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On the L 1 -convergence of Fourier series

S. Fridli (1997)

Studia Mathematica

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...

Recurrence for cosine series with bounded gaps

Katusi Fukuyama, Dinesh Neupane (2010)

Colloquium Mathematicae

Ullrich, Grubb and Moore proved that a lacunary trigonometric series satisfying Hadamard's gap condition is recurrent a.e. We prove the existence of a recurrent trigonometric series with bounded gaps.

Some remarks on quasi-Cohen sets

Pascal Lefèvre, Daniel Li (2001)

Colloquium Mathematicae

We are interested in Banach space geometry characterizations of quasi-Cohen sets. For example, it turns out that they are exactly the subsets E of the dual of an abelian compact group G such that the canonical injection C ( G ) / C E c ( G ) L ² E ( G ) is a 2-summing operator. This easily yields an extension of a result due to S. Kwapień and A. Pełczyński. We also investigate some properties of translation invariant quotients of L¹ which are isomorphic to subspaces of L¹.

Spectral isomorphisms of Morse flows

T. Downarowicz, Jan Kwiatkowski, Y. Lacroix (2000)

Fundamenta Mathematicae

A combinatorial description of spectral isomorphisms between Morse flows is provided. We introduce the notion of a regular spectral isomorphism and we study some invariants of such isomorphisms. In the case of Morse cocycles taking values in G = p , where p is a prime, each spectral isomorphism is regular. The same holds true for arbitrary finite abelian groups under an additional combinatorial condition of asymmetry in the defining Morse sequence, and for Morse flows of rank one. Rank one is shown to...

The support of the associated measure to the Cowen's tridiagonal matrix.

Dolores Barrios, Venancio Tomeo, Emilio Torrano (1994)

Extracta Mathematicae

In this paper we consider a class of three-term recurrence relations, whose associated tridiagonal matrices are subnormal operators. In this cases, there are measures associated to the polynomials given by such relations. We study the support of these measures.

Topological Dichotomy and Unconditional Convergence

Lefevre, Pascal (1999)

Serdica Mathematical Journal

In this paper, we give a criterion for unconditional convergence with respect to some summability methods, dealing with the topological size of the set of choices of sign providing convergence. We obtain similar results for boundedness. In particular, quasi-sure unconditional convergence implies unconditional convergence.

Two random constructions inside lacunary sets

Stefan Neuwirth (1999)

Annales de l'institut Fourier

We study the relationship between the growth rate of an integer sequence and harmonic and functional properties of the corresponding sequence of characters. In particular we show that every polynomial sequence contains a set that is Λ ( p ) for all p but is not a Rosenthal set. This holds also for the sequence of primes.

Currently displaying 41 – 60 of 80