关键词: one-dimensional Schrödinger operator, generalized Thue-Morse sequence, Hausdorff dimension

Abstract: Let $\tau$ be a generalized Thue-Morse substitution on a two-letter alphabet $\{a, b\}$:$\tau(a)=a^mb^m$, $\tau(b)=b^ma^ms$ for the integer $m\ge 2$. Let $\xi$ be a sequence in $\{a, b\}^{\mathbb{Z}}$ that is generated by $\tau$. We study the one-dimensional Schrödinger operator $H_{m, \lambda}$ on $l^2(\mathbb{Z})$ with a potential given by $$v(n)=\lambda V_{\xi}(n), $$ where $\lambda>0$ is the coupling and $V_\xi(n)=1$ ($V_\xi(n)=-1$) if $\xi(n)=a$ ($\xi(n)=b$). Let $\Lambda_2=2$, and for $m>2$, let $\Lambda_m=m$ if $m\equiv0\mod 4$; let $\Lambda_m=m-3$ if $m\equiv1\mod 4$; let $\Lambda_m=m-2$ if $m\equiv2\mod 4$; let $\Lambda_m=m-1$ if $m\equiv3\mod 4$. We show that the Hausdorff dimension of the spectrum $\sigma(H_{m, \lambda})$ satisfies that $$\dim_H \sigma(H_{m, \lambda})> \frac{\log \Lambda_m}{\log 64m+4}.$$ It is interesting to see that $\dim_H \sigma(H_{m, \lambda})$ tends to $1$ as $m$ tends to infinity.

Key words: one-dimensional Schrödinger operator, generalized Thue-Morse sequence, Hausdorff dimension