Let v=2ms+t be a positive integer, where t divides 2ms, and let J be the subgroup of order t of the cyclic group Zv. An integer Heffter array Ht(m,n;s,k) over Zv relative to J is an m×n partially filled array with elements in Zv such that: (a) each row contains s filled cells and each column contains k filled cells; (b) for every x∈Zv∖J, either x or −x appears in the array; (c) the elements in every row and column, viewed as integers in [Formula presented], sum to 0 in Z. In this paper we study the existence of an integer Ht(m,n;s,k) when s and k are both even, proving the following results. Suppose that 4≤s≤n and 4≤k≤m are such that ms=nk. Let t be a divisor of 2ms. (a) If s,k≡0(mod4), there exists an integer Ht(m,n;s,k). (b) If s≡2(mod4) and k≡0(mod4), there exists an integer Ht(m,n;s,k) if and only if m is even. (c) If s≡0(mod4) and k≡2(mod4), then there exists an integer Ht(m,n;s,k) if and only if n is even. (d) Suppose that m and n are both even. If s,k≡2(mod4), then there exists an integer Ht(m,n;s,k).

On the existence of integer relative Heffter arrays / Morini, F.; Pellegrini, M. A.. - In: DISCRETE MATHEMATICS. - ISSN 0012-365X. - 343:11(2020), p. 112088. [10.1016/j.disc.2020.112088]

### On the existence of integer relative Heffter arrays

#### Abstract

Let v=2ms+t be a positive integer, where t divides 2ms, and let J be the subgroup of order t of the cyclic group Zv. An integer Heffter array Ht(m,n;s,k) over Zv relative to J is an m×n partially filled array with elements in Zv such that: (a) each row contains s filled cells and each column contains k filled cells; (b) for every x∈Zv∖J, either x or −x appears in the array; (c) the elements in every row and column, viewed as integers in [Formula presented], sum to 0 in Z. In this paper we study the existence of an integer Ht(m,n;s,k) when s and k are both even, proving the following results. Suppose that 4≤s≤n and 4≤k≤m are such that ms=nk. Let t be a divisor of 2ms. (a) If s,k≡0(mod4), there exists an integer Ht(m,n;s,k). (b) If s≡2(mod4) and k≡0(mod4), there exists an integer Ht(m,n;s,k) if and only if m is even. (c) If s≡0(mod4) and k≡2(mod4), then there exists an integer Ht(m,n;s,k) if and only if n is even. (d) Suppose that m and n are both even. If s,k≡2(mod4), then there exists an integer Ht(m,n;s,k).
##### Scheda breve Scheda completa Scheda completa (DC)
2020
On the existence of integer relative Heffter arrays / Morini, F.; Pellegrini, M. A.. - In: DISCRETE MATHEMATICS. - ISSN 0012-365X. - 343:11(2020), p. 112088. [10.1016/j.disc.2020.112088]
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Utilizza questo identificativo per citare o creare un link a questo documento: `https://hdl.handle.net/11381/2879826`
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