We have used the Hubble Space Telescope (HST) WFPC2 camera to survey 132 BL Lac objects comprising seven complete radio-, X-ray-, and optically selected samples. We obtained useful images for 110 targets spanning the redshift range 0

We report on a large Hubble Space Telescope imaging survey of BL Lac objects, at spatial resolution >~10 times better than previous ground-based surveys. We focus on data reduction and analysis, describing the procedures used to model the host galaxy surface brightness radial profiles. A total of 69 host galaxies were resolved out of 110 objects

We study the dominant decays of the lightest Higgs boson in models with 2 and 3 Higgs doublets, for the case when its couplings to fermions are absent at tree-level. It is found that the branching ratio for the decay $H o gammagamma$ is above the one into fermion pairs, which is evaluated also at the 1-loop level.

The errors associated with a segmented primary mirror limit the image quality obtainable with those astronomical telescopes which employ them. It is necessary to derive the effects of segmentation errors on image quality in order to determine realistic error budgets for such telescopes. The main segmentation errors are misalignment and piston of

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At sufficiently low frequencies, no ground-based radio array will be able to produce high resolution images while looking through the ionosphere. A space-based array will be needed to explore the objects and processes which dominate the sky at the lowest radio frequencies. An imaging radio interferometer based on a large number of small