72,168 research outputs found
An Elliptical Galaxy Luminosity Function and Velocity Dispersion Sample of Relevance for Gravitational Lensing Statistics
We have selected 42 elliptical galaxies from the literature and estimated
their velocity dispersions at the effective radius (\sigma_{\re}) and at 0.54
effective radii (\vff). We find by a dynamical analysis that the normalized
velocity dispersion of the dark halo of an elliptical galaxy \vdm is roughly
\sigma_{\re} multiplied by a constant, which is almost independent of the
core radius or the anisotropy parameter of each galaxy. Our sample analysis
suggests that \vdm^{*} lies in the range 178-198 km s. The power law
relation we find between the luminosity and the dark matter velocity dispersion
measured in this way is (L/L^{*}) = (\vdm/\vdm^{*})^\gamma, where is
between 2-3. These results are of interest for strong gravitational lensing
statistics studies.
In order to determine the value of \vdm^{*}, we calculate \mstar in the
same \bt band in which \vdm^{*} has been estimated. We select 131
elliptical galaxies as a complete sample set with apparent magnitudes \bt
between 9.26 and 12.19. We find that the luminosity function is well fitted to
the Schechter form, with parameters \mstar = -19.66 + 5, , and the normalization constant Mpc, with the Hubble constant
\hnot = 100 km s Mpc. This normalization implies that
morphology type E galaxies make up (10.8 1.2) per cent of all galaxies.Comment: 18 pages latex, with ps figs included. accepted by New Astronomy
(revised to incorporate referees comments
Comparisons between Nimbus 6 satellite and rawinsonde soundings for several geographical areas
Good agreement between satellite and weighted (linearly interpolated) rawinsonde temperature and temperature derived parameters was found in most instances with the poorest agreement either near the tropopause region or near the ground. However, satellite moisture data are highly questionable. The smallest discrepancy between satellite and weighted mean rawinsonde temperature and parameters derived from temperature was found over water and the largest discrepancy was found over mountains. Cumulative frequency distributions show that discrepancies between satellite and rawinsonde data can be represented by a normal distribution except for dew point temperature
Using fractals and power laws to predict the location of mineral deposits
Around the world the mineral exploration industry is interested in getting that small increase in probability measure on the earth's surface of where the next large undiscovered deposit might be found. In particular WMC Resources Ltd has operations world wide looking for just that edge in the detection of very large deposits of, for example, gold. Since the pioneering work of Mandelbrot, geologists have been familiar with the concept of fractals and self similarity over a few orders of magnitude for geological features. This includes the location and size of deposits within a particular mineral province. Fractal dimensions have been computed for such provinces and similarities of these aggregated measures between provinces have been noted. This paper explores the possibility of making use of known information to attempt the inverse process. That is, from lesser dimensional measures of a mineral province, for example, fractal dimension or more generally multi-fractal measures, is it possible to infer, even with small increase in probability, where the unknown (preferably large) deposits might be located
Hadronic B Decays to Charmed Baryons
We study exclusive B decays to final states containing a charmed baryon
within the pole model framework. Since the strong coupling for is larger than that for , the two-body charmful decay
has a rate larger than
as the former proceeds via the pole while the latter via the
pole. By the same token, the three-body decay receives less baryon-pole contribution than
. However, because the important charmed-meson
pole diagrams contribute constructively to the former and destructively to the
latter, has a rate slightly larger than
. It is found that one quarter of the rate comes from the resonant contributions. We discuss
the decays and
and stress that they are not color suppressed even though they can only proceed
via an internal W emission.Comment: 25 pages, 6 figure
Collective Quartics and Dangerous Singlets in Little Higgs
Any extension of the standard model that aims to describe TeV-scale physics
without fine-tuning must have a radiatively-stable Higgs potential. In little
Higgs theories, radiative stability is achieved through so-called collective
symmetry breaking. In this letter, we focus on the necessary conditions for a
little Higgs to have a collective Higgs quartic coupling. In one-Higgs doublet
models, a collective quartic requires an electroweak triplet scalar. In
two-Higgs doublet models, a collective quartic requires a triplet or singlet
scalar. As a corollary of this study, we show that some little Higgs theories
have dangerous singlets, a pathology where collective symmetry breaking does
not suppress quadratically-divergent corrections to the Higgs mass.Comment: 4 pages; v2: clarified the existing literature; v3: version to appear
in JHE
Inversion For Permeability From Stoneley Wave Velocity And Attenuation
The in situ permeability of a formation is obtained by the inversion of Stoneley wave
phase velocity and attenuation, which are evaluated by applying the Extended Prony's
method to the array sonic logging data. The Maximum Likelihood inversion is used
together with logarithmic parameterization of the permeabilities. Formation shear
wave velocity is also inverted for. This process is tested on both synthetic and field
data. Logarithmic parameterization contributes to rapid convergence of the algorithm.
Permeabilities estimated from field data are in good agreement with core measurements.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu
Fourth-Order Finite Difference Acoustic Logs In A Transversely Isotropic Formation
In this paper we present a finite difference scheme for seismic wave propagation in
a fluid-filled borehole in a transversely isotropic formation. The first-order hyperbolic
differential equations are approximated explicitly on a staggered grid using an algorithm
that is fourth-order accurate in space and second-order accurate in time. The grid
dispersion and grid anisotropy are analyzed. Grid dispersion and anisotropy are well
suppressed by a grid size of 10 points per wavelength. The stability condition is also
obtained from the dispersion analysis. This finite difference scheme is implemented
on the nCUBE2 parallel computer with a grid decomposition algorithm. The finite
difference synthetic waveforms are compared with those generated using the discrete
wavenumber method. They are in good agreement. The damping layers effectively
absorbed the boundary reflections. Four vertically heterogeneous borehole models: a
horizontal layered formation, a borehole with a radius change, a semi-infinite borehole,
and a semi-infinite borehole with a layer, are studied using the finite difference method. Snapshots from the finite difference results provide pictures of the radiating wavefields.Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu
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