1. Department of Mathematics, Portland State University, Portland, OR 97207, USA; 2. Institute for Mathematics and Its Applications, University of Minnesota, Minneapolis, MN 55455, USA
Abstract:
We show that a Lipschitz domain can be expanded solely near a part of its boundary, assuming that the part is enclosed by a piecewise C1 curve. The expanded domain as well as the extended part are both Lipschitz. We apply this result to prove a regular decomposition of standard vector Sobolev spaces with vanishing traces only on part of the boundary. Another application in the construction of low-regularity projectors into finite element spaces with partial boundary conditions is also indicated.