Balanced measures, sparse domination and complexity-dependent weight classes

We study sparse domination for operators defined with respect to an atomic filtration on a space equipped with a general measure \(\mu \) $\mu$ . In the case of Haar shifts, \(L^p\) $L^p$ -boundedness is known to require a weak regularity condition, which we prove to be sufficient to have a sparse domination-like theorem. Our result allows us to characterize the class of weights where Haar shifts are bounded. A surprising novelty is that said class depends on the complexity of the Haar shift operator under consideration. Our results are qualitatively sharp.