In this paper we prove that every collection of measurable functions fα , |α| = m, coincides a.e. withmth order derivatives of a function g ∈ Cm−1 whose derivatives of order m − 1 may have any modulus of continuity weaker than that of a Lipschitz function. This is a stronger version of earlier results of Lusin, Moonens-Pfeffer and Francos. As an application we construct surfaces in the Heisenberg group with tangent spaces being horizontal a.e.
@article{bwmeta1.element.doi-10_2478_agms-2013-0008, author = {Piotr Haj\l asz and Jacob Mirra}, title = {The Lusin Theorem and Horizontal Graphs in the Heisenberg Group}, journal = {Analysis and Geometry in Metric Spaces}, volume = {1}, year = {2013}, pages = {295-301}, zbl = {1286.46036}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.doi-10_2478_agms-2013-0008} }
Piotr Hajłasz; Jacob Mirra. The Lusin Theorem and Horizontal Graphs in the Heisenberg Group. Analysis and Geometry in Metric Spaces, Tome 1 (2013) pp. 295-301. http://gdmltest.u-ga.fr/item/bwmeta1.element.doi-10_2478_agms-2013-0008/
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