 Kronecker sum of discrete Laplacians

The Kronecker sum is a mathematical operation often used in the context of linear algebra, particularly in the study of differential equations on grids and networks. When we talk about the Kronecker sum of discrete Laplacians, we usually refer to the combination of discrete Laplacian matrices corresponding to multiple dimensions or subspaces. To better understand this, let's first define what a discrete Laplacian is.