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In Memoriam - Bas Edixhoven

On January 16, 2022, our respected and beloved colleague Prof. dr. Bas Edixhoven passed away after a short period of serious illness.

Bas was born on March 12, 1962 in Leiden and grew up in Pijnacker. He graduated in Mathematics in Utrecht in 1985 and obtained his PhD there in 1989 with Frans Oort.

After his PhD, Bas worked for two years as a Morrey assistant professor at the University of California, Berkeley. After a short period as a Huygens fellow at Utrecht University he was appointed professor in Rennes, where he remained for almost 10 years. In September 2002 Bas was appointed Professor of Geometry in Leiden, succeeding Hansjörg Geiges. Since 2009 he has been a member of the Royal Netherlands Academy of Arts and Sciences.

Bas' field of expertise was in arithmetic algebraic geometry. He used his amazing geometric intuition to study problems in number theory. The subject of his PhD thesis was modular curves; already very early in his career he was one of the global experts in this field. He did important work on the techniques involved in the famous proof of Fermat's Last Theorem from the early 1990s, and on the related conjecture of Fields medalist and Abel Prize winner Jean-Pierre Serre.

After that period, Bas made a decisive contribution to resolving a conjecture proposed by his French colleague Yves André and his promotor Oort. Among other topics he also worked on making modular forms and their associated Galois representations accessible computationally. In 2004 he was awarded a VICI for a project proposal in this direction. Bas made another important contribution very recently by geometrically interpreting the so-called quadratic Chabauty method.

Bas' influence on mathematicians all over the world is impressive. He generously shared his insight with students and colleagues. Bas was averse to status and hierarchy, and was easily approachable. Many will remember how a twinkle came to his eye when he was posed an interesting mathematical question.

He seemed to find the answers to the most profound questions without difficulty, as if reading them from the stars. His aim was always to gain a deeper understanding and to uncover the underlying structure of a problem.

Bas has supervised approximately 30 PhD students, almost half of them in cotutelle. As a passionate teacher, he gave lectures at all levels and always with the same enthusiasm, regardless of the subject, endearing him to the students. In his lectures he attached great importance to the correct formulation of a result and the correct choice of notation. He has given shape to his unique way of thinking in various beautiful syllabi.

Bas has taught in numerous summer and winter schools in his field, and in initiatives such as CIMPA, a non-profit organization dedicated to promoting research in mathematics in developing countries.

In 2004, Bas and Peter Stevenhagen laid the foundations from Leiden for the ALGANT consortium, which developed into a French-Italian-German-Canadian-Dutch collaborative program in algebra, geometry and number theory, as part of which more than 100 master's students and 30 PhD students graduated in Leiden. 

Bas was an involved and critical member of numerous international and national boards and committees. In this way he has left his mark on many developments within the mathematical community, very often in educational matters. Within the Platform Wiskunde Nederland, he was a member of both the Research Committee and the Education Committee.

His commitment to education also formed the basis of a program that contributes to solving the national shortage of mathematics teachers by training lateral entrants. This program originally had a place within Mastermath, the joint master's program in Mathematics of the Dutch universities, and was recently merged into the national beta4all program under the leadership of Bas and under the name wisk4all.

As part of his membership of the think tank "Bèta-lerarenkamer", Bas has made possible the welcome-teacher-app, with which more than a hundred refugee teachers have worked to become proficient in the Dutch language and in mathematics didactics, so as to improve their chances on the Dutch labor market.

Within the Faculty of Mathematics and Natural Sciences of Leiden University, Bas was a member and for many years chairman of the committee that organizes the annual C.J. Kok prizes. For the Mathematics program he was a member of the examination and program committee, and in the period 2007-2011 he was program director. After that he became director of Mastermath from 2012 to 2017.

In the period 2003-2012 Bas was one of the editors-in-chief of the internationally leading mathematics journal Compositio Mathematica. After that he continued to play an important role in the board of the Compositio Mathematica Foundation. He was also editor of a number of other journals, including Indagationes Mathematicae, and from 2014-2016 director of the national mathematics research cluster DIAMANT.

In addition to his academic research, education and committee work, Bas devoted himself to many other areas as a volunteer. Since 2003 Bas was the chairman of the board of the Foundation Vierkant voor Wiskunde. He was also one of the driving forces behind the re-edition of the monumental Séminaires de Géométrie Algébrique from the 1960s.

Only six months ago, Bas started working two days less each week, as an advance on his retirement and to start working as an energy coach, among other things. Bas was proud of the fact that, as a pioneer in his neighborhood, he was the first to have a ground source heat pump installed at his home.

Bas had a warm personality. He committed himself to a better world, starting on a small scale around himself. He was convinced that everyone can take steps towards a better world for themselves. He thought about what might work best from a larger perspective and talked about this with many of us. One of his main conclusions was that the greatest changes for the better may be achieved through education, by teaching young people to think critically and clearly.

Our thoughts go out to Bas' wife Reinie and their two sons. We wish them strength in bearing this great loss. We will miss Bas tremendously as a person and as a colleague.

Book of condolence

A book of condolence has been set up in Bas' office (238a, Snellius building). Everyone is welcome to write their last greetings or memories of Bas here. Are you unable to come to the Snellius building but would you like to leave a message? You can leave your message in the online condolence register

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