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Search: MSC category 57R20 ( Characteristic classes and numbers )

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1. CMB Online first

Basu, Samik; Subhash, B
Topology of certain quotient spaces of Stiefel manifolds
We compute the cohomology of the right generalised projective Stiefel manifolds. Following this, we discuss some easy applications of the computations to the ranks of complementary bundles, and bounds on the span and immersibility.

Keywords:projective Stiefel manifold, span, spectral sequence
Categories:55R20, 55R25, 57R20

2. CMB 2011 (vol 55 pp. 586)

Nie, Zhaohu
On Sha's Secondary Chern-Euler Class
For a manifold with boundary, the restriction of Chern's transgression form of the Euler curvature form over the boundary is closed. Its cohomology class is called the secondary Chern-Euler class and was used by Sha to formulate a relative Poincaré-Hopf theorem under the condition that the metric on the manifold is locally product near the boundary. We show that the secondary Chern-Euler form is exact away from the outward and inward unit normal vectors of the boundary by explicitly constructing a transgression form. Using Stokes' theorem, this evaluates the boundary term in Sha's relative Poincaré-Hopf theorem in terms of more classical indices of the tangential projection of a vector field. This evaluation in particular shows that Sha's relative Poincaré-Hopf theorem is equivalent to the more classical law of vector fields.

Keywords:transgression, secondary Chern-Euler class, locally product metric, law of vector fields
Categories:57R20, 57R25

3. CMB 2011 (vol 55 pp. 368)

Nie, Zhaohu
The Secondary Chern-Euler Class for a General Submanifold
We define and study the secondary Chern-Euler class for a general submanifold of a Riemannian manifold. Using this class, we define and study the index for a vector field with non-isolated singularities on a submanifold. As an application, we give conceptual proofs of a result of Chern.

Keywords:secondary Chern-Euler class, normal sphere bundle, Euler characteristic, index, non-isolated singularities, blow-up

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