Timeline for Subsets of $\mathbb{R}^+$ closed under addition
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| Oct 9, 2022 at 17:16 | comment | added | LSpice | @BenjaminSteinberg's answer referenced above (1 2). | |
| Oct 9, 2022 at 17:16 | history | edited | LSpice | CC BY-SA 4.0 |
Link to article, while this is on the front page
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| Apr 3, 2012 at 16:08 | history | edited | user6976 | CC BY-SA 3.0 |
Added update
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| Apr 3, 2012 at 7:18 | history | undeleted | user6976 | ||
| Apr 3, 2012 at 7:07 | history | deleted | user6976 | ||
| Apr 2, 2012 at 22:59 | comment | added | Benjamin Steinberg | He also said description which is why I linked to the above paper. | |
| Apr 2, 2012 at 22:51 | comment | added | user6976 | @Ben: Michael Hardy wanted a catalog. That is impossible. Individually subsemigroups of $\mathbb{Z}_+$ are not too difficult to describe: they are virtually arithmetic progressions. Subsemigroups of $\mathbb{R}_+$ and even $\mathbb{Q}_+$ are much harder. An interesting question is to describe subsemigroups of $\mathbb{Q}_+$ that are residually finite. I spent quite some time on that when I was an undergraduate student - without much success. Some non-trivial problems from descriptive topology appeared, as far as I remember. | |
| Apr 2, 2012 at 22:41 | comment | added | Benjamin Steinberg | This is what I meant by in some sense in my answer. There is no catalog but rather an axiomatization of embedability. | |
| Apr 2, 2012 at 22:39 | history | answered | user6976 | CC BY-SA 3.0 |