Gravitational field of twisted Baby Skyrmion strings and loops

TL;DR

This paper investigates the gravitational effects of twisted Baby Skyrmion strings and loops, revealing how internal twist influences gravity, stability, and potential dark matter candidates, with implications for cosmic string models.

Contribution

It provides an approximate solution for the gravitational field of twisted Baby Skyrmion strings and analyzes the stability and dark matter relevance of various loop configurations.

Findings

Twist induces a long-range gravitational acceleration similar to massive shells.

Small loops are stabilized by rigidity energy when their radius is comparable to the string width.

Certain loops could serve as dark matter candidates, while others are excluded due to rapid decay.

Abstract

We consider the gravitational field of infinite straight and stationary twisted Baby Skyrmion cosmic string. Using the approximate solution of Einstein equations, it is shown that the internal phase rotation (twist) along the string axis is responsible for a long-range gravitational acceleration resembling that of massive cylindrical shell. We also study the stability and gravitational field of circular loops. When the loop radius becomes comparable with the string width, the rigidity energy tends to stabilize small loops against radial collapse. The nucleon scale-toroidal knot with Hopf charge Q=1 is found to decay very rapidly on the scale of the age of the universe due to low energy cost to flux lines crossings. Such knot is therefore excluded from the dark matter scenario of Spergel and Steinhardt. However, the Q = 0 loop, stabilized by rigidity, could be a candidate for this scenario. In contrast, the electroweak strings are prevented from intercommuting due to much larger energy cost to intersection. This makes them a possible candidate for the solid dark matter scenario of Bucher and Spergel.