345 research outputs found
Topological Defects from First Order Gauge Theory Phase Transitions
We investigate the mechanism by which topological defects form in first order
phase transitions with a charged order parameter. We show how thick
superconductor vortices and heavy cosmic strings form by trapping of magnetic
flux. In an external magnetic field, intermediate objects such as strips and
membranes of magnetic flux and chains of single winding defects are produced.
At non-zero temperature, a variety of spontaneous defects of different winding
numbers arise. In cosmology, our results mean that the magnetic flux thermal
fluctuations get trapped in a primordial multi-tension string network. The
mechanism may also apply to the production of cosmic-like strings in brane
collisions. In a thin type-I superconductor film, flux strips are found to be
meta-stable while thick vortices are stable up to some critical value of the
winding number which increases with the thickness of the film. In addition, a
non-dissipative Josephson-like current is obtained across the strips of
quantized magnetic flux.Comment: Corrections made on sections 4,5. Higher quality figures in published
versio
Electromagnetic Vacuum of Complex Media: Dipole Emission vs. Light Propagation, Vacuum Energy, and Local Field Factors
We offer a unified approach to several phenomena related to the
electromagnetic vacuum of a complex medium made of point electric dipoles. To
this aim, we apply the linear response theory to the computation of the
polarization field propagator and study the spectrum of vacuum fluctuations.
The physical distinction among the local density of states which enter the
spectra of light propagation, total dipole emission, coherent emission, total
vacuum energy and Schwinger-bulk energy is made clear. Analytical expressions
for the spectrum of dipole emission and for the vacuum energy are derived.
Their respective relations with the spectrum of external light and with the
Schwinger-bulk energy are found. The light spectrum and the Schwinger-bulk
energy are determined by the Dyson propagator. The emission spectrum and the
total vacuum energy are determined by the polarization propagator. An exact
relationship of proportionality between both propagators is found in terms of
local field factors. A study of the nature of stimulated emission from a single
dipole is carried out. Regarding coherent emission, it contains two components.
A direct one which is transferred radiatively and directly from the emitter
into the medium and whose spectrum is that of external light. And an indirect
one which is radiated by induced dipoles. The induction is mediated by one (and
only one) local field factor. Regarding the vacuum energy, we find that in
addition to the Schwinger-bulk energy the vacuum energy of an effective medium
contains local field contributions proportional to the resonant frequency and
to the spectral line-width.Comment: Typos fixed, journal ref. adde
Traveling wave enantioselective electron paramagnetic resonance
Producción CientíficaWe propose a novel method for enantioselective electron paramagnetic resonance (EPR)
spectroscopy based on magneto-chiral anisotropy. We elaborate a theoretical model to estimate the
strength of this effect and propose a dedicated interferometer setup for its experimental observation.Agence Nationale de la Recherche (SECRETS, (ANR PRC 20-CE06-0023-01)Laboratory of Excellence NanoX (ANR-17-EURE-0009
Thermal Casimir effect with general boundary conditions
In this paper we study the system of a scalar quantum field confined between
two plane, isotropic, and homogeneous parallel plates at thermal equilibrium.
We represent the plates by the most general lossless and frequency-independent
boundary conditions that satisfy the conditions of isotropy and homogeneity and
are compatible with the unitarity of the quantum field theory. Under these
conditions we compute the thermal correction to the quantum vacuum energy as a
function of the temperature and the parameters encoding the boundary condition.
The latter enables us to obtain similar results for the pressure between plates
and the quantum thermal correction to the entropy. We find out that our system
is thermodynamically stable for any boundary conditions, and we identify a
critical temperature below which certain boundary conditions yield attractive,
repulsive, and null Casimir forces.Comment: 17 pages, 14 figures. Substantial changes along the text have been
introduce
Determinación de mecanismos de deslizamientosa en áreas urbanizadas de la Sierra de las Apretaderas, término de Alcuzcuz, Benahavís, Málaga
La naturaleza intrínseca del material mantiene una estrecha relación con el tipo de inestabilidad. El trabajo recoge la experiencia en la determinación de mecanismo de deslizamientos en el área de la Sierra de Las Apretaderas, término de Alcuzcuz, en Benahavís, Málaga. La intensa urbanización de amplias áreas serranas conlleva la transformación del medio a través de la construcción de infraestructuras de comunicación y extensas áreas residenciales y la interacción de dichas construcciones con el medio provoca a menudo el desencadenamiento de siniestros relacionados con los deslizamientos de ladera en ocasiones poco sospechosos. El trabajo que se presenta recoge la experiencia de un siniestro acaecido bajo estas circunstancias y provocando numerosos daños materiales en edificaciones de lujo e infraestructuras anejas
The EMPIRE Survey: Systematic Variations in the Dense Gas Fraction and Star Formation Efficiency from Full-Disk Mapping of M51
We present the first results from the EMPIRE survey, an IRAM large program
that is mapping tracers of high density molecular gas across the disks of nine
nearby star-forming galaxies. Here, we present new maps of the 3-mm transitions
of HCN, HCO+, and HNC across the whole disk of our pilot target, M51. As
expected, dense gas correlates with tracers of recent star formation, filling
the "luminosity gap" between Galactic cores and whole galaxies. In detail, we
show that both the fraction of gas that is dense, f_dense traced by HCN/CO, and
the rate at which dense gas forms stars, SFE_dense traced by IR/HCN, depend on
environment in the galaxy. The sense of the dependence is that high surface
density, high molecular gas fraction regions of the galaxy show high dense gas
fractions and low dense gas star formation efficiencies. This agrees with
recent results for individual pointings by Usero et al. 2015 but using unbiased
whole-galaxy maps. It also agrees qualitatively with the behavior observed
contrasting our own Solar Neighborhood with the central regions of the Milky
Way. The sense of the trends can be explained if the dense gas fraction tracks
interstellar pressure but star formation occurs only in regions of high density
contrast.Comment: 7 pages, 5 figures, ApJL accepte
Defect formation in superconducting rings: external fields and finite-size effects
Consistent with the predictions of Kibble and Zurek, scaling behaviour has
been seen in the production of fluxoids during temperature quenches of
superconducting rings. However, deviations from the canonical behaviour arise
because of finite-size effects and stray external fields.
Technical developments, including laser heating and the use of long Josephson
tunnel junctions, have improved the quality of data that can be obtained. With
new experiments in mind we perform large-scale 3D simulations of quenches of
small, thin rings of various geometries with fully dynamical electromagnetic
fields, at nonzero externally applied magnetic flux. We find that the outcomes
are, in practice, indistinguishable from those of much simpler Gaussian
analytical approximations in which the rings are treated as one-dimensional
systems and the magnetic field fluctuation-free.Comment: 10 pages, 3 figures, presentation at QFS2012, to appear in JLT
Asthma patient satisfaction with different dry powder inhalers
Altres ajuts: The study was supported by Orion Pharma, which also funded the writing.Background: The preferences and opinions of patients are important when choosing the optimal inhaler device for asthma management. We compared patient satisfaction of three dry powder inhalers in patients with moderate to severe asthma. Methods: We selected a group of patients treated with Easyhaler (n = 164) and a second group of patients treated with Turbuhaler (n = 100) or Diskus (Accuhaler ) (n = 64) from the register of an observational, multicenter study. Data of patients were paired according to age, gender, and asthma severity. Patient satisfaction with the inhaler type was assessed with the specific 'Feeling of Satisfaction with Inhaler' (FSI-10) questionnaire. Results: Specific satisfaction with inhaler was statistically significantly higher with Easyhaler , as well as the percentage of patients with high satisfaction with inhaler. (FSI-10 score ≥43). Scores for Easyhaler were also statistically significantly better for individual FSI-10 items such as learning how to use, inhaler preparation, inhaler use, weight and size, and portability. There were no significant differences in asthma control (ACT, Mini-AQLQ) and adherence (TAI global score). Conclusions: Specific satisfaction with inhaler was higher with Easyhaler in a homogeneous population of patients with moderate to severe asthma. However, the relationship between satisfaction with the inhaler and adherence and asthma control deserves more investigation
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