Published online by Cambridge University Press: 20 November 2018
A complex linear homogeneous differential equation of the nth order is called strong disconjugate in a domain G if, for every n points z 1,…, z n in G and for every set of positive integers, k 1…, k l, k 1 + … + k l = n, the only solution y(z) of the equation which satisfies
is the trivial one y(z) = 0. The equation y (n)(z) = 0 is strong disconjugate in the whole plane and for every other set of conditions of the form y(m k (z k ) = 0, k = 1 , . . . , n, m 1 ≤ m 2... m n , there exist, in any given domain, points z 1 , . . . , z n and nontrivial polynomials of degree smaller than n, which satisfy these conditions. An analogous results holds also for real disconjugate differential equations.