Jordan counterparts of Rickart and Baer ∗*-algebras, II

We introduce and investigate new classes of Jordan algebras which are close to but wider than Rickart and Baer Jordan algebras considered in our previous paper. Such Jordan algebras are called RJ- and BJ-algebras respectively. Criterions are given for a Jordan algebra to be a BJ-algebra. Also, it is proved that every finite dimensional Jordan algebra without nilpotent elements, which have square roots, is a BJ-algebra.Comment: 10 page

2-Local Derivations on Von Neumann Algebras of Type I

In the present paper we prove that every 2-local derivation on a von Neumann algebra of type I is a derivation.Comment: 8 page

Local derivations on finite-dimensional Lie algebras

We prove that every local derivation on a finite-dimensional semisimple Lie algebra over an algebraically closed field of characteristic zero is a derivation. We also give examples of finite-dimensional nilpotent Lie algebras $\mathcal{L}$ with $\dim\mathcal{L}\geq 3$ which admit local derivations which are not derivations.Comment: 14 page

22-Local derivations on von Neumann algebras

The paper is devoted to the description of $2$-local derivations on von Neumann algebras. Earlier it was proved that every $2$-local derivation on a semi-finite von Neumann algebra is a derivation. In this paper, using the analogue of Gleason Theorem for signed measures, we extend this result to type $III$ von Neumann algebras. This implies that on arbitrary von Neumann algebra each $2$-local derivation is a derivation.Comment: 7 page

2-Local derivations on AW∗^*-algebras of type I

It is proved that every 2-local derivation on an AW$^*$-algebra of type I is a derivation. Also an analog of Gleason theorem for signed measures on projections of homogenous AW$^*$-algebras except the cases of an AW$^*$-algebra of type I$_2$ and a factor of type I$_m$, $2<m<\infty$ is proved.Comment: 17 page

2-local derivations on infinite-dimensional Lie algebras

The present paper is devoted to study 2-local derivations on infinite-dimensional Lie algebras over a field of characteristic zero. We prove that all 2-local derivations on the Witt algebra as well as on the positive Witt algebra are (global)derivations, and give an example of infinite-dimensional Lie algebra with a 2-local derivation which is not a derivation.Comment: 9 page

Reversible AJW-algebras

In this article it is proved that for every special AJW-algebra $A$ there exist central projections $e$, $f$, $g\in A$, $e+f+g=1$ such that (1) $eA$ is reversible and there exists a norm-closed two sided ideal $I$ of $C^*(eA)$ such that $eA={{}^\perp}(^\perp(I_{sa})_+)_+$; (2) $fA$ is reversible and $R^*(fA)\cap iR^*(fA)=\{0\}$; (3) $gA$ is a totally nonreversible AJW-algebra.Comment: 7 page

Local And 2-Local Derivations On Algebras Of Measurable Operators

The present paper presents a survey of some recent results devoted to derivations, local derivations and 2-local derivations on various algebras of measurable operators affiliated with von Neumann algebras. We give a complete description of derivation on these algebras, except the case where the von Neumann algebra is of type II$_1$. In the latter case the result is obtained under an extra condition of measure continuity of derivations. Local and 2-local derivations on the above algebras are also considered. We give sufficient conditions on a von Neumann algebra $M$, under which every local or 2-local derivation on the algebra of measurable operators affiliated with $M$ is automatically becomes a derivation. We also give examples of commutative algebras of measurable operators admitting local and 2-local derivations which are not derivations.Comment: accepted to Contem. Math. AMS, 21 pages. arXiv admin note: text overlap with arXiv:0901.2983, arXiv:0808.014

Two-Local derivations on associative and Jordan matrix rings over commutative rings

In the present paper we prove that every 2-local inner derivation on the matrix ring over a commutative ring is an inner derivation and every derivation on an associative ring has an extension to a derivation on the matrix ring over this associative ring. We also develop a Jordan analog of the above method and prove that every 2-local inner derivation on the Jordan matrix ring over a commutative ring is a derivation.Comment: 19 pages, Linear Algebra and its Applications 201

Innerness of continuous derivations on algebras of measurable operators affiliated with finite von Neumann algebras

This paper is devoted to derivations on the algebra $S(M)$ of all measurable operators affiliated with a finite von Neumann algebra $M.$ We prove that if $M$ is a finite von Neumann algebra with a faithful normal semi-finite trace $\tau$, equipped with the locally measure topology $t,$ then every $t$-continuous derivation $D:S(M)\rightarrow S(M)$ is inner. A similar result is valid for derivation on the algebra $S(M,\tau)$ of $\tau$-measurable operators equipped with the measure topology $t_{\tau}$.Comment: Accepted for publication in the Journal of Mathematical Analysis and Application