VACUUM TUNNELING BY COSMIC STRINGS

We consider vacuum tunneling of a new kind where the false vacua are n ot translationally invariant, but have topological defects that break some of their translational symmetries. In the particular case where t he topological defects are cosmic strings, we show the existence of an O(2) x O(2) symmetric bounce configuration that allows a semiclassica l estimate of the rate of cosmic string induced tunneling. A method of reduction is then suggested for simplifying the computation of the bo unce action. Some phenomenological applications are described. (C) 199 7 Elsevier Science B.V.