Diophantine approximation on matrices and Lie groups
Abstract
We study the general problem of extremality for metric Diophantine approximation on submanifolds of matrices. We formulate a criterion for extremality in terms of a certain family of algebraic obstructions and show that it is sharp. In general, the almost sure diophantine exponent of a submanifold is shown to depend only on its Zariski closure, and when the latter is defined over the rational numbers, we prove that the exponent is rational and give a method to effectively compute it. This method is applied to a number of cases of interest, in particular, we manage to determine the diophantine exponent of random subgroups of certain nilpotent Lie groups in terms of representation theoretic data.
Cite
@article{arxiv.1603.03800,
title = {Diophantine approximation on matrices and Lie groups},
author = {Menny Aka and Emmanuel Breuillard and Lior Rosenzweig and Nicolas de Saxcé},
journal= {arXiv preprint arXiv:1603.03800},
year = {2017}
}
Comments
52 pages. Final version, to appear in GAFA. This version contains only minor changes from the previous version, which had two extras: a weighted analogue of the formula for the diophantine exponent of rational submanifolds, and the proof of the rationality and stability of the diophantine exponent of an arbitrary rational nilpotent Lie group