-Institut/University of Maryland on ISEE-1 and ISEE-3. Close to the bow shock the particle distribution is more or less isotropic and indicates strong scattering of these particles in the upstream wave field. At ISEE-3 the particles move essentially scatter-free from the general bow shock direction. The temporal evolution of the particle bursts is discussed in terms of the interplanetary magnetic field topology and the scattering conditions.

  13. ISEE-C attitude determination using fine sun sensor data only

    NASA Technical Reports Server (NTRS)

    Gunshol, L. P.

    1978-01-01

    Techniques developed to determine the spin axis attitude using Fine Sun Sensor (FSS) data only are described. At any given time, the Sun angle specifies the orientation of the spin axis relative to the sunline. The instantaneous time rate of change of the sun angle is directly proportional to the orientation of the spin axis relative to a reference plane that is normal to the ecliptic. Thus, the spin axis attitude can be determined when sufficient data has been collected to accurately measure the rate of change of the sun angle. The uncertainties can be computed directly from the uncertainties in the coefficients of the smoothed sun angle curve. The FSS-only technique is unique in that ephemeris vectors are required only to transform the attitude results to more conventional coordinate frames. The combination of the mission geometry and the FSS accuracy make ISEE-C an ideal mission for applying this method. However, the technique can be used on other missions, such as spin stabilized geosynchronous missions.

  14. Plasma wave experiment for the ISEE-3 mission

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.

    1982-01-01

    Analysis of data from a scientific instrument designed to study solar wind and plasma wave phenomena on the ISEE-3 mission is presented. The performance of work on the data analysis phase is summarized.

  15. Linear relaxation in large two-dimensional Ising models

    NASA Astrophysics Data System (ADS)

    Lin, Y.; Wang, F.

    2016-02-01

    Critical dynamics in two-dimension Ising lattices up to 2048 ×2048 is simulated on field-programmable-gate-array- based computing devices. Linear relaxation times are measured from extremely long Monte Carlo simulations. The longest simulation has 7.1 ×1016 spin updates, which would take over 37 years to simulate on a general purpose computer. The linear relaxation time of the Ising lattices is found to follow the dynamic scaling law for correlation lengths as long as 2048. The dynamic exponent z of the system is found to be 2.179(12), which is consistent with previous studies of Ising lattices with shorter correlation lengths. It is also found that Monte Carlo simulations of critical dynamics in Ising lattices larger than 512 ×512 are very sensitive to the statistical correlations between pseudorandom numbers, making it even more difficult to study such large systems.

  16. Applications of ISES for coastal zone studies

    NASA Technical Reports Server (NTRS)

    Bartlett, D. S.

    1990-01-01

    In contrast to the discipline- and process-oriented topics addressed, coastal zone studies are defined geographically by the special circumstances inherent in the interface between land and water. The characteristics of coastal zones which make them worthy of separate consideration are: (1) the dynamic nature of natural and anthropogenic processes taking place; (2) the relatively restricted spatial domain of the narrow land/water interface; and (3) the large proportion of the Earth's population living within coastal zones, and the resulting extreme pressure on natural and human resources. These characteristics place special constraints and priorities on remote sensing applications, even though the applications themselves bear close relation to those addressed by other elements of this report (e.g., oceans, ice, vegetation/land use). The discussion which follows first describes the suite of remote sensing activities relevant to coastal zone studies. Potential Information Sciences Experiment System (ISES) experiments will then be addressed within two general categories: applications of real-time data transmission and applications of onboard data acquisition and processing.

  17. Continuous error correction for Ising anyons

    NASA Astrophysics Data System (ADS)

    Hutter, Adrian; Wootton, James R.

    2016-04-01

    Quantum gates in topological quantum computation are performed by braiding non-Abelian anyons. These braiding processes can presumably be performed with very low error rates. However, to make a topological quantum computation architecture truly scalable, even rare errors need to be corrected. Error correction for non-Abelian anyons is complicated by the fact that it needs to be performed on a continuous basis, and further errors may occur while we are correcting existing ones. Here, we prove the feasibility of this task, establishing non-Abelian anyons as a viable platform for scalable quantum computation. We thereby focus on Ising anyons as the most prominent example of non-Abelian anyons and show that for these a finite error rate can indeed be corrected continuously. There is a threshold error rate pc>0 such that for all error rates p

  18. Hypothalamus-Pituitary-Thyroid Axis.

    PubMed

    Ortiga-Carvalho, Tania M; Chiamolera, Maria I; Pazos-Moura, Carmen C; Wondisford, Fredic E

    2016-01-01

    The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016. PMID:27347897

  19. Vertical axis wind turbine

    SciTech Connect

    Kato, Y.; Seki, K.; Shimizu, Y.

    1981-01-27

    Wind turbines are largely divided into vertical axis wind turbines and propeller (Horizontal axis) wind turbines. The present invention discloses a vertical axis high speed wind turbine provided with a starting and braking control system. This vertical axis wind turbine is formed by having blades of a proper airfoil fitted to respective supporting arms provided radially from a vertical rotary axis by keeping the blade span-wise direction in parallel with the axis and being provided with a low speed control windmill in which the radial position of each operating piece varies with a centrifugal force produced by the rotation of the vertical rotary axis.

  20. Monte Carlo study of the two-dimensional site-diluted dipolar Ising model

    NASA Astrophysics Data System (ADS)

    Alonso, Juan J.; Allés, B.

    2010-08-01

    By tempered Monte Carlo simulations, we study two-dimensional site-diluted dipolar Ising systems. Dipoles are randomly placed on a fraction x of all L2 sites in a square lattice and point along a common crystalline axis. For xc0 range. Our results enable us to obtain an estimate of the critical exponent associated to the correlation length at T=0 , 1/ν=0.35(10) .

  1. Frustrated Ising chains on the triangular lattice in Sr3NiIrO6

    NASA Astrophysics Data System (ADS)

    Toth, S.; Wu, W.; Adroja, D. T.; Rayaprol, S.; Sampathkumaran, E. V.

    2016-05-01

    Inelastic neutron scattering study on the spin-chain compound Sr3NiIrO6 reveals gapped quasi-1D magnetic excitations. The observed one-magnon band between 29.5 and 39 meV consists of magnon modes of the Ni2 + ions. The fitting of the spin wave spectrum reveals strongly coupled Ising-like chains along the c axis that are weakly coupled into a frustrated triangular lattice in the a b plane. The magnetic excitations survive up to 200 K well above the magnetic ordering temperature of TN˜75 K, also indicating a quasi-1D nature of the magnetic interactions in Sr3NiIrO6 . Our microscopic model is in agreement with ab initio electronic structure calculations and explains the giant spin-flip field observed in bulk magnetization measurements.

  2. Barkhausen noise in the random field Ising magnet Nd2Fe14B

    NASA Astrophysics Data System (ADS)

    Xu, J.; Silevitch, D. M.; Dahmen, K. A.; Rosenbaum, T. F.

    2015-07-01

    With sintered needles aligned and a magnetic field applied transverse to its easy axis, the rare-earth ferromagnet Nd2Fe14B becomes a room-temperature realization of the random field Ising model. The transverse field tunes the pinning potential of the magnetic domains in a continuous fashion. We study the magnetic domain reversal and avalanche dynamics between liquid helium and room temperatures at a series of transverse fields using a Barkhausen noise technique. The avalanche size and energy distributions follow power-law behavior with a cutoff dependent on the pinning strength dialed in by the transverse field, consistent with theoretical predictions for Barkhausen avalanches in disordered materials. A scaling analysis reveals two regimes of behavior: one at low temperature and high transverse field, where the dynamics are governed by the randomness, and the second at high temperature and low transverse field, where thermal fluctuations dominate the dynamics.

  3. Cosmic ray composition investigations using ICE/ISEE-3

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, Mark E.

    1992-01-01

    The analysis of data from the high energy cosmic experiment on ISEE-3 and associated modeling and interpretation activities are discussed. The ISEE-3 payload included two instruments capable of measuring the composition of heavy cosmic rays. The designs of these two instruments incorporated innovations which made it possible, for the first time, to measure isotopic as well as the chemical composition for a wide range of elements. As the result of the demonstrations by these two instruments of the capability to resolve individual cosmic ray isotopes, a new generation of detectors was developed using very similar designs, but having improved reliability and increased sensitive area. The composition measurements which were obtained from the ISEE-3 experiment are summarized.

  4. An Ising spin state explanation for financial asset allocation

    NASA Astrophysics Data System (ADS)

    Horvath, Philip A.; Roos, Kelly R.; Sinha, Amit

    2016-03-01

    We build on the developments in the application of statistical mechanics, notably the identity of the spin degree of freedom in the Ising model, to explain asset price dynamics in financial markets with a representative agent. Specifically, we consider the value of an individual spin to represent the proportional holdings in various assets. We use partial moment arguments to identify asymmetric reactions to information and develop an extension of a plunging and dumping model. This unique identification of the spin is a relaxation of the conventional discrete state limitation on an Ising spin to accommodate a new archetype in Ising model-finance applications wherein spin states may take on continuous values, and may evolve in time continuously, or discretely, depending on the values of the partial moments.

  5. One-dimensional Ising model with multispin interactions

    NASA Astrophysics Data System (ADS)

    Turban, Loïc

    2016-09-01

    We study the spin-1/2 Ising chain with multispin interactions K involving the product of m successive spins, for general values of m. Using a change of spin variables the zero-field partition function of a finite chain is obtained for free and periodic boundary conditions and we calculate the two-spin correlation function. When placed in an external field H the system is shown to be self-dual. Using another change of spin variables the one-dimensional Ising model with multispin interactions in a field is mapped onto a zero-field rectangular Ising model with first-neighbour interactions K and H. The 2D system, with size m × N/m, has the topology of a cylinder with helical BC. In the thermodynamic limit N/m\\to ∞ , m\\to ∞ , a 2D critical singularity develops on the self-duality line, \\sinh 2K\\sinh 2H=1.

  6. Random field Ising model and community structure in complex networks

    NASA Astrophysics Data System (ADS)

    Son, S.-W.; Jeong, H.; Noh, J. D.

    2006-04-01

    We propose a method to determine the community structure of a complex network. In this method the ground state problem of a ferromagnetic random field Ising model is considered on the network with the magnetic field Bs = +∞, Bt = -∞, and Bi≠s,t=0 for a node pair s and t. The ground state problem is equivalent to the so-called maximum flow problem, which can be solved exactly numerically with the help of a combinatorial optimization algorithm. The community structure is then identified from the ground state Ising spin domains for all pairs of s and t. Our method provides a criterion for the existence of the community structure, and is applicable equally well to unweighted and weighted networks. We demonstrate the performance of the method by applying it to the Barabási-Albert network, Zachary karate club network, the scientific collaboration network, and the stock price correlation network. (Ising, Potts, etc.)

  7. Vertical axis windmill

    SciTech Connect

    Zheug, Y.K.

    1984-03-06

    A vertical axis windmill has a blade pivotally connected to a rotatable support structure on an axis passing through its center of gravity which is arranged to lie forward of its aerodynamic center whereby the blade automatically swings outwardly and inwardly when moving on the windward and leeward sides respectively of the axis of rotation of said support means.

  8. Quantum quench in an atomic one-dimensional Ising chain.

    PubMed

    Meinert, F; Mark, M J; Kirilov, E; Lauber, K; Weinmann, P; Daley, A J; Nägerl, H-C

    2013-08-01

    We study nonequilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to antiferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response. PMID:23952393

  9. Self-organizing Ising model of financial markets

    NASA Astrophysics Data System (ADS)

    Zhou, W.-X.; Sornette, D.

    2007-01-01

    We study a dynamical Ising-like model of agents' opinions (buy or sell) with learning, in which the coupling coefficients are re-assessed continuously in time according to how past external news (time-varying magnetic field) have explained realized market returns. By combining herding, the impact of external news and private information, we find that the stylized facts of financial markets are reproduced only when agents misattribute the success of news to predict return to herding effects, thereby providing positive feedbacks leading to the model functioning close to the Ising critical point.

  10. Bootstrapping Critical Ising Model on Three Dimensional Real Projective Space.

    PubMed

    Nakayama, Yu

    2016-04-01

    Given conformal data on a flat Euclidean space, we use crosscap conformal bootstrap equations to numerically solve the Lee-Yang model as well as the critical Ising model on a three dimensional real projective space. We check the rapid convergence of our bootstrap program in two dimensions from the exact solutions available. Based on the comparison, we estimate that our systematic error on the numerically solved one-point functions of the critical Ising model on a three dimensional real projective space is less than 1%. Our method opens up a novel way to solve conformal field theories on nontrivial geometries.

  11. Simultaneous observation of the plasma sheet in the near earth and distant magnetotail - ISEE-1 and ISEE-3

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Hovestadt, D.; Klecker, B.; Baumjohann, W.; Gloeckler, G.; Ipavich, F. M.; Baker, D. N.; Zwickl, R. D.; Tsurutani, B. T.

    1984-01-01

    Particle data have been acquired by the 1981-025 and 1982-019 spacecraft at geosynchronous orbit, as well as ISEE-1 in the near earth geomagnetic tail, and ISEE-3 in the distant geomagnetic tail. These observations are supplemented by ground-based magnetograms from near local midnight stations. Attention is given to a substorm recovery phase, and to observations of ion beams at the plasma sheet boundary in the near earth and distant tail, respectively, which are found to flow in opposite directions.

  12. Internet Access to ISEE-1 and 2 Magnetometer Data

    NASA Technical Reports Server (NTRS)

    1997-01-01

    It is reported that the entire ISEE-1 and -2 magnetometer data are placed on-line, using an 8 Gbyte disk drive. The data are stored at 4-s and 60-s resolution. Also, an interactive world wide web page, which allows to plot, on request, any interval for which magnetometer data are available, is developed.

  13. Duality Between Spin Networks and the 2D Ising Model

    NASA Astrophysics Data System (ADS)

    Bonzom, Valentin; Costantino, Francesco; Livine, Etera R.

    2016-06-01

    The goal of this paper is to exhibit a deep relation between the partition function of the Ising model on a planar trivalent graph and the generating series of the spin network evaluations on the same graph. We provide respectively a fermionic and a bosonic Gaussian integral formulation for each of these functions and we show that they are the inverse of each other (up to some explicit constants) by exhibiting a supersymmetry relating the two formulations. We investigate three aspects and applications of this duality. First, we propose higher order supersymmetric theories that couple the geometry of the spin networks to the Ising model and for which supersymmetric localization still holds. Secondly, after interpreting the generating function of spin network evaluations as the projection of a coherent state of loop quantum gravity onto the flat connection state, we find the probability distribution induced by that coherent state on the edge spins and study its stationary phase approximation. It is found that the stationary points correspond to the critical values of the couplings of the 2D Ising model, at least for isoradial graphs. Third, we analyze the mapping of the correlations of the Ising model to spin network observables, and describe the phase transition on those observables on the hexagonal lattice. This opens the door to many new possibilities, especially for the study of the coarse-graining and continuum limit of spin networks in the context of quantum gravity.

  14. Plasma wave experiment for the ISEE-3 mission

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.

    1983-01-01

    An analysis of data from a scientific instrument designed to study solar wind and plasma wave phenomena on the ISEE-3 Mission is provided. Work on the data analysis phase of the contract from 1 October 1982 through 30 March 1983 is summarized.

  15. Phase transitions in Ising models on directed networks

    NASA Astrophysics Data System (ADS)

    Lipowski, Adam; Ferreira, António Luis; Lipowska, Dorota; Gontarek, Krzysztof

    2015-11-01

    We examine Ising models with heat-bath dynamics on directed networks. Our simulations show that Ising models on directed triangular and simple cubic lattices undergo a phase transition that most likely belongs to the Ising universality class. On the directed square lattice the model remains paramagnetic at any positive temperature as already reported in some previous studies. We also examine random directed graphs and show that contrary to undirected ones, percolation of directed bonds does not guarantee ferromagnetic ordering. Only above a certain threshold can a random directed graph support finite-temperature ferromagnetic ordering. Such behavior is found also for out-homogeneous random graphs, but in this case the analysis of magnetic and percolative properties can be done exactly. Directed random graphs also differ from undirected ones with respect to zero-temperature freezing. Only at low connectivity do they remain trapped in a disordered configuration. Above a certain threshold, however, the zero-temperature dynamics quickly drives the model toward a broken symmetry (magnetized) state. Only above this threshold, which is almost twice as large as the percolation threshold, do we expect the Ising model to have a positive critical temperature. With a very good accuracy, the behavior on directed random graphs is reproduced within a certain approximate scheme.

  16. Vertical Axis Wind Turbine

    2002-04-01

    Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). VAWT-SAL Vertical Axis Wind Turbine- Stochastic Aerodynamic Loads Ver 3.2 numerically simulates the stochastic (random0 aerodynamic loads of the Vertical-Axis Wind Turbine (VAWT) created by the atomspheric turbulence. The program takes into account the rotor geometry, operating conditions, and assumed turbulence properties.

  17. Applications of ISES for vegetation and land use

    NASA Technical Reports Server (NTRS)

    Wilson, R. Gale

    1990-01-01

    Remote sensing relative to applications involving vegetation cover and land use is reviewed to consider the potential benefits to the Earth Observing System (Eos) of a proposed Information Sciences Experiment System (ISES). The ISES concept has been proposed as an onboard experiment and computational resource to support advanced experiments and demonstrations in the information and earth sciences. Embedded in the concept is potential for relieving the data glut problem, enhancing capabilities to meet real-time needs of data users and in-situ researchers, and introducing emerging technology to Eos as the technology matures. These potential benefits are examined in the context of state-of-the-art research activities in image/data processing and management.

  18. Thermalization, Error Correction, and Memory Lifetime for Ising Anyon Systems

    NASA Astrophysics Data System (ADS)

    Brell, Courtney G.; Burton, Simon; Dauphinais, Guillaume; Flammia, Steven T.; Poulin, David

    2014-07-01

    We consider two-dimensional lattice models that support Ising anyonic excitations and are coupled to a thermal bath. We propose a phenomenological model for the resulting short-time dynamics that includes pair creation, hopping, braiding, and fusion of anyons. By explicitly constructing topological quantum error-correcting codes for this class of system, we use our thermalization model to estimate the lifetime of the quantum information stored in the encoded spaces. To decode and correct errors in these codes, we adapt several existing topological decoders to the non-Abelian setting. We perform large-scale numerical simulations of these two-dimensional Ising anyon systems and find that the thresholds of these models range from 13% to 25%. To our knowledge, these are the first numerical threshold estimates for quantum codes without explicit additive structure.

  19. A brief study on coevolution of Ising dynamics

    NASA Astrophysics Data System (ADS)

    Hajra, K. B.; Chandra, A. K.

    2012-01-01

    We consider coevolution of site state and network structures from different initial substrates: a one dimensional Ising chain, a scale free network and network with non-linear degree dependence. The dynamics is governed by a preassigned stability parameter S, and a rewiring factor φ, that determines whether the Ising spin at the chosen site flips or whether the site gets rewired to another site in the system. We have observed the steady state average stability and magnetisation for both kinds of systems to have an idea about the effect of initial network topology. Although the average stability shows almost similar behaviour, the magnetisation depends on the initial condition we start from. Apart from the local dynamics, the global effect on the dynamics has also been studied. These studies show interesting variations in the steady state values of average stability and magnetisation for different values of S and φ, which helps in indicating the gradual change of existing social networks.

  20. A MATLAB GUI to study Ising model phase transition

    NASA Astrophysics Data System (ADS)

    Thornton, Curtislee; Datta, Trinanjan

    We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.

  1. Phase transition of the Ising model on a fractal lattice.

    PubMed

    Genzor, Jozef; Gendiar, Andrej; Nishino, Tomotoshi

    2016-01-01

    The phase transition of the Ising model is investigated on a planar lattice that has a fractal structure. On the lattice, the number of bonds that cross the border of a finite area is doubled when the linear size of the area is extended by a factor of 4. The free energy and the spontaneous magnetization of the system are obtained by means of the higher-order tensor renormalization group method. The system exhibits the order-disorder phase transition, where the critical indices are different from those of the square-lattice Ising model. An exponential decay is observed in the density-matrix spectrum even at the critical point. It is possible to interpret that the system is less entangled because of the fractal geometry. PMID:26871057

  2. OpenCL Implementation of NeuroIsing

    NASA Astrophysics Data System (ADS)

    Zapart, C. A.

    Recent advances in graphics card hardware combined with anintroduction of the OpenCL standard promise to accelerate numerical simulations across diverse scientific disciplines. One such field benefiting from new hardware/software paradigms is econophysics. The paper describes an OpenCL implementation of a selected econophysics model: NeuroIsing, which has been designed to execute in parallel on a vendor-independent graphics card. Originally introduced in the paper [C.~A.~Zapart, ``Econophysics in Financial Time Series Prediction'', PhD thesis, Graduate University for Advanced Studies, Japan (2009)], at first it was implemented on a CELL processor running inside a SONY PS3 games console. The NeuroIsing framework can be applied to predicting and trading foreign exchange as well as stock market index futures.

  3. Precision islands in the Ising and O( N ) models

    NASA Astrophysics Data System (ADS)

    Kos, Filip; Poland, David; Simmons-Duffin, David; Vichi, Alessandro

    2016-08-01

    We make precise determinations of the leading scaling dimensions and operator product expansion (OPE) coefficients in the 3d Ising, O(2), and O(3) models from the conformal bootstrap with mixed correlators. We improve on previous studies by scanning over possible relative values of the leading OPE coefficients, which incorporates the physical information that there is only a single operator at a given scaling dimension. The scaling dimensions and OPE coefficients obtained for the 3d Ising model, (Δ σ , Δ ɛ , λ σσɛ , λ ɛɛɛ ) = (0 .5181489(10) , 1 .412625(10) , 1 .0518537(41) , 1 .532435(19) , give the most precise determinations of these quantities to date.

  4. Nature versus nurture: predictability in low-temperature Ising dynamics.

    PubMed

    Ye, J; Machta, J; Newman, C M; Stein, D L

    2013-10-01

    Consider a dynamical many-body system with a random initial state subsequently evolving through stochastic dynamics. What is the relative importance of the initial state ("nature") versus the realization of the stochastic dynamics ("nurture") in predicting the final state? We examined this question for the two-dimensional Ising ferromagnet following an initial deep quench from T=∞ to T=0. We performed Monte Carlo studies on the overlap between "identical twins" raised in independent dynamical environments, up to size L=500. Our results suggest an overlap decaying with time as t(-θ)(h) with θ(h)=0.22 ± 0.02; the same exponent holds for a quench to low but nonzero temperature. This "heritability exponent" may equal the persistence exponent for the two-dimensional Ising ferromagnet, but the two differ more generally. PMID:24229093

  5. The 2014 Earth return of the ISEE-3/ICE spacecraft

    NASA Astrophysics Data System (ADS)

    Dunham, David W.; Farquhar, Robert W.; Loucks, Michel; Roberts, Craig E.; Wingo, Dennis; Cowing, Keith L.; Garcia, Leonard N.; Craychee, Tim; Nickel, Craig; Ford, Anthony; Colleluori, Marco; Folta, David C.; Giorgini, Jon D.; Nace, Edward; Spohr, John E.; Dove, William; Mogk, Nathan; Furfaro, Roberto; Martin, Warren L.

    2015-05-01

    In 1978, the 3rd International Sun-Earth Explorer (ISEE-3) became the first libration-point mission, about the Sun-Earth L1 point. Four years later, a complex series of lunar swingbys and small propulsive maneuvers ejected ISEE-3 from the Earth-Moon system, to fly by a comet (Giacobini-Zinner) for the first time in 1985, as the rechristened International Cometary Explorer (ICE). In its heliocentric orbit, ISEE-3/ICE slowly drifted around the Sun to return to the Earth's vicinity in 2014. Maneuvers in 1986 targeted a 2014 August 10th lunar swingby to recapture ISEE-3 into Earth orbit. In 1999, ISEE-3/ICE passed behind the Sun; after that, tracking of the spacecraft ceased and its control center at Goddard was shut down. In 2013, meetings were held to assess the viability of "re-awakening" ISEE-3. The goal was to target the 2014 lunar swingby, to recapture the spacecraft back into a halo-like Sun-Earth L1 orbit. However, special hardware for communicating with the spacecraft via NASA's Deep Space Network stations was discarded after 1999, and NASA had no funds to reconstruct the lost equipment. After ISEE-3's carrier signal was detected on March 1st with the 20 m antenna at Bochum, Germany, Skycorp, Inc. decided to initiate the ISEE-3 Reboot Project, to use software-defined radio with a less costly S-band transmitter that was purchased with a successful RocketHub crowdsourcing effort. NASA granted Skycorp permission to command the spacecraft. Commanding was successfully accomplished using the 300 m radio telescope at Arecibo. New capture trajectories were computed, including trajectories that would target the August lunar swingby and use a second ΔV (velocity change) that could target later lunar swingbys that would allow capture into almost any desired final orbit, including orbits about either the Sun-Earth L1 or L2 points, a lunar distant retrograde orbit, or targeting a flyby of the Earth-approaching active Comet Wirtanen in 2018. A tiny spinup maneuver was

  6. Nature versus nurture: Predictability in low-temperature Ising dynamics

    NASA Astrophysics Data System (ADS)

    Ye, J.; Machta, J.; Newman, C. M.; Stein, D. L.

    2013-10-01

    Consider a dynamical many-body system with a random initial state subsequently evolving through stochastic dynamics. What is the relative importance of the initial state (“nature”) versus the realization of the stochastic dynamics (“nurture”) in predicting the final state? We examined this question for the two-dimensional Ising ferromagnet following an initial deep quench from T=∞ to T=0. We performed Monte Carlo studies on the overlap between “identical twins” raised in independent dynamical environments, up to size L=500. Our results suggest an overlap decaying with time as t-θh with θh=0.22±0.02; the same exponent holds for a quench to low but nonzero temperature. This “heritability exponent” may equal the persistence exponent for the two-dimensional Ising ferromagnet, but the two differ more generally.

  7. Nature versus nurture: predictability in low-temperature Ising dynamics.

    PubMed

    Ye, J; Machta, J; Newman, C M; Stein, D L

    2013-10-01

    Consider a dynamical many-body system with a random initial state subsequently evolving through stochastic dynamics. What is the relative importance of the initial state ("nature") versus the realization of the stochastic dynamics ("nurture") in predicting the final state? We examined this question for the two-dimensional Ising ferromagnet following an initial deep quench from T=∞ to T=0. We performed Monte Carlo studies on the overlap between "identical twins" raised in independent dynamical environments, up to size L=500. Our results suggest an overlap decaying with time as t(-θ)(h) with θ(h)=0.22 ± 0.02; the same exponent holds for a quench to low but nonzero temperature. This "heritability exponent" may equal the persistence exponent for the two-dimensional Ising ferromagnet, but the two differ more generally.

  8. Conversational Dominance.

    ERIC Educational Resources Information Center

    Esau, Helmut; Poth, Annette

    Details of conversational behavior can often not be interpreted until the social interaction, including the rights and obligations of the participants, their intent, the topic, etc., has been defined. This paper presents a model of conversation in which the conversational image a person presents in a given conversational situation is a function of…

  9. Numerically exact solvable random-bond Ising model

    NASA Astrophysics Data System (ADS)

    Morgenstern, I.

    1981-06-01

    Exact free energies are calculated numerically for a L×L-Ising lattice ( L≦800) with constant nearest neighbour coupling between adjacent columns and random n.n. coupling between adjacent rows. For the latter a gaussian and a double-peaked δ-distribution are investigated. The result should be useful as a check of the controversially discussed replica trick [1]. In agreement with the numerical treatment a mean field approximation shows a transition to a spinglass phase.

  10. A review of the ISEE-3 geotail magnetic field results

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Goldstein, B. E.; Burton, M. E.; Jones, D. E.

    1986-01-01

    This review presents a summary of past work on the ISEE-3 distant tail magnetic field observations. An attempt has been made to bring the many results together as a coherent whole, in the hope that the reader can envision the direction of future research necessary to achieve an understanding of the dynamics of the magnetotail from 60 to 240 earth radii and perhaps beyond.

  11. Long range Ising model for credit risk modeling

    NASA Astrophysics Data System (ADS)

    Molins, Jordi; Vives, Eduard

    2005-07-01

    Within the framework of maximum entropy principle we show that the finite-size long-range Ising model is the adequate model for the description of homogeneous credit portfolios and the computation of credit risk when default correlations between the borrowers are included. The exact analysis of the model suggest that when the correlation increases a first-order-like transition may occur inducing a sudden risk increase.

  12. Quantum algorithm for an additive approximation of Ising partition functions

    NASA Astrophysics Data System (ADS)

    Matsuo, Akira; Fujii, Keisuke; Imoto, Nobuyuki

    2014-08-01

    We investigate quantum-computational complexity of calculating partition functions of Ising models. We construct a quantum algorithm for an additive approximation of Ising partition functions on square lattices. To this end, we utilize the overlap mapping developed by M. Van den Nest, W. Dür, and H. J. Briegel [Phys. Rev. Lett. 98, 117207 (2007), 10.1103/PhysRevLett.98.117207] and its interpretation through measurement-based quantum computation (MBQC). We specify an algorithmic domain, on which the proposed algorithm works, and an approximation scale, which determines the accuracy of the approximation. We show that the proposed algorithm performs a nontrivial task, which would be intractable on any classical computer, by showing that the problem that is solvable by the proposed quantum algorithm is BQP-complete. In the construction of the BQP-complete problem coupling strengths and magnetic fields take complex values. However, the Ising models that are of central interest in statistical physics and computer science consist of real coupling strengths and magnetic fields. Thus we extend the algorithmic domain of the proposed algorithm to such a real physical parameter region and calculate the approximation scale explicitly. We found that the overlap mapping and its MBQC interpretation improve the approximation scale exponentially compared to a straightforward constant-depth quantum algorithm. On the other hand, the proposed quantum algorithm also provides partial evidence that there exist no efficient classical algorithm for a multiplicative approximation of the Ising partition functions even on the square lattice. This result supports the observation that the proposed quantum algorithm also performs a nontrivial task in the physical parameter region.

  13. Ising model observables and non-backtracking walks

    SciTech Connect

    Helmuth, Tyler

    2014-08-15

    This paper presents an alternative proof of the connection between the partition function of the Ising model on a finite graph G and the set of non-backtracking walks on G. The techniques used also give formulas for spin-spin correlation functions in terms of non-backtracking walks. The main tools used are Viennot's theory of heaps of pieces and turning numbers on surfaces.

  14. Coupled modified baker's transformations for the Ising model.

    PubMed

    Sakaguchi, H

    1999-12-01

    An invertible coupled map lattice is proposed for the Ising model. Each elemental map is a modified baker's transformation, which is a two-dimensional map of X and Y. The time evolution of the spin variable is memorized in the binary representation of the Y variable. The temporal entropy and time correlation of the spin variable are calculated from the snapshot configuration of the Y variables.

  15. The Ising model in physics and statistical genetics.

    PubMed

    Majewski, J; Li, H; Ott, J

    2001-10-01

    Interdisciplinary communication is becoming a crucial component of the present scientific environment. Theoretical models developed in diverse disciplines often may be successfully employed in solving seemingly unrelated problems that can be reduced to similar mathematical formulation. The Ising model has been proposed in statistical physics as a simplified model for analysis of magnetic interactions and structures of ferromagnetic substances. Here, we present an application of the one-dimensional, linear Ising model to affected-sib-pair (ASP) analysis in genetics. By analyzing simulated genetics data, we show that the simplified Ising model with only nearest-neighbor interactions between genetic markers has statistical properties comparable to much more complex algorithms from genetics analysis, such as those implemented in the Allegro and Mapmaker-Sibs programs. We also adapt the model to include epistatic interactions and to demonstrate its usefulness in detecting modifier loci with weak individual genetic contributions. A reanalysis of data on type 1 diabetes detects several susceptibility loci not previously found by other methods of analysis.

  16. The ISEE 1 and 2 Medium Energy Particles Experiment

    NASA Technical Reports Server (NTRS)

    Williams, D. J.; Fritz, T. A.; Keppler, E.; Wilken, B.; Wibberenz, G.

    1978-01-01

    The Medium Energy Particles Experiment (MEPE) on board ISEE 1 and 2 consists of the WIM instrument on ISEE 1 and the KED instrument on ISEE 2. Both instruments employ solid-state detectors and magnetic analysis to measure the angular, energy, and intensity distributions of protons (ions) above 24 keV and electrons above 20 keV. The WIM instrument also includes a composition measurement employing Delta E-by-E and time-of-flight techniques. Three-parameter analysis is performed above 250 keV/nucleon, and single parameter analysis is performed above 125 keV/nucleon for helium through oxygen. Three-dimensional angular distributions are obtained through the use of a scan platform in the WIM instrument and multiple detector heads in the KED instrument. A variety of operational modes are used to optimize data collection from both instruments. Resolutions up to 128 channels in energy, 192 samples over the unit sphere in angle, and 0.095 sec in time are available.

  17. Ising Quantum Hall Ferromagnetism in AlAs Quantum Wells.

    NASA Astrophysics Data System (ADS)

    de Poortere, Etienne

    2002-03-01

    Though quantum Hall ferromagnetic transitions in two-dimensional (2D) systems are observed in several materials, such transitions in AlAs 2D electrons offer a unique combination of two remarkable properties: (1) the resistance of the carrier system increases sharply at the transition, and (2) these resistance spikes are hysteretic at low temperatures [1]. We have been able to uncover these properties thanks to recent improvements in the quality of our AlAs samples [2], which now attain a mobility as high as 31 m^2/Vs at a density 5 × 10^11 cm-2. These transport phenomena at Ising transitions result in part from the electronic properties of AlAs, which favor a strong competition between exchange, cyclotron and Zeeman energies. Indeed, 2D electrons in AlAs have a high and anisotropic effective band mass comparable to that of Si, and a band g-factor close to 2. In addition, high-density AlAs 2D electrons occupy two X-point valleys of the Brillouin zone, allowing for inter-valley Ising transitions. In this talk we present results from our study of Ising transitions in AlAs 2D electrons. We observe that the hysteretic resistance of a given transition depends sensitively on the occupation of the two levels involved in the transition, increasing in amplitude as these levels are depleted. We also analyze the spike temperature dependence, which shows that unlike the nearby quantum Hall resistance minima, the resistance spikes themselves are not activated. Other parameters are also varied, such as total carrier density and transverse electric field in the AlAs quantum well. A Hartree-Fock picture of these Ising transitions has been drawn, involving magnetic domains and increased scattering at the domain boundaries [3]. Nevertheless, many of the measured dependencies of the Ising transition resistance spikes are not yet qualitatively understood, forming thus a jigsaw puzzle of many parts. [1] E. P. De Poortere et al., Science 290, 1546 (2000). [2] E. P. De Poortere et al

  18. Single-Axis Accelerometer

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis Stephen (Inventor); Capo-Lugo, Pedro A. (Inventor)

    2016-01-01

    A single-axis accelerometer includes a housing defining a sleeve. An object/mass is disposed in the sleeve for sliding movement therein in a direction aligned with the sleeve's longitudinal axis. A first piezoelectric strip, attached to a first side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The first piezoelectric strip includes a first strip of a piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A second piezoelectric strip, attached to a second side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The second piezoelectric strip includes a second strip of the piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A voltage sensor is electrically coupled to at least one of the first and second piezoelectric strips.

  19. Network of time-multiplexed optical parametric oscillators as a coherent Ising machine

    NASA Astrophysics Data System (ADS)

    Marandi, Alireza; Wang, Zhe; Takata, Kenta; Byer, Robert L.; Yamamoto, Yoshihisa

    2014-12-01

    Finding the ground states of the Ising Hamiltonian maps to various combinatorial optimization problems in biology, medicine, wireless communications, artificial intelligence and social network. So far, no efficient classical and quantum algorithm is known for these problems and intensive research is focused on creating physical systems—Ising machines—capable of finding the absolute or approximate ground states of the Ising Hamiltonian. Here, we report an Ising machine using a network of degenerate optical parametric oscillators (OPOs). Spins are represented with above-threshold binary phases of the OPOs and the Ising couplings are realized by mutual injections. The network is implemented in a single OPO ring cavity with multiple trains of femtosecond pulses and configurable mutual couplings, and operates at room temperature. We programmed a small non-deterministic polynomial time-hard problem on a 4-OPO Ising machine and in 1,000 runs no computational error was detected.

  20. Quantum cluster algorithm for frustrated Ising models in a transverse field

    NASA Astrophysics Data System (ADS)

    Biswas, Sounak; Rakala, Geet; Damle, Kedar

    2016-06-01

    Working within the stochastic series expansion framework, we introduce and characterize a plaquette-based quantum cluster algorithm for quantum Monte Carlo simulations of transverse field Ising models with frustrated Ising exchange interactions. As a demonstration of the capabilities of this algorithm, we show that a relatively small ferromagnetic next-nearest-neighbor coupling drives the transverse field Ising antiferromagnet on the triangular lattice from an antiferromagnetic three-sublattice ordered state at low temperature to a ferrimagnetic three-sublattice ordered state.

  1. Exact results for a random frustrated Ising model on the Kagome lattice

    SciTech Connect

    Giacomini, H.J.; Riera, J.A.

    1987-11-01

    The authors perform a slight modification of the decoration-decimation transformation which allows us to map the homogeneous Ising model on the honeycomb lattice on an inhomogeneous Ising model on the Kagome lattice. Then, we obtain exact results for a class of random bond Ising model on the Kagome lattice with competing interactions and show that the different types of frustration make the critical point of the pure model disappear.

  2. Partially disordered antiferromagnetism and multiferroic behavior in a frustrated Ising system CoCl2–2SC(NH2)2

    DOE PAGES

    Mun, Eundeok; Weickert, Dagmar Franziska; Kim, Jaewook; Scott, Brian L.; Miclea, Corneliu Florin; Movshovich, Roman; Wilcox, Jason; Manson, Jamie; Zapf, Vivien S.

    2016-03-01

    We investigate partially disordered antiferromagnetism in CoCl2-2SC(NH2)2, in which ab-plane hexagonal layers are staggered along the c axis rather than stacked. A robust 1/3 state forms in applied magnetic fields in which the spins are locked, varying as a function of neither temperature nor field. By contrast, in zero field and applied fields at higher temperatures, partial antiferromagnetic order occurs, in which free spins are available to create a Curie-like magnetic susceptibility. We report measurements of the crystallographic structure and the specific heat, magnetization, and electric polarization down to T = 50mK and up to μ0H = 60T. The Co2+more » S = 3/2 spins are Ising-like and form distorted hexagonal layers. The Ising energy scale is well separated from the magnetic exchange, and both energy scales are accessible to the measurements, allowing us to cleanly parametrize them. In transverse fields, a quantum Ising phase transition can be observed at 2 T. Lastly, we find that magnetic exchange striction induces changes in the electric polarization up to 3μC/m2, and single-ion magnetic anisotropy effects induce a much larger electric polarization change of 300μC/m2.« less

  3. Partially disordered antiferromagnetism and multiferroic behavior in a frustrated Ising system CoCl2-2 SC (NH2)2

    NASA Astrophysics Data System (ADS)

    Mun, Eundeok; Weickert, Franziska; Kim, Jaewook; Scott, Brian L.; Miclea, Corneliu Florin; Movshovich, Roman; Wilcox, Jason; Manson, Jamie; Zapf, Vivien S.

    2016-03-01

    We investigate partially disordered antiferromagnetism in CoCl2-2SC(NH2)2, in which a b -plane hexagonal layers are staggered along the c axis rather than stacked. A robust 1/3 state forms in applied magnetic fields in which the spins are locked, varying as a function of neither temperature nor field. By contrast, in zero field and applied fields at higher temperatures, partial antiferromagnetic order occurs, in which free spins are available to create a Curie-like magnetic susceptibility. We report measurements of the crystallographic structure and the specific heat, magnetization, and electric polarization down to T =50 mK and up to μ0H =60 T . The Co2 +S =3 /2 spins are Ising-like and form distorted hexagonal layers. The Ising energy scale is well separated from the magnetic exchange, and both energy scales are accessible to the measurements, allowing us to cleanly parametrize them. In transverse fields, a quantum Ising phase transition can be observed at 2 T. Finally, we find that magnetic exchange striction induces changes in the electric polarization up to 3 μ C /m2 , and single-ion magnetic anisotropy effects induce a much larger electric polarization change of 300 μ C /m2 .

  4. Magnetic Order in the Frustrated Ising Quasi-One Dimensional Compound NaCo(acac)3 • Benzene

    NASA Astrophysics Data System (ADS)

    Karaki, Yoshitomo; Kuga, Kentaro; Kimura, Kenta; Nakatsuji, Satoru; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya

    2015-08-01

    We report the results of susceptibility, magnetization curve, and specific heat measurements on single crystals of NaCo(acac)3 • benzene, which forms a triangular lattice on the ab-plane with Ising ferromagnetic chains along the c-axis. We found a long-range order below 62 mK by specific heat measurement, a steplike increase in susceptibility at this temperature, and a plateau of one-third of the full moment in the M-H curve at 20 mK. We also observed a spin relaxation that obeys the Arrhenius law in the ordered state. The existence of a partially disordered antiferromagnetic state is discussed on the basis of the results.

  5. Low-temperature spin-glass behavior in a diluted dipolar Ising system

    NASA Astrophysics Data System (ADS)

    Alonso, Juan J.

    2015-03-01

    Using Monte Carlo simulations, we study the character of the spin-glass (SG) state of a site-diluted dipolar Ising model. We consider systems of dipoles randomly placed on a fraction x of all L3 sites of a simple cubic lattice that point up or down along a given crystalline axis. For x ≲0.65 these systems are known to exhibit an equilibrium spin-glass phase below a temperature Tsg∝x . At high dilution and very low temperatures, well deep in the SG phase, we find spiky distributions of the overlap parameter q that are strongly sample dependent. We focus on spikes associated with large excitations. From cumulative distributions of q and a pair correlation function averaged over several thousands of samples we find that, for the system sizes studied, the average width of spikes, and the fraction of samples with spikes higher than a certain threshold, does not vary appreciably with L . This is compared with the behavior found for the Sherrington-Kirkpatrick model.

  6. Magnetic structure of Yb2Pt2Pb: Ising moments on the Shastry-Sutherland lattice

    DOE PAGES

    Miiller, W.; Zaliznyak, I.; Wu, L. S.; Kim, M. S.; Orvis, T.; Simonson, J. W.; Gamza, M.; McNally, D. M.; Nelson, C. S.; Ehlers, G.; et al

    2016-03-22

    Neutron diffraction measurements were carried out on single crystals and powders of Yb2Pt2Pb, where Yb moments form two interpenetrating planar sublattices of orthogonal dimers, a geometry known as Shastry-Sutherland lattice, and are stacked along the c axis in a ladder geometry. Yb2Pt2Pb orders antiferromagnetically at TN=2.07K, and the magnetic structure determined from these measurements features the interleaving of two orthogonal sublattices into a 5×5×1 magnetic supercell that is based on stripes with moments perpendicular to the dimer bonds, which are along (110) and (–110). Magnetic fields applied along (110) or (–110) suppress the antiferromagnetic peaks from an individual sublattice, butmore » leave the orthogonal sublattice unaffected, evidence for the Ising character of the Yb moments in Yb2Pt2Pb that is supported by point charge calculations. Furthermore, specific heat, magnetic susceptibility, and electrical resistivity measurements concur with neutron elastic scattering results that the longitudinal critical fluctuations are gapped with ΔE≃0.07meV.« less

  7. Complex replica zeros of ±J Ising spin glass at zero temperature

    NASA Astrophysics Data System (ADS)

    Obuchi, Tomoyuki; Kabashima, Yoshiyuki; Nishimori, Hidetoshi

    2009-02-01

    Zeros of the nth moment of the partition function [Zn] are investigated in a vanishing temperature limit β → ∞, n → 0 keeping y = βn ~ O(1). In this limit, the moment parameterized by y characterizes the distribution of the ground-state energy. We numerically investigate the zeros for ±J Ising spin-glass models with tree and several other systems, which can be carried out with a feasible computational cost by a symbolic operation based on the Bethe-Peierls method. For several tree systems we find that the zeros tend to approach the real axis of y in the thermodynamic limit implying that the moment cannot be described by a single analytic function of y as the system size tends to infinity, which may be associated with breaking of the replica symmetry. However, examination of the analytical properties of the moment function and assessment of the spin-glass susceptibility indicate that the breaking of analyticity is relevant to neither one-step nor full replica symmetry breaking.

  8. The immature HPO axis.

    PubMed

    Buttram, V C

    1975-01-01

    One cause or anovulation may be an immature hypothalamic-pituitary-ovarian axis. The fact that initial menstrual cycles are usually irregular and often anovulatory implies that a maturation process is taking place in the HPO axis and that cyclic ovulatory menstruation begins only when adequate maturation occurs. Moreover, the external appearance of the ovary of a severely oligomenorrheic or amenorrheic female frequently is similar to that of a prepubertal female--this is, the ovary appears normal in size of slightly smaller, has a smooth, glistening surface without convolutions, and its capsule-like outer surface reveals few, if any, underlying follicles. A reasonable assumption is that there is inadequate gonadotropin stimulation of these ovaries possibly as a result of an immature HPO axis. The studies by radioimmunoassay of FSH and LH levels in prepubertal and pubertal females offer no statistical data by which to measure the maturity of the HPO axis, although consistently low FSH and LH levels may prove meaningful. Studies of FSH and LH in patients exhibiting gonadal dysgenesis neither support or disprove the immature HPO axis theory, but studies of idiopathic sexual precocity tend to support it. Studies using LH-RF in prepubertal and pubertal females indicate a pattern of response which may give useful information in the area.

  9. Interacting damage models mapped onto ising and percolation models

    SciTech Connect

    Toussaint, Renaud; Pride, Steven R.

    2004-03-23

    The authors introduce a class of damage models on regular lattices with isotropic interactions between the broken cells of the lattice. Quasistatic fiber bundles are an example. The interactions are assumed to be weak, in the sense that the stress perturbation from a broken cell is much smaller than the mean stress in the system. The system starts intact with a surface-energy threshold required to break any cell sampled from an uncorrelated quenched-disorder distribution. The evolution of this heterogeneous system is ruled by Griffith's principle which states that a cell breaks when the release in potential (elastic) energy in the system exceeds the surface-energy barrier necessary to break the cell. By direct integration over all possible realizations of the quenched disorder, they obtain the probability distribution of each damage configuration at any level of the imposed external deformation. They demonstrate an isomorphism between the distributions so obtained and standard generalized Ising models, in which the coupling constants and effective temperature in the Ising model are functions of the nature of the quenched-disorder distribution and the extent of accumulated damage. In particular, they show that damage models with global load sharing are isomorphic to standard percolation theory, that damage models with local load sharing rule are isomorphic to the standard ising model, and draw consequences thereof for the universality class and behavior of the autocorrelation length of the breakdown transitions corresponding to these models. they also treat damage models having more general power-law interactions, and classify the breakdown process as a function of the power-law interaction exponent. Last, they also show that the probability distribution over configurations is a maximum of Shannon's entropy under some specific constraints related to the energetic balance of the fracture process, which firmly relates this type of quenched-disorder based damage model

  10. Globally nilpotent differential operators and the square Ising model

    NASA Astrophysics Data System (ADS)

    Bostan, A.; Boukraa, S.; Hassani, S.; Maillard, J.-M.; Weil, J.-A.; Zenine, N.

    2009-03-01

    We recall various multiple integrals with one parameter, related to the isotropic square Ising model, and corresponding, respectively, to the n-particle contributions of the magnetic susceptibility, to the (lattice) form factors, to the two-point correlation functions and to their λ-extensions. The univariate analytic functions defined by these integrals are holonomic and even G-functions: they satisfy Fuchsian linear differential equations with polynomial coefficients and have some arithmetic properties. We recall the explicit forms, found in previous work, of these Fuchsian equations, as well as their Russian-doll and direct sum structures. These differential operators are selected Fuchsian linear differential operators, and their remarkable properties have a deep geometrical origin: they are all globally nilpotent, or, sometimes, even have zero p-curvature. We also display miscellaneous examples of globally nilpotent operators emerging from enumerative combinatorics problems for which no integral representation is yet known. Focusing on the factorized parts of all these operators, we find out that the global nilpotence of the factors (resp. p-curvature nullity) corresponds to a set of selected structures of algebraic geometry: elliptic curves, modular curves, curves of genus five, six,..., and even a remarkable weight-1 modular form emerging in the three-particle contribution χ(3) of the magnetic susceptibility of the square Ising model. Noticeably, this associated weight-1 modular form is also seen in the factors of the differential operator for another n-fold integral of the Ising class, Φ(3)H, for the staircase polygons counting, and in Apéry's study of ζ(3). G-functions naturally occur as solutions of globally nilpotent operators. In the case where we do not have G-functions, but Hamburger functions (one irregular singularity at 0 or ∞) that correspond to the confluence of singularities in the scaling limit, the p-curvature is also found to verify new

  11. ISEES: an institute for sustainable software to accelerate environmental science

    NASA Astrophysics Data System (ADS)

    Jones, M. B.; Schildhauer, M.; Fox, P. A.

    2013-12-01

    Software is essential to the full science lifecycle, spanning data acquisition, processing, quality assessment, data integration, analysis, modeling, and visualization. Software runs our meteorological sensor systems, our data loggers, and our ocean gliders. Every aspect of science is impacted by, and improved by, software. Scientific advances ranging from modeling climate change to the sequencing of the human genome have been rendered possible in the last few decades due to the massive improvements in the capabilities of computers to process data through software. This pivotal role of software in science is broadly acknowledged, while simultaneously being systematically undervalued through minimal investments in maintenance and innovation. As a community, we need to embrace the creation, use, and maintenance of software within science, and address problems such as code complexity, openness,reproducibility, and accessibility. We also need to fully develop new skills and practices in software engineering as a core competency in our earth science disciplines, starting with undergraduate and graduate education and extending into university and agency professional positions. The Institute for Sustainable Earth and Environmental Software (ISEES) is being envisioned as a community-driven activity that can facilitate and galvanize activites around scientific software in an analogous way to synthesis centers such as NCEAS and NESCent that have stimulated massive advances in ecology and evolution. We will describe the results of six workshops (Science Drivers, Software Lifecycles, Software Components, Workforce Development and Training, Sustainability and Governance, and Community Engagement) that have been held in 2013 to envision such an institute. We will present community recommendations from these workshops and our strategic vision for how ISEES will address the technical issues in the software lifecycle, sustainability of the whole software ecosystem, and the critical

  12. Quantum simulation with arrays of transmon qubits: Ising dynamics

    NASA Astrophysics Data System (ADS)

    Ramasesh, Vinay; Hacohen-Gourgy, Shay; Kiendl, Thomas; Marquardt, Florian; Siwak, Nathan; Richardson, Christopher; Siddiqi, Irfan

    2015-03-01

    Chains of coupled qubits are known to realize the transverse-field Ising Hamiltonian in the two-level approximation. In this model, the qubit transition frequencies map onto the external magnetic field, so the ground and excited states play the role of spin-up and spin-down atoms. We implement this structure in a planar, on-chip architecture, with a one dimensional linear array of capacitively-coupled transmon qubits, where the two terminal qubits are dispersively coupled to microwave independent resonators for state readout. We present spectroscopic data and describe coherent manipulations in the array. This work is supported by the AFOSR.

  13. Hamiltonian Determination with Restricted Access in Transverse Field Ising Chain

    NASA Astrophysics Data System (ADS)

    Fasihi, Mohammad Ali; Tanaka, Shu; Nakahara, Mikio; Kondo, Yasushi

    2011-04-01

    We propose a method to evaluate parameters in the Hamiltonian of the Ising chain under site-dependent transverse fields, with a proviso that we can control and measure one of the edge spins only. We evaluate the eigenvalues of the Hamiltonian and the time-evoultion operator exactly for a three-spin chain, from which we obtain the expectation values of σx of the first spin. The parameters are found from the peak positions of the Fourier transform of the expectation value. There are four assumptions in our method, which are mild enough to be satisfied in many physical systems.

  14. Frustration and correlations in stacked triangular-lattice Ising antiferromagnets

    NASA Astrophysics Data System (ADS)

    Burnell, F. J.; Chalker, J. T.

    2015-12-01

    We study multilayer triangular-lattice Ising antiferromagnets with interlayer interactions that are weak and frustrated in an abc stacking. By analyzing a coupled height model description of these systems, we show that they exhibit a classical spin liquid regime at low temperature, in which both intralayer and interlayer correlations are strong but there is no long-range order. Diffuse scattering in this regime is concentrated on a helix in reciprocal space, as observed for charge ordering in the materials LuFe2O4 and YbFe2O4 .

  15. Ising nanowire with random field at surface; its unconventional effects

    NASA Astrophysics Data System (ADS)

    Kaneyoshi, T.

    2016-10-01

    The phase diagrams and temperature dependences of total magnetization mT in an Ising nanowire with a random magnetic field at the surface are studied by the uses of the effective-field theory with correlations. Many unconventional and novel phenomena have been obtained in them, although one section of the system is consisted of one spin-1/2 surface shell atom and one spin-1/2 core atom and they are coupled with a positive or a negative shell-core exchange interaction.

  16. Roaming form factors for the tricritical to critical Ising flow

    NASA Astrophysics Data System (ADS)

    Horváth, D. X.; Dorey, P. E.; Takács, G.

    2016-07-01

    We study the massless flows described by the staircase model introduced by Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon S-matrix, focusing on the renormalisation group flow from the tricritical to the critical Ising model. We show that the properly defined roaming limits of certain sinh-Gordon form factors are identical to the form factors of the order and disorder operators for the massless flow. As a by-product, we also construct form factors for a semi-local field in the sinh-Gordon model, which can be associated with the twist field in the ultraviolet limiting free massless bosonic theory.

  17. Ising model of financial markets with many assets

    NASA Astrophysics Data System (ADS)

    Eckrot, A.; Jurczyk, J.; Morgenstern, I.

    2016-11-01

    Many models of financial markets exist, but most of them simulate single asset markets. We study a multi asset Ising model of a financial market. Each agent has two possible actions (buy/sell) for every asset. The agents dynamically adjust their coupling coefficients according to past market returns and external news. This leads to fat tails and volatility clustering independent of the number of assets. We find that a separation of news into different channels leads to sector structures in the cross correlations, similar to those found in real markets.

  18. n-vicinities method for three dimensional Ising Model

    NASA Astrophysics Data System (ADS)

    Kryzhanovsky, Boris; Litinskii, Leonid

    2016-08-01

    The n -vicinities method for approximate calculations of the partition function of a spin system was proposed previously. The equation of state was obtained in the most general form. In the present publication these results are adapted to the Ising model on the D - dimensional cubic lattice. The state equation is solved for an arbitrary dimension D and the behavior of the free energy is analyzed. For large values of D (D > 2) the obtained results are in good agreement with the ones obtained by means of computer simulations. For small values of D, there are noticeable discrepancies with the exact results.

  19. Impurity effects of transverse Ising model with multi-impurity

    NASA Astrophysics Data System (ADS)

    Huang, Xuchu; Yang, Zhihua

    2015-02-01

    We study the transverse Ising spin model with multi-impurity under the exact solution. The influence mechanisms of the concentration, configuration, impurity-inducing-interaction are investigated through the deformation energy, long-range order and the specific heat. It reveals a way that the impurities have crucial effects on the magnetic order of the system, which can be used to scale the order-disorder transition. In particular, the change of the exchange coupling interaction or magnetic field can lead to the deviation of the phase point. Moreover, the impurity excitation cannot be neglected in thermodynamic properties even though the concentration is only a few percent.

  20. Simulation of financial market via nonlinear Ising model

    NASA Astrophysics Data System (ADS)

    Ko, Bonggyun; Song, Jae Wook; Chang, Woojin

    2016-09-01

    In this research, we propose a practical method for simulating the financial return series whose distribution has a specific heaviness. We employ the Ising model for generating financial return series to be analogous to those of the real series. The similarity between real financial return series and simulated one is statistically verified based on their stylized facts including the power law behavior of tail distribution. We also suggest the scheme for setting the parameters in order to simulate the financial return series with specific tail behavior. The simulation method introduced in this paper is expected to be applied to the other financial products whose price return distribution is fat-tailed.

  1. Vertical axis windmill

    SciTech Connect

    Campbell, J.S.

    1980-04-08

    A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.

  2. High spacecraft potentials on ISEE-1 in sunlight

    NASA Technical Reports Server (NTRS)

    Whipple, E. C., Jr.; Olsen, R. C.

    1987-01-01

    Data from two electric field experiments and from the plasma composition experiment on ISEE-1 show that the spacecraft charged to close to -70 V in sunlight at about 0700 UT on March 17, 1978. Data from the electron spectrometer experiment show that there was a potential barrier of some -10 to -20 V about the spacecraft during this event. The potential barrier was effective in turning back emitted photoelectrons to the spacecraft. Potential barriers can be formed by differential charging on the spacecraft or by the presence of space charge. The stringent electrostatic cleanliness specifications imposed on ISEE made the presence of differential charging seem unlikely, if these precautions were effective. Modeling of the event to determine if the barrier was produced by the presence of space charge suggested that this could not explain the observed barrier. The angular shape of the distribution could be successfully modeled as a product of differential charging on the solar arrays. This implies that the conductive coating was not completely effective in preventing differential charging, and that differential charging did occur.

  3. Ising tricriticality in the extended Hubbard model with bond dimerization

    NASA Astrophysics Data System (ADS)

    Ejima, Satoshi; Essler, Fabian H. L.; Lange, Florian; Fehske, Holger

    2016-06-01

    We explore the quantum phase transition between Peierls and charge-density-wave insulating states in the one-dimensional, half-filled, extended Hubbard model with explicit bond dimerization. We show that the critical line of the continuous Ising transition terminates at a tricritical point, belonging to the universality class of the tricritical Ising model with central charge c =7 /10 . Above this point, the quantum phase transition becomes first order. Employing a numerical matrix-product-state based (infinite) density-matrix renormalization group method we determine the ground-state phase diagram, the spin and two-particle charge excitations gaps, and the entanglement properties of the model with high precision. Performing a bosonization analysis we can derive a field description of the transition region in terms of a triple sine-Gordon model. This allows us to derive field theory predictions for the power-law (exponential) decay of the density-density (spin-spin) and bond-order-wave correlation functions, which are found to be in excellent agreement with our numerical results.

  4. Embedded trees and the support of the ISE

    PubMed Central

    Drmota, Michael

    2013-01-01

    Embedded trees are labelled rooted trees, where the root has zero label and where the labels of adjacent vertices differ (at most) by ±1. Recently it has been proved (see Chassaing and Schaeffer (2004) [8] and Janson and Marckert (2005) [11]) that the distribution of the maximum and minimum labels are closely related to the support of the density of the integrated superbrownian excursion (ISE). The purpose of this paper is to make this probabilistic limiting relation more explicit by using a generating function approach due to Bouttier et al. (2003) [6] that is based on properties of Jacobi’s θ-functions. In particular, we derive an integral representation of the joint distribution function of the supremum and infimum of the support of the ISE in terms of the Weierstrass ℘-function. Furthermore we re-derive the limiting radius distribution in random quadrangulations (by Chassaing and Schaeffer (2004) [8]) with the help of exact counting generating functions. PMID:27087725

  5. Neutral sheet crossings by ISEE-3 in the distant magnetotail

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.; Slavin, J. A.; Smith, E. J.; Baker, D. N.; Zwickl, R. D.

    1986-01-01

    The magnetic field data from ISEE-3 in the distant magnetotail at crossings of the field reversal (or neutral sheet) region are analyzed to determine the instantaneous direction of the normal component B(z) at the crossing. Crossings in the middle of the aberrated magnetotail near the apogee A2 of the first deep-tail orbit of ISEE-3 in January-February, 1983 were selected. Data for an interval of one hour is discussed at length to illustrate some of the difficulties that can occur. One particular smooth crossing at 15:56 UT, February 4, 1983, shows that complicated microstructure can occur in times shorter than one minute; averaging over long times may eliminate essential information for this purpose. By inspecting the magnetic field data at the highest resolution, however, it is shown that the direction of the plasma sheet flows and the sense of B(z) across the neutral sheet do not always agree with the reconnection models. Rather, they indicate that the low latitude boundary layer may play a significant role in the dynamics of the magnetotail.

  6. The hobbyhorse of magnetic systems: the Ising model

    NASA Astrophysics Data System (ADS)

    Ibarra-García-Padilla, Eduardo; Gerardo Malanche-Flores, Carlos; Poveda-Cuevas, Freddy Jackson

    2016-11-01

    In undergraduate statistical mechanics courses the Ising model always plays an important role because it is the simplest non-trivial model used to describe magnetic systems. The one-dimensional model is easily solved analytically, while the two-dimensional one can be solved exactly by the Onsager solution. For this reason, numerical simulations are usually used to solve the two-dimensional model. Keeping in mind that the two-dimensional model is the platform for studying phase transitions, it is usually an exercise in computational undergraduate courses because its numerical solution is relatively simple to implement and its critical exponents are perfectly known. The purpose of this article is to present a detailed numerical study of the second-order phase transition in the two-dimensional Ising model at an undergraduate level, allowing readers not only to compare the mean-field solution, the exact solution and the numerical one through a complete study of the order parameter, the correlation function and finite-size scaling, but to present the techniques, along with hints and tips, for solving it themselves. We present the elementary theory of phase transitions and explain how to implement Markov chain Monte Carlo simulations and perform them for different lattice sizes with periodic boundary conditions. Energy, magnetization, specific heat, magnetic susceptibility and the correlation function are calculated and the critical exponents determined by finite-size scaling techniques. The importance of the correlation length as the relevant parameter in phase transitions is emphasized.

  7. Oscillating hysteresis in the q-neighbor Ising model.

    PubMed

    Jȩdrzejewski, Arkadiusz; Chmiel, Anna; Sznajd-Weron, Katarzyna

    2015-11-01

    We modify the kinetic Ising model with Metropolis dynamics, allowing each spin to interact only with q spins randomly chosen from the whole system, which corresponds to the topology of a complete graph. We show that the model with q≥3 exhibits a phase transition between ferromagnetic and paramagnetic phases at temperature T*, which linearly increases with q. Moreover, we show that for q=3 the phase transition is continuous and that it is discontinuous for larger values of q. For q>3, the hysteresis exhibits oscillatory behavior-expanding for even values of q and shrinking for odd values of q. Due to the mean-field-like nature of the model, we are able to derive the analytical form of transition probabilities and, therefore, calculate not only the probability density function of the order parameter but also precisely determine the hysteresis and the effective potential showing stable, unstable, and metastable steady states. Our results show that a seemingly small modification of the kinetic Ising model leads not only to the switch from a continuous to a discontinuous phase transition, but also to an unexpected oscillating behavior of the hysteresis and a puzzling phenomenon for q=5, which might be taken as evidence for the so-called mixed-order phase transition.

  8. ISEE 1 and 2 observation of the oscillating magnetopause

    NASA Technical Reports Server (NTRS)

    Song, PU; Elphic, R. C.; Russell, C. T.

    1988-01-01

    The ISEE 1 and 2 magnetometer data for 10 years between October 1977 and September 1987 were used to identify magnetopause crossings that occurred in this period in the northward, horizontal, and southward IMFs and to determine the dependence of the oscillation amplitude of surface waves with periods greater than about 2 min on latitude, local time, and the direction of the IMF. The IMP 8 and ISEE 3 data were used to determine the IMF in the geocentric solar magnetosphere coordinates during the crossings. More than 1000 magnetopause passes were identified, with half of them with multiple crossings. The number of crossings per pass and the inferred average amplitude of the oscillation under southward conditions were nearly three times higher than under northward conditions. The amplitude increased with increasing angle from the subsolar point, when under southward, but not when under northward, conditions. The results suggest that the Kelvin-Helmholtz instability plays a very minor role in causing the surface waves on the dayside magnetopause.

  9. ISE; Catalyst for Change. Expanding Opportunities. Vol. 3, No. 2, July 1968.

    ERIC Educational Resources Information Center

    Institute for Services to Education, Inc., Washington, DC.

    The major thrust of the Institute for Services to Education (ISE) is to broaden the range of opportunities for Negroes in higher education. ISE does this through long-range programs at predominantly Negro institutions. The institute's major functions are curriculum reform and attracting funds to get new educational programs started. But it also…

  10. Yu-Shiba-Rusinov states and topological superconductivity in Ising paired superconductors

    NASA Astrophysics Data System (ADS)

    Sharma, Girish; Tewari, Sumanta

    2016-09-01

    An unusual form of superconductivity, called Ising superconductivity, has recently been uncovered in mono- and few-layered transition metal dichalcogenides. This 2D superconducting state is characterized by the so-called Ising spin-orbit coupling (SOC), which produces strong oppositely oriented effective Zeeman fields perpendicular to the 2D layer in opposite momentum space valleys. We examine the Yu-Shiba-Rusinov (YSR) bound states localized at magnetic impurities in Ising superconductors and show that the unusual SOC manifests itself in unusually strong anisotropy in magnetic field response observable in STM experiments. For a chain of magnetic impurities with moments parallel to the plane of Ising superconductors we show that the low energy YSR band hosts topological superconductivity and Majorana excitations as a direct manifestation of topological effects induced by Ising spin-orbit coupling.

  11. Information theory and local learning rules in a self-organizing network of Ising spins

    NASA Astrophysics Data System (ADS)

    Haft, Michael; Schlang, Martin; Deco, Gustavo

    1995-09-01

    The Boltzmann machine uses the relative entropy as a cost function to fit the Boltzmann distribution to a fixed given distribution. Instead of the relative entropy, we use the mutual information between input and output units to define an unsupervised analogy to the conventional Boltzmann machine. Our network of Ising spins is fed by an external field via the input units. The output units should self-organize to form an ``internal'' representation of the ``environmental'' input, thereby compressing the data and extracting relevant features. The mutual information and its gradient with respect to the weights principally require nonlocal information, e.g., in the form of multipoint correlation functions. Hence the exact gradient can hardly be boiled down to a local learning rule. Conversely, by using only local terms and two-point interactions, the entropy of the output layer cannot be ensured to reach the maximum possible entropy for a fixed number of output neurons. Some redundancy may remain in the representation of the data at the output. We account for this limitation from the very beginning by reformulating the cost function correspondingly. From this cost function, local Hebb-like learning rules can be derived. Some experiments with these local learning rules are presented.

  12. Multiple axis reticle

    NASA Astrophysics Data System (ADS)

    Barns, Chris E.; Gunter, William D.

    1990-09-01

    A reticle permits the alignment of three orthogonal axes (X, Y and Z) that intersect at a common target point. Thin, straight filaments are supported on a frame. The filaments are each contained in a different orthogonal plane (S sub xy, S sub xz, and S sub yz) and each filament intersects two of the three orthogonal axes. The filaments, as viewed along the frame axis, give the appearance of a triangle with a V extending from each triangle vertex. When axial alignment is achieved, the filament portions adjacent to a triangle vertex are seen (along the axis of interest) as a right-angle cross, whereas these filament portions are seen to intersect at an oblique angle when axial misalignment occurs. The reticle is open in the region near the target point leaving ample space for alignment aids such as a pentaprism or a cube mirror.

  13. Multiple axis reticle

    NASA Technical Reports Server (NTRS)

    Barns, Chris E. (Inventor); Gunter, William D. (Inventor)

    1990-01-01

    A reticle permits the alignment of three orthogonal axes (X, Y and Z) that intersect at a common target point. Thin, straight filaments are supported on a frame. The filaments are each contained in a different orthogonal plane (S sub xy, S sub xz, and S sub yz) and each filament intersects two of the three orthogonal axes. The filaments, as viewed along the frame axis, give the appearance of a triangle with a V extending from each triangle vertex. When axial alignment is achieved, the filament portions adjacent to a triangle vertex are seen (along the axis of interest) as a right-angle cross, whereas these filament portions are seen to intersect at an oblique angle when axial misalignment occurs. The reticle is open in the region near the target point leaving ample space for alignment aids such as a pentaprism or a cube mirror.

  14. Contentious Conversations

    ERIC Educational Resources Information Center

    Zuidema, Leah A.

    2011-01-01

    The idea of joining a conversation through reading and writing is not new; in his 1941 book "The Philosophy of Literary Form: Studies in Symbolic Action," Kenneth Burke suggests that the acts of reading and writing are like entering a parlor where others are already conversing. The author explores the place of professional debate within NCTE and…

  15. Toward an Ising Model of Cancer and Beyond

    PubMed Central

    Torquato, Salvatore

    2011-01-01

    The holy grail of tumor modeling is to formulate theoretical and computational tools that can be utilized in the clinic to predict neoplastic progression and propose individualized optimal treatment strategies to control cancer growth. In order to develop such a predictive model, one must account for the numerous complex mechanisms involved in tumor growth. Here we review resarch work that we have done toward the development of an “Ising model” of cancer. The Ising model is an idealized statistical-mechanical model of ferromagnetism that is based on simple local-interaction rules, but nonetheless leads to basic insights and features of real magnets, such as phase transitions with a critical point. The review begins with a description of a minimalist four-dimensional (three dimensions in space and one in time) cellular automaton (CA) model of cancer in which healthy cells transition between states (proliferative, hypoxic, and necrotic) according to simple local rules and their present states, which can viewed as a stripped-down Ising model of cancer. This model is applied to model the growth of glioblastoma multiforme, the most malignant of brain cancers. This is followed by a discussion of the extension of the model to study the effect on the tumor dynamics and geometry of a mutated subpopulation. A discussion of how tumor growth is affected by chemotherapeutic treatment, including induced resistance, is then described. How angiogenesis as well as the heterogeneous and confined environment in which a tumor grows is incorporated in the CA model is discussed. The characterization of the level of organization of the invasive network around a solid tumor using spanning trees is subsequently described. Then, we describe open problems and future promising avenues for future research, including the need to develop better molecular-based models that incorporate the true heterogeneous environment over wide range of length and time scales (via imaging data), cell

  16. Toward an Ising model of cancer and beyond

    NASA Astrophysics Data System (ADS)

    Torquato, Salvatore

    2011-02-01

    The holy grail of tumor modeling is to formulate theoretical and computational tools that can be utilized in the clinic to predict neoplastic progression and propose individualized optimal treatment strategies to control cancer growth. In order to develop such a predictive model, one must account for the numerous complex mechanisms involved in tumor growth. Here we review the research work that we have done toward the development of an 'Ising model' of cancer. The Ising model is an idealized statistical-mechanical model of ferromagnetism that is based on simple local-interaction rules, but nonetheless leads to basic insights and features of real magnets, such as phase transitions with a critical point. The review begins with a description of a minimalist four-dimensional (three dimensions in space and one in time) cellular automaton (CA) model of cancer in which cells transition between states (proliferative, hypoxic and necrotic) according to simple local rules and their present states, which can viewed as a stripped-down Ising model of cancer. This model is applied to study the growth of glioblastoma multiforme, the most malignant of brain cancers. This is followed by a discussion of the extension of the model to study the effect on the tumor dynamics and geometry of a mutated subpopulation. A discussion of how tumor growth is affected by chemotherapeutic treatment, including induced resistance, is then described. We then describe how to incorporate angiogenesis as well as the heterogeneous and confined environment in which a tumor grows in the CA model. The characterization of the level of organization of the invasive network around a solid tumor using spanning trees is subsequently discussed. Then, we describe open problems and future promising avenues for future research, including the need to develop better molecular-based models that incorporate the true heterogeneous environment over wide range of length and time scales (via imaging data), cell motility

  17. Robust criticality of an Ising model on rewired directed networks

    NASA Astrophysics Data System (ADS)

    Lipowski, Adam; Gontarek, Krzysztof; Lipowska, Dorota

    2015-06-01

    We show that preferential rewiring, which is supposed to mimic the behavior of financial agents, changes a directed-network Ising ferromagnet with a single critical point into a model with robust critical behavior. For the nonrewired random graph version, due to a constant number of out-links for each site, we write a simple mean-field-like equation describing the behavior of magnetization; we argue that it is exact and support the claim with extensive Monte Carlo simulations. For the rewired version, this equation is obeyed only at low temperatures. At higher temperatures, rewiring leads to strong heterogeneities, which apparently invalidates mean-field arguments and induces large fluctuations and divergent susceptibility. Such behavior is traced back to the formation of a relatively small core of agents that influence the entire system.

  18. Crystallization in Ising quantum magnets and Rydberg superatoms

    NASA Astrophysics Data System (ADS)

    Schauss, Peter

    2016-05-01

    Dominating finite-range interactions in many-body systems can lead to intriguing self-ordered phases of matter. For quantum magnets, Ising models with power-law interactions are among the most elementary systems that support such phases. These models can be implemented by laser coupling ensembles of ultracold atoms to Rydberg states. In this talk, I will report on the experimental preparation of crystalline ground states of such spin systems. We observe a magnetization staircase as a function of the system size and show directly the emergence of crystalline states with vanishing susceptibility. Recent results connect these findings with the picture of Rydberg superatoms. We investigated their scalability and observed collective Rabi oscillations with the perspective of using Rydberg superatoms as collective qubits. Experiments performed at Max-Planck Institute of Quantum Optics, Garching, Germany.

  19. Reentrance of disorder in the anisotropic shuriken Ising model

    NASA Astrophysics Data System (ADS)

    Pohle, Rico; Benton, Owen; Jaubert, L. D. C.

    2016-07-01

    Frustration is often a key ingredient for reentrance mechanisms. Here we study the frustrated anisotropic shuriken Ising model, where it is possible to extend the notion of reentrance between disordered phases, i.e., in absence of phase transitions. By tuning the anisotropy of the lattice, we open a window in the phase diagram where magnetic disorder prevails down to zero temperature, in a classical analogy with a quantum critical point. In this region, the competition between multiple disordered ground states gives rise to a double crossover where both the low- and high-temperature regimes are less correlated than the intervening classical spin liquid. This reentrance of disorder is characterized by an entropy plateau and a multistep Curie law crossover. Our theory is developed based on Monte Carlo simulations, analytical Husimi-tree calculations and an exact decoration-iteration transformation. Its relevance to experiments, in particular, artificial lattices, is discussed.

  20. Spin-1 Ising model on tetrahedron recursive lattices: Exact results

    NASA Astrophysics Data System (ADS)

    Jurčišinová, E.; Jurčišin, M.

    2016-11-01

    We investigate the ferromagnetic spin-1 Ising model on the tetrahedron recursive lattices. An exact solution of the model is found in the framework of which it is shown that the critical temperatures of the second order phase transitions of the model are driven by a single equation simultaneously on all such lattices. It is also shown that this general equation for the critical temperatures is equivalent to the corresponding polynomial equation for the model on the tetrahedron recursive lattice with arbitrary given value of the coordination number. The explicit form of these polynomial equations is shown for the lattices with the coordination numbers z = 6, 9, and 12. In addition, it is shown that the thermodynamic properties of all possible physical phases of the model are also completely driven by the corresponding single equations simultaneously on all tetrahedron recursive lattices. In this respect, the spontaneous magnetization, the free energy, the entropy, and the specific heat of the model are studied in detail.

  1. Neutral sheet crossings by ISEE-3 in the distant magnetotail

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.; Slavin, J. A.; Smith, E. J.; Baker, D. N.; Zwickl, R. D.

    1986-01-01

    Magnetic field data from ISEE-3 in the distant magnetotail at crossings of the field reversal (or neutral sheet) region were analyzed to determine the instantaneous direction of the normal component Bz at the crossing. A crossing identified as being almost always tailward of the steady-state X-line was selected. Data for 1 hr are discussed to illustrate difficulties. One particular smooth crossing shows that complicated microstructure can occur in times less than 1 min. Averaging over long times may eliminate essential information. Inspection of the magnetic field data at the highest resolution, however, shows that the direction of the plasma sheet flows and the sense of Bz across the neutral sheet do not always agree with the reconnection models. Rather, they indicate that the low latitude boundary layer may play a significant role in the dynamics of the magnetotail.

  2. The ISEE-C gamma ray burst spectrometer

    NASA Technical Reports Server (NTRS)

    Teegarden, B. J.; Porreca, G.; Stilwell, D.; Desai, U. D.; Cline, T. L.; Hovestadt, D.

    1978-01-01

    The technical properties, operation, and expected sensitivity are discussed for an experiment intended to search for narrow lines in the spectra of gamma ray bursts during the ISEE-C mission. At the heart of the experiment is a radiatively cooled germanium solid state photon detector. The instrumentation is capable of storing the entire spectrum of all but the largest bursts in the energy range 0.05-6.5 MeV. In addition, it analyzes the signals from two CsI detectors in two other experiments on the spacecraft and records event time histories from these to a few millisecond accuracy. A background mode permits spectral analysis during quiet times and will allow the determination of physically interesting upper limits for narrow lines in the diffuse gamma ray background radiation.

  3. Entanglement entropy in a periodically driven Ising chain

    NASA Astrophysics Data System (ADS)

    Russomanno, Angelo; Santoro, Giuseppe E.; Fazio, Rosario

    2016-07-01

    In this work we study the entanglement entropy of a uniform quantum Ising chain in transverse field undergoing a periodic driving of period τ. By means of Floquet theory we show that, for any subchain, the entanglement entropy tends asymptotically to a value τ-periodic in time. We provide a semi-analytical formula for the leading term of this asymptotic regime: It is constant in time and obeys a volume law. The entropy in the asymptotic regime is always smaller than the thermal one: because of integrability the system locally relaxes to a generalized Gibbs ensemble (GGE) density matrix. The leading term of the asymptotic entanglement entropy is completely determined by this GGE density matrix. Remarkably, the asymptotic entropy shows marked features in correspondence to some non-equilibrium quantum phase transitions undergone by a Floquet state analog of the ground state.

  4. Plasma wave experiment for the ISEE-3 mission

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.

    1982-01-01

    Results of analyses of data received from a scientific instrument designed to study solar wind and plasma wave phenomena on the ISEE-3 mission are discussed in two papers prepared for publication. A study of plasma wave levels in and interplanetary magnetic field orientation preceding observations of interplanetary shocks by the satellite infers that quasi-parallel, interplanetary shocks are preceded by foreshocks whose presence is not obviously attributable to scattering of ion beams generated at quasi-perpendicular zones of these interplanetary shocks. Investigations of whistler mode turbulence in the disturbed solar wind resulted in various indirect lines of evidence indicating that these whistler waves are generated propagating at large angles to the local interplanetary field, a fact which helps identify possible free energy sources for their growth.

  5. Destroying a topological quantum bit by condensing Ising vortices.

    PubMed

    Hao, Zhihao; Inglis, Stephen; Melko, Roger

    2014-12-09

    The imminent realization of topologically protected qubits in fabricated systems will provide not only an elementary implementation of fault-tolerant quantum computing architecture, but also an experimental vehicle for the general study of topological order. The simplest topological qubit harbours what is known as a Z2 liquid phase, which encodes information via a degeneracy depending on the system's topology. Elementary excitations of the phase are fractionally charged objects called spinons, or Ising flux vortices called visons. At zero temperature, a Z2 liquid is stable under deformations of the Hamiltonian until spinon or vison condensation induces a quantum-phase transition destroying the topological order. Here we use quantum Monte Carlo to study a vison-induced transition from a Z2 liquid to a valence-bond solid in a quantum dimer model on the kagome lattice. Our results indicate that this critical point is beyond the description of the standard Landau paradigm.

  6. The Ising Model Applied on Chronification of Pain

    PubMed Central

    2016-01-01

    This is a hypothesis-article suggesting an entirely new framework for understanding and treating longstanding pain. Most medical and psychological models are described with boxes and arrows. Such models are of little clinical and explanatory use when describing the phenomenon of chronification of pain due to unknown causes. To date no models that have been provided - and tested in a scientific satisfactory way - lays out a plan for specific assessment due to a specific causal explanation, and in the end serves the clinicians, patients and researcher with tools on how to address the specific pain condition to every individual pain patient's condition. By applying the Ising model (from physics) on the phenomenon of chronification of pain, one is able to detangle all these factors, and thus have a model that both suggests an explanation of the condition and outlines how one might target the treatment of chronic pain patients with the use of network science. PMID:26398917

  7. Quantum annealing speedup over simulated annealing on random Ising chains

    NASA Astrophysics Data System (ADS)

    Zanca, Tommaso; Santoro, Giuseppe E.

    2016-06-01

    We show clear evidence of a quadratic speedup of a quantum annealing (QA) Schrödinger dynamics over a Glauber master equation simulated annealing (SA) for a random Ising model in one dimension, via an equal-footing exact deterministic dynamics of the Jordan-Wigner fermionized problems. This is remarkable, in view of the arguments of H. G. Katzgraber et al. [Phys. Rev. X 4, 021008 (2014), 10.1103/PhysRevX.4.021008], since SA does not encounter any phase transition, while QA does. We also find a second remarkable result: that a "quantum-inspired" imaginary-time Schrödinger QA provides a further exponential speedup, i.e., an asymptotic residual error decreasing as a power law τ-μ of the annealing time τ .

  8. Bootstrapping mixed correlators in the 3D Ising model

    NASA Astrophysics Data System (ADS)

    Kos, Filip; Poland, David; Simmons-Duffin, David

    2014-11-01

    We study the conformal bootstrap for systems of correlators involving nonidentical operators. The constraints of crossing symmetry and unitarity for such mixed correlators can be phrased in the language of semidefinite programming. We apply this formalism to the simplest system of mixed correlators in 3D CFTs with a ℤ2 global symmetry. For the leading ℤ2-odd operator σ and ℤ2-even operator ɛ, we obtain numerical constraints on the allowed dimensions (Δ σ , Δ ɛ ) assuming that σ and ɛ are the only relevant scalars in the theory. These constraints yield a small closed region in (Δ σ , Δ ɛ ) space compatible with the known values in the 3D Ising CFT.

  9. Measurements of distributed polarized radio sources from spinning spacecraft - Effect of a tilted axial antenna ISEE-3 application and results

    NASA Technical Reports Server (NTRS)

    Fainberg, J.; Hoang, S.; Manning, R.

    1985-01-01

    An analysis is presented of the system response of a satellite receiver-antenna system to locate a radio source when the satellite is tilted on its axis. The satellite is spin stabilized but experiences a tilt due to either a mechanical misalignment or a shift in the electrical axis caused by parasitic currents in other spacecraft structures. The shorter the antenna, the more significant the effects. Numerical techniques are developed for obtaining the Stokes parameters and the angular parameters of a uniform conical source sensed by a linear antenna in order to derive the average power response of a synthesized dipole to a point on a distributed polarized source. Relative gains are calculated along the antenna at different angles to the source. The techniques are applied to sample ISEE-3 satellite data for Type III solar radio bursts which were sensed by an axial and an equatorial antenna. The two antennas permit localization of the source and quantification of the polarization and angular extent of the source. The resulting high precision in calculations of all three source parameters commends use of the model in analyses of data from the planned ULYSSES mission.

  10. Non-self-averaging in Ising spin glasses and hyperuniversality.

    PubMed

    Lundow, P H; Campbell, I A

    2016-01-01

    Ising spin glasses with bimodal and Gaussian near-neighbor interaction distributions are studied through numerical simulations. The non-self-averaging (normalized intersample variance) parameter U_{22}(T,L) for the spin glass susceptibility [and for higher moments U_{nn}(T,L)] is reported for dimensions 2,3,4,5, and 7. In each dimension d the non-self-averaging parameters in the paramagnetic regime vary with the sample size L and the correlation length ξ(T,L) as U_{nn}(β,L)=[K_{d}ξ(T,L)/L]^{d} and so follow a renormalization group law due to Aharony and Harris [Phys. Rev. Lett. 77, 3700 (1996)PRLTAO0031-900710.1103/PhysRevLett.77.3700]. Empirically, it is found that the K_{d} values are independent of d to within the statistics. The maximum values [U_{nn}(T,L)]_{max} are almost independent of L in each dimension, and remarkably the estimated thermodynamic limit critical [U_{nn}(T,L)]_{max} peak values are also practically dimension-independent to within the statistics and so are "hyperuniversal." These results show that the form of the spin-spin correlation function distribution at criticality in the large L limit is independent of dimension within the ISG family. Inspection of published non-self-averaging data for three-dimensional Heisenberg and XY spin glasses the light of the Ising spin glass non-self-averaging results show behavior which appears to be compatible with that expected on a chiral-driven ordering interpretation but incompatible with a spin-driven ordering scenario. PMID:26871035

  11. Non-self-averaging in Ising spin glasses and hyperuniversality

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Campbell, I. A.

    2016-01-01

    Ising spin glasses with bimodal and Gaussian near-neighbor interaction distributions are studied through numerical simulations. The non-self-averaging (normalized intersample variance) parameter U22(T ,L ) for the spin glass susceptibility [and for higher moments Un n(T ,L ) ] is reported for dimensions 2 ,3 ,4 ,5 , and 7. In each dimension d the non-self-averaging parameters in the paramagnetic regime vary with the sample size L and the correlation length ξ (T ,L ) as Un n(β ,L ) =[Kdξ (T ,L ) /L ] d and so follow a renormalization group law due to Aharony and Harris [Phys. Rev. Lett. 77, 3700 (1996), 10.1103/PhysRevLett.77.3700]. Empirically, it is found that the Kd values are independent of d to within the statistics. The maximum values [Unn(T,L ) ] max are almost independent of L in each dimension, and remarkably the estimated thermodynamic limit critical [Unn(T,L ) ] max peak values are also practically dimension-independent to within the statistics and so are "hyperuniversal." These results show that the form of the spin-spin correlation function distribution at criticality in the large L limit is independent of dimension within the ISG family. Inspection of published non-self-averaging data for three-dimensional Heisenberg and X Y spin glasses the light of the Ising spin glass non-self-averaging results show behavior which appears to be compatible with that expected on a chiral-driven ordering interpretation but incompatible with a spin-driven ordering scenario.

  12. Note: Evidence against 2D-Ising criticality in aqueous solutions with added salt

    NASA Astrophysics Data System (ADS)

    Troncoso, Jacobo; Cerdeiriña, Claudio A.

    2013-11-01

    Coexistence-curve data in the refractive index-temperature plane for solutions of 3-methyl-pyridine in heavy water with a small amount of added sodium tetraphenylborate have been determined. The analysis of such data indicates that this system belongs to the universality class of the three-dimensional Ising model (3D-Ising). This finding contrasts with previous work by Sadakane et al. [Soft Matter 7, 1334 (2011)] in which 2D-Ising criticality is invoked, but agrees with the recent assessment by Leys et al. [Soft Matter 9, 9326 (2013)].

  13. Conversation Analysis.

    ERIC Educational Resources Information Center

    Schiffrin, Deborah

    1990-01-01

    Summarizes the current state of research in conversation analysis, referring primarily to six different perspectives that have developed from the philosophy, sociology, anthropology, and linguistics disciplines. These include pragmatics; speech act theory; interactional sociolinguistics; ethnomethodology; ethnography of communication; and…

  14. Vertical axis wind turbines

    DOEpatents

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  15. Semimajor Axis Estimation Strategies

    NASA Technical Reports Server (NTRS)

    How, Jonathan P.; Alfriend, Kyle T.; Breger, Louis; Mitchell, Megan

    2004-01-01

    This paper extends previous analysis on the impact of sensing noise for the navigation and control aspects of formation flying spacecraft. We analyze the use of Carrier-phase Differential GPS (CDGPS) in relative navigation filters, with a particular focus on the filter correlation coefficient. This work was motivated by previous publications which suggested that a "good" navigation filter would have a strong correlation (i.e., coefficient near -1) to reduce the semimajor axis (SMA) error, and therefore, the overall fuel use. However, practical experience with CDGPS-based filters has shown this strong correlation seldom occurs (typical correlations approx. -0.1), even when the estimation accuracies are very good. We derive an analytic estimate of the filter correlation coefficient and demonstrate that, for the process and sensor noises levels expected with CDGPS, the expected value will be very low. It is also demonstrated that this correlation can be improved by increasing the time step of the discrete Kalman filter, but since the balance condition is not satisfied, the SMA error also increases. These observations are verified with several linear simulations. The combination of these simulations and analysis provide new insights on the crucial role of the process noise in determining the semimajor axis knowledge.

  16. Recommendation for measuring and reporting chloride by ISEs in undiluted serum, plasma or blood.

    PubMed

    Rayana, Mohammed C Ben; Burnett, Robert W; Covington, Arthur K; D'Orazio, Paul; Fogh-Andersen, Niels; Jacobs, Ellis; Kataky, Ritu; Külpmann, Wolf R; Kuwa, Katsuhiko; Larsson, Lasse; Lewenstam, Andrzej; Maas, Anton H J; Mager, Gerhard; Naskalski, Jerzy W; Okorodudu, Anthony O; Ritter, Christoph; St John, Andrew

    2006-01-01

    The proposed recommendation for measuring and reporting chloride in undiluted plasma or blood by ion-selective electrodes (ISEs) will provide results that are identical to chloride concentrations measured by coulometry for standardized normal plasma or blood samples. It is applicable to all current ISEs dedicated to chloride measurement in undiluted samples that meet the requirements. However, in samples with reduced water concentration, results by coulometry are lower than by ion-selective electrode due to volume displacement. The quantity measured by this standardized ISE procedure is called the ionized chloride concentration. It may be clinically more relevant than the chloride concentration as determined by coulometry, photometry or by ISE after dilution of the sample.

  17. Inhomogeneous and Self-Organized Temperature in Schelling-Ising Model

    NASA Astrophysics Data System (ADS)

    Müller, Katharina; Schulze, Christian; Stauffer, Dietrich

    The Schelling model of 1971 is a complicated version of a square-lattice Ising model at zero temperature, to explain urban segregation, based on the neighbor preferences of the residents, without external reasons. Various versions between Ising and Schelling models give about the same results. Inhomogeneous "temperatures" T do not change the results much, while a feedback between segregation and T leads to a self-organization of an average T.

  18. A 16-bit Coherent Ising Machine for One-Dimensional Ring and Cubic Graph Problems

    PubMed Central

    Takata, Kenta; Marandi, Alireza; Hamerly, Ryan; Haribara, Yoshitaka; Maruo, Daiki; Tamate, Shuhei; Sakaguchi, Hiromasa; Utsunomiya, Shoko; Yamamoto, Yoshihisa

    2016-01-01

    Many tasks in our modern life, such as planning an efficient travel, image processing and optimizing integrated circuit design, are modeled as complex combinatorial optimization problems with binary variables. Such problems can be mapped to finding a ground state of the Ising Hamiltonian, thus various physical systems have been studied to emulate and solve this Ising problem. Recently, networks of mutually injected optical oscillators, called coherent Ising machines, have been developed as promising solvers for the problem, benefiting from programmability, scalability and room temperature operation. Here, we report a 16-bit coherent Ising machine based on a network of time-division-multiplexed femtosecond degenerate optical parametric oscillators. The system experimentally gives more than 99.6% of success rates for one-dimensional Ising ring and nondeterministic polynomial-time (NP) hard instances. The experimental and numerical results indicate that gradual pumping of the network combined with multiple spectral and temporal modes of the femtosecond pulses can improve the computational performance of the Ising machine, offering a new path for tackling larger and more complex instances. PMID:27659312

  19. A 16-bit Coherent Ising Machine for One-Dimensional Ring and Cubic Graph Problems

    NASA Astrophysics Data System (ADS)

    Takata, Kenta; Marandi, Alireza; Hamerly, Ryan; Haribara, Yoshitaka; Maruo, Daiki; Tamate, Shuhei; Sakaguchi, Hiromasa; Utsunomiya, Shoko; Yamamoto, Yoshihisa

    2016-09-01

    Many tasks in our modern life, such as planning an efficient travel, image processing and optimizing integrated circuit design, are modeled as complex combinatorial optimization problems with binary variables. Such problems can be mapped to finding a ground state of the Ising Hamiltonian, thus various physical systems have been studied to emulate and solve this Ising problem. Recently, networks of mutually injected optical oscillators, called coherent Ising machines, have been developed as promising solvers for the problem, benefiting from programmability, scalability and room temperature operation. Here, we report a 16-bit coherent Ising machine based on a network of time-division-multiplexed femtosecond degenerate optical parametric oscillators. The system experimentally gives more than 99.6% of success rates for one-dimensional Ising ring and nondeterministic polynomial-time (NP) hard instances. The experimental and numerical results indicate that gradual pumping of the network combined with multiple spectral and temporal modes of the femtosecond pulses can improve the computational performance of the Ising machine, offering a new path for tackling larger and more complex instances.

  20. Next nearest neighbour Ising models on random graphs

    NASA Astrophysics Data System (ADS)

    Raymond, Jack; Wong, K. Y. Michael

    2012-09-01

    This paper develops results for the next nearest neighbour Ising model on random graphs. Besides being an essential ingredient in classic models for frustrated systems, second neighbour interactions arise naturally in several applications, such as the colour diversity problem and graphical games. We demonstrate ensembles of random graphs, including regular connectivity graphs, that have a periodic variation of free energy, with either the ratio of nearest to next nearest couplings, or the mean number of nearest neighbours. When the coupling ratio is integer then paramagnetic phases can be found at zero temperature. This is shown to be related to the locked or unlocked nature of the interactions. For anti-ferromagnetic couplings, spin glass phases are demonstrated at low temperature. The interaction structure is formulated as a factor graph, the solution on a tree is developed. The replica symmetric and energetic one-step replica symmetry breaking solution is developed using the cavity method. We calculate within these frameworks the phase diagram and demonstrate the existence of dynamical transitions at zero temperature for cases of anti-ferromagnetic coupling on regular and inhomogeneous random graphs.

  1. Entanglement entropy in a periodically driven quantum Ising ring

    NASA Astrophysics Data System (ADS)

    Apollaro, Tony J. G.; Palma, G. Massimo; Marino, Jamir

    2016-10-01

    We numerically study the dynamics of entanglement entropy, induced by an oscillating time periodic driving of the transverse field, h (t ) , of a one-dimensional quantum Ising ring. We consider several realizations of h (t ) , and we find a number of results in analogy with entanglement entropy dynamics induced by a sudden quantum quench. After a short-time relaxation, the dynamics of entanglement entropy synchronizes with h (t ) , displaying an oscillatory behavior at the frequency of the driving. Synchronization in the dynamics of entanglement entropy is spoiled by the appearance of quasirevivals which fade out in the thermodynamic limit, and which we interpret using a quasiparticle picture adapted to periodic drivings. We show that the time-averaged entanglement entropy in the synchronized regime obeys a volume law scaling with the subsystem's size. Such result is reminiscent of a thermal state or a generalized Gibbs ensemble, although the system does not heat up towards infinite temperature as a consequence of the integrability of the model.

  2. Periodic Striped Ground States in Ising Models with Competing Interactions

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandro; Seiringer, Robert

    2016-11-01

    We consider Ising models in two and three dimensions, with short range ferromagnetic and long range, power-law decaying, antiferromagnetic interactions. We let J be the ratio between the strength of the ferromagnetic to antiferromagnetic interactions. The competition between these two kinds of interactions induces the system to form domains of minus spins in a background of plus spins, or vice versa. If the decay exponent p of the long range interaction is larger than d + 1, with d the space dimension, this happens for all values of J smaller than a critical value J c ( p), beyond which the ground state is homogeneous. In this paper, we give a characterization of the infinite volume ground states of the system, for p > 2 d and J in a left neighborhood of J c ( p). In particular, we prove that the quasi-one-dimensional states consisting of infinite stripes ( d = 2) or slabs ( d = 3), all of the same optimal width and orientation, and alternating magnetization, are infinite volume ground states. Our proof is based on localization bounds combined with reflection positivity.

  3. Critical behavior of the Ising model on random fractals.

    PubMed

    Monceau, Pascal

    2011-11-01

    We study the critical behavior of the Ising model in the case of quenched disorder constrained by fractality on random Sierpinski fractals with a Hausdorff dimension d(f) is approximately equal to 1.8928. This is a first attempt to study a situation between the borderline cases of deterministic self-similarity and quenched randomness. Intensive Monte Carlo simulations were carried out. Scaling corrections are much weaker than in the deterministic cases, so that our results enable us to ensure that finite-size scaling holds, and that the critical behavior is described by a new universality class. The hyperscaling relation is compatible with an effective dimension equal to the Hausdorff one; moreover the two eigenvalues exponents of the renormalization flows are shown to be different from the ones calculated from ε expansions, and from the ones obtained for fourfold symmetric deterministic fractals. Although the space dimensionality is not integer, lack of self-averaging properties exhibits some features very close to the ones of a random fixed point associated with a relevant disorder.

  4. Upstream waves simultaneously observed by ISEE and UKS

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Luhmann, J. G.; Elphic, R. C.; Southwood, D. J.; Smith, M. F.

    1987-01-01

    Measurements obtained in the solar wind by ISEE-2 and the United Kingdom Subsatellite (UKS) have been examined for observations of upstream waves. These data reveal that the waves in the foreshock region are enhanced at all frequencies from at least 0.003 Hz to 0.5 Hz. The wave spectra generally have a spectral peak, but this peak is usually broad and the peak frequency depends on the position of the spacecraft. Generally, the spectra seen at the two spacecraft are most similar at high frequencies and least similar at low frequencies. The geometry of the interaction is displayed in the plane containing the magnetic field, the solar wind velocity, and the spacecraft location. However, this coordinate system does not order all the observed wave properties. It does not clearly explain or order the handedness of the waves, or their direction of propagation. It is clear that the upstream region is inherently three-dimensional. The position-dependent nature of the upstream waves indicates that comparisons between ground-based measurements and in-situ observations must be undertaken with some caution.

  5. Hamiltonian truncation approach to quenches in the Ising field theory

    NASA Astrophysics Data System (ADS)

    Rakovszky, T.; Mestyán, M.; Collura, M.; Kormos, M.; Takács, G.

    2016-10-01

    In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1 + 1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.

  6. Topological defects on the lattice: I. The Ising model

    NASA Astrophysics Data System (ADS)

    Aasen, David; Mong, Roger S. K.; Fendley, Paul

    2016-09-01

    In this paper and its sequel, we construct topologically invariant defects in two-dimensional classical lattice models and quantum spin chains. We show how defect lines commute with the transfer matrix/Hamiltonian when they obey the defect commutation relations, cousins of the Yang-Baxter equation. These relations and their solutions can be extended to allow defect lines to branch and fuse, again with properties depending only on topology. In this part I, we focus on the simplest example, the Ising model. We define lattice spin-flip and duality defects and their branching, and prove they are topological. One useful consequence is a simple implementation of Kramers-Wannier duality on the torus and higher genus surfaces by using the fusion of duality defects. We use these topological defects to do simple calculations that yield exact properties of the conformal field theory describing the continuum limit. For example, the shift in momentum quantization with duality-twisted boundary conditions yields the conformal spin 1/16 of the chiral spin field. Even more strikingly, we derive the modular transformation matrices explicitly and exactly.

  7. Two Dimensional Ising Superconductivity in Gated MoS2

    NASA Astrophysics Data System (ADS)

    Yuan, Noah; Lu, Jianming; Law, Kam Tuen; Zheliuk, Oleksandr; Leermakers, Inge; Zeitler, Ulrich; Ye, Jianting

    The Zeeman effect, which is usually considered to be detrimental to superconductivity, can surprisingly protect the superconducting states created by gating a layered transition metal dichalcogenide. This effective Zeeman field, which is originated from intrinsic spin orbit coupling induced by breaking in-plane inversion symmetry, can reach nearly a hundred Tesla in magnitude. It strongly pins the spin orientation of the electrons to the out-of-plane directions and protects the superconductivity from being destroyed by an in-plane external magnetic field. In magnetotransport experiments of ionic-gate MoS2 transistors, where gating prepares individual superconducting state with different carrier doping, we indeed observe a spin-protected superconductivity by measuring an in-plane critical field Bc 2 far beyond the Pauli paramagnetic limit. The gating-enhanced Bc 2 is more than an order of magnitude larger compared to the bulk superconducting phases where the effective Zeeman field is weakened by interlayer coupling. Our study gives the first experimental evidence of an Ising superconductor, in which spins of the pairing electrons are strongly pinned by an effective Zeeman field.

  8. Geometrical clusters of Darcy's reservoir model and Ising universality class

    NASA Astrophysics Data System (ADS)

    Najafi, M. N.; Ghaedi, M.

    2015-06-01

    In this paper the geometrical features of the fluid propagation in two-dimensional petroleum reservoir described by Darcy equations are studied. The porous media are considered to be tuned by the occupancy parameter p being the probability that a pore is occupied. We analyze the statistical geometrical observables of the Darcy model. To this end we let the water to be injected into random sites of the porous media and solve numerically the Darcy equations to describe the flow motion pattern, using the control volume finite difference (CVFD) method. The fractal dimension of the frontier of the avalanches (defined as the set of the sites through which the fluid passed) and the distribution functions of gyration radius, loop length and cluster mass are numerically obtained revealing that at p =pc (the critical occupancy parameter above which there is definitely a spanning cluster in the system) this model lies within a universality class compatible with the Ising model. We observe that for p >pc, although the model shows critical behaviors, this duality is broken. The mentioned exponents are reported in this paper.

  9. Periodic Striped Ground States in Ising Models with Competing Interactions

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandro; Seiringer, Robert

    2016-06-01

    We consider Ising models in two and three dimensions, with short range ferromagnetic and long range, power-law decaying, antiferromagnetic interactions. We let J be the ratio between the strength of the ferromagnetic to antiferromagnetic interactions. The competition between these two kinds of interactions induces the system to form domains of minus spins in a background of plus spins, or vice versa. If the decay exponent p of the long range interaction is larger than d + 1, with d the space dimension, this happens for all values of J smaller than a critical value J c (p), beyond which the ground state is homogeneous. In this paper, we give a characterization of the infinite volume ground states of the system, for p > 2d and J in a left neighborhood of J c (p). In particular, we prove that the quasi-one-dimensional states consisting of infinite stripes (d = 2) or slabs (d = 3), all of the same optimal width and orientation, and alternating magnetization, are infinite volume ground states. Our proof is based on localization bounds combined with reflection positivity.

  10. Topological defects on the lattice: I. The Ising model

    NASA Astrophysics Data System (ADS)

    Aasen, David; Mong, Roger S. K.; Fendley, Paul

    2016-09-01

    In this paper and its sequel, we construct topologically invariant defects in two-dimensional classical lattice models and quantum spin chains. We show how defect lines commute with the transfer matrix/Hamiltonian when they obey the defect commutation relations, cousins of the Yang–Baxter equation. These relations and their solutions can be extended to allow defect lines to branch and fuse, again with properties depending only on topology. In this part I, we focus on the simplest example, the Ising model. We define lattice spin-flip and duality defects and their branching, and prove they are topological. One useful consequence is a simple implementation of Kramers–Wannier duality on the torus and higher genus surfaces by using the fusion of duality defects. We use these topological defects to do simple calculations that yield exact properties of the conformal field theory describing the continuum limit. For example, the shift in momentum quantization with duality-twisted boundary conditions yields the conformal spin 1/16 of the chiral spin field. Even more strikingly, we derive the modular transformation matrices explicitly and exactly.

  11. Upstream waves simultaneously observed by ISEE and UKS

    SciTech Connect

    Russell, C.T.; Luhmann, J.G.; Elphic, R.C. ); Southwood, D.J. ); Smith, M.F.; Johnstone, A.D. )

    1987-07-01

    Measurements obtained in the solar wind by ISEE-2 and the United Kingdom Subsatellite (UKS) have been examined for observations of upstream waves. These data reveal that the waves in the foreshock region are enhanced at all frequencies from at least 0.003 Hz to 0.5 Hz. The wave spectra generally have a spectral peak, but this peak is usually broad and the peak frequency depends on the position of the spacecraft. Generally, the spectra seen at the two spacecraft are most similar at high frequencies and least similar at low frequencies. The geometry of the interaction is displayed in the plane containing the magnetic field, the solar wind velocity, and the spacecraft location. However, this coordinate system does not order all the observed wave properties. It does not clearly explain or order the handedness of the waves, or their direction of propagation. It is clear that the upstream region is inherently three-dimensional. The position-dependent nature of the upstream waves indicates that comparisons between ground-based measurements and in-situ observations must be undertaken with some caution.

  12. Interaction Versus Entropic Repulsion for Low Temperature Ising Polymers

    NASA Astrophysics Data System (ADS)

    Ioffe, Dmitry; Shlosman, Senya; Toninelli, Fabio Lucio

    2015-03-01

    Contours associated to many interesting low-temperature statistical mechanics models (2D Ising model, (2+1)D SOS interface model, etc) can be described as self-interacting and self-avoiding walks on . When the model is defined in a finite box, the presence of the boundary induces an interaction, that can turn out to be attractive, between the contour and the boundary of the box. On the other hand, the contour cannot cross the boundary, so it feels entropic repulsion from it. In various situations of interest (in Caputo et al. Ann. Probab., arXiv:1205.6884, J. Eur. Math. Soc., arXiv:1302.6941, arXiv:1406.1206, Ioffe and Shlosman, in preparation), a crucial technical problem is to prove that entropic repulsion prevails over the pinning interaction: in particular, the contour-boundary interaction should not modify significantly the contour partition function and the related surface tension should be unchanged. Here we prove that this is indeed the case, at least at sufficiently low temperature, in a quite general framework that applies in particular to the models of interest mentioned above.

  13. Dynamical scaling in Ising and vector spin glasses

    NASA Astrophysics Data System (ADS)

    Katzgraber, Helmut G.; Campbell, I. A.

    2005-07-01

    We have studied numerically the dynamics of spin glasses with Ising and XY symmetry (gauge glass) in space dimensions 2, 3, and 4. The nonequilibrium spin-glass susceptibility χne(tw,T) and the nonequilibrium energy per spin, ene(tw,T) , of samples of large size Lb are measured as a function of anneal time tw after a quench to temperatures T . The two observables are compared to the equilibrium spin-glass susceptibility χeq(L,T) and the equilibrium energy eeq(L,T) , respectively, measured as functions of temperature T and system size L for a range of system sizes. For any time and temperature a nonequilibrium time-dependent length scale L*(tw,T) can be defined by writing χne(tw,T)=χeq(L*,T) (or the equivalent expression for the energy). Our analysis shows that for all systems studied, an “effective dynamical critical exponent” parametrization L*(tw,T)=A(T)t1/z(T) fits the data well at each temperature within the whole temperature range studied, which extends from well above the critical temperature Tc to near T=0 for dimension 2 or to well below Tc for the other space dimensions studied. In addition, the data suggest that the dynamical exponent z varies smoothly when crossing the transition temperature.

  14. Exact solution of the spin-1/2 Ising model on the Shastry Sutherland (orthogonal-dimer) lattice

    NASA Astrophysics Data System (ADS)

    Strečka, Jozef

    2006-01-01

    A star-triangle mapping transformation is used to establish an exact correspondence between the spin-1/2 Ising model on the Shastry Sutherland (orthogonal-dimer) lattice and respectively, the spin-1/2 Ising model on a bathroom tile (4 8) lattice. Exact results for the critical temperature and spontaneous magnetization are obtained and compared with corresponding results on the regular Ising lattices.

  15. Conversational sensemaking

    NASA Astrophysics Data System (ADS)

    Preece, Alun; Webberley, Will; Braines, Dave

    2015-05-01

    Recent advances in natural language question-answering systems and context-aware mobile apps create opportunities for improved sensemaking in a tactical setting. Users equipped with mobile devices act as both sensors (able to acquire information) and effectors (able to act in situ), operating alone or in collectives. The currently- dominant technical approaches follow either a pull model (e.g. Apple's Siri or IBM's Watson which respond to users' natural language queries) or a push model (e.g. Google's Now which sends notifications to a user based on their context). There is growing recognition that users need more flexible styles of conversational interaction, where they are able to freely ask or tell, be asked or told, seek explanations and clarifications. Ideally such conversations should involve a mix of human and machine agents, able to collaborate in collective sensemaking activities with as few barriers as possible. Desirable capabilities include adding new knowledge, collaboratively building models, invoking specific services, and drawing inferences. As a step towards this goal, we collect evidence from a number of recent pilot studies including natural experiments (e.g. situation awareness in the context of organised protests) and synthetic experiments (e.g. human and machine agents collaborating in information seeking and spot reporting). We identify some principles and areas of future research for "conversational sensemaking".

  16. Conversational sensing

    NASA Astrophysics Data System (ADS)

    Preece, Alun; Gwilliams, Chris; Parizas, Christos; Pizzocaro, Diego; Bakdash, Jonathan Z.; Braines, Dave

    2014-05-01

    Recent developments in sensing technologies, mobile devices and context-aware user interfaces have made it pos- sible to represent information fusion and situational awareness for Intelligence, Surveillance and Reconnaissance (ISR) activities as a conversational process among actors at or near the tactical edges of a network. Motivated by use cases in the domain of Company Intelligence Support Team (CoIST) tasks, this paper presents an approach to information collection, fusion and sense-making based on the use of natural language (NL) and controlled nat- ural language (CNL) to support richer forms of human-machine interaction. The approach uses a conversational protocol to facilitate a ow of collaborative messages from NL to CNL and back again in support of interactions such as: turning eyewitness reports from human observers into actionable information (from both soldier and civilian sources); fusing information from humans and physical sensors (with associated quality metadata); and assisting human analysts to make the best use of available sensing assets in an area of interest (governed by man- agement and security policies). CNL is used as a common formal knowledge representation for both machine and human agents to support reasoning, semantic information fusion and generation of rationale for inferences, in ways that remain transparent to human users. Examples are provided of various alternative styles for user feedback, including NL, CNL and graphical feedback. A pilot experiment with human subjects shows that a prototype conversational agent is able to gather usable CNL information from untrained human subjects.

  17. Bimodal and Gaussian Ising spin glasses in dimension two

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Campbell, I. A.

    2016-02-01

    An analysis is given of numerical simulation data to size L =128 on the archetype square lattice Ising spin glasses (ISGs) with bimodal (±J ) and Gaussian interaction distributions. It is well established that the ordering temperature of both models is zero. The Gaussian model has a nondegenerate ground state and thus a critical exponent η ≡0 , and a continuous distribution of energy levels. For the bimodal model, above a size-dependent crossover temperature T*(L ) there is a regime of effectively continuous energy levels; below T*(L ) there is a distinct regime dominated by the highly degenerate ground state plus an energy gap to the excited states. T*(L ) tends to zero at very large L , leaving only the effectively continuous regime in the thermodynamic limit. The simulation data on both models are analyzed with the conventional scaling variable t =T and with a scaling variable τb=T2/(1 +T2) suitable for zero-temperature transition ISGs, together with appropriate scaling expressions. The data for the temperature dependence of the reduced susceptibility χ (τb,L ) and second moment correlation length ξ (τb,L ) in the thermodynamic limit regime are extrapolated to the τb=0 critical limit. The Gaussian critical exponent estimates from the simulations, η =0 and ν =3.55 (5 ) , are in full agreement with the well-established values in the literature. The bimodal critical exponents, estimated from the thermodynamic limit regime analyses using the same extrapolation protocols as for the Gaussian model, are η =0.20 (2 ) and ν =4.8 (3 ) , distinctly different from the Gaussian critical exponents.

  18. Bimodal and Gaussian Ising spin glasses in dimension two.

    PubMed

    Lundow, P H; Campbell, I A

    2016-02-01

    An analysis is given of numerical simulation data to size L=128 on the archetype square lattice Ising spin glasses (ISGs) with bimodal (±J) and Gaussian interaction distributions. It is well established that the ordering temperature of both models is zero. The Gaussian model has a nondegenerate ground state and thus a critical exponent η≡0, and a continuous distribution of energy levels. For the bimodal model, above a size-dependent crossover temperature T(*)(L) there is a regime of effectively continuous energy levels; below T(*)(L) there is a distinct regime dominated by the highly degenerate ground state plus an energy gap to the excited states. T(*)(L) tends to zero at very large L, leaving only the effectively continuous regime in the thermodynamic limit. The simulation data on both models are analyzed with the conventional scaling variable t=T and with a scaling variable τ(b)=T(2)/(1+T(2)) suitable for zero-temperature transition ISGs, together with appropriate scaling expressions. The data for the temperature dependence of the reduced susceptibility χ(τ(b),L) and second moment correlation length ξ(τ(b),L) in the thermodynamic limit regime are extrapolated to the τ(b)=0 critical limit. The Gaussian critical exponent estimates from the simulations, η=0 and ν=3.55(5), are in full agreement with the well-established values in the literature. The bimodal critical exponents, estimated from the thermodynamic limit regime analyses using the same extrapolation protocols as for the Gaussian model, are η=0.20(2) and ν=4.8(3), distinctly different from the Gaussian critical exponents. PMID:26986300

  19. Smeared spin-flop transition in random antiferromagnetic Ising chain

    SciTech Connect

    Timonin, P. N.

    2012-12-15

    At T = 0 and in a sufficiently large field, the nearest-neighbor antiferromagnetic Ising chain undergoes a first-order spin-flop transition into the ferromagnetic phase. We consider its smearing under the random-bond disorder such that all independent random bonds are antiferromagnetic (AF). It is shown that the ground-state thermodynamics of this random AF chain can be described exactly for an arbitrary distribution P(J) of AF bonds. Moreover, the site magnetizations of finite chains can be found analytically in this model. We consider a continuous P(J) that is zero above some -J{sub 1} and behaves near it as (-J{sub 1}-J){sup {lambda}}, {lambda} > -1. In this case, the ferromagnetic phase emerges continuously in a field H > H{sub c} = 2J{sub 1}. At 0 > {lambda} > -1, it has the usual second-order anomalies near H{sub c} with the critical indices obeying the scaling relation and depending on {lambda}. At {lambda} > 0, higher-order transitions occur (third, fourth, etc.), marked by a divergence of the corresponding nonlinear susceptibilities. In the chains with an even number of spins, the intermediate 'bow-tie' phase with linearly modulated AF order exists between the AF and ferromagnetic phases at J{sub 1} < H < H{sub c}. Its origin can be traced to the infinite correlation length of the degenerate AF phase from which it emerges. This implies the existence of similar inhomogeneous phases with size- and form-dependent order in a number of other systems with infinite correlation length. The possibility to observe the signs of the 'bow-tie' phase in low-T neutron diffraction experiments is discussed.

  20. Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3V2O8 in a transverse magnetic field

    DOE PAGES

    Fritsch, Katharina; Ehlers, G.; Rule, K. C.; Habicht, Klaus; Ramazanoglu, Mehmet K.; Dabkowska, H. A.; Gaulin, Bruce D.

    2015-11-05

    We study the application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional kagome staircase magnet, Co3V2O8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. Also, at least one of the transitions to incommensurate phases at μ0Hc1~6.25 T and μ0Hc2~7 T is discontinuous, while the final quantum critical point at μ0Hc3~13 T ismore » continuous.« less

  1. Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3V2O8 in a transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Fritsch, K.; Ehlers, G.; Rule, K. C.; Habicht, K.; Ramazanoglu, M.; Dabkowska, H. A.; Gaulin, B. D.

    2015-11-01

    The application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional kagome staircase magnet, Co3V2O8 , induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. At least one of the transitions to incommensurate phases at μ0Hc 1˜6.25 T and μ0Hc 2˜7 T is discontinuous, while the final quantum critical point at μ0Hc 3˜13 T is continuous.

  2. Monte Carlo study of the spin-glass phase of the site-diluted dipolar Ising model

    NASA Astrophysics Data System (ADS)

    Alonso, Juan J.; Fernández, Julio F.

    2010-02-01

    By tempered Monte Carlo simulations, we study site-diluted Ising systems of magnetic dipoles. All dipoles are randomly placed on a fraction x of all L3 sites of a simple cubic lattice, and point along a given crystalline axis. For xc

  3. Magnetic ordering in the frustrated J1 - J2 Ising chain candidate BaNd2O4

    DOE PAGES

    Aczel, Adam A.; Li, Ling; Garlea, Vasile O.; Yan, Jiaqiang; Weickert, Franziska; Jaime, M.; Maiorov, B.; Movshovich, R.; Civale, L.; Keppens, V.; et al

    2014-10-06

    The AR2O4 family (R = rare earth) has recently been attracting interest as a new series of frustrated magnets, with the magnetic R atoms forming zigzag chains running along the c axis. In this paper, we have investigated polycrystalline BaNd2O4 with a combination of magnetization, heat-capacity, and neutron powder diffraction measurements. Magnetic Bragg peaks are observed below TN = 1.7 K, and they can be indexed with a propagation vector of k = (0,1/2,1/2). The signal from magnetic diffraction is well described by long-range ordering of only one of the two types of Nd zigzag chains, with collinear up-up-down-down intrachainmore » spin configurations (double Néel state). Furthermore, low-temperature magnetization and heat-capacity measurements reveal two magnetic-field-induced spin transitions at 2.75 and 4 T for T = 0.46 K. The high-field phase is paramagnetic, while the intermediate-field state may arise from a spin transition of the long-range ordered Nd chains. Finally, one possible candidate for the field-induced ordered state corresponds to an up-up-down intrachain spin configuration, as predicted for a classical J1-J2 Ising chain with a double Néel ground state in zero field.« less

  4. Large-scale Ising spin network based on degenerate optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Inagaki, Takahiro; Inaba, Kensuke; Hamerly, Ryan; Inoue, Kyo; Yamamoto, Yoshihisa; Takesue, Hiroki

    2016-06-01

    Solving combinatorial optimization problems is becoming increasingly important in modern society, where the analysis and optimization of unprecedentedly complex systems are required. Many such problems can be mapped onto the ground-state-search problem of the Ising Hamiltonian, and simulating the Ising spins with physical systems is now emerging as a promising approach for tackling such problems. Here, we report a large-scale network of artificial spins based on degenerate optical parametric oscillators (DOPOs), paving the way towards a photonic Ising machine capable of solving difficult combinatorial optimization problems. We generate >10,000 time-division-multiplexed DOPOs using dual-pump four-wave mixing in a highly nonlinear fibre placed in a cavity. Using those DOPOs, a one-dimensional Ising model is simulated by introducing nearest-neighbour optical coupling. We observe the formation of spin domains and find that the domain size diverges near the DOPO threshold, which suggests that the DOPO network can simulate the behaviour of low-temperature Ising spins.

  5. Axis I and Axis II diagnostic parameters of homicide.

    PubMed

    Yarvis, R M

    1990-01-01

    A series of 100 murderers was examined to discern overall patterns of psychopathology. In addition, demographic and other discriminating factors were used to test the hypothesis that murderers do not constitute a homogenous population and that subgroups will differ diagnostically. DSM-III diagnostic criteria were used to make each diagnosis. The sample was found to be representative of the universe from which it was drawn at least as could be determined by available comparative criteria. Four Axis I (psychoses, substance abuse, dysthymia, no Axis I) and three Axis II (antisocial, borderline, no Axis II) diagnostic categories accounted for more than 80 percent of the study population. The murderers were found to be a heterogenous population, and subgroups based on a combination of assailant's crime pattern, sex, prior criminal history, and relationship to victim manifested different prevailing diagnostic patterns.

  6. A new wind energy conversion system

    NASA Technical Reports Server (NTRS)

    Smetana, F. O.

    1975-01-01

    It is presupposed that vertical axis wind energy machines will be superior to horizontal axis machines on a power output/cost basis and the design of a new wind energy machine is presented. The design employs conical cones with sharp lips and smooth surfaces to promote maximum drag and minimize skin friction. The cones are mounted on a vertical axis in such a way as to assist torque development. Storing wind energy as compressed air is thought to be optimal and reasons are: (1) the efficiency of compression is fairly high compared to the conversion of mechanical energy to electrical energy in storage batteries; (2) the release of stored energy through an air motor has high efficiency; and (3) design, construction, and maintenance of an all-mechanical system is usually simpler than for a mechanical to electrical conversion system.

  7. SKRYN: A fast semismooth-Krylov-Newton method for controlling Ising spin systems

    NASA Astrophysics Data System (ADS)

    Ciaramella, G.; Borzì, A.

    2015-05-01

    The modeling and control of Ising spin systems is of fundamental importance in NMR spectroscopy applications. In this paper, two computer packages, ReHaG and SKRYN, are presented. Their purpose is to set-up and solve quantum optimal control problems governed by the Liouville master equation modeling Ising spin-1/2 systems with pointwise control constraints. In particular, the MATLAB package ReHaG allows to compute a real matrix representation of the master equation. The MATLAB package SKRYN implements a new strategy resulting in a globalized semismooth matrix-free Krylov-Newton scheme. To discretize the real representation of the Liouville master equation, a norm-preserving modified Crank-Nicolson scheme is used. Results of numerical experiments demonstrate that the SKRYN code is able to provide fast and accurate solutions to the Ising spin quantum optimization problem.

  8. Truncated Wigner theory of coherent Ising machines based on degenerate optical parametric oscillator network

    NASA Astrophysics Data System (ADS)

    Maruo, Daiki; Utsunomiya, Shoko; Yamamoto, Yoshihisa

    2016-08-01

    We present the quantum theory of coherent Ising machines based on networks of degenerate optical parametric oscillators (DOPOs). In a simple model consisting of two coupled DOPOs, both positive-P representation and truncated Wigner representation predict quantum correlation and inseparability between the two DOPOs in spite of the open-dissipative nature of the system. Here, we apply the truncated Wigner representation method to coherent Ising machines with thermal, vacuum, and squeezed reservoir fields. We find that the probability of finding the ground state of a one-dimensional Ising model increases substantially as a result of reducing excess thermal noise and squeezing the incident vacuum fluctuation on the out-coupling port.

  9. Initial survey of the wave distribution functions for plasmaspheric hiss observed by ISEE 1

    NASA Technical Reports Server (NTRS)

    Storey, L. R. O.; Lefeuvre, F.; Parrot, M.; Cairo, L.; Anderson, R. R.

    1991-01-01

    The generation mechanism of hiss observed by ISEE 1 satellite in the earth magnetosphere is investigated by analyzing the ELF/VLF wave data obtained from four passes of ISEE 1, all of which occurring during magnetically quiet periods. The results of these measurements, together with those published earlier, indicate that the generation mechanisms proposed by Kennel alnd Petschek (1966), by Thorne et al. (1979), and by Solomon et al. (1988, 1989) are all physically possible and can come into action whenever the necessary conditions exist. However, plasmaspheric hiss was observed by ISEE even when the conditions for any of these mechanisms existed; under these conditions, hiss appears to be generated near the equatorial plane over a wide range of L values, with the wave normals at large angles to the field. The generation mechanism that applies in such cases is still unknown.

  10. Volatility behavior of visibility graph EMD financial time series from Ising interacting system

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Wang, Jun; Fang, Wen

    2015-08-01

    A financial market dynamics model is developed and investigated by stochastic Ising system, where the Ising model is the most popular ferromagnetic model in statistical physics systems. Applying two graph based analysis and multiscale entropy method, we investigate and compare the statistical volatility behavior of return time series and the corresponding IMF series derived from the empirical mode decomposition (EMD) method. And the real stock market indices are considered to be comparatively studied with the simulation data of the proposed model. Further, we find that the degree distribution of visibility graph for the simulation series has the power law tails, and the assortative network exhibits the mixing pattern property. All these features are in agreement with the real market data, the research confirms that the financial model established by the Ising system is reasonable.

  11. Statistical Properties and Multifractal Behaviors of Market Returns by Ising Dynamic Systems

    NASA Astrophysics Data System (ADS)

    Fang, Wen; Wang, Jun

    An interacting-agent model of speculative activity explaining price formation in financial markets is considered in the present paper, which based on the stochastic Ising model and the mean field theory. The model describes the interaction strength among the agents as well as an external field, and the corresponding random logarithmic price return process is investigated. According to the empirical research of the model, the time series formed by this Ising model exhibits the bursting typical of volatility clustering, the fat-tail phenomenon, the power-law distribution tails and the long-time memory. The statistical properties of the returns of Hushen 300 Index, Shanghai Stock Exchange (SSE) Composite Index and Shenzhen Stock Exchange (SZSE) Component Index are also studied for comparison between the real time series and the simulated ones. Further, the multifractal detrended fluctuation analysis is applied to investigate the time series returns simulated by Ising model have the distribution multifractality as well as the correlation multifractality.

  12. Mean-field theory for the inverse Ising problem at low temperatures.

    PubMed

    Nguyen, H Chau; Berg, Johannes

    2012-08-01

    The large amounts of data from molecular biology and neuroscience have lead to a renewed interest in the inverse Ising problem: how to reconstruct parameters of the Ising model (couplings between spins and external fields) from a number of spin configurations sampled from the Boltzmann measure. To invert the relationship between model parameters and observables (magnetizations and correlations), mean-field approximations are often used, allowing the determination of model parameters from data. However, all known mean-field methods fail at low temperatures with the emergence of multiple thermodynamic states. Here, we show how clustering spin configurations can approximate these thermodynamic states and how mean-field methods applied to thermodynamic states allow an efficient reconstruction of Ising models also at low temperatures.

  13. Two-axis tracking solar collector mechanism

    DOEpatents

    Johnson, K.C.

    1992-12-08

    This invention is a novel solar tracking mechanism incorporating a number of practical features that give it superior environmental resilience and exceptional tracking accuracy. The mechanism comprises a lightweight space-frame assembly supporting an array of point-focus Fresnel lenses in a two-axis tracking structure. The system is enclosed under a glass cover which isolates it from environmental exposure and enhances tracking accuracy by eliminating wind loading. Tracking accuracy is also enhanced by the system's broad-based tracking support. The system's primary intended application would be to focus highly concentrated sunlight into optical fibers for transmission to core building illumination zones, and the system may also have potential for photovoltaic or photothermal solar energy conversion. 16 figs.

  14. Two-axis tracking solar collector mechanism

    DOEpatents

    Johnson, Kenneth C.

    1990-01-01

    This invention is a novel solar tracking mechanism incorporating a number of practical features that give it superior environmental resilience and exceptional tracking accuracy. The mechanism comprises a lightweight space-frame assembly supporting an array of point-focus Fresnel lenses in a two-axis tracking structure. The system is enclosed under a glass cover which isolates it from environmental exposure and enhances tracking accuracy by eliminating wind loading. Tracking accuracy is also enhanced by the system's broad-based tracking support. The system's primary intended application would be to focus highly concentrated sunlight into optical fibers for transmission to core building illumination zones, and the system may also have potential for photovoltaic or photothermal solar energy conversion.

  15. Two-axis tracking solar collector mechanism

    DOEpatents

    Johnson, Kenneth C.

    1992-01-01

    This invention is a novel solar tracking mechanism incorporating a number of practical features that give it superior environmental resilience and exceptional tracking accuracy. The mechanism comprises a lightweight space-frame assembly supporting an array of point-focus Fresnel lenses in a two-axis tracking structure. The system is enclosed under a glass cover which isolates it from environmental exposure and enhances tracking accuracy by eliminating wind loading. Tracking accuracy is also enhanced by the system's broad-based tracking support. The system's primary intended application would be to focus highly concentrated sunlight into optical fibers for transmission to core building illumination zones, and the system may also have potential for photovoltaic or photothermal solar energy conversion.

  16. Ising-model description of long-range correlations in DNA sequences

    NASA Astrophysics Data System (ADS)

    Colliva, A.; Pellegrini, R.; Testori, A.; Caselle, M.

    2015-05-01

    We model long-range correlations of nucleotides in the human DNA sequence using the long-range one-dimensional (1D) Ising model. We show that, for distances between 103 and 106 bp, the correlations show a universal behavior and may be described by the non-mean-field limit of the long-range 1D Ising model. This allows us to make some testable hypothesis on the nature of the interaction between distant portions of the DNA chain which led to the DNA structure that we observe today in higher eukaryotes.

  17. Ising spin glasses: Corrections to finite size scaling, freezing temperatures, and critical exponents

    NASA Astrophysics Data System (ADS)

    Mari, P. O.; Campbell, I. A.

    1999-03-01

    We compare simulation data from different sources on two canonical three-dimensional Ising spin glasses (ISGs): the binomial +/-J near-neighbor interaction ISG and the Gaussian interaction ISG. We allow for the possibility of corrections to finite size scaling and estimate the correction exponent w. Consistent estimates for the critical temperatures Tg and for the critical exponents for each system are obtained. The data strongly indicate that critical exponents in the two systems are significantly different from each other. These results thus confirm a breakdown of standard universality rules in Ising spin glasses.

  18. ISEE 3 magnetopause crossings - Evidence for the Kelvin-Helmholtz instability

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Slavin, J. A.; Smith, E. J.

    1987-01-01

    The role of the Kelvin-Helmholtz instability in driving magnetopause motion is investigated on the basis of correlated ISEE-3 magnetometer measurements and IMP-8 solar-wind/magnetosheath velocities. The data are presented in graphs and briefly characterized, comparing the daily frequency of magnetopause crossings by ISEE-3 with the velocities. It is found that the instability criterion for longitudinal waves is only rarely satisfied in these measurements, while that for waves with an azimuthal component is satisfied in over 50 percent of the cases. It is inferred that the Kelvin-Helmholtz instability is probably the cause of motions with magnetotail-boundary interarrival times of 20 min or less.

  19. Canonical vs. micro-canonical sampling methods in a 2D Ising model

    SciTech Connect

    Kepner, J.

    1990-12-01

    Canonical and micro-canonical Monte Carlo algorithms were implemented on a 2D Ising model. Expressions for the internal energy, U, inverse temperature, Z, and specific heat, C, are given. These quantities were calculated over a range of temperature, lattice sizes, and time steps. Both algorithms accurately simulate the Ising model. To obtain greater than three decimal accuracy from the micro-canonical method requires that the more complicated expression for Z be used. The overall difference between the algorithms is small. The physics of the problem under study should be the deciding factor in determining which algorithm to use. 13 refs., 6 figs., 2 tabs.

  20. Cyclic period-3 window in antiferromagnetic potts and Ising models on recursive lattices

    NASA Astrophysics Data System (ADS)

    Ananikian, N. S.; Ananikyan, L. N.; Chakhmakhchyan, L. A.

    2011-09-01

    The magnetic properties of the antiferromagnetic Potts model with two-site interaction and the antiferromagnetic Ising model with three-site interaction on recursive lattices have been studied. A cyclic period-3 window has been revealed by the recurrence relation method in the antiferromagnetic Q-state Potts model on the Bethe lattice (at Q < 2) and in the antiferromagnetic Ising model with three-site interaction on the Husimi cactus. The Lyapunov exponents have been calculated, modulated phases and a chaotic regime in the cyclic period-3 window have been found for one-dimensional rational mappings determined the properties of these systems.

  1. Ground-state candidate for the classical dipolar kagome Ising antiferromagnet

    NASA Astrophysics Data System (ADS)

    Chioar, I. A.; Rougemaille, N.; Canals, B.

    2016-06-01

    We have investigated the low-temperature thermodynamic properties of the classical dipolar kagome Ising antiferromagnet using Monte Carlo simulations, in the quest for the ground-state manifold. In spite of the limitations of a single-spin-flip approach, we managed to identify certain ordering patterns in the low-temperature regime and we propose a candidate for this unknown state. This configuration presents some intriguing features and is fully compatible with the extrapolations of the at-equilibrium thermodynamic behavior sampled so far, making it a very likely choice for the dipolar long-range ordered state of the classical kagome Ising antiferromagnet.

  2. A new look on the two-dimensional Ising model: thermal artificial spins

    NASA Astrophysics Data System (ADS)

    Arnalds, Unnar B.; Chico, Jonathan; Stopfel, Henry; Kapaklis, Vassilios; Bärenbold, Oliver; Verschuuren, Marc A.; Wolff, Ulrike; Neu, Volker; Bergman, Anders; Hjörvarsson, Björgvin

    2016-02-01

    We present a direct experimental investigation of the thermal ordering in an artificial analogue of an asymmetric two-dimensional Ising system composed of a rectangular array of nano-fabricated magnetostatically interacting islands. During fabrication and below a critical thickness of the magnetic material the islands are thermally fluctuating and thus the system is able to explore its phase space. Above the critical thickness the islands freeze-in resulting in an arrested thermalized state for the array. Determining the magnetic state we demonstrate a genuine artificial two-dimensional Ising system which can be analyzed in the context of nearest neighbor interactions.

  3. Exponentially improved classical and quantum algorithms for three-body Ising models

    NASA Astrophysics Data System (ADS)

    Van den Nest, M.; Dür, W.

    2014-01-01

    We present an algorithm to approximate partition functions of three-body classical Ising models on two-dimensional lattices of arbitrary genus, in the real-temperature regime. Even though our algorithm is purely classical, it is designed by exploiting a connection to topological quantum systems, namely, the color codes. The algorithm performance (in achievable accuracy) is exponentially better than other approaches that employ mappings between partition functions and quantum state overlaps. In addition, our approach gives rise to a protocol for quantum simulation of such Ising models by simply measuring local observables on color codes.

  4. Self-Organizing Two-Temperature Ising Model Describing Human Segregation

    NASA Astrophysics Data System (ADS)

    Ódor, Géza

    A two-temperature Ising-Schelling model is introduced and studied for describing human segregation. The self-organized Ising model with Glauber kinetics simulated by Müller et al. exhibits a phase transition between segregated and mixed phases mimicking the change of tolerance (local temperature) of individuals. The effect of external noise is considered here as a second temperature added to the decision of individuals who consider a change of accommodation. A numerical evidence is presented for a discontinuous phase transition of the magnetization.

  5. Thermal Ising transitions in the vicinity of two-dimensional quantum critical points

    NASA Astrophysics Data System (ADS)

    Hesselmann, S.; Wessel, S.

    2016-04-01

    The scaling of the transition temperature into an ordered phase close to a quantum critical point as well as the order parameter fluctuations inside the quantum critical region provide valuable information about universal properties of the underlying quantum critical point. Here, we employ quantum Monte Carlo simulations to examine these relations in detail for two-dimensional quantum systems that exhibit a finite-temperature Ising-transition line in the vicinity of a quantum critical point that belongs to the universality class of either (i) the three-dimensional Ising model for the case of the quantum Ising model in a transverse magnetic field on the square lattice or (ii) the chiral Ising transition for the case of a half-filled system of spinless fermions on the honeycomb lattice with nearest-neighbor repulsion. While the first case allows large-scale simulations to assess the scaling predictions to a high precision in terms of the known values for the critical exponents at the quantum critical point, for the later case, we extract values of the critical exponents ν and η , related to the order parameter fluctuations, which we discuss in relation to other recent estimates from ground-state quantum Monte Carlo calculations as well as analytical approaches.

  6. Transient time of an Ising machine based on injection-locked laser network

    NASA Astrophysics Data System (ADS)

    Takata, Kenta; Utsunomiya, Shoko; Yamamoto, Yoshihisa

    2012-01-01

    We numerically study the dynamics and frequency response of the recently proposed Ising machine based on the polarization degrees of freedom of an injection-locked laser network (Utsunomiya et al 2011 Opt. Express 19 18091). We simulate various anti-ferromagnetic Ising problems, including the ones with symmetric Ising and Zeeman coefficients, which enable us to study the problem size up to M = 1000. Transient time, to reach a steady-state polarization configuration after a given Ising problem is mapped onto the system, is inversely proportional to the locking bandwidth and does not scale exponentially with the problem size. In the Fourier analysis with first-order linearization approximation, we find that the cut-off frequency of a system's response is almost identical to the locking bandwidth, which supports the time-domain analysis. It is also shown that the Zeeman term, which is created by the horizontally polarized injection signal from the master laser, serves as an initial driving force on the system and contributes to the transient time in addition to the inverse locking bandwidth.

  7. One-dimensional random field Ising model and discrete stochastic mappings

    SciTech Connect

    Behn, U.; Zagrebnov, V.A.

    1987-06-01

    Previous results relating the one-dimensional random field Ising model to a discrete stochastic mapping are generalized to a two-valued correlated random (Markovian) field and to the case of zero temperature. The fractal dimension of the support of the invariant measure is calculated in a simple approximation and its dependence on the physical parameters is discussed.

  8. Phase diagrams of the Ising-Heisenberg chain with S = 1/2 triangular XXZ clusters

    SciTech Connect

    Ohanyan, V.

    2010-03-15

    The one-dimensional spin system consisted of triangular S = 1/2 XXZ Heisenberg clusters alternating with single Ising spins is considered. Partition function of the system is calculated exactly within the transfer-matrix formalism. T = 0 ground state phase diagrams, corresponding to different regions of the values of system parameters, are obtained.

  9. Physics and financial economics (1776-2014): puzzles, Ising and agent-based models.

    PubMed

    Sornette, Didier

    2014-06-01

    This short review presents a selected history of the mutual fertilization between physics and economics--from Isaac Newton and Adam Smith to the present. The fundamentally different perspectives embraced in theories developed in financial economics compared with physics are dissected with the examples of the volatility smile and of the excess volatility puzzle. The role of the Ising model of phase transitions to model social and financial systems is reviewed, with the concepts of random utilities and the logit model as the analog of the Boltzmann factor in statistical physics. Recent extensions in terms of quantum decision theory are also covered. A wealth of models are discussed briefly that build on the Ising model and generalize it to account for the many stylized facts of financial markets. A summary of the relevance of the Ising model and its extensions is provided to account for financial bubbles and crashes. The review would be incomplete if it did not cover the dynamical field of agent-based models (ABMs), also known as computational economic models, of which the Ising-type models are just special ABM implementations. We formulate the 'Emerging Intelligence Market Hypothesis' to reconcile the pervasive presence of 'noise traders' with the near efficiency of financial markets. Finally, we note that evolutionary biology, more than physics, is now playing a growing role to inspire models of financial markets. PMID:24875470

  10. 24-th Order high temperature expansion for the 3-d Ising model

    SciTech Connect

    Glaessner, U.; Schilling, K.; Bhanot, G.; Creutz, M.

    1994-12-01

    The authors present the series for the free energy and their estimate for the critical exponent {alpha}, as computed by a recursive bookkeeping algorithm on the CM5. They begin with a discussion of the algorithm to compute the High-Temperature expansion on finite 3-D Ising lattices.

  11. Increasing Student Performance on the Independent School Entrance Exam (ISEE) Using the Gap Analysis Approach

    ERIC Educational Resources Information Center

    Sarshar, Shanon Etty

    2013-01-01

    Using the Gap Analysis problem-solving framework (Clark & Estes, 2008), this study examined the performance gap experienced by 6th grade students on the math sections of the ISEE (Independent School Entrance Exam). The purpose of the study was to identify and validate the knowledge, motivation, and organization causes of the students' low…

  12. Physics and financial economics (1776-2014): puzzles, Ising and agent-based models

    NASA Astrophysics Data System (ADS)

    Sornette, Didier

    2014-06-01

    This short review presents a selected history of the mutual fertilization between physics and economics—from Isaac Newton and Adam Smith to the present. The fundamentally different perspectives embraced in theories developed in financial economics compared with physics are dissected with the examples of the volatility smile and of the excess volatility puzzle. The role of the Ising model of phase transitions to model social and financial systems is reviewed, with the concepts of random utilities and the logit model as the analog of the Boltzmann factor in statistical physics. Recent extensions in terms of quantum decision theory are also covered. A wealth of models are discussed briefly that build on the Ising model and generalize it to account for the many stylized facts of financial markets. A summary of the relevance of the Ising model and its extensions is provided to account for financial bubbles and crashes. The review would be incomplete if it did not cover the dynamical field of agent-based models (ABMs), also known as computational economic models, of which the Ising-type models are just special ABM implementations. We formulate the ‘Emerging Intelligence Market Hypothesis’ to reconcile the pervasive presence of ‘noise traders’ with the near efficiency of financial markets. Finally, we note that evolutionary biology, more than physics, is now playing a growing role to inspire models of financial markets.

  13. Physics and financial economics (1776-2014): puzzles, Ising and agent-based models.

    PubMed

    Sornette, Didier

    2014-06-01

    This short review presents a selected history of the mutual fertilization between physics and economics--from Isaac Newton and Adam Smith to the present. The fundamentally different perspectives embraced in theories developed in financial economics compared with physics are dissected with the examples of the volatility smile and of the excess volatility puzzle. The role of the Ising model of phase transitions to model social and financial systems is reviewed, with the concepts of random utilities and the logit model as the analog of the Boltzmann factor in statistical physics. Recent extensions in terms of quantum decision theory are also covered. A wealth of models are discussed briefly that build on the Ising model and generalize it to account for the many stylized facts of financial markets. A summary of the relevance of the Ising model and its extensions is provided to account for financial bubbles and crashes. The review would be incomplete if it did not cover the dynamical field of agent-based models (ABMs), also known as computational economic models, of which the Ising-type models are just special ABM implementations. We formulate the 'Emerging Intelligence Market Hypothesis' to reconcile the pervasive presence of 'noise traders' with the near efficiency of financial markets. Finally, we note that evolutionary biology, more than physics, is now playing a growing role to inspire models of financial markets.

  14. Ising antiferromagnet on a finite triangular lattice with free boundary conditions

    NASA Astrophysics Data System (ADS)

    Kim, Seung-Yeon

    2015-11-01

    The exact integer values for the density of states of the Ising model on an equilateral triangular lattice with free boundary conditions are evaluated up to L = 24 spins on a side for the first time by using the microcanonical transfer matrix. The total number of states is 2 N s = 2300 ≈ 2.037 × 1090 for L = 24, where N s = L( L+1)/2 is the number of spins. Classifying all 2300 spin states according to their energy values is an enormous work. From the density of states, the exact partition function zeros in the complex temperature plane of the triangular-lattice Ising model are evaluated. Using the density of states and the partition function zeros, we investigate the properties of the triangularlattice Ising antiferromagnet. The scaling behavior of the ground-state entropy and the form of the correlation length at T = 0 are studied for the triangular-lattice Ising antiferromagnet with free boundary conditions. Also, the scaling behavior of the Fisher edge singularity is investigated.

  15. Test of crossover scaling in the two-dimensional random-field Ising model

    NASA Astrophysics Data System (ADS)

    Binder, K.

    1984-05-01

    The random-field-induced rounding of the specific-heat singularity observed in transfer-matrix calculations of two-dimensional Ising models by Morgenstern, Binder, and Hornreich is interpreted in terms of the Fishman-Aharony scaling theory. Results qualitatively similar to recent experimental work on Rb2Co0.85Mg0.15F4 are obtained.

  16. Vertical axis wind turbine airfoil

    DOEpatents

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

    2012-12-18

    A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

  17. Gut Microbiota-brain Axis

    PubMed Central

    Wang, Hong-Xing; Wang, Yu-Ping

    2016-01-01

    Objective: To systematically review the updated information about the gut microbiota-brain axis. Data Sources: All articles about gut microbiota-brain axis published up to July 18, 2016, were identified through a literature search on PubMed, ScienceDirect, and Web of Science, with the keywords of “gut microbiota”, “gut-brain axis”, and “neuroscience”. Study Selection: All relevant articles on gut microbiota and gut-brain axis were included and carefully reviewed, with no limitation of study design. Results: It is well-recognized that gut microbiota affects the brain's physiological, behavioral, and cognitive functions although its precise mechanism has not yet been fully understood. Gut microbiota-brain axis may include gut microbiota and their metabolic products, enteric nervous system, sympathetic and parasympathetic branches within the autonomic nervous system, neural-immune system, neuroendocrine system, and central nervous system. Moreover, there may be five communication routes between gut microbiota and brain, including the gut-brain's neural network, neuroendocrine-hypothalamic-pituitary-adrenal axis, gut immune system, some neurotransmitters and neural regulators synthesized by gut bacteria, and barrier paths including intestinal mucosal barrier and blood-brain barrier. The microbiome is used to define the composition and functional characteristics of gut microbiota, and metagenomics is an appropriate technique to characterize gut microbiota. Conclusions: Gut microbiota-brain axis refers to a bidirectional information network between the gut microbiota and the brain, which may provide a new way to protect the brain in the near future. PMID:27647198

  18. Two-axis angular effector

    DOEpatents

    Vaughn, Mark R.; Robinett, III, Rush D.; Phelan, John R.; Van Zuiden, Don M.

    1997-01-21

    A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.

  19. An FGF3-BMP Signaling Axis Regulates Caudal Neural Tube Closure, Neural Crest Specification and Anterior-Posterior Axis Extension

    PubMed Central

    Anderson, Matthew J.; Schimmang, Thomas; Lewandoski, Mark

    2016-01-01

    During vertebrate axis extension, adjacent tissue layers undergo profound morphological changes: within the neuroepithelium, neural tube closure and neural crest formation are occurring, while within the paraxial mesoderm somites are segmenting from the presomitic mesoderm (PSM). Little is known about the signals between these tissues that regulate their coordinated morphogenesis. Here, we analyze the posterior axis truncation of mouse Fgf3 null homozygotes and demonstrate that the earliest role of PSM-derived FGF3 is to regulate BMP signals in the adjacent neuroepithelium. FGF3 loss causes elevated BMP signals leading to increased neuroepithelium proliferation, delay in neural tube closure and premature neural crest specification. We demonstrate that elevated BMP4 depletes PSM progenitors in vitro, phenocopying the Fgf3 mutant, suggesting that excessive BMP signals cause the Fgf3 axis defect. To test this in vivo we increased BMP signaling in Fgf3 mutants by removing one copy of Noggin, which encodes a BMP antagonist. In such mutants, all parameters of the Fgf3 phenotype were exacerbated: neural tube closure delay, premature neural crest specification, and premature axis termination. Conversely, genetically decreasing BMP signaling in Fgf3 mutants, via loss of BMP receptor activity, alleviates morphological defects. Aberrant apoptosis is observed in the Fgf3 mutant tailbud. However, we demonstrate that cell death does not cause the Fgf3 phenotype: blocking apoptosis via deletion of pro-apoptotic genes surprisingly increases all Fgf3 defects including causing spina bifida. We demonstrate that this counterintuitive consequence of blocking apoptosis is caused by the increased survival of BMP-producing cells in the neuroepithelium. Thus, we show that FGF3 in the caudal vertebrate embryo regulates BMP signaling in the neuroepithelium, which in turn regulates neural tube closure, neural crest specification and axis termination. Uncovering this FGF3-BMP signaling axis is

  20. Anatomical study of the gastrointestinal tract in free-living axis deer (Axis axis).

    PubMed

    Pérez, W; Erdogan, S; Ungerfeld, R

    2015-02-01

    The macroscopic anatomy of the stomach and intestines of adult axis deer (Axis axis), a cervid species considered intermediate/mixed feeder, was observed and recorded. Nine adult wild axis deers of both sexes were used and studied by simple dissection. The ruminal papillae were distributed unevenly in the overall area of the inner surface of rumen and primarily were more large and abundant within the atrium. The ruminal pillars had no papillae. There was an additional ruminal pillar located between the right longitudinal and right coronary ventral pillars connected to the caudal pillar. No dorsal coronary pillars were found, and the ventral coronary pillars are connected. The reticulum was the third compartment in size, and the maximum height of the reticular crests was 1.0 mm. The Cellulae reticuli were not divided and rarely contained secondary crests. There were no Papillae unguiculiformes. The omasum was the smallest gastric compartment. The abomasum had about twelve spiral plicae, and a small pyloric torus was present. The intraruminal papillation was similar to those species that are characterized by a higher proportion of grass in their natural diet. The finding of the small reticular crests is typical for browser ruminants and was coincident with data reported for other deer. The comparative ratio of the small intestine to the large intestine was 1.69, in terms of length measurements in axis deer and appears below of the 'browser range'. We concluded that the gastrointestinal system of axis deer reflected similar morphological characteristics of the both types of ruminants: browser and grazer, and we consider it as an intermediate feeder.

  1. Three axis velocity probe system

    DOEpatents

    Fasching, George E.; Smith, Jr., Nelson S.; Utt, Carroll E.

    1992-01-01

    A three-axis velocity probe system for determining three-axis positional velocities of small particles in fluidized bed systems and similar applications. This system has a sensor head containing four closely-spaced sensing electrodes of small wires that have flat ends to establish a two axis plane, e.g. a X-Y plane. Two of the sensing electrodes are positioned along one of the axes and the other two are along the second axis. These four sensing electrodes are surrounded by a guard electrode, and the outer surface is a ground electrode and support member for the sensing head. The electrodes are excited by, for example, sinusoidal voltage having a peak-to-peak voltage of up to 500 volts at a frequency of 2 MHz. Capacitive currents flowing between the four sensing electrodes and the ground electrode are influenced by the presence and position of a particle passing the sensing head. Any changes in these currents due to the particle are amplified and synchronously detected to produce positional signal values that are converted to digital form. Using these digital forms and two values of time permit generation of values of the three components of the particle vector and thus the total velocity vector.

  2. Bound states in two-dimensional spin systems near the Ising limit: A quantum finite-lattice study

    SciTech Connect

    Dusuel, Sebastien; Kamfor, Michael; Schmidt, Kai Phillip; Thomale, Ronny; Vidal, Julien

    2010-02-01

    We analyze the properties of low-energy bound states in the transverse-field Ising model and in the XXZ model on the square lattice. To this end, we develop an optimized implementation of perturbative continuous unitary transformations. The Ising model is studied in the small-field limit which is found to be a special case of the toric code model in a magnetic field. To analyze the XXZ model, we perform a perturbative expansion about the Ising limit in order to discuss the fate of the elementary magnon excitations when approaching the Heisenberg point.

  3. Fetal and Neonatal HPA Axis.

    PubMed

    Wood, Charles E; Walker, Claire-Dominique

    2015-01-01

    Stress is an integral part of life. Activation of the hypothalamus-pituitary-adrenal (HPA) axis in the adult can be viewed as mostly adaptive to restore homeostasis in the short term. When stress occurs during development, and specifically during periods of vulnerability in maturing systems, it can significantly reprogram function, leading to pathologies in the adult. Thus, it is critical to understand how the HPA axis is regulated during developmental periods and what are the factors contributing to shape its activity and reactivity to environmental stressors. The HPA axis is not a passive system. It can actively participate in critical physiological regulation, inducing parturition in the sheep for instance or being a center stage actor in the preparation of the fetus to aerobic life (lung maturation). It is also a major player in orchestrating mental function, metabolic, and cardiovascular function often reprogrammed by stressors even prior to conception through epigenetic modifications of gametes. In this review, we review the ontogeny of the HPA axis with an emphasis on two species that have been widely studied-sheep and rodents-because they each share many similar regulatory mechanism applicable to our understanding of the human HPA axis. The studies discussed in this review should ultimately inform us about windows of susceptibility in the developing brain and the crucial importance of early preconception, prenatal, and postnatal interventions designed to improve parental competence and offspring outcome. Only through informed studies will our public health system be able to curb the expansion of many stress-related or stress-induced pathologies and forge a better future for upcoming generations.

  4. Stress and the reproductive axis.

    PubMed

    Toufexis, D; Rivarola, M A; Lara, H; Viau, V

    2014-09-01

    There exists a reciprocal relationship between the hypothalamic-pituitary-adrenal (HPA) and the hypothalamic-pituitary-gonadal (HPG) axes, wherein the activation of one affects the function of the other and vice versa. For example, both testosterone and oestrogen modulate the response of the HPA axis, whereas activation of the stress axis, especially activation that is repeating or chronic, has an inhibitory effect upon oestrogen and testosterone secretion. Alterations in maternal care can produce significant effects on both HPG and HPA physiology, as well as behaviour in the offspring at adulthood. For example, changes in reproductive behaviour induced by altered maternal care may alter the expression of sex hormone receptors such as oestrogen receptor (ER)α that govern sexual behaviour, and may be particularly important in determining the sexual strategies utilised by females. Stress in adulthood continues to mediate HPG activity in females through activation of a sympathetic neural pathway originating in the hypothalamus and releasing norepinephrine into the ovary, which produces a noncyclic anovulatory ovary that develops cysts. In the opposite direction, sex differences and sex steroid hormones regulate the HPA axis. For example, although serotonin (5-HT) has a stimulatory effect on the HPA axis in humans and rodents that is mediated by the 5-HT1A receptor, only male rodents respond to 5-HT1A antagonism to show increased corticosterone responses to stress. Furthermore, oestrogen appears to decrease 5-HT1A receptor function at presynaptic sites, yet increases 5-HT1A receptor expression at postsynaptic sites. These mechanisms could explain the heightened stress HPA axis responses in females compared to males. Studies on female rhesus macaques show that chronic stress in socially subordinate female monkeys produces a distinct behavioural phenotype that is largely unaffected by oestrogen, a hyporesponsive HPA axis that is hypersensitive to the modulating effects

  5. Stress and the Reproductive Axis

    PubMed Central

    Toufexis, Donna; Rivarola, Maria Angelica; Lara, Hernan; Viau, Victor

    2014-01-01

    There exists a reciprocal relationship between the hypothalamic-pituitary-adrenal (HPA) and the hypothalamic-pituitary-gonadal (HPG) axes wherein the activation of one affects the function of the other and vice versa. For instance, both testosterone and oestrogen modulate the response of the HPA axis, while activation of the stress axis, especially activation that is repeating or chronic, has an inhibitory effect upon oestrogen and testosterone secretion. Alterations in maternal care can produce significant effects on both HPG and HPA physiology and behaviour in the offspring at adulthood. For example, changes in reproductive behaviour induced by altered maternal care may alter the expression of sex hormone receptors like ERα that govern sexual behaviour, and may be particularly important in determining the sexual strategies utilized by females. Stress in adulthood continues to mediate HPG activity in females through activation of a sympathetic neural pathway originating in the hypothalamus and releasing norepinephrine (NE) into the ovary, which produces a non-cyclic anovulatory ovary that develops cysts. In the opposite direction, sex differences and sex steroid hormones regulate the HPA axis. For example, although serotonin (5-HT) has a stimulatory effect on the HPA axis in humans and rodents that is mediated by the 5-HT1A receptor, only male rodents respond to 5-HT1A antagonism to show increased corticosterone responses to stress. Furthermore, oestrogen appears to decrease 5-HT1A receptor function at presynaptic sites, yet increase 5-HT1A receptor expression at postsynaptic sites. These mechanisms could explain heightened stress HPA axis responses in females compared to males. Studies on female rhesus macaques show that chronic stress in socially subordinate female monkeys produces a distinct behavioral phenotype that is largely unaffected by oestrogen, a hypo-responsive HPA axis that is hypersensitive to the modulating effects of oestrogen, and changes in 5-HT

  6. International sun-earth explorer 1 and 2 (ISEE 1 and 2) magnetospheric and interplanetary plasma instruments

    NASA Technical Reports Server (NTRS)

    Frank, L. A.

    1995-01-01

    Major accomplishments are summarized for ISEE 1 and 2, and a bibliographic list of publications resulting from this University of Iowa research is attached. Most accomplishments center on the magnetotail, magnetosheath, and plasma sheet.

  7. Assessing change of environmental dynamics by legislation in Japan, using red tide occurrence in Ise Bay as an indicator.

    PubMed

    Suzuki, Chika

    2016-01-30

    Tokyo Bay, Ise Bay, and the Seto Inland Sea are the total pollutant load control target areas in Japan. A significant correlation between the incidence of red tides and water quality has been observed in the Seto Inland Sea (Honjo, 1991). However, while red tides also occur in Ise Bay and Tokyo Bay, similar correlations have not been observed. Hence, it is necessary to understand what factors cause red tides to effectively manage these semi-closed systems. This study aims to investigate the relationship between the dynamics of the Red Tide Index and nitrogen regulation as well as phosphorus regulation, even in Ise Bay where, unlike Tokyo Bay, there are few observation items, by selecting a suitable objective variable. The introduction of a new technique that uses the Red Tide Index has revealed a possibility that the total pollution load control has influenced the dynamics of red tide blooms in Ise Bay.

  8. Assessing change of environmental dynamics by legislation in Japan, using red tide occurrence in Ise Bay as an indicator.

    PubMed

    Suzuki, Chika

    2016-01-30

    Tokyo Bay, Ise Bay, and the Seto Inland Sea are the total pollutant load control target areas in Japan. A significant correlation between the incidence of red tides and water quality has been observed in the Seto Inland Sea (Honjo, 1991). However, while red tides also occur in Ise Bay and Tokyo Bay, similar correlations have not been observed. Hence, it is necessary to understand what factors cause red tides to effectively manage these semi-closed systems. This study aims to investigate the relationship between the dynamics of the Red Tide Index and nitrogen regulation as well as phosphorus regulation, even in Ise Bay where, unlike Tokyo Bay, there are few observation items, by selecting a suitable objective variable. The introduction of a new technique that uses the Red Tide Index has revealed a possibility that the total pollution load control has influenced the dynamics of red tide blooms in Ise Bay. PMID:26337227

  9. Angle interferometer cross axis errors

    SciTech Connect

    Bryan, J.B.; Carter, D.L.; Thompson, S.L.

    1994-01-01

    Angle interferometers are commonly used to measure surface plate flatness. An error can exist when the centerline of the double comer cube mirror assembly is not square to the surface plate and the guide bar for the mirror sled is curved. Typical errors can be one to two microns per meter. A similar error can exist in the calibration of rotary tables when the centerline of the double comer cube mirror assembly is not square to the axes of rotation of the angle calibrator and the calibrator axis is not parallel to the rotary table axis. Commercial double comer cube assemblies typically have non-parallelism errors of ten milli-radians between their centerlines and their sides and similar values for non-squareness between their centerlines and end surfaces. The authors have developed a simple method for measuring these errors and correcting them by remachining the reference surfaces.

  10. Emergent long-range synchronization of oscillating ecological populations without external forcing described by Ising universality.

    PubMed

    Noble, Andrew E; Machta, Jonathan; Hastings, Alan

    2015-01-01

    Understanding the synchronization of oscillations across space is fundamentally important to many scientific disciplines. In ecology, long-range synchronization of oscillations in spatial populations may elevate extinction risk and signal an impending catastrophe. The prevailing assumption is that synchronization on distances longer than the dispersal scale can only be due to environmental correlation (the Moran effect). In contrast, we show how long-range synchronization can emerge over distances much longer than the length scales of either dispersal or environmental correlation. In particular, we demonstrate that the transition from incoherence to long-range synchronization of two-cycle oscillations in noisy spatial population models is described by the Ising universality class of statistical physics. This result shows, in contrast to all previous work, how the Ising critical transition can emerge directly from the dynamics of ecological populations.

  11. Solution of the antiferromagnetic Ising model on a tetrahedron recursive lattice.

    PubMed

    Jurčišinová, E; Jurčišin, M

    2014-03-01

    We consider the antiferromagnetic spin-1/2 Ising model on the recursive tetrahedron lattice on which two elementary tetrahedrons are connected at each site. The model represents the simplest approximation of the antiferromagnetic Ising model on the real three-dimensional tetrahedron lattice which takes into account effects of frustration. An exact analytical solution of the model is found and discussed. It is shown that the model exhibits neither the first-order nor the second-order phase transitions. A detailed analysis of the magnetization of the model in the presence of the external magnetic field is performed and the existence of the magnetization plateaus for low temperatures is shown. All possible ground states of the model are found and discussed. The existence of nontrivial singular ground states is proven and exact explicit expressions for them are found.

  12. Some peculiarities in the behavior of non-Ising spin glasses

    NASA Astrophysics Data System (ADS)

    Tareyeva, E. E.; Schelkacheva, T. I.; Chtchelkatchev, N. M.

    2015-03-01

    This paper is a review. We outline the main directions in the modern theory of spin glasses. The main content is based on our recent papers, devoted to studying replica symmetry breaking in non-Ising spin glasses. Studying a series of generalized models showed a certain uniformity of the behavior of these generalized spin glasses. Essentially, we observe a significant difference between their behavior and the behavior of the known systems with random couplings of Ising spins—the Sherrington-Kirkpatrick model and the corresponding p-spin model. We find the bifurcation point for the solution with the first replica symmetry breaking, study the form and stability of the solution near the bifurcation point, and show in which cases the transition to the glass state occurs continuously and in which cases, with a jump of the order parameters.

  13. Critical adsorption in the undersaturated regime: Scaling and exact results in Ising strips

    NASA Astrophysics Data System (ADS)

    Ciach, A.; Maciolek, A.; Stecki, J.

    1998-04-01

    Critical adsorption for weak surface field h1 is reconsidered. On the basis of physical heuristic arguments, approximate behavior of the scaling function is derived. New form of a scaling for weak h1 in finite systems is proposed and verified by testing against exact results obtained for this purpose in the 2D Ising strips. For weak h1 we find the approximate behavior of adsorption Γ˜τβ-Δ1 for the reduced temperatures h11/Δ1˜τ≪1. This behavior is consistent with experimental data [N. S. Desai, S. Peach, and C. Franck, Phys. Rev. E 52, 4129 (1995)] obtained for τ=10-5, and is in a very good agreement with exact results in the 2D Ising strip.

  14. XY ring exchange model with frustrated Ising coupling on the triangular lattice

    NASA Astrophysics Data System (ADS)

    Owerre, S. A.

    2016-07-01

    We investigate the nature of a Z2-invariant XY ring-exchange interaction with a frustrated Ising coupling on the triangular lattice. Within the limits of pure XY ring-exchange interaction, we show that the classical ground state is degenerate resulting from the Z2-invariance of the Hamiltonian. Quantum fluctuations lift these classical degenerate ground states and produce an unusual state whose excitation spectrum exhibits a gapped maximum quadratic dispersion near k = 0 and vanishes at the midpoints of each side of the Brillouin zone. This result is in contrast to a gapless quadratic dispersion near k = 0 in the U(1)-invariant counterpart. We also study the effects of frustration when competing with a classically frustrated Ising interaction. We provide a glimpse into the possible quantum phases that could emerge. A comprehensive understanding of this Hamiltonian, however, cannot be elucidated analytically and requires an explicit numerical simulation.

  15. Tricritical Ising phase transition in a two-ladder Majorana fermion lattice

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoyu; Franz, M.

    2016-05-01

    We introduce a two-ladder lattice model with interacting Majorana fermions that could be realized on the surfaces of a topological insulator film. We study this model with a combination of analytical and numerical techniques, and we find a phase diagram that features both gapless and gapped phases as well as interesting phase transitions including a quantum critical point in the tricritical Ising (TCI) universality class. The latter occurs at an intermediate-coupling strength at a meeting point of a first-order transition line and an Ising critical line, and it is known to be described by a superconformal field theory with central charge c =7/10 . We discuss the experimental feasibility of constructing the model and tuning parameters to the vicinity of the TCI point where signatures of the elusive supersymmetry can be observed.

  16. Self-overlap as a method of analysis in Ising models.

    PubMed

    Ferrera, A; Luque, B; Lacasa, L; Valero, E

    2007-06-01

    The damage spreading (DS) method provided a useful tool to obtain analytical results of the thermodynamics and stability of the two-dimensional (2D) Ising model--amongst many others--but it suffered both from ambiguities in its results and from large computational costs. In this paper we propose an alternative method, the so-called self-overlap method, based on the study of correlation functions measured at subsequent time steps as the system evolves towards its equilibrium. Applying Markovian and mean-field approximations to a 2D Ising system we obtain both analytical and numerical results on the thermodynamics that agree with the expected behavior. We also provide some analytical results on the stability of the system. Since only a single replica of the system needs to be studied, this method would seem to be free from the ambiguities that afflicted the DS method. It also seems to be numerically more efficient and analytically simpler.

  17. Exactly solved mixed spin-(1,1/2) Ising-Heisenberg distorted diamond chain

    NASA Astrophysics Data System (ADS)

    Lisnyi, Bohdan; Strečka, Jozef

    2016-11-01

    The mixed spin-(1,1/2) Ising-Heisenberg model on a distorted diamond chain with the spin-1 nodal atoms and the spin-1/2 interstitial atoms is exactly solved by the transfer-matrix method. An influence of the geometric spin frustration and the parallelogram distortion on the ground state, magnetization, susceptibility and specific heat of the mixed-spin Ising-Heisenberg distorted diamond chain are investigated in detail. It is demonstrated that the zero-temperature magnetization curve may involve intermediate plateaus just at zero and one-half of the saturation magnetization. The temperature dependence of the specific heat may have up to three distinct peaks at zero magnetic field and up to four distinct peaks at a non-zero magnetic field. The origin of multipeak thermal behavior of the specific heat is comprehensively studied.

  18. Single-file water as a one-dimensional Ising model.

    PubMed

    Köfinger, Jürgen; Dellago, Christoph

    2010-09-27

    We show that single-file water in nanopores can be viewed as a one-dimensional Ising model and investigate, on this basis, the static dielectric response of a chain of hydrogen-bonded water molecules to an external field. To this end, we use a recently developed dipole lattice model which accurately captures the free energetics of nanopore water. In this model, the total energy of the system can be expressed as a sum of effective interactions of chain ends and orientational defects. Neglecting these interactions, we essentially obtain the one-dimensional Ising model which allows us to derive analytical expressions for the free energy as a function of the total dipole moment and for the dielectric susceptibility. Our expressions, which agree very well with simulation results, provide the basis for the interpretation of future dielectric spectroscopy experiments on water-filled nanopore membranes.

  19. Applying Tabu Search to the Two-Dimensional Ising Spin Glass

    NASA Astrophysics Data System (ADS)

    Laguna, Manuel; Laguna, Pablo

    A variety of problems in statistical physics, such as Ising-like systems, can be modeled as integer programs. Physicists have relied mostly on Monte Carlo methods to find approximate solutions to these computationally difficult problems. In some cases, optimal solutions to relatively small problems have been found using standard optimization techniques, e.g., cutting plane and branch-and-bound algorithms. Motivated by the success of tabu search (TS) in finding optimal or near-optimal solutions to combinatorial optimization problems in a number of different settings, we study the application of this methodology to Ising-like systems. Particularly, we develop a TS method to find ground states of two-dimensional spin glasses. Our method performs a search at different levels of resolution in the spin lattice, and it is designed to obtain optimal or near-optimal solutions to problem instances with several different characteristics. Results are reported for computational experiments with up to 64×64 lattices.

  20. Characterizing correlations with full counting statistics: classical Ising and quantum XY spin chains.

    PubMed

    Ivanov, Dmitri A; Abanov, Alexander G

    2013-02-01

    We propose to describe correlations in classical and quantum systems in terms of full counting statistics of a suitably chosen discrete observable. The method is illustrated with two exactly solvable examples: the classical one-dimensional Ising model and the quantum spin-1/2 XY chain. For the one-dimensional Ising model, our method results in a phase diagram with two phases distinguishable by the long-distance behavior of the Jordan-Wigner strings. For the anisotropic spin-1/2 XY chain in a transverse magnetic field, we compute the full counting statistics of the magnetization and use it to classify quantum phases of the chain. The method, in this case, reproduces the previously known phase diagram. We also discuss the relation between our approach and the Lee-Yang theory of zeros of the partition function. PMID:23496467

  1. Magnetic and Ising quantum phase transitions in a model for isoelectronically tuned iron pnictides

    NASA Astrophysics Data System (ADS)

    Wu, Jianda; Si, Qimiao; Abrahams, Elihu

    2016-03-01

    Considerations of the observed bad-metal behavior in Fe-based superconductors led to an early proposal for quantum criticality induced by isoelectronic P for As doping in iron arsenides, which has since been experimentally confirmed. We study here an effective model for the isoelectronically tuned pnictides using a large-N approach. The model contains antiferromagnetic and Ising-nematic order parameters appropriate for J1-J2 exchange-coupled local moments on an Fe square lattice, and a damping caused by coupling to itinerant electrons. The zero-temperature magnetic and Ising transitions are concurrent and essentially continuous. The order-parameter jumps are very small, and are further reduced by the interplane coupling; consequently, quantum criticality occurs over a wide dynamical range. Our results reconcile recent seemingly contradictory experimental observations concerning the quantum phase transition in the P-doped iron arsenides.

  2. The Signed Loop Approach to the Ising Model: Foundations and Critical Point

    NASA Astrophysics Data System (ADS)

    Kager, Wouter; Lis, Marcin; Meester, Ronald

    2013-07-01

    The signed loop approach is a beautiful way to rigorously study the two-dimensional Ising model with no external field. In this paper, we explore the foundations of the method, including details that have so far been neglected or overlooked in the literature. We demonstrate how the method can be applied to the Ising model on the square lattice to derive explicit formal expressions for the free energy density and two-point functions in terms of sums over loops, valid all the way up to the self-dual point. As a corollary, it follows that the self-dual point is critical both for the behaviour of the free energy density, and for the decay of the two-point functions.

  3. Non-equilibrium critical properties of the Ising model on product graphs

    NASA Astrophysics Data System (ADS)

    Burioni, Raffaella; Corberi, Federico; Vezzani, Alessandro

    2010-12-01

    We study numerically the non-equilibrium critical properties of the Ising model defined on direct products of graphs, obtained from factor graphs without phase transition (Tc = 0). On this class of product graphs, the Ising model features a finite temperature phase transition, and we find a pattern of scaling behaviors analogous to the one known on regular lattices: observables take a scaling form in terms of a function L(t) of time, with the meaning of a growing length inside which a coherent fractal structure, the critical state, is progressively formed. Computing universal quantities, such as the critical exponents and the limiting fluctuation-dissipation ratio X_\\infty , allows us to comment on the possibility to extend universality concepts to the critical behavior on inhomogeneous substrates.

  4. The peak effect (PE) region of the antiferromagnetic two layer Ising nanographene

    NASA Astrophysics Data System (ADS)

    Şarlı, Numan; Akbudak, Salih; Ellialtıoğlu, Mehmet Recai

    2014-11-01

    In this work, the magnetic properties of the ferromagnetic and antiferromagnetic two layer spin-1/2 Ising nanographene systems are investigated within the effective field theory. We find that the magnetizations and the hysteresis behaviors of the central graphene atoms are similar to those of the edge graphene atoms in the ferromagnetic case. But, they are quite different in the antiferromagnetic case. The antiferromagnetic central graphene atoms exhibit type II superconductivity and they have triple hysteresis loop. The peak effect (PE) region is observed on the hysteresis curves of the antiferromagnetic Ising nanographene system. Therefore, we suggest that there is a strong relationship between the antiferromagnetism and the peak effect. Our results are in agreement with some experimental works in recent literature.

  5. Quenched Central Limit Theorems for the Ising Model on Random Graphs

    NASA Astrophysics Data System (ADS)

    Giardinà, Cristian; Giberti, Claudio; van der Hofstad, Remco; Prioriello, Maria Luisa

    2015-09-01

    The main goal of the paper is to prove central limit theorems for the magnetization rescaled by for the Ising model on random graphs with N vertices. Both random quenched and averaged quenched measures are considered. We work in the uniqueness regime or and , where is the inverse temperature, is the critical inverse temperature and B is the external magnetic field. In the random quenched setting our results apply to general tree-like random graphs (as introduced by Dembo, Montanari and further studied by Dommers and the first and third author) and our proof follows that of Ellis in . For the averaged quenched setting, we specialize to two particular random graph models, namely the 2-regular configuration model and the configuration model with degrees 1 and 2. In these cases our proofs are based on explicit computations relying on the solution of the one dimensional Ising models.

  6. An analysis of intergroup rivalry using Ising model and reinforcement learning

    NASA Astrophysics Data System (ADS)

    Zhao, Feng-Fei; Qin, Zheng; Shao, Zhuo

    2014-01-01

    Modeling of intergroup rivalry can help us better understand economic competitions, political elections and other similar activities. The result of intergroup rivalry depends on the co-evolution of individual behavior within one group and the impact from the rival group. In this paper, we model the rivalry behavior using Ising model. Different from other simulation studies using Ising model, the evolution rules of each individual in our model are not static, but have the ability to learn from historical experience using reinforcement learning technique, which makes the simulation more close to real human behavior. We studied the phase transition in intergroup rivalry and focused on the impact of the degree of social freedom, the personality of group members and the social experience of individuals. The results of computer simulation show that a society with a low degree of social freedom and highly educated, experienced individuals is more likely to be one-sided in intergroup rivalry.

  7. Influence of Boundary Conditions on Metastable Lifetimes for The Ising Model on the Hyperbolic Plane

    NASA Astrophysics Data System (ADS)

    Richards, Howard L.; Sharma Chapagain, Dipendra; Molchanoff, James

    2012-02-01

    Some corals grow in shapes that resemble 3D models of the hyperbolic plane, since this allows them to have greater area for a given growth radius. Each polyp could be represented by an Ising site, with ``feeding'' = ``up'' and ``retracted'' = ``down''. The mechanisms of metastable decay could be interpreted as how the coral as a whole reacts to changing conditions of food availability or predation. Previous studies have shown that there is a spinodal field for the Ising model on a regular lattice in the hyperbolic plane if it is infinite or has periodic or mean-field boundary conditions. This happens because the size of the boundary grows asymptotically at the same rate as the droplet volume, in clear contrast with droplets in the Euclidean plane. Our simulations show, however, that the spinodal field disappears if more physically relevant open boundary conditions are used instead.

  8. The Finite-Size Scaling Relation for the Order-Parameter Probability Distribution of the Six-Dimensional Ising Model

    NASA Astrophysics Data System (ADS)

    Merdan, Ziya; Karakuş, Özlem

    2016-07-01

    The six dimensional Ising model with nearest-neighbor pair interactions has been simulated and verified numerically on the Creutz Cellular Automaton by using five bit demons near the infinite-lattice critical temperature with the linear dimensions L=4,6,8,10. The order parameter probability distribution for six dimensional Ising model has been calculated at the critical temperature. The constants of the analytical function have been estimated by fitting to probability function obtained numerically at the finite size critical point.

  9. Control of Wannier orbitals for generating tunable Ising interactions of ultracold atoms in an optical lattice

    SciTech Connect

    Inaba, Kensuke; Tamaki, Kiyoshi; Igeta, Kazuhiro; Yamashita, Makoto; Tokunaga, Yuuki

    2014-12-04

    In this study, we propose a method for generating cluster states of atoms in an optical lattice. By utilizing the quantum properties of Wannier orbitals, we create an tunable Ising interaction between atoms without inducing the spin-exchange interactions. We investigate the cause of errors that occur during entanglement generations, and then we propose an error-management scheme, which allows us to create high-fidelity cluster states in a short time.

  10. Evidence against an Almeida-Thouless line in disordered systems of Ising dipoles

    NASA Astrophysics Data System (ADS)

    Fernández, Julio F.

    2010-10-01

    By tempered Monte Carlo simulations, an Almeida-Thouless (AT) phase-boundary line in site-diluted Ising spin systems is searched for. Spins interact only through dipolar fields and occupy a small fraction of lattice sites. The spin-glass susceptibility of these systems and of the Sherrington-Kirkpatrick model are compared. The correlation length as a function of system size and temperature is also studied. The results obtained are contrary to the existence of an AT line.

  11. Correlation functions in the two-dimensional Ising model in a magnetic field at T = Tc

    NASA Astrophysics Data System (ADS)

    Delfino, G.; Simonetti, P.

    1996-02-01

    The one- and two-particle form factors of the energy operator in the two-dimensional Ising model in a magnetic field at T = Tc are exactly computed within the form factor bootstrap approach. Together with the matrix elements of the magnetisation operator already computed by G. Delfino and G. Mussardo [Nucl. Phys. B 455 (1995) 724], they are used to write down the large distance expansion for the correlators of the two relevant fields of the model.

  12. Ising-like phase transition of an n-component Eulerian face-cubic model.

    PubMed

    Ding, Chengxiang; Guo, Wenan; Deng, Youjin

    2013-11-01

    By means of Monte Carlo simulations and a finite-size scaling analysis, we find a critical line of an n-component Eulerian face-cubic model on the square lattice and the simple cubic lattice in the region v>1, where v is the bond weight. The phase transition belongs to the Ising universality class independent of n. The critical properties of the phase transition can also be captured by the percolation of the complement of the Eulerian graph. PMID:24329232

  13. Ising-like phase transition of an n-component Eulerian face-cubic model

    NASA Astrophysics Data System (ADS)

    Ding, Chengxiang; Guo, Wenan; Deng, Youjin

    2013-11-01

    By means of Monte Carlo simulations and a finite-size scaling analysis, we find a critical line of an n-component Eulerian face-cubic model on the square lattice and the simple cubic lattice in the region v>1, where v is the bond weight. The phase transition belongs to the Ising universality class independent of n. The critical properties of the phase transition can also be captured by the percolation of the complement of the Eulerian graph.

  14. Inference of the sparse kinetic Ising model using the decimation method.

    PubMed

    Decelle, Aurélien; Zhang, Pan

    2015-05-01

    In this paper we study the inference of the kinetic Ising model on sparse graphs by the decimation method. The decimation method, which was first proposed in Decelle and Ricci-Tersenghi [Phys. Rev. Lett. 112, 070603 (2014)] for the static inverse Ising problem, tries to recover the topology of the inferred system by setting the weakest couplings to zero iteratively. During the decimation process the likelihood function is maximized over the remaining couplings. Unlike the ℓ(1)-optimization-based methods, the decimation method does not use the Laplace distribution as a heuristic choice of prior to select a sparse solution. In our case, the whole process can be done auto-matically without fixing any parameters by hand. We show that in the dynamical inference problem, where the task is to reconstruct the couplings of an Ising model given the data, the decimation process can be applied naturally into a maximum-likelihood optimization algorithm, as opposed to the static case where pseudolikelihood method needs to be adopted. We also use extensive numerical studies to validate the accuracy of our methods in dynamical inference problems. Our results illustrate that, on various topologies and with different distribution of couplings, the decimation method outperforms the widely used ℓ(1)-optimization-based methods. PMID:26066148

  15. Ising spin network states for loop quantum gravity: a toy model for phase transitions

    NASA Astrophysics Data System (ADS)

    Feller, Alexandre; Livine, Etera R.

    2016-03-01

    Non-perturbative approaches to quantum gravity call for a deep understanding of the emergence of geometry and locality from the quantum state of the gravitational field. Without background geometry, the notion of distance should emerge entirely from the correlations between the gravity fluctuations. In the context of loop quantum gravity, quantum states of geometry are defined as spin networks. These are graphs decorated with spin and intertwiners, which represent quantized excitations of areas and volumes of the space geometry. Here, we develop the condensed-matter point of view on extracting the physical and geometrical information from spin network states: we introduce new Ising spin network states, both in 2d on a square lattice and in 3d on a hexagonal lattice, whose correlations map onto the usual Ising model in statistical physics. We construct these states from the basic holonomy operators of loop gravity and derive a set of local Hamiltonian constraints that entirely characterize our states. We discuss their phase diagram and show how the distance can be reconstructed from the correlations in the various phases. Finally, we propose generalizations of these Ising states, which open the perspective to study the coarse-graining and dynamics of spin network states using well-known condensed-matter techniques and results.

  16. Observation of 2D Ising criticality of liquid-gas transition by the flowgram method

    NASA Astrophysics Data System (ADS)

    Yarmolinsky, Max; Kuklov, Anatoly

    We study the critical properties of the transition in 2D liquid-gas system with the square-well potential interaction by Monte Carlo simulations in the grand canonical ensemble. Due to lack of the underlying Ising symmetry, the analysis cannot be done reliably by the standard methods applicable to lattice systems. In contrast, the analysis based on the flowgram method allowed us to find the critical point to significantly higher (and controllable) accuracy than in previous studies by other authors. Simulations were performed in a progression of sizes L up to size L = 84 , with the particle numbers varying over 3 orders of magnitude and the subcritical behavior not extending beyond L = 10 - 15 . The finite size scaling analysis of the critical exponents and their ratio, μ and γ / ν , gives values consistent with the 2D Ising universality class within 1-2% of errors. Our result essentially closes proposals that the nature of the liquid-gas transition might be different from the Ising model in systems with short-range interactions. This work was supported by the NSF Grant PHY1314469.

  17. Non-Ising-like effects in the liquid-vapor transition: Equations of state

    NASA Astrophysics Data System (ADS)

    Vause, C.; Sak, J.

    1980-06-01

    A Landau-Ginzburg-Wilson model is derived for a single-component fluid whose particles interact via a two-body potential. The effective Hamiltonian contains both even and odd powers in the order parameter (local fluid density). We study the effect of quintic interactions absent in the Ising model, and characterized by a new exponent φ5, on various singular thermodynamic functions near the critical point. Mean-field, scaling, and renormalization-group (in d=4-ɛ dimensions) theories are used to evaluate the non-Ising effects due to φ5. One of the main results of the asymmetry in this model is that it produces the leading singularity of the liquid-vapor coexistence diameter near the critical point: |t|β-φ5, where β is the usual order-parameter exponent and t is the reduced temp˙erature. The singularity |t|1-α (α being the specific heat exponent) predicted by earlier phenomenological theories is not present in this theory. The problems associated with observing the non-Ising effects are briefly discussed.

  18. Intercomparison of DPASV and ISE for the measurement of Cu complexation characteristics of NOM in freshwater

    SciTech Connect

    Rozan, T.F.; Benoit, G.; Marsh, H.; Chin, Y.P.

    1999-05-15

    Complexation by dissolved humic substances has an important influence on trace metal behavior in natural systems. Unfortunately, few analytical techniques are available with adequate sensitivity and selectivity to measure free metal ions reliably at the low concentrations under which they occur in natural waters. In the past, differential pulse anodic stripping voltammetry with a thin mercury film rotating disk glassy carbon electrode (DPASV-TMF-RDGCE) has been used to measure complexation capacities and conditional metal-ligand binding constants in oceanic and estuarine waters. In contrast, few studies have been conducted to validate DPASV`s use in freshwaters. The current study compares DPASV and Cu ion-selective electrode (CuISE) methods for measuring free copper, complexation capacities, and conditional binding constants on samples of synthetic and isolated natural organics. Titration data show that DPASV and CuISE are able to measure similar amounts of labile copper when the two methods` detection windows overlap. Furthermore, the greater sensitivity of DPASV allows it to measure free copper at lower concentrations, which correlated well with CuISE data extrapolated into that same region. This strong correlation between these analytical methods provides positive evidence for the use of DPASV (TMF-RDGCE) in measuring free Cu{sup 2+}, complexation capacities, and conditional binding constants in freshwaters.

  19. Universality of the glassy transitions in the two-dimensional ±J Ising model.

    PubMed

    Parisen Toldin, Francesco; Pelissetto, Andrea; Vicari, Ettore

    2010-08-01

    We investigate the zero-temperature glassy transitions in the square-lattice ±J Ising model, with bond distribution P(J{xy})=pδ(J{xy}-J)+(1-p)δ(J{xy}+J) ; p=1 and p=1/2 correspond to the pure Ising model and to the Ising spin glass with symmetric bimodal distribution, respectively. We present finite-temperature Monte Carlo simulations at p=4/5 , which is close to the low-temperature paramagnetic-ferromagnetic transition line located at p≈0.89 , and at p=1/2 . Their comparison provides a strong evidence that the glassy critical behavior that occurs for 1-p{0}

  20. Dynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence

    NASA Astrophysics Data System (ADS)

    Foss-Feig, M.; Hazzard, K. R. A.; Bollinger, J. J.; Rey, A. M.; Clark, C. W.

    2013-11-01

    Ising models, and the physical systems described by them, play a central role in generating entangled states for use in quantum metrology and quantum information. In particular, ultracold atomic gases, trapped ion systems, and Rydberg atoms realize long-ranged Ising models, which even in the absence of a transverse field can give rise to highly non-classical dynamics and long-range quantum correlations. In the first part of this paper, we present a detailed theoretical framework for studying the dynamics of such systems driven (at time t = 0) into arbitrary unentangled non-equilibrium states, thus greatly extending and unifying the work of Foss-Feig et al (2013 Phys. Rev. A 87 042101). Specifically, we derive exact expressions for closed-time-path ordered correlation functions, and use these to study experimentally relevant observables, e.g. Bloch vector and spin-squeezing dynamics. In the second part, these correlation functions are then used to derive closed-form expressions for the dynamics of arbitrary spin-spin correlation functions in the presence of both T1 (spontaneous spin relaxation/excitation) and T2 (dephasing) type decoherence processes. Even though the decoherence is local, our solution reveals that the competition between Ising dynamics and T1 decoherence gives rise to an emergent non-local dephasing effect, thereby drastically amplifying the degradation of quantum correlations. In addition to identifying the mechanism of this deleterious effect, our solution points toward a scheme to eliminate it via measurement-based coherent feedback.

  1. Exact ground states of large two-dimensional planar Ising spin glasses

    NASA Astrophysics Data System (ADS)

    Pardella, G.; Liers, F.

    2008-11-01

    Studying spin-glass physics through analyzing their ground-state properties has a long history. Although there exist polynomial-time algorithms for the two-dimensional planar case, where the problem of finding ground states is transformed to a minimum-weight perfect matching problem, the reachable system sizes have been limited both by the needed CPU time and by memory requirements. In this work, we present an algorithm for the calculation of exact ground states for two-dimensional Ising spin glasses with free boundary conditions in at least one direction. The algorithmic foundations of the method date back to the work of Kasteleyn from the 1960s for computing the complete partition function of the Ising model. Using Kasteleyn cities, we calculate exact ground states for huge two-dimensional planar Ising spin-glass lattices (up to 30002 spins) within reasonable time. According to our knowledge, these are the largest sizes currently available. Kasteleyn cities were recently also used by Thomas and Middleton in the context of extended ground states on the torus. Moreover, they show that the method can also be used for computing ground states of planar graphs. Furthermore, we point out that the correctness of heuristically computed ground states can easily be verified. Finally, we evaluate the solution quality of heuristic variants of the L. Bieche approach.

  2. Diagonal Ising susceptibility: elliptic integrals, modular forms and Calabi-Yau equations

    NASA Astrophysics Data System (ADS)

    Assis, M.; Boukraa, S.; Hassani, S.; van Hoeij, M.; Maillard, J.-M.; McCoy, B. M.

    2012-02-01

    We give the exact expressions of the partial susceptibilities χ(3)d and χ(4)d for the diagonal susceptibility of the Ising model in terms of modular forms and Calabi-Yau ODEs, and more specifically, 3F2([1/3, 2/3, 3/2], [1, 1] z) and 4F3([1/2, 1/2, 1/2, 1/2], [1, 1, 1] z) hypergeometric functions. By solving the connection problems we analytically compute the behavior at all finite singular points for χ(3)d and χ(4)d. We also give new results for χ(5)d. We see, in particular, the emergence of a remarkable order-6 operator, which is such that its symmetric square has a rational solution. These new exact results indicate that the linear differential operators occurring in the n-fold integrals of the Ising model are not only ‘derived from geometry’ (globally nilpotent), but actually correspond to ‘special geometry’ (homomorphic to their formal adjoint). This raises the question of seeing if these ‘special geometry’ Ising operators are ‘special’ ones, reducing, in fact systematically, to (selected, k-balanced, ...) q + 1Fq hypergeometric functions, or correspond to the more general solutions of Calabi-Yau equations.

  3. The scaling limit of the energy correlations in non-integrable Ising models

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandro; Greenblatt, Rafael L.; Mastropietro, Vieri

    2012-09-01

    We obtain an explicit expression for the multipoint energy correlations of a non-solvable two-dimensional Ising models with nearest neighbor ferromagnetic interactions plus a weak finite range interaction of strength λ, in a scaling limit in which we send the lattice spacing to zero and the temperature to the critical one. Our analysis is based on an exact mapping of the model into an interacting lattice fermionic theory, which generalizes the one originally used by Schultz, Mattis, and Lieb for the nearest neighbor Ising model. The interacting model is then analyzed by a multiscale method first proposed by Pinson and Spencer. If the lattice spacing is finite, then the correlations cannot be computed in closed form: rather, they are expressed in terms of infinite, convergent, power series in λ. In the scaling limit, these infinite expansions radically simplify and reduce to the limiting energy correlations of the integrable Ising model, up to a finite renormalization of the parameters. Explicit bounds on the speed of convergence to the scaling limit are derived.

  4. Raman conversion in intense femtosecond Bessel beams in air

    NASA Astrophysics Data System (ADS)

    Scheller, Maik; Chen, Xi; Ariunbold, Gombojav O.; Born, Norman; Moloney, Jerome; Kolesik, Miroslav; Polynkin, Pavel

    2014-05-01

    We demonstrate experimentally that bright and nearly collimated radiation can be efficiently generated in air pumped by an intense femtosecond Bessel beam. We show that this nonlinear conversion process is driven by the rotational Raman response of air molecules. Under optimum conditions, the conversion efficiency from the Bessel pump into the on-axis propagating beam exceeds 15% and is limited by the onset of intensity clamping and plasma refraction on the beam axis. Our experimental findings are in excellent agreement with numerical simulations based on the standard model for the ultrafast nonlinear response of air.

  5. ScaphoLunate Axis Method.

    PubMed

    Yao, Jeffrey; Zlotolow, Dan A; Lee, Steve K

    2016-03-01

    Background Treating chronic scapholunate ligament injuries without the presence of arthritis remains an unsolved clinical problem facing wrist surgeons. This article highlights a technique for reconstructing the scapholunate ligament using novel fixation, the ScaphoLunate Axis Method (SLAM). Materials and Methods In a preliminary review of the early experience of this technique, 13 patients were evaluated following scapholunate ligament reconstruction utilizing the SLAM technique. Description of Techinque The scapholunate interval is reconstructed utilizing a palmaris longus autograft passed between the scaphoid and lunate along the axis of rotation in the sagittal plane. It is secured in the lunate using a graft anchor and in the scaphoid utilizing an interference screw. The remaining graft is passed dorsally to reconstruct the dorsal scapholunate ligament. Results At an average follow-up of 11 months, the mean postoperative scapholunate gap was 2.1 mm. The mean postoperative scapholunate angle was 59 degrees. The mean postoperative wrist flexion and extension was 45 and 56 degrees, respectively. The mean grip strength was 24.9 kg, or 62% of the contralateral side. The mean pain score (VAS) was 1.7. There was 1 failure with recurrence of the pathologic scapholunate gap and the onset of pain. Conclusion While chronic scapholunate ligament instability remains an unsolved problem facing wrist surgeons, newer techniques are directed toward restoring the normal relationships of the scaphoid and lunate in both the coronal and sagittal planes. The SLAM technique has demonstrated promise in preliminary clinical studies. PMID:26855838

  6. Centration axis in refractive surgery.

    PubMed

    Arba Mosquera, Samuel; Verma, Shwetabh; McAlinden, Colm

    2015-01-01

    The human eye is an asymmetric optical system and the real cornea is not a rotationally symmetrical volume. Each optical element in the eye has its own optical and neural axes. Defining the optimum center for laser ablation is difficult with many available approaches. We explain the various centration approaches (based on these reference axes) in refractive surgery and review their clinical outcomes. The line-of-sight (LOS) (the line joining the entrance pupil center with the fixation point) is often the recommended reference axis for representing wavefront aberrations of the whole eye (derived from the definition of chief ray in geometrical optics); however pupil centration can be unstable and change with the pupil size. The corneal vertex (CV) represents a stable preferable morphologic reference which is the best approximate for alignment to the visual axis. However, the corneal light reflex can be considered as non-constant, but dependent on the direction of gaze of the eye with respect to the light source. A compromise between the pupil and CV centered ablations is seen in the form of an asymmetric offset where the manifest refraction is referenced to the CV while the higher order aberrations are referenced to the pupil center. There is a need for a flexible choice of centration in excimer laser systems to design customized and non-customized treatments optimally. PMID:26605360

  7. Flexible helical-axis stellarator

    DOEpatents

    Harris, Jeffrey H.; Hender, Timothy C.; Carreras, Benjamin A.; Cantrell, Jack L.; Morris, Robert N.

    1988-01-01

    An 1=1 helical winding which spirals about a conventional planar, circular central conductor of a helical-axis stellarator adds a significant degree of flexibility by making it possible to control the rotational transform profile and shear of the magnetic fields confining the plasma in a helical-axis stellarator. The toroidal central conductor links a plurality of toroidal field coils which are separately disposed to follow a helical path around the central conductor in phase with the helical path of the 1=1 winding. This coil configuration produces bean-shaped magnetic flux surfaces which rotate around the central circular conductor in the same manner as the toroidal field generating coils. The additional 1=1 winding provides flexible control of the magnetic field generated by the central conductor to prevent the formation of low-order resonances in the rotational transform profile which can produce break-up of the equilibrium magnetic surfaces. Further, this additional winding can deepen the magnetic well which together with the flexible control provides increased stability.

  8. Stress and the HPA Axis

    PubMed Central

    Stephens, Mary Ann C.; Wand, Gary

    2012-01-01

    Stress has long been suggested to be an important correlate of uncontrolled drinking and relapse. An important hormonal response system to stress—the hypothalamic–pituitary–adrenal (HPA) axis—may be involved in this process, particularly stress hormones known as glucocorticoids and primarily cortisol. The actions of this hormone system normally are tightly regulated to ensure that the body can respond quickly to stressful events and return to a normal state just as rapidly. The main determinants of HPA axis activity are genetic background, early-life environment, and current life stress. Alterations in HPA axis regulation are associated with problematic alcohol use and dependence; however, the nature of this dysregulation appears to vary with respect to stage of alcohol dependence. Much of this research has focused specifically on the role of cortisol in the risk for, development of, and relapse to chronic alcohol use. These studies found that cortisol can interact with the brain’s reward system, which may contribute to alcohol’s reinforcing effects. Cortisol also can influence a person’s cognitive processes, promoting habit-based learning, which may contribute to habit formation and risk of relapse. Finally, cortisol levels during abstinence may be useful clinical indicators of relapse vulnerability in alcohol-dependent people. PMID:23584113

  9. Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3V2O8 in a transverse magnetic field

    SciTech Connect

    Fritsch, Katharina; Ehlers, G.; Rule, K. C.; Habicht, Klaus; Ramazanoglu, Mehmet K.; Dabkowska, H. A.; Gaulin, Bruce D.

    2015-11-05

    We study the application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional kagome staircase magnet, Co3V2O8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. Also, at least one of the transitions to incommensurate phases at μ0Hc1~6.25 T and μ0Hc2~7 T is discontinuous, while the final quantum critical point at μ0Hc3~13 T is continuous.

  10. Quantum Phase Transitions and De-Coupling of Magnetic Sublattices in the Quasi-Two Dimensional Ising Magnet Co3V2O8 in a Transverse Magnetic Field

    NASA Astrophysics Data System (ADS)

    Fritsch, K.; Ehlers, G.; Rule, K. C.; Habicht, K.; Ramazanoglu, M.; Dabkowska, H. A.; Gaulin, B. D.

    2015-03-01

    The application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two dimensional Kagome staircase magnet, Co3V2O8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allows the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. At least one of the transitions to incommensurate phases at μ0Hc 1 ~ 6 . 25 T and μ0Hc 2 ~ 7 T are discontinuous, while the final quantum critical point at μ0Hc 3 ~ 13 T is continuous.

  11. Thermal entanglement and sharp specific-heat peak in an exactly solved spin-1/2 Ising-Heisenberg ladder with alternating Ising and Heisenberg inter-leg couplings

    NASA Astrophysics Data System (ADS)

    Rojas, Onofre; Strečka, J.; de Souza, S. M.

    2016-11-01

    The spin-1/2 Ising-Heisenberg two-leg ladder accounting for alternating Ising and Heisenberg inter-leg couplings in addition to the Ising intra-leg coupling is rigorously mapped onto to a mixed spin-(3/2,1/2) Ising-Heisenberg diamond chain with the nodal Ising spins S = 3 / 2 and the interstitial spin-1/2 Heisenberg dimers. The latter effective model with higher-order interactions between the nodal and interstitial spins is subsequently exactly solved within the transfer-matrix method. The model under investigation exhibits five different ground states: ferromagnetic, antiferromagnetic, superantiferromagnetic and two types of frustrated ground states with a non-zero residual entropy. A detailed study of thermodynamic properties reveals an anomalous specific-heat peak at low enough temperatures, which is strongly reminiscent because of its extraordinary height and sharpness to an anomaly accompanying a phase transition. It is convincingly evidenced, however, that the anomalous peak in the specific heat is finite and it comes from vigorous thermal excitations from a two-fold degenerate ground state towards a macroscopically degenerate excited state. Thermal entanglement between the nearest-neighbor Heisenberg spins is also comprehensively explored by taking advantage of the concurrence. The threshold temperature delimiting a boundary between the entangled and disentangled parameter space may show presence of a peculiar temperature reentrance.

  12. Biotechnology of biomass conversion

    SciTech Connect

    Wayman, M.; Parekh, S.R.

    1990-01-01

    This book covers: An introduction to biomass crops; The microbiology of fermentation processes; The production of ethanol from biomass crops, such as sugar cane and rubbers; The energy of biomass conversion; and The economics of biomass conversion.

  13. Emergent Ising degrees of freedom in the J1-J2-J3 model for the iron tellurides

    NASA Astrophysics Data System (ADS)

    Zhang, Guanghua; Fernandes, Rafael; Flint, Rebecca

    The iron-telluride family of superconductors form a double-stripe [ Q = (π / 2 , π / 2) ] magnetic order, which can be captured within a J1 -J2 -J3 Heisenberg model in the regime J3 >>J2 >>J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground state manifold has three additional Ising degrees of freedom. Via their coupling to the lattice, they give rise to a monoclinic distortion and to two non-uniform lattice distortions with wave-vector (π , π) . Because the ground state is four-fold degenerate (mod rotations in spin space), only two of these Ising order parameters are independent. Here we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order. All three transitions (corresponding to the condensations of two Ising and one magnetic order parameter) are simultaneous and first order in three dimensions, but lower dimensionality (or equivalently weaker interlayer coupling) and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions.

  14. Long-range Ising and Kitaev models: phases, correlations and edge modes

    NASA Astrophysics Data System (ADS)

    Vodola, Davide; Lepori, Luca; Ercolessi, Elisa; Pupillo, Guido

    2016-01-01

    We analyze the quantum phases, correlation functions and edge modes for a class of spin-1/2 and fermionic models related to the one-dimensional Ising chain in the presence of a transverse field. These models are the Ising chain with anti-ferromagnetic long-range interactions that decay with distance r as 1/{r}α , as well as a related class of fermionic Hamiltonians that generalize the Kitaev chain, where both the hopping and pairing terms are long-range and their relative strength can be varied. For these models, we provide the phase diagram for all exponents α, based on an analysis of the entanglement entropy, the decay of correlation functions, and the edge modes in the case of open chains. We demonstrate that violations of the area law can occur for α ≲ 1, while connected correlation functions can decay with a hybrid exponential and power-law behavior, with a power that is α-dependent. Interestingly, for the fermionic models we provide an exact analytical derivation for the decay of the correlation functions at every α. Along the critical lines, for all models breaking of conformal symmetry is argued at low enough α. For the fermionic models we show that the edge modes, massless for α ≳ 1, can acquire a mass for α \\lt 1. The mass of these modes can be tuned by varying the relative strength of the kinetic and pairing terms in the Hamiltonian. Interestingly, for the Ising chain a similar edge localization appears for the first and second excited states on the paramagnetic side of the phase diagram, where edge modes are not expected. We argue that, at least for the fermionic chains, these massive states correspond to the appearance of new phases, notably approached via quantum phase transitions without mass gap closure. Finally, we discuss the possibility to detect some of these effects in experiments with cold trapped ions.

  15. Indentation Size Effect (ISE) in Copper Subjected to Severe Plastic Deformation (SPD)

    NASA Astrophysics Data System (ADS)

    Gale, Joshua D.; Achuthan, Ajit; Morrison, David J.

    2014-05-01

    The characteristic length scale of deformation in copper specimens subjected to severe plastic deformation (SPD) through surface mechanical attrition treatment (SMAT) was studied with indentation experiments. Annealed copper disks were shot peened with 6-mm diameter tungsten carbide spheres with an average velocity of 2.3 m/s for 15 minutes in a vibrating chamber. The SMAT-treated specimens were cross-sectioned, and the exposed face was studied under nanoindentation in order to determine the effect of dislocation density on surface hardness and indentation size effect (ISE). Since the specimen preparation of the exposed face involved mechanical polishing, which in turn introduced additional SPD on the indenting face, the effect of mechanical polishing on hardness measurement was investigated first. To this end, the mechanically polished specimens were subjected to various durations of electrochemical polishing. Hardness measurements on these specimens showed that the effect of mechanical polishing was substantial for both microindentation and nanoindentation, the impact being significantly larger for nanoindentation. Consequently, the measured depth of influence of the SMAT process, determined on specimens subjected to longer durations of electrochemical polishing, shows larger values compared to those previously reported in the literature. The ISE shows a bilinear relationship between the square of hardness and the reciprocal of indentation depth. The slope of this behavior, corresponding to smaller indentation loads, which is a measure of the ISE associated with a strain gradient, shows a power-law relationship with an increase in the distance away from the SMAT surface, instead of the constant value expected with the Nix-Gao type model.

  16. Noncyclic geometric quantum computation and preservation of entanglement for a two-qubit Ising model

    NASA Astrophysics Data System (ADS)

    Rangani Jahromi, H.; Amniat-Talab, M.

    2015-10-01

    After presenting an exact analytical solution of time-dependent Schrödinger equation, we study the dynamics of entanglement for a two-qubit Ising model. One of the spin qubits is driven by a static magnetic field applied in the direction of the Ising interaction, while the other is coupled with a rotating magnetic field. We also investigate how the entanglement can be controlled by changing the external parameters. Because of the important role of maximally entangled Bell states in quantum communication, we focus on the generalized Bell states as the initial states of the system. It is found that the entanglement evolution is independent of the initial Bell states. Moreover, we can preserve the initial maximal entanglement by adjusting the angular frequency of the rotating field or controlling the exchange coupling between spin qubits. Besides, our calculation shows that the entanglement dynamics is unaffected by the static magnetic field imposed in the direction of the Ising interaction. This is an interesting result, because, as we shall show below, this driving field can be used to control and manipulate the noncyclic geometric phase without affecting the system entanglement. Besides, the nonadiabatic and noncyclic geometric phase for evolved states of the present system are calculated and described in detail. In order to identify the unusable states for quantum communication, completely deviated from the initial maximally entangled states, we also study the fidelity between the initial Bell state and the evolved state of the system. Interestingly, we find that these unusable states can be detected by geometric quantum computation.

  17. Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian

    2013-05-01

    Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions (>100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings, facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled 9Be+ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be+ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, d, may be varied continuously from 1 /d0 to 1 /d3. An effective transverse magnetic field is applied via microwave radiation at the ~124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states. We acknowledge support from NIST and the DARPA-OLE program.

  18. Design of multi-energy Helds coupling testing system of vertical axis wind power system

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Yang, Z. X.; Li, G. S.; Song, L.; Ma, C.

    2016-08-01

    The conversion efficiency of wind energy is the focus of researches and concerns as one of the renewable energy. The present methods of enhancing the conversion efficiency are mostly improving the wind rotor structure, optimizing the generator parameters and energy storage controller and so on. Because the conversion process involves in energy conversion of multi-energy fields such as wind energy, mechanical energy and electrical energy, the coupling effect between them will influence the overall conversion efficiency. In this paper, using system integration analysis technology, a testing system based on multi-energy field coupling (MEFC) of vertical axis wind power system is proposed. When the maximum efficiency of wind rotor is satisfied, it can match to the generator function parameters according to the output performance of wind rotor. The voltage controller can transform the unstable electric power to the battery on the basis of optimizing the parameters such as charging times, charging voltage. Through the communication connection and regulation of the upper computer system (UCS), it can make the coupling parameters configure to an optimal state, and it improves the overall conversion efficiency. This method can test the whole wind turbine (WT) performance systematically and evaluate the design parameters effectively. It not only provides a testing method for system structure design and parameter optimization of wind rotor, generator and voltage controller, but also provides a new testing method for the whole performance optimization of vertical axis wind energy conversion system (WECS).

  19. Direct Conversion of Energy.

    ERIC Educational Resources Information Center

    Corliss, William R.

    This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. Direct energy conversion involves energy transformation without moving parts. The concepts of direct and dynamic energy conversion plus the laws governing energy conversion are investigated. Among the topics…

  20. High-temperature expansions of the higher susceptibilities for the Ising model in general dimension d.

    PubMed

    Butera, P; Pernici, M

    2012-07-01

    The high-temperature expansion coefficients of the ordinary and the higher susceptibilities of the spin-1/2 nearest-neighbor Ising model are calculated exactly up to the 20th order for the general d-dimensional (hyper)simple-cubical lattices. These series are analyzed to study the dependence of critical parameters on the lattice dimensionality. Using the general d expression of the ordinary susceptibility, we have more than doubled the length of the existing series expansion of the critical temperature in powers of 1/d.

  1. Universal free-energy distribution in the critical point of a random Ising ferromagnet

    NASA Astrophysics Data System (ADS)

    Dotsenko, Victor; Holovatch, Yurij

    2014-11-01

    We discuss the non-self-averaging phenomena in the critical point of weakly disordered Ising ferromagnet. In terms of the renormalized replica Ginzburg-Landau Hamiltonian in dimensions D <4 , we derive an explicit expression for the probability distribution function (PDF) of the critical free-energy fluctuations. In particular, using known fixed-point values for the renormalized coupling parameters, we obtain the universal curve for such PDF in the dimension D =3 . It is demonstrated that this function is strongly asymmetric: its left tail is much slower than the right one.

  2. History Dependent Phenomena in the Transverse Ising Ferro-Glass: the Free Energy Landscape

    SciTech Connect

    KAO,YING-JER; GREST,GARY S.; LEVIN,K.; ROSENBAUM,T.F.; AEPPLI,G.

    2000-11-08

    In this paper the authors investigate the relationship between glassy and ferromagnetic phases in disordered Ising ferromagnets in the presence of transverse magnetic fields, {Lambda}. Iterative mean field simulations probe the free energy landscape and suggest the existence of a glass transition line in the {Lambda}, temperature T plane well within the ferromagnetic phase. New experimental field-cooled and zero-field-cooled data on LiHo{sub x} Y{sub 1{minus}x}F{sub 4} provide support for our theoretical picture.

  3. Phase transitions and universality in nonequilibrium steady states of stochastic Ising models

    SciTech Connect

    Wang, J.S.; Lebowitz, J.L.

    1988-06-01

    We present results of direct computer simulations and of Monte Carlo renormalization group (MCRG) studies of the nonequilibrium steady states of a spin system with competing dynamics and of the voter model. The MCRG method, previously used only for equilibrium systems, appears to give useful information also for these nonequilibrium systems. The critical exponents are found to be of Ising type for the competing dynamics model at its second-order phase transitions, and of mean-field type for the voter model (consistent with known results for the latter).

  4. Comparison of Ising spin glass noise to flux and inductance noise in SQUIDs.

    PubMed

    Chen, Zhi; Yu, Clare C

    2010-06-18

    Recent experiments implicate spins on the surface of metals as the source of flux and inductance noise in SQUIDs. We present Monte Carlo simulations of 2D and 3D Ising spin glasses that produce magnetization noise S(M) consistent with flux noise. At low frequencies S(M) is a maximum at the critical temperature T(C) in three dimensions, implying that flux noise should be a maximum at T(C). The second spectra of the magnetization noise and the noise in the susceptibility are consistent with experimentally measured SQUID inductance noise.

  5. Dynamics in the Sherrington-Kirkpatrick Ising spin glass at and above Tg

    NASA Astrophysics Data System (ADS)

    Billoire, Alain; Campbell, I. A.

    2011-08-01

    A detailed numerical study is made of relaxation at equilibrium in the Sherrington-Kirkpatrick Ising spin glass (ISG) model, at and above the critical temperature Tg. The data show a long time stretched exponential relaxation q(t)˜exp{-[t/τ(T)]β(T)} with an exponent β(T) tending to ≈1/3 at Tg. The results are compared to those which were observed by A. T. Ogielski, [Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.32.7384 32, 7384 (1985)] in the three-dimensional ISG model and are discussed in terms of a phase space percolation transition scenario.

  6. A threaded Java concurrent implementation of the Monte-Carlo Metropolis Ising model

    PubMed Central

    Castañeda-Marroquín, Carlos; de la Puente, Alfonso Ortega; Alfonseca, Manuel; Glazier, James A.; Swat, Maciej

    2010-01-01

    This paper describes a concurrent Java implementation of the Metropolis Monte-Carlo algorithm that is used in 2D Ising model simulations. The presented method uses threads, monitors, shared variables and high level concurrent constructs that hide the low level details. In our algorithm we assign one thread to handle one spin flip attempt at a time. We use special lattice site selection algorithm to avoid two or more threads working concurently in the region of the lattice that “belongs” to two or more different spins undergoing spin-flip transformation. Our approach does not depend on the current platform and maximizes concurrent use of the available resources. PMID:21814633

  7. Density of zeros of the ferromagnetic Ising model on a family of fractals.

    PubMed

    Knežević, Milan; Knežević, Dragica

    2012-06-01

    We studied distribution of zeros of the partition function of the ferromagnetic Ising model near the Yang-Lee edge on a family of Sierpinski gasket lattices whose members are labeled by an integer b (2 ≤ b<∞). The obtained exact results on the first seven members of this family show that, for b ≥ 4, associated correlation length diverges more slowly than any power law when distance δh from the edge tends to zero, ξ_{YL}∼exp[ln(b)sqrt[|ln(δh)|/ln(λ{0})

  8. On the p-spin interaction transverse Ising spin-glass model without replicas

    NASA Astrophysics Data System (ADS)

    De Cesare, L.; Lukierska-Walasek, K.; Rabuffo, I.; Walasek, K.

    1995-02-01

    The p-spin interaction Ising spin glass model in the presence of a transverse field is studied in the large p-limit by means of a convenient operator extension of the cavity fields method avoiding replicas and the Trotter-Suzuki transformation. The results appear quite consistent with those recently obtained for the same model using conventional treatments within the replica trick. This gives additional support to the cavity fields approach as a promising tool towards a general theory of classical and quantum spin glasses.

  9. A theoretical study of the hysteresis behaviors of a transverse spin-1/2 Ising nanocube

    NASA Astrophysics Data System (ADS)

    El Hamri, M.; Bouhou, S.; Essaoudi, I.; Ainane, A.; Ahuja, R.

    2016-09-01

    The applied magnetic field dependencies of the surface shell, core and total magnetizations of a transverse spin-1/2 Ising nanocube are investigated within the effective-field theory with correlations, based on the probability distribution technique, for both ferro- and antiferromagnetic exchange interactions. We have found that interfacial coupling has a strong effect on the shape and the number of hysteresis loops and also on the coercive field and remanent magnetization behaviors. Furthermore, when the temperature exceeds a critical one, the coercivities of the core, the surface shell and the system become zero.

  10. Ising nanowires with simple core-shell structure; Their characteristic phenomena

    NASA Astrophysics Data System (ADS)

    Kaneyoshi, T.

    2016-09-01

    The phase diagrams and magnetizations of Ising nanowires with simple core-shell structure are investigated by the use of the effective field theory with correlations. A lot of characteristic behaviors observed in ferromagnetic and ferrimagnetic materials as well as novel phenomena have been obtained, although one section of the system is consisted of one spin-1/2 surface shell atom and one spin-1/2 core atom and they are coupled with a positive or a negative shell-core exchange interaction.

  11. Scaling and universality in the two-dimensional Ising model with a magnetic field

    NASA Astrophysics Data System (ADS)

    Mangazeev, Vladimir V.; Dudalev, Michael Yu.; Bazhanov, Vladimir V.; Batchelor, Murray T.

    2010-06-01

    The scaling function of the two-dimensional Ising model on the square and triangular lattices is obtained numerically via Baxter’s variational corner transfer-matrix approach. The use of Aharony-Fisher nonlinear scaling variables allowed us to perform calculations sufficiently away from the critical point and to confirm all predictions of the scaling and universality hypotheses. Our results are in excellent agreement with quantum field theory calculations of Fonseca and Zamolodchikov as well as with many previously known exact and numerical calculations, including susceptibility results by Barouch, McCoy, Tracy, and Wu.

  12. Tricritical behaviour of the frustrated Ising antiferromagnet on the honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Bobák, A.; Lučivjanský, T.; Žukovič, M.; Borovský, M.; Balcerzak, T.

    2016-08-01

    We use the effective-field theory with correlations based on different cluster sizes to investigate phase diagrams of the frustrated Ising antiferromagnet on the honeycomb lattice with isotropic interactions of the strength J1 < 0 between nearest-neighbour pairs and J2 < 0 between next-nearest neighbour pairs of spins. We present results for the ground-state energy as a function of the frustration parameter R =J2 / |J1 |. We find that the cluster-size has a considerable effect on the existence and location of a tricritical point in the phase diagram at which the phase transition changes from the second order to the first one.

  13. Ground State Properties of Ising Chain with Random Monomer-Dimer Couplings

    NASA Astrophysics Data System (ADS)

    Ardebili, S. Bahareh Seyedein; Sepehrinia, Reza

    2016-05-01

    We study analytically the one-dimensional Ising model with a random binary distribution of ferromagnetic and antiferromagnetic exchange couplings at zero temperature. We introduce correlations in the disorder by assigning a dimer of one type of coupling with probability x, and a monomer of the other type with probability 1-x. We find that the magnetization behaves differently from the original binary model. In particular, depending on which type of coupling comes in dimers, magnetization jumps vanish at a certain set of critical fields. We explain the results based on the structure of ground state spin configuration.

  14. Universal critical behavior of the two-dimensional Ising spin glass

    NASA Astrophysics Data System (ADS)

    Fernandez, L. A.; Marinari, E.; Martin-Mayor, V.; Parisi, G.; Ruiz-Lorenzo, J. J.

    2016-07-01

    We use finite size scaling to study Ising spin glasses in two spatial dimensions. The issue of universality is addressed by comparing discrete and continuous probability distributions for the quenched random couplings. The sophisticated temperature dependency of the scaling fields is identified as the major obstacle that has impeded a complete analysis. Once temperature is relinquished in favor of the correlation length as the basic variable, we obtain a reliable estimation of the anomalous dimension and of the thermal critical exponent. Universality among binary and Gaussian couplings is confirmed to a high numerical accuracy.

  15. Dissipative transverse-field Ising model: Steady-state correlations and spin squeezing

    NASA Astrophysics Data System (ADS)

    Lee, Tony E.; Chan, Ching-Kit

    2013-12-01

    We study the transverse-field Ising model with infinite-range coupling and spontaneous emission on every site. We find that there is spin squeezing in steady state due to the presence of the transverse field. This means that there is still entanglement, despite the decoherence from spontaneous emission. We analytically calculate fluctuations beyond mean-field theory using a phase-space approach, which involves converting the master equation into a Fokker-Planck equation for the Wigner function. Our calculations are relevant to current experiments with trapped ions.

  16. Static conversion systems

    NASA Astrophysics Data System (ADS)

    Ewell, R.; Mondt, J.

    Historically, all space power systems that have actually flown in space have relied on static energy conversion technology. Thus, static conversion is being considered for space nuclear power systems as well. There are four potential static conversion technologies which should be considered. These include: the alkali metal thermoelectric converter (AMTEC), the thermionic converter, the thermoelectric converter, and the thermophotovoltaic converter (TPV). These four conversion technologies will be described in brief detail along with their current status and development needs. In addition, the systems implications of using each of these conversion technologies with a space nuclear reactor power system will be evaluated and some comparisons made.

  17. Spreadsheet analysis of stability and meta-stability of low-dimensional magnetic particles using the Ising approach

    NASA Astrophysics Data System (ADS)

    Ehrmann, Andrea; Blachowicz, Tomasz; Zghidi, Hafed

    2015-05-01

    Modelling hysteresis behaviour, as it can be found in a broad variety of dynamical systems, can be performed in different ways. An elementary approach, applied for a set of elementary cells, which uses only two possible states per cell, is the Ising model. While such Ising models allow for a simulation of many systems with sufficient accuracy, they nevertheless depict some typical features which must be taken into account with proper care, such as meta-stability or the externally applied field sweeping speed. This paper gives a general overview of recent results from Ising models from the perspective of a didactic model, based on a 2D spreadsheet analysis, which can be used also for solving general scientific problems where direct next-neighbour interactions take place.

  18. Disappearance of Ising nature in Ca3ZnMnO6 studied by high-field ESR.

    PubMed

    Ruan, M Y; Ouyang, Z W; Guo, Y M; Cheng, J J; Sun, Y C; Xia, Z C; Rao, G H; Okubo, S; Ohta, H

    2014-06-11

    High-field electron spin resonance measurements of an antiferromagnet Ca3ZnMnO6 isostructure, with the Ising-chain multiferroic Ca3CoMnO6, have been carried out. Two distinct resonance modes were observed below TN = 25 K, which is well explained by conventional antiferromagnetic resonance theory with easy-plane anisotropy. The zero-field spin gap is derived to be about 166 GHz, originating from the easy-plane anisotropy and exchange interaction. Our result suggests that the Dzyaloshinsky-Moriya interaction, which may induce spin canting, is absent. Disappearance of Ising anisotropy in Ca3ZnMnO6 suggests that the Co(4+) ion, as well as the Co-Mn superexchange, plays an important role for the Ising nature in Ca3CoMnO6. PMID:24828049

  19. A numerical method of tracing a vortical axis along local topological axis line

    NASA Astrophysics Data System (ADS)

    Nakayama, Katsuyuki; Hasegawa, Hideki

    2016-06-01

    A new numerical method is presented to trace or identify a vortical axis in flow, which is based on Galilean invariant flow topology. We focus on the local flow topology specified by the eigenvalues and eigenvectors of the velocity gradient tensor, and extract the axis component from its flow trajectory. Eigen-vortical-axis line is defined from the eigenvector of the real eigenvalue of the velocity gradient tensor where the tensor has the conjugate complex eigenvalues. This numerical method integrates the eigen-vortical-axis line and traces a vortical axis in terms of the invariant flow topology, which enables to investigate the feature of the topology-based vortical axis.

  20. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, Allan; Boozer, Allen H.

    1987-01-01

    A helical axis stellarator using only noninterlocking planar, non-circular coils, generates magnetic fields having a magnetic well and large rotational transform with resultant large equilibrium beta.

  1. Principles of the prolactin/vasoinhibin axis

    PubMed Central

    Bertsch, Thomas; Bollheimer, Cornelius; Rios-Barrera, Daniel; Pearce, Christy F.; Hüfner, Michael; Martínez de la Escalera, Gonzalo; Clapp, Carmen

    2015-01-01

    The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed. PMID:26310939

  2. Principles of the prolactin/vasoinhibin axis.

    PubMed

    Triebel, Jakob; Bertsch, Thomas; Bollheimer, Cornelius; Rios-Barrera, Daniel; Pearce, Christy F; Hüfner, Michael; Martínez de la Escalera, Gonzalo; Clapp, Carmen

    2015-11-15

    The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.

  3. Comparison of the dipolar magnetic field generated by two Ising-like models

    NASA Astrophysics Data System (ADS)

    Peqini, Klaudio; Duka, Bejo

    2015-04-01

    We consider two Ising-like models named respectively the "domino" model and the Rikitake disk dynamo model. Both models are based on some collective interactions that can generate a dipolar magnetic field which reproduces the well-known features of the geomagnetic field: the reversals and secular variation (SV). The first model considers the resultant dipolar magnetic field as formed by the superposition of the magnetic fields generated by the dynamo elements called macrospins, while the second one, starting from the two-disk dynamo action, takes in consideration the collective interactions of several disk dynamo elements. We will apply two versions of each model: the short-range and the long-range coupled dynamo elements. We will study the statistical properties of the time series generated by the simulation of all models. The comparison of these results with the paleomagnetic data series and long series of SV enables us to conclude which of these Ising-like models better match with the geomagnetic field time series. Key words: geomagnetic field, domino model, Rikitake disk dynamo, dipolar moment

  4. Anisotropies and flows of suprathermal particles in the distant magnetotail - ISEE 3 observations

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Hovestadt, D.; Klecker, B.; Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.

    1983-01-01

    The ISEE-3 spacecraft has been transferred in 1982 into an earth orbit which brings the satellite close to the tailward Lagrangian point L2 at about 220 R(E) and thus allows exploration of the distant geomagnetic tail. An initial analysis of energetic proton measurements greater than 30 keV from the Max-Planck-Institut/University of Maryland sensor system on ISEE-3 is reported. It has been found that suprathermal protons are a persistent feature of the distant tail. Differential intensitites at 30 keV are essentially constant between the lunar distance and 220 R(E) and about one order of magnitude smaller than in the near earth, or greater than about 20 R(E), plasma sheet. Assuming that these protons are convected with the local plasma flow, it is possible to derive plasma velocities. During time periods where a comparison is possible, these velocities compare favourably well with the velocities derived from the Los Alamos National Laboratory plasma analyzer on board the same spacecraft. The appearance of the plasma sheet, as evidenced by the suprathermal particles, is rather bursty. Anisotropies are large, and predominantly tailward.

  5. Simulating the Kibble-Zurek mechanism of the Ising model with a superconducting qubit system.

    PubMed

    Gong, Ming; Wen, Xueda; Sun, Guozhu; Zhang, Dan-Wei; Lan, Dong; Zhou, Yu; Fan, Yunyi; Liu, Yuhao; Tan, Xinsheng; Yu, Haifeng; Yu, Yang; Zhu, Shi-Liang; Han, Siyuan; Wu, Peiheng

    2016-01-01

    The Kibble-Zurek mechanism (KZM) predicts the density of topological defects produced in the dynamical processes of phase transitions in systems ranging from cosmology to condensed matter and quantum materials. The similarity between KZM and the Landau-Zener transition (LZT), which is a standard tool to describe the dynamics of some non-equilibrium physics in contemporary physics, is being extensively exploited. Here we demonstrate the equivalence between KZM in the Ising model and LZT in a superconducting qubit system. We develop a time-resolved approach to study quantum dynamics of LZT with nano-second resolution. By using this technique, we simulate the key features of KZM in the Ising model with LZT, e.g., the boundary between the adiabatic and impulse regions, the freeze-out phenomenon in the impulse region, especially, the scaling law of the excited state population as the square root of the quenching speed. Our results provide the experimental evidence of the close connection between KZM and LZT, two textbook paradigms to study the dynamics of the non-equilibrium phenomena. PMID:26951775

  6. A mean field Ising model for cortical rotation in amphibian one-cell stage embryos.

    PubMed

    Tuszynski, Jack A; Gordon, Richard

    2012-09-01

    We propose a new physical mechanism of cortical rotation generation in one-cell embryos of amphibians based on a phase transition in the ensemble of microtubules localized to the cortical region of the cell interior. Microtubules, protein polymers formed from tubulin heterodimers, are highly negatively charged, which results in strong electrostatic interactions over tens of nanometers, even in the presence of counterions that partially screen electrostatic interactions. A simplified model that offers a plausible representation of these effects is based on the Ising Hamiltonian, which has been robustly applied to explain a wide range of order-disorder transitions in physics, chemistry and other sciences. An Ising model phase transition, especially with the supercooperative flow alignment effect of global rotation of the cortex, provides an alternative to models of cortical rotation based on microtubule polymerization or motor molecules. Insofar as there is any reality to the concept that microtubules are involved in consciousness, we propose that cortical rotation in the one-cell embryo is a better place to look for the purported microtubule entanglement or coherence properties than the adult brain. PMID:22626532

  7. Combined analysis of ferromagnetic materials using the Heisenberg Green functions and Ising EFT methods

    NASA Astrophysics Data System (ADS)

    Moujaes, Elie A.; Khater, A.; Abou Ghantous, M.

    2015-10-01

    Ferromagnetic phase diagrams were, for a long time, unsuccessfully determined theoretically, despite the important Callen's 1963 [21] theoretical model. A great variety of experimental data for the magnetization over the entire range of temperature defining the ordered phase compared well with an empirical formula recently determined by Kuz'min (2005) [22]. Nonetheless, the Ising effective field theory (EFT), which can be of enormous support to both methods, was never given attention. The present work intends to show how the Ising EFT technique, when combined with the Green functions in Callen's work, is able to reconcile theoretical work with experimental data. The ratio kTc / JZS(S + 1) plays an important role in finding values for the exchange parameter J, whose first-principles calculation, often depending on the package used, is not properly done. J can be determined for a variety of ferromagnetic materials represented by general spin systems S with a number of nearest neighbours Z and critical temperature Tc, even for models including a percolative feature, characteristic of diluted interactive systems. We demonstrate that EFT is capable of estimating a value of J, which can substitute the use of more complex theoretical models or the performance of ab initio/DFT calculations.

  8. A simulation of the mixed spin 3-spin 3/2 ferrimagnetic Ising model

    NASA Astrophysics Data System (ADS)

    Özkan, Aycan

    2016-01-01

    The mixed spin 3-spin 3/2 ferrimagnetic Ising model was simulated using cooling algorithm on cellular automaton (CA). The simulations were carried out in the intervals -4 ≤ DA/J ≤ 8 and -4 ≤ DB/J ≤ 8 for the square lattices with periodic boundary conditions. The ground-state phase diagram of the model has different types of ferrimagnetic phases. Although only the antiferromagnetic nearest-neighbor interaction was contained in the Hamiltonian, the compensation points emerged through DA/J = 2 at kT/J = 0. The values of the critical exponents (ν, α , β and γ) were estimated within the framework of the finite-size scaling theory and power-law relations for the selected DA/J values (-2, 0, 1, 2, and 4). The estimated critical exponent values were in good agreement with the universal values of the two-dimensional Ising model (ν = 1, α = α‧ = 0, β = 0.125, β‧ = 0.875 and γ = γ‧ = 1.75).

  9. Efficient Algorithms for the Two-Dimensional Ising Model with a Surface Field

    NASA Astrophysics Data System (ADS)

    Wu, Xintian

    2014-12-01

    The bond propagation and site propagation algorithms are extended to the two-dimensional (2D) Ising model with a surface field. With these algorithms we can calculate the free energy, internal energy, specific heat, magnetization, correlation functions, surface magnetization, surface susceptibility and surface correlations. The method can handle continuous and discrete bond and surface-field disorder and is especially efficient in the case of bond or site dilution. To test these algorithms, we study the wetting transition of the 2D Ising model, which was solved exactly by Abraham. We can locate the transition point accurately with a relative error of . We carry out the calculation of the specific heat and surface susceptibility on lattices with sizes up to . The results show that a finite jump develops in the specific heat and surface susceptibility at the transition point as the lattice size increases. For lattice size the parallel correlation length exponent is , while Abraham's exact result is . The perpendicular correlation length exponent for lattice size is , whereas its exact value is.

  10. Phase transitions and multicritical behavior in the Ising model with dipolar interactions

    NASA Astrophysics Data System (ADS)

    Bab, M. A.; Horowitz, C. M.; Rubio Puzzo, M. L.; Saracco, G. P.

    2016-10-01

    In this work, the phase diagram of the ferromagnetic Ising model with dipole interactions is revisited with the aim of determining the nature of the phase transition between stripe-ordered phases with width n (hn) and tetragonal liquid (TL) phases. Extensive Monte Carlo simulations are performed in order to study the short-time dynamic behavior of the observables for selected values of the ratio between the ferromagnetic exchange and dipolar constants δ . The obtained results indicate that the h1-TL phase transition line is continuous up to δ =1.2585 , while for the h2-TL line a weak first-order character is found in the interval 1.2585 ≤δ ≤1.36 and becomes continuous for 1.37 ≤δ ≤1.9 . This result suggests the existence of a tricritical point close to δ =1.37 . When it is appropriate, the complete set of critical exponents is obtained, and in all the studied cases they depend on δ but do not belong to the Ising universality class. Furthermore, short-time dynamic studies reveal that at the point where the mentioned lines meet the h1-h2 line, i.e., at δ =1.2585 , the critical phase corresponding to the h1-TL transition coexists with the h2 phase.

  11. Frustrated mixed spin-1/2 and spin-1 Ising ferrimagnets on a triangular lattice

    NASA Astrophysics Data System (ADS)

    Žukovič, M.; Bobák, A.

    2015-05-01

    Mixed spin-1/2 and spin-1 Ising ferrimagnets on a triangular lattice with sublattices A, B, and C are studied for two spin-value distributions (SA,SB,SC) =(1 /2 ,1 /2 ,1 ) and (1 /2 ,1 ,1 ) by Monte Carlo simulations. The nonbipartite character of the lattice induces geometrical frustration in both systems, which leads to the critical behavior rather different from their ferromagnetic counterparts. We confirm second-order phase transitions belonging to the standard Ising universality class occurring at higher temperatures, however, in both models these change at tricritical points (TCP) to first-order transitions at lower temperatures. In the model (1 /2 ,1 /2 ,1 ) , TCP occurs on the boundary between paramagnetic and ferrimagnetic (±1 /2 ,±1 /2 ,∓1 ) phases. The boundary between two ferrimagnetic phases (±1 /2 ,±1 /2 ,∓1 ) and (±1 /2 ,∓1 /2 ,0 ) at lower temperatures is always first order and it is joined by a line of second-order phase transitions between the paramagnetic and the ferrimagnetic (±1 /2 ,∓1 /2 ,0 ) phases at a critical endpoint. The tricritical behavior is also confirmed in the model (1 /2 ,1 ,1 ) on the boundary between the paramagnetic and ferrimagnetic (0 ,±1 ,∓1 ) phases.

  12. Can an Ising-like cluster expansion describe atomic relaxations in alloys?

    NASA Astrophysics Data System (ADS)

    Zunger, Alex; Wolverton, C.

    1996-03-01

    Ising-like lattice models are often described as ``fixed lattice'' models, incapable of describing the effects of structural relaxation. However, we have recently demonstrated^1 the ability of generalized k-space^2 Ising-like cluster expansions to describe the energetics and thermodynamics associated with large atomic displacements in alloys. Although the expansion is constructed only from the energies of a few (small-unit-cell) ordered structures, it provides accurate predictions of the atomically-relaxed energies of random, ordered, or partially ordered alloys, as compared with direct, large scale ( ~1000 atom) energy-minimizing simulations. Moreover, unlike molecular dynamics, here relaxed energies are obtained without having to compute relaxed geometries. Combination of the cluster expansion with Monte Carlo calculations is shown to provide a far more efficient means for calculating thermodynamic properties than explicit molecular dynamics or other structural minimization methods. [1] C. Wolverton and A. Zunger, Phys. Rev. Lett. 75, 3162 (1995). [2] D. B. Laks, L. G. Ferreira, S. Froyen, and A. Zunger, Phys. Rev. B 46, 12587 (1992). Supported by BES/OER/DMS under contract DE-AC36-83CH10093.

  13. Critical behavior of a triangular lattice Ising AF/FM bilayer

    NASA Astrophysics Data System (ADS)

    Žukovič, M.; Bobák, A.

    2016-03-01

    We study a bilayer Ising spin system consisting of antiferromagnetic (AF) and ferromagnetic (FM) triangular planes, coupled by ferromagnetic exchange interaction, by standard Monte Carlo and parallel tempering methods. The AF/FM bilayer is found to display the critical behavior completely different from both the single FM and AF constituents as well as the FM/FM and AF/AF bilayers. Namely, by finite-size scaling (FSS) analysis we identify at the same temperature a standard Ising transition from the paramagnetic to FM state in the FM plane that induces a ferrimagnetic state with a finite net magnetic moment in the AF plane. At lower temperatures there is another phase transition, that takes place only in the AF plane, to different ferrimagnetic state with spins on two sublattices pointing parallel and on one sublattice antiparallel to the spins on the FM plane. FSS indicates that the corresponding critical exponents are close to the two-dimensional three-state ferromagnetic Potts model values.

  14. Flocking with discrete symmetry: The two-dimensional active Ising model

    NASA Astrophysics Data System (ADS)

    Solon, A. P.; Tailleur, J.

    2015-10-01

    We study in detail the active Ising model, a stochastic lattice gas where collective motion emerges from the spontaneous breaking of a discrete symmetry. On a two-dimensional lattice, active particles undergo a diffusion biased in one of two possible directions (left and right) and align ferromagnetically their direction of motion, hence yielding a minimal flocking model with discrete rotational symmetry. We show that the transition to collective motion amounts in this model to a bona fide liquid-gas phase transition in the canonical ensemble. The phase diagram in the density-velocity parameter plane has a critical point at zero velocity which belongs to the Ising universality class. In the density-temperature "canonical" ensemble, the usual critical point of the equilibrium liquid-gas transition is sent to infinite density because the different symmetries between liquid and gas phases preclude a supercritical region. We build a continuum theory which reproduces qualitatively the behavior of the microscopic model. In particular, we predict analytically the shapes of the phase diagrams in the vicinity of the critical points, the binodal and spinodal densities at coexistence, and the speeds and shapes of the phase-separated profiles.

  15. Phase Transitions for Quantum Markov Chains Associated with Ising Type Models on a Cayley Tree

    NASA Astrophysics Data System (ADS)

    Mukhamedov, Farrukh; Barhoumi, Abdessatar; Souissi, Abdessatar

    2016-05-01

    The main aim of the present paper is to prove the existence of a phase transition in quantum Markov chain (QMC) scheme for the Ising type models on a Cayley tree. Note that this kind of models do not have one-dimensional analogous, i.e. the considered model persists only on trees. In this paper, we provide a more general construction of forward QMC. In that construction, a QMC is defined as a weak limit of finite volume states with boundary conditions, i.e. QMC depends on the boundary conditions. Our main result states the existence of a phase transition for the Ising model with competing interactions on a Cayley tree of order two. By the phase transition we mean the existence of two distinct QMC which are not quasi-equivalent and their supports do not overlap. We also study some algebraic property of the disordered phase of the model, which is a new phenomena even in a classical setting.

  16. Plasma analogy and non-Abelian statistics for Ising-type quantum Hall states

    SciTech Connect

    Bonderson, Parsa; Gurarie, Victor; Nayak, Chetan

    2011-02-15

    We study the non-Abelian statistics of quasiparticles in the Ising-type quantum Hall states which are likely candidates to explain the observed Hall conductivity plateaus in the second Landau level, most notably the one at filling fraction {nu}=5/2. We complete the program started in V. Gurarie and C. Nayak, [Nucl. Phys. B 506, 685 (1997)]. and show that the degenerate four-quasihole and six-quasihole wave functions of the Moore-Read Pfaffian state are orthogonal with equal constant norms in the basis given by conformal blocks in a c=1+(1/2) conformal field theory. As a consequence, this proves that the non-Abelian statistics of the excitations in this state are given by the explicit analytic continuation of these wave functions. Our proof is based on a plasma analogy derived from the Coulomb gas construction of Ising model correlation functions involving both order and (at most two) disorder operators. We show how this computation also determines the non-Abelian statistics of collections of more than six quasiholes and give an explicit expression for the corresponding conformal block-derived wave functions for an arbitrary number of quasiholes. Our method also applies to the anti-Pfaffian wave function and to Bonderson-Slingerland hierarchy states constructed over the Moore-Read and anti-Pfaffian states.

  17. Importance of positive feedbacks and overconfidence in a self-fulfilling Ising model of financial markets

    NASA Astrophysics Data System (ADS)

    Sornette, Didier; Zhou, Wei-Xing

    2006-10-01

    Following a long tradition of physicists who have noticed that the Ising model provides a general background to build realistic models of social interactions, we study a model of financial price dynamics resulting from the collective aggregate decisions of agents. This model incorporates imitation, the impact of external news and private information. It has the structure of a dynamical Ising model in which agents have two opinions (buy or sell) with coupling coefficients, which evolve in time with a memory of how past news have explained realized market returns. We study two versions of the model, which differ on how the agents interpret the predictive power of news. We show that the stylized facts of financial markets are reproduced only when agents are overconfident and mis-attribute the success of news to predict return to herding effects, thereby providing positive feedbacks leading to the model functioning close to the critical point. Our model exhibits a rich multifractal structure characterized by a continuous spectrum of exponents of the power law relaxation of endogenous bursts of volatility, in good agreement with previous analytical predictions obtained with the multifractal random walk model and with empirical facts.

  18. Simulating the Kibble-Zurek mechanism of the Ising model with a superconducting qubit system

    NASA Astrophysics Data System (ADS)

    Gong, Ming; Wen, Xueda; Sun, Guozhu; Zhang, Dan-Wei; Lan, Dong; Zhou, Yu; Fan, Yunyi; Liu, Yuhao; Tan, Xinsheng; Yu, Haifeng; Yu, Yang; Zhu, Shi-Liang; Han, Siyuan; Wu, Peiheng

    2016-03-01

    The Kibble-Zurek mechanism (KZM) predicts the density of topological defects produced in the dynamical processes of phase transitions in systems ranging from cosmology to condensed matter and quantum materials. The similarity between KZM and the Landau-Zener transition (LZT), which is a standard tool to describe the dynamics of some non-equilibrium physics in contemporary physics, is being extensively exploited. Here we demonstrate the equivalence between KZM in the Ising model and LZT in a superconducting qubit system. We develop a time-resolved approach to study quantum dynamics of LZT with nano-second resolution. By using this technique, we simulate the key features of KZM in the Ising model with LZT, e.g., the boundary between the adiabatic and impulse regions, the freeze-out phenomenon in the impulse region, especially, the scaling law of the excited state population as the square root of the quenching speed. Our results provide the experimental evidence of the close connection between KZM and LZT, two textbook paradigms to study the dynamics of the non-equilibrium phenomena.

  19. Electromagnetic waves with frequencies near the local proton gyrofrequency: ISEE-3 1 AU observations

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Arballo, John K.; Mok, John; Smith, Edward J.; Mason, Glenn M.; Tan, Lun C.

    1994-01-01

    Low Frequency (LF) electromagnetic waves with periods near the local proton gyrofrequency have been detected in interplanetary space by the magnetometer onboard International-Sun-Earth-Explorer-3 (ISEE-3). Transverse peak-to-peak amplitudes as large as delta vector B/absolute value of B approximately 0.4 have been noted with compressional components (Delta absolute value of B/absolute value of B) typically less than or = 0.1. Generally, the waves have even smaller amplitudes, or are not detectable within the solar wind turbulence. The waves are elliptically/linearly polarized and are often, but not always, found to propagate nearly along vector B(sub zero). Both right- and left-hand polarizations in the spacecraft-frame have been detected. The waves are observed during all orientations of the interplanetary magnetic field, with the Parker spiral orientation being the most common case. Because the waves are detected at and near the local proton cyclotron frequency, the generation mechanism must almost certainly be solar wind pickup of freshly created hydrogen ions. Possible sources for the hydrogen are the Earth's atmosphere, coronal mass ejections from the Sun, comets and interstellar neutral atoms. At this time it is not obvious which potential source is the correct one. Statistical tests employing over one year of ISEE-3 data will be done in the near future to eliminate/confirm some of these possibilities.

  20. Spatial distribution of electron plasma oscillations in the Earth`s foreshock at ISEE 3

    SciTech Connect

    Greenstadt, E.W.; Moses, S.L.; Coroniti, F.V.

    1995-10-01

    Electric field oscillations recorded by the 10-56 kHz channels of TRW`s plasma wave detector during parts of two of the ISEE 3 circumterrestrial orbits in 1983 have been used to make the first mapping of Earth`s electron plasma wave foreshock. By combining data from the two trajectory segments, each of which provided relatively meager spatial sampling outside the bow shock, but high variation of interplanetary magnetic field (IMF) direction, a first-order pattern of occurrence of electron plasma waves, hence also backstreaming electrons, has been determined. The authors depict the pattern with an adaptation of the mapping program previously used for the Venus electron foreshock. As at Venus, plasma wave activity was concentrated most densely along the IMF line tangent to the bow shock. Their mappings with three additional ISEE 3 channels surrounding the local electron plasma frequency indicate a richer distribution of waves in the foreshock than the single electron frequency channel of Pioneer Venus Orbiter could detect around Venus. 14 refs., 4 figs.

  1. Simulating the Kibble-Zurek mechanism of the Ising model with a superconducting qubit system

    PubMed Central

    Gong, Ming; Wen, Xueda; Sun, Guozhu; Zhang, Dan-Wei; Lan, Dong; Zhou, Yu; Fan, Yunyi; Liu, Yuhao; Tan, Xinsheng; Yu, Haifeng; Yu, Yang; Zhu, Shi-Liang; Han, Siyuan; Wu, Peiheng

    2016-01-01

    The Kibble-Zurek mechanism (KZM) predicts the density of topological defects produced in the dynamical processes of phase transitions in systems ranging from cosmology to condensed matter and quantum materials. The similarity between KZM and the Landau-Zener transition (LZT), which is a standard tool to describe the dynamics of some non-equilibrium physics in contemporary physics, is being extensively exploited. Here we demonstrate the equivalence between KZM in the Ising model and LZT in a superconducting qubit system. We develop a time-resolved approach to study quantum dynamics of LZT with nano-second resolution. By using this technique, we simulate the key features of KZM in the Ising model with LZT, e.g., the boundary between the adiabatic and impulse regions, the freeze-out phenomenon in the impulse region, especially, the scaling law of the excited state population as the square root of the quenching speed. Our results provide the experimental evidence of the close connection between KZM and LZT, two textbook paradigms to study the dynamics of the non-equilibrium phenomena. PMID:26951775

  2. Hearing the Shape of the Ising Model with a Programmable Superconducting-Flux Annealer

    PubMed Central

    Vinci, Walter; Markström, Klas; Boixo, Sergio; Roy, Aidan; Spedalieri, Federico M.; Warburton, Paul A.; Severini, Simone

    2014-01-01

    Two objects can be distinguished if they have different measurable properties. Thus, distinguishability depends on the Physics of the objects. In considering graphs, we revisit the Ising model as a framework to define physically meaningful spectral invariants. In this context, we introduce a family of refinements of the classical spectrum and consider the quantum partition function. We demonstrate that the energy spectrum of the quantum Ising Hamiltonian is a stronger invariant than the classical one without refinements. For the purpose of implementing the related physical systems, we perform experiments on a programmable annealer with superconducting flux technology. Departing from the paradigm of adiabatic computation, we take advantage of a noisy evolution of the device to generate statistics of low energy states. The graphs considered in the experiments have the same classical partition functions, but different quantum spectra. The data obtained from the annealer distinguish non-isomorphic graphs via information contained in the classical refinements of the functions but not via the differences in the quantum spectra. PMID:25029660

  3. Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions

    NASA Astrophysics Data System (ADS)

    Alves, G. A.; Vasconcelos, M. S.; Alves, T. F. A.

    2016-04-01

    We address the study of quasiperiodic interactions on a square lattice by using an Ising model with ferromagnetic and antiferromagnetic exchange interactions following a quasiperiodic Fibonacci sequence in both directions of a square lattice. We applied the Monte Carlo method, together with the Metropolis algorithm, to calculate the thermodynamic quantities of the system. We obtained the Edwards-Anderson order parameter qEA, the magnetic susceptibility χ , and the specific heat c in order to characterize the universality class of the phase transition. We also use the finite size scaling method to obtain the critical temperature of the system and the critical exponents β ,γ , and ν . In the low-temperature limit we obtained a spin-glass phase with critical temperature around Tc≈2.274 , and the critical exponents β ,γ , and ν , indicating that the quasiperiodic order induces a change in the universality class of the system. Also, we discovered a spin-glass ordering in a two-dimensional system which is rare and, as far as we know, the unique example is an under-frustrated Ising model.

  4. Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions.

    PubMed

    Alves, G A; Vasconcelos, M S; Alves, T F A

    2016-04-01

    We address the study of quasiperiodic interactions on a square lattice by using an Ising model with ferromagnetic and antiferromagnetic exchange interactions following a quasiperiodic Fibonacci sequence in both directions of a square lattice. We applied the Monte Carlo method, together with the Metropolis algorithm, to calculate the thermodynamic quantities of the system. We obtained the Edwards-Anderson order parameter q_{EA}, the magnetic susceptibility χ, and the specific heat c in order to characterize the universality class of the phase transition. We also use the finite size scaling method to obtain the critical temperature of the system and the critical exponents β,γ, and ν. In the low-temperature limit we obtained a spin-glass phase with critical temperature around T_{c}≈2.274, and the critical exponents β,γ, and ν, indicating that the quasiperiodic order induces a change in the universality class of the system. Also, we discovered a spin-glass ordering in a two-dimensional system which is rare and, as far as we know, the unique example is an under-frustrated Ising model. PMID:27176258

  5. 2D-Ising critical behavior in mixtures of water and 3-methylpyridine

    SciTech Connect

    Sadakane, Koichiro; Iguchi, Kazuya; Nagao, Michihiro; Seto, Hideki

    2011-01-01

    The effect of an antagonistic salt on the phase behavior and nanoscale structure of a mixture of D{sub 2}O and 3-methylpyridine was investigated by visual inspection and small-angle neutron scattering (SANS). The addition of the antagonistic salt, namely sodium tetraphenylborate (NaBPh{sub 4}), induces the shrinking of the two-phase region in contrast to the case in which a normal (hydrophilic) salt is added. Below the phase separation point, the SANS profiles cannot be described by the Ornstein-Zernike function owing to the existence of a long-range periodic structure. With increasing salt concentration, the critical exponents change from the values of 3D-Ising and approach those of 2D-Ising. These results suggest that the concentration fluctuation of the mixture of solvents is limited to a quasi two-dimensional space by the periodic structure induced by the adding the salt. The same behaviors were also observed in mixtures composed of water, 3-methylpyridine, and ionic surfactant.

  6. Ising-nematic order in the bilinear-biquadratic model for the iron pnictides

    NASA Astrophysics Data System (ADS)

    Bilbao Ergueta, Patricia; Nevidomskyy, Andriy H.

    2015-10-01

    Motivated by the recent inelastic neutron scattering (INS) measurements in the iron pnictides which show a strong anisotropy of spin excitations even above the magnetic transition temperature TN, we study the spin dynamics within the frustrated Heisenberg model with biquadratic spin-spin exchange interactions. Using the Dyson-Maleev (DM) representation, which proves appropriate for all temperature regimes, we find that the spin-spin dynamical structure factors are in excellent agreement with experiment, exhibiting breaking of the C4 symmetry even into the paramagnetic region TNIsing-nematic phase. In addition to the Heisenberg spin interaction, we include the biquadratic coupling -K (Si.Sj) 2 and study its effect on the dynamical temperature range Tσ-TN of the Ising-nematic phase. We find that this range reduces dramatically when even small values of the interlayer exchange Jc and biquadratic coupling K are included. To supplement our analysis, we benchmark the results obtained using full decoupling in the DM method against those from different nonlinear spin-wave theories, including the recently developed generalized spin-wave theory (GSWT), and find good qualitative agreement among the different theoretical approaches as well as experiment for both the spin-wave dispersions and the dynamical structure factors.

  7. Nonequilibrium dynamics of the Ising chain in a fluctuating transverse field

    NASA Astrophysics Data System (ADS)

    Roósz, Gergő; Juhász, Róbert; Iglói, Ferenc

    2016-04-01

    We study nonequilibrium dynamics of the quantum Ising chain at zero temperature when the transverse field is varied stochastically. In the equivalent fermion representation, the equation of motion of Majorana operators is derived in the form of a one-dimensional, continuous-time quantum random walk with stochastic, time-dependent transition amplitudes. This type of external noise gives rise to decoherence in the associated quantum walk and the semiclassical wave packet generally has a diffusive behavior. As a consequence, in the quantum Ising chain, the average entanglement entropy grows in time as t1 /2 and the logarithmic average magnetization decays in the same form. In the case of a dichotomous noise, when the transverse field is changed in discrete time steps, τ , there can be excitation modes, for which coherence is maintained, provided their energy satisfies ɛkτ ≈n π with a positive integer n . If the dispersion of ɛk is quadratic, the long-time behavior of the entanglement entropy and the logarithmic magnetization is dominated by these ballistically traveling coherent modes and both will have a t3 /4 time dependence.

  8. Energetic neutral atoms (E approximately 50 keV) from the ring current - IMP 7/8 and ISEE 1

    NASA Technical Reports Server (NTRS)

    Roelof, E. C.; Mitchell, D. G.; Williams, D. J.

    1985-01-01

    Energetic neutral atoms (ENA), emitted from the magnetosphere with energies of about 50 keV, have been measured with solid state detectors on the IMP 7/8 and ISEE 1 spacecraft; they are produced when singly charged trapped ions collide with the exosphere neutral hydrogen geocorona and the energetic ions are neutralized by charge exchange. ENA observations during the recovery phase of two moderate geomagnetic storms are analyzed: November 22-23, 1973, from IMP 8 at 33 earth radii and December 17, 1977, from ISEE 1 at 20 earth radii.

  9. FAST TRACK COMMUNICATION: Variational approach to the scaling function of the 2D Ising model in a magnetic field

    NASA Astrophysics Data System (ADS)

    Mangazeev, Vladimir V.; Batchelor, Murray T.; Bazhanov, Vladimir V.; Dudalev, Michael Yu

    2009-01-01

    The universal scaling function of the square lattice Ising model in a magnetic field is obtained numerically via Baxter's variational corner transfer matrix approach. The high precision numerical data are in perfect agreement with the remarkable field theory results obtained by Fonseca and Zamolodchikov, as well as with many previously known exact and numerical results for the 2D Ising model. This includes excellent agreement with analytic results for the magnetic susceptibility obtained by Orrick, Nickel, Guttmann and Perk. In general, the high precision of the numerical results underlines the potential and full power of the variational corner transfer matrix approach.

  10. Dannie Heineman Prize for Mathematical Physics Prize Lecture: Correlation Functions in Integrable Models: Ising Model and Monodromy Preserving Deformation

    NASA Astrophysics Data System (ADS)

    Miwa, Tetsuji

    2013-03-01

    Studies on integrable models in statistical mechanics and quantum field theory originated in the works of Bethe on the one-dimensional quantum spin chain and the work of Onsager on the two-dimensional Ising model. I will talk on the discovery in 1977 of the link between quantum field theory in the scaling limit of the two-dimensional Ising model and the theory of monodromy preserving linear ordinary differential equations. This work was the staring point of our journey with Michio Jimbo in integrable models, the journey which finally led us to the exact results on the correlation functions of quantum spin chains in 1992.

  11. Revisiting 2D Lattice Based Spin Flip-Flop Ising Model: Magnetic Properties of a Thin Film and Its Temperature Dependence

    ERIC Educational Resources Information Center

    Singh, Satya Pal

    2014-01-01

    This paper presents a brief review of Ising's work done in 1925 for one dimensional spin chain with periodic boundary condition. Ising observed that no phase transition occurred at finite temperature in one dimension. He erroneously generalized his views in higher dimensions but that was not true. In 1941 Kramer and Wannier obtained…

  12. Morping blade design for vertical axis wind turbines

    NASA Astrophysics Data System (ADS)

    Macphee, David; Beyene, Asfaw

    2015-11-01

    Wind turbines operate at peak efficiency at a certain set of operational conditions. Away from these conditions, conversion efficiency drops significantly, requiring pitch and yaw control schemes to mitigate these losses. These efforts are an example of geometric variability, allowing for increased power production but with an unfortunate increase in investment cost to the energy conversion system. In Vertical-Axis Wind Turbines (VAWTs), the concept of pitch control is especially complicated due to a dependence of attack angle on armature azimuth. As a result, VAWT pitch control schemes, both active and passive, are as of yet unfeasible. This study investigates a low-cost, passive pitch control system, in which VAWT blades are constructed of a flexible material, allowing for continuous shape-morphing in response to local aerodynamic loading. This design is analyzed computationally using a finite-volume fluid-structure interaction routine and compared to a geometrically identical rigid rotor. The results indicate that the flexible blade increases conversion efficiency by reducing the severity of vortex shedding, allowing for greater average torque over a complete revolution.

  13. Concentrating solar cookers with eccentric axis

    SciTech Connect

    Wang Xiping; Sha Yong Ling; Hou Shugin; Liu Zude

    1992-12-31

    This paper describes the design, development and use of a concentrating solar cooker with eccentric axis in China. For the same power, the older circular parabolic cookers are large in volume and less convenient to operate than the cooker with eccentric axis. Calculations are presented for the design of the cooker and for obtaining an accurate test of its efficiency.

  14. Conversing with Computers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    I/NET, Inc., is making the dream of natural human-computer conversation a practical reality. Through a combination of advanced artificial intelligence research and practical software design, I/NET has taken the complexity out of developing advanced, natural language interfaces. Conversational capabilities like pronoun resolution, anaphora and ellipsis processing, and dialog management that were once available only in the laboratory can now be brought to any application with any speech recognition system using I/NET s conversational engine middleware.

  15. Chronic kidney disease and hypothalamic-pituitary axis dysfunction: the chicken or the egg?

    PubMed

    Meuwese, Christiaan Lucas; Carrero, Juan Jesús

    2013-11-01

    Hormonal derangements at the level of the hypothalamic-pituitary axis are often seen with the worsening of kidney function. This may not be surprising given the role of the kidney in synthesis, metabolism and elimination of many of these hormones. Traditionally, these derangements have been understood as a consequence of kidney failure. Conversely, recent evidence points towards the implication of such hormonal disorders in the genesis of CKD. In this review we present arguments supporting both the role of hypothalamic-pituitary axis dysfunction as a consequence of uremic complications and a culprit in disease incidence and progression. Focus is given to evidence regarding thyroidal, adrenal and gonadal axes.

  16. Competition between supersolid phases and magnetization plateaus in the frustrated easy-axis antiferromagnet on a triangular lattice

    NASA Astrophysics Data System (ADS)

    Seabra, Luis; Shannon, Nic

    2011-04-01

    The majority of magnetic materials possess some degree of magnetic anisotropy, either at the level of a single ion, or in the exchange interactions between different magnetic ions. Where these exchange interactions are also frustrated, the competition between them and anisotropy can stabilize a wide variety of new phases in applied magnetic field. Motivated by the hexagonal delafossite 2H-AgNiO2, we study the Heisenberg antiferromagnet on a layered triangular lattice with competing first- and second-neighbor interactions and single-ion easy-axis anisotropy. Using a combination of classical Monte Carlo simulation, mean-field analysis, and Landau theory, we establish the magnetic phase diagram of this model as a function of temperature and magnetic field for a fixed ratio of exchange interactions, but with values of easy-axis anisotropy D extending from the Heisenberg (D=0) to the Ising (D=∞) limits. We uncover a rich variety of different magnetic phases. These include several phases which are magnetic supersolids (in the sense of Matsuda and Tsuneto or Liu and Fisher), one of which may already have been observed in AgNiO2. We explore how this particular supersolid arises through the closing of a gap in the spin-wave spectrum, and how it competes with rival collinear phases as the easy-axis anisotropy is increased. The finite temperature properties of this phase are found to be different from those of any previously studied magnetic supersolid.

  17. In-Situ Ion Analysis of Fresh Waters via an ISE Multiprobe and Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Mueller, A. V.; Hemond, H.

    2010-12-01

    The ecological and geochemical sciences stand to substantially gain from capability for comprehensive, real-time, in-situ characterization of the chemical constituents of natural waters, e.g. by facilitating rapid high-resolution adaptive sampling campaigns and avoiding the potential errors and high costs related to traditional grab sample collection, transportation and in-lab analysis. In-situ chemical instrumentation also promotes the goals of large-scale monitoring networks, such as CUASHI and WATERS, by reducing the financial and human resources overhead required for traditional sampling at this scale. Problems of environmental remediation and monitoring of industrial waste waters would additionally benefit from such instrumental capacity. We have pursued in-situ measurement of all major ions contributing to the charge makeup (>99%) of oxic natural fresh waters via an instrument combining an array of ion-selective electrode (ISE) hardware with an appropriate multivariate signal processing architecture. Commercially available electrochemical sensors promote low cost and a fast development schedule, as well as easy maintenance and reproduction. Data processing techniques are adapted from artificial intelligence and chemometrics to extract accurate information from the corresponding in-situ data matrix. This architecture takes into account temperature, conductivity, and non-linearity effects, as well as taking advantage of sensor cross-selectivities traditionally considered as interferences. Chemical and mathematical constraints, e.g. charge balance and total ionic strength, provide further system-level information. Maximizing data recovery from the sensor array allows use of the instrument without the standard additions or ionic strength adjustment traditionally-required with use of ISEs. Initial work demonstrates the effectiveness of this methodology at predicting inorganic cations (sodium, potassium, calcium, and ammonium ) and hydrogen ion in a simplified

  18. Thermal entanglement of a spin-1/2 Ising-Heisenberg model on a symmetrical diamond chain.

    PubMed

    Ananikian, N S; Ananikyan, L N; Chakhmakhchyan, L A; Rojas, Onofre

    2012-06-27

    The entanglement quantum properties of a spin-1/2 Ising-Heisenberg model on a symmetrical diamond chain were analyzed. Due to the separable nature of the Ising-type exchange interactions between neighboring Heisenberg dimers, calculation of the entanglement can be performed exactly for each individual dimer. Pairwise thermal entanglement was studied in terms of the isotropic Ising-Heisenberg model and analytical expressions for the concurrence (as a measure of bipartite entanglement) were obtained. The effects of external magnetic field H and next-nearest neighbor interaction J(m) between nodal Ising sites were considered. The ground state structure and entanglement properties of the system were studied in a wide range of coupling constant values. Various regimes with different values of ground state entanglement were revealed, depending on the relation between competing interaction strengths. Finally, some novel effects, such as the two-peak behavior of concurrence versus temperature and coexistence of phases with different values of magnetic entanglement, were observed.

  19. On discrete field theory properties of the dimer and Ising models and their conformal field theory limits

    SciTech Connect

    Kriz, Igor; Loebl, Martin; Somberg, Petr

    2013-05-15

    We study various mathematical aspects of discrete models on graphs, specifically the Dimer and the Ising models. We focus on proving gluing formulas for individual summands of the partition function. We also obtain partial results regarding conjectured limits realized by fermions in rational conformal field theories.

  20. The infinite-range quantum transverse Ising spin glass: new estimate of the critical line via thermo-field method

    NASA Astrophysics Data System (ADS)

    Kopeć, T. K.; Büttner, G.; Usadel, K. D.

    1990-10-01

    The infinite-range quantum Ising spin glass in a transverse field Γ is studied by means of the thermo-field dynamics as a substitute for the n-replica trick. A new estimate of the critical line Tc(Γ) is obtained by the improved treatment of the dynamic self-interaction - in considerable agreement with the Trotter-Suzuki method.

  1. The Conversation Class

    ERIC Educational Resources Information Center

    Jackson, Acy L.

    2012-01-01

    The conversation class occupies a unique place in the process of learning English as a second or foreign language. From the author's own experience in conducting special conversation classes with Persian-speaking adults, he has drawn up a number of simple but important guidelines, some of which he hopes may provide helpful suggestions for the…

  2. NUCLEAR CONVERSION APPARATUS

    DOEpatents

    Seaborg, G.T.

    1960-09-13

    A nuclear conversion apparatus is described which comprises a body of neutron moderator, tubes extending therethrough, uranium in the tubes, a fluid- circulating system associated with the tubes, a thorium-containing fluid coolant in the system and tubes, and means for withdrawing the fluid from the system and replacing it in the system whereby thorium conversion products may be recovered.

  3. Energy conversion alternatives study

    NASA Technical Reports Server (NTRS)

    Shure, L. T.

    1979-01-01

    Comparison of coal based energy systems is given. Study identifies and compares various advanced energy conversion systems using coal or coal derived fuels for baselaoad electric power generation. Energy Conversion Alternatives Study (ECAS) reports provede government, industry, and general public with technically consistent basis for comparison of system's options of interest for fossilfired electric-utility application.

  4. Common conversion factors.

    PubMed

    2001-05-01

    This appendix presents tables of some of the more common conversion factors for units of measure used throughout Current Protocols manuals, as well as prefixes indicating powers of ten for SI units. Another table gives conversions between temperatures on the Celsius (Centigrade) and Fahrenheit scales. PMID:18770653

  5. Assessment through Conversation.

    ERIC Educational Resources Information Center

    Fu, Danling; Lamme, Linda L.

    2002-01-01

    Presents conversations with parents, teachers, and children around portfolios that provide a better picture of a child's growth and understanding than standardized test scores ever can. Concludes that the involvement of students, teachers, and parents in conversation about children's literacy development brings the potential of a common vision and…

  6. Off-axis reflective optical apparatus

    NASA Technical Reports Server (NTRS)

    Ames, Lawrence L. (Inventor); Leary, David F. (Inventor); Mammini, Paul V. (Inventor)

    2005-01-01

    Embodiments of the present invention are directed to a simple apparatus and a convenient and accurate method of mounting the components to form an off-axis reflective optical apparatus such as a collimator. In one embodiment, an off-axis reflective optical apparatus comprises a mounting block having a ferrule holder support surface and an off-axis reflector support surface which is generally perpendicular to the ferrule holder support surface. An optical reflector is mounted on the off-axis reflector support surface and has a reflected beam centerline. The optical reflector has a conic reflective surface and a conic center. A ferrule holder is mounted on the ferrule holder support surface. The ferrule holder provides a ferrule for coupling to an optical fiber and orienting a fiber tip of the optical fiber along a fiber axis toward the optical reflector. The fiber axis is nonparallel to the reflected beam centerline. Prior to mounting the optical reflector to the off-axis reflector support surface and prior to mounting the ferrule holder to the ferrule holder support surface, the optical reflector is movable on the off-axis reflector surface and the ferrule holder is movable on the ferrule holder support surface to align the conic center of the optical reflector with respect to the fiber tip of the optical fiber, and the apparatus has at least one of the following features: (1) the optical reflector is movable on the off-axis reflector support surface to adjust a focus of the fiber tip with respect to the optical reflector, and (2) the ferrule holder is movable on the ferrule holder support surface to adjust the focus of the fiber tip with respect to the optical reflector.

  7. A New Mechanism for ISE in Alumina Shock Deformed at 6.5 GPa

    NASA Astrophysics Data System (ADS)

    Chakraborty, R.; Dey, A.; Mukhopadhyay, A. K.; Joshi, K. D.; Rav, A.; Ghosh, J.; Mandal, A. K.; Bysakh, S.; Biswas, S. K.; Gupta, S. C.

    2012-07-01

    With a view to understand how high strain rate flyer plate impact affects the nanohardness of a coarse (10 μm) grain high density (3.978 gm.cc-1) alumina, load controlled nanoindentation experiments were conducted with a Berkovich indenter on as received alumina (ARA) and shocked alumina fragments (SA) of obtained from a flyer plate shock impact study at 6.5 GPa. The results showed that the nanohardness of the shocked alumina (SA) samples was much lower than that of the as received alumina (ARA) samples and that the indentation size effect (ISE) was mild in the ARA but quite severe in the SA samples. Extensive additional characterization by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and a physical model based analysis of the experimental load depth data were utilized to provide a new explanation for the presence of strong indentation size effect in the shock recovered alumina.

  8. Magnetic Field Investigation for ISEE mother and daughter spacecraft. [magnetometer design, capability, and results

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1981-01-01

    Highlights of the design and fabrication of fluxgate magnetometers for the ISEE A and B satellites which were launched from a single launch vehicle into the same highly elliptical orbit are presented. The instrument consisted of four basic assemblies: the sensors, the drive and sense electronics, the data handling unit; and the flipper. The digital handling data handling assembly contained a digital filter that mantained a uniform transfer function for all three axes of both spacecraft. Initial studies centered on the bow shock and the magnetopause and show that both boundaries are in rapid motion. The bow shock was found to be very thin, close to an ion inertial length in thickness, but the magnetopause was much thicker than expected, about 400 to 1000 km on average. The magnetometers have each logged over 3 2/3 years of continuous operation.

  9. Stimulation of plasma waves by electron guns on the ISEE-1 satellite

    NASA Technical Reports Server (NTRS)

    Lebreton, J.-P.; Torbert, R.; Anderson, R.; Harvey, C.

    1982-01-01

    The results of the ISEE-1 satellite experiment relating to observations of the waves stimulated during electron injections, when the spacecraft is passing through the magnetosphere, the magnetosheath, and the solar wind, are discussed. It is shown that the injection of an electron beam current of the order of 10 to 60 microamperes with energies ranging from 0 to 40 eV produces enhancements in the electric wave spectrum. An attempt has been made to identify the low-frequency electrostatic wave observed below the ion plasma frequency as an ion acoustic mode, although the excitation mechanism is not clear. A coupling mechanism between the electron plasma mode and streaming electrons with energies higher than the thermal speed of the cold electron population has been proposed to explain the observations above the electron plasma frequency.

  10. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    SciTech Connect

    Kocakaplan, Yusuf; Keskin, Mustafa

    2014-09-07

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

  11. Hysteresis in random-field Ising model on a Bethe lattice with a mixed coordination number

    NASA Astrophysics Data System (ADS)

    Shukla, Prabodh; Thongjaomayum, Diana

    2016-06-01

    We study zero-temperature hysteresis in the random-field Ising model on a Bethe lattice where a fraction c of the sites have coordination number z = 4 while the remaining fraction 1-c have z = 3. Numerical simulations as well as probabilistic methods are used to show the existence of critical hysteresis for all values of c\\gt 0. This extends earlier results for c = 0 and c = 1 to the entire range 0≤slant c≤slant 1, and provides new insight in non-equilibrium critical phenomena. Our analysis shows that a spanning avalanche can occur on a lattice even in the absence of a spanning cluster of z = 4 sites.

  12. Order by disorder in the antiferromagnetic Ising model on an elastic triangular lattice

    PubMed Central

    Shokef, Yair; Souslov, Anton; Lubensky, T. C.

    2011-01-01

    Geometrically frustrated materials have a ground-state degeneracy that may be lifted by subtle effects, such as higher-order interactions causing small energetic preferences for ordered structures. Alternatively, ordering may result from entropic differences between configurations in an effect termed order by disorder. Motivated by recent experiments in a frustrated colloidal system in which ordering is suspected to result from entropy, we consider in this paper the antiferromagnetic Ising model on a deformable triangular lattice. We calculate the displacements exactly at the microscopic level and, contrary to previous studies, find a partially disordered ground state of randomly zigzagging stripes. Each such configuration is deformed differently and thus has a unique phonon spectrum with distinct entropy, lifting the degeneracy at finite temperature. Nonetheless, due to the free-energy barriers between the ground-state configurations, the system falls into a disordered glassy state. PMID:21730164

  13. Evidence for two-dimensional Ising superconductivity in gated MoS₂.

    PubMed

    Lu, J M; Zheliuk, O; Leermakers, I; Yuan, N F Q; Zeitler, U; Law, K T; Ye, J T

    2015-12-11

    The Zeeman effect, which is usually detrimental to superconductivity, can be strongly protective when an effective Zeeman field from intrinsic spin-orbit coupling locks the spins of Cooper pairs in a direction orthogonal to an external magnetic field. We performed magnetotransport experiments with ionic-gated molybdenum disulfide transistors, in which gating prepared individual superconducting states with different carrier dopings, and measured an in-plane critical field B(c2) far beyond the Pauli paramagnetic limit, consistent with Zeeman-protected superconductivity. The gating-enhanced B(c2) is more than an order of magnitude larger than it is in the bulk superconducting phases, where the effective Zeeman field is weakened by interlayer coupling. Our study provides experimental evidence of an Ising superconductor, in which spins of the pairing electrons are strongly pinned by an effective Zeeman field. PMID:26563134

  14. Evidence for two-dimensional Ising superconductivity in gated MoS2

    NASA Astrophysics Data System (ADS)

    Lu, J. M.; Zheliuk, O.; Leermakers, I.; Yuan, N. F. Q.; Zeitler, U.; Law, K. T.; Ye, J. T.

    2015-12-01

    The Zeeman effect, which is usually detrimental to superconductivity, can be strongly protective when an effective Zeeman field from intrinsic spin-orbit coupling locks the spins of Cooper pairs in a direction orthogonal to an external magnetic field. We performed magnetotransport experiments with ionic-gated molybdenum disulfide transistors, in which gating prepared individual superconducting states with different carrier dopings, and measured an in-plane critical field Bc2 far beyond the Pauli paramagnetic limit, consistent with Zeeman-protected superconductivity. The gating-enhanced Bc2 is more than an order of magnitude larger than it is in the bulk superconducting phases, where the effective Zeeman field is weakened by interlayer coupling. Our study provides experimental evidence of an Ising superconductor, in which spins of the pairing electrons are strongly pinned by an effective Zeeman field.

  15. Almost Gibbsianness and Parsimonious Description of the Decimated 2d-Ising Model

    NASA Astrophysics Data System (ADS)

    Le Ny, Arnaud

    2013-07-01

    In this paper, we complete and provide details for the existing characterizations of the decimation of the Ising model on {Z}2 in the generalized Gibbs context. We first recall a few features of the Dobrushin program of restoration of Gibbsianness and present the construction of global specifications consistent with the extremal decimated measures. We use them to prove that these renormalized measures are almost Gibbsian at any temperature and to analyse in detail its convex set of DLR measures. We also recall the weakly Gibbsian description and complete it using a potential that admits a quenched correlation decay, i.e. a well-defined configuration-dependent length beyond which this potential decays exponentially. We use these results to incorporate these decimated measures in the new framework of parsimonious random fields that has been recently developed to investigate probability aspects related to neurosciences.

  16. Critical two-dimensional Ising model with free, fixed ferromagnetic, fixed antiferromagnetic, and double antiferromagnetic boundaries.

    PubMed

    Wu, Xintian; Izmailyan, Nickolay

    2015-01-01

    The critical two-dimensional Ising model is studied with four types boundary conditions: free, fixed ferromagnetic, fixed antiferromagnetic, and fixed double antiferromagnetic. Using bond propagation algorithms with surface fields, we obtain the free energy, internal energy, and specific heat numerically on square lattices with a square shape and various combinations of the four types of boundary conditions. The calculations are carried out on the square lattices with size N×N and 30

  17. Parity Symmetry and Parity Breaking in the Quantum Rabi Model with Addition of Ising Interaction

    NASA Astrophysics Data System (ADS)

    Wang, Qiong; He, Zhi; Yao, Chun-Mei

    2015-04-01

    We explore the possibility to generate new parity symmetry in the quantum Rabi model after a bias is introduced. In contrast to a mathematical treatment in a previous publication [J. Phys. A 46 (2013) 265302], we consider a physically realistic method by involving an additional spin into the quantum Rabi model to couple with the original spin by an Ising interaction, and then the parity symmetry is broken as well as the scaling behavior of the ground state by introducing a bias. The rule can be found that the parity symmetry is broken by introducing a bias and then restored by adding new degrees of freedom. Experimental feasibility of realizing the models under discussion is investigated. Supported by the National Natural Science Foundation of China under Grant Nos. 61475045 and 11347142, the Natural Science Foundation of Hunan Province, China under Grant No. 2015JJ3092

  18. Effective-field theory on the kinetic spin-3/2 Ising model

    NASA Astrophysics Data System (ADS)

    Shi, Xiaoling; Qi, Yang

    2015-11-01

    The effective-field theory (EFT) is used to study the dynamical response of the kinetic spin-3/2 Ising model in the presence of a sinusoidal oscillating magnetic field. The effective-field dynamic equations are given for the honeycomb lattices (Z = 3). The dynamic order parameter, the dynamic quadrupole moment are calculated. We have found that the behavior of the system strongly depends on the crystal field interaction D. The dynamic phase boundaries are obtained, and there is no dynamic tricritical point on the dynamic phase transition line. The results are also compared with previous results which obtained from the mean-field theory (MFT) and the effective-field theory (EFT) for the square lattices (Z = 4). Different dynamic phase transition lines show that the thermal fluctuations are a key factor of the dynamic phase transition.

  19. Conformal perturbation of off-critical correlators in the 3D Ising universality class

    NASA Astrophysics Data System (ADS)

    Caselle, M.; Costagliola, G.; Magnoli, N.

    2016-07-01

    Thanks to the impressive progress of conformal bootstrap methods we have now very precise estimates of both scaling dimensions and operator product expansion coefficients for several 3D universality classes. We show how to use this information to obtain similarly precise estimates for off-critical correlators using conformal perturbation. We discuss in particular the ⟨σ (r )σ (0 )⟩ , ⟨ɛ (r )ɛ (0 )⟩ and ⟨σ (r )ɛ (0 )⟩ two-point functions in the high and low temperature regimes of the 3D Ising model and evaluate the leading and next to leading terms in the s =trΔt expansion, where t is the reduced temperature. Our results for ⟨σ (r )σ (0 )⟩ agree both with Monte Carlo simulations and with a set of experimental estimates of the critical scattering function.

  20. Low energy proton bidirectional anisotropies and their relation to transient interplanetary magnetic structures: ISEE-3 observations

    NASA Technical Reports Server (NTRS)

    Marsden, R. G.; Sanderson, T. R.; Wenzel, K. P.; Smith, E. J.

    1985-01-01

    It is known that the interplanetary medium in the period approaching solar maximum is characterized by an enhancement in the occurrence of transient solar wind streams and shocks and that such systems are often associated with looplike magnetic structures or clouds. There is observational evidence that bidirectional, field aligned flows of low energy particles could be a signature of such looplike structures, although detailed models for the magnetic field configuration and injection mechanisms do not exist at the current time. Preliminary results of a survey of low energy proton bidirectional anisotropies measured on ISEE-3 in the interplanetary medium between August 1978 and May 1982, together with magnetic field data from the same spacecraft are presented.

  1. Critical behavior of the two-dimensional Ising model with long-range correlated disorder

    NASA Astrophysics Data System (ADS)

    Dudka, M.; Fedorenko, A. A.; Blavatska, V.; Holovatch, Yu.

    2016-06-01

    We study critical behavior of the diluted two-dimensional Ising model in the presence of disorder correlations which decay algebraically with distance as ˜r-a . Mapping the problem onto two-dimensional Dirac fermions with correlated disorder we calculate the critical properties using renormalization group up to two-loop order. We show that beside the Gaussian fixed point the flow equations have a nontrivial fixed point which is stable for 0.995

  2. The scaling window of the 5D Ising model with free boundary conditions

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Markström, K.

    2016-10-01

    The five-dimensional Ising model with free boundary conditions has recently received a renewed interest in a debate concerning the finite-size scaling of the susceptibility near the critical temperature. We provide evidence in favour of the conventional scaling picture, where the susceptibility scales as L2 inside a critical scaling window of width 1 /L2. Our results are based on Monte Carlo data gathered on system sizes up to L = 79 (ca. three billion spins) for a wide range of temperatures near the critical point. We analyse the magnetisation distribution, the susceptibility and also the scaling and distribution of the size of the Fortuin-Kasteleyn cluster containing the origin. The probability of this cluster reaching the boundary determines the correlation length, and its behaviour agrees with the mean field critical exponent δ = 3, that the scaling window has width 1 /L2.

  3. The cellular Ising model: a framework for phase transitions in multicellular environments.

    PubMed

    Weber, Marc; Buceta, Javier

    2016-06-01

    Inspired by the Ising model, we introduce a gene regulatory network that induces a phase transition that coordinates robustly the behaviour of cell ensembles. The building blocks of the design are the so-called toggle switch interfaced with two quorum sensing modules, Las and Lux. We show that as a function of the transport rate of signalling molecules across the cell membrane the population undergoes a spontaneous symmetry breaking from cells individually switching their phenotypes to a global collective phenotypic organization. By characterizing the critical behaviour, we reveal some properties, such as phenotypic memory and hypersensitivity, with relevance in the field of synthetic biology. We argue that our results can be extrapolated to other multicellular systems and be a generic framework for collective decision-making processes. PMID:27307510

  4. Behavior of Early Warnings near the Critical Temperature in the Two-Dimensional Ising Model

    PubMed Central

    Morales, Irving O.; Landa, Emmanuel; Angeles, Carlos Calderon; Toledo, Juan C.; Rivera, Ana Leonor; Temis, Joel Mendoza; Frank, Alejandro

    2015-01-01

    Among the properties that are common to complex systems, the presence of critical thresholds in the dynamics of the system is one of the most important. Recently, there has been interest in the universalities that occur in the behavior of systems near critical points. These universal properties make it possible to estimate how far a system is from a critical threshold. Several early-warning signals have been reported in time series representing systems near catastrophic shifts. The proper understanding of these early-warnings may allow the prediction and perhaps control of these dramatic shifts in a wide variety of systems. In this paper we analyze this universal behavior for a system that is a paradigm of phase transitions, the Ising model. We study the behavior of the early-warning signals and the way the temporal correlations of the system increase when the system is near the critical point. PMID:26103513

  5. Wave mode identification of electrostatic noise observed with ISEE 3 in the deep tail boundary layer

    NASA Technical Reports Server (NTRS)

    Tsutsui, M.; Matsumoto, H.; Strangeway, R. J.; Tsurutani, B. T.; Phillips, J. L.

    1991-01-01

    The characteristics of the VLF electrostatic noise observed with ISEE 3 in the low-latitude boundary layer of distant geomagnetic tail are examined using a display format for the wave dynamic spectra different from that used by Scarf et al. (1984). It is shown that the observed noise is composed of impulsive bursts. The results of the detailed analysis of the noise parameters are used to develop a model of plasma wave behavior in the plasma rest frame. A hypothesis is proposed that the wide frequency extent of the noise spectra is composed of Doppler effects of waves propagating nearly omnidirectionally within the plasma rest frame, which is moving with the electron bulk speed. On the basis of this hypothesis, the wavelength of the observed waves were determined from the width of the frequency extent and the measured electron bulk speed. It is shown that the wavelength ranges from 2 to 8 times the plasma Debye length.

  6. Fortuin-Kasteleyn and damage-spreading transitions in random-bond Ising lattices

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Campbell, I. A.

    2012-10-01

    The Fortuin-Kasteleyn and heat-bath damage-spreading temperatures TFK(p) and TDS(p) are studied on random-bond Ising models of dimensions 2-5 and as functions of the ferromagnetic interaction probability p; the conjecture that TDS(p)˜TFK(p) is tested. It follows from a statement by Nishimori that in any such system, exact coordinates can be given for the intersection point between the Fortuin-Kasteleyn TFK(p) transition line and the Nishimori line [pNL,FK,TNL,FK]. There are no finite-size corrections for this intersection point. In dimension 3, at the intersection concentration [pNL,FK], the damage spreading TDS(p) is found to be equal to TFK(p) to within 0.1%. For the other dimensions, however, TDS(p) is observed to be systematically a few percent lower than TFK(p).

  7. Ising nematic quantum critical point in a metal: a Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Lederer, Samuel

    The Ising nematic quantum critical point (QCP) associated with the zero temperature transition from a symmetric to a nematic metal is an exemplar of metallic quantum criticality. We have carried out a minus sign-free quantum Monte Carlo study of this QCP for a two dimensional lattice model with sizes up to 24 × 24 sites. The system remains non-superconducting down to the lowest accessible temperatures. The results exhibit critical scaling behavior over the accessible ranges of temperature, (imaginary) time, and distance. This scaling behavior has remarkable similarities with recently measured properties of the Fe-based superconductors proximate to their putative nematic QCP. With Yoni Schattner, Steven A. Kivelson, and Erez Berg.

  8. LETTER TO THE EDITOR: Magnetic correlation length and universal amplitude of the lattice ? Ising model

    NASA Astrophysics Data System (ADS)

    Batchelor, M. T.; Seaton, K. A.

    1997-08-01

    The perturbation approach is used to derive the exact correlation length 0305-4470/30/15/001/img6 of the dilute 0305-4470/30/15/001/img7 lattice models in regimes 1 and 2 for L odd. In regime 2 the 0305-4470/30/15/001/img8 model is the 0305-4470/30/15/001/img9 lattice realization of the two-dimensional Ising model in a magnetic field h at 0305-4470/30/15/001/img10. When combined with the singular part 0305-4470/30/15/001/img11 of the free energy the result for the 0305-4470/30/15/001/img8 model gives the universal amplitude 0305-4470/30/15/001/img13 as 0305-4470/30/15/001/img14 in precise agreement with the result obtained by Delfino and Mussardo via the form-factor bootstrap approach.

  9. Self-organizing Ising model of artificial financial markets with small-world network topology

    NASA Astrophysics Data System (ADS)

    Zhao, Haijie; Zhou, Jie; Zhang, Anghui; Su, Guifeng; Zhang, Yi

    2013-01-01

    We study a self-organizing Ising-like model of artificial financial markets with underlying small-world (SW) network topology. The asset price dynamics results from the collective decisions of interacting agents which are located on a small-world complex network (the nodes symbolize the agents of a financial market). The model incorporates the effects of imitation, the impact of external news and private information. We also investigate the influence of different network topologies, from regular lattice to random graph, on the asset price dynamics by adjusting the probability of the rewiring procedure. We find that a specific combination of model parameters reproduce main stylized facts of real-world financial markets.

  10. Short-time dynamics of an Ising system on fractal structures

    SciTech Connect

    Zheng, Guang-Ping; Li, Mo

    2000-11-01

    The short-time critical relaxation of an Ising model on a Sierpinski carpet is investigated using Monte Carlo simulation. We find that when the system is quenched from high temperature to the critical temperature, the evolution of the order parameter and its persistence probability, the susceptibility, and the autocorrelation function all show power-law scaling behavior at the short-time regime. The results suggest that the spatial heterogeneity and the fractal nature of the underlying structure do not influence the scaling behavior of the short-time critical dynamics. The critical temperature, dynamic exponent z, and other equilibrium critical exponents {beta} and {nu} of the fractal spin system are determined accurately using conventional Monte Carlo simulation algorithms. The mechanism for short-time dynamic scaling is discussed.

  11. Effective time reversal and echo dynamics in the transverse field Ising model

    NASA Astrophysics Data System (ADS)

    Schmitt, Markus; Kehrein, Stefan

    2016-09-01

    The question of thermalisation in closed quantum many-body systems has received a lot of attention in the past few years. An intimately related question is whether a closed quantum system shows irreversible dynamics. However, irreversibility and what we actually mean by this in a quantum many-body system with unitary dynamics has been explored very little. In this work we investigate the dynamics of the Ising model in a transverse magnetic field involving an imperfect effective time reversal. We propose a definition of irreversibility based on the echo peak decay of observables. Inducing the effective time reversal by different protocols we find an algebraic decay of the echo peak heights or an ever persisting echo peak indicating that the dynamics in this model is well reversible.

  12. Billion-atom synchronous parallel kinetic Monte Carlo simulations of critical 3D Ising systems

    SciTech Connect

    Martinez, E.; Monasterio, P.R.; Marian, J.

    2011-02-20

    An extension of the synchronous parallel kinetic Monte Carlo (spkMC) algorithm developed by Martinez et al. [J. Comp. Phys. 227 (2008) 3804] to discrete lattices is presented. The method solves the master equation synchronously by recourse to null events that keep all processors' time clocks current in a global sense. Boundary conflicts are resolved by adopting a chessboard decomposition into non-interacting sublattices. We find that the bias introduced by the spatial correlations attendant to the sublattice decomposition is within the standard deviation of serial calculations, which confirms the statistical validity of our algorithm. We have analyzed the parallel efficiency of spkMC and find that it scales consistently with problem size and sublattice partition. We apply the method to the calculation of scale-dependent critical exponents in billion-atom 3D Ising systems, with very good agreement with state-of-the-art multispin simulations.

  13. Partition function zeros and magnetization plateaus of the spin-1 Ising-Heisenberg diamond chain

    NASA Astrophysics Data System (ADS)

    Hovhannisyan, V. V.; Ananikian, N. S.; Kenna, R.

    2016-07-01

    We study the properties of the generalized spin-1 Ising-Heisenberg model on a diamond chain, which can be considered as a theoretical model for the homometallic magnetic complex [Ni3(C4H2O4)2 -(μ3 - OH) 2(H2O)4 ] n ṡ(2H2 O) n. The model possesses a large variety of ground-state phases due to the presence of biquadratic and single-ion anisotropy parameters. Magnetization and quadrupole moment plateaus are observed at one- and two-thirds of the saturation value. The distributions of Yang-Lee and Fisher zeros are studied numerically for a variety of values of the model parameters. The usual value σ = -1/2 alongside an unusual value σ = -2/3 ​is determined for the Yang-Lee edge singularity exponents.

  14. Long-range random transverse-field Ising model in three dimensions

    NASA Astrophysics Data System (ADS)

    Kovács, István A.; Juhász, Róbert; Iglói, Ferenc

    2016-05-01

    We consider the random transverse-field Ising model in d =3 dimensions with long-range ferromagnetic interactions which decay as a power α >d with the distance. Using a variant of the strong-disorder renormalization group method we study numerically the phase-transition point from the paramagnetic side. We find that the fixed point controlling the transition is of the strong-disorder type, and based on experience with other similar systems, we expect the results to be qualitatively correct, but probably not asymptotically exact. The distribution of the (sample dependent) pseudocritical points is found to scale with 1 /lnL , L being the linear size of the sample. Similarly, the critical magnetization scales with (lnL) χ/Ld and the excitation energy behaves as L-α. Using extreme-value statistics we argue that extrapolating from the ferromagnetic side the magnetization approaches a finite limiting value and thus the transition is of mixed order.

  15. The nitrogen cycle in tidal flats and eelgrass beds of Ise Bay

    NASA Astrophysics Data System (ADS)

    Hata, Kyoko; Nakata, Kisaburo; Suzuki, Teruaki

    2004-04-01

    A tidal flat-sea grass bed ecosystem model was formulated and applied to Ise Bay to evaluate the purification capability of the shallow-water region where a new airport is expected to be built. The model results were in the range of the observed biomass for each state variable in the model. The purification capability of this shallow-water region is estimated from the model results. The inorganic nitrogen removal is estimated at 56 kg N day -1; the organic particulate nitrogen removal by suspension feeders is 95 kg N day -1; the organic nitrogen removal by harvest and fish predation is 25 kg N day -1, and the purification capability of this site is 51 kg N day -1. Potential loss of the sea grass bed by reclamation will reduce the removal ability of inorganic nitrogen as well as food sources for juvenile fishes.

  16. Evidence for two-dimensional Ising superconductivity in gated MoS₂.

    PubMed

    Lu, J M; Zheliuk, O; Leermakers, I; Yuan, N F Q; Zeitler, U; Law, K T; Ye, J T

    2015-12-11

    The Zeeman effect, which is usually detrimental to superconductivity, can be strongly protective when an effective Zeeman field from intrinsic spin-orbit coupling locks the spins of Cooper pairs in a direction orthogonal to an external magnetic field. We performed magnetotransport experiments with ionic-gated molybdenum disulfide transistors, in which gating prepared individual superconducting states with different carrier dopings, and measured an in-plane critical field B(c2) far beyond the Pauli paramagnetic limit, consistent with Zeeman-protected superconductivity. The gating-enhanced B(c2) is more than an order of magnitude larger than it is in the bulk superconducting phases, where the effective Zeeman field is weakened by interlayer coupling. Our study provides experimental evidence of an Ising superconductor, in which spins of the pairing electrons are strongly pinned by an effective Zeeman field.

  17. Optimal control in nonequilibrium systems: Dynamic Riemannian geometry of the Ising model

    NASA Astrophysics Data System (ADS)

    Rotskoff, Grant M.; Crooks, Gavin E.

    2015-12-01

    A general understanding of optimal control in nonequilibrium systems would illuminate the operational principles of biological and artificial nanoscale machines. Recent work has shown that a system driven out of equilibrium by a linear response protocol is endowed with a Riemannian metric related to generalized susceptibilities, and that geodesics on this manifold are the nonequilibrium control protocols with the lowest achievable dissipation. While this elegant mathematical framework has inspired numerous studies of exactly solvable systems, no description of the thermodynamic geometry yet exists when the metric cannot be derived analytically. Herein, we numerically construct the dynamic metric of the two-dimensional Ising model in order to study optimal protocols for reversing the net magnetization.

  18. Quantum phase transition of the transverse-field quantum Ising model on scale-free networks.

    PubMed

    Yi, Hangmo

    2015-01-01

    I investigate the quantum phase transition of the transverse-field quantum Ising model in which nearest neighbors are defined according to the connectivity of scale-free networks. Using a continuous-time quantum Monte Carlo simulation method and the finite-size scaling analysis, I identify the quantum critical point and study its scaling characteristics. For the degree exponent λ=6, I obtain results that are consistent with the mean-field theory. For λ=4.5 and 4, however, the results suggest that the quantum critical point belongs to a non-mean-field universality class. Further simulations indicate that the quantum critical point remains mean-field-like if λ>5, but it continuously deviates from the mean-field theory as λ becomes smaller.

  19. The Ising Model on Pure Husimi Lattices: A General Formulation and the Critical Temperatures

    NASA Astrophysics Data System (ADS)

    Jurčišinová, E.; Jurčišin, M.

    2012-07-01

    We consider the Ising spin 1/2 model on arbitrary pure Husimi lattices. An effective representation for the recursion relations is found which allows to write the general solution of the model in an fluent unified way for all pure Husimi lattices. In this respect, explicit expressions for the spontaneous magnetization, for the susceptibility, for the free energy, and for the specific heat are found. Besides, it is shown that this representation allows also to determine exactly the position of the critical temperature on arbitrary pure Husimi lattice. It is found that the critical temperatures for all pure Husimi lattices are driven by a single polynomial equation with coefficients given by parameters that uniquely describe the lattices.

  20. Complexity in mean-field spin-glass models: Ising p-spin

    SciTech Connect

    Crisanti, A.; Leuzzi, L.; Rizzo, T.

    2005-03-01

    The complexity of the Thouless-Anderson-Palmer (TAP) solutions of the Ising p-spin is investigated in the temperature regime where the equilibrium phase is one-step replica symmetry breaking. Two solutions of the resulting saddle point equations are found. One is supersymmetric (SUSY) and includes the equilibrium value of the free energy while the other is non-SUSY. The two solutions cross exactly at a value of the free energy where the replicon eigenvalue is zero; at low free energy the complexity is described by the SUSY solution while at high free energy it is described by the non-SUSY solution, the latter accounting for the total number of solutions. The relevant TAP solutions counted by the non-SUSY complexity share the same features of the corresponding solutions in the Sherrington-Kirkpatrick model; in particular their Hessian has a vanishing isolated eigenvalue. The TAP solutions corresponding to the SUSY complexity, instead, are well separated minima.

  1. Entanglement and quantum phase transition in the Heisenberg—Ising model

    NASA Astrophysics Data System (ADS)

    Tan, Xiao-Dong; Jin, Bai-Qi; Gao, Wei

    2013-02-01

    We use the quantum renormalization-group (QRG) method to study the entanglement and quantum phase transition (QPT) in the one-dimensional spin-1/2 Heisenberg—Ising model [Lieb E, Schultz T and Mattis D 1961 Ann. Phys. (N.Y.) 16 407]. We find the quantum phase boundary of this model by investigating the evolution of concurrence in terms of QRG iterations. We also investigate the scaling behavior of the system close to the quantum critical point, which shows that the minimum value of the first derivative of concurrence and the position of the minimum scale with an exponent of the system size. Also, the first derivative of concurrence between two blocks diverges at the quantum critical point, which is directly associated with the divergence of the correlation length.

  2. Solar wind observations with the ion composition instrument aboard the ISEE-3 ICE spacecraft

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Coplan, M. A.; Bochsler, P.; Geiss, J.

    1989-01-01

    The principal observations obtained by the Ion Composition Instrument (ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind from September 1978 to the end of 1982, before being directed to the far magnetotail of the Earth are discussed. Almost continuous observations were made of the abundances of 3He++, 4He++, O6+, O7+, Ne, Si and Fe in various charge states, and of their bulk speeds and temperatures. The results show that there is a strong tendency in the collisionless solar wind for the ionic temperatures to be proportional to the masses. For heavier ions these temperatures exceed typical coronal electron temperatures. 4He++, especially in high speed streams, moves faster than H+, and travels at the same speed as heavier ions. The mechanism leading to this heating and rapid streaming is still not entirely clear.

  3. Reconnection versus Kelvin-Helmholtz instability in magnetospheric energy transfer - ISEE observations

    NASA Technical Reports Server (NTRS)

    Song, PU; Elphic, R. C.; Russell, C. T.

    1990-01-01

    Examination of multiple magnetopause crossings observed with the magnetometers on ISEE 1 and 2 makes it possible to determine the amplitude of the oscillation of surface waves on the magnetopause with periods greater than about 2 min and its dependence on latitude, local time, and the direction of the IMF. The magnetopause is more oscillatory for southward IMF than for northward IMF. When the IMF is southward, the amplitude of the oscillation increases with increasing angle from the subsolar point, which suggests that reconnection-related phenomena can generate surface waves on the magnetopause. When the IMF is northward, the oscillation does not grow with distance from the subsolar point, which is contrary to the expected growth of the Kelvin-Helmholtz (K-H) instability. It is also found that solar-wind pressure fluctuations may cause all of the observed boundary oscillations for northward IMF.

  4. Further determination of the characteristics of magnetospheric plasma vortices with Isee 1 and 2

    NASA Technical Reports Server (NTRS)

    Hones, E. W., Jr.; Bame, S. J.; Asbridge, J. R.; Birn, J.; Paschmann, G.; Sckopke, N.; Haerendel, G.

    1981-01-01

    Further studies of the vortices in magnetospheric plasma flow with the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI) fast plasma experiment on Isee 1 and 2 have revealed that the pattern of vortical flow has a wavelength of approximately 20-40 earth radii and moves tailward through the magnetosphere at speeds of several hundred kilometers per second. The tendency toward vorticity pervades the total breadth of the plasma sheet tailward of the dawn-dusk meridian. The sense of rotation of the plasma flow (as viewed from above the ecliptic plane) is clockwise in the morning side of the plasma sheet and counterclockwise in the evening side. The sense of rotation in the morning and evening boundary layers is reversed from that in the contiguous regions of the plasma sheet. The occurrence of vortical flow is independent of the level of geomagnetic activity but is associated with long-period geomagnetic pulsations.

  5. Initial observations of low energy charged particles near the earth's bow shock on ISEE-1

    NASA Technical Reports Server (NTRS)

    Ipavich, F. M.; Gloeckler, G.; Fan, C. Y.; Fisk, L. A.; Hovestadt, D.; Klecker, B.; Scholer, M.; Ogallagher, J. J.

    1979-01-01

    Initial measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE 1 are reported. ULECA is an electrostatic deflection - total energy sensor consisting of a collimator, a deflection analyzer, and an array of solid-state detectors. The position of a given detector, which determines the energy per charge of an incident particle, together with the measured energy, determines the particle's charge state. It is found that a rich variety of phenomena are operative in the transthermal energy regime (about 10 keV/Q to 100 keV/Q) covered by ULECA. Specifically, observations are presented of locally accelerated protons, alpha particles, and heavier ions in the magnetosheath and upstream of earth's bow shock. Preliminary analysis indicates that the behavior of these locally accelerated particles is most similar at the same energy per charge.

  6. Plasma properties of driver gas following interplanetary shocks observed by ISEE-3

    NASA Technical Reports Server (NTRS)

    Zwickl, R. D.; Ashbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

    1982-01-01

    Plasma fluid parameters calculated from solar wind and magnetic field data obtained on ISEE 3 were studied. The characteristic properties of driver gas following interplanetary shocks was determined. Of 54 shocks observed from August 1978 to February 1980, nine contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature across a tangential discontinuity. While helium enhancements were present in all of nine of these events, only about half of them contained simultaneous changes in the two quantities. Often the He/H ratio changed over a period of minutes. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance and by an increase in the ratio of parallel to perpendicular temperature. The drive gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

  7. The range of high-efficiency silicon solar cells fabricated at Fraunhofer ISE

    SciTech Connect

    Glunz, S.W.; Knobloch, J.; Hebling, C.; Wettling, W.

    1997-12-31

    An overview of the high-efficiency solar cell development with crystalline silicon at Fraunhofer ISE is given. Seven types of cells are discussed: (1) LBSF cells (local back surface field); (2) RP-PERL cells (random pyramids, passivated emitter rear locally-diffused); (3) RP-PERC (random pyramids, passivated emitter and rear cell); (4) MESC (mesh-structured emitter cell); (5) cells with interdigitated contacts; (6) high-efficiency thin film cell based on SOI (silicon ion insulator); and (7) mini modules integrated on one 4 inch SOI-wafer. All these cells show very good efficiencies close to or well above 20%, respectively. The goal of all activities is to develop technologies for efficiencies as high as possible but at the same time as simple as possible. Many of the developments are performed in close cooperation with German PV companies and/or with European research teams in the framework of projects of the European Commission.

  8. On the two-dimensional dynamical Ising model in the phase coexistence region

    NASA Astrophysics Data System (ADS)

    Martinelli, F.

    1994-09-01

    We consider a Glauber dynamics reversible with respect to the two-dimensional Ising model in a finite square of side L, in the absence of an external field and at large inverse temperature β. We first consider the gap in the spectrum of the generator of the dynamics in two different cases: with plus and open boundary conditions. We prove that, when the symmetry under global spin flip is broken by the boundary conditions, the gap is much larger than the case in which the symmetry is present. For this latter we compute exactly the asymptotics of -(1/β L) log(gap) as L→∞ and show that it coincides with the surface tension along one of the coordinate axes. As a consequence we are able to study quite precisely the large deviations in time of the magnetization and to obtain an upper bound on the spin-spin time correlation in the infinite-volume plus phase. Our results establish a connection between the dynamical large deviations and those of the equilibrium Gibbs measure studied by Shlosman in the framework of the rigorous description of the Wulff shape for the Ising model. Finally we show that, in the case of open boundary conditions, it is possible to rescale the time with L in such a way that, as L→∞, the finite-dimensional distributions of the time-rescaled magnetization converge to those of a symmetric continuous-time Markov chain on the two-state space {- m *(β), m *(β)}, m *(β) being the spontaneous magnetization. Our methods rely upon a novel combination of techniques for bounding from below the gap of symmetric Markov chains on complicated graphs, developed by Jerrum and Sinclair in their Markov chain approach to hard computational problems, and the idea of introducing "block Glauber dynamics" instead of the standard single-site dynamics, in order to put in evidence more effectively the effect of the boundary conditions in the approach to equilibrium.

  9. Paramagnetic atom number and paramagnetic critical pressure of the sc, bcc and fcc Ising nanolattices

    NASA Astrophysics Data System (ADS)

    Şarlı, Numan

    2015-01-01

    The effects of the magnetic atom number in the unit volume on the magnetic properties are investigated by using sc (n=8), bcc (n=9) and fcc (n=14) Ising NLs within the effective field theory with correlations. We find that the magnetic properties expand as the magnetic atom number increases in the unit volume and this expanding constitutes an elliptical path at TC. The effect of the magnetic atom number (n) in the unit volume on the magnetic properties (mp) appear as nscIsing NLs at TC. We define the paramagnetic magnetic atom number in the unit volume as np=n(1-M(T)).

  10. Vertical Axis Wind Turbine Foundation parameter study

    SciTech Connect

    Lodde, P.F.

    1980-07-01

    The dynamic failure criterion governing the dimensions of prototype Vertical Axis Wind Turbine Foundations is treated as a variable parameter. The resulting change in foundation dimensions and costs is examined.

  11. Eight Pulse Performance of DARHT Axis II - Preliminary Results

    SciTech Connect

    Schulze, Martin E.

    2015-12-08

    The DARHT-II accelerator produces a 1.65-kA, 17-MeV beam in a 1600-ns pulse. Standard operation of the DARHT Axis II accelerator involves extracting four short pulses from the 1.6 us long macro-pulse produced by the LIA. The four short pulses are extracted using a fast kicker in combination with a quadrupole septum magnet and then transported for several meters to a high-Z material target for conversion to x-rays for radiography. The ability of the DARHT Axis 2 kicker to produce more than the standard four pulse format has been previously demonstrated. This capability was developed to study potential risks associated with beam transport during an initial commissioning phase at low energy (8 MeV) and low current (1.0 kA).The ability of the kicker to deliver more than four pulses to the target has been realized for many years. This note describes the initial results demonstrating this capability.

  12. Electrical-Discharge Machining With Additional Axis

    NASA Technical Reports Server (NTRS)

    Malinzak, Roger M.; Booth, Gary N.

    1991-01-01

    Proposed electrical-discharge-machining (EDM) apparatus uses moveable vertical wire as electrode. Wire positionable horizontally along one axis as it slides vertically past workpiece. Workpiece indexed in rotation about horizontal axis. Because of symmetry of parts, process used to make two such parts at a time by defining boundary between them. Advantages: cost of material reduced, imparts less residual stress to workpiece, and less time spent machining each part when parts produced in such symmetrical pairs.

  13. Postoperative conversion disorder.

    PubMed

    Afolabi, Kola; Ali, Sameer; Gahtan, Vivian; Gorji, Reza; Li, Fenghua; Nussmeier, Nancy A

    2016-05-01

    Conversion disorder is a psychiatric disorder in which psychological stress causes neurologic deficits. A 28-year-old female surgical patient had uneventful general anesthesia and emergence but developed conversion disorder 1 hour postoperatively. She reported difficulty speaking, right-hand numbness and weakness, and right-leg paralysis. Neurologic examination and imaging revealed no neuronal damage, herniation, hemorrhage, or stroke. The patient mentioned failing examinations the day before surgery and discontinuing her prescribed antidepressant medication, leading us to diagnose conversion disorder, with eventual confirmation by neuroimaging and follow-up examinations.

  14. Postoperative conversion disorder.

    PubMed

    Afolabi, Kola; Ali, Sameer; Gahtan, Vivian; Gorji, Reza; Li, Fenghua; Nussmeier, Nancy A

    2016-05-01

    Conversion disorder is a psychiatric disorder in which psychological stress causes neurologic deficits. A 28-year-old female surgical patient had uneventful general anesthesia and emergence but developed conversion disorder 1 hour postoperatively. She reported difficulty speaking, right-hand numbness and weakness, and right-leg paralysis. Neurologic examination and imaging revealed no neuronal damage, herniation, hemorrhage, or stroke. The patient mentioned failing examinations the day before surgery and discontinuing her prescribed antidepressant medication, leading us to diagnose conversion disorder, with eventual confirmation by neuroimaging and follow-up examinations. PMID:27041258

  15. Sex differences in the HPA axis.

    PubMed

    Goel, Nirupa; Workman, Joanna L; Lee, Tiffany T; Innala, Leyla; Viau, Victor

    2014-07-01

    The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development. Despite this, many studies use male subjects exclusively, while fewer reports involve females or provide direct sex comparisons. The purpose of this article is to present sex comparisons in the functional and molecular aspects of the HPA axis, through various phases of activity, including basal, acute stress, and chronic stress conditions. The HPA axis in females initiates more rapidly and produces a greater output of stress hormones. This review focuses on the interactions between the gonadal hormone system and the HPA axis as the key mediators of these sex differences, whereby androgens increase and estrogens decrease HPA activity in adulthood. In addition to the effects of gonadal hormones on the adult response, morphological impacts of hormone exposure during development are also involved in mediating sex differences. Additional systems impinging on the HPA axis that contribute to sex differences include the monoamine neurotransmitters norepinephrine and serotonin. Diverse signals originating from the brain and periphery are integrated to determine the level of HPA axis activity, and these signals are, in many cases, sex-specific.

  16. Geometrical theory of aberrations near the axis in classical off-axis reflecting telescopes.

    PubMed

    Chang, Seunghyuk; Prata, Aluizio

    2005-11-01

    A geometrical theory of aberrations for the vicinity of the focus of arbitrary off-axis sections of conic mirrors is derived. It is shown that an off-axis conic mirror introduces linear astigmatism in the image. However, in classical two-mirror telescopes this aberration can be eliminated by tilting the secondary parent mirror axis. It is also shown that the practical geometrical-optics performance of a classical off-axis two-mirror telescope with no linear astigmatism is equivalent to the performance of an on-axis system, proving that both systems have identical third-order coma. To demonstrate the applicability of the theory developed in a practical system, a fast (i.e., f/2), compact, obstruction-free classical off-axis Cassegrain telescope is designed.

  17. Responsive Teaching through Conversation

    ERIC Educational Resources Information Center

    Dozier, Cheryl; Garnett, Susan; Tabatabai, Simeen

    2011-01-01

    Conversations are the heart of responsive teaching. By talking with struggling learners, teachers can find out about their interests in order to design effective, personalized instruction; build relationships; work through complexities in teaching and learning; and celebrate successes.

  18. Photochemical Energy Conversion.

    ERIC Educational Resources Information Center

    Batschelet, William H.; George, Arnold

    1986-01-01

    Describes procedures for two demonstrations: (1) photochemical energy conversion using ferric oxalate actinometry and (2) liquification of gases using Freon 114. Safety precautions are given for both demonstrations, as are procedures and material specifications. (JM)

  19. Methane conversion process

    SciTech Connect

    Gaffney, A.M.; Jones, C.A.; Sofranko, J.A.

    1989-01-03

    This patent describes a process for the conversion of methane to higher hydrocarbons and coproduct water wherein methane is contacted at reactive conditions with a conversion catalyst comprised of a reducible metal oxide selected from the group consisting of an oxide of manganese, tin, indium, germanium, antimony, leads, bismuth, cerium, praseodymium, terbium, iron, and ruthenium. The improvement consists of: pretreating the catalyst before use in the conversion of methane to higher hydrocarbons and coproduct water with a reducing agent at 650/sup 0/C to 1200/sup 0/C for a time sufficient to improve the bulk density and attrition resistance of the catalyst and thereafter contacting the pretreated catalyst with methane at methane conversion conditions effective to form higher hydrocarbons and coproduct water.

  20. Actuator assembly including a single axis of rotation locking member

    DOEpatents

    Quitmeyer, James N.; Benson, Dwayne M.; Geck, Kellan P.

    2009-12-08

    An actuator assembly including an actuator housing assembly and a single axis of rotation locking member fixedly attached to a portion of the actuator housing assembly and an external mounting structure. The single axis of rotation locking member restricting rotational movement of the actuator housing assembly about at least one axis. The single axis of rotation locking member is coupled at a first end to the actuator housing assembly about a Y axis and at a 90.degree. angle to an X and Z axis providing rotation of the actuator housing assembly about the Y axis. The single axis of rotation locking member is coupled at a second end to a mounting structure, and more particularly a mounting pin, about an X axis and at a 90.degree. angle to a Y and Z axis providing rotation of the actuator housing assembly about the X axis. The actuator assembly is thereby restricted from rotation about the Z axis.

  1. Critical Crossover Functions for Simple Fluids: Non-Analytical Scaling Determination of the Ising-Like Crossover Parameter

    NASA Astrophysics Data System (ADS)

    Garrabos, Yves; Lecoutre, Carole; Marre, Samuel; LeNeindre, Bernard

    2016-08-01

    A non-analytical scaling determination of the Ising-like crossover parameter is proposed considering the critical isochore of a simple fluid at finite distance from its critical temperature. The mean crossover functions, estimated from the bounded results of the massive renormalization scheme in field theory applied to the ( Φ 2) d2( n) model in three dimensions (d=3) and scalar order parameter (n=1), are used to formulate the corresponding scaling equations valid in two well-defined temperature ranges from the critical temperature. The validity range and the Ising-like nature of the corresponding crossover description are discussed in terms of a single Ising-like scale factor characterizing the critical isochore. The asymptotic value of this scale factor can be predicted within the Ising-like preasymptotic domain. Unfortunately, the absence of precise experimental data in such a close vicinity of the critical point leads the direct testing impossible. A contrario, from our scaling equations and the use of precise measurements performed at finite distance from the critical point, its local value can be estimated beyond the Ising-like preasymptotic domain. This non-analytical scaling determination only needs to make reference to the universal features estimated from the mean crossover functions and to introduce a single master dimensionless length common to all the simple fluids. This latter parameter guaranties the uniqueness of the physical length unit used for the theoretical crossover functions and the fluid singular properties when the generalized critical coordinates of the vapor-liquid critical point of each fluid are known. Xenon case along its critical isochore is considered as a typical example to demonstrate the singleness of the Ising-like crossover parameter. With the measurements at finite temperature range of the effective singular behaviors of the isothermal compressibility in the homogeneous domain, and the vapor-liquid coexisting densities in the

  2. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  3. Conversion of solar energy

    NASA Astrophysics Data System (ADS)

    Semenov, N. N.; Shilov, A. E.

    The papers presented in this volume provide an overview of current theoretical and experimental research related to the conversion and practical utilization of solar energy. Topics discussed include semiconductor photovoltaic cells, orbital solar power stations, chemical and biological methods of solar energy conversion, and solar energy applications. Papers are included on new theoretical models of solar cells and prospects for increasing their efficiency, metrology and optical studies of solar cells, and some problems related to the thermally induced deformations of large space structures.

  4. Environmental epidemiology: What's at stake: open issues and methodologies -- report from the 26th Annual Conference of the International Society for Environmental Epidemiology (ISEE).

    PubMed

    Carugno, Michele

    2015-01-01

    At the end of last August, the University of Washington (UW) in Seattle welcomed over 1,100 attendees at the 26th Annual ISEE Conference - "From Local to Global: Advancing Science for Policy in Environmental Health"...

  5. POGAL B-Axis Motor Test

    SciTech Connect

    Hale, L C; Wulff, T A

    2004-06-28

    The Aerotech model S-180-69-A, a brushless DC motor of slotless design, was selected as the B-axis drive for the Precision Optical Grinder and Lathe (POGAL). It is common knowledge that a slotless motor will have effectively no magnetic cogging and much less torque ripple than a traditional slot-type motor. It is logical to believe that the radial and axial forces generated between the rotor and stator would also be smaller for a slotless design. This is important when a frameless motor is directly coupled to the axis, as these forces directly influence the axis and affect its error motion. It is the purpose of this test to determine the radial and axial forces generated by the Aerotech motor and to estimate their effect on the error motion of the axis using a mathematical model of the hydrostatic bearing being designed for POGAL. The test results combined with a mathematical model of the POGAL B axis indicate that the directly coupled Aerotech motor will be quite acceptable. In the radial direction, the residual motor force, after subtracting out the one-cycle force, could cause sub nanometer level error motion at the tool point. The axial direction is not in a sensitive direction for turning.

  6. Superconductivity from a confinement transition out of a fractionalized Fermi liquid with Z2 topological and Ising-nematic orders

    NASA Astrophysics Data System (ADS)

    Chatterjee, Shubhayu; Qi, Yang; Sachdev, Subir; Steinberg, Julia

    2016-07-01

    The Schwinger boson theory of the frustrated square lattice antiferromagnet yields a stable, gapped Z2 spin liquid ground state with time-reversal symmetry, incommensurate spin correlations, and long-range Ising-nematic order. We obtain an equivalent description of this state using fermionic spinons (the fermionic spinons can be considered to be bound states of the bosonic spinons and the visons). Upon doping, the Z2 spin liquid can lead to a fractionalized Fermi liquid (FL*) with small Fermi pockets of electronlike quasiparticles, while preserving the Z2 topological and Ising-nematic orders. We describe a Higgs transition out of this deconfined metallic state into a confining superconducting state which is almost always of the Fulde-Ferrell-Larkin-Ovchinnikov type, with spatial modulation of the superconducting order.

  7. Solving the inverse Ising problem by mean-field methods in a clustered phase space with many states.

    PubMed

    Decelle, Aurélien; Ricci-Tersenghi, Federico

    2016-07-01

    In this work we explain how to properly use mean-field methods to solve the inverse Ising problem when the phase space is clustered, that is, many states are present. The clustering of the phase space can occur for many reasons, e.g., when a system undergoes a phase transition, but also when data are collected in different regimes (e.g., quiescent and spiking regimes in neural networks). Mean-field methods for the inverse Ising problem are typically used without taking into account the eventual clustered structure of the input configurations and may lead to very poor inference (e.g., in the low-temperature phase of the Curie-Weiss model). In this work we explain how to modify mean-field approaches when the phase space is clustered and we illustrate the effectiveness of our method on different clustered structures (low-temperature phases of Curie-Weiss and Hopfield models). PMID:27575082

  8. Solving the inverse Ising problem by mean-field methods in a clustered phase space with many states

    NASA Astrophysics Data System (ADS)

    Decelle, Aurélien; Ricci-Tersenghi, Federico

    2016-07-01

    In this work we explain how to properly use mean-field methods to solve the inverse Ising problem when the phase space is clustered, that is, many states are present. The clustering of the phase space can occur for many reasons, e.g., when a system undergoes a phase transition, but also when data are collected in different regimes (e.g., quiescent and spiking regimes in neural networks). Mean-field methods for the inverse Ising problem are typically used without taking into account the eventual clustered structure of the input configurations and may lead to very poor inference (e.g., in the low-temperature phase of the Curie-Weiss model). In this work we explain how to modify mean-field approaches when the phase space is clustered and we illustrate the effectiveness of our method on different clustered structures (low-temperature phases of Curie-Weiss and Hopfield models).

  9. Observation of Ising spin-nematic order and its close relationship to the superconductivity in FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Yuan, Dongna; Yuan, Jie; Huang, Yulong; Ni, Shunli; Feng, Zhongpei; Zhou, Huaxue; Mao, Yiyuan; Jin, Kui; Zhang, Guangming; Dong, Xiaoli; Zhou, Fang; Zhao, Zhongxian

    2016-08-01

    Superconducting FeSe single crystals of (001) orientation are synthesized via a hydrothermal ion-release route. An Ising spin-nematic order is identified by our systematic measurements of in-plane angular-dependent magnetoresistance (AMR) and static magnetization. The turn-on temperature of anisotropic AMR signifies the Ising spin-nematic ordering temperature Tsn, below which a twofold rotational symmetry is observed in the iron plane. A downward curvature appears below Tsn in the temperature dependence of static magnetization for the weak in-plane magnetic field as reported previously. Remarkably, we find a universal linear relationship between Tc and Tsn among various superconducting samples, indicating that the spin nematicity and the superconductivity in FeSe have a common microscopic origin.

  10. Aeroelastically coupled blades for vertical axis wind turbines

    DOEpatents

    Paquette, Joshua; Barone, Matthew F.

    2016-02-23

    Various technologies described herein pertain to a vertical axis wind turbine blade configured to rotate about a rotation axis. The vertical axis wind turbine blade includes at least an attachment segment, a rear swept segment, and optionally, a forward swept segment. The attachment segment is contiguous with the forward swept segment, and the forward swept segment is contiguous with the rear swept segment. The attachment segment includes a first portion of a centroid axis, the forward swept segment includes a second portion of the centroid axis, and the rear swept segment includes a third portion of the centroid axis. The second portion of the centroid axis is angularly displaced ahead of the first portion of the centroid axis and the third portion of the centroid axis is angularly displaced behind the first portion of the centroid axis in the direction of rotation about the rotation axis.

  11. Scaling and super-universality in the coarsening dynamics of the 3D random field Ising model

    NASA Astrophysics Data System (ADS)

    Aron, Camille; Chamon, Claudio; Cugliandolo, Leticia F.; Picco, Marco

    2008-05-01

    We study the coarsening dynamics of the three-dimensional random field Ising model using Monte Carlo numerical simulations. We test the dynamic scaling and super-scaling properties of global and local two-time observables. We treat in parallel the three-dimensional Edward-Anderson spin glass and we recall results on Lennard-Jones mixtures and colloidal suspensions to highlight the common and different out of equilibrium properties of these glassy systems.

  12. Exploring the renormalization of quantum discord and Bell non-locality in the one-dimensional transverse Ising model

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-cheng; Shi, Jia-dong; Ding, Zhi-yong; Ye, Liu

    2016-08-01

    In this paper, the effect of external magnet field g on the relationship among the quantum discord, Bell non-locality and quantum phase transition by employing quantum renormalization-group (QRG) method in the one-dimensional transverse Ising model is investigated. In our model, external magnet field g can influence the phase diagrams. The results have shown that both the two quantum correlation measures can develop two saturated values, which are associated with two distinct phases: long-ranged ordered Ising phase and the paramagnetic phase with the number of QRG iterations increasing. Additionally, quantum non-locality always existent in the long-ranged ordered Ising phase no matter whatever the value of g is and what times QRG steps are carried out and we conclude that the quantum non-locality always exists not only suitable for the two sites of block, but for nearest-neighbor blocks in the long-ranged ordered Ising phase. However, the block-block correlation in the paramagnetic phase is not strong enough to violate the Bell-CHSH inequality as the size of system becomes large. Furthermore, when the system violates the CHSH inequality, i.e., satisfies quantum non-locality, it needs to be entangled. On the other way, if the system obeys the CHSH inequality, it may be entangled or not. To gain further insight, the non-analytic and scaling behavior of QD and Bell non-locality have also been analyzed in detail and this phenomenon indicates that the behavior of the correlation can perfectly help one to observe the quantum critical properties of the model.

  13. CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES: Reduced Fidelity Susceptibility in One-Dimensional Transverse Field Ising Model

    NASA Astrophysics Data System (ADS)

    Ma, Jian; Xu, Lei; Wang, Xiao-Guang

    2010-01-01

    We study critical behaviors of the reduced fidelity susceptibility for two neighboring sites in the one-dimensional transverse field Ising model. It is found that the divergent behaviors of the susceptibility take the form of square of logarithm, in contrast with the global ground-state fidelity susceptibility which is power divergence. In order to perform a scaling analysis, we take the square root of the susceptibility and determine the scaling exponent analytically and the result is further confirmed by numerical calculations.

  14. Phase Transition of Two-Dimensional Ising Models on the Honeycomb and Related Lattices with Striped Random Impurities

    NASA Astrophysics Data System (ADS)

    Morita, Satoshi; Suzuki, Sei

    2016-01-01

    Two-dimensional Ising models on the honeycomb lattice and the square lattice with striped random impurities are studied to obtain their phase diagrams. Assuming bimodal distributions of the random impurities where all the non-zero couplings have the same magnitude, exact critical values for the fraction p of ferromagnetic bonds at the zero-temperature (T=0) are obtained. The critical lines in the p-T plane are drawn by numerically evaluating the Lyapunov exponent of random matrix products.

  15. Isomolybdate conversion coatings

    NASA Technical Reports Server (NTRS)

    Minevski, Zoran (Inventor); Maxey, Jason (Inventor); Nelson, Carl (Inventor); Eylem, Cahit (Inventor)

    2002-01-01

    A conversion coating solution and process forms a stable and corrosion-resistant layer on metal substrates or layers or, more preferably, on a boehmite layer or other base conversion coating. The conversion coating process involves contacting the substrate, layer or coating with an aqueous alkali metal isomolybdate solution in order to convert the surface of the substrate, layer or coating to a stable conversion coating. The aqueous alkali metal molybdates are selected from sodium molybdate (Na.sub.2 MoO.sub.4), lithium molybdate (Li.sub.2 MoO.sub.4), potassium molybdate (K.sub.2 MoO.sub.4), or combinations thereof, with the most preferred alkali metal molybdate being sodium molybdate. The concentration of alkali metal molybdates in the solution is preferably less than 5% by weight. In addition to the alkali metal molybdates, the conversion coating solution may include alkaline metal passivators selected from lithium nitrate (LiNO.sub.3), sodium nitrate (NaNO.sub.3), ammonia nitrate (NH.sub.4 NO.sub.3), and combinations thereof; lithium chloride, potassium hexafluorozirconate (K.sub.2 ZrF.sub.6) or potassium hexafluorotitanate (K.sub.2 TiF.sub.6).

  16. Laser energy conversion

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1989-01-01

    The conversion of laser energy to other, more useful, forms is an important element of any space power transmission system employing lasers. In general the user, at the receiving sight, will require the energy in a form other than laser radiation. In particular, conversion to rocket power and electricity are considered to be two major areas where one must consider various conversion techniques. Three systems (photovoltaic cells, MHD generators, and gas turbines) have been identified as the laser-to-electricity conversion systems that appear to meet most of the criteria for a space-based system. The laser thruster also shows considerable promise as a space propulsion system. At this time one cannot predict which of the three laser-to-electric converters will be best suited to particular mission needs. All three systems have some particular advantages, as well as disadvantages. It would be prudent to continue research on all three systems, as well as the laser rocket thruster. Research on novel energy conversion systems, such as the optical rectenna and the reverse free-electron laser, should continue due to their potential for high payoff.

  17. Exercise, Training, and the Hypothalamic-Pituitary-Gonadal Axis in Men and Women.

    PubMed

    Cano Sokoloff, Natalia; Misra, Madhusmita; Ackerman, Kathryn E

    2016-01-01

    The hypothalamic-pituitary-gonadal (HPG) axis is essential for adequate responses to exercise and training both acutely and chronically. Both testosterone and estrogen play leading roles in neuromuscular adaptation to exercise in males and females. The purpose of this chapter is to illustrate the physiological and pathological changes that occur in the HPG axis secondary to exercise and training. In males, testosterone increases with acute bouts of exercise, but long-term effects are less clear, with evidence of lower testosterone in endurance athletes. Restricted energy availability may negatively affect hormone levels in male endurance athletes, but data regarding low energy availability and its impact on the HPG axis are limited in male athletes. Conversely, in females there is significant evidence that decreased energy availability inhibits the HPG axis, leading to menstrual irregularities and lower bone density. Hormonal changes secondary to acute bouts of exercise are more challenging to interpret in females due to menstrual variability, which traditionally has not been taken into account in many studies. However, some evidence supports an increase in testosterone and estradiol with acute exercise. More work is needed to elucidate the relationships among energy availability, basal hormonal fluctuations, and exercise, and their collective effects on the HPG axis.

  18. The hypothalamic-pituitary-adrenal axis and the female reproductive system.

    PubMed

    Magiakou, M A; Mastorakos, G; Webster, E; Chrousos, G P

    1997-06-17

    The hypothalamic-pituitary-adrenal (HPA) axis and the female reproductive system are intertwined and exhibit a complex relationship. Thus, the HPA axis exerts profound, mostly inhibitory effects, on the reproductive axis, with corticotropin-releasing hormone (CRH) and CRH-induced propiomelanocortin peptides inhibiting hypothalamic GnRH secretion, and with glucocorticoids inhibiting pituitary LH and ovarian estrogen and progesterone secretion and rendering estrogen-target tissues, such as the endometrium, resistant to the gonadal steroid. These effects of the HPA axis are responsible for the "hypothalamic" amenorrhea of stress, depression and eating disorders, and the hypogonadism of Cushing's syndrome. Conversely, estrogen directly stimulates the CRH gene, which may explain the slight hypercortisolism of females and the preponderance of depressive, anxiety, and eating disorders, as well as Cushing's disease in women. Interestingly, several components of the HPA axis and their receptors are present in reproductive tissues, as autocoid regulators of their various functions. These include ovarian and endometrial CRH, which may participate in the inflammatory processes of the ovary, that is, ovulation and luteolysis, and of the endometrium, that is, implantation and menstruation. Finally, the hypercortisolism of the latter half of pregnancy can be explained by high levels of placenta CRH in plasma. This hypercortisolism causes a transient adrenal suppression in the postpartum period, which may explain the postpartum blues/depression and autoimmune phenomena of this period.

  19. Gut-microbiota-brain axis and effect on neuropsychiatric disorders with suspected immune dysregulation

    PubMed Central

    Petra, Anastasia I.; Panagiotidou, Smaro; Hatziagelaki, Erifili; Stewart, Julia M.; Conti, Pio; Theoharides, Theoharis C.

    2015-01-01

    Purpose Gut microbiota regulate intestinal function and health. However, mounting evidence indicates that they can also influence the immune and nervous systems and vice versa. Here we reviewed the bidirectional relationship between the gut microbiota and the brain, termed microbiota-gut-brain (MGB) axis, and we discuss how it contributes to the pathogenesis of certain disorders, that may involve brain inflammation. Methods Articles were chosen from Medline since 1980 using the key words anxiety, attention-deficit hypersensitivity disorder (ADHD), autism, cytokines, depression, gut, hypothalamic-pituitary-adrenal (HPA) axis, inflammation, immune system, microbiota, nervous system, neurologic, neurotransmitters, neuroimmune conditions, psychiatric, stress. Findings Various afferent or efferent pathways are involved in the MGB axis. Antibiotics, environmental and infectious agents, intestinal neurotransmitters/neuromodulators, sensory vagal fibers, cytokines, essential metabolites, all convey information about the intestinal state to the CNS. Conversely, the HPA axis, the CNS regulatory areas of satiety and neuropeptides released from sensory nerve fibers affect the gut microbiota composition directly or through nutrient availability. Such interactions appear to influence the pathogenesis of a number of disorders in which inflammation is implicated such as mood disorder, autism-spectrum disorders (ASDs), attention-deficit hypersensitivity disorder (ADHD), multiple sclerosis (MS) and obesity. Implications Recognition of the relationship between the MGB axis and the neuroimmune systems provides a novel approach for better understanding and management of these disorders. Appropriate preventive measures early in life or corrective measures such as use of psychobiotics, fecal microbiota transplantation and flavonoids are discussed. PMID:26046241

  20. Modular off-axis solar concentrator

    SciTech Connect

    Plesniak, Adam P; Hall, John C

    2015-01-27

    A solar concentrator including a housing defining a vertical axis and including a receiving wall connected to a reflecting wall to define an internal volume and an opening into the internal volume, wherein the reflecting wall defines at least one primary optical element, and wherein at least a portion of the reflecting wall includes a layer of reflective material, the housing further including a cover connected to the receiving wall and the reflecting wall to seal the opening, and at least one receiver mounted on the receiving wall such that a vertical axis of the receiver is disposed at a non-zero angle relative to the vertical axis of the housing, the receiver including at least one photovoltaic cell.

  1. Enclosed, off-axis solar concentrator

    DOEpatents

    Benitez, Pablo; Grip, Robert E; Minano, Juan C; Narayanan, Authi A; Plesniak, Adam; Schwartz, Joel A

    2013-11-26

    A solar concentrator including a housing having receiving wall, a reflecting wall and at least two end walls, the receiving, reflecting and end walls defining a three-dimensional volume having an inlet, wherein a vertical axis of the housing is generally perpendicular to the inlet, a receiver mounted on the receiving wall of the housing, the receiver including at least one photovoltaic cell, wherein a vertical axis of the receiver is disposed at a non-zero angle relative to the vertical axis of the housing, at least one clip disposed on the reflecting wall an optical element received within the three-dimensional volume, the optical element including at least one tab, the tab being engaged by the clip to align the optical element with the receiver, and a window received over the inlet to enclose the housing.

  2. Ground states, magnetization plateaus and bipartite entanglement of frustrated spin-1/2 Ising-Heisenberg and Heisenberg triangular tubes

    NASA Astrophysics Data System (ADS)

    Alécio, Raphael C.; Lyra, Marcelo L.; Strečka, Jozef

    2016-11-01

    The ground-state phase diagram, magnetization process and bipartite entanglement of the frustrated spin-1/2 Ising-Heisenberg and Heisenberg triangular tube (three-leg ladder) are investigated in a non-zero external magnetic field. The exact ground-state phase diagram of the spin-1/2 Ising-Heisenberg tube with Heisenberg intra-rung and Ising inter-rung couplings consists of six distinct gapped phases, which manifest themselves in a magnetization curve as intermediate plateaus at zero, one-third and two-thirds of the saturation magnetization. Four out of six available ground states exhibit quantum entanglement between two spins from the same triangular unit evidenced by a non-zero concurrence. Density-matrix renormalization group calculations are used in order to construct the ground-state phase diagram of the analogous but purely quantum spin-1/2 Heisenberg tube with Heisenberg intra- and inter-rung couplings, which consists of four gapped and three gapless phases. The Heisenberg tube shows a continuous change of the magnetization instead of a plateau at zero magnetization, while the intermediate one-third and two-thirds plateaus may be present or not in the zero-temperature magnetization curve.

  3. Levels and ages of selenium and metals in sedimentary cores of Ise Bay as determined by 210-Pb dating technique

    SciTech Connect

    Itoh, K.; Chikuma, M.; Tanaka, H.

    1987-08-01

    Ise Bay is connected with estuaries of Nagoya harbor which is one of the most active industrial areas in Japan. Nagoya harbor estuaries are recipient of a large quantity of municipal and industrial discharge. The land boundaries of estuaries are sites of the manufacturing industries and they are utilized by oil tankers and cargo vessels. Accumulation of various kinds of metal such as selenium, mercury, zinc, copper, lead, and chromium have occurred in sediments for many years. The authors have carried out an extensive investigation on the selenium pollution of sea water and sediments of Nagoya harbor estuaries. The input of selenium to Ise Bay has occurred ever since the industrial activity was established in Nagoya city. Investigators have reported the sedimentary record of metals of Tokyo Bay, Osaka Bay and Seto Inland Sea. Some investigators reported the pollution caused by polynuclear aromatic hydrocarbon in sediments of Ise Bay, but did not mention metals. The authors determined metals including selenium in sedimentary core samples. The ages of those samples were already estimated by 210-Pb dating technique.

  4. Effect of Ising-type Tb3+ ions on the low-temperature magnetism of La, Ca cobaltite.

    PubMed

    Knížek, K; Jirák, Z; Hejtmánek, J; Veverka, M; Kaman, O; Maryško, M; Santavá, E; André, G

    2014-03-19

    Crystal and magnetic structures of the x = 0.2 member of the La0.8-xTbxCa0.2CoO3 perovskite series have been determined from powder neutron diffraction. Enhancement of the diffraction peaks due to ferromagnetic or cluster glass ordering is observed below TC = 55 K. The moments first evolve on Co sites, and ordering of Ising-type Tb(3+) moments is induced at lower temperatures by a molecular field due to Co ions. The final magnetic configuration is collinear Fx for the cobalt subsystem, while it is canted FxCy for terbium ions. The rare-earth moments align along local Ising axes within the ab-plane of the orthorhombic Pbnm structure. The behavior in external fields up to 70-90 kOe has been probed by magnetization and heat capacity measurements. The dilute terbium ions contribute to significant coercivity and remanence that both steeply increase with decreasing temperature. A remarkable manifestation of the Tb(3+) Ising character is the observation of a low-temperature region with an anomalously large linear term of heat capacity and its field dependence. Similar behaviors are detected also for other terbium dopings x = 0.1 and 0.3. PMID:24590179

  5. Heat capacity peak at the quantum critical point of the transverse Ising magnet CoNb2O6

    PubMed Central

    Liang, Tian; Koohpayeh, S. M.; Krizan, J. W.; McQueen, T. M.; Cava, R. J.; Ong, N. P.

    2015-01-01

    The transverse Ising magnet Hamiltonian describing the Ising chain in a transverse magnetic field is the archetypal example of a system that undergoes a transition at a quantum critical point (QCP). The columbite CoNb2O6 is the closest realization of the transverse Ising magnet found to date. At low temperatures, neutron diffraction has observed a set of discrete collective spin modes near the QCP. Here, we ask if there are low-lying spin excitations distinct from these relatively high-energy modes. Using the heat capacity, we show that a significant band of gapless spin excitations exists. At the QCP, their spin entropy rises to a prominent peak that accounts for 30% of the total spin degrees of freedom. In a narrow field interval below the QCP, the gapless excitations display a fermion-like, temperature-linear heat capacity below 1 K. These novel gapless modes are the main spin excitations participating in, and affected by, the quantum transition. PMID:26146018

  6. Isodynamic axisymmetric equilibrium near the magnetic axis

    SciTech Connect

    Arsenin, V. V.

    2013-08-15

    Plasma equilibrium near the magnetic axis of an axisymmetric toroidal magnetic confinement system is described in orthogonal flux coordinates. For the case of a constant current density in the vicinity of the axis and magnetic surfaces with nearly circular cross sections, expressions for the poloidal and toroidal magnetic field components are obtained in these coordinates by using expansion in the reciprocal of the aspect ratio. These expressions allow one to easily derive relationships between quantities in an isodynamic equilibrium, in which the absolute value of the magnetic field is constant along the magnetic surface (Palumbo’s configuration)

  7. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  8. Direct conversion technology

    NASA Technical Reports Server (NTRS)

    Massier, Paul F.; Bankston, C. P.; Williams, R.; Underwood, M.; Jeffries-Nakamura, B.; Fabris, G.

    1989-01-01

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. This report contains progress of research on the Alkali Metal Thermal-to-Electric Converter (AMTEC), and on the Two-Phase Liquid-Metal Magnetohydrodynamic Electrical Generator (LMMHD) for the period January 1, 1989 through December 31, 1989. Research on these concepts was initiated during October 1987. Reports prepared on previous occasions contain discussions on the following other direct conversion concepts: thermoelectric, pyroelectric, thermionic, thermophotovoltaic, thermoacoustic, thermomagnetic, thermoelastic (nitinol heat engines); and also, more complete discussions of AMTEC and LMMHD systems.

  9. Direct conversion technology

    SciTech Connect

    Massier, P.F.; Back, L.H.; Ryan, M.A.; Fabris, G.

    1992-01-07

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. This report contains progress of research on the Alkali Metal Thermal-to-Electric Converter (AMTEC) and on the Two-Phase Liquid-Metal MHD Electrical Generator (LMMHD) for the period January 1, 1991 through December 31, 1991. Research on AMTEC and on LMMHD was initiated during October 1987. Reports prepared on previous occasions (Refs. 1--5) contain descriptive and performance discussions of the following direct conversion concepts: thermoelectric, pyroelectric, thermionic, thermophotovoltaic, thermoacoustic, thermomagnetic, thermoelastic (Nitionol heat engine); and also, more complete descriptive discussions of AMTEC and LMMHD systems.

  10. Digital optical conversion module

    DOEpatents

    Kotter, D.K.; Rankin, R.A.

    1988-07-19

    A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer. 2 figs.

  11. Digital optical conversion module

    DOEpatents

    Kotter, Dale K.; Rankin, Richard A.

    1991-02-26

    A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer.

  12. Dipolar magnets and glasses: Neutron-scattering, dynamical, and calorimetric studies of randomly distributed Ising spins

    SciTech Connect

    Reich, D.H.; Ellman, B.; Yang, J.; Rosenbaum, T.F. . James Franck Institute University of Chicago, Chicago, IL . Department of Physics); Aeppli, G. ); Belanger, D.P. )

    1990-09-01

    We have measured the magnetic correlations, susceptibility, specific heat, and thermal relaxation in the dipolar-coupled Ising system LiHo{sub {ital x}}Y{sub 1{minus}{ital x}}F{sub 4}. The material is ferromagnetic for spin concentrations at least as low as {ital x}=0.46, with a Curie temperature obeying mean-field scaling relative to that of pure LiHoF{sub 4}. In contrast, an {ital x}=0.167 sample behaves as a spin glass above its transition temperature, while an {ital x}=0.045 crystal shows very different glassy properties characterized by decreasing barriers to relaxation and nonexponential thermal relaxation as {ital T}{r arrow}0. We find the properties of the {ital x}=0.045 system to be consistent with a single low-degeneracy ground state with a large gap for excitations. The {ital x}=0.167 sample, however, supports a complex ground state with no appreciable gap, in accordance with prevailing theories of spin glasses. The underlying causes of such disparate behavior are discussed in terms of random clusters as probed by neutron studies of the {ital x}=0.167 sample.

  13. Quantum correlated cluster mean-field theory applied to the transverse Ising model

    NASA Astrophysics Data System (ADS)

    Zimmer, F. M.; Schmidt, M.; Maziero, Jonas

    2016-06-01

    Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations.

  14. Critical wetting in the two-dimensional Ising ferromagnet confined between inhomogeneous walls

    NASA Astrophysics Data System (ADS)

    Trobo, Marta L.; Albano, Ezequiel V.

    2014-12-01

    We present a numerical study of the critical wetting behavior of an Ising magnet confined between two walls, separated by a distance L, where short-range inhomogeneous surface magnetic fields act. So, samples are assumed to have a size L × M, L being the width and M the length, respectively. By considering surface fields varying spatially with a given wavelength or period (λ), H1(x,λ) with 1 ≤ x ≤ M, we found that the wetting temperature is given by the exact result of Abraham [D.B. Abraham, Phys. Rev. Lett. 44, 1165 (1980)] provided that an effective field given by the spacial average[-3.4mm] value (Heff ≡ 1/λ ƒ0 λH1(x,λ)dx > 0) is considered. The above results hold in the low wavelength regime, while for λ → ∞ and a bivaluated surface field (i.e., Hmax for x ≤ M/ 2, and δHmax for x>M/ 2, with 0 <δ< 1), one observes two almost independent wetting transitions, both being compatible with Abraham's exact results corresponding to Hmax and δHmax, respectively. On the other hand, for H1(x,λ) ≠ 0 but Heff = 0 bulk standard critical behavior results is observed.

  15. The Finite-Size Scaling Study of the Ising Model for the Fractals

    NASA Astrophysics Data System (ADS)

    Merdan, Z.; Bayirli, M.; Günen, A.; Bülbül, M.

    2016-04-01

    The fractals are obtained by using the model of diffusion-limited aggregation (DLA) for 40 ≤ L ≤ 240. The two-dimensional Ising model is simulated on the Creutz cellular automaton for 40 ≤ L ≤ 240. The critical exponents and the fractal dimensions are computed to be β = 0.124(8), γ = 1.747(10), α = 0.081(21), δ = 14.994(11), η = 0.178(10), ν = 0.960(23) and df^{β } =1.876(8), df^{γ } =3.747(10), df^{α } =2.081(68), df^{δ } =1.940(22), df^{η } =2.178(10), df^{ν } =2.960(22), which are consistent with the theoretical values of β = 0.125, γ = 1.75, α = 0, δ = 15, η = 0.25, ν = 1 and df^{β } =1.875, df^{γ } =3.75, df^{α } =2, df^{δ } =1.933, df^{η } =2.25, df^{ν } =3.

  16. Finite-size critical scaling in Ising spin glasses in the mean-field regime

    NASA Astrophysics Data System (ADS)

    Aspelmeier, T.; Katzgraber, Helmut G.; Larson, Derek; Moore, M. A.; Wittmann, Matthew; Yeo, Joonhyun

    2016-03-01

    We study in Ising spin glasses the finite-size effects near the spin-glass transition in zero field and at the de Almeida-Thouless transition in a field by Monte Carlo methods and by analytical approximations. In zero field, the finite-size scaling function associated with the spin-glass susceptibility of the Sherrington-Kirkpatrick mean-field spin-glass model is of the same form as that of one-dimensional spin-glass models with power-law long-range interactions in the regime where they can be a proxy for the Edwards-Anderson short-range spin-glass model above the upper critical dimension. We also calculate a simple analytical approximation for the spin-glass susceptibility crossover function. The behavior of the spin-glass susceptibility near the de Almeida-Thouless transition line has also been studied, but here we have only been able to obtain analytically its behavior in the asymptotic limit above and below the transition. We have also simulated the one-dimensional system in a field in the non-mean-field regime to illustrate that when the Imry-Ma droplet length scale exceeds the system size one can then be erroneously lead to conclude that there is a de Almeida-Thouless transition even though it is absent.

  17. Minority-spin dynamics in the nonhomogeneous Ising model: Diverging time scales and exponents

    NASA Astrophysics Data System (ADS)

    Mullick, Pratik; Sen, Parongama

    2016-05-01

    We investigate the dynamical behavior of the Ising model under a zero-temperature quench with the initial fraction of up spins 0 ≤x ≤1 . In one dimension, the known results for persistence probability are verified; it shows algebraic decay for both up and down spins asymptotically with different exponents. It is found that the conventional finite-size scaling is valid here. In two dimensions, however, the persistence probabilities are no longer algebraic; in particular for x ≤0.5 , persistence for the up (minority) spins shows the behavior Pmin(t ) ˜t-γexp[-(t/τ ) δ] with time t , while for the down (majority) spins, Pmaj(t ) approaches a finite value. We find that the timescale τ diverges as (xc-x ) -λ, where xc=0.5 and λ ≃2.31 . The exponent γ varies as θ2 d+c0(xc-x ) β where θ2 d≃0.215 is very close to the persistence exponent in two dimensions; β ≃1 . The results in two dimensions can be understood qualitatively by studying the exit probability, which for different system size is found to have the form E (x ) =f [(x/-xc xc) L1 /ν] , with ν ≈1.47 . This result suggests that τ ˜Lz ˜ , where z ˜=λ/ν =1.57 ±0.11 is an exponent not explored earlier.

  18. Bond-cluster approximation to the axial next-nearest-neighbor Ising model

    NASA Astrophysics Data System (ADS)

    Taylor, James H.; Desjardins, J. S.

    1984-11-01

    The three-dimensional simple-cubic spin- 1/2 axial next-nearest-neighbor Ising model is studied by means of Kikuchi's cluster-variation method employing a new technique described previously [J. S. Desjardins and O. Steinsvoll,

    [Phys. Scr. 28, 565 (1983)]
    for the solution of the general equations of equilibrium. The particular solution employed in this paper is equivalent to Bethe's first approximation and yields a surprisingly rich phase diagram with modulated structures appearing up to a repeat distance of 15 planes (the highest studied). The phase diagram obtained by our technique resembles closely the mean-field, spin- 1/2 phase diagram of von Boehm and Bak with some significant differences: The second-order boundary of the paramagnetic region is at a significantly lower temperature with a minimum at | κ |˜0.4, where κ is the ratio of the antiferromagnetic to the ferromagnetic coupling constant. In addition, we are able to follow the temperature dependence of the shape of the modulated solutions from the squared-off, low-temperature behavior of Selke and Fisher to the sinusoidal behavior of the high-temperature, mean-field results. The position of our Lifshitz point is in good agreement with previous results, as is the conclusion that transitions between phases are of first order. By contrast, in two dimensions the same approximation completely fails to reproduce reported features of the phase diagram.

  19. Relations between short-range and long-range Ising models.

    PubMed

    Angelini, Maria Chiara; Parisi, Giorgio; Ricci-Tersenghi, Federico

    2014-06-01

    We perform a numerical study of the long-range (LR) ferromagnetic Ising model with power law decaying interactions (J∝r{-d-σ}) on both a one-dimensional chain (d=1) and a square lattice (d=2). We use advanced cluster algorithms to avoid the critical slowing down. We first check the validity of the relation connecting the critical behavior of the LR model with parameters (d,σ) to that of a short-range (SR) model in an equivalent dimension D. We then study the critical behavior of the d=2 LR model close to the lower critical σ, uncovering that the spatial correlation function decays with two different power laws: The effect of the subdominant power law is much stronger than finite-size effects and actually makes the estimate of critical exponents very subtle. By including this subdominant power law, the numerical data are consistent with the standard renormalization group (RG) prediction by Sak [Phys. Rev. B 8, 281 (1973)], thus making not necessary (and unlikely, according to Occam's razor) the recent proposal by Picco [arXiv:1207.1018] of having a new set of RG fixed points in addition to the mean-field one and the SR one. PMID:25019738

  20. Linking market interaction intensity of 3D Ising type financial model with market volatility

    NASA Astrophysics Data System (ADS)

    Fang, Wen; Ke, Jinchuan; Wang, Jun; Feng, Ling

    2016-11-01

    Microscopic interaction models in physics have been used to investigate the complex phenomena of economic systems. The simple interactions involved can lead to complex behaviors and help the understanding of mechanisms in the financial market at a systemic level. This article aims to develop a financial time series model through 3D (three-dimensional) Ising dynamic system which is widely used as an interacting spins model to explain the ferromagnetism in physics. Through Monte Carlo simulations of the financial model and numerical analysis for both the simulation return time series and historical return data of Hushen 300 (HS300) index in Chinese stock market, we show that despite its simplicity, this model displays stylized facts similar to that seen in real financial market. We demonstrate a possible underlying link between volatility fluctuations of real stock market and the change in interaction strengths of market participants in the financial model. In particular, our stochastic interaction strength in our model demonstrates that the real market may be consistently operating near the critical point of the system.

  1. Effects of global brightening on primary production and hypoxia in Ise Bay, Japan

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoji; Kanno, Ariyo; Shinohara, Ryuichiro

    2014-07-01

    In many parts of the world, annual mean surface solar radiation (SSR) has undergone significant decadal changes; however, its effect on the coastal water environment has not been investigated. This study investigates the effects of changes in the SSR on hypoxia and the primary production of phytoplankton in a eutrophic bay in Japan (Ise Bay), where the annual SSR increased by 13.3% from 1980 to 2010. We numerically simulated the hydrodynamics and ecosystem of 2010 using a three-dimensional model (case O). We used this model to simulate the case where SSR was reduced by 10% (case A) and estimated the effect of an increase in SSR from the difference between case O and case A. With the 10% increase in SSR, the primary production in the bay increased by only 2.8%. This limited increase was the result of the negative effects by the nonlinearity of the light limitation function (including the photoinhibition) and the limitation in PO4-P availability and a significant positive effect by the increased water temperature. Similarly, the overall volume of hypoxic water increased, and in August, it increased by 5.8%. This is because water temperature and biomass such as phytoplankton increased with the increase in SSR; consequently, all oxygen consumption terms such as biological respiration also increased. These results imply that recent global brightening has the potential to amplify the primary production and hypoxia in a eutrophic bay.

  2. Ising model of cardiac thin filament activation with nearest-neighbor cooperative interactions

    NASA Technical Reports Server (NTRS)

    Rice, John Jeremy; Stolovitzky, Gustavo; Tu, Yuhai; de Tombe, Pieter P.; Bers, D. M. (Principal Investigator)

    2003-01-01

    We have developed a model of cardiac thin filament activation using an Ising model approach from equilibrium statistical physics. This model explicitly represents nearest-neighbor interactions between 26 troponin/tropomyosin units along a one-dimensional array that represents the cardiac thin filament. With transition rates chosen to match experimental data, the results show that the resulting force-pCa (F-pCa) relations are similar to Hill functions with asymmetries, as seen in experimental data. Specifically, Hill plots showing (log(F/(1-F)) vs. log [Ca]) reveal a steeper slope below the half activation point (Ca(50)) compared with above. Parameter variation studies show interplay of parameters that affect the apparent cooperativity and asymmetry in the F-pCa relations. The model also predicts that Ca binding is uncooperative for low [Ca], becomes steeper near Ca(50), and becomes uncooperative again at higher [Ca]. The steepness near Ca(50) mirrors the steep F-pCa as a result of thermodynamic considerations. The model also predicts that the correlation between troponin/tropomyosin units along the one-dimensional array quickly decays at high and low [Ca], but near Ca(50), high correlation occurs across the whole array. This work provides a simple model that can account for the steepness and shape of F-pCa relations that other models fail to reproduce.

  3. Finite-size critical scaling in Ising spin glasses in the mean-field regime.

    PubMed

    Aspelmeier, T; Katzgraber, Helmut G; Larson, Derek; Moore, M A; Wittmann, Matthew; Yeo, Joonhyun

    2016-03-01

    We study in Ising spin glasses the finite-size effects near the spin-glass transition in zero field and at the de Almeida-Thouless transition in a field by Monte Carlo methods and by analytical approximations. In zero field, the finite-size scaling function associated with the spin-glass susceptibility of the Sherrington-Kirkpatrick mean-field spin-glass model is of the same form as that of one-dimensional spin-glass models with power-law long-range interactions in the regime where they can be a proxy for the Edwards-Anderson short-range spin-glass model above the upper critical dimension. We also calculate a simple analytical approximation for the spin-glass susceptibility crossover function. The behavior of the spin-glass susceptibility near the de Almeida-Thouless transition line has also been studied, but here we have only been able to obtain analytically its behavior in the asymptotic limit above and below the transition. We have also simulated the one-dimensional system in a field in the non-mean-field regime to illustrate that when the Imry-Ma droplet length scale exceeds the system size one can then be erroneously lead to conclude that there is a de Almeida-Thouless transition even though it is absent. PMID:27078308

  4. Long-range Ising model for credit portfolios with heterogeneous credit exposures

    NASA Astrophysics Data System (ADS)

    Kato, Kensuke

    2016-11-01

    We propose the finite-size long-range Ising model as a model for heterogeneous credit portfolios held by a financial institution in the view of econophysics. The model expresses the heterogeneity of the default probability and the default correlation by dividing a credit portfolio into multiple sectors characterized by credit rating and industry. The model also expresses the heterogeneity of the credit exposure, which is difficult to evaluate analytically, by applying the replica exchange Monte Carlo method to numerically calculate the loss distribution. To analyze the characteristics of the loss distribution for credit portfolios with heterogeneous credit exposures, we apply this model to various credit portfolios and evaluate credit risk. As a result, we show that the tail of the loss distribution calculated by this model has characteristics that are different from the tail of the loss distribution of the standard models used in credit risk modeling. We also show that there is a possibility of different evaluations of credit risk according to the pattern of heterogeneity.

  5. Ising Critical Behavior of Inhomogeneous Curie-Weiss Models and Annealed Random Graphs

    NASA Astrophysics Data System (ADS)

    Dommers, Sander; Giardinà, Cristian; Giberti, Claudio; van der Hofstad, Remco; Prioriello, Maria Luisa

    2016-11-01

    We study the critical behavior for inhomogeneous versions of the Curie-Weiss model, where the coupling constant {J_{ij}(β)} for the edge {ij} on the complete graph is given by {J_{ij}(β)=β w_iw_j/( {sum_{kin[N]}w_k})}. We call the product form of these couplings the rank-1 inhomogeneous Curie-Weiss model. This model also arises [with inverse temperature {β} replaced by {sinh(β)} ] from the annealed Ising model on the generalized random graph. We assume that the vertex weights {(w_i)_{iin[N]}} are regular, in the sense that their empirical distribution converges and the second moment converges as well. We identify the critical temperatures and exponents for these models, as well as a non-classical limit theorem for the total spin at the critical point. These depend sensitively on the number of finite moments of the weight distribution. When the fourth moment of the weight distribution converges, then the critical behavior is the same as on the (homogeneous) Curie-Weiss model, so that the inhomogeneity is weak. When the fourth moment of the weights converges to infinity, and the weights satisfy an asymptotic power law with exponent {τ} with {τin(3,5)}, then the critical exponents depend sensitively on {τ}. In addition, at criticality, the total spin {S_N} satisfies that {S_N/N^{(τ-2)/(τ-1)}} converges in law to some limiting random variable whose distribution we explicitly characterize.

  6. Quantum Quench Dynamics in the Transverse Field Ising Model at Non-zero Temperatures

    NASA Astrophysics Data System (ADS)

    Abeling, Nils; Kehrein, Stefan

    The recently discovered Dynamical Phase Transition denotes non-analytic behavior in the real time evolution of quantum systems in the thermodynamic limit and has been shown to occur in different systems at zero temperature [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. In this talk we present the extension of the analysis to non-zero temperature by studying a generalized form of the Loschmidt echo, the work distribution function, of a quantum quench in the transverse field Ising model. Although the quantitative behavior at non-zero temperatures still displays features derived from the zero temperature non-analyticities, it is shown that in this model dynamical phase transitions do not exist if T > 0 . This is a consequence of the system being initialized in a thermal state. Moreover, we elucidate how the Tasaki-Crooks-Jarzynski relation can be exploited as a symmetry relation for a global quench or to obtain the change of the equilibrium free energy density. This work was supported through CRC SFB 1073 (Project B03) of the Deutsche Forschungsgemeinschaft (DFG).

  7. Initial survey of the wave distribution functions for plasmaspheric hiss observed by ISEE 1

    SciTech Connect

    Storey, L.R.O. ); Lefeuvre, F.; Parrot, M.; Cairo, L. ); Anderson, R.R. )

    1991-11-01

    Multicomponent ELF/VLF wave data from the ISEE 1 satellite have been analyzed with the aim of identifying the generation mechanism of plasmaspheric hiss, and especially of determining whether it involves wave propagation of cyclic trajectories. The data were taken from four passes of the satellite, of which two were close to the geomagnetic equatorial plane and two were farther from it; all four occurred during magnetically quiet periods. The principal method of analysis was calculation of the wave distribution functions. The waves appear to have been generated over a wide range of altitudes within the plasmasphere, and most, though not all, of them were propagating obliquely with respect to the Earth's magnetic field. On one of the passes near the equator, some wave energy was observed at small wave normal angles, and these waves may have been propagating on cyclic trajectories. Even here, however, obliquely propagating waves were predominant, a finding that is difficult to reconcile with the classical quasi-linear generation mechanism or its variants. The conclusion is that another mechanism, probably nonlinear, must have been generating most of the hiss observed on these four passes.

  8. Ising Models, Universality and the Non Renormalization of the Quantum Anomalies

    NASA Astrophysics Data System (ADS)

    Mastropietro, Vieri

    2010-03-01

    A number of universal relations (proposed by Kadanoff, Luther, Peschel and Haldane) are believed to be true in a wide class of systems with continuously varying indices, among which are interacting planar Ising models, vertex or Ashkin-Teller models, quantum spin chains and 1D Fermi systems; by such relations one can predict several quantities in terms of a few measurable parameters without relying on the specific microscopic details. The validity of such relations can be checked in special solvable models but, despite several attempts, the proof of their general validity was up to now an open problem. A rigorous derivation of several of such relations (for solvable and not solvable models and without any use of exact solutions) has been recently obtained in [8] and [11] through Renormalization Group methods. The proof is based on the representation in terms of Grassmann integrals and the validity of the Adler-Bardeen property of the non renormalization of the quantum anomalies in the asymptotic Ward identities. Gauge invariance is exact only in the scaling limit but the lattice corrections can be rigorously taken into account.

  9. Belief-propagation algorithm and the Ising model on networks with arbitrary distributions of motifs

    NASA Astrophysics Data System (ADS)

    Yoon, S.; Goltsev, A. V.; Dorogovtsev, S. N.; Mendes, J. F. F.

    2011-10-01

    We generalize the belief-propagation algorithm to sparse random networks with arbitrary distributions of motifs (triangles, loops, etc.). Each vertex in these networks belongs to a given set of motifs (generalization of the configuration model). These networks can be treated as sparse uncorrelated hypergraphs in which hyperedges represent motifs. Here a hypergraph is a generalization of a graph, where a hyperedge can connect any number of vertices. These uncorrelated hypergraphs are treelike (hypertrees), which crucially simplifies the problem and allows us to apply the belief-propagation algorithm to these loopy networks with arbitrary motifs. As natural examples, we consider motifs in the form of finite loops and cliques. We apply the belief-propagation algorithm to the ferromagnetic Ising model with pairwise interactions on the resulting random networks and obtain an exact solution of this model. We find an exact critical temperature of the ferromagnetic phase transition and demonstrate that with increasing the clustering coefficient and the loop size, the critical temperature increases compared to ordinary treelike complex networks. However, weak clustering does not change the critical behavior qualitatively. Our solution also gives the birth point of the giant connected component in these loopy networks.

  10. Droplets pinned at chemically inhomogenous substrates: A simulation study of the two-dimensional Ising case.

    PubMed

    Trobo, Marta L; Albano, Ezequiel V; Binder, Kurt

    2016-05-01

    As a simplified model of a liquid nanostripe adsorbed on a chemically structured substrate surface, a two-dimensional Ising system with two boundaries at which surface fields act is studied. At the upper boundary, the surface field is uniformly negative, while at the lower boundary (a distance L apart), the surface field is negative only outside a range of extension b, where a positive surface stabilizes a droplet of the phase with positive magnetization for temperatures T exceeding the critical temperature T_{w} of the wetting transition of this model. We investigate the local order parameter profiles across the droplet, both in the directions parallel and perpendicular to the substrate, varying both b and T. Also, precursor effects to droplet formation as T approaches T_{w} from below are studied. In accord with theoretical predictions, for T>T_{w} the droplet is found to have the shape of a semiellipse, where the width (distance of the interface from the substrate) scale is proportional to b (b^{1/2}). So, the area of the droplet is proportional to b^{3/2}, and the temperature dependence of the corresponding prefactor, which also involves the interfacial stiffness, is studied. PMID:27300962

  11. Exact Enumeration of the Phase Space of an Ising Model of Ni2MnGa

    SciTech Connect

    Eisenbach, Markus; Brown, Greg; Rusanu, Aurelian; Odbadrakh, Khorgolkhuu; Nicholson, Don M; McCarthy, Carrie V.

    2013-01-01

    Exact evaluations of partition functions are generally prohibitively expensive due to exponential growth of phase space with the number of degrees of freedom. For an Ising model with sites the number of possible states is requiring the use of better scaling methods such as importance sampling Monte-Carlo calculations for all but the smallest systems. Yet the ability to obtain exact solutions for as large as possible systems can provide important benchmark results and opportunities for unobscured insight into the underlying physicsofthesystem.HerewepresentanIsingmodelforthemagneticsublatticesoftheimportantmagneto-caloricmaterialNi MnGa and use an exact enumeration algorithm to calculate the number of states for each energy and sublattice magne- tizations and . This allows the efficient calculation of the partition function and derived thermodynamic quantities such as specific heat and susceptibility. Utilizing the jaguarpf system at Oak Ridge we are able to calculate for systems of up to48sites,whichprovidesimportantinsightintothemechanismforthelargemagnet-caloriceffectinNi MnGaaswellasanimportant benchmark for Monte-Carlo (esp. Wang-Landau method).

  12. Quantum critical behavior of the quantum Ising model on fractal lattices

    NASA Astrophysics Data System (ADS)

    Yi, Hangmo

    2015-01-01

    I study the properties of the quantum critical point of the transverse-field quantum Ising model on various fractal lattices such as the Sierpiński carpet, Sierpiński gasket, and Sierpiński tetrahedron. Using a continuous-time quantum Monte Carlo simulation method and finite-size scaling analysis, I identify the quantum critical point and investigate its scaling properties. Among others, I calculate the dynamic critical exponent and find that it is greater than one for all three structures. The fact that it deviates from one is a direct consequence of the fractal structures not being integer-dimensional regular lattices. Other critical exponents are also calculated. The exponents are different from those of the classical critical point and satisfy the quantum scaling relation, thus confirming that I have indeed found the quantum critical point. I find that the Sierpiński tetrahedron, of which the dimension is exactly 2, belongs to a different universality class than that of the two-dimensional square lattice. I conclude that the critical exponents depend on more details of the structure than just the dimension and the symmetry.

  13. Spot size variation FCS in simulations of the 2D Ising model

    NASA Astrophysics Data System (ADS)

    Burns, Margaret C.; Nouri, Mariam; Veatch, Sarah L.

    2016-06-01

    Spot variation fluorescence correlation spectroscopy (svFCS) was developed to study the movement and organization of single molecules in plasma membranes. This experimental technique varies the size of an illumination area while measuring correlations in time using standard fluorescence correlation methods. Frequently, this data is interpreted using the assumption that correlation measurements reflect the dynamics of single molecule motions, and not motions of the average composition. Here, we explore how svFCS measurements report on the dynamics of components diffusing within simulations of a 2D Ising model with a conserved order parameter. Simulated correlation functions report on both the fast dynamics of single component mobility and the slower dynamics of the average composition. Over a range of simulation conditions, a conventional svFCS analysis suggests the presence of anomalous diffusion even though single molecule motions are nearly Brownian in these simulations. This misinterpretation is most significant when the surface density of the fluorescent label is elevated, therefore we suggest future measurements be made over a range of tracer densities. Some simulation conditions reproduce qualitative features of published svFCS experimental data. Overall, this work emphasizes the need to probe membranes using multiple complimentary experimental methodologies in order to draw conclusions regarding the nature of spatial and dynamical heterogeneity in these systems.

  14. Hysteresis in DNA compaction by Dps is described by an Ising model.

    PubMed

    Vtyurina, Natalia N; Dulin, David; Docter, Margreet W; Meyer, Anne S; Dekker, Nynke H; Abbondanzieri, Elio A

    2016-05-01

    In all organisms, DNA molecules are tightly compacted into a dynamic 3D nucleoprotein complex. In bacteria, this compaction is governed by the family of nucleoid-associated proteins (NAPs). Under conditions of stress and starvation, an NAP called Dps (DNA-binding protein from starved cells) becomes highly up-regulated and can massively reorganize the bacterial chromosome. Although static structures of Dps-DNA complexes have been documented, little is known about the dynamics of their assembly. Here, we use fluorescence microscopy and magnetic-tweezers measurements to resolve the process of DNA compaction by Dps. Real-time in vitro studies demonstrated a highly cooperative process of Dps binding characterized by an abrupt collapse of the DNA extension, even under applied tension. Surprisingly, we also discovered a reproducible hysteresis in the process of compaction and decompaction of the Dps-DNA complex. This hysteresis is extremely stable over hour-long timescales despite the rapid binding and dissociation rates of Dps. A modified Ising model is successfully applied to fit these kinetic features. We find that long-lived hysteresis arises naturally as a consequence of protein cooperativity in large complexes and provides a useful mechanism for cells to adopt unique epigenetic states.

  15. Monte Carlo simulation of domain growth in the kinetic Ising model on the connection machine

    NASA Astrophysics Data System (ADS)

    Amar, Jacques G.; Sullivan, Francis

    1989-10-01

    A fast multispin algorithm for the Monte Carlo simulation of the two-dimensional spin-exchange kinetic Ising model, previously described by Sullivan and Mountain and used by Amar et al. has been adapted for use on the Connection Machine and applied as a first test in a calculation of domain growth. Features of the code include: (a) the use of demon bits, (b) the simulation of several runs simultaneously to improve the efficiency of the code, (c) the use of virtual processors to simulate easily and efficiently a larger system size, (d) the use of the (NEWS) grid for last communication between neighbouring processors and updating of boundary layers, (e) the implementation of an efficient random number generator much faster than that provided by Thinking Machines Corp., and (f) the use of the LISP function "funcall" to select which processors to update. Overall speed of the code when run on a (128x128) processor machine is about 130 million attempted spin-exchanges per second, about 9 times faster than the comparable code, using hardware vectorised-logic operations and 64-bit multispin coding on the Cyber 205. The same code can be used on a larger machine (65 536 processors) and should produce speeds in excess of 500 million attempted spin-exchanges per second.

  16. Dynamic magnetizations and dynamic phase transitions in a transverse cylindrical Ising nanowire

    NASA Astrophysics Data System (ADS)

    Deviren, Bayram; Ertaş, Mehmet; Keskin, Mustafa

    2012-05-01

    In this paper, we extend the paper of Kaneyoshi (2010 J. Magn. Magn. Mater. 322 3410-5) to investigate the dynamic magnetizations and dynamic phase transitions of a transverse cylindrical Ising nanowire system by using the effective field theory with correlations and the Glauber-type stochastic dynamics under a time-dependent oscillating external magnetic field. The dynamic effective field equations for the average longitudinal and transverse magnetizations on the surface shell and core are derived by using the Glauber transition rates. Temperature dependences of the dynamic longitudinal magnetizations, the transverse magnetizations and the total magnetizations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system is strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, four different types of compensation behaviors in the Néel classification nomenclature exist in the system. The results are compared with some theoretical works and good overall agreement is observed.

  17. Counterstreaming hydrogen and oxygen ions observed in the magnetosphere on ISEE-1

    NASA Technical Reports Server (NTRS)

    Horita, R. E.; Ungstrup, E.; Sharp, R. D.; Anderson, R. R.; Fitzenreiter, R. J.

    1985-01-01

    Counterstreaming ions or ions travelling simultaneously both parallel and antiparallel to the magnetic field direction have been briefly noted in the literature but have not been studied previously in depth. Over 60 counterstreaming ion (CSI) events observed on the ISEE-1 satellite have been studied. They were found to occur at altitudes of about 2 to 8 earth radii on L shells of about 5 to 12 in the evening-to-morning sector from about 1700-0900 LT. Often both oxygen and hydrogen ions at a number of energy levels are counterstreaming but some events show only either oxygen or hydrogen ions involved. One particularly interesting event shows only counterstreaming oxygen ions with 417 eV energy; oxygen ions of lower energy (215 eV) and above (630-17,000 eV) and all the hydrogen ions between 215-17,000 eV energy have lower fluxes and/or nearly isotropic pitch angle distributions. This event correlates well with wave activity in the 17-100 Hz band and is also accompanied by 200 eV downgoing and 400 eV upgoing electrons. Details of this event and the other counterstreaming events are presented.

  18. Hidden rotational symmetry in a generalized Ising model with rectangular symmetry

    NASA Astrophysics Data System (ADS)

    Deng, Hai-Yao; Hu, Kaige

    2011-08-01

    Novel quantum phases are of interest both fundamentally and practically. In this paper, a toy lattice model with exact four-fold rotational symmetry (C4), which can be taken as a straightforward generalization of the usual Ising model, is studied. The phase diagram in the t-T plane is plotted, where t is the energy controlling quantum fluctuations and T is the temperature. The diagram features an exotic phase (termed the S-phase), which meets the conventional ordered and disordered phases at a tri-critical point. The S-phase distinguishes itself from the conventional ordered phase by its symmetry properties. In fact, it is shown to arise from the spontaneous breaking of the continuous rotational symmetry rather than the C4 symmetry. This is manifested in the long-wavelength fluctuations, which are shown to be the gapless Nambu-Goldstone modes following a quadratic dispersion relation, similar to that of the XY model. Further, discontinuous quantum phase transitions are found and they are argued to occur subsequent to the S-phase.

  19. Quantum correlated cluster mean-field theory applied to the transverse Ising model.

    PubMed

    Zimmer, F M; Schmidt, M; Maziero, Jonas

    2016-06-01

    Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations.

  20. Ion composition experiment. [ISEE-C solar wind ion mass spectroscopy

    NASA Technical Reports Server (NTRS)

    Coplan, M. A.; Ogilvie, K. W.; Bochsler, P. A.; Geiss, J.

    1978-01-01

    An investigation using a novel ion mass spectrometer for measuring the ionic composition of the solar wind from the ISEE-C spacecraft is described. The resolution and dynamic range of the instrument are sufficient to be able to resolve up to twelve individual ions or groups of ions. This will permit the solution of a number of fundamental problems related to solar abundances and the formation of the solar wind. The spectrometer is composed of a stigmatic Wien filter and hemispherical electrostatic energy analyzer. The use of curved electric field plates in the filter results in a substantial saving of weight with respect to a conventional filter of the same resolution and angular acceptance. The spectrometer is controlled by a microprocessor based on a special purpose computer which has three modes of operations: full and partial survey modes and a search mode. In the search mode, the instrument locks on to the solar wind. This allows four times the time resolution of the full survey mode and yields a full mass spectrum every 12.6 min.

  1. Spinodals of the Ising model on the order-4 pentagonal tiling of the hyperbolic plane

    NASA Astrophysics Data System (ADS)

    Richards, Howard L.

    In the Euclidean plane, the Ising model on a regular lattice does not have a true spinodal - that is, there is no local minimum of the free energy that persists forever (in the limit of infinitely large systems) except for the global minimum, which characterizes the stable state. However, a local minimum can persist for a very long time, so the minimum can be referred to as a ``metastable'' state. The manner in which the metastable state decays depends on the strength of the magnetic field and the system size; the ``thermodynamic spinodal'' is the transition between systems large enough to contain a single critical droplet and systems that are too small to do so, and the ``dynamic spinodal'' marks the transition between decay as a Poisson process to decay that is ``deterministic'', meaning the standard deviation of the lifetime of the metastable state is small compared with its mean value. However, in the hyperbolic plane, true metastability exists, and evidence shows that the thermodynamic spinodal and dynamic spinodal are numerically close to the true spinodal, the field below which the metastable state cannot decay through the nucleation and growth of droplets. This research was supported by NSF Grant OCI-1005117.

  2. Droplets pinned at chemically inhomogenous substrates: A simulation study of the two-dimensional Ising case.

    PubMed

    Trobo, Marta L; Albano, Ezequiel V; Binder, Kurt

    2016-05-01

    As a simplified model of a liquid nanostripe adsorbed on a chemically structured substrate surface, a two-dimensional Ising system with two boundaries at which surface fields act is studied. At the upper boundary, the surface field is uniformly negative, while at the lower boundary (a distance L apart), the surface field is negative only outside a range of extension b, where a positive surface stabilizes a droplet of the phase with positive magnetization for temperatures T exceeding the critical temperature T_{w} of the wetting transition of this model. We investigate the local order parameter profiles across the droplet, both in the directions parallel and perpendicular to the substrate, varying both b and T. Also, precursor effects to droplet formation as T approaches T_{w} from below are studied. In accord with theoretical predictions, for T>T_{w} the droplet is found to have the shape of a semiellipse, where the width (distance of the interface from the substrate) scale is proportional to b (b^{1/2}). So, the area of the droplet is proportional to b^{3/2}, and the temperature dependence of the corresponding prefactor, which also involves the interfacial stiffness, is studied.

  3. Quantum correlated cluster mean-field theory applied to the transverse Ising model.

    PubMed

    Zimmer, F M; Schmidt, M; Maziero, Jonas

    2016-06-01

    Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations. PMID:27415217

  4. Information transfer and criticality in the Ising model on the human connectome.

    PubMed

    Marinazzo, Daniele; Pellicoro, Mario; Wu, Guorong; Angelini, Leonardo; Cortés, Jesús M; Stramaglia, Sebastiano

    2014-01-01

    We implement the Ising model on a structural connectivity matrix describing the brain at two different resolutions. Tuning the model temperature to its critical value, i.e. at the susceptibility peak, we find a maximal amount of total information transfer between the spin variables. At this point the amount of information that can be redistributed by some nodes reaches a limit and the net dynamics exhibits signature of the law of diminishing marginal returns, a fundamental principle connected to saturated levels of production. Our results extend the recent analysis of dynamical oscillators models on the connectome structure, taking into account lagged and directional influences, focusing only on the nodes that are more prone to became bottlenecks of information. The ratio between the outgoing and the incoming information at each node is related to the the sum of the weights to that node and to the average time between consecutive time flips of spins. The results for the connectome of 66 nodes and for that of 998 nodes are similar, thus suggesting that these properties are scale-independent. Finally, we also find that the brain dynamics at criticality is organized maximally to a rich-club w.r.t. the network of information flows.

  5. Predictability of Conversation Partners

    NASA Astrophysics Data System (ADS)

    Takaguchi, Taro; Nakamura, Mitsuhiro; Sato, Nobuo; Yano, Kazuo; Masuda, Naoki

    2011-08-01

    Recent developments in sensing technologies have enabled us to examine the nature of human social behavior in greater detail. By applying an information-theoretic method to the spatiotemporal data of cell-phone locations, [C. Song , ScienceSCIEAS0036-8075 327, 1018 (2010)] found that human mobility patterns are remarkably predictable. Inspired by their work, we address a similar predictability question in a different kind of human social activity: conversation events. The predictability in the sequence of one’s conversation partners is defined as the degree to which one’s next conversation partner can be predicted given the current partner. We quantify this predictability by using the mutual information. We examine the predictability of conversation events for each individual using the longitudinal data of face-to-face interactions collected from two company offices in Japan. Each subject wears a name tag equipped with an infrared sensor node, and conversation events are marked when signals are exchanged between sensor nodes in close proximity. We find that the conversation events are predictable to a certain extent; knowing the current partner decreases the uncertainty about the next partner by 28.4% on average. Much of the predictability is explained by long-tailed distributions of interevent intervals. However, a predictability also exists in the data, apart from the contribution of their long-tailed nature. In addition, an individual’s predictability is correlated with the position of the individual in the static social network derived from the data. Individuals confined in a community—in the sense of an abundance of surrounding triangles—tend to have low predictability, and those bridging different communities tend to have high predictability.

  6. Somatization and conversion disorder.

    PubMed

    Hurwitz, Trevor A

    2004-03-01

    Somatization is the psychological mechanism whereby psychological distress is expressed in the form of physical symptoms. The psychological distress in somatization is most commonly caused by a mood disorder that threatens mental stability. Conversion disorder occurs when the somatic presentation involves any aspect of the central nervous system over which voluntary control is exercised. Conversion reactions represent fixed ideas about neurologic malfunction that are consciously enacted, resulting in psychogenic neurologic deficits. Treatment is complex and lengthy; it includes recovery of neurologic function aided by narcoanalysis and identification and treatment of the primary psychiatric disorder, usually a mood disorder. PMID:15101499

  7. ADEPT: Efficient Power Conversion

    SciTech Connect

    2011-01-01

    ADEPT Project: In today’s increasingly electrified world, power conversion—the process of converting electricity between different currents, voltage levels, and frequencies—forms a vital link between the electronic devices we use every day and the sources of power required to run them. The 14 projects that make up ARPA-E’s ADEPT Project, short for “Agile Delivery of Electrical Power Technology,” are paving the way for more energy efficient power conversion and advancing the basic building blocks of power conversion: circuits, transistors, inductors, transformers, and capacitors.

  8. Changes in the Proteome of Langat-Infected Ixodes scapularis ISE6 Cells: Metabolic Pathways Associated with Flavivirus Infection

    PubMed Central

    Grabowski, Jeffrey M.; Perera, Rushika; Roumani, Ali M.; Hedrick, Victoria E.; Inerowicz, Halina D.; Hill, Catherine A.; Kuhn, Richard J.

    2016-01-01

    Background Ticks (Family Ixodidae) transmit a variety of disease causing agents to humans and animals. The tick-borne flaviviruses (TBFs; family Flaviviridae) are a complex of viruses, many of which cause encephalitis and hemorrhagic fever, and represent global threats to human health and biosecurity. Pathogenesis has been well studied in human and animal disease models. Equivalent analyses of tick-flavivirus interactions are limited and represent an area of study that could reveal novel approaches for TBF control. Methodology/Principal Findings High resolution LC-MS/MS was used to analyze the proteome of Ixodes scapularis (Lyme disease tick) embryonic ISE6 cells following infection with Langat virus (LGTV) and identify proteins associated with viral infection and replication. Maximal LGTV infection of cells and determination of peak release of infectious virus, was observed at 36 hours post infection (hpi). Proteins were extracted from ISE6 cells treated with LGTV and non-infectious (UV inactivated) LGTV at 36 hpi and analyzed by mass spectrometry. The Omics Discovery Pipeline (ODP) identified thousands of MS peaks. Protein homology searches against the I. scapularis IscaW1 genome assembly identified a total of 486 proteins that were subsequently assigned to putative functional pathways using searches against the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. 266 proteins were differentially expressed following LGTV infection relative to non-infected (mock) cells. Of these, 68 proteins exhibited increased expression and 198 proteins had decreased expression. The majority of the former were classified in the KEGG pathways: “translation”, “amino acid metabolism”, and “protein folding/sorting/degradation”. Finally, Trichostatin A and Oligomycin A increased and decreased LGTV replication in vitro in ISE6 cells, respectively. Conclusions/Significance Proteomic analyses revealed ISE6 proteins that were differentially expressed at the peak of LGTV

  9. Dual-axis energy recovery linac.

    SciTech Connect

    Wang, C.-x.; Noonan, J.; Lewellen, J.

    2007-01-01

    In this paper we propose a new type of energy-recovery linac (ERL) for ERL applications. The envisioned dualaxis energy-recovery linac allows energy recovery of parallel beams, accelerating/decelerating along different axes, via the same dual-axis superconducting cavity. This new scheme offers many advantages over conventional ERLs in various applications. Preliminary feasibility considerations are presented.

  10. Multi-axis control of telemanipulators

    NASA Technical Reports Server (NTRS)

    Mckinnon, G. M.; Kruk, Ron

    1989-01-01

    The development of multi-axis hand controllers for use in telemanipulator systems is described. Experience in the control of the SRMS (shuttle remote manipulator system) arm is reviewed together with subsequent tests involving a number of simulators and configurations, including use as a side-arm flight control for helicopters. The factors affecting operator acceptability are reviewed.

  11. Horizontal Axis Levitron--A Physics Demonstration

    ERIC Educational Resources Information Center

    Michaelis, Max M.

    2014-01-01

    After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the "spignet". Precession is fundamental to nuclear magnetic…

  12. Tennis Rackets and the Parallel Axis Theorem

    NASA Astrophysics Data System (ADS)

    Christie, Derek

    2014-04-01

    This simple experiment uses an unusual graph straightening exercise to confirm the parallel axis theorem for an irregular object. Along the way, it estimates experimental values for g and the moment of inertia of a tennis racket. We use Excel to find a 95% confidence interval for the true values.

  13. Tennis Rackets and the Parallel Axis Theorem

    ERIC Educational Resources Information Center

    Christie, Derek

    2014-01-01

    This simple experiment uses an unusual graph straightening exercise to confirm the parallel axis theorem for an irregular object. Along the way, it estimates experimental values for g and the moment of inertia of a tennis racket. We use Excel to find a 95% confidence interval for the true values.

  14. Catalyst increases COS conversion

    SciTech Connect

    Goodboy, K.P.

    1985-02-18

    Increasingly stringent air quality legislation is placing greater emphasis on conversion of COS and CS/sub 2/ in Claus plants for the maximum sulfur recovery. Overall sulfur recovery goals are dependent upon outstanding service from the Claus catalyst in each reactor because catalyst activity is a major factor influencing plant performance. Today's catalyst are much improved over those used 10 years ago for the Claus (H/sub 2/S/SO/sub 2/) reaction. Recent technical efforts have focused on the conversion of COS and CS/sub 2/. These carbon-sulfur compounds can account for as much as 50% of the sulfur going to the incinerator, which essentially converts all remaining sulfur species to SO/sub 2/ for atmospheric dispersion. Previously, the mechanism of Claus COS conversion, i.e., hydrolysis or oxidation by SO/sub 2/, was studied and the conclusion was that oxidation by SO/sub 2/ appears to be the predominate mode of COS conversion on sulfated alumina catalysts.

  15. Ocean thermal energy conversion

    SciTech Connect

    Avery, W.H.

    1983-03-17

    A brief explanation of the Ocean Thermal Energy Conversion (OTEC) concept and an estimate of the amount of energy that can be produced from the ocean resource without introducing environmental concerns are presented. Use of the OTEC system to generate electric power and products which can replace fossil fuels is shown. The OTEC program status and its prospects for the future are discussed.

  16. Clinical Linguistics: Conversational Reflections

    ERIC Educational Resources Information Center

    Crystal, David

    2013-01-01

    This is a report of the main points I made in an informal "conversation" with Paul Fletcher and the audience at the 14th ICPLA conference in Cork. The observations arose randomly, as part of an unstructured 1-h Q&A, so they do not provide a systematic account of the subject, but simply reflect the issues which were raised by the conference…

  17. Evaluating Energy Conversion Efficiency

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Smith, B. T.; Buoncristiani, A. M.

    1983-01-01

    Devices that convert solar radiation directly into storable chemical or electrical energy, have characteristic energy absorption spectrum; specifically, each of these devices has energy threshold. The conversion efficiency of generalized system that emcompasses all threshold devices is analyzed, resulting in family of curves for devices of various threshold energies operating at different temperatures.

  18. National conversion pilot project

    SciTech Connect

    Floyd, D.; Nichols, F.; Lily, A.

    1994-12-31

    Manufacturing Sciences Corporation (MSC) has undertaken a project from the U.S. Department of Energy (DOE) to convert buildings that are currently contaminated at Rocky Flats into buildings that are capable of producing commercial products. This conversion project is called the National Conversion Pilot Project (NCPP). The mission of the NCPP is to explore and demonstrate at the Rocky Flats site the feasibility of economic conversion at DOE facilities. This project was officially started on April 1 with the signing of a Cooperative Assistance Agreement between MSC and the DOE. The NCPP was jointly announced by Roy Romer, Governor of the State of Colorado; Mark Silverman, Manager of the Department of Energy Rocky Flats Office; Jack McGraw, Activity Administrator for U.S. Environmental Protection Agency (EPA) Region 8; and Tom Looby, Director of the Office of Environment from the Colorado Department of Health. On March 25, 1994, Hazel O`Leary, the Secretary of the DOE, toured the site of the NCPP and heartily endorsed the project as an example of how the DOE and commercial industry can jointly accomplish the conversion and cleanup of government facilities into productive commercial ventures.

  19. Mechanochemical Energy Conversion

    ERIC Educational Resources Information Center

    Pines, E.; And Others

    1973-01-01

    Summarizes the thermodynamics of macromolecular systems, including theories and experiments of cyclic energy conversion with rubber and collagen as working substances. Indicates that an early introduction into the concept of chemical potential and solution thermodynamics is made possible through the study of the cyclic processes. (CC)

  20. Teaching Conversation with Trivia.

    ERIC Educational Resources Information Center

    Crawford, Michael J.

    2002-01-01

    Presents a rationale for utilizing trivia to teach conversation. Shows how trivia-based materials fit into communicative language teaching approaches and provides examples of trivia-based activities and explains how to use them in the classroom. (Author/VWL)

  1. Planetary image conversion task

    NASA Technical Reports Server (NTRS)

    Martin, M. D.; Stanley, C. L.; Laughlin, G.

    1985-01-01

    The Planetary Image Conversion Task group processed 12,500 magnetic tapes containing raw imaging data from JPL planetary missions and produced an image data base in consistent format on 1200 fully packed 6250-bpi tapes. The output tapes will remain at JPL. A copy of the entire tape set was delivered to US Geological Survey, Flagstaff, Ariz. A secondary task converted computer datalogs, which had been stored in project specific MARK IV File Management System data types and structures, to flat-file, text format that is processable on any modern computer system. The conversion processing took place at JPL's Image Processing Laboratory on an IBM 370-158 with existing software modified slightly to meet the needs of the conversion task. More than 99% of the original digital image data was successfully recovered by the conversion task. However, processing data tapes recorded before 1975 was destructive. This discovery is of critical importance to facilities responsible for maintaining digital archives since normal periodic random sampling techniques would be unlikely to detect this phenomenon, and entire data sets could be wiped out in the act of generating seemingly positive sampling results. Reccomended follow-on activities are also included.

  2. A Conversation about Observation

    NASA Technical Reports Server (NTRS)

    Mather, John C.; Mao, Minnie Yuan

    2012-01-01

    In the spirit of the Lindau Meeting, we present a dialogue between a Nobel laureate and a young researcher. This interchange started online, where it continues to unfold. Here is a digest of this conversation, which has developed across time and space.

  3. Leadership is a conversation.

    PubMed

    Groysberg, Boris; Slind, Michael

    2012-06-01

    Globalization and new technologies have sharply reduced the efficacy of command-and-control management and its accompanying forms of corporate communication. In the course of a recent research project, the authors concluded that by talking with employees, rather than simply issuing orders, leaders can promote operational flexibility, employee engagement, and tight strategic alignment. Groysberg and Slind have identified four elements of organizational conversation that reflect the essential attributes of interpersonal conversation: intimacy, interactivity, inclusion, and intentionality. Intimacy shifts the focus from a top-down distribution of information to a bottom-up exchange of ideas. Organizational conversation is less corporate in tone and more casual. And it's less about issuing and taking orders than about asking and answering questions. Interactivity entails shunning the simplicity of monologue and embracing the unpredictable vitality of dialogue. Traditional one-way media-print and broadcast, in particular-give way to social media buttressed by social thinking. Inclusion turns employees into full-fledged conversation partners, entitling them to provide their own ideas, often on company channels. They can create content and act as brand ambassadors, thought leaders, and storytellers. Intentionality enables leaders and employees to derive strategically relevant action from the push and pull of discussion and debate. PMID:22741420

  4. Conversation with Copland

    ERIC Educational Resources Information Center

    Music Educators Journal, 1973

    1973-01-01

    Records a conversation between American composer Aaron Copland and Malcolm E. Besson, editor of Music Educators Journal. Mr. Copland discusses teaching, American music, and notes the greater number of composers writing today, and the livelier atmosphere of college music departments. (DS)

  5. Leadership is a conversation.

    PubMed

    Groysberg, Boris; Slind, Michael

    2012-06-01

    Globalization and new technologies have sharply reduced the efficacy of command-and-control management and its accompanying forms of corporate communication. In the course of a recent research project, the authors concluded that by talking with employees, rather than simply issuing orders, leaders can promote operational flexibility, employee engagement, and tight strategic alignment. Groysberg and Slind have identified four elements of organizational conversation that reflect the essential attributes of interpersonal conversation: intimacy, interactivity, inclusion, and intentionality. Intimacy shifts the focus from a top-down distribution of information to a bottom-up exchange of ideas. Organizational conversation is less corporate in tone and more casual. And it's less about issuing and taking orders than about asking and answering questions. Interactivity entails shunning the simplicity of monologue and embracing the unpredictable vitality of dialogue. Traditional one-way media-print and broadcast, in particular-give way to social media buttressed by social thinking. Inclusion turns employees into full-fledged conversation partners, entitling them to provide their own ideas, often on company channels. They can create content and act as brand ambassadors, thought leaders, and storytellers. Intentionality enables leaders and employees to derive strategically relevant action from the push and pull of discussion and debate.

  6. Kinetic Alfven Waves at the Magnetopause--Mode Conversion, Transport and Formation of LLBL

    SciTech Connect

    Jay R. Johnson; C.Z. Cheng

    2002-05-31

    At the magnetopause, large amplitude, low-frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the Alfven velocity [Johnson and Cheng, Geophys. Res. Lett. 24 (1997) 1423]. The mode-conversion process can explain the following wave observations typically found during satellite crossings of the magnetopause: (1) a dramatic change in wave polarization from compressional in the magnetosheath to transverse at the magnetopause, (2) an amplification of wave amplitude at the magnetopause, (3) a change in Poynting flux from cross-field in the magnetosheath to field-aligned at the magnetopause, and (4) a steepening in the wave power spectrum at the magnetopause. We examine magnetic field data from a set of ISEE1, ISEE2, and WIND magnetopause crossings and compare with the predictions of theoretical wave solutions based on the kinetic-fluid model with particular attention to the role of magnetic field rotation across the magnetopause. The results of the study suggest a good qualitative agreement between the observations and the theory of mode conversion to kinetic Alfven waves. Because mode-converted kinetic Alfven waves readily decouple particles from the magnetic field lines, efficient quasilinear transport (D {approx} 109m2/s) can occur. Moreover, if the wave amplitude is sufficiently large (Bwave/B0 > 0.2) stochastic particle transport also occurs. This wave-induced transport can lead to significant heating and particle entry into the low latitude boundary layer across closed field lines.At the magnetopause, large amplitude, low-frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the

  7. Solar energy conversion.

    SciTech Connect

    Crabtree, G. W.; Lewis, N. S.

    2008-03-01

    If solar energy is to become a practical alternative to fossil fuels, we must have efficient ways to convert photons into electricity, fuel, and heat. The need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience. The Sun has the enormous untapped potential to supply our growing energy needs. The barrier to greater use of the solar resource is its high cost relative to the cost of fossil fuels, although the disparity will decrease with the rising prices of fossil fuels and the rising costs of mitigating their impact on the environment and climate. The cost of solar energy is directly related to the low conversion efficiency, the modest energy density of solar radiation, and the costly materials currently required. The development of materials and methods to improve solar energy conversion is primarily a scientific challenge: Breakthroughs in fundamental understanding ought to enable marked progress. There is plenty of room for improvement, since photovoltaic conversion efficiencies for inexpensive organic and dye-sensitized solar cells are currently about 10% or less, the conversion efficiency of photosynthesis is less than 1%, and the best solar thermal efficiency is 30%. The theoretical limits suggest that we can do much better. Solar conversion is a young science. Its major growth began in the 1970s, spurred by the oil crisis that highlighted the pervasive importance of energy to our personal, social, economic, and political lives. In contrast, fossil-fuel science has developed over more than 250 years, stimulated by the Industrial Revolution and the promise of abundant fossil fuels. The science of thermodynamics, for example, is intimately intertwined with the development of the steam engine. The Carnot cycle, the mechanical equivalent of heat, and entropy all played starring roles in the development of thermodynamics and the technology of heat engines. Solar-energy science faces

  8. Degenerate Ising model for atomistic simulation of crystal-melt interfaces.

    PubMed

    Schebarchov, D; Schulze, T P; Hendy, S C

    2014-02-21

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level. PMID:24559357

  9. Percolation features of cooperative Jahn-Teller systems: Ising EFT framework

    NASA Astrophysics Data System (ADS)

    Moujaes, Elie A.; Abou Ghantous, Michel

    2014-08-01

    Elastic exchange between two nearest Jahn-Teller (JT) centers in two or three dimensional dense crystals, can give an ordered macroscopic distortion known as cooperative JT effect (CJTE). A very diluted JT crystal does not show this effect. In the dynamic JT effect (DJTE), tunneling between different equivalent distorted wells has a pronounced influence on the CJTE. We investigate this phenomenon using a progressive increase in the concentration of these centers in the JT crystals, based on a bond percolation vector spin analogy technique within the framework of effective field theory (EFT). Mean field theory (MFT) was extensively used in previous studies of CJTE; however it neither includes correlation between JT centers in the lattice due to the complexity of the distortion field in the crystal nor the effect of tunneling between wells. We resort to an alternative procedure, by describing a JT center as a pseudo-spin vector , induced to represent the degenerate JT-distorted states, where two nearest JT centers interact via an elastic exchange described by an Ising type spin interaction. The DJTE is considered to be similar to an elastic transverse field term in the Hamiltonian portraying the effect of tunneling between equivalent wells in the adiabatic potential energy surface (APES). We will be particularly discussing S = 1, S = 3/2 and S = 5/2 spin cases, where 2 S + 1 wells in the APES are present and what JT systems they actually represent, with a percolative mechanism applied to the interactions between different JT centers. The different lattices are distinguished by their coordination numbers. Strong tunneling effects can suppress the CJTE and lead to a new state of criticality. Generalizations to higher spin systems will be obtained using a scaling technique. For the relevant distortions, we determine single site correlations, the macroscopic average distortion describing a structural phase transition and the elastic isothermal susceptibility as a

  10. Adaptive multi-GPU Exchange Monte Carlo for the 3D Random Field Ising Model

    NASA Astrophysics Data System (ADS)

    Navarro, Cristóbal A.; Huang, Wei; Deng, Youjin

    2016-08-01

    This work presents an adaptive multi-GPU Exchange Monte Carlo approach for the simulation of the 3D Random Field Ising Model (RFIM). The design is based on a two-level parallelization. The first level, spin-level parallelism, maps the parallel computation as optimal 3D thread-blocks that simulate blocks of spins in shared memory with minimal halo surface, assuming a constant block volume. The second level, replica-level parallelism, uses multi-GPU computation to handle the simulation of an ensemble of replicas. CUDA's concurrent kernel execution feature is used in order to fill the occupancy of each GPU with many replicas, providing a performance boost that is more notorious at the smallest values of L. In addition to the two-level parallel design, the work proposes an adaptive multi-GPU approach that dynamically builds a proper temperature set free of exchange bottlenecks. The strategy is based on mid-point insertions at the temperature gaps where the exchange rate is most compromised. The extra work generated by the insertions is balanced across the GPUs independently of where the mid-point insertions were performed. Performance results show that spin-level performance is approximately two orders of magnitude faster than a single-core CPU version and one order of magnitude faster than a parallel multi-core CPU version running on 16-cores. Multi-GPU performance is highly convenient under a weak scaling setting, reaching up to 99 % efficiency as long as the number of GPUs and L increase together. The combination of the adaptive approach with the parallel multi-GPU design has extended our possibilities of simulation to sizes of L = 32 , 64 for a workstation with two GPUs. Sizes beyond L = 64 can eventually be studied using larger multi-GPU systems.

  11. Tunable two-dimensional arrays of single Rydberg atoms for realizing quantum Ising models.

    PubMed

    Labuhn, Henning; Barredo, Daniel; Ravets, Sylvain; de Léséleuc, Sylvain; Macrì, Tommaso; Lahaye, Thierry; Browaeys, Antoine

    2016-06-30

    Spin models are the prime example of simplified many-body Hamiltonians used to model complex, strongly correlated real-world materials. However, despite the simplified character of such models, their dynamics often cannot be simulated exactly on classical computers when the number of particles exceeds a few tens. For this reason, quantum simulation of spin Hamiltonians using the tools of atomic and molecular physics has become a very active field over the past years, using ultracold atoms or molecules in optical lattices, or trapped ions. All of these approaches have their own strengths and limitations. Here we report an alternative platform for the study of spin systems, using individual atoms trapped in tunable two-dimensional arrays of optical microtraps with arbitrary geometries, where filling fractions range from 60 to 100 per cent. When excited to high-energy Rydberg D states, the atoms undergo strong interactions whose anisotropic character opens the way to simulating exotic matter. We illustrate the versatility of our system by studying the dynamics of a quantum Ising-like spin-1/2 system in a transverse field with up to 30 spins, for a variety of geometries in one and two dimensions, and for a wide range of interaction strengths. For geometries where the anisotropy is expected to have small effects on the dynamics, we find excellent agreement with ab initio simulations of the spin-1/2 system, while for strongly anisotropic situations the multilevel structure of the D states has a measurable influence. Our findings establish arrays of single Rydberg atoms as a versatile platform for the study of quantum magnetism.

  12. Two-dimensional Ising transition through a technique from two-state opinion-dynamics models.

    PubMed

    Galam, Serge; Martins, André C R

    2015-01-01

    The Ising ferromagnetic model on a square lattice is revisited using the Galam unifying frame (GUF), set to investigate two-state opinion-dynamics models. When combined with Metropolis dynamics, an unexpected intermediate "dis/order" regime is found with the coexistence of two attractors associated, respectively, to an ordered and a disordered phases. The basin of attraction of initial conditions for the disordered phase attractor starts from zero size at a first critical temperature T(c1) to embody the total landscape of initial conditions at a second critical temperature T(c2), with T(c1)≈1.59 and T(c2)≈2.11 in J/k(B) units. It appears that T(c2) is close to the Onsager result T(c)≈2.27. The transition, which is first-order-like, exhibits a vertical jump to the disorder phase at T(c2), reminiscent of the rather abrupt vanishing of the corresponding Onsager second-order transition. However, using Glauber dynamics combined with GUF does not yield the intermediate phase and instead the expected classical mean-field transition is recovered at T(c)≈3.09. Accordingly, although the "dis/order" regime produced by the GUF-Metropolis combination is not physical, it is an intriguing result to be understood. In particular the fact that Glauber and Metropolis dynamics yield so different results using GUF needs an explanation. The possibility of extending GUF to larger clusters is discussed. PMID:25679571

  13. Slow quenches in a quantum Ising chain: Dynamical phase transitions and topology

    NASA Astrophysics Data System (ADS)

    Sharma, Shraddha; Divakaran, Uma; Polkovnikov, Anatoli; Dutta, Amit

    2016-04-01

    We study the slow quenching dynamics (characterized by an inverse rate τ-1) of a one-dimensional transverse Ising chain with nearest neighbor ferromagentic interactions across the quantum critical point (QCP) and analyze the Loschmidt overlap measured using the subsequent temporal evolution of the final wave function (reached at the end of the quenching) with the final time-independent Hamiltonian. Studying the Fisher zeros of the corresponding generalized "partition function," we probe nonanalyticities manifested in the rate function of the return probability known as dynamical phase transitions (DPTs). In contrast to the sudden quenching case, we show that DPTs survive in the subsequent temporal evolution following the quenching across two critical points of the model for a sufficiently slow rate; furthermore, an interesting "lobe" structure of Fisher zeros emerge. We have also made a connection to topological aspects studying the dynamical topological order parameter [νD(t ) ] as a function of time (t ) measured from the instant when the quenching is complete. Remarkably, the time evolution of νD(t ) exhibits drastically different behavior following quenches across a single QCP and two QCPs. In the former case, νD(t ) increases stepwise by unity at every DPT (i.e., Δ νD=1 ). In the latter case, on the other hand, νD(t ) essentially oscillates between 0 and 1 (i.e., successive DPTs occur with Δ νD=1 and Δ νD=-1 , respectively), except for instants where it shows a sudden jump by a factor of unity when two successive DPTs carry a topological charge of the same sign.

  14. Tunable two-dimensional arrays of single Rydberg atoms for realizing quantum Ising models

    NASA Astrophysics Data System (ADS)

    Labuhn, Henning; Barredo, Daniel; Ravets, Sylvain; de Léséleuc, Sylvain; Macrì, Tommaso; Lahaye, Thierry; Browaeys, Antoine

    2016-06-01

    Spin models are the prime example of simplified many-body Hamiltonians used to model complex, strongly correlated real-world materials. However, despite the simplified character of such models, their dynamics often cannot be simulated exactly on classical computers when the number of particles exceeds a few tens. For this reason, quantum simulation of spin Hamiltonians using the tools of atomic and molecular physics has become a very active field over the past years, using ultracold atoms or molecules in optical lattices, or trapped ions. All of these approaches have their own strengths and limitations. Here we report an alternative platform for the study of spin systems, using individual atoms trapped in tunable two-dimensional arrays of optical microtraps with arbitrary geometries, where filling fractions range from 60 to 100 per cent. When excited to high-energy Rydberg D states, the atoms undergo strong interactions whose anisotropic character opens the way to simulating exotic matter. We illustrate the versatility of our system by studying the dynamics of a quantum Ising-like spin-1/2 system in a transverse field with up to 30 spins, for a variety of geometries in one and two dimensions, and for a wide range of interaction strengths. For geometries where the anisotropy is expected to have small effects on the dynamics, we find excellent agreement with ab initio simulations of the spin-1/2 system, while for strongly anisotropic situations the multilevel structure of the D states has a measurable influence. Our findings establish arrays of single Rydberg atoms as a versatile platform for the study of quantum magnetism.

  15. Finite-size effects for anisotropic 2D Ising model with various boundary conditions

    NASA Astrophysics Data System (ADS)

    Izmailian, N. Sh

    2012-12-01

    We analyze the exact partition function of the anisotropic Ising model on finite M × N rectangular lattices under four different boundary conditions (periodic-periodic (pp), periodic-antiperiodic (pa), antiperiodic-periodic (ap) and antiperiodic-antiperiodic (aa)) obtained by Kaufman (1949 Phys. Rev. 76 1232), Wu and Hu (2002 J. Phys. A: Math. Gen. 35 5189) and Kastening (2002 Phys. Rev. E 66 057103)). We express the partition functions in terms of the partition functions Zα, β(J, k) with (α, β) = (0, 0), (1/2, 0), (0, 1/2) and (1/2, 1/2), J is an interaction coupling and k is an anisotropy parameter. Based on such expressions, we then extend the algorithm of Ivashkevich et al (2002 J. Phys. A: Math. Gen. 35 5543) to derive the exact asymptotic expansion of the logarithm of the partition function for all boundary conditions mentioned above. Our result is f = fbulk + ∑∞p = 0fp(ρ, k)S-p - 1, where f is the free energy of the system, fbulk is the free energy of the bulk, S = MN is the area of the lattice and ρ = M/N is the aspect ratio. All coefficients in this expansion are expressed through analytical functions. We have introduced the effective aspect ratio ρeff = ρ/sinh 2Jc and show that for pp and aa boundary conditions all finite size correction terms are invariant under the transformation ρeff → 1/ρeff. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  16. A Renormalization Group Study of the Ising Model on the Hierarchical Hanoi Networks

    NASA Astrophysics Data System (ADS)

    Brunson, Clifton Trent

    Despite all the remarkable breakthroughs in the area of complex networks over the last two decades, there still lacks a complete and general understanding of effects that occur when long-range connections are present in a system. This thesis explores the Ising model using recursive hierarchical networks called Hanoi networks (HN) as a substrate. Hanoi networks are purely synthetic and are not found in nature, so it is important to establish and not lose sight of why they worth studying. In essence, we are not strictly interested in HNs themselves, but the generalized statements about phase transitions on complex networks that they provide via the renormalization group (RG). The RG framework on HNs is established in this study and the thermodynamic observables for statistical models are derived from it. Traditionally, the RG has given physicists insight into the critical exponents of a system or model, which leads to universal behavior; however, hyperbolic networks, like the ones currently under investigation, do not contain constant exponents and do not exhibit universality. Instead, it is found that the scaling exponents are functions of the temperature. We ultimately want to answer the questions: What is it about long-range connections that create a break in universal behavior and can complex networks be designed to produce predicted and intended effects in phase behavior? The current state of research is several years or perhaps decades away from fully comprehending the answers to these questions. The research presented here is motivated by these questions, and our contribution here is intended to show a generalized picture of phase transitions on networks.

  17. Critical behaviour of the Ising ferromagnet confined in quasi-cylindrical pores: a Monte Carlo study.

    PubMed

    Guisandez, Leandro E; Zarragoicoechea, Guillermo J; Albano, Ezequiel V

    2013-10-21

    The critical behaviour of the Ising ferromagnet confined in pores of radius R and length L is studied by means of Monte Carlo computer simulations. Quasi-cylindrical pores are obtained by replicating n-times a triangular lattice disc of radius R, where L = na and a is the spacing between consecutive replications. So, spins placed at the surface of the pores have less nearest-neighbours (NN) as compared to 8 NN for spins in the bulk. These "missing neighbour" effects undergone by surface spins cause a strong suppression of surface ordering, leading to an ordinary surface transition. Also, the effect propagates into the bulk for small tubes (R ≤ 12) and the effective critical temperature of the pores is shifted towards lower values than in the bulk case. By applying the standard finite-size scaling theory, subsequently supported by numerical data, we concluded that data collapse of relevant observables, e.g., magnetization (m), susceptibility, specific heat, etc., can only be observed by comparing simulation results obtained by keeping the aspect ratio C ≡ R∕L constant. Also, by extrapolating "effective" R-dependent critical temperatures to the thermodynamic limit (R → ∞, C fixed), we obtained T(C)(∞) = 6.208(4). As suggested by finite-size scaling arguments, the magnetization is measured at the critical point scales according to [|m|]Tc R(β/ν) is proportional to [R/L](1/2), where β and ν are the standard exponents for the order parameter and the correlation length, respectively. Furthermore, it is shown that close to criticality the axial correlation length decreases exponentially with the distance. That result is the signature of the formation of (randomly distributed) alternating domains of different magnetization, which can be directly observed by means of snapshot configurations, whose typical length (ξ) is given by the characteristic length of the exponential decay of correlations. Moreover, we show that at criticality ξ = 0.43(2)R.

  18. Tunable two-dimensional arrays of single Rydberg atoms for realizing quantum Ising models.

    PubMed

    Labuhn, Henning; Barredo, Daniel; Ravets, Sylvain; de Léséleuc, Sylvain; Macrì, Tommaso; Lahaye, Thierry; Browaeys, Antoine

    2016-06-30

    Spin models are the prime example of simplified many-body Hamiltonians used to model complex, strongly correlated real-world materials. However, despite the simplified character of such models, their dynamics often cannot be simulated exactly on classical computers when the number of particles exceeds a few tens. For this reason, quantum simulation of spin Hamiltonians using the tools of atomic and molecular physics has become a very active field over the past years, using ultracold atoms or molecules in optical lattices, or trapped ions. All of these approaches have their own strengths and limitations. Here we report an alternative platform for the study of spin systems, using individual atoms trapped in tunable two-dimensional arrays of optical microtraps with arbitrary geometries, where filling fractions range from 60 to 100 per cent. When excited to high-energy Rydberg D states, the atoms undergo strong interactions whose anisotropic character opens the way to simulating exotic matter. We illustrate the versatility of our system by studying the dynamics of a quantum Ising-like spin-1/2 system in a transverse field with up to 30 spins, for a variety of geometries in one and two dimensions, and for a wide range of interaction strengths. For geometries where the anisotropy is expected to have small effects on the dynamics, we find excellent agreement with ab initio simulations of the spin-1/2 system, while for strongly anisotropic situations the multilevel structure of the D states has a measurable influence. Our findings establish arrays of single Rydberg atoms as a versatile platform for the study of quantum magnetism. PMID:27281203

  19. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    SciTech Connect

    Schebarchov, D.; Schulze, T. P.; Hendy, S. C.

    2014-02-21

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.

  20. Spin-lattice relaxation within a dimerized Ising chain in a magnetic field

    SciTech Connect

    Erdem, Rıza E-mail: rerdem29@hotmail.com; Gülpınar, Gül; Yalçın, Orhan; Pawlak, Andrzej

    2014-07-21

    A qualitative study of the spin-lattice relaxation within a dimerized Ising chain in a magnetic field is presented. We have first determined the time dependence of the deviation of the lattice distortion parameter δΔ from the equilibrium state within framework of a technique combining the statistical equilibrium theory based on the transfer matrix method and the linear theory of irreversible thermodynamics. We have shown that the time dependence of the lattice distortion parameter is characterized by a single time constant (τ) which diverges around the critical point in both dimerized (Δ≠0) and uniform (Δ=0) phase regions. When the temperature and magnetic field are fixed to certain values, the time τ depends only on exchange coupling between the spins. It is a characteristic time associated with the long wavelength fluctuations of distortion. We have also taken into account the effects of spatial fluctuations on the relaxation time using the full Landau-Ginzburg free energy functional. We have found an explicit expression for the relaxation time as a function of temperature, coupling constant and wave vector (q) and shown that the critical mode corresponds to the case q=0. Finally, our results are found to be in good qualitative agreement with the results obtained in recent experimental study on synchrotron x-ray scattering and muon spin relaxation in diluted material Cu{sub 1−y}Mg{sub y}GeO{sub 3} where the composition y is very close to 0.0209. These results can be considered as natural extensions of some previous works on static aspects of the problem.