English

Growth of values of binary quadratic forms and Conway rivers

Dynamical Systems 2020-05-06 v3 Number Theory

Abstract

We study the growth of the values of binary quadratic forms QQ on a binary planar tree as it was described by Conway. We show that the corresponding Lyapunov exponents ΛQ(x)\Lambda_Q(x) as a function of the path determined by xRP1x\in \mathbb RP^1 are twice the values of the corresponding exponents for the growth of Markov numbers \cite{SV}, except for the paths corresponding to the Conway rivers, when ΛQ(x)=0.\Lambda_Q(x)=0. The relation with Galois results about continued fraction expansions for quadratic irrationals is explained and interpreted geometrically.

Keywords

Cite

@article{arxiv.1703.00038,
  title  = {Growth of values of binary quadratic forms and Conway rivers},
  author = {K. Spalding and A. P. Veselov},
  journal= {arXiv preprint arXiv:1703.00038},
  year   = {2020}
}

Comments

A few typos and the claim in Proposition 5 about semidefinite case are corrected