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David Feldman

Publications and source records attributed to David Feldman.

6 recordsLinked to original sources
arXiv2026

Non-isomorphism of rings of integer-coefficient holomorphic functions on disks of varying radius

For $\rho \in (0,1]$, let $R(\rho) = \mathbb{Z}[[z]] \cap O(B(0,\rho))$ denote the ring of power series with integer Taylor coefficients converging on the open disk $B(0,\rho)$. We prove that these rings are pairwise non-isomorphic as abstract rings. Three ingredients drive the proof: the ideal $(z)$ is the unique principal ideal with quotient $\mathbb{Z}$, so any isomorphism sends $z$ to a generator $g$ of $(z)$; every isomorphism is substitution by $g$, because it respects the $(z)$-adic filtration; and a Hadamard gap series with a natural boundary at $|w| = \rho_1$ forces the image $g(B(0,\rho_2))$ into $B(0,\rho_1)$, after which the Schwarz lemma and integrality of coefficients force $g = \pm z$ and $\rho_1 = \rho_2$.

math.RA↗
arXiv2026

Integer Coefficient Power Series with Prescribed Zero Sets

We prove that a discrete effective divisor on the open unit disk $\mathbb{D}$ is the zero divisor of a holomorphic function on $\mathbb{D}$ with integer Taylor coefficients if and only if it is invariant under complex conjugation. The construction uses a one-parameter deformation of the Weierstrass elementary factors in which each modified factor of order $n$ leaves all Taylor coefficients of degree $\leq n$ unchanged while shifting the coefficient of degree $n+1$ by a controlled affine amount. These modified factors act as elementary jet-correction operators: the triangular structure of the coefficient map permits an inductive rounding scheme compatible with canonical-product convergence. As a consequence, every holomorphic function on $\mathbb{D}$ differs from one with Gaussian-integer Taylor coefficients by multiplication by a nowhere-vanishing holomorphic factor.

math.CV↗
arXiv2010

Tiling Lattices with Sublattices, I

We use Fourier methods to prove that if $n > 1$ translates of sublattices of $Z^d$ tile $Z^d$, and all the sublattices are Cartesian products of arithmetic progressions, then two of the tiles must be translates of each other. This is a multi-dimensional generalization of the Mirsky-Newman Theorem.

math.CO↗
arXiv2010

Tiling Lattices with Sublattices, II

Our earlier article proved that if $n > 1$ translates of sublattices of $Z^d$ tile $Z^d$, and all the sublattices are Cartesian products of arithmetic progressions, then two of the tiles must be translates of each other. We re-prove this Theorem, this time using generating functions. We also show that for $d \geq 1$, not every finite tiling of $Z^d$ by lattices can be obtained from the trivial tiling by the process of repeatedly subdividing a tile into sub-tiles that are translates of one another.

math.CO↗
arXiv2008

Generalizing Hartogs' Trichotomy Theorem

A celebrated argument of F. Hartogs (1915) deduces the Axiom of Choice from the hypothesis of comparability for any pair of cardinals. We show how each of a sequence of seemingly much weaker hypotheses suffices. Fixing a finite number $k>1$, the Axiom of Choice follows if merely any family of $k$ cardinals contains at least one comparable pair.

math.LO↗