Heriot-Watt Mathematics Report Series
HWM98-69, 20 Jan 1999

Hausdorff dimension and a generalized form of simultaneous Diophantine approximation

B P Rynne and H Dickinson


Abstract

Suppose that $m$ and $n$ are positive integers, $\btau = (\tau_1,\dots,\tau_m) \in \R_+^m$ is a vector of strictly positive numbers, and $Q\subset\Z^n$ is an infinite set of integer vectors. Let $X$ denote a general point in $\R^{mn}$, which we will write in the form $X=(\x_{1},\dots, \x_{m})$, with $\x_{i} \in \R^n$, $i=1,\dots,m,$ and let $W_Q(m,n;\btau)$ be the set $$ \{ X \in \R^{mn} : \|\x_{i} . \q \| < |\q|^{-\tau_i} , \ 1 \le i \le m,\ \mbox{for infinitely many } \q \in Q \}. $$ In this paper we obtain the Hausdorff dimension of this set. We also consider a generalization of the set $W_Q(m,n;\btau)$, where the error terms $|\q|^{-\tau_i}$ in the inequalities are replaced by $\psi_i(\q)$, for general functions $\psi_i$ satisfying a certain condition `at infinity'.

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Full text: http://www.ma.hw.ac.uk/~bryan/ps_files/gnm.pdf


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