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Added some content to display map from Taylor’s book. Not very deep, mostly as a reference to the respective section for me.
Nice! You left out an important part in one clause of the definition, which actually makes the other clause redundant (although I know that Taylor stated it). Explicitly, a pullback of a display must not only exist but also be a display.
Thanks for fixing that. I certainly meant to say that. Not sure why I didn’t.
I put in the example of a category with a singleton pretopology - which is a concept identical to a class of display maps which are closed under composition (including nullary)
Thanks, David, I don’t know why I never made that connection!
Toby - it’s quite amazing how many classes of maps are pretopologies and people don’t state the fact e.g. Remarks 4.2 and 4.3 (stable under pullbacks and closed under composition resp.) in the stacks project chapter http://www.math.columbia.edu/algebraic_geometry/stacks-git/spaces.pdf - over 20 pretopologies on $Sch$ listed.
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