On the CMB Kurtosis from Cosmic Strings

ALEJANDRO GANGUI

ASTROPHYSICAL LETTERS AND COMMUNICATIONS

Gordon and Breach Publishers

Lugar: The Netherlands; Año: 1996 vol. 33 p. 25 - 31

0888-6512

We report here on some recent work based on a simple analytical model for computing correlations in the Cosmic Microwave Background (CMB) radiation temperature field.  Under simple assumptions on the way in which CMB photons get perturbed by cosmic strings we are able to derive an expression for the q-point temperature correlation function.  Our analysis is sensible specially for large angular scales where the Kaiser-Stebbins effect is dominant. We then concentrate our analysis on the excess kurtosis parameter.  We also estimate the cosmic variance for the kurtosis due to a Gaussian fluctuation field, showing its dependence on the primordial spectral index of density fluctuations $n$ and finding agreement with previous published results for the particular case of a flat Harrison-Zel'dovich spectrum.  Our value for the kurtosis agree with previous analyses but falls below the threshold imposed by the cosmic variance when commonly accepted parameters from string simulations are considered.  In particular the non-Gaussian signal is found to be inversely proportional to the scaling number of defects, as could be expected by the central limit theorem.