The last algorithm (proposed by Zhou et al.) that we need to analyze is called label spreading, and it's based on the normalized graph Laplacian:
This matrix has each a diagonal element lii equal to 1, if the degree deg(lii) > 0 (0 otherwise) and all the other elements equal to:
The behavior of this matrix is analogous to a discrete Laplacian operator, whose real-value version is the fundamental element of all diffusion equations. To better understand this concept, let's consider the generic heat equation:
This equation describes ...
