In order to help me understand my infinites, I started reading up on Ordinal Numbers on MathWorld. I’ve run into three snags so far. If you know the answers to these, feel free to be terse; I don’t need an in-depth explanation.
My snag has to do with A and B being disjoint. If 2 = {0, 1} and 3 = {0, 1, 2} then 2 and 3 clearly aren’t disjoint. Is 2 + 3 undefined?
[Quote]
Let (A, <=) and (B, <=) be totally ordered sets. Let C = A × B be the Cartesian Product and define order as follows. For any a[sub]1[/sub], a[sub]2[/sub] in A and b[sub]1[/sub], b[sub]2[/sub] in B,[ol][li]If a[sub]1[/sub] < a[sub]2[/sub], then (a[sub]1[/sub], b[sub]1[/sub]) < (a[sub]2[/sub], b[sub]2[/sub]),If a[sub]1[/sub] = a[sub]2[/sub], then (a[sub]1[/sub], b[sub]1[/sub]) and (a[sub]2[/sub], b[sub]2[/sub]) compare the same way as b[sub]1[/sub], b[sub]2[/sub] (i.e., lexicographical order)[/ol][/li][/Quote]
This seems straightforward enough, but I get the opposite result as I expect from transfinite multiplication. That is:
omega × 2 = {(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1), (3, 0), (3, 1), ··· } = omega
2 × omega = {(0, 0), (0, 1), (0, 2), (0, 3), ···, (1, 0), (1, 1), (1, 2), ···} = omega + omega
What’s going on here?
- Ordinal Exponentiation. This is the one that’s really bugging me.
I don’t even understand what this is saying. Is * supposed to denote ordinal multiplication? What does gamma have to do with anything?