title: Singularity theory study of overdetermination in models for L-H transitions
abstract: Two dynamical models that have been proposed to describe transitions between low- and high-confinement states in confined plasmas are analyzed using singularity theory and stability theory. It is shown that the stationary-state bifurcation sets have qualitative properties identical to standard normal forms for the pitchfork and transcritical bifurcations. The analysis yields the codimension of the highest-order singularities, from which we find that the unperturbed systems are overdetermined bifurcation problems and derive appropriate universal unfoldings. Questions of mutual equivalence and the character of the state transitions are addressed.
authors.affiliation: Department of Theoretical Physics and Plasma Research Laboratory, Research School of Physical Sciences & Engineering, The Australian National University, Canberra 0200 Australia.
authors.initials: R
authors.lastname: Ball
authors.initials: RL
authors.lastname: Dewar