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Olli (Nov 16 2020 at 06:56):Does anyone have a recommendation for learning about comma categories? I have seen them come up in a few places as examples or generalizations of something, but I am looking for something where they are treated as the main topic
Antonin Delpeuch (Nov 16 2020 at 15:40):I think I remember reading about it in Borceux's Handbook of Categorical Algebra (not sure which volume) and it was well explained.
John Baez (Nov 16 2020 at 16:15):I remember using Borceux's book when I needed a comma category to have colimits. It seemed to have a nice amount of stuff about comma categories. It had a theorem about when comma categories have colimits, but I needed a stronger result and wanted a reference for that, which I eventually found and added to the nLab.
Olli (Nov 17 2020 at 06:11):Thanks, I found it and it looks like what I was looking for.