10,456 research outputs found
The Bargmann representation for the quantum mechanics on a sphere
The Bargmann representation is constructed corresponding to the coherent
states for a particle on a sphere introduced in: K. Kowalski and J.
Rembielinski, J. Phys. A: Math. Gen. 33, 6035 (2000). The connection is
discussed between the introduced formalism and the standard approach based on
the Hilbert space of square integrable functions on a sphere S^2.Comment: LaTe
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
Near-UV absorption in very cool DA white dwarfs
The atmospheres of very cool, hydrogen-rich white dwarfs (Teff <6000 K) are
challenging to models because of the increased complexity of the equation of
state, chemical equilibrium, and opacity sources in a low-temperature, weakly
ionized dense gas. In particular, many models that assume relatively simple
models for the broadening of atomic levels and mostly ideal gas physics
overestimate the flux in the blue part of their spectra. A solution to this
problem that has met with some success is that additional opacity at short
wavelengths comes for the extreme broadening of the Lyman alpha line of atomic
H by collisions primarily with H2. For the purpose of validating this model
more rigorously, we acquired Hubble Space Telescope STIS spectra of 8 very cool
white dwarfs (5 DA and 3 DC stars). Combined with their known parallaxes,
BVRIJHK and Spitzer IRAC photometry, we analyze their entire spectral energy
distribution (from 0.24 to 9.3 micron) with a large grid of model atmospheres
and synthetic spectra. We find that the red wing of the Lyman alpha line
reproduces the rapidly decreasing near-UV flux of these very cool stars very
well. We determine better constrained values of Teff and gravity as well as
upper limits to the helium abundance in their atmospheres.Comment: 41 pages, 9 figures. Accepted for publication in the Ap
Bagchi's Theorem for families of automorphic forms
We prove a version of Bagchi's Theorem and of Voronin's Universality Theorem
for family of primitive cusp forms of weight and prime level, and discuss
under which conditions the argument will apply to general reasonable family of
automorphic -functions.Comment: 15 page
The status and future of EUV astronomy
The Extreme Ultraviolet wavelength range was one of the final windows to be
opened up to astronomy. Nevertheless, it provides very important diagnostic
tools for a range of astronomical objects, although the opacity of the
interstellar medium restricts the majority of observations to sources in our
own galaxy. This review gives a historical overview of EUV astronomy, describes
current instrumental capabilities and examines the prospects for future
facilities on small and medium-class satellite platforms.Comment: Published in Advances in Space Researc
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
Homogeneity and plane-wave limits
We explore the plane-wave limit of homogeneous spacetimes. For plane-wave
limits along homogeneous geodesics the limit is known to be homogeneous and we
exhibit the limiting metric in terms of Lie algebraic data. This simplifies
many calculations and we illustrate this with several examples. We also
investigate the behaviour of (reductive) homogeneous structures under the
plane-wave limit.Comment: In memory of Stanley Hobert, 33 pages. Minor corrections and some
simplification of Section 4.3.
The release of eosinophil chemotactic activity and eosinophil chemokinesis inhibitory activity by mononuclear cells from atopic asthmatic and non-atopic subjects.
The goal of our study was to assess the chemotactic activity for eosinophils (ECA) and neutrophils (NCA) and histamine releasing activity (HRA) in crude supernatants of mononuclear cells in monosensitized atopic asthmatics and healthy controls. Chemotactic activity for ECA and neutrophils was measured in supernatants of cultured mononuclear cells with modified Boyden's chamber and HRA was assessed on healthy donor basophils. With respect to ECA generation two distinct subgroups of subjects were distinguished: releasers [ECA (+)] and non-releasers [ECA (-)]. In atopic and non-atopic ECA (+) the mean ECA index was 3.78 +/- 0.49 and 2.47 +/- 0.27 respectively (P > 0.05). Supernatants from the remaining subjects (seven of 22 atopic and five of 11 non-atopic) did not express ECA, but revealed significant inhibitory activity for chemokinesis of eosinophils (mean chemotactic index 0.25 +/- 0.16 and 0.48 +/- 0.22 for atopic and non-atopic non-releasers respectively). Stimulation with antigen of MNC from atopic and with PHA from non-atopic ECA (-) restored cells ability to release ECA. Sephadex gel chromatography revealed that supernatants of MNC contained chemotactic and chemokinesis inhibitory activity in different fractions. The spontaneous productions of NCA and HRA by mononuclear cells was similar in ECA releasers and non-releasers, although the HRA was higher following stimulation with PHA in the non-atopic ECA (+) subgroup. Our study demonstrated, for the first time, that MNC are capable of generating not only chemotactic activity but also chemokinesis inhibitory activity for eosinophils
Quantum mechanics on a circle: Husimi phase space distributions and semiclassical coherent state propagators
We discuss some basic tools for an analysis of one-dimensionalquantum systems
defined on a cyclic coordinate space. The basic features of the generalized
coherent states, the complexifier coherent states are reviewed. These states
are then used to define the corresponding (quasi)densities in phase space. The
properties of these generalized Husimi distributions are discussed, in
particular their zeros.Furthermore, the use of the complexifier coherent states
for a semiclassical analysis is demonstrated by deriving a semiclassical
coherent state propagator in phase space.Comment: 29 page
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