Cosmic strings and their induced non-Gaussianities in the cosmic
  microwave background
  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. In this article,
after having reviewed the basic cosmological properties of a string network, we
present the signatures Nambu-Goto cosmic strings would induce in various
observables ranging from the one-point function of the temperature anisotropies
to the bispectrum and trispectrum. It is shown that string imprints are
significantly different than those expected from the primordial type of
non-Gaussianity and could therefore be easily distinguished.
