Newtonian spaces based on quasi-Banach function lattices
arXiv:1210.1442
Abstract
In this paper, first-order Sobolev-type spaces on abstract metric measure spaces are defined using the notion of (weak) upper gradients, where the summability of a function and its upper gradient is measured by the "norm" of a quasi-Banach function lattice. This approach gives rise to so-called Newtonian spaces. Tools such as moduli of curve families and Sobolev capacity are developed, which allows us to study basic properties of these spaces. The absolute continuity of Newtonian functions along curves and the completeness of Newtonian spaces in this general setting are established.
Minor revision: added remarks on equivalent definitions of the Newtonian norm and the Sobolev capacity; updated the reference list; corrected Example 2.1(d); the numbering of theorems etc. is now consistent with the current version of the paper that will appear in Mathematica Scandinavica