Skip to main content
9 events
when toggle format what by license comment
Nov 25, 2023 at 12:53 comment added Kasper Andersen @MikhailBorovoi Yes $\text{tr}$ is short for transfer also known as restriction.
Nov 25, 2023 at 10:19 vote accept Mikhail Borovoi
Nov 25, 2023 at 10:15 comment added Mikhail Borovoi Excellent! Many thanks! You write: $$H_k(G,M)\stackrel{\text{tr}}{\rightarrow} H_k(S,M)\stackrel{i_{S,*}}{\rightarrow} H_k(G,M)$$ is multiplication by $[G:S]$. What is $\rm tr$? Is it the restriction map?
Nov 25, 2023 at 10:01 comment added Kasper Andersen @MikhailBorovoi I replaced the original incorrect argument by a much simpler one.
Nov 25, 2023 at 9:59 history edited Kasper Andersen CC BY-SA 4.0
Corrected wrong argument
Nov 24, 2023 at 19:11 comment added Mikhail Borovoi (cont.) Therefore, the natural homomorphism $H_1(P,M)\to H_1(G,M)$ cannot be surjective. What do you think about this?
Nov 24, 2023 at 19:10 comment added Mikhail Borovoi The following seems to be a counter-example to your assertion. Let $G={\Bbb Z}/3{\Bbb Z}\times {\Bbb Z}/2{\Bbb Z}$, $M={\Bbb Z}$. Then $$H_1(G,M)\cong G/[G,G]=G={\Bbb Z}/3{\Bbb Z}\times {\Bbb Z}/2{\Bbb Z},$$ whereas $$H_1(P,M)\cong{\Bbb Z}/3{\Bbb Z}/[{\Bbb Z}/3{\Bbb Z}, Z/3{\Bbb Z}]={\Bbb Z}/3{\Bbb Z}.$$
Nov 24, 2023 at 13:18 history edited Kasper Andersen CC BY-SA 4.0
added 63 characters in body
Nov 24, 2023 at 13:11 history answered Kasper Andersen CC BY-SA 4.0