COMMUNICATION

Michel Talagrand Awarded

The Shaw Foundation has announced the awarding of the 2019 Shaw Prize in Mathematical Sciences to Michel Tala- grand of the French National Centre for Scientific Research (CNRS), , “for his work on concentration inequalities, on suprema of stochastic processes and on rigorous results for spin glasses.”

The Shaw Foundation’s state- areas as diverse as the geometry of convex bodies, graph the- ment reads: “ ory, and theoretical computer science. One of Talagrand's has made profound contri- great achievements has been to examine this phenomenon butions to probability and in detail and hugely improve our understanding of it. In high-dimensional geometry, particular, he proved famous inequalities, using completely at least three of which could new techniques, that give new concentration results that are be described as revolutionary. widely used in many different important settings. “A first major theme of Ta- “A third family of results for which he is famous concern lagrand’s research is the study objects known as spin glasses, which provide a mathe- of suprema of stochastic pro- matical model of a physical phenomenon involving very cesses. A is disordered systems. Unlike many models from statistical a collection of interacting ran- physics, spin glasses have a double layer of randomness. Michel Talagrand dom variables. When one is First, the way in which different random variables (the given a large such collection, spins in the spin glass language) will interact is chosen at it is often of crucial importance to obtain information random, which creates a very complex energy landscape, about how its maximum value is distributed. Starting with and then the random variables themselves are sampled the case of Gaussian processes (here the random variables randomly. One would then like to understand this large each have a Gaussian distribution, given by the famous ‘bell family of randomly interacting random variables and curve,’ and can be correlated in a certain way) and then for describe its typical features. Spin glasses have a short and more general cases, Talagrand has developed tools, such simple definition, but they are notoriously hard to analyze. as majorizing measures or generic chaining, that provide A significant advance was made by the theoretical powerful and very useful bounds for how these maximum , who proposed a formula for the free energy values behave. of a spin glass, which is an important quantity that encap- “The second group of contributions concerns a phe- sulates information about this random energy landscape. nomenon known as concentration of measure. Broadly However, turning predictions of statistical into speaking, this says that many functions that depend on a mathematically rigorous arguments is often extremely hard, large number of reasonably independent random variables and a rich source of fascinating mathematical problems. are extremely likely to take values close to their average. For Finding a complete rigorous proof in this case seemed to example, if one tosses a coin a thousand times, then the be way beyond what it was realistic to hope for, despite probability that the number of heads will be between 450 remarkable insights and progress by Francesco Guerra, and 550 is roughly 99.7 percent, and the probability that but Talagrand managed to do it, thereby providing for the it will be more than 600 is approximately 2 millionths of first time a complete mathematical underpinning for this 1 percent. In such a situation, we say that the number of extremely important physical theory. heads is concentrated. This phenomenon, often associated “One notable feature of Talagrand’s career that marks with the name of the mathematician Vitali Milman, is him out from many other mathematicians is that when remarkably general and has a multitude of applications in he solves a problem, he does not just leave it and move

1336 Notices of the American Mathematical Society Volume 66, Number 8 COMMUNICATION on. Rather, he continues to work on it, improving his About the Prize understanding and reworking his arguments until he has The Shaw Prize is an international award established to a well-developed theory that can be more easily used by honor individuals who are currently active in their respec- other mathematicians. He has written monumental and tive fields and who have achieved distinguished and signif- highly influential textbooks on all the three topics just icant advances, who have made outstanding contributions mentioned, and these have played a very significant part in culture and the arts, or who have achieved excellence in in the spread of his ideas, which are now central to the other domains. The award is dedicated to furthering societal work of large numbers of other mathematicians. Talagrand progress, enhancing quality of life, and enriching humani- is a true one-off, nearly always working on his own, and ty’s spiritual civilization. Preference is given to individuals obtaining extraordinary and highly unexpected results that whose significant work was recently achieved. have changed the mathematical landscape.” The Shaw Prize consists of three annual awards: the Prize in Astronomy, the Prize in Science and Medicine, and Biographical Sketch the Prize in Mathematical Sciences. Established under the Michel Talagrand was born in 1952 in France. He ob- auspices of Run Run Shaw in November 2002, the prize is tained his PhD in mathematical sciences in 1977 from managed and administered by the Shaw Prize Foundation the University of VI, France, under the direction based in Hong Kong. The prize carries a cash award of of Gustave Choquet. From 1974 until his retirement in US$1,200,000. 2017, he was part of the Functional Analysis Team of the Previous recipients of the Shaw Prize in Mathematical Institute of of the University Paris IV. He was Sciences are: successively research trainee, research associate, researcher •• (2018) and senior researcher for the French National Centre for •• János Kollár and (2017) Scientific Research (CNRS). He is a member of the French •• Nigel J. Hitchin (2016) Academy of Sciences. Talagrand has been the recipient of •• and (2015) the Peccot-Vimont Prize of the French Collège de France •• (2014) (1980), the Servant Prize of the French Académie des •• David L. Donoho (2013) Sciences (1985), the Loève Prize (1995), and the Fermat •• (2012) Prize (1997). He was an invited speaker at the International •• and Richard S. Hamilton Congress of Mathematicians (ICM) in 1990 and an ICM (2011) plenary speaker in 1998. •• (2010) •• Simon K. Donaldson and Clifford H. Taubes (2009) •• and Ludwig Faddeev (2008) •• and Richard Taylor (2007) •• and Wen-Tsun Wu (2006) •• (2005) •• Shiing-Shen Chern (2004)

—Shaw Foundation announcement

September 2019 Notices of the American Mathematical Society 1337