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Direct Product#

Definition: Direct Product

Let \((G_1, \cdot_1), \dotsc, (G_n, \cdot_n)\) be groups and let \(\mathcal{G}\) be their Cartesian product.

Their direct product is \(\mathcal{G}\) with the operation \(\cdot: \mathcal{G} \times \mathcal{G} \to \mathcal{G}\) defined in the following way:

\[ (a_1, \dotsc, a_n) \cdot (b_1, \dotsc, b_n) = (a_1 \cdot_1 b_1, \dotsc, a_n \cdot_n b_n) \]

Theorem: Direct Product is a Group

The direct product is itself a group.

Proof

TODO