PreprintCC BY 4.0arXiv
Existence of regular sets in circulant quartic graphs: a complete characterization
Abstract
Let Γ=(V,E) be a graph and let a,b be nonnegative integers. A nonempty proper subset C⊂ V is an \emph{(a,b)-regular set} if each vertex of C has exactly a neighbors in C and each vertex outside C has exactly b neighbors in C. Perfect codes and total perfect codes are the (0,1)- and (1,1)-regular sets. For every connected circulant quartic graph Cay(ℤn,{x± k,x±ℓ}) and every pair (a,b) we decide, in terms of n, k and ℓ, whether an (a,b)-regular set exists. Existence is proved by exhibiting unions of residue classes; non-existence comes from a Fourier-analytic obstruction combined with the fact that certain sums of roots of unity cannot vanish.
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BibTeX
@misc{abdollahi2026existence,
title = {{Existence of regular sets in circulant quartic graphs: a complete characterization}},
author = {A. Abdollahi and J. Bagherian and F. Jafari and M. Khatami and Z. Shokoohi and R. Sobhani},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.09414},
eprint = {2609.09414},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09414},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Existence of regular sets in circulant quartic graphs: a complete characterization
AU - A. Abdollahi
AU - J. Bagherian
AU - F. Jafari
AU - M. Khatami
AU - Z. Shokoohi
AU - R. Sobhani
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2609.09414
UR - https://arxiv.org/abs/2609.09414
AB - Let Γ=(V,E) be a graph and let a,b be nonnegative integers. A nonempty proper subset C⊂ V is an \emph{(a,b)-regular set} if each vertex of C has exactly a neighbors in C and each vertex outside C has exactly b neighbors in C. Perfect codes and total perfect codes are the (0,1)- and (1,1)-regular sets. For every connected circulant quartic graph Cay(ℤ_n,{x^± k,x^±ℓ}) and every pair (a,b) we decide, in terms of n, k and ℓ, whether an (a,b)-regular set exists. Existence is proved by exhibiting unions of residue classes; non-existence comes from a Fourier-analytic obstruction combined with the fact that certain sums of roots of unity cannot vanish.
ER -