Observational constraints on the types of cosmic strings

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 $$\delta T \approx 10~\upmu \hbox {K}$$ in a background of $$\delta T \approx 100~\upmu \hbox {K}$$ . The comparison of these with previously known results on search string network shows that strings can only be semilocal in the range of $$1 \div 5$$ , with the upper restriction on individual string tension (linear density) of $$G\mu /c^2 \le 7.36 \times 10^{-7}$$ . The texture model is also legal. There are no strings with $$G\mu /c^2 > 7.36 \times 10^{-7}$$ . 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 $$G\mu /c^2 \le 4.83 \times 10^{-7}$$ the MHF method is ineffective because of unverifiable spurious string candidates. Thus the existence of strings with tensions $$G\mu /c^2 \le 4.83 \times 10^{-7}$$ 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.