English

Irrationality exponent and rational approximations with prescribed growth

Number Theory 2012-02-13 v1

Abstract

Let ξ\xi be a real irrational number. We are interested in sequences of linear forms in 1 and ξ\xi, with integer coefficients, which tend to 0. Does such a sequence exist such that the linear forms are small (with given rate of decrease) and the coefficients have some given rate of growth? If these rates are essentially geometric, a necessary condition for such a sequence to exist is that the linear forms are not too small, a condition which can be expressed precisely using the irrationality exponent of ξ\xi. We prove that this condition is actually sufficient, even for arbitrary rates of growth and decrease. We also make some remarks and ask some questions about multivariate generalizations connected to Fischler-Zudilin's new proof of Nesterenko's linear independence criterion.

Cite

@article{arxiv.0910.4448,
  title  = {Irrationality exponent and rational approximations with prescribed growth},
  author = {Stéphane Fischler and Tanguy Rivoal},
  journal= {arXiv preprint arXiv:0910.4448},
  year   = {2012}
}

Comments

11 pages, to appear in Proc. Amer. Math. Soc

R2 v1 2026-06-21T14:02:27.297Z