33,856 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
Fractional statistics in the fractional quantum Hall effect
A microscopic confirmation of the fractional statistics of the {\em
quasiparticles} in the fractional quantum Hall effect has so far been lacking.
We calculate the statistics of the composite-fermion quasiparticles at
and by evaluating the Berry phase for a closed loop
encircling another composite-fermion quasiparticle. A careful consideration of
subtle perturbations in the trajectory due to the presence of an additional
quasiparticle is crucial for obtaining the correct value of the statistics. The
conditions for the applicability of the fractional statistics concept are
discussed.Comment: Phys. Rev. Lett., in pres
Employment equity in Canada and South Africa: a comparative review
The South African Government has sought to redress the historical legacy of workplace discrimination by introducing the Employment Equity Act (1998), which was largely modeled on the Canadian Employment Equity Act. Although there is very little comparative information between South Africa and Canada, we fill this gap by reviewing the literature in both countries, highlighting common features of the legislation, discussing the effectiveness of legislation in both countries as well as the progress made by the designated groups covered by the legislation. This paper provides a background on the rationale for employment equity and associated human resource management policies in both Canada and South Africa. The analysis is largely based on institutional theories of organizations. Our evaluation provides overall conclusions for policy makers and organizational leaders, taking into consideration socio-historical, political, and demographic differences between the jurisdictions. Issues include top management commitment, organizational culture, Black economic empowerment, and diversity policies and practice
Managing Equipment for Emergency Obstetric Care in Rural Hospitals
In resource poor countries substantial sums of money, from governments and international donors, are used to purchase equipment for health facilities. WHO estimates that 50-80% of such equipment remains non-functional. This article is based on the experiences from various projects in developing countries in Asia and Africa. The key issues in the purchase, distribution, installation, management and maintenance of equipment for emergency obstetric care (EmOC) services are identified and discussed. Some positive examples are described to show how common equipment management problems are solved.
Civics and Citizenship Education in India and Pakistan
The idea of citizen and the school discipline of civics, which is entrusted with the responsibility to create an ideal citizen, have colonial imprints. Both citizenship and civics have traversed through postcolonial histories of nation-building, state formation, modernity, and democracy/authoritarianism in South Asian nation-states of India and Pakistan. In the context of globalization, the idea of a citizen has also been marked with discourses of global citizenship, identity-based movements, and a reassertion of nationalism. This chapter situates civics in the context of these histories and transitions. Drawing on existing research, it also analyses the contestations over inclusions and exclusions from citizenship as represented in the school subjects of civics, social studies, and citizenship education. The dominant pedagogic practices of the subject and alternatives to them, along with a discussion of gaps in existing research and potential news areas of study are highlighted
One-Dimensional Theory of the Quantum Hall System
We consider the lowest Landau level on a torus as a function of its
circumference . When , the ground state at general rational
filling fraction is a crystal with a gap--a Tao-Thouless state. For filling
fractions , these states are the limits of Laughlin's or Jain's
wave functions describing the gapped quantum Hall states when .
For the half-filled Landau level, there is a transition to a Fermi sea of
non-interacting neutral dipoles, or rather to a Luttinger liquid modification
thereof, at magnetic lengths. This state is a version of the
Rezayi-Read state, and develops continuously into the state that is believed to
describe the observed metallic phase as . Furthermore, the
effective Landau level structure that emerges within the lowest Landau level
follows from the magnetic symmetries.Comment: 4 pages, 1 figur
Standard Model with Cosmologically Broken Quantum Scale Invariance
We argue that scale invariance is not anomalous in quantum field theory,
provided it is broken cosmologically. We consider a locally scale invariant
extension of the Standard Model of particle physics and argue that it fits both
the particle and cosmological observations. The model is scale invariant both
classically and quantum mechanically. The scale invariance is broken
cosmologically producing all the dimensionful parameters. The cosmological
constant or dark energy is a prediction of the theory and can be calculated
systematically order by order in perturbation theory. It is expected to be
finite at all orders. The model does not suffer from the hierarchy problem due
to absence of scalar particles, including the Higgs, from the physical
spectrum.Comment: 13 pages, no figures significant revisions, no change in results or
conclusion
Two-photon exchange in elastic electron-nucleon scattering
A detailed study of two-photon exchange in unpolarized and polarized elastic
electron--nucleon scattering is presented, taking particular account of nucleon
finite size effects. Contributions from nucleon elastic intermediate states are
found to have a strong angular dependence, which leads to a partial resolution
of the discrepancy between the Rosenbluth and polarization transfer
measurements of the proton electric to magnetic form factor ratio, G_E/G_M. The
two-photon exchange contribution to the longitudinal polarization transfer P_L
is small, whereas the contribution to the transverse polarization transfer P_T
is enhanced at backward angles by several percent, increasing with Q^2. This
gives rise to a small, ~3% suppression of G_E/G_M obtained from the
polarization transfer ratio P_T/P_L at large Q^2. We also compare the
two-photon exchange effects with data on the ratio of e^+ p to e^- p cross
sections, which is predicted to be enhanced at backward angles. Finally, we
evaluate the corrections to the form factors of the neutron, and estimate the
elastic intermediate state contribution to the ^3He form factors
Generation of helical magnetic fields from inflation
The generation of helical magnetic fields during single field inflation due
to an axial coupling of the electromagnetic field to the inflaton is discussed.
We find that such a coupling always leads to a blue spectrum of magnetic fields
during slow roll inflation. Though the helical magnetic fields further evolve
during the inverse cascade in the radiation era after inflation, we conclude
that the magnetic fields generated by such an axial coupling can not lead to
observed field strength on cosmologically relevant scales.Comment: 4 pages, 1 figure; Contribution to the proceedings of the
International Conference on Gravitation and Cosmology (ICGC), Goa, India,
December, 201
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