Let Y be a real algebraic subset of $𝑹^m$ and $F:Y → 𝑹^n$ be a polynomial map. We show that there exist real polynomial functions $g_1, ..., g_s$ on $𝑹^n$ such that the Euler characteristic of fibres of $F$ is the sum of signs of $g_i$.
Institute of Mathematics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland
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