The Mac Lane method of construction and classification of extensions of cyclic groups by their automorphism groups.
The maximum order of finite groups of outer automorphisms of free groups.
The monoid of semisimple multiclasses of the group .
The nilpotency of some groups with all subgroups subnormal.
Let G be a group with all subgroups subnormal. A normal subgroup N of G is said to be G-minimax if it has a finite G-invariant series whose factors are abelian and satisfy either max-G or min- G. It is proved that if the normal closure of every element of G is G-minimax then G is nilpotent and the normal closure of every element is minimax. Further results of this type are also obtained.
The number of conjugacy classes of elements of the Cremona group of some given finite order
This note presents the study of the conjugacy classes of elements of some given finite order in the Cremona group of the plane. In particular, it is shown that the number of conjugacy classes is infinite if is even, or , and that it is equal to (respectively ) if (respectively if ) and to for all remaining odd orders. Some precise representative elements of the classes are given.
The Number of Stem Covers of an Elementary Abelian p-Group.
The Obstruction theory of Group Extensions and H^3(Q, A) in Abstract Categories
The p-adic Topology on a Free Group: A Counterexample.
The periodic groups saturated by finitely many finite simple groups.
The p-period of an infinite group.
For Γ a group of finite virtual cohomological dimension and a prime p, the p-period of Γ is defined to be the least positive integer d such that Farrell cohomology groups Hi(Γ; M) and Hi+d(Γ; M) have naturally isomorphic ZΓ modules M.We generalize a result of Swan on the p-period of a finite p-periodic group to a p-periodic infinite group, i.e., we prove that the p-period of a p-periodic group Γ of finite vcd is 2LCM(|N(〈x〉) / C(〈x〉)|) if the Γ has a finite quotient whose a p-Sylow subgroup is elementary...
The probability that elements of a rank free group generate a rank subgroup.
The Profinite Completion of Certain Residually-Finite p-Groups.
The pro-unipotent radical of the pro-algebraic fundamental group of a compact Kähler manifold
The aim of this paper is to study the pro-algebraic fundamental group of a compact Kähler manifold. Following work by Simpson, the structure of this group’s pro-reductive quotient is already well understood. We show that Hodge-theoretic methods can also be used to establish that the pro-unipotent radical is quadratically presented. This generalises both Deligne et al.’s result on the de Rham fundamental group, and Goldman and Millson’s result on deforming representations of Kähler groups, and can...
The rank of actions on -trees
The rank of the factor-group modulo the hypercenter and the rank of the some hypocenter of a group
We compare the special rank of the factors of the upper central series and terms of the lower central series of a group. As a consequence we are able to show some generalizations of a theorem of Reinhold Baer.
The ratio and generating function of cogrowth coefficients of finitely generated groups
Let G be a group generated by r elements . Among the reduced words in of length n some, say , represent the identity element of the group G. It has been shown in a combinatorial way that the 2nth root of has a limit, called the cogrowth exponent with respect to the generators . We show by analytic methods that the numbers vary regularly, i.e. the ratio is also convergent. Moreover, we derive new precise information on the domain of holomorphy of γ(z), the generating function associated...
The Recent Generalizations of Colored Symmetry
The Residual Finiteness of Certain Amalgameted Free Products.
The rhombic dodecahedron and semisimple actions of Aut(Fₙ) on CAT(0) spaces
We consider actions of automorphism groups of free groups by semisimple isometries on complete CAT(0) spaces. If n ≥ 4 then each of the Nielsen generators of Aut(Fₙ) has a fixed point. If n = 3 then either each of the Nielsen generators has a fixed point, or else they are hyperbolic and each Nielsen-generated ℤ⁴ ⊂ Aut(F₃) leaves invariant an isometrically embedded copy of Euclidean 3-space 𝔼³ ↪ X on which it acts as a discrete group of translations with the rhombic dodecahedron as a Dirichlet...
The Ribes-Zalesskii property of some one relator groups
The profinite topology on any abstract group , is one such that the fundamental system of neighborhoods of the identity is given by all its subgroups of finite index. We say that a group has the Ribes-Zalesskii property of rank , or is RZ with a natural number, if any product of finitely generated subgroups is closed in the profinite topology on . And a group is said to have the Ribes-Zalesskii property or is RZ if it is RZ for any natural number . In this paper we characterize groups...