multifurcation

Multifurcation is a concept in dynamical systems and bifurcation theory describing a scenario in which a single bifurcation point gives rise to multiple new solution branches or modes, rather than a single emerging branch. It generalizes the idea of bifurcation to situations where the set of small-amplitude solutions is multi-valued or consists of several distinct modes, often due to higher degeneracy or symmetry.

Mathematically, consider a parametrized system F(x, λ) = 0 with x in R^n and λ in R. A bifurcation point occurs at (x0, λ0) where F(x0, λ0) = 0 and the linearization D_x F(x0, λ0) is singular. Multifurcation typically requires that the kernel of D_x F at the critical point has dimension greater than one, or that higher-order degeneracies (often tied to symmetry) are present. Under these conditions, standard implicit function arguments do not select a unique nearby branch, and center-manifold reduction or Lyapunov-Schmidt methods are used to derive reduced equations that describe several competing branches.

In systems with symmetry, multifurcation is common and analyzed by equivariant bifurcation theory. Symmetry can force multiple equivalent modes to emerge simultaneously, producing a family of branches related by the symmetry group. The resulting normal forms often reveal interactions among modes and can lead to rich patterns of equilibria or periodic orbits.

Consequences of multifurcation include the coexistence or competition of multiple equilibria, periodic solutions, or more complex invariant sets near the critical point. It is a codimension-two or higher phenomenon in many classical settings and is a subject of study in physics, biology, chemistry, and engineering.