The direct sum representation of 2 representation D1 and D2 of a group G: D=D1 "+" D2
D(g) =
| D1 0 |
| 0 D2 |

D(g1)D(g2)= D(g1g2)

source
jl@crush.caltech.edu index
regular_representation
Clebsh-Gordan
reducible