43,780 research outputs found
Robust Preparation of GHZ and W States of Three Distant Atoms
Schemes to generate Greenberger-Horne-Zeilinger(GHZ) and W states of three
distant atoms are proposed in this paper. The schemes use the effects of
quantum statistics of indistinguishable photons emitted by the atoms inside
optical cavities. The advantages of the schemes are their robustness against
detection inefficiency and asynchronous emission of the photons. Moreover, in
Lamb-Dicke limit, the schemes do not require simultaneous click of the
detectors, this makes the schemes more realizable in experiments.Comment: 5 pages, 1 fiure. Phys. Rev. A 75, 044301 (2007
Euler equation of the optimal trajectory for the fastest magnetization reversal of nano-magnetic structures
Based on the modified Landau-Lifshitz-Gilbert equation for an arbitrary
Stoner particle under an external magnetic field and a spin-polarized electric
current, differential equations for the optimal reversal trajectory, along
which the magnetization reversal is the fastest one among all possible reversal
routes, are obtained. We show that this is a Euler-Lagrange problem with
constrains. The Euler equation of the optimal trajectory is useful in designing
a magnetic field pulse and/or a polarized electric current pulse in
magnetization reversal for two reasons. 1) It is straightforward to obtain the
solution of the Euler equation, at least numerically, for a given magnetic
nano-structure characterized by its magnetic anisotropy energy. 2) After
obtaining the optimal reversal trajectory for a given magnetic nano-structure,
finding a proper field/current pulse is an algebraic problem instead of the
original nonlinear differential equation
Model for a Light Z' Boson
A model of a light boson is constructed and phenomenological bounds are
derived. This boson arises from a very simple extension to the Standard
Model, and it is constrained to be light because the vacuum expectation values
which generate its mass also break the electroweak gauge group. It is difficult
to detect experimentally because it couples exclusively or primarily (depending
on symmetry breaking details) to second and third generation leptons. However,
if the boson is sufficiently light, then there exists the possibility of
the two-body decay occuring. This will provide a
striking signature to test the model.Comment: 20 pages + 5 pages of figures (appended as postscipt files), LaTeX,
OITS-53
Lattice Boltzmann Model for Axisymmetric Multiphase Flows
In this paper, a lattice Boltzmann (LB) model is presented for axisymmetric
multiphase flows. Source terms are added to a two-dimensional standard lattice
Boltzmann equation (LBE) for multiphase flows such that the emergent dynamics
can be transformed into the axisymmetric cylindrical coordinate system. The
source terms are temporally and spatially dependent and represent the
axisymmetric contribution of the order parameter of fluid phases and inertial,
viscous and surface tension forces. A model which is effectively explicit and
second order is obtained. This is achieved by taking into account the discrete
lattice effects in the Chapman-Enskog multiscale analysis, so that the
macroscopic axisymmetric mass and momentum equations for multiphase flows are
recovered self-consistently. The model is extended to incorporate reduced
compressibility effects. Axisymmetric equilibrium drop formation and
oscillations, breakup and formation of satellite droplets from viscous liquid
cylindrical jets through Rayleigh capillary instability and drop collisions are
presented. Comparisons of the computed results with available data show
satisfactory agreement.Comment: 17 pages, 11 figures, to be published in Physical Review
Anomalous Phase Transition in Strained SrTiO Thin Films
We have studied the cubic to tetragonal phase transition in epitaxial
SrTiO films under various biaxial strain conditions using synchrotron X-ray
diffraction. Measuring the superlattice peak associated with TiO octahedra
rotation in the low temperature tetragonal phase indicates the presence of a
phase transition whose critical temperature is a strong function of strain,
with T as much as 50K above the corresponding bulk temperature.
Surprisingly, the lattice constants evolve smoothly through the transition with
no indication of a phase change. This signals an important change in the nature
of the phase transition due to the epitaxy strain and substrate clamping
effect. The internal degrees of freedom (TiO rotations) have become
uncoupled from the overall lattice shape.Comment: 4 pages, 3 figures, REVTeX
Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses
A novel radiation pressure acceleration (RPA) regime of heavy ion beams from
laser-irradiated ultrathin foils is proposed by self-consistently taking into
account the ionization dynamics. In this regime, the laser intensity is
required to match with the large ionization energy gap when the successive
ionization of high-Z atoms passing the noble gas configurations [such as
removing an electron from the helium-like charge state to
]. While the target ions in the laser wing region are ionized
to low charge states and undergo rapid dispersions due to instabilities, a
self-organized, stable RPA of highly-charged heavy ion beam near the laser axis
is achieved. It is also found that a large supplement of electrons produced
from ionization helps preserving stable acceleration. Two-dimensional
particle-in-cell simulations show that a monoenergetic beam
with peak energy and energy spread of is obtained by
lasers at intensity .Comment: 5 pages, 4 figure
Mathematical control of complex systems 2013
Mathematical control of complex systems have already become an ideal research area for control engineers, mathematicians, computer scientists, and biologists to understand, manage, analyze, and interpret functional information/dynamical behaviours from real-world complex dynamical systems, such as communication systems, process control, environmental systems, intelligent manufacturing systems, transportation systems, and structural systems. This special issue aims to bring together the latest/innovative knowledge and advances in mathematics for handling complex systems. Topics include, but are not limited to the following: control systems theory (behavioural systems, networked control systems, delay systems, distributed systems, infinite-dimensional systems, and positive systems); networked control (channel capacity constraints, control over communication networks, distributed filtering and control, information theory and control, and sensor networks); and stochastic systems (nonlinear filtering, nonparametric methods, particle filtering, partial identification, stochastic control, stochastic realization, system identification)
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