# Discrete Mathematics and Combinatorics Commons™

960 Full-Text Articles 1,121 Authors 104,022 Downloads 95 Institutions

## All Articles in Discrete Mathematics and Combinatorics

960 full-text articles. Page 1 of 36.

List-Distinguishing Cartesian Products Of Cliques, 2019 University of Colorado, Denver

#### List-Distinguishing Cartesian Products Of Cliques, Michael Ferrara, Zoltan Füredi, Sogol Jahanbekam, Paul Wenger

##### Sogol Jahanbekam

The distinguishing number of a graph G, denoted D(G), is the minimum number of colors needed to produce a coloring of the vertices of G so that every nontrivial isomorphism interchanges vertices of different colors. A list assignment L on a graph G is a function that assigns each vertex of G a set of colors. An L-coloring of G is a coloring in which each vertex is colored with a color from L(v). The list distinguishing number of G, denoted Dℓ(G) is the minimum k such that every list assignment L that assigns a list ...

The Determinant And Complex Gershgorin Circles, 2019 Hamburg University of Technology

#### The Determinant And Complex Gershgorin Circles, Florian Bünger, Siegfried M. Rump 428783027

##### Electronic Journal of Linear Algebra

Each connected component of the Gershgorin circles of a matrix contains exactly as many eigenvalues as circles are involved. Thus, the Minkowski (set) product of all circles contains the determinant if all circles are disjoint. In [S.M. Rump. Bounds for the determinant by Gershgorin circles. Linear Algebra and its Applications, 563:215--219, 2019.], it was proved that statement to be true for real matrices whose circles need not to be disjoint. Moreover, it was asked whether the statement remains true for complex matrices. This note answers that in the affirmative. As a by-product, a parameterization of the outer loop ...

On The Intersection Number Of Finite Groups, 2019 University of Texas at Tyler

#### On The Intersection Number Of Finite Groups, Humberto Bautista Serrano

##### Math Theses

Let G be a finite, nontrivial group. In a paper in 1994, Cohn defined the covering number of a finite group as the minimum number of nontrivial proper subgroups whose union is equal to the whole group. This concept has received considerable attention lately, mainly due to the importance of recent discoveries. In this thesis we study a dual concept to the covering number. We define the intersection number of a finite group as the minimum number of maximal subgroups whose intersection is equal to the Frattini subgroup. Similarly we define the inconjugate intersection number of a finite group as ...

Behind The Tiles: Mathematics Of Carcassonne, 2019 Merrimack College

#### Behind The Tiles: Mathematics Of Carcassonne, Emilia Dewyngaert

##### Across the Bridge: The Merrimack Undergraduate Research Journal

Carcassonne is a tile-placing game where players take turns choosing a tile from a stack and attempting to create a city, road or a meadow. In addition to this, there is a river expansion pack that has river tiles to be placed. This paper focuses on how many different layouts or configurations of the river expansion pack can be created. It also discusses the Matlab code adapted to create a simulation of possible configurations of the river expansion pack.

Maximum Oriented Forcing Number For Complete Graphs, 2019 University of Haifa-Oranim

#### Maximum Oriented Forcing Number For Complete Graphs, Yair Caro, Ryan Pepper

##### Theory and Applications of Graphs

The \emph{maximum oriented $k$-forcing number} of a simple graph $G$, written $\MOF_k(G)$, is the maximum \emph{directed $k$-forcing number} among all orientations of $G$. This invariant was recently introduced by Caro, Davila and Pepper in~\cite{CaroDavilaPepper}, and in the current paper we study the special case where $G$ is the complete graph with order $n$, denoted $K_n$. While $\MOF_k(G)$ is an invariant for the underlying simple graph $G$, $\MOF_k(K_n)$ can also be interpreted as an interesting property for tournaments. Our main results further focus on the case when $k=1$. These include a ...

Proof Of A Conjecture Of Graham And Lovasz Concerning Unimodality Of Coefficients Of The Distance Characteristic Polynomial Of A Tree, 2019 Iowa State University

#### Proof Of A Conjecture Of Graham And Lovasz Concerning Unimodality Of Coefficients Of The Distance Characteristic Polynomial Of A Tree, Ghodratollah Aalipour, Aida Abiad, Zhanar Berikkyzy, Leslie Hogben, Franklin H.J. Kenter, Jephian C.-H. Lin, Michael Tait

##### Leslie Hogben

The conjecture of Graham and Lov ́asz that the (normalized) coefficients of the distance characteristic polynomial of a tree are unimodal is proved; it is also shown that the (normalized) coefficients are log-concave. Upper and lower bounds on the location of the peak are established.

Multi-Part Nordhaus-Gaddum Type Problems For Tree-Width, Colin De Verdière Type Parameters, And Hadwiger Number, 2019 Iowa State University and American Institute of Mathematics

#### Multi-Part Nordhaus-Gaddum Type Problems For Tree-Width, Colin De Verdière Type Parameters, And Hadwiger Number, Leslie Hogben, Jephian C.-H. Lin, Michael Young

##### Leslie Hogben

A traditional Nordhaus-Gaddum problem for a graph parameter β is to find a (tight) upper or lower bound on the sum or product of β(G)and β(G¯) (where G¯ denotes the complement of G). An r-decomposition G1,…,Gr of the complete graph Kn is a partition of the edges of Kn among r spanning subgraphs G1,…,Gr. A traditional Nordhaus-Gaddum problem can be viewed as the special case for r=2 of a more general r-part sum or product Nordhaus-Gaddum type problem. We determine the values of the r-part sum and product upper bounds asymptotically as n goes ...

Graphs That Are Cospectral For The Distance Laplacian, 2019 Rice University

#### Graphs That Are Cospectral For The Distance Laplacian, Boris Brimkov, Ken Duna, Leslie Hogben, Kate Lorenzen, Carolyn Reinhart, Sung-Yell Song, Mark Yarrow

##### Leslie Hogben

The distance matrix D(G) of a graph G is the matrix containing the pairwise distances between vertices, and the distance Laplacian matrix is DL(G)=T(G)−D(G), where T(G) is the diagonal matrix of row sums of D(G). We establish several general methods for producing DL-cospectral graphs that can be used to construct infinite families. We provide examples showing that various properties are not preserved by DL-cospectrality, including examples of DL-cospectral strongly regular and circulant graphs. We establish that the absolute values of coefficients of the distance Laplacian characteristic polynomial ...

Cop Throttling Number: Bounds, Values, And Variants, 2019 Ryerson University

#### Cop Throttling Number: Bounds, Values, And Variants, Anthony Bonato, Jane Breen, Boris Brimkov, Joshua Carlson, Sean English, Jesse Geneson, Leslie Hogben, K. E. Perry, Carolyn Reinhart

##### Leslie Hogben

The cop throttling number thc(G) of a graph G for the game of Cops and Robbers is the minimum of k+captk(G), where k is the number of cops and captk(G) is the minimum number of rounds needed for k cops to capture the robber on G over all possible games in which both players play optimally. In this paper, we answer in the negative a question from [Breen et al., Throttling for the game of Cops and Robbers on graphs, {\em Discrete Math.}, 341 (2018) 2418--2430.] about whether the cop throttling number of any graph is ...

2019 Iowa State University

#### Nordhaus-Gaddum Problems For Colin De Verdière Type Parameters, Variants Of Tree-Width, And Related Parameters, Leslie Hogben

##### Leslie Hogben

A Nordhaus-Gaddum problem for a graph parameter is to determine a tight lower or upper bound for the sum or product of the parameter evaluated on a graph and on its complement. This article surveys Nordhaus-Gaddum results for the Colin de Verdiere type parameters mu, nu, and xi; tree-width and its variants largeur d'arborescence, path-width, and proper path-width; and minor monotone ceilings of vertex connectivity and minimum degree.

Spn Graphs And Rank-1 Cp-Completable Graphs, 2019 Iowa State University

#### Spn Graphs And Rank-1 Cp-Completable Graphs, Leslie Hogben, Naomi Shaked-Monderer

##### Leslie Hogben

A simple graph G is an SPN graph if every copositive matrix having graph G is the sum of a positive semidefinite and nonnegative matrix. SPN graphs were introduced in [Shaked-Monderer, SPN graphs: When copositive = SPN, Linear Algebra Appl., 509(15):82-113, 2016], where it was conjectured that the complete subdivision graph of K4 is an SPN graph. We disprove this conjecture, which in conjunction with results in the Shaked-Monderer paper show that a subdivision of K4 is a SPN graph if and only if at most one edge is subdivided. We conjecture that a graph is an SPN graph ...

Zero Forcing And Maximum Nullity For Hypergraphs, 2019 Iowa State University and American Institute of Mathematics

#### Zero Forcing And Maximum Nullity For Hypergraphs, Leslie Hogben

##### Leslie Hogben

The concept of zero forcing is extended from graphs to uniform hypergraphs in analogy with the way zero forcing was defined as an upper bound for the maximum nullity of the family of symmetric matrices whose nonzero pattern of entries is described by a given graph: A family of symmetric hypermatrices is associated with a uniform hypergraph and zeros are forced in a null vector. The value of the hypergraph zero forcing number and maximum nullity are determined for various families of uniform hypergraphs and the effects of several graph operations on the hypergraph zero forcing number are determined. The ...

Rigid Linkages And Partial Zero Forcing, 2019 Texas State University - San Marcos

#### Rigid Linkages And Partial Zero Forcing, Daniela Ferrero, Mary Flagg, H. Tracy Hall, Leslie Hogben, Jephian C.-H. Lin, Seth A. Meyer, Shahla Nasserasr, Bryan Shader

##### Leslie Hogben

Connections between vital linkages and zero forcing are established. Specifically, the notion of a rigid linkage is introduced as a special kind of unique linkage and it is shown that spanning forcing paths of a zero forcing process form a spanning rigid linkage and thus a vital linkage. A related generalization of zero forcing that produces a rigid linkage via a coloring process is developed. One of the motivations for introducing zero forcing is to provide an upper bound on the maximum multiplicity of an eigenvalue among the real symmetric matrices described by a graph. Rigid linkages and a related ...

The Inverse Eigenvalue Problem Of A Graph: Multiplicities And Minors, 2019 Brigham Young University

#### The Inverse Eigenvalue Problem Of A Graph: Multiplicities And Minors, Wayne Barrett, Steve Butler, Shaun M. Fallat, H. Tracy Hall, Leslie Hogben, Jephian C.-H. Lin, Bryan L. Shader, Michael Young

##### Leslie Hogben

The inverse eigenvalue problem of a given graph G is to determine all possible spectra of real symmetric matrices whose off-diagonal entries are governed by the adjacencies in G. Barrett et al. introduced the Strong Spectral Property (SSP) and the Strong Multiplicity Property (SMP) in [8]. In that paper it was shown that if a graph has a matrix with the SSP (or the SMP) then a supergraph has a matrix with the same spectrum (or ordered multiplicity list) augmented with simple eigenvalues if necessary, that is, subgraph monotonicity. In this paper we extend this to a form of minor ...

The Principal Rank Characteristic Sequence Over Various Fields, 2019 Brigham Young University

#### The Principal Rank Characteristic Sequence Over Various Fields, Wayne Barrett, Steve Butler, Minerva Catral, Shaun M. Fallat, H. Tracy Hall, Leslie Hogben, P. Van Den Driessche, Michael Young

##### Leslie Hogben

Given an n x n matrix, its principal rank characteristic sequence is a sequence of length n+1 of 0s and 1s where, for k = 0, 1, . . . , n, a 1 in the kth position indicates the existence of a principal submatrix of rank k and a 0 indicates the absence of such a submatrix. The principal rank characteristic sequences for symmetric matrices over various fields are investigated, with all such attainable sequences determined for all n over any field with characteristic 2. A complete list of attainable sequences for real symmetric matrices of order 7 is reported.

Matching Preclusion Of The Generalized Petersen Graph, 2019 Novi High School

#### Matching Preclusion Of The Generalized Petersen Graph, Ajay Arora, Eddie Cheng, Christopher Melekian

##### Theory and Applications of Graphs

The matching preclusion number of a graph with an even number of vertices is the minimum number of edges whose deletion results in a graph with no perfect matchings. In this paper we determine the matching preclusion number for the generalized Petersen graph $P(n,k)$ and classify the optimal sets.

Perfect Double Roman Domination Of Trees, 2019 East Tennessee State University

#### Perfect Double Roman Domination Of Trees, Ayotunde Egunjobi

##### Electronic Theses and Dissertations

See supplemental content for abstract

2019 East Tennessee State University

#### Taking Notes: Generating Twelve-Tone Music With Mathematics, Nathan Molder

##### Electronic Theses and Dissertations

There has often been a connection between music and mathematics. The world of musical composition is full of combinations of orderings of diﬀerent musical notes, each of which has diﬀerent sound quality, length, and em phasis. One of the more intricate composition styles is twelve-tone music, where twelve unique notes (up to octave isomorphism) must be used before they can be repeated. In this thesis, we aim to show multiple ways in which mathematics can be used directly to compose twelve-tone musical scores.

2019 University of Lynchburg

#### Mathematical Models: The Lanchester Equations And The Zombie Apocalypse, Hailey Bauer

##### Undergraduate Theses and Capstone Projects

This research study used mathematical models to analyze and depicted specific battle situations and the outcomes of the zombie apocalypse. The original models that predicted warfare were the Lanchester models, while the zombie apocalypse models were fictional expansions upon mathematical models used to examine infectious diseases. In this paper, I analyzed and compared different mathematical models by examining each model’s set of assumptions and the impact of the change in variables on the population classes. The purpose of this study was to understand the basics of the discrete dynamical systems and to determine the similarities between imaginary and realistic ...

Series-Parallel Operations With Alpha-Graphs, 2019 Valencia College

#### Series-Parallel Operations With Alpha-Graphs, Christian Barrientos, Sarah Minion

##### Theory and Applications of Graphs

Among difference vertex labelings of graphs, $\alpha$-labelings are the most restrictive one. A graph is an $\alpha$-graph if it admits an $\alpha$-labeling. In this work, we study a new alternative to construct $\alpha$-graphs using, the well-known, series-parallel operations on smaller $\alpha$-graphs. As an application of the series operation, we show that all members of a subfamily of all trees with maximum degree 4, obtained using vertex amalgamation of copies of the path $P_{11}$, are $\alpha$-graphs. We also show that the one-point union of up to four copies of $K_{n,n}$ is an ...