4,046 research outputs found
Isotope shifts and hyperfine structure of the laser cooling Fe I 358-nm line
We report on the measurement of the isotope shifts of the Fe~I line at 358~nm between all four
stable isotopes Fe, Fe, Fe and Fe, as well
as the hyperfine structure of that line for Fe, the only stable
isotope having a nonzero nuclear spin. This line is of primary importance for
laser cooling applications. In addition, an experimental value of the field and
specific mass shift coefficients of the transition is reported as well as the
hyperfine structure magnetic dipole coupling constant of the transition
excited state in Fe, namely
MHz. The measurements were carried out by means of laser-induced fluorescence
spectroscopy performed on an isotope-enriched iron atomic beam. All measured
frequency shifts are reported with uncertainties below the third percent level.Comment: 5 pages, 5 figure
La no-opresión y los estudios de paz
La paz es algo más que la mera ausencia de violencia. Construir
una paz verdadera necesita del entendimiento profundo de los
instintos humanos, y de las formas en que éstos nos pueden
ayudar a crear, en lugar de determinarnos hacia la destrucción.
Nuestra propia naturaleza y búsqueda de la libertad nos pueden
llevar a la guerra o a la paz. En lugar de centrarnos únicamente
en evitar la violencia, debemos empezar a entender sus causas:
la opresión. Así, descubrimos un nuevo concepto, una capacidad
inherente al ser humano: la no-opresión, o la facultad de
conseguir la libertad con los demás
Electroweak Baryogenesis with dimension-6 Higgs interactions
We present the computation of the baryon asymmetry in the SM amplified by
dimension-6 Higgs interactions using the WKB approximation. Analyzing the
one-loop potential it turns out that the phase transition is strongly first
order in a wide range of the parameters. It is ensured not to wash out the net
baryon number gained previously even for Higgs masses up to at least 170 GeV.
In addition dimension-6 operators induce new sources of CP violation. Novel
source terms which enhance the generated baryon asymmetry emerge in the
transport equations. This model predicts a baryon to entropy ratio close to the
observed value for a large part of the parameter space.Comment: 10 pages, 4 figures, Talk given at the 8th International Moscow
School of Physic
The Euler-Heisenberg Lagrangian beyond one loop
We review what is presently known about higher loop corrections to the
Euler-Heisenberg Lagrangian and its Scalar QED analogue. The use of those
corrections as a tool for the study of the properties of the QED perturbation
series is outlined. As a further step in a long-term effort to prove or
disprove the convergence of the N photon amplitudes in the quenched
approximation, we present a parameter integral representation of the three-loop
Euler-Heisenberg Lagrangian in 1+1 dimensional QED, obtained in the worldline
formalism.Comment: 11 pages, 2 figures, talk given by Christian Schubert at QFEXT11,
Benasque, Spain, Sept. 18-24, 2011, to appear in the conference proceeding
Generating TV summaries for CE-devices
Automatically generated summaries of TV content are indispensable for content selection and navigation in CE-devices. We show two types of summaries: Short video trailers and visual overviews consisting of representative frames. The demo does not only show the feasibility of the proposed algorithms, but also shows how different types of generated summaries can be used in future CE-devices
Quality Assurance System to monitor the teaching and learning process at the University of Aveiro (Portugal)
At the University of Aveiro (UA), in Portugal, institutional initiatives are being undertaken so that high levels of quality teaching and learning are achieved. This paper presents (a) the design of an evaluation model for quality assurance of teaching and learning and (b) the results of its application in a pilot study that ran in 2008/09 at the Departments of Electronics and Telecommunications, and Physics, of the UA. The Quality Assurance System (QAS) to monitor the process of teaching and learning at the UA emerges as extremely important, not only to regulate the teaching and learning process, following the quality assurance orientations at a national and international level, but also to reflect and share teaching practices that enhance the whole academic experience, both from students, teachers, and researchers‟ perspectives. The authors explore the design of the model and some findings of the pilot study, more specifically the identification of problematic and good practice situations identified by the students‟ survey and reports
Isotope shifts and hyperfine structure of the Fe I 372 nm resonance line
We report measurements of the isotope shifts of the Fe I resonance line at 372 nm between all four stable
isotopes Fe, Fe, Fe, and Fe, as well as the
complete hyperfine structure of that line for Fe, the only stable
isotope having a non-zero nuclear spin. The field and specific mass shift
coefficients of the transition have been derived from the data, as well as the
experimental value for the hyperfine structure magnetic dipole coupling
constant of the excited state of the transition in Fe: MHz. The measurements were done by means of Doppler-free
laser saturated-absorption spectroscopy in a Fe-Ar hollow cathode using both
natural and enriched iron samples. The measured isotope shifts and hyperfine
constants are reported with uncertainties at the percent level.Comment: 5 pages, 5 figure
Particle Currents in a Space-Time dependent and CP-violating Higgs Background: a Field Theory Approach
Motivated by cosmological applications like electroweak baryogenesis, we
develop a field theoretic approach to the computation of particle currents on a
space-time dependent and CP-violating Higgs background. We consider the
Standard Model model with two Higgs doublets and CP violation in the scalar
sector, and compute both fermionic and Higgs currents by means of an expansion
in the background fields. We discuss the gauge dependence of the results and
the renormalization of the current operators, showing that in the limit of
local equilibrium, no extra renormalization conditions are needed in order to
specify the system completely.Comment: 21 pages, LaTeX file, uses epsf.sty. 4 figures available as a
compressed .ep
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