Structure formation by cosmic strings with a cosmological constant

We investigate cosmic string models for structure formation which include a non-zero cosmological constant. We nd that the background evolution of density perturbations and modi cations to the scaling behaviour of the strings both act to increase the amount of power present on 100h Mpc scales. We estimate the size of this e ect using an analytic model for the evolution of the string network and nd that a bias b 2 can give acceptable agreement with the current observations. An interesting by product of these modi cations is a broad peak in the cosmic microwave background (CMB) angular power spectrum around l = 400 600.