Simple Graph

up:: 040 MOC Complex Systems

A simple graph is a double $(V,E)$, where $V$ is a set of nodes, and $E$ is the set of edges between nodes in $V$.

More generally, one can think of $E$ as a subset of $\mathcal{P}(V)\times \mathcal{P}(V)$, that is, edges have sources and targets that are subsets of $V$.

For the case of simple graphs, all edges are composed of doubles of singleton sets of nodes, i.e. one-to-one relations between nodes. Thus, one can unambiguously define their Adjacency Matrix.

Other types of graphs

Other types of graphs can have different compositions of elements of $E$, for instance Hypergraphs, which can encode more complex relationships between nodes, such as one-to-many (e.g. lectures), many-to-one (e.g. protests) and many-to-many (e.g. complex chemical reactions, I guess?) relationships.

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References

• Casas, Alberto Aleta. “Networks, epidemics and collective behavior: from physics to data science”. PhD Thesis, Universidad de Zaragoza, 2019. https://dialnet.unirioja.es/servlet/tesis?codigo=300533.