Analysis Mathematica
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The pointwise James type constant
Analysis Mathematica - Tập 49 - Trang 651-659 - 2023
In 2008, Takahashi introduced the James type constants. We discuss here the
pointwise James type constant: for all x ∈ X, ∥x∥ = 1, We show that in almost
transitive Banach spaces, the map x ∈ X, ∥x∥ = 1 ↦ J(x, X, t) is constant. As a
consequence and having in mind the Mazur’s rotation problem, we prove that for
almost transitive Banach spaces, the condition $$J(x,X,t) = \sqrt 2 $$ for some
unit ve...
On the absence of stability of bases in some Fréchet spaces
Analysis Mathematica - Tập 46 - Trang 761-768 - 2020
We show that, for each compact subset of the real line of infinite cardinality
with an isolated point, the space of Whitney jets on the set does not possess a
basis consisting only of polynomials. On the other hand, polynomials are dense
in any Whitney space. Thus, there are no general results about stability of
bases in Fréchet spaces.
Comparison of certain summability methods by speeds of convergence
Analysis Mathematica - Tập 29 - Trang 227-242 - 2003
We deal with families of summability methods which depend on a continuous
parameter and where two different methods are connected either by a Cesàro-type
or Euler–Knopp-type method. Extending and applying some results of [14], we are
able to compare speeds of convergence in families of generalized Nörlund methods
and to give certain Tauberian remainder theorems. Particular cases are the
families o...
Lower estimate of Tandori’s norm
Analysis Mathematica - Tập 40 - Trang 25-30 - 2014
The conventional monotonicity hypothesis on the coefficients given in the
sharpest lower estimate of the celebrated Tandori-norm is weakened to locally
almost monotonicity assumption.
A Characterization of Unitary-Antiunitary Similarity Transformations via Kubo–Ando Means
Analysis Mathematica - Tập 45 - Trang 311-319 - 2018
In this note, we characterize all those bijective transformations on the set of
positive semidefinite matrices which preserve an arbitrary unitarily invariant
norm of any given Kubo–Ando mean corresponding to an n-monotone strictly concave
generating function. This result strengthens a former theorem of Molnár and
Szokol.
Об абсолютной суммируемости рядов Фурье почти-периодических функций
Analysis Mathematica - Tập 39 - Trang 259-270 - 2013
In the article we establish some criteria of absolute summability of Fourier
series of almost periodic functions in the Besicovitch space. We consider the
case where the Fourier exponents have a limit point at infinity.
A remark on the continuity of metric projections
Analysis Mathematica - Tập 4 - Trang 13-15 - 1978
Доказывается, Что мет рическая проекция че бышевского подпространства кон ечной
ко-размерности в рефл ексивном банаховом п ространстве является слабо непре
рывной. С помощью этого резул ьтата дается отрицат ельный ответ на следующий во
прос В. Клее: «Следует ли из слабой непрерывности метри ческой проекции ее
непрерыв ность по норме?»
Composition Operators and Closures of Dirichlet Type Spaces Dμ in Bloch Type Spaces
Analysis Mathematica - Tập 45 - Trang 121-132 - 2018
We characterize the closure of Dirichlet type spaces Dμ in Bloch type spaces.
Moreover, we study the boundedness and compactness of composition operators from
Bloch type spaces to closures of Dirichlet type spaces Dμ in Bloch type spaces.
On interpolating discrete varieties for weighted spaces of entire functions
Analysis Mathematica - Tập 29 - Trang 59-74 - 2003
We study interpolating discrete varieties for weighted spaces Ap(Cn) of entire
functions such that supz∈C n|f(z)|exp(-B p(z))<∞ for some B>0. We give a
necessary and sufficient condition for a finite union of interpolating discrete
varieties to be itself interpolating. Then we use L2 techniques for ∂ to give a
sufficient geometric interpolating condition.
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