5,330 research outputs found
Gauge invariance, radiative interferences and properties of vector mesons
We state the implications on the properties of vector mesons due to gauge
invariance. In particular, we find that polarized vector mesons exhibit a
property in the radiation distribution of order in the photon
energy, namely it is null when the gyromagnetic ratio becomes . Therefore,
the generalization of the Burnett-Kroll theorem for polarized vector-meson
states is held only if . In addition, radiative interferences between the
electric charge and any gauge invariant term is found to be parametrized by a
common global factor which can be used to extract information of the involved
states by a proper choice of the kinematical region, where they could be
relevant.Comment: 5 pages, 1 figure. To appear in the Proceedings of the IX Mexican
Workshop on Particles and Fields, Colima Mexico. Uses RevTex
Integral Field Spectroscopy of HH 262: The Spectral Atlas
HH 262 is a group of emitting knots displaying an "hour-glass" morphology in
the Halpha and [SII] lines, located 3.5' to the northeast of the young stellar
object L1551-IRS5, in Taurus. We present new results of the kinematics and
physical conditions of HH 262 based on Integral Field Spectroscopy covering a
field of 1.5'x3', which includes all the bright knots in HH 262. These data
show complex kinematics and significant variations in physical conditions over
the mapped region of HH 262 on a spatial scale of <3". A new result derived
from the IFS data is the weakness of the [NII] emission (below detection limit
in most of the mapped region of HH 262), including the brightest central knots.
Our data reinforce the association of HH 262 with the redshifted lobe of the
evolved molecular outflow L1551-IRS5. The interaction of this outflow with a
younger one, powered by L1551 NE, around the position of HH 262 could give rise
to the complex morphology and kinematics of HH 262.Comment: Accepted for publication in MNRA
Deep Near-Infrared Surface Photometry and Properties of Local Volume Dwarf Irregular Galaxies
We present deep H-band surface photometry and analysis of 40 Local Volume
galaxies, a sample primarily composed of dwarf irregulars in the Cen A group,
obtained using the IRIS2 detector at the 3.9m Anglo-Australian Telescope. We
probe to a surface brightness of ~25 mag arcsec, reaching a 40 times
lower stellar density than the Two Micron All Sky Survey (2MASS). Employing
extremely careful and rigorous cleaning techniques to remove contaminating
sources, we perform surface photometry on 33 detected galaxies deriving the
observed total magnitude, effective surface brightness and best fitting
S\'ersic parameters. We make image quality and surface photometry comparisons
to 2MASS and VISTA Hemispheric Survey (VHS) demonstrating that deep targeted
surveys are still the most reliable means of obtaining accurate surface
photometry. We investigate the B-H colours with respect to mass for Local
Volume galaxies, finding that the colours of dwarf irregulars are significantly
varied, eliminating the possibility of using optical-NIR colour transformations
to facilitate comparison to the more widely available optical data sets. The
structure-luminosity relationships are investigated for our `clean' sample of
dwarf irregulars. We demonstrate that a significant fraction of the Local
Volume dwarf irregular population have underlying structural properties similar
to both Local Volume and Virgo Cluster dwarf ellipticals. Linear regressions to
structure-luminosity relationships for the Local Volume galaxies and Virgo
Cluster dwarf ellipticals show significant differences in both slope and
scatter around the established trend lines, suggesting that environment might
regulate the structural scaling relationships of dwarf galaxies in comparison
to their more isolated counterparts.Comment: 27 pages, 14 figures, 5 table
The complex structure of HH 110 as revealed from Integral Field Spectroscopy
HH 110 is a rather peculiar Herbig-Haro object in Orion that originates due
to the deflection of another jet (HH 270) by a dense molecular clump, instead
of being directly ejected from a young stellar object. Here we present new
results on the kinematics and physical conditions of HH 110 based on Integral
Field Spectroscopy. The 3D spectral data cover the whole outflow extent (~4.5
arcmin, ~0.6 pc at a distance of 460 pc) in the spectral range 6500-7000 \AA.
We built emission-line intensity maps of H, [NII] and [SII] and of
their radial velocity channels. Furthermore, we analysed the spatial
distribution of the excitation and electron density from [NII]/H,
[SII]/H, and [SII] 6716/6731 integrated line-ratio maps, as well as
their behaviour as a function of velocity, from line-ratio channel maps. Our
results fully reproduce the morphology and kinematics obtained from previous
imaging and long-slit data. In addition, the IFS data revealed, for the first
time, the complex spatial distribution of the physical conditions (excitation
and density) in the whole jet, and their behaviour as a function of the
kinematics. The results here derived give further support to the more recent
model simulations that involve deflection of a pulsed jet propagating in an
inhomogeneous ambient medium. The IFS data give richer information than that
provided by current model simulations or laboratory jet experiments. Hence,
they could provide valuable clues to constrain the space parameters in future
theoretical works.Comment: 12 pages, 15 figures Accepted in MNRA
Enseñanza de ELE a través de un sistema informático de análisis textual disponible en Internet
La creciente importancia de los corpus de textos digitalizados para la enseñanza de lenguas ha sido puesta de manifiesto por distintos autores a lo largo de los últimos años. Tribble y Jones (1990), Flowerdew (1993), Botley et al. (1996) y Sánchez (2000), entre otros, han subrayado la utilidad didáctica de los corpus textuales y de los sistemas informáticos que permiten consultarlos
Kramers polarization in strongly correlated carbon nanotube quantum dots
Ferromagnetic contacts put in proximity with carbon nanotubes induce spin and
orbital polarizations. These polarizations affect dramatically the Kondo
correlations occurring in quantum dots formed in a carbon nanotube, inducing
effective fields in both spin and orbital sectors. As a consequence, the carbon
nanotube quantum dot spectral density shows a four-fold split SU(4) Kondo
resonance. Furthermore, the presence of spin-orbit interactions leads to the
occurrence of an additional polarization among time-reversal electronic states
(polarization in the time-reversal symmetry or Kramers sector). Here, we
estimate the magnitude for the Kramer polarization in realistic carbon nanotube
samples and find that its contribution is comparable to the spin and orbital
polarizations. The Kramers polarization generates a new type of effective field
that affects only the time-reversal electronic states. We report new splittings
of the Kondo resonance in the dot spectral density which can be understood only
if Kramers polarization is taken into account. Importantly, we predict that the
existence of Kramers polarization can be experimentally detected by performing
nonlinear differential conductance measurements. We also find that, due to the
high symmetry required to build SU(4) Kondo correlations, its restoration by
applying an external field is not possible in contrast to the compensated SU(2)
Kondo state observed in conventional quantum dots.Comment: 8 pages, 4figure
Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 m with PlanetCam-UPV/EHU
We provide measurements of the absolute reflectivity of Jupiter and Saturn
along their central meridians in filters covering a wide range of visible and
near-infrared wavelengths (from 0.38 to 1.7 m) that are not often
presented in the literature. We also give measurements of the geometric albedo
of both planets and discuss the limb-darkening behavior and temporal
variability of their reflectivity values for a period of four years
(2012-2016). This work is based on observations with the PlanetCam-UPV/EHU
instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory
(Spain). The instrument simultaneously observes in two channels: visible (VIS;
0.38-1.0 m) and short-wave infrared (SWIR; 1.0--1.7 m). We obtained
high-resolution observations via the lucky-imaging method. We show that our
calibration is consistent with previous independent determinations of
reflectivity values of these planets and, for future reference, provide new
data extended in the wavelength range and in the time. Our results have an
uncertainty in absolute calibration of 10--20\%. We show that under the
hypothesis of constant geometric albedo, we are able to detect absolute
reflectivity changes related to planetary temporal evolution of about 5-10\%.Comment: 13 pages, 18 figures, (in press
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