A sandwich in thin lie algebras

A thin Lie algebra is a Lie algebra $L$ , graded over the positive integers, with its first homogeneous component $L_1$ of dimension two and generating $L$ , and such that each non-zero ideal of $L$ lies between consecutive terms of its lower central series. All homogeneous components of a thin Lie algebra have dimension one or two, and the two-dimensional components are called diamonds. Suppose the second diamond of $L$ (that is, the next diamond past $L_1$ ) occurs in degree $k$ . We prove that if $k>5$ , then $[Lyy]=0$ for some non-zero element $y$ of $L_1$ . In characteristic different from two this means $y$ is a sandwich element of $L$ . We discuss the relevance of this fact in connection with an important theorem of Premet on sandwich elements in modular Lie algebras.

Representations of automorphism groups of algebras associated to star polygons

In this paper, we consider the algebra [Formula: see text] associated to Hasse graph of a star polygon. We determine the automorphism group for this algebra and the graded traces [Formula: see text] for each [Formula: see text], which are the graded trace generating functions of [Formula: see text]. Furthermore, we study the representations of [Formula: see text] acting on each homogeneous component of [Formula: see text] and we apply the same technique to the dual algebra [Formula: see text] of [Formula: see text]. More precisely, we consider the algebras associated to Hasse graph of star polygons [Formula: see text] with [Formula: see text] odd.

Multiplicity-Free Gradings on Semisimple Lie and Jordan Algebras and Skew Root Systems

A G-grading on an algebra, where G is an abelian group, is called multiplicity-free if each homogeneous component of the grading is 1-dimensional. We introduce skew root systems of Lie type and skew root systems of Jordan type, and use them to construct multiplicity-free gradings on semisimple Lie algebras and on semisimple Jordan algebras respectively. Under certain conditions the corresponding Lie (resp., Jordan) algebras are simple. Two families of skew root systems of Lie type (resp., of Jordan type) are constructed and the corresponding Lie (resp., Jordan) algebras are identified. This is a new approach to study abelian group gradings on Lie and Jordan algebras.

On the Conjecture About the Linear Structures of Rotation Symmetric Boolean Functions

In this paper, we study the conjecture that [Formula: see text]-variable ([Formula: see text] odd) rotation symmetric Boolean functions with degree [Formula: see text] have no non-zero linear structures. We show that if this class of RSBFs have non-zero linear structures, then the linear structures are invariant linear structures and the homogeneous component of degree [Formula: see text] in the function’s algebraic normal form has only two possibilities. Moreover, it is checked that the conjecture is true for [Formula: see text], and then a more explicit conjecture is proposed.

Maximal finite abelian subgroups of E8

The maximal finite abelian subgroups, up to conjugation, of the simple algebraic group of type E8 over an algebraically closed field of characteristic 0 are computed. This is equivalent to the determination of the fine gradings on the simple Lie algebra of type E8 with trivial neutral homogeneous component. The Brauer invariant of the irreducible modules for graded semisimple Lie algebras plays a key role.

On the Structure of Graded Leibniz Algebras

We study the structure of graded Leibniz algebras with arbitrary dimension and over an arbitrary base field 𝕂. We show that any of such algebras 𝔏 with a symmetric G-support is of the form [Formula: see text] with U a subspace of 𝔏1, the homogeneous component associated to the unit element 1 in G, and any Ij a well described graded ideal of 𝔏, satisfying [Ij, Ik]=0 if j ≠ k. In the case of 𝔏 being of maximal length, we characterize the gr-simplicity of the algebra in terms of connections in the support of the grading.

ON THE DIMENSION OF PRODUCTS OF HOMOGENEOUS SUBSPACES IN FREE LIE ALGEBRAS

Let L be a free Lie algebra of finite rank over a field K and let Ln denote the degree n homogeneous component of L. Formulae for the dimension of the subspaces [Lm, Ln] for all m and n were obtained by the second author and Michael Vaughan-Lee. In this note we consider subspaces of the form [Lm, Ln, Lk] = [[Lm, Ln], Lk]. Surprisingly, in contrast to the case of a product of two homogeneous components, the dimension of such products may depend on the characteristic of the field K. For example, the dimension of [L2, L2, L1] over fields of characteristic 2 is different from the dimension over fields of characteristic other than 2. Our main results are formulae for the dimension of [Lm, Ln, Lk]. Under certain conditions on m, n and k they lead to explicit formulae that do not depend on the characteristic of K, and express the dimension of [Lm, Ln, Lk] in terms of Witt's dimension function.

Convolution Powers of the Identity

International audience We study convolution powers $\mathtt{id}^{\ast n}$ of the identity of graded connected Hopf algebras $H$. (The antipode corresponds to $n=-1$.) The chief result is a complete description of the characteristic polynomial - both eigenvalues and multiplicity - for the action of the operator $\mathtt{id}^{\ast n}$ on each homogeneous component $H_m$. The multiplicities are independent of $n$. This follows from considering the action of the (higher) Eulerian idempotents on a certain Lie algebra $\mathfrak{g}$ associated to $H$. In case $H$ is cofree, we give an alternative (explicit and combinatorial) description in terms of palindromic words in free generators of $\mathfrak{g}$. We obtain identities involving partitions and compositions by specializing $H$ to some familiar combinatorial Hopf algebras. Nous étudions les puissances de convolution $\mathtt{id}^{\ast n}$ de l’identité d’une algèbre de Hopf graduée et connexe $H$ quelconque. (L’antipode correspond à $n=-1$.) Le résultat principal est une description complète du polynôme caractéristique (des valeurs propres et de leurs multiplicités) de l’opérateur $\mathtt{id}^{\ast n}$ agissant sur chaque composante homogène $H_m$. Les multiplicités sont indépendants de $n$. Ceci résulte de l’examen de l’action des idempotents eulériens (supérieures) sur une algèbre de Lie $\mathfrak{g}$ associée à $H$. Dans le cas où $H$ est colibre, nous donnons une description alternative (explicite et combinatoire) en termes de mots palindromes dans les générateurs libres de $\mathfrak{g}$. Nous obtenons des identités impliquant des partitions et compositions en choisissant comme $H$ certaines algèbres de Hopf combinatoires connues.

Extraction, Purification and Antioxidant Activity of Intracellular Polysaccharides from a Strain of Lachnum sp.

The microwave method was used to extract Lachnum calyculiforme polysaccharides (LCP). By orthogonal experiments, the optimal conditions of extraction were the microwave temperature was 120 °C, extraction time was 20 min, ratio of water to raw material was 60:1, and the yield of polysaccharides was 12.56 %. LCP-1 was separated and sequentially purified from LCP through Sephadex G-100 column chromatography, which was detected as the homogeneous component. LCP -1 had strong scavenging abilities on O2ˉ•, •OH and DPPH free radicals.