On the identity of minimal and maximal realizations related to Fourier series operators
Boulahia and the present authors introduced the Orlicz norm in the class -a.p. of Besicovitch-Orlicz almost periodic functions and gave several formulas for it; they also characterized the reflexivity of this space [Comment. Math. Univ. Carolin. 43 (2002)]. In the present paper, we consider the problem of k-convexity of -a.p. with respect to the Orlicz norm; we give necessary and sufficient conditions in terms of strict convexity and reflexivity.
Since the trigonometric Fourier series of an integrable function does not necessarily converge to the function in the mean, several additional conditions have been devised to guarantee the convergence. For instance, sufficient conditions can be constructed by using the Fourier coefficients or the integral modulus of the corresponding function. In this paper we give a Hardy-Karamata type Tauberian condition on the Fourier coefficients and prove that it implies the convergence of the Fourier series...
The norm of a trigonometric polynomial with non zero coefficients of absolute value not less than 1 exceeds a fixed positive multiple of
We show that the functions in L2(Rn) given by the sum of infinitely sparse wavelet expansions are regular, i.e. belong to C∞L2 (x0), for all x0 ∈ Rn which is outside of a set of vanishing Hausdorff dimension.