Sweedler notation
= Sweedler notation
{c}
{title2=$\Delta h=\sum h_{(1)}\otimes h_{(2)}$}
The notation $\Delta h=\sum h_{(1)}\otimes h_{(2)}$ suppresses the summation index of a <comultiplication>; iterated indices use coassociativity. For a <comodule>, write $\rho(u)=\sum u_{(0)}\otimes u_{(1)}$.