 Tetrahedral three-Skyrmion

The familiar low-energy $B=3$ Skyrmion has tetrahedral baryon-density symmetry $T_d$. Proper rotations form the tetrahedral symmetry group $T\cong A_4$, acting on the field with compensating isorotations. An angular approximation is $R(z)=(i\sqrt{3}{z}^2-1)/(z^3-i\sqrt{3}z)$. Its Wronskian of a rational map is proportional to $z^4+2i\sqrt{3}{z}^2+1$. The four branch directions are the face-hole directions of a tetrahedral shell. A rational map and a variational radial profile approximate the actual field, and baryon-density symmetry must be distinguished from invariance of the pion field under an unaccompanied spatial rotation.