Tensor product with a 1-dimensional representation
Let
Proof
For any
where is a subspace, , Hence the invariant subspaces of are the same as those of , and thus if is irreducible so is .
As a result, 1-dimensional irreps form a group.
Let
Proof
For any
where is a subspace, , Hence the invariant subspaces of are the same as those of , and thus if is irreducible so is .
As a result, 1-dimensional irreps form a group.