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Timeline for The "interior" of a convex set?

Current License: CC BY-SA 4.0

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Jun 16, 2022 at 9:25 comment added Yann Dubois if that was for all b (rather than exist) that would be the definition of relative interior for convex set A.
May 5, 2021 at 14:56 comment added Jochen Wengenroth In Köthe's book Topological Vector Spaces there is a notion of internal points of a convex set $A$ which means that $x$ is an interior point of the intersection of $A$ with every real line through $x$ (of course, interior refers to the usual topology of the reals).
May 5, 2021 at 8:11 comment added mlk The weird thing about this definition is that it is non-local. As the cone shows, if I know $A$ only in a neighborhood of $a$, then there are cases where I cannot decide if $a\in ci(A)$ or not. Possibly a more natural condition would be "For all $b\notin A$, there exists $\epsilon$", but I think that should be equivalent to the topological interior. Maybe the important question is, what are you trying to achieve with this definition?
May 5, 2021 at 5:37 comment added user130903 I see the following cases: 1. A is an affine subspace, in which case there are no convex interior points. 2. A is a pointed cone in which case the cusp is the only ci point. 3. All other cases, in which every point is ci.
May 5, 2021 at 4:33 history edited Lemma1 CC BY-SA 4.0
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May 5, 2021 at 4:33 comment added Lemma1 I am mainly asking if this definition is well known or equivalent to some well-known definitions.
May 5, 2021 at 4:17 review Close votes
May 10, 2021 at 3:01
May 5, 2021 at 3:59 comment added Ryan Budney I'm not certain what your question is. It seems that if you write down a condition for "interior" you will have answered your own question. But if you have no criterion for interior, your question can not be answered.
May 5, 2021 at 3:51 history edited Lemma1
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May 5, 2021 at 3:42 history asked Lemma1 CC BY-SA 4.0