Lecture Notes in Mathematics 1826 Editors: J.--M.Morel,Cachan F.Takens,Groningen B.Teissier,Paris 3 Berlin Heidelberg NewYork HongKong London Milan Paris Tokyo Klaus Dohmen Improved Bonferroni Inequalities via Abstract Tubes Inequalities and Identities of Inclusion-Exclusion Type 1 3 Author KlausDohmen DepartmentofMathematics MittweidaUniversityofAppliedSciences Technikumplatz17 09648Mittweida Germany e-mail:[email protected] http://www.dohmen.htwm.de Cataloging-in-PublicationDataappliedfor BibliographicinformationpublishedbyDieDeutscheBibliothek DieDeutscheBibliothekliststhispublicationintheDeutscheNationalbibliografie; detailedbibliographicdataisavailableintheInternetathttp://dnb.ddb.de MathematicsSubjectClassification(2000): primary:05A19,05A20,60C05,60E15 secondary:05A15,05B35,05C15,06A15,62N05,68M15,68R10,90B15,90B25 ISSN0075-8434 ISBN3-540-20025-8Springer-VerlagBerlinHeidelbergNewYork Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerialis concerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broadcasting, reproductiononmicrofilmorinanyotherway,andstorageindatabanks.Duplicationofthispublication orpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLawofSeptember9,1965, initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer-Verlag.Violationsare liableforprosecutionundertheGermanCopyrightLaw. Springer-VerlagBerlinHeidelbergNewYorkamemberofBertelsmannSpringer Science+BusinessMediaGmbH springer.de (cid:1)c Springer-VerlagBerlinHeidelberg2003 PrintedinGermany Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublicationdoesnotimply, evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotectivelaws andregulationsandthereforefreeforgeneraluse. Typesetting:Camera-readyTEXoutputbytheauthors SPIN:10957806 41/3142/du-543210-Printedonacid-freepaper Preface This workis basedonmy habilitationthesis whichI preparedatBerlin’s Hum- boldt-University while I was an assistant professor at the computer science de- partment in the years 1994–2000. The material has been re-arranged, some parts have been significantly shortened, while other parts have been expanded. I am especially grateful to Professor Egmar R¨odel at Humboldt-University for giving me the opportunity to work on this subject. Special thanks go to the referees of my habilitation thesis as well as to the anonymous referees of Springer-Verlagfortheirworthysuggestionsthatresultedinanimprovementof themanuscript. ParticularthanksareowedtoProfessorDouglasShier(Clemson University) for his valuable comments. Finally, I would like to thank my wife Imke and my children Sophie, Emily and Justus for their never-ending patience. Mittweida, Germany Klaus Dohmen July, 2003 Contents 1 Introduction and Overview 1 2 Preliminaries 5 2.1 Graphs and posets . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 Bonferroni Inequalities via Abstract Tubes 9 3.1 An outline of abstract tube theory . . . . . . . . . . . . . . . . . 9 3.1.1 The notion of an abstract tube . . . . . . . . . . . . . . . 9 3.1.2 Two fundamental theorems on abstract tubes . . . . . . . 11 3.1.3 An importance sampling scheme . . . . . . . . . . . . . . 13 3.2 Examples of abstract tubes . . . . . . . . . . . . . . . . . . . . . 14 3.2.1 Abstract tubes for convex polyhedra . . . . . . . . . . . . 14 3.2.2 Abstract tubes for unions of balls and spherical caps . . . 15 4 Abstract Tubes via Closure and Kernel Operators 19 4.1 Abstract tubes via closure operators . . . . . . . . . . . . . . . . 19 4.1.1 Closure operators. . . . . . . . . . . . . . . . . . . . . . . 19 4.1.2 How closure operators lead to abstract tubes . . . . . . . 21 4.2 Abstract tubes via kernel operators . . . . . . . . . . . . . . . . . 25 4.2.1 Kernel operators . . . . . . . . . . . . . . . . . . . . . . . 25 4.2.2 How kernel operators lead to abstract tubes . . . . . . . . 26 4.3 Alternative proofs . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.3.1 Improved identities via closure operators. . . . . . . . . . 28 4.3.2 Improved inequalities via kernel operators . . . . . . . . . 33 4.3.3 Additional proofs of identities . . . . . . . . . . . . . . . . 35 4.4 The chordal graph sieve . . . . . . . . . . . . . . . . . . . . . . . 37 5 Recursive Schemes 44 5.1 Recursive schemes for semilattices . . . . . . . . . . . . . . . . . 44 5.2 Dynamic programming approach . . . . . . . . . . . . . . . . . . 45 VIII Contents 6 Reliability Applications 47 6.1 System reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 6.1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 47 6.1.2 Abstract tubes for system reliability . . . . . . . . . . . . 48 6.1.3 Shier’s pseudopolynomial algorithm . . . . . . . . . . . . 49 6.1.4 Inclusion-exclusion and domination theory . . . . . . . . . 52 6.2 Special reliability systems . . . . . . . . . . . . . . . . . . . . . . 53 6.2.1 Communications networks . . . . . . . . . . . . . . . . . . 53 6.2.2 k-out-of-n systems . . . . . . . . . . . . . . . . . . . . . . 66 6.2.3 Consecutive k-out-of-n systems . . . . . . . . . . . . . . . 70 6.3 Reliability covering problems . . . . . . . . . . . . . . . . . . . . 75 6.3.1 The hypergraph model . . . . . . . . . . . . . . . . . . . . 75 6.3.2 Abstract tubes and polynomial algorithms . . . . . . . . . 75 6.4 Chapter notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 7 Combinatorial Applications and Related Topics 82 7.1 Inclusion-exclusion on partition lattices . . . . . . . . . . . . . . 82 7.2 Chromatic polynomials and broken circuits . . . . . . . . . . . . 83 7.2.1 The usual chromatic polynomial . . . . . . . . . . . . . . 84 7.2.2 The generalized chromatic polynomial . . . . . . . . . . . 86 7.3 Sums over partially ordered sets. . . . . . . . . . . . . . . . . . . 89 7.3.1 A general theorem on sums . . . . . . . . . . . . . . . . . 89 7.3.2 Application to inclusion-exclusion . . . . . . . . . . . . . 90 7.4 Matroid polynomials and the β invariant . . . . . . . . . . . . . . 91 7.4.1 The Tutte polynomial . . . . . . . . . . . . . . . . . . . . 91 7.4.2 The characteristic polynomial . . . . . . . . . . . . . . . . 93 7.4.3 The β invariant . . . . . . . . . . . . . . . . . . . . . . . . 94 7.5 Euler characteristics and M¨obius functions . . . . . . . . . . . . . 95 7.5.1 Euler characteristics . . . . . . . . . . . . . . . . . . . . . 95 7.5.2 Mo¨bius functions . . . . . . . . . . . . . . . . . . . . . . . 96 Bibliography 100 Author Index 111 Subject Index 113 1 Introduction and Overview Many problems in combinatorics, number theory, probability theory, reliabil- ity theory and statistics can be solved by applying a unifying method, which is known as the principle of inclusion-exclusion. The principle of inclusion- exclusion expressesthe indicator function of a union of finitely many sets as an alternating sum of indicator functions of their intersections. More precisely, for anyfinite family ofsets{Av}v∈V the principleofinclusion-exclusionstatesthat (cid:1) (cid:3) (cid:1) (cid:3) (cid:2) (cid:4) (cid:5) (1.1) χ Av = (−1)|I|−1χ Ai , v∈V I⊆V i∈I I(cid:2)=∅ where χ(A) denotes the indicator function of A with respect to some universal setΩ,thatis,χ(A)(ω)=1(cid:6)if(cid:7)ω ∈A,an(cid:8)dχ((cid:9)A)(ω)=0ifω(cid:6)∈(cid:7)Ω\A. E(cid:8)quivalently, (1.1)canbe expressedasχ v∈V Av =(cid:7) I⊆V(−1)|I|χ i∈IAi ,where Av denotes the complement of Av in(cid:0)Ω and i∈∅Ai = Ω. A proof by induc(cid:0)tion on the number of sets is a common task in undergraduate courses. Usually, the Av’s are measurable with respect to some finite measure µ on a σ-field of subsets of Ω. Integration of the indicator function identity (1.1) with respect to µ then gives (cid:1) (cid:3) (cid:1) (cid:3) (cid:2) (cid:4) (cid:5) (1.2) µ Av = (−1)|I|−1µ Ai , v∈V I⊆V i∈I I(cid:2)=∅ whichnowexpressesthemeasureofaunionoffinitelymanysetsasanalternat- ing sum of measures of their intersections. The step leading from (1.1) to (1.2) is referred to as the method of indicators [GS96b]. Naturally, two special cases are of particular interest, namely the case where µ is the counting measure on thepowersetofΩ,andthecasewhereµisaprobabilitymeasureonaσ-fieldof subsets of Ω. These special cases are sometimes attributed to Sylvester (1883) and Poincar´e (1896), although the second edition of Montmort’s book “Essai d’Analyse sur les Jeux de Hazard”, which appeared in 1714, already contains animplicituse ofthe method, basedona letter byN.Bernoulliin1710. A first K.Dohmen:LNM1826,pp.1–4,2003. (cid:1)c Springer-VerlagBerlinHeidelberg2003
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