Next questions about proof details.
Red shape 1: From where we have this?
Red shape 2: How we used fact that this algebra is semi-simple?
PS. Here is link to the original paper http://matwbn.icm.edu.pl/ksiazki/sm/sm29/sm29126.pdf
Next questions about proof details.
Red shape 1: From where we have this?
Red shape 2: How we used fact that this algebra is semi-simple?
PS. Here is link to the original paper http://matwbn.icm.edu.pl/ksiazki/sm/sm29/sm29126.pdf
1. The fact that is just condition (2) from earlier in the paper (which holds because f is multiplicative).
2. Equation (10) says that for each multiplicative linear functional f on the algebra. The semisimplicity condition says that there are enough such functions to separate elements of the algebra. So if T(xy) and T(x)T(y) have the same value at each f then they must be equal.