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(draft) Banach algebras and geometric series #318

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@zstone1 zstone1 commented Jan 12, 2021

Building on my previous PR that defines the topology of compact convergence, I prove that the geometric series converges compactly in the open unit ball. This is very much a draft, as it does an OK job introducing Banach algebras. I should probably build the whole hierarchy of NormedRing-> NormedAlgebra -> BanachAlgebra. Too bad Hierarchy Builder can't be applied for this PR.

This is an essential lemma in complex analysis and spectral theory, because it'll let contour integrals exchange freely with geometric series.

@zstone1 zstone1 changed the title Banach algebras and geometric series (draft) Banach algebras and geometric series Jan 14, 2021
@CohenCyril CohenCyril marked this pull request as draft January 18, 2021 17:28
@zstone1 zstone1 closed this Jul 22, 2021
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@zstone1 why did you close this one?

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zstone1 commented Jul 22, 2021

Oh, sorry I should have left a closing comment. With #397 (Arzela-Ascoli), it will dramatically simplify this proof. So while the banach space definitions are still useful, that should be a separate diff.

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