Abstract:Chapter 1. Introduction Chapter 2. Banach algebras and their second duals Chapter 3. Semigroups Chapter 4. Semigroup algebras Chapter 5. Stone-Čech compactifications Chapter 6. The semigroup (βS, 2) Chapter 7. Second duals of semigroup algebras Chapter 8. Related spaces and compactifications Chapter 9. Amenability for semigroups Chapter 10. Amenability of semigroup algebras Chapter 11. Amenability and weak amenability for certain Banach algebras Chapter 12. Topological centres Chapter 13. Open problems
“…Then L 1 (G) * * does not have any nonzero continuous point derivation corresponding to any character φ ∈ σ(L 1 (G) * * ). It follows from [4,Theorem 11.17] that G is finite.…”
Section: Examples Of Left Introverted Subspaces Of L ∞ (G) Containingmentioning
Abstract. We obtain characterizations of left character amenable Banach algebras in terms of the existence of left φ-approximate diagonals and left φ-virtual diagonals. We introduce the left character amenability constant and find this constant for some Banach algebras. For all locally compact groups G, we show that the Fourier-Stieltjes algebra B(G) is C-character amenable with C < 2 if and only if G is compact. We prove that if A is a character amenable, reflexive, commutative Banach algebra, then A ∼ = C n for some n ∈ N. We show that the left character amenability of the double dual of a Banach algebra A implies the left character amenability of A, but the converse statement is not true in general. In fact, we give characterizations of character amenability of L 1 (G) * * and A(G) * * . We show that a natural uniform algebra on a compact space X is character amenable if and only if X is the Choquet boundary of the algebra. We also introduce and study character contractibility of Banach algebras.
“…Then L 1 (G) * * does not have any nonzero continuous point derivation corresponding to any character φ ∈ σ(L 1 (G) * * ). It follows from [4,Theorem 11.17] that G is finite.…”
Section: Examples Of Left Introverted Subspaces Of L ∞ (G) Containingmentioning
Abstract. We obtain characterizations of left character amenable Banach algebras in terms of the existence of left φ-approximate diagonals and left φ-virtual diagonals. We introduce the left character amenability constant and find this constant for some Banach algebras. For all locally compact groups G, we show that the Fourier-Stieltjes algebra B(G) is C-character amenable with C < 2 if and only if G is compact. We prove that if A is a character amenable, reflexive, commutative Banach algebra, then A ∼ = C n for some n ∈ N. We show that the left character amenability of the double dual of a Banach algebra A implies the left character amenability of A, but the converse statement is not true in general. In fact, we give characterizations of character amenability of L 1 (G) * * and A(G) * * . We show that a natural uniform algebra on a compact space X is character amenable if and only if X is the Choquet boundary of the algebra. We also introduce and study character contractibility of Banach algebras.
Abstract. Let A = 1 (B) be the semigroup algebra of B, the bicyclic semigroup. We give a resolution of ∞ (B) which simplifies the computation of the cohomology of 1 (B) dual bimodules. We apply this to the dual module ∞ (B) and show that the simplicial cohomology groups H n (A, A ) vanish for n ≥ 2. Using the Connes-Tzygan exact sequence, these results are used to show that the cyclic cohomology groups HC n (A, A ) vanish when n is odd and are one-dimensional when n is even (n ≥ 2).
“…With this perspective it is also important that results about algebras 1 (S) are obtained with a minimal appeal to specific semi-group properties. In a recent treatise ( [4]), a rather encompassing account of Banach algebraic properties of semi-group algebras is given, in particular, the authors conclude the description of amenability in terms of algebraic properties of the semi-group ( [4,Theorem 10.12]). …”
Abstract. We give sufficient conditions and necessary conditions for a Banach algebra, which is 1 −graded over a semi-lattice, to be biflat or biprojective. As an application we characterise biflat and biprojective discrete convolution algebras for commutative semi-groups.
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