Slicing and fine properties for functions with bounded $\mathcal A$-variation

Abstract

We study the slicing and fine properties of functions in $\mathrm{BV}^{\mathcal A}$, the space of functions with bounded $\mathcal A$-variation. Here, $\mathcal A$ is a homogeneous linear differential operator with constant coefficients (of arbitrary order). Our main result is the characterization of all $\mathcal A$ satisfying the following one-dimensional structure theorem: every $u \in \mathrm{BV}^{\mathcal A}$ can be sliced into one-dimensional $\mathrm{BV}$-sections. Moreover, decomposing $\mathcal A u$ into an absolutely continuous part $\mathcal A^a u$, a Cantor part $\mathcal A^c u$ and a jump part $\mathcal A^j u$, each of these measures can be recovered from the corresponding classical $D^a,D^c$ and $D^j$ $BV$-derivatives of its one-dimensional sections. By means of this result, we are able to analyze the set of Lebesgue points as well as the set of jump points where these functions have approximate one-sided limits. Thus, proving a structure and fine properties theorem in $\mathrm{BV}^{\mathcal A}$. Our results extend most of the classical fine properties of $\mathrm{BV}$ (and all of those known for $\mathrm{BD}$). In particular, we establish a slicing theory and fine properties for $\mathscr {BV}^k, \mathrm{BD}^k$ and a whole class of $\mathrm{BV}^{\mathcal A}$-spaces that is not covered by the existing theory.