8,825 research outputs found
Pseudoclassical model for Weyl particle in 10 dimensions
A pseudoclassical model to describe Weyl particle in 10 dimensions is
proposed. In course of quantization both the massless Dirac equation and the
Weyl condition are reproduced automatically. The construction can be relevant
to Ramond-Neveu-Schwarz strings where the Weyl reduction in the Ramond sector
has to be made by hand.Comment: 5 page
CAN JURISDICTIONAL UNCERTAINTY AND CAPITAL CONTROLS EXPLAIN THE HIGH LEVEL OF REAL INTEREST RATES IN BRAZIL? EVIDENCE FROM PANEL DATA
The phenomenon of high and persistent short-term real interest rates in Brazil has stimulated an extensive literature attempting to explain its causes. Among the various contributions on the topic, one that has received considerable attention is the article by Arida, Bacha, and Lara-Resende (2004) (henceforth, ABL), which argues that risks associated with the jurisdiction and currency inconvertibility are relevant determinants of the level of short-term real interest rates. In the present paper, we formulate a methodology based on ABL's definition of jurisdiction uncertainty, use a set of institutional variables that proxy the degree of jurisdictional uncertainty, build an index of currency inconvertibility based on capital controls and use them to test ABL's conjecture and variants of it. The results are by and large unfavorable not only to ABL's conjecture, but also to variants of their argument. The results further indicate that traditional monetary and fiscal factors are far more relevant to explain the level of short-term real interest rates than the binomial jurisdictional uncertainty/ currency inconvertibility is.
Spatially resolved physical and chemical properties of the planetary nebula NGC 3242
Optical integral-field spectroscopy was used to investigate the planetary
nebula NGC 3242. We analysed the main morphological components of this source,
including its knots, but not the halo. In addition to revealing the properties
ofthe physical and chemical nature of this nebula, we also provided reliable
spatially resolved constraints that can be used for future photoionisation
modelling of the nebula. The latter is ultimately necessary to obtain a fully
self-consistent 3D picture of the physical and chemical properties of the
object. The observations were obtained with the VIMOS instrument attached to
VLT-UT3. Maps and values for specific morphological zones for the detected
emission-lines were obtained and analysed with routines developed by the
authors to derive physical and chemical conditions of the ionised gas in a 2D
fashion. We obtained spatially resolved maps and mean values of the electron
densities, temperatures, and chemical abundances, for specific morphological
structures in NGC 3242. These results show the pixel-to-pixel variations of the
the small- and large-scale structures of the source. These diagnostic maps
provide information free from the biases introduced by traditional single
long-slit observations. In general, our results are consistent with a uniform
abundance distribution for the object, whether we look at abundance maps or
integrated fluxes from specified morphological structures. The results indicate
that special care should be taken with the calibration of the data and that
only data with extremely good signal-to-noise ratio and spectral coverage
should be used to ensure the detection of possible spatial variations.Comment: 11 pages, 8 figures accepted for publication in Astronomy &
Astrophysic
No-horizon theorem for spacetimes with spacelike G1 isometry groups
We consider four-dimensional spacetimes which obey the
Einstein equations , and admit a global spacelike
isometry group. By means of dimensional reduction and local
analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on
which guarantees that cannot contain apparent
horizons. Given any (3+1) spacetime with spacelike translational isometry, the
no-horizon condition can be readily tested without the need for dimensional
reduction. This provides thus a useful and encompassing apparent horizon test
for -symmetric spacetimes. We argue that this adds further evidence
towards the validity of the hoop conjecture, and signals possible violations of
strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra
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