Structure Formation by Cosmic Strings with a Cosmological Constant

We investigate cosmic string models for structure formation which include a nonzero cosmological constant. We find that the background evolution of density perturbations and modifications to the scaling behavior of the strings both act to increase the amount of power present on ${100h}^{-1\mathrm{}}\mathrm{Mpc}$ scales. We estimate the size of this effect using an analytic model for the evolution of the string network and find that a bias $b\sim 2$ can give acceptable agreement with the current observations. An interesting by-product of these modifications is a broad peak in the cosmic microwave background angular power spectrum around $l=400\mathrm{}–600$.