The affine invariant partition of the set of quadratic systems with one finite singular point of the 4th multiplicity with respect to different topological classes is accomplished. The conditions corresponding to this partition are semi-algebraic, i.e. they are expressed as equalities or inequalities between polynomials.
@article{urn:eudml:doc:41265, title = {Affine invariant conditions for the topological distinction of quadratic systems with a critical point of the 4th multiplicity.}, journal = {Publicacions Matem\`atiques}, volume = {40}, year = {1996}, pages = {431-441}, mrnumber = {MR1425629}, zbl = {0872.34013}, language = {en}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:41265} }
Voldman, Mark; Calin, Iu. T.; Vulpe, Nicolae I. Affine invariant conditions for the topological distinction of quadratic systems with a critical point of the 4th multiplicity.. Publicacions Matemàtiques, Tome 40 (1996) pp. 431-441. http://gdmltest.u-ga.fr/item/urn:eudml:doc:41265/