58 citations · 116 across the 14 of their papers we have counts for
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Frames generated by actions of countable discrete groups
Kjetil Roysland
We consider dual frames generated by actions of countable discrete groups on a Hilbert space. Module frames in a class of modules over a group algebra are shown to coincide with a…
Symmetries in projective multiresolution analyses
Kjetil Røysland
We give an equivariant version of Packer and Rieffel's theorem on sufficient conditions for the existence of orthonormal wavelets in projective multiresolution analyses. The scalin…
Covariant representations for matrix-valued transfer operators
Dorin Ervin Dutkay, Kjetil Roysland
Motivated by the multivariate wavelet theory, and by the spectral theory of transfer operators, we construct an abstract affine structure and a multiresolution associated to a matr…
The algebra of harmonic functions for a matrix-valued transfer operator
Dorin Ervin Dutkay, Kjetil Roysland
We analyze matrix-valued transfer operators. We prove that the fixed points of transfer operators form a finite dimensional -algebra. For matrix weights satisfying a low-pass…