  A lump (2D Skyrmion) can be constructed as a sine-Gordon kink (1D Skyrmion)
inside a domain wall in the massive O(3) sigma model. In this paper, we discuss
relations between Skyrmions in 2+1 and 3+1 dimensions. We first construct a
Bogomol'nyi-Prasad-Sommerfield 3D Skyrmion as a lump inside a non-Abelian
domain wall in an O(4) sigma model with a potential term admitting two discrete
vacua. Next, we construct a conventional 3D Skyrmion as a baby Skyrmion in a
non-Abelian domain wall in the Skyrme model with a modified mass term admitting
two discrete vacua. We also construct a spinning 3D Skyrmion as a Q-lump in the
non-Abelian domain wall.

High Energy Physics - Theory;Other Condensed Matter;High Energy Physics - Phenomenology