3,185 research outputs found
TeV Cherenkov Events as Bose-Einstein Gamma Condensations
The recent detection of gamma radiation from Mkn 501 at energies as high as
25 TeV suggests stringent upper bounds on the diffuse, far infrared,
extragalactic radiation density. The production of electron-positron pairs
through photon-photon collisions would prevent gamma photons of substantially
higher energies from reaching us across distances of order 100 Mpc. However,
coherently arriving TeV or sub-TeV gammas - Bose-Einstein condensations of
photons at these energies - could mimic the Cherenkov shower signatures of
extremely energetic gammas. To better understand such events, we describe their
observational traits and discuss how they might be generated.Comment: 12 pages, 2 figures, accepted for publication in Ap.J.(Lett.
Ultra High Energy Cosmic Rays from Sequestered X Bursts
Assuming that there is no GZK (Greisen-Zatsepin-Kuzmin) cut-off and that
super-GZK cosmic rays correlate with AGN (Active Galactic Nuclei) at
cosmological distances, it is speculated that a relic superheavy particle (X)
has its lifetime enhanced by sequestration in an extra dimension. This
sequestration is assumed to be partially liberated by proximity of merging
supermassive black holes in an AGN, temporarily but drastically reducing the
lifetime, thus stimulating an X burst. Based on sequestration of the decay
products of X, a speculative explanation of the observed ratio is
proposed.Comment: 12 pages LaTe
Wind-Tunnel Investigation of Rectangular Air-Duct Entrances in the Leading Edge of an NACA 23018 Wing, Special Report
A preliminary investigation of a number of duct entrances of rectangular shape installed in the leading edge of a wing was conducted in the NACA 20-foot tunnel to determine the external drag, the available pressure, the critical Mach numbers, and the effect on the maximum lift. The results showed that the most satisfactory entrances, which had practically no effect on the wing characteristics, had their lips approximately in the vertical plane of the leading edge of the wing. This requirement necessitated extending the lips outside the wing contour for all except the small entrances. Full dynamic pressure was found to be available over a fairly wide range of angle of attack. The critical Mach number for a small entrance was calculated to be as high as that for the plain wing but was slightly lower for the larger entrances tested
The Drag of Airplane Wheels, Wheel Fairings, and Landing Gears - III
The tests reported in this report conclude the investigation of landing-gear drag that has been carried out in the NACA 20-foot wind tunnel. They supplement earlier tests (reported in Technical Report No. 485) made with full-scale dummy wheels, wheel fairings, and landing gears intended for airplanes of 3,000 pounds gross weight and include tests of tail wheels and tail skids
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