Abstract:
Omni-Lie color algebras over an abelian group with a bicharacter are studied. The notions of 2-term color $L_{\infty}$-algebras and Lie color 2-algebras are introduced. It is proved that there is a one-to-one correspondence between Lie color 2-algebras and 2-term color $L_{\infty}$-algebras.

Abstract:
We introduce the notion of omni-Lie 2-algebra, which is a categorification of Weinstein's omni-Lie algebras. We prove that there is a one-to-one correspondence between strict Lie 2-algebra structures on 2-sub-vector spaces of a 2-vector space $\V$ and Dirac structures on the omni-Lie 2-algebra $ \gl(\V)\oplus \V $. In particular, strict Lie 2-algebra structures on $\V$ itself one-to-one correspond to Dirac structures of the form of graphs. Finally, we introduce the notion of twisted omni-Lie 2-algebra to describe (non-strict) Lie 2-algebra structures. Dirac structures of a twisted omni-Lie 2-algebra correspond to certain (non-strict) Lie 2-algebra structures, which include string Lie 2-algebra structures.

Abstract:
In characteristic 2, for Lie algebras, a (2,4)-structure is introduced in addition to the known, "classical", restrictedness. For Lie superalgebras, the classical restrictedness of Lie algebras has two analogs: $(2|4)$- and $(2|2)$-structures; a $(2,4)|4$-structure on Lie superalgebras is the analog of a (2,4)-structure on the Lie algebras. In characteristic 2, two procedures that to every simple Lie algebra assign simple Lie superalgebras, most of them new, are offered. We proved that every simple finite-dimensional Lie superalgebra is obtained as the result of one of these procedures, so we described all simple finite-dimensional Lie superalgebras modulo non-existing at the moment classification of simple finite-dimensional Lie algebras. We give references to papers containing a conjectural method to obtain the latter classification and (currently incomplete) collections of examples of simple Lie algebras. In characteristic 3, we prove that the known exceptional simple finite-dimensional vectorial Lie (super)algebras are restricted.

Abstract:
In a paper by Su and Zhao, the Lie algebra $A[D]=A\otimes F[D]$ of Weyl type was defined and studied, where $A$ is a commutative associative algebra with an identity element over a field $F$ of arbitrary characteristic, and $F[D]$ is the polynomial algebra of a commutative derivation subalgebra $D$ of $A$. The 2-cocycles of a class of $A[D]$ were determined by Su. In the present paper, we determine the 2-cocycles of a class of Lie superalgebras of Weyl type over a field $F$ of characteristic 0.

Abstract:
We continue the study of the filiform Z2xZ2-color Lie superalgebras. All of them can be obtained by using infinitesimal deformations, i.e. cocycles. In this work we give the total dimension of such cocycles (for any dimensions n, m, p and t of the Z2xZ2-color Lie superalgebras). Also, we give a basis of such cocycles in some generic and concrete cases.

Abstract:
We consider the $\delta$-derivations of classical Lie superalgebras and prove that these superalgebras admit nonzero $\delta$-derivations only when $\delta = 0,1/2,1$. The structure of $1/2$-derivations for classical Lie superalgebras is completely determined.

Abstract:
In this paper, we study Rota-Baxter operators and super $\mathcal{O}$-operator of associative superalgebras, Lie superalgebras, pre-Lie superalgebras and $L$-dendriform superalgebras. Then we give some properties of pre-Lie superalgebras constructed from associative superalgebras, Lie superalgebras and $L$-dendriform superalgebras. Moreover, we provide all Rota-Baxter operators of weight zero on complex pre-Lie superalgebras of dimensions $2$ and $3$.

Abstract:
This is a companion article to my papers on Kazhdan-Lusztig polynomials and character formulae for the Lie superalgebras gl(m|n) (much revised!) and q(n). The goal is to develop the general theory of tilting modules for Lie superalgebras, working in a general graded setting very similar to work of Soergel (Character formulae for tilting modules over Kac-Moody algebras, Represent. Theory 2 (1998), 432-438) in the Lie algebra case. Examples are given involving the Lie superalgebras gl(m|n) and q(n), but maybe this will also be useful for the other classical and affine Lie superalgebras.

Abstract:
We explicitly compute the first and second cohomology groups of the classical Lie superalgebras $sl_{m|n}$ and $osp_{2|2n}$ with coefficients in the finite dimensional irreducible modules and the Kac modules. We also show that the second cohomology groups of these Lie superalgebras with coefficients in the respective universal enveloping algebras (under the adjoint action) vanish. The latter result in particular implies that the universal enveloping algebras $U(sl_{m|n})$ and $U(osp_{2|2n})$ do not admit any non-trivial formal deformations of Gerstenhaber type.

Abstract:
For the orthogonal Lie algebra O(2n+1), in addition to the conventional set of orthogonal polynomials, another set is produced with the help of the Lie superalgebra OSP(1|2n). Difficulties related with expression of Dyson's constant for the Lie superalgebras are discussed.