On structures of normal forms of complex points of small ${\mathcal C}^2$-perturbations of real $4$-manifolds embedded in a complex $3$-manifoldStarčič, Tadej (Avtor) CR manifoldsclosure graphscomplex pointsnormal formsperturbationsWe 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.20242024-05-06 12:45:16Neznano18874UDK: 517.5ISSN pri članku: 1578-7303DOI: 10.1007/s13398-023-01545-0COBISS_ID: 194449155sl