English

Globally simple Heffter arrays $H(n;k)$ when $k\equiv 0,3\mod 4$

Combinatorics 2019-07-29 v2

Abstract

Square Heffter arrays are n×nn\times n arrays such that each row and each column contains kk filled cells, each row and column sum is divisible by 2nk+12nk+1 and either xx or x-x appears in the array for each integer 1xnk1\leq x\leq nk. Archdeacon noted that a Heffter array, satisfying two additional conditions, yields a face 22-colourable embedding of the complete graph K2nk+1K_{2nk+1} on an orientable surface, where for each colour, the faces give a kk-cycle system. Moreover, a cyclic permutation on the vertices acts as an automorphism of the embedding. These necessary conditions pertain to cyclic orderings of the entries in each row and each column of the Heffter array and are: (1) for each row and each column the sequential partial sums determined by the cyclic ordering must be distinct modulo 2nk+12nk+1; (2) the composition of the cyclic orderings of the rows and columns is equivalent to a single cycle permutation on the entries in the array. We construct Heffter arrays that satisfy condition (1) whenever (a) k0mod4k\equiv 0\mod 4; or (b) n1mod4n\equiv 1\mod 4 and k3mod4k\equiv 3\mod 4; or (c) n0mod4n\equiv 0\mod 4, k3mod4k\equiv3\mod 4 and nkn\gg k. As corollaries to the above we obtain pairs of orthogonal kk-cycle decompositions of K2nk+1K_{2nk+1}.

Keywords

Cite

@article{arxiv.1906.07366,
  title  = {Globally simple Heffter arrays $H(n;k)$ when $k\equiv 0,3\mod 4$},
  author = {K. Burrage and Nicholas J. Cavenagh and D. Donovan and E. Ş. Yazıcı},
  journal= {arXiv preprint arXiv:1906.07366},
  year   = {2019}
}