Timeline for Does $\bf pSet$ admit products?
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
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| Feb 8, 2012 at 10:27 | comment | added | fosco | @Martin: no, the idea is much more simpler: in $\bf Set$ you take as $\hom(X,Y)$ the set of functions everywhere defined on $X$. In $\bf pSet$ you relax this taking any function defined on any $D\subset X$... | |
| Feb 8, 2012 at 10:14 | comment | added | Martin Brandenburg | I don't understand the definition of the morphisms in pSet. Does $D$ belong to the data? | |
| Feb 8, 2012 at 9:51 | vote | accept | fosco | ||
| Feb 8, 2012 at 9:49 | comment | added | fosco | @you: let me please understand if I'm wrong in saying that "naif" products doesn't work... | |
| Feb 7, 2012 at 23:18 | comment | added | fosco | The answer is that the only admissible function $\varnothing\to A\times B$ is the empty one. But now the diagram doesn't commute. | |
| Feb 7, 2012 at 23:17 | comment | added | fosco | Given partial functions $f\colon X\to A, g\colon X\to B$ I should be able to define a unique $u\colon X\to A\times B$ such that the right diagram commute. But what if $dom(f)\cap dom(g)=\varnothing$? | |
| Feb 7, 2012 at 23:17 | answer | added | Owen Biesel | timeline score: 5 | |
| Feb 7, 2012 at 23:11 | comment | added | William | I don't understand the confusion. Can you not define the product of objects $A$ and $B$ (sets) as the normal Cartesian product $A\times B$ with the normal projection maps (functions are clearly partial functions), and the product for partial functions $f,g$ (defined on $U\subset A$ and $V\subset B$ respectively) to be the partial function $f\times g$ defined on $U\times V\subset A\times B$? Also, maybe curly brackets do not appear because your/the author's notation isn't very good? | |
| Feb 7, 2012 at 23:09 | history | edited | fosco | CC BY-SA 3.0 |
added 22 characters in body
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| Feb 7, 2012 at 23:03 | history | asked | fosco | CC BY-SA 3.0 |