Volume 219, Nº 4 (2016)
- Ano: 2016
- Artigos: 9
- URL: https://journals.rcsi.science/1072-3374/issue/view/14790
Article
Hochschild Cohomology of Algebras of Semidihedral Type. V. The Family \( SD\left(3\mathcal{K}\right) \)
Resumo
The Hochschild cohomology groups are calculated for the algebras of semidihedral type that form the family \( SD\left(3\mathcal{K}\right) \) (from the famous K. Erdmann’s classification). In the calculation, the bimodule resolution previously constructed for the algebras belonging to the family under discussion is used.
Decomposition of Elementary Transvection in Elementary Group
Resumo
Let σ = (σij ) be an elementary net (elementary carpet) of additive subgroups of a commutative ring (in other words, a net without diagonal), n the order of σ, ω = (ωij ) the derived net with respect to σ, and Ω = (Ωij ) the net associated with the elementary group E(σ). It is assumed that ω ⊆ σ ⊆ Ω and Ω is the smallest (complemented) net containing σ. The main result consists in finding the decomposition of any elementary transvection tij(α) into the product of two matrices M1 ∈ 〈tij(σij), tji(σji)〉 and M2 ∈ G(τ), where \( \uptau =\left(\begin{array}{ll}{\varOmega}_{11}\hfill & {\upomega}_{12}\hfill \\ {}{\upomega}_{21}\hfill & {\varOmega}_{22}\hfill \end{array}\right) \).
Ultrasolvable Covering of the Group Z2 by the Groups Z8, Z16, AND Q8
Resumo
Infinite series of nontrivial ultrasolvable embedding problems with cyclic kernel of order 8, 16, and quaternion kernel of order 8 are constructed. Among the embedding problems of a quadratic extension into a Galois algebra, 2-local nonsplit universally solvable problems with generalized quaternion or cyclic kernels are found. Bibliography: 14 titles.
Formal Modules for Generalized Lubin–Tate Groups
Resumo
The structure, endomorphism ring, and point group of a generalized Lubin–Tate formal group are studied. The primary elements are examined and an explicit formula for the generalized Hilbert symbol is proved. Bibliography: 10 titles.
On Schur 2-Groups
Resumo
A finite group G is called a Schur group if every Schur ring over G is the transitivity module of a point stabilizer in a subgroup of Sym(G) that contains all permutations induced by the right multiplications in G. It is proved that the group \( {\mathrm{\mathbb{Z}}}_2\times {\mathrm{\mathbb{Z}}}_{2^n} \) is Schur, which completes the classification of Abelian Schur 2-groups. It is also proved that any non-Abelian Schur 2-group of order larger than 32 is dihedral (the Schur 2-groups of smaller orders are known). Finally, the Schur rings over a dihedral 2-group G are studied. It turns out that among such rings of rank at most 5, the only obstacle for G to be a Schur group is a hypothetical ring of rank 5 associated with a divisible difference set.
A Variant of the Levine–Morel Moving Lemma
Resumo
A version of the lemma proved by M. Levine and F. Morel in their book “Algebraic cobordisms,” is reformulated in the Chow group context. The obtained statement turns out to be valid in any characteristic and its proof is substantially shortened.
The Width of Extraspecial Unipotent Radical with Respect to a Set of Root Elements
Resumo
Let G = G(Φ,K) be a Chevalley group of type Φ over a field K, where Φ is a simply laced root system. By studying the extraspecial unipotent radical of G, it is proved that any its element is a product of at most three root elements. Moreover, it is shown that up to conjugation by an element of the Levi subgroup, any element of the radical is the product of six elementary root elements.