摘要:Two types of matrix Lie algebras are presented. We make use of the first loop algebra to obtain a new ( 1 + 1 ) $(1+1)$ -dimensional integrable discrete hierarchy, which generalizes a result given by Gordoa et al., whose reduction is a discrete modified KdV system. Then we produce another new ( 2 + 1 ) $(2+1)$ -dimensional integrable discrete hierarchy with three fields under a ( 2 + 1 ) $(2+1)$ -dimensional non-isospectral linear problem. We again generalize the ( 1 + 1 ) $(1+1)$ - and ( 2 + 1 ) $(2+1)$ -dimensional discrete hierarchies to obtain a positive and negative integrable discrete hierarchy. In addition, we obtain a discrete integrable coupling system of the ( 1 + 1 ) $(1+1)$ -dimensional discrete hierarchy presented in the paper by enlarging such the loop algebras. Next, we apply the second matrix loop algebra to introduce an isospectral problem and deduce a new integrable discrete hierarchy, whose quasi-Hamiltonian structure is derived from the trace identity proposed by Tu Guizhang, which can be reduced to some modified Toda lattice equations. A type of Darboux transformation of a reduced discrete system of the latter integrable discrete hierarchy is obtained as well. We introduce two types of operator-Lie algebras according to a given spectral problem by a matrix Lie algebra and apply the r-matrix theory to obtain a few lattice integrable systems, including two ( 2 + 1 ) $(2+1)$ -dimensional lattice systems.