17 research outputs found
Sampling Geometric Inhomogeneous Random Graphs in Linear Time
Real-world networks, like social networks or the internet infrastructure,
have structural properties such as large clustering coefficients that can best
be described in terms of an underlying geometry. This is why the focus of the
literature on theoretical models for real-world networks shifted from classic
models without geometry, such as Chung-Lu random graphs, to modern
geometry-based models, such as hyperbolic random graphs.
With this paper we contribute to the theoretical analysis of these modern,
more realistic random graph models. Instead of studying directly hyperbolic
random graphs, we use a generalization that we call geometric inhomogeneous
random graphs (GIRGs). Since we ignore constant factors in the edge
probabilities, GIRGs are technically simpler (specifically, we avoid hyperbolic
cosines), while preserving the qualitative behaviour of hyperbolic random
graphs, and we suggest to replace hyperbolic random graphs by this new model in
future theoretical studies.
We prove the following fundamental structural and algorithmic results on
GIRGs. (1) As our main contribution we provide a sampling algorithm that
generates a random graph from our model in expected linear time, improving the
best-known sampling algorithm for hyperbolic random graphs by a substantial
factor O(n^0.5). (2) We establish that GIRGs have clustering coefficients in
{\Omega}(1), (3) we prove that GIRGs have small separators, i.e., it suffices
to delete a sublinear number of edges to break the giant component into two
large pieces, and (4) we show how to compress GIRGs using an expected linear
number of bits.Comment: 25 page
On the second largest component of random hyperbolic graphs
We show that in the random hyperbolic graph model as formalized by [GPP12] in the most interesting range of 1/2 0
Strong-majority bootstrap percolation on regular graphs with low dissemination threshold
International audienceConsider the following model of strong-majority bootstrap percolation on a graph. Let r ≥ 1 be some integer, and p ∈ [0, 1]. Initially, every vertex is active with probability p, independently from all other vertices. Then, at every step of the process, each vertex v of degree deg(v) becomes active if at least (deg(v) + r)/2 of its neighbours are active. Given any arbitrarily small p > 0 and any integer r, we construct a family of d = d(p, r)-regular graphs such that with high probability all vertices become active in the end. In particular, the case r = 1 answers a question and disproves a conjecture of Rapaport, Suchan, Todinca and Verstraëte [38]
Scale-free percolation mixing time
Assign to each vertex of the one-dimensional torus i.i.d. weights with a heavy-tail of index τ −1 > 0.
Connect then each couple of vertices with probability roughly proportional to the product of their weights
and that decays polynomially with exponent α > 0 in their distance. The resulting graph is called scalefree percolation. The goal of this work is to study the mixing time of the simple random walk on this
structure. We depict a rich phase diagram in α and τ . In particular we prove that the presence of hubs
can speed up the mixing of the chain. We use different techniques for each phase, the most interesting
of which is a bootstrap procedure to reduce the model from a phase where the degrees have bounded
averages to a setting with unbounded averages