NUMERICAL SIMULATIONS OF STRING NETWORKS IN THE ABELIAN-HIGGS MODEL

We present the results of a field theory simulation of networks of str ings in the Abelian-Higgs model. From a random initial configuration t he resulting vortex tangle approaches a self-similar regime in which t he length density of lines of zeros of phi reduces as t(-2). The netwo rk loses energy directly into scalar and gauge radiations supporting a recent claim that particle production, not gravitational radiation, i s the dominant energy loss mechanism for cosmic strings. This means th at cosmic strings in grand unified theories are severely constrained b y high energy cosmic ray fluxes: Either they are ruled out, or an impl ausibly small fraction of their energy ends up in quarks and leptons.