Cubic four-Skyrmion
= Cubic four-Skyrmion
{title2=$B=4$}
The familiar low-energy $B=4$ <Skyrmion> has a cubic baryon-density shell with six face-hole directions and full density symmetry $O_h$, the <symmetry group of a cube>. The proper subgroup is $O\cong S_4$, the <rotational symmetry group of a cube>; its field invariance includes compensating <isorotations>. A useful <rational map approximation for Skyrmions> has $R(z)=(z^4+2i\sqrt3z^2+1)/(z^4-2i\sqrt3z^2+1)$. The relation $R(iz)=1/R(z)$ pairs a spatial quarter-turn with a target half-turn. Its branch directions are $z=0,\infty,\pm1,\pm i$, corresponding to the six coordinate-axis directions. The map gives an approximate field, not an exact analytic energy-minimizing solution.