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A note on a construction of J. F. Feinstein

M. J. Heath (2005)

Studia Mathematica

In [6] J. F. Feinstein constructed a compact plane set X such that R(X), the uniform closure of the algebra of rational functions with poles off X, has no non-zero, bounded point derivations but is not weakly amenable. In the same paper he gave an example of a separable uniform algebra A such that every point in the character space of A is a peak point but A is not weakly amenable. We show that it is possible to modify the construction in order to produce examples which are also regular.

A note on regular elements in Calkin algebras.

Vladimir Rakocevic (1992)

Collectanea Mathematica

An element a of the Banach algebra A is said to be regular provided there is an element b belonging to A such that a = aba. In this note we study the set of regular elements in the Calkin algebra C(X) over an infinite-dimensional complex Banach space X.

A note on the differences of the consecutive powers of operators

Andrzej Święch (1997)

Banach Center Publications

We present two examples. One of an operator T such that T n ( T - I ) n = 1 is precompact in the operator norm and the spectrum of T on the unit circle consists of an infinite number of points accumulating at 1, and the other of an operator T such that T n ( T - I ) n = 1 is convergent to zero but T is not power bounded.

A note on the singular spectrum.

L. Lindeboom (Groenewald), H. Raubenheimer (1998)

Extracta Mathematicae

We compare the singular spectrum of a Banach algebra element with the usual spectrum and exponential spectrum.

A note on topologically nilpotent Banach algebras

P. Dixon, V. Müller (1992)

Studia Mathematica

A Banach algebra A is said to be topologically nilpotent if s u p x . . . . . . x n 1 / n : x i A , x i 1 ( 1 i n ) tends to 0 as n → ∞. We continue the study of topologically nilpotent algebras which was started in [2]

A properly infinite Banach *-algebra with a non-zero, bounded trace

H. G. Dales, Niels Jakob Laustsen, Charles J. Read (2003)

Studia Mathematica

A properly infinite C*-algebra has no non-zero traces. We construct properly infinite Banach *-algebras with non-zero, bounded traces, and show that there are even such algebras which are fairly "close" to the class of C*-algebras, in the sense that they can be hermitian or *-semisimple.

A property for locally convex *-algebras related to property (T) and character amenability

Xiao Chen, Anthony To-Ming Lau, Chi-Keung Ng (2015)

Studia Mathematica

For a locally convex *-algebra A equipped with a fixed continuous *-character ε (which is roughly speaking a generalized F*-algebra), we define a cohomological property, called property (FH), which is similar to character amenability. Let C c ( G ) be the space of continuous functions with compact support on a second countable locally compact group G equipped with the convolution *-algebra structure and a certain inductive topology. We show that ( C c ( G ) , ε G ) has property (FH) if and only if G has property (T). On...

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