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

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