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Simple case. Take $X_{\bullet}$ a cosimplicial space. Is it true that the chain complex of its homotopy totalization is quasi-isomorphic to the homotopy totalization of its chain complex? Because of the computations listed in "homotopy totalization" at nlab, this boils down to a quasi-isomorphism between $$ C_* Hom( \mathbb{\Delta}^{\bullet}, X_{\bullet}) \ \ \ \textrm{ and }\ \ \ \textrm{Tot}(N(C_* X_{\bullet}))$$ where $\textrm{Tot}$ is the product totalization functor and $N$ is the normalized chain complex appearing in the dold-kan correspondence. Since this seems to be explicitly expressible, do you know a reference?

Hard case. Now consider $X$ to be a homotopy coherent cosimplicial space, that is a map $N(\Delta) \to N(\textrm{Top})[W^{-1}]$, where $[W^{-1}]$ is the $\infty$-localization at the homotopy equivalences. Consider also the $\infty$-category $N(\textrm{Ch})[Q^{-1}]$, where $\textrm{Ch}$ are chain complexes in abelian groups and $Q$ are quasi-isomorphisms. We can define a chain complex functor $C_* : N(\textrm{Top})[W^{-1}] \to N(\textrm{Ch})[Q^{-1}]$ by taking the nerve and localizing the classical chain complex functor $C_* : \textrm{Top} \to \textrm{Ch}$. At this point, the homotopy totalization is just a limit along $\Delta$, so is the following equivalence in chain complexes true? $$ C_* \left (\lim^{\infty}_{\Delta} X_{\bullet} \right ) \simeq \lim^{\infty}_{\Delta} C_* X_{\bullet} $$ It is a sort of continuity for cosimplicial diagrams only. A reference would be highly appreciated.

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    $\begingroup$ If I am interpreting correctly, the answer to both questions (which are the same as Dmitri says, there's no coherence issues) is "No, in general" and is a well studied problem having to do with the convergence of the Bousfield-Kan sseq (see, e.g. homepages.math.uic.edu/~bshipley/specseq.pdf ) $\endgroup$ Jun 1 at 18:59
  • $\begingroup$ Thank you very much to both of you. Very insightful comments! I do even know the BK sseq, but I hadn't realized its convergence was essentially the failure or not of the qi above... $\endgroup$ Jun 1 at 20:16

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The first part of the question was previously asked and answered here: Reference for homotopy colimit = total complex.

The second part can be easily reduced to the first part by rectifying homotopy coherent cosimplicial spaces to ordinary cosimplicial spaces. Since the second part part seems to be talking about quasicategories, Lurie's rectification result (Proposition 4.2.4.4 in Higher Topos Theory) works fine here.

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    $\begingroup$ Thanks! The rectification result solves even other issues I had in a neighborhood of this one! $\endgroup$ Jun 1 at 20:18

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