4,862 research outputs found
Higher-dimensional models of networks
Networks are often studied as graphs, where the vertices stand for entities
in the world and the edges stand for connections between them. While relatively
easy to study, graphs are often inadequate for modeling real-world situations,
especially those that include contexts of more than two entities. For these
situations, one typically uses hypergraphs or simplicial complexes.
In this paper, we provide a precise framework in which graphs, hypergraphs,
simplicial complexes, and many other categories, all of which model higher
graphs, can be studied side-by-side. We show how to transform a hypergraph into
its nearest simplicial analogue, for example. Our framework includes many new
categories as well, such as one that models broadcasting networks. We give
several examples and applications of these ideas
Quasirandomness in hypergraphs
An -vertex graph of edge density is considered to be quasirandom
if it shares several important properties with the random graph . A
well-known theorem of Chung, Graham and Wilson states that many such `typical'
properties are asymptotically equivalent and, thus, a graph possessing one
such property automatically satisfies the others.
In recent years, work in this area has focused on uncovering more quasirandom
graph properties and on extending the known results to other discrete
structures. In the context of hypergraphs, however, one may consider several
different notions of quasirandomness. A complete description of these notions
has been provided recently by Towsner, who proved several central equivalences
using an analytic framework. We give short and purely combinatorial proofs of
the main equivalences in Towsner's result.Comment: 19 page
Finding the K shortest hyperpaths using reoptimization
The shortest hyperpath problem is an extension of the classical shortest path problem and has applications in many different areas. Recently, algorithms for finding the K shortest hyperpaths in a directed hypergraph have been developed by Andersen, Nielsen and Pretolani. In this paper we improve the worst-case computational complexity of an algorithm for finding the K shortest hyperpaths in an acyclic hypergraph. This result is obtained by applying new reoptimization techniques for shortest hyperpaths. The algorithm turns out to be quite effective in practice and has already been successfully applied in the context of stochastic time-dependent networks, for finding the K best strategies and for solving bicriterion problems.Network programming; Directed hypergraphs; K shortest hyperpaths; K shortest paths
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