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Ted123
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Homework Statement
Let [itex]\mathfrak{g}[/itex] be the vector subspace in the general linear lie algebra [itex]\mathfrak{gl}_4 \mathbb{C}[/itex] consisting of all block matrices [tex]A=\begin{bmatrix} X & Z\\ 0 & Y \end{bmatrix}[/tex] where [itex]X,Y[/itex] are any 2x2 matrices of trace 0 and [itex]Z[/itex] is any 2x2 matrix.
You are given that [itex]\mathfrak{g}[/itex] is a lie subalgebra in [itex]\mathfrak{gl}_4 \mathbb{C}[/itex].
Consider [itex]\mathfrak{g}[/itex] as a lie algebra.
Prove that the radical of [itex]\mathfrak{g}[/itex] consists of all matrices [itex]A[/itex] where [itex]X=Y=0[/itex].
You may use the fact that the lie algebra [itex]\mathfrak{sl}_2 \mathbb{C}[/itex] which consists of all 2x2 matrices of trace 0 is simple.
The Attempt at a Solution
How would I go about this?