Abstract: | Summary Generalizations of principle axes are found for surfaces in E4. The singularities generalize umbilics. The generic indicies are computed. For these computations the Thom Transversality Theorem as applied by Feldman to geometry is used. Hower we ? reduce the group ? rendering the calculations more tractible. Also we show that a torus or sphere cannot be immersed in E4 with everywhere nonzero curvature of the normal bundle. Entrata in Redazione il 19 novembre 1968. |