Revisit the Lovász local lemma (Q1366732)

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scientific article; zbMATH DE number 1061818
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Revisit the Lovász local lemma
scientific article; zbMATH DE number 1061818

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    Revisit the Lovász local lemma (English)
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    16 March 1998
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    Let \(A_1,A_2,\dots,A_n\) be events on a given probability space. Let \(G= (H,D)\), \(H=\{1,2,\dots,n\}\), be a graph and assume that if \((i,j)\not\in D\), then \(A_i\) and \(A_j\) are independent. Under very complicated conditions on \(P(A_j)\), \(1\leq j\leq n\), the author establishes a lower bound on \(u=P\left(\bigcap^n_{j=1} A^0_j\right)\) with the aim of obtaining sufficient conditions for \(u>0\). The theorems discussed are not always applicable because of the conditions on \(P(A_j)\). However, the Kounias form of a second degree Bonferroni-type bound \[ u\geq 1-\sum^n_{j= 1}P(A_j)+ \sum_{\substack{ 1\leq j\leq n\\ i\neq j}} P(A_i\cap A_j)\geq 1-\sum^n_{j=1} P(A_j)+ P(A_i) \sum_{\substack{ 1\leq j\leq n\\ (i,j)\not\in D}} P(A_j) \] is not only always applicable, whatever the \(P(A_j)\), but gives superior bounds to those discussed in the paper, and certainly \(u>0\) easily follows for all examples of the paper. The classical Bonferroni bound \(u\geq 1-\sum^n_{j= 1}P(A_j)\), mentioned in the paper, is clearly inadequate for utilizing independence. For the cited Bonferroni-type bound see [the reviewer and \textit{I. Simonelli}, ``Bonferroni-type inequalities with applications'' (1996; Zbl 0869.60014)].
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    finite number of events
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    lower bound
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    probability of intersection
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    Bonferroni-type inequalities
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