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On the Euler characteristic of fibres of real polynomial maps

Adam Parusiński, Zbigniew Szafraniec (1998)

Banach Center Publications

Let Y be a real algebraic subset of m and F : Y n be a polynomial map. We show that there exist real polynomial functions g 1 , . . . , g s on n such that the Euler characteristic of fibres of F is the sum of signs of g i .

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 Fundamental Group of self-affine plane Tiles

Jun Luo, Jörg M. Thuswaldner (2006)

Annales de l’institut Fourier

Let A 2 × 2 be an expanding matrix, 𝒟 2 a set with | det ( A ) | elements and define 𝒯 via the set equation A 𝒯 = 𝒯 + 𝒟 . If the two-dimensional Lebesgue measure of 𝒯 is positive we call 𝒯 a self-affine plane tile. In the present paper we are concerned with topological properties of 𝒯 . We show that the fundamental group π 1 ( 𝒯 ) of 𝒯 is either trivial or uncountable and provide criteria for the triviality as well as the uncountability of π 1 ( 𝒯 ) . Furthermore, we give a short proof of the fact that the closure of each component of int ( 𝒯 ) is a locally...

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