Séminaire N. Bourbaki

27 mars 2021

Le Séminaire N. Bourbaki a lieu en principe à l'Institut Henri Poincaré (IHP) mais cette session aura lieu à distance. — [iCal] [Affiche] [Résumés]

16h30

Thomas Bloom — Quantitative inverse theory of Gowers uniformity norms after F. Manners [PDF] [YouTube]
Gowers uniformity norms are the central object of higher-order Fourier analysis, one of the cornerstones of additive combinatorics, and play an important role in both Gowers' proof of Szemerédi's theorem and the Green–Tao theorem. The inverse theorem states that if a function has a large uniformity norm, which is a robust combinatorial measure of structure, then it must correlate with a nilsequence, which is a highly structured algebraic object. This was proved in a qualitative sense by Green, Tao, and Ziegler, but with a proof that was incapable of providing reasonable bounds. In 2018 Manners achieved a breakthrough by giving a new proof of the inverse theorem. Not only does this new proof give a wealth of new insights but it also, for the first time, provides quantitative bounds, that are at worst only doubly exponential. This talk will give a high-level overview of what the inverse theorem says, why it is important, and the new proof of Manners.