Degeneracy locus

There is a line of degeneracies at the equilateral geometries, S — 0, and deviations from the degeneracy line are expressed in terms of u and v, subject at a given value of Q to Q, this bounding circle being the locus of linear... 

Fig. 8.9. The locus A of double-zero eigenvalue degeneracies of the Hopf bifurcation for cubic autocatalysis with decay. Also shown, as broken curves, are the loci of stationary-state degeneracies, corresponding to the boundaries for isola and mushroom patterns. The curve A lies completely within the parameter regions for multiple stationary states.

Consider now the case of AB2-type systems formed from 2S atoms. In this case, the only possibility of degeneracy arises for C2v geometries, as anticipated from the London equation. Yet, since the symmetry is not forced, the intersection locus may be infinite or finite in extent. In fact, though the intersection condition for C2v (R2 = K3) geometries requires that... 

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