This is an archived version pinned as of the submission of my master's thesis. An up-to-date version may be found online.

Circuits in undirected graphs

module graph-theory.circuits-undirected-graphs where
Imports 
open import elementary-number-theory.natural-numbers

open import foundation.dependent-pair-types
open import foundation.universe-levels

open import graph-theory.polygons
open import graph-theory.totally-faithful-morphisms-undirected-graphs
open import graph-theory.undirected-graphs

Idea

A circuit in an undirected graph G consists of a k-gon H equipped with a totally faithful morphism of undirected graphs from H to G. In other words, a circuit is a closed walk with no repeated edges.

Definition

module _
  {l1 l2 : Level} (k : ℕ) (G : Undirected-Graph l1 l2)
  where

  circuit-Undirected-Graph : UU (lsuc lzero ⊔ l1 ⊔ l2)
  circuit-Undirected-Graph =
    Σ ( Polygon k)
      ( λ H →
        totally-faithful-hom-Undirected-Graph (undirected-graph-Polygon k H) G)