One-dimensional Discrete Anderson Model in a Decaying Random Potential: from a.c. Spectrum to Dynamical Localization

We consider a one-dimensional Anderson model where the potential decays in average like $n^{-\alpha}$, $\alpha>0$. This simple model is known to display a rich phase diagram with different kinds of spectrum arising as the decay rate $\alpha$ varies. We review an article of Kiselev, Last and Simon where the authors show a.c. spectrum in the super-critical case $\alpha>\frac12$, a transition from singular continuous to pure point spectrum in the critical case $\alpha=\frac12$, and dense pure point spectrum in the sub-critical case $\alpha<\frac12$. We present complete proofs of the cases $\alpha\ge\frac12$ and simplify some arguments along the way. We complement the above result by discussing the dynamical aspects of the model. We give a simple argument showing that, despite of the spectral transition, transport occurs for all energies for $\alpha=\frac12$. Finally, we discuss a theorem of Simon on dynamical localization in the sub-critical region $\alpha<\frac12$. This implies, in particular, that the spectrum is pure point in this regime.