Eur. Phys. J. C (2014) 74: 2972
https://doi.org/10.1140/epjc/s10052-014-2972-6

Regular Article - Theoretical Physics

Observational constraints on the types of cosmic strings

¹ Moscow M.V. Lomonosov State University, Sternberg Astronomical Institute (SAI MSU), 13, Universitetskij pr., Moscow, 119992, Russia
² University of Naples Federico II, via Cinthia, 6, 80126 , Naples, Italy

^* e-mail: cosmologia@yandex.ru

Received: 30 June 2014
Accepted: 8 July 2014
Published online: 26 August 2014

Abstract

This paper is aimed at setting observational limits to the number of cosmic strings (Nambu–Goto, Abelian-Higgs, semilocal) and other topological defects (textures). Radio maps of CMB anisotropy, provided by the space mission Planck for various frequencies, were filtered and then processed by the method of convolution with modified Haar functions (MHF) to search for cosmic string candidates. This method was designed to search for solitary strings, without additional assumptions as regards the presence of networks of such objects. The sensitivity of the MHF method is δT ≈ 10 μK in a background of δT ≈ 100 μK. The comparison of these with previously known results on search string network shows that strings can only be semilocal in the range of 1÷5, with the upper restriction on individual string tension (linear density) of Gμ/c² ≤ 7.36×10⁻⁷. The texture model is also legal. There are no strings with Gμ/c² > 7.36×10⁻⁷. However, a comparison with the data for the search of non-Gaussian signals shows that the presence of several (up to three) Nambu–Goto strings is also possible. For Gμ/c² ≤ 4.83×10⁻⁷ the MHF method is ineffective because of unverifiable spurious string candidates. Thus the existence of strings with tensions Gμ/c² ≤ 4.83×10⁻⁷ is not prohibited but it is beyond the Planck data possibilities. The same string candidates have been found in the WMAP 9-year data. Independence of Planck and WMAP data sets serves as an additional argument to consider those string candidates as very promising. However, the final proof should be given by optical deep surveys.