All a b c d e f g h i j k l m n o p q r s t u v w x y z Other

Previous Page 29 Next

Displaying 561 – 580 of 914

Showing per page

Podal subspaces on the unit polydisk

Kunyu Guo (2002)

Studia Mathematica

Beurling's classical theorem gives a complete characterization of all invariant subspaces in the Hardy space H²(D). To generalize the theorem to higher dimensions, one is naturally led to determining the structure of each unitary equivalence (resp. similarity) class. This, in turn, requires finding podal (resp. s-podal) points in unitary (resp. similarity) orbits. In this note, we find that H-outer (resp. G-outer) functions play an important role in finding podal (resp. s-podal) points. By the methods...

Pointwise multiplication operators on weighted Banach spaces of analytic functions

J. Bonet, P. Domański, M. Lindström (1999)

Studia Mathematica

For a wide class of weights we find the approximative point spectrum and the essential spectrum of the pointwise multiplication operator M φ , M φ ( f ) = φ f , on the weighted Banach spaces of analytic functions on the disc with the sup-norm. Thus we characterize when M φ ' is Fredholm or is an into isomorphism. We also study cyclic phenomena for the adjoint map M φ ' .

Power boundedness in Banach algebras associated with locally compact groups

E. Kaniuth, A. T. Lau, A. Ülger (2014)

Studia Mathematica

Let G be a locally compact group and B(G) the Fourier-Stieltjes algebra of G. Pursuing our investigations of power bounded elements in B(G), we study the extension property for power bounded elements and discuss the structure of closed sets in the coset ring of G which appear as 1-sets of power bounded elements. We also show that L¹-algebras of noncompact motion groups and of noncompact IN-groups with polynomial growth do not share the so-called power boundedness property. Finally, we give a characterization...

Power-bounded elements and radical Banach algebras

Graham Allan (1997)

Banach Center Publications

Firstly, we give extensions of results of Gelfand, Esterle and Katznelson--Tzafriri on power-bounded operators. Secondly, some results and questions relating to power-bounded elements in the unitization of a commutative radical Banach algebra are discussed.

Products of n open subsets in the space of continuous functions on [0,1]

Ehrhard Behrends (2011)

Studia Mathematica

Let O₁,...,Oₙ be open sets in C[0,1], the space of real-valued continuous functions on [0,1]. The product O₁ ⋯ Oₙ will in general not be open, and in order to understand when this can happen we study the following problem: given f₁,..., fₙ ∈ C[0,1], when is it true that f₁ ⋯ fₙ lies in the interior of B ε ( f ₁ ) ⋯ B ε ( f ₙ ) for all ε > 0 ? ( B ε denotes the closed ball with radius ε and centre f.) The main result of this paper is a characterization in terms of the walk t ↦ γ(t): = (f₁(t),..., fₙ(t)) in ℝⁿ. It has to...

Projections on Hardy spaces in the Lie ball.

David Bekollé (1994)

Publicacions Matemàtiques

On the Lie ball w of Cn, n ≥ 3, we prove that for all p ∈ [1,∞), p ≠ 2, the Hardy space Hp(w) is an uncomplemented subspace of the Lebesgue space Lp(∂0w, dσ), where ∂0w denotes the Shilov boundary of w and dσ is a normalized invariant measure of ∂0w.

Currently displaying 561 – 580 of 914