共查询到20条相似文献,搜索用时 31 毫秒
1.
Algebras and Representation Theory - Let G be a group. If for every proper normal subgroup N and element x of G with N〈x〉≠G, N〈x〉 is an FC-group, but G is not an... 相似文献
2.
Let G be a finite group andA be a normal subgroup ofG. We denote by ncc(A) the number ofG-conjugacy classes ofA andA is calledn-decomposable, if ncc(A)= n. SetK
G = {ncc(A)|A ⊲ G}. LetX be a non-empty subset of positive integers. A groupG is calledX-decomposable, ifK
G =X.
Ashrafi and his co-authors [1-5] have characterized theX-decomposable non-perfect finite groups forX = {1, n} andn ≤ 10. In this paper, we continue this problem and investigate the structure ofX-decomposable non-perfect finite groups, forX = {1, 2, 3}. We prove that such a group is isomorphic to Z6, D8, Q8, S4, SmallGroup(20, 3), SmallGroup(24, 3), where SmallGroup(m, n) denotes the mth group of ordern in the small group library of GAP [11]. 相似文献
3.
Let Out(F
n
) denote the outer automorphism group of the free group F
n
with n>3. We prove that for any finite index subgroup Γ<Out(F
n
), the group Aut(Γ) is isomorphic to the normalizer of Γ in Out(F
n
). We prove that Γ is co-Hopfian: every injective homomorphism Γ→Γ is surjective. Finally, we prove that the abstract commensurator Comm(Out(F
n
)) is isomorphic to Out(F
n
). 相似文献
4.
5.
Michal Sadowski 《Central European Journal of Mathematics》2004,2(2):332-338
Let E
Aff(Γ,G, m) be the set of affine equivalence classes of m-dimensional complete flat manifolds with a fixed fundamental group Γ and a fixed holonomy group G. Let n be the dimension of a closed flat manifold whose fundamental group is isomorphic to Γ. We describe E
Aff(Γ,G, m) in terms of equivalence classes of pairs (ε, ρ), consisting of epimorphisms of Γ onto G and representations of G in ℝ
m-n
. As an application we give some estimates of card E
Aff(Γ,G, m). 相似文献
6.
A. K. Shlyopkin 《Algebra and Logic》1998,37(5):345-350
A group G is saturated with groups of the set X if every finite subgroup K≤G is embedded in G into a subgroup L isomorphic
to some group of X. We study periodic conjugate biprimitive finite groups saturated with groups in the set {U3(2n)}. It is proved that every such group is isomorphic to a simple group U3(Q) over a locally finite field Q of characteristic 2.
Supported by the RF State Committee of Higher Education.
Translated fromAlgebra i Logika, Vol. 37, No. 5, pp. 606–615, September–October, 1998. 相似文献
7.
A. I. Budkin 《Algebra and Logic》2008,47(5):304-313
Let A be a universal algebra and H its subalgebra. The dominion of H in A (in a class {ie304-01}) is the set of all elements
a ∈ A such that every pair of homomorphisms f, g: A → ∈ {ie304-02} satisfies the following: if f and g coincide on H, then
f(a) = g(a). A dominion is a closure operator on a set of subalgebras of a given algebra. The present account treats of closed
subalgebras, i.e., those subalgebras H whose dominions coincide with H. We introduce projective properties of quasivarieties
which are similar to the projective Beth properties dealt with in nonclassical logics, and provide a characterization of closed
algebras in the language of the new properties. It is also proved that in every quasivariety of torsion-free nilpotent groups
of class at most 2, a divisible Abelian subgroup H is closed in each group 〈H, a〉 generated by one element modulo H.
Translated from Algebra i Logika, Vol. 47, No. 5, pp. 541–557, September–October, 2008. 相似文献
8.
V. E. Kislyakov 《Algebra and Logic》1998,37(6):363-370
We study a group G containing an element g such that CG(g)∩gG is finite. The nonoriented graph Γ is defined as follows. The vertex set of Γ is the conjugacy class gG. Vertices x and y of the graph G are bridged by an edge iff x≠y and xy=yx. Let Γ0 be some connected component of G. On a condition that any two vertices of Γ0 generate a nilpotent group, it is proved that a subgroup generated by the vertex set of Γ0 is locally nilpotent.
Supported by the RF State Committee of Higher Education.
Translated fromAlgebra i Logika, Vol. 37, No. 6, pp. 637–650, November–December, 1998. 相似文献
9.
Hatem Hamrouni 《manuscripta mathematica》2008,127(4):511-519
Let G be a connected and simply connected nilpotent Lie group and A a closed connected subgroup of G. Let Γ be a discrete cocompact subgroup of G. In the first part of this paper we give the direct integral decomposition of the up–down representation . As a consequence, we establish a necessary and sufficient condition for A to act ergodically on G/Γ in the case when Γ is a lattice subgroup of G and A is a one-parameter subgroup of G. 相似文献
10.
Let {ie166-01} be a set of finite groups. A group G is said to be saturated by the groups in {ie166-02} if every finite subgroup
of G is contained in a subgroup isomorphic to a member of {ie166-03}. It is proved that a periodic group G saturated by groups
in a set {U3(2m) | m = 1, 2, …} is isomorphic to U3(Q) for some locally finite field Q of characteristic 2; in particular, G is locally finite.
__________
Translated from Algebra i Logika, Vol. 47, No. 3, pp. 288–306, May–June, 2008. 相似文献
11.
V. D. Mazurov 《Algebra and Logic》1998,37(6):371-379
For G a finite group, ω(G) denotes the set of orders of elements in G. If ω is a subset of the set of natural numbers, h(ω)
stands for the number of nonisomorphic groups G such that ω(G)=ω. We say that G is recognizable (by ω(G)) if h(ω(G))=1. G
is almost recognizable (resp., nonrecognizable) if h(ω(G)) is finite (resp., infinite). It is shown that almost simple groups
PGLn(q) are nonrecognizable for infinitely many pairs (n, q). It is also proved that a simple group S4(7) is recognizable, whereas A10, U3(5), U3(7), U4(2), and U5(2) are not. From this, the following theorem is derived. Let G be a finite simple group such that every prime divisor of
its order is at most 11. Then one of the following holds: (i) G is isomorphic to A5, A7, A8, A9, A11, A12, L2(q), q=7, 8, 11, 49, L3(4), S4(7), U4(3), U6(2), M11, M12, M22, HS, or McL, and G is recognizable by the set ω(G); (ii) G is isomorphic to A6, A10, U3(3), U4(2), U5(2), U3(5), or J2, and G is nonrecognizable; (iii) G is isomorphic to S6(2) or O
8
+
(2), and h(ω(G))=2.
Supported by RFFR grant No. 96-01-01893.
Translated fromAlgebra i Logika, Vol. 37, No. 6, pp. 651–666, November–December, 1998. 相似文献
12.
13.
V. E. Kislyakov 《Algebra and Logic》1996,35(5):305-309
We study the problem as to which is the cardinality of connected components of the graph Γα, defined as follows. Let G be a group and a an element of G. The vertex set V(Γα) of the graph is the conjugacy class of elements,Cl
G(a), and two vertices x and y of the graph Γα are bridged by an edge iff x=y. If the intersectionC
G(a)∩Cl
G(a) is finite, Γα is locally finite. We prove that connected components of the locally finite graph Γα are finite in some classes of groups.
Supported by RFFR grant No. 94-01-01084.
Translated fromAlgebra i Logika, Vol. 35, No. 5, pp. 543–551, September–October, 1996. 相似文献
14.
Richard Sharp 《Geometriae Dedicata》2007,125(1):63-74
Let Γ be a convex co-compact group of isometries of a CAT(−1) space X and let Γ0 be a normal subgroup of Γ. We show that, provided Γ is a free group, a sufficient condition for Γ and Γ0 to have the same critical exponent is that Γ / Γ0 is amenable.
相似文献
15.
A. K. Shlyopkin 《Algebra and Logic》1998,37(2):127-138
A group G is saturated with groups of the set X if every finite subgroup K≤G is embedded in G into a subgroup L isomorphic
to some group of X. We study periodic biprimitive finite groups saturated with groups of the sets {L2(pn)}, {Re(32n+1)}, and {Sz(22n+1)}. It is proved thai such groups are all isomorphic to {L2(P)}, {Re(Q)}, or {Sr(Q)} over locally finite fields.
Supported by the RF State Committee of Higher Education.
Translated fromAlgebra i Logika, Vol. 37, No. 2, pp. 224–245, March–April, 1998. 相似文献
16.
Consider a non-connected algebraic group G = G ⋉ Γ with semisimple identity component G and a subgroup of its diagram automorphisms Γ. The identity component G acts
on a fixed exterior component Gτ, id ≠ τ ∈ Γ by conjugation. In this paper we will describe the conjugacy classes and the
invariant theory of this action. Let T be a τ -stable maximal torus of G and its Weyl group W. Then the quotient space Gτ//G
is isomorphic to (T/(1 − τ )(T))/Wτ. Furthermore, exploiting the Jordan decomposition, the reduced fibres of this quotient map are naturally associated bundles
over semisimple G-orbits. Similar to Steinberg's connected and simply connected case [22] and under additional assumptions
on the fundamental group of G, a global section to this quotient map exists. The material presented here is a synopsis of
the Ph.D thesis of the author, cf. [15]. 相似文献
17.
Summary We study embeddings between torsion-free nilpotent groups having isomorphic localizations. Firstly, we show that for finitely
generated torsion-free nilpotent groups of nilpotency class 2, the property of having isomorphicP-localizations (whereP denotes any set of primes) is equivalent to the existence of mutual embeddings of finite index not divisible by any prime
inP. We then focus on a certain family Γ of nilpotent groups whose Mislin genera can be identified with quotient sets of ideal
class groups in quadratic fields. We show that the multiplication of equivalence classes of groups in Γ induced by the ideal
class group structure can be described by means of certain pull-back diagrams reflecting the existence of enough embeddings
between members of each Mislin genus. In this sense, the family Γ resembles the family N0 of infinite, finitely generated nilpotent groups with finite commutator subgroup. We also show that, in further analogy with
N0, two groups in Γ with isomorphic localizations at every prime have isomorphic localizations at every finite set of primes.
We supply counterexamples showing that this is not true in general, neither for finitely generated torsion-free nilpotent
groups of class 2 nor for torsion-free abelian groups of finite rank.
Supported by DGICYT grant PB94-0725
This article was processed by the author using the LATEX style filecljour1 from Springer-Verlag. 相似文献
18.
Jeremy Rickard 《Publications Mathématiques de L'IHéS》1994,80(1):81-94
If a finite group G acts on a quasi-projective variety X, then H*c(X,Z/n), the étale cohomology with compact support of X with coefficients inZ/n, has aZ/n[G]-module structure. It is well known that there is a finer invariant, an object RΓc(X,Z/n) of the derived category ofZ/n[G]-modules, whose cohomology is H*c(X,Z/n). We show that there is a finer invariant still, a bounded complex Λc(X,Z/n) of direct summands of permutationZ/n[G]-modules, well-defined up to chain homotopy equivalence, which is isomorphic to RΓc(X,Z/n) in the derived category. This complex has many properties analogous to those of the simplicial chain complex of a simplicial
complex with a group action. There are similar results forl-adic cohomology. 相似文献
19.
20.
Barak Weiss 《Israel Journal of Mathematics》2006,152(1):221-227
The author proves a conjecture of the author: IfG is a semisimple real algebraic defined over ℚ, Γ is an arithmetic subgroup (with respect to the given ℚ-structure) andA is a diagonalizable subgroup admitting a divergent trajectory inG/Γ, then dimA≤ rankℚ
G. 相似文献