A kite is a graph which can be obtained by joining an edge to any vertex of . A kite with edge set can be denoted as . If every vertex of a kite in the decomposition lies in different partite sets, then we say that a kite decomposition of a multipartite graph is a gregarious kite decomposition. In this manuscript, it is shown that there exists a decomposition of into gregarious kites if and only if
where and denote the wreath product and tensor product of graphs respectively. We denote a gregarious kite decomposition as -decomposition.
Many authors have been studied on kite-design and kite decomposition/
kite factorization and their special properties such as gregarious kite
decomposition/ gregarious kite factorization. Bermond and Schonheim
[1] proved that a kite-design
of order exists if and only if
. Wang and
Chang [2,3] considered the
problem of a resolvable
and -group
divisible designs of type
Wang [4] have proven that the
necessary conditions to find a resolvable -group divisible design of type
are also sufficient. Fu et al.
[5] have demonstrated that
there exists a -decomposition
of if and only if for odd or for even Gionfriddo
and Milici [6] considered the
uniformly resolvable decompositions of and into paths and kites. To know more about kite designs, refer
[7-11]. Further, the
authors A. Tamil Elakkiya and A. Muthusamy [12] have shown that there is a -decomposition of if and only if Moreover,
the authors A. Tamil Elakkiya and A. Muthusamy [13] considered the existence of a factorization of tensor product of
complete graphs.
In this way, our main concern is to find a existence of a -decomposition of . In this document, it is demonstrated that a
-decomposition of holds, if and only if,
2. Preliminary Results
Definition 1. [12] A partition of a graph into a collection of subgraphs such that each
one of it is distinct mutually by their edges together with is called a
decomposition of We then write as where denotes
edge-disjoint sum of subgraphs. For an integer denotes copies of
Definition 2. [12] A kite is a graph which can be obtained by
joining an edge to any vertex of , for instance see Figure 1. A kite
with edge set
can be denoted as .
Figure 1
If every vertex of a kite in the decomposition lies in different
partite sets, then we say that a kite decomposition of a multipartite
graph is a gregarious kite decomposition. Here we
may consider a Gregarious Kite decomposition as a -decomposition for short.
Definition 3. [12] The tensor product and the wreath
product of
two graphs and are defined as follows: = = = and
and = and or
As tensor product has commutative and distributive property over
an edge-disjoint sum of subgraphs, if decomposition of = holds, we then write as =
Definition 4. [12] A graph having partite sets with and ={ and } is called complete -partite graph and is
denoted by Note that is same as the where is the complement of a
complete graph on
vertices.
In order to prove our key result, we require the following:
Theorem 1. [5] There exists a -decomposition of if and only if for all odd (or) for even
Remark 1. [5] Let is a kite. Then there exists a -decomposition of for all
Lemma 1. [12] For all , there exists a -decomposition of where is a
kite.
Theorem 2. [12] There exists a -decomposition of if and only if
3. Existence
of -decomposition of
Lemma 2. A -decomposition of exists, if
and for all
Proof. By Theorem 1, we have a -decomposition of Then = = Now As we
have a kite decomposition of from Lemma 1, we then write as =
= A -decomposition of can be obtained
from Remark 1. Thus all together provides a -decomposition of
Lemma 3. A -decomposition of exists, if
and for all
Proof.Case 1: Let and for all We write = = =
Theorem 2 gives a -decomposition for . Now, we write as = =
A -decomposition exists for according to Remark
1. As a
consequence of it, a -decomposition of has been
derived.
Case 2: A -decomposition for have been described as follows:
Let and for all One can obtain a
-decomposition of from Theorem
1.
Then = =
Now A kite decomposition exits for by using Lemma 1. Moreover, we then
write, = = According to
Remark 1, a -decomposition of has been
proved.
Consequently, Cases and lead a -decomposition for when and for all
Lemma 4. A -decomposition of exists, if
and for all
Proof.Case 1: Let and for all Let us consider = = = By
Theorem 2, a -decomposition exists for . Now = =
Now, a -decomposition of follows from Remark
1. Thus,
the above construction provides a -decomposition of .
Case 2: Let and for all By Theorem 1, there is a -decomposition for . Then = =
Now By Lemma 1, we have a kite
decomposition of Then
= = A -decomposition of follows from
Remark 1. Thus, all together gives a -decomposition of
Lemma 5. A -decomposition of exists, if
and for all
Proof. Let us consider We
write as By Theorem 2, we have a -decomposition of Then =
= By Remark 1, we can obtain a -decomposition of Further, = = A -decomposition of follows from Remark 1. Thus, all together
gives a -decomposition of
Lemma 6. A -decomposition of exists, if
and
Proof. A -decomposition of can be obtained from Theorem 1. We then write,
= = Now, we write as
A kite decomposition of has been derived from Lemma
1.
Then = = A -decomposition of exists according
to Remark 1. Consequently, a -decomposition exists for .
Lemma 7. A -decomposition of exists, if
and
Proof. We write Now By Theorem 2, we have a -decomposition of Then =
= A -decomposition of can be obtained
from Remark 1. Further, =
= . A -decomposition of follows from
Remark 1. Thus the above describes a -decomposition for
4. Main Result
Theorem 3. There exists a -decomposition of if and only if
Proof. Necessity: The number of edges of is and number of edges of a kite is . Therefore, the edge divisibility
condition for a graph is .
Sufficiency: It has been derived from Lemmas 2 – 7.
5. Conclusion
In Section 3, we give a complete solution for the existence of a
-decomposition of In future, one can find the existence of a
-factorization of Tensor
product complete multipartite graph.
Funding Information
No funds, grants, or other support were received during preparation
of this manuscript.
Conflict of
Interest
The author have no conflict of interest.
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