If $A$ is a lattice (i.e. a fin. gen. free $\mathbb{Z}$-module), and $G$ is some group which acts on $A$, will $A$ be a projective $\mathbb{Z}[G]$-module?
Thanks
If $A$ is a lattice (i.e. a fin. gen. free $\mathbb{Z}$-module), and $G$ is some group which acts on $A$, will $A$ be a projective $\mathbb{Z}[G]$-module?
Thanks
Clearly not, as the action can be trivial!