# The first cohomology of group

I would like to ask if G is a group of order $p^4 (p\neq 2)$ as form $C_{p^3}\rtimes C_p$ (a semidirect product of cyclic group of order $p^3$ by a group of order $p$). Then can we obtain the first co-homology $H^1(C_p,C_{p^3} )$? Is there any upper bound on the order of $H^1(C_p, C_{p^3})$?

yours,

-
(If you want cohomology, you should put the index as an upper index lest the wrath of the Gods Of Notation fall upon thee) –  Mariano Suárez-Alvarez Sep 4 '12 at 20:25
Do you want the action on $C_p$ to be trivial? Do you want the cohomology of what group? You mention $G$ in the first sentence byt in the end you ask about the cohomology of $C_{p^3}$... –  Mariano Suárez-Alvarez Sep 4 '12 at 21:17
Are you sure you don't mean $H^1(C_p,C_{p^3})$, which would correspond to the conjugacy classes of complements in the semidirect product? If so, then the answer depends on the action of $C_p$ on $C_{p^3}$. –  Derek Holt Sep 4 '12 at 22:23
Your edit did not clarify what role the group G plays in your question. –  Mariano Suárez-Alvarez Sep 5 '12 at 6:28
You have still not explained what is the connection between the group $G$ and your question about a cohomology group. –  Derek Holt Sep 5 '12 at 11:14