English

On modular balanced partition designs

Combinatorics 2026-07-20 v1

Abstract

Let XX be a finite set of integers with cardinality ν=κλ\nu = \kappa \lambda. A \emph{modular balanced partition design} is a triplet (X,A,B)(X, \mathcal{A}, \mathcal{B}) satisfying the following conditions: \begin{itemize} \item A\mathcal{A} is a partition of XX into κ\kappa blocks of size λ\lambda, such that every element of XX appears in exactly one block. If A={A1,A2,,Aκ}\mathcal{A} = \{A_1, A_2, \ldots, A_{\kappa}\}, then aAiaiλ(modν)\sum_{a\in A_i} a \equiv i \lambda \pmod{\nu}, for each i=1,2,,κi=1,2,\ldots,\kappa \item B\mathcal{B} is a partition of XX into λ\lambda blocks of size κ\kappa, such that every element of XX appears in exactly one block. If B={B1,B2,,Bλ}\mathcal{B} = \{B_1, B_2, \ldots, B_{\lambda}\}, then bBjbjκ(modν)\sum_{b\in B_j} b \equiv j \kappa \pmod{\nu}, for each j=1,2,,λj=1,2,\ldots,\lambda \item AiBjA_i \cap B_j has exactly one element, for any AiAA_i \in \mathcal{A}, and BjBB_j \in \mathcal{B}. \itemize} We prove the necessary conditions for the existence of a modular balanced partition design. Moreover, we investigate and identify a relationship between a modular balanced partition design and a subgroup magic rectangle. Then by using affine automorphisms of an Abelian group, we prove the existence of non-isomorphic modular balanced partition designs. Finally, we provide a method to construct a transversal design via a modular balanced partition design.

Cite

@article{arxiv.2607.18087,
  title  = {On modular balanced partition designs},
  author = {S. Karthik and Peter J. Cameron and Krishnan Paramasivam},
  journal= {arXiv preprint arXiv:2607.18087},
  year   = {2026}
}