Fitting Cosmic Microwave Background Data with Cosmic Strings and Inflation

We perform a multiparameter likelihood analysis to compare measurements of the cosmic microwave background (CMB) power spectra with predictions from models involving cosmic strings. Adding strings to the standard case of a primordial spectrum with power-law tilt n_s, we find a 2σ detection of strings: f₁₀=0.11±0.05, where f₁₀ is the fractional contribution made by strings in the temperature power spectrum (at ℓ=10). CMB data give moderate preference to the model n_s=1 with cosmic strings over the standard zero-strings model with variable tilt. When additional non-CMB data are incorporated, the two models become on a par. With variable n_s and these extra data, we find that f₁₀<0.11, which corresponds to G_μ<0.7×10^-6 (where μ is the string tension and G is the gravitational constant).