Christoph Sorger Discusses the IMU

Christoph Sorger is the secretary general of the International Mathematical Union (IMU). The IMU has no individual members—its members are national mathematics organizations (the United States is represented by its Committee of Mathematics, now chaired by Eric Friedlander, and the adhering organization is the National Academy of Sciences). The IMU currently has 84 members. I interviewed Christoph Sorger in late 2024. —Ed.

Figure 1.

Q: What are the IMU’s main activities?

A: Since its beginnings, the IMU’s mission is to foster international collaboration in mathematics and between mathematicians, and one of the main activities of the IMU is the organization—together with the relevant Local Organization Committee (LOC)—of the quadrennial International Congress of Mathematicians (ICM). The next ICM will take place in Philadelphia in 2026. The 2026 LOC is chaired by Jalal Shatah and cochaired by Yuri Tschinkel.

As you know, ICMs are held every four years. The first official ICM was held in Zürich in 1897, preceded by the so-called “pre-ICM” in 1893 at the World’s Columbian Exposition in Chicago, often referred to as the Chicago Congress. Chicago’s Department of Mathematics had been founded only one year before, and its first faculty members were Eliakim Hastings Moore, Oskar Bolza, and Heinrich Maschke, who played a key role in coordinating the event. The congress itself was notably influenced by Felix Klein, who attended as the “imperial” representative of Germany and delivered its opening address titled “The Present State of Mathematics.” Looking at the proceedings of the Chicago Congress, one gets the impression that many leading mathematicians from all over the world attended, but this was not the case—only 4 of the 45 participants were not from the United States.

There were exceptions to this four-year rule already for the second ICM held as part of the Exposition Universelle in Paris in 1900. This congress is best known for David Hilbert’s address and his list of the 23 problems that shaped much of twentieth-century mathematics. However, apart from the two world wars when there were no ICMs and one exception in 1983, the four-year rule has been observed ever since.

This puts IMU’s internal organization pretty much on a four-year cycle. We hold our General Assembly (GA) every four years, a few days before the ICM, and our internal agenda is mostly organized as $y-3, y-2, y-1$, and $y$, where $y$ is the year of the next ICM. Following this internal calendar, we are currently in $y-1$, with $y=2026$.

During the GA, the members of the IMU elect the president, the two vice-presidents, and the six members-at-large of the Executive Committee (EC) as well as the IMU secretary general, who is responsible for the overall organization of the IMU and the Secretariat, which has been located in Berlin since 2007.

Q: What is the IMU’s responsibility in the organization of the ICM?

A: The IMU’s main responsibility is the scientific program of the ICM, including the selection of the speakers and the selection of the IMU awards, such as the Fields Medal. The overall structure, such as the number of plenary lectures, the definition and scope of the sections, and the number of section lectures, is the responsibility of the ICM Structure Committee (SC), now chaired by Terence Tao. At the next ICM, there will be about 220 invited speakers for about 20 plenary, 180 sectional, and 20 special lectures. The Program Committee (PC), now chaired by Claire Voisin, is responsible for selecting all the speakers. Only the name of the PC chair is publicly known. To ensure impartiality and avoid outside pressure or lobbying, the identities of the other committee members are traditionally kept confidential until the Congress. At its first meeting in $y-3$, the newly elected IMU EC selects the members of the PC, the choice of its chair being the privilege of IMU’s president, currently Hiraku Nakajima. The PC has about 12 members, who must abide by very strict rules on conflicts of interest, unconscious bias, and confidentiality of the committee’s work. The PC then selects one panel for each section—the sectional panels. The PC selects only the panel’s core members, and the panel itself then selects some additional members, completing the panel. The section panels make proposals to the PC for the choice of the above 180 sectional speakers as well as proposals for the special lectures. Given that there are usually four to eight sectional panel members, depending on the size of the sections, all in all more than 150 mathematicians are involved in determining the scientific program. The PC is expected to finalize its choice in March $y-1$, that is, March 2025 for the next ICM. Then the chair of the LOC sends out the invitation letters, and once the program is finalized, it is posted on the ICM website, usually icm($y$).org (thus for Philadelphia, it is https://www.icm2026.org). The editors of the 2026 proceedings, Susan Friedlander, Alex Kontorovich, and Yuri Tschinkel, will then contact the speakers to ask for their manuscripts. Except for the first volume, the “Prize Lectures,” all volumes will be available when the ICM starts.

At its first meeting in $y-3$, the EC also selects the members of the Fields Medal Committee. The chair is usually the president of the IMU, and the committee also consists of about 12 members. Again, only the chair is publicly known; the members are announced only when the Fields Medals are awarded.

Q: What are the special lectures?

A: For ICM 2022, a distinction was made between “traditional” and “special” sectional and plenary lectures, based on the recommendations of the previous SC. The special lectures are sectional or plenary lectures that deviate from the traditional format of presenting contemporary research by their authors. They are selected by the PC from proposals made by the section panels through a separate bidding process, independent of section allocations. Examples include talks that foster new connections between different areas of mathematics or their applications, interdisciplinary or emerging topics that don’t fit into existing section structures, timely surveys of subfields presented by experts not necessarily involved in the latest developments, or talks that use innovative methods or formats that are uncommon in standard section talks. The PC has 20 additional section slots and one or two plenary slots that it can decide to allocate to such special lectures.

Q: Apart from ICM organization, what does the IMU do?

A: The IMU works through various commissions and committees, each of which deals with specific aspects of mathematics. It is difficult to give a quick overview of the “C&Cs,” as we call them, because they are responsible for so many of the IMU’s activities. However, let me try.

Commissions

The International Commission on Mathematical Instruction (ICMI), with current President Merrilyn Goos (Australia), promotes international collaboration and research in mathematical education at all levels. The ICMI was founded in 1908 at the ICM in Rome, with Felix Klein as its first president, and joined the IMU in the 1950s. The ICMI organizes conferences (such as the International Congress on Mathematical Education that takes place every four years in between ICMs), publishes research, and supports initiatives to improve mathematics teaching and learning worldwide.

The Commission for Developing Countries (CDC), with current President Andrea Solotar (Argentina), supports the development of mathematics in developing countries. As we all know, mathematical talent is equally distributed around the world, but the conditions for becoming a mathematician very much depend on the place where you are born. The CDC provides grants, organizes workshops, and facilitates collaborations to enhance mathematical research and education in less-resourced regions. Two programs are aimed at graduate students: Graduate Research Assistantships in Developing Countries⁠¹ (GRAID) and IMU Breakout Graduate Fellowships.⁠² Donations for these programs are administered through the “Friends of the IMU,” which in turn receives crucial administrative support from the AMS. GRAID has been made possible by the very generous donations from AMS members, and Breakout made possible by substantial contributions from the Breakthrough Prize winners. Another program is the IMU Simons Research Fellowship Program, funded by the Simons Foundation, which supports mathematicians based in developing countries to undertake collaborative research at mathematical institutions abroad.

¹

https://www.ams.org/journals/notices/202308/rnoti-p1281.pdf

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²

https://www.ams.org/journals/notices/201908/rnoti-p1294.pdf

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The International Commission on the History of Mathematics (ICHM), now chaired by June Barrow-Green (UK), encourages the study and appreciation of the history of mathematics. The ICHM is an inter-union commission joining the IMU and the Division of History of Science and Technology of the International Union of History and Philosophy of Science and Technology, and it is composed of representatives of some 55 nations. The ICHM promotes research, organizes symposia, and disseminates information on historical developments in mathematics.

Committees

The Committee on Electronic Information and Communication (CEIC), now chaired by Ilka Agricola (Germany), advises the IMU on matters related to digital publishing, open access, the use of technology in mathematical research and education, the new questions about citation farms, or crucial infrastructures such as the arXiv. Its committee on permissions, now chaired by Tom Brennan (US), recently rendered its final report and recommendations to the IMU EC. The report is available on the IMU website.

The Committee for Women in Mathematics (CWM), now chaired by Carolina Araujo (Brazil), is the committee of the IMU concerned with issues related to women in mathematics worldwide. The CWM supports initiatives to increase the participation of women in mathematics, organizes events, and provides resources to address gender disparities. The CWM has been at the origin of the Standing Committee for Gender Equality in Science (SCGES), which partners now more than 20 international scientific unions and organizations and has “Ambassadors” in more than 100 countries—more than the number of IMU members!

Finally, the ad hoc Committee on Diversity (CoD), now chaired by Elena Vázquez-Abal (Spain), focuses on ensuring that discrimination is not present at ICM in any form and develops strategies and recommendations to welcome participants from different geographical regions, disciplines, and lived experiences.

The IMU also has outreach activities, such as the International Day of Mathematics (IDM), celebrated on March 14. The IDM is a worldwide celebration of the beauty and importance of mathematics, and it is a joint project of the IMU and the United Nations Educational, Scientific, and Cultural Organization (UNESCO). The UNESCO proclaimed March 14 as the International Day of Mathematics in 2019, and the first celebration took place in 2020. The 2025 theme is “Mathematics, Art, and Creativity.” The IDM Governing Board has been chaired since its inception by Christiane Rousseau (Canada). From 2025 on, it will be chaired by Betül Tanbay (Türkiye).

The IMU has a Secretariat, currently located in Berlin. The Secretariat is responsible for the day-to-day operations of the IMU, and its role is to support all of the above activities, including the IMU EC, IMU finance and accounting, and IT and website support. The Secretariat also hosts the IMU Archive and provides archival facilities for all IMU activities and committees with varying rules of confidentiality. For example, the Archive contains the deliberations of the IMU Awards Committees, with a confidentiality rule of 70 years after the awarding of the prize.

Q: What are the main challenges for the IMU that you see?

A: One of the biggest challenges is the future of ICMs. While the Chicago Congress had only 45 participants, over the years, ICMs have become very large, expensive, and increasingly difficult to organize.

There is also the question of the ICM itself in a rapidly changing world. What will the ICM look like in the future? Of course, the ICM will continue to be seen as one of the leading gatherings of mathematicians in the world. Historically, the congress has been an important platform for sharing the latest research and facilitating interaction between individual mathematicians. Today, these roles can often be fulfilled equally well by other physical and online venues. Nevertheless, ICMs will continue to excel in presenting and synthesizing groundbreaking developments across mathematical subfields through the quality of its lectures and the rigorous selection of its speakers, and in shaping future directions of the field. It also recognizes outstanding contributions through its awards and invitations, while serving as a high-profile event to advocate for mathematics with the public and policymakers. Should the ICM evolve into a more hybrid, smaller, or even entirely different event? Of course, we all know how important in-person congresses are, especially for younger mathematicians to connect with leading mathematicians not only in their own field but also in other fields. To understand new ideas, nothing is faster than asking a direct question in person or, even better, an informal discussion in front of a blackboard or in a café.

And what about the format of the ICM itself? Should the traditional format of plenary and breakout sessions, divided into about 20 sections, remain set in stone? The SC considered all these questions, and some possible answers are given in its 2023 report. One of the answers was the introduction of Special Lectures, as discussed above; others are outlined in the very interesting paragraph 3.8 (Future offerings for the ICM) of that report. I particularly like the idea of “broadcasting a single lecture simultaneously to multiple physical locations, using state-of-the-art technology to allow full audience participation at each location.” This kind of “public viewing” in a math department is very different from watching a lecture in your office or at home. Live streaming is expensive for the organizers of an event, but the cost could be shared through a subscribe-to-open mechanism, allowing departments from less privileged parts of the world to participate.

More generally, of course, the IMU is all about promoting international cooperation in mathematics. In a more and more divided world, with sanctions and visa problems for scientists, it is increasingly difficult to connect the different mathematical communities, with only the shared interest in mathematics in mind, and to avoid all political aspects of this cooperation. Norbert Schappacher’s book Framing Global Mathematics,⁠³ written on the occasion of the centennial of the founding of the IMU in 1920, has the subtitle The International Mathematical Union Between Theorems and Politics. Let’s try to stay on the “Theorems” side, but also stand by our values. As written in our statutes, “The Union adheres to the International Science Council’s principle of embodying the free and responsible practice of science, freedom of movement, association, expression and communication for scientists, as well as equitable opportunities for access to science, its production and benefits, access to data, information and research material; and actively upholds this principle, by opposing any discrimination on the basis of such factors as ethnic origin, religion, citizenship, language, political or other opinion, gender, gender identity and sexual orientation, disability or age.”

³

https://doi.org/10.1007/978-3-030-95683-7

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Q: How can an individual mathematician get involved in the IMU?

A: Come to see us in 2026 at the ICM in Philadelphia! Registration is open. There are no individual members of the IMU, as members of the IMU are countries. They are represented either by learned societies, academies, or committees of mathematicians. So one way is to become a delegate from your country to the GA. The GA is the governing body of the IMU, and the participation of all member countries is crucial. Another, more direct way is to get in touch with the commissions and committees of the IMU. For example, if you are interested in the activities of the IMU CDC, contact the CDC; if you are interested in open access publishing, don’t hesitate to contact the CEIC. Or become a CWM Ambassador!

Q: How can readers find out more about IMU activities?

A: All information about the IMU is available on our website. A good starting point would be to subscribe to our newsletter, IMU News.⁠⁴ We also have a YouTube channel⁠⁵ with the last three ICMs and the prize videos online. Recently, the IMU CDC started a series of webinars, and these webinars offer an effective channel to learn more about its programs and grants. And, here at the Secretariat, we recently started using LinkedIn for the IMU—just search for International Mathematical Union and connect. We have just started, and it may take some time, but eventually all important information will be posted there with links to more detailed content on the website.

⁴

https://www.mathunion.org/organization/imu-news

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⁵

https://www.youtube.com/@InternationalMathematicalUnion

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Q: What led you to be in the position you are now?

A: I received a phone call from Wendelin Werner, the chair of the 2022 Nominating Committee. He asked me about the position of IMU secretary general. I was quite surprised, especially since I had not previously been involved in any IMU activities (he was formerly director of the Institut National des Sciences Mathématiques et de leurs Interactions [Insmi] of CNRS [2013–2017], so he had some administrative experience! —Ed.), but also honored. I discussed the duties and responsibilities of the secretary general with the then IMU secretary general Helge Holden and the IMU president Carlos Kenig, France had nominated me, and after some hesitation, I decided to give it a try.

Q: What does your job consist of, and what are your plans?

A: As secretary general, I am responsible for the overall organization of the IMU and the Secretariat. As such, I oversee the day-to-day administrative operations of the IMU and its scientific programs, and serve as a liaison between the IMU’s members, its committees, and the EC. One of my responsibilities is to ensure effective communication with the local ICM organizers and the scientific committees as well as ensure transparency and integrity in the selection and awarding processes. Another role is to follow up on the IMU’s representation at the international level and its communication with other scientific unions or the International Science Council. Finally I have to ensure compliance of our operations with the IMU’s statutes and regulations and keep up with deadlines! Luckily the Secretariat team is excellent. What are my plans? A secretary general has always served two terms since the beginning of the IMU, because it takes quite some time to learn the job. So maybe I will too, but that is up to the GA in 2026 to decide.