Asymptotics and monodromy of the algebraic spectrum of quasi-exactly   solvable sextic oscillator
  Below we study theoretically and numerically the asymptotics of the algebraic part of the spectrum for the quasi-exactly solvable sextic potential, its level crossing points, and its monodromy in the complex plane of its parameter. We also discuss connection between the quasi-exactly solvable sextic and the classical quartic potential. 
Boris Shapiro and Milos Tater
math-ph math.CA math.MP quant-ph