Timeline for Union star symbol in set theory
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 3, 2021 at 3:28 | review | First posts | |||
| Jan 3, 2021 at 4:01 | |||||
| Dec 28, 2020 at 7:00 | comment | added | Tobias Fritz | @BrandNewStory: now I don't know what you mean by $a\bullet b$. All I meant is that $\cup^*$ may stand for the intersection of sets, just as $\cup$ stands for the union of sets. That's my guess. | |
| Dec 28, 2020 at 1:56 | comment | added | BrandNewStory | @TobiasFritz I'm not sure if I understand you correctly. In that case, if given a•b, what should it be under ∪∗ operation? | |
| Dec 28, 2020 at 1:52 | comment | added | BrandNewStory | @AndreasBlass Yeah I checked that paper but didn't find the definition of this symbol. I guess in that paper they define the lineage and Tannen worked on this symbol for the semiring. | |
| Dec 27, 2020 at 7:56 | review | Close votes | |||
| Jan 3, 2021 at 3:01 | |||||
| Dec 27, 2020 at 7:40 | comment | added | Tobias Fritz | A wild guess: the bottom of the slide suggests that $\cup$ and $\cup^*$ are operations defining a semiring structure, which in particular means that one distributes over the other. This suggets that $\cup^*$ stands for intersection. The slide also seems to be saying that the neutral elements are $\emptyset$ and $\emptyset^*$. So perhaps the author writes $*$ for set-theoretic complement (relative to a ground set), so that $\cup^*$ denotes the de Morgan dual of $\cup$. | |
| Dec 27, 2020 at 4:35 | comment | added | Andreas Blass | If you can find the paper cited two lines earlier on page 24, that should define $\cup^*$, because it's not a standard set-theoretic notation. Otherwise, you might ask Tannen by email. | |
| Dec 27, 2020 at 3:13 | history | asked | BrandNewStory | CC BY-SA 4.0 |