### Abstract

Planck data have been used to provide stringent new
constraints on cosmic strings and other defects. We
describe forecasts of the CMB power spectrum induced by
cosmic strings, calculating these from network models and
simulations using line-of-sight Boltzmann solvers. We
have studied Nambu-Goto cosmic strings, as well as field
theory strings for which radiative effects are important,
thus spanning the range of theoretical uncertainty in the
underlying strings models. We have added the angular
power spectrum from strings to that for a simple
adiabatic model, with the extra fraction defined as f10
at multipole l = 10. This parameter has been added to the
standard six parameter fit using COSMOMC with flat
priors. For the Nambu-Goto string model, we have obtained
a constraint on the string tension of Gµ/c2 <1.5 * 10-7
and f10 <0.015 at 95% confidence that can be improved to
Gµ/c2 <1.3 * 10-7 and f10 <0.010 on inclusion of high-l
CMB data. For the Abelian-Higgs field theory model we
find, GµAH/c2<3.2 * 10-7 and f10 <0.028. The
marginalised likelihoods for f10 and in the f10-Obh2
plane are also presented. We have additionally obtained
comparable constraints on f10 for models with semilocal
strings and global textures. In terms of the effective
defect energy scale these are somewhat weaker at Gµ/c2 < 1.1 * 10-6. We have made complementarity searches for the
specific non-Gaussian signatures of cosmic strings,
calibrating with all-sky Planck resolution CMB maps
generated from networks of post-recombination strings. We
have validated our non-Gaussian searches using these
simulated maps in a Planck-realistic context, estimating
sensitivities of up to ?Gµ/c2 ~ 4 * 10-7. We have
obtained upper limits on the string tension at 95%
confidence of Gµ/c2 <9.0 * 10-7 with modal bispectrum
estimation and Gµ/c2 <7.8 * 10-7 for real space searches
with Minkowski functionals. These are conservative upper
bounds because only post-recombination string
contributions have been included in the non-Gaussian
analysis.

Original language | English |
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Article number | A25 |

Number of pages | 21 |

Journal | Astronomy and Astrophysics |

Volume | 571 |

DOIs | |

Publication status | Published - 2014 |

MoE publication type | A1 Journal article-refereed |

### Keywords

- cosmic background radiation
- cosmological parameters
- early Universe
- large-scale structure of Universe
- cosmology

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## Cite this

Varis, J., Tuovinen, J., Moss, A., & Planck Collaboration (2014). Planck 2013 results. XXV. Searches for cosmic strings and other topological defects.

*Astronomy and Astrophysics*,*571*, [A25]. https://doi.org/10.1051/0004-6361/201321621