Notes for AKT-090929/0:10:43

Definition. Primitive: [math]\displaystyle{ \mathcal{P}(\mathcal{A})=\{a \in \mathcal{A}: \square a= a \otimes 1 + 1 \otimes a\} }[/math], where [math]\displaystyle{ \square }[/math] denotes the coproduct.