Noether's problem for central extensions of metacyclic $p$-groups

TL;DR

This paper extends the positive resolution of Noether's problem to all central extensions of metacyclic p-groups over infinite fields with enough roots of unity, broadening the class of groups for which rationality is confirmed.

Contribution

It provides a new proof that Noether's problem has a positive answer for central extensions of metacyclic p-groups over suitable fields, generalizing previous results.

Findings

Confirmed rationality of fixed fields for central extensions of metacyclic p-groups.

Extended previous results to a broader class of group extensions.

Applicable over infinite fields containing sufficient roots of unity.

Abstract

Let $K$ be a field and $G$ be a finite group. Let $G$ act on the rational function field $K(x(g):g\in G)$ by $K$ automorphisms defined by $g\cdot x(h)=x(gh)$ for any $g,h\in G$. Denote by $K(G)$ the fixed field $K(x(g):g\in G)^G$. Noether's problem then asks whether $K(G)$ is rational over $K$. In [M. Kang, Noether's problem for metacyclic $p$-groups, Adv. Math. 203(2005), 554-567], Kang proves the rationality of $K(G)$ over $K$ if $G$ is any metacyclic $p$-group and $K$ is any field containing enough roots of unity. In this paper, we give a positive answer to the Noether's problem for all central group extensions of the general metacyclic $p$-group, provided that $K$ is infinite and it contains sufficient roots of unity.