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Apr 24 at 8:37 answer added KConrad timeline score: 9
Apr 24 at 6:41 comment added YCor This lies in $\mathbf{Z}_2[\![X]\!]$, where there is a natural compact topology.
Apr 24 at 6:40 history edited YCor
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Apr 24 at 4:25 comment added LSpice Re, yes.
Apr 24 at 4:01 comment added joaopa Thanks, product topology means convergence coefficient by coefficient, right?
Apr 24 at 3:55 comment added LSpice Well, you can put any topology you like; it's your question. One possibility would be to equip $\mathbb Q_2[[X]]$ with the product topology coming from viewing it as a product of infinitely many copies of $\mathbb Q_2$. Is that what you want?
Apr 24 at 3:54 comment added joaopa Is it possible?
Apr 24 at 3:52 comment added LSpice But then the product can't possibly converge, because even the $X$ term never stabilises. So do you want a topology on $\mathbb Q_2[[X]]$ that takes into account the topology on $\mathbb Q_2$?
Apr 24 at 3:51 comment added joaopa this one induced by the order of a formal power series: $F=\sum_{j\ge k}a_jX^j$ ($a_j\in\mathbb Q_2,\ a_k\ne0$), $\mathrm{ord}(F)=k$.
Apr 24 at 3:50 history edited LSpice CC BY-SA 4.0
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Apr 24 at 3:49 comment added LSpice What's the topology on $\mathbb Q_2[[X]]$?
Apr 24 at 3:44 history asked joaopa CC BY-SA 4.0