We present a short proof of the following theorems simultaneously: Kuratowski’s theorem, Fary’s theorem, and the theorem of Tutte that every 3-connected planar graph has a convex representation. We stress the importance of Kuratowski’s theorem by showing how it implies a result of Tutte on planar representations with prescribed vertices on the same facial cycle as well as the planarity criteria...

A graph G is inexhaustible if whenever a vertex of G is deleted the remaining graph is isomorphic to G. We address a question of Cameron [6], who asked which countable graphs are inexhaustible. In particular, we prove that there are continuum many countable inexhaustible graphs with properties in common with the infinite random graph, including adjacency properties and universality. Locally fin...

Solving a problem of Diestel [8] we show that the Freudenthal compactification of a locally finite graph can have connected subsets that are not path-connected. However we prove that connectedness and pathconnectedness do coincide for all but a few sets, which have a complicated structure.

We consider recurrence versus transience for models of random walks on growing in time, connected subsets Gt of some fixed locally finite, connected graph, in which monotone interaction enforces such growth as a result of visits by the walk (or probes it sent), to the neighborhood of the boundary of Gt.

A circle in a graph G is a homeomorphic image of the unit circle in the Freudenthal compactification of G, a topological space formed from G and the ends of G. Bruhn conjectured that every locally finite 4-connected planar graph G admits a Hamilton circle, a circle containing all points in the Freudenthal compactification of G that are vertices and ends of G. We prove this conjecture for graphs...

We consider branching random walks and contact processes on infinite, connected, locally finite graphs whose reproduction and infectivity rates across edges are inversely proportional to vertex degree. We show that when the ambient graph is a Galton-Watson tree then, in certain circumstances, the branching random walks and contact processes will have weak survival phases. We also provide bounds...

A Lefschetz formula is given that relates loops in a regular finite graph to traces of a certain representation. As an application the poles of the Ihara/Bass zeta function are expressed as dimensions of global section spaces of locally constant sheaves.

in this paper a guided tabu search (gts) is utilized for optimal nodal ordering of finite element models (fems) leading to small profile for the stiffness matrices of the models. the search strategy is accelerated and a graph-theoretical approach is used as guidance. the method is evaluated by minimization of graph matrices pattern equivalent to stiffness matrices of finite element models. comp...

By an edge-neighborhood of an edge f in a graph we mean the subgraph induced by nodes outside f which are adjacent to some node on f. Connected graphs whose line graphs have the same edge-neighborhood of any edge are characterized. There are P 4 , stars, complete graphs and regular triangle-free graphs in which any two nodes with the distance two have the same number of common neighbors. Object...

We expand on Tutte’s theory of 3-blocks for 2-connected graphs, generalizing it to apply to infinite, locally finite graphs, and giving necessary and sufficient conditions for a labeled tree to be the 3-block tree of a 2-connected graph. Mathematics Subject Classification: 05C40, 05C38, and 05C05.