Abstract :
LetRbe an arbitrary commutative ring with identity. Denote bytthe Lie algebra overRconsisting of all upper triangularnbynmatrices overRand letbbe the Lie subalgebra oftconsisting of all matrices of trace 0. The aim of this paper is to give an explicit description of the automorphism group of the Lie algebrat, which extends a result given by Dokoviimage. In addition, we explicitly describe the automorphism group of the Lie algebrabwhennis a unit ofR.
