Direct and inverse problems for restricted signed sumsets in integers

Let $A=\{a_0, a_1,\ldots, a_{k-1}\}$ be a nonempty finite subset of an additive abelian group $G$. For a positive integer $h$ $(\leq k)$, we let $h^{\wedge}_{\pm}A = \{\Sigma_{i=0}^{k-1} \lambda_{i} a_{i}: \lambda_{i} \in \{-1,0,1\} \text{ for } i=0, 1, \ldots, k-1,~~\Sigma_{i=0}^{k-1} |\lambda_{i}|=h\},$ be the $h$-fold restricted signed sumset of $A$. The direct problem for the restricted signed sumset is to find the minimum number of elements in $h^{\wedge}_{\pm}A$ in terms of $\lvert A\rvert$, where $\lvert A\rvert$ is the cardinality of $A$. The {\it inverse problem} for the restricted signed sumset is to determine the structure of the finite set $A$ for which the minimum value of $|h^{\wedge}_{\pm}A|$ is achieved. In this article, we solve some cases of both direct and inverse problems for $h^{\wedge}_{\pm}A$ in the group of integers. In this connection, we also mention some conjectures in the remaining cases

Direct and inverse problems for restricted signed sumsets in integers

Let $A=\{a_0, a_1,\ldots, a_{k-1}\}$ be a nonempty finite subset of an additive abelian group $G$. For a positive integer $h$ $(\leq k)$, we let $h^{\wedge}_{\pm}A = \{\Sigma_{i=0}^{k-1} \lambda_{i} a_{i}: \lambda_{i} \in \{-1,0,1\} \text{ for } i=0, 1, \ldots, k-1,~~\Sigma_{i=0}^{k-1} |\lambda_{i}|=h\},$ be the $h$-fold restricted signed sumset of $A$. The direct problem for the restricted signed sumset is to find the minimum number of elements in $h^{\wedge}_{\pm}A$ in terms of $\lvert A\rvert$, where $\lvert A\rvert$ is the cardinality of $A$. The {\it inverse problem} for the restricted signed sumset is to determine the structure of the finite set $A$ for which the minimum value of $|h^{\wedge}_{\pm}A|$ is achieved. In this article, we solve some cases of both direct and inverse problems for $h^{\wedge}_{\pm}A$ in the group of integers. In this connection, we also mention some conjectures in the remaining cases

Additive Combinatorics: A Menu of Research Problems

This text contains over three hundred specific open questions on various topics in additive combinatorics, each placed in context by reviewing all relevant results. While the primary purpose is to provide an ample supply of problems for student research, it is hopefully also useful for a wider audience. It is the author's intention to keep the material current, thus all feedback and updates are greatly appreciated.Comment: This August 2017 version incorporates feedback and updates from several colleague

Sumset Valuations of Graphs and Their Applications

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Sets with few distinct distances do not have heavy lines

Let $P$ be a set of $n$ points in the plane that determines at most $n/5$ distinct distances. We show that no line can contain more than $O(n^{43/52}{\rm polylog}(n))$ points of $P$. We also show a similar result for rectangular distances, equivalent to distances in the Minkowski plane, where the distance between a pair of points is the area of the axis-parallel rectangle that they span