Timothy M. Brauch1, André E. Kézdy1, Hunter S. Snevily2
1Department of Mathematics University of Louisville Louisville, KY 40292 USA
2Department of Mathematics University of Idaho Moscow, ID 83844 USA
Abstract:

The paper begins with a simple circular lock problem that shows how the Combinatorial Nullstellensatz relates to the discrete Fourier Transform.Specifically, the lock shows a relationship between detecting perfect matchings in bipartite graphs using the Combinatorial Nullstellensatz and detecting a maximum rank independent set in the intersection of two matroids in the Fourier transform of a specially chosen function. Finally, an application of the uncertainity principle computes a lower bound for the product of perfect matchings and the number of independent sets.

Gek L. Chia1, Angeline P.L. Lee1
1Institute of Mathematical Sciences University of Malaya 50603 Kuala Lumpur Malaysia
Abstract:

A \({magic\; square}\) of order \(n\) is an \(n \times n\) array of integers from \(1, 2, \ldots, n^2\) such that the sum of the integers in each row, column, and diagonal is the same number. Two magic squares are \({equivalent}\) if one can be obtained from the other by rotation or reflection. The \({complement}\) of a magic square \(M\) of order \(n\) is obtained by replacing every entry \(a\) with \(n^2 + 1 – a\), yielding another magic square. A magic square is \({self-complementary}\) if it is equivalent to its complement. In this paper, we prove a structural theorem characterizing self-complementary magic squares and present a method for constructing self-complementary magic squares of even order. Combining this construction with the structural theorem and known results on magic squares, we establish the existence of self-complementary magic squares of order \(n\) for every \(n \geq 3\).

Emlee W. Nicholson1,2, Bing Wei1
1Department of Mathematics, University of Mississippi University, MS 38677, USA
2Winthrop University Department of Mathematics Rock Hill, SC 29788, USA
Abstract:

Let \(G\) be a graph on \(n\) vertices. If for any ordered set of vertices \(S = \{v_1, v_2, \ldots, v_k\}\), where the vertices in \(S\) appear in the sequence order \(v_1, v_2, \ldots, v_k\), there exists a \(v_1-v_k\) (Hamiltonian) path containing \(S\) in the given order, then \(G\) is \(k\)-ordered (Hamiltonian) connected. In this paper, we show that if \(G\) is \((k+1)\)-connected and \(k\)-ordered connected, then for any ordered set \(S\), there exists a \(v_1-v_k\) path \(P\) containing \(S\) in the given order such that \(|P| \geq \min\{n, \sigma_2(G) – 1\}\), where \(\sigma_2(G) = \min\{d_G(u) + d_G(v) : u,v \in V(G); uv \notin E(G)\}\) when \(G\) is not complete, and \(\sigma_2(G) = \infty\) otherwise. Our result generalizes several related results known before.

Weizhong Wang1,2, Yanfeng Luo3, Xing Gao3
1 Department of mathematics, Lanzhou University, Lanzhou 730000, PR China
2Department of mathematics, Lanzhou Jiaotong University, Lanzhou 730070, PR China
3Department of mathematics, Lanzhou University, Lanzhou 730000, PR China
Abstract:

Let \(G\) be a simple graph. The incidence energy ( \(IE\) for short ) of \(G\) is defined as the sum of the singular values of the incidence matrix. In this paper, a new lower bound for \(IE\) of graphs in terms of the maximum degree is given. Meanwhile, an upper bound and a lower bound for \(IE\) of the subdivision graph and the total graph of a regular graph \(G\) are obtained, respectively.

Shou-Jun Xu1, Hai-Yang Chen1, Qiu-Xia Zhang1, Liangping Tu2
1School of Mathematics and Statistics, Lanzhou University, Lanzhou, Gansu 780000, China
2School of Science, University of Science and Technology, Anshan, Liaoning 114051, China
Abstract:

The Hosoya polynomial of a graph \(G\) with vertex set \(V(G)\) is defined as \(H(G, z) = \sum_{u,v \in V(G)} x^{d_G(u,v)}\), where \(d_G(u,v)\) is the distance between vertices \(u\) and \(v\). A toroidal polyhex \(H(p,q,t)\) is a cubic bipartite graph embedded on the torus such that each face is a hexagon, described by a string \((p,q,t)\) of three integers \((p \geq 2, q \geq 1, 0 \leq t \leq p-1)\). In this paper, we derive an analytical formula for calculating the Hosoya polynomial of \(H(p,q,t)\) for \(t = 0\) or \(p\leq 2q\) or \(p \leq q+t\). Notably, some earlier results in [2, 6, 26] are direct corollaries of our main findings.

Elizabeth Moseman1, Christopher Storm2
1Department of Mathematical Sciences, United States Military Academy at West Point,
2Department of Mathematics and Computer Science, Adelphi University,
Abstract:

Kotani and Sunada introduced the oriented line graph as a tool in the study of the Ihara zeta function of a finite graph. The spectral properties of the adjacency operator on the oriented line graph can be linked to the Ramanujan condition of the graph. Here, we present a partial characterization of oriented line graphs in terms of forbidden subgraphs. We also give a Whitney-type result, as a special case of a result by Balof and Storm, establishing that if two graphs have the same oriented line graph, they are isomorphic.

Shu-Guang Guo1, Meiling Xu1,2, Guanglong Yu1
1Department of Mathematics, Yancheng Teachers University, Yancheng, 224002, Jiangsu, P.R. China
2Department of Mathematics, Jiangsu Normal University, Xuzhou, 221116, Jiangsu, P.R. China
Abstract:

Let \(A\) be the \((0,1)\)-adjacency matrix of a simple graph \(G\), and \(D\) be the diagonal matrix \(diag(d_1, d_2, \ldots, d_n)\), where \(d_i\) is the degree of the vertex \(v_i\). The matrix \(Q(G) = D + A\) is called the signless Laplacian of \(G\). In this paper, we characterize the extremal graph for which the least signless Laplacian eigenvalue attains its minimum among all non-bipartite unicyclic graphs with given order and diameter.

M.A. Javed1, M. Aslam1
1Department of Mathematics GC University, Lahore, Pakistan
Abstract:

In this paper, we investigate some commutativity conditions and extend a remarkable result of Ram Awtar, when Lie ideal \(U\) becomes the part of the centre of \(M\) \(A\)-semiring \(R\).

Yongsheng Ye1, Mei Liu1, Jie Gao1
1School of Mathematical Sciences, Huaibei Normal University, Huaibei, Anhui, 235000, China
Abstract:

A pebbling move involves removing two pebbles from one vertex and placing one on an adjacent vertex. The optimal pebbling number of a graph \(G\), denoted by \(f_{opt}(G)\), is the least positive integer \(n\) such that \(n\) pebbles are placed suitably on vertices of \(G\) and, for any specified vertex \(v\) of \(G\), one pebble can be moved to \(v\) through a sequence of pebbling moves. In this paper, we determine the optimal pebbling number of the square of paths and cycles.

Jingjing Tian1, Xin Zhang2
1Department of Applied Mathematics Northwestern Polytechnical University, Xi’an 710072, P.R. China
2Department of Mathematics Xidian University, Xi’an 710071, PR. China
Abstract:

In this paper, we verify the list edge coloring conjecture for pseudo- outerplanar graphs with maximum degree at least \(5\) and the equitable \(\Delta\)-coloring conjecture for all pseudo-outerplanar graphs.

Zbigniew R. Bogdanowicz1
1Armament Research, Development and Engineering Center Picatinny, New Jersey 07806, U.S.A.
Abstract:

We prove that the Cartesian product of two directed cycles of lengths \(n_1\) and \(n_2\) contains an antidirected Hamilton cycle, and hence is decomposable into antidirected Hamilton cycles, if and only if \(\gcd(n_1, n_2) = 2\). For the Cartesian product of \(k > 2\) directed cycles, we establish new sufficient conditions for the existence of an antidirected Hamilton cycle.

Yiqiao Wang1
1School of Management, Beijing University of Chinese Medicine, Beijing 100029, China
Abstract:

Let \(T\) be a tree with no vertices of degree \(2\) and at least one vertex of degree \(3\) or more. A Halin graph \(G\) is a plane graph obtained by connecting the leaves of \(T\) in the cyclic order determined by the planar drawing of \(T\). Let \(\Delta\), \(\lambda(G)\), and \(\chi(G^2)\) denote, respectively, the maximum degree, the \(L(2,1)\)-labeling number, and the chromatic number of the square of \(G\). In this paper, we prove the following results for any Halin graph \(G\): (1) \(\chi(G^2) \leq \Delta + 3\), and moreover \(\chi(G^2) = \Delta + 1\) if \(\Delta \geq 6\); (2) \(\lambda(G) \leq \Delta + 7\), and moreover \(\lambda(G) \leq \Delta + 2\) if \(\Delta \geq 9\).

Hongxing Liu1
1School of Mathematical Sciences, Shandong Normal University, 250014, Jinan, P. R. China
Abstract:

In this paper, we investigate the zero divisor graph \(G_I(P)\) of a poset \(P\) with respect to a semi-ideal \(I\). We show that the girth of \(G_I(P)\) is \(3\), \(4\), or \(\infty\). In addition, it is shown that the diameter of such a graph is either \(1\), \(2\), or \(3\). Moreover, we investigate the properties of a cut vertex in \(G_I(P)\) and study the relation between semi-ideal \(I\) and the graph \(G_I(P)\), as established in (Theorem 3.9).

Yingzhi Tian1, Jixiang Meng1
1College of Mathematics and System Sciences, Xinjiang University, Urumdi, Xinjiang, 830046, Peoples Republic of China.
Abstract:

A graph \(G\) is \({super-connected}\), or \({super-\(\kappa\)}\), if every minimum vertex-cut isolates a vertex of \(G\). Similarly, \(G\) is \({super-restricted \;edge-connected}\), or \({super-\(\lambda’\)}\), if every minimum restricted edge-cut isolates an edge. We consider the total graph \(T(G)\) of \(G\), which is formed by combining the disjoint union of \(G\) and the line graph \(L(G)\) with the lines of the subdivision graph \(S(G)\); for each line \(l = (u,v)\) in \(G\), there are two lines in \(S(G)\), namely \((l,u)\) and \((l,v)\). In this paper, we prove that \(T(G)\) is super-\(\kappa\) if \(G\) is super-\(\kappa\) graph with \(\delta(G) \geq 4\). \(T(G)\) is super-\(\lambda’\) if \(G\) is \(k\)-regular with \(\kappa(G) \geq 3\). Furthermore, we provide examples demonstrating that these results are best possible.

Yunsheng Zhang 1, Yichao Chen2
1BUSINESS SCHOOL, HUNAN UNIVERSITY, 410082 CHANGSHA, CHINA
2COLLEGE OF MATHEMATICS AND ECONOMETRICS, HUNAN UNIVERSITY, 410082 CHanc- SHA, CHINA
Abstract:

The paper construct infinite classes of non-isomorphic \(3\)-connected simple graphs with the same total genus polynomial, using overlap matrix, symmetry and Gustin representation. This answers a problem (Problem \(3\) of Page \(38\)) of L.A. McGeoch in his PHD thesis.
The result is helpful for firms to make marketing decisions by calculating the graphs of user demand relationships of different complex ecosystems of platform products and comparing genus polynomials.

Xu Liping1, Liu Zhishan2, Li Zhi1
1School of Mathematics, Yangtze University, Jingzhou 434023, P.R.China.
2Yang-En University, Quanzhou, 362014, P.R.China.
Abstract:

A necessary and sufficient condition of the complement to be cordial and its application are obtained.

Sapna Jain1
1Department of Mathematics University of Delhi Delhi 110 007 India
Abstract:

In this paper, we introduce the notion of blockwise-bursts in array codes equippped with m-metric \([13]\) and obtain some bounds on the parameters of $m$-metric array codes for the detection and correction of blockwise-burst array errors.

Sizhong Zhou1
1School of Mathematics and Physics Jiangsu University of Science and Technology Mengxi Road 2, Zhenjiang, Jiangsu 212003 People’s Republic of China
Abstract:

Let \(G\) be a graph, and let \(a\) and \(b\) be integers with \(1 \leq a \leq b\). An \([a, b]\)-factor of \(G\) is defined as a spanning subgraph \(F\) of \(G\) such that \(a \leq d_F(v) \leq b\) for each \(v \in V(G)\). In this paper, we obtain a sufficient condition for a graph to have \([a, b]\)-factors including given edges, extending a well-known sufficient condition for the existence of a \(k\)-factor.

Saeid Alikhani1,2, Yee-hock Peng2,3
1Department of Mathematics, Faculty of Science Shiraz University of Technology 71555-318, Shiraz, Iran
2Institute for Mathematical Research, and University Putra Malaysia, 48400 UPM Serdang, Malaysia
3Department of Mathematics, University Putra Malaysia, 48400 UPM Serdang, Malaysia
Abstract:

We introduce the domination polynomial of a graph \(G\). The domination polynomial of a graph \(G\) of order \(n\) is defined as \(D(G, x) = \sum_{i=\gamma(G)}^{n} d(G, i)x^i\), where \(d(G, i)\) is the number of dominating sets of \(G\) of size \(i\), and \(\gamma(G)\) is the domination number of \(G\). We obtain some properties of \(D(G, x)\) and its coefficients, and compute this polynomial for specific graphs.

Masao Tsugaki 1, Yao Zhang1
1Academy of Mathematics and Systems Science Chinese Academy of Sciences, Beijing 100190, China
Abstract:

For a tree \(T\), \(Leaf(T)\) denotes the set of leaves of \(T\), and \(T – Leaf(T)\) is called the stem of \(T\). For a graph \(G\) and a positive integer \(m\), \(\sigma_m(G)\) denotes the minimum degree sum of \(m\) independent vertices of \(G\). We prove the following theorem: Let \(G\) be a connected graph and \(k \geq 2\) be an integer. If \(\sigma_3(G) \geq |G| – 2k + 1\), then \(G\) has a spanning tree whose stem has at most \(k\) leaves.

Zhidan Yan1, Wei Wang1
1College of Information Engineering, Tarim University, Alar, Xinjiang, 843300, P.R.China
Abstract:

A proper vertex coloring of a graph is equitable if the sizes of color classes differ by at most \(1\). The equitable chromatic threshold of a graph \(G\), denoted by \(\chi_m^*(G)\), is the minimum \(k\) such that \(G\) is equitably \(k’\)-colorable for all \(k’ > k\). Let \(G \times H\) denote the direct product of graphs \(G\) and \(H\). For \(n \geq m \geq 2\), we prove that \(\chi_m^*(K_m \times K_n)\) equals \(\left\lceil \frac{mn}{m+1} \right\rceil\) if \(n \equiv 2, \ldots, m \pmod{m+1}\), and equals \(m\left\lceil \frac{n}{s^*} \right\rceil\) if \(n \equiv 0, 1 \pmod{m+1}\), where \(s^*\) is the minimum positive integer such that \(s^* \nmid n\) and \(s^* \geq m+2\).

Salvatore Milici1, Gaetano Quattrocchi1, Zsolt Tuza2
1Department of Mathematics, University of Catania, viale A. Doria, 6, 95125 Cata- nia, Italy
2Alfréd Rényi Institute of Mathematics, Hungarian Academy of Sciences, Budapest ; and Department of Computer Science and Systems Technology, University of Pannonia, Veszprém, Hungary
Abstract:

For an undirected graph \(G\) and a natural number \(n\), a \(G\)-design of order \(n\) is an edge partition of the complete graph \(K_n\) with \(n\) vertices into subgraphs \(G_1, G_2, \ldots\), each isomorphic to \(G\). A set \(T \subset V(K_n)\) is called a blocking set if it intersects the vertex set \(V(G_i)\) of each \(G_i\) in the decomposition but contains none of them. Extending previous work [J. Combin. Designs \(4 (1996), 135-142]\), where the authors proved that cycle designs admit no blocking sets, we establish that this result holds for all graphs \(G\). Furthermore, we show that for every graph \(G\) and every integer \(k \geq 2\), there exists a non-\(k\)-colorable \(G\)-design.

Changqing Xu1, Jingjing Chang1
1Department of Applied Mathematics, Hebei University of Technology, Tianjin 300401 P. R. China
Abstract:

Let \(G\) be a planar graph with maximum degree \(\Delta(G)\). The least integer \(k\) such that \(G\) can be partitioned into \(k\) edge-disjoint forests, where each component is a path of length at most \(2\), is called the linear \(2\)-arboricity of \(G\), denoted by \(la_2(G)\). We establish new upper bounds for the linear \(2\)-arboricity of certain planar graphs.

Yaping Wu1,2, Qiong FAN2
1Faculty of Math.and Computer Jianghan University, Wuhan, China
2School of Math.and Statistics Central China Normal University, Wuhan, China
Abstract:

A graph \(G\) of order \(n\) is called a bicyclic graph if \(G\) is connected and the number of edges of \(G\) is \(n+ 1\). In this paper, we study the lexicographic ordering of bicyclic graphs by spectral moments. For each of the three basic types of bicyclic graphs on a fixed number of vertices maximal and minimal graphs in the mentioned order are determined.

Ali Ahmad1, Martin Baca2
1Abdus Salam School of Mathematical Sciences, GC University 68-B, New Muslim Town, Lahore, Pakistan
2Department of Appl. Mathematics, Technical University Letné 9, 042 00 Koiice, Slovak Republic
Abstract:

An edge irregular total \(k\)-labeling of a graph \(G = (V, E)\) is a labeling \(f: V \cup E \to \{1, 2, \ldots, k\}\) such that the total edge-weights \(wt(xy) = f(x) + f(xy) + f(y)\) are distinct for all pairs of distinct edges. The minimum \(k\) for which \(G\) has an edge irregular total \(k\)-labeling is called the total edge irregularity strength of \(G\). In this paper, we determine the exact value of the total edge irregularity strength of the Cartesian product of two paths \(P_n\) and \(P_m\). Our result provides further evidence supporting a recent conjecture of Ivančo and Jendrol.

Hengzhe Li1, Xueliang Li1, Yaping Mao1, Yuefang Sun1
1Center for Combinatorics and LPMC-TJKLC Nankai University, Tianjin 300071, China
Abstract:

For a vertex set \(S\) with cardinality at least \(2\) in a graph \(G\), a tree connecting \(S\), known as a Steiner tree or \(S\)-tree, is required. Two \(S\)-trees \(T\) and \(T’\) are internally disjoint if \(V(T) \cap V(T’) = S\) and \(E(T) \cap E(T’) = \emptyset\). Let \(\kappa_G(G)\) denote the maximum number of internally disjoint Steiner trees connecting \(S\) in \(G\). The generalized \(k\)-connectivity \(\kappa_k(G)\) of \(G\), introduced by Chartrand et al., is defined as \(\min_{S \subseteq V(G), |S|=k} \kappa_G(S)\). This paper establishes a sharp upper bound for generalized \(k\)-connectivity. Furthermore, graphs of order \(n\) with \(\kappa_3(G) = n-2,n-3\) are characterized.

Mitre C. Dourado1, Fabio Protti2, Jayme L. Szwarcfiter3
1ICE, Universidade Federal Rural do Rio de Janeiro and NCE, UFRJ, Brazil
2Instituto de Matematica and NCE, Universidade Federal do Rio de Janeiro, Brazil
3Instituto de Matematica, NCE and COPPE, Universidade Federal do Rio de Janeiro Caixa Postal 2324, 20001-970, Rio de Janeiro, RJ, Brasil.
Abstract:

A hypergraph \(\mathcal{H}\) is said to be \(p\)-Helly when every \(p\)-wise intersecting partial hypergraph \(\mathcal{H}’\) of \(H\) has nonempty total intersection. Such hypergraphs were characterized by Berge and Duchet in 1975, and since then they have appeared in various contexts, particularly for \(p=2\), where they are known as Helly hypergraphs. An interesting generalization due to Voloshin considers both the number of intersecting sets and their intersection sizes: a hypergraph \(\mathcal{H}\) is \((p,q,s)\)-Helly if every \(p\)-wise \(q\)-intersecting partial hypergraph \(\mathcal{H}’\) of \(H\) has total intersection of cardinality at least \(s\). This work proposes a characterization for \((p,q,s)\)-Helly hypergraphs, leading to an efficient algorithm for recognizing such hypergraphs when \(p\) and \(q\) are fixed parameters.

Naoki Matsumoto1, Kenta Noguchi2
1Graduate School of Environment and Information Sciences, Yokohama National Uni- versity, 79-1 Tokiwadai, Hodogaya-Ku, Yekohama 240-8501, Japan
2Department of Mathematics, Keio University, 3-14-1 Hiyoshi, Kohoku-Ku, Yoko- hama, 223-8522, Japan
Abstract:

A \(k\)-chromatic graph \(G\) is \(uniquely\) \(k\)-\(colorable\) if \(G\) has only one \(k\)-coloring up to permutation of the colors. In this paper, we focus on uniquely \(k\)-colorable graphs on surfaces. Let \({F}^2\) be a closed surface, excluding the sphere, and let \(\chi({F}^2)\) denote the maximum chromatic number of graphs embeddable on \({F}^2\). We shall prove that the number of uniquely \(k\)-colorable graphs on \({F}^2\) is finite if \(k \geq 5\), and characterize uniquely \(\chi({F}^2)\)-colorable graphs on \({F}^2\). Moreover, we completely determine uniquely \(k\)-colorable graphs on the projective plane for \(k \geq 5\).

Xu Han1, Zhiping Wang1, Xincui Wang1
1Department of Mathematics, Dalian Maritime University, 116026 Dalian, P.R. China
Abstract:

Given a distribution \(D\) of pebbles on the vertices of a graph \(G\), a pebbling move consists of removing two pebbles from a vertex and placing one on an adjacent vertex (the other is discarded). The pebbling number of a graph, denoted by \(f(G)\), is the minimal integer \(k\) such that any distribution of \(k\) pebbles on \(G\) allows one pebble to be moved to any specified vertex by a sequence of pebbling moves. In this paper, we calculate the pebbling number of the graph \(D_{n,C_m}\) and consider the relationship the pebbling number between the graph \(D_{n,C_m}\) and the subgraphs of \(D_{n,C_m}\).

S. Akbari1,2, M. Ghanbari1, S. Jahanbekam1
1Department of Mathematical Sciences, Sharif University of Technology
2School of Mathematics, Institute for Research in Fundamental Sciences (IPM)
Abstract:

Let \(G\) and \(H\) be two graphs. A proper vertex coloring of \(G\) is called a dynamic coloring if, for every vertex \(v\) with degree at least \(2\), the neighbors of \(v\) receive at least two different colors. The smallest integer \(k\) such that \(G\) has a dynamic coloring with \(k\) colors is denoted by \(\chi_2(G)\). We denote the Cartesian product of \(G\) and \(H\) by \(G \square H\). In this paper, we prove that if \(G\) and \(H\) are two graphs and \(\delta(G) \geq 2\), then \(\chi_2(G \square H) \leq \max(\chi_2(G), \chi(H))\). We show that for every two natural numbers \(m\) and \(n\), \(m, n \geq 2\), \(\chi_2(P_m \square P_n) = 4\). Additionally, among other results, it is shown that if \(3\mid mn\), then \(\chi_2(C_m \square C_n) = 3\), and otherwise \(\chi_2(C_m \square C_n) = 4\).

Lihua You1, Jieshan Yang1, Zhifu You2
1School of Mathematical Sciences, South China Normal University, Guangzhou, 510631, P.R. China
2Detartment of Computer Science, Guangdong Polytechnic Normal University, Guangzhou, 510665, P.R. China
Abstract:

In \([1]\), Hosam Abdo and Darko Dimitrov introduced the total irregularity of a graph. For a graph \(G\), it is defined as
\[\text{irr}_t(G) =\frac{1}{2} \sum_{{u,v} \in V(G)} |d_G(u) – d_G(v)|,\]
where \(d_G(u)\) denotes the vertex degree of a vertex \(u \in V(G)\). In this paper, we introduce two transformations to study the total irregularity of unicyclic graphs and determine the graph with the maximal total irregularity among all unicyclic graphs with \(n\) vertices.

Naiomi T. Cameron 1, Lynnell S. Matthews2
1Lewis & CLARK COLLEGE
2GETTYSBURG COLLEGE
Abstract:

We consider a variation on the Tennis Ball Problem studied by Mallows-Shapiro and Merlini, \(et \;al\). The solution to the original problem is the well known Catalan numbers, while the variations discussed in this paper yield the Motzkin numbers and other related sequences. For this variation, we present a generating function for the sum of the labels on the balls.

Liu Mu-huo1,2, Wei Fu-yi1, Bolian Liu2
1Department of Applied Mathematics, South China Agricultural University, Guangzhou, P. R. China, 510642
2College of Mathematic Science, South China Normal University, Guangzhou, P. R. China, 510631
Abstract:

A graph \(G\) of order \(n\) is called a tricyclic graph if \(G\) is connected and the number of edges of \(G\) is \(n + 2\). Let \(\mathcal{T}_n\) denote the set of all tricyclic graphs on \(n\) vertices. In this paper, we determine the first to nineteenth largest Laplacian spectral radii among all graphs in the class \(\mathcal{T}_n\) (for \(n \geq 11\)), together with the corresponding graphs.

Shuchao Li1, Zhongxun, Zhu2
1Faculty of Mathematics and Statistics, Central China Normal University, Wuhan 430079, P.R. China
2Department of Computer Science, South Central University for Nationalities, Wuhan 430074, P.R. China
Abstract:

The Hosoya index of a graph is defined as the total number of the matchings of the graph. In this paper, we determine the lower bounds for the Hosoya index of unicyclic graph with a given diameter. The corresponding extrenal graphs are characterized.

Dejan Delic 1, Changping Wang2
1DEPARTMENT OF MATHEMATICS, RYERSON UNIVERSITY, TORONTO, ON, CANADA, M5B 2K3
2DEPARTMENT OF MATHEMaTICS, RYERSON UnrversiTy, ToronTO, ON, CANADA, M5B 2K3
Abstract:

A subset \(S\) of vertices of a graph \(G\) is called a global connected dominating set if \(S\) is both a global dominating set and a connected dominating set. The global connected domination number, denoted by \(\gamma_{gc}(G)\), is the minimum cardinality of a global connected dominating set of \(G\). In this paper, sharp bounds for \(\gamma_{gc}\) are supplied, and all graphs attaining those bounds are characterized. We also characterize all graphs of order \(n\) with \(\gamma_{gc} = k\), where \(3 \leq k \leq n-1\). Exact values of this number for trees and cycles are presented as well.

Junli Liu1
1Math. and Inf. College, Langfang Teachers’ College, Langfang, 065000, China
Abstract:

Let \(\mathbb{F}_q^n\) denote the \(n\)-dimensional row vector space over the finite field \(\mathbb{F}_q\), where \(n \geq 2\). An \(l\)-partial linear map of \(\mathbb{F}_q^n\) is a pair \((V, f)\), where \(V\) is an \(l\)-dimensional subspace of \(\mathbb{F}_q^n\) and \(f: V \to \mathbb{F}_q^n\) is a linear map. Let \(\mathcal{L}\) be the set of all partial linear maps of \(\mathbb{F}_q^n\) containing \(1\). Ordered \(\mathcal{L}\) by ordinary and reverse inclusion, two families of finite posets are obtained. This paper proves that these posets are lattices, discusses their geometricity, and computes their characteristic polynomials.

Meirun Chen1, Shaohui Zhai1
1School of Applied Mathematics, Xiamen University of Technology, Xiamen Fujian 361024, China
Abstract:

A total coloring of a graph \(G\) is a coloring of both the edges and the vertices. A total coloring is proper if no two adjacent or incident elements receive the same color. An adjacent vertex-distinguishing total coloring \(h\) of a simple graph \(G = (V, E)\) is a proper total coloring of \(G\) such that \(H(u) \neq H(v)\) for any two adjacent vertices \(u\) and \(v\), where \(H(u) = \{h(wu) \mid wu \in E(G)\} \cup \{h(u)\}\) and \(H(v) = \{h(xv) \mid xv \in E(G)\} \cup \{h(v)\}\). The minimum number of colors required for a proper total coloring (resp. an adjacent vertex-distinguishing total coloring) of \(G\) is called the total chromatic number (resp. adjacent vertex-distinguishing total chromatic number) of \(G\) and denoted by \(\chi_t(G)\) (resp. \(\chi_{at}(G)\)). The Total Coloring Conjecture (TCC) states that for every simple graph \(G\), \(\chi(G) + 1 \leq \chi_t(G) \leq \Delta(G) + 2\). \(G\) is called Type 1 (resp. Type 2) if \(\chi_t(G) = \Delta(G) + 1\) (resp. \(\chi_t(G) = \Delta(G) + 2\)). In this paper, we prove that the augmented cube \(AQ_n\) is of Type 1 for \(n \geq 4\). We also consider the adjacent vertex-distinguishing total chromatic number of \(AQ_n\) and prove that \(\chi_{at}(AQ_n) = \Delta(AQ_n) + 2\) for \(n \geq 3 \).

Abstract:

The Channel Assignment Problem is often modeled by integer vertex-labelings of graphs. We will examine \(L(2,1)\)-labelings that realize the span \(\lambda\) of a simple, connected graph \(G = (V, E)\). We define the utility of \(G\) to be the number of possible expansions that can occur on \(G\), where an expansion refers to an opportunity to add a new vertex \(u\) to \(G\), with label \(\lambda(u)\), such that:

  1. edges are added between \(u\) and \(v\);
  2. edges are added between \(u\) and the neighbors of \(v\); and
  3. the resulting labeling of the graph is a valid \(L(2, 1)\)-labeling.

Building upon results of Griggs, Jin, and Yeh, we use known values of \(\lambda\) to compute utility for several infinite families and analyze the utility of specific graphs that are of interest elsewhere.

Charles C.Y. Lam1, Alan C.H. Ling2
1Department of Mathematics, California State University, Bakersfield, Bakersfield, California 93311, USA
2Department of Computer Science, University of Vermont, Burlington, Vermont 05405, USA
Abstract:

A Sidon set \(S\) is a set of integers where the number of solutions to any integer equation \(k = k_1 + k_2\) with \(k_1, k_2 \in S\) is at most \(2\). If \(g \geq 2\), the set \(S\) is a generalized Sidon set. We consider Sidon sets modulo \(n\), where the solutions to addition of elements are considered under a given modulus. In this note, we give a construction of a generalized Sidon set modulo \(n\) from any known Sidon set.

Manouchehr Zaker1
1Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
Abstract:

In an ordered graph \(G\), a set of vertices \(S\) with a pre-coloring of the vertices of \(S\) is said to be a greedy defining set (GDS) if the greedy coloring of \(G\) with fixed colors of \(S\) yields a \(\chi(G)\)-coloring of \(G\). This concept first appeared in [M. Zaker, Greedy defining sets of graphs, Australas. J. Combin, 2001]. The smallest size of any GDS in a graph \(G\) is called the greedy defining number of \(G\). We show that determining the greedy defining number of bipartite graphs is an NP-complete problem, affirmatively answering a problem mentioned in a previous paper. Additionally, we demonstrate that this number for forests can be determined in linear time. Furthermore, we present a method for obtaining greedy defining sets in Latin squares and, using this method, show that any \(n \times n\) Latin square has a GDS of size at most \(n^2 – (n \log 4n)/4\).

Xiuli Wang1
1College of Science, Civil Aviation University of China, Tianjin, 300300, P.R.China.
Abstract:

Multi-receiver authentication codes allow one sender to construct an authenticated message for a group of receivers such that each receiver can verify authenticity of the received message. In this paper, we construct one multi-receiver authentication codes from pseudo-symplectic geometry over finite fields. The parameters and the probabilities of deceptions of this codes are also computed.

Lihua Feng1,2, Guihai Yu2, Kexiang Xu3, Zhengtao Jiang4
1Department of Mathematics, Central South University Railway Campus, Changsha, Hunan, 410075, P.R. China.
2School of Mathematics, Shandong Institute of Business and Technology 191 Binhaizhong Road, Yantai, Shandong, 264005, P.R. China.
3College of Science, Nanjing University of Aeronautics & Astronautics, Nanjing, 210016, P.R. China
4School of Computer Science, Communication University of China Beijing 100024, P.R. China. e-mail: fenglh0163.com
Abstract:

Resistance distance was introduced by Klein and Randic as a generalization of the classical distance. The Kirchhoff index \(Kf(G)\) of a graph \(G\) is the sum of resistance distances between all pairs of vertices. In this paper, we determine the bicyclic graph of order \(n \geq 8\) with maximal Kirchhoff index. This improves and extends an earlier result by Zhang \(et\; al. [19]\).

Stephan Wagner1
1DEPARTMENT OF MATHEMATICAL SCIENCES, STELLENBOSCH UNIVERSITY, PRIVATE Bac X1, MATIELAND 7602, SoUTH AFRICA
Abstract:

Bereg and Wang defined a new class of highly balanced \(d\)-ary trees which they call \(k\)-trees; these trees have the interesting property that the internal path length and thus the Wiener index can be calculated quite easily. A \(k\)-tree is characterized by the property that all levels, except for the last \(k\) levels, are completely filled. Bereg and Wang claim that the number of \(k\)-trees is exponentially increasing, but do not give an asymptotic formula for it. In this paper, we study the number of \(d\)-ary \(k\)-trees and the number of mutually non-isomorphic \(d\)-ary \(k\)-trees, making use of a technique due to Flajolet and Odlyzko.

Yuanlin Li1, Yilan Tan2
1 DEPARTMENT OF MATHEMATICS, Brock UNIVERSITY, ST. CATHARINES, ONTARIO, CANADA L2S 3Al
2DEPARTMENT OF MATHEMATICS, Brock UNIversiTy, ST. CATHARINES, ONTARIO, Canapa L2S 3A1
Abstract:

A group \(G\) is said to be a \(B_k\)-group if for any \(k\)-subset \(\{a_1, \ldots, a_k\}\) of \(G\), \(\left|\{a_ia_j \mid 1 \leq i, j \leq k\}\right| \leq \frac{k(k+1)}{2}\). In this paper, a complete classification of \(B_5\)-groups is given.

Juan Liu1, Xindong Zhang1, Jiziang Meng2
1School of Mathematical Sciences, Xinjiang Normal University Urumgi, Xinjiang 830054, P.R. China
2College of Mathematics and System Sciences, Xinjiang University Urumgi, Xinjiang 830046, P.R. China
Abstract:

The local-restricted-edge-connectivity \(\lambda'(e, f)\) of two nonadjacent edges \(e\) and \(f\) in a graph \(G\) is the maximum number of edge-disjoint \(e\)-\(f\) paths in \(G\). It is clear that \(\lambda'(G) = \min\{\lambda'(e, f) \mid e \text{ and } f \text{ are nonadjacent edges in } G\}\), and \(\lambda'(e, f) \leq \min\{\xi(e), \xi(f)\}\) for all pairs \(e\) and \(f\) of nonadjacent edges in \(G\), where \(\lambda(G)\), \(\xi(e)\), and \(\xi(f)\) denote the restricted-edge-connectivity of \(G\), the edge-degree of edges \(e\) and \(f\), respectively. Let \(\xi(G)\) be the minimum edge-degree of \(G\). We call a graph \(G\) optimally restricted-edge-connected when \(\lambda'(G) = \xi(G)\) and optimally local-restricted-edge-connected if \(\lambda'(e, f) = \min\{\xi(e),\xi(f)\}\) for all pairs \(e\) and \(f\) of nonadjacent edges in \(G\). In this paper, we show that some known sufficient conditions that guarantee that a graph is optimally restricted-edge-connected also guarantee that it is optimally local-restricted-edge-connected.

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