Cosmological Constraints from Current Cosmic Microwave Background and Type Ia Supernova Data: A Brute Force, Eight-Parameter Analysis

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Abstract
We describe constraints on a "standard" eight-parameter, open cold dark matter (CDM) model from the most recent cosmic microwave background and Type Ia supernova data. Our parameters are the densities of CDM, baryons, vacuum energy and curvature, the reionization optical depth, and the normalization and tilt for both scalar and tensor fluctuations. We find that although the possibility of reionization and of gravity waves substantially weakens the constraints on the CDM and baryon density, the tilt, and the Hubble constant and curvature, allowing, e.g., a closed universe, open models with a vanishing cosmological constant are still strongly disfavored.