Jagannath Bhanja
In this note we find the optimal lower bound for the size of the sumsets $HA$ and $H\,\hat{}A$ over finite sets $H, A$ of nonnegative integers, where $HA = \bigcup_{h\in H} hA$ and $H\,\hat{}A = \bigcup_{h\in H} h\,\hat{}A$. We also find the underlying algebraic structure of the sets $A$ and $H$ for which the size of the sumsets $HA$ and $H\,\hat{}A$ is minimum.
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Restricted sumsets in multiplicative subgroups
本文研究了有限域上乘法子群及整数完美幂中的受限和集，扩展了Shkredov的结果，并提出了一个受限和集的van Lint-MacWilliams猜想的类比。
For finite subsets A_1,...,A_n of a field, their sumset is given by {a_1+...+a_n: a_1 in A_1,...,a_n in A_n}. In this paper we study various restricted sumsets of A_1,...,A_n with restrictions of the following forms: a_i-a_j not in S_{ij}, or alpha_ia_i not=alpha_ja_j, or a_i+b_i not=a_j+b_j (mod m_{ij}). Furthermore, we gain an insight into relations among recent results on this area obtained in quite different ways.
Suppose that $A$, $B$ and $S$ are non-empty subsets of a finite abelian group $G$. Then the generalized restricted sumset $$ A\stackrel{S}+B:=\{a+b:\,a\in A,\ b\in B,\ a-b\not\in S\} $$ contains at least $$ \min\{|A|+|B|-3|S|,p(G)\} $$ elements, where $p(G)$ is the least prime factor of $|G|$. Further, we also have $$ |A\stackrel{S}+B|\geq \min\{|A|+|B|-|S|-2,p(G)\}, $$ provided that both $|A|$ and $|B|$ are large with respect to $|S|$.
Let $k\geqslant 3$ and let $A=\{0=a_{0}<a_{1}<\cdots<a_{k-1}\}$ with $\gcd(A)=1$. Freiman-Lev conjecture [V.F. Lev, Restricted set addition in groups, I. The classical setting, J. London Math. Soc. 62(2000), 27-40] is a well-known conjecture which related to restricted sumsets. Up to now, Freiman-Lev conjecture is open for all $a_{k-1}\geqslant 2k-2$. In this paper, we prove the Freiman-Lev conjecture is true for $a_{k-1}\geqslant 2k-2$ and $a_{k-2}<2k-4$. That is, Freiman-Lev conjecture is still open for the case $a_{k-1}\geqslant 2k-2$ and $a_{k-2}\geq 2k-4$.
Let A,B,S be finite subsets of an abelian group G. Suppose that the restricted sumset C={a+b: a in A, b in B, and a-b not in S} is nonempty and some c in C can be written as a+b with a in A and b in B in at most m ways. We show that if G is torsion-free or elementary abelian then |C|\geq |A|+|B|-|S| -m. We also prove that |C|\geq |A|+|B|-2|S|-m if the torsion subgroup of G is cyclic. In the case S={0} this provides an advance on a conjecture of Lev.
We consider restricted sumsets over field $F$. Let\begin{align*}C=\{a_1+\cdots+a_n:a_1\in A_1,\ldots,a_n\in A_n, a_i-a_j\notin S_{ij}\ \text{if}\ i\not=j\},\end{align*} where $S_{ij}(1\leqslant i\not=j\leqslant n)$ are finite subsets of $F$ with cardinality $m$, and $A_1,\ldots, A_n$ are finite nonempty subsets of $F$ with $|A_1|=\cdots=|A_n|=k$. Let $p(F)$ be the additive order of the identity of $F$. It is proved that $|C|\geqslant \min\{p(F),\ \ n(k-1)-mn(n-1)+1\}$ if $p(F)>mn$. This conclusion refines the result of Hou and Sun.
Let G be any additive abelian group with cyclic torsion subgroup, and let A, B and C be finite subsets of G with cardinality n>0. We show that there is a numbering {a_i}_{i=1}^n of the elements of A, a numbering {b_i}_{i=1}^n of the elements of B and a numbering {c_i}_{i=1}^n of the elements of C, such that all the sums a_i+b_i+c_i (i=1,...,n) are distinct. Consequently, each subcube of the Latin cube formed by the Cayley addition table of Z/NZ contains a Latin transversal. This additive theorem can be further extended via restricted sumsets in a field.
We investigate sumset decompositions of quite general sets with restricted prime factors. We manage to handle certain sets, such as the smooth numbers, even though they have little sieve amenability, and conclude that these sets cannot be written as a ternary sumset. This proves a conjecture by Sárközy. We also clean up and sharpen existing results on sumset decompositions of the prime numbers.
Direct and Inverse Problems for Restricted Signed Sumsets -- II
本文研究受限h重带符号和集的直接与逆问题，在非负整数集合上完全证明了Bhanja等人提出的h≥4情形猜想，从而彻底解决了所有相关猜想。
The restricted sumsets in finite abelian groups
该研究针对有限阿贝尔群的非空子集，给出了由不同元素构成的k元限制和集的基数下界，为相关数论与组合问题提供了定量结果。
Suppose that $A,B$ are two non-empty subsets of the finite nilpotent group $G$. If $A\not=B$, then the cardinality of the restricted sumset $$A\dotplus B={a+b: a\in A, b\in B, a\neq b} $$ is at least $$\min{p(G),|A|+|B|-2},$$ where $p(G)$ denotes the least prime factor of $|G|$.
Multiplicative subgroups are not restricted sumsets
研究素域中哪些真乘法子群可表示为特定形式的限制和集，证明\(|H|\geq7\)时不满足，\(|H|\in\{1,3,6\}\)时存在并分类，解决了广义Sárközy猜想限制和集类似问题，扩展细化前人结果。
In this paper, we develop Terence Tao's harmonic analysis method and apply it to restricted sumsets. The well known Cauchy-Davenport theorem asserts that if $A$ and $B$ are nonempty subsets of $Z/pZ$ with $p$ a prime, then $|A+B|\ge min{p,|A|+|B|-1}$, where $A+B={a+b: a\in A, b\in B}$. In 2005, Terence Tao gave a harmonic analysis proof of the Cauchy-Davenport theorem, by applying a new form of the uncertainty principle on Fourier transform. We modify Tao's method so that it can be used to prove the following extension of the Erdos-Heilbronn conjecture: If $A,B,S$ are nonempty subsets of $Z/pZ…
On an inverse problem for restricted sumsets
本文研究了限制和集的反问题，在Liu和Sun于2002年给出的下界基础上，确定了当该下界达到时集合A的结构。
A note on iterated sumsets races
本文构造同直径有限整数集 A、B，使迭代和集基数差序列的符号至少改变 n 次，回答 Nathanson 的迭代和集竞赛问题，并作为理解 Kravitz 更强结果的铺垫。
Let G be an additive abelian group whose finite subgroups are all cyclic. Let A_1,...,A_n (n>1) be finite subsets of G with cardinality k>0, and let b_1,...,b_n be pairwise distinct elements of G with odd order. We show that for every positive integer m\leq (k-1)/(n-1) there are more than (k-1)n-(m+1)n(n-1)/2 sets {a_1,...,a_n} such that a_1\in A_1,..., a_n\in A_n, and both a_i\not=a_j and ma_i+b_i\not=ma_j+b_j (or both ma_i\not=ma_j and a_i+b_i\not=a_j+b_j) for all 1\leq i<j\leq n. This extends a recent result of Dasgupta, Károlyi, Serra and Szegedy on Snevily's conjecture. Actually stronger …
These notes basically contain a material of two mini--courses which were read in Göteborg in April 2015 during the author visit of Chalmers & Göteborg universities and in Beijing in November 2015 during "Chinese--Russian Workshop on Exponential Sums and Sumsets". The article is a short introduction to a new area of Additive Combinatorics which is connected which so--called the higher sumsets as well as with the higher energies. We hope the notes will be helpful for a reader who is interested in the field.
Equidistribution in 2-Nilpotent Polish Groups and triple restricted sumsets
本文研究2-幂零局部紧波兰群的等分布定理，证明了在任意可数离散阿贝尔群中，正密度子集存在三重受限和集。
Direct and Inverse Problems for Restricted Signed Sumsets -- I
本文研究整数加法群中受限h重带符号和集的直接与逆问题，完整证明了Bhanja等人对正整数集合在h≥4时提出的最优大小与结构猜想。
Judicious partitions for restricted self-sumsets in cyclic groups
本文研究循环群着色中受限自和集的极小极大问题，确定素数情形的精确最小值，并给出一般情形的紧界，结合受限Erdős–Heilbronn现象与块/陪集着色证明最优着色结构。
Let $A$ and $B$ be additive sets of $\mathbb{Z}_{2k}$, where $A$ has cardinality $k$ and $B=v.\complement A$ with $v\in\mathbb{Z}_{2k}^{\times}$. In this note some bounds for the cardinality of $A+B$ are obtained, using four different approaches. We also prove that in a special case the bound is not sharp and we can recover the whole group as a sumset.
Extended inverse results for restricted h-fold sumset in integers
本文研究整数有限集的限制 h 重和集逆问题，将 h=2、3、4 的已有结果推广到任意 h≥3，并刻画特定和集基数下集合 A 的全部可能结构。
Let $A$ be a multiplicative subgroup of $\mathbb Z_p^*$. Define the $k$-fold sumset of $A$ to be $kA=\{x_1+\dots+x_k:x_i \in A,1\leq i\leq k\}$. We show that $6A\supseteq \mathbb Z_p^*$ for $|A| > p^{\frac {11}{23} +ε}$. In addition, we extend a result of Shkredov to show that $|2A|\gg |A|^{\frac 85-ε}$ for $|A|\ll p^{\frac 59}$.
A Note on the Sum-Product Problem and the Convex Sumset Problem
该文为实数集上的求和-乘积猜想和凸求和集问题提供了新的指数界。
In this paper we present a procedure which allows to transform a subset $A$ of $\mathbb{Z}_{p}$ into a set $ A'$ such that $ |2\hspace{0.15cm}\widehat{} A'|\leq|2\hspace{0.15cm}\widehat{} A | $, where $2\hspace{0.15cm}\widehat{} A$ is defined to be the set $\left\{a+b:a\neq b,\;a,b\in A\right\}$. From this result, we get some lower bounds for $ |2\hspace{0.15cm}\widehat{} A| $. Finally, we give some remarks related to the problem for which sets $A\subset \mathbb{Z}_{p}$ we have the equality $|2\hspace{0.15cm}\widehat{} A|=2|A|-1$.
Let $d \geq 4$ be a natural number and let $A$ be a finite, non-empty subset of $\mathbb{R}^d$ such that $A$ is not contained in a translate of a hyperplane. In this setting, we show that \[ |A-A| \geq \bigg(2d - 2 + \frac{1}{d-1} \bigg) |A| - O_{d}(|A|^{1- δ}), \] for some absolute constant $δ>0$ that only depends on $d$. This provides a sharp main term, consequently answering questions of Ruzsa and Stanchescu up to an $O_{d}(|A|^{1- δ})$ error term. We also prove new lower bounds for restricted type difference sets and asymmetric sumsets in $\mathbb{R}^d$.
Note on the sumset of squares
本文证明了平方数有限子集的和集大小下界，但该结果已被 Mei-Chu Chang 证明，作者决定撤回论文。
Critical Numbers for Restricted Sumsets: Rigidity and Collapse in Finite Abelian Groups
本文研究了有限阿贝尔群中受限和集的临界数，揭示了偶数阶群的刚性特征与奇数阶群的崩溃现象，并解决了代数编码理论中的一个猜想。
For finite sets of integers $A_1, A_2 ... A_n$ we study the cardinality of the $n$-fold sumset $A_1+... +A_n$ compared to those of $n-1$-fold sumsets $A_1+... +A_{i-1}+A_{i+1}+... A_n$. We prove a superadditivity and a submultiplicativity property for these quantities. We also examine the case when the addition of elements is restricted to an addition graph between the sets.
On restricted sumsets with bounded degree relations
该研究在有限域素数域的限制和集问题中，证实了Lev关于匹配关系下限制和集下界的猜想（当两集合大小和不超过(1-ε)p且p足够大时），方法可推广到有界度关系，还构造了新的匹配关系下的和集上界例子，揭示了与经典Erdős–Heilbronn问题的差异。
Critical Restricted Sumsets at the Boundary $\lvert A\rvert+\lvert B\rvert=p$
本文分类了满足 $|A|+|B|=p$ 且 $|A\RS B|=p-2$ 的临界受限和集，给出显式模型和等价类计数，并构造反例反驳边界下方的逆命题。
Linear Algebraic Method and the Erdős-Heilbronn Conjecture
本文通过发展Das的线性代数方法，给出了受限和集的Alon-Nathanson-Ruzsa定理的新初等证明，从而证明了埃罗什-海林浓猜想。
A set of positive integers $A \subset \mathbb{Z}_{> 0}$ is \emph{log-sparse} if there is an absolute constant $C$ so that for any positive integer $x$ the sequence contains at most $C$ elements in the interval $[x,2x)$. In this note we study arithmetic progressions in sums of log-sparse subsets of $\mathbb{Z}_{> 0}$. We prove that for any log-sparse subsets $S_1, \dots, S_n$ of $\mathbb{Z}_{> 0},$ the sumset $S = S_1 + \cdots + S_n$ cannot contain an arithmetic progression of size greater than $n^{(1+o(1))n}.$ We also show that this is nearly tight by proving that there exist log-sparse sets $…
When Do Restricted Sumsets Cover a Finite Abelian Group?
该研究针对有限阿贝尔群的受限和集覆盖问题，证明奇阶群的尖锐大阶阈值，解决相关极限阈值问题，还将结果应用于MDS椭圆码，改进半尺度猜想并得到精确尺度界。
A note on arithmetic progressions with restricted differences
本文通过调整陶的切片排名方法，将Ellenberg-Gijswijt定理扩展到禁止具有受限差值的等差数列问题，证明了当q为奇素数幂时，若集合S包含0且大小超过(q+1)/2，且A中不含三元等差数列的公差在S^n中，则A的大小上限为q^{(1-ε_q)n}。
Let $\mathcal{A}=(a_n)_{n\in\mathbb{N}_+}$ be a sequence of positive integers. Let $p_\mathcal{A}(n,k)$ denote the number of multi-color partitions of $n$ into parts in $\{a_1,\ldots,a_k\}$. We examine several arithmetic properties of the sequence $(p_\mathcal{A}(n,k) \pmod{m})_{n\in\mathbb{N}}$ for an arbitrary fixed integer $m\geqslant2$. We investigate periodicity of the sequence and lower and upper bounds for the density of the set $\{n\in\mathbb{N}: p_\mathcal{A}(n,k) \equiv i \pmod{m}\}$ for a fixed positive integer $k$ and $i\in\{0,1,\ldots, m-1\}$. In particular, we apply our results t…
Stabilizers, Measures and IP-sets
本文受 Hrushovski 稳定子定理启发，用初等模型论方法重新证明和集现象与 IP 集的相关已有结果。
A note on congruences modulo 7 and 11 for two restricted partition functions
本文通过q级数技术研究了某些受限划分函数在7和11模下的同余关系，并推广了之前使用模形式方法得到的结果。
Let $D$ be a strongly connected digraph. An arc set $S$ of $D$ is a \emph{restricted arc-cut} of $D$ if $D-S$ has a non-trivial strong component $D_{1}$ such that $D-V(D_{1})$ contains an arc. The \emph{restricted arc-connectivity} $λ'(D)$ of a digraph $D$ is the minimum cardinality over all restricted arc-cuts of $D$. A strongly connected digraph $D$ is \emph{$λ'$-connected} when $λ'(D)$ exists. This paper presents a family $\cal{F}$ of strong digraphs of girth four that are not $λ'$-connected and for every strong digraph $D\notin \cal{F}$ with girth four it follows that it is $λ'$-connected.…
The restricted online Ramsey numbers were introduced by Conlon, Fox, Grinshpun and He in 2019. In a recent paper, Briggs and Cox studied the restricted online Ramsey numbers of matchings and determined a general upper bound for them. They proved that for $n=3r-1=R_2(r K_2)$ we have $\tilde{R}_{2}(r K_2;n) \leq n-1$ and asked whether this was tight. In this short note, we provide a general lower bound for these Ramsey numbers. As a corollary, we answer this question of Briggs and Cox, and confirm that for $n=3r-1$ we have $\tilde{R}_{2}(r K_2;n) = n-1$. We also show that for $n'=4r-2=R_3(r K_2)…
In this note, we provide a simple derivation of expressions for the restricted partition function and its polynomial part. Our proof relies on elementary algebra on rational functions and a lemma that expresses the polynomial part as an average of the partition function.
In this note we investigate mixed partitions with extra condition on the sizes of the blocks. We give a general formula and the generating function. We consider in more details a special case, determining the generating functions, some recurrences and a connection to r-Stirling numbers. To obtain our results, we use pure combinatorial arguments, classical manipulations of generating functions and to derive the generating functions we apply the symbolic method.
Note on polychromatic coloring of hereditary hypergraph families
本文展示了一个5一致超图反驳了Keszegh和作者关于多色染色的猜想，推进了对遗传超图族多色染色的理解，并指出该方法不适用于任意高一致性超图。
Distribution of sets of descent tops and descent bottoms on restricted permutations
本文研究模式避免排列上下降顶集与下降底集的分布，通过双射证明3字母模式下231、312避免排列的两类集合联合等分布，提出4字母模式相关猜想，且部分猜想已被他人证明。
Note on a conjecture of Talagrand: expectation thresholds vs. fractional expectation thresholds
本文利用 Park–Pham 已证明的选择器过程猜想及其 Bednorz 等人的定量强化，推出 Talagrand 期望阈值与分数期望阈值关系猜想的一个受限版本。
The goal of this note is to give a systematic method of constructing zero-free regions for the permanent in the sense of A. Barvinok, i.e. regions in the complex plane such that the permanent of a square matrix of any size with entries from this region is nonzero. We do so by refining the approach of Barvinok, which is based on his clever observation that a certain restriction on a set S involving angles implies zero-freeness; we call sets satisfying this requirement angle-restricted. This allows us to reduce the question to a low-dimensional geometry problem (notably, independent of the size …
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