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I mean by the nerve functor.

Given a 2-category $\mathcal{C}$, if we forget the 2-category structure (just view $\mathcal{C}$ as a category), the nerve functor will give us a simplicial set $N\mathcal{C}$. However, $\mathcal{C}$ is a 2-category, thus for any two objects $x,y\in\mathcal{C}$, $Hom_{\mathcal{C}}(x,y)$ is a category, applying the nerve functor gives us a simplicial set $N(Hom(x,y))$.

My question is, can these two simplicial set structure compatible in some way, gives us a bisimplicial set $N_{p,q}(\mathcal{C})$, say? Or is there another way to give a bisimplicial structure on a 2-category?

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Yes. This is called the double nerve of a 2-category.

See in particular the first reference cited at that link.

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Thanks a lot! But I can't open the .pdf file of the first reference. Am I the only one suffering from this problem? – Fei Nov 17 '09 at 13:40
I have added the arXiv link now: – Urs Schreiber Nov 17 '09 at 13:51
Yeah, it works, thank you very much – Fei Nov 17 '09 at 16:56

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