>>761 余談ですが

Infinity wikipedia に下記の
Wiles's proof of Fermat's Last Theorem
と Grothendieck universes の関係が書いてあった
これ面白いわ（＾＾；

https://en.wikipedia.org/wiki/Infinity
Infinity

The mathematical concept of infinity and the manipulation of infinite sets are used everywhere in mathematics, even in areas such as combinatorics that may seem to have nothing to do with them. For example, Wiles's proof of Fermat's Last Theorem implicitly relies on the existence of very large infinite sets[7] for solving a long-standing problem that is stated in terms of elementary arithmetic.

References
[7]
McLarty, Colin (2010). "What does it take to prove Fermat's Last Theorem? Grothendieck and the logic of number theory". The Bulletin of Symbolic Logic. 16 (3): 359–377. doi:10.2178/bsl/1286284558.
https://www.cambridge.org/core/journals/bulletin-of-symbolic-logic/article/what-does-it-take-to-prove-fermats-last-theorem-grothendieck-and-the-logic-of-number-theory/80EDFF3616F8D58590EBA0DCB9FD2E3E
（PDF）
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/80EDFF3616F8D58590EBA0DCB9FD2E3E/S1079898600000810a.pdf/what-does-it-take-to-prove-fermats-last-theorem-grothendieck-and-the-logic-of-number-theory.pdf

Abstract. This paper explores the set theoretic assumptions used in the current published
proof of Fermat’s Last Theorem, how these assumptions figure in the methods Wiles uses,
and the currently known prospects for a proof using weaker assumptions.

Does the proof of Fermat’s Last Theorem (FLT) go beyond Zermelo
Fraenkel set theory (ZFC)? Or does it merely use Peano Arithmetic (PA)
or some weaker fragment of that? The answers depend on what is meant
by “proof” and “use,” and are not entirely known. This paper surveys
the current state of these questions and briefly sketches the methods of
cohomological number theory used in the existing proof.

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