We investigate the relations between the Poissonnian loop ensembles, their occupation fields, non ramified Galois coverings of a graph, the associated gauge fields, and random Eulerian networks.

We present a characterization of Eulerian graphs that have a k-arc-connected orientation so that the deletion of any vertex results in a (k− 1)-arc-connected directed graph. This provides an affirmative answer for a conjecture of Frank [2]. The special case, when k = 2, describes Eulerian graphs admitting 2-vertexconnected orientations. This case was proved earlier by Berg and Jordán [1]. These...

We show that every 6-edge connected graph admits a circulation whose range lies in the interval 1; 3). The circular ow number c (G) of a ((nite) graph G is deened by c (G) = inffr 2 R: some orientation ~ G admits a circulation f : E(~ G) ! 1; r ? 1]g: This parameter is a reenement of the well studied ow number (G) := d c (G)e, which was introduced by Tutte as a dual to the chromatic number. Sin...

In rotor walk on a graph, the exits from each vertex follow a prescribed periodic sequence. We show that any rotor walk on the d-dimensional lattice Z visits at least on the order of t distinct sites in t steps. This result extends to Eulerian graphs with a volume growth condition. In a uniform rotor walk the first exit from each vertex is to a neighbor chosen uniformly at random. We prove a sh...

We study the complexity of algorithms for graph traversal problems on quantum computers. More precisely, we look at eulerian tours, hamiltonian tours, travelling salesman problem and project scheduling. We present quantum algorithms and quantum lower bounds for these problems. Our results improve the best classical algorithms for the corresponding problems. In particular, we prove that the quan...

By means of Monte Carlo simulations and a finite-size scaling analysis, we find a critical line of an n-component Eulerian face-cubic model on the square lattice and the simple cubic lattice in the region v>1, where v is the bond weight. The phase transition belongs to the Ising universality class independent of n. The critical properties of the phase transition can also be captured by the perc...

Let G be an eulerian digraph with a fixed edge coloring (not necessarily a proper edge coloring). A compatible circuit of G is an eulerian circuit such that every two consecutive edges in the circuit have different colors. We characterize the existence of compatible circuits for directed graphs avoiding certain vertices of outdegree three. Our result is analogous to a result of Kotzig for compa...

For an integer l¿0, de ne SE(l) to be the family of graphs such that G ∈SE(l) if and only if for any edge subset X ⊆E(G) with |X |6l, G has a spanning eulerian subgraph H with X ⊆E(H). The graphs in SE(0) are known as supereulerian graphs. Let f(l) be the minimum value of k such that every k-edge-connected graph is in SE(l). Jaeger and Catlin independently proved f(0) = 4. We shall determine f(...

Let G(V,E) be a graph of order n and size m. A graceful labeling of G is an injection f : V (G) → {0, 1, 2, ...,m} such that, when each edge uv is assigned the label f(uv) = |f(u)− f(v)|, the resultant edge labels are distinct. We focus on general results in graceful labeling, and provide an affirmative answer to the following open problem: Can every connected graph be embedded as an induced su...

We show that the edge disjoint paths problem is NP-complete in directed or undirected rectangular grids, even if the union G + H of the supply and the demand graph is Eulerian.