Celebratio Mathematica

Per­son­ally, over the last forty years, I owe a lot to Friedrich Hirzebruch for his un­fail­ing sup­port and con­tinu­ous in­spir­a­tion. I met him in Bonn in 1970 while I was vis­it­ing Wil­helm Klin­gen­berg as a very young re­search­er in dif­fer­en­tial geo­metry. It was really dur­ing the aca­dem­ic year 1976–77, spent in Bonn with my fam­ily as guest of the Son­der­forschungs­bereich 40, that I got to know him bet­ter.

The Arbeit­sta­gung, a ma­jor math­em­at­ic­al event that he or­gan­ized with his Bonn col­leagues for more than thirty years, offered each year in June a broad over­view of the most ex­cit­ing math­em­at­ics of the time. It was an ex­cep­tion­al place to meet math­em­aticians of all sorts, fam­ous and less fam­ous, seni­or or just be­gin­ning. Like many young math­em­aticians, I be­nefited a lot from it, dir­ectly through the new per­spect­ives gained by listen­ing to the lec­tures and in­dir­ectly through the great num­ber of en­coun­ters, some of which had a great im­pact on my pro­fes­sion­al life.

He was al­ways curi­ous to know what kind of math­em­at­ics was on your mind and showed spe­cial in­terest in young math­em­aticians. Also worthy of re­mark was his de­term­inedly pro­act­ive at­ti­tude to­wards wo­men math­em­aticians at a time when gender equal­ity was not giv­en much pri­or­ity. Sev­er­al wo­men col­leagues con­sider that they owe him a lot be­cause of his con­tin­ued sup­port.

The nu­mer­ous en­coun­ters with him that fol­lowed the won­der­ful year in Bonn gave me ample op­por­tun­ity to wit­ness his many tal­ents: as an out­stand­ing math­em­atician of course, but also as a re­mark­ably clear lec­turer, an ef­fi­cient com­mu­nic­at­or, and an ex­cep­tion­ally tal­en­ted man­ager. Some of them were quite un­ex­pec­ted for me, such as ac­com­pa­ny­ing him to a press con­fer­ence with Ger­man journ­al­ists to dis­cuss the de­vel­op­ment of math­em­at­ics in his coun­try.

He was a great sup­port­er of the col­lab­or­a­tion between the In­sti­tut des Hautes Études Sci­en­ti­fiques (IHÉS) and the Max-Planck-Gesell­schaft (MPG). He rep­res­en­ted the MPG on the board of dir­ect­ors of IHÉS for sev­er­al years. Both he, as dir­ect­or of the Max-Planck-In­sti­tut für Math­em­atik, and Sir Mi­chael Atiyah, as found­ing dir­ect­or of the Isaac New­ton In­sti­tute in the Math­em­at­ic­al Sci­ences, en­dorsed im­me­di­ately the idea of the European Post-Doc­tor­al In­sti­tute (EP­DI) which I pro­posed in the fall of 1994 shortly after be­com­ing the dir­ect­or of IHÉS. Already in 1995 the three in­sti­tu­tions could join forces to get young postdocs to move around Europe. For the in­aug­ur­al ce­re­mony in Bures-sur-Yvette, Hirzebruch gave a very in­spir­ing speech on the role of in­sti­tutes in math­em­at­ics.

All along his ca­reer, Friedrich Hirzebruch had a lot of in­ter­ac­tions with Henri Cartan, a ded­ic­ated European very early on: his first in­ter­ac­tion was in re­la­tion to Cartan’s ef­forts to re­new con­tact between Ger­man and French math­em­aticians after the Second World War. In­deed, as early as Novem­ber 1946, Henri Cartan lec­tured in the Loren­zen­hof in Ober­wolfach.

In this con­nec­tion, Friedrich Hirzebruch wrote the fol­low­ing:

The “As­so­ci­ation Européenne des En­sei­gnants” (European As­so­ci­ation of Teach­ers) was foun­ded in Par­is in 1956. Henri Cartan was pres­id­ent of the French sec­tion. As such he took the ini­ti­at­ive to in­vite par­ti­cipants from eight European coun­tries to a meet­ing in Par­is in Oc­to­ber 1960. Emil Artin, Hein­rich Behnke and I were the Ger­man mem­bers. The second meet­ing of this com­mit­tee was in Düssel­dorf in March 1962. As a res­ult, the “Livret Européen de l’Etu­di­ant” (European Stu­dent’s Re­cord) was pub­lished and dis­trib­uted by the As­so­ci­ation. The book­let con­tained a de­scrip­tion of min­im­al re­quire­ments for ba­sic courses. It was sup­posed to in­crease the mo­bil­ity of stu­dents from one coun­try to an­oth­er. The pro­fess­or of one uni­versity would mark in the book­let the con­tents of courses at­ten­ded by the stu­dent. The pro­fess­or at the next uni­versity would then be able to ad­vise the stu­dent in which courses to en­roll. The book­let was not used very much. This was in­deed the early form of the by now well-es­tab­lished “Erasmus Pro­gram”.

A lot about their re­la­tion­ship can be learned from read­ing the let­ter that Friedrich Hirzebruch wrote in 1994 to Henri Cartan on the oc­ca­sion of his nineti­eth birth­day.

The European Coun­cil of Math­em­at­ics (EMC) opened the way to the European Math­em­at­ic­al So­ci­ety (EMS). The found­a­tion­al meet­ing of the EMS was held in Oc­to­ber 1990 in Mad­ral­in and was not an easy af­fair, as op­pos­ite views on the struc­ture of the EMS were presen­ted by some del­eg­a­tions: should it be a fed­er­a­tion of so­ci­et­ies or a so­ci­ety with in­di­vidu­al mem­bers? Friedrich Hirzebruch, who had agreed to be con­sidered as the first EMS pres­id­ent, led to suc­cess the rather tense meet­ing be­hind closed doors between sup­port­ers of the con­flict­ing po­s­i­tions. The next day the new so­ci­ety could be cre­ated with stat­utes en­sur­ing a good bal­ance between in­di­vidu­al mem­bers and mem­ber so­ci­et­ies, a fea­ture that still re­mains op­er­a­tion­al to this day.

Un­der Friedrich Hirzebruch’s lead­er­ship, the EMS de­veloped suc­cess­fully. A lot had to be achieved in a short time to take ad­vant­age of the dy­nam­ics that ac­com­pan­ied the cre­ation of the so­ci­ety. Among mile­stones of his man­date, one can single out the set­ting up of the first European Con­gress of Math­em­at­ics in Par­is in 1992 and lay­ing the ground­work for the Journ­al of the European Math­em­at­ic­al So­ci­ety (JEMS) that was fi­nally cre­ated in 1999.

To my great sur­prise, he asked me to be­come his suc­cessor as EMS pres­id­ent in 1994 to serve for the second term, 1995–98, an­oth­er great hon­or that he be­stowed on me.