Cosmic Microwave Background Anisotropy Spectrum from Primordial Density Perturbations

Abstract

The origin of large scale structure in the Universe is one of the key fundamental issues in cosmology. Gravitational instability models hold that large-scale structure forms as the result of gravitational amplification of initially small perturbations in the primordial density distribution. These density perturbations leave their imprint as anisotropies in the Cosmic Microwave Background (CMB) radiation. The COBE Differential Microwave Radiometers (DMR) maps of the cosmic microwave background anisotropy measure the primordial density distribution on super-horizon scales and offer a unique probe of the“initial conditions” for structure formation. On smaller angular scales there can be significant processing and movement of the primordial perturbations. The resulting CMB anisotropy power spectrum is rich in content and information on these processes and important cosmological parameters. This paper presents a discussion aimed at giving the reader a heuristic understanding of the significant effects.