Let K'/K be a field extension and L' a central (simple?) K'-Lie algebra. Can we find a K-Lie algebra, such that $L'=K'\otimes_K L$.
in other words:
Let K'/K be a field extension and L' a central (simple?) K'-Lie algebra. Can we find a K'-base B of L', which satisfies $[B,B]\subseteq <B>_K$?