Abstract: In this paper, the study of the structural arrangement of generalized normal forms (GNFs) is continued. A planar system that is real-analytic at the origin of coordinates is considered. Its unperturbed part forms a first degree quasi-homogeneous polynomial (αx21 + x2, x1x2) with weight (1, 2), in which parameter α ∈ (–1/2, 0) ∪ (0, 1/2]. For the given values of α, this polynomial is a generatrix in the canonical form of an equivalence class with respect to quasi-homogeneous zero order substitutions into which any first order quasi-homogeneous polynomial with weight (1, 2) should be divided according to the chosen structural principles. It makes sense to reduce to GNF only the systems with different canonical forms in their unperturbed part. The constructive method of resonance equations and sets is used to write the resonance equations with the perturbations of the acquired system satisfying these equations using a formal, almost identical quasi-homogeneous substitution in the original system. The fulfillment of these conditions ensures the formal equivalence of the systems. In addition, the resonance sets of coefficients are specified, which allow obtaining all possible GNF structures and proving that the original system is reducible to a GNF with any of the specified structures. Some examples of characteristic GNFs are presented, including the GNFs with parameter α implying the appearance of an additional resonance equation and the second nonzero coefficient in the appropriate orders of GNFs.

Original languageEnglish
Pages (from-to)8-21
Number of pages14
JournalVestnik St. Petersburg University: Mathematics
Volume54
Issue number1
DOIs
StatePublished - Jan 2021

    Research areas

  • generalized normal form, quasi-homogeneous polynomial, resonance equation

    Scopus subject areas

  • Mathematics(all)

ID: 76272301