arXiv subjects

Saeid Alikhani

Publications and source records attributed to Saeid Alikhani.

At least 55 records · Page 3Linked to original sources

arXiv2022

Distinguishing threshold for some graph operations

A vertex coloring of a graph $G$ is distinguishing if non-identity automorphisms do not preserve it. The distinguishing number, $D(G)$, is the minimum number of colors required for such a coloring and the distinguishing threshold, $θ(G)$, is the minimum number of colors~$k$ such that any arbitrary $k$-coloring is distinguishing. Moreover, $Φ_k (G)$ is the number of distinguishing coloring of $G$ using at most $k$ colors. In this paper, for some graph operations, namely, vertex-sum, rooted product, corona product and lexicographic product, we find formulae of the distinguishing number and threshold using $Φ_k (G)$.

math.CO↗

arXiv2022

Introduction to total coalitions in graphs

Let $G$ be a graph with vertex set $V$. Two disjoint sets $V_1, V_2\subseteq V$ are called a total coalition in $G$, if neither $V_1$ and $V_2$ is a total dominating set of $G$ but $V_1\cup V_2$ is a total dominating set. A total coalition partition of $G$ is a vertex partition $π=\{V_1,V_2,\ldots, V_k\}$ such that no set of $π$ is a total dominating set but each set $V_i\in π$ forms a total coalition with another set $V_j\in π$. The maximum cardinality of a total coalition partition of $G$ is called the total coalition number of $G$, denoted by $TC(G)$. In this paper, we initiate the study of the total coalition in graphs and its properties.

math.CO↗

arXiv2022

Sombor-index-like invariants of some graphs

The Sombor index (SO) is a vertex-degree-based graph invariant, defined as the sum over all pairs of adjacent vertices of $\sqrt{d_i^2+d_j^2}$, where $d_i$ is the degree of the $i$-th vertex. It has been conceived using geometric considerations. Recently, a series of new SO-like degree-based graph invariants (denoted by $SO_1, SO_2,..., SO_6$) is taken into consideration, when the geometric background of several classical topological indices (Zagreb, Albertson) has considered. In this paper, we compute and study these new indices for some graphs, cactus chains and polymers.

math.CO↗

arXiv2022

Strong domination number of a modified graph

Let $G=(V,E)$ be a simple graph. A set $D\subseteq V$ is a strong dominating set of $G$, if for every vertex $x\in V\setminus D$ there is a vertex $y\in D$ with $xy\in E(G)$ and $deg(x)\leq deg(y)$. The strong domination number $γ_{st}(G)$ is defined as the minimum cardinality of a strong dominating set. In this paper, we study the effects on $γ_{st}(G)$ when $G$ is modified by operations on vertex and edge of $G$.

math.CO↗

arXiv2022

Strong domination number of some operations on a graph

Let $G=(V(G),E(G))$ be a simple graph. A set $D\subseteq V(G)$ is a strong dominating set of $G$, if for every vertex $x\in V(G)\setminus D$ there is a vertex $y\in D$ with $xy\in E(G)$ and $deg(x)\leq deg(y)$. The strong domination number $γ_{st}(G)$ is defined as the minimum cardinality of a strong dominating set. In this paper, we examine the effects on $γ_{st}(G)$ when $G$ is modified by operations on edge (or edges) of $G$.

math.CO↗

arXiv2022

Number of colors needed to break symmetries of a graph by an arbitrary edge coloring

A coloring is distinguishing (or symmetry breaking) if no non-identity automorphism preserves it. The distinguishing threshold of a graph $G$, denoted by $θ(G)$, is the minimum number of colors $k$ so that every $k$-coloring of $G$ is distinguishing. We generalize this concept to edge-coloring by defining an alternative index $θ'(G)$. We consider $θ'$ for some families of graphs and find its connection with edge-cycles of the automorphism group. Then we show that $θ'(G)=2$ if and only if $G\simeq K_{1,2}$ and $θ'(G)=3$ if and only if $G\simeq P_4, K_{1,3}$ or $K_3$. Moreover, we prove some auxiliary results for graphs whose distinguishing threshold is 3 and show that although there are infinitely many such graphs, but they are not line graphs. Finally, we compute $θ'(G)$ when $G$ is the Cartesian product of simple prime graphs.

math.CO↗

arXiv2021

Sequence pairs related to produced graphs from a method for dividing a natural number by two

This paper is about producing a new kind of the pairs which we call it MS-pairs. To produce these pairs, we use an algorithm for dividing a natural number $x$ by two for two arbitrary numbers and consider their related graphs. We present some applications of these pairs that show their interesting properties such as unpredictability, irreversible, aperiodicity and chaotic behavior.

cs.CR↗

arXiv2021

Exploring Water Governing System Fit Through a Statistical Mechanics Approach

Water governing systems are twisted with complex interplays among levels and scales which embody their structures. Typically, the mismatch between human-generated and natural systems produces externalities and inefficiencies reflectable in spatial scales. The largely known problem of fit in water governance is investigated to detect the issues of fit between administrative/institutional scales and the hydrological one in a lake basin. To implement the idea, constraining the level of analysis interlinked to the concentrated levels of administration in spatial scales, the fit of the governing system was analyzed by means of statistical mechanics. Modeling the structure of water demand/supply governing system in a given region through the Curie-Weiss Mean Field approximation, the system cost in relation to its structure and fit was appraised and compared with two other conceptual structures in the Urmia Lake Basin in Iran. The methodology articulated an analysis framework for exploring the effectiveness of the formulated water demand/supply governing system and its fit to the relevant hydrological system. The findings of this study may help developing strategies to encourage adaptations, rescaling/reforms for effective watershed management.

physics.ao-ph↗

arXiv2021

On the number of fair dominating sets of graphs

Let $G=(V,E)$ be a simple graph. A dominating set of $G$ is a subset $D\subseteq V$ such that every vertex not in $D$ is adjacent to at least one vertex in $D$.The cardinality of a smallest dominating set of $G$, denoted by $γ(G)$, is the domination number of $G$.For $k \geq 1$, a $k$-fair dominating set($kFD$-set) in $G$, is a dominating set $S$ such that $|N(v) \cap D|=k$ for every vertex $ v \in V\setminus D$.A fair dominating set, in $G$ is a $kFD$-set for some integer $k\geq 1$.In this paper, after presenting preliminaries, we count the number of fair dominating sets of some specific graphs.

math.CO↗

arXiv2021

On the semitotal dominating sets of graphs

A set $D$ of vertices in an isolate-free graph $G$ is a semitotal dominating set of $G$ if $D$ is a dominating set of $G$ and every vertex in $D$ is within distance $2$ from another vertex of $D$.The semitotal domination number of $G$ is the minimum cardinality of a semitotal dominating set of $G$ and is denoted by $γ_{t2}(G)$. In this paper after computation of semitotal domination number of specific graphs, we count the number of this kind of dominating sets of arbitrary size in some graphs.

math.CO↗

arXiv2021

More on total domination polynomial and $\mathcal{D}_t$-equivalence classes of some graphs

Let $G = (V, E)$ be a simple graph of order $n$. The total dominating set of $G$ is a subset $D$ of $V$ that every vertex of $V$ is adjacent to some vertices of $D$. The total domination number of $G$ is equal to minimum cardinality of total dominating set in $G$ and is denoted by $γ_t(G)$. The total domination polynomial of $G$ is the polynomial $D_t(G,x)=\sum_{i=γ_t(G)}^n d_t(G,i)x^i$, where $d_t(G,i)$ is the number of total dominating sets of $G$ of size $i$. Two graphs $G$ and $H$ are said to be total dominating equivalent or simply $\mathcal{D}_t$-equivalent, if $D_t(G,x)=D_t(H,x)$. The equivalence class of $G$, denoted $[G]$, is the set of all graphs $\mathcal{D}_t$-equivalent to $G$. In this paper, we investigate $\mathcal{D}_t$-equivalence classes of some graphs. Also we introduce some families of graphs whose total domination polynomials are unimodal.

math.CO↗

arXiv2021

Mostar index and edge Mostar index of polymers

Let $G=(V,E)$ be a graph and $e=uv\in E$. Define $n_u(e,G)$ be the number of vertices of $G$ closer to $u$ than to $v$. The number $n_v(e,G)$ can be defined in an analogous way. The Mostar index of $G$ is a new graph invariant defined as $Mo(G)=\sum_{uv\in E(G)}|n_u(uv,G)-n_v(uv,G)|$. The edge version of Mostar index is defined as $Mo_e(G)=\sum_{e=uv\in E(G)} |m_u(e|G)-m_v(G|e)|$, where $m_u(e|G)$ and $m_v(e|G)$ are the number of edges of $G$ lying closer to vertex $u$ than to vertex $v$ and the number of edges of $G$ lying closer to vertex $v$ than to vertex $u$, respectively. Let $G$ be a connected graph constructed from pairwise disjoint connected graphs $G_1,\ldots ,G_k$ by selecting a vertex of $G_1$, a vertex of $G_2$, and identifying these two vertices. Then continue in this manner inductively. We say that $G$ is a polymer graph, obtained by point-attaching from monomer units $G_1,...,G_k$. In this paper, we consider some particular cases of these graphs that are of importance in chemistry and study their Mostar and edge Mostar indices.

math.CO↗

arXiv2021

Sombor Index of Polymers

Let $G=(V,E)$ be a finite simple graph. The Sombor index $SO(G)$ of $G$ is defined as $\sum_{uv\in E(G)}\sqrt{d_u^2+d_v^2}$, where $d_u$ is the degree of vertex $u$ in $G$. Let $G$ be a connected graph constructed from pairwise disjoint connected graphs $G_1,\ldots ,G_k$ by selecting a vertex of $G_1$, a vertex of $G_2$, and identifying these two vertices. Then continue in this manner inductively. We say that $G$ is a polymer graph, obtained by point-attaching from monomer units $G_1,...,G_k$. In this paper, we consider some particular cases of these graphs that are of importance in chemistry and study their Sombor index.

math.CO↗

arXiv2021

Sombor index of certain graphs

Let $G=(V,E)$ be a finite simple graph. The Sombor index $SO(G)$ of $G$ is defined as $\sum_{uv\in E(G)}\sqrt{d_u^2+d_v^2}$, where $d_u$ is the degree of vertex $u$ in $G$. In this paper, we study this index for certain graphs and we examine the effects on $SO(G)$ when $G$ is modified by operations on vertex and edge of $G$. Also we present bounds for the Sombor index of join and corona product of two graphs.

math.CO↗

arXiv2021

Enumeration of accurate dominating sets

Let $G=(V,E)$ be a simple graph. A dominating set of $G$ is a subset $D\subseteq V$ such that every vertex not in $D$ is adjacent to at least one vertex in $D$. The cardinality of a smallest dominating set of $G$, denoted by $γ(G)$, is the domination number of $G$. A dominating set $D$ is an accurate dominating set of $G$, if no $|D|$-element subset of $V\setminus D$ is a dominating set of $G$. The accurate domination number, $γ_a(G)$, is the cardinality of a smallest accurate dominating set $D$. In this paper, after presenting preliminaries, we count the number of accurate dominating sets of some specific graphs.

math.CO↗

arXiv2021

On the number of isolate dominating sets of certain graphs

Let $G=(V,E)$ be a simple graph. A dominating set of $G$ is a subset $S\subseteq V$ such that every vertex not in $S$ is adjacent to at least one vertex in $S$. The cardinality of a smallest dominating set of $G$, denoted by $γ(G)$, is the domination number of $G$. A dominating set $S$ is an isolate dominating set of $G$, if the induced subgraph $G[S]$ has at least one isolated vertex. The isolate domination number, $γ_0(G)$, is the minimum cardinality of an isolate dominating set of $G$. In this paper, we count the number of isolate dominating sets of some specific graphs.

math.CO↗

arXiv2020

A graph related to Euler $ϕ$ function

Euler function $ϕ(n)$ is the number of positive integers less than $n$ and relatively prime to $n$. Suppose that $ϕ^1(n)=ϕ(n)$ and $ϕ^i(n)=ϕ(ϕ^{i-1}(n))$. Let $A\subseteq \mathbb{N}$, and $A_ϕ=\{ ϕ^k(n)| n\in A , k\in \mathbb{N} \cup \{0\}\}.$ We consider a graph $G_ϕ(A)=(V,E)$, where $V=A_ϕ$ and $E=\{\{r,s\}| r,s\in V, ϕ(r)=s \}$. We say a graph $H$ is a $G_ϕ$-graph, if there exists a set of natural numbers $A$, such that $H=G_ϕ(A)$. In this paper we study the graph $G_ϕ(A)$ and investigate some specific graphs and some chemical trees as $G_ϕ$-graph.

math.CO↗

arXiv2020

On the edge chromatic vertex stability number of graphs

For an arbitrary invariant $ρ(G)$ of a graph $G$, the $ρ-$vertex stability number $vs_ρ(G)$ is the minimum number of vertices of $G$ whose removal results in a graph $H\subseteq G$ with $ρ(H)\neq ρ(G)$ or with $E(H)=\varnothing$. In this paper, first we give some general lower and upper bounds for the $ρ$-vertex stability number, and then study the edge chromatic stability number of graphs, $vs_{χ^{\prime}}(G)$, where $χ^{\prime}=χ^{\prime}(G)$ is edge chromatic number (chromatic index) of $G$. We prove some general results for this parameter and determine $vs_{χ^{\prime}}(G)$ for specific classes of graphs.

math.CO↗