1. On the Enhanced Power Graph of a Semigroup.
- Author
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Dalal, Sandeep, Kumar, Jitender, and Singh, Siddharth
- Subjects
- *
TREE graphs , *PLANAR graphs , *CAYLEY graphs , *SPANNING trees - Abstract
The enhanced power graph P E (S) of a semigroup S is a simple graph whose vertex set is S and two vertices x , y ∈ S are adjacent if and only if x , y ∈ ⟨ z ⟩ for some z ∈ S , where ⟨ z ⟩ is the subsemigroup generated by z. In this paper, we first describe the structure of P E (S) for an arbitrary semigroup S , and then discuss the connectedness of P E (S). Further, we characterize the semigroup S in the cases when P E (S) is separately a complete, bipartite, regular, tree and null graph. The planarity, together with the minimum degree and independence number, of P E (S) is also investigated. The chromatic number of a spanning subgraph, i.e., the cyclic graph, of P E (S) is proved to be countable. In the final part of this paper, we construct an example of a semigroup S such that the chromatic number of P E (S) need not be countable. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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