SCALING LIMITS OF RANDOM GRAPH MODELS AT CRITICALITY: UNIVERSALITY AND THE BASIN OF ATTRACTION OF THE ERDŐS-RÉNYI RANDOM GRAPH

ABSTRACT. Over the last few years a wide array of random graph models have been pos-tulated to understand properties of empirically observed networks. Most of these models come with a parameter t (usually related to edge density) and a (model dependent) critical time tc which specifies when a giant component emerges. There is evidence to support that for a wide class of models, under moment conditions, the nature of this emergence is universal and looks like the classical Erdős-Rényi random graph, in the sense of the critical scaling window and (a) the sizes of the components in this window (all maximal component sizes scaling like n2/3) and (b) the structure of components (rescaled by n−1/3) converge to random fractals related to the continuum random tree. Till date, (a) has been proven for a number of models using different techniques while (b) has been proven for only two models, the classical Erdős-Rényi random graph and the rank-1 inhomogeneous random graph. The aim of this paper is to develop a general program for proving such results. The program requires three main ingredients: (i) in the critical scaling window, components merge approximately like the multiplicative coalescent (ii) scaling exponents of susceptibility functions are the same as the Erdős-Rényi random graph and (iii) macro-scopic averaging of expected distances between random points in the same component in the barely subcritical regime. We show that these apply to a number of fundamental ran-dom graph models including the configuration model, inhomogeneous random graphs modulated via a finite kernel and bounded size rules. Thus these models all belong to the domain of attraction of the classical Erdős-Rényi random graph. As a by product we also get results for component sizes at criticality for a general class of inhomogeneous random graphs. 1