Zh. Chen et Cl. Qian, ON THE DIFFERENCE OF CONSECUTIVE EIGENVALUES OF UNIFORMLY ELLIPTIC-OPERATORS OF HIGHER ORDERS, Chinese annals of mathematics. Ser. B, 14(4), 1993, pp. 435-442
This paper considers the upper bound for the difference of consecutive
eigenvalues of a class of uniformly elliptic operators of higher orde
rs. The upper bound of lambda(n+1) - lambda(n) is dependent on the fir
st n - 1 eigenvalues and the coefficients in equations.