4,252 research outputs found
Dark Energy and the Statistical Study of the Observed Image Separations of the Multiply Imaged Systems in the CLASS Statistical Sample
The present day observations favour a universe which is flat, accelerated and
composed of matter (baryonic + dark) and of a negative
pressure component, usually referred to as dark energy or quintessence. The
Cosmic Lens All Sky Survey (CLASS), the largest radio-selected galactic mass
scale gravitational lens search project to date, has resulted in the largest
sample suitable for statistical analyses. In the work presented here, we
exploit observed image separations of the multiply imaged lensed radio sources
in the sample. We use two different tests: (1) image separation distribution
function of the lensed radio sources and (2)
{\dtheta}_{\mathrm{pred}} vs {\dtheta}_{\mathrm{obs}} as observational
tools to constrain the cosmological parameters and \Om. The results are
in concordance with the bounds imposed by other cosmological tests.Comment: 20 pages latex; Modified " Results and Discussion " section, new
references adde
Four Zero Texture Fermion Mass Matrices in SO(10) GUT
We attempt the integration of the phenomenologically successful four zero
texture of fermion mass matrices with the renormalizable SO(10) GUT. The
resulting scenario is found to be highly predictive. Firstly, we examine the
phenomenological implications of a class of the lepton mass matrices with
parallel texture structures and obtain interesting constraints on the
parameters of the charged lepton and the neutrino mass matrices. We combine
these phenomenological constraints with the constraints obtained from SO(10)
GUT to reduce the number of the free parameters and to further constrain the
allowed ranges of the free parameters. The solar/atmospheric mixing angles
obtained in this analysis are in fairly good agreement with the data.Comment: 14 pages, 3 figures, 1 tabl
Replicating Nanostructures on Silicon by Low Energy Ion Beams
We report on a nanoscale patterning method on Si substrates using
self-assembled metal islands and low-energy ion-beam irradiation. The Si
nanostructures produced on the Si substrate have a one-to-one correspondence
with the self-assembled metal (Ag, Au, Pt) nanoislands initially grown on the
substrate. The surface morphology and the structure of the irradiated surface
were studied by high-resolution transmission electron microscopy (HRTEM). TEM
images of ion-beam irradiated samples show the formation of sawtooth-like
structures on Si. Removing metal islands and the ion-beam induced amorphous Si
by etching, we obtain a crystalline nanostructure of Si. The smallest
structures emit red light when exposed to a UV light. The size of the
nanostructures on Si is governed by the size of the self-assembled metal
nanoparticles grown on the substrate for this replica nanopatterning. The
method can easily be extended for tuning the size of the Si nanostructures by
the proper choice of the metal nanoparticles and the ion energy in
ion-irradiation. It is suggested that off-normal irradiation can also be used
for tuning the size of the nanostructures.Comment: 12 pages, 7 figures, regular paper submitted to Nanotechnolog
Determining the CP properties of the Higgs boson
The search and the probe of the fundamental properties of Higgs boson(s) and,
in particular, the determination of their charge conjugation and parity (CP)
quantum numbers, is one of the main tasks of future high-energy colliders. We
demonstrate that the CP properties of a Standard Model-like Higgs particle can
be unambiguously assessed by measuring just the total cross section and the top
polarization in associated Higgs production with top quark pairs in e+e-
collisions.Comment: 4 pages, revtex, uses axodraw (style file included in the submission
Compact anisotropic spheres with prescribed energy density
New exact interior solutions to the Einstein field equations for anisotropic
spheres are found. We utilise a procedure that necessitates a choice for the
energy density and the radial pressure. This class contains the constant
density model of Maharaj and Maartens (Gen. Rel. Grav., Vol 21, 899-905, 1989)
and the variable density model of Gokhroo and Mehra (Gen. Rel. Grav., Vol 26,
75-84, 1994) as special cases. These anisotropic spheres match smoothly to the
Schwarzschild exterior and gravitational potentials are well behaved in the
interior. A graphical analysis of the matter variables is performed which
points to a physically reasonable matter distribution.Comment: 22 pages, 3 figures, to appear in Gen. Rel. Gra
Light propagation in nanorod arrays
We study propagation of TM- and TE-polarized light in two-dimensional arrays
of silver nanorods of various diameters in a gelatin background. We calculate
the transmittance, reflectance and absorption of arranged and disordered
nanorod arrays and compare the exact numerical results with the predictions of
the Maxwell-Garnett effective-medium theory. We show that interactions between
nanorods, multipole contributions and formations of photonic gaps affect
strongly the transmittance spectra that cannot be accounted for in terms of the
conventional effective-medium theory. We also demonstrate and explain the
degradation of the transmittance in arrays with randomly located rods as well
as weak influence of their fluctuating diameter. For TM modes we outline the
importance of skin-effect, which causes the full reflection of the incoming
light. We then illustrate the possibility of using periodic arrays of nanorods
as high-quality polarizers.Comment: 6 pages, 7 figure
Functional co-monotony of processes with applications to peacocks and barrier options
We show that several general classes of stochastic processes satisfy a
functional co-monotony principle, including processes with independent
increments, Brownian diffusions, Liouville processes. As a first application,
we recover some recent results about peacock processes obtained by Hirsch et
al. which were themselves motivated by a former work of Carr et al. about the
sensitivity of Asian Call options with respect to their volatility and residual
maturity (seniority). We also derive semi-universal bounds for various barrier
options.Comment: 27 page
Anisotropic static solutions in modelling highly compact bodies
Einstein field equations for anisotropic spheres are solved and exact
interior solutions obtained. This paper extends earlier treatments to include
anisotropic models which accommodate a wider variety of physically viable
energy densities. Two classes of solutions are possible. The first class
contains the limiting case for the energy density which
arises in many astrophysical applications. In the second class the singularity
at the center of the star is not present in the energy density. The models
presented in this paper allow for increasing and decreasing profiles in the
behavior of the energy density.Comment: 9 pages, to appear in Pramana - J. Phy
Spas: Redefining the Market
Spas have long been a part of the American hospitality scene. The definition of exactly what constitutes a spa has changed considerably in recent years--and so has the potential market
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