648 research outputs found
Gauge and Lorentz transformation placed on the same foundation
In this note we show that a "dynamical" interaction for arbitrary spin can be
constructed in a straightforward way if gauge and Lorentz transformations are
placed on the same foundation. As Lorentz transformations act on space-time
coordinates, gauge transformations are applied to the gauge field. Placing
these two transformations on the same ground means that all quantized field
like spin-1/2 and spin-3/2 spinors are functions not only of the coordinates
but also of the gauge field components. This change of perspective solves a
couple of problems occuring for higher spin fields like the loss of causality,
bad high-energy properties and the deviation of the gyromagnetic ratio from its
constant value g=2 for any spin, as caused by applying the minimal coupling.
Starting with a "dynamical" interaction, a non-minimal coupling can be derived
which is consistent with causality, the expectation for the gyromagnetic ratio,
and well-behaved for high energies. As a consequence, on this stage the
(elektromagnetic) gauge field has to be considered as classical field.
Therefore, standard quantum field theory cannot be applied. Despite this
inconvenience, such a common ground is consistent with an old dream of
physicists almost a century ago. Our approach, therefore, indicates a
straightforward way to realize this dream.Comment: 12 pages, no figures, published version. arXiv admin note:
substantial text overlap with arXiv:0908.376
Lymph Nodes of the Head, Neck and Shoulder Region of Swine
A review of various textbooks and other publications concerned with the lymph system, clearly indicated a great variety of terminology used to group the lymph nodes of swine in region of the head, neck and shoulder. Probably the statement made by Baum (1912) was true that, the grouping of the lymph nodes is basically very uncertain and will always depend upon the individual viewpoint of the author. Nevertheless, an attempt will be made to clarify the controversies found in literature about the descriptive information and terms used
Interactions of the magnetospheres of stars and close-in giant planets
Since the first discovery of an extrasolar planetary system more than a
decade ago, hundreds more have been discovered. Surprisingly, many of these
systems harbor Jupiter-class gas giants located close to the central star, at
distances of 0.1 AU or less. Observations of chromospheric 'hot spots' that
rotate in phase with the planetary orbit, and elevated stellar X-ray
luminosities,suggest that these close-in planets significantly affect the
structure of the outer atmosphere of the star through interactions between the
stellar magnetic field and the planetary magnetosphere. Here we carry out the
first detailed three-dimensional MagnetoHydroHynamics (MHD) simulation
containing the two magnetic bodies and explore the consequences of such
interactions on the steady-state coronal structure. The simulations reproduce
the observable features of 1) increase in the total X-ray luminosity, 2)
appearance of coronal hot spots, and 3) phase shift of these spots with respect
to the direction of the planet. The proximate cause of these is an increase in
the density of coronal plasma in the direction of the planet, which prevents
the corona from expanding and leaking away this plasma via a stellar wind. The
simulations produce significant low temperature heating. By including dynamical
effects, such as the planetary orbital motion, the simulation should better
reproduce the observed coronal heating
The Lymph Nodes and the Lymph Vessels of the Abdominal Wall, Pelvic Wall and the Pelvic Limb of Swine
This article is the continuation of previously published papers regarding the lymph nodes of swine and their drainage areas. The details of the material and methods have been described and discussed previously
The Lymph Vessels of the Thoracic Limb of Swine
This article is the continuation of previously published papers regarding the lymph nodes of swine and their afferent and efferent lymph vessels (drainage areas). The details of the materials and methods have been described and discussed previously
Flux- and volume-limited groups/clusters for the SDSS galaxies: catalogues and mass estimation
We provide flux-limited and volume-limited galaxy group and cluster
catalogues, based on the spectroscopic sample of the SDSS data release 10
galaxies. We used a modified friends-of-friends (FoF) method with a variable
linking length in the transverse and radial directions to identify as many
realistic groups as possible. The flux-limited catalogue incorporates galaxies
down to m_r = 17.77 mag. It includes 588193 galaxies and 82458 groups. The
volume-limited catalogues are complete for absolute magnitudes down to M_r =
-18.0, -18.5, -19.0, -19.5, -20.0, -20.5, and -21.0; the completeness is
achieved within different spatial volumes, respectively. Our analysis shows
that flux-limited and volume-limited group samples are well compatible to each
other, especially for the larger groups/clusters. Dynamical mass estimates,
based on radial velocity dispersions and group extent in the sky, are added to
the extracted groups. The catalogues can be accessed via http://cosmodb.to.ee
and the Strasbourg Astronomical Data Center (CDS).Comment: 16 pages, 18 figures, 2 tables, accepted for publication in A&
Semiclassical theory of a quantum pump
In a quantum charge pump, the periodic variation of two parameters that
affect the phase of the electronic wavefunction causes the flow of a direct
current. The operating mechanism of a quantum pump is based on quantum
interference, the phases of interfering amplitudes being modulated by the
external parameters. In a ballistic quantum dot, there is a minimum time before
which quantum interference can not occur: the Ehrenfest time. Here we calculate
the current pumped through a ballistic quantum dot when the Ehrenfest time is
comparable to the mean dwell time. Remarkably, we find that the pumped current
has a component that is not suppressed if the Ehrenfest time is much larger
than the mean dwell time.Comment: 14 pages, 8 figures. Revised version, minor change
Wavelet analysis of the formation of the cosmic web
According to the modern cosmological paradigm galaxies and galaxy systems
form from tiny density perturbations generated during the very early phase of
the evolution of the Universe. Using numerical simulations we study the
evolution of phases of density perturbations of different scales to understand
the formation and evolution of the cosmic web. We apply the wavelet analysis to
follow the evolution of high-density regions (clusters and superclusters) of
the cosmic web. We show that the positions of maxima and minima of density
waves (their spatial phases) almost do not change during the evolution of the
structure. Positions of extrema of density perturbations are the more stable,
the larger is the wavelength of perturbations. Combining observational and
simulation data we conclude that the skeleton of the cosmic web was present
already in an early stage of structure evolution.Comment: 12 pages, 8 figures, revised versio
- …