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1.
Let G be a finite group and suppose that G = AB, where A andB are abelian subgroups. By a theorem of Ito, the derived subgroupG' is known to be abelian. If either of the subgroups A or Bis cyclic, then more can be said. The paper shows, for example,that G'/(G'A) is isomorphic to a subgroup of B in this case. 相似文献
2.
It is shown that if a group G = AB is the product of two subgroups A and B, each of which has an abelian subgroup of index at most 2 satisfying the minimum condition and such that one of the subgroups
A or B is of dihedral type, then G is abelian-by-finite with minimum condition. 相似文献
3.
In §2, we prove that if a 2-group G and all its nonabelian maximal sub-groups are two-generator, then G is either metacyclic or minimal non-abelian. In §3, we consider a similar question for p > 2. In §4 the 2-groups all of whose minimal nonabelian subgroups have order 16 and a cyclic subgroup of index 2, are classified.
It is proved, in §5, that if G is a nonmetacyclic two-generator 2-group and A, B, C are all its maximal subgroups with d(A) ≤ d(B) ≤ d(C), then d(C) = 3 and either d(A) = d(B) = 3 (this occurs if and only if G/G′ has no cyclic subgroup of index 2) or else d(A) = d(B) = 2. Some information on the last case is obtained in Theorem 5.3. 相似文献
4.
Zvonimir Janko 《Mathematische Zeitschrift》2008,258(3):629-635
We determine here up to isomorphism the structure of any finite nonabelian 2-group G in which every two distinct maximal abelian subgroups have cyclic intersection. We obtain five infinite classes of such 2-groups
(Theorem 1.1). This solves for p = 2 the problem Nr. 521 stated by Berkovich (in preparation). The more general problem Nr. 258 stated by Berkovich (in preparation)
about the structure of finite nonabelian p-groups G such that A ∩ B = Z(G) for every two distinct maximal abelian subgroups A and B is treated in Theorems 3.1 and 3.2. In Corollary 3.3 we get a new result for an arbitrary finite 2-group. As an application
of Theorems 3.1 and 3.2, we solve for p = 2 a problem of Heineken-Mann (Problem Nr. 169 stated in Berkovich, in preparation), classifying finite 2-groups G such that A/Z(G) is cyclic for each maximal abelian subgroup A (Theorem 4.1).
相似文献
5.
It is proved that every group of the form G = AB with subgroups A and B each of which has a cyclic subgroup of index at most 2 is metacyclicby-finite.
Received: 13 July 2007 相似文献
6.
Arie Bialostocki 《Israel Journal of Mathematics》1975,20(2):178-188
LetG be a finite group with an abelian Sylow 2-subgroup. LetA be a nilpotent subgroup ofG of maximal order satisfying class (A)≦k, wherek is a fixed integer larger than 1. Suppose thatA normalizes a nilpotent subgroupB ofG of odd order. ThenAB is nilpotent. Consequently, ifF(G) is of odd order andA is a nilpotent subgroup ofG of maximal order, thenF(G)?A. 相似文献
7.
Ryan McCulloch 《代数通讯》2018,46(7):3092-3096
It is an open question in the study of Chermak-Delgado lattices precisely which finite groups G have the property that 𝒞𝒟(G) is a chain of length 0. In this note, we determine two classes of groups with this property. We prove that if G = AB is a finite group, where A and B are abelian subgroups of relatively prime orders with A normal in G, then the Chermak-Delgado lattice of G equals {ACB(A)}, a strengthening of earlier known results. 相似文献
8.
This paper resolves the following conjecture of R. Merris: Let dGλ be the generalized matrix function determined by a subgroup G of the symmetric group Sm and an irreducible complex character λ of G. If A, B, and A?B are m-square positive semidefinite hermitian m-square matrices and dGλ(A)=dGλ(B)≠0, then A=B. 相似文献
9.
Let G be a locally compact group. We show that its Fourier algebra A(G) is amenable if and only if G has an abelian subgroup of finite index, and that its Fourier–Stieltjes algebra B(G) is amenable if and only if G has a compact, abelian subgroup of finite index. We then show that A(G) is weakly amenable if the component of the identity of G is abelian, and we prove some partial results towards the converse.Research supported by NSERC under grant no. 90749-00.Research supported by NSERC under grant no. 227043-00. 相似文献
10.
Let G be a finite group and cd(G) be the set of all complex irreducible character degrees of G. Bertram Huppert conjectured that if H is a finite nonabelian simple group such that cd(G) = cd(H), then G???H × A, where A is an abelian group. In this paper, we verify the conjecture for the family of simple exceptional groups of Lie type 3 D 4(q), when q?≥?3. 相似文献
11.
Ariel Yadin 《Israel Journal of Mathematics》2009,174(1):203-219
Let A, B be two random subsets of a finite group G. We consider the event that the products of elements from A and B span the whole group, i.e. [AB ∪ BA = G]. The study of this event gives rise to a group invariant we call Θ(G). Θ(G) is between 1/2 and 1, and is 1 if and only if the group is abelian. We show that a phase transition occurs as the size of
A and B passes √Θ(G)|G| log |G|; i.e. for any ɛ > 0, if the size of A and B is less than (1 − ɛ)√Θ(G)|G| log |G|, then with high probability AB ∪ BA ≠ G. If A and B are larger than (1 + ɛ)√Θ(G)|G| log |G|, then AB ∪ BA = G with high probability. 相似文献
12.
P. X. Gallagher 《Archiv der Mathematik》2014,102(3):201-207
For each finite group G, the product in the group ring of all the conjugacy class sums is a positive integer multiple of the sum of the elements in a special coset of the commutator subgroup G′, as Brauer and Wielandt first observed in the case G′ = G. We show that the corresponding special element G! in A := G/G′ is the product of B! over specified subgroups B of A. Somewhat analogously, the product of all the irreducible characters of G, restricted to the center Z of G, is a multiple of a special linear character !G of Z, and !G is the product of !(Z/Y) over specified subgroups Y of Z. 相似文献
13.
Manfred Dugas 《Journal of Pure and Applied Algebra》2007,208(1):117-126
In [J. Buckner, M. Dugas, Co-local subgroups of abelian groups, in: Abelian Groups, Rings, Modules, and Homological Algebra, in: Lect. Notes Pure and Applied Math., vol. 249, Taylor and Francis/CRC Press, pp. 25-33] the notion of a co-local subgroup of an abelian group was introduced. A subgroup K of A is called co-local if the natural map is an isomorphism. At the center of attention in [J. Buckner, M. Dugas, Co-local subgroups of abelian groups, in: Abelian Groups, Rings, Modules, and Homological Algebra, in: Lect. Notes Pure and Applied Math., vol. 249, Taylor and Francis/CRC Press, pp. 25-33] were co-local subgroups of torsion-free abelian groups. In the present paper we shift our attention to co-local subgroups K of mixed, non-splitting abelian groups A with torsion subgroup t(A). We will show that any co-local subgroup K is a pure, cotorsion-free subgroup and if D/t(A) is the divisible part of A/t(A)=D/t(A)⊕H/t(A), then K∩D=0, and one may assume that K⊆H. We will construct examples to show that K need not be a co-local subgroup of H. Moreover, we will investigate connections between co-local subgroups of A and A/t(A). 相似文献
14.
Thomas P. Wakefield 《Algebras and Representation Theory》2011,14(4):609-623
Let G be a finite group and cd(G) be the set of irreducible character degrees of G. Bertram Huppert conjectured that if H is a finite nonabelian simple group such that cd(G) = cd(H), then G ≅ H×A, where A is an abelian group. In this paper, we verify the conjecture for the twisted Ree groups 2
G
2(q
2) for q
2 = 32m + 1, m ≥ 1. The argument involves verifying five steps outlined by Huppert in his arguments establishing his conjecture for many
of the nonabelian simple groups. 相似文献
15.
V. S. Monakhov 《Mathematical Notes》2013,93(3-4):460-464
The solvability of a finite group G = AB is established under the assumption that the subgroups A and B are solvable and the Carter subgroups of A commute with the Carter subgroups of B. 相似文献
16.
B.P. Duggal 《Linear algebra and its applications》2008,428(4):1109-1116
A Hilbert space operator A∈B(H) is p-hyponormal, A∈(p-H), if |A∗|2p?|A|2p; an invertible operator A∈B(H) is log-hyponormal, A∈(?-H), if log(TT∗)?log(T∗T). Let dAB=δAB or ?AB, where δAB∈B(B(H)) is the generalised derivation δAB(X)=AX-XB and ?AB∈B(B(H)) is the elementary operator ?AB(X)=AXB-X. It is proved that if A,B∗∈(?-H)∪(p-H), then, for all complex λ, , the ascent of (dAB-λ)?1, and dAB satisfies the range-kernel orthogonality inequality ‖X‖?‖X-(dAB-λ)Y‖ for all X∈(dAB-λ)-1(0) and Y∈B(H). Furthermore, isolated points of σ(dAB) are simple poles of the resolvent of dAB. A version of the elementary operator E(X)=A1XA2-B1XB2 and perturbations of dAB by quasi-nilpotent operators are considered, and Weyl’s theorem is proved for dAB. 相似文献
17.
Thomas P. Wakefield 《Algebras and Representation Theory》2012,15(3):427-448
Let G denote a finite group and cd (G) the set of irreducible character degrees of G. Bertram Huppert conjectured that if H is a finite nonabelian simple group such that cd (G) = cd (H), then G ≅ H × A, where A is an abelian group. Huppert verified the conjecture for PSp4(q) when q = 3, 4, 5, or 7. In this paper, we extend Huppert’s results and verify the conjecture for PSp4(q) for all q. This demonstrates progress toward the goal of verifying the conjecture for all nonabelian simple groups of Lie type of rank
two. 相似文献
18.
A. Ballester-Bolinches John Cossey R. Esteban-Romero 《Annali di Matematica Pura ed Applicata》2010,189(4):567-570
For a finite group G we define the graph Γ(G) to be the graph whose vertices are the conjugacy classes of cyclic subgroups of G and two conjugacy classes ${\mathcal {A}, \mathcal {B}}For a finite group G we define the graph Γ(G) to be the graph whose vertices are the conjugacy classes of cyclic subgroups of G and two conjugacy classes A, B{\mathcal {A}, \mathcal {B}} are joined by an edge if for some A ? A, B ? B A{A \in \mathcal {A},\, B \in \mathcal {B}\, A} and B permute. We characterise those groups G for which Γ(G) is complete. 相似文献
19.
Let the soluble-by-finite group G=AB=AC=BC be the product of two nilpotent subgroups A and B and a subgroup C. It is shown that, if G has finite abelian section rank and C is hypercentral (hypercyclic), then G is hypercentral (hypercyclic). Moreover, if G is an L
1-group and C is nilpotent, then G is nilpotent.Dedicated to Professor Guido Zappa on the occasion of his 75th birthday 相似文献
20.
Alexander Pott 《Geometriae Dedicata》1994,52(2):181-193
We consider projective planes Π of ordern with abelian collineation group Γ of ordern(n?1) which is generated by (A, m)-elations and (B, l)-homologies wherem =AB andA εl. We prove
- Ifn is even thenn=2e and the Sylow 2-subgroup of Γ is elementary abelian.
- Ifn is odd then the Sylow 2-subgroup of Γ is cyclic.
- Ifn is a prime then Π is Desarguesian.
- Ifn is not a square thenn is a prime power.