3,903 research outputs found
Quantum invariants of motion in a generic many-body system
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
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
We study excitation and ionization in the 1.5 MeV/amu O-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 -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 O ions
We study the process of single ionization of Li in collisions with H and
O 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 O 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 -shell vacancy production in lithium by fast O ion impact
Inner-shell vacancy production for the O-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
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
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
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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