Morava K-theory rings of the extensions of C_2 by the products of cyclic 2-groups

Abstract

In \cite{SCH1} Schuster proved that $mod$ 2 Morava $K$-theory $K(s{)}^{\ast }(BG)$ is evenly generated for all groups $G$ of order 32. There exist 51 non-isomorphic groups of order 32. In \cite{H}, these groups are numbered by $1,\cdots ,51$. For the groups $G_{38},\cdots ,G_{41}$, that fit in the title, the explicit ring structure is determined in \cite{BJ}. In particular, $K(s{)}^{\ast }(BG)$ is the quotient of a polynomial ring in 6 variables over $K(s{)}^{\ast }(pt)$ by an ideal generated by explicit polynomials. In this article we present some calculations using the same arguments in combination with a theorem of \cite{B0} on good groups in the sense of Hopkins-Kuhn-Ravenel. In particular, we consider the groups $G_{36},G_{37}$, each isomorphic to a semidirect product $(C_4\times C_2\times C_2)⋊C_2$, the group $G_{34}\cong (C_4\times C_4)⋊C_2$ and its non-split version $G_{35}$. For these groups the action of $C_2$ is diagonal, i.e., simpler than for the groups $G_{38},\cdots ,G_{41}$, however the rings $K(s{)}^{\ast }(BG)$ have the same complexity.

arXiv comment16 pages. Accepted in Moscow Math. Journal. arXiv admin note: text overlap with arXiv:1102.3378, arXiv:1412.2274