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On the Euler characteristic of the link of a weighted homogeneous mapping

Piotr Dudziński (2003)

Annales Polonici Mathematici

The paper is concerned with an effective formula for the Euler characteristic of the link of a weighted homogeneous mapping F : k with an isolated singularity. The formula is based on Szafraniec’s method for calculating the Euler characteristic of a real algebraic manifold (as the signature of an appropriate bilinear form). It is shown by examples that in the case of a weighted homogeneous mapping it is possible to make the computer calculations of the Euler characteristics much more effective.

On the existence of 2-fields in 8-dimensional vector bundles over 8-complexes

Martin Čadek, Jiří Vanžura (1995)

Commentationes Mathematicae Universitatis Carolinae

Necessary and sufficient conditions for the existence of two linearly independent sections in an 8-dimensional spin vector bundle over a CW-complex of the same dimension are given in terms of characteristic classes and a certain secondary cohomology operation. In some cases this operation is computed.

On the first secondary invariant of Molino's central sheaf

Jesús A. Álvarez López (1996)

Annales Polonici Mathematici

For a Riemannian foliation on a closed manifold, the first secondary invariant of Molino's central sheaf is an obstruction to tautness. Another obstruction is the class defined by the basic component of the mean curvature with respect to some metric. Both obstructions are proved to be the same up to a constant, and other geometric properties are also proved to be equivalent to tautness.

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