Cosmic microwave background constraints on interacting cosmological models

Non-canonical scaling of the form ρx ∝ ρmaζ, where ρx and ρm are the energy densities of dark energy and dark matter, respectively, provides a natural way to address the coincidence problem - why the two densities are comparable today. This non-canonical scaling is achieved by a suitable interaction between the two dark components. We study the observational constraints imposed on such models from the cosmic microwave background (CMB) anisotropy spectrum. Using the recent WMAP results for the location of the CMB peaks, we determine the admissible parameter space and find that interacting models are well consistent with current observational bounds. © 2004 IOP Publishing Ltd.