Dynamics of topological defects and inflation

We study the dynamics of topological defects in the context of ``topological inflation'' proposed by Vilenkin and Linde independently. Analyzing the time evolution of planar domain walls and of global monopoles, we find that the defects undergo inflationary expansion if {η}{}0.33mPl, where {η} is the vacuum expectation value of the Higgs field and mPl is the Planck mass. This result confirms the estimates by Vilenkin and Linde. The critical value of {η} is independent of the coupling constant {λ} and the initial size of the defect. Even for defects with an initial size much greater than the horizon scale, inflation does not occur at all if {η} is smaller than the critical value. We also examine the effect of gauge fields for static monopole solutions and find that the spacetime with a gauge monopole has an attractive nature, contrary to the spacetime with a global monopole. It suggests that gauge fields affect the onset of inflation. {} 1996 The American Physical Society.