gl(2,R) — real general linear Lie algebra

The real general linear Lie algebra $\mathfrak{gl}(2,\mathbb R)$ is the real vector space of all $2\times2$ matrices over $\mathbb R$ , with commutator bracket.

\mathfrak{gl}(2,\mathbb R)=M_{2}(\mathbb R),\qquad [X,Y]=XY-YX.

Dimension and structure

The matrix units $E_{ij}$ form a basis, so its real dimension is $4$ . The commutator of an associative matrix algebra satisfies the Jacobi identity by expansion.

Its center is the scalar matrices; the trace-zero subspace is an ideal because $\operatorname{tr}[X,Y]=0$ .

The family definition explains its general construction.

Scalar convention

This record retains $\mathbb R$ as its defining field. Its complexification is a different catalogue object; a matrix presentation over complex numbers does not change this field automatically.