Jahresbericht 2012 - Der Fachbereich Mathematik

Transcription

Jahresbericht 2012 - Der Fachbereich Mathematik
Mathematisch-Naturwisenschaliche Fakultät
Faberei Mathematik • Arbeitsberei Funktionalanalysis
Jahresberit 
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 Schloerbeck (ulsc@fa.uni-tuebingen.de)
Prof. Dr. Ulrich Groh (ulgr@fa.uni-tuebingen.de)
Arbeitsbereich Funktionalanalysis (AGFA)
Mathematisch-Naturwissenschaliche 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 Bria Dorn kommt als Juniordozentin (Informatik) zurück nach Tübingen
Romseminar: Leidenschaf()t Mathematik
Mai Marjeta Kramar (Ljubljana – AGFA ) ist Gastprofessorin in Tübingen
Fatih Bayzit, Bria 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 schriliche 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 Schloerbeck (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-Stiung)
• 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 Studienstiung 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 Schloerbeck
.. Wintersemester /
• Proseminar Analysis, Roland Derndinger, Ulrich Groh
• Hauptseminar Lineare dynamische Systeme, Rainer Nagel

. Lehrauräge
• Höhere Mathematik I (HT Stugart), Fatih Bayazit
• Höhere Mathematik II (HT Stugart), 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 Wirtschasingenieurwesen (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)
. Baelorarbeiten
• Viktor Strehlau, Die Asymptotik von exp(tA) (Rainer Nagel)
. Zulassungsarbeiten
.. Fertiggestellte Arbeiten
• Kai Dangel, Lineare inhomogene Cauchyprobleme (Ulf Schloerbeck)
• Carina Gerlach, Henstock-Kurzweil Integral (Ulf Schloerbeck)

• 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 Schloerbeck)
• 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 Eigenschaen positiver linearer Systeme, Teil II (Rainer
Nagel)
• Elja Spielvogel, Die matrixwertige Logarithmusfunktion und ihre Anwendung (Ulf
Schloerbeck)
• Franziska Steudle, alitative Eigenschaen positiver linearer Systeme, Teil I (Rainer Nagel)
.. Laufende Arbeiten
• Carolin Konzelmann, Von A zu exp(A) (Ulrich Groh)
• Mahias Köbler, Spektralkontraktionen und Perron–Frobenius eorem (Ulf Schlotterbeck)
• Sebastian Schneckenburger, Ramseytheorie (Bria Dorn)
• Manuel Tomaszewski, Troer–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)

 Forsung
. Publikationen
.. Büer
• 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 Arbeitsgemeinsa 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 . . 
.. Weinatstreffen der AGFA
T. Eisner, R. Nagel, Von DNP zu EFHN:  Jahre Ergodentheorie in AGFA
Horb, . . 
. Vortragsreisen und Konferenzbesue
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. Sreiber
. 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

 Versiedenes
. Romseminare
Das Romseminar ist eine interdisziplinäre Veranstaltung, die seit  mit jährlich wechselnden emen in Rom stafindet. Siehe
http://www.fa.uni-tuebingen.de/lehre/romsem

Das Romseminar  vom . bis .. hae 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 (Haceepe Ankara, Türkei)
Cerem tzbay (Haceepe Ankara, Türkei)
Duygu nlü (Haceepe Ankara, Türkei)
Edward Bryden (Washington University, St. Louis, USA)
WS /
Alessandro Arrigoni (L’Aquila, Italien)
Marco Baffei (Trento, Italien)
Cansu Balamut (Haceepe 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 (Haceepe Ankara, Türkei)

Riia Peltoniemi (Oulu, Finnland)
Marco Peruzzeo (Trento, Italien)
Ernesto Rivera Mora (Guanajuato, Mexico)
Seda Saygin (Haceepe 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)