An inequality for certain random sequences more general than martingales or nonnegative submartingales is proved. Three special cases are deduced, one of which generalizes and refines a result of Austin. As an application of the inequality, the special cases are used to give new proofs of Burkholder's $L \log L$ and $L_p$ (for $1 < p \leqslant 2$) inequalities for the square function of a martingale or a nonnegative submartingale.
@article{1176994898,
author = {Chen, Louis H. Y.},
title = {A Martingale Inequality for the Square and Maximal Functions},
journal = {Ann. Probab.},
volume = {7},
number = {6},
year = {1979},
pages = { 1051-1055},
language = {en},
url = {http://dml.mathdoc.fr/item/1176994898}
}
Chen, Louis H. Y. A Martingale Inequality for the Square and Maximal Functions. Ann. Probab., Tome 7 (1979) no. 6, pp. 1051-1055. http://gdmltest.u-ga.fr/item/1176994898/