1,811 research outputs found
Planetoid strings : solutions and perturbations
A novel ansatz for solving the string equations of motion and constraints in
generic curved backgrounds, namely the planetoid ansatz, was proposed recently
by some authors. We construct several specific examples of planetoid strings in
curved backgrounds which include Lorentzian wormholes, spherical Rindler
spacetime and the 2+1 dimensional black hole. A semiclassical quantisation is
performed and the Regge relations for the planetoids are obtained. The general
equations for the study of small perturbations about these solutions are
written down using the standard, manifestly covariant formalism. Applications
to special cases such as those of planetoid strings in Minkowski and spherical
Rindler spacetimes are also presented.Comment: 24 pages (including two figures), RevTex, expanded and figures adde
Antisymmetric tensor coupling and conformal invariance in sigma models corresponding to gauged WZNW theories
String backgrounds associated with gauged WZNW models generically
depend on or . The exact expressions for the corresponding
metric G_{\m\n}, antisymmetric tensor B_{\m\n}, and dilaton can be
obtained by eliminating the gauge field from the local part of the
effective action of the gauged WZNW model. We show that there exists a
manifestly gauge-invariant prescription for the derivation of the antisymmetric
tensor coupling. When the subgroup is one-dimensional and is simple the
antisymmetric tensor is given by the semiclassical (-independent)
expression. We consider in detail the simplest non-trivial example with
non-trivial B_{\m\n} -- the D=3 sigma model corresponding to the gauged WZNW theory (`charged black string') and show that the exact
expressions for G_{\m\n}, B_{\m\n} and solve the Weyl invariance
conditions in the two-loop approximation. Similar conclusion is reached for the
closely related chiral gauged WZNW model. We find that there exists
a scheme in which the semiclassical background is also a solution of the
two-loop conformal invariance equations (but the tachyon equation takes a
non-canonical form). We discuss in detail the role of field redefinitions
(scheme dependence) in establishing a correspondence between the sigma model
and conformal field theory results.Comment: 55 pages, harvmac, CERN-TH.6969/93, THU-93/25, Imperial/TP/92-93/59.
(Another prescription for extracting the exact antisymmetric tensor is
described leading to a purely semiclassical expression for it
Regular S-Brane Backgrounds
We construct time-dependent S-brane solutions to the supergravity field
equations in various dimensions which (unlike most such geometries) do not
contain curvature singularities. The configurations we consider are less
symmetric than are earlier solutions, with our simplest solution being obtained
by a simple analytical continuation of the Kerr geometry. We discuss in detail
the global structure and properties of this background. We then generalize it
to higher dimensions and to include more complicated field configurations -
like non vanishing scalars and antisymmetric tensor gauge potentials - by the
usual artifice of applying duality symmetries.Comment: 22 pages, 3 figures. Typos in eq.(2.6) correcte
Black Holes and Flop Transitions in M-Theory on Calabi-Yau Threefolds
We present fivedimensional extreme black hole solutions of M-theory
compactified on Calabi-Yau threefolds and study these solutions in the context
of flop transitions in the extended Kahler cone. In particular we consider a
specific model and present black hole solutions, breaking half of N=2
supersymmetry, in two regions of the extended Kahler cone, which are connected
by a flop transition. The conditions necessary to match both solutions at the
flop transition are analysed. Finally we also discuss the conditions to obtain
massless black holes at the flop transition.Comment: 19 pp, LaTe
Job satisfaction and motivation of health workers in public and private sectors: cross-sectional analysis from two Indian states
<p>Abstract</p> <p>Background</p> <p>Ensuring health worker job satisfaction and motivation are important if health workers are to be retained and effectively deliver health services in many developing countries, whether they work in the public or private sector. The objectives of the paper are to identify important aspects of health worker satisfaction and motivation in two Indian states working in public and private sectors.</p> <p>Methods</p> <p>Cross-sectional surveys of 1916 public and private sector health workers in Andhra Pradesh and Uttar Pradesh, India, were conducted using a standardized instrument to identify health workers' satisfaction with key work factors related to motivation. Ratings were compared with how important health workers consider these factors.</p> <p>Results</p> <p>There was high variability in the ratings for areas of satisfaction and motivation across the different practice settings, but there were also commonalities. Four groups of factors were identified, with those relating to job content and work environment viewed as the most important characteristics of the ideal job, and rated higher than a good income. In both states, public sector health workers rated "good employment benefits" as significantly more important than private sector workers, as well as a "superior who recognizes work". There were large differences in whether these factors were considered present on the job, particularly between public and private sector health workers in Uttar Pradesh, where the public sector fared consistently lower (<it>P </it>< 0.01). Discordance between what motivational factors health workers considered important and their perceptions of actual presence of these factors were also highest in Uttar Pradesh in the public sector, where all 17 items had greater discordance for public sector workers than for workers in the private sector (<it>P </it>< 0.001).</p> <p>Conclusion</p> <p>There are common areas of health worker motivation that should be considered by managers and policy makers, particularly the importance of non-financial motivators such as working environment and skill development opportunities. But managers also need to focus on the importance of locally assessing conditions and managing incentives to ensure health workers are motivated in their work.</p
Mortality Measurement Matters: Improving Data Collection and Estimation Methods for Child and Adult Mortality
Colin Mathers and Ties Boerma discuss three research articles in PLoS Medicine that address the measurement and analysis of child and adult mortality data collected through death registration, censuses, and household surveys
Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV
Two-particle correlations of direct photons were measured in central
208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were
extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged
pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was
extracted from the correlation strength and compared to theoretical
calculations.Comment: 5 pages, 4 figure
Event-by-Event Fluctuations in Particle Multiplicities and Transverse Energy Produced in 158.A GeV Pb+Pb collisions
Event-by-event fluctuations in the multiplicities of charged particles and
photons, and the total transverse energy in 158 GeV Pb+Pb collisions
are studied for a wide range of centralities. For narrow centrality bins the
multiplicity and transverse energy distributions are found to be near perfect
Gaussians. The effect of detector acceptance on the multiplicity fluctuations
has been studied and demonstrated to follow statistical considerations. The
centrality dependence of the charged particle multiplicity fluctuations in the
measured data has been found to agree reasonably well with those obtained from
a participant model. However for photons the multiplicity fluctuations has been
found to be lower compared to those obtained from a participant model. The
multiplicity and transverse energy fluctuations have also been compared to
those obtained from the VENUS event generator.Comment: To appear in Physical Review C; changes : more detailed discussion on
errors and few figures modifie
Particle density fluctuations
Event-by-event fluctuations in the multiplicities of charged particles and
photons at SPS energies are discussed. Fluctuations are studied by controlling
the centrality of the reaction and rapidity acceptance of the detectors.
Results are also presented on the event-by-event study of correlations between
the multiplicity of charged particles and photons to search for DCC-like
signals.Comment: Talk presented at Quark Matter 2002, Nantes, Franc
Update of the Search for the Neutrinoless Decay
We present an update of the search for the lepton family number violating
decay using a complete CLEO II data sample of 12.6 million
pairs. No evidence of a signal has been found and the
corresponding upper limit is \BR(\tau \to \mu\gamma) < 1.0 \times 10^{-6}
at 90% CL, significantly smaller than previous limits. All quoted results are
preliminary.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
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