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Jun 14, 2023 at 11:03 vote accept ChesterX
Jun 14, 2023 at 9:51 comment added Connor Malin @ChesterX Yes, that's correct provided $Z$ is connected.
Jun 14, 2023 at 4:03 comment added ChesterX I am still a bit confused about the $A_\infty$-multiplication part! If I understand your argument correctly, then you are saying that if $\mu_Z : \Omega Z \times \Omega Z \to \Omega Z$ is an $A_\infty$ map, then $Z$ is a loop space. In particular, $\Omega Z$ is actually an $E_2$-space. Am I correct?
Jun 13, 2023 at 18:36 comment added Connor Malin @ChesterX And the easiest reason to see why the bar construction produces an $A_\infty$ map is to just use the rectification theorem for $A_\infty$ monoids which means we can assume every multiplication is strictly associative. Then just apply bar constructions to the associativity of the multiplication $\Omega Z$.
Jun 13, 2023 at 18:15 history edited Connor Malin CC BY-SA 4.0
added 123 characters in body
Jun 13, 2023 at 17:11 comment added Connor Malin @ChesterX You are right, but you have actually added the information needed to correct the argument. Suppose $G$ is a homotopy commutative $A_\infty$ space which is not a double loop space (for example, the loop space of an $H$-space which is not $A_\infty$ should do). Then your observation shows the argument above can be applied to $BG$. I will edit the answer to correct the argument.
Jun 13, 2023 at 11:15 comment added ChesterX Why is the bar construction producing an $A_\infty$-map? Also, note that I'm assuming that $\theta$ is an $A_2$ map. If I understand it correctly, the multiplication map on $\Omega Z$ is $A_2$ if and only if $\Omega Z$ is homotopy commutative.
Jun 13, 2023 at 10:13 history answered Connor Malin CC BY-SA 4.0