Tangent space at the identity of a Lie group, equipped with a bracket [X,Y] = XY − YX. Generators of infinitesimal symmetry transformations; commutation relations encode the symmetry structure (e.g. [J_i,J_j] = iε_{ijk}J_k for su(2)).
Tangent space at the identity of a Lie group, equipped with a bracket [X,Y] = XY − YX. Generators of infinitesimal symmetry transformations; commutation relations encode the symmetry structure (e.g. [J_i,J_j] = iε_{ijk}J_k for su(2)).