Fr.: effet de Sachs-Wolfe
The effect of gravitational potentials on the → anisotropy of the → cosmic microwave background radiation, in which photons from the → CMB are gravitationally → redshifted, causing the CMB spectrum to appear uneven. This effect is the predominant source of fluctuations in the CMB for angular scales above about 10 degrees. It involves two parts: the effect of the potential at the → surface of last scattering, which is the ordinary Sachs-Wolfe effect. And the integrated Sachs-Wolfe effect, which depends on the change of the gravitational potential while photons of the CMB are passing through a → potential well.
Named after Rainer Kurt Sachs (1932- ) and Arthur Michael Wolfe (1939- ), who were the first to calculate this effect in 1967 (ApJ 147, 73); → effect.