SIGNATURES OF COSMIC STRINGS ON THE MICROWAVE BACKGROUND

We review recent progress on testing the hypothesis of the existence o f cosmic string perturbations in microwave background maps. Using an a nalytical model for the string network we show that the predicted ampl itude and spectrum of MBR fluctuations are consistent with the COBE da ta for a reasonable value of the single free parameter of the string m odel (the mass per unit length of the string mu). To distinguish the p redictions of cosmic strings from those of Gaussian models it is neces sary to apply specific statistical tests which are sensitive to non-ra ndom phases of the MBR temperature maps. We discuss two such statistic al tests: First, the probability distribution and the moments of fluct uations delta T/T and second the corresponding statistical quantities for the gradient of fluctuations along a fixed direction. We show that the second statistic can detect cosmic string specific signatures on MBR temperature maps with resolution of a few arcminutes or smaller.