MATTER-MICROWAVE CORRELATIONS IN AN OPEN UNIVERSE

In an intriguing recent paper, Crittenden and Turok proposed cross-cor relating the cosmic microwave background with tracers of the matter de nsity to probe the existence of a cosmological constant. Here I emphas ize that a similar cross correlation arises in an open universe and, d epending on the redshift distribution of the tracer population and the matter density, may be comparable to or stronger than that in a hat c osmological-constant universe with the same matter density. The two ca ses can be distinguished through cross correlation with tracer populat ions with different redshift distributions.