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Category Archives: Uncategorized
Dcpos and convergence spaces I: Scott and Heckmann convergences
Every dcpo can be seen as a topological space, once we equip it with the Scott topology. And every topological space can be seen as a convergence space, so every dcpo can be seen as a convergence space. In 2003, Reinhold … Continue reading
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FS-domains of discs and formal balls
Only a short post this month: I would like to explain Lawson’s construction of an FS-domain that is not known to be an RB-domain. Roughly speaking, this is the domain of closed discs of the under with reverse inclusion, and … Continue reading
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Forbidden substructures
Characterizing properties of graphs, posets, and even dcpos by forbidden substructures is an intriguing approach. Xiaodong Jia managed to show that every CCC of quasi-continuous domains must consist of continuous domains exclusively, and I would like to explain how this rests … Continue reading
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Meet-continuous spaces
Meet-continuous dcpos were defined and studied by Hui Kou, Ying-Ming Liu, and Mao-Kang Luo about 14 years ago, and their importance only starts to be appreciated now. One of the leading results in the theory of meet-continuous dcpos is that a dcpo is continuous if … Continue reading
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Markowsky or Cohn?
I have already mentioned Markowsky’s Theorem (1976): every chain-complete poset is a dcpo. This is a non-trivial theorem, and I’ve given you a proof of it based on Iwamura’s Lemma and ordinals in a previous post. Maurice Pouzet recently pointed … Continue reading
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Integration
At the start of the book, I had stated: “Topological convexity, topological measure theory, hyperspaces, and powerdomains will be treated in further volumes.” The book got out in 2013, but I wrote that in 2011, almost seven years ago now. What … Continue reading
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In memoriam: Klaus Keimel
Klaus Keimel passed away on Saturday, November 18th, 2017, and this is sad news. I would like to pay homage to his memory, through a partial recollection of my own path with Klaus.
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A characterization of FAC spaces
In the open problem section, I defined a FAC space as a topological space in which every closed subspace is a finite union of irreducible closed subspaces. FAC is for “finite antichain property”, since it generalizes the following theorem, due … Continue reading
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Isbell’s density theorem and intersection of sublocales
When I wrote my latest blog post, there were many things I thought would be useful to know about sublocales. Those eventually turned out to be useless in that context. However, I think they should be known, in a more … Continue reading
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The O functor does not preserve binary products
In Exercise 8.4.23 of the book, I said: “Exercise 8.4.21 may give you the false impression that the O functor preserves binary products. This is wrong, although an explicit counterexample seems too complicated to study here: see Johnstone (1982, 2.14).” … Continue reading
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