6,869 research outputs found
Variable Metric Forward-Backward Splitting with Applications to Monotone Inclusions in Duality
We propose a variable metric forward-backward splitting algorithm and prove
its convergence in real Hilbert spaces. We then use this framework to derive
primal-dual splitting algorithms for solving various classes of monotone
inclusions in duality. Some of these algorithms are new even when specialized
to the fixed metric case. Various applications are discussed
Two component spin-fermion model for high- cuprates: Applications to neutron scattering and ARPES experiments
Motivated by neutron scattering experiments in the high- cuprates, we
propose the two-component spin-fermion model as a minimal phenomenological
model which has both local spins and itinerant fermions as independent degrees
of freedom. Our calculations of the dynamic spin correlation function provide a
successful description of the puzzling neutron experiment data and show that:
(1) the upward dispersion branch of magnetic excitations is mostly due to the
local spin excitations; (2) the downward dispersion branch is from collective
particle-hole excitations of fermions; and (3) the resonance mode is a mixture
of both degrees of freedom. Using the same model with the same set of
parameters we calculated the renormalized quasiparticle dispersion and
successfully reproduced one of the key features of the angle resolved
photoemission spectroscopy (ARPES) experiments, i.e., the high energy kink
structure in the fermion quasiparticle dispersion, hence further support the
two component spin-fermion phenomenology.Comment: 7 figures, 12 pages. arXiv admin note: substantial text overlap with
arXiv:0706.138
Technology Expertise Alone is not Enough: Toward a Conceptualization of the Purposive Indirect Social Influence Behavior of IT Professionals
This paper proposes a behavioral construct called Purposive Indirect Social Influence (PISI) and its conceptual framework to examine a particular subordinate-supervisor influence behavior of IT professionals in the workplace. This article answers two questions (1) Why and how do IT professionals engage in PISI attempts? (2) What are personal and organizational benefits of PISI activities? This study postulates that (a) PISI is a response to cultural, social, organizational, and professional constraints and limitations, which IT professionals are subject to, and (b) PISI helps improve perceived performance, alleviate job stresses, defuse workplace tensions, increase social capital, and strengthen social effectiveness on both intra and extra organizational relationships
Bubble generation in a twisted and bent DNA-like model
The DNA molecule is modeled by a parabola embedded chain with long-range
interactions between twisted base pair dipoles. A mechanism for bubble
generation is presented and investigated in two different configurations. Using
random normally distributed initial conditions to simulate thermal
fluctuations, a relationship between bubble generation, twist and curvature is
established. An analytical approach supports the numerical results.Comment: 7 pages, 8 figures. Accepted for Phys. Rev. E (in press
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Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser
The kinetic energy of hot (multi-keV) ions from the laser-driven Coulomb explosion of deuterium clusters and the resulting fusion yield in plasmas formed from these exploding clusters has been investigated under a variety of conditions using the Texas Petawatt laser. An optimum laser intensity was found for producing neutrons in these cluster fusion plasmas with corresponding average ion energies of 14 keV. The substantial volume (1-10 mm(3)) of the laser-cluster interaction produced by the petawatt peak power laser pulse led to a fusion yield of 1.6x10(7) neutrons in a single shot with a 120 J, 170 fs laser pulse. Possible effects of prepulses are discussed. DOI: 10.1103/PhysRevE.87.023106Glenn Focht Memorial FellowshipNNSA DE-FC52-08NA28512DOE Office of Basic Energy SciencesPhysic
Anomalous specific heat jump in the heavy fermion superconductor CeCoIn
We study the anomalously large specific heat jump and its systematic change
with pressure in CeCoIn superconductor. Starting with the general free
energy functional of the superconductor for a coupled electron boson system, we
derived the analytic result of the specific heat jump of the strong coupling
superconductivity occurring in the coupled electron boson system. Then using
the two component spin-fermion model we calculate the specific heat coefficient
both for the normal and superconducting states and show a good
agreement with the experiment of CeCoIn. Our result also clearly
demonstrated that the specific heat coefficient of a coupled electron
boson system can be freely interpreted as a renormalization either of the
electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure
Hyperfine Interactions in the Heavy Fermion CeMIn_5 Systems
The CeMIn_5 heavy fermion compounds have attracted enormous interest since
their discovery six years ago. These materials exhibit a rich spectrum of
unusual correlated electron behavior, and may be an ideal model for the high
temperature superconductors. As many of these systems are either
antiferromagnets, or lie close to an antiferromagnetic phase boundary, it is
crucial to understand the behavior of the dynamic and static magnetism. Since
neutron scattering is difficult in these materials, often the primary source of
information about the magnetic fluctuations is Nuclear Magnetic Resonance
(NMR). Therefore, it is crucial to have a detailed understanding of how the
nuclear moments interact with conduction electrons and the local moments
present in these systems. Here we present a detailed analysis of the hyperfine
coupling based on anisotropic hyperfine coupling tensors between nuclear
moments and local moments. Because the couplings are symmetric with respect to
bond axes rather than crystal lattice directions, the nuclear sites can
experience non-vanishing hyperfine fields even in high symmetry sites.Comment: 15 pages, 5 figure
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