SECONDARY GRAVITATIONAL COSMIC MICROWAVE BACKGROUND ANISOTROPIES FROM FLATTENED COSMIC STRUCTURES

The anisotropies of the microwave background radiation due to gravitational evolution of non-linear, pancake-type cosmic structures are studied in the framework of the potential approximation method. Simple models of a uniform-density thin collapsing disc and an infinite uniform 'sheet' of matter are investigated. We apply the thin-disc model to the case of highly flattened clusters of galaxies and the infinite-sheet model to the case of the 'Great Wall'. Predicted anisotropies are well below present observational upper limits - in particular the anisotropy generated by the 'Great Wall' turns out to be less than or similar to 10(-6). The lack of increase of microwave background anisotropies from flattened cosmic structures with respect to those generated by spherical ones is mainly due to the fact that, during a pancake-type collapse, the gravitational potential remains non-singular.