English

A generalization of the Lebesgue density theorem via modulus density

General Topology 2026-04-16 v1

Abstract

In this paper, we introduce the notion of a γ\gamma-density point for Lebesgue-measurable subsets of R\mathbb{R}, where γ\gamma is a modulus function, and study its basic measure-theoretic properties. We show that every γ\gamma-density point is a Lebesgue density point, while under Condition~(A) the two notions coincide. Consequently, for such modulus functions, the set of γ\gamma-density points of a measurable set differs from the set itself only by a null set, yielding a modulus version of the Lebesgue Density Theorem. We then define the associated γ\gamma-density topology τγ\tau_\gamma and investigate its structure. In general, τγ\tau_\gamma is contained in the classical Lebesgue density topology, and if γ\gamma satisfies Condition~(A), then τγ=τd\tau_\gamma=\tau_d. We also compare τγ\tau_\gamma with ψ\psi-density topologies and establish several topological properties of τγ\tau_\gamma, including that countable sets are τγ\tau_\gamma-closed and that (R,τγ)(\mathbb{R},\tau_\gamma) is nonseparable, nonregular, and nonmetrizable. Finally, we introduce γ\gamma-approximately continuous functions, prove that they form a vector space, and show that the bounded class of such functions is a Banach space under the supremum norm.

Keywords

Cite

@article{arxiv.2604.13626,
  title  = {A generalization of the Lebesgue density theorem via modulus density},
  author = {H. S. Behmanush and M. Küçükaslan},
  journal= {arXiv preprint arXiv:2604.13626},
  year   = {2026}
}
R2 v1 2026-07-01T12:10:22.205Z