Formalizing the solution to the cap set problem

Sander R. Dahmen, Johannes Hölzl, Robert Y. Lewis

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Abstract

In 2016, Ellenberg and Gijswijt established a new upper bound on the size of subsets of 픽nq with no three-term arithmetic progression. This problem has received much mathematical attention, particularly in the case q = 3, where it is commonly known as the cap set problem. Ellenberg and Gijswijt’s proof was published in the Annals of Mathematics and is noteworthy for its clever use of elementary methods. This paper describes a formalization of this proof in the Lean proof assistant, including both the general result in 픽nq and concrete values for the case q = 3. We faithfully follow the pen and paper argument to construct the bound. Our work shows that (some) modern mathematics is within the range of proof assistants.

Original languageEnglish
Title of host publication10th International Conference on Interactive Theorem Proving (ITP 2019)
EditorsJohn Harrison, John O'Leary, Andrew Tolmach
PublisherSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
Pages1-19
Number of pages19
ISBN (Print)9783959771221
DOIs
Publication statusPublished - 2019
Event10th International Conference on Interactive Theorem Proving, ITP 2019 - Portland, United States
Duration: 9 Sept 201912 Sept 2019

Publication series

NameLeibniz International Proceedings in Informatics, LIPIcs
Volume141
ISSN (Print)1868-8969

Conference

Conference10th International Conference on Interactive Theorem Proving, ITP 2019
Country/TerritoryUnited States
CityPortland
Period9/09/1912/09/19

Funding

Funding Sander R. Dahmen: NWO Vidi grant No. 639.032.613, New Diophantine Directions Johannes Hölzl: ERC grant agreement No. 713999, Matryoshka Robert Y. Lewis: ERC grant agreement No. 713999, Matryoshka Acknowledgements We are grateful to the Lean mathlib maintainers and contributors on whose work this project is based. We thank Jeremy Avigad and Jasmin Blanchette for helpful comments on this paper, Dion Gijswijt for suggesting an improvement to our asymptotic bound argument, and Manuel Eberl for pointing us to related work.

FundersFunder number
NWO VIDI639.032.613
Horizon 2020 Framework Programme713999
European Research Council

    Keywords

    • Cap set problem
    • Combinatorics
    • Formal proof
    • Lean

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