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Feb 6, 2019 at 12:25 comment added Denis Nardin @NajibIdrissi I probably interpreted "homotopy coherent action" in a different way than you: I interpreted it as a map of $E_1$-spaces $G→\mathrm{Map}(Y,Y)$ where $\mathrm{Map}$ is the derived mapping space of $Y$. Then since $\mathrm{Map}(Y,Y)\cong \mathrm{Map}(X,X)$ as $E_1$-spaces we are done.
Feb 6, 2019 at 12:21 comment added Najib Idrissi @Lukas Yes, if an algebra $A$ is Koszul then the operad $(0,A,0,0,\dots)$ is Koszul if I'm not mistaken. The HTT is probably overkill here, but I think that if you write down the details of the strategy from your question, you essentially end up reproving HTT for $A$-modules, no?
Feb 6, 2019 at 12:20 comment added Najib Idrissi @Denis Okay, but given chain complexes $X \simeq Y$ and a $G$-action on $X$, how do you find a $G$-action on $Y$?
Feb 6, 2019 at 12:15 comment added Phil Tosteson @Denis Also over the integers.
Feb 6, 2019 at 11:41 comment added Lukas Woike Thank you, Naijib. Just to be sure that I am following your argument correctly: You mention that the group algebra is Koszul because that implies that the corresponding operad (being non-trivial only in arity 1) is Koszul such that you can apply that HT theorem? Another small question: I was also briefly thinking about applying HTT here, but it seemed a bit of an overkill. In the question I sketched I very naive way of transferring which should work in this special case. Do you think that would also work?
Feb 6, 2019 at 11:31 vote accept Lukas Woike
Feb 6, 2019 at 11:10 comment added rori @DenisNardin it appears that the question itself speaks of "vector spaces" so presumably it is not answerer's fault that they assume that everything is over a field
Feb 6, 2019 at 11:06 comment added Denis Nardin Over a field the chain complex is quasi-isomorphic to its cohomology...
Feb 6, 2019 at 10:47 history answered Najib Idrissi CC BY-SA 4.0