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The classification of weighted projective spaces

Anthony Bahri, Matthias Franz, Dietrich Notbohm, Nigel Ray (2013)

Fundamenta Mathematicae

We obtain two classifications of weighted projective spaces: up to hoeomorphism and up to homotopy equivalence. We show that the former coincides with Al Amrani's classification up to isomorphism of algebraic varieties, and deduce the latter by proving that the Mislin genus of any weighted projective space is rigid.

The cobordism of Real manifolds

Po Hu (1999)

Fundamenta Mathematicae

We calculate completely the Real cobordism groups, introduced by Landweber and Fujii, in terms of homotopy groups of known spectra.

The computation of Stiefel-Whitney classes

Pierre Guillot (2010)

Annales de l’institut Fourier

The cohomology ring of a finite group, with coefficients in a finite field, can be computed by a machine, as Carlson has showed. Here “compute” means to find a presentation in terms of generators and relations, and involves only the underlying (graded) ring. We propose a method to determine some of the extra structure: namely, Stiefel-Whitney classes and Steenrod operations. The calculations are explicitly carried out for about one hundred groups (the results can be consulted on the Internet).Next,...

The diffeomorphism group of a Lie foliation

Gilbert Hector, Enrique Macías-Virgós, Antonio Sotelo-Armesto (2011)

Annales de l’institut Fourier

We describe explicitly the group of transverse diffeomorphisms of several types of minimal linear foliations on the torus T n , n 2 . We show in particular that non-quadratic foliations are rigid, in the sense that their only transverse diffeomorphisms are ± Id and translations. The description derives from a general formula valid for the group of transverse diffeomorphisms of any minimal Lie foliation on a compact manifold. Our results generalize those of P. Donato and P. Iglesias for T 2 , P. Iglesias and...

The directional dimension of subanalytic sets is invariant under bi-Lipschitz homeomorphisms

Satoshi Koike, Laurentiu Paunescu (2009)

Annales de l’institut Fourier

Let A n be a set-germ at 0 n such that 0 A ¯ . We say that r S n - 1 is a direction of A at 0 n if there is a sequence of points { x i } A { 0 } tending to 0 n such that x i x i r as i . Let D ( A ) denote the set of all directions of A at 0 n .Let A , B n be subanalytic set-germs at 0 n such that 0 A ¯ B ¯ . We study the problem of whether the dimension of the common direction set, dim ( D ( A ) D ( B ) ) is preserved by bi-Lipschitz homeomorphisms. We show that although it is not true in general, it is preserved if the images of A and B are also subanalytic. In particular if two subanalytic...

The discriminant and oscillation lengths for contact and Legendrian isotopies

Vincent Colin, Sheila Sandon (2015)

Journal of the European Mathematical Society

We define an integer-valued non-degenerate bi-invariant metric (the discriminant metric) on the universal cover of the identity component of the contactomorphism group of any contact manifold. This metric has a very simple geometric definition, based on the notion of discriminant points of contactomorphisms. Using generating functions we prove that the discriminant metric is unbounded for the standard contact structures on 2 n × S 1 and P 2 n + 1 . On the other hand we also show by elementary arguments that the...

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