Supercritical bifurcation
= Supercritical bifurcation
A supercritical branch emerges on the parameter side where the original state loses stability. In the cubic <Landau amplitude equation> $\dot A=\mu A-g|A|^2A$ with $g>0$, the nonzero branch $|A|^2=\mu/g$ lies at $\mu>0$ and is stable to radial amplitude perturbations. Continuous phase symmetry still leaves a neutral phase direction. The direction of a branch and its stability should both be checked in a general problem of <bifurcation theory>.