15,861 research outputs found
Natural Gauge Hierarchy in SO(10)
It is shown that a natural gauge hierarchy and doublet-triplet splitting can
be achieved in SO(10) using the Dimopoulos-Wilczek mechanism. Artificial
cancellations (fine-tuning) and arbitrary forms of the superpotential are
avoided, the superpotential being the most general compatible with a symmetry.
It is shown by example that the Dimopoulos-Wilczek mechanism can be protected
against the effects of higher-dimension operators possibly induced by
Planck-scale physics. Natural implementation of the mechanism leads to an
automatic Peccei-Quinn symmetry. The same local symmetries that would protect
the gauge hierarchy against Planck-scale effects tend to protect the axion
also. It is shown how realistic quark and lepton masses might arise in this
framework. It is also argued that ``weak suppression'' of proton decay can be
implemented more economically than can ``strong suppression'', offering some
grounds to hope (in the context of SO(10)) that proton decay could be seen at
Superkamiokande.Comment: 26 pages in plain LaTeX, 5 figures available on request, BA-94-0
Simple supersymmetric solution to the strong CP problem
It is shown that the minimal supersymmetric left-right model can provide a
natural solution to the strong {\it CP} problem without the need for an axion,
nor any additional symmetries beyond supersymmetry and parity.Comment: Plain Latex. 10 pages, including two figures which are part of the
Latex file. Shortened version, to appear in Phys. Rev. Lett. 7
Can we improve the prediction of hip fracture by assessing bone structure using shape and appearance modelling?
Copyright 2013 Elsevier B.V., All rights reserved.Peer reviewedPreprin
Ruling out a higher spin field solution to the cosmological constant problem
We consider the modification of Newton's gravity law in Dolgov's higher spin
models designed to compensate the cosmological constant. We find that the
effective Planck mass is unacceptably large in these models. We also point out
that the properties of gravitational waves are entirely different in these
models as compared to general relativity.Comment: 7 pages, LaTe
Fermion Doubling and a Natural Solution of the Strong CP Problem
We suggest the fermion doubling for all quarks and leptons. It is a
generalization of the neutrino doubling of the seesaw mechanism. The new quarks
and leptons are singlets and carry the electromagnetic charges of their
lighter counterparts. An {\it anomaly free global symmetry} or a
discrete symmetry can be introduced to restrict the Yukawa couplings. The form
of mass matrix is belonging to that of Nelson and Barr even though our model
does not belong to Barr's criterion. The weak CP violation of the
Kobayashi-Maskawa form is obtained through the spontaneous breaking of CP
symmetry at high energy scale. The strong CP solution is through a specific
form of the mass matrix. At low energy, the particle content is the same as in
the standard model. For a model with a global symmetry, in addition there
exists a massless majoron.Comment: SNUTP 93-68, 19 pages 1 TeX figure, ReVTeX 3.
Simulating Impacts of Extreme Weather Events on Urban Transport Infrastructure in the UK
Urban areas face many risks from future climate change and their infrastructure will be placed under more pressure
due to changes in climate extremes. Using the Tyndall Centre Urban Integrated Assessment Framework, this paper
describes a methodology used to assess the impacts of future climate extremes on transport infrastructure in
London. Utilising high-resolution projections for future climate in the UK, alongside stochastic weather generators
for downscaling, urban temperature and flooding models are used to provide information on the likelihood of future
extremes. These are then coupled with spatial network models of urban transport infrastructure and, using thresholds
to define the point at which systems cease to function normally, disruption to the networks can be simulated.
Results are shown for both extreme heat and urban surface water flooding events and the impacts on the travelling
population, in terms of both disruption time and monetary cost
Towards Analytics for Wholistic School Improvement: Hierarchical Process Modelling and Evidence Visualization
Central to the mission of most educational institutions is the task of preparing the next generation of citizens to contribute to society. Schools, colleges, and universities value a range of outcomes â e.g., problem solving, creativity, collaboration, citizenship, service to community â as well as academic outcomes in traditional subjects. Often referred to as âwider outcomes,â these are hard to quantify. While new kinds of monitoring technologies and public datasets expand the possibilities for quantifying these indices, we need ways to bring that data together to support sense-making and decision-making. Taking a systems perspective, the hierarchical process modelling (HPM) approach and the âPerimetaâ visual analytic provides a dashboard that informs leadership decision-making with heterogeneous, often incomplete evidence. We report a prototype of Perimeta modelling from education, aggregating wider outcomes data across a network of schools, and calculating their cumulative contribution to key performance indicators, using the visual analytic of the Italian flag to make explicit not only the supporting evidence, but also the challenging evidence, as well as areas of uncertainty. We discuss the nature of the modelling decisions and implicit values involved in quantifying these kinds of educational outcomes
Role of oxygen in the electron-doped superconducting cuprates
We report on resistivity and Hall measurements in thin films of the
electron-doped superconducting cuprate PrCeCuO.
Comparisons between x = 0.17 samples subjected to either ion-irradiation or
oxygenation demonstrate that changing the oxygen content has two separable
effects: 1) a doping effect similar to that of cerium, and 2) a disorder
effect. These results are consistent with prior speculations that apical oxygen
removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure
The Dodd-Frank Wall Street Reform Act\u27s Turn to International Law
The development of a harmonized system for resolving the failures of large, international financial institutions is considered by academics and policy-makers to be critical to reducing systemic risk and reducing the probability that the insolvency of a major bank will lead to a global economic collapse. Reaching agreement on how to develop this harmonized system for financial institutions with significant transnational assets and liabilities has proved elusive thus far. Commentators in favor of a more international and less parochial approach to resolving bank failures can point to a number of extremely high-profile events that demonstrate the manifest unfairness of resolving bank failures on an individual basis. The bankruptcies of Lehman Brothers and the Bank of Credit and Commerce International (BCCI) are two of many such examples
Flavor Alignment Solutions to the Strong CP Problem in Supersymmetry
An approach to solving the Strong CP Problem in supersymmetric theories is
discussed which uses abelian family symmetries to align the mass matrices of
the quarks and squarks. In this way both the Strong CP Problem and the
characteristic flavor and CP problems of supersymmetry can be solved in a
single way.Comment: 13 pages, LaTe
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