arXiv subjects
Publications and source records attributed to Melvyn B. Nathanson.
The set $A$ is an asymptotic nonbasis of order $h$ for an additive abelian group $X$ if there are infinitely many elements of $X$ not in the $h$-fold sumset $hA$. For all $h \geq 2$, this paper constructs new classes of asymptotic nonbases of order $h$ for $\mathbf{Z}$ and for $\mathbf{N}_0$ that are not subsets of maximal asymptotic nonbases.
Applied to a nonnegative $m\times n$ matrix with a nonzero $σ$-diagonal, the sequence of matrices constructed by alternate row and column scaling conveges to a doubly stochastic matrix. It is proved that if this sequence converges after only a finite number of scalings, then it converges after at most two scalings.
A polynomial is real-rooted if all of its roots are real. This note gives a simple proof of the Hermite-Sylvester theorem that a polynomial $f(x) \in {\mathbf R}[x]$ is real-rooted if and only if an associated quadratic form is positive semidefinite.
Sinkhorn's alternative minimization algorithm applied to a positive $n\times n$ matrix converges to a doubly stochastic matrix. If the algorithm, applied to a $2\times 2$ matrix, converges in a finite number of iterations, then it converges in at most two iterations, and the structure of such matrices is determined.
This is an introduction to the class of groups that are locally embeddable into finite groups.
The process of alternately row scaling and column scaling a positive $n \times n$ matrix $A$ converges to a doubly stochastic positive $n \times n$ matrix $S(A)$, often called the \emph{Sinkhorn limit} of $A$. The main result in this paper is the computation of exact formulae for the Sinkhorn limits of certain symmetric positive $3\times 3$ matrices.
The alternate row and column scaling algorithm applied to a positive $n\times n$ matrix $A$ converges to a doubly stochastic matrix $S(A)$, sometimes called the \emph{Sinkhorn limit} of $A$. For every positive integer $n$, a two parameter family of row but not column stochastic $n\times n$ positive matrices is constructed that become doubly stochastic after exactly one column scaling.
The process of alternately row scaling and column scaling a positive $n \times n$ matrix $A$ converges to a doubly stochastic positive $n \times n$ matrix $S(A)$, called the \emph{Sinkhorn limit} of $A$. Exact formulae for the Sinkhorn limits of certain symmetric positive $3\times 3$ matrices are computed, and related problems in diophantine approximation are considered.
Let $\mathcal A = (A_1,\ldots, A_n)$ be a sequence of nonempty finite sets of positive real numbers, and let $\mathcal{B} = (B_1,\ldots, B_n)$ be a sequence of infinite discrete sets of positive real numbers. A weighted real Egyptian number with numerators $\mathcal{A}$ and denominators $\mathcal{B}$ is a real number $c$ that can be represented in the form \[ c = \sum_{i=1}^n \frac{a_i}{b_i} \] with $a_i \in A_i$ and $b_i \in B_i$ for $i \in \{1,\ldots, n\}$. In this paper, classical results of Sierpinski for Egyptian fractions are extended to the set of weighted real Egyptian numbers.
Every set $A$ of positive integers with upper Banach density 1 contains an infinite sequence of pairwise disjoint subsets $(B_i)_{i=1}^{\infty}$ such that $B_i$ has upper Banach density 1 for all $i \in \mathbf{N}$ and $\sum_{i\in I} B_i \subseteq A$ for every nonempty finite set $I$ of positive integers.
Let $R$ be a commutative ring $R$ with $1_R$ and with group of units $R^{\times}$. Let $Φ= Φ(t_1,\ldots, t_h) = \sum_{i=1}^h φ_it_i$ be an $h$-ary linear form with nonzero coefficients $φ_1,\ldots, φ_h \in R$. Let $M$ be an $R$-module. For every subset $A$ of $M$, the image of $A$ under $Φ$ is \[ Φ(A) = \{ Φ(a_1,\ldots, a_h) : (a_1,\ldots, a_h) \in A^h \}. \] For every subset $I$ of $\{1,2,\ldots, h\}$, there is the subset sum $ s_I = \sum_{i\in I} φ_i. $ Let $ \mathcal{S} (Φ) = \{s_I: \emptyset \neq I \subseteq \{1,2,\ldots, h\} \}. $ Theorem. Let $Υ(t_1,\ldots, t_g) = \sum_{i=1}^g \upsilon_it_i$ and $Φ(t_1,\ldots, t_h) = \sum_{i=1}^h φ_it_i$ be linear forms with nonzero coefficients in the ring $R$. If $\{0, 1\} \subseteq \mathcal{S} (Υ)$ and $\mathcal{S} (Φ) \subseteq R^{\times}$, then for every $\varepsilon > 0$ and $c > 1$ there exist a finite $R$-module $M$ with $|M| > c$ and a subset $A$ of $M$ such that $Υ(A \cup \{0\}) = M$ and $|Φ(A)| < \varepsilon |M|$.
An additive system for the nonnegative integers is a family (A_i)_{i\in I} of sets of nonnegative integers with 0 \in A_i for all i \in I such that every nonnegative integer can be written uniquely in the form \sum_{i\in I} a_i with a_i \in A_i for all i and a_i \neq 0 for only finitely many i. In 1956, de Bruijn proved that every additive system is constructed from an infinite sequence (g_i)_{i \in \N} of integers with g_i \geq 2 for all i, or is a contraction of such a system. This paper gives a complete classification of the "uncontractable" or "indecomposable" additive systems, and also considers limits and stability of additive systems.
A partition of a positive integer $n$ is a representation of $n$ as a sum of a finite number of positive integers (called parts). A trapezoidal number is a positive integer that has a partition whose parts are a decreasing sequence of consecutive integers, or, more generally, whose parts form a finite arithmetic progression. This paper reviews the relation between trapezoidal numbers, partitions, and the set of divisors of a positive integer. There is also a complete proof of a theorem of Sylvester that produces a stratification of the partitions of an integer into odd parts and partitions into disjoint trapezoids.
This is an expository paper in which it is proved that, for every infinite field ${\mathbf{F}}$, the polynomial ring ${\mathbf{F}}[t_1,\ldots, t_n]$ has Krull dimension $n$. The proof uses only "high school algebra" and the rudiments of undergraduate "abstract algebra."
The dimensions of certain varieties defined by monomials are computed using only high school algebra.
An MSTD set is a finite set with more pairwise sums than differences. $(Υ,Φ)$-ismorphisms are generalizations of Freiman isomorphisms to arbitrary linear forms. These generalized isomorphisms are used to prove that every finite set of real numbers is Freiman isomorphic to a finite set of integers. This implies that there exists no MSTD set $A$ of real numbers with $|A| \leq 7$, and, up to Freiman isomorphism, there exists exactly one MSTD set $A$ of real numbers with $|A| = 8$.
An MSTD set is a finite set of integers with more sums than differences. It is proved that, for infinitely many positive integers $k$, there are infinitely many affinely inequivalent MSTD sets of cardinality $k$. There are several related open problems.