Automatic continuity conditions for a linear mapping from a banach algebra onto a semi-simple Banach algebra

1983 ◽  
pp. 313-316 ◽  
Author(s):  
Bernard Aupetit
Keyword(s):  
Banach Algebra ◽  
Linear Mapping ◽  
Automatic Continuity

scholarly journals Automatic continuity for Banach algebras with finite-dimensional radical

2006 ◽  
Vol 81 (2) ◽  
pp. 279-296 ◽  
Author(s):  
Hung Le Pham
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
Automatic Continuity ◽  
Algebraic Condition ◽  
Finite Dimensional ◽  
Complete Algebra

AbstractThe paper [3] proved a necessary algebraic condition for a Banach algebra A with finite-dimensional radical R to have a unique complete (algebra) norm, and conjectured that this condition is also sufficient. We extend the above theorem. The conjecture is confirmed in the case where A is separable and A/R is commutative, but is shown to fail in general. Similar questions for derivations are discussed.

Spectrally bounded traces on C*-algebras

2003 ◽  
Vol 68 (1) ◽  
pp. 169-173 ◽  
Author(s):  
Martin Mathieu
Keyword(s):  
Banach Algebra ◽  
Spectral Radius ◽  
Linear Mapping ◽  
C Algebras ◽  
Spectrally Bounded ◽  
Bounded Trace

A linear mapping T from a subspace E of a Banach algebra into another Banach algebra is called spectrally bounded if there is a constant M ≥ 0 such that r(T x) ≤ Mr(x) for all x ∈ E, where r (·) denotes the spectral radius. We establish the equivalence of the following properties of a unital linear mapping T from a unital C* -algebra A into its centre:(a) T is spectrally bounded;(b) T is a spectrally bounded trace;(c) T is a bounded trace.

Automatic Continuity of Homomorphisms in Non-associative Banach Algebras

2013 ◽  
Vol 65 (5) ◽  
pp. 989-1004
Author(s):  
C-H. Chu ◽  
M. V. Velasco
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
Surjective Homomorphism ◽  
Automatic Continuity ◽  
Normed Algebra ◽  
Associative Algebras ◽  
Rare Element ◽  
Rare Elements

AbstractWe introduce the concept of a rare element in a non-associative normed algebra and show that the existence of such an element is the only obstruction to continuity of a surjective homomorphism from a non-associative Banach algebra to a unital normed algebra with simple completion. Unital associative algebras do not admit any rare elements, and hence automatic continuity holds.

scholarly journals Topologically simple Banach algebras with derivation

1999 ◽  
Vol 60 (1) ◽  
pp. 153-161
Author(s):  
El Hossein Illoussamen ◽  
Volker Runde
Keyword(s):  
Power Series ◽  
Banach Algebra ◽  
Banach Algebras ◽  
Pivotal Role ◽  
Automatic Continuity

It is not known if a commutative, topologically simple, radical Banach algebra exists. If, however, every derivation on such an algebra is continuous, this yields the automatic continuity of all derivations on commutative, semiprime Banach algebras. Utilising techniques used by Thomas in his proof of the Singer-Wermer conjecture, we show that, if A is a commutative, topologically simple Banach algebra with a non-zero derivation on it, then a quotient of a certain localisation of A has a power series structure. A pivotal role is played by what we call ample sets of denominators.

scholarly journals Automatic continuity of positive functionals on topological involution algebras

1981 ◽  
Vol 23 (2) ◽  
pp. 265-281 ◽  
Author(s):  
P.G. Dixon
Keyword(s):  
Banach Algebra ◽  
Spectral Theory ◽  
Banach Algebras ◽  
Approximate Identity ◽  
Automatic Continuity ◽  
Topological Algebras ◽  
Positive Functional ◽  
Open Questions ◽  
Positive Functionals ◽  
Locally Convex

This paper surveys the known results on automatic continuity of positive functionals on topological *-algebras and then shows how two theorems on Banach *-algebras extend to complete metrizable topological *-algebras. The two theorems concerned are Loy's theorem on separable Banach *-algebras A with centre Z such that AZ is of countable codimension and Varopoulos' result on Banach *-algebras with bounded approximate identity. Both theorems have the conclusion that all positive functionals on such algebras are continuous. The extension of the second theorem requires the algebra to be locally convex and the approximate identity to be ‘uniformly bounded’. Neither extension requires the algebra to be LMC. This means that the proof of the first theorem is quite different from the corresponding Banach algebra result (which used spectral theory). The proof of the second is closer to the previously known LMC version, but actually neater by being more general. It is also shown that the well-known estimate of |f(a*ba)| for a positive functional f on a Banach *-algebra may be obtained without the usual use of spectral theory. The paper concludes with a list of open questions.

AUTOMATIC CONTINUITY OF 3-HOMOMORPHISMS ON TERNARY BANACH ALGEBRAS

2013 ◽  
Vol 10 (10) ◽  
pp. 1320013 ◽  
Author(s):  
MADJID ESHAGHI GORDJI ◽  
ALI JABBARI ◽  
ALI EBADIAN ◽  
SAEID OSTADBASHI
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
Automatic Continuity

In this paper we consider automatic continuity of 3-homomorphism and anti-3-homomorphism between non-unital ternary Banach algebras. We show that every surjective 3-homomorphism (anti-3-homomorphism) from ternary Banach algebra A into semisimple ternary Banach algebra B is continuous.

(σ, τ)-amenability of C*-algebras

2011 ◽  
Vol 18 (1) ◽  
pp. 137-145
Author(s):  
Madjid Mirzavaziri ◽  
Mohammad Sal Moslehian
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
Linear Mapping ◽  
Inner Derivation ◽  
C Algebras

Abstract Suppose that is an algebra, σ, τ : → are two linear mappings such that both σ() and τ() are subalgebras of and 𝒳 is a (τ(), σ())-bimodule. A linear mapping D : → 𝒳 is called a (σ, τ)-derivation if D(ab) = D(a) · σ(b) + τ(a) · D(b) (a, b ∈ ). A (σ, τ)-derivation D is called a (σ, τ)-inner derivation if there exists an x ∈ 𝒳 such that D is of the form either or . A Banach algebra is called (σ, τ)-amenable if every (σ, τ)-derivation from into a dual Banach (τ(), σ())-bimodule is (σ, τ)-inner. Studying some general algebraic aspects of (σ, τ)-derivations, we investigate the relation between the amenability and the (σ, τ)-amenability of Banach algebras in the case where σ, τ are homomorphisms. We prove that if 𝔄 is a C*-algebra and σ, τ are *-homomorphisms with ker(σ) = ker(τ), then 𝔄 is (σ, τ)-amenable if and only if σ(𝔄) is amenable.

scholarly journals Amenability of A⊕_T X as an extension of Banach algebra

2020 ◽  
Vol 49 ◽  
pp. 39-48
Author(s):  
M. Ghorbai ◽  
◽  
Davood Ebrahimi Bagha
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
Linear Mapping ◽  
Module Amenability ◽  
Weak Module ◽  
Approximate Amenability

Let 𝐴𝐴,𝑋𝑋,𝔘𝔘 be Banach algebras and 𝐴𝐴 be a Banach 𝔘𝔘-bimodule also 𝑋𝑋 be a Banach 𝐴𝐴−𝔘𝔘-module. In this paper we study the relation between module amenability, weak module amenability and module approximate amenability of Banach algebra 𝐴𝐴⊕𝑇𝑇𝑋𝑋 and that of Banach algebras 𝐴𝐴,𝑋𝑋. Where 𝑇𝑇: 𝐴𝐴×𝐴𝐴→𝑋𝑋 is a bounded bi-linear mapping with specificconditions.

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