SEARCHING FOR LONG STRINGS IN CMB MAPS - ART. NO. 103507

Using analytical methods and Monte Carlo simulations, we analyze new s tatistics designed to detect isolated step-like discontinuities which are coherent over large areas of cosmic microwave background pixel map s. Such coherent temperature discontinuities are predicted by the Kais er-Stebbins effect to form due to long cosmic strings in our present h orizon. The background of the coherent step-like seed is assumed to be a scale invariant Gaussian random field which could have been produce d by a superposition of seeds on smaller scales and/or by inflationary quantum fluctuations. We find that the proposed statistics can detect the presence of a coherent discontinuity at a sensitivity level almos t an order of magnitude better compared to more conventional statistic s such as skewness or kurtosis. [S0556-2821(98)11720-4].