New Limits on the Shear and Rotation of the Universe from the X-ray Background

Abstract

It is shown that recently set upper limits of 1 percent on 12- and 24hour angular variations in the X-ray background radiation lead to restrictions on large-scale shear and vorticity for approximately haff of the sky. Because of a global analogy to the Compton-Getting effect, the limiting values placed on the shear and vorticity are of the same order as those set by the isotropy of the microwave background (over a small solid angle) if intergalactic hydrogen now exists at densities >106 for the shear model, and > 10 for the vorticity model. If intergalactic hydrogen does not exist, the limits are not as significant as those implied by the microwave background, but are still important because of the large solid angle scanned in the observations. A "Euclidean," axisymmetric world model with shear, and two models containing vorticity and having open and closed geometries, are used in the calculations.