Non-Gaussianity in the Cosmic Microwave Backgroundtemperature fluctuations from cosmic (super-)strings

Abstract

We compute analytically the small-scale temperature fluctuationsof the cosmic microwave background from cosmic (super-)stringsand study the dependence on the string intercommuting probability P.We develop an analytical model which describes the evolutionof a string network and calculate the numbers ofstring segments and kinks in a horizon volume.Then we derive the probability distribution function (pdf)which takes account of finite angular resolution of observation. The resultant pdf consists of a Gaussian part due to frequent scatteringsby long string segments and a non-Gaussian tail due to closeencounters with kinks. The dispersion of the Gaussian part isreasonably consistent with that obtained by numerical simulationsby Fraisse et al.. On the other hand, the non-Gaussian tail containstwo phenomenological parameters which are determined by comparisonwith the numerical results for P = 1. Extrapolating the pdfto the cases with P < 1, we predict that the non-Gaussianfeature is suppressed for small P.