13,840 research outputs found
The impact of the air-fluorescence yield on the reconstructed shower parameters of ultra-high energy cosmic rays
An accurate knowledge of the fluorescence yield and its dependence on
atmospheric properties such as pressure, temperature or humidity is essential
to obtain a reliable measurement of the primary energy of cosmic rays in
experiments using the fluorescence technique. In this work, several sets of
fluorescence yield data (i.e. absolute value and quenching parameters) are
described and compared. A simple procedure to study the effect of the assumed
fluorescence yield on the reconstructed shower parameters (energy and shower
maximum depth) as a function of the primary features has been developed. As an
application, the effect of water vapor and temperature dependence of the
collisional cross section on the fluorescence yield and its impact on the
reconstruction of primary energy and shower maximum depth has been studied.Comment: Accepted in Astroparticle Physic
Ricci Solitons on Lorentzian Manifolds with Large Isometry Groups
We show that Lorentzian manifolds whose isometry group is of dimension at
least are expanding, steady and shrinking Ricci solitons
and steady gradient Ricci solitons. This provides examples of complete locally
conformally flat and symmetric Lorentzian Ricci solitons which are not rigid
On the exposure to mobile phone radiation in trains
This report presents theoretical estimates of the Power Density levels which
may be reached inside trains. Two possible sources of high levels of radiation
are discussed. The first one arises since the walls of the wagons are metallic
and therefore bounce back almost all radiation impinging on them. The second is
due to the simultaneous emission of a seemingly large number of nearby
telephones. The theoretical study presented here shows that Power Densities
stay at values below reference levels always.Comment: 9 pages, 1 figur
Stanilov-Tsankov-Videv Theory
We survey some recent results concerning Stanilov-Tsankov-Videv theory,
conformal Osserman geometry, and Walker geometry which relate algebraic
properties of the curvature operator to the underlying geometry of the
manifold.Comment: This is a contribution to the Proceedings of the 2007 Midwest
Geometry Conference in honor of Thomas P. Branson, published in SIGMA
(Symmetry, Integrability and Geometry: Methods and Applications) at
http://www.emis.de/journals/SIGMA
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