Cosmic strings in a universe with non-critical matter density

Abstract

In the light of recent work which suggests that structure formation by cosmic strings in a critical matter density universe requires large biases, we discuss the effects of reducing the matter density. Using a full linear Einstein-Boltzmann solver, we com pute the cold dark matter density field and the microwave background anisotropies/polarization in a flat universe with a non-zero cosmological constant. We find that universes with $Ω_Λ=0.7-0.8$ give a good fit to the shape of the observed ga laxy distribution, albeit with a bias of around 2. This has interesting implications for the anisotropy and polarization of the microwave background. Finally, we discuss the effects of relaxing the assumption that the universe is flat.