Title: CMB non-Gaussianities induced by Nambu-Goto cosmic strings
Speaker: Christophe Ringeval (Louvain University)

Abstract: Motivated by the fact that cosmological perturbations of inflationary quantum origin were born Gaussian, the search for non-Gaussianities in the cosmic microwave background (CMB) anisotropies is considered as the privileged probe of non-linear physics in the early universe.  Cosmic strings are active sources of gravitational perturbations and incessantly produce non-Gaussian distortions in the CMB. Even if, on the currently observed angular scales, they can only contribute a small fraction of the CMB angular power spectrum, cosmic strings could actually be the main source of its non-Gaussianities.  We analytically derive the bispectrum and trispectrum of their induced temperature anisotropies for the small angular scales and show that they are significantly different than those associated with the primordial type of non-Gaussianity.