6 research outputs found
Fractional colorings of cubic graphs with large girth
We show that every (sub)cubic n-vertex graph with sufficiently large girth
has fractional chromatic number at most 2.2978 which implies that it contains
an independent set of size at least 0.4352n. Our bound on the independence
number is valid to random cubic graphs as well as it improves existing lower
bounds on the maximum cut in cubic graphs with large girth
First order convergence of matroids
The model theory based notion of the first order convergence unifies the
notions of the left-convergence for dense structures and the Benjamini-Schramm
convergence for sparse structures. It is known that every first order
convergent sequence of graphs with bounded tree-depth can be represented by an
analytic limit object called a limit modeling. We establish the matroid
counterpart of this result: every first order convergent sequence of matroids
with bounded branch-depth representable over a fixed finite field has a limit
modeling, i.e., there exists an infinite matroid with the elements forming a
probability space that has asymptotically the same first order properties. We
show that neither of the bounded branch-depth assumption nor the
representability assumption can be removed.Comment: Accepted to the European Journal of Combinatoric
Cubic bridgeless graphs have more than a linear number of perfect matchings
International audienc
On computing the minimum 3-path vertex cover and dissociation number of graphs
The dissociation number of a graph G is the number of vertices in a maximum size induced subgraph of G with vertex degree at most 1. A k-path vertex cover of a graph G is a subset S of vertices of G such that every path of order k in G contains at least one vertex from S. The minimum 3-path vertex cover is a dual problem to the dissociation number. For this problem we present an exact algorithm with a running time of O ∗ (1.5171 n) on a graph with n vertices. We also provide a polynomial time randomized approximation algorithm with an for the minimum 3-path vertex cover. expected approximation ratio of 23/11 for th