About the euler-poincaré characteristic of semi-algebraic sets defined with two inequalities
نویسندگان
چکیده
منابع مشابه
About the Euler-poincaré Characteristic of Semi-algebraic Sets Defined with Two Inequalities
We express the Euler-Poincaré characteristic of a semi-algebraic set, which is the intersection of a non-singular complete intersection with two polynomial inequalities, in terms of the signatures of appropriate bilinear symmetric forms.
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Unlike the well known classical bounds due to Oleinik and Petrovskii, Thom and Milnor on the Betti numbers of (possibly non-symmetric) real algebraic varieties and semialgebraic sets, the above bound is polynomial in k when the degrees of the defining polynomials are bounded by a constant. Moreover, our bounds are asymptotically tight. As an application we improve the best known bound on the Be...
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For any l > 0, we present an algorithm which takes as input a semi-algebraic set, S, defined by P1 ≤ 0, . . . , Ps ≤ 0, where each Pi ∈ R[X1, . . . ,Xk ] has degree ≤ 2, and computes the top l Betti numbers of S, bk−1(S), . . . , bk−l(S), in polynomial time. The complexity of the algorithm, stated more precisely, is ∑l+2 i=0 ( s i ) k2 O(min(l,s)) . For fixed l, the complexity of the algorithm ...
متن کاملOn Projections of Semi-Algebraic Sets Defined by Few Quadratic Inequalities
Let S ⊂ Rk+m be a compact semi-algebraic set defined by P1 ≥ 0, . . . , P` ≥ 0, where Pi ∈ R[X1, . . . , Xk, Y1, . . . , Ym], and deg(Pi) ≤ 2, 1 ≤ i ≤ `. Let π denote the standard projection from Rk+m onto Rm. We prove that for any q > 0, the sum of the first q Betti numbers of π(S) is bounded by (k +m). We also present an algorithm for computing the the first q Betti numbers of π(S), whose com...
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ژورنال
عنوان ژورنال: Revista Matemática Complutense
سال: 2001
ISSN: 1988-2807,1139-1138
DOI: 10.5209/rev_rema.2001.v14.n1.17038