We investigate the rotation of the polarization planes for radiation freely traveling in homogeneous anisotropic spaces (Brans effect). Solving the parallel-transport equations in Bianchi type-I and type-V spaces, we find that the rotation angle is at most about 1 rad. The scrambling of the polarization states due to the Brans effect and the finite thickness of the last-scattering surface is negligible in any realistic model, so that any primeval polarization can survive up to the present epoch.

• Received 10 August 1977

DOI:https://doi.org/10.1103/PhysRevD.17.1901