Spectral asymptotics for canonical systems
  Based on continuity properties of the de Branges correspondence, we develop a new approach to study the high-energy behavior of Weyl-Titchmarsh and spectral functions of $2\times2$ first order canonical systems. Our results improve several classical results and solve open problems posed by previous authors. Furthermore, they are applied to radial Dirac and radial Schr\"odinger operators as well as to Krein strings and generalized indefinite strings. 
Jonathan Eckhardt, Aleksey Kostenko, and Gerald Teschl
math.SP math-ph math.MP