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Mar 29, 2011 at 15:20 comment added Todd Trimble I'll need some time to think about your question, Dylan. In the meantime, I've added some possibly more meaningful observations to my answer.
Mar 29, 2011 at 15:19 history edited Todd Trimble CC BY-SA 2.5
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Mar 29, 2011 at 3:32 comment added Dylan Wilson Thanks! Does the notion of bordism equivalence that this gives have any use for common problems? Like, in some (specific) non-geometric category, what properties of a map are bordism invariant in this case that we care about?
Mar 27, 2011 at 6:23 comment added Todd Trimble @Qiaochu: yes. Either is a simple example, but I thought the arrow category was simpler. My guess is that it's well-known.
Mar 27, 2011 at 5:47 comment added Qiaochu Yuan Isn't that a subcategory of the cospan category anyway? (Those are just the cospans with $Y = 0$, right?)
Mar 27, 2011 at 5:38 comment added Todd Trimble Well, heck, why don't I just take the arrow category instead and define $\partial (f: X \to Y) = (0 \to X)$? That works too. I guess the reason is that I was thinking also of composition of cobordisms, and how that generalizes to taking pushouts of cospans.
Mar 27, 2011 at 3:49 history answered Todd Trimble CC BY-SA 2.5