3,047 research outputs found
Random Surfaces that Suppress Single Scattering
We present a method for generating numerically a one-dimensional random
surface, defined by the equation x_3 = \zx, that suppresses single-scattering
processes in the scattering of light from it within a specified range of
scattering angles. Rigorous numerical calculations of the scattering of light
from surfaces generated by this approach show that the single-scattering
contribution to the mean scattered intensity is indeed suppressed within that
range of angles.Comment: 3 pagers (Latex), 3 figure
Design of one-dimensional Lambertian diffusers of light
We describe a method for designing a one-dimensional random surface that acts
as a Lambertian diffuser. The method is tested by means of rigorous computer
simulations and is shown to yield the desired scattering pattern.Comment: 6 pages, 2 figure
Approaching Space Time Through Velocity in Doubly Special Relativity
We discuss the definition of velocity as dE/dp, where E,p are the energy and
momentum of a particle, in Doubly Special Relativity (DSR). If this definition
matches dx/dt appropriate for the space-time sector, then space-time can in
principle be built consistently with the existence of an invariant length
scale. We show that, within different possible velocity definitions, a
space-time compatible with momentum-space DSR principles can not be derived.Comment: 11 pages, no figures, minor changes, references added, final version
to appear in PR
The pseudobulge of NGC 1292
The photometric and kinematic properties of Sb NGC 1292 suggest it hosts a
pseudobulge. The properties of the stellar population of such a pseudobulge are
consistent with a slow buildup within a scenario of secular evolution.Comment: 2 pages, 1 figure to appear in the proceedings of "Formation and
Evolution of Galaxy Disks", Rome, October 2007, Eds. J. Funes and E. M.
Corsin
Azimuthal Correlation in Lepton-Hadron Scattering via Charged Weak-Current Processes
We consider the azimuthal correlation of the final-state particles in charged
weak-current processes. This correlation provides a test of perturbative
quantum chromodynamics. The azimuthal asymmetry is large in the semi-inclusive
processes in which we identify a final-state hadron, say, a charged pion
compared to that in the inclusive processes in which we do not identify
final-state particles and use only the calorimetric information. In
semi-inclusive processes the azimuthal asymmetry is more conspicuous when the
incident lepton is an antineutrino or a positron than when the incident lepton
is a neutrino or an electron. We analyze all the possible charged weak-current
processes and study the quantitative aspects of each process. We also compare
this result to the ep scattering with a photon exchange.Comment: 25 pages, 2 Postscript figures, uses RevTeX, fixes.st
Dependence of the Frequency of the Kilohertz Quasi-Periodic Oscillations on X-ray Count Rate and Colors in 4U 1608-52
We present new results based on observations carried out with the Rossi X-ray
Timing Explorer during the decay of an outburst of the low-mass X-ray binary
(LMXB) and atoll source 4U 1608-52. Our results appear to resolve, at least in
4U 1608-52, one of the long-standing issues about the phenomenology of the
kilohertz quasi-periodic oscillations (kHz QPOs), namely, the lack of a unique
relation between the frequency of the kHz QPOs and the X-ray flux. We show that
despite its complex dependence on the X-ray flux, the frequency of the kHz QPOs
is monotonically related to the position of the source in the color-color
diagram. Our findings strengthen the idea that, as in the case of Z sources, in
the atoll sources the X-ray flux is not a good indicator of , and that
the observed changes in the frequency of the kHz QPOs in LMXBs are driven by
changes in . These results raise some concern about the recently
reported detection of the orbital frequency at the innermost stable orbit in 4U
1820-30.Comment: Accepted for publication in The Astrophysical Journal Letters. Uses
AAS LaTex v4.0 (5 pages plus 4 postscript figures
Combinatorial approach to generalized Bell and Stirling numbers and boson normal ordering problem
We consider the numbers arising in the problem of normal ordering of
expressions in canonical boson creation and annihilation operators. We treat a
general form of a boson string which is shown to be associated with
generalizations of Stirling and Bell numbers. The recurrence relations and
closed-form expressions (Dobiski-type formulas) are obtained for these
quantities by both algebraic and combinatorial methods. By extensive use of
methods of combinatorial analysis we prove the equivalence of the
aforementioned problem to the enumeration of special families of graphs. This
link provides a combinatorial interpretation of the numbers arising in this
normal ordering problem.Comment: 10 pages, 5 figure
Modified Special Relativity on a fluctuating spacetime
It was recently proposed that deformations of the relativistic symmetry, as
those considered in Deformed Special Relativity (DSR), can be seen as the
outcome of a measurement theory in the presence of non-negligible (albeit
small) quantum gravitational fluctuations [1,2]. In this paper we explicitly
consider the case of a spacetime described by a flat metric endowed with
stochastic fluctuations and, for a free particle, we show that DSR-like
nonlinear relations between the spaces of the measured and classical momenta,
can result from the average of the stochastic fluctuations over a scale set be
the de Broglie wavelength of the particle. As illustrative examples we consider
explicitly the averaging procedure for some simple stochastic processes and
discuss the physical implications of our results.Comment: 7 pages, no figure
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