Dynamics of Nambu monopole in two Higgs doublet models -- Cosmological Monopole Collider --

Understand

We study the dynamics of the Nambu monopole in two Higgs doublet models, which is a magnetic monopole attached by two topological $Z$ strings ($Z$ flux tubes) from two opposite sides.

• The monopole is a topologically stable solution of the equation of motions when the Higgs potential has global $U(1)$ and $\mathbb{Z}_2$ symmetries.
• In this paper, we consider more general cases without the $\mathbb{Z}_2$ symmetry, and find that it is no longer a static solution but moves along the $Z$ string being pulled by the heavier string.
• After analytically constructing an asymptotic form of the monopole, we confirm such a motion using the numerical relaxation method.