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Banach algebras with unique uniform norm II

S. J. Bhatt; H. V. Dedania — 2001

Studia Mathematica

Semisimple commutative Banach algebras 𝓐 admitting exactly one uniform norm (not necessarily complete) are investigated. 𝓐 has this Unique Uniform Norm Property iff the completion U(𝓐) of 𝓐 in the spectral radius r(·) has UUNP and, for any non-zero spectral synthesis ideal ℐ of U(𝓐), ℐ ∩ 𝓐 is non-zero. 𝓐 is regular iff U(𝓐) is regular and, for any spectral synthesis ideal ℐ of 𝓐, 𝓐/ℐ has UUNP iff U(𝓐) is regular and for any spectral synthesis ideal ℐ of U(𝓐), ℐ = k(h(𝓐 ∩ ℐ)) (hulls...

Beurling algebras and uniform norms

S. J. Bhatt; H. V. Dedania — 2004

Studia Mathematica

Given a locally compact abelian group G with a measurable weight ω, it is shown that the Beurling algebra L¹(G,ω) admits either exactly one uniform norm or infinitely many uniform norms, and that L¹(G,ω) admits exactly one uniform norm iff it admits a minimum uniform norm.

Weighted measure algebras and uniform norms

S. J. Bhatt; H. V. Dedania — 2006

Studia Mathematica

Let ω be a weight on an LCA group G. Let M(G,ω) consist of the Radon measures μ on G such that ωμ is a regular complex Borel measure on G. It is proved that: (i) M(G,ω) is regular iff M(G,ω) has unique uniform norm property (UUNP) iff L¹(G,ω) has UUNP and G is discrete; (ii) M(G,ω) has a minimum uniform norm iff L¹(G,ω) has UUNP; (iii) M₀₀(G,ω) is regular iff M₀₀(G,ω) has UUNP iff L¹(G,ω) has UUNP, where M₀₀(G,ω) := {μ ∈ M(G,ω) : μ̂ = 0 on Δ(M(G,ω))∖Δ(L¹(G,ω))}.

Beurling algebra analogues of theorems of Wiener-Lévy-Żelazko and Żelazko

S. J. Bhatt; P. A. Dabhi; H. V. Dedania — 2009

Studia Mathematica

Let 0 < p ≤ 1, let ω: ℤ → [1,∞) be a weight on ℤ and let f be a nowhere vanishing continuous function on the unit circle Γ whose Fourier series satisfies $\sum_{n \in ℤ} {| f ̂ (n) |}^{p} ω (n) < \infty$ . Then there exists a weight ν on ℤ such that $\sum_{n \in ℤ} {| \hat{(1 / f)} (n) |}^{p} ν (n) < \infty$ . Further, ν is non-constant if and only if ω is non-constant; and ν = ω if ω is non-quasianalytic. This includes the classical Wiener theorem (p = 1, ω = 1), Domar theorem (p = 1, ω is non-quasianalytic), Żelazko theorem (ω = 1) and a recent result of Bhatt and Dedania (p = 1). An analogue of...

Spectral well-behaved *-representations

S. J. Bhatt; M. Fragoulopoulou; A. Inoue — 2005

Banach Center Publications

In this brief account we present the way of obtaining unbounded *-representations in terms of the so-called "unbounded" C*-seminorms. Among such *-representations we pick up a special class with "good behaviour" and characterize them through some properties of the Pták function.

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Currently displaying 1 – 5 of 5

Banach algebras with unique uniform norm II

Beurling algebras and uniform norms

Weighted measure algebras and uniform norms

Beurling algebra analogues of theorems of Wiener-Lévy-Żelazko and Żelazko

Spectral well-behaved *-representations