8,364 research outputs found
Microwave background constraints on inflationary parameters
We use a compilation of cosmic microwave anisotropy data (including the
recent VSA, CBI and Archeops results), supplemented with an additional
constraint on the expansion rate, to directly constrain the parameters of
slow-roll inflation models. We find good agreement with other papers concerning
the cosmological parameters, and display constraints on the power spectrum
amplitude from inflation and the first two slow-roll parameters, finding in
particular that . The technique we use for parametrizing
inflationary spectra may become essential once the data quality improves
significantly.Comment: 6 pages LaTeX file with figures incorporated. Major revisions
including incorporation of new datasets (CBI and Archeops). Slow-roll
inflation module for use with the CAMB program can be found at
http://astronomy.cpes.susx.ac.uk/~sleach/inflation
From the production of primordial perturbations to the end of inflation
In addition to generating the appropriate perturbation power spectrum, an
inflationary scenario must take into account the need for inflation to end
subsequently. In the context of single-field inflation models where inflation
ends by breaking of the slow-roll condition, we constrain the first and second
derivatives of the inflaton potential using this additional requirement. We
compare this with current observational constraints from the primordial
spectrum and discuss several issues relating to our results.Comment: RevTex4, 6 pages, 7 figures. To match version accepted by PR
Coarse-grained Interaction Potentials for Anisotropic Molecules
We have proposed an efficient parameterization method for a recent variant of
the Gay-Berne potential for dissimilar and biaxial particles and demonstrated
it for a set of small organic molecules. Compared to the previously proposed
coarse-grained models, the new potential exhibits a superior performance in
close contact and large distant interactions. The repercussions of thermal
vibrations and elasticity has been studied through a statistical method. The
study justifies that the potential of mean force is representable with the same
functional form, extending the application of this coarse-grained description
to a broader range of molecules. Moreover, the advantage of employing
coarse-grained models over truncated atomistic summations with large distance
cutoffs has been briefly studied.Comment: 8 pages, 4 tables and 6 figures. To appear in J. Chem. Phy
Lie symmetries of (1+2) nonautonomous evolution equations in Financial Mathematics
We analyse two classes of evolution equations which are of special
interest in Financial Mathematics, namely the Two-dimensional Black-Scholes
Equation and the equation for the Two-factor Commodities Problem. Our approach
is that of Lie Symmetry Analysis. We study these equations for the case in
which they are autonomous and for the case in which the parameters of the
equations are unspecified functions of time. For the autonomous Black-Scholes
Equation we find that the symmetry is maximal and so the equation is reducible
to the Classical Heat Equation. This is not the case for the
nonautonomous equation for which the number of symmetries is submaximal. In the
case of the two-factor equation the number of symmetries is submaximal in both
autonomous and nonautonomous cases. When the solution symmetries are used to
reduce each equation to a equation, the resulting equation is of
maximal symmetry and so equivalent to the Classical Heat Equation.Comment: 15 pages, 1 figure, to be published in Mathematics in the Special
issue "Mathematical Finance
The WMAP normalization of inflationary cosmologies
We use the three-year WMAP observations to determine the normalization of the
matter power spectrum in inflationary cosmologies. In this context, the
quantity of interest is not the normalization marginalized over all parameters,
but rather the normalization as a function of the inflationary parameters n and
r with marginalization over the remaining cosmological parameters. We compute
this normalization and provide an accurate fitting function. The statistical
uncertainty in the normalization is 3 percent, roughly half that achieved by
COBE. We use the k-l relation for the standard cosmological model to identify
the pivot scale for the WMAP normalization. We also quote the inflationary
energy scale corresponding to the WMAP normalization.Comment: 4 pages RevTex4 with two figure
Analytic Behaviour of Competition among Three Species
We analyse the classical model of competition between three species studied
by May and Leonard ({\it SIAM J Appl Math} \textbf{29} (1975) 243-256) with the
approaches of singularity analysis and symmetry analysis to identify values of
the parameters for which the system is integrable. We observe some striking
relations between critical values arising from the approach of dynamical
systems and the singularity and symmetry analyses.Comment: 14 pages, to appear in Journal of Nonlinear Mathematical Physic
Gender violence in schools: taking the ‘girls-as-victims’ discourse forward
This paper draws attention to the gendered nature of violence in schools. Recent recognition that schools can be violent places has tended to ignore the fact that many such acts originate in unequal and antagonistic gender relations, which are tolerated and ‘normalised’ by everyday school structures and processes. After examining some key concepts and definitions, we provide a brief overview of the scope and various manifestations of gender violence in schools, noting that most research to date has focused on girls as victims of gender violence within a heterosexual context and ignores other forms such as homophobic and girl violence. We then move on to look at a few interventions designed to address gender violence in schools in the developing world and end by highlighting the need for more research and improved understanding of the problem and how it can be addressed
Characterization of solar-grade silicon produced by the SiF4-Na process
A process was developed for producing low cost solar grade silicon by the reaction between SiF4 gas and sodium metal. The results of the characterization of the silicon are presented. These results include impurity levels, electronic properties of the silicon after crystal growth, and the performance of solar photovoltaic cells fabricated from wafers of the single crystals. The efficiency of the solar cells fabricated from semiconductor silicon and SiF4-Na silicon was the same
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