Electroweak strings with dark scalar condensates and their (in)stability

TL;DR

This paper studies the stability of electroweak cosmic strings within an extended Standard Model that includes a dark sector, revealing that dark scalar condensates can enhance stability under certain conditions, but instability reemerges near the physical electroweak angle.

Contribution

It introduces a minimal dark sector coupled via Higgs-portal and gauge mixing, analyzing its impact on electroweak string stability, a novel extension of previous models.

Findings

Dark scalar condensates improve string stability near $ heta_W=\pi/2$

Strings become unstable as $ heta_W$ approaches its physical value

W-boson condensation is identified as the instability mechanism

Abstract

The stability of "visible" electroweak-type cosmic strings is investigated in an extension of the Standard Model (SM) by a minimal dark sector, consisting of a U(1) gauge field, broken spontaneously by a scalar. The "visible" and dark sectors are coupled through a Higgs-portal and a gauge-kinetic mixing term. It is found that strings whose core is "filled" with a dark scalar condensate exhibit better stability properties than their analogues in the SM, when the electroweak mixing angle is close to $\theta_{\rm W}=\pi/2$. They become unstable as one lets $\theta_{\rm W}$ approach its physical value. The instability mechanism appears to be a $W$-boson condensation mechanism found in previous studies on the stability of electroweak strings.