Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with ct.category-theory
Search options not deleted
user 39521
Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.
40
votes
2
answers
3k
views
Ultrafilters as a double dual
Given a set $X$, let $\beta X$ denote the set of ultrafilters. The following theorems are known:
$X$ canonically embeds into $\beta X$ (by taking principal ultrafilters);
If $X$ is finite, then ther …
- 12.4k
15
votes
What is an explicit bijection in combinatorics?
Here's an example (credit: Paul Russell) of the sort of bijection you want to rule out.
Question: Find an explicit bijection $f$ between the size-$k$ and size-$(k + 1)$ subsets of $\{1, 2, \dots, 2k+ …
- 12.4k
7
votes
When were triples called monads for the first time?
P. T. Johnstone (who wrote several books on Topos Theory) gave a Category Theory lecture in which he said this was originally called 'the standard construction', then 'triples', and finally 'monads' - …
- 12.4k
1
vote
1
answer
251
views
Natural bijection between sets with coloured elements?
In Andreas Blass's famous paper `Seven Trees in One', the existence of a natural bijection between binary trees and 7-tuples of binary trees is related to the equation $T^7 = T$ being satisfied by a c …
- 12.4k