Measuring cosmological parameters with the JVAS and CLASS gravitational lens surveys

The JVAS and CLASS are well-defined surveys containing about ten thousand flat-spectrum radio sources. For many reasons, flat-spectrum radio sources are particularly well-suited as a population in which to look for unbiased samples of gravitational lenses. These are by far the largest gravitational (macro)lens surveys, and particular attention was paid to constructing a cleanly-defined sample for the survey itself and and for the underlying luminosity function. Here we present the constraints on cosmological parameters, particularly the cosmological constant, derived from these surveys and compare them with other current estimates.