Where d e r ( \\ displaystyle ( \\ mathfrak ( der ) ) ) denotes the Lie algebra of derivations of an algebra .
The subscript 0 denotes the trace - free part .
where d e r ( \\ displaystyle ( \\ mathfrak ( der ) ) ) denotes the Lie algebra of derivations of an algebra , and the subscript 0 denotes the trace - free part .