نتایج جستجو برای: transversal

تعداد نتایج: 12171  

1999
Dimitris J. Kavvadias Elias C. Stavropoulos

The Transversal Hypergraph Problem is the problem of computing, given a hypergraph, the set of its minimal transversals, i.e. the hypergraph whose hyperedges are all minimal hitting sets of the given one. This problem turns out to be central in various fields of Computer Science. We present and experimentally evaluate a heuristic algorithm for the problem, which seems able to handle large insta...

2013
ALIN ŞTEFAN B. Ichim

A polymatroid is a generalization of the classical notion of matroid. The main results of this paper are formulas for computing the type of base ring associated to a product of transversal polymatroids. We also present some extensive computational experiments which were needed in order to deduce the formulas. The base ring associated to a product of transversal polymatroids has multiplicity ver...

2008
Dorin Popescu

In this thesis, we focus on the study of the base rings associated to some transversal polymatroids. A transversal polymatroid is a special kind of discrete polymatroid. Discrete polymatroids were introduced by Herzog and Hibi [16] in 2002. The thesis is structured in four chapters. Chapter 1 starts with a short excursion into convex geometry. Next, we look at some properties of affine semigrou...

Journal: :Theor. Comput. Sci. 2010
Ge Xia Yong Zhang

We consider the problem of finding a k-edge transversal set that covers all (simple) cycles of length at most s in a planar graph, where s ≥ 3 is a constant. This problem, referred to as Small Cycle Transversal, is known to be NP-complete. We present a polynomial-time algorithm that computes a linear kernel of size 36sk for Small Cycle Transversal. In order to achieve this kernel, we extend the...

Journal: :CoRR 2017
Nicolas Bonichon Benjamin Lévêque

Transversal structures (also known as regular edge labelings) are combinatorial structures defined over 4-connected plane triangulations with quadrangular outer-face. They have been intensively studied and used for many applications (drawing algorithm, random generation, enumeration. . . ). In this paper we introduce and study a generalization of these objects for the toroidal case. Contrary to...

Journal: :Electr. J. Comb. 2015
Seyed Hadi Afzali Borujeni Hiu-Fai Law Malte Müller

This sequel to Afzali Borujeni et. al. (2015) considers minors and duals of infinite gammoids. We prove that the class of gammoids defined by digraphs not containing a certain type of substructure, called an outgoing comb, is minor-closed. Also, we prove that finite-rank minors of gammoids are gammoids. Furthermore, the topological gammoids of Carmesin (2014) are proved to coincide, as matroids...

Journal: :Discrete Applied Mathematics 2008
Flavia Bonomo Maria Chudnovsky Guillermo Durán

A clique-transversal of a graph G is a subset of vertices that meets all the cliques of G. A clique-independent set is a collection of pairwise vertex-disjoint cliques. The clique-transversal number and clique-independence number of G are the sizes of a minimum clique-transversal and a maximum clique-independent set of G, respectively. A graph G is clique-perfect if these two numbers are equal ...

2006
Elisabetta Barletta Sorin Dragomir Krishan L. Duggal

Using screen distributions and lightlike transversal vector bundles we develop a theory of degenerate foliations of semiRiemannian manifolds. We build lightlike foliations of a semiRiemannian manifold by suspension of a group homomorphism φ : π1(B, x0) → Isom(T ). We compute the basic cohomology groups of the flow determined by a lightlike Killing vector field on a complete semi-Riemannian mani...

2012
John Mathews

This paper presents a lattice structure for adaptive Volterra systems. The stucture is applicable to arbitrary planes of support of the Volterra kernels. A fast least squares lattice and a fast QR-lattice adaptive nonlinear filtering algorithms based on the lattice structure are also presented. These algorithms share the fast convergence property of fast least squares transversal Volterra filte...

Journal: :Comput. Geom. 2005
Otfried Cheong Xavier Goaoc Hyeon-Suk Na

We show that a set of n disjoint unit spheres in R admits at most two distinct geometric permutations if n ≥ 9, and at most three if 3 ≤ n ≤ 8. This result improves a Helly-type theorem on line transversals for disjoint unit spheres in R: if any subset of size 18 of a family of such spheres admits a line transversal, then there is a line transversal for the entire family.

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