So I'm reading a paper about deriving polynomial invariants for links in an arbitrary surface, and I'm stuck on some under explained notation.
The full quote states that something is a 'right module over the Noetherian Ring
$\mathbb{Z}[H_1\Gamma \times \mathbb{Z}^d] \simeq (\mathbb{Z}[\mathbb{Z}^{2g}])[t_1^{\pm1}, \ldots, t_d^{\pm1}]$
Where in this case $H_1\Gamma$ is (if I've read this correctly) the quotient group of deck transformations of the covering space by the commutator group, the $t_i$s are meridians of link components and $g$ is the genus of the surface.
I'm not fully sure, however, about $(\mathbb{Z}[\mathbb{Z}^{2g}])$ and it's not explained in the paper. Any takers?