1,148 research outputs found
Realizing degree sequences with graphs having nowhere-zero 3-flows
The following open problem was proposed by Archdeacon: Characterize all graphical sequences π such that some realization of π admits a nowhere-zero 3-flow. The purpose of this paper is to resolve this problem and present a complete characterization: A graphical sequence π = (d I,d2,...,dn) with minimum degree at least two has a realization that admits a nowhere-zero 3-flow if and only if π ≠ (34,2), (k,3k), (k2,3k-1), where k is an odd integer. © 2008 Society for Industrial and Applied Mathematics.published_or_final_versio
Totally balanced combinatorial optimization games
Combinatorial optimization games deal with cooperative games for which the value of every subset of players is obtained by solving a combinatorial optimization problem on the resources collectively owned by this subset. A solution of the game is in the core if no subset of players is able to gain advantage by breaking away from this collective decision of all players. The game is totally balanced if and only if the core is non-empty for every induced subgame of it. We study the total balancedness of several combinatorial optimization games in this paper. For a class of the partition game [5], we have a complete characterization for the total balancedness. For the packing and covering games [3], we completely clarify the relationship between the related primal/dual linear programs for the corresponding games to be totally balanced. Our work opens up the question of fully characterizing the combinatorial structures of totally balanced packing and covering games, for which we present some interesting examples: the totally balanced matching, vertex cover, and minimum coloring games.link_to_subscribed_fulltex
Realizing Degree Sequences with Graphs Having Nowhere-Zero 3-Flows
The following open problem was proposed by Archdeacon: Characterize all graphical sequences π such that some realization of π admits a nowhere-zero 3-flow. The purpose of this paper is to resolve this problem and present a complete characterization: A graphical sequence π = (d1, d2, ., dn) with minimum degree at least two has a realization that admits a nowhere-zero 3-flow if and only if π ≠ (34, 2), (k, 3k), (k2, 3k―1), where k is an odd integer
Coarse geometry of the fire retaining property and group splittings
Given a non-decreasing function we
define a single player game on (infinite) connected graphs that we call fire
retaining. If a graph admits a winning strategy for any initial
configuration (initial fire) then we say that has the -retaining
property; in this case if is a polynomial of degree , we say that
has the polynomial retaining property of degree .
We prove that having the polynomial retaining property of degree is a
quasi-isometry invariant in the class of uniformly locally finite connected
graphs. Henceforth, the retaining property defines a quasi-isometric invariant
of finitely generated groups. We prove that if a finitely generated group
splits over a quasi-isometrically embedded subgroup of polynomial growth of
degree , then has polynomial retaining property of degree . Some
connections to other work on quasi-isometry invariants of finitely generated
groups are discussed and some questions are raised.Comment: 16 pages, 1 figur
An extremal problem on group connectivity of graphs
Let A be an Abelian group, n \u3e 3 be an integer, and ex(n, A) be the maximum integer such that every n-vertex simple graph with at most ex(n, A) edges is not A-connected. In this paper, we study ex(n, A) for IAI \u3e 3 and present lower and upper bounds for 3 \u3c IAI 5. 0 2012 Elsevier Ltd. All rights reserved
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