9,398 research outputs found
Equivariant Dimensional Reduction and Quiver Gauge Theories
We review recent applications of equivariant dimensional reduction techniques
to the construction of Yang-Mills-Higgs-Dirac theories with dynamical mass
generation and exactly massless chiral fermions.Comment: 10 pages; Based on invited talk given by the first author at the 2nd
School on "Quantum Gravity and Quantum Geometry" session of the 9th Hellenic
School on Elementary Particle Physics and Gravity, Corfu, Greece, September
13-20 2009. To be published in General Relativity and Gravitatio
Implications of Particle Acceleration in Active Galactic Nuclei for Cosmic Rays and High Energy Neutrino Astronomy
We consider the production of high energy neutrinos and cosmic rays in
radio-quiet active galactic nuclei (AGN) or in the central regions of
radio-loud AGN. We use a model in which acceleration of protons takes place at
a shock in an accretion flow onto a supermassive black hole, and follow the
cascade that results from interactions of the accelerated protons in the AGN
environment. We use our results to estimate the diffuse high energy neutrino
intensity and cosmic ray intensity due to AGN. We discuss our results in the
context of high energy neutrino telescopes under construction, and measurements
of the cosmic ray composition in the region of the ``knee'' in the energy
spectrum at GeV.Comment: 37 pages of compressed and uuencoded postscript; hardcopy available
on request; to be published in Astroparticle Physics; ADP-AT-94-
Adaptive finite element analysis based on p-convergence
The results of numerical experiments are presented in which a posteriori estimators of error in strain energy were examined on the basis of a typical problem in linear elastic fracture mechanics. Two estimators were found to give close upper and lower bounds for the strain energy error. The potential significance of this is that the same estimators may provide a suitable basis for adaptive redistribution of the degrees of freedom in finite element models
Attractive Bose-Einstein Condensates in three dimensions under rotation: Revisiting the problem of stability of the ground state in harmonic traps
We study harmonically trapped ultracold Bose gases with attractive
interparticle interactions under external rotation in three spatial dimensions
and determine the critical value of the attraction strength where the gas
collapses as a function of the rotation frequency. To this end we examine the
stationary state in the corotating frame with a many-body approach as well as
within the Gross-Pitaevskii theory of systems in traps with different
anisotropies. In contrast to recently reported results [N. A. Jamaludin, N. G.
Parker, and A. M. Martin, Phys. Rev. A \textbf{77}, 051603(R) (2008)], we find
that the collapse is not postponed in the presence of rotation. Unlike
repulsive gases, the properties of the attractive system remain practically
unchanged under rotation in isotropic and slightly anisotropic traps.Comment: 15 pages, 1 figure, 1 tabl
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