Ari Laptev, Sergej Naboko, Oleg Safronov
Absolutely continuous spectrum of Jacobi matrices
(115K, Postscript)

ABSTRACT.  We study the discrete Schr\"odinger operator 
perturbed by a three diagonal matrix of a certain class. 
We follow the approach of Deift and Killip and prove 
that the absolutely continuous 
part of the spectrum is essentially supported by [-2,2].