On the Noether Problem for torsion subgroups of tori

Abstract

We consider the Noether Problem for stable and retract rationality for the sequence of $d$-torsion subgroups $T[d]$ of a torus $T$, $d\ge 1$. We show that the answer to these questions only depends on $d(\mathrm{mod}e(T))$, where $e(T)$ is the period of the generic $T$-torsor. When $T$ is the norm one torus associated to a finite Galois extension, we find all $d$ such that the Noether Problem for retract rationality has a positive solution for $d$. We also give an application to the Grothendieck ring of stacks.

References in corpus (2)

• Motivic classes of some classifying stacks
• Retract rationality and algebraic tori

Cited by in corpus (1)

• On retract rationality for finite connected group schemes