Lecture Notes in Economics and Mathematical Systems 613 FoundingEditors: M.Beckmann H.P.Künzi ManagingEditors: Prof.Dr.G.Fandel FachbereichWirtschaftswissenschaften FernuniversitätHagen Feithstr.140/AVZII,58084Hagen,Germany Prof.Dr.W.Trockel InstitutfürMathematischeWirtschaftsforschung(IMW) UniversitätBielefeld Universitätsstr.25,33615Bielefeld,Germany EditorialBoard: A.Basile,A.Drexl,H.Dawid,K.Inderfurth,W.Kürsten . . Ahmad K. Naimzada Silvana Stefani Anna Torriero (Eds.) Networks, Topology and Dynamics Theory and Applications to Economics and Social Systems ABC Prof. Ahmad K. Naimzada Prof. Anna Torriero Università degli Studi di Università Cattolica del Sarcro Milano-Bicocca Cuore Dipto. Economia Politica Largo A. Gemelli, 1 Piazza dell' Ateneo Nuovo, 1 20123 Milano 20126Milano Italy Italy [email protected] [email protected] Prof. Silvana Stefani Università degli Studi di Milano-Bicocca Dipto. Economia Politica Piazza dell' Ateneo Nuovo, 1 20126 Milano Italy [email protected] ISBN978-3-540-68407-7 e-ISBN978-3-540-68409-1 DOI10.1007/978-3-540-68409-1 LectureNotesinEconomicsandMathematicalSystemsISSN0075-8442 LibraryofCongressControlNumber:2008928718 The volume has been published with the financial contribution of the Quantitative Methods Depart- ment of the University of Milano-Bicocca, Italy. © 2009 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, b roadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permissions for use must always be obtained from Springer-Verlag. 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Cover design: WMXDesign GmbH, Heidelberg Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com Preface There is convergent consensus among scientists that many social, economic and financial phenomena can be described by a network of agents and their interac- tions.Surprisingly,eventhoughtheapplicationfieldsarequitedifferent,thosenet- worksoftenshowacommonbehaviour.Thus,theirtopologicalpropertiescangive useful insights on how the network is structured, which are the most “important” nodes/agents,howthenetworkreactstonewarrivals.Moreoverthenetwork,once includedintoadynamiccontext,helpstomodelmanyphenomena.Amongthetop- ics in which topology and dynamics are the essential tools, we will focus on the diffusion of technologies and fads, the rise of industrial districts, the evolution of financial markets, cooperation and competition, information flows, centrality and prestige. Thevolume,includingrecentcontributionstothefieldofnetworkmodelling,is based on the communications presented at NET 2006 (Verbania, Italy) and NET 2007 (Urbino, Italy); offers a wide range of recent advances, both theoretical and methodological,thatwillinterestacademicsaswellaspractitioners. Theoryandapplicationsarenicelyintegrated:theoreticalpapersdealwithgraph theory,gametheory,coalitions,dynamics,consumerbehavior,segregationmodels andnewcontributionstotheabovementionedarea.Theapplicationscoverawide range:airlinetransportation,financialmarkets,workteamorganization,labourand creditmarket. The volume can be used as a reference book for graduate and postgraduate coursesonNetworkTheoryandComplexSystemsinFacultiesofEconomics,Math- ematics, Engineering and Social Sciences. In Part I, the invited tutorials introduce GraphTheoryfromthetheoreticalpointofview(Marusic)andthepossibleappli- cationstoeconomics(Battiston).InPartII,thecontributionscoverlocalandglobal interaction,complexbehavior,networkgames,whileinPartIIItheyrefertoMarkov chainsandtopology.TheapplicationsareallplacedinPartIV. Fifteenpapershavebeenselectedamongroughlythirtysubmittedextendedab- stracts; each paper has been reviewed by two referees. Space limitations are the mainreasonwhynomorepapershavebeenaccepted,althoughmanyofthemwere reallyinteresting. v vi Preface We are grateful to the scholars who have made NET 2006, NET 2007 and this bookpossible,tothemembersofthescientificcommitteesofthetwoconferences andthereferees: • Gian-ItaloBISCHI–UniversityofUrbino,Italy • SergioCURARINI–UniversityofVenice,Italy • DomenicoDELLIGATTI–CatholicUniversityofMilan,Italy • AndreaDEMONTIS–UniversityofSassari,Italy • MauroGALLEGATI–UniversityofAncona,Italy • LauraGARDINI–UniversityofUrbino,Italy • RosannaGRASSI–UniversityofMilan-Bicocca,Italy • JosefLAURI–UniversityofMalta,Malta • RaimondoMANCA–UniversityofRome“LaSapienza”,Italy • MarcoA.MARINI–UniversityofUrbino,Italy • DraganMARUSIC–UniversityofPrimorskaandLiublijana,Slovenia • FaustoMIGNANEGO–CatholicUniversity,Italy • AntonioPALESTRINI–UniversityofTeramo,Italy • ArturoPATARNELLO–UniversityofMilan-Bicocca,Italy • AuraREGGIANI–UniversityofBologna,Italy • MassimoRICOTTILLI–UniversityofBologna,Italy • GiuliaRIVELLINI–CatholicUniversityofMilan,Italy • PierluigiSACCO–IUAVVenezia,Italy • RaffaeleSCAPELLATO–PolytechnicofMilan,Italy • ChristosH.SKIADAS–TechnicalUniversityofCrete,Greece • FabioTRAMONTANA–MarchePolytechnicUniversity,Italy • GiovanniZAMBRUNO–UniversityofMilan-Bicocca,Italy • LucaZARRI–UniversityofVerona,Italy Finally, we would like to acknowledge the support, hospitality and encourage- mentofthefollowinginstitutions: – Dipartimento di Metodi Quantitativi per le Scienze Economiche e Aziendali, Universita` degliStudidiMilano-Bicocca, – DipartimentodiDisciplineMatematiche,FinanzaMatematicaedEconometria, Universita` CattolicadiMilano – IstitutodiScienzeEconomiche,Universita` degliStudidiUrbino. March2008 AhmadK.Naimzada Milan SilvanaStefani AnnaTorriero Contents PartI Tutorials SomeTopicsinGraphTheory..................................... 3 KlavdijaKutnarandDraganMarusˇicˇ FromGraphTheorytoModelsofEconomicNetworks.ATutorial ...... 23 MichaelD.Ko¨nigandStefanoBattiston PartII StrategicInteraction,EconomicModelsandNetworks GamesofCoalitionandNetworkFormation:ASurvey................ 67 MarcoA.Marini NetworkFormationwithClosenessIncentives ....................... 95 BernoBuechel ADynamicModelofSegregationinSmall-WorldNetworks............ 111 GiorgioFagiolo,MarcoValente,andNicolaasJ.Vriend InterdependentPreferences....................................... 127 AhmadK.NaimzadaandFabioTramontana Co-EvolutiveModelsforFirmsDynamics ........................... 143 GiuliaRotundoandAndreaScozzari PartIII MarkovChainsandTopology BetweennessCentrality:ExtremalValuesandStructuralProperties..... 161 R.Grassi,R.Scapellato,S.Stefani,andA.Torriero HowtoReduceUnnecessaryNoiseinTargetedNetworks .............. 177 GiacomoAlettiandDianeSaada vii viii Contents The DynamicBehaviourofNon-HomogeneousSingle-Unireducible MarkovandSemi-MarkovChains ................................. 195 GuglielmoD’Amico,JacquesJanssen,andRaimondoManca PartIV Applications ShareholdingNetworksandCentrality:AnApplicationtotheItalian FinancialMarket................................................ 215 M.D’Errico,R.Grassi,andS.Stefani,andA.Torriero NetworkDynamicswhenSelectingWorkTeamMembers.............. 229 AriannaDalFornoandUgoMerlone Empirical Analysis of the Architecture of the Interbank Market andCreditMarketUsingNetworkTheory .......................... 241 GiuliaDeMasi NetworkMeasuresinCivilAirTransport:ACaseStudyofLufthansa... 257 AuraReggiani,SaraSignoretti,PeterNijkamp,andAlessandroCento OnCertainGraphTheoryApplications............................. 283 KlavdijaKutnarandDraganMarusˇicˇ Part I Tutorials Some Topics in Graph Theory KlavdijaKutnarandDraganMarusˇicˇ AbstractInthisshortintroductorycoursetographtheory,possiblyoneofthemost propulsive areas of contemporarymathematics, some of the basic graph-theoretic conceptstogetherwithsomeopenproblemsinthisscientificfieldarepresented. 1 SomeBasicConcepts A simple graph X is an orderedpair of sets X =(V,E). Elements ofV are called verticesofX andelementsofE arecallededgesofX.Anedgejoinstwovertices, calleditsendvertices.Formally,wecanthinkoftheelementsofEassubsetsofV of size2.Asimplegraphisthusanundirectedgraphwithnoloopsormultipleedges. Ifu(cid:1)=vareverticesofasimplegraphX and{u,v}(sometimesshortenedtouv) isanedgeofX,thenthisedgeissaidtobeincidenttouandv.Equivalently,uand varesaidtobeadjacentorneighbors,andwewriteu∼v.Phraseslike,“anedge joinsuandv”and“theedgebetweenuandv”arealsocommonlyused. Graphscanbenicelyrepresentedwith diagramsconsistingofdotsstandingfor verticesandlinesstandingforedges(seeFig.1). Inasimplegraphthereisatmostoneedgejoiningapairofvertices.Inamulti- graph, multiple edges are permitted between pairs of vertices. There may also be edges,calledloops,thatconnectavertextoitself(seeFig.2). As opposedto asimple graphwhereedgesare undirected,adirectedgraph(in short,digraph)isanorderedpairofsets(V,E)whereV isasetofverticesandE is K.Kutnar UniversityofPrimorska,FAMNIT,Glagoljasˇka8,6000Koper,Slovenia [email protected] D.Marusˇicˇ University of Primorska, FAMNIT, Glagoljasˇka 8, 6000 Koper, Slovenia and University of Ljubljana,IMFM,Jadranska19,1000Ljubljana,Slovenia [email protected] A.K.Naimzadaetal.(eds.),Networks,TopologyandDynamics, 3 LectureNotesinEconomicsandMathematicalSystems613, (cid:1)c Springer-VerlagBerlinHeidelberg2009 4 K.Kutnar,D.Marusˇicˇ Fig. 1 A diagram of a graph X =(V,E) where V ={1,2,3,4} and E = {{1,2},{1,3},{2,3},{3,4}} Fig. 2 An example of a 1 multigraphwiththreeedges betweenvertices1and2and 3 looponvertex3 4 2 Fig.3 Adirectedgraph 1 6 2 5 3 4 Fig.4 Aweightedgraph 1 10 2 6 5 3 3 4 a subsetof orderedpairsof verticesfromV. Now the edgesmaybe thoughtofas arrowsgoingfromatail(vertex)toahead(vertex)(seeFig.3). Sometimesitis usefulto associate a number,oftencalledits weight, with each edgeinagraph.Suchgraphsarecallededge-weightedorsimplyweightedgraphs; theymaybesimple,directed,etc.(seeFig.4). From now on by a graph we shall mean a simple and, unless otherwise speci- fied,finite,undirectedandconnectedgraph.LetX =(V,E)beagraph.Thedegree d(v)ofavertexv∈V isthenumberofedgeswithwhichitisincident.Thesetof