How to show that $\text{Spec}(\mathbb{Z}[x_1,x_2,\ldots, x_n]) \cong (\mathbb{G}_m)^n$? Here $\mathbb{G}_m$ is the multiplicative group.
Thank you very much.
Edit: $\mathbb{G}_m = k - \{0\}$ is the multiplicative group of the ground field $k$. This isomorphism is in line 10 of Section 5 on page 10 of this paper.
Edit: as pointed out by Mariano Suárez-Alvarez, we should have $\text{Spec}(\mathbb{Z}[x_1^{\pm 1},x_2^{\pm 1},\ldots, x_n^{\pm 1}]) \cong (\mathbb{G}_m)^n$.