Graph-Theoretic Problems and Their New Applications • Frank Werner Graph-Theoretic Problems and Their New Applications
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Coloring Problems in Graph Theory Kacy Messerschmidt Iowa State University
Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2018 Coloring problems in graph theory Kacy Messerschmidt Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Mathematics Commons Recommended Citation Messerschmidt, Kacy, "Coloring problems in graph theory" (2018). Graduate Theses and Dissertations. 16639. https://lib.dr.iastate.edu/etd/16639 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Coloring problems in graph theory by Kacy Messerschmidt A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Mathematics Program of Study Committee: Bernard Lidick´y,Major Professor Steve Butler Ryan Martin James Rossmanith Michael Young The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2018 Copyright c Kacy Messerschmidt, 2018. All rights reserved. TABLE OF CONTENTS LIST OF FIGURES iv ACKNOWLEDGEMENTS vi ABSTRACT vii 1. INTRODUCTION1 2. DEFINITIONS3 2.1 Basics . .3 2.2 Graph theory . .3 2.3 Graph coloring . .5 2.3.1 Packing coloring . .6 2.3.2 Improper coloring . -
Odd Harmonious Labeling on Pleated of the Dutch Windmill Graphs
CAUCHY – JURNAL MATEMATIKA MURNI DAN APLIKASI Volume 4 (4) (2017), Pages 161-166 p-ISSN: 2086-0382; e-ISSN: 2477-3344 Odd Harmonious Labeling on Pleated of the Dutch Windmill Graphs Fery Firmansah1, Muhammad Ridlo Yuwono2 1, 2Mathematics Edu. Depart. University of Widya Dharma Klaten, Indonesia Email: [email protected], [email protected] ABSTRACT A graph 퐺(푉(퐺), 퐸(퐺)) is called graph 퐺(푝, 푞) if it has 푝 = |푉(퐺)| vertices and 푞 = |퐸(퐺)| edges. The graph 퐺(푝, 푞) is said to be odd harmonious if there exist an injection 푓: 푉(퐺) → {0,1,2, … ,2푞 − 1} such that the induced function 푓∗: 퐸(퐺) → {1,3,5, … ,2푞 − 1} defined by 푓∗(푢푣) = 푓(푢) + 푓(푣). The function 푓∗ is a bijection and 푓 is said to be odd harmonious labeling of 퐺(푝, 푞). In this paper we prove that pleated of the (푘) Dutch windmill graphs 퐶4 (푟) with 푘 ≥ 1 and 푟 ≥ 1 are odd harmonious graph. Moreover, we also give odd (푘) (푘) harmonious labeling construction for the union pleated of the Dutch windmill graph 퐶4 (푟) ∪ 퐶4 (푟) with 푘 ≥ 1 and 푟 ≥ 1. Keywords: odd harmonious labeling, pleated graph, the Dutch windmill graph INTRODUCTION In this paper we consider simple, finite, connected and undirected graph. A graph 퐺(푝, 푞) with 푝 = |푉(퐺)| vertices and 푞 = |퐸(퐺)| edges. A graph labeling which has often been motivated by practical problems is one of fascinating areas of research. Labeled graphs serves as useful mathematical models for many applications in coding theory, communication networks, and mobile telecommunication system. -
Strong Edge Graceful Labeling of Windmill Graphs ∑
International Journal of Mathematics Research. ISSN 0976-5840 Volume 5, Number 1 (2013), pp. 19-26 © International Research Publication House http://www.irphouse.com Strong Edge Graceful Labeling of Windmill Graphs Dr. M. Subbiah VKS College Of Engineering& Technology Desiyamangalam, Karur - 639120 [email protected]. Abstract A (p, q) graph G is said to have strong edge graceful labeling if there 3q exists an injection f from the edge set to 1,2, ... so that the 2 induced mapping f+ defined on the vertex set given by f x fxy xy EG mod 2p are distinct. A graph G is said to be strong edge graceful if it admits a strong edge graceful labeling. In this paper we investigate strong edge graceful labeling of Windmill graph. (n) Definition: The windmill graphs Km (n >3) to be the family of graphs consisting of n copies of Km with a vertex in common. (n) Theorem: 1. The windmill graph K4 is strong edge graceful for all n 3 when n is even. (n) Proof: Let {v1, v2, v3, ..., v3n, } be the vertices of K4 and {e1, e2, e3, ...,e3n- (n) 1, e3n, , f1, ,f2, ,f3, . .f3n-1, f3n. } be the edges of K4 which are denoted as in the following Fig. 1. 20 Dr. M. Subbiah . v e 3 3 n n -1 . -1 . v . 3 n f . 3 n -2 f 3 e n . 3 -1 n e 3 2 n n -2 f v v 3 3n 0 2 v 3 . n-2 f v 1 . 2 f 2 f 3 f . -
Three Topics in Online List Coloring∗
Three Topics in Online List Coloring∗ James Carraher†, Sarah Loeb‡, Thomas Mahoney‡, Gregory J. Puleo‡, Mu-Tsun Tsai‡, Douglas B. West§‡ February 15, 2013 Abstract In online list coloring (introduced by Zhu and by Schauz in 2009), on each round the set of vertices having a particular color in their lists is revealed, and the coloring algorithm chooses an independent subset to receive that color. The paint number of a graph G is the least k such that there is an algorithm to produce a successful coloring with no vertex being shown more than k times; it is at least the choice number. We study paintability of joins with complete or empty graphs, obtaining a partial result toward the paint analogue of Ohba’s Conjecture. We also determine upper and lower bounds on the paint number of complete bipartite graphs and characterize 3-paint- critical graphs. 1 Introduction The list version of graph coloring, introduced by Vizing [18] and Erd˝os–Rubin–Taylor [2], has now been studied in hundreds of papers. Instead of having the same colors available at each vertex, each vertex v has a set L(v) (called its list) of available colors. An L-coloring is a proper coloring f such that f(v) L(v) for each vertex v. A graph G is k-choosable if an ∈ L-coloring exists whenever L(v) k for all v V (G). The choosability or choice number | | ≥ ∈ χℓ(G) is the least k such that G is k-choosable. Since the lists at vertices could be identical, always χ(G) χ (G). -
A Survey of Graph Coloring - Its Types, Methods and Applications
FOUNDATIONS OF COMPUTING AND DECISION SCIENCES Vol. 37 (2012) No. 3 DOI: 10.2478/v10209-011-0012-y A SURVEY OF GRAPH COLORING - ITS TYPES, METHODS AND APPLICATIONS Piotr FORMANOWICZ1;2, Krzysztof TANA1 Abstract. Graph coloring is one of the best known, popular and extensively researched subject in the eld of graph theory, having many applications and con- jectures, which are still open and studied by various mathematicians and computer scientists along the world. In this paper we present a survey of graph coloring as an important subeld of graph theory, describing various methods of the coloring, and a list of problems and conjectures associated with them. Lastly, we turn our attention to cubic graphs, a class of graphs, which has been found to be very interesting to study and color. A brief review of graph coloring methods (in Polish) was given by Kubale in [32] and a more detailed one in a book by the same author. We extend this review and explore the eld of graph coloring further, describing various results obtained by other authors and show some interesting applications of this eld of graph theory. Keywords: graph coloring, vertex coloring, edge coloring, complexity, algorithms 1 Introduction Graph coloring is one of the most important, well-known and studied subelds of graph theory. An evidence of this can be found in various papers and books, in which the coloring is studied, and the problems and conjectures associated with this eld of research are being described and solved. Good examples of such works are [27] and [28]. In the following sections of this paper, we describe a brief history of graph coloring and give a tour through types of coloring, problems and conjectures associated with them, and applications. -
5Th Lecture : Modular Decomposition MPRI 2013–2014 Schedule A
5th Lecture : Modular decomposition MPRI 2013–2014 5th Lecture : Modular decomposition MPRI 2013–2014 Schedule 5th Lecture : Modular decomposition Introduction MPRI 2013–2014 Graph searches Michel Habib Applications of LBFS on structured graph classes [email protected] http://www.liafa.univ-Paris-Diderot.fr/~habib Chordal graphs Cograph recognition Sophie Germain, 22 octobre 2013 A nice conjecture 5th Lecture : Modular decomposition MPRI 2013–2014 5th Lecture : Modular decomposition MPRI 2013–2014 Introduction A hierarchy of graph models 1. Undirected graphs (graphes non orient´es) 2. Tournaments (Tournois), sometimes 2-circuits are allowed. 3. Signed graphs (Graphes sign´es) each edge is labelled + or - (for example friend or enemy) Examen le mardi 26 novembre de 9h `a12h 4. Oriented graphs (Graphes orient´es), each edge is given a Salle habituelle unique direction (no 2-circuits) An interesting subclass are the DAG Directed Acyclic Graphs (graphes sans circuit), for which the transitive closure is a partial order (ordre partiel) 5. Partial orders and comparability graphs an intersting particular case. Duality comparability – cocomparability (graphes de comparabilit´e– graphes d’incomparabilit´e) 6. Directed graphs or digraphs (Graphes dirig´es) 5th Lecture : Modular decomposition MPRI 2013–2014 5th Lecture : Modular decomposition MPRI 2013–2014 Introduction Introduction The problem has to be defined in each model and sometimes it could be hard. ◮ What is the right notion for a coloration in a directed graph ? For partial orders, comparability graphs or uncomparability graphs ◮ No directed cycle unicolored, seems to be the good one. the independant set and maximum clique problems are polynomial. ◮ It took 20 years to find the right notion of oriented matro¨ıd ◮ What is the right notion of treewidth for directed graphs ? ◮ Still an open question. -
Graphs with Flexible Labelings
Graphs with Flexible Labelings Georg Grasegger∗ Jan Legersk´yy Josef Schichoy For a flexible labeling of a graph, it is possible to construct infinitely many non-equivalent realizations keeping the distances of connected points con- stant. We give a combinatorial characterization of graphs that have flexible labelings, possibly non-generic. The characterization is based on colorings of the edges with restrictions on the cycles. Furthermore, we give necessary criteria and sufficient ones for the existence of such colorings. 1 Introduction Given a graph together with a labeling of its edges by positive real numbers, we are interested in the set of all functions from the set of vertices to the real plane such that the distance between any two connected vertices is equal to the label of the edge connecting them. Apparently, any such \realization" gives rise to infinitely many equivalent ones, by the action of the group of Euclidean congruence transformations. If the set of equivalence classes is finite and non-empty, then we say that the labeled graph is rigid; if this set is infinite, then we say that the labeling is flexible. The main result in this paper is a combinatorial characterization of graphs that have a flexible labeling. The characterization of graphs such that a generically chosen assign- ment of the vertices to the real plane gives a flexible labeling is classical: by a theorem of Geiringer-Pollaczek [8] which was rediscovered by Laman [6], this is true if the graph contains no Laman subgraph with the same set of vertices. Here, a graph G = (VG;EG) is called a Laman graph if and only if jEGj = 2jVGj − 3 and jEH j ≤ 2jVH j − 3 for any ∗Johann Radon Institute for Computational and Applied Mathematics (RICAM), Austrian Academy of Sciences arXiv:1708.05298v2 [math.CO] 19 Nov 2018 yResearch Institute for Symbolic Computation (RISC), Johannes Kepler University Linz This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk lodowska-Curie grant agreement No 675789. -
Tight Bounds for Online Edge Coloring
Tight Bounds for Online Edge Coloring Ilan Reuven Cohen∗1, Binghui Peng†‡2, and David Wajc§¶k3 1Carnegie Mellon University and University of Pittsburgh 2Tsinghua University 3Carnegie Mellon University Abstract Vizing’s celebrated theorem asserts that any graph of maximum degree ∆ admits an edge coloring using at most ∆ + 1 colors. In contrast, Bar-Noy, Motwani and Naor showed over a quarter century ago that the trivial greedy algorithm, which uses 2∆ 1 colors, is optimal among online algorithms. Their lower bound has a caveat, however: it− only applies to low- degree graphs, with ∆ = O(log n), and they conjectured the existence of online algorithms using ∆(1 + o(1)) colors for ∆= ω(log n). Progress towards resolving this conjecture was only made under stochastic arrivals (Aggarwal et al., FOCS’03 and Bahmani et al., SODA’10). We resolve the above conjecture for adversarial vertex arrivals in bipartite graphs, for which we present a (1+ o(1))∆-edge-coloring algorithm for ∆= ω(log n) known a priori. Surprisingly, if ∆ is not known ahead of time, we show that no e Ω(1) ∆-edge-coloring algorithm exists. e−1 − We then provide an optimal, e + o(1) ∆-edge-coloring algorithm for unknown ∆= ω(log n). e−1 Key to our results, and of possible independent interest, is a novel fractional relaxation for edge coloring, for which we present optimal fractional online algorithms and a near-lossless online rounding scheme, yielding our optimal randomized algorithms. ∗Email address: [email protected]. †Email address: [email protected]. ‡Work done in part while the author was visiting Carnegie Mellon University. -
Hamilton Cycle Heuristics in Hard Graphs (Under the Direction of Pro- Fessor Carla D
ABSTRACT SHIELDS, IAN BEAUMONT Hamilton Cycle Heuristics in Hard Graphs (Under the direction of Pro- fessor Carla D. Savage) In this thesis, we use computer methods to investigate Hamilton cycles and paths in several families of graphs where general results are incomplete, including Kneser graphs, cubic Cayley graphs and the middle two levels graph. We describe a novel heuristic which has proven useful in finding Hamilton cycles in these families and compare its performance to that of other algorithms and heuristics. We describe methods for handling very large graphs on personal computers. We also explore issues in reducing the possible number of generating sets for cubic Cayley graphs generated by three involutions. Hamilton Cycle Heuristics in Hard Graphs by Ian Beaumont Shields A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Computer Science Raleigh 2004 APPROVED BY: ii Dedication To my wife Pat, and my children, Catherine, Brendan and Michael, for their understanding during these years of study. To the memory of Hanna Neumann who introduced me to combinatorial group theory. iii Biography Ian Shields was born on March 10, 1949 in Melbourne, Australia. He grew up and attended school near the foot of the Dandenong ranges. After a short time in actuarial work he attended the Australian National University in Canberra, where he graduated in 1973 with first class honours in pure mathematics. Ian worked for IBM and other companies in Australia, Canada and the United States, before resuming part-time study for a Masters Degree in Computer Science at North Carolina State University which he received in May 1995. -
Are Highly Connected 1-Planar Graphs Hamiltonian? Arxiv:1911.02153V1 [Cs.DM] 6 Nov 2019
Are highly connected 1-planar graphs Hamiltonian? Therese Biedl Abstract It is well-known that every planar 4-connected graph has a Hamiltonian cycle. In this paper, we study the question whether every 1-planar 4-connected graph has a Hamiltonian cycle. We show that this is false in general, even for 5-connected graphs, but true if the graph has a 1-planar drawing where every region is a triangle. 1 Introduction Planar graphs are graphs that can be drawn without crossings. They have been one of the central areas of study in graph theory and graph algorithms, and there are numerous results both for how to solve problems more easily on planar graphs and how to draw planar graphs (see e.g. [1, 9, 10])). We are here interested in a theorem by Tutte [17] that states that every planar 4-connected graph has a Hamiltonian cycle (definitions are in the next section). This was an improvement over an earlier result by Whitney that proved the existence of a Hamiltonian cycle in a 4-connected triangulated planar graph. There have been many generalizations and improvements since; in particular we can additionally fix the endpoints and one edge that the Hamiltonian cycle must use [16, 12]. Also, 4-connected planar graphs remain Hamiltonian even after deleting 2 vertices [14]. Hamiltonian cycles in planar graphs can be computed in linear time; this is quite straightforward if the graph is triangulated [2] and a bit more involved for general 4-connected planar graphs [5]. There are many graphs that are near-planar, i.e., that are \close" to planar graphs. -
Math.RA] 25 Sep 2013 Previous Paper [3], Also Relying in Conceptually Separated Tools from Them, Such As Graphs and Digraphs
Certain particular families of graphicable algebras Juan Núñez, María Luisa Rodríguez-Arévalo and María Trinidad Villar Dpto. Geometría y Topología. Facultad de Matemáticas. Universidad de Sevilla. Apdo. 1160. 41080-Sevilla, Spain. [email protected] [email protected] [email protected] Abstract In this paper, we introduce some particular families of graphicable algebras obtained by following a relatively new line of research, ini- tiated previously by some of the authors. It consists of the use of certain objects of Discrete Mathematics, mainly graphs and digraphs, to facilitate the study of graphicable algebras, which are a subset of evolution algebras. 2010 Mathematics Subject Classification: 17D99; 05C20; 05C50. Keywords: Graphicable algebras; evolution algebras; graphs. Introduction The main goal of this paper is to advance in the research of a novel mathematical topic emerged not long ago, the evolution algebras in general, and the graphicable algebras (a subset of them) in particular, in order to obtain new results starting from those by Tian (see [4, 5]) and others already obtained by some of us in a arXiv:1309.6469v1 [math.RA] 25 Sep 2013 previous paper [3], also relying in conceptually separated tools from them, such as graphs and digraphs. Concretely, our goal is to find some particular types of graphicable algebras associated with well-known types of graphs. The motivation to deal with evolution algebras in general and graphicable al- gebras in particular is due to the fact that at present, the study of these algebras is very booming, due to the numerous connections between them and many other branches of Mathematics, such as Graph Theory, Group Theory, Markov pro- cesses, dynamic systems and the Theory of Knots, among others. -
Algorithms for Generating Star and Path of Graphs Using BFS Dr
Web Site: www.ijettcs.org Email: [email protected], [email protected] Volume 1, Issue 3, September – October 2012 ISSN 2278-6856 Algorithms for Generating Star and Path of Graphs using BFS Dr. H. B. Walikar2, Ravikumar H. Roogi1, Shreedevi V. Shindhe3, Ishwar. B4 2,4Prof. Dept of Computer Science, Karnatak University, Dharwad, 1,3Research Scholars, Dept of Computer Science, Karnatak University, Dharwad Abstract: In this paper we deal with BFS algorithm by 1.8 Diamond Graph: modifying it with some conditions and proper labeling of The diamond graph is the simple graph on nodes and vertices which results edges illustrated Fig.7. [2] and on applying it to some small basic 1.9 Paw Graph: class of graphs. The BFS algorithm has to modify The paw graph is the -pan graph, which is also accordingly. Some graphs will result in and by direct application of BFS where some need modifications isomorphic to the -tadpole graph. Fig.8 [2] in the algorithm. The BFS algorithm starts with a root vertex 1.10 Gem Graph: called start vertex. The resulted output tree structure will be The gem graph is the fan graph illustrated Fig.9 [2] in the form of Structure or in Structure. 1.11 Dart Graph: Keywords: BFS, Graph, Star, Path. The dart graph is the -vertex graph illustrated Fig.10.[2] 1.12 Tetrahedral Graph: 1. INTRODUCTION The tetrahedral graph is the Platonic graph that is the 1.1 Graph: unique polyhedral graph on four nodes which is also the A graph is a finite collection of objects called vertices complete graph and therefore also the wheel graph .