Knots from wall--anti-wall annihilations with stretched strings

A pair of a domain wall and an anti-domain wall is unstable to decay. We show that when a vortex-string is stretched between the walls, there remains a knot soliton (Hopfion) after the pair annihilation.Comment: 10 pages, 6 figures, published version. arXiv admin note: text overlap with arXiv:1205.244

Incarnations of Instantons

Yang-Mills instantons in a pure Yang-Mills theory in four Euclidean space can be promoted to particle-like topological solitons in d=4+1 dimensional space-time. When coupled to Higgs fields, they transform themselves in the Higgs phase into Skyrmions, lumps and sine-Gordon kinks, with trapped inside a non-Abelian domain wall, non-Abelian vortex and monopole string, respectively. Here, we point out that a closed monopole string, non-Abelian vortex sheet and non-Abelian domain wall in $S^1$, $S^2$ and $S^3$ shapes, respectively, are all Yang-Mills instantons if their $S^1$, $S^2$ and $S^3$ moduli, respectively, are twisted along their world-volumes.Comment: 17 pages, 3 figures, v2: published versio

Fractional instantons and bions in the principal chiral model on R2×S1{\mathbb R}^2\times S^1 with twisted boundary conditions

Bions are multiple fractional instanton configurations with zero instanton charge playing important roles in quantum field theories on a compactified space with a twisted boundary condition. We classify fractional instantons and bions in the $SU(N)$ principal chiral model on ${\mathbb R}^2 \times S^1$ with twisted boundary conditions. We find that fractional instantons are global vortices wrapping around $S^1$ with their $U(1)$ moduli twisted along $S^1$, that carry $1/N$ instanton (baryon) numbers for the ${\mathbb Z}_N$ symmetric twisted boundary condition and irrational instanton numbers for generic boundary condition. We work out neutral and charged bions for the $SU(3)$ case with the ${\mathbb Z}_3$ symmetric twisted boundary condition. We also find for generic boundary conditions that only the simplest neutral bions have zero instanton charges but instanton charges are not canceled out for charged bions. A correspondence between fractional instantons and bions in the $SU(N)$ principal chiral model and those in Yang-Mills theory is given through a non-Abelian Josephson junction.Comment: 30 pages, 2 figures. v2: published version. arXiv admin note: text overlap with arXiv:1412.768

Josephson junction of non-Abelian superconductors and non-Abelian Josephson vortices

A Josephson junction is made of two superconductors sandwiching an insulator, and a Josephson vortex is a magnetic vortex (flux tube) absorbed into the Josephson junction, whose dynamics can be described by the sine-Gordon equation. In a field theory framework, a flexible Josephson junction was proposed, in which the Josephson junction is represented by a domain wall separating two condensations and a Josephson vortex is a sine-Gordon soliton in the domain wall effective theory. In this paper, we propose a Josephson junction of non-Abelian color superconductors, that is described by a non-Abelian domain wall, and show that a non-Abelian vortex (color magnetic flux tube) absorbed into it is a non-Abelian Josephson vortex represented as a non-Abelian sine-Gordon soliton in the domain wall effective theory, that is the $U(N)$ principal chiral model.Comment: 19 pages, 3 figures, v2: published versio