7,333 research outputs found
The Vector Analyzing Power in Elastic Electron-Nucleus Scattering
The vector analyzing power A_n is calculated for elastic electron scattering
from a variety of spin zero nuclei at energies from 14 MeV to 3 GeV. Time
reversal symmetry insures that A_n vanish in first Born approximation.
Therefore A_n depends on Coulomb distortions and can be large for scattering
from heavy nuclei. The vector analyzing power is a potential source of
systematic error for parity violation experiments. We find that A_n=-0.361 ppm
for the kinematics of the Parity Radius Experiment (PREX) involving 850 MeV
electrons scattering at six degrees from 208Pb. This is comparable to the
parity violating asymmetry. However for HAPPEX He involving 3 GeV electrons
scattering on 4He we find that A_n is very small.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Towards first-principles understanding of the metal-insulator transition in fluid alkali metals
By treating the electron-ion interaction as perturbation in the
first-principles Hamiltonian, we have calculated the density response functions
of a fluid alkali metal to find an interesting charge instability due to
anomalous electronic density fluctuations occurring at some finite wave vector
{\bi Q} in a dilute fluid phase above the liquid-gas critical point. Since
|{\bi Q}| is smaller than the diameter of the Fermi surface, this instability
necessarily impedes the electric conduction, implying its close relevance to
the metal-insulator transition in fluid alkali metals.Comment: 11 pages, 5 figure
Study of inexact modeling techniques Final report
Scale modeling antenna systems for aircraft and missiles with anechoic chamber evaluation and us
Magnetoresistance scaling in the layered cobaltate Ca3Co4O9
We investigate the low temperature magnetic field dependences of both the
resistivity and the magnetization in the misfit cobaltate Ca3Co4O9 from 60 K
down to 2 K. The measured negative magnetoresistance reveals a scaling behavior
with the magnetization which demonstrates a spin dependent diffusion mechanism.
This scaling is also found to be consistent with a shadowed metalliclike
conduction over the whole temperature range. By explaining the observed
transport crossover, this result shed a new light on the nature of the
elementary excitations relevant to the transport
Low-energy excitations of the one-dimensional half-filled SU(4) Hubbard model with an attractive on-site interaction: Density-matrix renormalization-group calculations and perturbation theory
We investigate low-energy excitations of the one-dimensional half-filled
SU(4) Hubbard model with an attractive on-site interaction U < 0 using the
density matrix renormalization group method as well as a perturbation theory.
We find that the ground state is a charge density wave state with a long range
order. The ground state is completely incompressible since all the excitations
are gapful. The charge gap which is the same as the four-particle excitation
gap is a non-monotonic function of U, while the spin gap and others increase
with increasing |U| and have linear asymptotic behaviors.Comment: 4 pages, 3 figures, submitte
Spin-gap opening accompanied by a strong magnetoelastic response in the S=1 magnetic dimer system Ba3BiRu2O9
Neutron diffraction, magnetization, resistivity, and heat capacity
measurements on the 6H-perovskite Ba3BiRu2O9 reveal simultaneous magnetic and
structural dimerization driven by strong magnetoelastic coupling. An
isostructural but strongly displacive first-order transition on cooling through
T*=176 K is associated with a change in the nature of direct Ru-Ru bonds within
Ru2O9 face-sharing octahedra. Above T*, Ba3BiRu2O9 is an S=1 magnetic dimer
system with intradimer exchange interactions J0/kB=320 K and interdimer
exchange interactions J'/kB=-160 K. Below T*, a spin-gapped state emerges with
\Delta\approx220 K. Ab initio calculations confirm antiferromagnetic exchange
within dimers, but the transition is not accompanied by long range-magnetic
order.Comment: 5 pages, 5 figures, accepted by Physical Review
Study of techniques and applications of satellite imagery to small scale mapping
There are no author-identified significant results in this report
Epitaxial Growth of LaSrFeO thin films by laser ablation
We report on the synthesis of high quality LaSrFeO (LSFO)
thin films using the pulsed laser deposition technique on both SrTiO (STO)
and LaAlO (LAO) substrates (100)-oriented. From X-Ray diffraction (XRD)
studies, we find that the films have an out-of-plane lattice parameter around
0.3865nm, almost independent of the substrate (i.e. the nature of the strains).
The transport properties reveal that, while LSFO films deposited on STO exhibit
an anomaly in the resistivity vs temperature at 180K (corresponding to the
charge-ordered transition and associated with a transition from a paramagnetic
to an antiferromagnetic state), the films grown on LAO display a very small
magnetoresistance behavior and present an hysteresis around 270K under the
application of a 4T magnetic field. The changes in transport properties between
both substrates are discussed and compared with the corresponding single
crystals.Comment: 9 pages, 4 figure
Entanglement between static and flying qubits in quantum wires
A weakly bound electron in a semiconductor quantum wire is shown to become
entangled with an itinerant electron via the coulomb interaction. The degree of
entanglement and its variation with energy of the injected electron, may be
tuned by choice of spin and initial momentum. Full entanglement is achieved
close to energies where there are spin-dependent resonances. Possible
realisations of related device structures are discussed
Cartographic research in EREP program for small scale mapping
The author has identified the following significant results. Skylab photography is suitable for producing planimetric maps with graphical representation of landform at scales up to 1:100,000. It cannot supply all the detail necessary for maps at this scale, but it may be used to produce a sound framework which can be completed by detail from other sources. Its principal cartographic use is for original mapping of undeveloped areas of the world, but it would also be useful for the revision of existing maps and for monitoring extensive urban changes
- …