Alejandro Adem, Jianquan Ge, Jianzhong Pan and Nansen Petrosyan

Compatible actions and cohomology of crystallographic groups

Abstract. We compute the cohomology of crystallographic groups
$\Gamma = \Z^n \rtimes \Z/p$ with holonomy of prime order by 
establishing the collapse at $E_2$ of the spectral sequence
associated to their defining extension. As an application we
compute the group of gerbes associated to many six-dimensional
toroidal orbifolds arising in string theory.