Dedekind domains and their class groups are notions in commutative algebra that are essential in algebraic number theory. We formalized these structures and several fundamental properties, including number theoretic finiteness results for class groups, in the Lean prover as part of the mathlib mathematical library. This paper describes the formalization process, noting the idioms we found useful in our development and mathlib’s decentralized collaboration processes involved in this project.
@InProceedings{baanen_et_al:LIPIcs.ITP.2021.5, author = {Baanen, Anne and Dahmen, Sander R. and Narayanan, Ashvni and Nuccio Mortarino Majno di Capriglio, Filippo A. E.}, title = {{A Formalization of Dedekind Domains and Class Groups of Global Fields}}, booktitle = {12th International Conference on Interactive Theorem Proving (ITP 2021)}, pages = {5:1--5:19}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-188-7}, ISSN = {1868-8969}, year = {2021}, volume = {193}, editor = {Cohen, Liron and Kaliszyk, Cezary}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2021.5}, URN = {urn:nbn:de:0030-drops-139004}, doi = {10.4230/LIPIcs.ITP.2021.5}, annote = {Keywords: formal math, algebraic number theory, commutative algebra, Lean, mathlib} }
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