86,722 research outputs found
Poincare submersions
We prove two kinds of fibering theorems for maps X --> P, where X and P are
Poincare spaces. The special case of P = S^1 yields a Poincare duality analogue
of the fibering theorem of Browder and Levine.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-2.abs.html Version 5:
Statement of Theorem B corrected, see footnote p2
Electrodynamics at the Highest Energies
At very high energies, the bremsstrahlung and pair production cross sections
exhibit complex behavior due to the material in which the interactions occur.
The cross sections in dense media can be dramatically different than for
isolated atoms. This writeup discusses these in-medium effects, emphasizing how
the cross section has different energy and target density dependencies in
different regimes. Data from SLAC experiment E-146 will be presented to confirm
the energy and density scaling. Finally, QCD analogs of the electrodynamics
effects will be discussed.Comment: 10 pages with 7 figures. Invited talk presented at the Workshop on
Electromagnetic Probes of Fundamental Physics, Oct. 16-21, 2001, Erice, Ital
Localized Beampipe Heating due to Capture and Nuclear Excitation in Heavy Ion Colliders
At heavy ion colliders, two major sources of beam loss are expected to be
production, where the is bound to one of the nuclei, and
photonuclear excitation and decay via neutron emission. Both processes alter
the ions charged to mass ratio by well defined amounts, creating beams of
particles with altered magnetic rigidity. These beams will deposit their energy
in a localized region of the accelerator, causing localized heating, The size
of the target region depends on the collider optics. For medium and heavy ions,
at design luminosity at the Large Hadron Collider, local heating may be more
than an order of magnitude higher than expected. This could cause magnet
quenches if the local cooling is inadequate. The altered-rigidity beams will
also produce localized radiation damage. The beams could also be extracted and
used for fixed target experiments.Comment: Numerical Error fixed; to appear in NIM. 15 pages, no figure
ARIANNA: A radio detector array for cosmic neutrinos on the Ross Ice Shelf
ARIANNA (The Antarctic Ross Ice Shelf Antenna Neutrino Array) is a proposed
100 km^3 detector for ultra-high energy (above 10^17 eV) astrophysical
neutrinos. It will study the origins of ultra-high energy cosmic rays by
searching for the neutrinos produced when these cosmic rays interact with the
cosmic microwave background. Over 900 independently operating stations will
detect the coherent radio Cherenkov emission produced when astrophysical
neutrinos with energy above 10^17 eV interact in the Antarctic Ross Ice Shelf.
Each station will use 8 log periodic dipole antennas to look for short RF
pulses, with the most important frequencies between 80 MHz and 1 GHz. By
measuring the pulse polarization and frequency spectrum, the neutrino arrival
direction can be determined. In one year of operation, the full array should
observe a clear GZK neutrino signal, with different models predicting between 3
and 51 events, depending on the nuclear composition of the cosmic-rays and on
the cosmic evolution of their sources.Comment: 8 pages, presented at SORMA12. Many small improvements, per referee
comment
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