30,100 research outputs found
The CO A-X System for Constraining Cosmological Drift of the Proton-Electron Mass Ratio
The band system of carbon monoxide,
which has been detected in six highly redshifted galaxies (), is
identified as a novel probe method to search for possible variations of the
proton-electron mass ratio () on cosmological time scales. Laboratory
wavelengths of the spectral lines of the A-X (,0) bands for have
been determined at an accuracy of
through VUV Fourier-transform absorption spectroscopy, providing a
comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0)
bands, two-photon Doppler-free laser spectroscopy has been applied at the accuracy level, verifying the absorption data. Sensitivity
coefficients for a varying have been calculated for the CO A-X
bands, so that an operational method results to search for -variation.Comment: 7 pages (main article), 3 figures, includes supplementary materia
Equivalence between different classical treatments of the O(N) nonlinear sigma model and their functional Schrodinger equations
In this work we derive the Hamiltonian formalism of the O(N) non-linear sigma
model in its original version as a second-class constrained field theory and
then as a first-class constrained field theory. We treat the model as a
second-class constrained field theory by two different methods: the
unconstrained and the Dirac second-class formalisms. We show that the
Hamiltonians for all these versions of the model are equivalent. Then, for a
particular factor-ordering choice, we write the functional Schrodinger equation
for each derived Hamiltonian. We show that they are all identical which
justifies our factor-ordering choice and opens the way for a future
quantization of the model via the functional Schrodinger representation.Comment: Revtex version, 17 pages, substantial change
Novel techniques in VUV high-resolution spectroscopy
Novel VUV sources and techniques for VUV spectroscopy are reviewed.
Laser-based VUV sources have been developed via non-linear upconversion of
laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs)
domain, and are applied in high-resolution gas phase spectroscopic studies.
While the ns and ps pulsed laser sources, at Fourier-transform limited
bandwidths, are used in wavelength scanning spectroscopy, the fs laser source
is used in a two-pulse time delayed mode. In addition a Fourier-transform
spectrometer for high resolution gas-phase spectroscopic studies in the VUV is
described, exhibiting the multiplex advantage to measure many resonances
simultaneously.Comment: 17 Pages, 8 figures, Conference proceedings of the VUV/X-ray 2013 at
Hefei, Chin
Off-axis retrieval of orbital angular momentum of light stored in cold atoms
We report on the storage of orbital angu- lar momentum (OAM) of light of a
Laguerre-Gaussian mode in an ensemble of cold cesium atoms and its re- trieval
along an axis different from the incident light beam. We employed a
time-delayed four-wave mixing configuration to demonstrate that at small angle
(2o), after storage, the retrieved beam carries the same OAM as the one encoded
in the input beam. A calculation based on mode decomposition of the retrieved
beam over the Laguerre-Gaussian basis is in agreement with the experimental
observations done at small angle values. However, the calculation shows that
the OAM retrieving would get lost at larger angles, reducing the fidelity of
such storing-retrieving process. In addition, we have also observed that by
applying an external magnetic field to the atomic ensemble the retrieved OAM
presents Larmor oscillations, demonstrating the possibility of its manipulation
and off-axis retrieval.Comment: 9 pages, 4 figure
How hole defects modify vortex dynamics in ferromagnetic nanodisks
Defects introduced in ferromagnetic nanodisks may deeply affect the structure
and dynamics of stable vortex-like magnetization. Here, analytical techniques
are used for studying, among other dynamical aspects, how a small cylindrical
cavity modify the oscillatory modes of the vortex. For instance, we have
realized that if the vortex is nucleated out from the hole its gyrotropic
frequencies are shifted below. Modifications become even more pronounced when
the vortex core is partially or completely captured by the hole. In these
cases, the gyrovector can be partially or completely suppressed, so that the
associated frequencies increase considerably, say, from some times to several
powers. Possible relevance of our results for understanding other aspects of
vortex dynamics in the presence of cavities and/or structural defects are also
discussed.Comment: 9 pages, 4 page
Classificacao de sitio para povoamento de Pinus taeda no sul do Brasil.
Edição dos Anais do Congresso Florestal Brasileiro, 6., 1990, Campos do Jordão
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