Fitting Cosmic Microwave Background Data with Cosmic Strings and Inflation

Abstract

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 $2\ensuremath{\sigma}$ detection of strings: ${f}_{10}=0.11\ifmmode\pm\else\textpm\fi{}0.05$, where ${f}_{10}$ is the fractional contribution made by strings in the temperature power spectrum (at $\ensuremath{\ell}=10$). 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 ${f}_{10}<0.11$, which corresponds to ${G}_{\ensuremath{\mu}}<0.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ (where $\ensuremath{\mu}$ is the string tension and $G$ is the gravitational constant).