Phase transition in U(1) configuration space: Oscillons as remnants of vortex-antivortex annihilation

We show that the annihilation of vortex-antivortex pairs can lead to very long-lived oscillon states in 2d Abelian Higgs models. The emergence of oscillons is controlled by the ratio of scalar and vector field masses, β=(mₛ/mᵥ)² and can be described as a phase transition in field configuration space with critical value βc0.13(6)±2: only models with β<βc lead to oscillonlike remnants. The critical behavior of the system obeys a power law O(β)~|β-βc|ᵒ, where O is an order parameter indicating the presence of oscillons and o=0.2(2)±2 is the critical exponent.