Yulia Karpeshina, Young-Ran Lee
Absolutely continuous spectrum of a polyharmonic operator with a limit periodic potential in dimension two.
(522K, pdf)

ABSTRACT.  We consider a polyharmonic operator 
$H=(-\Delta)^l+V(x)$ in dimension two with $l\geq 6$, $l$ being an 
integer, and a limit-periodic potential $V(x)$. We prove that the 
spectrum contains a semiaxis of absolutely continuous spectrum.