How Anisotropic is our Universe?
ArXiv astro-ph/9605123 (1996)
Abstract:
Large-scale cosmic microwave background anisotropies in homogeneous, globally anisotropic cosmologies are investigated. We perform a statistical analysis in which the four-year data from the Cosmic Background Explorer satellite is searched for the specific anisotropy patterns predicted by these models and thereby set definitive upper limits on the amount of shear, $(\sigma/H)_0$ and vorticity, $(\omega/H)_0$, which are orders of magnitude stronger than previous constraints. We comment on how these results might impact our understanding of primordial global anisotropy.The structure of Doppler peaks induced by active perturbations
ArXiv astro-ph/9605047 (1996)
Abstract:
We investigate how the qualitative structure of Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy is affected by basic assumptions going into theories of structure formation. We define the concepts of ``coherent'' and ``incoherent'' fluctuations, and also of ``active'' and ``passive'' fluctuations. In these terms inflationary fluctuations are passive and coherent while topological defects are active incoherent fluctuations. Causality and scale invariance are shown to have different implementations in theories differing in the above senses. We then extend the formalism of Hu and Sugiyama to treat models with cosmic defects. Using this formalism we show that the existence or absence of secondary Doppler peaks and the rough placing of the primary peak are very sensitive to the fundamental properties defined. We claim therefore that even a rough measurement of the angular power spectrum $C_l$ shape at $100Causality, randomness, and the microwave background
PHYSICAL REVIEW LETTERS 76:9 (1996) 1413-1416
Doppler peaks from active perturbations
PHYSICAL REVIEW LETTERS 76:15 (1996) 2617-2620
How anisotropic is our Universe?
PHYSICAL REVIEW LETTERS 77:14 (1996) 2883-2886