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@felixpernegger felixpernegger commented Dec 26, 2025

Once #1555 and #1553 are merged, this completes S36 and S141.

@felixpernegger felixpernegger changed the title Completing two ordinal(-like) spaces S36 and S141 Completing two ordinal(-like) spaces (S36 and S141) Dec 26, 2025
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Similar as in #1555, I could make a theorem Rothberger (P68) + Ordinal space (P190) implies Countable (P57). The proof I thought of would be: show ω 1 isnt Rothberger (this is done via automatic deduction), then argue that ω 1 + 1 isnt Rotheberger (as I did) and then say that ω 1 + 1 is a closed subset of any other uncountable ordinal space.

This argument is therefore invalid.

@felixpernegger felixpernegger marked this pull request as draft December 26, 2025 15:45
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felixpernegger commented Dec 26, 2025

Is it fine now? I didnt find strategically rothberger explained anywhere properly, so I hope I understood it properly.

@felixpernegger felixpernegger marked this pull request as ready for review December 26, 2025 16:29
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yhx-12243 commented Dec 27, 2025

I know what you want to mean, but it is not that “first player is not to pick point, etc.”

The definition is, in 𝑛th round, first player (A) choose an open cover, second player (B) choose one open set from cover. After 𝜔 rounds, if 𝜔 open sets chosen by second player (B) form a cover, then he (B) wins.

You can adapt the trait of S17|P151, very similar.

The proof #1556 (comment) I wrote is just copied from S17|P151.

Co-authored-by: yhx-12243 <yhx12243@gmail.com>
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prabau commented Dec 27, 2025

S36 | P151: Sorry, but this does not make sense. This does not seem related to the "game" for Strategically Rothberger. In that game, Player 1 chooses an open cover, then Player 2 chooses a member of that cover. Etc.

Added later: @yhx-12243 already addressed this above.

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prabau commented Dec 27, 2025

S141 | P103: the subspace omega_1 + 1 is actually closed. I think you meant to use omega_1.

felixpernegger and others added 2 commits December 27, 2025 08:04
Co-authored-by: Patrick Rabau <70125716+prabau@users.noreply.github.com>
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Sorry this is really embarrassing. I hope is it good now?

@prabau prabau merged commit 9e42a8c into main Dec 28, 2025
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@prabau prabau deleted the completing-s36-s141 branch December 28, 2025 00:19
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4 participants