Graph theory MOC

Adjacency matrix

Let Γ be a general graph (which may be the underlying graph of a quiver). Given two vertices 𝑣,𝑤 V(Γ), the adjacency number |Γ(𝑣,𝑤)| is the number of arcs 𝑣 𝑤.1 If the vertices are enumerated 𝑣1,,𝑣𝑟, then these may be collected in an adjacency matrix 𝐴Γ =(𝑎𝑖𝑗) where graph

𝑎𝑖𝑗=|Γ(𝑣𝑖,𝑣𝑗)|


develop | en | SemBr

Footnotes

  1. Thinking of A(Γ) as a multiset with characteristic function 𝜒A(Γ), this is just 𝜒A(Γ)(𝑣,𝑤). The notation is preferred since it gives a uniform treatment to quivers and their underlying graphs.