Riccati equations, zeroes and independece.
A problem about representations of countable, commutative semigroups leads to an analytic non-Borel set.
Méthode probabiliste pour les moyennes de Fourier, sur un groupe fini, relatives à des mesures singulières.
The note discusses a probabilistic method for constructing “small” sets, with regard to differentiable transformations and to quantitative measures of independence.
We obtain three theorems about transformation of sets of multiplicity onto Kronecker sets, by means of functions of various differentiability classes. The same method yields an improved theorem on the union of two Kronecker sets.
We study the class of singular measures whose Fourier partial sums converge to 0 in the metric of the weak space; symmetric sets of constant ratio occur in an unexpected way.
Doubling measures appear in relation to quasiconformal mappings of the unit disk of the complex plane onto itself. Each such map determines a homeomorphism of the unit circle on itself, and the problem arises, which mappings f can occur as boundary mappings?
According to a theorem of Martio, Rickman and Väisälä, all nonconstant C-smooth quasiregular maps in , ≥3, are local homeomorphisms. Bonk and Heinonen proved that the order of smoothness is sharp in . We prove that the order of smoothness is sharp in . For each ≥5 we construct a C-smooth quasiregular map in with nonempty branch set.
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