Cutting edges at random in large recursive trees

We comment on old and new results related to the destruction of a random recursive tree (RRT), in which its edges are cut one after the other in a uniform random order. In particular, we study the number of steps needed to isolate or disconnect certain distinguished vertices when the size of the tree tends to infinity. New probabilistic explanations are given in terms of the so-called cut-tree and the tree of component sizes, which both encode different aspects of the destruction process. Finally, we establish the connection to Bernoulli bond percolation on large RRT's and present recent results on the cluster sizes in the supercritical regime.Comment: 29 pages, 3 figure

On large deviation properties of Erdos-Renyi random graphs

We show that large deviation properties of Erd\"os-R\'enyi random graphs can be derived from the free energy of the $q$-state Potts model of statistical mechanics. More precisely the Legendre transform of the Potts free energy with respect to $\ln q$ is related to the component generating function of the graph ensemble. This generalizes the well-known mapping between typical properties of random graphs and the $q\to 1$ limit of the Potts free energy. For exponentially rare graphs we explicitly calculate the number of components, the size of the giant component, the degree distributions inside and outside the giant component, and the distribution of small component sizes. We also perform numerical simulations which are in very good agreement with our analytical work. Finally we demonstrate how the same results can be derived by studying the evolution of random graphs under the insertion of new vertices and edges, without recourse to the thermodynamics of the Potts model.Comment: 38 pages, 9 figures, Latex2e, corrected and extended version including numerical simulation result

The forwarding diameter of graphs

AbstractA routing R in a graph G is a set of paths {Rxy : x, y ϵ V(G)} where, for each ordered pair of vertices (x, y), Rxy links x to y. The load ξ(G, R, x) of a vertex x in the routing R is the number of paths of R for which x is an interior vertex. We define the forwarding diameter μ(G, R) of the pair (G, R) by μ(G, R)=maxx,y∑zϵRxy−{x,y}ξ(G,R,Z) and the forwarding diameter μ(G) of G as the minimum of μ(G, R) taken over all possible routings. In this paper, the introduction of the parameter μ(G) is motivated by a natural model of message transmission in networks and we present several properties of μ(G). In particular, we study the value of μ for several families of graphs such as the hypercube and the de Bruijn graphs and we also study the connection of μ(G) with previously introduced transmission parameters

The Giant Component Is Normal

We prove a central limit theorem for the fluctuations of the size of the Giant Component in a random graph with small edge probability