Let C be the model category of simplicial commutative monoids (with underlying weak equivalences and fibrations), or equivalently the (&infin;,1)-category P<sub>&Sigma;</sub>(T<sup>op</sup>), where T is the Lawvere theory for commutative monoids.  In C, as in any pointed (&infin;,1)-category with finite limits and colimits, we can define adjoint functors &Sigma;<sub>C</sub> and &Omega;<sub>C</sub> as &Sigma;<sub>C</sub>X = hocolim [&bull; &larr; X &rarr; &bull;] and &Omega;<sub>C</sub>X = holim [&bull; &rarr; X &larr; &bull;].

The category CommMon of commutative monoids sits inside C as a full subcategory (as the constant objects, or the objectwise-discrete presheaves).  Consider the two functors CommMon &rarr; C given by sending M to &Omega;<sub>C</sub>&Sigma;<sub>C</sub>M and to the group completion of M, respectively.  Is there a natural equivalence between these functors?

(This question is closely related to <a href="https://mathoverflow.net/questions/430/homological-algebra-for-commutative-monoids">Chris's question here</a>.  A thorough answer to that question would probably yield this immediately.)