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2
votes
1answer
71 views

Separating Differences of Open Sets

Has anyone ever considered something like the following separation axiom? $(*)$ For any pair of open sets $O$ and $N$, there exist disjoint open sets containing $O\setminus N$ and $N\setminus O$. ...
2
votes
1answer
223 views

Browder's fixed point theorem in non-Hausdorff topological vector spaces

Browder proved the following fixed point theorem in his 1968 Mathematische Annelen paper (Theorem 1): Theorem. Let $K$ be a non-empty compact convex subset of a topological vector space $E$ (where we ...
3
votes
2answers
491 views

Separation axioms

Reading about separation axioms, I wonder: Is there a separation axiom weaker than $T_2$ but stronger than $T_1$? $T_{1.5}$? I suppose there are some separation axioms stronger that $T_6$, how many ...
5
votes
1answer
533 views

Stack with affine stabilizers but not quasi-affine diagonal

Give an example of a stack X with affine stabilizer groups and separated but not quasi-affine diagonal. Remarks: 1) If X has finite stabilizer groups then the diagonal is quasi-finite and separated, ...