Optical redshifts due to correlations in quasar plasmas

While it is commonly accepted that cosmic redshifts are caused by the expansion of space, there are some puzzling cases. For example, a number of quasars having very large redshifts appear to be close to galaxies having much lower redshifts. If the standard cosmological model of the universe is correct, then the apparent proximity of quasars and galaxies must be incorrect, and the quasars must be much farther away. Then we are puzzled by the enormous luminosity of the quasars, which must be thousands of times more energetic than an entire galaxy, and by their enormous speeds, which must approach the speed of light. But if the quasar redshifts have a significant contribution from another mechanism besides expansion, then their proximity to low redshift galaxies and the quasar energy and speed puzzles would be resolved. One physical mechanism that produces redshifts is optical correlations. In fact, correlation-induced spectral changes on scattering from gases or plasmas can mimic the major features of redshifts caused by expansion. We will present a high-level, hopefully intuitive, overview of the theory that has been developed over the past decade and try to draw some concrete conclusions about the relevancy of the effect to the redshifts from quasars.