Viscosity and the monopole density of the Universe

The influence of viscosity on the monopole density of the Universe is investigated. The result is that if the bulk viscosity coefficient in the GUT continuum after symmetry breaking exceeds a critical value, then viscosity can drive an exponential expansion diluting monopoles below the observational limit. This critical value of the viscosity coefficient means a lower bound for the energy scale parameter of the GUT, somewhere above 1015 GeV. Nevertheless, since the behaviour of the GUT continuum near the phase transition is not yet reliably known, the exact value of this lower bound cannot be precisely calculated. 27 refs. (author)