One-Dimensional Simulations of the Topological Defects in a 3:1 $U(1)$ Model

Abstract

The domain wall is a kind of topological defect that can appear when a discrete symmetry is broken. If the discrete symmetry appears as an intermediate symmetry during a $U(1)$ symmetry breaking, the domain walls are connected to cosmic strings, forming walls bounded by strings. Intuitively, the domain wall disappears if the breaking scale of the discrete symmetry is comparable to that of the $U(1)$ symmetry. In this paper, relying on a 3:1 $U(1)$ model, we show the detailed processes of the disappearance of the domain wall. Due to the existence of the non-negligible ``bias angle'' $β$, the relevance of the ``$Z_3$ symmetry'' and the domain wall is blurred, and thereby the evaluations of the string profiles in a hybrid wall-string network should be revised. We also made some preliminary calculations of the gravitational waves generated by the wall-string network created in the early universe.