In [7] an open set of structurally unstable families of vector fields on a sphere was
constructed. More precisely, a vector field with a degeneracy of codimension three was discovered
whose bifurcation in a generic three-parameter family has a numeric invariant. This vector field
has a polycycle and two saddles, one inside and one outside this polycycle; one separatrix of
the outside saddle winds towards the polycycle and one separatrix of the inside saddle winds
from it. Families with functional invariants were constructed also. In [2] a hyperbolic polycycle
with five vertices and no saddles outside it was constructed whose bifurcations in its arbitrary
narrow neighborhood (semilocal bifurcations in other words) have a numeric invariant and thus
are structurally unstable. This paper deals with semilocal bifurcations. A hyperbolic polycycle
with nine edges is constructed whose semilocal bifurcation in an open set of nine-parameter
families has a functional invariant.
Keywords:
polycycles, semilocal bifurcations, functional invariants
Citation:
Ilyashenko Y. S., Functional Invariants in Semilocal Bifurcations, Regular and Chaotic Dynamics,
2025, Volume 30, Number 4,
pp. 618-627