Line bundles with . A six dimensional example
We exhibit a six dimensional manifold with a line bundle on it which is not the pullback of a bundle on .
On manifolds diffeomorphic on the complement of a point
We prove that four manifolds diffeomorphic on the complement of a point have the same Donaldson invariants.
Line bundles with . Higher order obstruction
We study secondary obstructions to representing a line bundle as the pull-back of a line bundle on and we interpret them geometrically.
Group actions on rational homology spheres
We study the homology of the fixed point set on a rational homology sphere under the action of a finite group.
Line bundles with
We prove that on a -complex the obstruction for a line bundle to be the fractional power of a suitable pullback of the Hopf bundle on a 2-dimensional sphere is the vanishing of the square of the first Chern class of . On the other hand we show that if one looks at integral powers then further secondary obstructions exist.
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