n This book deals with several aspects of fractal geometry in ? which
are closely connected with Fourier analysis, function spaces, and
appropriate (pseudo)differ- tial operators. It emerged quite recently
that some modern techniques in the theory of function spaces are
intimately related to methods in fractal geometry. Special attention is
paid to spectral properties of fractal (pseudo)differential operators;
in particular we shall play the drum with a fractal layer. In some sense
this book may be considered as the fractal twin of [ET96], where we
developed adequate methods to handle spectral problems of degenerate n
pseudodifferential operators in ? and in bounded domains. Besides a few
special properties of function spaces we relied there on sharp estimates
of entropy numbers of compact embeddings between these spaces and their
relations to the distribution of eigenvalues. Some of the main
assertions of the present book are based on just these techniques but
now in a fractal setting. Since virtually nothing of these new methods
is available in literature, a substantial part of what we have to say
deals with recent developments in the theory of function spaces, also
for their own sake. In this respect the book might also be considered as
a continuation of [Tri83] and [Tri92].