5,333 research outputs found
Higgs Decay to Two Photons
The amplitude for Higgs decay to two photons is calculated in renormalizable
and unitary gauges using dimensional regularization at intermediate steps. The
result is finite, gauge independent, and in agreement with previously published
results. The large Higgs mass limit is examined using the Goldstone-boson
equivalence theorem as a check on the use of dimensional regularization and to
explain the absence of decoupling.Comment: 15 pages, 5 figures; references adde
Population genetic analysis of Bartonella bacilliformis isolates from areas of Peru where Carrion\u27s disease is endemic and epidemic
Carrion's disease is caused by infection with the α-proteobacterium Bartonella bacilliformis. Distribution of the disease is considered coincident with the distribution of its known vector, the sand fly Lutzomyia verrucarum. Recent epidemics of B. bacilliformis infections associated with atypical symptomatology in nonendemic regions have raised questions regarding the historic and present distribution of this bacterium and the scope of disease that infection causes. Phylogenetic relationships and genomic diversity of 18 B. bacilliformis isolates (10 isolates from a region where Carrion's disease is epidemic, Cuzco, Peru, and 8 isolates from a region where Carrion's disease is endemic, Caraz, Peru) were assessed using genomic data generated by infrequent restriction site PCR and gene sequence analysis of the flagellin gltA and ialB genes. A population genetic analysis of the genomic diversity suggests that what was once considered an epidemic region of Peru did not result from the recent introduction of B. bacilliformis
Connecting does not necessarily mean learning: Course handbooks as mediating tools in school-university partnerships
This is the author's accepted manuscript (titled "Course handbooks as mediating tools in learning to teach"). The final published article is available from the link below. Copyright @ 2011 American Association of Colleges for Teacher Education.Partnerships between schools and universities in England use course handbooks to guide student teacher learning during long field experiences. Using data from a yearlong ethnographic study of a postgraduate certificate of education programme in one English university, the function of course handbooks in mediating learning in two high school subject departments (history and modern foreign languages) is analyzed. Informed by Cultural Historical Activity Theory, the analysis focuses on the handbooks as mediating tools in the school-based teacher education activity systems. Qualitative differences in the mediating functions of the handbooks-in-use are examined and this leads to a consideration of the potential of such tools for teacher learning in school–university partnerships. Following Zeichner’s call for rethinking the relationships between schools and universities, the article argues that strong structural connections between different institutional sites do not necessarily enhance student teacher learning
Colorado Native Plant Society Newsletter, Vol. 5 No. 2, April-June 1981
https://epublications.regis.edu/aquilegia/1157/thumbnail.jp
Topology and Fragility in Cosmology
We introduce the notion of topological fragility and briefly discuss some
examples from the literature. An important example of this type of fragility is
the way globally anisotropic Bianchi V generalisations of the FLRW model
result in a radical restriction on the allowed topology of spatial sections,
thereby excluding compact cosmological models with negatively curved
three-sections with anisotropy. An outcome of this is to exclude chaotic mixing
in such models, which may be relevant, given the many recent attempts at
employing compact FLRW models to produce chaotic mixing in the cosmic
microwave background radiation, if the Universe turns out to be globally
anisotropic.Comment: 12 pages, LaTex file, to appear in Gen. Rel. Grav. (1998
Future asymptotic expansions of Bianchi VIII vacuum metrics
Bianchi VIII vacuum solutions to Einstein's equations are causally
geodesically complete to the future, given an appropriate time orientation, and
the objective of this article is to analyze the asymptotic behaviour of
solutions in this time direction. For the Bianchi class A spacetimes, there is
a formulation of the field equations that was presented in an article by
Wainwright and Hsu, and in a previous article we analyzed the asymptotic
behaviour of solutions in these variables. One objective of this paper is to
give an asymptotic expansion for the metric. Furthermore, we relate this
expansion to the topology of the compactified spatial hypersurfaces of
homogeneity. The compactified spatial hypersurfaces have the topology of
Seifert fibred spaces and we prove that in the case of NUT Bianchi VIII
spacetimes, the length of a circle fibre converges to a positive constant but
that in the case of general Bianchi VIII solutions, the length tends to
infinity at a rate we determine.Comment: 50 pages, no figures. Erronous definition of Seifert fibred spaces
correcte
Supersymmetry Breaking in the Early Universe
Supersymmetry breaking in the early universe induces scalar soft potentials
with curvature of order the Hubble constant. This has a dramatic effect on the
coherent production of scalar fields along flat directions. For the moduli
problem it generically gives a concrete realization of the problem by
determining the field value subsequent to inflation. However it might suggest a
solution if the minimum of the induced potential coincides with the true
minimum. The induced Hubble scale mass also has important implications for the
Affleck-Dine mechanism of baryogenesis. This mechanism requires large squark or
slepton expectation values to develop along flat directions in the early
universe. This is generally not the case if the induced mass squared is
positive, but does occur if it is negative. The resulting baryon to entropy
ratio depends mainly on the dimension of the nonrenormalizable operator in the
superpotential which stabilizes the flat direction, and the reheat temperature
after inflation. Unlike the original scenario, it is possible to obtain an
acceptable baryon asymmetry without subsequent entropy releases.Comment: 11 pages, requires phyzz
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