2,117 research outputs found
Two computerized stream searches among meteor orbits: Among 865 precise photographic orbits; among 2401 photographic orbits
Computerized searches for meteor streams in photographic meteor orbit
The distribution of 1/a in photographic meteor orbits
The distribution of reciprocal semi-major axes in photographic meteor orbits is studied. A detailed classification of the orbits is made according to quality. The distribution of 1/a in precise orbits is multimodal with two broad maxima approximately centered on 0.05 and 0.40 (AU)/1. Minima in the distribution appear near 0.20 and 0.66 (AU)/1 corresponding to Jupiter's and Mars' position in the 1/a diagram. Considerable fine structure appears in the 1/a distribution. Resonance gaps corresponding to commensurabilities with Jupiter are detected. The gaps are similar to the well studied Kirkwood gaps in the asteroid belt
On Conserved Current in Markovian Open Quantum Systems
We reexamine the markovian approximation of local current in open quantum
systems, discussed recently by Gebauer and Car. Our derivation is more
transparent, the proof of current conservation becomes explicit and easy.Comment: 3 page
Basic Concepts in the Application of Immunological Adjuvants
No abstract availabl
Quantum decoherence in the theory of open systems
In the framework of the Lindblad theory for open quantum systems, we
determine the degree of quantum decoherence of a harmonic oscillator
interacting with a thermal bath. It is found that the system manifests a
quantum decoherence which is more and more significant in time. We calculate
also the decoherence time scale and analyze the transition from quantum to
classical behaviour of the considered system.Comment: 6 pages; talk at the 3rd International Workshop "Quantum Physics and
Communication" (QPC 2005), Dubna, Russia, 200
Quantum dissipative systems from theory of continuous measurements
We apply the restricted-path-integral (RPI) theory of non-minimally
disturbing continuous measurements for correct description of frictional
Brownian motion. The resulting master equation is automatically of the Lindblad
form, so that the difficulties typical of other approaches do not exist. In the
special case of harmonic oscillator the known familiar master equation
describing its frictionally driven Brownian motion is obtained. A thermal
reservoir as a measuring environment is considered.Comment: 10 pages in LATE
Environment Induced Entanglement in Markovian Dissipative Dynamics
We show that two, non interacting 2-level systems, immersed in a common bath,
can become mutually entangled when evolving according to a Markovian,
completely positive reduced dynamics.Comment: 4 pages, LaTex, no figures, added reference
Giant Molecular Clouds are More Concentrated to Spiral Arms than Smaller Clouds
From our catalog of Milky Way molecular clouds, created using a temperature
thresholding algorithm on the Bell Laboratories 13CO Survey, we have extracted
two subsets:(1) Giant Molecular Clouds (GMCs), clouds that are definitely
larger than 10^5 solar masses, even if they are at their `near distance', and
(2) clouds that are definitely smaller than 10^5 solar masses, even if they are
at their `far distance'. The positions and velocities of these clouds are
compared to the loci of spiral arms in (l, v) space. The velocity separation of
each cloud from the nearest spiral arm is introduced as a `concentration
statistic'. Almost all of the GMCs are found near spiral arms. The density of
smaller clouds is enhanced near spiral arms, but some clouds (~10%) are
unassociated with any spiral arm. The median velocity separation between a GMC
and the nearest spiral arm is 3.4+-0.6 km/s, whereas the median separation
between smaller clouds and the nearest spiral arm is 5.5+-0.2 km/s.Comment: 11 pages, 3 figure
A Dust-Penetrated Classification Scheme for Bars as Inferred from their Gravitational Force Fields
The division of galaxies into ``barred'' (SB) and ``normal'' (S) spirals is a
fundamental aspect of the Hubble galaxy classification system. This ``tuning
fork'' view was revised by de Vaucouleurs, whose classification volume
recognized apparent ``bar strength'' (SA, SAB, SB) as a continuous property of
galaxies called the ``family''. However, the SA, SAB, and SB families are
purely visual judgments that can have little bearing on the actual bar strength
in a given galaxy. Until very recently, published bar judgments were based
exclusively on blue light images, where internal extinction or star formation
can either mask a bar completely or give the false impression of a bar in a
nonbarred galaxy. Near-infrared camera arrays, which principally trace the old
stellar populations in both normal and barred galaxies, now facilitate a
quantification of bar strength in terms of their gravitational potentials and
force fields. In this paper, we show that the maximum value, Qb, of the ratio
of the tangential force to the mean radial force is a quantitative measure of
the strength of a bar. Qb does not measure bar ellipticity or bar shape, but
rather depends on the actual forcing due to the bar embedded in its disk. We
show that a wide range of true bar strengths characterizes the category ``SB'',
while de Vaucouleurs category ``SAB'' corresponds to a much narrower range of
bar strengths. We present Qb values for 36 galaxies, and we incorporate our bar
classes into a dust-penetrated classification system for spiral galaxies.Comment: Accepted for publication in the Astrophysical Journal (LaTex, 30
pages + 3 figures); Figs. 1 and 3 are in color and are also available at
http://bama.ua.edu/~rbuta/bars
Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 6782
NGC 6782 is an early-type barred spiral galaxy exhibiting a rich and complex
morphology with multiple ring patterns. To provide a physical understanding of
its structure and kinematical properties, two-dimensional hydrodynamical
simulations have been carried out. Numerical calculations reveal that the
striking features in NGC 6782 can be reproduced provided that the gas flow is
governed by the gravitational potential associated with a slowly rotating
strong bar. In particular, the response of the gaseous disk to the bar
potential leads to the excitation of spiral density waves at the inner Lindblad
resonance giving rise to the appearance of a nearly circular nuclear ring with
a pair of dust lanes. For a sufficiently strong bar potential, the inner 4:1
spiral density waves are also excited. The interaction of the higher harmonic
waves with the waves excited at the inner Lindblad resonance and confined by
the outer Lindblad resonance results in the observed diamond-shaped (or pointy
oval) inner ring structure. The overall gas morphology and kinematical features
are both well reproduced by the model provided that the pattern speed of the
bar is km s kpc.Comment: 35 pages, 14 figure
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