• Accepted Paper

CMB anisotropies from cosmic strings and superstrings in light of ACT DR6

Anastasios Avgoustidis, Edmund J. Copeland, Adam Moss, and Juhan Raidal

Phys. Rev. D - Accepted 11 September, 2026

DOI: https://doi.org/10.1103/hkmh-m7s8

Abstract

We present updated constraints on cosmic string and superstring parameters derived from Cosmic Microwave Background (CMB) anisotropies. The constraints are obtained via Markov Chain Monte Carlo (MCMC) analyses of the full temperature and polarization data combined with the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6). For ordinary cosmic strings, we constrain the string tension Gμ, the string wiggliness parameter α, and the self-chopping efficiency c̃. For cosmic superstrings, we constrain the fundamental string tension GμF, the string coupling gs, and a parameter w describing the volume of the compact extra dimensions. In both cases, we find significantly tighter bounds on the string tension compared to previous analyses, obtaining 2σ upper limits of Gμ<3.66×10−8 and GμF<1.38×10−8. We also discuss the significant prior-dependence of these results. The computational pipeline used in this work, including a modified version of capable of computing CMB anisotropies sourced by any active network described via unequal-time correlators, is released publicly as .

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