Fitting CMB data with cosmic strings and inflation

TL;DR

This study analyzes CMB data to assess the contribution of cosmic strings, finding a moderate detection of strings and constraints on string tension, with implications for inflationary models.

Contribution

It provides the first multiparameter likelihood analysis combining CMB and non-CMB data to constrain cosmic string contributions and tension.

Findings

2-sigma detection of cosmic strings with f_10 = 0.11 +/- 0.05

Preference for n=1 inflationary spectrum with strings

Upper limit on string tension G mu < 0.7x10^-6

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, we find a 2-sigma detection of strings: f_10 = 0.11 +/- 0.05, where f_10 is the fractional contribution made by strings in the temperature power spectrum (at multipole l = 10). CMB data give moderate preference to the model n = 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 and these extra data, we find that f_10 < 0.11, which corresponds to G mu < 0.7x10^-6 (where mu is the string tension and G is the gravitational constant).