Anisotropy of the Microwave Background in the Inflationary Cosmology

The inflationary cosmology [1] makes a prediction for the spectrum of energy-density fluctuations in the early universe [2]. The result is the scale-invariant Harrison Zel'dovich spectrum [3] : fluctuations of wavelength L at a tune t ~ Lie (the tune of horizon crossing) are predicted to have an amplitude 6 a which is independent of L. The scale-invariant spectrum is a model-independent prediction o f inflation, while the value of the constant e H depends on parameters of the particular theory being considered. A determination of the validity of the Harrison-Zel 'dovich spectrum v~ould test the inflationary hypothesis and an accurate measurement o f e H would have a direct unpact on model building. Unfortunately, our present knowledge of galactic structure can provide neither of these. Fluctuations on the galactic scale have become nonlinear and have clearly gone through an extremely complex evolution to become present-day galaxies and galactic clusters. However, the inflationary cosmology also predicts that fluctuations o f much longer wavelength exist, and have amplitude e H when they enter the horizon. Fluctuations which entered the horizon since the time of recombina-