8,713 research outputs found
Coherent states of a charged particle in a uniform magnetic field
The coherent states are constructed for a charged particle in a uniform
magnetic field based on coherent states for the circular motion which have
recently been introduced by the authors.Comment: 2 eps figure
On the uncertainty relations and squeezed states for the quantum mechanics on a circle
The uncertainty relations for the position and momentum of a quantum particle
on a circle are identified minimized by the corresponding coherent states. The
sqeezed states in the case of the circular motion are introduced and discussed
in the context of the uncertainty relations.Comment: 4 figure
Toward a numerical deshaker for PFS
The Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEx) is the
instrument with the highest spectral resolution observing Mars from orbit since
January 2004. It permits studying the atmospheric structure, major and minor
compounds. The present time version of the calibration is limited by the
effects of mechanical vibration, currently not corrected. We proposed here a
new approach to correct for the vibrations based on semi-blind deconvolution of
the measurements. This new approach shows that a correction can be done
efficiently with 85% reduction of the artefacts, in a equivalent manner to the
stacking of 10 spectra. Our strategy is not fully automatic due to the
dependence on some regularisation parameters. It may be applied on the complete
PFS dataset, correcting the large-scale perturbation due to microvibrations for
each spectrum independently. This approach is validated on actual PFS data of
Short Wavelength Channel (SWC), perturbed by microvibrations. A coherence check
can be performed and also validate our approach. Unfortunately, the coherence
check can be done only on the first 310 orbits of MEx only, until the laser
line has been switch off. More generally, this work may apply to numerically
"deshake" Fourier Transform Spectrometer (FTS), widely used in space
experiments or in the laboratory.Comment: 18 pages, 8 figures, submitted to Planetary and Space Scienc
Curvature homogeneous spacelike Jordan Osserman pseudo-Riemannian manifolds
Let s be at least 2. We construct Ricci flat pseudo-Riemannian manifolds of
signature (2s,s) which are not locally homogeneous but whose curvature tensors
never the less exhibit a number of important symmetry properties. They are
curvature homogeneous; their curvature tensor is modeled on that of a local
symmetric space. They are spacelike Jordan Osserman with a Jacobi operator
which is nilpotent of order 3; they are not timelike Jordan Osserman. They are
k-spacelike higher order Jordan Osserman for ; they are k-timelike
higher order Jordan Osserman for , and they are not k timelike
higher order Jordan Osserman for .Comment: Update bibliography, fix minor misprint
Physics of Quantum Relativity through a Linear Realization
The idea of quantum relativity as a generalized, or rather deformed, version
of Einstein (special) relativity has been taking shape in recent years.
Following the perspective of deformations, while staying within the framework
of Lie algebra, we implement explicitly a simple linear realization of the
relativity symmetry, and explore systematically the resulting physical
interpretations. Some suggestions we make may sound radical, but are arguably
natural within the context of our formulation. Our work may provide a new
perspective on the subject matter, complementary to the previous approach(es),
and may lead to a better understanding of the physics.Comment: 27 pages in Revtex, no figure; proof-edited version to appear in
Phys.Rev.
Relativistic ideal Fermi gas at zero temperature and preferred frame
We discuss the limit T->0 of the relativistic ideal Fermi gas of luxons
(particles moving with the speed of light) and tachyons (hypothetical particles
faster than light) based on observations of our recent paper: K. Kowalski, J.
Rembielinski and K.A. Smolinski, Phys. Rev. D, 76, 045018 (2007). For bradyons
this limit is in fact the nonrelativistic one and therefore it is not studied
herein
MnAs dots grown on GaN(0001)-(1x1) surface
MnAs has been grown by means of MBE on the GaN(0001)-(1x1) surface. Two
options of initiating the crystal growth were applied: (a) a regular MBE
procedure (manganese and arsenic were delivered simultaneously) and (b)
subsequent deposition of manganese and arsenic layers. It was shown that
spontaneous formation of MnAs dots with the surface density of 1
cm and cm, respectively (as observed by AFM),
occurred for the layer thickness higher than 5 ML. Electronic structure of the
MnAs/GaN systems was studied by resonant photoemission spectroscopy. That led
to determination of the Mn 3d - related contribution to the total density of
states (DOS) distribution of MnAs. It has been proven that the electronic
structures of the MnAs dots grown by the two procedures differ markedly. One
corresponds to metallic, ferromagnetic NiAs-type MnAs, the other is similar to
that reported for half-metallic zinc-blende MnAs. Both system behave
superparamagnetically (as revealed by magnetization measurements), but with
both the blocking temperatures and the intra-dot Curie temperatures
substantially different. The intra-dot Curie temperature is about 260 K for the
former system while markedly higher than room temperature for the latter one.
Relations between growth process, electronic structure and other properties of
the studied systems are discussed. Possible mechanisms of half-metallic MnAs
formation on GaN are considered.Comment: 20+ pages, 8 figure
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