3,881 research outputs found

    Quantum invariants of motion in a generic many-body system

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    Dynamical Lie-algebraic method for the construction of local quantum invariants of motion in non-integrable many-body systems is proposed and applied to a simple but generic toy model, namely an infinite kicked t−Vt-V chain of spinless fermions. Transition from integrable via {pseudo-integrable (\em intermediate}) to quantum ergodic (quantum mixing) regime in parameter space is investigated. Dynamical phase transition between ergodic and intermediate (neither ergodic nor completely integrable) regime in thermodynamic limit is proposed. Existence or non-existence of local conservation laws corresponds to intermediate or ergodic regime, respectively. The computation of time-correlation functions of typical observables by means of local conservation laws is found fully consistent with direct calculations on finite systems.Comment: 4 pages in REVTeX with 5 eps figures include

    Role of two-electron processes in the excitation-ionization of lithium atoms by fast ion impact

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    We study excitation and ionization in the 1.5 MeV/amu O8+^{8+}-Li collision system, which was the subject of a recent reaction-microscope-type experiment [Fischer \textit{et al.}, Phys. Rev. Lett. \textbf{109}, 113202 (2012)]. Starting from an independent-electron model based on determinantal wave functions and using single-electron basis generator method and continuum distorted-wave with eikonal initial-state calculations we show that pure single ionization of a lithium KK-shell electron is too weak a process to explain the measured single differential cross section. Rather, our analysis suggests that two-electron excitation-ionization processes occur and have to be taken into account when comparing with the data. Good agreement is obtained only if we replace the independent-electron calculation by an independent-event model for one of the excitation-ionization processes and also take a shake-off process into account

    Differential cross sections for single ionization of Li in collisions with fast protons and O8+^{8+} ions

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    We study the process of single ionization of Li in collisions with H+^+ and O8+^{8+} projectile ions at 6 MeV and 1.5-MeV/amu impact energies, respectively. Using the frameworks of the independent-electron model and the impact parameter picture, fully (FDCS) and doubly (DDCS) differential cross sections are evaluated in the continuum distorted-wave with eikonal initial-state approximation. Comparisons are made with the recent measurements of LaForge \textit{et al} [J. Phys. B \textbf{46} 031001 (2013)] for the DDCS and Hubele \textit{et al} [Phys. Rev. Lett. \textbf{110} 133201 (2013)] for the FDCS, respectively. For O8+^{8+} impact inclusion of the heavy particle (NN) interaction in the calculations is crucial and effects of polarization due to the presence of the projectile ion have also to be taken into account for getting very good agreement with the measured data. Our calculation reproduces the satellite peak structure seen in the FDCS for the Li(2s) measurement, which we explain as being formed by a combination of the binary and NN interactions

    Doubly-differential cross section calculations for KK-shell vacancy production in lithium by fast O8+^{8+} ion impact

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    Inner-shell vacancy production for the O8+^{8+}-Li collision system at 1.5 MeV/amu is studied theoretically. The theory combines single-electron amplitudes for each electron in the system to extract multielectron information about the collision process. Doubly-differential cross sections obtained in this way are then compared with the recent experimental data by LaForge et al. [J. Phys. B 46, 031001 (2013)] yielding good resemblance, especially for low outgoing electron energy. A careful analysis of the processes that contribute to inner-shell vacancy production shows that the improvement of the results as compared to single-active-electron calculations can be attributed to the leading role of two-electron excitation-ionization processes

    The Effects of Cognitive-Behavioral Motivation for Health Improvement on Anthropometric Measurements in High Risk Individuals

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    Unhealthy lifestyles cost businesses, governmental organizations, and the United States military billions of dollars every year. To fight this rising cost as well as potentially save lives this study sought to understand if a cognitive-behavioral motivation treatment could positively affect the cognitive variables (attitude, self-efficacy, and locus of control) that induce long term behavior change. Anthropometric measurements, specifically body mass index, abdominal circumference, and abdominal height, were used to determine if long term behavior change resulted from the treatment. The Theory of Planned Behavior was the basis of this thesis\u27 model, while the Valence, Instrumentality, and Expectancy (VIE) theory was the foundation for the cognitive-behavioral motivation treatment. Structural Equation Modeling (SEM) tested the theory based model and found two results: a cognitive-behavioral motivation treatment can positively affect cognitive changes that improve behavior and health and, a causal or mediation relationship among the cognitive variables of locus of control and self-efficacy was found instead of the predicted parallel relationship. Effective implementation of an intervention like the one used in this study could lower the United States Air Force\u27s health care bill by as much as $40 million, improve employee efficiency and mission capability, enable longer healthier lives, and prevent premature death

    External impact of arts management research: An extended analysis

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    Arts management is a discipline whose research domain has grown in impact over the last quarter century.This study provides an external thematic, content and citation analysis of arts management articles in top-tiermainstream management and marketing journals between 1987 and 2010. It explicates article, author andcitation frequencies based on author information, publication patterns and thematic citation metrics, thuscontributing to the development of the arts management body of knowledge. Specifically, the study examinesthe function of arts management research as a bridging mechanism to its parent disciplines in managementand marketing. The authors identify thematic citation metrics of research published in mainstream journalsas well as frequencies and publication patterns, so that scholars can make decisions affecting their futureresearch directions. The authors conclude that there is little correlation between age/rank of journal andfrequency of citations, with younger journals becoming established as key players within relatively shortperiods

    Continuous-Time Monte Carlo study of the pseudogap Bose-Fermi Kondo model

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    We study the pseudogap Bose-Fermi Anderson model with a continuous-time quantum Monte Carlo (CT-QMC) method. We discuss some delicate aspects of the transformation from this model to the Bose-Fermi Kondo model. We show that the CT-QMC method can be used at sufficiently low temperatures to access the quantum critical properties of these models.Comment: SCES 2010 Proceeding
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