If there exist a non-trivial algebra homomorphism from $M_n(\mathbb R)$ to $M_m(\mathbb R)$, prove $n|m$
I find that the homomorphism is injective because $M_n(\mathbb R)$ is simple,but i dont know what should i do next
If there exist a non-trivial algebra homomorphism from $M_n(\mathbb R)$ to $M_m(\mathbb R)$, prove $n|m$
I find that the homomorphism is injective because $M_n(\mathbb R)$ is simple,but i dont know what should i do next