Matryoshka Skyrmions

We construct a stable Skyrmion in 3+1$3+1$ dimensions as a sine-Gordon kink inside a domain wall within a domain wall in an O(4)$O(4)$ sigma model with hierarchical mass terms without the Skyrme term. We also find that higher dimensional Skyrmions can stably exist with a help of non-Abelian domain walls in an O(N)$O(N)$ model with hierarchical mass terms without a Skyrme term, which leads to a matryoshka structure of Skyrmions.