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The rational homotopy of Thom spaces and the smoothing of isolated singularities

Stefan Papadima (1985)

Annales de l'institut Fourier

Rational homotopy methods are used for studying the problem of the topological smoothing of complex algebraic isolated singularities. It is shown that one may always find a suitable covering which is smoothable. The problem of the topological smoothing (including the complex normal structure) for conical singularities is considered in the sequel. A connection is established between the existence of certain relations between the normal Chern degrees of a smooth projective variety and the question...

The reduction of quantum invariants of 4-thickenings

Ivelina Bobtcheva, Frank Quinn (2005)

Fundamenta Mathematicae

We study the sensibility of an invariant of 2-dimensional CW complexes in the case when it comes as a reduction (through a change of ring) of a modular invariant of 4-dimensional thickenings of such complexes: it is shown that if the Euler characteristic of the 2-complex is greater than or equal to 1, its invariant depends only on homology. To see what is happening when the Euler characteristic is smaller than 1, we use ideas of Kerler and construct, from any tortile category, an invariant of 4-thickenings...

The Reidemeister-Turaev torsion of standard Spin c structures on Seifert fibered 3-manifolds

Yuya Koda (2012)

Annales de la faculté des sciences de Toulouse Mathématiques

The Reidemeister-Turaev torsion is an invariant of 3-manifolds equipped with Spin c structures. Here, a Spin c structure of a 3-manifold is a homology class of non-singular vector fields on it. Each Seifert fibered 3-manifold has a standard Spin c structure, which is represented as a non-singular vector field the set of whose orbits give a Seifert fibration. We provide an algorithm for computing the Reidemeister-Turaev torsion of the standard Spin c structure on a Seifert fibered 3-manifold. The machinery...

The relative coincidence Nielsen number

Jerzy Jezierski (1996)

Fundamenta Mathematicae

We define a relative coincidence Nielsen number N r e l ( f , g ) for pairs of maps between manifolds, prove a Wecken type theorem for this invariant and give some formulae expressing N r e l ( f , g ) by the ordinary Nielsen numbers.

The rhombic dodecahedron and semisimple actions of Aut(Fₙ) on CAT(0) spaces

Martin R. Bridson (2011)

Fundamenta Mathematicae

We consider actions of automorphism groups of free groups by semisimple isometries on complete CAT(0) spaces. If n ≥ 4 then each of the Nielsen generators of Aut(Fₙ) has a fixed point. If n = 3 then either each of the Nielsen generators has a fixed point, or else they are hyperbolic and each Nielsen-generated ℤ⁴ ⊂ Aut(F₃) leaves invariant an isometrically embedded copy of Euclidean 3-space 𝔼³ ↪ X on which it acts as a discrete group of translations with the rhombic dodecahedron as a Dirichlet...

The S1-CW decomposition of the geometric realization of a cyclic set

Zbigniew Fiedorowicz, Wojciech Gajda (1994)

Fundamenta Mathematicae

We show that the geometric realization of a cyclic set has a natural, S 1 -equivariant, cellular decomposition. As an application, we give another proof of a well-known isomorphism between cyclic homology of a cyclic space and S 1 -equivariant Borel homology of its geometric realization.

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