453 research outputs found
Public firm incentives under asymmetric information and prospect of deregulation and privatization
Governments dislike poorly performing public firms and often see deregulation and privatisation as a way to improve performance and social welfare. From a theoretical point of view poor performance may be due to information asymmetries between the informed public firm and the relatively uninformed regulator.
The point of view in the paper is that the information asymmetries that makes the regulator unable to achieve first best during regulation, is also the cause of deregulation and privatization failure.
The effect on public firm incentives from introducing deregulation as a consequence from choosing a specific regulation contract is analysed
Public firm incentives under asymmetric information and prospect of deregulation and privatization
Governments dislike poorly performing public firms and often see deregulation and privatisation as a way to improve performance and social welfare. From a theoretical point of view poor performance may be due to information asymmetries between the informed public firm and the relatively uninformed regulator.
The point of view in the paper is that the information asymmetries that makes the regulator unable to achieve first best during regulation, is also the cause of deregulation and privatization failure.
The effect on public firm incentives from introducing deregulation as a consequence from choosing a specific regulation contract is analysed
Entropy Functions with 5D Chern-Simons terms
In this note we reconsider Sen's entropy function analysis for 5D
supergravity actions containing Chern-Simons terms. The apparent lack of gauge
invariance is usually tackled via a 4D reduction. Here we motivate how a
systematic 5D procedure also works. In doing so, it becomes important to
identify the correct 5D charges. In particular, we perform explicit
calculations for the black ring and 5D black hole. In the black ring analysis,
we find Chern-Simons induced spectral flow shifts emerging out of Sen's
formalism. We find that the entropy function nevertheless remains gauge
invariant and the resulting electric charges are identified as Page charges.
For the black hole too, 5D gauge invariance is confirmed. Our 5D analysis
enables us to fix a mismatch that arose in the electric charges of Goldstein
and Jena's 4D-reduced calculation. Finally we provide an interpretation for the
e^0 - p^0 exchange in the entropy function as an interpolation between black
hole and black ring geometries in Taub-NUT.Comment: 27 page
Supergravity brane worlds and tachyon potentials
We study massless and massive graviton modes that bind on thick branes which
are supergravity domain walls solutions in -dimensional supergravity
theories where only the supergravity multiplet and the scalar supermultiplet
are turned on. The domain walls are bulk solutions provided by tachyon
potentials. Such domain walls are regarded as BPS branes of one lower dimension
that are formed due to tachyon potentials on a non-BPS D-brane.Comment: RevTex4, 6 pages; version to appear in Phys. Rev.
Entropy Function for Non-extremal D1D5 and D2D6NS5-branes
We apply the entropy function formalism to non-extremal D1D5 and
D2D6NS5-branes whose throat approximation is given by the Schwarzschild black
hole in AdS_3\times S^3\times T^4 and AdS_3\times S^2\times S^1\times T^4,
respectively. We find the Bekenstein-Hawking entropy and the (alpha')^3R^4
corrections from the value of the entropy function at its saddle point. While
the higher derivative terms have no effect on the temperature, they decrease
the value of the entropy.Comment: 17 Pages, Latex file; Minor additions, version published in JHE
Inflation, cold dark matter, and the central density problem
A problem with high central densities in dark halos has arisen in the context
of LCDM cosmologies with scale-invariant initial power spectra. Although n=1 is
often justified by appealing to the inflation scenario, inflationary models
with mild deviations from scale-invariance are not uncommon and models with
significant running of the spectral index are plausible. Even mild deviations
from scale-invariance can be important because halo collapse times and
densities depend on the relative amount of small-scale power. We choose several
popular models of inflation and work out the ramifications for galaxy central
densities. For each model, we calculate its COBE-normalized power spectrum and
deduce the implied halo densities using a semi-analytic method calibrated
against N-body simulations. We compare our predictions to a sample of dark
matter-dominated galaxies using a non-parametric measure of the density. While
standard n=1, LCDM halos are overdense by a factor of 6, several of our example
inflation+CDM models predict halo densities well within the range preferred by
observations. We also show how the presence of massive (0.5 eV) neutrinos may
help to alleviate the central density problem even with n=1. We conclude that
galaxy central densities may not be as problematic for the CDM paradigm as is
sometimes assumed: rather than telling us something about the nature of the
dark matter, galaxy rotation curves may be telling us something about inflation
and/or neutrinos. An important test of this idea will be an eventual consensus
on the value of sigma_8, the rms overdensity on the scale 8 h^-1 Mpc. Our
successful models have values of sigma_8 approximately 0.75, which is within
the range of recent determinations. Finally, models with n>1 (or sigma_8 > 1)
are highly disfavored.Comment: 13 pages, 6 figures. Minor changes made to reflect referee's
Comments, error in Eq. (18) corrected, references updated and corrected,
conclusions unchanged. Version accepted for publication in Phys. Rev. D,
scheduled for 15 August 200
Constraining warm dark matter with cosmic shear power spectra
We investigate potential constraints from cosmic shear on the dark matter
particle mass, assuming all dark matter is made up of light thermal relic
particles. Given the theoretical uncertainties involved in making cosmological
predictions in such warm dark matter scenarios we use analytical fits to linear
warm dark matter power spectra and compare (i) the halo model using a mass
function evaluated from these linear power spectra and (ii) an analytical fit
to the non-linear evolution of the linear power spectra. We optimistically
ignore the competing effect of baryons for this work. We find approach (ii) to
be conservative compared to approach (i). We evaluate cosmological constraints
using these methods, marginalising over four other cosmological parameters.
Using the more conservative method we find that a Euclid-like weak lensing
survey together with constraints from the Planck cosmic microwave background
mission primary anisotropies could achieve a lower limit on the particle mass
of 2.5 keV.Comment: 26 pages, 9 figures, minor changes to match the version accepted for
publication in JCA
One entropy function to rule them all
We study the entropy of extremal four dimensional black holes and five
dimensional black holes and black rings is a unified framework using Sen's
entropy function and dimensional reduction. The five dimensional black holes
and black rings we consider project down to either static or stationary black
holes in four dimensions. The analysis is done in the context of two derivative
gravity coupled to abelian gauge fields and neutral scalar fields. We apply
this formalism to various examples including minimal supergravity.Comment: 29 pages, 2 figures, revised version for publication, details adde
Anthropogenic Space Weather
Anthropogenic effects on the space environment started in the late 19th
century and reached their peak in the 1960s when high-altitude nuclear
explosions were carried out by the USA and the Soviet Union. These explosions
created artificial radiation belts near Earth that resulted in major damages to
several satellites. Another, unexpected impact of the high-altitude nuclear
tests was the electromagnetic pulse (EMP) that can have devastating effects
over a large geographic area (as large as the continental United States). Other
anthropogenic impacts on the space environment include chemical release ex-
periments, high-frequency wave heating of the ionosphere and the interaction of
VLF waves with the radiation belts. This paper reviews the fundamental physical
process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure
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