Mass-deformed spherical sigma model
= Mass-deformed spherical sigma model
{title2=$V(\phi)=\frac{rm^2}{4}\sin^2\phi$}
A spherical sigma model in polar fields $\phi,\alpha$ has kinetic metric $r(d\phi^2+\sin^2\phi\,d\alpha^2)/2$ in the usual one-half kinetic convention. The displayed positive potential selects the two polar vacua. For $r>0$ it supports static and rotating charged <kinks>, and a topological theta term shifts their canonical internal charge without changing the bulk equations.