Derivations of noncommutative Arens algebras

The present paper deals with derivations of noncommutative Arens algebras. We prove that every derivation of an Arens algebra associated with a von Neumann algebra and a faithful normal finite trace is inner. In particular, each derivation on such algebras is automatically continuous in the natural topology, and in the commutative case, even for semi-finite traces, all derivations are identically zero. At the same time, the existence of noninner derivations is proved for noncommutative Arens algebras with a semi-finite but nonfinite trace.     

Non-commutative Arens algebras and their derivations

Given a von Neumann algebra M with a faithful normal semi-finite trace τ, we consider the non-commutative Arens algebra Lω(M,τ)=_?p?1Lp(M,τ) and the related algebras and which are proved to be complete metrizable locally convex *-algebras. The main purpose of the present paper is to prove that any derivation of the algebra is inner and all derivations of the algebras Lω(M,τ) and are spatial and implemented by elements of . In particular we obtain that if the trace τ is finite then any derivation on the non-commutative Arens algebra Lω(M,τ) is inner.     

Local derivations on certain CSL algebras

In this paper, it is shown that every norm continuous linear local derivation from an arbitrary CSL algebra whose lattice is generated by finitely many independent nests into any ultraweakly closed subalgebra which contains the algebra is an inner derivation, and that every norm continuous linear local derivation from an arbitrary CSL algebra whose lattice is completely distributive into any ultraweakly closed subalgebra which contains the algebra is a derivation.     

Local derivations of finitary incidence algebras

Let P be a partially ordered set, R a commutative ring with identity and FI(P,R) the finitary incidence algebra of P over R. We prove that each R-linear local derivation of FI(P,R) is a derivation, which partially generalizes Theorem 3 of [21].     

Stability of derivations under weak-2-local continuous perturbations

Let $${Omega}$$     

Arens semi-regular Banach algebras

For some important Banach algebras, the first and the second Arens product on their biduals are different, i. e. these algebras are not (Arens) regular. Arens semi-regularity is a property strictly weaker than regularity; it characterizes those non-regular algebras (having a bounded two-sided approximate identity) for which the Arens products, though different, still behave in a reasonable way. The definition of semi-regularity is based on the relation of two natural embeddings of the space of double multipliers into the bidual of the Banach algebra. It is shown that each commutative Banach algebra is semi-regular and that semi-regularity is equivalent to the equality of the Arens products on certain subspaces of the bidual. Among others, group algebras and algebras of compact operators are treated as examples.     

Module Arens regularity for semigroup algebras

We extend the concept of Arens regularity of a Banach algebra to the case that there is an -module structure on , and show that when S is an inverse semigroup with totally ordered subsemigroup E of idempotents, then A=ℓ ¹(S) is module Arens regular if and only if an appropriate group homomorphic image of S is finite. When S is a discrete group, this is just Young’s theorem which asserts that ℓ ¹(S) is Arens regular if and only if S is finite. An erratum to this article can be found at     

Module derivations on semigroup algebras

We show that for an inverse semigroup S with the set idempotents E acting on S trivially from left and by multiplication from right, any bounded module derivation from \(\ell ^1(S)\) to \(({\ell ^1(S)}/{J})^*=J^{\perp }\) is inner, where J is the closed ideal generated by elements of the form \(\delta _{set}-\delta _{st}\) with \(s,t\in S\) and \(e\in E\).     

Quaternion algebras with derivations

We study derivations on quaternion algebras that stabilise quadratic subfields. Following the work of L. Juan and A. Magid [10], we provide an explicit construction of a differential splitting field for a given differential quaternion algebra. We also examine the presence and impact of those derivations on quaternion algebras that admit new constants.     

Jordan higher derivations on triangular algebras

In this paper, we show that any Jordan higher derivation on a triangular algebra is a higher derivation. This extends the main result in [13] to the case of higher derivations.     

Generalized derivations on some convolution algebras

Let G be a locally compact abelian group, \(\omega \) be a weighted function on \({\mathbb {R}}^+\), and let \(\mathfrak {D}\) be the Banach algebra \(L_0^\infty (G)^*\) or \(L_0^\infty (\omega )^*\). In this paper, we investigate generalized derivations on the noncommutative Banach algebra \(\mathfrak {D}\). We characterize \(\textsf {k}\)-(skew) centralizing generalized derivations of \(\mathfrak {D}\) and show that the zero map is the only \(\textsf {k}\)-skew commuting generalized derivation of \(\mathfrak {D}\). We also investigate the Singer–Wermer conjecture for generalized derivations of \(\mathfrak {D}\) and prove that the Singer–Wermer conjecture holds for a generalized derivation of \(\mathfrak {D}\) if and only if it is a derivation; or equivalently, it is nilpotent. Finally, we investigate the orthogonality of generalized derivations of \(L_0^\infty (\omega )^*\) and give several necessary and sufficient conditions for orthogonal generalized derivations of \(L_0^\infty (\omega )^*\).     

Generalized Lie derivations on triangular algebras

Let A be a unital algebra and let M be a unitary A-bimodule. We consider generalized Lie derivations mapping from A to M. Our results are applied to triangular algebras, in particular to nest algebras and (block) upper triangular matrix algebras. We prove that under certain conditions each generalized Lie derivation of a triangular algebra A is the sum of a generalized derivation and a central map which vanishes on all commutators of A.     

Generalized derivations associated with Hochschild 2-cocycles on some algebras

We investigate a new type of generalized derivations associated with Hochschild 2-cocycles which was introduced by A. Nakajima. We show that every generalized Jordan derivation of this type from CSL algebras or von Neumann algebras into themselves is a generalized derivation under some reasonable conditions. We also study generalized derivable mappings at zero point associated with Hochschild 2-cocycles on CSL algebras.