Cosmic Strings as the Source of Small-Scale Microwave Background Anisotropy

TL;DR

Cosmic string networks actively generate small-scale anisotropies in the cosmic microwave background, potentially dominating over inflationary signals at high multipoles, with current observations constraining their contribution.

Contribution

This paper analyzes the impact of cosmic strings on small-scale CMB anisotropies and predicts their dominance at high multipoles, providing testable observational signatures.

Findings

String-induced anisotropy is limited to less than 10% on large scales.

At small scales (l>2000), string effects could dominate over inflation.

Upcoming experiments can test the cosmic string contribution.

Abstract

Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy seeded by inflation. The spectrum of perturbations generated by strings does not match the observed CMB spectrum on large angular scales (l<1000) and is bounded to contribute no more than 10% of the total power on those scales. However, when this bound is marginally saturated, the anisotropy created by cosmic strings on small angular scales l>2000 will dominate over that created by the primary inflationary perturbations. This range of angular scales in the CMB is presently being measured by a number of experiments; their results will test this prediction of cosmic string networks soon.