© 1994 by London Mathematical Society
© The London Mathematical Society
Smooth Approximation of Sobolev Functions on Planar Domains
Department of Mathematics, University of Hawaii Honolulu, Hawaii 96822, USA
Received 19 March 1992. Revision received 27 July 1992.
We examine two related problems concerning a planar domain
. The first is whether Sobolev functions on
can be approximated by global C
functions, and the second is whether approximation can be done by functions in C
(
) which, together with all derivatives, are bounded on
. We find necessary and sufficient conditions for certain types of domains, such as starshaped domains, and we construct several examples which show that the general problem is quite difficult, even in the simply connected case.
E-mail: waynes{at}math.hawaii.edu
alex{at}math.hawaii.edu
davids{at}math.hawaii.edu
The first author is supported in part by a grant from the National Science Foundation.