On the number of subsequence sums related to the support of a sequence in finite abelian groups

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Auteurs principaux: Wang, Rui, Chao, Han, Peng, Jiangtao
Format: Preprint
Publié: 2024
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author Wang, Rui
Chao, Han
Peng, Jiangtao
author_facet Wang, Rui
Chao, Han
Peng, Jiangtao
contents Let $G$ be a finite abelian group and $S$ a sequence with elements of $G$. Let $|S|$ denote the length of $S$ and $\mathrm{supp}(S)$ the set of all the distinct terms in $S$. For an integer $k$ with $k\in [1, |S|]$, let $Σ_{k}(S) \subset G$ denote the set of group elements which can be expressed as a sum of a subsequence of $S$ with length $k$. Let $Σ(S)=\cup_{k=1}^{|S|}Σ_{k}(S)$ and $Σ_{\geq k}(S)=\cup_{t=k}^{|S|}Σ_{t}(S)$. It is known that if $0\not\in Σ(S)$, then $|Σ(S)|\geq |S|+|\mathrm{supp}(S)|-1$. In this paper, we determine the structure of a sequence $S$ satisfying $0\notin Σ(S)$ and $|Σ(S)|= |S|+|\mathrm{supp}(S)|-1$. As a consequence, we can give a counterexample of a conjecture of Gao, Grynkiewicz, and Xia. Moreover, we prove that if $|S|>k$ and $0\not\in Σ_{\geq k}(S)\cup \mathrm{supp}(S)$, then $|Σ_{\geq k}(S)|\geq |S|-k+|\mathrm{supp}(S)|$. Then we can give an alternative proof of a conjecture of Hamidoune, which was first proved by Gao, Grynkiewicz, and Xia.
format Preprint
id arxiv_https___arxiv_org_abs_2404_11307
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On the number of subsequence sums related to the support of a sequence in finite abelian groups
Wang, Rui
Chao, Han
Peng, Jiangtao
Combinatorics
Number Theory
11P70, 11B50, 11B13
Let $G$ be a finite abelian group and $S$ a sequence with elements of $G$. Let $|S|$ denote the length of $S$ and $\mathrm{supp}(S)$ the set of all the distinct terms in $S$. For an integer $k$ with $k\in [1, |S|]$, let $Σ_{k}(S) \subset G$ denote the set of group elements which can be expressed as a sum of a subsequence of $S$ with length $k$. Let $Σ(S)=\cup_{k=1}^{|S|}Σ_{k}(S)$ and $Σ_{\geq k}(S)=\cup_{t=k}^{|S|}Σ_{t}(S)$. It is known that if $0\not\in Σ(S)$, then $|Σ(S)|\geq |S|+|\mathrm{supp}(S)|-1$. In this paper, we determine the structure of a sequence $S$ satisfying $0\notin Σ(S)$ and $|Σ(S)|= |S|+|\mathrm{supp}(S)|-1$. As a consequence, we can give a counterexample of a conjecture of Gao, Grynkiewicz, and Xia. Moreover, we prove that if $|S|>k$ and $0\not\in Σ_{\geq k}(S)\cup \mathrm{supp}(S)$, then $|Σ_{\geq k}(S)|\geq |S|-k+|\mathrm{supp}(S)|$. Then we can give an alternative proof of a conjecture of Hamidoune, which was first proved by Gao, Grynkiewicz, and Xia.
title On the number of subsequence sums related to the support of a sequence in finite abelian groups
topic Combinatorics
Number Theory
11P70, 11B50, 11B13
url https://arxiv.org/abs/2404.11307