English

inf(M \ L)=3

Number Theory 2024-11-12 v1 Dynamical Systems

Abstract

The Lagrange and Markov spectra LL and MM describe the best constants of Diophantine approximations for irrational numbers and binary quadratic forms. In 1880, A. Markov showed that the initial portions of these spectra coincide: indeed, L(0,3)=M(0,3)L\cap (0,3) = M\cap (0,3) is a discrete set of explicit quadratic irrationals accumulating only at 33. In this article, we show that the statement above ceases to be true immediately after 33: in particular, L(3,3+ε)M(3,3+ε)L\cap (3,3+\varepsilon)\neq M\cap (3,3+\varepsilon) for all ε>0\varepsilon>0, and thus inf(ML)=3\inf(M\setminus L)=3. In fact, we derive this result as a by-product of lower bounds on the Hausdorff dimension of (ML)(3,3+ε)(M\setminus L)\cap (3,3+\varepsilon) implying that lim infε0dimH((ML)(3,3+ε))dimH(M(3,3+ε))12\liminf\limits_{\varepsilon\to 0} \frac{\dim_H((M\setminus L)\cap(3,3+\varepsilon))}{\dim_H(M\cap (3,3+\varepsilon))}\geq \frac{1}{2} and, as it turns out, these bounds are obtained from the study of projections of Cartesian products of almost affine dynamical Cantor sets via an argument of probabilistic flavor based on Baker--W\"ustholz theorem on linear forms in logarithms of algebraic numbers.

Keywords

Cite

@article{arxiv.2411.06933,
  title  = {inf(M \ L)=3},
  author = {Harold Erazo and Davi Lima and Carlos Matheus and Carlos Gustavo Moreira and Sandoel Vieira},
  journal= {arXiv preprint arXiv:2411.06933},
  year   = {2024}
}

Comments

46 pages, 5 figures

R2 v1 2026-06-28T19:55:28.961Z