CMB temperature trispectrum of cosmic strings
  We provide an analytical expression for the trispectrum of the Cosmic
Microwave Background (CMB) temperature anisotropies induced by cosmic strings.
Our result is derived for the small angular scales under the assumption that
the temperature anisotropy is induced by the Gott-Kaiser-Stebbins effect. The
trispectrum is predicted to decay with a non-integer power-law exponent l^(-r)
with 6<r<7, depending on the string microstructure, and thus on the string
model. For Nambu-Goto strings, this exponent is related to the string mean
square velocity and the loop distribution function. We then explore two classes
of wavenumber configuration in Fourier space, the kite and trapezium
quadrilaterals. The trispectrum can be of any sign and appears to be strongly
enhanced for all squeezed quadrilaterals.
