Magnetic Wormholes and Topological Symmetry*

We investigate the wormhole solutions that arise in the semiclassical analysis of euclidean gravity coupled to gauge fields. In 2 + 1 dimensions, "magnetic monopole" solutions can be constructed, for either abelian or nonabelian gauge fields. The low-energy physics induced by these wormholes qualitatively resembles, but is quantitatively distinguishable from, the tow-energy physics of a gauge theory (without wormholes) that undergoes the Higgs mechanism at the wormhole mass scale. Wormholes are suppressed if matter fields are introduced that transform suitably under the gauge group. In 3 + 1 dimensions, "meron'" solutions can be constructed, for nonabelian gauge fields only. We argue, however, that these wormhole solutions do not contribute to the semiclassical evaluation of the path integral.