Construction of exchange-correlation functionals through interpolation between the non-interacting and the strong-correlation limit

International Nuclear Information System (INIS)

Zhou, Yongxi; Ernzerhof, Matthias; Bahmann, Hilke

2015-01-01

Drawing on the adiabatic connection of density functional theory, exchange-correlation functionals of Kohn-Sham density functional theory are constructed which interpolate between the extreme limits of the electron-electron interaction strength. The first limit is the non-interacting one, where there is only exchange. The second limit is the strong correlated one, characterized as the minimum of the electron-electron repulsion energy. The exchange-correlation energy in the strong-correlation limit is approximated through a model for the exchange-correlation hole that is referred to as nonlocal-radius model [L. O. Wagner and P. Gori-Giorgi, Phys. Rev. A 90, 052512 (2014)]. Using the non-interacting and strong-correlated extremes, various interpolation schemes are presented that yield new approximations to the adiabatic connection and thus to the exchange-correlation energy. Some of them rely on empiricism while others do not. Several of the proposed approximations yield the exact exchange-correlation energy for one-electron systems where local and semi-local approximations often fail badly. Other proposed approximations generalize existing global hybrids by using a fraction of the exchange-correlation energy in the strong-correlation limit to replace an equal fraction of the semi-local approximation to the exchange-correlation energy in the strong-correlation limit. The performance of the proposed approximations is evaluated for molecular atomization energies, total atomic energies, and ionization potentials

Strong correlations in few-fermion systems

Energy Technology Data Exchange (ETDEWEB)

Bergschneider, Andrea

2017-07-26

In this thesis, I report on the deterministic preparation and the observation of strongly correlated few-fermion systems in single and double-well potentials. In a first experiment, we studied a system of one impurity interacting with a number of majority atoms which we prepared in a single potential well in the one-dimensional limit. With increasing number of majority particles, we observed a decrease in the quasi-particle residue which is in agreement with expectations from the Anderson orthogonality catastrophe. In a second experiment, we prepared two fermions in a double-well potential which represents the fundamental building block of the Fermi-Hubbard model. By increasing the repulsion between the two fermions, we observed the crossover into the antiferromagnetic Mott-insulator regime. Furthermore, I describe a new imaging technique, which allows spin-resolved single-atom detection both in in-situ and in time-of-flight. We use this technique to investigate the emergence of momentum correlations of two repulsive fermions in the ground state of the double well. With the methods developed in this thesis, we have established a framework for quantum simulation of strongly correlated many-body systems in tunable potentials.

Pair correlation of particles in strongly nonideal systems

International Nuclear Information System (INIS)

Vaulina, O. S.

2012-01-01

A new semiempirical model is proposed for describing the spatial correlation between interacting particles in nonideal systems. The developed model describes the main features in the behavior of the pair correlation function for crystalline structures and can also be used for qualitative and quantitative description of the spatial correlation of particles in strongly nonideal liquid systems. The proposed model is compared with the results of simulation of the pair correlation function.

Strongly Correlated Electron Systems: An Operatorial Perspective

Science.gov (United States)

Di Ciolo, Andrea; Avella, Adolfo

2018-05-01

We discuss the operatorial approach to the study of strongly correlated electron systems and show how the exact solution of target models on small clusters chosen ad-hoc (minimal models) can suggest very efficient bulk approximations. We use the Hubbard model as case study (target model) and we analyze and discuss the crucial role of spin fluctuations in its 2-site realization (minimal model). Accordingly, we devise a novel three-pole approximation for the 2D case, including in the basic field an operator describing the dressing of the electronic one by the nearest-neighbor spin-fluctuations. Such a solution is in very good agreement with the exact one in the minimal model (2-site case) and performs very well once compared to advanced (semi-)numerical methods in the 2D case, being by far less computational-resource demanding.

Transport phenomena in strongly correlated Fermi liquids

International Nuclear Information System (INIS)

Kontani, Hiroshi

2013-01-01

Comprehensive overview. Written by an expert of this topic. Provides the reader with current developments in the field. In conventional metals, various transport coefficients are scaled according to the quasiparticle relaxation time, τ, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems, reflecting their unique electronic states. The most famous example would be cuprate high-Tc superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. To better understand the origin of this discrepancy, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. Near the magnetic quantum critical point, the current vertex correction (CVC), which describes the electron-electron scattering beyond the relaxation time approximation, gives rise to various anomalous transport phenomena. We explain anomalous transport phenomena in cuprate HTSCs and other metals near their magnetic or orbital quantum critical point using a uniform approach. We also discuss spin related transport phenomena in strongly correlated systems. In many d- and f-electron systems, the spin current induced by the spin Hall effect is considerably greater because of the orbital degrees of freedom. This fact attracts much attention due to its potential application in spintronics. We discuss various novel charge, spin and heat transport phenomena in strongly correlated metals.

Strong correlation effects on surfaces of topological insulators via holography

Science.gov (United States)

Seo, Yunseok; Song, Geunho; Sin, Sang-Jin

2017-07-01

We investigate the effects of strong correlation on the surface state of a topological insulator (TI). We argue that electrons in the regime of crossover from weak antilocalization to weak localization are strongly correlated, and calculate the magnetotransport coefficients of TIs using the gauge-gravity principle. Then, we examine the magnetoconductivity (MC) formula and find excellent agreement with the data of chrome-doped Bi2Te3 in the crossover regime. We also find that the cusplike peak in MC at low doping is absent, which is natural since quasiparticles disappear due to the strong correlation.

Towards TDDFT for Strongly Correlated Materials

Directory of Open Access Journals (Sweden)

Shree Ram Acharya

2016-09-01

Full Text Available We present some details of our recently-proposed Time-Dependent Density-Functional Theory (TDDFT for strongly-correlated materials in which the exchange-correlation (XC kernel is derived from the charge susceptibility obtained using Dynamical Mean-Field Theory (the TDDFT + DMFT approach. We proceed with deriving the expression for the XC kernel for the one-band Hubbard model by solving DMFT equations via two approaches, the Hirsch–Fye Quantum Monte Carlo (HF-QMC and an approximate low-cost perturbation theory approach, and demonstrate that the latter gives results that are comparable to the exact HF-QMC solution. Furthermore, through a variety of applications, we propose a simple analytical formula for the XC kernel. Additionally, we use the exact and approximate kernels to examine the nonhomogeneous ultrafast response of two systems: a one-band Hubbard model and a Mott insulator YTiO3. We show that the frequency dependence of the kernel, i.e., memory effects, is important for dynamics at the femtosecond timescale. We also conclude that strong correlations lead to the presence of beats in the time-dependent electric conductivity in YTiO3, a feature that could be tested experimentally and that could help validate the few approximations used in our formulation. We conclude by proposing an algorithm for the generalization of the theory to non-linear response.

Structural and functional correlates of hypnotic depth and suggestibility.

Science.gov (United States)

McGeown, William Jonathan; Mazzoni, Giuliana; Vannucci, Manila; Venneri, Annalena

2015-02-28

This study explores whether self-reported depth of hypnosis and hypnotic suggestibility are associated with individual differences in neuroanatomy and/or levels of functional connectivity. Twenty-nine people varying in suggestibility were recruited and underwent structural, and after a hypnotic induction, functional magnetic resonance imaging at rest. We used voxel-based morphometry to assess the correlation of grey matter (GM) and white matter (WM) against the independent variables: depth of hypnosis, level of relaxation and hypnotic suggestibility. Functional networks identified with independent components analysis were regressed with the independent variables. Hypnotic depth ratings were positively correlated with GM volume in the frontal cortex and the anterior cingulate cortex (ACC). Hypnotic suggestibility was positively correlated with GM volume in the left temporal-occipital cortex. Relaxation ratings did not correlate significantly with GM volume and none of the independent variables correlated with regional WM volume measures. Self-reported deeper levels of hypnosis were associated with less connectivity within the anterior default mode network. Taken together, the results suggest that the greater GM volume in the medial frontal cortex and ACC, and lower connectivity in the DMN during hypnosis facilitate experiences of greater hypnotic depth. The patterns of results suggest that hypnotic depth and hypnotic suggestibility should not be considered synonyms. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Correlates of the Gudjonsson Suggestibility Scale in delinquent adolescents.

Science.gov (United States)

Muris, Peter; Meesters, Cor; Merckelbach, Harald

2004-02-01

Correlations between scores on the Gudjonsson Suggestibility Scale and a number of relevant personality characteristics, i.e., intelligence, memory, social inadequacy, social desirability, and fantasy proneness, were examined in a sample of 71 delinquent boys. Analysis showed that intelligence and memory were negatively related to suggestibility scores. That is, lower memory and intelligence were associated with higher suggestibility. No significant correlations were found between suggestibility and other personality characteristics.

Mismeasurement and the resonance of strong confounders: correlated errors.

Science.gov (United States)

Marshall, J R; Hastrup, J L; Ross, J S

1999-07-01

Confounding in epidemiology, and the limits of standard methods of control for an imperfectly measured confounder, have been understood for some time. However, most treatments of this problem are based on the assumption that errors of measurement in confounding and confounded variables are independent. This paper considers the situation in which a strong risk factor (confounder) and an inconsequential but suspected risk factor (confounded) are each measured with errors that are correlated; the situation appears especially likely to occur in the field of nutritional epidemiology. Error correlation appears to add little to measurement error as a source of bias in estimating the impact of a strong risk factor: it can add to, diminish, or reverse the bias induced by measurement error in estimating the impact of the inconsequential risk factor. Correlation of measurement errors can add to the difficulty involved in evaluating structures in which confounding and measurement error are present. In its presence, observed correlations among risk factors can be greater than, less than, or even opposite to the true correlations. Interpretation of multivariate epidemiologic structures in which confounding is likely requires evaluation of measurement error structures, including correlations among measurement errors.

Optical spectral weight anomalies and strong correlation

International Nuclear Information System (INIS)

Toschi, A.; Capone, M.; Ortolani, M.; Calvani, P.; Lupi, S.; Castellani, C.

2007-01-01

The anomalous behavior observed in the optical spectral weight (W) of the cuprates provides valuable information about the physics of these compounds. Both the doping and the temperature dependences of W are hardly explained through conventional estimates based on the f-sum rule. By computing the optical conductivity of the doped Hubbard model with the Dynamical Mean Field Theory, we point out that the strong correlation plays a key role in determining the basic features of the observed anomalies: the proximity to a Mott insulating phase accounts simultaneously for the strong temperature dependence of W and for its zero temperature value

Phase transition transistors based on strongly-correlated materials

Science.gov (United States)

Nakano, Masaki

2013-03-01

The field-effect transistor (FET) provides electrical switching functions through linear control of the number of charges at a channel surface by external voltage. Controlling electronic phases of condensed matters in a FET geometry has long been a central issue of physical science. In particular, FET based on a strongly correlated material, namely ``Mott transistor,'' has attracted considerable interest, because it potentially provides gigantic and diverse electronic responses due to a strong interplay between charge, spin, orbital and lattice. We have investigated electric-field effects on such materials aiming at novel physical phenomena and electronic functions originating from strong correlation effects. Here we demonstrate electrical switching of bulk state of matter over the first-order metal-insulator transition. We fabricated FETs based on VO2 with use of a recently developed electric-double-layer transistor technique, and found that the electrostatically induced carriers at a channel surface drive all preexisting localized carriers of 1022 cm-3 even inside a bulk to motion, leading to bulk carrier delocalization beyond the electrostatic screening length. This non-local switching of bulk phases is achieved with just around 1 V, and moreover, a novel non-volatile memory like character emerges in a voltage-sweep measurement. These observations are apparently distinct from those of conventional FETs based on band insulators, capturing the essential feature of collective interactions in strongly correlated materials. This work was done in collaboration with K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M. Kawasaki, Y. Iwasa, and Y. Tokura. This work was supported by the Japan Society for the Promotion of Science (JSAP) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program).''

Nonperturbative stochastic dynamics driven by strongly correlated colored noise

Science.gov (United States)

Jing, Jun; Li, Rui; You, J. Q.; Yu, Ting

2015-02-01

We propose a quantum model consisting of two remote qubits interacting with two correlated colored noises and establish an exact stochastic Schrödinger equation for this open quantum system. It is shown that the quantum dynamics of the qubit system is profoundly modulated by the mutual correlation between baths and the bath memory capability through dissipation and fluctuation. We report a physical effect on generating inner correlation and entanglement of two distant qubits arising from the strong bath-bath correlation.

Interplay between strong correlation and adsorption distances: Co on Cu(001)

Science.gov (United States)

Bahlke, Marc Philipp; Karolak, Michael; Herrmann, Carmen

2018-01-01

Adsorbed transition metal atoms can have partially filled d or f shells due to strong on-site Coulomb interaction. Capturing all effects originating from electron correlation in such strongly correlated systems is a challenge for electronic structure methods. It requires a sufficiently accurate description of the atomistic structure (in particular bond distances and angles), which is usually obtained from first-principles Kohn-Sham density functional theory (DFT), which due to the approximate nature of the exchange-correlation functional may provide an unreliable description of strongly correlated systems. To elucidate the consequences of this popular procedure, we apply a combination of DFT with the Anderson impurity model (AIM), as well as DFT + U for a calculation of the potential energy surface along the Co/Cu(001) adsorption coordinate, and compare the results with those obtained from DFT. The adsorption minimum is shifted towards larger distances by applying DFT+AIM, or the much cheaper DFT +U method, compared to the corresponding spin-polarized DFT results, by a magnitude comparable to variations between different approximate exchange-correlation functionals (0.08 to 0.12 Å). This shift originates from an increasing correlation energy at larger adsorption distances, which can be traced back to the Co 3 dx y and 3 dz2 orbitals being more correlated as the adsorption distance is increased. We can show that such considerations are important, as they may strongly affect electronic properties such as the Kondo temperature.

Observations of strong ion-ion correlations in dense plasmas

Energy Technology Data Exchange (ETDEWEB)

Ma, T.; Fletcher, L.; Pak, A.; Chapman, D. A.; Falcone, R. W.; Fortmann, C.; Galtier, E.; Gericke, D. O.; Gregori, G.; Hastings, J.; Landen, O. L.; Le Pape, S.; Lee, H. J.; Nagler, B.; Neumayer, P.; Turnbull, D.; Vorberger, J.; White, T. G.; Wünsch, K.; Zastrau, U.; Glenzer, S. H.; Döppner, T.

2014-05-01

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ~3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4k=4Å-1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are however in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. We have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.

Quasiparticles of strongly correlated Fermi liquids at high temperatures and in high magnetic fields

International Nuclear Information System (INIS)

Shaginyan, V. R.

2011-01-01

Strongly correlated Fermi systems are among the most intriguing, best experimentally studied and fundamental systems in physics. There is, however, lack of theoretical understanding in this field of physics. The ideas based on the concepts like Kondo lattice and involving quantum and thermal fluctuations at a quantum critical point have been used to explain the unusual physics. Alas, being suggested to describe one property, these approaches fail to explain the others. This means a real crisis in theory suggesting that there is a hidden fundamental law of nature. It turns out that the hidden fundamental law is well forgotten old one directly related to the Landau-Migdal quasiparticles, while the basic properties and the scaling behavior of the strongly correlated systems can be described within the framework of the fermion condensation quantum phase transition (FCQPT). The phase transition comprises the extended quasiparticle paradigm that allows us to explain the non-Fermi liquid (NFL) behavior observed in these systems. In contrast to the Landau paradigm stating that the quasiparticle effective mass is a constant, the effective mass of new quasiparticles strongly depends on temperature, magnetic field, pressure, and other parameters. Our observations are in good agreement with experimental facts and show that FCQPT is responsible for the observed NFL behavior and quasiparticles survive both high temperatures and high magnetic fields.

Phase structure of strongly correlated Fermi gases

International Nuclear Information System (INIS)

Roscher, Dietrich

2015-01-01

Strongly correlated fermionic many-body systems are ubiquitous in nature. Their theoretical description poses challenging problems which are further complicated when imbalances in, e.g., the particle numbers of the involved species or their masses are introduced. In this thesis, a number of different approaches is developed and applied in order to obtain predictions for physical observables of such systems that mutually support and confirm each other. In a first step, analytically well-founded mean-field analyses are carried through. One- and three-dimensional ultracold Fermi gases with spin and mass imbalance as well as Gross-Neveu and NJL-type relativistic models at finite baryon chemical potential are investigated with respect to their analytic properties in general and the occurrence of spontaneous breaking of translational invariance in particular. Based on these studies, further methods are devised or adapted allowing for investigations also beyond the mean-field approximation. Lattice Monte Carlo simulations with imaginary imbalance parameters are employed to surmount the infamous sign problem and compute the equation of state of the respective unitary Fermi gases. Moreover, in-medium two-body analyses are used to confirm and explain the characteristics of inhomogeneously ordered phases. Finally, functional RG methods are applied to the unitary Fermi gas with spin and mass imbalance. Besides quantitatively competitive predictions for critical temperatures for the superfluid state, strong hints on the stability of inhomogeneous phases with respect to order parameter fluctuations in the regime of large mass imbalance are obtained. Combining the findings from these different theoretical studies suggests the possibility to find such phases in experiments presently in preparation.

Strong Correlation in Kohn-Sham Density Functional Theory

NARCIS (Netherlands)

Malet, F.; Gori Giorgi, P.

2012-01-01

We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to approximate the exchange-correlation energy of the restricted Kohn-Sham scheme. Our approximation corresponds to a highly nonlocal density functional whose functional derivative can be easily constructed,

Strongly-correlated ultracold atoms in optical lattices

International Nuclear Information System (INIS)

Dao, Tung-Lam

2008-01-01

This thesis is concerned with the theoretical study of strongly correlated quantum states of ultra-cold fermionic atoms trapped in optical lattices. This field has grown considerably in recent years, following the experimental progress made in cooling and controlling atomic gases, which has led to the observation of the first Bose-Einstein condensation (in 1995). The trapping of these gases in optical lattices has opened a new field of research at the interface between atomic physics and condensed matter physics. The observation of the transition from a superfluid to a Mott insulator for bosonic atoms paved the way for the study of strongly correlated phases and quantum phase transitions in these systems. Very recently, the investigation of the Mott insulator state of fermionic atoms provides additional motivation to conduct such theoretical studies. This thesis can be divided broadly into two types of work: - On the one hand, we have proposed a new type of spectroscopy to measure single-particle correlators and associated physical observables in these strongly correlated states. - On the other hand, we have studied the ground state of the fermionic Hubbard model under different conditions (mass imbalance, population imbalance) by using analytical techniques and numerical simulations. In a collaboration with J. Dalibard and C. Salomon (LKB at the ENS Paris) and I. Carusotto (Trento, Italy), we have proposed and studied a novel spectroscopic method for the measurement and characterization of single particle excitations (in particular, the low energy excitations, namely the quasiparticles) in systems of cold fermionic atoms, with energy and momentum resolution. This type of spectroscopy is an analogue of angular-resolved photoemission in solid state physics (ARPES). We have shown, via simple models, that this method of measurement can characterize quasiparticles not only in the 'conventional' phases such as the weakly interacting gas in the lattice or in Fermi

Electron-muon correlation as a new probe of strongly interacting quark-gluon plasma

International Nuclear Information System (INIS)

Akamatsu, Yukinao; Hatsuda, Tetsuo; Hirano, Tetsufumi

2009-01-01

As a new and clean probe to the strongly interacting quark-gluon plasma (sQGP), we propose an azimuthal correlation of an electron and a muon that originate from the semileptonic decay of charm and bottom quarks. By solving the Langevin equation for the heavy quarks under the hydrodynamic evolution of the hot plasma, we show that substantial quenching of the away-side peak in the electron-muon correlation can be seen if the sQGP drag force acting on heavy quarks is large enough as suggested from the gauge/gravity correspondence. The effect could be detected in high-energy heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider.

Strongly correlated perovskite fuel cells

Science.gov (United States)

Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

2016-06-01

Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

Noise Spectroscopy in Strongly Correlated Oxides

Science.gov (United States)

Alsaqqa, Ali M.

Strongly correlated materials are an interesting class of materials, thanks to the novel electronic and magnetic phenomena they exhibit as a result of the interplay of various degrees of freedom. This gives rise to an array of potential applications, from Mott-FET to magnetic storage. Many experimental probes have been used to study phase transitions in strongly correlated oxides. Among these, resistance noise spectroscopy, together with conventional transport measurements, provides a unique viewpoint to understand the microscopic dynamics near the phase transitions in these oxides. In this thesis, utilizing noise spectroscopy and transport measurements, four different strongly correlated materials were studied: (1) neodymium nickel oxide (NdNiO 3) ultrathin films, (2) vanadium dioxide (VO2) microribbons, (3) copper vanadium bronze (CuxV2O 5) microribbons and (4) niobium triselenide (NbSe3) microribbons. Ultra thin films of rare-earth nickelates exhibit several temperature-driven phase transitions. In this thesis, we studied the metal-insulator and Neel transitions in a series of NdNiO3 films with different lattice mismatches. Upon colling down, the metal-insulator phase transition is accompanied by a structural (orthorohombic to monoclinic) and magnetic (paramagnetic to antiferromagnetic) transitions as well, making the problem more interesting and complex at the same time. The noise is of the 1/f type and is Gaussian in the high temperature phase, however deviations are seen in the low temperature phases. Below the metal-insulator transition, noise magnitude increases by orders of magnitude: a sign of inhomogeneous electrical conduction as result of phase separation. This is further assured by the non-Gaussian noise signature. At very low temperatures (T switches between Gaussian and non-Gaussian over several hours, possibly arising from dynamically competing ground states. VO2 is one of the most widely studied strongly correlated oxides and is important from the

Theoretical development and first-principles analysis of strongly correlated systems

Energy Technology Data Exchange (ETDEWEB)

Liu, Chen [Iowa State Univ., Ames, IA (United States)

2016-12-17

A variety of quantum many-body methods have been developed for studying the strongly correlated electron systems. We have also proposed a computationally efficient and accurate approach, named the correlation matrix renormalization (CMR) method, to address the challenges. The initial implementation of the CMR method is designed for molecules which have theoretical advantages, including small size of system, manifest mechanism and strongly correlation effect such as bond breaking process. The theoretic development and benchmark tests of the CMR method are included in this thesis. Meanwhile, ground state total energy is the most important property of electronic calculations. We also investigated an alternative approach to calculate the total energy, and extended this method for magnetic anisotropy energy (MAE) of ferromagnetic materials. In addition, another theoretical tool, dynamical mean- field theory (DMFT) on top of the DFT , has also been used in electronic structure calculations for an Iridium oxide to study the phase transition, which results from an interplay of the d electrons' internal degrees of freedom.

Eigenvalue distributions of correlated multichannel transfer matrices in strongly scattering systems

NARCIS (Netherlands)

Sprik, R.; Tourin, A.; de Rosny, J.; Fink, M.

2008-01-01

We experimentally study the effects of correlations in the propagation of ultrasonic waves in water from a multielement source to a multielement detector through a strongly scattering system of randomly placed vertical rods. Due to the strong scattering, the wave transport in the sample is in the

Residual correlation in two-proton interferometry from Λ-proton strong interactions

International Nuclear Information System (INIS)

Wang, Fuqiang

1999-01-01

We investigate the residual effect of Λp strong interactions in pp correlations with one proton from Λ decays. It is found that the residual correlation is about 10% of the Λp correlation strength, and has a broad distribution centered around q≅40 MeV/c. The residual correlation cannot explain the observed structure on the tail of the recently measured pp correlation function in central Pb+Pb collisions by NA49 at the Super Proton Synchrotron. (c) 1999 The American Physical Society

Machine Learning Phases of Strongly Correlated Fermions

Directory of Open Access Journals (Sweden)

Kelvin Ch’ng

2017-08-01

Full Text Available Machine learning offers an unprecedented perspective for the problem of classifying phases in condensed matter physics. We employ neural-network machine learning techniques to distinguish finite-temperature phases of the strongly correlated fermions on cubic lattices. We show that a three-dimensional convolutional network trained on auxiliary field configurations produced by quantum Monte Carlo simulations of the Hubbard model can correctly predict the magnetic phase diagram of the model at the average density of one (half filling. We then use the network, trained at half filling, to explore the trend in the transition temperature as the system is doped away from half filling. This transfer learning approach predicts that the instability to the magnetic phase extends to at least 5% doping in this region. Our results pave the way for other machine learning applications in correlated quantum many-body systems.

Phase diagram of strongly correlated Fermi systems

International Nuclear Information System (INIS)

Zverev, M.V.; Khodel', V.A.; Baldo, M.

2000-01-01

Phase transitions in uniform Fermi systems with repulsive forces between the particles caused by restructuring of quasiparticle filling n(p) are analyzed. It is found that in terms of variables, i.e. density ρ, nondimensional binding constant η, phase diagram of a strongly correlated Fermi system for rather a wide class of interactions reminds of a puff-pastry pie. Its upper part is filled with fermion condensate, the lower one - with normal Fermi-liquid. They are separated by a narrow interlayer - the Lifshits phase, characterized by the Fermi multibound surface [ru

Atomic physics of strongly correlated systems

International Nuclear Information System (INIS)

Lin, C.D.

1986-01-01

This abstract summarizes the progress made in the last year and the future plans of our research in the study of strongly correlated atomic systems. In atomic structure and atomic spectroscopy we are investigating the classification and supermultiplet structure of doubly excited states. We are also beginning the systematic study of triply excited states. In ion-atom collisions, we are exploring an AO-MO matching method for treating multi-electron collision systems to extract detailed information such as subshell cross sections, alignment and orientation parameters, etc. We are also beginning ab initio calculations on the angular distributions for electron transfer processes in low-energy (about 10-100eV/amu) ion-atom collisions in a full quantum mechanical treatment of the motion of heavy particles

Selected results on strong and coulomb-induced correlations from the STAR experiment

International Nuclear Information System (INIS)

Sumbera, M.

2007-01-01

Using recent high-statistics STAR data from Au + Au and Cu + Cu collisions at full RHIC energy I discuss strong and Coulomb-induced final state interaction effects on identical (pi-pi) and non-identical (pi-XI) particle correlations. Analysis of pi-XI correlations reveals the strong and Coulomb-induced FSI effects, allowing for the first time to estimate spatial extension of pi and XI sources and the average shift between them. Source imaging techniques provide clean separation of details of the source function and are applied to the one-dimensional relative momentum correlation function of identical pions. For low momentum pions, and/or non-central collisions, a large departure from a single-Gaussian shape is observed. (author)

Strongly correlated electrons on two coupled chains

International Nuclear Information System (INIS)

Weihong, Z.; Oitmaa, J.; Hamer, C.J.

2000-01-01

Full text: The discovery of materials containing S = 1/2 ions which form a 2-leg ladder structure has led to much current research on ladder systems. Pure spin ladders show an unexpected difference between odd-legged ladders (including the single chain) which are gapless with long-range correlations and even-legged ladders which have a spin gap and short range correlations. Even more interesting behaviour occurs when these systems are doped, creating a system of strongly correlated mobile holes, as in the cuprate superconductors. The simplest models in this context are the Hubbard model and the t-J model. Considerable work has been reported on both of these models, using both numerical calculations and approximate analytic theories. We have used series expansion methods to study both of these systems. Our results, in some cases, confirm those of other approaches. In other cases we are able to probe regions of the phase diagram inaccessible to other methods, or to obtain results of increased precision. In this paper we focus on:- 1. The energy and dispersion relation of 1-hole states. 2.The existence of a 2-hole bound state and its energy and dispersion. 3. Spin and charge gaps and the question of phase separation

Robust mesoscopic superposition of strongly correlated ultracold atoms

International Nuclear Information System (INIS)

Hallwood, David W.; Ernst, Thomas; Brand, Joachim

2010-01-01

We propose a scheme to create coherent superpositions of annular flow of strongly interacting bosonic atoms in a one-dimensional ring trap. The nonrotating ground state is coupled to a vortex state with mesoscopic angular momentum by means of a narrow potential barrier and an applied phase that originates from either rotation or a synthetic magnetic field. We show that superposition states in the Tonks-Girardeau regime are robust against single-particle loss due to the effects of strong correlations. The coupling between the mesoscopically distinct states scales much more favorably with particle number than in schemes relying on weak interactions, thus making particle numbers of hundreds or thousands feasible. Coherent oscillations induced by time variation of parameters may serve as a 'smoking gun' signature for detecting superposition states.

Exact time-dependent exchange-correlation potentials for strong-field electron dynamics

International Nuclear Information System (INIS)

Lein, Manfred; Kuemmel, Stephan

2005-01-01

By solving the time-dependent Schroedinger equation and inverting the time-dependent Kohn-Sham scheme we obtain the exact time-dependent exchange-correlation potential of density-functional theory for the strong-field dynamics of a correlated system. We demonstrate that essential features of the exact exchange-correlation potential can be related to derivative discontinuities in stationary density-functional theory. Incorporating the discontinuity in a time-dependent density-functional calculation greatly improves the description of the ionization process

Reduced larval feeding rate is a strong evolutionary correlate of ...

Indian Academy of Sciences (India)

Home; Journals; Journal of Genetics; Volume 85; Issue 3. Reduced larval feeding rate is a strong evolutionary correlate of rapid development in Drosophila melanogaster. M. Rajamani N. Raghavendra ... Keywords. life-history evolution; development time; larval feeding rate; competition; tradeoffs; Drosophila melanogaster.

Disorder and pseudogap in strongly correlated systems: Phase diagram in the DMFT + Σ approach

International Nuclear Information System (INIS)

Kuleeva, N. A.; Kuchinskii, E. Z.

2013-01-01

The influence of disorder and pseudogap fluctuations on the Mott insulator-metal transition in strongly correlated systems has been studied in the framework of the generalized dynamic mean field theory (DMFT + Σ approach). Using the results of investigations of the density of states (DOS) and optical conductivity, a phase diagram (disorder-Hubbard interaction-temperature) is constructed for the paramagnetic Anderson-Hubbard model, which allows both the effects of strong electron correlations and the influence of strong disorder to be considered. Strong correlations are described using the DMFT, while a strong disorder is described using a generalized self-consistent theory of localization. The DOS and optical conductivity of the paramagnetic Hubbard model have been studied in a pseudogap state caused by antiferromagnetic spin (or charge) short-range order fluctuations with a finite correlation length, which have been modeled by a static Gaussian random field. The effect of a pseudogap on the Mott insulator-metal transition has been studied. It is established that, in both cases, the static Gaussian random field (related to the disorder or pseudogap fluctuations) leads to suppression of the Mott transition, broadening of the coexistence region of the insulator and metal phases, and an increase in the critical temperature at which the coexistence region disappears

Observation of the two-electron cusp in atomic collisions. Evidence for strong electron-electron correlation

International Nuclear Information System (INIS)

Sarkadi, L.; Orban, A.

2007-01-01

the projectile. The two-electron emission from a moving center strongly suggests the picture of formation of quasi-stationary low-lying two-electron continuum states around the projectile. On the basis of this picture the observed strong energy correlation can be explained by an angular correlation of 180 deg in the projectile-centered reference system: The correlation between the low and high-energy emission in the laboratory system corresponds to that between backward and forward emission in the projectile frame. This result is consistent with the Wannier theory

Describing a Strongly Correlated Model System with Density Functional Theory.

Science.gov (United States)

Kong, Jing; Proynov, Emil; Yu, Jianguo; Pachter, Ruth

2017-07-06

The linear chain of hydrogen atoms, a basic prototype for the transition from a metal to Mott insulator, is studied with a recent density functional theory model functional for nondynamic and strong correlation. The computed cohesive energy curve for the transition agrees well with accurate literature results. The variation of the electronic structure in this transition is characterized with a density functional descriptor that yields the atomic population of effectively localized electrons. These new methods are also applied to the study of the Peierls dimerization of the stretched even-spaced Mott insulator to a chain of H 2 molecules, a different insulator. The transitions among the two insulating states and the metallic state of the hydrogen chain system are depicted in a semiquantitative phase diagram. Overall, we demonstrate the capability of studying strongly correlated materials with a mean-field model at the fundamental level, in contrast to the general pessimistic view on such a feasibility.

Fast electronic structure methods for strongly correlated molecular systems

International Nuclear Information System (INIS)

Head-Gordon, Martin; Beran, Gregory J O; Sodt, Alex; Jung, Yousung

2005-01-01

A short review is given of newly developed fast electronic structure methods that are designed to treat molecular systems with strong electron correlations, such as diradicaloid molecules, for which standard electronic structure methods such as density functional theory are inadequate. These new local correlation methods are based on coupled cluster theory within a perfect pairing active space, containing either a linear or quadratic number of pair correlation amplitudes, to yield the perfect pairing (PP) and imperfect pairing (IP) models. This reduces the scaling of the coupled cluster iterations to no worse than cubic, relative to the sixth power dependence of the usual (untruncated) coupled cluster doubles model. A second order perturbation correction, PP(2), to treat the neglected (weaker) correlations is formulated for the PP model. To ensure minimal prefactors, in addition to favorable size-scaling, highly efficient implementations of PP, IP and PP(2) have been completed, using auxiliary basis expansions. This yields speedups of almost an order of magnitude over the best alternatives using 4-center 2-electron integrals. A short discussion of the scope of accessible chemical applications is given

Quantum correlations responsible for remote state creation: strong and weak control parameters

Science.gov (United States)

Doronin, S. I.; Zenchuk, A. I.

2017-03-01

We study the quantum correlations between the two remote qubits (sender and receiver) connected by the transmission line (homogeneous spin-1/2 chain) depending on the parameters of the sender's and receiver's initial states (control parameters). We consider two different measures of quantum correlations: the entanglement (a traditional measure) and the informational correlation (based on the parameter exchange between the sender and receiver). We find the domain in the control parameter space yielding (i) zero entanglement between the sender and receiver during the whole evolution period and (ii) non-vanishing informational correlation between the sender and receiver, thus showing that the informational correlation is responsible for the remote state creation. Among the control parameters, there are the strong parameters (which strongly effect the values of studied measures) and the weak ones (whose effect is negligible), therewith the eigenvalues of the initial state are given a privileged role. We also show that the problem of small entanglement (concurrence) in quantum information processing is similar (in certain sense) to the problem of small determinants in linear algebra. A particular model of 40-node spin-1/2 communication line is presented.

Communication: Thermodynamics of condensed matter with strong pressure-energy correlations

DEFF Research Database (Denmark)

Ingebrigtsen, Trond; Bøhling, Lasse; Schrøder, Thomas

2012-01-01

We show that for any liquid or solid with strong correlation between its NVT virial and potential-energy equilibrium fluctuations, the temperature is a product of a function of excess entropy per particle and a function of density, T = f(s)h(ρ). This implies that (1) the system's isomorphs (curve...

Magnetic properties of metallic impurities with strongly correlated electrons

Czech Academy of Sciences Publication Activity Database

Janiš, Václav; Ringel, Matouš

2009-01-01

Roč. 115, č. 1 (2009), s. 30-35 ISSN 0587-4246 R&D Projects: GA ČR GA202/07/0644 Institutional research plan: CEZ:AV0Z10100520 Keywords : And erson impurity * strong electron correlations * spin-polarized solution * three-channel parquet equations * magnetic field Subject RIV: BE - Theoretical Physics Impact factor: 0.433, year: 2009 http://przyrbwn.icm.edu.pl/APP/ABSTR/115/a115-1-5.html

High plasma triglyceride levels strongly correlate with low kisspeptin in the arcuate nucleus of male rats

DEFF Research Database (Denmark)

Overgaard, A; Axel, A M; Lie, M E

2015-01-01

OBJECTIVE: It is well known that reproductive capacity is lower in obese individuals, but what mediators and signals are involved is unclear. Kisspeptin is a potent stimulator of GnRH release, and it has been suggested that kisspeptin neurons located in the arcuate nucleus transmit metabolic...... signals to the GnRH neurons. METHODS: In this study, we measured body weight and plasma concentrations of leptin, insulin, testosterone, and triglycerides after high fat diet exposure and correlated these parameters with the number of kisspeptin-immunoreactive neurons in the arcuate nucleus of male rats...... with increased fat in the diet. Kisspeptin-immunoreactive cells are not correlated with body weight, testosterone, leptin or insulin. However, we find that the number of kisspeptin-immunoreactive cells is strongly and negatively correlated with the level of plasma triglycerides (R2=0.49, p=0.004). CONCLUSION: We...

Three-qutrit correlations violate local realism more strongly than those of three qubits

International Nuclear Information System (INIS)

Kaszlikowski, Dagomir; Gosal, Darwin; Ling, E.J.; Oh, C.H.; Kwek, L.C.; Zukowski, Marek

2002-01-01

We present numerical data showing that three-qutrit correlations for a pure state, which is not maximally entangled, violate local realism more strongly than three-qubit correlations. The strength of violation is measured by the minimal amount of noise that must be admixed to the system so that the noisy correlations have a local and realistic model

International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)

Science.gov (United States)

2018-05-01

The 2017 International Conference on Strongly Correlated Electron Systems, SCES 2017, took place at the Clarion Congress Hotel in Prague, Czech Republic from July 17 to 21, 2017. The meeting was held under the auspices of the Department of Condensed Matter Physics of the Faculty of Mathematics and Physics of the Charles University.

Surface correlation effects in two-band strongly correlated slabs.

Science.gov (United States)

Esfahani, D Nasr; Covaci, L; Peeters, F M

2014-02-19

Using an extension of the Gutzwiller approximation for an inhomogeneous system, we study the two-band Hubbard model with unequal band widths for a slab geometry. The aim is to investigate the mutual effect of individual bands on the spatial distribution of quasi-particle weight and charge density, especially near the surface of the slab. The main effect of the difference in band width is the presence of two different length scales corresponding to the quasi-particle profile of each band. This is enhanced in the vicinity of the critical interaction of the narrow band where an orbitally selective Mott transition occurs and a surface dead layer forms for the narrow band. For the doped case, two different regimes of charge transfer between the surface and the bulk of the slab are revealed. The charge transfer from surface/center to center/surface depends on both the doping level and the average relative charge accumulated in each band. Such effects could also be of importance when describing the accumulation of charges at the interface between structures made of multi-band strongly correlated materials.

Algorithmic implementation of particle-particle ladder diagram approximation to study strongly-correlated metals and semiconductors

Science.gov (United States)

Prayogi, A.; Majidi, M. A.

2017-07-01

In condensed-matter physics, strongly-correlated systems refer to materials that exhibit variety of fascinating properties and ordered phases, depending on temperature, doping, and other factors. Such unique properties most notably arise due to strong electron-electron interactions, and in some cases due to interactions involving other quasiparticles as well. Electronic correlation effects are non-trivial that one may need a sufficiently accurate approximation technique with quite heavy computation, such as Quantum Monte-Carlo, in order to capture particular material properties arising from such effects. Meanwhile, less accurate techniques may come with lower numerical cost, but the ability to capture particular properties may highly depend on the choice of approximation. Among the many-body techniques derivable from Feynman diagrams, we aim to formulate algorithmic implementation of the Ladder Diagram approximation to capture the effects of electron-electron interactions. We wish to investigate how these correlation effects influence the temperature-dependent properties of strongly-correlated metals and semiconductors. As we are interested to study the temperature-dependent properties of the system, the Ladder diagram method needs to be applied in Matsubara frequency domain to obtain the self-consistent self-energy. However, at the end we would also need to compute the dynamical properties like density of states (DOS) and optical conductivity that are defined in the real frequency domain. For this purpose, we need to perform the analytic continuation procedure. At the end of this study, we will test the technique by observing the occurrence of metal-insulator transition in strongly-correlated metals, and renormalization of the band gap in strongly-correlated semiconductors.

Bound states in strongly correlated magnetic and electronic systems

International Nuclear Information System (INIS)

Trebst, S.

2002-02-01

A novel strong coupling expansion method to calculate two-particle spectra of quantum lattice models is developed. The technique can be used to study bosonic and fermionic models and in principle it can be applied to systems in any dimension. A number of strongly correlated magnetic and electronic systems are examined including the two-leg spin-half Heisenberg ladder, the dimerized Heisenberg chain with a frustrating next-nearest neighbor interaction, coupled Heisenberg ladders, and the one-dimensional Kondo lattice model. In the various models distinct bound states are found below the two-particle continuum. Quantitative calculations of the dispersion, coherence length and binding energy of these bound states are used to describe spectroscopic experiments on (Ca,La) 14 Cu 24 O 41 and NaV 2 O 5 . (orig.)

Quantum simulation of strongly correlated condensed matter systems

Science.gov (United States)

Hofstetter, W.; Qin, T.

2018-04-01

We review recent experimental and theoretical progress in realizing and simulating many-body phases of ultracold atoms in optical lattices, which gives access to analog quantum simulations of fundamental model Hamiltonians for strongly correlated condensed matter systems, such as the Hubbard model. After a general introduction to quantum gases in optical lattices, their preparation and cooling, and measurement techniques for relevant observables, we focus on several examples, where quantum simulations of this type have been performed successfully during the past years: Mott-insulator states, itinerant quantum magnetism, disorder-induced localization and its interplay with interactions, and topological quantum states in synthetic gauge fields.

Strong phase correlations of solitons of nonlinear Schroedinger equation

International Nuclear Information System (INIS)

Litvak, A.G.; Mironov, V.A.; Protogenov, A.P.

1994-06-01

We discuss the possibility to suppress the collapse in the nonlinear 2+1 D Schroedinger equation by using the gauge theory of strong phase correlations. It is shown that invariance relative to q-deformed Hopf algebra with deformation parameter q being the fourth root of unity makes the values of the Chern-Simons term coefficient, k=2, and of the coupling constant, g=1/2, fixed; no collapsing solutions are present at those values. (author). 21 refs

Peculiarities of the momentum distribution functions of strongly correlated charged fermions

Science.gov (United States)

Larkin, A. S.; Filinov, V. S.; Fortov, V. E.

2018-01-01

New numerical version of the Wigner approach to quantum thermodynamics of strongly coupled systems of particles has been developed for extreme conditions, when analytical approximations based on different kinds of perturbation theories cannot be applied. An explicit analytical expression of the Wigner function has been obtained in linear and harmonic approximations. Fermi statistical effects are accounted for by effective pair pseudopotential depending on coordinates, momenta and degeneracy parameter of particles and taking into account Pauli blocking of fermions. A new quantum Monte-Carlo method for calculations of average values of arbitrary quantum operators has been developed. Calculations of the momentum distribution functions and the pair correlation functions of degenerate ideal Fermi gas have been carried out for testing the developed approach. Comparison of the obtained momentum distribution functions of strongly correlated Coulomb systems with the Maxwell-Boltzmann and the Fermi distributions shows the significant influence of interparticle interaction both at small momenta and in high energy quantum ‘tails’.

Rydberg-atom formation in strongly correlated ultracold plasmas

International Nuclear Information System (INIS)

Bannasch, G.; Pohl, T.

2011-01-01

In plasmas at very low temperatures, the formation of neutral atoms is dominated by collisional three-body recombination, owing to the strong ∼T -9/2 scaling of the corresponding recombination rate with the electron temperature T. While this law is well established at high temperatures, the unphysical divergence as T→0 clearly suggests a breakdown in the low-temperature regime. Here, we present a combined molecular dynamics Monte Carlo study of electron-ion recombination over a wide range of temperatures and densities. Our results reproduce the known behavior of the recombination rate at high temperatures, but reveal significant deviations with decreasing temperature. We discuss the fate of the kinetic bottleneck and resolve the divergence problem as the plasma enters the ultracold, strongly coupled domain.

Strong correlation effects in theoretical STM studies of magnetic adatoms

Science.gov (United States)

Dang, Hung T.; dos Santos Dias, Manuel; Liebsch, Ansgar; Lounis, Samir

2016-03-01

We present a theoretical study for the scanning tunneling microscopy (STM) spectra of surface-supported magnetic nanostructures, incorporating strong correlation effects. As concrete examples, we study Co and Mn adatoms on the Cu(111) surface, which are expected to represent the opposite limits of Kondo physics and local moment behavior, using a combination of density functional theory and both quantum Monte Carlo and exact diagonalization impurity solvers. We examine in detail the effects of temperature T , correlation strength U , and impurity d electron occupancy Nd on the local density of states. We also study the effective coherence energy scale, i.e., the Kondo temperature TK, which can be extracted from the STM spectra. Theoretical STM spectra are computed as a function of STM tip position relative to each adatom. Because of the multiorbital nature of the adatoms, the STM spectra are shown to consist of a complicated superposition of orbital contributions, with different orbital symmetries, self-energies, and Kondo temperatures. For a Mn adatom, which is close to half-filling, the STM spectra are featureless near the Fermi level. On the other hand, the quasiparticle peak for a Co adatom gives rise to strongly position-dependent Fano line shapes.

First-principles study of strong correlation effects in pyrochlore iridates

Energy Technology Data Exchange (ETDEWEB)

Shinaoka, Hiroshi [Department of Physics, Saitama University (Japan); Hoshino, Shintaro [Department of Basic Science, The University of Tokyo (Japan); Troyer, Matthias [Theoretische Physik, ETH Zuerich (Switzerland); Werner, Philipp [Department of Physics, University of Fribourg (Switzerland)

2016-07-01

The pyrochlore iridates A{sub 2}Ir{sub 2}O{sub 7} (A=Pr, Nd, Y, etc.) are an ideal system to study fascinating phenomena induced by strong electron correlations and spin-orbit coupling. In this talk, we study strong correlation effects in the prototype compound Y{sub 2}Ir{sub 2}O{sub 7} using the local density approximation and dynamical mean-field theory (LDA+DMFT). We map out the phase diagram in the space of temperature, onsite Coulomb repulsion U, and filling. Consistent with experiments, we find that an all-in/all-out ordered insulating phase is stable for realistic values of U. We reveal the importance of the hybridization between j{sub eff} = 1/2 and j{sub eff} = 3/2 states under the Coulomb interaction and trigonal crystal field. We demonstrate a substantial band narrowing in the paramagnetic metallic phase and non-Fermi liquid behavior in the electron/hole doped system originating from long-lived quasi-spin moments induced by nearly flat bands. We further compare our results with recent experimental results of Eu{sub 2}Ir{sub 2}O{sub 7} under hydrostatic pressure.

Small Fermi surfaces and strong correlation effects in Dirac materials with holography

Science.gov (United States)

Seo, Yunseok; Song, Geunho; Park, Chanyong; Sin, Sang-Jin

2017-10-01

Recent discovery of transport anomaly in graphene demonstrated that a system known to be weakly interacting may become strongly correlated if system parameter (s) can be tuned such that fermi surface is sufficiently small. We study the strong correlation effects in the transport coefficients of Dirac materials doped with magnetic impurity under the magnetic field using holographic method. The experimental data of magneto-conductivity are well fit by our theory, however, not much data are available for other transports of Dirac material in such regime. Therefore, our results on heat transport, thermo-electric power and Nernst coefficients are left as predictions of holographic theory for generic Dirac materials in the vicinity of charge neutral point with possible surface gap. We give detailed look over each magneto-transport observable and 3Dplots to guide future experiments.

Transport phenomena in strongly correlated Fermi liquids

CERN Document Server

Kontani, Hiroshi

2013-01-01

In conventional metals, various transport coefficients are scaled according to the quasiparticle relaxation time, \\tau, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems, reflecting their unique electronic states. The most famous example would be cuprate high-Tc superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. To better understand the origin of this discrepancy, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. Near the magnetic quantum critical point, the current vertex correction (CVC), which describes the electron-electron scattering beyond the relaxation time approximation, gives rise to various anomalous transport phenomena. We explain anomalous transport phenomena in cuprate HTSCs and other metals near their magnetic or orbital quantum critical poi...

Strongly correlated electron systems and neutron scattering. Magnetism, superconductivity, structural phase transition

Energy Technology Data Exchange (ETDEWEB)

Katano, Susumu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-03-01

Neutron scattering experiments in our group on strongly correlated electron systems are reviewed Metal-insulator transitions caused by structural phase transitions in (La{sub 1-x}Sr{sub x}) MnO{sub 3}, a novel magnetic transition in the CeP compound, correlations between antiferromagnetism and superconductivity in UPd{sub 2}Al{sub 3} and so forth are discussed. Here, in this note, the phase transition of Mn-oxides was mainly described. (author)

Doubly excited helium. From strong correlation to chaos

International Nuclear Information System (INIS)

Jiang, Yuhai

2006-03-01

In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I 15 , and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I 5 to I 9 and I 7 , respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I 4 were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I 4 by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

Mott Transition In Strongly Correlated Materials: Many-Body Methods And Realistic Materials Simulations

Science.gov (United States)

Lee, Tsung-Han

Strongly correlated materials are a class of materials that cannot be properly described by the Density Functional Theory (DFT), which is a single-particle approximation to the original many-body electronic Hamiltonian. These systems contain d or f orbital electrons, i.e., transition metals, actinides, and lanthanides compounds, for which the electron-electron interaction (correlation) effects are too strong to be described by the single-particle approximation of DFT. Therefore, complementary many-body methods have been developed, at the model Hamiltonians level, to describe these strong correlation effects. Dynamical Mean Field Theory (DMFT) and Rotationally Invariant Slave-Boson (RISB) approaches are two successful methods that can capture the correlation effects for a broad interaction strength. However, these many-body methods, as applied to model Hamiltonians, treat the electronic structure of realistic materials in a phenomenological fashion, which only allow to describe their properties qualitatively. Consequently, the combination of DFT and many body methods, e.g., Local Density Approximation augmented by RISB and DMFT (LDA+RISB and LDA+DMFT), have been recently proposed to combine the advantages of both methods into a quantitative tool to analyze strongly correlated systems. In this dissertation, we studied the possible improvements of these approaches, and tested their accuracy on realistic materials. This dissertation is separated into two parts. In the first part, we studied the extension of DMFT and RISB in three directions. First, we extended DMFT framework to investigate the behavior of the domain wall structure in metal-Mott insulator coexistence regime by studying the unstable solution describing the domain wall. We found that this solution, differing qualitatively from both the metallic and the insulating solutions, displays an insulating-like behavior in resistivity while carrying a weak metallic character in its electronic structure. Second, we

Correlation potential of a test ion near a strongly charged plate.

Science.gov (United States)

Lu, Bing-Sui; Xing, Xiangjun

2014-03-01

We analytically calculate the correlation potential of a test ion near a strongly charged plate inside a dilute m:-n electrolyte. We do this by calculating the electrostatic Green's function in the presence of a nonlinear background potential, the latter having been obtained using the nonlinear Poisson-Boltzmann theory. We consider the general case where the dielectric constants of the plate and the electrolyte are distinct. The following generic results emerge from our analyses: (1) If the distance to the plate Δz is much larger than a Gouy-Chapman length, the plate surface will behave effectively as an infinitely charged surface, and the dielectric constant of the plate effectively plays no role. (2) If Δz is larger than a Gouy-Chapman length but shorter than a Debye length, the correlation potential can be interpreted in terms of an image charge that is three times larger than the source charge. This behavior is independent of the valences of the ions. (3) The Green's function vanishes inside the plate if the surface charge density is infinitely large; hence the electrostatic potential is constant there. In this respect, a strongly charged plate behaves like a conductor plate. (4) If Δz is smaller than a Gouy-Chapman length, the correlation potential is dominated by the conventional image charge due to the dielectric discontinuity at the interface. (5) If Δz is larger than a Debye length, the leading order behavior of the correlation potential will depend on the valences of the ions in the electrolyte. Furthermore, inside an asymmetric electrolyte, the correlation potential is singly screened, i.e., it undergoes exponential decay with a decay width equal to the Debye length.

Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas

Science.gov (United States)

Adams, Allan; Carr, Lincoln D.; Schaefer, Thomas; Steinberg, Peter; Thomas, John E.

2013-04-01

interdisciplinary appeal and include new studies of high temperature superfluidity, viscosity, spin-transport, spin-imbalanced mixtures, and three-component gases, this last having a close parallel to color superconductivity. Another system important for the field of strongly-interacting quantum fluids was revealed by analysis of data from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Despite naive expectations based on asymptotic freedom that the deconfinement of quarks and gluons at high temperatures would lead to a weakly-interacting quark gluon plasma (QGP), the system appeared to be quite strongly coupled. Subsequent estimates of the viscosity-to-entropy ratio suggest that the system is tantalizingly close to the postulated bound from AdS/CFT calculations. The field is quite dynamic at the moment; new measurements are expected from upgraded detectors at RHIC, and an entirely new energy regime is being opened up by heavy ion collisions at the Large Hadron Collider (LHC) at CERN. On the theoretical side, much work remains to be done to extract the precise values of the transport coefficients, and to characterize the nature of quasi-particle excitations in the plasma. Finally, holographic dualities such as anti-de Sitter/conformal field theory (AdS/CFT) have opened a new theoretical window on strongly correlated fluids. Holography relates strongly-interacting quantum many-body systems to weakly-coupled semi-classical gravitational systems, replacing quasiparticles with geometry and translating various difficult questions about quantum fluids into simple and calculable geometric exercises. Already, some of the earliest lessons of holography, such as the conjectural bound on the viscosity-to-entropy ratio, have had a considerable impact on the theoretical and experimental study of strongly correlated fluids, from RHIC to ultracold atoms. More recently, the study of holographic superconductors, non-Fermi liquids and unitary quantum gases has touched

The Role of screening in the strongly correlated 2D systems

CERN Document Server

Hwang, E H

2003-01-01

We investigate recently observed experiments in the strongly correlated 2D systems (r sub s >> 1) (low-density 2D plasmons, metallic behaviour of 2D systems and frictional drag resistivity between two 2D hole layers). We compare them with our theoretical results calculated within a conventional Fermi liquid theory with RPA screening.

Strong correlations and the search for high-Tc superconductivity in chromium pnictides and chalcogenides

Science.gov (United States)

Pizarro, J. M.; Calderón, M. J.; Liu, J.; Muñoz, M. C.; Bascones, E.

2017-02-01

Undoped iron superconductors accommodate n =6 electrons in five d orbitals. Experimental and theoretical evidence shows that the strength of correlations increases with hole doping, as the electronic filling approaches half filling with n =5 electrons. This evidence delineates a scenario in which the parent compound of iron superconductors is the half-filled system, in analogy to cuprate superconductors. In cuprates the superconductivity can be induced upon electron or hole doping. In this work we propose to search for high-Tc superconductivity and strong correlations in chromium pnictides and chalcogenides with n slave-spin and multiorbital random-phase-approximation calculations we analyze the strength of the correlations and the superconducting and magnetic instabilities in these systems with the main focus on LaCrAsO. We find that electron-doped LaCrAsO is a strongly correlated system with competing magnetic interactions, with (π ,π ) antiferromagnetism and nodal d -wave pairing being the most plausible magnetic and superconducting instabilities, respectively.

Strongly correlated Fermi-Bose mixtures in disordered optical lattices

International Nuclear Information System (INIS)

Sanchez-Palencia, L; Ahufinger, V; Kantian, A; Zakrzewski, J; Sanpera, A; Lewenstein, M

2006-01-01

We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the boson-fermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes

Strongly correlated Fermi-Bose mixtures in disordered optical lattices

Energy Technology Data Exchange (ETDEWEB)

Sanchez-Palencia, L [Laboratoire Charles Fabry de l' Institut d' Optique, CNRS and Universite Paris-Sud XI, Bat 503, Centre scientifique, F-91403 Orsay Cedex (France); Ahufinger, V [ICREA and Grup d' optica, Departament de FIsica, Universitat Autonoma de Barcelona, E-08193 Belaterra (Barcelona) (Spain); Kantian, A [Institut fuer Theoretische Physik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Zakrzewski, J [Instytut Fizyki imienia Mariana Smoluchowskiego i Centrum Badan Ukladow Zlozonych imienia Marka Kaca, Uniwersytet Jagiellonski, ulica Reymonta 4, PL-30-059 Krakow (Poland); Sanpera, A [ICREA and Grup de FIsica Teorica, Departament de FIsica, Universitat Autonoma de Barcelona, E-08193 Belaterra (Barcelona) (Spain); Lewenstein, M [ICREA and ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la TecnologIa, E-08860 Castelldefels (Barcelona) (Spain); Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany)

2006-05-28

We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the boson-fermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes.

Subgap Two-Photon States in Polycyclic Aromatic Hydrocarbons: Evidence for Strong Electron Correlations

OpenAIRE

Aryanpour, K.; Roberts, A.; Sandhu, A.; Rathore, R.; Shukla, A.; Mazumdar, S.

2013-01-01

Strong electron correlation effects in the photophysics of quasi-one-dimensional $\\pi$-conjugated organic systems such as polyenes, polyacetylenes, polydiacetylenes, etc., have been extensively studied. Far less is known on correlation effects in two-dimensional $\\pi$-conjugated systems. Here we present theoretical and experimental evidence for moderate repulsive electron-electron interactions in a number of finite polycyclic aromatic hydrocarbon molecules with $D_{6h}$ symmetry. We show that...

Doubly excited helium. From strong correlation to chaos

Energy Technology Data Exchange (ETDEWEB)

Jiang, Yuhai

2006-03-15

In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I{sub 15}, and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I{sub 5} to I{sub 9} and I{sub 7}, respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I{sub 4} were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I{sub 4} by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

Strongly correlated quantum fluids: ultracold quantum gases, quantum chromodynamic plasmas and holographic duality

OpenAIRE

Adams, Allan; Carr, Lincoln D.; Schafer, Thomas; Steinberg, Peter; Thomas, John E.

2012-01-01

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These sy...

Strongly correlated quantum transport out-of-equilibrium

Science.gov (United States)

Dutt, Prasenjit

The revolutionary advances in nanotechnology and nanofabrication have facilitated the precise control and manipulation of mesoscopic systems where quantum effects are pronounced. Quantum devices with tunable gates have made it possible to access regimes far beyond the purview of linear response theory. In particular, the influence of strong voltage and thermal biases has led to the observation of novel phenomena where the non-equilibrium characteristics of the system are of paramount importance. We study transport through quantum-impurity systems in the regime of strong correlations and determine the effects of large temperature and potential gradients on its many-body physics. In Part I of this thesis we focus on the steady-state dynamics of the system, a commonly encountered experimental scenario. For a system consisting of several leads composed of non-interacting electrons, each individually coupled to a quantum impurity with interactions and maintained at different chemical potentials, we reformulate the system in terms of an effective-equilibrium density matrix. This density matrix has a simple Boltzmann-like form in terms of the system's Lippmann-Schwinger (scattering) operators. We elaborate the conditions for this description to be valid based on the microscopic Hamiltonian of the system. We then prove the equivalence of physical observables computed using this formulation with corresponding expressions in the Schwinger-Keldysh approach and provide a dictionary between Green's functions in either scheme. An imaginary-time functional integral framework to compute finite temperature Green's functions is proposed and used to develop a novel perturbative expansion in the interaction strength which is exact in all other system parameters. We use these tools to study the fate of the Abrikosov-Suhl regime on the Kondo-correlated quantum dot due to the effects of bias and external magnetic fields. Next, we expand the domain of this formalism to additionally

Anomalous Behavior of Electronic Heat Capacity of Strongly Correlated Iron Monosilicide

Science.gov (United States)

Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.

2018-04-01

The paper deals with the electronic heat capacity of iron monosilicide FeSi subjected to semiconductor-metal thermal transition during which the formation of its spintronic properties is observed. The proposed model which considers pd-hybridization of strongly correlated d-electrons with non-correlated p-electrons, demonstrates a connection of their contribution to heat capacity in the insulator phase with paramagnon effects and fluctuations of occupation numbers for p- and d-states. In a slitless state, the temperature curve of heat capacity is characterized by a maximum appeared due to normalization of the electron density of states using fluctuating exchange fields. At higher temperatures, a linear growth in heat capacity occurs due to paramagnon effects. The correlation between the model parameters and the first-principles calculation provides the electron contribution to heat capacity, which is obtained from the experimental results on phonon heat capacity. Anharmonicity of phonons is connected merely with the thermal expansion of the crystal lattice.

Many-body Tunneling and Nonequilibrium Dynamics of Doublons in Strongly Correlated Quantum Dots.

Science.gov (United States)

Hou, WenJie; Wang, YuanDong; Wei, JianHua; Zhu, ZhenGang; Yan, YiJing

2017-05-30

Quantum tunneling dominates coherent transport at low temperatures in many systems of great interest. In this work we report a many-body tunneling (MBT), by nonperturbatively solving the Anderson multi-impurity model, and identify it a fundamental tunneling process on top of the well-acknowledged sequential tunneling and cotunneling. We show that the MBT involves the dynamics of doublons in strongly correlated systems. Proportional to the numbers of dynamical doublons, the MBT can dominate the off-resonant transport in the strongly correlated regime. A T 3/2 -dependence of the MBT current on temperature is uncovered and can be identified as a fingerprint of the MBT in experiments. We also prove that the MBT can support the coherent long-range tunneling of doublons, which is well consistent with recent experiments on ultracold atoms. As a fundamental physical process, the MBT is expected to play important roles in general quantum systems.

Quantum group random walks in strongly correlated 2+1 D spin systems

International Nuclear Information System (INIS)

Protogenov, A.P.; Rostovtsev, Yu.V.; Verbus, V.A.

1994-06-01

We consider the temporal evolution of strong correlated degrees of freedom in 2+1 D spin systems using the Wilson operator eigenvalues as variables. It is shown that the quantum-group diffusion equation at deformation parameter q being the k-th root of unity has the polynomial solution of degree k. (author). 20 refs, 1 tab

On strong-coupling correlation functions of circular Wilson loops and local operators

International Nuclear Information System (INIS)

Alday, Luis F; Tseytlin, Arkady A

2011-01-01

Motivated by the problem of understanding 3-point correlation functions of gauge-invariant operators in N=4 super Yang-Mills theory we consider correlators involving Wilson loops and a 'light' operator with fixed quantum numbers. At leading order in the strong-coupling expansion such correlators are given by the 'light' vertex operator evaluated on a semiclassical string world surface ending on the corresponding loops at the boundary of AdS 5 x S 5 . We study in detail the example of a correlator of two concentric circular Wilson loops and a dilaton vertex operator. The resulting expression is given by an integral of combinations of elliptic functions and can be computed analytically in some special limits. We also consider a generalization of the minimal surface ending on two circles to the case of non-zero angular momentum J in S 5 and discuss a special limit when one of the Wilson loops is effectively replaced by a 'heavy' operator with charge J. (paper)

Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

Directory of Open Access Journals (Sweden)

Z. T. Guo

2009-02-01

Full Text Available We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ¹⁸O and carbon isotope (δ¹³C values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO₂ and CH₄ concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO₂ changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ¹⁸O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of

Microscopic theory of photon-correlation spectroscopy in strong-coupling semiconductors

Energy Technology Data Exchange (ETDEWEB)

Schneebeli, Lukas

2009-11-27

would be a great contribution in the growing field of quantum optics in semiconductors. The efforts in QD systems are again driven by the atomic systems which not only have shown the vacuum Rabi splitting, but also the second rung, e.g. via direct spectroscopy and via photon-correlation measurements. In this thesis, it is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states. Using a microscopic theory, the second-rung resonance of Jaynes-Cummings ladder is analyzed and optimum excitation conditions are determined. The computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second-rung emission. The resonance fluorescence equations are derived and solved for strong-coupling semiconductor quantum-dot systems using a fully quantized multimode theory and a cluster-expansion approach. A reduced model is developed to explain the origin of auto- and cross-correlation resonances in the two-photon emission spectrum of the fluorescent light. These resonances are traced back to the two-photon strong-coupling states of Jaynes-Cummings ladder. The accuracy of the reduced model is verified via numerical solution of the resonance fluorescence equations. The analysis reveals the direct relation between the squeezed-light emission and the strong-coupling states in optically excited semiconductor systems. (orig.)

Baryon femtoscopy considering residual correlations as a tool to extract strong interaction potentials

Directory of Open Access Journals (Sweden)

Szymański Maciej

2015-01-01

Full Text Available In this article, the analysis of baryon-antibaryon femtoscopic correlations is presented. In particular, it is shown that taking into account residual correlations is crucial for the description of pΛ¯$\\bar \\Lambda $ and p̄Λ correlation functions measured by the STAR experiment in Au–Au collisions at the centre-of-mass energy per nucleon pair √sNN = 200 GeV. This approach enables to obtain pΛ¯$\\bar \\Lambda $ (p̄Λ source size consistent with the sizes extracted from correlations in pΛ (p̄Λ¯$\\bar \\Lambda $ and lighter pair systems as well as with model predictions. Moreover, with this analysis it is possible to derive the unknown parameters of the strong interaction potential for baryon-antibaryon pairs under several assumptions.

Strongly correlated states of a small cold-atom cloud from geometric gauge fields

International Nuclear Information System (INIS)

Julia-Diaz, B.; Dagnino, D.; Barberan, N.; Guenter, K. J.; Dalibard, J.; Grass, T.; Lewenstein, M.

2011-01-01

Using exact diagonalization for a small system of cold bosonic atoms, we analyze the emergence of strongly correlated states in the presence of an artificial magnetic field. This gauge field is generated by a laser beam that couples two internal atomic states, and it is related to Berry's geometrical phase that emerges when an atom follows adiabatically one of the two eigenstates of the atom-laser coupling. Our approach allows us to go beyond the adiabatic approximation, and to characterize the generalized Laughlin wave functions that appear in the strong magnetic-field limit.

Strongly correlated states of a small cold-atom cloud from geometric gauge fields

Energy Technology Data Exchange (ETDEWEB)

Julia-Diaz, B. [Dept. ECM, Facultat de Fisica, U. Barcelona, E-08028 Barcelona (Spain); ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Barcelona (Spain); Dagnino, D.; Barberan, N. [Dept. ECM, Facultat de Fisica, U. Barcelona, E-08028 Barcelona (Spain); Guenter, K. J.; Dalibard, J. [Laboratoire Kastler Brossel, CNRS, UPMC, Ecole Normale Superieure, 24 rue Lhomond, F-75005 Paris (France); Grass, T. [ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Barcelona (Spain); Lewenstein, M. [ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Barcelona (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain)

2011-11-15

Using exact diagonalization for a small system of cold bosonic atoms, we analyze the emergence of strongly correlated states in the presence of an artificial magnetic field. This gauge field is generated by a laser beam that couples two internal atomic states, and it is related to Berry's geometrical phase that emerges when an atom follows adiabatically one of the two eigenstates of the atom-laser coupling. Our approach allows us to go beyond the adiabatic approximation, and to characterize the generalized Laughlin wave functions that appear in the strong magnetic-field limit.

Strongly correlated photons generated by coupling a three- or four-level system to a waveguide

Science.gov (United States)

Zheng, Huaixiu; Gauthier, Daniel J.; Baranger, Harold U.

2012-04-01

We study the generation of strongly correlated photons by coupling an atom to photonic quantum fields in a one-dimensional waveguide. Specifically, we consider a three-level or four-level system for the atom. Photon-photon bound states emerge as a manifestation of the strong photon-photon correlation mediated by the atom. Effective repulsive or attractive interaction between photons can be produced, causing either suppressed multiphoton transmission (photon blockade) or enhanced multiphoton transmission (photon-induced tunneling). As a result, nonclassical light sources can be generated on demand by sending coherent states into the proposed system. We calculate the second-order correlation function of the transmitted field and observe bunching and antibunching caused by the bound states. Furthermore, we demonstrate that the proposed system can produce photon pairs with a high degree of spectral entanglement, which have a large capacity for carrying information and are important for large-alphabet quantum communication.

Strong associations between national prevalence of various STIs suggests sexual network connectivity is a common underpinning risk factor.

Science.gov (United States)

Kenyon, Chris

2017-10-12

If national peak Human Immunodeficiency Virus (HIV) prevalence is positively associated with the prevalence of other sexually transmitted infections (STIs) from before or early on in the HIV epidemics this would suggest common underlying drivers. Pearson's correlations were calculated between the prevalence of seven STIs at a country-level: chlamydia, gonorrhoea, trichomoniasis, syphilis, bacterial vaginosis, herpes simplex virus-2 (HSV-2) and HIV. The prevalence of all the STIs was highest in the sub-Saharan African region excluding chlamydia. The prevalence of all seven STIs were positively correlated excluding chlamydia. The correlations were strongest for HIV-HSV-2 (r = 0.85, P < 0.0001) and HSV-2-trichomoniasis (r = 0.82, P < 0.0001). Our results of a generally positive association between the prevalences of a range of STIs suggests that higher prevalences were driven by common underlying determinants. We review different types of evidence which suggest that differential sexual connectivity is a plausible common determinant.

[NEUROSEMANTIC AND PSYCHOPHYSIOLOGICAL CORRELATES OF RHYTHM-SUGGESTIVE CORRECTION OF STRESS CONDITIONS].

Science.gov (United States)

Ushakov, I B; Ivanov, A V; Kvasovets, S V; Bubeev, Yu A

2015-01-01

Correlates of successful rhythm-suggestive compensation of stress in sportsmen with neurotic symptoms developed in consequence of painful experience of failure were studied. Effectiveness of the rhythm-suggestive and rational psychological methods was compared by measuring the evoked potentials response to emotionally significant extramental verbal stimuli and images, and using psychophysiological test MASTER to track dynamics of a number of body functional parameters. The rational compensation has been shown to reduce the psychic tension and to set right the voluntary control process. Rhythm-suggestive programs are good for compensation of post-stress emotions and affectations, and the involuntary control process. It was found that correction potentialities of the rhythm-suggestive programs together with the psychodiagnostic advantages of test MASTER are promising instruments for dynamic monitoring of the mental state with the aim to prevent workplace stresses and to provide rehabilitation treatment of aftermaths.

Stabilizing strongly correlated photon fluids with non-Markovian reservoirs

Science.gov (United States)

Lebreuilly, José; Biella, Alberto; Storme, Florent; Rossini, Davide; Fazio, Rosario; Ciuti, Cristiano; Carusotto, Iacopo

2017-09-01

We introduce a frequency-dependent incoherent pump scheme with a square-shaped spectrum as a way to study strongly correlated photons in arrays of coupled nonlinear resonators. This scheme can be implemented via a reservoir of population-inverted two-level emitters with a broad distribution of transition frequencies. Our proposal is predicted to stabilize a nonequilibrium steady state sharing important features with a zero-temperature equilibrium state with a tunable chemical potential. We confirm the efficiency of our proposal for the Bose-Hubbard model by computing numerically the steady state for finite system sizes: first, we predict the occurrence of a sequence of incompressible Mott-insulator-like states with arbitrary integer densities presenting strong robustness against tunneling and losses. Secondly, for stronger tunneling amplitudes or noninteger densities, the system enters a coherent regime analogous to the superfluid state. In addition to an overall agreement with the zero-temperature equilibrium state, exotic nonequilibrium processes leading to a finite entropy generation are pointed out in specific regions of parameter space. The equilibrium ground state is shown to be recovered by adding frequency-dependent losses. The promise of this improved scheme in view of quantum simulation of the zero-temperature many-body physics is highlighted.

Non perturbative aspects of strongly correlated electron systems

International Nuclear Information System (INIS)

Controzzi, D.

2000-01-01

In this thesis we report some selected works on Strongly Correlated Electron Systems. A common ingredient of these works is the use of non-perturbative techniques available in low dimensions. In the first part we use the Bethe Ansatz to study some properties of two families of integrable models introduced by Fateev. We calculate the Thermodynamics of the models and show how they can be interpreted as effective Landau-Ginzburg theories for coupled two-dimensional superconductors interacting with an insulating substrate. This allows us to study exactly the dependence of the critical temperature on the thickness of the insulating layer, and on the interaction between the order parameters of two different superconducting planes. In the second part of the thesis we study the optical conductivity of the sine-Gordon model using the Form Factor method and Conformal Perturbation Theory. This allows us to develop, for the first time, a complete theory of the optical conductivity of one-dimensional Mott insulators, in the Quantum Field Theory limit. (author)

Correlated individual differences suggest a common mechanism underlying metacognition in visual perception and visual short-term memory.

Science.gov (United States)

Samaha, Jason; Postle, Bradley R

2017-11-29

Adaptive behaviour depends on the ability to introspect accurately about one's own performance. Whether this metacognitive ability is supported by the same mechanisms across different tasks is unclear. We investigated the relationship between metacognition of visual perception and metacognition of visual short-term memory (VSTM). Experiments 1 and 2 required subjects to estimate the perceived or remembered orientation of a grating stimulus and rate their confidence. We observed strong positive correlations between individual differences in metacognitive accuracy between the two tasks. This relationship was not accounted for by individual differences in task performance or average confidence, and was present across two different metrics of metacognition and in both experiments. A model-based analysis of data from a third experiment showed that a cross-domain correlation only emerged when both tasks shared the same task-relevant stimulus feature. That is, metacognition for perception and VSTM were correlated when both tasks required orientation judgements, but not when the perceptual task was switched to require contrast judgements. In contrast with previous results comparing perception and long-term memory, which have largely provided evidence for domain-specific metacognitive processes, the current findings suggest that metacognition of visual perception and VSTM is supported by a domain-general metacognitive architecture, but only when both domains share the same task-relevant stimulus feature. © 2017 The Author(s).

PREFACE: International Conference on Strongly Correlated Electron Systems (SCES 2011)

Science.gov (United States)

Littlewood, P. B.; Lonzarich, G. G.; Saxena, S. S.; Sutherland, M. L.; Sebastian, S. E.; Artacho, E.; Grosche, F. M.; Hadzibabic, Z.

2012-11-01

The Strongly Correlated Electron Systems Conference (SCES) 2011, was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 was dedicated to 100 years of superconductivity and covered a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The meeting welcomed to Cambridge 657 participants from 23 countries, who presented 127 talks (including 16 plenary, 57 invited, and 54 contributed) and 736 posters in 40 sessions over five full days of meetings. This proceedings volume contains papers reporting on the science presented at the meeting. This work deepens our understanding of the rich physical phenomena that arise from correlation effects. Strongly correlated systems are known for their remarkable array of emergent phenomena: the traditional subjects of superconductivity, magnetism and metal-insulator transitions have been joined by non-Fermi liquid phenomena, topologically protected quantum states, atomic and photonic gases, and quantum phase transitions. These are some of the most challenging and interesting phenomena in science. As well as the science driver, there is underlying interest in energy-dense materials, which make use of 'small' electrons packed to the highest possible density. These are by definition 'strongly correlated'. For example: good photovoltaics must be efficient optical absorbers, which means that photons will generate tightly bound electron-hole pairs (excitons) that must then be ionised at a heterointerface and transported to contacts; efficient solid state refrigeration depends on substantial entropy changes in a unit cell, with large local electrical or magnetic moments; efficient lighting is in a real sense the inverse of photovoltaics; the limit of an efficient battery is a supercapacitor employing mixed valent ions; fuel cells and solar to fuel conversion

Energy deposition of heavy ions in the regime of strong beam-plasma correlations.

Science.gov (United States)

Gericke, D O; Schlanges, M

2003-03-01

The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.

Full-gap superconductivity with strong electron correlations in the β-pyrochlore KOs2O6

International Nuclear Information System (INIS)

Kasahara, Y.; Shimono, Y.; Kato, T.; Hashimoto, K.; Shibauchi, T.; Matsuda, Y.; Yonezawa, S.; Muraoka, Y.; Yamaura, J.; Nagao, Y.; Hiroi, Z.

2008-01-01

To elucidate the superconducting gap structure and the influence of rattling motion on quasiparticle dynamics in the superconducting state of KOs 2 O 6 , the thermal conductivity and microwave surface impedance were measured at low temperatures. The magnetic field dependence of thermal conductivity and temperature dependence of penetration depth demonstrate full-gap superconductivity in KOs 2 O 6 . The quasiparticle scattering time is strongly enhanced in the superconducting state, indicating a strong electron inelastic scattering in the normal state. These results highlight that KOs 2 O 6 is unique among superconductors with strong electron correlations

High energy x-ray scattering studies of strongly correlated oxides

International Nuclear Information System (INIS)

Hatton, Peter D; Wilkins, S B; Spencer, P D; Zimmermann, M v; D'Almeida, T

2003-01-01

Many transition metal oxides display strongly correlated charge, spin, or orbital ordering resulting in varied phenomena such as colossal magnetoresistance, high temperature superconductivity, metal-insulator transitions etc. X-ray scattering is one of the principle techniques for probing the structural response to such effects. In this paper, we discuss and review the use of synchrotron radiation high energy x-rays (50-200 keV) for the study of transition metal oxides such as nickelates (La 2-x Sr x NiO 4 ) and manganites (La 2-2x Sr 1+2x Mn 2 O 7 ). High energy x-rays have sufficient penetration to allow us to study large flux-grown single crystals. The huge increase in sample scattering volume means that extremely weak peaks can be observed. This allows us to study very weak charge ordering. Measurements of the intensity, width and position of the charge ordering satellites as a function of temperature provide us with quantitative measures of the charge amplitude, inverse correlation length and wavevector of the charge ordering

Exact results relating spin-orbit interactions in two-dimensional strongly correlated systems

Science.gov (United States)

Kucska, Nóra; Gulácsi, Zsolt

2018-06-01

A 2D square, two-bands, strongly correlated and non-integrable system is analysed exactly in the presence of many-body spin-orbit interactions via the method of Positive Semidefinite Operators. The deduced exact ground states in the high concentration limit are strongly entangled, and given by the spin-orbit coupling are ferromagnetic and present an enhanced carrier mobility, which substantially differs for different spin projections. The described state emerges in a restricted parameter space region, which however is clearly accessible experimentally. The exact solutions are provided via the solution of a matching system of equations containing 74 coupled, non-linear and complex algebraic equations. In our knowledge, other exact results for 2D interacting systems with spin-orbit interactions are not present in the literature.

Numerical path integral solution to strong Coulomb correlation in one dimensional Hooke's atom

Science.gov (United States)

Ruokosenmäki, Ilkka; Gholizade, Hossein; Kylänpää, Ilkka; Rantala, Tapio T.

2017-01-01

We present a new approach based on real time domain Feynman path integrals (RTPI) for electronic structure calculations and quantum dynamics, which includes correlations between particles exactly but within the numerical accuracy. We demonstrate that incoherent propagation by keeping the wave function real is a novel method for finding and simulation of the ground state, similar to Diffusion Monte Carlo (DMC) method, but introducing new useful tools lacking in DMC. We use 1D Hooke's atom, a two-electron system with very strong correlation, as our test case, which we solve with incoherent RTPI (iRTPI) and compare against DMC. This system provides an excellent test case due to exact solutions for some confinements and because in 1D the Coulomb singularity is stronger than in two or three dimensional space. The use of Monte Carlo grid is shown to be efficient for which we determine useful numerical parameters. Furthermore, we discuss another novel approach achieved by combining the strengths of iRTPI and DMC. We also show usefulness of the perturbation theory for analytical approximates in case of strong confinements.

Oscillating molecular dipoles require strongly correlated electronic and nuclear motion

International Nuclear Information System (INIS)

Chang, Bo Y; Shin, Seokmin; Palacios, Alicia; Martín, Fernando; Sola, Ignacio R

2015-01-01

To create an oscillating electric dipole in an homonuclear diatomic cation without an oscillating driver one needs (i) to break the symmetry of the system and (ii) to sustain highly correlated electronic and nuclear motion. Based on numerical simulations in H 2 + we present results for two schemes. In the first one (i) is achieved by creating a superposition of symmetric and antisymmetric electronic states freely evolving, while (ii) fails. In a second scheme, by preparing the system in a dressed state of a strong static field, both conditions hold. We then analyze the robustness of this scheme with respect to features of the nuclear wave function and its intrinsic sources of decoherence. (tutorial)

Superconductivity, Antiferromagnetism, and Kinetic Correlation in Strongly Correlated Electron Systems

Directory of Open Access Journals (Sweden)

Takashi Yanagisawa

2015-01-01

Full Text Available We investigate the ground state of two-dimensional Hubbard model on the basis of the variational Monte Carlo method. We use wave functions that include kinetic correlation and doublon-holon correlation beyond the Gutzwiller ansatz. It is still not clear whether the Hubbard model accounts for high-temperature superconductivity. The antiferromagnetic correlation plays a key role in the study of pairing mechanism because the superconductive phase exists usually close to the antiferromagnetic phase. We investigate the stability of the antiferromagnetic state when holes are doped as a function of the Coulomb repulsion U. We show that the antiferromagnetic correlation is suppressed as U is increased exceeding the bandwidth. High-temperature superconductivity is possible in this region with enhanced antiferromagnetic spin fluctuation and pairing interaction.

Effects of strong and electromagnetic correlations on neutrino interactions in dense matter

International Nuclear Information System (INIS)

Reddy, S.; Prakash, M.; Lattimer, J.M.; Reddy, S.; Pons, J.A.

1999-01-01

An extensive study of the effects of correlations on both charged and neutral current weak interaction rates in dense matter is performed. Both strong and electromagnetic correlations are considered. The propagation of particle-hole interactions in the medium plays an important role in determining the neutrino mean free paths. The effects due to Pauli blocking and density, spin, and isospin correlations in the medium significantly reduce the neutrino cross sections. As a result of the lack of experimental information at high density, these correlations are necessarily model dependent. For example, spin correlations in nonrelativistic models are found to lead to larger suppressions of neutrino cross sections compared to those of relativistic models. This is due to the tendency of the nonrelativistic models to develop spin instabilities. Notwithstanding the above caveats, and the differences between nonrelativistic and relativistic approaches such as the spin- and isospin-dependent interactions and the nucleon effective masses, suppressions of order 2 - 3, relative to the case in which correlations are ignored, are obtained. Neutrino interactions in dense matter are especially important for supernova and early neutron star evolution calculations. The effects of correlations for protoneutron star evolution are calculated. Large effects on the internal thermodynamic properties of protoneutron stars, such as the temperature, are found. These translate into significant early enhancements in the emitted neutrino energies and fluxes, especially after a few seconds. At late times, beyond about 10 s, the emitted neutrino fluxes decrease more rapidly compared to simulations without the effects of correlations, due to the more rapid onset of neutrino transparency in the protoneutron star. copyright 1999 The American Physical Society

Dissociation, personality, suggestibility, alexithymia, and problems with emotional regulation: A correlational study

Directory of Open Access Journals (Sweden)

Ángeles Serrano

2016-12-01

Full Text Available The present paper explores the relationship between psychological and somatic dissociation and different personality and emotional variables, including suggestibility, alexithymia, and emotional regulation and dysregulation. The results with a sample of 355 partipants of a normal population reveal that there is a positive relationship between both types of dissociation, suggestibility and emotional dysregulation. Likewise, there were different patterns of personality associated both to psychological and somatic dissociation. Correlations found in this study put forward the importance to take into account both types of dissociactive symptoms, psychological and somatic ones.

Nonlinear phononics and structural control of strongly correlated materials

Energy Technology Data Exchange (ETDEWEB)

Mankowsky, Roman

2016-01-20

Mid-infrared light pulses can be used to resonantly excite infrared-active vibrational modes for the phase control of strongly correlated materials on subpicosecond timescales. As the energy is transferred directly into atomic motions, dissipation into the electronic system is reduced, allowing for the emergence of unusual low energy collective properties. Light-induced superconductivity, insulator-metal transitions and melting of magnetic order demonstrate the potential of this method. An understanding of the mechanism, by which these transitions are driven, is however missing. The aim of this work is to uncover this process by investigating the nonlinear lattice dynamics induced by the excitation and to elucidate their contribution to the modulation of collective properties of strongly correlated materials. The first signature of nonlinear lattice dynamics was reported in the observation of coherent phonon oscillations, resonant with the excitation of an infrared-active phonon mode in a manganite. This nonlinear phononic coupling can be described within a model, which predicts not only oscillatory coherent phonons dynamics but also directional atomic displacements along the coupled modes on average, which could cause the previously observed transitions. We verified this directional response and quantified the anharmonic coupling constant by tracing the atomic motions in a time-resolved hard X-ray diffraction experiment with sub-picometer spatial and femtosecond temporal resolution. In a subsequent study, we investigated the role of nonlinear lattice dynamics in the emergence of superconductivity far above the equilibrium transition temperature, an intriguing effect found to follow lattice excitation of YBa{sub 2}Cu{sub 3}O{sub 6+x}. By combining density functional theory (DFT) calculations of the anharmonic coupling constants with time-resolved X-ray diffraction experiments, we identified a structural rearrangement, which appears and decays with the same temporal

Adler Award Lecture: Fermi-Liquid Instabilities in Strongly Correlated f-Electron Materials.^*

Science.gov (United States)

Maple, M. Brian

1996-03-01

Strongly correlated f-electron materials are replete with novel electronic states and phenomena ; e. g. , a metallic ``heavy electron'' state with a quasiparticle effective mass of several hundred times the free electron mass, anisotropic superconductivity with an energy gap that may vanish at points or along lines on the Fermi surface, the coexistence of superconductivity and antiferromagnetism over different parts of the Fermi surface, multiple superconducting phases in the hyperspace of chemical composition, temperature, pressure, and magnetic field, and an insulating phase, in so-called ``hybridization gap semiconductors'' or ``Kondo insulators'', with a small energy gap of only a few meV. During the last several years, a new low temperature non-Fermi-liquid (NFL) state has been observed in a new class of strongly correlated f-electron materials which currently consists of certain Ce and U intermetallics into which a nonmagnetic element has been substituted.(M. B. Maple et al./) , J. Low Temp. Phys. 99 , 223 (1995). The Ce and U ions have partially-filled f-electron shells and carry magnetic dipole or electric quadrupole moments which interact with the spins and charges of the conduction electrons and can participate in magnetic or quadrupolar ordering at low temperatures. The physical properties of these materials exhibit weak power law or logarithmic divergences in temperature and suggest the existence of a critical point at T=0 K. Possible origins of the 0 K critical point include an unconventional moment compensation process, such as a multichannel Kondo effect, and fluctuations of the order parameter in the vicinity of a 0 K second order phase transition. In some systems, such as Y_1-xU_xPd 3 and U_1-xTh_xPd _2Al 3 , the NFL characteristics appear to be single ion effects since they persist to low concentrations of f-moments, whereas in other systems, such as CeCu _5.9Au _0.1 , the NFL behavior seems to be associated with interactions between the f

Microscopic origin of marginal Fermi-liquid in strongly correlated spin systems

International Nuclear Information System (INIS)

Protogenov, A.P.; Ryndyk, D.A.

1992-08-01

We consider the consequences of separation of spin and charge degrees of freedom in 2+1D strongly correlated spin systems. Self-consistent spin and charge motions induced by doping in sites of ground and dual lattices form such a spectrum of quasiparticles which together with the dispersionless character of the collective excitation spectrum and the chemical potential pinning in the band centre yield the necessary behavior of charge and spin polarizability to support the theory of marginal liquid formulated by C.M. Varma et al. (Phys. Rev. Lett. 63, 1996 (1989)). (author). 28 refs, 4 figs

Strong correlation and ferromagnetism in (Ga,Mn)As and (Ga,Mn)N

International Nuclear Information System (INIS)

Filippetti, A.; Spaldin, N.A.; Sanvito, S.

2005-01-01

The band energies of the ferromagnetic diluted magnetic semiconductors (Ga,Mn)As and (Ga,Mn)N are calculated using a self-interaction-free approach which describes covalent and strongly correlated electrons without adjustable parameters. Both materials are half-metallic, although the contribution of Mn-derived d states to the bands around the Fermi energy is very different in the two cases. In (Ga,Mn)As the bands are strongly p-d hybridized, with a dominance of As p states. In contrast in (Ga,Mn)N the Fermi energy lies within three flat bands of mainly d character that are occupied by two electrons. Thus the Mn ion in (Ga,Mn)N behaves as a deep trap acceptor, with the hole at 1.39 eV above the GaN valence band top, and is in excellent agreement with the experimental data

Self-consistent field model for strong electrostatic correlations and inhomogeneous dielectric media.

Science.gov (United States)

Ma, Manman; Xu, Zhenli

2014-12-28

Electrostatic correlations and variable permittivity of electrolytes are essential for exploring many chemical and physical properties of interfaces in aqueous solutions. We propose a continuum electrostatic model for the treatment of these effects in the framework of the self-consistent field theory. The model incorporates a space- or field-dependent dielectric permittivity and an excluded ion-size effect for the correlation energy. This results in a self-energy modified Poisson-Nernst-Planck or Poisson-Boltzmann equation together with state equations for the self energy and the dielectric function. We show that the ionic size is of significant importance in predicting a finite self energy for an ion in an inhomogeneous medium. Asymptotic approximation is proposed for the solution of a generalized Debye-Hückel equation, which has been shown to capture the ionic correlation and dielectric self energy. Through simulating ionic distribution surrounding a macroion, the modified self-consistent field model is shown to agree with particle-based Monte Carlo simulations. Numerical results for symmetric and asymmetric electrolytes demonstrate that the model is able to predict the charge inversion at high correlation regime in the presence of multivalent interfacial ions which is beyond the mean-field theory and also show strong effect to double layer structure due to the space- or field-dependent dielectric permittivity.

Self-consistent field model for strong electrostatic correlations and inhomogeneous dielectric media

Energy Technology Data Exchange (ETDEWEB)

Ma, Manman, E-mail: mmm@sjtu.edu.cn; Xu, Zhenli, E-mail: xuzl@sjtu.edu.cn [Department of Mathematics, Institute of Natural Sciences, and MoE Key Laboratory of Scientific and Engineering Computing, Shanghai Jiao Tong University, Shanghai 200240 (China)

2014-12-28

Electrostatic correlations and variable permittivity of electrolytes are essential for exploring many chemical and physical properties of interfaces in aqueous solutions. We propose a continuum electrostatic model for the treatment of these effects in the framework of the self-consistent field theory. The model incorporates a space- or field-dependent dielectric permittivity and an excluded ion-size effect for the correlation energy. This results in a self-energy modified Poisson-Nernst-Planck or Poisson-Boltzmann equation together with state equations for the self energy and the dielectric function. We show that the ionic size is of significant importance in predicting a finite self energy for an ion in an inhomogeneous medium. Asymptotic approximation is proposed for the solution of a generalized Debye-Hückel equation, which has been shown to capture the ionic correlation and dielectric self energy. Through simulating ionic distribution surrounding a macroion, the modified self-consistent field model is shown to agree with particle-based Monte Carlo simulations. Numerical results for symmetric and asymmetric electrolytes demonstrate that the model is able to predict the charge inversion at high correlation regime in the presence of multivalent interfacial ions which is beyond the mean-field theory and also show strong effect to double layer structure due to the space- or field-dependent dielectric permittivity.

Density functional theory and dynamical mean-field theory. A way to model strongly correlated systems

International Nuclear Information System (INIS)

Backes, Steffen

2017-04-01

The study of the electronic properties of correlated systems is a very diverse field and has lead to valuable insight into the physics of real materials. In these systems, the decisive factor that governs the physical properties is the ratio between the electronic kinetic energy, which promotes delocalization over the lattice, and the Coulomb interaction, which instead favours localized electronic states. Due to this competition, correlated electronic systems can show unique and interesting properties like the Metal-Insulator transition, diverse phase diagrams, strong temperature dependence and in general a high sensitivity to the environmental conditions. A theoretical description of these systems is not an easy task, since perturbative approaches that do not preserve the competition between the kinetic and interaction terms can only be applied in special limiting cases. One of the most famous approaches to obtain the electronic properties of a real material is the ab initio density functional theory (DFT) method. It allows one to obtain the ground state density of the system under investigation by mapping onto an effective non-interacting system that has to be found self-consistently. While being an exact theory, in practical implementations certain approximations have to be made to the exchange-correlation potential. The local density approximation (LDA), which approximates the exchange-correlation contribution to the total energy by that of a homogeneous electron gas with the corresponding density, has proven quite successful in many cases. Though, this approximation in general leads to an underestimation of electronic correlations and is not able to describe a metal-insulator transition due to electronic localization in the presence of strong Coulomb interaction. A different approach to the interacting electronic problem is the dynamical mean-field theory (DMFT), which is non-perturbative in the kinetic and interaction term but neglects all non

Density functional theory and dynamical mean-field theory. A way to model strongly correlated systems

Energy Technology Data Exchange (ETDEWEB)

Backes, Steffen

2017-04-15

The study of the electronic properties of correlated systems is a very diverse field and has lead to valuable insight into the physics of real materials. In these systems, the decisive factor that governs the physical properties is the ratio between the electronic kinetic energy, which promotes delocalization over the lattice, and the Coulomb interaction, which instead favours localized electronic states. Due to this competition, correlated electronic systems can show unique and interesting properties like the Metal-Insulator transition, diverse phase diagrams, strong temperature dependence and in general a high sensitivity to the environmental conditions. A theoretical description of these systems is not an easy task, since perturbative approaches that do not preserve the competition between the kinetic and interaction terms can only be applied in special limiting cases. One of the most famous approaches to obtain the electronic properties of a real material is the ab initio density functional theory (DFT) method. It allows one to obtain the ground state density of the system under investigation by mapping onto an effective non-interacting system that has to be found self-consistently. While being an exact theory, in practical implementations certain approximations have to be made to the exchange-correlation potential. The local density approximation (LDA), which approximates the exchange-correlation contribution to the total energy by that of a homogeneous electron gas with the corresponding density, has proven quite successful in many cases. Though, this approximation in general leads to an underestimation of electronic correlations and is not able to describe a metal-insulator transition due to electronic localization in the presence of strong Coulomb interaction. A different approach to the interacting electronic problem is the dynamical mean-field theory (DMFT), which is non-perturbative in the kinetic and interaction term but neglects all non

Non-equilibrium magnetic interactions in strongly correlated systems

Energy Technology Data Exchange (ETDEWEB)

Secchi, A., E-mail: a.secchi@science.ru.nl [Institute for Molecules and Materials, Radboud University Nijmegen, 6525 AJ Nijmegen (Netherlands); Brener, S.; Lichtenstein, A.I. [Institut für Theoretische Physik, Universitat Hamburg, Jungiusstraße 9, D-20355 Hamburg (Germany); Katsnelson, M.I. [Institute for Molecules and Materials, Radboud University Nijmegen, 6525 AJ Nijmegen (Netherlands)

2013-06-15

We formulate a low-energy theory for the magnetic interactions between electrons in the multi-band Hubbard model under non-equilibrium conditions determined by an external time-dependent electric field which simulates laser-induced spin dynamics. We derive expressions for dynamical exchange parameters in terms of non-equilibrium electronic Green functions and self-energies, which can be computed, e.g., with the methods of time-dependent dynamical mean-field theory. Moreover, we find that a correct description of the system requires, in addition to exchange, a new kind of magnetic interaction, that we name twist exchange, which formally resembles Dzyaloshinskii–Moriya coupling, but is not due to spin–orbit, and is actually due to an effective three-spin interaction. Our theory allows the evaluation of the related time-dependent parameters as well. -- Highlights: •We develop a theory for magnetism of strongly correlated systems out of equilibrium. •Our theory is suitable for laser-induced ultrafast magnetization dynamics. •We write time-dependent exchange parameters in terms of electronic Green functions. •We find a new magnetic interaction, a “twist exchange”. •We give general expressions for magnetic noise in itinerant-electron systems.

Universal Behavior of Pair Correlations in a Strongly Interacting Fermi Gas

International Nuclear Information System (INIS)

Kuhnle, E. D.; Hu, H.; Liu, X.-J.; Dyke, P.; Mark, M.; Drummond, P. D.; Hannaford, P.; Vale, C. J.

2010-01-01

We show that short-range pair correlations in a strongly interacting Fermi gas follow a simple universal law described by Tan's relations. This is achieved through measurements of the static structure factor which displays a universal scaling proportional to the ratio of Tan's contact to the momentum C/q. Bragg spectroscopy of ultracold 6 Li atoms from a periodic optical potential is used to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We calibrate our Bragg spectra using the f-sum rule, which is found to improve the accuracy of the structure factor measurement.

STRONG CORRELATIONS AND ELECTRON-PHONON COUPLING IN HIGH-TEMPERATURE SUPERCONDUCTORS - A QUANTUM MONTE-CARLO STUDY

NARCIS (Netherlands)

MORGENSTERN, [No Value; FRICK, M; VONDERLINDEN, W

We present quantum simulation studies for a system of strongly correlated fermions coupled to local anharmonic phonons. The Monte Carlo calculations are based on a generalized version of the Projector Quantum Monte Carlo Method allowing a simultaneous treatment of fermions and dynamical phonons. The

Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

Science.gov (United States)

Wang, Jigang

2014-03-01

Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

A toy model to investigate the existence of excitons in the ground state of strongly-correlated semiconductor

Science.gov (United States)

Karima, H. R.; Majidi, M. A.

2018-04-01

Excitons, quasiparticles associated with bound states between an electron and a hole and are typically created when photons with a suitable energy are absorbed in a solid-state material. We propose to study a possible emergence of excitons, created not by photon absorption but the effect of strong electronic correlations. This study is motivated by a recent experimental study of a substrate material SrTiO3 (STO) that reveals strong exitonic signals in its optical conductivity. Here we conjecture that some excitons may already exist in the ground state as a result of the electronic correlations before the additional excitons being created later by photon absorption. To investigate the existence of excitons in the ground state, we propose to study a simple 4-energy-level model that mimics a situation in strongly-correlated semiconductors. The four levels are divided into two groups, lower and upper groups separated by an energy gap, Eg , mimicking the valence and the conduction bands, respectively. Further, we incorporate repulsive Coulomb interactions between the electrons. The model is then solved by exact diagonalization method. Our result shows that the toy model can demonstrate band gap widening or narrowing and the existence of exciton in the ground state depending on interaction parameter values.

Holstein-Primakoff representation and supercoherent states for strongly correlated electron systems

International Nuclear Information System (INIS)

Azakov, S.

1999-09-01

First we show that the algebra of operators entering the Hamiltonian of the t-J model describing the strongly correlated electron system is graded spl(2.1) algebra. Then after a brief discussion of its atypical representations we construct the Holstein-Primakoff nonlinear realization of these operators which allows to carry out the systematic semiclassical approximation, similarly to the spin-wave theory of localized magnetism. The fact that the t-J model describes the itinerant magnetism is reflected in the presence of the spinless fermions. For the supersymmetric spl(2.1) algebra the supercoherent states are proposed and the partition function of the t-J model is represented as a path integral with the help of these states. (author)

Strongly correlated impurity band superconductivity in diamond: X-ray spectroscopic evidence

Directory of Open Access Journals (Sweden)

G. Baskaran

2006-01-01

Full Text Available In a recent X-ray absorption study in boron doped diamond, Nakamura et al. have seen a well isolated narrow boron impurity band in non-superconducting samples and an additional narrow band at the chemical potential in a superconducting sample. We interpret the beautiful spectra as evidence for upper Hubbard band of a Mott insulating impurity band and an additional metallic 'mid-gap band' of a conducting 'self-doped' Mott insulator. This supports the basic framework of a recent theory of the present author of strongly correlated impurity band superconductivity (impurity band resonating valence bond, IBRVB theory in a template of a wide-gap insulator, with no direct involvement of valence band states.

High-order Path Integral Monte Carlo methods for solving strongly correlated fermion problems

Science.gov (United States)

Chin, Siu A.

2015-03-01

In solving for the ground state of a strongly correlated many-fermion system, the conventional second-order Path Integral Monte Carlo method is plagued with the sign problem. This is due to the large number of anti-symmetric free fermion propagators that are needed to extract the square of the ground state wave function at large imaginary time. In this work, I show that optimized fourth-order Path Integral Monte Carlo methods, which uses no more than 5 free-fermion propagators, in conjunction with the use of the Hamiltonian energy estimator, can yield accurate ground state energies for quantum dots with up to 20 polarized electrons. The correlations are directly built-in and no explicit wave functions are needed. This work is supported by the Qatar National Research Fund NPRP GRANT #5-674-1-114.

Strongly correlated electrons at high pressure: an approach by inelastic X-Ray scattering

International Nuclear Information System (INIS)

Rueff, J.P.

2007-06-01

Inelastic X-ray scattering (IXS) and associated methods has turn out to be a powerful alternative for high-pressure physics. It is an all-photon technique fully compatible with high-pressure environments and applicable to a vast range of materials. Standard focalization of X-ray in the range of 100 microns is typical of the sample size in the pressure cell. Our main aim is to provide an overview of experimental results obtained by IXS under high pressure in 2 classes of materials which have been at the origin of the renewal of condensed matter physics: strongly correlated transition metal oxides and rare-earth compounds. Under pressure, d and f-electron materials show behaviors far more complex that what would be expected from a simplistic band picture of electron delocalization. These spectroscopic studies have revealed unusual phenomena in the electronic degrees of freedom, brought up by the increased density, the changes in the charge-carrier concentration, the over-lapping between orbitals, and hybridization under high pressure conditions. Particularly we discuss about pressure induced magnetic collapse and metal-insulator transitions in 3d compounds and valence fluctuations phenomena in 4f and 5f compounds. Thanks to its superior penetration depth, chemical selectivity and resonant enhancement, resonant inelastic X-ray scattering has appeared extremely well suited to high pressure physics in strongly correlated materials. (A.C.)

Study of rare earth local moment magnetism and strongly correlated phenomena in various crystal structures

Energy Technology Data Exchange (ETDEWEB)

Kong, Tai [Iowa State Univ., Ames, IA (United States)

2016-12-17

Benefiting from unique properties of 4f electrons, rare earth based compounds are known for offering a versatile playground for condensed matter physics research as well as industrial applications. This thesis focuses on three specific examples that further explore the rare earth local moment magnetism and strongly correlated phenomena in various crystal structures.

The ALPS project release 2.0: open source software for strongly correlated systems

International Nuclear Information System (INIS)

Bauer, B; Gamper, L; Gukelberger, J; Hehn, A; Isakov, S V; Ma, P N; Mates, P; Carr, L D; Evertz, H G; Feiguin, A; Freire, J; Koop, D; Fuchs, S; Gull, E; Guertler, S; Igarashi, R; Matsuo, H; Parcollet, O; Pawłowski, G; Picon, J D

2011-01-01

We present release 2.0 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. The code development is centered on common XML and HDF5 data formats, libraries to simplify and speed up code development, common evaluation and plotting tools, and simulation programs. The programs enable non-experts to start carrying out serial or parallel numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), the density matrix renormalization group (DMRG) both in a static version and a dynamic time-evolving block decimation (TEBD) code, and quantum Monte Carlo solvers for dynamical mean field theory (DMFT). The ALPS libraries provide a powerful framework for programmers to develop their own applications, which, for instance, greatly simplify the steps of porting a serial code onto a parallel, distributed memory machine. Major changes in release 2.0 include the use of HDF5 for binary data, evaluation tools in Python, support for the Windows operating system, the use of CMake as build system and binary installation packages for Mac OS X and Windows, and integration with the VisTrails workflow provenance tool. The software is available from our web server at http://alps.comp-phys.org/

Quantum Monte Carlo methods and strongly correlated electrons on honeycomb structures

Energy Technology Data Exchange (ETDEWEB)

Lang, Thomas C.

2010-12-16

In this thesis we apply recently developed, as well as sophisticated quantum Monte Carlo methods to numerically investigate models of strongly correlated electron systems on honeycomb structures. The latter are of particular interest owing to their unique properties when simulating electrons on them, like the relativistic dispersion, strong quantum fluctuations and their resistance against instabilities. This work covers several projects including the advancement of the weak-coupling continuous time quantum Monte Carlo and its application to zero temperature and phonons, quantum phase transitions of valence bond solids in spin-1/2 Heisenberg systems using projector quantum Monte Carlo in the valence bond basis, and the magnetic field induced transition to a canted antiferromagnet of the Hubbard model on the honeycomb lattice. The emphasis lies on two projects investigating the phase diagram of the SU(2) and the SU(N)-symmetric Hubbard model on the hexagonal lattice. At sufficiently low temperatures, condensed-matter systems tend to develop order. An exception are quantum spin-liquids, where fluctuations prevent a transition to an ordered state down to the lowest temperatures. Previously elusive in experimentally relevant microscopic two-dimensional models, we show by means of large-scale quantum Monte Carlo simulations of the SU(2) Hubbard model on the honeycomb lattice, that a quantum spin-liquid emerges between the state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. This unexpected quantum-disordered state is found to be a short-range resonating valence bond liquid, akin to the one proposed for high temperature superconductors. Inspired by the rich phase diagrams of SU(N) models we study the SU(N)-symmetric Hubbard Heisenberg quantum antiferromagnet on the honeycomb lattice to investigate the reliability of 1/N corrections to large-N results by means of numerically exact QMC simulations. We study the melting of phases

Evidence for a glassy state in strongly driven carbon

International Nuclear Information System (INIS)

Brown, C.R.D.; Gericke, D.O.; Wunsch, K.; Cammarata, M.; Fritz, D.; Glenzer, S.H.; Heimann, P.; Lee, H.J.; Lemke, H.; Nagler, B.; Zhu, D.; Galtier, E.; Moinard, A.; Rosmej, F.B.

2014-01-01

Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. (authors)

Computational time-resolved and resonant x-ray scattering of strongly correlated materials

Energy Technology Data Exchange (ETDEWEB)

Bansil, Arun [Northeastern Univ., Boston, MA (United States)

2016-11-09

Basic-Energy Sciences of the Department of Energy (BES/DOE) has made large investments in x-ray sources in the U.S. (NSLS-II, LCLS, NGLS, ALS, APS) as powerful enabling tools for opening up unprecedented new opportunities for exploring properties of matter at various length and time scales. The coming online of the pulsed photon source, literally allows us to see and follow the dynamics of processes in materials at their natural timescales. There is an urgent need therefore to develop theoretical methodologies and computational models for understanding how x-rays interact with matter and the related spectroscopies of materials. The present project addressed aspects of this grand challenge of x-ray science. In particular, our Collaborative Research Team (CRT) focused on developing viable computational schemes for modeling x-ray scattering and photoemission spectra of strongly correlated materials in the time-domain. The vast arsenal of formal/numerical techniques and approaches encompassed by the members of our CRT were brought to bear through appropriate generalizations and extensions to model the pumped state and the dynamics of this non-equilibrium state, and how it can be probed via x-ray absorption (XAS), emission (XES), resonant and non-resonant x-ray scattering, and photoemission processes. We explored the conceptual connections between the time-domain problems and other second-order spectroscopies, such as resonant inelastic x-ray scattering (RIXS) because RIXS may be effectively thought of as a pump-probe experiment in which the incoming photon acts as the pump, and the fluorescent decay is the probe. Alternatively, when the core-valence interactions are strong, one can view K-edge RIXS for example, as the dynamic response of the material to the transient presence of a strong core-hole potential. Unlike an actual pump-probe experiment, here there is no mechanism for adjusting the time-delay between the pump and the probe. However, the core hole

Strong correlation in acene sheets from the active-space variational two-electron reduced density matrix method: effects of symmetry and size.

Science.gov (United States)

Pelzer, Kenley; Greenman, Loren; Gidofalvi, Gergely; Mazziotti, David A

2011-06-09

Polyaromatic hydrocarbons (PAHs) are a class of organic molecules with importance in several branches of science, including medicine, combustion chemistry, and materials science. The delocalized π-orbital systems in PAHs require highly accurate electronic structure methods to capture strong electron correlation. Treating correlation in PAHs has been challenging because (i) traditional wave function methods for strong correlation have not been applicable since they scale exponentially in the number of strongly correlated orbitals, and (ii) alternative methods such as the density-matrix renormalization group and variational two-electron reduced density matrix (2-RDM) methods have not been applied beyond linear acene chains. In this paper we extend the earlier results from active-space variational 2-RDM theory [Gidofalvi, G.; Mazziotti, D. A. J. Chem. Phys. 2008, 129, 134108] to the more general two-dimensional arrangement of rings--acene sheets--to study the relationship between geometry and electron correlation in PAHs. The acene-sheet calculations, if performed with conventional wave function methods, would require wave function expansions with as many as 1.5 × 10(17) configuration state functions. To measure electron correlation, we employ several RDM-based metrics: (i) natural-orbital occupation numbers, (ii) the 1-RDM von Neumann entropy, (iii) the correlation energy per carbon atom, and (iv) the squared Frobenius norm of the cumulant 2-RDM. The results confirm a trend of increasing polyradical character with increasing molecular size previously observed in linear PAHs and reveal a corresponding trend in two-dimensional (arch-shaped) PAHs. Furthermore, in PAHs of similar size they show significant variations in correlation with geometry. PAHs with the strictly linear geometry (chains) exhibit more electron correlation than PAHs with nonlinear geometries (sheets).

Interrogative suggestibility: its relationship with assertiveness, social-evaluative anxiety, state anxiety and method of coping.

Science.gov (United States)

Gudjonsson, G H

1988-05-01

This paper attempts to investigate empirically in 30 subjects some of the theoretical components related to individual differences that are thought by Gudjonsson & Clark (1986) to mediate interrogative suggestibility as measured by the Gudjonsson Suggestibility Scale (GSS; Gudjonsson, 1984a). The variables studied were: assertiveness, social-evaluative anxiety, state anxiety and the coping methods subjects are able to generate and implement during interrogation. Low assertiveness and high evaluative anxiety were found to correlate moderately with suggestibility, but no significant correlations emerged for 'social avoidance and distress'. State anxiety correlated significantly with suggestibility, particularly after negative feedback had been administered. Coping methods (active-cognitive/behavioural vs. avoidance) significantly predicted suggestibility scores. The findings give strong support to the theoretical model of Gudjonsson & Clark.

SO(8) fermion dynamical symmetry and strongly correlated quantum Hall states in monolayer graphene

Science.gov (United States)

Wu, Lian-Ao; Murphy, Matthew; Guidry, Mike

2017-03-01

A formalism is presented for treating strongly correlated graphene quantum Hall states in terms of an SO(8) fermion dynamical symmetry that includes pairing as well as particle-hole generators. The graphene SO(8) algebra is isomorphic to an SO(8) algebra that has found broad application in nuclear physics, albeit with physically very different generators, and exhibits a strong formal similarity to SU(4) symmetries that have been proposed to describe high-temperature superconductors. The well-known SU(4) symmetry of quantum Hall ferromagnetism for single-layer graphene is recovered as one subgroup of SO(8), but the dynamical symmetry structure associated with the full set of SO(8) subgroup chains extends quantum Hall ferromagnetism and allows analytical many-body solutions for a rich set of collective states exhibiting spontaneously broken symmetry that may be important for the low-energy physics of graphene in strong magnetic fields. The SO(8) symmetry permits a natural definition of generalized coherent states that correspond to symmetry-constrained Hartree-Fock-Bogoliubov solutions, or equivalently a microscopically derived Ginzburg-Landau formalism, exhibiting the interplay between competing spontaneously broken symmetries in determining the ground state.

Signals of strong electronic correlation in ion scattering processes

Science.gov (United States)

Bonetto, F.; Gonzalez, C.; Goldberg, E. C.

2016-05-01

Previous measurements of neutral atom fractions for S r+ scattered by gold polycrystalline surfaces show a singular dependence with the target temperature. There is still not a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied a first-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinless approach, where two charge channels are considered (S r0 and S r+ ) and the spin degeneration is neglected; (ii) the infinite-U approach, with the same charge channels (S r0 and S r+ ) but considering the spin degeneration; and (iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, but finitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-U approach, indicating that e -correlation plays a significant role in charge-transfer processes. However, none of them is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible for that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.

Two strongly correlated electron systems: the Kondo mode in the strong coupling limit and a 2-D model of electrons close to an electronic topological transition

International Nuclear Information System (INIS)

Bouis, F.

1999-01-01

Two strongly correlated electron systems are considered in this work, Kondo insulators and high Tc cuprates. Experiments and theory suggest on one hand that the Kondo screening occurs on a rather short length scale and on the other hand that the Kondo coupling is renormalized to infinity in the low energy limit. The strong coupling limit is then the logical approach although the real coupling is moderate. A systematic development is performed around this limit in the first part. The band structure of these materials is reproduced within this scheme. Magnetic fluctuations are also studied. The antiferromagnetic transition is examined in the case where fermionic excitations are shifted to high energy. In the second part, the Popov and Fedotov representation of spins is used to formulate the Kondo and the antiferromagnetic Heisenberg model in terms of a non-polynomial action of boson fields. In the third part the properties of high Tc cuprates are explained by a change of topology of the Fermi surface. This phenomenon would happen near the point of optimal doping and zero temperature. It results in the appearance of a density wave phase in the under-doped regime. The possibility that this phase has a non-conventional symmetry is considered. The phase diagram that described the interaction and coexistence of density wave and superconductivity is established in the mean-field approximation. The similarities with the experimental observations are numerous in particular those concerning the pseudo-gap and the behavior of the resistivity near optimal doping. (author)

Tree-level correlations in the strong field regime

Science.gov (United States)

Gelis, François

2017-09-01

We consider the correlation function of an arbitrary number of local observables in quantum field theory, in situations where the field amplitude is large. Using a quasi-classical approximation (valid for a highly occupied initial mixed state, or for a coherent initial state if the classical dynamics has instabilities), we show that at tree level these correlations are dominated by fluctuations at the initial time. We obtain a general expression of the correlation functions in terms of the classical solution of the field equation of motion and its derivatives with respect to its initial conditions, that can be arranged graphically as the sum of labeled trees where the nodes are the individual observables, and the links are pairs of derivatives acting on them. For 3-point (and higher) correlation functions, there are additional tree-level terms beyond the quasi-classical approximation, generated by fluctuations in the bulk.

Vector neural net identifying many strongly distorted and correlated patterns

Science.gov (United States)

Kryzhanovsky, Boris V.; Mikaelian, Andrei L.; Fonarev, Anatoly B.

2005-01-01

We suggest an effective and simple algorithm providing a polynomial storage capacity of a network of the form M ~ N2s+1, where N is the dimension of the stored binary patterns. In this problem the value of the free parameter s is restricted by the inequalities N >> slnN >= 1. The algorithm allows us to identify a large number of highly distorted similar patterns. The negative influence of correlations of the patterns is suppressed by choosing a sufficiently large value of the parameter s. We show the efficiency of the algorithm by the example of a perceptron identifier, but it also can be used to increase the storage capacity of full connected systems of associative memory.

Theory of L -edge spectroscopy of strongly correlated systems

Science.gov (United States)

Lüder, Johann; Schött, Johan; Brena, Barbara; Haverkort, Maurits W.; Thunström, Patrik; Eriksson, Olle; Sanyal, Biplab; Di Marco, Igor; Kvashnin, Yaroslav O.

2017-12-01

X-ray absorption spectroscopy measured at the L edge of transition metals (TMs) is a powerful element-selective tool providing direct information about the correlation effects in the 3 d states. The theoretical modeling of the 2 p →3 d excitation processes remains to be challenging for contemporary ab initio electronic structure techniques, due to strong core-hole and multiplet effects influencing the spectra. In this work, we present a realization of the method combining the density-functional theory with multiplet ligand field theory, proposed in Haverkort et al. [Phys. Rev. B 85, 165113 (2012), 10.1103/PhysRevB.85.165113]. In this approach, a single-impurity Anderson model (SIAM) is constructed, with almost all parameters obtained from first principles, and then solved to obtain the spectra. In our implementation, we adopt the language of the dynamical mean-field theory and utilize the local density of states and the hybridization function, projected onto TM 3 d states, in order to construct the SIAM. The developed computational scheme is applied to calculate the L -edge spectra for several TM monoxides. A very good agreement between the theory and experiment is found for all studied systems. The effect of core-hole relaxation, hybridization discretization, possible extensions of the method as well as its limitations are discussed.

Strongly correlated quasi-one-dimensional bands: Ground states, optical absorption, and phonons

International Nuclear Information System (INIS)

Campbell, D.K.; Gammel, J.T.; Loh, E.Y. Jr.

1989-01-01

Using the Lanczos method for exact diagonalization on systems up to 14 sites, combined with a novel ''phase randomization'' technique for extracting more information from these small systems, we investigate several aspects of the one-dimensional Peierls-Hubbard Hamiltonian, in the context of trans-polyacetylene: the dependence of the ground state dimerization on the strength of the electron-electron interactions, including the effects of ''off-diagonal'' Coulomb terms generally ignored in the Hubbard model; the phonon vibrational frequencies and dispersion relations, and the optical absorption properties, including the spectrum of absorptions as a function of photon energy. These three different observables provide considerable insight into the effects of electron-electron interactions on the properties of real materials and thus into the nature of strongly correlated electron systems. 29 refs., 11 figs

Respiratory insufficiency correlated strongly with mortality of rodents infected with West Nile virus.

Directory of Open Access Journals (Sweden)

John D Morrey

Full Text Available West Nile virus (WNV disease can be fatal for high-risk patients. Since WNV or its antigens have been identified in multiple anatomical locations of the central nervous system of persons or rodent models, one cannot know where to investigate the actual mechanism of mortality without careful studies in animal models. In this study, depressed respiratory functions measured by plethysmography correlated strongly with mortality. This respiratory distress, as well as reduced oxygen saturation, occurred beginning as early as 4 days before mortality. Affected medullary respiratory control cells may have contributed to the animals' respiratory insufficiency, because WNV antigen staining was present in neurons located in the ventrolateral medulla. Starvation or dehydration would be irrelevant in people, but could cause death in rodents due to lethargy or loss of appetite. Animal experiments were performed to exclude this possibility. Plasma ketones were increased in moribund infected hamsters, but late-stage starvation markers were not apparent. Moreover, daily subcutaneous administration of 5% dextrose in physiological saline solution did not improve survival or other disease signs. Therefore, infected hamsters did not die from starvation or dehydration. No cerebral edema was apparent in WNV- or sham-infected hamsters as determined by comparing wet-to-total weight ratios of brains, or by evaluating blood-brain-barrier permeability using Evans blue dye penetration into brains. Limited vasculitis was present in the right atrium of the heart of infected hamsters, but abnormal electrocardiograms for several days leading up to mortality did not occur. Since respiratory insufficiency was strongly correlated with mortality more than any other pathological parameter, it is the likely cause of death in rodents. These animal data and a poor prognosis for persons with respiratory insufficiency support the hypothesis that neurological lesions affecting respiratory

Local Magnetism in Strongly Correlated Electron Systems with Orbital Degrees of Freedom

Science.gov (United States)

Ducatman, Samuel Charles

The central aim of my research is to explain the connection between the macroscopic behavior and the microscopic physics of strongly correlated electron systems with orbital degrees of freedom through the use of effective models. My dissertation focuses on the sub-class of these materials where electrons appear to be localized by interactions, and magnetic ions have well measured magnetic moments. This suggests that we can capture the low-energy physics of the material by employing a minimal model featuring localized spins which interact with each other through exchange couplings. I describe Fe1+y Te and beta-Li2IrO3 with effective models primarily focusing on the spins of the magnetic ions, in this case Fe and Ir, respectively. The goal with both materials is to gain insight and make predictions for experimentalists. In chapter 2, I focus on Fe1+yTe. I describe why we believe the magnetic ground state of this material, with an observed Bragg peak at Q +/- pi/2, pi/2), can be described by a Heisenberg model with 1st, 2nd, and 3rd neighbor interactions. I present two possible ground states of this model in the small J1 limit, the bicollinear and plaquette states. In order to predict which ground state the model prefers, I calculate the spin wave spectrum with 1/S corrections, and I find the model naturally selects the "plaquette state." I give a brief description of the ways this result could be tested using experimental techniques such as polarized neutron scattering. In chapter 3, I extend the model used in chapter 2. This is necessary because the Heisenberg model we employed cannot explain why Fe1+yTe undergoes a phase transition as y is increased. We add an additional elements to our calculation; we assume that electrons in some of the Fe 3D orbitals have selectively localized while others remain itinerant. We write a new Hamiltonian, where localized moments acquire a new long-range RKKY-like interaction from interactions with the itinerant electrons. We are

Auxiliary-Field Quantum Monte Carlo Simulations of Strongly-Correlated Systems, the Final Report

Energy Technology Data Exchange (ETDEWEB)

Chang, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-11-07

In this final report, we present preliminary results of ground state phases of interacting spinless Dirac fermions. The name "Dirac fermion" originates from the fact that low-energy excitations of electrons hopping on the honeycomb lattice are described by a relativistic Dirac equation. Dirac fermions have received much attention particularly after the seminal work of Haldale1 which shows that the quantum Hall physics can be realized on the honeycomb lattice without magnetic fields. Haldane's work later becomes the foundation of topological insulators (TIs). While the physics of TIs is based largely on spin-orbit coupled non-interacting electrons, it was conjectured that topological insulators can be induced by strong correlations alone.

Quantum phase transition in strongly correlated many-body system

Science.gov (United States)

You, Wenlong

The past decade has seen a substantial rejuvenation of interest in the study of quantum phase transitions (QPTs), driven by experimental advance on the cuprate superconductors, the heavy fermion materials, organic conductors, Quantum Hall effect, Fe-As based superconductors and other related compounds. It is clear that strong electronic interactions play a crucial role in the systems of current interest, and simple paradigms for the behavior of such systems near quantum critical points remain unclear. Furthermore, the rapid progress in Feshbach resonance and optical lattice provides a flexible platform to study QPT. Quantum Phase Transition (QPT) describes the non-analytic behaviors of the ground-state properties in a many-body system by varying a physical parameter at absolute zero temperature - such as magnetic field or pressure, driven by quantum fluctuations. Such quantum phase transitions can be first-order phase transition or continuous. The phase transition is usually accompanied by a qualitative change in the nature of the correlations in the ground state, and describing this change shall clearly be one of our major interests. We address this issue from three prospects in a few strong correlated many-body systems in this thesis, i.e., identifying the ordered phases, studying the properties of different phases, characterizing the QPT points. In chapter 1, we give an introduction to QPT, and take one-dimensional XXZ model as an example to illustrate the QPT therein. Through this simple example, we would show that when the tunable parameter is varied, the system evolves into different phases, across two quantum QPT points. The distinct phases exhibit very different behaviors. Also a schematic phase diagram is appended. In chapter 2, we are engaged in research on ordered phases. Originating in the work of Landau and Ginzburg on second-order phase transition, the spontaneous symmetry breaking induces nonzero expectation of field operator, e.g., magnetization M

Spin-flip configuration interaction singles with exact spin-projection: Theory and applications to strongly correlated systems.

Science.gov (United States)

Tsuchimochi, Takashi

2015-10-14

Spin-flip approaches capture static correlation with the same computational scaling as the ordinary single reference methods. Here, we extend spin-flip configuration interaction singles (SFCIS) by projecting out intrinsic spin-contamination to make it spin-complete, rather than by explicitly complementing it with spin-coupled configurations. We give a general formalism of spin-projection for SFCIS, applicable to any spin states. The proposed method is viewed as a natural unification of SFCIS and spin-projected CIS to achieve a better qualitative accuracy at a low computational cost. While our wave function ansatz is more compact than previously proposed spin-complete SF approaches, it successfully offers more general static correlation beyond biradicals without sacrificing good quantum numbers. It is also shown that our method is invariant with respect to open-shell orbital rotations, due to the uniqueness of spin-projection. We will report benchmark calculations to demonstrate its qualitative performance on strongly correlated systems, including conical intersections that appear both in ground-excited and excited-excited degeneracies.

Charge- and parity-projected Hartree-Fock method for the strong tensor correlation and its application to the alpha particle

International Nuclear Information System (INIS)

Sugimoto, Satoru; Ikeda, Kiyomi; Toki, Hiroshi

2004-01-01

We propose a new mean-field-type framework which can treat the strong correlation induced by the tensor force. To treat the tensor correlation we break the charge and parity symmetries of a single-particle state and restore these symmetries of the total system by the projection method. We perform the charge and parity projections before variation and obtain a Hartree-Fock-like equation, which is solved self-consistently. We apply the Hartree-Fock-like equation to the alpha particle and find that by breaking the parity and charge symmetries, the correlation induced by the tensor force is obtained in the projected mean-field framework. We emphasize that the projection before the variation is important to pick up the tensor correlation in the present framework

Quantum criticality and emergence of the T/B scaling in strongly correlated metals

International Nuclear Information System (INIS)

Watanabe, Shinji; Miyake, Kazumasa

2016-01-01

A new type of scaling observed in heavy-electron metal β-YbAlB_4, where the magnetic susceptibility is expressed as a single scaling function of the ratio of temperature T and magnetic field B over four decades, is examined theoretically. We develop the mode-coupling theory for critical Yb-valence fluctuations under a magnetic field, verifying that the T/B scaling behavior appears near the QCP of the valence transition. Emergence of the T/B scaling indicates the presence of the small characteristic temperature of the critical Yb-valence fluctuation due to the strong local correlation effect. It is discussed that the T/B scaling as well as the unconventional criticality is explained from the viewpoint of the quantum valence criticality in a unified way.

Thermal properties of UO2 from density functional theory: role of strong correlations

International Nuclear Information System (INIS)

Panigrahi, Puspamitra; Kaur Gurpreet; Valsakumar, M.C.

2011-01-01

We report a study of ground state magnetic structure of Uranium-dioxide (UO 2 ) using ab initio calculations employing PAW pseudopotentials and Dudarev's version of GGA+U formalism as implemented in VASP to take into account the strong on-site Coulomb correlation among the localized Uranium-5f electrons. By choosing the value of the Hubbard parameter U eff to be 4.0 eV, we have confirmed the experimental observation that the ground state of UO 2 is an insulator with an anti-ferromagnetic (AFM) ordering. We study systematically the ground state structural, electronic, and magnetic properties of UO 2 and focus on the structure sensitive thermal properties such as specific heat, thermal expansion and comment on the calculation of thermal conductivity. (author)

Finite-Temperature Variational Monte Carlo Method for Strongly Correlated Electron Systems

Science.gov (United States)

Takai, Kensaku; Ido, Kota; Misawa, Takahiro; Yamaji, Youhei; Imada, Masatoshi

2016-03-01

A new computational method for finite-temperature properties of strongly correlated electrons is proposed by extending the variational Monte Carlo method originally developed for the ground state. The method is based on the path integral in the imaginary-time formulation, starting from the infinite-temperature state that is well approximated by a small number of certain random initial states. Lower temperatures are progressively reached by the imaginary-time evolution. The algorithm follows the framework of the quantum transfer matrix and finite-temperature Lanczos methods, but we extend them to treat much larger system sizes without the negative sign problem by optimizing the truncated Hilbert space on the basis of the time-dependent variational principle (TDVP). This optimization algorithm is equivalent to the stochastic reconfiguration (SR) method that has been frequently used for the ground state to optimally truncate the Hilbert space. The obtained finite-temperature states allow an interpretation based on the thermal pure quantum (TPQ) state instead of the conventional canonical-ensemble average. Our method is tested for the one- and two-dimensional Hubbard models and its accuracy and efficiency are demonstrated.

Neuromimetic Circuits with Synaptic Devices Based on Strongly Correlated Electron Systems

Science.gov (United States)

Ha, Sieu D.; Shi, Jian; Meroz, Yasmine; Mahadevan, L.; Ramanathan, Shriram

2014-12-01

Strongly correlated electron systems such as the rare-earth nickelates (R NiO3 , R denotes a rare-earth element) can exhibit synapselike continuous long-term potentiation and depression when gated with ionic liquids; exploiting the extreme sensitivity of coupled charge, spin, orbital, and lattice degrees of freedom to stoichiometry. We present experimental real-time, device-level classical conditioning and unlearning using nickelate-based synaptic devices in an electronic circuit compatible with both excitatory and inhibitory neurons. We establish a physical model for the device behavior based on electric-field-driven coupled ionic-electronic diffusion that can be utilized for design of more complex systems. We use the model to simulate a variety of associate and nonassociative learning mechanisms, as well as a feedforward recurrent network for storing memory. Our circuit intuitively parallels biological neural architectures, and it can be readily generalized to other forms of cellular learning and extinction. The simulation of neural function with electronic device analogs may provide insight into biological processes such as decision making, learning, and adaptation, while facilitating advanced parallel information processing in hardware.

Entropy excess in strongly correlated Fermi systems near a quantum critical point

Energy Technology Data Exchange (ETDEWEB)

Clark, J.W., E-mail: jwc@wuphys.wustl.edu [McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Zverev, M.V. [Russian Research Centre Kurchatov Institute, Moscow, 123182 (Russian Federation); Moscow Institute of Physics and Technology, Moscow, 123098 (Russian Federation); Khodel, V.A. [Russian Research Centre Kurchatov Institute, Moscow, 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States)

2012-12-15

A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum {epsilon}(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n{sup 2}(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum {epsilon}(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincare mapping associated with the fundamental Landau equation connecting n(p) and {epsilon}(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario. - Highlights: Black-Right-Pointing-Pointer Extension of Landau

Cross-species correlation between queen mating numbers and worker ovary sizes suggests kin conflict may influence ovary size evolution in honeybees

Science.gov (United States)

Rueppell, Olav; Phaincharoen, Mananya; Kuster, Ryan; Tingek, Salim

2011-09-01

During social evolution, the ovary size of reproductively specialized honey bee queens has dramatically increased while their workers have evolved much smaller ovaries. However, worker division of labor and reproductive competition under queenless conditions are influenced by worker ovary size. Little comparative information on ovary size exists in the different honey bee species. Here, we report ovariole numbers of freshly dissected workers from six Apis species from two locations in Southeast Asia. The average number of worker ovarioles differs significantly among species. It is strongly correlated with the average mating number of queens, irrespective of body size. Apis dorsata, in particular, is characterized by numerous matings and very large worker ovaries. The relation between queen mating number and ovary size across the six species suggests that individual selection via reproductive competition plays a role in worker ovary size evolution. This indicates that genetic diversity, generated by multiple mating, may bear a fitness cost at the colony level.

Strong-coupling theory of superconductivity

International Nuclear Information System (INIS)

Rainer, D.; Sauls, J.A.

1995-01-01

The electronic properties of correlated metals with a strong electron-phonon coupling may be understood in terms of a combination of Landau''s Fermi liquid theory and the strong-coupling theory of Migdal and Eliashberg. In these lecture notes we discuss the microscopic foundations of this phenomenological Fermi-liquid model of correlated, strong-coupling metals. We formulate the basic equations of the model, which are quasiclassical transport equations that describe both equilibrium and non-equilibrium phenomena for the normal and superconducting states of a metal. Our emphasis is on superconductors close to equilibrium, for which we derive the general linear response theory. As an application we calculate the dynamical conductivity of strong-coupling superconductors. (author)

TRANSPORT PROPERTIES OF THE STRONGLY CORRELATED SYSTEMS

Directory of Open Access Journals (Sweden)

T.Domanski

2004-01-01

Full Text Available The transport properties of various systems are studied here in the context of three different models. These are: - the disordered Hubbard model applicable to correlated binary alloys with a general disorder, - the Anderson model used in describing the Kondo physics of a quantum dot connected to the external superconducting leads, and - the Ranninger-Robaszkiewicz model applied to the study of optical properties of the system with preformed electron pairs above the temperature of transition to the superconducting state. We calculate the density of states, specific heat, the Wilson ratio and conductivity of the correlated binary alloy with off-diagonal disorder. We investigate the conditions under which the Kondo peak appears in the density of states and in the conductance of a dot coupled to the external superconducting leads. We analyze the effect of the pseudogap on the optical spectra in the high temperature superconductors described by the boson-fermion model.

Quantum criticality and emergence of the T/B scaling in strongly correlated metals

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Shinji [Department of Basic Sciences, Kyushu Institute of Technology, Kitakyushu (Japan); Miyake, Kazumasa [Toyota Physical and Chemical Research Institute, Nagakute (Japan)

2016-02-15

A new type of scaling observed in heavy-electron metal β-YbAlB{sub 4}, where the magnetic susceptibility is expressed as a single scaling function of the ratio of temperature T and magnetic field B over four decades, is examined theoretically. We develop the mode-coupling theory for critical Yb-valence fluctuations under a magnetic field, verifying that the T/B scaling behavior appears near the QCP of the valence transition. Emergence of the T/B scaling indicates the presence of the small characteristic temperature of the critical Yb-valence fluctuation due to the strong local correlation effect. It is discussed that the T/B scaling as well as the unconventional criticality is explained from the viewpoint of the quantum valence criticality in a unified way.

Quantum physics of light and matter photons, atoms, and strongly correlated systems

CERN Document Server

Salasnich, Luca

2017-01-01

This compact but exhaustive textbook, now in its significantly revised and expanded second edition, provides an essential introduction to the field quantization of light and matter with applications to atomic physics and strongly correlated systems. Following an initial review of the origins of special relativity and quantum mechanics, individual chapters are devoted to the second quantization of the electromagnetic field and the consequences of light field quantization for the description of electromagnetic transitions. The spin of the electron is then analyzed, with particular attention to its derivation from the Dirac equation. Subsequent topics include the effects of external electric and magnetic fields on the atomic spectra and the properties of systems composed of many interacting identical particles. The book also provides a detailed explanation of the second quantization of the non-relativistic matter field, i.e., the Schrödinger field, which offers a powerful tool for the investigation of many-body...

Strongly correlated Fermi-systems: Non-Fermi liquid behavior, quasiparticle effective mass and their interplay

Energy Technology Data Exchange (ETDEWEB)

Shaginyan, V.R. [Petersburg Nuclear Physics Institute, RAS, Gatchina 188300 (Russian Federation); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)], E-mail: vrshag@thd.pnpi.spb.ru; Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Popov, K.G. [Komi Science Center, Ural Division, RAS, Syktyvkar 167982 (Russian Federation)

2009-06-15

Basing on the density functional theory of fermion condensation, we analyze the non-Fermi liquid behavior of strongly correlated Fermi-systems such as heavy-fermion metals. When deriving equations for the effective mass of quasiparticles, we consider solids with a lattice and homogeneous systems. We show that the low-temperature thermodynamic and transport properties are formed by quasiparticles, while the dependence of the effective mass on temperature, number density, magnetic fields, etc., gives rise to the non-Fermi liquid behavior. Our theoretical study of the heat capacity, magnetization, energy scales, the longitudinal magnetoresistance and magnetic entropy are in good agreement with the remarkable recent facts collected on the heavy-fermion metal YbRh{sub 2}Si{sub 2}.

Strongly correlated Fermi-systems: Non-Fermi liquid behavior, quasiparticle effective mass and their interplay

International Nuclear Information System (INIS)

Shaginyan, V.R.; Amusia, M.Ya.; Popov, K.G.

2009-01-01

Basing on the density functional theory of fermion condensation, we analyze the non-Fermi liquid behavior of strongly correlated Fermi-systems such as heavy-fermion metals. When deriving equations for the effective mass of quasiparticles, we consider solids with a lattice and homogeneous systems. We show that the low-temperature thermodynamic and transport properties are formed by quasiparticles, while the dependence of the effective mass on temperature, number density, magnetic fields, etc., gives rise to the non-Fermi liquid behavior. Our theoretical study of the heat capacity, magnetization, energy scales, the longitudinal magnetoresistance and magnetic entropy are in good agreement with the remarkable recent facts collected on the heavy-fermion metal YbRh 2 Si 2 .

Effect of strong correlations on the high energy anomaly in hole- and electron-doped high-Tc superconductors

International Nuclear Information System (INIS)

Moritz, B; Johnston, S; Greven, M; Shen, Z-X; Devereaux, T P; Schmitt, F; Meevasana, W; Motoyama, E M; Lu, D H; Kim, C; Scalettar, R T

2009-01-01

Recently, angle-resolved photoemission spectroscopy (ARPES) has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the high energy 'waterfall' or high energy anomaly (HEA). This paper demonstrates, using a combination of new ARPES measurements and quantum Monte Carlo simulations, that the HEA is not simply the by-product of matrix element effects, but rather represents a cross-over from a quasi-particle band at low binding energies near the Fermi level to valence bands at higher binding energy, assumed to be of strong oxygen character, in both hole- and electron-doped cuprates. While photoemission matrix elements clearly play a role in changing the aesthetic appearance of the band dispersion, i.e. the 'waterfall'-like behavior, they provide an inadequate description for the physics that underlies the strong band renormalization giving rise to the HEA. Model calculations of the single-band Hubbard Hamiltonian showcase the role played by correlations in the formation of the HEA and uncover significant differences in the HEA energy scale for hole- and electron-doped cuprates. In addition, this approach properly captures the transfer of spectral weight accompanying both hole and electron doping in a correlated material and provides a unifying description of the HEA across both sides of the cuprate phase diagram.

Atomic physics of strongly correlated systems: Progress report, 1 February 1988--15 January 1989

International Nuclear Information System (INIS)

Lin Chii-Dong.

1989-01-01

This report presents the progress made in our continuing study of strongly correlated atomic systems for the last contract period. In the area of hyperspherical coordinates for Coulombic three-body systems of arbitrary masses a general computing code has been developed. Calculation of the adiabatic potential curves have been accomplished for the e/sup /minus//e + e/sup /minus// system of arbitrary L, S and parity π. It was found that these curves behave very similar to the potential curves of H/sup /minus// except for a mass scaling. We have also examined the mass dependence of the ground state potential curves for systems of three charged particles, AAB, and showed that the curves become more attractive as the mass m/sub A/ becomes larger than m/sub B/. For ion-atom collisions we have examined the transfer-excitation (TE) processes to establish the importance of electron correlations in these two-electron transitions. We have also examined the orientation parameters for excited states formed in collisions with positive and negative charged particles to establish the relation between the sign of the charge of the incident particles to the sign of

Velocity correlations in laboratory insect swarms

Science.gov (United States)

Ni, R.; Ouellette, N. T.

2015-12-01

In contrast to animal groups such as bird flocks or migratory herds that display net, directed motion, insect swarms do not possess global order. Without such order, it is difficult to define and characterize the transition to collective behavior in swarms; nevertheless, visual observation of swarms strongly suggests that swarming insects do behave collectively. It has recently been suggested that correlation rather than order is the hallmark of emergent collective behavior. Here, we report measurements of spatial velocity correlation functions in laboratory mating swarms of the non-biting midge Chironomus riparius. Although we find some correlation at short distances, our swarms are in general only weakly correlated, in contrast to what has been observed in field studies. Our results hint at the potentially important role of environmental conditions on collective behavior, and suggest that general indicators of the collective nature of swarming are still needed.

Electron-mediated relaxation following ultrafast pumping of strongly correlated materials: model evidence of a correlation-tuned crossover between thermal and nonthermal states.

Science.gov (United States)

Moritz, B; Kemper, A F; Sentef, M; Devereaux, T P; Freericks, J K

2013-08-16

We examine electron-electron mediated relaxation following ultrafast electric field pump excitation of the fermionic degrees of freedom in the Falicov-Kimball model for correlated electrons. The results reveal a dichotomy in the temporal evolution of the system as one tunes through the Mott metal-to-insulator transition: in the metallic regime relaxation can be characterized by evolution toward a steady state well described by Fermi-Dirac statistics with an increased effective temperature; however, in the insulating regime this quasithermal paradigm breaks down with relaxation toward a nonthermal state with a complicated electronic distribution as a function of momentum. We characterize the behavior by studying changes in the energy, photoemission response, and electronic distribution as functions of time. This relaxation may be observable qualitatively on short enough time scales that the electrons behave like an isolated system not in contact with additional degrees of freedom which would act as a thermal bath, especially when using strong driving fields and studying materials whose physics may manifest the effects of correlations.

Strong-Field Modulated Diffraction Effects in the Correlated Electron-Nuclear Motion in Dissociating H2+

International Nuclear Information System (INIS)

He Feng; Becker, Andreas; Thumm, Uwe

2008-01-01

We show that the electronic dynamics in a molecule driven by a strong field is complex and potentially even counterintuitive. As a prototype example, we simulate the interaction of a dissociating H 2 + molecule with an intense infrared laser pulse. Depending on the laser intensity, the direction of the electron's motion between the two nuclei is found to follow or oppose the classical laser-electric force. We explain the sensitive dependence of the correlated electronic-nuclear motion in terms of the diffracting electronic momentum distribution of the dissociating two-center system. The distribution is dynamically modulated by the nuclear motion and periodically shifted in the oscillating infrared electric field

Strong correlation effects on the d-wave superconductor- spectral weight analysis by variational wave functions

International Nuclear Information System (INIS)

Chou, C-P; Lee, T K; Ho, C-M

2009-01-01

We examine the strong correlation effects of the d-wave superconducting state by including the Gutzwiller projection for no electron double occupancy at each lattice site. The spectral weights (SW's) for adding and removing an electron on the projected superconducting state, the ground state of the 2-dimensional t-t'-t - J model with moderate doped holes describing the high T c cuprates, are studied numerically on finite lattices and compared with the observation made by low-temperature tunneling (particle asymmetry of tunneling conductance) and angle-resolved photoemission (SW transfer from the projected Fermi liquid state) spectroscopies. The contrast with the d-wave case without projection is alo presented.

Hypnosis, suggestion, and suggestibility: an integrative model.

Science.gov (United States)

Lynn, Steven Jay; Laurence, Jean-Roch; Kirsch, Irving

2015-01-01

This article elucidates an integrative model of hypnosis that integrates social, cultural, cognitive, and neurophysiological variables at play both in and out of hypnosis and considers their dynamic interaction as determinants of the multifaceted experience of hypnosis. The roles of these variables are examined in the induction and suggestion stages of hypnosis, including how they are related to the experience of involuntariness, one of the hallmarks of hypnosis. It is suggested that studies of the modification of hypnotic suggestibility; cognitive flexibility; response sets and expectancies; the default-mode network; and the search for the neurophysiological correlates of hypnosis, more broadly, in conjunction with research on social psychological variables, hold much promise to further understanding of hypnosis.

Aspects of Strongly Correlated Many-Body Fermi Systems

Science.gov (United States)

Porter, William J., III

A, by now, well-known signal-to-noise problem plagues Monte Carlo calculations of quantum-information-theoretic observables in systems of interacting fermions, particularly the Renyi entanglement entropies Sn, even in many cases where the infamous sign problem does not appear. Several methods have been put forward to circumvent this affliction including ensemble-switching techniques using auxiliary partition-function ratios. This dissertation presents an algorithm that modifies the recently proposed free-fermion decomposition in an essential way: we incorporate the entanglement-sensitive correlations directly into the probability measure in a natural way. Implementing this algorithm, we demonstrate that it is compatible with the hybrid Monte Carlo algorithm, the workhorse of the lattice quantum chromodynamics community and an essential tool for studying gauge theories that contain dynamical fermions. By studying a simple one-dimensional Hubbard model, we demonstrate that our method does not exhibit the same debilitating numerical difficulties that naive attempts to study entanglement often encounter. Following that, we illustrate some key probabilistic insights, using intuition derived from the previous method and its successes to construct a simpler, better behaved, and more elegant algorithm. Using this method, in combination with new identities which allow us to avoid seemingly necessary numerical difficulties, the inversion of the restricted one-body density matrices, we compute high order Renyi entropies and perform a thorough comparison to this new algorithm's predecessor using the Hubbard model mentioned before. Finally, we characterize non-perturbatively the Renyi entropies of degree n = 2,3,4, and 5 of three-dimensional, strongly coupled many-fermion systems in the scale-invariant regime of short interaction range and large scattering length, i.e. in the unitary limit using the algorithms detailed herein. We also detail an exact, few-body projective method

The Electron-Phonon Interaction in Strongly Correlated Systems

International Nuclear Information System (INIS)

Castellani, C.; Grilli, M.

1995-01-01

We analyze the effect of strong electron-electron repulsion on the electron-phonon interaction from a Fermi-liquid point of view and show that the electron-electron interaction is responsible for vertex corrections, which generically lead to a strong suppression of the electron-phonon coupling in the v F q/ω >>1 region, while such effect is not present when v F q/ω F is the Fermi velocity and q and ω are the transferred momentum and frequency respectively. In particular the e-ph scattering is suppressed in transport properties which are dominated by low-energy-high-momentum processes. On the other hand, analyzing the stability criterion for the compressibility, which involves the effective interactions in the dynamical limit, we show that a sizable electron-phonon interaction can push the system towards a phase-separation instability. Finally a detailed analysis of these ideas is carried out using a slave-boson approach for the infinite-U three-band Hubbard model in the presence of a coupling between the local hole density and a dispersionless optical phonon. (author)

Excitonic condensation in systems of strongly correlated electrons

Czech Academy of Sciences Publication Activity Database

Kuneš, Jan

2015-01-01

Roč. 27, č. 33 (2015), s. 333201 ISSN 0953-8984 Institutional support: RVO:68378271 Keywords : electronic correlations * exciton * Bose-Einstein condensation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.209, year: 2015

Electronic structure calculations of atomic transport properties in uranium dioxide: influence of strong correlations

International Nuclear Information System (INIS)

Dorado, B.

2010-09-01

Uranium dioxide UO 2 is the standard nuclear fuel used in pressurized water reactors. During in-reactor operation, the fission of uranium atoms yields a wide variety of fission products (FP) which create numerous point defects while slowing down in the material. Point defects and FP govern in turn the evolution of the fuel physical properties under irradiation. In this study, we use electronic structure calculations in order to better understand the fuel behavior under irradiation. In particular, we investigate point defect behavior, as well as the stability of three volatile FP: iodine, krypton and xenon. In order to take into account the strong correlations of uranium 5f electrons in UO 2 , we use the DFT+U approximation, based on the density functional theory. This approximation, however, creates numerous metastable states which trap the system and induce discrepancies in the results reported in the literature. To solve this issue and to ensure the ground state is systematically approached as much as possible, we use a method based on electronic occupancy control of the correlated orbitals. We show that the DFT+U approximation, when used with electronic occupancy control, can describe accurately point defect and fission product behavior in UO 2 and provide quantitative information regarding point defect transport properties in the oxide fuel. (author)

Record statistics of a strongly correlated time series: random walks and Lévy flights

Science.gov (United States)

Godrèche, Claude; Majumdar, Satya N.; Schehr, Grégory

2017-08-01

We review recent advances on the record statistics of strongly correlated time series, whose entries denote the positions of a random walk or a Lévy flight on a line. After a brief survey of the theory of records for independent and identically distributed random variables, we focus on random walks. During the last few years, it was indeed realized that random walks are a very useful ‘laboratory’ to test the effects of correlations on the record statistics. We start with the simple one-dimensional random walk with symmetric jumps (both continuous and discrete) and discuss in detail the statistics of the number of records, as well as of the ages of the records, i.e. the lapses of time between two successive record breaking events. Then we review the results that were obtained for a wide variety of random walk models, including random walks with a linear drift, continuous time random walks, constrained random walks (like the random walk bridge) and the case of multiple independent random walkers. Finally, we discuss further observables related to records, like the record increments, as well as some questions raised by physical applications of record statistics, like the effects of measurement error and noise.

Types of suggestibility: Relationships among compliance, indirect, and direct suggestibility.

Science.gov (United States)

Polczyk, Romuald; Pasek, Tomasz

2006-10-01

It is commonly believed that direct suggestibility, referring to overt influence, and indirect suggestibility, in which the intention to influence is hidden, correlate poorly. This study demonstrates that they are substantially related, provided that they tap similar areas of influence. Test results from 103 students, 55 women and 48 men, were entered into regression analyses. Indirect suggestibility, as measured by the Sensory Suggestibility Scale for Groups, and compliance, measured by the Gudjonsson Compliance Scale, were predictors of direct suggestibility, assessed with the Barber Suggestibility Scale. Spectral analyses showed that indirect suggestibility is more related to difficult tasks on the BSS, but compliance is more related to easy tasks on this scale.

Designing, Probing, and Stabilizing Exotic Fabry-Perot Cavities for Studying Strongly Correlated Light

Science.gov (United States)

Ryou, Albert

Synthetic materials made of engineered quasiparticles are a powerful platform for studying manybody physics and strongly correlated systems due to their bottom-up approach to Hamiltonian modeling. Photonic quasiparticles called polaritons are particularly appealing since they inherit fast dynamics from light and strong interaction from matter. This thesis describes the experimental demonstration of cavity Rydberg polaritons, which are composite particles arising from the hybridization of an optical cavity with Rydberg EIT, as well as the tools for probing and stabilizing the cavity. We first describe the design, construction, and testing of a four-mirror Fabry-Perot cavity, whose small waist size on the order of 10 microns is comparable to the Rydberg blockade radius. By achieving strong coupling between the cavity photon and an atomic ensemble undergoing electromagnetically induced transparency (EIT), we observe the emergence of the dark-state polariton and characterize its single-body properties as well as the single-quantum nonlinearity. We then describe the implementation of a holographic spatial light modulator for exciting different transverse modes of the cavity, an essential tool for studying polariton-polariton scattering. For compensating optical aberrations, we employ a digital micromirror device (DMD), combining beam shaping with adaptive optics to produce diffraction-limited light. We quantitatively measure the purity of the DMD-produced Hermite-Gauss modes and confirm up to 99.2% efficiency. One application of the technique is to create Laguerre-Gauss modes, which have been used to probe synthetic Landau levels for photons in a twisted, nonplanar cavity. Finally, we describe the implementation of an FPGA-based FIR filter for stabilizing the cavity. We digitally cancel the acoustical resonances of the feedback-controlled mechanical system, thereby demonstrating an order-of-magnitude enhancement in the feedback bandwidth from 200 Hz to more than 2 k

Strong population genetic structuring in an annual fish, Nothobranchius furzeri, suggests multiple savannah refugia in southern Mozambique.

Science.gov (United States)

Bartáková, Veronika; Reichard, Martin; Janko, Karel; Polačik, Matej; Blažek, Radim; Reichwald, Kathrin; Cellerino, Alessandro; Bryja, Josef

2013-09-12

Intraspecific genetic variation of African fauna has been significantly affected by pronounced climatic fluctuations in Plio-Pleistocene, but, with the exception of large mammals, very limited empirical data on diversity of natural populations are available for savanna-dwelling animals. Nothobranchius furzeri is an annual fish from south-eastern Africa, inhabiting discrete temporary savannah pools outside main river alluvia. Their dispersal is limited and population processes affecting its genetic structure are likely a combination of those affecting terrestrial and aquatic taxa. N. furzeri is a model taxon in ageing research and several populations of known geographical origin are used in laboratory studies. Here, we analysed the genetic structure, diversity, historical demography and temporal patterns of divergence in natural populations of N. furzeri across its entire distribution range. Genetic structure and historical demography of N. furzeri were analysed using a combination of mitochondrial (partial cytochrome b sequences, 687 bp) and nuclear (13 microsatellites) markers in 693 fish from 36 populations. Genetic markers consistently demonstrated strong population structuring and suggested two main genetic groups associated with river basins. The split was dated to the Pliocene (>2 Mya). The northern group inhabits savannah pools across the basin of the intermittent river Chefu in south-western Mozambique and eastern Zimbabwe. The southern group (from southernmost Mozambique) is subdivided, with the River Limpopo forming a barrier (maximum divergence time 1 Mya). A strong habitat fragmentation (isolated temporary pools) is reflected in significant genetic structuring even between adjacent pools, with a major influence of genetic drift and significant isolation-by-distance. Analysis of historical demography revealed that the expansion of both groups is ongoing, supported by frequent founder effects in marginal parts of the range and evidence of secondary

PREFACE: International Conference on Strongly Correlated Electron Systems 2014 (SCES2014)

Science.gov (United States)

2015-03-01

The 2014 International Conference on Strongly Correlated Electron Systems (SCES) was held in Grenoble from the 7th to 11th of July on the campus of the University of Grenoble. It was a great privilege to have the conference in Grenoble after the series of meetings in Sendai (1992), San Diego (1993), Amsterdam (1994), Goa (1995), Zürich (1996), Paris (1998), Nagano (1999), Ann Arbor (2001), Krakow (2002), Karlsruhe (2004), Vienna (2005), Houston (2007), Buzios (2008), Santa Fe (2010), Cambridge (2011) and Tokyo (2013). Every three years, SCES joins the triennial conference on magnetism ICM. In 2015, ICM will take place in Barcelona. The meeting gathered an audience of 875 participants who actively interacted inside and outside of conference rooms. A large number of posters (530) was balanced with four parallel oral sessions which included 86 invited speakers and 141 short oral contributions. A useful arrangement was the possibility to put poster presentations on the website so participants could see them all through the conference week. Each morning two plenary sessions were held, ending on Friday with experimental and theoretical summaries delivered by Philipp Gegenwart (Augsburg) and Andrew Millis (Columbia). The plenary sessions were given by Gabriel Kotliar (Rutgers), Masashi Kawasaki (Tokyo), Jennifer Hoffman (Harvard), Mathias Vojta (Dresden), Ashvin Vishwanath (Berkeley), Andrea Cavalleri (Hamburg), Marc-Henri Julien (Grenoble), Neil Mathur (Cambridge), Giniyat Khaliullin (Stuttgart), and Toshiro Sakakibara (Tokyo). The parallel oral sessions were prepared by 40 symposium organizers selected by the chairman (Antoine Georges) and co-chairman (Kamran Behnia) of the Program Committee with the supplementary rule that speakers had not delivered an invited talk at the previous SCES conference held in 2013 in Tokyo. Special attention was given to help young researchers via grants to 40 overseas students. Perhaps due to the additional possibility of cheap

Superconductivity in strongly correlated electron systems: successes and open questions

International Nuclear Information System (INIS)

Shastry, B. Sriram

2000-01-01

Correlated electronic systems and superconductivity is a field which has unique track record of producing exciting new phases of matter. The article gives an overview of trends in solving the problems of superconductivity and correlated electronic systems

Strongly correlated electrons at high pressure: an approach by inelastic X-Ray scattering; Electrons correles sous haute pression: une approche par diffusion inelastique des rayons X

Energy Technology Data Exchange (ETDEWEB)

Rueff, J.P

2007-06-15

Inelastic X-ray scattering (IXS) and associated methods has turn out to be a powerful alternative for high-pressure physics. It is an all-photon technique fully compatible with high-pressure environments and applicable to a vast range of materials. Standard focalization of X-ray in the range of 100 microns is typical of the sample size in the pressure cell. Our main aim is to provide an overview of experimental results obtained by IXS under high pressure in 2 classes of materials which have been at the origin of the renewal of condensed matter physics: strongly correlated transition metal oxides and rare-earth compounds. Under pressure, d and f-electron materials show behaviors far more complex that what would be expected from a simplistic band picture of electron delocalization. These spectroscopic studies have revealed unusual phenomena in the electronic degrees of freedom, brought up by the increased density, the changes in the charge-carrier concentration, the over-lapping between orbitals, and hybridization under high pressure conditions. Particularly we discuss about pressure induced magnetic collapse and metal-insulator transitions in 3d compounds and valence fluctuations phenomena in 4f and 5f compounds. Thanks to its superior penetration depth, chemical selectivity and resonant enhancement, resonant inelastic X-ray scattering has appeared extremely well suited to high pressure physics in strongly correlated materials. (A.C.)

Suggestibility and negative priming: two replication studies.

Science.gov (United States)

David, Daniel; Brown, Richard J

2002-07-01

Research suggests that inhibiting the effect of irrelevant stimuli on subsequent thought and action (cognitive inhibition) may be an important component of suggestibility. Two small correlation studies were conducted to address the relationship between different aspects of suggestibility and individual differences in cognitive inhibition, operationalized as the degree of negative priming generated by to-be-ignored stimuli in a semantic categorization task. The first study found significant positive correlations between negative priming, hypnotic suggestibility, and creative imagination; a significant negative correlation was obtained between negative priming and interrogative suggestibility, demonstrating the discriminant validity of the study results. The second study replicated the correlation between negative priming and hypnotic suggestibility, using a different suggestibility measurement procedure that assessed subjective experience and hypnotic involuntariness as well as objective responses to suggestions. These studies support the notion that the ability to engage in cognitive inhibition may be an important component of hypnotic responsivity and maybe of other forms of suggestibility.

Solar wind structure suggested by bimodal correlations of solar wind speed and density between the spacecraft SOHO and Wind

Science.gov (United States)

Ogilvie, K. W.; Coplan, M. A.; Roberts, D. A.; Ipavich, F.

2007-08-01

We calculate the cross-spacecraft maximum lagged-cross-correlation coefficients for 2-hour intervals of solar wind speed and density measurements made by the plasma instruments on the Solar and Heliospheric Observatory (SOHO) and Wind spacecraft over the period from 1996, the minimum of solar cycle 23, through the end of 2005. During this period, SOHO was located at L1, about 200 R E upstream from the Earth, while Wind spent most of the time in the interplanetary medium at distances of more than 100 R E from the Earth. Yearly histograms of the maximum, time-lagged correlation coefficients for both the speed and density are bimodal in shape, suggesting the existence of two distinct solar wind regimes. The larger correlation coefficients we suggest are due to structured solar wind, including discontinuities and shocks, while the smaller are likely due to Alfvénic turbulence. While further work will be required to firmly establish the physical nature of the two populations, the results of the analysis are consistent with a solar wind that consists of turbulence from quiet regions of the Sun interspersed with highly filamentary structures largely convected from regions in the inner solar corona. The bimodal appearance of the distributions is less evident in the solar wind speed than in the density correlations, consistent with the observation that the filamentary structures are convected with nearly constant speed by the time they reach 1 AU. We also find that at solar minimum the fits for the density correlations have smaller high-correlation components than at solar maximum. We interpret this as due to the presence of more relatively uniform Alfvénic regions at solar minimum than at solar maximum.

TP53 mutations in myelodysplastic syndrome are strongly correlated with aberrations of chromosome 5, and correlate with adverse prognosis.

Science.gov (United States)

Kulasekararaj, Austin G; Smith, Alexander E; Mian, Syed A; Mohamedali, Azim M; Krishnamurthy, Pramila; Lea, Nicholas C; Gäken, Joop; Pennaneach, Coralie; Ireland, Robin; Czepulkowski, Barbara; Pomplun, Sabine; Marsh, Judith C; Mufti, Ghulam J

2013-03-01

This study aimed to determine the incidence/prognostic impact of TP53 mutation in 318 myelodysplastic syndrome (MDS) patients, and to correlate the changes to cytogenetics, single nucleotide polymorphism array karyotyping and clinical outcome. The median age was 65 years (17-89 years) and median follow-up was 45 months [95% confidence interval (CI) 27-62 months]. TP53 mutations occurred in 30 (9.4%) patients, exclusively in isolated del5q (19%) and complex karyotype (CK) with -5/5q-(72%), correlated with International Prognostic Scoring System intermediate-2/high, TP53 protein expression, higher blast count and leukaemic progression. Patients with mutant TP53 had a paucity of mutations in other genes implicated in myeloid malignancies. Median overall survival of patients with TP53 mutation was shorter than wild-type (9 versus 66 months, P disappearance of the mutant clone or emergence of new clones, suggesting an early occurrence of TP53 mutations. A reduction in mutant clone correlated with response to 5-azacitidine, however clones increased in non-responders and persisted at relapse. The adverse impact of TP53 persists after adjustment for cytogenetic risk and is of practical importance in evaluating prognosis. The relatively common occurrence of these mutations in two different prognostic spectrums of MDS, i.e. isolated 5q- and CK with -5/5q-, possibly implies two different mechanistic roles for TP53 protein. © 2013 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

Strong Neutron Pairing in core+4n Nuclei.

Science.gov (United States)

Revel, A; Marqués, F M; Sorlin, O; Aumann, T; Caesar, C; Holl, M; Panin, V; Vandebrouck, M; Wamers, F; Alvarez-Pol, H; Atar, L; Avdeichikov, V; Beceiro-Novo, S; Bemmerer, D; Benlliure, J; Bertulani, C A; Boillos, J M; Boretzky, K; Borge, M J G; Caamaño, M; Casarejos, E; Catford, W N; Cederkäll, J; Chartier, M; Chulkov, L; Cortina-Gil, D; Cravo, E; Crespo, R; Datta Pramanik, U; Díaz Fernández, P; Dillmann, I; Elekes, Z; Enders, J; Ershova, O; Estradé, A; Farinon, F; Fraile, L M; Freer, M; Galaviz, D; Geissel, H; Gernhäuser, R; Golubev, P; Göbel, K; Hagdahl, J; Heftrich, T; Heil, M; Heine, M; Heinz, A; Henriques, A; Ignatov, A; Johansson, H T; Jonson, B; Kahlbow, J; Kalantar-Nayestanaki, N; Kanungo, R; Kelic-Heil, A; Knyazev, A; Kröll, T; Kurz, N; Labiche, M; Langer, C; Le Bleis, T; Lemmon, R; Lindberg, S; Machado, J; Marganiec, J; Movsesyan, A; Nacher, E; Najafi, M; Nilsson, T; Nociforo, C; Paschalis, S; Perea, A; Petri, M; Pietri, S; Plag, R; Reifarth, R; Ribeiro, G; Rigollet, C; Röder, M; Rossi, D; Savran, D; Scheit, H; Simon, H; Syndikus, I; Taylor, J T; Tengblad, O; Thies, R; Togano, Y; Velho, P; Volkov, V; Wagner, A; Weick, H; Wheldon, C; Wilson, G; Winfield, J S; Woods, P; Yakorev, D; Zhukov, M; Zilges, A; Zuber, K

2018-04-13

The emission of neutron pairs from the neutron-rich N=12 isotones ^{18}C and ^{20}O has been studied by high-energy nucleon knockout from ^{19}N and ^{21}O secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay ^{19}N(-1p)^{18}C^{*}→^{16}C+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a ^{14}C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay ^{21}O(-1n)^{20}O^{*}→^{18}O+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the ^{16}O core and reduces the number of pairs.

Footprints of electron correlation in strong-field double ionization of Kr close to the sequential-ionization regime

Science.gov (United States)

Li, Xiaokai; Wang, Chuncheng; Yuan, Zongqiang; Ye, Difa; Ma, Pan; Hu, Wenhui; Luo, Sizuo; Fu, Libin; Ding, Dajun

2017-09-01

By combining kinematically complete measurements and a semiclassical Monte Carlo simulation we study the correlated-electron dynamics in the strong-field double ionization of Kr. Interestingly, we find that, as we step into the sequential-ionization regime, there are still signatures of correlation in the two-electron joint momentum spectrum and, more intriguingly, the scaling law of the high-energy tail is completely different from early predictions on the low-Z atom (He). These experimental observations are well reproduced by our generalized semiclassical model adapting a Green-Sellin-Zachor potential. It is revealed that the competition between the screening effect of inner-shell electrons and the Coulomb focusing of nuclei leads to a non-inverse-square central force, which twists the returned electron trajectory at the vicinity of the parent core and thus significantly increases the probability of hard recollisions between two electrons. Our results might have promising applications ranging from accurately retrieving atomic structures to simulating celestial phenomena in the laboratory.

Instabilities in strongly coupled plasmas

CERN Document Server

Kalman, G J

2003-01-01

The conventional Vlasov treatment of beam-plasma instabilities is inappropriate when the plasma is strongly coupled. In the strongly coupled liquid state, the strong correlations between the dust grains fundamentally affect the conditions for instability. In the crystalline state, the inherent anisotropy couples the longitudinal and transverse polarizations, and results in unstable excitations in both polarizations. We summarize analyses of resonant and non-resonant, as well as resistive instabilities. We consider both ion-dust streaming and dust beam-plasma instabilities. Strong coupling, in general, leads to an enhancement of the growth rates. In the crystalline phase, a resonant transverse instability can be excited.

Transverse transport in coupled strongly correlated electronic chains

International Nuclear Information System (INIS)

Capponi, S.; Poilblanc, D.

1997-01-01

One-particle interchain hopping in a system of coupled Luttinger liquids is investigated by use of exact diagonalizations techniques. We give numerical evidence that inter-chain coherent hopping (defined by a non-vanishing splitting) can be totally suppressed for the Luttinger liquid exponent α ∝ 0.4 or even smaller α values. The transverse conductivity is shown to exhibit a strong incoherent part even when coherent inter-chain hopping is believed to occur. Implications for the optical experiments in quasi-1D organic or high-T c superconductors is outlined. (orig.)

Strong Country Level Correlation between Syphilis and HSV-2 Prevalence

Science.gov (United States)

Kenyon, Chris Richard; Tsoumanis, Achilleas

2016-01-01

Background. Syphilis is curable but Herpes Simplex Virus-2 (HSV-2) is not. As a result, the prevalence of syphilis but not HSV-2 may be influenced by the efficacy of national STI screening and treatment capacity. If the prevalence of syphilis and HSV-2 is found to be correlated, then this makes it more likely that something other than differential STI treatment is responsible for variations in the prevalence of both HSV-2 and syphilis. Methods. Simple linear regression was used to evaluate the relationship between national antenatal syphilis prevalence and HSV-2 prevalence in women in two time periods: 1990–1999 and 2008. Adjustments were performed for the laboratory syphilis testing algorithm used and the prevalence of circumcision. Results. The prevalence of syphilis was positively correlated with that of HSV-2 for both time periods (adjusted correlations, 20–24-year-olds: 1990–99: R 2 = 0.54, P < 0.001; 2008: R 2 = 0.41, P < 0.001 and 40–44-year-olds: 1990–99: R 2 = 0.42, P < 0.001; 2008: R 2 = 0.49, P < 0.001). Conclusion. The prevalence of syphilis and HSV-2 is positively correlated. This could be due to a common set of risk factors underpinning both STIs. PMID:27069710

Suicidality and interrogative suggestibility.

Science.gov (United States)

Pritchard-Boone, Lea; Range, Lillian M

2005-01-01

All people are subject to memory suggestibility, but suicidal individuals may be especially so. The link between suicidality and suggestibility is unclear given mixed findings and methodological weaknesses of past research. To test the link between suicidality and interrogative suggestibility, 149 undergraduates answered questions about suicidal thoughts and reasons for living, and participated in a direct suggestibility procedure. As expected, suggestibility correlated with suicidality but accounted for little overall variance (4%). Mental health professionals might be able to take advantage of client suggestibility by directly telling suicidal persons to refrain from suicidal thoughts or actions.

Correlated binomial models and correlation structures

International Nuclear Information System (INIS)

Hisakado, Masato; Kitsukawa, Kenji; Mori, Shintaro

2006-01-01

We discuss a general method to construct correlated binomial distributions by imposing several consistent relations on the joint probability function. We obtain self-consistency relations for the conditional correlations and conditional probabilities. The beta-binomial distribution is derived by a strong symmetric assumption on the conditional correlations. Our derivation clarifies the 'correlation' structure of the beta-binomial distribution. It is also possible to study the correlation structures of other probability distributions of exchangeable (homogeneous) correlated Bernoulli random variables. We study some distribution functions and discuss their behaviours in terms of their correlation structures

Effect of strong correlations on the high energy anomaly in hole- and electron-doped high-T{sub c} superconductors

Energy Technology Data Exchange (ETDEWEB)

Moritz, B; Johnston, S; Greven, M; Shen, Z-X; Devereaux, T P [Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory and Stanford University, Stanford, CA 94305 (United States); Schmitt, F; Meevasana, W; Motoyama, E M [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Lu, D H [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Kim, C [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Scalettar, R T [Physics Department, University of California-Davis, Davis, CA 95616 (United States)], E-mail: moritzb@slac.stanford.edu

2009-09-15

Recently, angle-resolved photoemission spectroscopy (ARPES) has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the high energy 'waterfall' or high energy anomaly (HEA). This paper demonstrates, using a combination of new ARPES measurements and quantum Monte Carlo simulations, that the HEA is not simply the by-product of matrix element effects, but rather represents a cross-over from a quasi-particle band at low binding energies near the Fermi level to valence bands at higher binding energy, assumed to be of strong oxygen character, in both hole- and electron-doped cuprates. While photoemission matrix elements clearly play a role in changing the aesthetic appearance of the band dispersion, i.e. the 'waterfall'-like behavior, they provide an inadequate description for the physics that underlies the strong band renormalization giving rise to the HEA. Model calculations of the single-band Hubbard Hamiltonian showcase the role played by correlations in the formation of the HEA and uncover significant differences in the HEA energy scale for hole- and electron-doped cuprates. In addition, this approach properly captures the transfer of spectral weight accompanying both hole and electron doping in a correlated material and provides a unifying description of the HEA across both sides of the cuprate phase diagram.

Exchange and spin-fluctuation superconducting pairing in the strong correlation limit of the Hubbard model

International Nuclear Information System (INIS)

Plakida, N. M.; Anton, L.; Adam, S. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO); Adam, Gh. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO)

2001-01-01

A microscopical theory of superconductivity in the two-band singlet-hole Hubbard model, in the strong coupling limit in a paramagnetic state, is developed. The model Hamiltonian is obtained by projecting the p-d model to an asymmetric Hubbard model with the lower Hubbard subband occupied by one-hole Cu d-like states and the upper Hubbard subband occupied by two-hole p-d singlet states. The model requires two microscopical parameters only, the p-d hybridization parameter t and the charge-transfer gap Δ. It was previously shown to secure an appropriate description of the normal state properties of the high -T c cuprates. To treat rigorously the strong correlations, the Hubbard operator technique within the projection method for the Green function is used. The Dyson equation is derived. In the molecular field approximation, d-wave superconducting pairing of conventional hole (electron) pairs in one Hubbard subband is found, which is mediated by the exchange interaction given by the interband hopping, J ij = 4 (t ij ) 2 / Δ. The normal and anomalous components of the self-energy matrix are calculated in the self-consistent Born approximation for the electron-spin-fluctuation scattering mediated by kinematic interaction of the second order of the intraband hopping. The derived numerical and analytical solutions predict the occurrence of singlet d x 2 -y 2 -wave pairing both in the d-hole and singlet Hubbard subbands. The gap functions and T c are calculated for different hole concentrations. The exchange interaction is shown to be the most important pairing interaction in the Hubbard model in the strong correlation limit, while the spin-fluctuation coupling results only in a moderate enhancement of T c . The smaller weight of the latter comes from two specific features: its vanishing inside the Brillouin zone (BZ) along the lines, |k x | + |k y |=π pointing towards the hot spots and the existence of a small energy shell within which the pairing is effective. By

Strong Tracking Filter for Nonlinear Systems with Randomly Delayed Measurements and Correlated Noises

Directory of Open Access Journals (Sweden)

Hongtao Yang

2018-01-01

Full Text Available This paper proposes a novel strong tracking filter (STF, which is suitable for dealing with the filtering problem of nonlinear systems when the following cases occur: that is, the constructed model does not match the actual system, the measurements have the one-step random delay, and the process and measurement noises are correlated at the same epoch. Firstly, a framework of decoupling filter (DF based on equivalent model transformation is derived. Further, according to the framework of DF, a new extended Kalman filtering (EKF algorithm via using first-order linearization approximation is developed. Secondly, the computational process of the suboptimal fading factor is derived on the basis of the extended orthogonality principle (EOP. Thirdly, the ultimate form of the proposed STF is obtained by introducing the suboptimal fading factor into the above EKF algorithm. The proposed STF can automatically tune the suboptimal fading factor on the basis of the residuals between available and predicted measurements and further the gain matrices of the proposed STF tune online to improve the filtering performance. Finally, the effectiveness of the proposed STF has been proved through numerical simulation experiments.

Histologically Measured Cardiomyocyte Hypertrophy Correlates with Body Height as Strongly as with Body Mass Index

Directory of Open Access Journals (Sweden)

Richard E. Tracy

2011-01-01

Full Text Available Cardiac myocytes are presumed to enlarge with left ventricular hypertrophy (LVH. This study correlates histologically measured myocytes with lean and fat body mass. Cases of LVH without coronary heart disease and normal controls came from forensic autopsies. The cross-sectional widths of myocytes in H&E-stained paraffin sections followed log normal distributions almost to perfection in all 104 specimens, with constant coefficient of variation across the full range of ventricular weight, as expected if myocytes of all sizes contribute proportionately to hypertrophy. Myocyte sizes increased with height. By regression analysis, height2.7 as a proxy for lean body mass and body mass index (BMI as a proxy for fat body mass, exerted equal effects in the multiple correlation with myocyte volume, and the equation rejected race and sex. In summary, myocyte sizes, as indexes of LVH, suggest that lean and fat body mass may contribute equally.

Statistical Evidence Suggests that Inattention Drives Hyperactivity/Impulsivity in Attention Deficit-Hyperactivity Disorder

Science.gov (United States)

Sokolova, Elena; Groot, Perry; Claassen, Tom; van Hulzen, Kimm J.; Glennon, Jeffrey C.; Franke, Barbara

2016-01-01

Background Numerous factor analytic studies consistently support a distinction between two symptom domains of attention-deficit/hyperactivity disorder (ADHD), inattention and hyperactivity/impulsivity. Both dimensions show high internal consistency and moderate to strong correlations with each other. However, it is not clear what drives this strong correlation. The aim of this paper is to address this issue. Method We applied a sophisticated approach for causal discovery on three independent data sets of scores of the two ADHD dimensions in NeuroIMAGE (total N = 675), ADHD-200 (N = 245), and IMpACT (N = 164), assessed by different raters and instruments, and further used information on gender or a genetic risk haplotype. Results In all data sets we found strong statistical evidence for the same pattern: the clear dependence between hyperactivity/impulsivity symptom level and an established genetic factor (either gender or risk haplotype) vanishes when one conditions upon inattention symptom level. Under reasonable assumptions, e.g., that phenotypes do not cause genotypes, a causal model that is consistent with this pattern contains a causal path from inattention to hyperactivity/impulsivity. Conclusions The robust dependency cancellation observed in three different data sets suggests that inattention is a driving factor for hyperactivity/impulsivity. This causal hypothesis can be further validated in intervention studies. Our model suggests that interventions that affect inattention will also have an effect on the level of hyperactivity/impulsivity. On the other hand, interventions that affect hyperactivity/impulsivity would not change the level of inattention. This causal model may explain earlier findings on heritable factors causing ADHD reported in the study of twins with learning difficulties. PMID:27768717

Magnetic field correlations in random flow with strong steady shear

International Nuclear Information System (INIS)

Kolokolov, I. V.; Lebedev, V. V.; Sizov, G. A.

2011-01-01

We analyze the magnetic kinematic dynamo in a conducting fluid where a stationary shear flow is accompanied by relatively weak random velocity fluctuations. The diffusionless and diffusion regimes are described. The growth rates of the magnetic field moments are related to the statistical characteristics of the flow describing divergence of the Lagrangian trajectories. The magnetic field correlation functions are examined, and their growth rates and scaling behavior are established. General assertions are illustrated by the explicit solution of a model where the velocity field is short-correlated in time.

The contribution of Diamond Light Source to the study of strongly correlated electron systems and complex magnetic structures.

Science.gov (United States)

Radaelli, P G; Dhesi, S S

2015-03-06

We review some of the significant contributions to the field of strongly correlated materials and complex magnets, arising from experiments performed at the Diamond Light Source (Harwell Science and Innovation Campus, Didcot, UK) during the first few years of operation (2007-2014). We provide a comprehensive overview of Diamond research on topological insulators, multiferroics, complex oxides and magnetic nanostructures. Several experiments on ultrafast dynamics, magnetic imaging, photoemission electron microscopy, soft X-ray holography and resonant magnetic hard and soft X-ray scattering are described. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Apolipoprotein B level and diabetic microvascular complications ( is there a correlation?

Directory of Open Access Journals (Sweden)

Mary N. Rizk

2013-01-01

Conclusion Apo B levels are strongly correlated to diabetic microvascular complications. The higher the degree of nephropathy, the higher the Apo B level. The presence of more than one microvascular complication correlates positively with high levels of Apo B. This suggests the possible use of Apo B as a sensitive biomarker of the presence of early diabetic microvascular complications.

Strong Bulk-Edge Coupling in the Compressible Half-Filled Quantum Hall State

International Nuclear Information System (INIS)

Milovanovic, M.V.; Shimshoni, E.

1999-01-01

We studied analytically static correlators in the compressible half-filled quantum Hall state, which characterize the nature of charged excitations in the bulk and on the edge of the system. We employ a modified version of the plasma analogy - namely, a mapping to a classical two-dimensional system of interacting particles - similarly to what has been done in studies of the incompressible (Laughlin) states. However, the 'fake plasma' corresponding to the half-filled state is found to have anomalously weak screening properties. As a consequence, the correlations along the edge do not decay algebraically as in the incompressible case, thus indicating the breakdown of Wen's edge theory. On the other hand, the bulk correlator (which parallels the Girvin-MacDonald algebraic off-diagonal long range order) decays algebraically in a similar way as in the incompressible states, signifying the presence of some kind of bosonic order even in the compressible state. The above results suggest that due to the strong coupling between charged modes on the edge and the neutral Fermions (dipoles) in the bulk, the (attractive) correlation hole is not well defined on the edge. Hence, the system there can be modeled as a free Fermi gas of electrons (with an appropriate boundary condition). A possible experimental indication of a strong bulk-edge coupling at half-filling has been indeed observed in non-local resistance measurements [1]. We also suggest, that while our results contradict the validity of an effective one-dimensional description of the edge excitations on the static level, the dynamics may decouple the edge and bulk so as to recover the Laughlin-like behavior apparent in the experiment of Grayson et al

Can strong correlations be experimentally revealed for Ҡ -mesons?

Directory of Open Access Journals (Sweden)

Hiesmayr Beatrix C.

2014-01-01

Full Text Available In 1964 the physicists John St. Bell working at CERN took the 1935-idea of Einstein-Podolsky-Rosen seriously and found that all theories based on local realism have to satisfy a certain inequality, nowadays dubbed Bell’s inequality. Experiments with ordinary matter systems or light show violations of Bell’s inequality favouring the quantum theory though a loophole free experiment has not yet been performed. This contribution presents an experimentally feasible Bell inequality for systems at higher energy scales, i.e. entangled neutral Ҡ -meson pairs that are typically produced in Φ -mesons decays or proton-antiproton annihilation processes. Strong requirements have to be overcome in order to achieve a conclusive tests, such a proposal was recently published. Surprisingly, this new Bell inequality reveals new features for weakly decaying particles, in particular, a strong sensitivity to the combined charge-conjugation-parity (CP symmetry. Here-with, a puzzling relation between a symmetry breaking for mesons and Bell’s inequality—which is a necessary and sufficient condition for the security of quantum cryptography protocols— is established. This becomes the more important since CP symmetry is related to the cosmological question why the antimatter disappeared after the Big Bang.

Some Applications of Holography to Study Strongly Correlated Systems

Directory of Open Access Journals (Sweden)

Bhatnagar Neha

2018-01-01

Full Text Available In this work, we study the transport coefficients of strongly coupled condensed matter systems using gauge/gravity duality (holography. We consider examples from the real world and evaluate the conductivities from their gravity duals. Adopting the bottom-up approach of holography, we obtain the frequency response of the conductivity for (1+1-dimensional systems. We also evaluate the DC conductivities for non-relativistic condensed matter systems with hyperscaling violating geometry.

Profumo di SUSY: Suggestive Correlations in the ATLAS and CMS High Jet Multiplicity Data

CERN Document Server

Li, Tianjun; Nanopoulos, Dimitri V; Walker, Joel W

2011-01-01

We present persistently amassing evidence that the CMS and ATLAS Collaborations may indeed be already registering supersymmetry events at the Large Hadron Collider (LHC). Our analysis is performed in the context of a highly phenomenologically favorable model named No-Scale F-SU(5), which represents the unification of the F-lipped SU(5) Grand Unified Theory (GUT), two pairs of hypothetical TeV-scale vector-like supersymmetric multiplets derived out of F-Theory, and the dynamically established boundary conditions of No-Scale supergravity. We document highly suggestive correlations between the first inverse femtobarn of observations by CMS and ATLAS, where seductive excesses in multijet events, particularly those with nine or more jets, are unambiguously accounted for by a precision Monte-Carlo simulation of the F-SU(5) model space. This intimate correspondence is optimized by a unified gaugino mass in the neighborhood of M_{1/2}=518 GeV. We supplement this analysis by extrapolating for the expected data profile...

Landform elevation suggests ecohydrologic footprints in subsurface geomorphology

Science.gov (United States)

Watts, A. C.; Watts, D.; Kaplan, D. A.; Mclaughlin, D. L.; Heffernan, J. B.; Martin, J. B.; Murray, A.; Osborne, T.; Cohen, M. J.; Kobziar, L. N.

2012-12-01

Many landscapes exhibit patterns in their arrangement of biota, or in their surface geomorphology as a result of biotic activity. Examples occur around the globe and include northern peatlands, Sahelian savannas, and shallow marine reefs. Such self-organized patterning is strongly suggestive of coupled, reciprocal feedbacks (i.e. locally positive, and distally negative) among biota and their environment. Much research on patterned landscapes has concerned emergent biogeomorphologic surfaces such as those found in peatlands, or the influence of biota on soil formation or transport. Our research concerns ecohydrologic feedbacks hypothesized to produce patterned occurrence of depressions in a subtropical limestone karst landscape. Our findings show strong evidence of self-organized patterning, in the form of overdispersed dissolution basins. Distributions of randomized bedrock elevation measurements on the landscape are bimodal, with means clustered about either higher- or lower-elevation modes. Measurements on the thin mantle of soil overlying this landscape, however, display reduced bimodality and mode separation. These observations indicate abiotic processes in diametric opposition to the biogenic forces which may be responsible for generating landscape pattern. Correlograms show higher spatial autocorrelation among soil measurements compared to bedrock measurements, and measurements of soil-layer thickness show high negative correlation with bedrock elevation. Our results are consistent with predictions of direct ecohydrologic feedbacks that would produce patterned "footprints" directly on bedrock, and of abiotic processes operating to obfuscate this pattern. The study suggests new steps to identify biogeochemical mechanisms for landscape patterning: an "ecological drill" by which plant communities modify geology.

Effective interactions in strongly-coupled quantum systems

International Nuclear Information System (INIS)

Chen, J.M.C.

1986-01-01

In this thesis, they study the role of effective interactions in strongly-coupled Fermi systems where the short-range correlations introduce difficulties requiring special treatment. The correlated basis function method provides the means to incorporate the short-range correlations and generate the matrix elements of the Hamiltonian and identity operators in a nonorthogonal basis of states which are so important to their studies. In the first half of the thesis, the particle-hole channel is examined to elucidate the effects of collective excitations. Proceeding from a least-action principle, a generalization of the random-phase approximation is developed capable of describing such strongly-interacting Fermi systems as nuclei, nuclear matter, neutron-star matter, and liquid 3 He. A linear response of dynamically correlated system to a weak external perturbation is also derived based on the same framework. In the second half of the thesis, the particle-particle channel is examined to elucidate the effects of pairing in nuclear and neutron-star matter

Excitonic condensation of strongly correlated electrons: the case of Pr.sub.0.5./sub. Ca.sub.0.5./sub. CoO.sub.3./sub..

Czech Academy of Sciences Publication Activity Database

Kuneš, Jan; Augustinský, Pavel

2014-01-01

Roč. 90, č. 23 (2014), "235112-1"-"235112-5" ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : excitonic condensation * strongly correlated electrons * cobaltites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

Scale-free correlations in the geographical spreading of obesity

Science.gov (United States)

Gallos, Lazaros; Barttfeld, Pablo; Havlin, Shlomo; Sigman, Mariano; Makse, Hernan

2012-02-01

Obesity levels have been universally increasing. A crucial problem is to determine the influence of global and local drivers behind the obesity epidemic, to properly guide effective policies. Despite the numerous factors that affect the obesity evolution, we show a remarkable regularity expressed in a predictable pattern of spatial long-range correlations in the geographical spreading of obesity. We study the spatial clustering of obesity and a number of related health and economic indicators, and we use statistical physics methods to characterize the growth of the resulting clusters. The resulting scaling exponents allow us to broadly classify these indicators into two separate universality classes, weakly or strongly correlated. Weak correlations are found in generic human activity such as population distribution and the growth of the whole economy. Strong correlations are recovered, among others, for obesity, diabetes, and the food industry sectors associated with food consumption. Obesity turns out to be a global problem where local details are of little importance. The long-range correlations suggest influence that extends to large scales, hinting that the physical model of obesity clustering can be mapped to a long-range correlated percolation process.

Current topics in condensed matter and particle physics. Non-perturbative phenomena and strongly correlated systems. Kathmandu summer school lecture notes. V. 2

International Nuclear Information System (INIS)

Pati, J.; Shafi, Q.; Yu Lu

1993-01-01

This is a collection of five lectures on quantum field theory and its applications, two lectures on aspects of particle and nuclear physics (unification in the superstring context; and topics in P and CP violation in nuclear and particle physics), and ten lectures mainly on the physics of strong correlations, all but one of which are within the INIS scope. Refs, figs and tabs

New developments in the theoretical treatment of low dimensional strongly correlated systems.

Science.gov (United States)

James, Andrew J A; Konik, Robert M; Lecheminant, Philippe; Robinson, Neil; Tsvelik, Alexei M

2017-10-09

We review two important non-perturbative approaches for extracting the physics of low- dimensional strongly correlated quantum systems. Firstly, we start by providing a comprehensive review of non-Abelian bosonization. This includes an introduction to the basic elements of confor- mal field theory as applied to systems with a current algebra, and we orient the reader by presenting a number of applications of non-Abelian bosonization to models with large symmetries. We then tie this technique into recent advances in the ability of cold atomic systems to realize complex symme- tries. Secondly, we discuss truncated spectrum methods for the numerical study of systems in one and two dimensions. For one-dimensional systems we provide the reader with considerable insight into the methodology by reviewing canonical applications of the technique to the Ising model (and its variants) and the sine-Gordon model. Following this we review recent work on the development of renormalization groups, both numerical and analytical, that alleviate the effects of truncating the spectrum. Using these technologies, we consider a number of applications to one-dimensional systems: properties of carbon nanotubes, quenches in the Lieb-Liniger model, 1+1D quantum chro- modynamics, as well as Landau-Ginzburg theories. In the final part we move our attention to consider truncated spectrum methods applied to two-dimensional systems. This involves combining truncated spectrum methods with matrix product state algorithms. We describe applications of this method to two-dimensional systems of free fermions and the quantum Ising model, including their non-equilibrium dynamics. © 2017 IOP Publishing Ltd.

Are You Suggesting That's My Hand? The Relation Between Hypnotic Suggestibility and the Rubber Hand Illusion.

Science.gov (United States)

Walsh, E; Guilmette, D N; Longo, M R; Moore, J W; Oakley, D A; Halligan, P W; Mehta, M A; Deeley, Q

2015-01-01

Hypnotic suggestibility (HS) is the ability to respond automatically to suggestions and to experience alterations in perception and behavior. Hypnotically suggestible participants are also better able to focus and sustain their attention on an experimental stimulus. The present study explores the relation between HS and susceptibility to the rubber hand illusion (RHI). Based on previous research with visual illusions, it was predicted that higher HS would lead to a stronger RHI. Two behavioral output measures of the RHI, an implicit (proprioceptive drift) and an explicit (RHI questionnaire) measure, were correlated against HS scores. Hypnotic suggestibility correlated positively with the implicit RHI measure contributing to 30% of the variation. However, there was no relation between HS and the explicit RHI questionnaire measure, or with compliance control items. High hypnotic suggestibility may facilitate, via attentional mechanisms, the multisensory integration of visuoproprioceptive inputs that leads to greater perceptual mislocalization of a participant's hand. These results may provide insight into the multisensory brain mechanisms involved in our sense of embodiment.

Microsatellite frequencies vary with body mass and body temperature in mammals, suggesting correlated variation in mutation rate

Directory of Open Access Journals (Sweden)

William Amos

2014-11-01

Full Text Available Substitution rate is often found to correlate with life history traits such as body mass, a predictor of population size and longevity, and body temperature. The underlying mechanism is unclear but most models invoke either natural selection or factors such as generation length that change the number of mutation opportunities per unit time. Here we use published genome sequences from 69 mammals to ask whether life history traits impact another form of genetic mutation, the high rates of predominantly neutral slippage in microsatellites. We find that the length-frequency distributions of three common dinucleotide motifs differ greatly between even closely related species. These frequency differences correlate with body mass and body temperature and can be used to predict the phenotype of an unknown species. Importantly, different length microsatellites show complicated patterns of excess and deficit that cannot be explained by a simple model where species with short generation lengths have experienced more mutations. Instead, the patterns probably require changes in mutation rate that impact alleles of different length to different extents. Body temperature plausibly influences mutation rate by modulating the propensity for slippage. Existing hypotheses struggle to account for a link between body mass and mutation rate. However, body mass correlates inversely with population size, which in turn predicts heterozygosity. We suggest that heterozygote instability, HI, the idea that heterozygous sites show increased mutability, could provide a plausible link between body mass and mutation rate.

Decoherence-induced transition from photon correlation to anti-correlation

International Nuclear Information System (INIS)

Xu, Q

2014-01-01

Decoherence tends to induce the quantum-to-classical transition, which leads to a crucial obstacle in the realization of reliable quantum information processing. Counterintuitively, we propose that the decoherence due to phase decay brings about the switch from photon correlation to anti-correlation. Stronger decoherence also gives rise to an enhancement of the transition from photon correlation to anti-correlation. This breaks the conventional correlation of strong decoherence with fast decorrelation. (letters)

Damping at positive frequencies in the limit J⊥-->0 in the strongly correlated Hubbard model

Science.gov (United States)

Mohan, Minette M.

1992-08-01

I show damping in the two-dimensional strongly correlated Hubbard model within the retraceable-path approximation, using an expansion around dominant poles for the self-energy. The damping half-width ~J2/3z occurs only at positive frequencies ω>5/2Jz, the excitation energy of a pure ``string'' state of length one, where Jz is the Ising part of the superexchange interaction, and occurs even in the absence of spin-flip terms ~J⊥ in contrast to other theoretical treatments. The dispersion relation for both damped and undamped peaks near the upper band edge is found and is shown to have lost the simple J2/3z dependence characteristic of the peaks near the lower band edge. The position of the first three peaks near the upper band edge agrees well with numerical simulations on the t-J model. The weight of the undamped peaks near the upper band edge is ~J4/3z, contrasting with Jz for the weight near the lower band edge.

Deterministic alternatives to the full configuration interaction quantum Monte Carlo method for strongly correlated systems

Science.gov (United States)

Tubman, Norm; Whaley, Birgitta

The development of exponential scaling methods has seen great progress in tackling larger systems than previously thought possible. One such technique, full configuration interaction quantum Monte Carlo, allows exact diagonalization through stochastically sampling of determinants. The method derives its utility from the information in the matrix elements of the Hamiltonian, together with a stochastic projected wave function, which are used to explore the important parts of Hilbert space. However, a stochastic representation of the wave function is not required to search Hilbert space efficiently and new deterministic approaches have recently been shown to efficiently find the important parts of determinant space. We shall discuss the technique of Adaptive Sampling Configuration Interaction (ASCI) and the related heat-bath Configuration Interaction approach for ground state and excited state simulations. We will present several applications for strongly correlated Hamiltonians. This work was supported through the Scientific Discovery through Advanced Computing (SciDAC) program funded by the U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences.

Cluster-cluster correlations and constraints on the correlation hierarchy

Science.gov (United States)

Hamilton, A. J. S.; Gott, J. R., III

1988-01-01

The hypothesis that galaxies cluster around clusters at least as strongly as they cluster around galaxies imposes constraints on the hierarchy of correlation amplitudes in hierachical clustering models. The distributions which saturate these constraints are the Rayleigh-Levy random walk fractals proposed by Mandelbrot; for these fractal distributions cluster-cluster correlations are all identically equal to galaxy-galaxy correlations. If correlation amplitudes exceed the constraints, as is observed, then cluster-cluster correlations must exceed galaxy-galaxy correlations, as is observed.

Ferromagnetic instabilities in disordered systems in the limit of strong correlations

International Nuclear Information System (INIS)

Magalhaes, A.N.; Troper, A.; Gomes, A.A.

1976-05-01

One derives the criterion for ferromagnetic instabilities in hybridized disordered systems, e.g. transition metal like systems and actinides, within the Coherent Potential Approximation (CPA), the electron-electron correlations being described by Hubbard' approximation. In the case of actinides, one treats approximately the motion of d electrons while the diagonal disorder within the f band is fully taken into account. In the case of a trnsition metal like system, except for Hubbard's approximation in dealing with d-d electron correlations, our procedure is exact within the spirit of CPA

Burst firing enhances neural output correlation

Directory of Open Access Journals (Sweden)

Ho Ka eChan

2016-05-01

Full Text Available Neurons communicate and transmit information predominantly through spikes. Given that experimentally observed neural spike trains in a variety of brain areas can be highly correlated, it is important to investigate how neurons process correlated inputs. Most previous work in this area studied the problem of correlation transfer analytically by making significant simplifications on neural dynamics. Temporal correlation between inputs that arises from synaptic filtering, for instance, is often ignored when assuming that an input spike can at most generate one output spike. Through numerical simulations of a pair of leaky integrate-and-fire (LIF neurons receiving correlated inputs, we demonstrate that neurons in the presence of synaptic filtering by slow synapses exhibit strong output correlations. We then show that burst firing plays a central role in enhancing output correlations, which can explain the above-mentioned observation because synaptic filtering induces bursting. The observed changes of correlations are mostly on a long time scale. Our results suggest that other features affecting the prevalence of neural burst firing in biological neurons, e.g., adaptive spiking mechanisms, may play an important role in modulating the overall level of correlations in neural networks.

Measuring Children's Suggestibility in Forensic Interviews.

Science.gov (United States)

Volpini, Laura; Melis, Manuela; Petralia, Stefania; Rosenberg, Melina D

2016-01-01

According to the scientific literature, childrens' cognitive development is not complete until adolescence. Therefore, the problems inherent in children serving as witnesses are crucial. In preschool-aged children, false memories may be identified because of misinformation and insight bias. Additionally, they are susceptible of suggestions. The aim of this study was to verify the levels of suggestibility in children between three and 5 years of age. Ninety-two children were examined (44 male, 48 female; M = 4.5 years, SD = 9.62). We used the correlation coefficient (Pearson's r) and the averages variance by SPSS statistical program. The results concluded that: younger children are almost always more susceptible to suggestibility. The dimension of immediate recall was negatively correlates with that of total suggestibility (r = -0.357 p suggestibility, because older children shift their answers more often (r = 0.394 p < 0.001). Younger children change their answers more times (r = -0.395 p < 0.001). © 2016 American Academy of Forensic Sciences.

Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming

KAUST Repository

Sawall, Yvonne

2015-03-10

Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12° latitudes featuring a steep temperature gradient between the northern (28.5°N, 21-27°C) and southern (16.5°N, 28-33°C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29°C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals.

Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming

KAUST Repository

Sawall, Yvonne; Al-Sofyani, Abdulmoshin; Hohn, Sö nke; Banguera Hinestroza, Eulalia; Voolstra, Christian R.; Wahl, Martin

2015-01-01

Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12° latitudes featuring a steep temperature gradient between the northern (28.5°N, 21-27°C) and southern (16.5°N, 28-33°C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29°C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals.

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Czech Academy of Sciences Publication Activity Database

Abelev, B. I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, B. D.; Arkhipkin, D.; Averichev, G. S.; Balewski, J.; Barannikova, O.; Barnby, L. S.; Baudot, J.; Baumgart, S.; Beavis, D.R.; Bellwied, R.; Benedosso, F.; Betancourt, M.J.; Betts, R. R.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielčík, Jaroslav; Bielčíková, Jana; Biritz, B.; Bland, L.C.; Bombara, M.; Bonner, B. E.; Botje, M.; Bouchet, J.; Braidot, E.; Brandin, A. V.; Bruna, E.; Bueltmann, S.; Burton, T. P.; Bysterský, Michal; Cai, X.Z.; Caines, H.; Sanchez, M.C.D.; Catu, O.; Cebra, D.; Cendejas, R.; Cervantes, M.C.; Chajecki, Z.; Chaloupka, Petr; Chattopadhyay, S.; Chen, H.F.; Chen, J.H.; Cheng, J.; Cherney, M.; Chikanian, A.; Choi, K.E.; Christie, W.; Clarke, R.F.; Codrington, M.J.M.; Corliss, R.; Cormier, T.M.; Coserea, R. M.; Cramer, J. G.; Crawford, H. J.; Das, D.; Dash, S.; Daugherity, M.; De Silva, L.C.; Dedovich, T. G.; DePhillips, M.; Derevschikov, A.A.; de Souza, R.D.; Didenko, L.; Djawotho, P.; Dunlop, J.C.; Mazumdar, M.R.D.; Edwards, W.R.; Efimov, L.G.; Elhalhuli, E.; Elnimr, M.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Eun, L.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Feng, A.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Gagliardi, C. A.; Gaillard, L.; Ganti, M. S.; Gangaharan, D.R.; Garcia-Solis, E.J.; Geromitsos, A.; Geurts, F.; Ghazikhanian, V.; Ghosh, P.; Gorbunov, Y.N.; Gordon, A.; Grebenyuk, O.; Grosnick, D.; Grube, B.; Guertin, S.M.; Guimaraes, K.S.F.F.; Gupta, A.; Gupta, N.; Guryn, W.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Heppelmann, S.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffman, A.M.; Hoffmann, G.W.; Hofman, D.J.; Hollis, R.S.; Huang, H.Z.; Humanic, T.J.; Igo, G.; Iordanova, A.; Jacobs, P.; Jacobs, W.W.; Jakl, Pavel; Jena, C.; Jin, F.; Jones, C.L.; Jones, P.G.; Joseph, J.; Judd, E.G.; Kabana, S.; Kajimoto, K.; Kang, K.; Kapitán, Jan; Keane, D.; Kechechyan, A.; Kettler, D.; Khodyrev, V.Yu.; Kikola, D.P.; Kiryluk, J.; Kisiel, A.; Klein, S.R.; Knospe, A.G.; Kocoloski, A.; Koetke, D.D.; Kopytine, M.; Korsch, W.; Kotchenda, L.; Kushpil, Vasilij; Kravtsov, P.; Kravtsov, V.I.; Krueger, K.; Krus, M.; Kuhn, C.; Kumar, L.; Kurnadi, P.; Lamont, M.A.C.; Landgraf, J.M.; LaPointe, S.; Lauret, J.; Lebedev, A.; Lednický, Richard; Lee, Ch.; Lee, J.H.; Leight, W.; LeVine, M.J.; Li, N.; Li, C.; Li, Y.; Lin, G.; Lindenbaum, S.J.; Lisa, M.A.; Liu, F.; Liu, J.; Liu, L.; Ljubicic, T.; Llope, W.J.; Longacre, R.S.; Love, W.A.; Lu, Y.; Ludlam, T.; Ma, G.L.; Ma, Y.G.; Mahapatra, D.P.; Majka, R.; Mall, O.I.; Mangotra, L.K.; Manweiler, R.; Margetis, S.; Markert, C.; Matis, H.S.; Matulenko, Yu.A.; McShane, T.S.; Meschanin, A.; Milner, R.; Minaev, N.G.; Mioduszewski, S.; Mischke, A.; Mitchell, J.; Mohanty, B.; Morozov, D.A.; Munhoz, M. G.; Nandi, B.K.; Nattrass, C.; Nayak, T. K.; Nelson, J.M.; Netrakanti, P.K.; Ng, M.J.; Nogach, L.V.; Nurushev, S.B.; Odyniec, G.; Ogawa, A.; Okada, H.; Okorokov, V.; Olson, D.; Pachr, M.; Page, B.S.; Pal, S.K.; Pandit, Y.; Panebratsev, Y.; Panitkin, S.Y.; Pawlak, T.; Peitzmann, T.; Perevoztchikov, V.; Perkins, C.; Peryt, W.; Phatak, S.C.; Poljak, N.; Poskanzer, A.M.; Potukuchi, B.V.K.S.; Prindle, D.; Pruneau, C.; Pruthi, N.K.; Putschke, J.; Raniwala, R.; Raniwala, S.; Ray, R.L.; Redwine, R.; Reed, R.; Ridiger, A.; Ritter, H.G.; Roberts, J.B.; Rogachevskiy, O.V.; Romero, J.L.; Rose, A.; Roy, C.; Ruan, L.; Russcher, M.J.; Sahoo, R.; Sakrejda, I.; Sakuma, T.; Salur, S.; Sandweiss, J.; Sarsour, M.; Schambach, J.; Scharenberg, R.P.; Schmitz, N.; Seger, J.; Selyuzhenkov, I.; Seyboth, P.; Shabetai, A.; Shahaliev, E.; Shao, M.; Sharma, M.; Shi, S.S.; Shi, X.H.; Sichtermann, E.P.; Simon, F.; Singaraju, R.N.; Skoby, M.J.; Smirnov, N.; Snellings, R.; Sorensen, P.; Sowinski, J.; Spinka, H.M.; Srivastava, B.; Stadnik, A.; Stanislaus, T.D.S.; Staszak, D.; Strikhanov, M.; Stringfellow, B.; Suaide, A.A.P.; Suarez, M.C.; Subba, N.L.; Šumbera, Michal; Sun, X.M.; Sun, Y.; Sun, Z.; Surrow, B.; Symons, T.J.M.; de Toledo, A. S.; Takahashi, J.; Tang, A.H.; Tang, Z.; Tarnowsky, T.; Thein, D.; Thomas, J.H.; Tian, J.; Timmins, A.R.; Timoshenko, S.; Tokarev, M. V.; Trainor, T.A.; Tram, V.N.; Trattner, A.L.; Trentalange, S.; Tribble, R. E.; Tsai, O.D.; Ulery, J.; Ullrich, T.; Underwood, D.G.; Van Buren, G.; van Leeuwen, M.; Vander Molen, A.M.; Vanfossen, J.A.; Varma, R.; Vasconcelos, G.S.M.; Vasilevski, I.M.; Vasiliev, A. N.; Videbaek, F.; Vigdor, S.E.; Viyogi, Y. P.; Vokal, S.; Voloshin, S.A.; Wada, M.; Walker, M.; Wang, F.; Wang, G.; Wang, J.S.; Wang, Q.; Wang, X.; Wang, X.L.; Wang, Y.; Webb, G.; Webb, J.C.; Westfall, G.D.; Whitten, C.; Wieman, H.; Wissink, S.W.; Witt, R.; Wu, Y.; Xie, W.; Xu, N.; Xu, Q.H.; Xu, Y.; Xu, Z.; Yang, Y.; Yepes, P.; Yip, K.; Yoo, I.K.; Yue, Q.; Zawisza, M.; Zbroszczyk, H.; Zhan, W.; Zhang, S.; Zhang, W.M.; Zhang, X.P.; Zhang, Y.; Zhang, Z.P.; Zhao, Y.; Zhong, C.; Zhou, J.; Zhu, X.; Zoulkarneev, R.; Zoulkarneeva, Y.; Zuo, J.X.; Tlustý, David

2009-01-01

Roč. 103, č. 25 (2009), 251601/1-251601/7 ISSN 0031-9007 R&D Projects: GA ČR GA202/07/0079; GA MŠk LC07048; GA MŠk LA09013 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100502 Keywords : heavy-ion collisions * local parity violation * strong interaction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 7.328, year: 2009

Strong cosmic censorship and the strong curvature singularities

International Nuclear Information System (INIS)

Krolak, A.

1987-01-01

Conditions are given under which any asymptotically simple and empty space-time that has a partial Cauchy surface with an asymptotically simple past is globally hyperbolic. It is shown that this result suggests that the Cauchy horizons of the type occurring in Reissner--Nordstroem and Kerr space-times are unstable. This in turn gives support for the validity of the strong cosmic censorship hypothesis

Endangerment of cultural heritage sites by strong rain

Science.gov (United States)

Krauß, Thomas; Fischer, Peter

2017-09-01

Due to climate change extreme weather conditions become more and more frequent in the last years. Especially in Germany nearly every year a large flood event happens. Most of these events are caused by strong rain. There are at most two causes for these floodings: The first is locally strong rain in the area of damage, the second happens at damage sites located near confluxes and strong rain in the upper stream areas of the joining rivers. The amount of damage is often strongly correlated with unreasonable designation of new construction in such endangered regions. Our presented study is based on an earlier project together with a German insurance company. In this project we analyzed correlations of geographical settings with the insurance data of flood damages over ten years. The result of this study was a strong relation of the terrain with the amount and the probability of damages. Further investigations allow us to derive a system for estimating potential endangerment due to strong rain just from suitable digital terrain models (DTMs). In the presented study we apply this method to different types of cultural heritage (CH) sites in Germany and other parts of the world to detect which type of CH sites were build with potential endangerment of strong rain events in mind and which ones are prone to such events.

The strength of electron electron correlation in Cs3C60

Science.gov (United States)

Baldassarre, L.; Perucchi, A.; Mitrano, M.; Nicoletti, D.; Marini, C.; Pontiroli, D.; Mazzani, M.; Aramini, M.; Riccó, M.; Giovannetti, G.; Capone, M.; Lupi, S.

2015-10-01

Cs3C60 is an antiferromagnetic insulator that under pressure (P) becomes metallic and superconducting below Tc = 38 K. The superconducting dome present in the T - P phase diagram close to a magnetic state reminds what found in superconducting cuprates and pnictides, strongly suggesting that superconductivity is not of the conventional Bardeen-Cooper-Schrieffer (BCS) type We investigate the insulator to metal transition induced by pressure in Cs3C60 by means of infrared spectroscopy supplemented by Dynamical Mean-Field Theory calculations. The insulating compound is driven towards a metallic-like behaviour, while strong correlations survive in the investigated pressure range. The metallization process is accompanied by an enhancement of the Jahn-Teller effect. This shows that electronic correlations are crucial in determining the insulating behaviour at ambient pressure and the bad metallic nature for increasing pressure. On the other hand, the relevance of the Jahn-Teller coupling in the metallic state confirms that phonon coupling survives in the presence of strong correlations.

Tunable emergent heterostructures in a prototypical correlated metal

Science.gov (United States)

Fobes, D. M.; Zhang, S.; Lin, S.-Z.; Das, Pinaki; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Harriger, L. W.; Ehlers, G.; Podlesnyak, A.; Bewley, R. I.; Sazonov, A.; Hutanu, V.; Ronning, F.; Batista, C. D.; Janoschek, M.

2018-05-01

At the interface between two distinct materials, desirable properties, such as superconductivity, can be greatly enhanced1, or entirely new functionalities may emerge2. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions3, the control of which would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom4. Here we report high-resolution neutron spectroscopy on the prototypical strongly correlated metal CeRhIn5, revealing competition between magnetic frustration and easy-axis anisotropy—a well-established mechanism for generating spontaneous superstructures5. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. The resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting6 and electronic nematic textures7 in CeRhIn5, suggesting that in situ tunable heterostructures can be realized in correlated electron materials.

LDA+DMFT Approach to Magnetocrystalline Anisotropy of Strong Magnets

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Jian-Xin Zhu

2014-05-01

Full Text Available The new challenges posed by the need of finding strong rare-earth-free magnets demand methods that can predict magnetization and magnetocrystalline anisotropy energy (MAE. We argue that correlated electron effects, which are normally underestimated in band-structure calculations, play a crucial role in the development of the orbital component of the magnetic moments. Because magnetic anisotropy arises from this orbital component, the ability to include correlation effects has profound consequences on our predictive power of the MAE of strong magnets. Here, we show that incorporating the local effects of electronic correlations with dynamical mean-field theory provides reliable estimates of the orbital moment, the mass enhancement, and the MAE of YCo_{5}.

Clayey landslide initiation and acceleration strongly modulated by soil swelling

Science.gov (United States)

Schulz, William; Smith, Joel B.; Wang, Gonghui; Jiang, Yao; Roering, Joshua J.

2018-01-01

Largely unknown mechanisms restrain motion of clay-rich, slow-moving landslides that are widespread worldwide and rarely accelerate catastrophically. We studied a clayey, slow-moving landslide typical of thousands in northern California, USA, to decipher hydrologic-mechanical interactions that modulate landslide dynamics. Similar to some other studies, observed pore-water pressures correlated poorly with landslide reactivation and speed. In situ and laboratory measurements strongly suggested that variable pressure along the landslide's lateral shear boundaries resulting from seasonal soil expansion and contraction modulated its reactivation and speed. Slope-stability modeling suggested that the landslide's observed behavior could be predicted by including transient swell pressure as a resistance term, whereas modeling considering only transient hydrologic conditions predicted movement 5–6 months prior to when it was observed. All clayey soils swell to some degree; hence, our findings suggest that swell pressure likely modulates motion of many landslides and should be considered to improve forecasts of clayey landslide initiation and mobility.

Ab initio optimization principle for the ground states of translationally invariant strongly correlated quantum lattice models.

Science.gov (United States)

Ran, Shi-Ju

2016-05-01

In this work, a simple and fundamental numeric scheme dubbed as ab initio optimization principle (AOP) is proposed for the ground states of translational invariant strongly correlated quantum lattice models. The idea is to transform a nondeterministic-polynomial-hard ground-state simulation with infinite degrees of freedom into a single optimization problem of a local function with finite number of physical and ancillary degrees of freedom. This work contributes mainly in the following aspects: (1) AOP provides a simple and efficient scheme to simulate the ground state by solving a local optimization problem. Its solution contains two kinds of boundary states, one of which play the role of the entanglement bath that mimics the interactions between a supercell and the infinite environment, and the other gives the ground state in a tensor network (TN) form. (2) In the sense of TN, a novel decomposition named as tensor ring decomposition (TRD) is proposed to implement AOP. Instead of following the contraction-truncation scheme used by many existing TN-based algorithms, TRD solves the contraction of a uniform TN in an opposite way by encoding the contraction in a set of self-consistent equations that automatically reconstruct the whole TN, making the simulation simple and unified; (3) AOP inherits and develops the ideas of different well-established methods, including the density matrix renormalization group (DMRG), infinite time-evolving block decimation (iTEBD), network contractor dynamics, density matrix embedding theory, etc., providing a unified perspective that is previously missing in this fields. (4) AOP as well as TRD give novel implications to existing TN-based algorithms: A modified iTEBD is suggested and the two-dimensional (2D) AOP is argued to be an intrinsic 2D extension of DMRG that is based on infinite projected entangled pair state. This paper is focused on one-dimensional quantum models to present AOP. The benchmark is given on a transverse Ising

Epicardial adipose tissue volume and adipocytokine imbalance are strongly linked to human coronary atherosclerosis.

Science.gov (United States)

Shimabukuro, Michio; Hirata, Yoichiro; Tabata, Minoru; Dagvasumberel, Munkhbaatar; Sato, Hiromi; Kurobe, Hirotsugu; Fukuda, Daiju; Soeki, Takeshi; Kitagawa, Tetsuya; Takanashi, Shuichiro; Sata, Masataka

2013-05-01

The impact of epicardial adipose tissue (EAT) over abdominal or overall adiposity on coronary artery disease (CAD) is currently unknown. We compared the association among EAT volume (EATV), cytokine/adipocytokine profiles in EAT and subcutaneous fat, and atherogenic CAD. Paired samples were obtained from EAT and subcutaneous adipose tissue during elective cardiac surgery for CAD (n=50) or non-CAD (n=50). EATV was the sum of cross-sectional EAT areas, and visceral and subcutaneous fat areas were determined at the umbilicus level on computed tomography scans. CD68(+), CD11c(+), and CD206(+) cells were counted using immunohistochemical staining. Cytokine/adipocytokine expression was evaluated using quantitative real-time polymerase chain reaction. Multivariate analysis indicated that male sex, age, diabetes mellitus, high triglycerides, and low high-density lipoprotein cholesterol, and EATV index (EATV/body surface area, cm(3)/m(2)) were significant CAD predictors (corrected R(2)=0.401; PEATV index positively correlated with the CD68(+) and CD11c(+) cell numbers and nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3), interleukin-1β, and interleukin-1R expression; and negatively correlated with adiponectin expression in EAT. A multivariate analysis model, including CD68(+) cells and interleukin-1β, and adiponectin expression in EAT strongly predicted CAD (corrected R(2)=0.756; PEATV and macrophage and cytokine/adipocytokine signals in EAT strongly correlated with CAD. Our findings suggest that EATV and adipocytokine imbalance are strongly linked to human coronary atherosclerosis.

Local condensate depletion at trap center under strong interactions

Science.gov (United States)

Yukalov, V. I.; Yukalova, E. P.

2018-04-01

Cold trapped Bose-condensed atoms, interacting via hard-sphere repulsive potentials are considered. Simple mean-field approximations show that the condensate distribution inside a harmonic trap always has the shape of a hump with the maximum condensate density occurring at the trap center. However, Monte Carlo simulations at high density and strong interactions display the condensate depletion at the trap center. The explanation of this effect of local condensate depletion at trap center is suggested in the frame of self-consistent theory of Bose-condensed systems. The depletion is shown to be due to the existence of the anomalous average that takes into account pair correlations and appears in systems with broken gauge symmetry.

Correlated electron-ion collisions in a strong laser field; Korrelierte Elektron-Ion-Stoesse in starken Laserfeldern

Energy Technology Data Exchange (ETDEWEB)

Ristow, T.

2007-12-17

Electron-ion-collisions in plasmas in the presence of an ultra-short intensive laser pulse can cause high energy transfers to the electrons. During the collision the oscillation energy of the electron in the laser field is changed into drift energy. In this regime, multi-photon processes, known from the ionization of neutral atoms (Above-Threshold Ionization), and successive, so called correlated collisions, are important. The subject of the thesis is a study of binary Coulomb collisions in strong laser fields. The collisions are treated both in the context of classical Newtonian mechanics and in the quantum-mechanical framework by the Schroedinger equation. In the classical case a simplified instantaneous collision model and a complete dynamical treatment are discussed. Collisions can be treated instantaneously, if the ratio of the impact parameter to the quiver amplitude is small. The energy distributions calculated in this approximation show an elastic peak and a broad plateau due to rescattered electrons. At incident velocities smaller than the quiver velocity, correlated collisions are observed in the electron trajectories of the dynamical model. This effect leads to characteristic momentum distributions of the electrons, that are explicitly calculated and compared with the results of the instantaneous model. In addition, the time-dependence of the collisions is discussed in the framework of a singular perturbation theory. The complete description of the Coulomb scattering requires a quantum-mechanical description. A time-dependent method of wave-packet scattering is used and the corresponding time-dependent three-dimensional Schroedinger equation is solved by an implicit ADImethod on a spatial grid. The momentum and the energy distributions of the scattered electrons are calculated by the Fourier transformation of the wavefunction. A comparison of the scattering from a repulsive and an attractive potential is used to distinguish between simple collisions and

Wheat yield vulnerability: relation to rainfall and suggestions for adaptation

Directory of Open Access Journals (Sweden)

Khalid Tafoughalti

2018-04-01

Full Text Available Wheat production is of paramount importance in the region of Meknes, which is mainly produced under rainfed conditions. It is the dominant cereal, the greater proportion being the soft type. During the past few decades, rainfall flaws have caused a number of cases of droughts. These flaws have seriously affecting wheat production. The main objective of this study is the assessment of rainfall variability at monthly, seasonal and annual scales and to determine their impact on wheat yields. To reduce this impact we suggested some mechanisms of adaptation. We used monthly rainfall records for three decades and wheat yields records of fifteen years. Rainfall variability is assessed utilizing the precipitation concentration index and the variation coefficient. The association between wheat yields and cumulative rainfall amounts of different scales was calculated based on a regression model to evaluate the impact of rainfall on wheat yields. Data analysis shown moderate seasonal and irregular annual rainfall distribution. Yields fluctuated from 210 to 4500 Kg/ha with 52% of coefficient of variation. The correlation results shows that soft wheat and hard wheat are strongly correlated with the period of January to March than with the whole growing-season. While they are adversely correlated with the mid-spring. This investigation concluded that synchronizing appropriate adaptation with the period of January to March was crucial to achieving success yield of wheat.

Quantum phase transitions of strongly correlated electron systems

International Nuclear Information System (INIS)

Imada, Masatoshi

1998-01-01

Interacting electrons in solids undergo various quantum phase transitions driven by quantum fluctuations. The quantum transitions take place at zero temperature by changing a parameter to control quantum fluctuations rather than thermal fluctuations. In contrast to classical phase transitions driven by thermal fluctuations, the quantum transitions have many different features where quantum dynamics introduces a source of intrinsic fluctuations tightly connected with spatial correlations and they have been a subject of recent intensive studies as we see below. Interacting electron systems cannot be fully understood without deep analyses of the quantum phase transitions themselves, because they are widely seen and play essential roles in many phenomena. Typical and important examples of the quantum phase transitions include metal-insulator transitions, (2, 3, 4, 5, 6, 7, 8, 9) metal-superconductor transitions, superconductor-insulator transitions, magnetic transitions to antiferromagnetic or ferromagnetic phases in metals as well as in Mott insulators, and charge ordering transitions. Here, we focus on three different types of transitions

2D Vis/NIR correlation spectroscopy of cooked chicken meats

Science.gov (United States)

Liu, Yongliang; Chen, Yud-Ren; Ozaki, Yukihiro

2000-03-01

Cooking of chicken meats was investigated by the generalized two-dimensional visible/near-infrared (2D Vis/NIR) correlation spectroscopy. Synchronous and asynchronous spectra in the 400-700 nm visible region suggested that the 445 and 560 nm bands be ascribed to deoxymyoglobin and oxymyoglobin, and at least one of the 475, 520, and 585 nm bands is assignable to the denatured species (metmyoglobin). The asynchronous 2D NIR correlation spectrum showed that CH bands change their spectral intensities before the OH/NH groups during the cooking process, indicating that CH fractions are easily oxidized and degraded. In addition, strong correlation peaks were observed correlating the bands in the visible and NIR spectral regions.

Assessing Hubbard-corrected AM05+U and PBEsol+U density functionals for strongly correlated oxides CeO_2 and Ce_2O_3

International Nuclear Information System (INIS)

Weck, Philippe F.; Kim, Eunja

2016-01-01

The structure–property relationships of bulk CeO_2 and Ce_2O_3 have been investigated using AM05 and PBEsol exchange–correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO_2 and Ce_2O_3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. Lastly, the present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

Interrogative suggestibility and perceptual motor performance.

Science.gov (United States)

Gudjonsson, G H

1984-04-01

This study investigates the relationship between interrogative suggestibility, as measured by the Gudjonsson Suggestibility Scale, and Arrow-Dot scores. The tendency of subjects (25 men and 25 women, mean age 30.2 yr.) to alter their answers once interpersonal pressure had been applied correlated significantly with poor Arrow-Dot Ego functioning.

Micropillar displacements by cell traction forces are mechanically correlated with nuclear dynamics

Energy Technology Data Exchange (ETDEWEB)

Li, Qingsen; Makhija, Ekta; Hameed, F.M. [Mechanobiology Institute, National University of Singapore (Singapore); Shivashankar, G.V., E-mail: shiva.gvs@gmail.com [Mechanobiology Institute, National University of Singapore (Singapore); Department of Biological Sciences, National University of Singapore (Singapore)

2015-05-29

Cells sense physical cues at the level of focal adhesions and transduce them to the nucleus by biochemical and mechanical pathways. While the molecular intermediates in the mechanical links have been well studied, their dynamic coupling is poorly understood. In this study, fibroblast cells were adhered to micropillar arrays to probe correlations in the physical coupling between focal adhesions and nucleus. For this, we used novel imaging setup to simultaneously visualize micropillar deflections and EGFP labeled chromatin structure at high spatial and temporal resolution. We observed that micropillar deflections, depending on their relative positions, were positively or negatively correlated to nuclear and heterochromatin movements. Our results measuring the time scales between micropillar deflections and nucleus centroid displacement are suggestive of a strong elastic coupling that mediates differential force transmission to the nucleus. - Highlights: • Correlation between focal adhesions and nucleus studied using novel imaging setup. • Micropillar and nuclear displacements were measured at high resolution. • Correlation timescales show strong elastic coupling between cell edge and nucleus.

Correlations between Strong Range Spread-F and GPS L-Band Scintillations Observed in Hainan in 2004

International Nuclear Information System (INIS)

Guo-Jun, Wang; Jian-Kui, Shi; She-Ping, Shang; Xiao, Wang

2009-01-01

Data from the DPS-4 digisonde and the GPS L-band ionospheric scintillation monitor are employed to study the correlations between strong range spread-F (SSF) and GPS L-band scintillations observed in the ionosphere over Hainan Island, China (19.5°N, 109.1°E geogr., dip lat. 9°N) in 2004. The SSF in the ionogram is different from the general range spread-F because it extends in frequency well beyond FoF2 and makes FoF2 difficult to be determined. The observations show that the SSF phenomenon is frequently accompanied by the occurrence of GPS L-band scintillations. The SSF and GPS L-band scintillations occur frequently in the equinoctial months (March, April, September, and October), but rarely in the winter (January, February, November, and December) and summer (May–August); especially, occurrence variations of the SSF and GPS L-band scintillations nearly have a same trend. The SSF and scintillations may be associated with the occurrence of topside plasma bubbles and could be explained by the generalized Rayleigh–Taylor instability

Strong eukaryotic IRESs have weak secondary structure.

Directory of Open Access Journals (Sweden)

Xuhua Xia

Full Text Available BACKGROUND: The objective of this work was to investigate the hypothesis that eukaryotic Internal Ribosome Entry Sites (IRES lack secondary structure and to examine the generality of the hypothesis. METHODOLOGY/PRINCIPAL FINDINGS: IRESs of the yeast and the fruit fly are located in the 5'UTR immediately upstream of the initiation codon. The minimum folding energy (MFE of 60 nt RNA segments immediately upstream of the initiation codons was calculated as a proxy of secondary structure stability. MFE of the reverse complements of these 60 nt segments was also calculated. The relationship between MFE and empirically determined IRES activity was investigated to test the hypothesis that strong IRES activity is associated with weak secondary structure. We show that IRES activity in the yeast and the fruit fly correlates strongly with the structural stability, with highest IRES activity found in RNA segments that exhibit the weakest secondary structure. CONCLUSIONS: We found that a subset of eukaryotic IRESs exhibits very low secondary structure in the 5'-UTR sequences immediately upstream of the initiation codon. The consistency in results between the yeast and the fruit fly suggests a possible shared mechanism of cap-independent translation initiation that relies on an unstructured RNA segment.

Atom-Pair Kinetics with Strong Electric-Dipole Interactions.

Science.gov (United States)

Thaicharoen, N; Gonçalves, L F; Raithel, G

2016-05-27

Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C_{3} coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.

Nonequilibrium self-energy functional theory. Accessing the real-time dynamics of strongly correlated fermionic lattice systems

Energy Technology Data Exchange (ETDEWEB)

Hofmann, Felix

2016-07-05

The self-energy functional theory (SFT) is extended to the nonequilibrium case and applied to the real-time dynamics of strongly correlated lattice-fermions. Exploiting the basic structure of the well established equilibrium theory the entire formalism is reformulated in the language of Keldysh-Matsubara Green's functions. To this end, a functional of general nonequilibrium self-energies is constructed which is stationary at the physical point where it moreover yields the physical grand potential of the initial thermal state. Nonperturbative approximations to the full self-energy can be constructed by reducing the original lattice problem to smaller reference systems and varying the functional on the space of the respective trial self-energies, which are parametrized by the reference system's one-particle parameters. Approximations constructed in this way can be shown to respect the macroscopic conservation laws related to the underlying symmetries of the original lattice model. Assuming thermal equilibrium, the original SFT is recovered from the extended formalism. However, in the general case, the nonequilibrium variational principle comprises functional derivatives off the physical parameter space. These can be carried out analytically to derive inherently causal conditional equations for the optimal physical parameters of the reference system and a computationally realizable propagation scheme is set up. As a benchmark for the numerical implementation the variational cluster approach is applied to the dynamics of a dimerized Hubbard model after fast ramps of its hopping parameters. Finally, the time-evolution of a homogeneous Hubbard model after sudden quenches and ramps of the interaction parameter is studied by means of a dynamical impurity approximation with a single bath site. Sharply separated by a critical interaction at which fast relaxation to a thermal final state is observed, two differing response regimes can be distinguished, where the

Disorder effects in strongly correlated uranium compounds

International Nuclear Information System (INIS)

Suellow, S.; Maple, M.B.; Tomuta, D.; Nieuwenhuys, G.J.; Menovsky, A.A.; Mydosh, J.A.; Chau, R.

2001-01-01

Moderate levels of crystallographic disorder can dramatically affect the ground-state properties of heavy fermion compounds. In particular, the role of disorder close to a quantum critical point has been investigated in detail. However, crystallographic disorder is equally effective in altering the properties of magnetically ordered heavy fermion compounds like URh 2 Ge 2 , where disorder-induced spin-glass behavior has been observed. In this system, moreover, the magnetic ground state can be tuned from a spin-glass to a long-range ordered antiferromagnetic one by means of an annealing treatment. The transformation of the magnetic state is accompanied by a transition in the transport properties from 'quasi-insulating' (dρ/dT 2 Ge 2 will be discussed. Of particular interest is the resistivity of as-grown URh 2 Ge 2 , which resembles the Non-Fermi-liquid system UCu 4 Pd, suggesting that a common mechanism - the crystallographic disorder - controls the transport properties of these materials

STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS

International Nuclear Information System (INIS)

Kilpua, E. K. J.; Olspert, N.; Grigorievskiy, A.; Käpylä, M. J.; Tanskanen, E. I.; Pelt, J.; Miyahara, H.; Kataoka, R.; Liu, Y. D.

2015-01-01

We study the relation between strong and extreme geomagnetic storms and solar cycle characteristics. The analysis uses an extensive geomagnetic index AA data set spanning over 150 yr complemented by the Kakioka magnetometer recordings. We apply Pearson correlation statistics and estimate the significance of the correlation with a bootstrapping technique. We show that the correlation between the storm occurrence and the strength of the solar cycle decreases from a clear positive correlation with increasing storm magnitude toward a negligible relationship. Hence, the quieter Sun can also launch superstorms that may lead to significant societal and economic impact. Our results show that while weaker storms occur most frequently in the declining phase, the stronger storms have the tendency to occur near solar maximum. Our analysis suggests that the most extreme solar eruptions do not have a direct connection between the solar large-scale dynamo-generated magnetic field, but are rather associated with smaller-scale dynamo and resulting turbulent magnetic fields. The phase distributions of sunspots and storms becoming increasingly in phase with increasing storm strength, on the other hand, may indicate that the extreme storms are related to the toroidal component of the solar large-scale field

STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS

Energy Technology Data Exchange (ETDEWEB)

Kilpua, E. K. J. [Department of Physics, University Helsinki (Finland); Olspert, N.; Grigorievskiy, A.; Käpylä, M. J.; Tanskanen, E. I.; Pelt, J. [ReSoLVE Centre of Excellence, Department of Computer Science, P.O. Box 15400, FI-00076 Aalto Univeristy (Finland); Miyahara, H. [Musashino Art University, 1-736 Ogawa-cho, Kodaira-shi, Tokyo 187-8505 (Japan); Kataoka, R. [National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518 (Japan); Liu, Y. D. [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China)

2015-06-20

We study the relation between strong and extreme geomagnetic storms and solar cycle characteristics. The analysis uses an extensive geomagnetic index AA data set spanning over 150 yr complemented by the Kakioka magnetometer recordings. We apply Pearson correlation statistics and estimate the significance of the correlation with a bootstrapping technique. We show that the correlation between the storm occurrence and the strength of the solar cycle decreases from a clear positive correlation with increasing storm magnitude toward a negligible relationship. Hence, the quieter Sun can also launch superstorms that may lead to significant societal and economic impact. Our results show that while weaker storms occur most frequently in the declining phase, the stronger storms have the tendency to occur near solar maximum. Our analysis suggests that the most extreme solar eruptions do not have a direct connection between the solar large-scale dynamo-generated magnetic field, but are rather associated with smaller-scale dynamo and resulting turbulent magnetic fields. The phase distributions of sunspots and storms becoming increasingly in phase with increasing storm strength, on the other hand, may indicate that the extreme storms are related to the toroidal component of the solar large-scale field.

Perceptual structure of adductor spasmodic dysphonia and its acoustic correlates.

Science.gov (United States)

Cannito, Michael P; Doiuchi, Maki; Murry, Thomas; Woodson, Gayle E

2012-11-01

To examine the perceptual structure of voice attributes in adductor spasmodic dysphonia (ADSD) before and after botulinum toxin treatment and identify acoustic correlates of underlying perceptual factors. Reliability of perceptual judgments is considered in detail. Pre- and posttreatment trial with comparison to healthy controls, using single-blind randomized listener judgments of voice qualities, as well as retrospective comparison with acoustic measurements. Oral readings were recorded from 42 ADSD speakers before and after treatment as well as from their age- and sex-matched controls. Experienced judges listened to speech samples and rated attributes of overall voice quality, breathiness, roughness, and brokenness, using computer-implemented visual analog scaling. Data were adjusted for regression to the mean and submitted to principal components factor analysis. Acoustic waveforms, extracted from the reading samples, were analyzed and measurements correlated with perceptual factor scores. Four reliable perceptual variables of ADSD voice were effectively reduced to two underlying factors that corresponded to hyperadduction, most strongly associated with roughness, and hypoadduction, most strongly associated with breathiness. After treatment, the hyperadduction factor improved, whereas the hypoadduction factor worsened. Statistically significant (P<0.01) correlations were observed between perceived roughness and four acoustic measures, whereas breathiness correlated with aperiodicity and cepstral peak prominence (CPPs). This study supported a two-factor model of ADSD, suggesting perceptual characterization by both hyperadduction and hypoadduction before and after treatment. Responses of the factors to treatment were consistent with previous research. Correlations among perceptual and acoustic variables suggested that multiple acoustic features contributed to the overall impression of roughness. Although CPPs appears to be a partial correlate of perceived

Two strongly correlated electron systems: the Kondo mode in the strong coupling limit and a 2-D model of electrons close to an electronic topological transition; Deux systemes d'electrons fortement correles: le modele de reseau Kondo dans la limite du couplage fort et un modele bidimensionnel d'electrons au voisinage d'une transition topologique electronique

Energy Technology Data Exchange (ETDEWEB)

Bouis, F

1999-10-14

Two strongly correlated electron systems are considered in this work, Kondo insulators and high Tc cuprates. Experiments and theory suggest on one hand that the Kondo screening occurs on a rather short length scale and on the other hand that the Kondo coupling is renormalized to infinity in the low energy limit. The strong coupling limit is then the logical approach although the real coupling is moderate. A systematic development is performed around this limit in the first part. The band structure of these materials is reproduced within this scheme. Magnetic fluctuations are also studied. The antiferromagnetic transition is examined in the case where fermionic excitations are shifted to high energy. In the second part, the Popov and Fedotov representation of spins is used to formulate the Kondo and the antiferromagnetic Heisenberg model in terms of a non-polynomial action of boson fields. In the third part the properties of high Tc cuprates are explained by a change of topology of the Fermi surface. This phenomenon would happen near the point of optimal doping and zero temperature. It results in the appearance of a density wave phase in the under-doped regime. The possibility that this phase has a non-conventional symmetry is considered. The phase diagram that described the interaction and coexistence of density wave and superconductivity is established in the mean-field approximation. The similarities with the experimental observations are numerous in particular those concerning the pseudo-gap and the behavior of the resistivity near optimal doping. (author)

Spin-Projected Matrix Product States: Versatile Tool for Strongly Correlated Systems.

Science.gov (United States)

Li, Zhendong; Chan, Garnet Kin-Lic

2017-06-13

, which are simple to implement with MPS. To illustrate the versatility of SP-MPS, we formulate algorithms for the optimization of ground and excited states, develop perturbation theory based on SP-MPS, and describe how to evaluate spin-independent and spin-dependent properties such as the reduced density matrices. We demonstrate the numerical performance of SP-MPS with applications to several models typical of strong correlation, including the Hubbard model, and [2Fe-2S] and [4Fe-4S] model complexes.

Radial correlation length measurements on ASDEX Upgrade using correlation Doppler reflectometry

International Nuclear Information System (INIS)

Schirmer, J; Conway, G D; Holzhauer, E; Suttrop, W; Zohm, H

2007-01-01

The technique of correlation Doppler reflectometry for providing radial correlation length L r measurements is explored in this paper. Experimental L r measurements are obtained using the recently installed dual channel Doppler reflectometer system on ASDEX Upgrade. The experimental measurements agree well with theory and with L r measured on other fusion devices using different diagnostic techniques. A strong link between L r and plasma confinement could be observed. From the L- to the H-mode, an increase in the absolute value of E r shear was detected at the same plasma edge region where a decrease in L r was measured. This observation is in agreement with theoretical models which predict that an increase in the absolute shear suppresses turbulent fluctuations in the plasma, leading to a reduction in L r . Furthermore, L r decreases from the plasma core to the edge and decreases with increasing plasma triangularity δ. The experimental results have been extensively modelled using a 2-dimensional finite difference time domain code. The simulations confirm that Doppler reflectometry provides robust radial correlation lengths of the turbulence with high resolution and suggests that L r is independent of the turbulence wavenumber k p erpendicular and its fluctuation level

Hypnotic suggestibility, cognitive inhibition, and dissociation.

Science.gov (United States)

Dienes, Zoltán; Brown, Elizabeth; Hutton, Sam; Kirsch, Irving; Mazzoni, Giuliana; Wright, Daniel B

2009-12-01

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.

Strong correlation between the 6-minute walk test and accelerometry functional outcomes in boys with Duchenne muscular dystrophy.

Science.gov (United States)

Davidson, Zoe E; Ryan, Monique M; Kornberg, Andrew J; Walker, Karen Z; Truby, Helen

2015-03-01

Accelerometry provides information on habitual physical capability that may be of value in the assessment of function in Duchenne muscular dystrophy. This preliminary investigation describes the relationship between community ambulation measured by the StepWatch activity monitor and the current standard of functional assessment, the 6-minute walk test, in ambulatory boys with Duchenne muscular dystrophy (n = 16) and healthy controls (n = 13). All participants completed a 6-minute walk test and wore the StepWatch™ monitor for 5 consecutive days. Both the 6-minute walk test and StepWatch accelerometry identified a decreased capacity for ambulation in boys with Duchenne compared to healthy controls. There were strong, significant correlations between 6-minute walk distance and all StepWatch parameters in affected boys only (r = 0.701-0.804). These data proffer intriguing observations that warrant further exploration. Specifically, accelerometry outcomes may compliment the 6-minute walk test in assessment of therapeutic interventions for Duchenne muscular dystrophy. © The Author(s) 2014.

Evidence of the correlation between a strong 4d-As/2p-N orbitals coupling and the bowing effect in GaAsN

International Nuclear Information System (INIS)

Mehnane, N.; Badi, F.; Abid, H.; Reda Aced, M.; Sekkal, N.

2008-05-01

By means of a simple physical argumentation, we give the proof that the giant bowing observed in GaAsN is correlated to a strong interaction between 4d-As and 2p-N orbitals. The calculations were carried out within the first principles full potential linear muffin-tin orbitals method (FPLMTO) method in its plane wave approximation (PLW) which enables an accurate treatment of the interstitial regions. The choice of this method ensures our work to be free from adjustable parameters and enables us to perform a microscopic study. (author)

Stable biexcitons in two-dimensional metal-halide perovskites with strong dynamic lattice disorder

Science.gov (United States)

Thouin, Félix; Neutzner, Stefanie; Cortecchia, Daniele; Dragomir, Vlad Alexandru; Soci, Cesare; Salim, Teddy; Lam, Yeng Ming; Leonelli, Richard; Petrozza, Annamaria; Kandada, Ajay Ram Srimath; Silva, Carlos

2018-03-01

With strongly bound and stable excitons at room temperature, single-layer, two-dimensional organic-inorganic hybrid perovskites are viable semiconductors for light-emitting quantum optoelectronics applications. In such a technological context, it is imperative to comprehensively explore all the factors—chemical, electronic, and structural—that govern strong multiexciton correlations. Here, by means of two-dimensional coherent spectroscopy, we examine excitonic many-body effects in pure, single-layer (PEA) 2PbI4 (PEA = phenylethylammonium). We determine the binding energy of biexcitons—correlated two-electron, two-hole quasiparticles—to be 44 ±5 meV at room temperature. The extraordinarily high values are similar to those reported in other strongly excitonic two-dimensional materials such as transition-metal dichalcogenides. Importantly, we show that this binding energy increases by ˜25 % upon cooling to 5 K. Our work highlights the importance of multiexciton correlations in this class of technologically promising, solution-processable materials, in spite of the strong effects of lattice fluctuations and dynamic disorder.

Representational constraints on children's suggestibility.

Science.gov (United States)

Ceci, Stephen J; Papierno, Paul B; Kulkofsky, Sarah

2007-06-01

In a multistage experiment, twelve 4- and 9-year-old children participated in a triad rating task. Their ratings were mapped with multidimensional scaling, from which euclidean distances were computed to operationalize semantic distance between items in target pairs. These children and age-mates then participated in an experiment that employed these target pairs in a story, which was followed by a misinformation manipulation. Analyses linked individual and developmental differences in suggestibility to children's representations of the target items. Semantic proximity was a strong predictor of differences in suggestibility: The closer a suggested distractor was to the original item's representation, the greater was the distractor's suggestive influence. The triad participants' semantic proximity subsequently served as the basis for correctly predicting memory performance in the larger group. Semantic proximity enabled a priori counterintuitive predictions of reverse age-related trends to be confirmed whenever the distance between representations of items in a target pair was greater for younger than for older children.

Functional importance of different patterns of correlation between adjacent cassette exons in human and mouse.

Science.gov (United States)

Peng, Tao; Xue, Chenghai; Bi, Jianning; Li, Tingting; Wang, Xiaowo; Zhang, Xuegong; Li, Yanda

2008-04-26

Alternative splicing expands transcriptome diversity and plays an important role in regulation of gene expression. Previous studies focus on the regulation of a single cassette exon, but recent experiments indicate that multiple cassette exons within a gene may interact with each other. This interaction can increase the potential to generate various transcripts and adds an extra layer of complexity to gene regulation. Several cases of exon interaction have been discovered. However, the extent to which the cassette exons coordinate with each other remains unknown. Based on EST data, we employed a metric of correlation coefficients to describe the interaction between two adjacent cassette exons and then categorized these exon pairs into three different groups by their interaction (correlation) patterns. Sequence analysis demonstrates that strongly-correlated groups are more conserved and contain a higher proportion of pairs with reading frame preservation in a combinatorial manner. Multiple genome comparison further indicates that different groups of correlated pairs have different evolutionary courses: (1) The vast majority of positively-correlated pairs are old, (2) most of the weakly-correlated pairs are relatively young, and (3) negatively-correlated pairs are a mixture of old and young events. We performed a large-scale analysis of interactions between adjacent cassette exons. Compared with weakly-correlated pairs, the strongly-correlated pairs, including both the positively and negatively correlated ones, show more evidence that they are under delicate splicing control and tend to be functionally important. Additionally, the positively-correlated pairs bear strong resemblance to constitutive exons, which suggests that they may evolve from ancient constitutive exons, while negatively and weakly correlated pairs are more likely to contain newly emerging exons.

Strong dynamics and lattice gauge theory

Science.gov (United States)

Schaich, David

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

Matrix-product states for strongly correlated systems and quantum information processing

International Nuclear Information System (INIS)

Saberi, Hamed

2008-01-01

This thesis offers new developments in matrix-product state theory for studying the strongly correlated systems and quantum information processing through three major projects: In the first project, we perform a systematic comparison between Wilson's numerical renormalization group (NRG) and White's density-matrix renormalization group (DMRG). The NRG method for solving quantum impurity models yields a set of energy eigenstates that have the form of matrix-product states (MPS). White's DMRG for treating quantum lattice problems can likewise be reformulated in terms of MPS. Thus, the latter constitute a common algebraic structure for both approaches. We exploit this fact to compare the NRG approach for the single-impurity Anderson model to a variational matrix-product state approach (VMPS), equivalent to single-site DMRG. For the latter, we use an ''unfolded'' Wilson chain, which brings about a significant reduction in numerical costs compared to those of NRG. We show that all NRG eigenstates (kept and discarded) can be reproduced using VMPS, and compare the difference in truncation criteria, sharp vs. smooth in energy space, of the two approaches. Finally, we demonstrate that NRG results can be improved upon systematically by performing a variational optimization in the space of variational matrix-product states, using the states produced by NRG as input. In the second project we demonstrate how the matrix-product state formalism provides a flexible structure to solve the constrained optimization problem associated with the sequential generation of entangled multiqubit states under experimental restrictions. We consider a realistic scenario in which an ancillary system with a limited number of levels performs restricted sequential interactions with qubits in a row. The proposed method relies on a suitable local optimization procedure, yielding an efficient recipe for the realistic and approximate sequential generation of any entangled multiqubit state. We give

Matrix-product states for strongly correlated systems and quantum information processing

Energy Technology Data Exchange (ETDEWEB)

Saberi, Hamed

2008-12-12

This thesis offers new developments in matrix-product state theory for studying the strongly correlated systems and quantum information processing through three major projects: In the first project, we perform a systematic comparison between Wilson's numerical renormalization group (NRG) and White's density-matrix renormalization group (DMRG). The NRG method for solving quantum impurity models yields a set of energy eigenstates that have the form of matrix-product states (MPS). White's DMRG for treating quantum lattice problems can likewise be reformulated in terms of MPS. Thus, the latter constitute a common algebraic structure for both approaches. We exploit this fact to compare the NRG approach for the single-impurity Anderson model to a variational matrix-product state approach (VMPS), equivalent to single-site DMRG. For the latter, we use an ''unfolded'' Wilson chain, which brings about a significant reduction in numerical costs compared to those of NRG. We show that all NRG eigenstates (kept and discarded) can be reproduced using VMPS, and compare the difference in truncation criteria, sharp vs. smooth in energy space, of the two approaches. Finally, we demonstrate that NRG results can be improved upon systematically by performing a variational optimization in the space of variational matrix-product states, using the states produced by NRG as input. In the second project we demonstrate how the matrix-product state formalism provides a flexible structure to solve the constrained optimization problem associated with the sequential generation of entangled multiqubit states under experimental restrictions. We consider a realistic scenario in which an ancillary system with a limited number of levels performs restricted sequential interactions with qubits in a row. The proposed method relies on a suitable local optimization procedure, yielding an efficient recipe for the realistic and approximate sequential generation of any

Cenozoic planktonic marine diatom diversity and correlation to climate change

Science.gov (United States)

Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

2014-01-01

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

Strong coupling phase in QED

International Nuclear Information System (INIS)

Aoki, Ken-ichi

1988-01-01

Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)

In-medium meson properties and screening correlators

International Nuclear Information System (INIS)

Bazavov, A; Karsch, F; Mukherjee, Swagato; Petreczky, P; Maezawa, Y

2014-01-01

We study spatial meson correlation functions consisting of strange quarks, strange and charm quarks and charm quarks in (2 + 1)-flavor QCD using the highly improved staggered quark action. We find that the in-medium modification of the meson correlators decreases with increasing charm quark content and decreasing size. In particular, we find strong in-medium modification of φ and D s meson correlators around the chiral transition temperature T c , while J/ψ and η c correlators show strong in-medium modification only at temperatures of 1.4T c .

Lensless ghost imaging through the strongly scattering medium

International Nuclear Information System (INIS)

Yang Zhe; Zhao Xueliang; Li Junlin; Zhao Lianjie; Qin Wei

2016-01-01

Lensless ghost imaging has attracted much interest in recent years due to its profound physics and potential applications. In this paper we report studies of the robust properties of the lensless ghost imaging system with a pseudo-thermal light source in a strongly scattering medium. The effects of the positions of the strong medium on the ghost imaging are investigated. In the lensless ghost imaging system, a pseudo-thermal light is split into two correlated beams by a beam splitter. One beam goes to a charge-coupled detector camera, labeled as CCD2. The other beam goes to an object and then is collected in another charge-coupled detector camera, labeled as CCD1, which serves as a bucket detector. When the strong medium, a pane of ground glass disk, is placed between the object and CCD1, the bucket detector, the quality of ghost imaging is barely affected and a good image could still be obtained. The quality of the ghost imaging can also be maintained, even when the ground glass is rotating, which is the strongest scattering medium so far. However, when the strongly scattering medium is present in the optical path from the light source to CCD2 or the object, the lensless ghost imaging system hardly retrieves the image of the object. A theoretical analysis in terms of the second-order correlation function is also provided. (paper)

Strong nonlinearity-induced correlations for counterpropagating photons scattering on a two-level emitter

DEFF Research Database (Denmark)

Nysteen, Anders; McCutcheon, Dara; Mørk, Jesper

2015-01-01

We analytically treat the scattering of two counterpropagating photons on a two-level emitter embedded in an optical waveguide. We find that the nonlinearity of the emitter can give rise to significant pulse-dependent directional correlations in the scattered photonic state, which could be quanti......We analytically treat the scattering of two counterpropagating photons on a two-level emitter embedded in an optical waveguide. We find that the nonlinearity of the emitter can give rise to significant pulse-dependent directional correlations in the scattered photonic state, which could...

The CO/NOx emissions of swirled, strongly pulsed jet diffusion flames

KAUST Repository

Liao, Ying-Hao

2014-05-28

The CO and NOx exhaust emissions of swirled, strongly pulsed, turbulent jet diffusion flames were studied experimentally in a coflow swirl combustor. Measurements of emissions were performed on the combustor centerline using standard emission analyzers combined with an aspirated sampling probe located downstream of the visible flame tip. The highest levels of CO emissions are generally found for compact, isolated flame puffs, which is consistent with the quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels by up to a factor of 2.5, suggesting more rapid and compete fuel/air mixing by imposing swirl in the coflow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off times. The swirled coflow air can, in some cases, increase the NO emissions due to a longer combustion residence time due to the flow recirculation within the swirl-induced recirculation zone. Scaling relations, when taking into account the impact of air dilution over an injection cycle on the flame length, reveal a strong correlation between the CO emissions and the global residence time. However, the NO emissions do not successfully correlate with the global residence time. For some specific cases, a compact flame with a simultaneous decrease in both CO and NO emissions compared to the steady flames was observed. © Copyright © Taylor & Francis Group, LLC.

A strong response to selection on mass-independent maximal metabolic rate without a correlated response in basal metabolic rate.

Science.gov (United States)

Wone, B W M; Madsen, P; Donovan, E R; Labocha, M K; Sears, M W; Downs, C J; Sorensen, D A; Hayes, J P

2015-04-01

Metabolic rates are correlated with many aspects of ecology, but how selection on different aspects of metabolic rates affects their mutual evolution is poorly understood. Using laboratory mice, we artificially selected for high maximal mass-independent metabolic rate (MMR) without direct selection on mass-independent basal metabolic rate (BMR). Then we tested for responses to selection in MMR and correlated responses to selection in BMR. In other lines, we antagonistically selected for mice with a combination of high mass-independent MMR and low mass-independent BMR. All selection protocols and data analyses included body mass as a covariate, so effects of selection on the metabolic rates are mass adjusted (that is, independent of effects of body mass). The selection lasted eight generations. Compared with controls, MMR was significantly higher (11.2%) in lines selected for increased MMR, and BMR was slightly, but not significantly, higher (2.5%). Compared with controls, MMR was significantly higher (5.3%) in antagonistically selected lines, and BMR was slightly, but not significantly, lower (4.2%). Analysis of breeding values revealed no positive genetic trend for elevated BMR in high-MMR lines. A weak positive genetic correlation was detected between MMR and BMR. That weak positive genetic correlation supports the aerobic capacity model for the evolution of endothermy in the sense that it fails to falsify a key model assumption. Overall, the results suggest that at least in these mice there is significant capacity for independent evolution of metabolic traits. Whether that is true in the ancestral animals that evolved endothermy remains an important but unanswered question.

Strongly correlated electron materials. I. Theory of the quasiparticle structure

International Nuclear Information System (INIS)

Lopez-Aguilar, F.; Costa-Quintana, J.; Puig-Puig, L.

1993-01-01

In this paper we give a method for analyzing the renormalized electronic structure of the Hubbard systems. The first step is the determination of effective interactions from the random-phase approximation (RPA) and from an extended RPA (ERPA) that introduces vertex effects within the bubble polarization. The second step is the determination of the density of states deduced from the spectral functions. Its analysis leads us to conclude that these systems can exhibit three types of resonances in their electronic structures: the lower-, middle-, and upper-energy resonances. Furthermore, we analyze the conditions for which there is only one type of resonance and the causes that lead to the disappearance of the heavy-fermion state. We finally introduce the RPA and ERPA effective interactions within the strong-coupling theory and we give the conditions for obtaining coupling and superconductivity

Working memory capacity and fluid intelligence are strongly related constructs: comment on Ackerman, Beier, and Boyle (2005).

Science.gov (United States)

Kane, Michael J; Hambrick, David Z; Conway, Andrew R A

2005-01-01

The authors agree with P. L. Ackerman, M. E. Beier, and M. O. Boyle (2005; see record 2004-22408-002) that working memory capacity (WMC) is not isomorphic with general fluid intelligence (Gf) or reasoning ability. However, the WMC and Gf/reasoning constructs are more strongly associated than Ackerman et al. (2005) indicate, particularly when considering the outcomes of latent-variable studies. The authors' reanalysis of 14 such data sets from 10 published studies, representing more than 3,100 young-adult subjects, suggests a strong correlation between WMC and Gf/reasoning factors (median r=.72), indicating that the WMC and Gf constructs share approximately 50% of their variance. This comment also clarifies the authors' "executive attention" view of WMC, it demonstrates that WMC has greater discriminant validity than Ackerman et al. (2005) implied, and it suggests some future directions and challenges for the scientific study of the convergence of WMC, attention control, and intelligence. Copyright (c) 2005 APA, all rights reserved.

Developmental dyslexia in adults: behavioural manifestations and cognitive correlates.

Science.gov (United States)

Nergård-Nilssen, Trude; Hulme, Charles

2014-08-01

This paper explores the nature of residual literacy and cognitive deficits in self-reported dyslexic Norwegian adults. The performance of 26 self-reported dyslexic adults was compared with that of a comparison group of 47 adults with no history of reading or spelling difficulties. Participants completed standardized and experimental measures tapping literacy skills, working memory, phonological awareness and rapid naming. Spelling problems were the most prominent marker of dyslexia in adults, followed by text reading fluency and nonword decoding. Working memory and phoneme awareness explained unique variance in spelling, whereas rapid automatized naming explained unique variance in reading fluency and nonword reading. The moderate to strong correlations between self-reported history, self-rating of current literacy skills and outcomes on literacy tests indicate that adults estimated their literacy skills fairly well. Results suggest that spelling impairments, more strongly than reading impairments, make adults perceive themselves as being dyslexic. A combination of three literacy and three cognitive tests predicted group membership with 90.4% accuracy. It appears that weaknesses in phoneme awareness, rapid automatized naming and working memory are strong and persistent correlates of literacy problems even in adults learning a relatively transparent orthography. Copyright © 2014 John Wiley & Sons, Ltd.

Strong paramagnon scattering in single atom Pd contacts

DEFF Research Database (Denmark)

Schendel, V.; Barreteau, Cyrille; Brandbyge, Mads

2017-01-01

Pd contacts shows a reduction with increasing bias, which gives rise to a peculiar Lambda-shaped spectrum. Supported by theoretical calculations, we correlate this finding with the lifetime of hot quasiparticles in Pd, which is strongly influenced by paramagnon scattering. In contrast to this, Co...

Massively parallel simulations of strong electronic correlations: Realistic Coulomb vertex and multiplet effects

Science.gov (United States)

Baumgärtel, M.; Ghanem, K.; Kiani, A.; Koch, E.; Pavarini, E.; Sims, H.; Zhang, G.

2017-07-01

We discuss the efficient implementation of general impurity solvers for dynamical mean-field theory. We show that both Lanczos and quantum Monte Carlo in different flavors (Hirsch-Fye, continuous-time hybridization- and interaction-expansion) exhibit excellent scaling on massively parallel supercomputers. We apply these algorithms to simulate realistic model Hamiltonians including the full Coulomb vertex, crystal-field splitting, and spin-orbit interaction. We discuss how to remove the sign problem in the presence of non-diagonal crystal-field and hybridization matrices. We show how to extract the physically observable quantities from imaginary time data, in particular correlation functions and susceptibilities. Finally, we present benchmarks and applications for representative correlated systems.

Reply to ``Comment on `Cluster methods for strongly correlated electron systems' ''

Science.gov (United States)

Biroli, G.; Kotliar, G.

2005-01-01

We reply to the Comment by Aryanpour, Maier, and Jarrell [Phys. Rev. B 71, 037101 (2005)] on our paper [Phys. Rev. B 65, 155112 (2002)]. We demonstrate, using general arguments and explicit examples, that whenever the correlation length is finite, local observables converge exponentially fast in the cluster size Lc within cellular dynamical mean field theory. This is a faster rate of convergence than the 1/ L2c behavior of the dynamical cluster approximation, thus refuting the central assertion of their Comment.

Lattice disorder in strongly correlated lanthanide and actinide intermetallics

International Nuclear Information System (INIS)

Booth, C.H.; Bauer, E.D.; Maple, M.B.; Lawrence, J.M.; Kwei, G.H.; Sarrao, J.L.

2001-01-01

Lanthanide and actinide intermetallic compounds display a wide range of correlated-electron behavior, including ferromagnetism, antiferromagnetism, nonmagnetic (Kondo) ground states, and so-called 'non-Fermi liquid' (NFL) behavior. The interaction between f electrons and the conduction band is a dominant factor in determining the ground state of a given system. However, lattice disorder can create a distribution of interactions, generating unusual physical properties. These properties may include NFL behavior in many materials. In addition, lattice disorder can cause deviations from standard Kondo behavior that is less severe than NFL behavior. A review of the lattice disorder mechanism within a tight-binding model is presented, along with measurements of the YbBCu 4 and UPd x Cu 5-x systems, demonstrating the applicability of the model. These measurements indicate that while the YbBCu 4 system appears to be well ordered, both site interchange and continuous bond-length disorder occur in the UPd x Cu 5-x series. Nevertheless, the measured bond-length disorder in UPdCu 4 does not appear to be enough to explain the NFL properties simply with the Kondo disorder model. (au)

Invariant mass dependence of two-pion inclusive correlation functions

International Nuclear Information System (INIS)

Berger, E.L.; Singer, R.; Thomas, G.H.; Kafka, T.

1976-06-01

High energy two-particle inclusive correlations are studied as a function of the invariant mass M of the pair. Using data from 205 GeV/c pp interactions, one compares the correlation functions C(M) for (+-) and (--) pairs of produced pions. Strong positive correlations are observed in both distributions in the form of a broad threshold enhancement at small M. The decrease of C(M) as M increases is interpreted in the Mueller-Regge framework. From the M dependence of C +- one extracts an effective trajectory intercept of roughly α(0) approximately equal to 0.5 +- 0.1, consistent with the (rho,f) pair. For the exotic (--) system, one finds a low intercept, α(0) approximately equal to -0.5. A rho resonance signal is observed above background in C +- (M). Near threshold, effects suggestive of Bose symmetry are seen but are not conclusive. In an exclusive picture, one relates most of the correlation in the threshold region to resonances involving three or more pions. One also examines the joint correlations in M and the azimuthal angle phi

Multiphoton above threshold effects in strong-field fragmentation

DEFF Research Database (Denmark)

B Madsen, C; Anis, F; B Madsen, L

2012-01-01

We present a study of multiphoton dissociative ionization from molecules. By solving the time-dependent Schrödinger equation for H2+ and projecting the solution onto double continuum scattering states, we observe the correlated electron-nuclear ionization dynamics in detail. We show—for the first...... time—how multiphoton structure prevails as long as one accounts for the energies of all the fragments. Our current work provides a new avenue to analyze strong-field fragmentation that leads to a deeper understanding of the correlated molecular dynamics....

Modification of jet-like correlations in Pb-Au collisions at 158A GeV/c

Science.gov (United States)

Ceres Collaboration; Adamová, D.; Agakichiev, G.; Antończyk, D.; Appelshäuser, H.; Belaga, V.; Bielčíková, J.; Braun-Munzinger, P.; Busch, O.; Cherlin, A.; Damjanović, S.; Dietel, T.; Dietrich, L.; Drees, A.; Dubitzky, W.; Esumi, S. I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glässel, P.; Holeczek, J.; Kalisky, M.; Kniege, S.; Kushpil, V.; Maas, A.; Marín, A.; Milošević, J.; Milov, A.; Miśkowiec, D.; Panebrattsev, Yu.; Petchenova, O.; Petráček, V.; Pfeiffer, A.; Płoskoń, M.; Rak, J.; Ravinovich, I.; Rehak, P.; Sako, H.; Schmitz, W.; Schuchmann, S.; Sedykh, S.; Shimansky, S.; Stachel, J.; Šumbera, M.; Tilsner, H.; Tserruya, I.; Wessels, J. P.; Wienold, T.; Wurm, J. P.; Xie, W.; Yurevich, S.; Yurevich, V.

2009-07-01

Results of a two-particle correlation analysis of high-p charged particles in Pb-Au collisions at 158A GeV/c are presented. The data have been recorded by the CERES experiment at the CERN-SPS. The correlations are studied as function of transverse momentum, particle charge and collision centrality. We observe a jet-like structure in the vicinity of a high-p trigger particle and a broad back-to-back distribution. The yields of associated particles per trigger show a strong dependence on the trigger/associate charge combination. A comparison to PYTHIA confirms the jet-like pattern at the near-side but suggests a strong modification at the away-side, implying significant energy transfer of the hard-scattered parton to the medium.

Earnings and Financial Compensation from Social Security Systems Correlate Strongly with Disability for Multiple Sclerosis Patients.

Science.gov (United States)

Kavaliunas, Andrius; Wiberg, Michael; Tinghög, Petter; Glaser, Anna; Gyllensten, Hanna; Alexanderson, Kristina; Hillert, Jan

2015-01-01

Multiple sclerosis (MS) patients earn lower incomes and receive higher benefits. However, there is limited knowledge of how this is correlated with their disability. To elucidate sources and levels of income among MS patients with different disability, assessed with the Expanded Disability Status Scale. A total of 7929 MS patients aged 21-64 years and living in Sweden in 2010 were identified for this cross-sectional study. Descriptive statistics, logistic and truncated linear regression models were used to estimate differences between MS patients regarding earnings, disability pension, sickness absence, disability allowance, unemployment compensation, and social assistance. The average level of earnings was ten times lower and the average level of health- related benefits was four times higher when comparing MS patients with severe and mild disability. MS patients with severe disability had on average SEK 166,931 less annual income from earnings and SEK 54,534 more income from benefits compared to those with mild disability. The combined average income for MS patients was 35% lower when comparing patients in the same groups. The adjusted risk ratio for having earnings among MS patients with severe disability compared to the patients with mild disability was 0.33 (95% CI 0.29-0.39), while the risk ratio for having benefits was 1.93 (95% CI 1.90-1.94). Disease progression affects the financial situation of MS patients considerably. Correlations between higher disability and patient income were observed, suggesting that earnings and benefits could be used as measures of MS progression and proxies of disability.

A note on the conditional correlation between energy prices: Evidence from future markets

International Nuclear Information System (INIS)

Marzo, Massimiliano; Zagaglia, Paolo

2008-01-01

We model the joint movements of daily returns on one-month futures for crude oil, heating oil and natural gas through the multivariate GARCH with dynamic conditional correlations and elliptical distributions introduced by Pelagatti and Rondena [Pelagatti, M.M., Rondena, S., 2007. 'Dynamic Conditional Correlation with Elliptical Distributions', unpublished manuscript. Universita di Milano - Bicocca, August]. Futures prices of crude and heating oil covary strongly. The conditional correlation between the futures prices of natural gas and crude oil has been rising over the last 5 years. However, this correlation has been low on average over two thirds of the sample, suggesting that future markets have no established tradition of pricing natural gas as a function of developments on oil markets. (author)

Exploring the effects of photon correlations from thermal sources on bacterial photosynthesis

Science.gov (United States)

Manrique, Pedro D.; Caycedo-Soler, Felipe; De Mendoza, Adriana; Rodríguez, Ferney; Quiroga, Luis; Johnson, Neil F.

Thermal light sources can produce photons with strong spatial correlations. We study the role that these correlations might potentially play in bacterial photosynthesis. Our findings show a relationship between the transversal distance between consecutive absorptions and the efficiency of the photosynthetic process. Furthermore, membranes where the clustering of core complexes (so-called RC-LH1) is high, display a range where the organism profits maximally from the spatial correlation of the incoming light. By contrast, no maximum is found for membranes with low core-core clustering. We employ a detailed membrane model with state-of-the-art empirical inputs. Our results suggest that the organization of the membrane's antenna complexes may be well-suited to the spatial correlations present in an natural light source. Future experiments will be needed to test this prediction.

General parenting styles are not strongly associated with fruit and vegetable intake and social-environmental correlates among 11-year-old children in four countries in Europe.

Science.gov (United States)

De Bourdeaudhuij, I; Te Velde, S J; Maes, L; Pérez-Rodrigo, C; de Almeida, M D V; Brug, J

2009-02-01

To investigate whether fruit and vegetable (F&V) intake in 11-year-olds, and social-environmental correlates of F&V intake such as parental modelling and encouragement, family food rules and home availability, differ according to general parenting styles in Belgium, The Netherlands, Portugal and Spain. Cross-sectional study. Primary schools in four countries. Pupils and one of their parents completed questionnaires to measure F&V intake, related social-environmental correlates and general parenting styles. The sample size was 4555 (49.3 % boys); 1180 for Belgium, 883 for The Netherlands, 1515 for Portugal and 977 for Spain. Parenting styles were divided into authoritative, authoritarian, indulgent and neglectful. No differences were found in F&V intake across parenting styles and only very few significant differences in social-environmental correlates. The authoritarian (more parental encouragement and more demands to eat fruit) and the authoritative (more availability of fruit and vegetables) parenting styles resulted in more favourable correlates. Despite earlier studies suggesting that general parenting styles are associated with health behaviours in children, the present study suggests that this association is weak to non-existent for F&V intakes in four different European countries.

Heteronuclear Long-Range Correlation

DEFF Research Database (Denmark)

Sørensen, Ole W.

The lecture will cover heteronuclear long-range correlation techniques like HMBC, H2BC, and HAT HMBC with the emphasis on determining the number of covalent bonds between two spins being correlated. H2BC and HMBC spectra are quite complementary as a peak can be strong in one of the two spectra...

Strong links between metal contamination, habitat modification and estuarine larval fish distributions

Energy Technology Data Exchange (ETDEWEB)

McKinley, Andrew C., E-mail: andrew.mckinley@hotmail.com [Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 (Australia); Miskiewicz, Anthony [Environment and Recreation, Wollongong City Council, 41 Burelli Street, Wollongong, New South Wales 2500 (Australia); Taylor, Matthew D.; Johnston, Emma L. [Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052 (Australia)

2011-06-15

Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages. - Highlights: > We examine contamination/habitat modification impacts on larval fish. > Larvae communities differ between modified/unmodified estuaries. > Larvae are more abundant/diverse in modified areas. > Trends are strongly related to sediment metals/seagrass cover. > Larval impacts have wider ecological importance. - We describe strong links between sediment metals contamination, habitat modification and substantial differences in the composition of the estuarine larval fish assemblage.

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

Energy Technology Data Exchange (ETDEWEB)

Lim, Dongwook; Hong, Seungsoo; Lee, Young-Wook, E-mail: dwlim@yonsei.ac.kr, E-mail: ywlee2@yonsei.ac.kr [Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 03722 (Korea, Republic of)

2017-07-20

We performed low-resolution spectroscopy of the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK′ (7.4 σ ) and CH (5.1 σ ) indices, while the CN-intermediate stars show no significant difference in the strength of the HK′ index from the CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN- and HK′-strong stars are also enhanced in the abundances of Fe and s -process elements. It appears, therefore, that these stars are later-generation stars affected by some supernova enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN–CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations, such as M22 and NGC 6273.

Nonlinearities in reservoir engineering: Enhancing quantum correlations

Science.gov (United States)

Hu, Xiangming; Hu, Qingping; Li, Lingchao; Huang, Chen; Rao, Shi

2017-12-01

There are two decisive factors for quantum correlations in reservoir engineering, but they are strongly reversely dependent on the atom-field nonlinearities. One is the squeezing parameter for the Bogoliubov modes-mediated collective interactions, while the other is the dissipative rates for the engineered collective dissipations. Exemplifying two-level atomic ensembles, we show that the moderate nonlinearities can compromise these two factors and thus enhance remarkably two-mode squeezing and entanglement of different spin atomic ensembles or different optical fields. This suggests that the moderate nonlinearities of the two-level systems are more advantageous for applications in quantum networks associated with reservoir engineering.

Quantum Glassiness in Strongly Correlated Clean Systems: An Example of Topological Overprotection

Science.gov (United States)

Chamon, Claudio

2005-01-01

This Letter presents solvable examples of quantum many-body Hamiltonians of systems that are unable to reach their ground states as the environment temperature is lowered to absolute zero. These examples, three-dimensional generalizations of quantum Hamiltonians proposed for topological quantum computing, (1)have no quenched disorder, (2)have solely local interactions, (3)have an exactly solvable spectrum, (4)have topologically ordered ground states, and (5)have slow dynamical relaxation rates akin to those of strong structural glasses.

Wavelet based correlation coefficient of time series of Saudi Meteorological Data

International Nuclear Information System (INIS)

Rehman, S.; Siddiqi, A.H.

2009-01-01

In this paper, wavelet concepts are used to study a correlation between pairs of time series of meteorological parameters such as pressure, temperature, rainfall, relative humidity and wind speed. The study utilized the daily average values of meteorological parameters of nine meteorological stations of Saudi Arabia located at different strategic locations. The data used in this study cover a period of 16 years between 1990 and 2005. Besides obtaining wavelet spectra, we also computed the wavelet correlation coefficients between two same parameters from two different locations and show that strong correlation or strong anti-correlation depends on scale. The cross-correlation coefficients of meteorological parameters between two stations were also calculated using statistical function. For coastal to costal pair of stations, pressure time series was found to be strongly correlated. In general, the temperature data were found to be strongly correlated for all pairs of stations and the rainfall data the least.

Inhomogeneous spectral moment sum rules for the retarded Green function and self-energy of strongly correlated electrons or ultracold fermionic atoms in optical lattices

International Nuclear Information System (INIS)

Freericks, J. K.; Turkowski, V.

2009-01-01

Spectral moment sum rules are presented for the inhomogeneous many-body problem described by the fermionic Falicov-Kimball or Hubbard models. These local sum rules allow for arbitrary hoppings, site energies, and interactions. They can be employed to quantify the accuracy of numerical solutions to the inhomogeneous many-body problem such as strongly correlated multilayered devices, ultracold atoms in an optical lattice with a trap potential, strongly correlated systems that are disordered, or systems with nontrivial spatial ordering such as a charge-density wave or a spin-density wave. We also show how the spectral moment sum rules determine the asymptotic behavior of the Green function, self-energy, and dynamical mean field when applied to the dynamical mean-field theory solution of the many-body problem. In particular, we illustrate in detail how one can dramatically reduce the number of Matsubara frequencies needed to solve the Falicov-Kimball model while still retaining high precision, and we sketch how one can incorporate these results into Hirsch-Fye quantum Monte Carlo solvers for the Hubbard (or more complicated) models. Since the solution of inhomogeneous problems is significantly more time consuming than periodic systems, efficient use of these sum rules can provide a dramatic speed up in the computational time required to solve the many-body problem. We also discuss how these sum rules behave in nonequilibrium situations as well, where the Hamiltonian has explicit time dependence due to a driving field or due to the time-dependent change in a parameter such as the interaction strength or the origin of the trap potential.

Estimation of shear viscosity based on transverse momentum correlations

International Nuclear Information System (INIS)

Sharma, Monika

2009-01-01

Event anisotropy measurements at RHIC suggest the strongly interacting matter created in heavy ion collisions flows with very little shear viscosity. Precise determination of 'shear viscosity-to-entropy' ratio is currently a subject of extensive study [S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302]. We present preliminary results of measurements of the evolution of transverse momentum correlation function with collision centrality of Au+Au interactions at √(s NN )=200 GeV. We compare two differential correlation functions, namely inclusive [J. Adams et al. (STAR Collaboration), Phys. Rev. C 72 (2005) 044902] and a differential version of the correlation measure C introduced by Gavin et al. [S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302; M. Sharma and C. A. Pruneau, Phys. Rev. C 79 (2009) 024905.]. These observables can be used for the experimental study of the shear viscosity per unit entropy.

Estimation of shear viscosity based on transverse momentum correlations

Science.gov (United States)

STAR Collaboration; Sharma, Monika; STAR Collaboration

2009-11-01

Event anisotropy measurements at RHIC suggest the strongly interacting matter created in heavy ion collisions flows with very little shear viscosity. Precise determination of “shear viscosity-to-entropy” ratio is currently a subject of extensive study [S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302]. We present preliminary results of measurements of the evolution of transverse momentum correlation function with collision centrality of Au+Au interactions at s=200 GeV. We compare two differential correlation functions, namely inclusive [J. Adams et al. (STAR Collaboration), Phys. Rev. C 72 (2005) 044902] and a differential version of the correlation measure C˜ introduced by Gavin et al. [S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302; M. Sharma and C. A. Pruneau, Phys. Rev. C 79 (2009) 024905.]. These observables can be used for the experimental study of the shear viscosity per unit entropy.

EPPUR SI MUOVE: POSITIONAL AND KINEMATIC CORRELATIONS OF SATELLITE PAIRS IN THE LOW Z UNIVERSE

International Nuclear Information System (INIS)

Ibata, Rodrigo A.; Famaey, Benoit; Martin, Nicolas; Lewis, Geraint F.; Ibata, Neil G.

2015-01-01

We have recently shown that pairs of satellite galaxies located diametrically opposite to each other around their host possess predominantly anti-correlated velocities. This is consistent with a scenario in which ≳50% of satellite galaxies belong to kinematically coherent rotating planar structures. Here we extend this analysis, examining satellites of giant galaxies drawn from an SDSS photometric redshift catalog. We find that there is a ∼17% overabundance (>3σ significance) of candidate satellites at positions diametrically opposite to a spectroscopically confirmed satellite. We show that ΛCDM cosmological simulations do not possess this property when contamination is included. After subtracting contamination, we find ∼2 times more satellites diametrically opposed to a spectroscopically confirmed satellite than at 90° from it, at projected distances ranging from 100 to 150 kpc from the host. This independent analysis thus strongly supports our previous results on anti-correlated velocities. We also find that those satellite pairs with anti-correlated velocities have a strong preference (∼3:1) to align with the major axis of the host whereas those with correlated velocities display the opposite behavior. We finally show that repeating a similar analysis to Ibata et al. with same-side satellites is generally hard to interpret, but is not inconsistent with our previous results when strong quality cuts are applied on the sample. This addresses all of the concerns recently raised by Cautun et al., who did not uncover any flaw in our previous analysis, but may simply have hinted at the physical extent of planar satellite structures by pointing out that the anti-correlation signal weakens at radii >150 kpc. All these unexpected positional and kinematic correlations strongly suggest that a substantial fraction of satellite galaxies are causally linked in their formation and evolution

EPPUR SI MUOVE: POSITIONAL AND KINEMATIC CORRELATIONS OF SATELLITE PAIRS IN THE LOW Z UNIVERSE

Energy Technology Data Exchange (ETDEWEB)

Ibata, Rodrigo A.; Famaey, Benoit; Martin, Nicolas [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France); Lewis, Geraint F. [Sydney Institute of Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia); Ibata, Neil G., E-mail: rodrigo.ibata@astro.unistra.fr [Trinity College, Trinity Street, Cambridge, CB2 1TQ (United Kingdom)

2015-05-20

We have recently shown that pairs of satellite galaxies located diametrically opposite to each other around their host possess predominantly anti-correlated velocities. This is consistent with a scenario in which ≳50% of satellite galaxies belong to kinematically coherent rotating planar structures. Here we extend this analysis, examining satellites of giant galaxies drawn from an SDSS photometric redshift catalog. We find that there is a ∼17% overabundance (>3σ significance) of candidate satellites at positions diametrically opposite to a spectroscopically confirmed satellite. We show that ΛCDM cosmological simulations do not possess this property when contamination is included. After subtracting contamination, we find ∼2 times more satellites diametrically opposed to a spectroscopically confirmed satellite than at 90° from it, at projected distances ranging from 100 to 150 kpc from the host. This independent analysis thus strongly supports our previous results on anti-correlated velocities. We also find that those satellite pairs with anti-correlated velocities have a strong preference (∼3:1) to align with the major axis of the host whereas those with correlated velocities display the opposite behavior. We finally show that repeating a similar analysis to Ibata et al. with same-side satellites is generally hard to interpret, but is not inconsistent with our previous results when strong quality cuts are applied on the sample. This addresses all of the concerns recently raised by Cautun et al., who did not uncover any flaw in our previous analysis, but may simply have hinted at the physical extent of planar satellite structures by pointing out that the anti-correlation signal weakens at radii >150 kpc. All these unexpected positional and kinematic correlations strongly suggest that a substantial fraction of satellite galaxies are causally linked in their formation and evolution.

Exploring the effects of photon correlations from thermal sources on bacterial photosynthesis

Directory of Open Access Journals (Sweden)

Pedro D. Manrique

Full Text Available Thermal light sources can produce photons with strong spatial correlations. We study the role that these correlations might potentially play in bacterial photosynthesis. Our findings show a relationship between the transversal distance between consecutive absorptions and the efficiency of the photosynthetic process. Furthermore, membranes where the clustering of core complexes (so-called RC-LH1 is high, display a range where the organism profits maximally from the spatial correlation of the incoming light. By contrast, no maximum is found for membranes with low core-core clustering. We employ a detailed membrane model with state-of-the-art empirical inputs. Our results suggest that the organization of the membrane’s antenna complexes may be well-suited to the spatial correlations present in an natural light source. Future experiments will be needed to test this prediction. Keywords: Photo-bunching, Spatial correlation, Photosynthesis, Purple bacteria

Activity-dependent increases in local oxygen consumption correlate with postsynaptic currents in the mouse cerebellum in vivo

DEFF Research Database (Denmark)

Mathiesen, Claus; Caesar, Kirsten; Thomsen, Kirsten Engelund

2011-01-01

Evoked neural activity correlates strongly with rises in cerebral metabolic rate of oxygen (CMRO(2)) and cerebral blood flow (CBF). Activity-dependent rises in CMRO(2) fluctuate with ATP turnover due to ion pumping. In vitro studies suggest that increases in cytosolic Ca(2+) stimulate oxidative m...

Bone bruise in magnetic resonance imaging strongly correlates with the production of joint effusion and with knee osteoarthritis

International Nuclear Information System (INIS)

Oda, Hiromi; Igarashi, Mitsuo; Sase, Hiroshi; Sase, Takeshi; Yamamoto, Seizo

2008-01-01

The findings of magnetic resonance imaging (MRI) have not been studied systematically in patients with osteoarthritis (OA). The objective here was to compare MRI findings with radiological findings in patients with knee pain and to identify factors that influence the progression of OA of the knee. Of 212 patients with knee pain and MRI of the knee joint, 161 patients were selected for the study after exclusion of cases of trauma and other arthritides. MRI was used to evaluate the presence and degree of bone bruise, hydrarthrosis, and injuries to the cruciate ligament and meniscus. Bone bruise was classified into four types, and hydrarthrosis into four grades. Radiologically, OA progression in the femorotibial and patellofemoral joints was analyzed according to the Kellgren-Lawrence classification. Age was divided into four groups based on distribution quartiles. Logistic regression analysis and a generalized linear model with Poisson regression were used to analyze correlations among these factors. Bone bruise was present in 87 cases, hydrarthrosis in 100, cruciate ligament injury in 20, and meniscus injury in 98. The presence of bone bruise was not related to age, cruciate ligament injury, meniscus injury, nor to OA of the patellofemoral joint, but was related to hydrarthrosis and to OA of the femorotibial joint. Femorotibial OA was much more strongly associated with bone bruise than with hydrarthrosis. Furthermore, analyzing the relation between the types of bone bruise and the degree of hydrarthrosis using a generalized linear model with Poisson regression, there was a positive correlation between the grade of bone bruise and the amount of hydrarthrosis. A factor associated with the degree of osteoarthritis of the knee is bone bruise observed on MRI. The degree of hydrarthrosis is related to the grade of bone bruise, but is not linked to the degree of osteoarthritis. (author)

Sequence elements correlating with circulating viral load in genotype 1b hepatitis C virus infection

International Nuclear Information System (INIS)

Watanabe, Hideki; Nagayama, Kazuyoshi; Enomoto, Nobuyuki; Itakura, Jun; Tanabe, Yoko; Hamano, Kosei; Izumi, Namiki; Sato, Chifumi; Watanabe, Mamoru

2003-01-01

The correlation between hepatitis C virus (HCV) genomic sequences and circulating HCV RNA levels was assessed to investigate the genetic elements affecting viral load. The interferon sensitivity-determining region (ISDR) sequence and the serum viral load were strongly correlated in 226 patients examined. Analysis of the entire HCV genome from six patients (three with a high and the others with a low viral load) with similar ISDR sequences identified several candidate residues associated with viral load. The amino acid (aa) sequences of these candidate residues and flanking regions in 67 additional patients revealed that only the residue at aa 962 varied significantly between the HCV patients with low and high serum loads (P 0.042). At this position, alanine was observed more frequently in the patients with a high viral load. In conclusion, our results strongly suggest that serum HCV RNA loads are inversely correlated with amino acid substitutions in the ISDR, and aa 962 was identified as a possible second determinant of serum HCV RNA load

A parallel form of the Gudjonsson Suggestibility Scale.

Science.gov (United States)

Gudjonsson, G H

1987-09-01

The purpose of this study is twofold: (1) to present a parallel form of the Gudjonsson Suggestibility Scale (GSS, Form 1); (2) to study test-retest reliabilities of interrogative suggestibility. Three groups of subjects were administered the two suggestibility scales in a counterbalanced order. Group 1 (28 normal subjects) and Group 2 (32 'forensic' patients) completed both scales within the same testing session, whereas Group 3 (30 'forensic' patients) completed the two scales between one week and eight months apart. All the correlations were highly significant, giving support for high 'temporal consistency' of interrogative suggestibility.

Hemodynamic Correlates of Abnormal Aortic Root Dimension in an Adult Population: The Strong Heart Study.

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de Simone, Giovanni; Roman, Mary J; De Marco, Marina; Bella, Jonathan N; Izzo, Raffaele; Lee, Elisa T; Devereux, Richard B

2015-09-28

We evaluated the relationship of aortic root dimension (ARD) with flow output and both peripheral and central blood pressure, using multivariable equations predicting ideal sex-specific ARD at a given age and body height. We measured echocardiographic diastolic ARD at the sinuses of Valsalva in 3160 adults (aged 42±16 years, 61% women) from the fourth examination of the Strong Heart Study who were free of prevalent coronary heart disease, and we compared measured data with the theoretical predicted value to calculate a z score. Central blood pressure was estimated by applanation tonometry of the radial artery in 2319 participants. ARD z scores were divided into tertiles representing small, normal, and large ARD. Participants with large ARD exhibited greater prevalence of central obesity and higher levels of inflammatory markers and lipids (0.05correlated to higher waist circumference and percentages of neutrophils and plasminogen activator inhibitor-1 (all P<0.01). Aortic root dilatation is associated with high diastolic blood pressure, high stroke volume, central fat distribution, and inflammatory status. In contrast, at a given diastolic blood pressure and stroke volume, aortic root dilatation is associated with lower pulse pressure and systolic blood pressure. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Impulsivity, self-control, and hypnotic suggestibility.

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Ludwig, V U; Stelzel, C; Krutiak, H; Prunkl, C E; Steimke, R; Paschke, L M; Kathmann, N; Walter, H

2013-06-01

Hypnotic responding might be due to attenuated frontal lobe functioning after the hypnotic induction. Little is known about whether personality traits linked with frontal functioning are associated with responsiveness to hypnotic suggestions. We assessed whether hypnotic suggestibility is related to the traits of self-control and impulsivity in 154 participants who completed the Brief Self-Control Scale, the Self-Regulation Scale, the Barratt Impulsiveness Scale (BIS-11), and the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:A). BIS-11 non-planning impulsivity correlated positively with HGSHS:A (Bonferroni-corrected). Furthermore, in the best model emerging from a stepwise multiple regression, both non-planning impulsivity and self-control positively predicted hypnotic suggestibility, and there was an interaction of BIS-11 motor impulsivity with gender. For men only, motor impulsivity tended to predict hypnotic suggestibility. Hypnotic suggestibility is associated with personality traits linked with frontal functioning, and hypnotic responding in men and women might differ. Copyright © 2013 Elsevier Inc. All rights reserved.

Are generic and disease-specific health related quality of life correlated? The case of chronic lung disease due to sulfur mustard

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Shervin Assari

2009-09-01

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• <strong>BACKGROUND>: The aim of this study was to investigate the association between the two most commonly used generic and disease specific health-related quality of life (HRQoL measures in patients with chronic lung disease due to SM: Medical Outcomes Study Short Form 36-Item (SF-36 and St George's Respiratory Questionnaire (SGRQ.
• <strong>METHODS>: This is a secondary analysis of Iranian Chemical Warfare Victims Health Assessment Study (ICWVHAS during October 2007 in Isfahan, Iran. In that survey, conducted in an outpatient setting, 292 patients with chronic lung disease due to SM were selected from all provinces in Iran. The total score and sub scores of correlations of SGRQ and SF-36 were assessed. Correlation of quality-of-life scores were evaluated using Pearson’s coefficient.
• <strong>RESULTS>: Samples were 276 patients who were selected for our analysis. No significant correlation was found between the total score or sub scores of SF-36 and the total score or sub scores of SGRQ (p > 0.05.
• <strong>CONCLUSIONS>: In patients with chronic lung disease due to SM, the SF-36 and SGRQ assess different aspects of HRQoL. Therefore applying both of them together, at least in the research setting is suggested.
• KEYWORDS>: Chronic Lung Disease, Health Related Quality of Life, Generic Health Related Quality of Life, Disease Specific Health Related Quality of Life, Sulfur Mustard.