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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.

Algebra of multipliers on the space of real analytic functions of one variable

Paweł Domański, Michael Langenbruch (2012)

Studia Mathematica

We consider the topological algebra of (Taylor) multipliers on spaces of real analytic functions of one variable, i.e., maps for which monomials are eigenvectors. We describe multiplicative functionals and algebra homomorphisms on that algebra as well as idempotents in it. We show that it is never a Q-algebra and never locally m-convex. In particular, we show that Taylor multiplier sequences cease to be so after most permutations.

Banach Algebra of Bounded Complex-Valued Functionals

Katuhiko Kanazashi, Hiroyuki Okazaki, Yasunari Shidama (2011)

Formalized Mathematics

In this article, we describe some basic properties of the Banach algebra which is constructed from all bounded complex-valued functionals.

Derivations into iterated duals of Banach algebras

H. Dales, F. Ghahramani, N. Grønbæek (1998)

Studia Mathematica

We introduce two new notions of amenability for a Banach algebra A. The algebra A is n-weakly amenable (for n ∈ ℕ) if the first continuous cohomology group of A with coefficients in the n th dual space A ( n ) is zero; i.e., 1 ( A , A ( n ) ) = 0 . Further, A is permanently weakly amenable if A is n-weakly amenable for each n ∈ ℕ. We begin by examining the relations between m-weak amenability and n-weak amenability for distinct m,n ∈ ℕ. We then examine when Banach algebras in various classes are n-weakly amenable; we study...

On the algebra of smooth operators

Tomasz Ciaś (2013)

Studia Mathematica

Let s be the space of rapidly decreasing sequences. We give the spectral representation of normal elements in the Fréchet algebra L(s',s) of so-called smooth operators. We also characterize closed commutative *-subalgebras of L(s',s) and establish a Hölder continuous functional calculus in this algebra. The key tool is the property (DN) of s.

Quasi-multipliers of the algebra of approximable operators and its duals

Michael Grosser (1997)

Studia Mathematica

Let A be the Banach algebra K 0 ( X ) of approximable operators on an arbitrary Banach space X. For the spaces of all bilinear continuous quasi-multipliers of A resp. its dual A* resp. its bidual A**, concrete representations as spaces of operators are given.

Strongly compact algebras.

Miguel Lacruz, Victor Lomonosov, Luis Rodríguez Piazza (2006)


An algebra of bounded linear operators on a Hilbert space is said to be strongly compact if its unit ball is relatively compact in the strong operator topology. A bounded linear operator on a Hilbert space is said to be strongly compact if the algebra generated by the operator and the identity is strongly compact. This notion was introduced by Lomonosov as an approach to the invariant subspace problem for essentially normal operators. First of all, some basic properties of strongly compact algebras...

Symmetric Banach *-algebras: invariance of spectrum

Bruce Barnes (2000)

Studia Mathematica

Let A be a Banach *-algebra which is a subalgebra of a Banach algebra B. In this paper, assuming that A is symmetric, various conditions are given which imply that A is inverse closed in B.

When is L(X) topologizable as a topological algebra?

W. Żelazko (2002)

Studia Mathematica

Let X be a locally convex space and L(X) be the algebra of all continuous endomorphisms of X. It is known (Esterle [2], [3]) that if L(X) is topologizable as a topological algebra, then the space X is subnormed. We show that in the case when X is sequentially complete this condition is also sufficient. In this case we also obtain some other conditions equivalent to the topologizability of L(X). We also exhibit a class of subnormed spaces X, called sub-Banach spaces, which are not necessarily sequentially...

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