5,434 research outputs found
Analytic solutions of the geodesic equation in axially symmetric space-times
The complete sets of analytic solutions of the geodesic equation in
Taub--NUT--(anti-)de Sitter, Kerr--(anti-)de Sitter and also in general
Plebanski--Demianski space--times without acceleration are presented. The
solutions are given in terms of the Kleinian sigma functions.Comment: 4 pages, 4 figures, accepted for publication in EP
Probability of Causation for Lung Cancer After Exposure to Radon Progeny: A Comparison of Models and Data
The estimates of lung cancer risk due to the exposure to radon decay products are based on different data sets from underground mining and on different mathematical models that are used to fit the data. Diagrams of the excess relative rate per 100 working level months in its dependence on age at exposure and age attained are shown to be a useful tool to elucidate the influence that is due to the choice of the model, and to assess the differences between the data from the major western cohorts and those from the Czech uranium miners. It is seen that the influence of the choice of the model is minor compared to the difference between the data sets. The results are used to derive attributable lifetime risks and probabilities of causation for lung cancer following radon progeny exposures
Fingerprinting dark energy
Dark energy perturbations are normally either neglected or else included in a
purely numerical way, obscuring their dependence on underlying parameters like
the equation of state or the sound speed. However, while many different
explanations for the dark energy can have the same equation of state, they
usually differ in their perturbations so that these provide a fingerprint for
distinguishing between different models with the same equation of state. In
this paper we derive simple yet accurate approximations that are able to
characterize a specific class of models (encompassing most scalar-field models)
which is often generically called "dark energy". We then use the approximate
solutions to look at the impact of the dark energy perturbations on the dark
matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic
microwave background radiation.Comment: 11 pages, 5 figures, minor changes to match published versio
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