docJahresbericht 2012 - Der Fachbereich Mathematik
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Jahresbericht 2012 - Der Fachbereich Mathematik
Mathematisch-Naturwisenschaliche Fakultät Faberei Mathematik • Arbeitsberei Funktionalanalysis Jahresberit created by: Miriam Bombieri (mibo@fa.uni-tuebingen.de) Pavel Zorin-Kranich (pazo@fa.uni-tuebingen.de) contact: Prof. Dr. Rainer Nagel (rana@fa.uni-tuebingen.de) Prof. Dr. Ulf Schloerbeck (ulsc@fa.uni-tuebingen.de) Prof. Dr. Ulrich Groh (ulgr@fa.uni-tuebingen.de) Arbeitsbereich Funktionalanalysis (AGFA) Mathematisch-Naturwissenschaliche Fakultät Fachbereich Mathematik Universität Tübingen Auf der Morgenstelle D– Tübingen Tel.: +--- Fax.: +--- http://www.fa.uni-tuebingen.de Zitate des Jahres Mathematics is a process of staring hard enough with enough perseverence at the fog of muddle and confusion to eventually break thorough to improved clarity. I’m happy when I can admit, at least to myself, that my thinking is muddled, and I try to overcome the embarassement that I might reveal ignorance or confusion. Over the years, this has helped me develop clarity in some things, but I remain muddled in many others. I enjoy questions that seem honest, even when they admit or reveal confusion, in preference to questions that appear designed to project sophistication. W P T (-) Wenn Wille und Leidenscha da sind, dann spielt das Alter keine Rolle. S S (-, Silbermedaille im Mountainbikerennen bei den Olympischen Spielen ) Das war AGFA Januar AGFA Arbeitstagung am Heinrich Fabri Institut (Blaubeuren) Timo Schmid (AGFA ) übernimmt eine Juniorprofessur (Angewandte Statistik) an der FU Berlin März Bria Dorn kommt als Juniordozentin (Informatik) zurück nach Tübingen Romseminar: Leidenschaf()t Mathematik Mai Marjeta Kramar (Ljubljana – AGFA ) ist Gastprofessorin in Tübingen Fatih Bayzit, Bria Dorn und Rainer Nagel beantworten bei der Kinderuni in Weil der Stadt die Frage: Mathematik wozu? Zum Kuchenteilen! Juni Fatih Bayazit promoviert und feiert mit Let’s dance my PhD https://www.fa.uni-tuebingen.de/p4/videos/fatih Juli Simon Brendle (Stanford – AGFA ) erhält den Preis der European Mathematical Society. “Yes, we can!” Workshop on female perspectives in mathematical research. September Miriam Bombieri erhält einen Preis der DMV ür die beste schriliche Arbeit im Rahmen der Studierendenkonferenz. Oktober Balint Farkas (Budapest – AGFA ) wird Professor an der Bergischen Universität Wuppertal November Ulrich Groh erhält den Titel apl. Professor Dezember AGFA Weihnachtstreffen in Horb Mitglieder der AGFA . Dozenten • Prof. Dr. Rainer Nagel (i.R.) • Prof. Ulf Schloerbeck (i.R.) • apl. Prof. Dr. Ulrich Groh • Dr. Roland Derndinger . Post-Doc • Dr. Nazife Erkursun (Stipendiatin des DAAD) . Doktoranden • Martin Adler (seit November ) • Fatih Bayazit (bis Juni , Stipendiat der Friedrich-Ebert-Stiung) • Miriam Bombieri (Stipendiatin der LGFG) • Waed Dada (Stipendiatin der syrischen Regierung) • Retha Heymann (Stipendiatin des DAAD) • Daniel Maier (Dozent, DHBW Horb) • Marco Schreiber (Stipendiat der Studienstiung des deutschen Volkes) • Fernanda Clara de França Silva (Stipendiatin des DAAD) . IT-Administrator • Dino Rezes . Erasmusteam • Christian Nowag • Nina Schumann • Stephan Walentin Lehre . Vorlesungen .. Wintersemester / • Analysis I, Ulrich Groh, http://goo.gl/wegFN • Analysis und Schulmathematik, Roland Derndinger, http://goo.gl/CWVbl • Ergodentheorie, Rainer Nagel .. Sommersemester • Analysis II, Ulrich Groh, http://goo.gl/6bdoW • Operatorentheorie, Marjeta Kramar Fijavž • Lineare Dynamische Systeme, Rainer Nagel .. Wintersemester / • Analysis III, Ulrich Groh, http://goo.gl/FchtH • Funktionalanalysis, Rainer Nagel . Seminare .. Wintersemester / • Internetseminar “Operator semigroup for numerical analysis”, Nazife Erkursun, Rainer Nagel • Operatorentheorie, Roland Derndinger, Rainer Nagel .. Sommersemester • Proseminar Analysis, Roland Derndinger, Ulf Schloerbeck .. Wintersemester / • Proseminar Analysis, Roland Derndinger, Ulrich Groh • Hauptseminar Lineare dynamische Systeme, Rainer Nagel . Lehrauräge • Höhere Mathematik I (HT Stugart), Fatih Bayazit • Höhere Mathematik II (HT Stugart), Fatih Bayazit • Mathematik (Leibniz Kolleg), Miriam Bombieri • Mathematik (Leibniz Kolleg), Retha Heymann • Mathematik II. ür Informatiker (DHBW Campus Horb), Daniel Maier • Mathematik II. ür Informatiker (DHBW Campus Horb), Daniel Maier • Mathematikvorkurs ür Informatik und Wirtschasingenieurwesen (DHBW Campus Horb), Nazife Erkursun . Dissertationen • Fatih Bayazith, On the Asymptotic Behavior of Periodic Evolution Families, Dr. Hut Verlag, ISBN 9783843905-480 . Diplomarbeiten .. Fertiggestellte Diplomarbeiten • Martin Adler, Operatorhalbgruppen ür Geburts- und Todesprozesse (Rainer Nagel) • Emiliano Bozzi (Parma), Evolution families and nonautonomous abstract Cauchy problems (Alessandra Lunardi, Rainer Nagel) • Sophia Jahns, Rosenthal representations of dynamical systems (Ulrich Groh) .. Laufende Projekte • Mathias Schickel, Translations- und Multiplikationshalbgruppen auf Banachraumwertigen Funktionenräumen (Rainer Nagel) • Johannes Winckler, Flachwasserhalbgruppen (Rainer Nagel, Petra Csomos) . Baelorarbeiten • Viktor Strehlau, Die Asymptotik von exp(tA) (Rainer Nagel) . Zulassungsarbeiten .. Fertiggestellte Arbeiten • Kai Dangel, Lineare inhomogene Cauchyprobleme (Ulf Schloerbeck) • Carina Gerlach, Henstock-Kurzweil Integral (Ulf Schloerbeck) • Linda Güdemann, Die Eulersche Formel eiπ + 1 = 0 (Ulrich Groh) • omas Heinz, Ordinalzahlen und deren topologische Anwendungen (Ulrich Groh) • Sabrina Herold, Das Cavalieri-Prinzip und Lebesgue-Integration (Ulf Schloerbeck) • Vivien McHardy, Peano- und verwandte Kurven (Ulrich Groh) • Anna Ruf, Spektrum und Konvergenz: diskreter Fall (Ulrich Groh) • Susanne Sauer, Bairesche Räume und Anwendungen (Ulrich Groh) • Franziska Schmidt, Kompaktheit in Banachräumen (Tanja Eisner) • Christina Schorp, Halbgruppen von Matrizen (Ulrich Groh) • Franziska Serra, alitative Eigenschaen positiver linearer Systeme, Teil II (Rainer Nagel) • Elja Spielvogel, Die matrixwertige Logarithmusfunktion und ihre Anwendung (Ulf Schloerbeck) • Franziska Steudle, alitative Eigenschaen positiver linearer Systeme, Teil I (Rainer Nagel) .. Laufende Arbeiten • Carolin Konzelmann, Von A zu exp(A) (Ulrich Groh) • Mahias Köbler, Spektralkontraktionen und Perron–Frobenius eorem (Ulf Schlotterbeck) • Sebastian Schneckenburger, Ramseytheorie (Bria Dorn) • Manuel Tomaszewski, Troer–Kato eorem (Rainer Nagel) • Stephan Walentin, Wohin laufen sie denn? Oder: Die Borelsummierbarkeit von Folgen (Rainer Nagel) • Helena Wenger, Vom Doppelpendel zur Halbgruppe (Ulrich Groh) Forsung . Publikationen .. Büer • T. Eisner, B. Farkas, M. Haase, R. Nagel, Operator eoretic Aspects of Ergodic eory, Erscheint als Graduate Text in Mathematics, Springer, .. Artikel • A. Bátkai, U. Groh, D. Kunszenti-Kovács, M. Schreiber, Decomposition of operator semigroups on W*-algebras, Semigroup Forum (), – • F. Bayazit, Evolution families for nonautonomous difference equations, Positivity (), – • F. Bayazit, R. Nagel, U. Groh, Floquet representations and asymptotic behavior of periodic evolution families, erscheint in Discrete and Continuous Dynamical Systems • F. Bayazit, B. Dorn, A. Rhandi, Flows in networks with delay in the vertices, erscheint in Math. Nachrichten • F. Bayazit, B. Dorn, M. Kramar Fijavž, Asymptotic periodicity of flows in timedepending networks, Preprint • F. Bayazit, R. Heymann, Stability of multiplication operators and multiplication semigroups, Preprint • T. Eisner, R. Nagel, Arithmetic progressions – an operator theoretic view, erscheint in Discrete Continuous Dynamical Systems – S • N. T. Huy, R. Nagel, Exponentially dichotomous generators of evolution bisemigroups on admissible function spaces, Houston J. Math. (), – • E. Yu. Emel’yanov, N. Erkursun, Asymptotically absorbing nets of positive operators, Siberian Advances Math. (), – • E. Yu. Emel’yanov, N. Erkursun, Asymptotically absorbing nets of continuous mappings, Preprint • M. Kramar Fijavž, M. Lakner, M. Skapin-Rugelj, An equal-area method for scalar conservation laws, e ANZIAM Journal (), – • M. Schreiber, Uniform families of ergodic operator nets, Semigroup Forum (), DOI: 10.1007/s00233-012-9444-9 • M. Schreiber, Topological Wiener-Wintner theorems for amenable operator semigroups, eingereicht bei Ergodic eory and Dynamical Systems. . Vorträge AG Funktionalanalysis .. P. Namayanja (Durban), Matrices and Poincaré’s inequality .. O. El Mennaoui (Agadir), Nonautonomous Cauchy Problems .. R. Nagel, Mathematik in Zeiten des Internets .. N. Erkursun, Polynomially mean ergodic theorem on Lp spaces .. M. Schreiber, Topologische Wiener-Wintner eoreme .. C. Guadagni (Salerno), Topological groups of homeomorphisms: topology, uniformity and proximity .. F. Bayazit, Asymptotik periodischer Evolutionsfamilien .. B. Bäumer (Dunedin), Fractional in space partial differential equations: derivation, boundary conditions and numerics .. H. T. Nguyen (Hanoi), Inertial manifolds for semi-linear parabolic evolution equations .. M. Kramar Fijavž (Ljubljana), Flüsse in Netzwerken – ein berblick .. K. J. Engel (L’Aquila), Verallgemeinerte Differenzoperatoren .. M. Schreiber, Verschränkte Ergodensätze ür amenable Halbgruppen .. M. Adler, Randstörungen ür unendliche Matrixoperatoren .. J. A. Goldstein (Memphis), Old and new asymptotic results for energies of waves .. D. Maier, Untergruppen des Torus und deren Charaktergruppe .. L. Maniar (Marrakesch), Approximate positive controllability for positive boundary systems .. T. Heinz, Ordinalzahlen und deren topologische Anwendungen .. T. Eisner (Amsterdam), Das Wiener-Wintner eorem ür Nilfolgen .. M. Schreiber, Intensität der Bragg-Peaks bei Streuung an asikristallen .. M. Adler, Generator property of operators on a product space .. P. Zorin-Kranich (Amsterdam), IP*-Mengen ganzer Zahlen .. R. Derndinger, Zwei Fragen aus Holland .. D. Maier, Realisierungen dynamischer Systeme mit diskretem Spektrum .. M. Schreiber, Topologische Wiener-Wintner eoreme und Beugung an asikristallen .. W. Dada, Numerische Wertebereiche bezüglich einer Familie von Projektionen .. A. Bátkai (Budapest), Nichtautonome Operatormatrizen .. R. Heymann, Selecting an Eigenfunction .. D. Mugnolo (Ulm), ber Differenzoperatoren auf Netzwerken und antengraphen .. A. Radl (Bern), Der numerische Wertebereich positiver Operatoren .. P. Csomós, J. Winckler (Innsbruck und Tübingen), Flachwasserhalbgruppen . Workshops und Tagungen .. Workshop der Arbeitsgemeinsa Funktionalanalysis Blaubeuren, . bis . . .. Romseminar Leidenschaf()t Mathematik – Emotionen Aversionen Obsessionen Rom, . bis . . https://www.fa.uni-tuebingen.de/lehre/romsem/2012 .. Yes, we can! Workshop on female perspectives in mathematical research Tübingen, . bis . . .. Weinatstreffen der AGFA T. Eisner, R. Nagel, Von DNP zu EFHN: Jahre Ergodentheorie in AGFA Horb, . . . Vortragsreisen und Konferenzbesue M. Adler . bis . . . bis . . . bis . . Romseminar: Leidenschaf()t Mathematik Generalized Solutions of Evolution Equations: eory, Numerical Approximation, and Applications, MPI Leipzig ISEM : Operator Semigroups for Numerical Analysis, Blaubeuren F. Bayazit . . . bis . . TU Clausthal Generalized Solutions of Evolution Equations: eory, Numerical Approximation, and Applications, MPI Leipzig M. Bombieri . bis . . . bis . . . bis . . . bis . . Romseminar: Leidenschaf()t Mathematik Generalized Solutions of Evolution Equations: eory, Numerical Approximation, and Applications, MPI Leipzig ISEM : Operator Semigroups for Numerical Analysis, Blaubeuren DMV Jahrestagung, Saarbrücken N. Erkursun . bis . . . bis . . . bis . . Selçuk University, Konya, Türkei Workshop on Operator eory and Operator Algebras, IST, Lissabon, Portugal Middle East Technical University, Ankara, Türkei R. Heymann . bis . . . . . . . . Romseminar: Leidenschaf()t Mathematik Potchefstroom, Südafrika Stellenbosch, Südafrika Budapest, Ungarn M. Kramar Fijavž . . . bis . . Universität Ulm Spectral eory and Differential Operators, TU Graz, sterreich R. Nagel . bis . . . bis . . . bis . . Romseminar: Leidenschaf()t Mathematik ISEM : Operator Semigroups for Numerical Analysis, Blaubeuren Arbeitsgemeinscha: Ergodic eory and Combinatorial Number eory, Oberwolfach M. Sreiber . bis . . . bis . . . bis . . Universität Jena Universität Amsterdam, Niederlande Ergodic eory and Dynamical Systems: Perspectives and Prospects, Warwick, UK W. Dada . bis . . . bis . . th Euro-Maghrebian workshop on Evolution Equations, Lecce, Italien Bern, Schweiz Versiedenes . Romseminare Das Romseminar ist eine interdisziplinäre Veranstaltung, die seit mit jährlich wechselnden emen in Rom stafindet. Siehe http://www.fa.uni-tuebingen.de/lehre/romsem Das Romseminar vom . bis .. hae das ema Leidenschaf()t Mathematik – Emotionen, Aversionen, Obsessionen Das Romseminar vom . bis .. hat das ema Fehler – Irrtum – Wiederspruch . Internationaler Studentenaustaus .. Outgoing WS / Phillipp Dietrich (Paris, Frankreich, WS/-SS) Demerci Sener (Paris, Frankreich, WS/) Michael Füllbier (Maynooth, Irland, WS/-SS) Julia Harle (Florenz, Italien, WS/-SS) Philipp Schmidt (Pisa, Italien SS-WS/) Caroline Arnold (Oslo Norwegen, WS/) Nils Schweinsberg (Oslo, Norwegen, WS/-SS) Hanna Walter (Granada, Spanien, WS/) Manuela Linke (Granada, Spanien, WS/-SS) Andreas Hühnerfuß (Valencia, Spanien, WS/-SS) Leonard Moskwa (Valencia, Spanien, WS/-SS) Fabian Dyga (Birmingham, UK, WS/) Paula Denner (Manchester, UK, WS/-SS) Sahra Hänle (Manchester, UK, WS/-SS) SS Philipp Dietrich (Paris, Frankreich, WS/-SS) Michael Füllbier (Maynooth, Irland, WS/-SS) Julia Harle (Florenz, Italien, WS/-SS) Nils Schweinsberg (Oslo, Norwegen, WS/-SS) Manuela Linke (Granada, Spanien, WS/-SS) Andreas Hühnerfuß (Valencia, Spanien, WS/-SS) Leonard Moskwa (Valencia, Spanien, WS/-SS) Paula Denner (Manchester, UK, WS/-SS) Sahra Hänle (Manchester, UK, WS/-SS) Svenja Simmel (Gent, Belgien, SS) Stephan Walentin (Marseille, Frankreich, SS) Kristina Brezonic (Paris Frankreich, SS) Udo Elsasser (Barcelona, Spanien, SS) Marie Lins (Granada, Spanien, SS) Philipp Gutsche (Maynooth, Irland, SS) Sener Demirci (Paris, Frankreich, WS/-SS) WS / David Harbecke (Paris, Frankreich, WS/-SS) Leonie Keller (Lecce, Italien, WS/-SS) Teresa Gentner (Maynooth, Irland, WS/) Sascha Muhr (Manchester, UK, WS/) Anne-Kathrin Fahrner (Birmingham, UK, WS/) Stefanie Layher (Valencia, Spanien, WS/) Armand Heim (Budapest, Ungarn, WS/) Erika Bor (Budapest, Ungarn, WS/) Paula Laßmann (Granada, Spanien, WS/) .. Incoming WS / Emiliano Bozzi (Parma, Italien) Paloma Meana Baamonde (Oviedo, Spanien) Stephen Shanahan (California-BW State Program, USA) SS Lilla Lomoschitz (Budapest, Ungarn) Hande Gizem zcan (Haceepe Ankara, Türkei) Cerem tzbay (Haceepe Ankara, Türkei) Duygu nlü (Haceepe Ankara, Türkei) Edward Bryden (Washington University, St. Louis, USA) WS / Alessandro Arrigoni (L’Aquila, Italien) Marco Baffei (Trento, Italien) Cansu Balamut (Haceepe Ankara, Türkei) Sigiswald Barbier (Gent, Belgien) Jacob Desmond (Louisiana State University, USA) Olivia Howells (California-BW State Program, USA) Katherine McLaughlin (California-BW State Program, USA) Alice Oatway (Manchester, UK) Sennur tztürk (Haceepe Ankara, Türkei) Riia Peltoniemi (Oulu, Finnland) Marco Peruzzeo (Trento, Italien) Ernesto Rivera Mora (Guanajuato, Mexico) Seda Saygin (Haceepe Ankara, Türkei) AGFA-Arbeitstagung Blaubeuren 2012 12. - 14. Januar Donnerstag 16 Uhr: Rainer Nagel: Ulrich Groh: 18:30 Uhr: Abendessen Mathematik in Zeiten des Internets Was ist TEX nicht und was ist es doch? Freitag 7 Uhr: early morning jogging 8 Uhr: Frühstück 9 Uhr: Tanja Eisner: Marco Schreiber: Martin Adler: Britta Dorn: Eine Verallgemeinerung des Wiener-Wintner Theorems Topologische Wiener-Wintner Theoreme Geburts- und Todeshalbgruppen Der Satz von Banach-Steinhaus, mal anders 11 Uhr: Proscovia Namayanja: Retha Heymann: Fatih Bayazit: Miriam Bombieri: Matrices and Poincaré’s inequality Stabilität von Multiplikatorhalbgruppen Nichtautonome Flüsse in Netzwerken Operatorhalbgruppen für unendlichdimensionale lineare Systeme 12:30 Uhr: Mittagessen 15 Uhr: Roland Derndinger: Kai Dangel: Franziska Serra: Franziska Steudle: Linda Güdemann: Susanne Sauer: Etwas über Schule und Mathematik Diskrete Kontrolltheorie Positive Kontrolltheorie Positive Kontrolltheorie Die Eulersche Formel Permanenzeigenschaften von Baireschen Räumen 17 Uhr: Matthias Lang: Sophia Jahns: Anna Ruf: Christina Schorp: Thomas Heinz: Mathias Schickel: Stabilität von Operatorhalbgruppen “Zahme” dynamische Systeme Konvergenzverhalten der Potenzen einer Matrix Konvergenzverhalten der matrixwertigen Exponentialfunktion Ordinalzahlen Über die Unendlichkeit 18:30 Uhr: Abendessen ab 20 Uhr: Musik und Spiele (Beiträge erwünscht) Kaffeepause Kaffeepause 1 Samstag 7 Uhr: early morning jogging 8 Uhr: Frühstück 9 Uhr: András Bátkai: Nazife Erkusun: Waed Dada: Agnes Radl: Daniel Maier: tba Higher rank numerical ranges of Hilbert space operators Higher rank numerical ranges of Hilbert space operators The numerical range of positive operators Dynamische Systeme mit diskretem Spektrum 11 Uhr: Ulf Schlotterbeck: Huy Nguyen: Carina Gerlach: Sabrina Herold: Johannes Winkler: tba Exponential dichotomy for evolution families Das Henstock-Kurzweil-Integral Das Cavalieri-Prinzip und Lebesgueintegration Schwebungen und Kombinationstöne bei Saiteninstrumenten 12:30 Uhr: Mittagessen 15 Uhr: Leonard Konrad: Dávid KunszentiKovács: Felix Pogorzelski: Pavel Zorin-Kranich: David Seifert: Etwas über Banachwertige additive Prozesse Ein polynomieller multipler Ergodensatz Der Satz von Katznelson-Tzafriri im Hilbertraum 17 Uhr: Bálint Farkas: Fernanda Silva: Daniel Hauer: Hafida Laasri: Ergodentheorie fast überall Spektraler Abbildungssatz für Evolutionshalbgruppen Über die gemeinsame Arbeit mit Abdel in Salerno Integral Product 18:30 Uhr: Abendessen ab 20 Uhr: Arbeitsgruppen Kaffeepause (nicht) schon wieder über Dilatationen Graphonen und graphinduzierte Funktionsnormen Kaffeepause Sonntag 8 Uhr: Frühstück ab 9 Uhr: Abreise 2 Mathematisches Kolloquium anlässlich der Verleihung des Titels apl. Professor an Dr. Ulrich Groh am 09. November 2012 um 16 Uhr c.t. Hörsaalzentrum der Universität Tübingen, Auf der Morgenstelle Hörsaal N3 Programm: • Begrüßung durch den Sprecher des Fachbereichs Mathematik • Überreichung der Ernennungsurkunde durch Prof. Dr. W. Rosenstiel, Dekan der Mathematisch-Naturwissenschaftlichen Fakultät • „Mäandern zwischen Wissenschaft und Industrie“ Prof. Dr. R. Nagel • „Archimedes oder die unendliche Erschöpfung“ Dr. Ulrich Groh Anschließend Empfang im Foyer des Hörsaalzentrums. Der Fachbereich Mathematik Semigroup Forum (2012) 85:1–4 DOI 10.1007/s00233-012-9383-5 TRIBUTE In admiration of Rainer Nagel Jerome A. Goldstein Received: 20 February 2012 / Published online: 15 March 2012 © Springer Science+Business Media, LLC 2012 Rainer Nagel is an outstanding research mathematician, teacher, mentor, organizer and friend. And he weaves these things together so seamlessly that it is difficult to discuss one of his attributes without bringing in the others. Communicated by László Márki. J.A. Goldstein () Department of Mathematical Sciences, University of Memphis, Memphis, TN 38152, USA e-mail: jgoldste@memphis.edu 2 J.A. Goldstein His academic life has been spent primarily at the University of Tübingen, where he was first a student and then a professor. His doctoral thesis advisor was Helmut Schaefer, under whose influence Rainer quickly became an expert in the functional analysis associated with positive linear operators on ordered Banach spaces. These operators arise naturally in problems of applied mathematics and differential equations where the solution is interpreted as a density or concentration or mass or something else which is a nonnegative function. The natural domain for these applications is the context of operator semigroups, and the theory of positive (or positivity preserving) semigroups in the early 1970s contained a major theorem of Ralph Phillips and little else. Rainer decided to create a complete theory of positive semigroups on ordered Banach spaces. This was an enormously broad and ambitious program that no individual could possibly do alone. So Rainer built up a large research group to do this in a teamwork context. This group became known as AGFA (Arbeitsgemeinschaft Funktionalanalysis), and its main focus was positive operator semigroups and applications. I first met Rainer in person in June 1981 in Tübingen, although we had gotten to know each other well through correspondence by then. I was stunned and amazed by the “high tea” in his office in the late afternoon on the day we first met. There were, as I still vividly recall, about twenty AGFA people there, including graduate students, postdoctoral fellows, faculty members and visitors. It was a banquet of high level discussions, conjectures, and ambitious plans and hopes. It was like a symphony orchestra with Rainer as conductor. The young researchers included the budding stars Wolfgang Arendt and Günther Greiner. And there were lots of excellent mature scholars such as Ulf Schlotterbeck. The mathematical level and the levels of cooperation, friendliness, informality and sharing ideas were amazing. I had never seen anything like it before, but although the names of the AGFA crowd regularly changes, the spirit of AGFA remains the same as does the brilliance and work ethic of its leader. Rainer was and remains a marvelous doctoral thesis advisor. Unlike many, I would say most thesis advisors, Rainer gives his best problems to his students, rather than saving them for himself. I suspect he has previously partially solved some of these problems prior to assigning them, but Rainer will not admit this. His deservedly great reputation as an advisor spread and he attracted students from all over the world. He is one of a select group of mathematicians who has advised over fifty doctoral theses. According to the Genealogy project he has had 56 successful doctoral students, plus there are 6 current students plus many more who were largely advised by Rainer but officially by someone else. Among the many current distinguished researchers coming from AGFA are Arendt and Greiner (who became a world class computer scientist) and, in alphabetical order, Simon Brendle, Tanja Eisner, Klaus-Jochen Engel, Matthias Hieber, Frank Neubrander, Abdelaziz Rhandi, Roland Schnaubelt, and many others. He has had long term scientific relations and collaborations with Silvia Romanelli (Bari), Eugenio Sinestrari (Rome), and many others. His great organizational skills and his legendary lectures resulted in seemingly uncountably many invitations to give conference lectures and short courses all over the world. He is the founder of the ongoing Internet Seminar, which is an annual course on semigroups, evolution equations, et al. for young researchers worldwide. At the end of the course in June, the participants meet in a great conference in Blaubeuren, an excellent In admiration of Rainer Nagel 3 Oberwolfach-like conference center. Rainer also runs seminars involving sports and mathematics (in awesome locations), an annual Rome Seminar on mathematics and philosophy, and other things such as the unique, legendary conference at Castel del Monte near Bari, combining history, architecture and geometry. Rainer has also been a successful advocate for student exchange and mobility programs involving Europe, Africa, North America and the Far East. He is (jointly) responsible for two major books, both milestones in the history of positive semigroup theory. The first is a Springer Lecture Note volume [1] published in 1986 with 9 authors. Rainer decided that AGFA (including some then current members and some alumni) should write a definitive selfcontained monograph on positive semigroups. He collected his collaborators, rented rooms at a conference center, and got the nine of them to revise, tie together, and unify the separate chapters written in advance by various subsets of the authors. It is amazing that this book has a smooth and consistent style, as well as a lot of new and recent research organized into one volume for the first time. It is as if he locked his “orchestra” into a room and led the composition of their symphony into a masterpiece before allowing them to leave the room. The result was wonderful, and only Rainer could have coordinated this in this way and in a very timely fashion. The application areas included Perron-Frobenius theory (a la AGFA), ergodic theory, age dependent population dynamics, mathematical biology, et al. The second book, a hard cover Springer book written jointly with K.-J. Engel, [2], is currently the best source for beginners (as a masterful text) and experts as well. It is filled with new results, new perspectives, new motivation, new applications; it has very broad scope. A shortened and updated version [3] of this book was published in 2006. Rainer remains a remarkable athlete, and he always liked to combine mathematics with athletics and group social activities. At his home in Horb, Rainer and his wife Ursula regularly hosted AGFA social activities. For many years, there was an annual AGFA miniconference at Tuebingen, followed by a 40 km bicycle race to Horb, and then a big party. Rainer won all these races except for one, when a young lady from AGFA was the best cyclist (showing again that one must always consider the possibility of counterexamples). Rainer still takes “character building” long bicycle rides in the mountains with friends who are former Tour de France competitors. In addition to his expert cycling, Rainer has long been an excellent runner and swimmer. He has run marathons and competed in many triathlons. An additional time consuming source of joy for him is playing with his five grandchildren, all born within the last five years. But he no longer does marathons and triathlons, although it would not surprise me if he decided to make a comeback at age 75. Rainer was cofounder of the Journal of Evolution Equations (with Wolfgang Arendt) and an important and effective editor of Semigroup Forum and many other journals as well. He continues his active research program in spectral theory, positive semigroups, delay and functional differential equations, flows in networks (which ties graph theory to positive semigroup theory), operator matrix theory with applications to partial differential equations, and other topics. When I give a lecture and refer to a result as Nagel’s theorem, Rainer always corrects me and says which of his collaborators deserves much of the credit. This is not merely a reflection of Rainer’s modesty. Rather it indicates his love for his students and collaborators and his generosity. 4 J.A. Goldstein Rainer officially retired in the fall of 2008. His retirement conference attracted several hundred attendees. Rainer, being Rainer, insisted that it be called AGFA 35, and that it was in honor of the 35th anniversary of AGFA. It was a remarkable event. It is hard to imagine the show of affection and admiration that so many people had for Rainer. But even though Rainer is officially retired, a visitor to Tübingen would never guess that. AGFA remains alive and vibrant, with remarkable high teas in Rainer’s office. He, his current doctoral students, faculty and visitors have exciting discussions with Rainer still providing the leadership. Rainer’s passion for thinking deeply and constantly about hard problems and new research directions continues with no indications of slowing down. I never met anyone else who is loved and respected so much both personally and scientifically by so many colleagues as Rainer. AGFA 35 proved this, and Rainer’s current activities continue to justify it. I am most fortunate to have Rainer as my good friend and mentor. I marvel at how he so gracefully maintains his charm, his athleticism, his brilliance and creativity, and his generosity. He remains the favorite role model for many, myself included. References 1. Arendt, W., Grabosch, A., Greiner, G., Groh, U., Lotz, H.P., Moustakas, U., Nagel, R., Neubrander, F., Schlotterbeck, U.: One-Parameter Semigroups of Positive Operators. Lecture Notes in Mathematics, vol. 1184. Springer, Berlin (1986) 2. Engel, K.-J., Nagel, R.: One-Parameter Semigroups for Linear Evolution Equations. Graduate Texts in Mathematics, vol. 194. Springer, New York (2000) (with contributions by S. Brendle, M. Campiti, T. Hahn, G. Metafune, G. Nickel, D. Pallara, C. Perazzoli, A. Rhandi, S. Romanelli, and R. Schnaubelt) 3. Engel, K.-J., Nagel, R.: A Short Course in Operator Semigroups. Springer, New York (2006)
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