arXiv subjects
Publications and source records attributed to Xuanji Hou.
We construct 1-dim difference Schr\"odinger operators with a class of Gevrey potentials such that Cantor spectrum occurs together with the estimations of open spectral gaps . The proof is based on KAM and Moser-P\"oschel argument .
We establish a close connection between acceleration and dynamical degree for one-frequency quasi-periodic compact cocycles, by showing that two vectors derived separately from each coincide. Based on this, we provide a dynamical classification of one-frequency quasi-periodic $\mathrm{SO}(3,\mathbb{R})$-cocycles.
In this paper, we prove that for any $d$-frequency analytic quasiperiodic Schr\"odinger operator, if the frequency is weak Liouvillean, and the potential is small enough, then the corresponding operator has absolutely continuous spectrum. Moreover, in the case $d=2$, we even establish the existence of ac spectrum under small potential and some super-Liouvillean frequency, and this result is optimal due to a recent counterexample of Avila and Jitomirskaya.
We consider the reducibility problem of cocycles $(α,A)$ on $\T^d\times U(n)$ in Gevrey classes, where $ α$ is a Diophantine vector. We prove that, if a Gevrey cocycle is conjugated to a constant cocycle $(α,C)$ by a suitable measurable conjugacy $(0,B)$, then for almost all $C$ it can be conjugated to $(α,C)$ in the same Gevrey class, provided that $A$ is sufficiently close to a constant. If $B$ is continuous we obtain it is Gevrey smooth. We consider as well the global problem of reducibility in Gevrey classes when $d=1$.