Cosmic string parameter constraints and model analysis using small scale Cosmic Microwave Background data

Abstract

We present a significant update of the constraints on the Abelian Higgs cosmic string tension by cosmic microwave background (CMB) data, enabled both by the use of new high-resolution CMB data from suborbital experiments as well as the latest results of the WMAP satellite, and by improved predictions for the impact of Abelian Higgs cosmic strings on the CMB power spectra. The new cosmic string spectra [1] were improved especially for small angular scales, through the use of larger Abelian Higgs string simulations and careful extrapolation. If Abelian Higgs strings are present then we find improved bounds on their contribution to the CMB anisotropies, f AH 10 < 0.095, and on their tension, GµAH < 0.57 × 10 −6 , both at 95% confidence level using WMAP7 data; and f AH 10 < 0.048 and GµAH < 0.42 × 10 −6 using all the CMB data. We also find that using all the CMB data, a scale invariant initial perturbation spectrum, ns = 1, is now disfavoured at 2.4σ even if strings are present. A Bayesian model selection analysis no longer indicates a preference for strings.

Planck2013 results. XXV. Searches for cosmic strings and other topological defects

“…There is now very little degeneracy between the f 10 and n S parameters, something that was not the case for WMAP alone (Battye et al 2006;Bevis et al 2008;Urrestilla et al 2011). This has implication for supersymmetric hybrid inflation models as discussed in that typically require n S > 0.98.…”

“…These WMAP constraints can be improved by adding small-scale CMB anisotropy in a joint analysis. The Nambu-Goto strings limit improves to become Gµ/c 2 < 1.7 × 10 −7 (using SPT data, Dvorkin et al 2011) and field theory strings yield Gµ AH /c 2 < 4.2 × 10 −7 (Urrestilla et al 2011). Power-spectrum based constraints on global textures were studied in Bevis et al (2004) and , with the latter paper giving a 95% limit of Gµ/c 2 < 4.5 × 10 −6 .…”

“…It is prudent in this paper, therefore, to constrain both varieties of strings, labelling the field theory constraints as AH from the Abelian-Higgs (local U(1)) model used to describe them. Given these quantitative differences, such as the lower density, field theory strings produce a weaker constraint Gµ AH /c 2 < 5.7 × 10 −7 using WMAP data alone ) and (Urrestilla et al 2011). The shape of the stringinduced power spectrum also has a different shape, which allows up to a 9.5% contribution at = 10.…”

Constraining topological defects with temperature and polarization anisotropies

“…The relative proportions of scalar, vector and tensor perturbations are essentially fixed for a given type of defect, so a constraint on one of the modes will imply constraints on the others. It is worth noting that even though defects are highly constrained via the CMB temperature anisotropies [16][17][18][19][20][21][22], they can still contribute importantly to the B-mode polarization.…”

Can Topological Defects Mimic the BICEP2B-Mode Signal?

“…Defect production at such a transition is natural and plausibly a subdominant contributor to the total temperature anisotropy. Many papers have used recent data to impose constraints on the fraction of defects, typically obtaining limits of a few percent contribution to the large-angle temperature anisotropies [7][8][9][10][11][12][13]. The tensor and defect spectra were previously compared in Refs.…”