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I have a naive question about the difference of Artin reciprocity in the number field versus function field case: In the number field case, the double quotient we look at is $$K^\times \backslash \mathbb{I}_K / \mathcal{O}$$ ($\mathcal{O}$ denoting the connected component) where as in the function field case we consider $$K^\times \backslash \mathbb{I}_K / \prod_v\mathcal{O}_v^\times.$$ My question is to the relation between the two double quotients, or equivalently to the relation between $\mathcal{O}$ and $\prod_v\mathcal{O}_v^\times$.

Is there some natural (dense) containment? Do these two double quotients "talk" to each other and does this explain why Artin reciprocity has a different form for number fields vs function fields?

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    $\begingroup$ You seem to be comparing everywhere unramified class field theory in the function field case to ramified class field theory in the number field case. Of course the groups will have different formulas. $\endgroup$
    – Will Sawin
    Commented Sep 22, 2022 at 20:00

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