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For questions related to the mathematical notion of site, which among others generalizes the notion of topological space. For questions on internet-sites, use online-resources, but note that these questions need to be very specific to research-level mathematics to be on-topic.

2 votes
1 answer
190 views

Necessary and sufficient conditions for all sheaves on a site to be continuous functors?

All representable functors are continuous. This makes it possible to associate additional natural operations with them, which are absent for arbitrary presheaves. What are the sufficient and what ar …
Arshak Aivazian's user avatar
19 votes
2 answers
387 views

Why is $1$ not a dense sub-site in a group with the trivial Grothendieck topology?

A friend of mine had the following question while reading the section "C2.2 The topos of sheaves" in "Sketches of an Elephant". Let $G$ be a group (considered as a category with one object) with trivi …
Arshak Aivazian's user avatar
8 votes
1 answer
450 views

Tensor product of sites

Let $C, D$ two Grothendieck sites. … Jonstone (in the $C$ part) defines a semidirect product of sites, but it talks about sites internal to the toposes. I'm not sure if this is related to my question yet. …
Arshak Aivazian's user avatar