Sabbatical Experiences
By Tom Trotter

 

     During the 1997/98 academic year, I had the good fortune to be able to take a full year sabbatical leave as a Guest Professor of Mathematics and Computer Science at the Free University of Berlin.  This was my first sabbatical since a one semester stay at M.I.T. in 1981, and it is difficult to overstate how rewarding it
was to be able to work full time on research and study projects.  In the Fall term, I gave a "Vorlesung" for faculty and graduate students, but that's not really teaching.  Also, I was one of four researchers who gave presentations and problems to graduate students at the Winter School sponsored by the Graduate College, a consortium linking the Berlin Universities.  But again, this is not the same as teaching, at least not in the way we use the term at ASU.

  I am very grateful to Arizona State University and my  departmental colleagues for the opportunity.  I am also grateful to Martin Aigner (Mathematics),  Stefan Felsner (Computer Science) and Helmut Alt (Computer Science) who hosted my visit to the Free University and to the Deutsche Forschungsgemeinschaft (the German equivalent of the NSF), whose support enabled me to extend our stay in Berlin for a full year.
     Berlin is an exciting city and has three strong universities.  In addition to the Free University, the city is also home to Humboldt University and to the Technical University of Berlin.  I have
strong research ties with all three universities in both the mathematics and computer science departments.  Also, the FU campus houses the ZIB Institute, a large research center in discrete optimization.  At the Free University, my office was in Computer Science and most of my day to day contacts were with colleagues in that unit.  The department is called "Theoretische Informatik" in German and specializes in computational geometry (Check out their CGAL project on the WWW).
     On scientific grounds alone, it was a very successful year.  Early in the year, Felsner, Peter Fishburn and I settled a long standing problem by showing that there is a finite (three dimensional) poset
which cannot be represented as spheres ordered by inclusion--in any euclidean space, regardless of how large the dimension of the space is allowed to be.  Later in the year, we made nice contributions with results on planar graphs, hypergraph and graph coloring, and ramsey theory.  During the Berlin stay, I wrote six research papers; meanwhile four other papers, representing work done before the sabbatical leave, appeared and another three have since appeared.  In January of 1998, I was named managing editor of ORDER, and in the spring of 1998, I completed work as a Guest Editor for a Special Issue of Discrete Mathematics on posets.  I was invited to do this project as a follow up to the plenary lecture I gave at the 1997 AMS meeting in San Diego.
     As is to be expected, I had the opportunity to travel extensively during the year, with visits to England, Mexico, Poland, China, Russia, Turkey, Italy, and the Czech Republic.  Of course, I travelled all over Germany giving talks in Braunschweig, Hamburg, Munich, Chemnitz, and Rostock as well at all three Berlin universities.  In fact, a number of tentative trips had to be postponed as I simply ran out of time.
     All the trips were interesting.  During the trip to Mexico, I made some research contacts which look promising for the future.   I went to Novosibirsk in December when the temperature hit -40 and at this level, you don't even have to ask whether this is Celsius or Fahrenheit.  There are many exceptionally talented researchers there, and I hope to go back again.
     Most of the other trips were to places I have been many times, places where I have strong research contacts and many good friends, with China the obvious exception.  And this three week trip is a special memory for my entire family.
     We started out in Beijing where I gave a plenary talk to a graph theory conference.    Of course, we also saw the Great Wall, the Ming Tombs, the Summer Palace, and lots of other "must sees'.  From Beijing, we went to Yangzhou, Suzhou, Nanjing and Inner Mongolia, travelling usually by train.  At each stop, I gave a colloquium talk (or two), met with faculty, students, university officers and government officials.  We were treated with incredible kindness and generosity everywhere we went.  The people were warm, friendly and very open.  We ate too much and drank too much (watch out for "Gambei!"), but what an experience.   As a side note, the ability to drink seems to be an absolute must for high level positions in China.  I'm afraid I would be doomed to second level slots!!
     A few random thoughts on individual stops.  In Inner Mongolia, I gave a scientific talk to an audience of 80 squeezed into a room which holds 40.  People were standing outside, six to a window and another ten or so packed into the doorway.  The talk was translated sentence by sentence into Mongolian.  I had never done that before!  The next day, I gave a general talk about the American educational system to a packed audience which of about 300 people.  Again this talk was translated.   Many interesting questions were raised, questions which most likely would not have been asked just a few years ago.
     At another stop, I had prepared slides and arrived to learn that there was no projector.  No problem.  The slides wouldn't have fit the audience anyway.  At every stop, except one, there was at least one faculty member who was fairly strong in combinatorics, but for obvious reasons, they are not in close contact with one another.  Many have studied in the US, and most have held visiting faculty positions here.  Perhaps most importantly, there is an abundant supply of bright young people, some of whom will no doubt want to study here in the US, perhaps at ASU.
     Before setting out for Germany, my family had a number of  thoughtful discussions about the year.  We anticipated it would be a time of growth and learning for all of us.  And it was.  We made a conscious effort to avoid Americans and to blend into (to the extent possible) German society.  Matt learned some German, while Millie and I learned to cope.  Actually, my reading isn't so bad, but I didn't make as much progress in learning to speak as I had hoped.  Still, we wouldn't trade this very special year for anything.