51,430 research outputs found
Weak universality of dynamical : non-Gaussian noise
We consider a class of continuous phase coexistence models in three spatial
dimensions. The fluctuations are driven by symmetric stationary random fields
with sufficient integrability and mixing conditions, but not necessarily
Gaussian. We show that, in the weakly nonlinear regime, if the external
potential is a symmetric polynomial and a certain average of it exhibits
pitchfork bifurcation, then these models all rescale to near their
critical point.Comment: 37 pages; updated introduction and reference
Matchings on infinite graphs
Elek and Lippner (2010) showed that the convergence of a sequence of
bounded-degree graphs implies the existence of a limit for the proportion of
vertices covered by a maximum matching. We provide a characterization of the
limiting parameter via a local recursion defined directly on the limit of the
graph sequence. Interestingly, the recursion may admit multiple solutions,
implying non-trivial long-range dependencies between the covered vertices. We
overcome this lack of correlation decay by introducing a perturbative parameter
(temperature), which we let progressively go to zero. This allows us to
uniquely identify the correct solution. In the important case where the graph
limit is a unimodular Galton-Watson tree, the recursion simplifies into a
distributional equation that can be solved explicitly, leading to a new
asymptotic formula that considerably extends the well-known one by Karp and
Sipser for Erd\"os-R\'enyi random graphs.Comment: 23 page
Percolation on dense graph sequences
In this paper we determine the percolation threshold for an arbitrary
sequence of dense graphs . Let be the largest eigenvalue of
the adjacency matrix of , and let be the random subgraph of
obtained by keeping each edge independently with probability . We
show that the appearance of a giant component in has a sharp
threshold at . In fact, we prove much more: if
converges to an irreducible limit, then the density of the largest component of
tends to the survival probability of a multi-type branching process
defined in terms of this limit. Here the notions of convergence and limit are
those of Borgs, Chayes, Lov\'asz, S\'os and Vesztergombi. In addition to using
basic properties of convergence, we make heavy use of the methods of
Bollob\'as, Janson and Riordan, who used multi-type branching processes to
study the emergence of a giant component in a very broad family of sparse
inhomogeneous random graphs.Comment: Published in at http://dx.doi.org/10.1214/09-AOP478 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
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