Cox, David C.; Kertz, Robert P. - In: Journal of Multivariate Analysis 18 (1986) 2, pp. 242-273
Exact comparisons are made relating EY0p, EYn-1p, and E(maxj<=n-1 Yjp), valid for all martingales Y0,...,Yn-1, for each p >= 1. Specifically, for p 1, the set of ordered triples {(x, y, z) : X = EY0p, Y = E Yn-1p, and Z = E(maxj<=n-1 Yjp) for some martingale Y0,...,Yn-1} is precisely the set {(x, y, z) : 0<=x<=y<=z<=[Psi]n,p(x, y)}, where [Psi]n,p(x, y) = x[psi]n,p(y/x) if x > 0, and = an-1,py if x = 0; here [psi]n,p is a specific recursively defined function. The result yields families of sharp...</=n-1></=n-1>