Large Angle CMB Fluctuations from Cosmic Strings with a Comological Constant

In this paper, we present results for large-angle CMB anisotropies generated from high resolution simulations of cosmic string networks in a range of flat FRW universes with a cosmological constant. Using an ensemble of all-sky maps, we compare with the COBE 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.