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• CommentRowNumber1.
• CommentAuthorjesse
• CommentTimeMar 8th 2017
• (edited Mar 8th 2017)

Created Fraïssé limit.

(I was pleasantly surprised to see @David_Corfield had posted about the these things a while ago for the n-Category Cafe.)

Mentioned a neat result of Olivia Caramello’s that omega-categorical structures presentable as Fraisse limits are determined by their automorphism groups $G$ with the topology of pointwise convergence in a very nice way: their classifying toposes are precisely the toposes of continuous $G$-sets.

To fill in a grey link, I also created an entry for the countable random graph.

• CommentRowNumber2.
• CommentAuthorDavid_Corfield
• CommentTimeMar 8th 2017

I hope the discussion at the Cafe got things right in the end. I recall plenty of terminological confusion about what kind of limits and embeddings were involved.

I see my follow-up didn’t generate much discussion.