Fourier integral operators with fold singularities.
We show that the Fourier-Laplace series of a distribution on the real, complex or quarternionic projective space is uniformly Cesàro-summable to zero on a neighbourhood of a point if and only if this point does not belong to the support of the distribution.
Two operator-valued Fourier multiplier theorems for Hölder spaces are proved, one periodic, the other on the line. In contrast to the -situation they hold for arbitrary Banach spaces. As a consequence, maximal regularity in the sense of Hölder can be characterized by simple resolvent estimates of the underlying operator.
We study Fourier multipliers resulting from martingale transforms of general Lévy processes.
In questo lavoro facciamo vedere, con un argomento di omogeneità di tipo Knapp, che se vale un teorema di restrizione per una ipersuperficie compatta, convessa e di tipo finito, allora si possono provare stime isotropiche ottimali per la trasformata di Fourier della misura di indotta dalla misura di Lebesgue sulla superficie.