Quantitative absolute continuity of planar measures with two independent Alberti representations

We study measures $\mu$ on the plane with two independent Alberti representations. It is known, due to Alberti, Cs"ornyei, and Preiss, that such measures are absolutely continuous with respect to Lebesgue measure. The purpose of this paper is to quantify the result of A-C-P. Assuming that the representations of $\mu$ are bounded from above, in a natural way to be defined in the introduction, we prove that $\mu \in L^2$. If the representations are also bounded from below, we show that $\mu$ satisfies a reverse H"older inequality with exponent $2$, and is consequently in $L^{2+ϵ}$ by Gehring’s lemma. A substantial part of the paper is also devoted to showing that both results stated above are optimal.