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tirix
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@tirix tirix commented Oct 13, 2025

This is (finally!) the proof of Bourbaki, Algebra 2, Chapter V, Proposition 5 of , as proposed by @savask.

From here, I should be able to loop back to (towers of) quadratic field extensions.

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savask commented Oct 13, 2025

I haven't been able to spot any problems in the PR. Seems like you're getting pretty close to the final result!

with integer coefficients of products of elements of ` A ` .
(Contributed by Thierry Arnoux, 5-Oct-2025.) $)
elrgspn $p |- ( ph -> ( X e. ( N ` A ) <-> E. g e. F
X = ( R gsum ( w e. Word A |-> ( ( g ` w ) .x. ( M gsum w ) ) ) ) ) ) $=
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Why is the new proof so much longer? Only to eliminate the former hypothesis "( ph -> X e. B )"?

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Yes, only to eliminate the hypothesis.
I eliminated the hypothesis by proving both X e. B from both sides of the final biconditional, which requires closure of the sums, both the (infinite) larger sum and the embedded sum over each word.

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3 participants