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Sun, Pak Kiu. "Incidence coloring : origins, developments and relation with other colorings." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/826.
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Araujo, Julio. "Graph coloring and graph convexity." Nice, 2012. http://www.theses.fr/2012NICE4032.
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Dans cette thèse, nous étudions plusieurs problèmes de théorie des graphes concernant la coloration et la convexité des graphes. La plupart des résultats figurant ici sont liés à la complexité de calcul de ces problèmes pour certaines classes de graphes. Dans la première, et principale, partie de cette thèse, nous traitons la coloration des graphes qui est l’un des domaines les plus étudiés de théorie des graphes. Nous considérons d’abord trois problèmes de coloration appelés coloration gloutonne, coloration pondérée et coloration pondérée impropre. Ensuite, nous traitons un problème de décision, appelé bon étiquetage d’arêtes, dont la définition a été motivée par le problème d’affectation de longueurs d’onde dans les réseaux optiques. La deuxième partie de cette thèse est consacrée à un paramètre d’optimisation des graphes appelé le nombre enveloppe (géodésique). La définition de ce paramètre est motivée par une extension aux graphes des notions d’ensembles et d’enveloppes convexes dans l’espace Euclidien. Enfin, nous présentons dans l’annexe d’autres travaux développés au cours de cette thèse, l’un sur les hypergraphes orientés Eulériens et Hamiltoniens et l’autre concernant les systèmes de stockage distribuésIn this thesis, we study several problems of Graph Theory concerning Graph Coloring and Graph Convexity. Most of the results contained here are related to the computational complexity of these problems for particular graph classes. In the first and main part of this thesis, we deal with Graph Coloring which is one of the most studied areas of Graph Theory. We first consider three graph coloring problems called Greedy Coloring, Weighted Coloring and Weighted Improper Coloring. Then, we deal with a decision problem, called Good Edge-Labelling, whose definition was motivated by the Wavelength Assignment problem in optical networks. The second part of this thesis is devoted to a graph optimization parameter called (geodetic) hull number. The definition of this parameter is motivated by an extension to graphs of the notions of convex sets and convex hulls in the Euclidean space. Finally, we present in the appendix other works developed during this thesis, one about Eulerian and Hamiltonian directed hypergraphs and the other concerning distributed storage systems
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Normann, Per. "Parallel graph coloring : Parallel graph coloring on multi-core CPUs." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227656.
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In recent times an evident trend in hardware is to opt for multi-core CPUs. This has lead to a situation where an increasing number of sequential algorithms are parallelized to fit these new multi-core environments. The greedy Multi-Coloring algorithm is a strictly sequential algorithm that is used in a wide range of applications. The application in focus is on decomposition by graph coloring for preconditioning techniques suitable for iterative solvers like the and methods. In order to perform all phases of these iterative solvers in parallel the graph analysis phase needs to be parallelized. Albeit many attempts have been made to parallelize graph coloring non of these attempts have successfully put the greedy Multi-Coloring algorithm into obsolescence. In this work techniques for parallel graph coloring are proposed and studied. Quantitative results, which represent the number of colors, confirm that the best new algorithm, the Normann algorithm, is performing on the same level as the greedy Multi-Coloring algorithm. Furthermore, in multi-core environments the parallel Normann algorithm fully outperforms the classical greedy Multi-Coloring algorithm for all large test matrices. With the features of the Normann algorithm quantified and presented in this work it is now possible to perform all phases of iterative solvers like and methods in parallel.
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Labelle, François. "Graph embeddings and approximate graph coloring." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0031/MQ64386.pdf.
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Le, Ngoc Khang. "Detecting and Coloring some Graph Classes." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN021/document.
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Les graphes sont des structures mathématiques utilisées pour modéliser les relations par paires entre objets. Malgré leur structure simple, les graphes ont des applications dans divers domaines tels que l'informatique, la physique, la biologie et la sociologie. L'objectif principal de ce travail est de continuer l'étude des problèmes de coloration et de détection dans le cadre de classes de graphes fermées par sous-graphes induits (que nous appelons classes de graphes héréditaires).La première classe que nous considérons est graphes sans ISK4 - les graphes qui ne contiennent aucune subdivision de en tant que sous-graphe induit. Nous montrons que le nombre chromatique de cette classe est limité à 24, une amélioration considérable par rapport à la borne existant précédemment. Nous donnons également une bien meilleure limite dans le cas sans triangle. De plus, nous prouvons qu'il existe un algorithme de complexité pour détecter cette classe, ce qui répond à une question de Chudnovsky et al. et Lévêque et al.La deuxième classe que nous étudions est celle des graphes sans trou pair et sans étoile d’articulation. Cela est motivé par l'utilisation de la technique de décomposition pour résoudre certains problèmes d'optimisation. Nous garantissons la fonction χ-bounding optimale pour cette classe. Nous montrons que la classe a rank-width bornée, ce qui implique l'existence d'un algorithme de coloration en temps polynomial. Enfin, la coloration gloutonne connexe dans les graphes sans griffes est considérée. Une façon naturelle de colorier un graphe est d'avoir un ordre de ses sommets et d'affecter pour chaque sommet la première couleur disponible. Beaucoup de recherches ont été faites pour des ordres généraux. Cependant, nous connaissons très peu de choses sur la caractérisation des bons graphes par rapport aux ordres connexes. Un graphe est bon si pour chaque sous-graphe induit connexe de , chaque ordre connexe donne à une coloration optimale. Nous donnons la caractérisation complète de bons graphes sans griffes en termes de sous-graphes induits minimaux interditsGraphs are mathematical structures used to model pairwise relations between objects. Despite their simple structures, graphs have applications in various areas like computer science, physics, biology and sociology. The main focus of this work is to continue the study of the coloring and detecting problems in the setting of graph classes closed under taking induced subgraphs (which we call hereditary graph classes). The first class we consider is ISK4-free graphs - the graphs that do not contain any subdivision of K4 as an induced subgraph. We prove that the chromatic number of this class is bounded by 24, a huge improvement compared to the best-known bound. We also give a much better bound in the triangle-free case. Furthermore, we prove that there exists an O(n 9) algorithm for detecting this class, which answers a question by Chudnovsky et al. and Lévêque et al. The second class we study is even-hole-free graphs with no star cutset. This was motivated by the use of decomposition technique in solving some optimization problems. We prove the optimal χ -bounding function for this class and show that it has bounded rank-width, which implies the existence of a polynomial-time coloring algorithm.Finally, the connected greedy coloring in claw-free graphs is considered. A natural way to color a graph is to have an order of its vertices and assign for each vertex the first available color. A lot of researches have been done for general orders. However, we know very little about the characterization of good graphs with respect to connected orders. A graph G is good if for every connected induced subgraph H of G, every connected order gives H an optimal coloring. We give the complete characterization of good claw-free graphs in terms of minimal forbidden induced subgraphs
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Casselgren, Carl Johan. "On some graph coloring problems." Doctoral thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43389.
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Bacak, Gökşen Ufuktepe Ünal. "Vertex Coloring of A Graph/." [s.l.] : [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/matematik/T000416.pdf.
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Beşeri, Tina Ufuktepe Ünal. "Edge Coloring of A Graph/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/matematik/T000439.pdf.
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Jiang, Yiting. "Many aspects of graph coloring." Electronic Thesis or Diss., Université Paris Cité, 2022. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=5613&f=42533.
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La coloration des graphes est un sujet central en théorie des graphes, et divers concepts de coloration ont été étudiés dans la littérature. Cette thèse étudie certains de ces concepts de coloration et les problèmes associés. Il s'agit notamment de la coloration des graphes signés généralisés, du nombre de choix fractionnels forts des graphes, du nombre de coloration généralisé des graphes, de la largeur gémellaire des graphes, de la discordance (combinatoire) des systèmes d'ensembles définissables et des classes de graphes chi_p-bornées. Un graphe signé est une paire (G, sigma), où G est un graphe et sigma: E(G) to {+,-} est une signature. Un graphe signé généralisé est également une paire (G, sigma), où la signature sigma attribue à chaque arête e une permutation sigma(e) dans un ensemble S comme son signe. Dans une coloration d'un graphe signé ou d'un graphe signé généralisé (G, sigma), le signe sigma(e) détermine les paires de couleurs qui doivent être évitées en tant que couleurs des sommets terminaux de e. Une question naturelle motivée par le théorème des quatre couleurs est de savoir pour quels sous-ensembles S de S_4, tout graphe planaire est S-4-colorable. Cette question a maintenant une réponse complète: seul S={id} posséde cette propriété, ce qui signifie que le théorème des quatre couleurs est strict au sens de la coloration généralisée des graphes signés. Ce résulat a été établi par une séquence de six articles, par différents groupes d'auteurs. L'une des contributions de cette thése est le résultat établi dans l'un de ces articles, à savoir que que de nombreux ensembles S n'ont pas la propriété désirée. La thèse considère également des questions similaires pour les graphes planaires sans triangle, ce qui peut être considéré comme une exploration de l'étanchéité du théorème de Grötzsch. Notre résultat montre que pour tout sous-ensemble S de S_3, si S n'est pas conjugué à un sous-ensemble de {id, (12)}, alors il existe un graphe planaire sans triangle qui n'est pas S-3-colorable. Une autre tentative pour renforcer le théorème de Grötzsch est de considérer le nombre de choix fractionnaire fort des graphes planaires sans triangle. Il a été prouvé par Voigt qu'il existe des graphes planaires sans triangle qui ne sont pas 3-choissables. Cette thèse prouve que le supremum du nombre de choix fractionnel fort des graphes planaires sans triangle est au moins 3+1/17. Un sujet important de la théorie structurelle des graphes est l'étude de la complexité structurelle des graphes. Quelques concepts et invariants de graphes sont largement étudiés dans la littérature. Récemment, le concept de largeur gémellaire a été introduit. Dans cette thèse, nous prouvons qu'un graphe G sans sous graphe K_{s,s} et de largeur gémellaire d a ses nombres de coloration forts (faibles) r bornés supérieurement par une fonction exponentielle en r et que nous pouvons construire des graphes réalisant une telle dépendance en r. L'une des deux notions centrales de la théorie structurelle des classes de graphes éparses est celle de classes d'expansion bornée. La discordance combinatoire est un sujet important. Elle mesure les irrégularités inévitables des systèmes d'ensembles et la difficulté intrinsèque de leur approximation. Dans cette thèse, nous donnons une nouvelle caractérisation des classes d'expansion bornée en termes de discordance de système définissables. La notion de chi-boundedness est un sujet central en théorie des graphes chromatiques. Dans cette thèse, les classes chi-bornées sont étudiées ici dans le contexte des colorations stellaires et, plus généralement, des chi_p-colorations. Considéré dans le cadre général de l'édute des classes éparses, il conduit à des extensions naturelles de la notion de classe d'expansion bornée. Nous résolvons ici deux conjectures liées à la limitation du nombre chromatique stellaire (i.e. chi_2). Nous donnons des caractérisations structurelles des classes (fortement et faiblement) chi_p-bornéeGraph coloring is a central topic in graph theory, and various coloring concepts have been studied in the literature. This thesis studies some of the coloring concepts and related problems. These include coloring of generalized signed graphs, strong fractional choice number of graphs, generalized coloring number of graphs, twin-width of graphs, (combinatorial) discrepancy of definable set systems and chi_p-bounded classes of graphs. A signed graph is a pair (G, sigma), where G is a graph and sigma: E(G) to {+,-} is a signature. A generalized signed graph is also a pair (G, sigma), where the signature sigma assigns to each edge e a permutation sigma(e) in a set S as its sign. In a coloring of a signed graph or a generalized signed graph (G, sigma), the sign sigma(e) determines the pairs of colors that need to be avoided as the colors of the end vertices of e. Let S_k be the set of all permutations of [k]. A natural question motivated by the four color theorem is for which subsets S of S_4, every planar graph is S-4-colorable. This question is now completely answered: only S={id} has this property, which means that the four color theorem is tight in the sense of generalized signed graph coloring. This answer is obtained in a sequence of six papers, by different groups of authors. The contribution of this thesis is the results in one of the papers, which shows that many sets S do not have the desired property. The thesis also considers similar questions for triangle-free planar graphs, which can be viewed as exploring the tightness of Grötzsch Theorem. Our result shows that for any subset S of S_3, if S is not conjugate to a subset of {id, (12)}, then there exists a triangle-free planar graph which is not S-3-colorable. Another attempt to strengthen Grötzsch Theorem is to consider multiple list coloring of triangle-free planar graphs. It was proved by Voigt that there are triangle-free planar graphs that are not 3-choosable. This thesis strengthens Voigt's result by considering the strong fractional choice number of graphs and proves that the supremum of the strong fractional choice number of triangle-free planar graphs is at least 3+1/17. One important subject in structural graph theory is to study the structural complexity of graphs or classes of graphs and a few concepts and graph invariants are studied extensively in the literature. These include treewidth of graphs, generalized coloring number, etc. Recently, the concept of twin-width was introduced by Bonnet, Kim, Thomassé and Watrigant. In this thesis, we study the relation between twin-width and generalized coloring number. We prove that a graph $G$ with no K_{s,s}-subgraph and twin-width d has strong(weak) r-coloring numbers bounded by an exponential function of r and that we can construct graphs achieving such a dependency in r. One of the two central notions in structural theory of classes of sparse graphs is the classes with bounded expansion. These classes have strong algorithmic and structural properties and enjoy numerous characterizations and applications. Combinatorial discrepancy is a significant subject in its own right. It measures the inevitable irregularities of set systems and the inherent difficulty to approximate them. In this thesis, we give a new characterization of bounded expansion classes in terms of discrepancy of definable set systems. The notion of chi-boundedness is a central topic in chromatic graph theory. This thesis studies chi-bounded classes in the context of star colorings and, more generally, chi_p-colorings, say chi_s-bounded and (strongly and weakly) chi_p-bounded classes. This fits to a general scheme of sparsity and leads to natural extensions of the notion of bounded expansion class. Here we solve two conjectures related to star coloring ({i.e.} chi_2) boundedness and give structural characterizations of strongly chi_p-bounded classes and weakly chi_p-bounded classes
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Gajewar, Amita Surendra. "Approximate edge 3-coloring of cubic graphs." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29735.
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Thesis (M. S.)--Computing, Georgia Institute of Technology, 2009.Committee Chair: Prof. Richard Lipton; Committee Member: Prof. Dana Randall; Committee Member: Prof. H. Venkateswaran. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Yerger, Carl Roger Jr. "Color-critical graphs on surfaces." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37197.
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A graph is (t+1)-critical if it is not t-colorable, but every proper subgraph is. In this thesis, we study the structure of critical graphs on higher surfaces. One major result in this area is Carsten Thomassen's proof that there are finitely many 6-critical graphs on a fixed surface. This proof involves a structural theorem about a precolored cycle C of length q. In general terms, he proves that a coloring, c, of C, can be extended inside the cycle, or there exists a subgraph H with at most a number of vertices exponential in q such that c can not be extended to a 5-coloring of H. In Chapter 2, we proved an alternative proof that reduces the number of vertices in H to be cubic in q. In Chapter 3, we find the nine 6-critical graphs among all graphs embeddable on the Klein bottle. In Chapter 4, we prove a result concerning critical graphs related to an analogue of Steinberg's conjecture for higher surfaces. We show that if G is a 4-critical graph embedded on surface S, with Euler genus g and has no cycles of length four through ten, then G has at most 2442g + 37 vertices.
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Poon, Hoifung. "Coloring clique hypergraphs." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1494.
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Ochem, Pascal. "Graph coloring and combinatorics on words." Bordeaux 1, 2005. http://www.theses.fr/2005BOR13083.
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Dans une première partie, nous nous intéressons à différentes colorations de graphes peu denses, en particulier des sous-classes des graphes planaires. Nous apportons de nouveaux résultats concernant les colorations impropres acycliques et la coloration orientée. Nous définissons également de nouvelles colorations d'arètes, les arboricités T-libres, qui généralisent notamment l'arboricité étoile et l'arboricité chenille. Dans une seconde partie, nous considérons certains problèmes de combinatoire des mots. Nous présentons des avancées algorithmiques nous permettant d'étudier assez finement une généralisation du seuil de répétition. Nous obtenons aussi des preuves de 2-évitabilité pour certains motifs. Enfin, nous améliorons des bornes sur la fréquence minimale ou maximale d'une lettre dans un mot infini évitant certaines répétitions.
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Sun, Wen. "Heuristic Algorithms for Graph Coloring Problems." Thesis, Angers, 2018. http://www.theses.fr/2018ANGE0027/document.
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Cette thèse concerne quatre problèmes de coloration de graphes NPdifficiles, à savoir le problème de coloration (GCP), le problème de coloration équitable (ECP), le problème de coloration des sommets pondérés et le problème de sous-graphe critique (k-VCS). Ces problèmes sont largement étudiés dans la littérature, non seulement pour leur difficulté théorique, mais aussi pour leurs applications réelles dans de nombreux domaines. Étant donné qu'ils appartiennent à la classe de problèmes NP-difficiles, il est difficile de les résoudre dans le cas général de manière exacte. Pour cette raison, cette thèse est consacrée au développement d'approches heuristiques pour aborder ces problèmes complexes. Plus précisément, nous développons un algorithme mémétique de réduction (RMA) pour la coloration des graphes, un algorithme de recherche réalisable et irréalisable (FISA) pour la coloration équitable et un réalisable et irréalisable (AFISA) pour le problème de coloration des sommets pondérés et un algorithme de suppression basé sur le retour en arrière (IBR) pour le problème k-VCS. Tous les algorithmes ont été expérimentalement évalués et comparés aux méthodes de l'état de l'artThis thesis concerns four NP-hard graph coloring problems, namely, graph coloring (GCP), equitable coloring (ECP), weighted vertex coloring (WVCP) and k-vertex-critical subgraphs (k-VCS). These problems are extensively studied in the literature not only for their theoretical intractability, but also for their real-world applications in many domains. Given that they belong to the class of NP-hard problems, it is computationally difficult to solve them exactly in the general case. For this reason, this thesis is devoted to developing effective heuristic approaches to tackle these challenging problems. We develop a reduction memetic algorithm (RMA) for the graph coloring problem, a feasible and infeasible search algorithm (FISA) for the equitable coloring problem, an adaptive feasible and infeasible search algorithm (AFISA) for the weighted vertex coloring problem and an iterated backtrack-based removal (IBR) algorithm for the k-VCS problem. All these algorithms were experimentally evaluated and compared with state-of-the-art methods
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Montgomery, Bruce Lee. "Dynamic coloring of graphs." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2109.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains viii, 52 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 51).
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AraÃjo, JÃlio CÃsar Silva. "Graph coloring and graph convexity / ColoraÃÃo em convexidade em grafos." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8346.
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MinistÃre de l'Enseignement SupÃrieur et de la RechercheNesta tese, estudamos vÃrios problemas de teoria dos grafos relativos à coloraÃÃo e convexidade em grafos. A maioria dos resultados contidos aqui sÃo ligados à complexidade computacional destes problemas para classes de grafos particulares. Na primeira, e principal, parte desta tese, discutimos coloraÃÃo de grafos que à uma das Ãreas mais importantes de teoria dos grafos. Primeiro, consideramos trÃs problemas de coloraÃÃo chamados coloraÃÃo gulosa, coloraÃÃo ponderada e coloraÃÃo ponderada imprÃpria. Em seguida, discutimos um problema de decisÃo, chamado boa rotulagem de arestas, cuja definiÃÃo foi motivada pelo problema de atribuiÃÃo de frequÃncias em redes Ãticas. A segunda parte desta tese à dedicada a um parÃmetro de otimizaÃÃo em grafos chamado de nÃmero de fecho (geodÃtico). A definiÃÃo deste parÃmetro à motivada pela extensÃo das noÃÃes de conjuntos e fecho convexos no espaÃo Euclidiano. Por m, apresentamos em anexo outros trabalhos desenvolvidos durante esta tese, um em hipergrafos dirigidos Eulerianos e Hamiltonianos e outro sobre sistemas de armazenamento distribuÃdo.
In this thesis, we study several problems of Graph Theory concerning Graph Coloring and Graph Convexity. Most of the results contained here are related to the computational complexity of these problems for particular graph classes. In the first and main part of this thesis, we deal with Graph Coloring which is one of the most studied areas of Graph Theory. We first consider three graph coloring problems called Greedy Coloring, Weighted Coloring and Weighted Improper Coloring. Then, we deal with a decision problem, called Good Edge-Labeling, whose definition was motivated by the Wavelength Assignment problem in optical networks. The second part of this thesis is devoted to a graph optimization parameter called (geodetic) hull number. The definition of this parameter is motivated by an extension to graphs of the notions of convex sets and convex hulls in the Euclidean space. Finally, we present in the appendix other works developed during this thesis, one about Eulerian and Hamiltonian directed hypergraphs and the other concerning distributed storage systems.
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Postle, Luke Jamison. "5-list-coloring graphs on surfaces." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45807.
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Thomassen proved that there are only finitely many 6-critical graphs embeddable on a fixed surface. He also showed that planar graphs are 5-list-colorable. This thesis develops new techniques to prove general theorems for 5-list-coloring graphs embedded in a fixed surface. Indeed, a general paradigm is established which improves a number of previous results while resolving several open conjectures. In addition, the proofs are almost entirely self-contained.
In what follows, let S be a fixed surface, G be a graph embedded in S and L a list assignment such that, for every vertex v of G, L(v) has size at least five. First, the thesis provides an independent proof of a theorem of DeVos, Kawarabayashi and Mohar that says if G has large edge-width, then G is 5-list-colorable. Moreover, the bound on the edge-width is improved from exponential to logarithmic in the Euler genus of S, which is best possible up to a multiplicative constant. Second, the thesis proves that there exist only finitely many 6-list-critical graphs embeddable in S, solving a conjecture of Thomassen from 1994. Indeed, it is shown that the number of vertices in a 6-list-critical graph is at most linear in genus, which is best possible up to a multiplicative constant. As a corollary, there exists a linear-time algorithm for deciding 5-list-colorability of graphs embeddable in S.
Furthermore, we prove that the number of L-colorings of an L-colorable graph embedded in S is exponential in the number of vertices of G, with a constant depending only on the Euler genus g of S. This resolves yet another conjecture of Thomassen from 2007. The thesis also proves that if X is a subset of the vertices of G that are pairwise distance Omega(log g) apart and the edge-width of G is Omega(log g), then any L-coloring of X extends to an L-coloring of G. For planar graphs, this was conjectured by Albertson and recently proved by Dvorak, Lidicky, Mohar, and Postle. For regular coloring, this was proved by Albertson and Hutchinson. Other related generalizations are examined.
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Song, Zengmin. "Cycles and coloring in graphs." HKBU Institutional Repository, 2001. http://repository.hkbu.edu.hk/etd_ra/285.
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Goyal, Mini, and University of Lethbridge Faculty of Arts and Science. "Graph coloring in sparse derivative matrix computation." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2005, 2005. http://hdl.handle.net/10133/260.
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There has been extensive research activities in the last couple of years to efficiently determine large sparse Jacobian matrices. It is now well known that the estimation of Jacobian matrices can be posed as a graph coloring problem. Unidirectional coloring by Coleman and More [9] and bidirectional coloring independently proposed by Hossain and Steihaug [23] and Coleman and Verma [12] are techniques that employ graph theoretic ideas. In this thesis we present heuristic and exact bidirectional coloring techniques. For bidirectional heuristic techniques we have implemented variants of largest first ordering, smallest last ordering, and incidence degree ordering schemes followed by the sequential algorithm to determine the Jacobian matrices. A "good" lower bound given by the maximum number of nonzero entries in any row of the Jacobian matrix is readily obtained in an unidirectional determination. However, in a bidirectional determination no such "good" lower bound is known. A significant goal of this thesis is to ascertain the effectiveness of the existing heuristic techniques in terms of the number of matrix-vector products required to determine the Jacobian matrix. For exact bidirectional techniques we have proposed an integer linear program to solve the bidirectional coloring problem. Part of exact bidirectional coloring results were presented at the "Second International Workshop on Cominatorial Scientific Computing (CSC05), Toulouse, France."viii, 83 leaves ; 29 cm.
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Adams, Sarah E. "Chromatic Polynomials for Graphs with Split Vertices." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1593819941367146.
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Li, Ching-man. "Various coloring problems on plane graphs." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39006542.
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Walls, Barrett Hamilton. "Coloring girth restricted graphs on surfaces." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/28939.
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Li, Ching-man, and 李靜文. "Various coloring problems on plane graphs." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39006542.
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Zickfeld, Florian. "On the Structure of Counterexamples to the Coloring Conjecture of Hajós." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4994.
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Hajós conjectured that, for any positive integer
k, every graph containing no K_(k+1)-subdivision is k-colorable. This is true when k is at most three, and false when k exceeds six. Hajós' conjecture remains open for k=4,5.
We will first present some known results on Hajós' conjecture. Then we derive a result on the structure of 2-connected graphs
with no cycle through three specified vertices. This result will then be used for the proof of the main result of this thesis. We show that any possible counterexample to Hajós' conjecture for
k=4 with minimum number of vertices must be 4-connected. This is
a step in an attempt to reduce Hajós' conjecture for k=4 to the conjecture of Seymour that any 5-connected non-planar graph contains a K_5-subdivision.
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Fowler, Thomas George. "Unique coloring of planar graphs." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30358.
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Dochtermann, Anton. "The topology of graph homomorphisms /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5754.
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Macon, Lisa Fischer. "Almost regular graphs and edge-face colorings of plane graphs." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002507.
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Li, Chao. "Semidefinite programming, binary codes and a graph coloring problem." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-theses/863.
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"Experts in information theory have long been interested in the maximal size, A(n, d), of a binary error-correcting code of length n and minimum distance d, The problem of determining A(n, d) involves both the construction of good codes and the search for good upper bounds. For quite some time now, Delsarte's linear programming approach has been the dominant approach to obtaining the strongest general purpose upper bounds on the efficiency of error-correcting codes. From 1973 forward, the linear programming bound found many applications, but there were few significant theoretical advances until Schrijver proposed a new code upper bound via semidefinite programming in 2003. Using the Terwilliger algebra, a recently introduced extension of the Bose-Mesner algebra, Schrijver formulated a new SDP strengthening of the LP approach. In this project we look at the dual solutions of the semidefinite programming bound for binary error-correcting codes. We explore the combinatorial meaning of these variables for small n and d, such as n = 4 and d = 2. To obtain information like this, we wrote a computer program with both Matlab and CVX modules to get solution of our primal SDP formulation. Our program efficiently generates the primal solutions with corresponding constraints for any n and d. We also wrote a program in C++ to parse the output of the primal SDP problem, and another Matlab script to generate the dual SDP problem, which could be used in assigning combinatorial meaning to the values given in the dual optimal solution. Our code not only computes both the primal and dual optimal variable values, but allows the researcher to display them in meaningful ways and to explore their relationship and dependence on arameters. These values are expected to be useful for later study of the combinatorial meaning of such solutions."
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Wu, Qinghua. "The maximum clique problems with applications to graph coloring." Angers, 2013. https://theses.hal.science/tel-01005886.
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Le problème de la clique maximum (MCP) est un problème d'optimisation combinatoire important avec un large éventail d'applications pratiques dans de nombreux domaines, y compris la recherche d'information, l'analyse de la transmission du signal, la théorie de la classification, l'économie, la planification et l'ingénierie biomédicale. En outre, un certain nombre de problèmes d'optimisation combinatoire sont étroitement liés au MCP, tels que la coloration de graphe, la somme coloration, réglez détermination du gagnant emballage et optimale. Cette thèse est consacrée à l'élaboration d'approches heuristiques efficaces pour s'attaquer au problème de la clique maximum et ses généralisations. Pour atteindre cet objectif, nous avons développé une approche de recherche tabou adaptative multistart pour le problème de clique maximum classique, un algorithme recherche tabou multi-voisinage pour la clique maximum de sommets pondérés, et une méthode métaheuristique hybride pour le problème de la clique maximum d'arêtes pondérés. En outre, nous appliquons ces méthodes heuristiques développées pour résoudre ces problèmes difficiles qui sont étroitement liés au problème de la clique maximum. Tous les algorithmes sont mis en oeuvre et testés avec succès sur un certain nombre de cas de référence provenant de divers domaines d'application. Les méthodes proposées concurrencent favorablement les autres approches de l'état de l'artThe maximum clique problem (MCP) is an important combinatorial optimization problem with a wide range of practical applications in numerous fields, including information retrieval, signal transmission analysis, classification theory, economics, scheduling, and biomedical engineering. Moreover, a number of combinatorial optimization problems are tightly related to MCP, such as graph coloring, sum coloring, set packing and optimal winner determination. This thesis is devoted to developing effective heuristic approaches to tackle the maximum clique problem and its generalizations. To achieve this, we developed an adaptive multistart tabu search approach for the classic maximum clique problem, a multi-neighborhood tabu search algorithm for the maximum vertex weight clique and a hybrid metaheuristic method for the maximum edge weight clique problem. Moreover, we apply these developed heuristic approaches to solve these hard problems which are tightly related to the maximum clique problem. All algorithms are implemented and successfully tested on a number of benchmark instances from diverse application areas. The proposed methods favorably compete with other state-of-art approaches
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Jin, Yan. "Hybrid metaheuristic algorithms for sum coloring and bandwidth coloring." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0062/document.
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Le problème de somme coloration minimum (MSCP) et le problème de coloration de bande passante (BCP) sont deux généralisations importantes du problème de coloration des sommets classique avec de nombreuses applications dans divers domaines, y compris la conception de circuits imprimés, la planication, l’allocation de ressource, l’affectation de fréquence dans les réseaux mobiles, etc. Les problèmes MSCP et BCP étant NP-difficiles, les heuristiques et métaheuristiques sont souvent utilisées en pratique pour obtenir des solutions de bonne qualité en un temps de calcul acceptable. Cette thèse est consacrée à des métaheuristiques hybrides pour la résolution efcace des problèmes MSCP et BCP. Pour le problème MSCP, nous présentons deux algorithmes mémétiques qui combinent l’évolution d’une population d’individus avec de la recherche locale. Pour le problème BCP, nous proposons un algorithme hybride à base d’apprentissage faisant coopérer une méthode de construction “informée” avec une procédure de recherche locale. Les algorithmes développés sont évalués sur des instances biens connues et se révèlent très compétitifs par rapport à l’état de l’art. Les principaux composants des algorithmes que nous proposons sont également analysésThe minimum sum coloring problem (MSCP) and the bandwidth coloring problem (BCP) are two important generalizations of the classical vertex coloring problem with numerous applications in diverse domains, including VLSI design, scheduling, resource allocation and frequency assignment in mobile networks, etc. Since the MSCP and BCP are NP-hard problems, heuristics and metaheuristics are practical solution methods to obtain high quality solutions in an acceptable computing time. This thesis is dedicated to developing effective hybrid metaheuristic algorithms for the MSCP and BCP. For the MSCP, we present two memetic algorithms which combine population-based evolutionary search and local search. An effective algorithm for maximum independent set is devised for generating initial solutions. For the BCP, we propose a learning-based hybrid search algorithm which follows a cooperative framework between an informed construction procedure and a local search heuristic. The proposed algorithms are evaluated on well-known benchmark instances and show highly competitive performances compared to the current state-of-the-art algorithms from the literature. Furthermore, the key issues of these algorithms are investigated and analyzed
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Macon, Lisa. "ALMOST REGULAR GRAPHS AND EDGE FACE COLORINGS OF PLANE GRAPHS." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2480.
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Regular graphs are graphs in which all vertices have the same degree. Many properties of these graphs are known. Such graphs play an important role in modeling network configurations where equipment limitations impose a restriction on the maximum number of links emanating from a node. These limitations do not enforce strict regularity, and it becomes interesting to investigate nonregular graphs that are in some sense close to regular. This dissertation explores a particular class of almost regular graphs in detail and defines generalizations on this class. A linear-time algorithm for the creation of arbitrarily large graphs of the discussed class is provided, and a polynomial-time algorithm for recognizing graphs in the class is given. Several invariants for the class are discussed. The edge-face chromatic number χef of a plane graph G is the minimum number of colors that must be assigned to the edges and faces of G such that no edge or face of G receives the same color as an edge or face with which it is incident or adjacent. A well-known result for the upper bound of χef exists for graphs with maximum degree Δ ≥ 10. We present a tight upper bound for plane graphs with Δ = 9.Ph.D.
Department of Mathematics
Sciences
Mathematics PhD
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Chan, Wai Hong. "The bandwidth and coloring problems of graphs." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/472.
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Legay, Sylvain. "Quelques problèmes d'algorithmique et combinatoires en théorie des grapphes." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS030/document.
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Le sujet de cette thèse est la théorie des graphes. Formellement, un graphe est un ensemble de sommets et un ensemble d’arêtes, c’est à dire de paires de sommets, qui relient les sommets. Cette thèse traite de différents problèmes de décisions binaires ou de minimisations liés à la notion de graphe, et cherche, pour chacun de ces problèmes, à déterminer sa classe de complexité, ou à fournir un algorithme. Le premier chapitre concerne le problème de trouver le plus petit sous-graphe connexe tropical dans un graphe sommet-colorié, c’est à dire le plus petit sous-graphe connexe contenant toutes les couleurs. Le deuxième chapitre concerne les problèmes d’homomorphisme tropical, une généralisation des problèmes de coloriage de graphe. On y trouve un lien entre ces problèmes et plusieurs classes de problèmes d’homomorphismes, dont la classe des Problèmes de Satisfaction de Contraintes. Le troisième chapitre concerne deux variantes lointaines du problème de domination, nommément les problèmes d’alliances globales dans un graphe pondéré et le problème de l’ensemble sûr. Le quatrième chapitre concerne la recherche d’une décomposition arborescente étoilée, c’est à dire une décomposition arborescente dont le rayon des sacs est 1. Enfin, le cinquième chapitre concerne une variante du problème de décider du comportement asymptotique de l’itéré du graphe des bicliquesThis thesis is about graph theory. Formally, a graph is a set of vertices and a set of edges, which are pair of vertices, linking vertices. This thesis deals with various decision problem linked to the notion of graph, and, for each of these problem, try to find its complexity class, or to give an algorithm. The first chapter is about the problem of finding the smallest connected tropical subgraph of a vertex-colored graph, which is the smallest connecter subgraph containing every colors. The second chapter is about problems of tropical homomorphism, a generalization of coloring problem. A link between these problems and several other class of homomorphism problems can be found in this chapter, especially with the class of Constraint Satisfaction Problem. The third chapter is about two variant of the domination problem, namely the global alliance problems in a weighted graph and the safe set problem. The fourth chapter is about the problem of finding a star tree-decomposition, which is a tree-decomposition where the radius of bags is 1. Finally, the fifth chapter is about a variant of the problem of deciding the asymptotic behavior of the iterated biclique graph
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Tahraoui, Mohammed Amin. "Coloring, packing and embedding of graphs." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00995041.
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In this thesis, we investigate some problems in graph theory, namelythe graph coloring problem, the graph packing problem and tree pattern matchingfor XML query processing. The common point between these problems is that theyuse labeled graphs.In the first part, we study a new coloring parameter of graphs called the gapvertex-distinguishing edge coloring. It consists in an edge-coloring of a graph G whichinduces a vertex distinguishing labeling of G such that the label of each vertex isgiven by the difference between the highest and the lowest colors of its adjacentedges. The minimum number of colors required for a gap vertex-distinguishing edgecoloring of G is called the gap chromatic number of G and is denoted by gap(G).We will compute this parameter for a large set of graphs G of order n and we evenprove that gap(G) 2 fn E 1; n; n + 1g.In the second part, we focus on graph packing problems, which is an area ofgraph theory that has grown significantly over the past several years. However, themajority of existing works focuses on unlabeled graphs. In this thesis, we introducefor the first time the packing problem for a vertex labeled graph. Roughly speaking,it consists of graph packing which preserves the labels of the vertices. We studythe corresponding optimization parameter on several classes of graphs, as well asfinding general bounds and characterizations.The last part deal with the query processing of a core subset of XML query languages:XML twig queries. An XML twig query, represented as a small query tree,is essentially a complex selection on the structure of an XML document. Matching atwig query means finding all the occurrences of the query tree embedded in the XMLdata tree. Many holistic twig join algorithms have been proposed to match XMLtwig pattern. Most of these algorithms find twig pattern matching in two steps. Inthe first one, a query tree is decomposed into smaller pieces, and solutions againstthese pieces are found. In the second step, all of these partial solutions are joinedtogether to generate the final solutions. In this part, we propose a novel holistictwig join algorithm, called TwigStack++, which features two main improvementsin the decomposition and matching phase. The proposed solutions are shown to beefficient and scalable, and should be helpful for the future research on efficient queryprocessing in a large XML database.
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Roussel, Nicolas. "Circular coloring and acyclic choosability of graphs." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13889/document.
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Dans cette thèse, nous nous intéressons à la coloration circulaire des graphes planaires. Des bornes supérieures ont été données pour des graphes avec degré maximum borné, avec girth, la longueur de son plus petit cycle, bornée, avec des cycles manquants, etc. Ici nous donnerons de nouvelles bornes pour les graphes avec degré moyen maximum borné. Nous étudions également la coloration totale et la coloration (d,1)-totale de plusieurs familles infinies de graphes. Nous décrivons le nouveau concept de coloration (d,1)-totale circulaire. Enfin, nous discutons les conditions nécessaires pour qu'un graphe planaire admette une coloration acyclique par listes de taille 4In this thesis, we study the circular coloring of planar graphs. Upper bounds have been given for graphs with bounded maximum degree, with bounded girth, that is the length of its smallest cycle, with missing cycles, and so on. It has also been studied for graphs with bounded maximum average degree. Here we give new upper bounds for that latter case. We also study the total coloring and ($d,1$)-total labeling of a few infinite families of graphs and describe the new concept of circular ($d,1$)-total labeling of graphs. In the last part, we will discuss conditions for a planar graph to be acyclically $4$-choosable
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Coker, Thomas David. "Graph colouring and bootstrap percolation with recovery." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610806.
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Ahadi, Moghaddam Masoumeh [Verfasser], and Dietmar [Akademischer Betreuer] Schweigert. "Graph Coloring Applications and Defining Sets in Graph Theory / Masoumeh Ahadi Moghaddam ; Betreuer: Dietmar Schweigert." Kaiserslautern : Technische Universität Kaiserslautern, 2017. http://d-nb.info/1127044435/34.
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Ren, Tiegeng. "Graph coloring algorithms for TDMA scheduling in wireless sensor networks /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3298376.
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Hesterberg, Adam Classen. "Closed quasigeodesics, escaping from polygons, and conflict-free graph coloring." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117875.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 56-58).
Closed quasigeodesics. A closed quasigeodesic on the surface of a polyhedron is a loop which can everywhere locally be unfolded to a straight line: thus, it's straight on faces, uniquely determined on edges, and has as much flexibility at a vertex as that vertex's curvature. On any polyhedron, at least three closed quasigeodesics are known to exist, by a nonconstructive topological proof. We present an algorithm to find one on any convex polyhedron in time O(n2[epsilon]-2- 2Ll-1 ), where [epsilon] e is the minimum curvature of a vertex, l is the length of the longest side, and t is the smallest distance within a face between a vertex and an edge not containing it. Escaping from polygons. You move continuously at speed 1 in the interior of a polygon P, trying to reach the boundary. A zombie moves continuously at speed r outside P, trying to be at the boundary when you reach it. For what r can you escape and for what r can the zombie catch you? We give exact results for some P. For general P, we give a simple approximation to within a factor of roughly 9.2504. We also give a pseudopolynomial-time approximation scheme. Finally, we prove NP-hardness and hardness of approximation results for related problems with multiple zombies and/or humans. Conflict-free graph coloring. A conflict-free k-coloring of a graph assigns one of k different colors to some of the vertices such that, for every vertex v, there is a color that is assigned to exactly one vertex among v and v's neighbors. We study the natural problem of the conflict-free chromatic number XCF(G) (the smallest k for which conflict-free k-colorings exist), with a focus on planar graphs.
by Adam Classen Hesterberg.
Ph. D.
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Bozdag, Doruk. "Graph Coloring and Clustering Algorithms for Science and Engineering Applications." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1229459765.
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Chen, Min. "Vertex coloring of graphs via the discharging method." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14090/document.
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Dans cette thèse, nous nous intéressons à differentes colorations des sommets d’un graphe et aux homomorphismes de graphes. Nous nous intéressons plus spécialement aux graphes planaires et aux graphes peu denses. Nous considérons la coloration propre des sommets, la coloration acyclique, la coloration étoilée, lak-forêt-coloration, la coloration fractionnaire et la version par liste de la plupart de ces concepts.Dans le Chapitre 2, nous cherchons des conditions suffisantes de 3-liste colorabilité des graphes planaires. Ces conditions sont exprimées en termes de sous-graphes interdits et nos résultats impliquent plusieurs résultats connus.La notion de la coloration acyclique par liste des graphes planaires a été introduite par Borodin, Fon-Der Flaass, Kostochka, Raspaud, et Sopena. Ils ont conjecturé que tout graphe planaire est acycliquement 5-liste coloriable. Dans le Chapitre 3, on obtient des conditions suffisantes pour qu’un graphe planaire admette une k-coloration acyclique par liste avec k 2 f3; 4; 5g.Dans le Chapitre 4, nous montrons que tout graphe subcubique est 6-étoilé coloriable.D’autre part, Fertin, Raspaud et Reed ont montré que le graphe de Wagner ne peut pas être 5-étoilé-coloriable. Ce fait implique que notre résultat est optimal. De plus, nous obtenons des nouvelles bornes supérieures sur la choisissabilité étoilé d’un graphe planaire subcubique de maille donnée.Une k-forêt-coloration d’un graphe G est une application ¼ de l’ensemble des sommets V (G) de G dans l’ensemble de couleurs 1; 2; ¢ ¢ ¢ ; k telle que chaque classede couleur induit une forêt. Le sommet-arboricité de G est le plus petit entier ktel que G a k-forêt-coloration. Dans le Chapitre 5, nous prouvons une conjecture de Raspaud et Wang affirmant que tout graphe planaire sans triangles intersectants admet une sommet-arboricité au plus 2.Enfin, au Chapitre 6, nous nous concentrons sur le problème d’homomorphisme des graphes peu denses dans le graphe de Petersen. Plus précisément, nous prouvons que tout graphe sans triangles ayant un degré moyen maximum moins de 5=2 admet un homomorphisme dans le graphe de Petersen. En outre, nous montrons que la borne sur le degré moyen maximum est la meilleure possibleIn this thesis, we are interested in various vertex coloring and homomorphism problems of graphs with special emphasis on planar graphs and sparsegraphs. We consider proper vertex coloring, acyclic coloring, star coloring, forestcoloring, fractional coloring and the list version of most of these concepts.In Chapter 2, we consider the problem of finding sufficient conditions for a planargraph to be 3-choosable. These conditions are expressed in terms of forbiddensubgraphs and our results extend several known results.The notion of acyclic list coloring of planar graphs was introduced by Borodin,Fon-Der Flaass, Kostochka, Raspaud, and Sopena. They conjectured that everyplanar graph is acyclically 5-choosable. In Chapter 3, we obtain some sufficientconditions for planar graphs to be acyclically k-choosable with k 2 f3; 4; 5g.In Chapter 4, we prove that every subcubic graph is 6-star-colorable. On theother hand, Fertin, Raspaud and Reed showed that the Wagner graph cannot be5-star-colorable. This fact implies that our result is best possible. Moreover, weobtain new upper bounds on star choosability of planar subcubic graphs with givengirth.A k-forest-coloring of a graph G is a mapping ¼ from V (G) to the set f1; ¢ ¢ ¢ ; kgsuch that each color class induces a forest. The vertex-arboricity of G is the smallestinteger k such that G has a k-forest-coloring. In Chapter 5, we prove a conjecture ofRaspaud and Wang asserting that every planar graph without intersecting triangleshas vertex-arboricity at most 2.Finally, in Chapter 6, we focus on the homomorphism problems of sparse graphsto the Petersen graph. More precisely, we prove that every triangle-free graph withmaximum average degree less than 5=2 admits a homomorphism to the Petersengraph. Moreover, we show that the bound on the maximum average degree in ourresult is best possible
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Djang, Claire. "Two-Coloring Cycles In Complete Graphs." Oberlin College Honors Theses / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1370618319.
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Clark, David. "Algebraic Analysis of Vertex-Distinguishing Edge-Colorings." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1053.
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Vertex-distinguishing edge-colorings (vdec colorings) are a restriction of proper edge-colorings. These special colorings require that the sets of edge colors incident to every vertex be distinct. This is a relatively new field of study. We present a survey of known results concerning vdec colorings. We also define a new matrix which may be used to study vdec colorings, and examine its properties. We find several bounds on the eigenvalues of this matrix, as well as results concerning its determinant, and other properties. We finish by examining related topics and open problems.
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HIRATA, Tomio, Takao ONO, and Xuzhen XIE. "On Approximation Algorithms for Coloring k-Colorable Graphs." Institute of Electronics, Information and Communication Engineers, 2003. http://hdl.handle.net/2237/15063.
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Jaeger, Robert. "Coloring the Square of Planar Graphs Without 4-Cycles or 5-Cycles." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3816.
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The famous Four Color Theorem states that any planar graph can be properly colored using at most four colors. However, if we want to properly color the square of a planar graph (or alternatively, color the graph using distinct colors on vertices at distance up to two from each other), we will always require at least \Delta + 1 colors, where \Delta is the maximum degree in the graph. For all \Delta, Wegner constructed planar graphs (even without 3-cycles) that require about \frac{3}{2} \Delta colors for such a coloring.
To prove a stronger upper bound, we consider only planar graphs that contain no 4-cycles and no 5-cycles (but which may contain 3-cycles). Zhu, Lu, Wang, and Chen showed that for a graph G in this class with \Delta \ge 9, we can color G^2 using no more than \Delta + 5 colors. In this thesis we improve this result, showing that for a planar graph G with maximum degree \Delta \ge 32 having no 4-cycles and no 5-cycles, at most \Delta + 3 colors are needed to properly color G^2. Our approach uses the discharging method, and the result extends to list-coloring and other related coloring concepts as well.
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Zickfeld, Florian. "On the structure of counterexamples to the coloring conjecture of Hajós." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-05202004-142057/unrestricted/zickfeld%5Fflorian%5F200407%5Fmast.pdf.
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Thesis (M.S.)--School of Mathematics, Georgia Institute of Technology, 2005. Directed by Xingxing Yu.Xingxing Yu, Committee Chair ; Robin Thomas, Committee Member ; Prasad Tetali, Committee Member ; Anurag Singh, Committee Member. Includes bibliographical references.
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Bonamy, Marthe. "Global discharging methods for coloring problems in graphs." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS261.
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Cette thèse s'inscrit dans le cadre de la théorie des graphes, et porte plus particulièrement sur des problèmes de coloration de graphes. Dans cette thèse, nous nous intéressons à l'utilisation et au développement de la méthode de déchargement, un argument de comptage qui exploite fortement la structure du graphe. Cette méthode est décisive dans la preuve du Théorème des Quatre Couleurs. Nous donnons d'abord une vue d'ensemble des outils de déchargement que nous utilisons dans ce travail, entre les méthodes élégantes mises en application, et les astuces développées. Dans le cadre de la coloration d'arêtes par liste, nous résolvons la Conjecture de Coloration par Liste faible dans le cas des graphes planaires de degré maximum 8, en prouvant qu'on peut colorier par liste les arêtes de ces derniers avec 9 couleurs seulement. Ceci améliore un résultat de Borodin de 1990. Enfin, nous présentons nos résultats dans le cadre de la coloration de carrés, où il s'agit de colorier les sommets sans qu'il y ait deux sommets adjacents ou avec un voisin commun qui soient de la même couleur. On s'intéresse en particulier à des conditions suffisantes sur la densité du graphe (c-à-d le degré moyen maximum d'un sous-graphe) pour qu'on puisse colorier son carré avec peu de couleursThis thesis falls within graph theory, and deals more precisely with graph coloring problems. In this thesis, we use and develop the discharging method, a counting argument that makes strong advantage of the graph structure. This method is decisive in the proof of the Four Color Theorem. We first give an illustrated overview of the discharging tools that are used for this work: nice methods that we apply, and handy tricks that we develop. In the realm of list edge coloring, we most notably prove that the weak List Coloring Conjecture is true for planar graphs of maximum degree 8 (i.e. that they are edge 9-choosable), thus improving over a result of Borodin from 1990. We finally present our results about square coloring, where the goal is to color the vertices in such a way that two vertices that are adjacent or have a common neighbor receive different colors. We look in particular into sufficient conditions on the density of a graph (i.e. the maximum average degree of a subgraph) for its square to be colorable with few colo
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Raman, Rajiv. "Chromatic scheduling." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/156.
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Moura, Phablo Fernando Soares. "Graph colorings and digraph subdivisions." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-23052017-100619/.
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The vertex coloring problem is a classic problem in graph theory that asks for a partition of the vertex set into a minimum number of stable sets. This thesis presents our studies on three vertex (re)coloring problems on graphs and on a problem related to a long-standing conjecture on subdivision of digraphs. Firstly, we address the convex recoloring problem in which an arbitrarily colored graph G is given and one wishes to find a minimum weight recoloring such that each color class induces a connected subgraph of G. We show inapproximability results, introduce an integer linear programming (ILP) formulation that models the problem and present some computational experiments using a column generation approach. The k-fold coloring problem is a generalization of the classic vertex coloring problem and consists in covering the vertex set of a graph by a minimum number of stable sets in such a way that every vertex is covered by at least k (possibly identical) stable sets. We present an ILP formulation for this problem and show a detailed polyhedral study of the polytope associated with this formulation. The last coloring problem studied in this thesis is the proper orientation problem. It consists in orienting the edge set of a given graph so that adjacent vertices have different in-degrees and the maximum in-degree is minimized. Clearly, the in-degrees induce a partition of the vertex set into stable sets, that is, a coloring (in the conventional sense) of the vertices. Our contributions in this problem are on hardness and upper bounds for bipartite graphs. Finally, we study a problem related to a conjecture of Mader from the eighties on subdivision of digraphs. This conjecture states that, for every acyclic digraph H, there exists an integer f(H) such that every digraph with minimum out-degree at least f(H) contains a subdivision of H as a subdigraph. We show evidences for this conjecture by proving that it holds for some particular classes of acyclic digraphs.O problema de coloração de grafos é um problema clássico em teoria dos grafos cujo objetivo é particionar o conjunto de vértices em um número mínimo de conjuntos estáveis. Nesta tese apresentamos nossas contribuições sobre três problemas de coloração de grafos e um problema relacionado a uma antiga conjectura sobre subdivisão de digrafos. Primeiramente, abordamos o problema de recoloração convexa no qual é dado um grafo arbitrariamente colorido G e deseja-se encontrar uma recoloração de peso mínimo tal que cada classe de cor induza um subgrafo conexo de G. Mostramos resultados sobre inaproximabilidade, introduzimos uma formulação linear inteira que modela esse problema, e apresentamos alguns resultados computacionais usando uma abordagem de geração de colunas. O problema de k-upla coloração é uma generalização do problema clássico de coloração de vértices e consiste em cobrir o conjunto de vértices de um grafo com uma quantidade mínima de conjuntos estáveis de tal forma que cada vértice seja coberto por pelo menos k conjuntos estáveis (possivelmente idênticos). Apresentamos uma formulação linear inteira para esse problema e fazemos um estudo detalhado do politopo associado a essa formulação. O último problema de coloração estudado nesta tese é o problema de orientação própria. Ele consiste em orientar o conjunto de arestas de um dado grafo de tal forma que vértices adjacentes possuam graus de entrada distintos e o maior grau de entrada seja minimizado. Claramente, os graus de entrada induzem uma partição do conjunto de vértices em conjuntos estáveis, ou seja, induzem uma coloração (no sentido convencional) dos vértices. Nossas contribuições nesse problema são em complexidade computacional e limitantes superiores para grafos bipartidos. Finalmente, estudamos um problema relacionado a uma conjectura de Mader, dos anos oitenta, sobre subdivisão de digrafos. Esta conjectura afirma que, para cada digrafo acíclico H, existe um inteiro f(H) tal que todo digrafo com grau mínimo de saída pelo menos f(H) contém uma subdivisão de H como subdigrafo. Damos evidências para essa conjectura mostrando que ela é válida para classes particulares de digrafos acíclicos.
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Pierron, Théo. "Induction Schemes : From Language Separation to Graph Colorings." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0119/document.
Full textAbstract:
Cette thèse présente des résultats obtenus dans deux domaines : la théorie des langages, et la théorie des graphes. En théorie des langages, on s’intéresse à des problèmes de caractérisation de classes de langages réguliers. Le problème générique consiste à déterminer si un langage régulier donné peut être défini dans un certain formalisme. Les méthodes actuelles font intervenir un problème plus général appelé séparation. On présente ici deux types de contributions : une généralisation d’un résultat de décidabilité au cadre des langages de mots infinis, ainsi que des bornes inférieures pour la complexité du problème de séparation. En théorie des graphes, on considère le problème classique de coloration de graphes, où on cherche à attribuer des couleurs aux sommets d’un graphe de sorte que les sommets adjacents reçoivent des couleurs différentes, le but étant d’utiliser le moins de couleurs possible. Dans le cas des graphes peu denses, la méthode de déchargement est un atout majeur. Elle a notamment joué un rôle décisif dans la preuve du théorème des quatre couleurs. Cette méthode peut être vue comme une construction non conventionnelle d’un schéma de preuve par induction, spécifique à la classe de graphes et à la propriété considérées, et où la validité du schéma est rarement immédiate. On utilise des variantes de la méthode de déchargement pour étudier deux types de problèmes de colorationIn this thesis, we present results obtained in two fields: formal language theory and graph theory. In formal language theory, we consider some problems of characterization of classes of regular languages. The generic problem consists in determining whether a given regular language can be defined in a fixed formalism. The current approaches use a more general problem called separation. We present here two types of contributions: a generalization of a decidability result to the setting of infinite words, together with lower bounds for the complexity of the separation problem. In graph theory, we consider the classical problem of graph coloring, where we assign colors to vertices of a graph in such a way that two adjacent vertices receive different colors. The goal is to use the fewest colors. When the graphs are sparse, a crucial tool for this is the discharging method. It is most notably decisive in the proof of the Four-Color Theorem. This method can be seen as an unconventional construction of an inductive proof scheme, specific to the considered problem and graph class, where arguing the validity of the scheme is rarely immediate. We use variants of the discharging method to study two types of coloring problems