Suppose that (ρ1,V1) and (ρ2,V2) are complex representations of the finite groups G1 and G2 respectively. Use ρ1 and ρ2 to construct a representation ρ1⊗ρ2 of G1×G2 on V1⊗V2 and show that its character satisfies
χρ1⊗ρ2(g1,g2)=χρ1(g1)χρ2(g2)
for each g1∈G1,g2∈G2.
Prove that if ρ1 and ρ2 are irreducible then ρ1⊗ρ2 is irreducible as a representation of G1×G2. Moreover, show that every irreducible complex representation of G1×G2 arises in this way.
Is it true that every complex representation of G1×G2 is of the form ρ1⊗ρ2 with ρi a complex representation of Gi for i=1,2? Justify your answer.