Let ${}_{\infty }\left(B_X\right)$ be the Banach space of all bounded and continuous functions on the closed unit ball $B_X$ of a complex Banach space X and holomorphic on the open unit ball, with sup norm, and let ${}_u\left(B_X\right)$ be the subspace of ${}_{\infty }\left(B_X\right)$ of those functions which are uniformly continuous on $B_X$. A subset $B\subset B_X$ is a boundary for ${}_{\infty }\left(B_X\right)$ if $\parallel f\parallel =su{p}_{x\in B}\left|f\left(x\right)\right|$ for every $f{\in }_{\infty }\left(B_X\right)$. We prove that for X = d(w,1) (the Lorentz sequence space) and X = C₁(H), the trace class operators, there is a minimal closed boundary for ${}_{\infty }\left(B_X\right)$. On the other hand, for X = , the Schreier space,...

We prove that certain maximal ideals in Beurling algebras on the unit disc have approximate identities, and show the existence of functions with certain properties in these maximal ideals. We then use these results to prove that if T is a bounded operator on a Banach space X satisfying $\parallel T^n\parallel =O\left(n^{\beta }\right)$ as n → ∞ for some β ≥ 0, then ${\sum }_{n=1}^{\infty }\parallel {(1-T)}^{n}x\parallel /\parallel {(1-T)}^{n-1}x\parallel$ diverges for every x ∈ X such that ${(1-T)}^{\left[\beta \right]+1}x\ne 0$.

Nous étudions les sous-espaces biinvariants du shift usuel sur les espaces à poids$$L_{\omega }^2=\left\{f\in L^2\left(𝕋\right):\parallel f{\parallel }_{\omega }={\left(\sum _{n\in \mathbb{Z}}\left|f\left(n\right)\right|{\omega }^2\left(n\right)\right)}^{1/2}\<+\infty \right\},$$où $\omega \left(n\right)=(1+n{)}^p,n\ge 0$ et $\frac{\omega \left(n\right)}{(1+|n|{)}^p}\overrightarrow{n\to -\infty }+\infty$, pour un certain entier $p\ge 1$. Nous montrons que la trace analytique de tout sous-espace biinvariant est de type spectral, lorsque ${\sum }_{n\ge 2}\frac{1}{nlog\omega (-n)}$ diverge, mais que ceci n’est plus valable lorsque ${\sum }_{n\ge 2}\frac{1}{nlog\omega (-n)}$ converge.

We study the spectrum of certain Banach algebras of holomorphic functions defined on a domain Ω where ∂̅-problems with certain estimates can be solved. We show that the projection of the spectrum onto ℂⁿ equals Ω̅ and that the fibers over Ω are trivial. This is used to solve a corona problem in the special case where all but one generator are continuous up to the boundary.

Let A be a semisimple commutative regular tauberian Banach algebra with spectrum ${\Sigma }_A$. In this paper, we study the norm spectra of elements of $\overline{span}{\Sigma }_A$ and present some applications. In particular, we characterize the discreteness of ${\Sigma }_A$ in terms of norm spectra. The algebra A is said to have property (S) if, for all $\phi \in \overline{}{\Sigma }_{A}0$, φ has a nonempty norm spectrum. For a locally compact group G, let ${ℳ}_2^d\left(Ĝ\right)$ denote the C*-algebra generated by left translation operators on $L^2\left(G\right)$ and $G_d$ denote the discrete group G. We prove that the Fourier...

We study the relation between standard ideals of the convolution Sobolev algebra ${₊}^{\left(n\right)}\left(tⁿ\right)$ and the convolution Beurling algebra L¹((1+t)ⁿ) on the half-line (0,∞). In particular it is proved that all closed ideals in ${₊}^{\left(n\right)}\left(tⁿ\right)$ with compact and countable hull are standard.