Bulletin of the London Mathematical Society Advance Access originally published online on March 11, 2008
Bulletin of the London Mathematical Society 2008 40(2):181-192; doi:10.1112/blms/bdm108
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© 2008 London Mathematical Society
Traces and extensions of matrix-weighted Besov spaces
Mathematics Department
University of Tennessee
Knoxville, TN 37996
USA
frazier@math.utk.edu
Department of Mathematics
Arizona State University
Tempe, AZ 85287-1804
USA
Received 26 February 2006. Revision received 27 July 2007.
Let V be a matrix weight on
n+1 and let W be a matrix weight on
n, satisfying, for example, the matrix Ap condition. Define the trace, or restriction, operator Tr by Tr (f)(x')=f(x', 0), where x'
n and f is a function on
n+1. If
–1/p>n (1/p–1)++(β–n)/p, where β is the doubling exponent of W, then the trace operator is bounded from
into
(matrix-weighted Besov spaces) if and only if the weights V and W uniformly satisfy an estimate controlling the average of
on any dyadic cube I
n by the average of
on Q(I)=Ix[0,
(I)], for all
. If V and W satisfy the converse inequality, then there exists a continuous linear map
. If both inequalities hold, then Tr
Ext is the identity on
.
2000 Mathematics Subject Classification 42B35, 47B38, 42B25 (primary).
Second author is partially supported by the NSF grants DMS-0401602 and DMS-0531337.