On the algebraic compactness of some quotients of product groups
On the algebraic form of Keller's conjecture
On the algebraic structure of the unitary group.
We consider the unitary group U of complex, separable, infinite-dimensional Hilbert space as a discrete group. It is proved that, whenever U acts by isometries on a metric space, every orbit is bounded. Equivalently, U is not the union of a countable chain of proper subgroups, and whenever E ⊆ U generates U, it does so by words of a fixed finite length.
On the arithmetic of arithmetical congruence monoids
Let ℕ represent the positive integers and ℕ₀ the non-negative integers. If b ∈ ℕ and Γ is a multiplicatively closed subset of , then the set is a multiplicative submonoid of ℕ known as a congruence monoid. An arithmetical congruence monoid (or ACM) is a congruence monoid where Γ = ā consists of a single element. If is an ACM, then we represent it with the notation M(a,b) = (a + bℕ₀) ∪ 1, where a, b ∈ ℕ and a² ≡ a (mod b). A classical 1954 result of James and Niven implies that the only ACM...
On the arity of idempotent reduct of abelian groups
On the arity of idempotent reducts of groups
On the asymptotic behavior of some counting functions
The investigation of certain counting functions of elements with given factorization properties in the ring of integers of an algebraic number field gives rise to combinatorial problems in the class group. In this paper a constant arising from the investigation of the number of algebraic integers with factorizations of at most k different lengths is investigated. It is shown that this constant is positive if k is greater than 1 and that it is also positive if k equals 1 and the class group satisfies...
On the asymptotic behavior of some counting functions, II
The investigation of the counting function of the set of integral elements, in an algebraic number field, with factorizations of at most k different lengths gives rise to a combinatorial constant depending only on the class group of the number field and the integer k. In this paper the value of these constants, in case the class group is an elementary p-group, is estimated, and determined under additional conditions. In particular, it is proved that for elementary 2-groups these constants are equivalent...
On the Automorphism Group of a Finite Group Having No Non-Identity Normal Subgroup of Odd Order.
On the automorphism group of a toroidal hypermap
On the automorphism group of Solomon's descent algebra.
On the automorphism group of the countable dense circular order
Let (C,R) be the countable dense circular ordering, and G its automorphism group. It is shown that certain properties of group elements are first order definable in G, and these results are used to reconstruct C inside G, and to demonstrate that its outer automorphism group has order 2. Similar statements hold for the completion C̅.
On the Automorphism Groups of Denumerable Boolean Algebras.
On the automorphism of a class of groups.
On the average number of Sylow subgroups in finite groups
We prove that if the average number of Sylow subgroups of a finite group is less than and not equal to , then is solvable or . In particular, if the average number of Sylow subgroups of a finite group is , then , where is the largest normal solvable subgroup of . This generalizes an earlier result by Moretó et al.
On the average values of the irreducible characters of finite groups of Lie type on geometric unipotent classes.
On the axiomatic rank of varieties generated by a semigroup or monoid with one defining relation.
On the Boffa alternative
Let G* denote a nonprincipal ultrapower of a group G. In 1986 M.~Boffa posed a question equivalent to the following one: if G does not satisfy a positive law, does G* contain a free nonabelian subsemigroup? We give the affirmative answer to this question in the large class of groups containing all residually finite and all soluble groups, in fact, all groups considered in traditional textbooks on group theory.
On the Breadth of a Finite p-Group.
On the “Bruhat graph” of a Coxeter system