Weighted maximal inequalities for
martingale~transforms
Michał Brzozowski
Adam Osękowski
Abstract:
We study the weighted maximal \(L^{1}\)-inequality for martingale transforms,
under the assumption that the underlying weight satisfies Muckenhoupt’s
condition \(A_\infty\) and that the filtration is regular.
The resulting linear dependence of the constant on the \(A_\infty\)
characteristic of the weight is optimal. The proof exploits certain special functions enjoying appropriate size conditions and concavity.
2010 AMS Mathematics Subject Classification: Primary 60G44; Secondary 60G42.
Keywords and phrases: martingale, weight, Bellman function, maximal function.