Abstract: We extend our previous result on the behaviour of the quadratic part of a complex points of a small ${\mathcal C}^2$-perturbation of a real $4$-manifold embedded in a complex $3$-manifold. We describe the change of the structure of the quadratic normal form of a complex point. It is an immediate consequence of a theorem clarifying how small perturbations can change the bundle of a pair of one arbitrary and one symmetric $2 \times 2$ matrix with respect to an action of a certain linear group.Keywords: CR manifolds, closure graphs, complex points, normal forms, perturbationsPublished in DiRROS: 06.05.2024; Views: 326; Downloads: 183 Full text (929,58 KB)This document has many files! More...