2,233 research outputs found
Ambient Isotopic Meshing of Implicit Algebraic Surface with Singularities
A complete method is proposed to compute a certified, or ambient isotopic,
meshing for an implicit algebraic surface with singularities. By certified, we
mean a meshing with correct topology and any given geometric precision. We
propose a symbolic-numeric method to compute a certified meshing for the
surface inside a box containing singularities and use a modified
Plantinga-Vegter marching cube method to compute a certified meshing for the
surface inside a box without singularities. Nontrivial examples are given to
show the effectiveness of the algorithm. To our knowledge, this is the first
method to compute a certified meshing for surfaces with singularities.Comment: 34 pages, 17 Postscript figure
Being Pragmatic About Forensic Linguistics
article published in law journalThis article aims to provide some legal context to the Authorship Attribution
Workshop (âconferenceâ). In particular, I want to offer some pragmatic observations on what courts will likely demand of forensic linguistics experts and tentatively suggest what the field should aspire to in both the short and long run
Search for Large Rapidity Gap Events in e^+ e^- Annihilation
We investigate the cross-section for the production of a low-mass
colour-singlet cluster in annihilation with a large rapidity gap
between the colour-singlet cluster and the other jets. It is argued that such
events are the cross-channel analogue of large-rapidity-gap events in
deep-inelastic scattering, and therefore could in principle be used to
investigate the analytic continuation of the BFKL pomeron to the positive-
kinematic regime, where one would expect the trajectory to pass through
glueball states. The cross section can be calculated in perturbative QCD, so
that the infrared scale arising from non-perturbative effects, which prevents
an exponential fall-off with rapidity gap in the case of deep-inelastic
scattering, is absent in annihilation. Correspondingly, the cross
section for such events decreases rapidly with increasing rapidity gap.Comment: LATEX file - 21 pages + 15 figure
Vacuum polarization calculations for hydrogenlike and alkalilike ions
Complete vacuum polarization calculations incorporating finite nuclear size
are presented for hydrogenic ions with principal quantum numbers n=1-5.
Lithiumlike, sodiumlike, and copperlike ions are also treated starting with
Kohn-Sham potentials, and including first-order screening corrections. In both
cases dominant Uehling terms are calculated with high accuracy, and smaller
Wichmann- Kroll terms are obtained using numerical electron Green's functions.Comment: 23 pages, 1 figur
Search for dark matter in the Sun with the ANTARES neutrino telescope in the CMSSM and mUED frameworks
ANTARES is the first neutrino telescope in the sea. It consists of a three-dimensional array of 885 photomultipliers to collect the Cherenkov light induced by relativistic muons produced in CC interactions of high energy neutrinos. One of the main scientific goals of the experiment is the search for dark matter. We present here the analysis of data taken during 2007 and 2008 to look for a WIMP signal in the Sun. WIMPs are one of the most popular scenarios to explain the dark matter content of the Universe. They would accumulate in massive objects like the Sun or the Galactic Center and their self-annihilation would produce (directly or indirectly) high energy neutrinos detectable by neutrino telescopes. Contrary to other indirect searches (like with gamma rays or positrons), the search for neutrinos in the Sun is free from other astrophysical contributions, so the interpretation of a potential signal in terms of dark matter is much more robust
Supernovae and Positron Annihilation
Radioactive nuclei, especially those created in SN explosion, have long been
suggested to be important contributors of galactic positrons. In this paper we
describe the findings of three independent OSSE/SMM/TGRS studies of positron
annihilation radiation, demonstrating that the three studies are largely in
agreement as to the distribution of galactic annihilation radiation. We then
assess the predicted yields and distributions of SN-synthesized radionuclei,
determining that they are marginally compatible with the findings of the
annihilation radiation studies.Comment: 7 pages, accepted for publication in New Astronomy Reviews (Astronomy
with Radioactivites III
Dynamics of Gravity in a Higgs Phase
We investigate the universal low-energy dynamics of the simplest Higgs phase
for gravity, `ghost condensation.' We show that the nonlinear dynamics of the
`ghostone' field dominate for all interesting gravitational sources. Away from
caustic singularities, the dynamics is equivalent to the irrotational flow of a
perfect fluid with equation of state p \propto \rho^2, where the fluid
particles can have negative mass. We argue that this theory is free from
catastrophic instabilities due to growing modes, even though the null energy
condition is violated. Numerical simulations show that solutions generally have
singularities in which negative energy regions shrink to zero size. We exhibit
partial UV completions of the theory in which these singularities are smoothly
resolved, so this does not signal any inconsistency in the effective theory. We
also consider the bounds on the symmetry breaking scale M in this theory. We
argue that the nonlinear dynamics cuts off the Jeans instability of the linear
theory, and allows M \lsim 100MeV.Comment: 54 pages, 15 figures; postscript figures downloadable from
http://schwinger.harvard.edu/~wiseman/Ghost/ghostepsfigs.tar.gz ; v2:
substantial revision to section 5 on bound
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