Cosmic strings from preheating

Abstract We investigate nonthermal phase transitions that may occur after post-inflationary preheating in a simple model of a two-component scalar field with the effective potential λ ( φ i 2 −v 2 ) 2 /4, where φ 1 is identified with the inflaton field. We use three-dimensional lattice simulations to investigate the full nonlinear dynamics of the model. Fluctuations of the fields generated during and after preheating temporarily make the effective potential convex in the φ 1 direction. The subsequent nonthermal phase transition with symmetry breaking leads to formation of cosmic strings even for v≫10 16 GeV. This mechanism of string formation, in a modulated (by the oscillating field φ 1 ) phase transition, is different from the usual Kibble mechanism.