In this paper, we present results for large-angle cosmic microwave background anisotropies generated from high resolution simulations of cosmic string networks in a range of flat Friedmann-Robertson-Walker universes with a cosmological constant. Using an ensemble of all-sky maps, we compare with the Cosmic Background Explorer data to infer a normalization (or upper bound) on the string linear energy density $\mu .$ For a flat matter-dominated model $({\Omega }_M=1)$ we find $G\mu {/c}^2\approx 0.7\times {10}^{-6},$ which is lower than previous constraints probably because of the more accurate inclusion of string small-scale structure. For a cosmological constant within an observationally acceptable range, we find a relatively weak dependence with $G\mu {/c}^2$ less than 10% higher.

• Received 10 February 2003

DOI:https://doi.org/10.1103/PhysRevD.69.023003