ar X iv : a st ro - p h / 00 09 17 1 v 1 1 1 Se p 20 00 The core - jet structure of the JVAS gravitational lens B 1030 + 074

ar X iv : a st ro - p h / 00 09 34 8 v 1 2 1 Se p 20 00 EVN Observations of GRS 1915 +

ar X iv : a st ro - p h / 00 08 32 9 v 3 1 4 M ay 2 00 1 Why is the Fraction of Four - Image Radio Lens Systems So High ?

We investigate the frequency of two-and four-image gravitational lens systems in the Jodrell-VLA Astrometric Survey (JVAS) and Cosmic Lens All-Sky Survey (CLASS), and the possible implications for dark matter halo properties. A simple lensing statistics model, which describes lens galaxies as singular isothermal ellipsoids with a projected axis ratio distribution derived from the surface bright...

ar X iv : a st ro - p h / 00 09 37 8 v 1 2 2 Se p 20 00 preprint VAND – TH – 00 – 7 , NUB

Directional clustering can be expected in cosmic ray observations due to purely statistical fluctuations for sources distributed randomly in the sky. We develop an analytic approach to estimate the probability of random cluster configurations, and use these results to study the strong potential of the HiRes, Auger, Telescope Array and EUSO/OWL/AirWatch facilities for deciding whether any observ...

ar X iv : a st ro - p h / 04 07 23 2 v 1 1 2 Ju l 2 00 4 B The Saas Fee Lectures on Strong Gravitational Lensing

ar X iv : a st ro - p h / 93 05 00 2 v 1 6 M ay 1 99 3 Visibility of Gravitational Lenses and the Cosmological Constant Problem

Recent observations suggest appreciable star formation activity in early-type galaxies down to redshift z ∼ 0.5. If so, there is likely to be dust in these galaxies. We consider the possibility that obscuration by dust can reconcile the observed frequency of gravitational lensing of quasar images with the considerably larger rate predicted in a low density cosmologically flat universe dominated...