2,893 research outputs found
Simplified models of electromagnetic and gravitational radiation damping
In previous work the authors analysed the global properties of an approximate
model of radiation damping for charged particles. This work is put into context
and related to the original motivation of understanding approximations used in
the study of gravitational radiation damping. It is examined to what extent the
results obtained previously depend on the particular model chosen. Comparisons
are made with other models for gravitational and electromagnetic fields. The
relation of the kinetic model for which theorems were proved to certain
many-particle models with radiation damping is exhibited
Atomic position localization via dual measurement
We study localization of atomic position when a three-level atom interacts
with a quantized standing-wave field in the Ramsey interferometer setup. Both
the field quadrature amplitude and the atomic internal state are measured to
obtain the atomic position information. It is found that this dual measurement
scheme produces an interference pattern superimposed on a diffraction-like
pattern in the atomic position distribution, where the former pattern
originates from the state-selective measurement and the latter from the field
measurement. The present scheme results in a better resolution in the position
localization than the field-alone measurement schemes. We also discuss the
measurement-correlated mechanical action of the standing-wave field on the atom
in the light of Popper's test.Comment: 6.5 pages and 5 figure
Feasibility study of full-reactor gas core demonstration test
Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved
Exact -cosmological model coming from the request of the existence of a Noether symmetry
We present an -cosmological model with an exact analytic solution,
coming from the request of the existence of a Noether symmetry, which is able
to describe a dust-dominated decelerated phase before the current accelerated
phase of the universe.Comment: 4 pages, 2 figures, Contribution to the proceedings of Spanish
Relativity Meeting 2008, Salamanca, Sapin, 15-19 September 200
High-resolution Smoothed Particle Hydrodynamics simulations of the merger of binary white dwarfs
We present the results of a set of high-resolution simulations of the merging
process of two white dwarfs. In order to do so, we use an up-to-date Smoothed
Particle Hydrodynamics code which incorporates very detailed input physics and
an improved treatment of the artificial viscosity. Our simulations have been
done using a large number of particles (4x10^5) and cover the full range of
masses and chemical compositions of the coalescing white dwarfs. We also
compare the time evolution of the system during the first phases of the
coalescence with that obtained using a simplified treatment of mass transfer,
we discuss in detail the characteristics of the final configuration, we assess
the possible observational signatures of the merger, like the associated
gravitational waveforms and the fallback X-ray flares, and we study the
long-term evolution of the coalescence.Comment: 14 pages, 9 figures. Accepted for publication in Astronomy and
Astrophysic
An Exploration of Co-Workersâ Group Identification as Moderator of the Leadership-Health Link
This study explores the leadership-health link from a social identity perspective. It focuses on leadership behaviors that seek to form a strong shared social identity (i.e., identity leadership) and the contextual influence of co-workersâ group identification. In a sample of 319 members in 77 workgroups, data supports the indirect link of identity leadership and reduced symptoms of burnout via perceived social support. However, contrary to our expectation, high levels of co-workersâ group identification weakened the relationship of identity leadership and perceived social support. The implications of this finding for the understanding of leadership as a group process are discussed
Resolved diffraction patterns from a reflection grating for atoms
We have studied atomic diffraction at normal incidence from an evanescent
standing wave with a high resolution using velocity selective Raman
transitions. We have observed up to 3 resolved orders of diffraction, which are
well accounted for by a scalar diffraction theory. In our experiment the
transverse coherence length of the source is greater than the period of the
diffraction grating.Comment: 8 pages, 4 figure
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