/ / Article

Research Article | Open Access

Volume 2017 |Article ID 4715421 | 9 pages | https://doi.org/10.1155/2017/4715421

# Morphism of -Polar Fuzzy Graph

Accepted19 Jul 2017
Published23 Aug 2017

#### Abstract

The main purpose of this paper is to introduce the notion of -polar -morphism on -polar fuzzy graphs. The action of -polar -morphism on -polar fuzzy graphs is studied. Some elegant theorems on weak and coweak isomorphism are obtained. Also, some properties of highly irregular, edge regular, and totally edge regular -polar fuzzy graphs are studied.

#### 1. Introduction

Akram  introduced the notion of bipolar fuzzy graphs describing various methods of their construction as well as investigating some of their important properties. Bhutani  discussed automorphism of fuzzy graphs. Chen et al.  generalized the concept of bipolar fuzzy set to obtain the notion of -polar fuzzy set. The notion of -polar fuzzy set is more advanced than fuzzy set and eliminates doubtfulness more absolutely. Ghorai and Pal  studied some operations and properties of -polar fuzzy graphs. Rashmanlou et al.  discussed some properties of bipolar fuzzy graphs and some of its results are investigated. Ramprasad et al.  studied product -polar fuzzy graph, product -polar fuzzy intersection graph, and product -polar fuzzy line graph. Values between 0 and 1 are used to develop a set theory based on fuzziness by Zadeh .

In the present work the authors introduce the concepts of -polar -morphism, edge regular -polar fuzzy graph, totally edge regular -polar fuzzy graph, and highly irregular -polar fuzzy graph in order to strengthen the decision-making in critical situations.

#### 2. Preliminaries

Definition 1. Throughout the paper, ( copies of the closed interval ) is considered to be a poset with pointwise order , where is a natural number, is given by , , where and is the th projection mapping. An -polar fuzzy set (or a -set) on is a mapping .

Definition 2. Let be an -polar fuzzy set on . An -polar fuzzy relation on is an -polar fuzzy set of such that for all , that is, for each , for all , .

Definition 3. A generalized -polar fuzzy graph of a graph is a pair , where is an -polar fuzzy set in and is an -polar fuzzy set in such that for all and for all is the smallest element in . is called the -polar fuzzy set of and is called -polar fuzzy edge set of .

Definition 4. An -polar fuzzy graph of the graph is said to be strong if for all , .

#### 3. A New Theory of Regularity in -Polar Fuzzy Graphs

Using the existing graph theories a new -polar fuzzy graph theory is introduced in this section.

Definition 5. Let be an -polar fuzzy graph. Then the degree of a vertex is defined for as

Definition 6. The degree of an edge in an -polar fuzzy graph is defined as

Definition 7. The total degree of an edge in an -polar fuzzy graph is defined as

Definition 8. The degree of an edge in a crisp graph is

Example 9. Consider an -polar fuzzy graph of , where as in Figure 1.

Then, we have

Definition 10. If every vertex in an -polar fuzzy graph has the same degree , then is called regular -polar fuzzy graph or -polar fuzzy graph of degree

Definition 11. If every edge in an -polar fuzzy graph has the same degree , then is called an edge regular -polar fuzzy graph.

Definition 12. If every edge in an -polar fuzzy graph has the same total degree , then is called totally edge regular -polar fuzzy graph.

Example 13. Consider an -polar fuzzy graph of , where as in Figure 2.

Then, we have

Theorem 14. Let be an -polar fuzzy graph on a cycle . Then

Proof. Suppose that is an -polar fuzzy graph and is a cycle .
Now, we get Hence,

Remark 15. Let be an -polar fuzzy graph on a crisp graph . Thenwhere , for all

Theorem 16. Let be an -polar fuzzy graph on a -regular crisp graph . Then

Proof. From Remark 15, we haveSince is a regular crisp graph, we have the degree of every vertex in as
That is, so

Theorem 17. Let be an -polar fuzzy graph on a crisp graph . Then

Proof. From the definition of total edge degree of , we getFrom Remark 15, we have

Theorem 18. Let be an -polar fuzzy graph. Then the function is a constant function if and only if the following conditions are equivalent.(i) is an edge regular -polar fuzzy graph.(ii) is a totally edge regular -polar fuzzy graph.

Proof. Suppose that is a constant function. Thenwhere are constants and . Let be an edge regular -polar fuzzy graph. Then, for all ,
Now we have to show that is a totally edge regular -polar fuzzy graph.
Now Thus is a totally edge regular graph.
Now, let be a -totally edge regular -polar fuzzy graph. Then So, we have Hence Then is an -edge regular -polar fuzzy graph.
Conversely, suppose that is an edge regular -polar fuzzy graph and is a totally edge regular -polar fuzzy graph which are equivalent. We have to prove that is a constant function. In a contrary way, we suppose that is not a constant function. Then for at least one pair of edges . Let be an -edge regular -polar fuzzy graph. Then . Hence, for every and for every , Since we have . Hence, is not a totally edge regular -polar fuzzy graph. This is a contradiction to our assumption. Hence, is a constant function. In the same way, we can prove that is a constant function, when is a totally edge regular -polar fuzzy graph.

Theorem 19. Let be a -regular crisp graph and be an -polar fuzzy graph on . Then, is a constant function if and only if is both regular -polar fuzzy graph and totally edge regular -polar fuzzy graph.

Proof. Let be an -polar fuzzy graph on and let be a -regular crisp graph. Assume that is a constant function. Then where are constants and . From the definition of degree of a vertex, we getSo . Therefore, is regular -polar fuzzy graph.
Now, for ,Hence, is also a totally edge regular -polar fuzzy graph.
Conversely, assume that is both regular and totally edge regular -polar fuzzy graph. Now we have to prove that is a constant function. Since is regular, for all . Also is totally edge regular. Hence, for all . From the definition of total edge degree, we get so Hence is a constant function.

#### 4. -Morphism on -Polar Fuzzy Graphs

Definition 20. Let and be two -polar fuzzy graphs of the graphs and , respectively.
A homomorphism from to is a mapping such that, for each ,An isomorphism from to is a bijective mapping which satisfies the following conditions:A weak isomorphism from to is a bijective mapping which satisfies the following conditions: is homomorphism and , A coweak isomorphism from to is a bijective mapping which satisfies the following conditions: is homomorphism and ,

Definition 21. The order of an -polar fuzzy graph is defined as

Definition 22. The size of an -polar fuzzy graph is defined as

Definition 23. Let and be two -polar graphs on and , respectively.
A bijective function is called an -polar morphism or -polar -morphism if there exists two numbers and such that , , , , . In such a case, will be called an -polar -morphism from to . If , we call , an -polar -morphism.

Example 24. Consider two -polar fuzzy graphs and as shown in Figure 3.
An -polar fuzzy graph is shown in Figure 3(a) where Another -polar fuzzy graph is shown in Figure 3(b) where Here, there is an -polar -morphism such that , , , , and .

Theorem 25. The relation -morphism is an equivalence relation in the collection of -polar fuzzy graphs.

Proof. Consider the collection of -polar fuzzy graphs. Define the relation if there exists a -morphism from to where both and . Consider the identity morphism to . It is a -morphism from to and hence is reflexive. Let . Then there exists a morphism from to for some and . Therefore, Consider . Let . Since is bijective, , , for some . Now,Thus there exists morphism from to . Therefore, and hence is symmetric.
Let and . Then there exists a morphism from to , say for some and , and there exists morphism from to , say for some and . So, for ,