# Supra-Laplacian matrix#Find similar titles

Laplacian matrix

From the diffusion equation

$$\frac{dx_i^K}{dt} = D_K \sum_{j=1}^{N} w_{ij}^K (x_j^K - x_i^K) + \sum_{L=1}^{M} D_{KL}(x_i^L - x_i^K),$$

$$\mathcal{L} = \left( \begin{array}{c|c} D_1 L_1 + D_x I & -D_x I \\\hline -D_x I & D_2 L_2 + D_x I \end{array} \right)$$

where $$L_i$$ is the Laplacian of layer $$i$$, $$D_i$$ is the diffusion coefficient of the layer.