English

On a Paley-type graph on $\mathbb{Z}_n$

Combinatorics 2021-10-08 v2 Number Theory

Abstract

Let qq be a prime power such that q1(mod4)q\equiv 1\pmod{4}. The Paley graph of order qq is the graph with vertex set as the finite field Fq\mathbb{F}_q and edges defined as, abab is an edge if and only if aba-b is a non-zero square in Fq\mathbb{F}_q. We attempt to construct a similar graph of order nn, where nNn\in\mathbb{N}. For suitable nn, we construct the graph where the vertex set is the finite commutative ring Zn\mathbb{Z}_n and edges defined as, abab is an edge if and only if abx2(modn)a-b\equiv x^2\pmod{n} for some unit xx of Zn\mathbb{Z}_n. We look at some properties of this graph. For primes p1(mod4)p\equiv 1\pmod{4}, Evans, Pulham and Sheehan computed the number of complete subgraphs of order 4 in the Paley graph. Very recently, Dawsey and McCarthy find the number of complete subgraphs of order 4 in the generalized Paley graph of order qq. In this article, for primes p1(mod4)p\equiv 1\pmod{4} and any positive integer α\alpha, we find the number of complete subgraphs of order 3 and 4 in our graph defined over Zpα\mathbb{Z}_{p^{\alpha}}.

Keywords

Cite

@article{arxiv.2012.09735,
  title  = {On a Paley-type graph on $\mathbb{Z}_n$},
  author = {Anwita Bhowmik and Rupam Barman},
  journal= {arXiv preprint arXiv:2012.09735},
  year   = {2021}
}

Comments

22 pages; To appear at Graphs and Combinatorics

R2 v1 2026-06-23T21:03:17.243Z