Large angle cosmic microwave background fluctuations from cosmic strings with a cosmological constant

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 $\ensuremath{\mu}.$ For a flat matter-dominated model $({\ensuremath{\Omega}}_{M}=1)$ we find $G\ensuremath{\mu}{/c}^{2}\ensuremath{\approx}0.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6},$ 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 $G\ensuremath{\mu}{/c}^{2}$ less than 10% higher.