scholarly journals The general position problem on Kneser graphs and on some graph operations

2019 ◽  
Author(s):  
Modjtaba Ghorbani ◽  
Sandi Klavžar ◽  
Hamid Reza Maimani ◽  
Mostafa Momeni ◽  
Farhad Rahimi Mahid ◽  
...  
Keyword(s):  
General Position ◽  
Graph Operations ◽  
Kneser Graphs ◽  
Position Problem

A GENERAL POSITION PROBLEM IN GRAPH THEORY

2018 ◽  
Vol 98 (2) ◽  
pp. 177-187 ◽  
Author(s):  
PAUL MANUEL ◽  
SANDI KLAVŽAR
Keyword(s):  
Graph Theory ◽  
Lower Bounds ◽  
General Position ◽  
Upper Bounds ◽  
Np Complete ◽  
Position Problem

The paper introduces a graph theory variation of the general position problem: given a graph $G$, determine a largest set $S$ of vertices of $G$ such that no three vertices of $S$ lie on a common geodesic. Such a set is a max-gp-set of $G$ and its size is the gp-number $\text{gp}(G)$ of $G$. Upper bounds on $\text{gp}(G)$ in terms of different isometric covers are given and used to determine the gp-number of several classes of graphs. Connections between general position sets and packings are investigated and used to give lower bounds on the gp-number. It is also proved that the general position problem is NP-complete.

The general position problem and strong resolving graphs

2019 ◽  
Vol 17 (1) ◽  
pp. 1126-1135 ◽  
Author(s):  
Sandi Klavžar ◽  
Ismael G. Yero
Keyword(s):  
Connected Graph ◽  
General Position ◽  
Clique Number ◽  
Bipartite Graphs ◽  
Complete Graphs ◽  
Direct Products ◽  
Strong Product ◽  
Product Graphs ◽  
Complete Bipartite Graphs ◽  
Position Problem

Abstract The general position number gp(G) of a connected graph G is the cardinality of a largest set S of vertices such that no three pairwise distinct vertices from S lie on a common geodesic. It is proved that gp(G) ≥ ω(GSR), where GSR is the strong resolving graph of G, and ω(GSR) is its clique number. That the bound is sharp is demonstrated with numerous constructions including for instance direct products of complete graphs and different families of strong products, of generalized lexicographic products, and of rooted product graphs. For the strong product it is proved that gp(G ⊠ H) ≥ gp(G)gp(H), and asked whether the equality holds for arbitrary connected graphs G and H. It is proved that the answer is in particular positive for strong products with a complete factor, for strong products of complete bipartite graphs, and for certain strong cylinders.

scholarly journals The Chromatic Number of Two Families of Generalized Kneser Graphs Related to Finite Generalized Quadrangles and Finite Projective 3-Spaces

2021 ◽  
Vol 28 (3) ◽  
Author(s):  
Klaus Metsch
Keyword(s):  
Projective Space ◽  
Chromatic Number ◽  
General Position ◽  
Independence Number ◽  
Independent Set ◽  
Generalized Quadrangle ◽  
Finite Projective Space ◽  
Maximal Independent Set ◽  
Generalized Quadrangles ◽  
Kneser Graphs

Let $\Gamma$ be the graph whose vertices are the chambers of the finite projective space $\mathrm{PG}(3,q)$ with two vertices being adjacent when the corresponding chambers are in general position. It is known that the independence number of this graph is $(q^2+q+1)(q+1)^2$. For $q\geqslant 43$ we determine the largest independent set of $\Gamma$ and show that every maximal independent set that is not a largest one has at most constant times $q^3$ elements. For $q\geqslant 47$, this information is then used to show that $\Gamma$ has chromatic number $q^2+q$. Furthermore, for many families of generalized quadrangles we prove similar results for the graph that is built in the same way on the chambers of the generalized quadrangle.

scholarly journals A Steiner general position problem in graph theory

2021 ◽  
Vol 40 (6) ◽  
Author(s):  
Sandi Klavžar ◽  
Dorota Kuziak ◽  
Iztok Peterin ◽  
Ismael G. Yero
Keyword(s):  
Graph Theory ◽  
General Position ◽  
Position Problem

On Hyper-Zagreb Index of Three Graph Operations

2019 ◽  
Vol 10 (2) ◽  
pp. 301-309
Author(s):  
A. Bharali ◽  
Amitav Doley
Keyword(s):  
Zagreb Index ◽  
Graph Operations

The Restricted Arc-Width of a Graph

10.37236/1734 ◽  
2003 ◽  
Vol 10 (1) ◽  
Author(s):  
David Arthur
Keyword(s):  
Unit Circle ◽  
Single Point ◽  
Minimum Width ◽  
Graph Operations ◽  
Function Mapping

An arc-representation of a graph is a function mapping each vertex in the graph to an arc on the unit circle in such a way that adjacent vertices are mapped to intersecting arcs. The width of such a representation is the maximum number of arcs passing through a single point. The arc-width of a graph is defined to be the minimum width over all of its arc-representations. We extend the work of Barát and Hajnal on this subject and develop a generalization we call restricted arc-width. Our main results revolve around using this to bound arc-width from below and to examine the effect of several graph operations on arc-width. In particular, we completely describe the effect of disjoint unions and wedge sums while providing tight bounds on the effect of cones.

Short proof that Kneser graphs are Hamiltonian for n ⩾ 4k

2021 ◽  
Vol 344 (7) ◽  
pp. 112430
Author(s):  
Johann Bellmann ◽  
Bjarne Schülke
Keyword(s):  
Short Proof ◽  
Kneser Graphs
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