Cotorsion pairs for Bext and a generalization of Whithead's problem [Elektronische Ressource] / von Nicole Hülsmann

COTORSION PAIRS FOR BEXT AND AGENERALIZATION OF WHITEHEAD’S PROBLEMDissertationzur Erlangung des akademischen Grades einesDoktors der Naturwissenschaften(Dr. rer. nat.)vorgelegt beim Fachbereich Mathematikder Universit¨at Duisburg–EssenCampus EssenvonNicole Hu¨lsmannaus EssenVorlage der Dissertation: 04.10.2006Tag der mund¨ lichen Pruf¨ ung: 17.11.2006Prufungs¨ ausschuss:Vorsitzender: Prof. Dr. M. KunzeGutachter: Prof. Dr. R. G¨obelProf. Dr. L. SalceNicht weil es unerreichbar ist, wagen wir es nicht,sondern weil wir es nicht wagen, ist es unerreichbar.(Seneca)AcknowledgementI would like to thank Prof. Dr. Rud¨ iger G¨obel and PD Dr. Lutz Strun¨ gmann for theirinvaluable advice. Without their daily support and concern this work could never havebeen completed.I am also grateful to Dr. Simone Wallutis for her instructive advice and support and to mycolleagues Dr. Daniel Herden, Christian Mu¨ller and Dr. Sebastian Pokutta for a pleasentworking atmosphere and many productive discussions.Furthermore, I would like to thank all my friends for giving me an enjoyable time apartfrom mathematics.Last but not least, I owe more than I can say to the support and encouragement of mypartner, Dr. Georg Hennecke.I would like to thank the German–Israeli Foundation for Scientific Research and Develop-ment for granting me a scholarship.Dedicated to my father.ContentsIntroduction 3List of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .