Free and Non-Free Subgroups of the Group UT(∞, ℤ)

We provide a method to find free groups of rank two in the group of infinite unitriangular matrices. Our groups are generated by two block-diagonal matrices, namely of the form A = diag(C, C, C…), B = diag(I _t , C, C…), where C is a matrix of finite dimension.

We give a necessary and sufficient condition for A and B defined above to generate a free group when C is a transvection. We formulate a sufficient condition to generate a free group, when C is a product of any number of commuting transvections.

We provide a classification of groups defined above, when C is of degree 3 or 4.     

Special representations of the groups U(∞, 1) and O(∞, 1) and the associated representations of the current groups U(∞, 1) X and O(∞, 1) X in quasi-poisson spaces

A method for constructing representations of the current groups O(n, 1) ^X and U(n, 1) ^X , n ε ℕ, developed in the previous papers by the authors is generalized to the case of infinite n. This leads to an interesting difference in construction (absent for finite n) between the cases of the orthogonal and unitary groups, which is due to the different character of special representations of the groups of coefficients.     

Essential Subgroups of group

ＥｓｓｅｎｔｉａｌＳｕｂｇｒｏｕｐｓｏｆｇｒｏｕｐＷ．Ｂ．ＶａｓａｎｔｈａＫａｎｄａｓａｍｙ（ＤｅＦｔ．ｏｆＭａｔｈ．，Ｉｎｄｉａｎｉｎｓｔ．ｏｆＴｅｃｈ．，Ｍａｄｒａｓ－６０００３６，Ｉｎｄｉａ）ＥｓｓｅｎｔｉａｌＳｕｂｇｒｏｕｐｓｏｆｇｒｏｕｐＷ...     

Normal Subgroups of B u Aut(Ω)

Aut(Ω) denotes the group of all order preserving permutations of the totally ordered set Ω, and if e ≤ u ∈ Aut(Ω), then B _u Aut(Ω) denotes the subgroup of all those permutations bounded pointwise by a power of u. It is known that if Aut(Ω) is highly transitive, then Aut(Ω) has just five normal subgroups. We show that if Aut(Ω) is highly transitive and u has just one interval of support, then B _u Aut(Ω) has normal subgroups, and there is a certain ideal of the lattice of subsets of (), the power set of the integers, such that the lattice of normal subgroups of every such Aut(Ω) is isomorphic to . To Bernhard Banaschewski on the occasion of his 80th birthday.     

Subgroups of Finite Symmetric Groups

Recent results about primitive permutation groups are surveyed.     

Spectral sequences in (∞,1)-categories

We explain how to set up the homotopy spectral sequence of a (co)simplicial object in an ∞-category, with an emphasis on how to construct the differentials in a model-invariant manner.     

Equicentralizer Subgroups of Sporadic Simple Groups

A subgroup H of a group C is called an equicentralizer subgroup of G if thecentralizers of its nonidentity elements are all equal. We discuss the equicentrali-zer subgroups of sporadic simple groups. Using the orders of centralizers of theelements and the structure of the maximal subgroups, we prove that the equicent-     

On the Universal Unfoldings of C~∞ Map Germs Under Some Subgroups of A and K

ＯｎｔｈｅＵｎｉｖｅｒｓａｌＵｎｆｏｌｄｉｎｇｓｏｆＣ￣∞ＭａｐＧｅｒｍｓＵｎｄｅｒＳｏｍｅＳｕｂｇｒｏｕｐｓｏｆＡａｎｄＫＸｉｏｎｇＪｉａｎｆｅｉ（熊剑飞）（ＩｎｓｔｉｔｕｔｅｏｆＡＰＰｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ＱｉｎｇｄａｏＵｎｉｖｅｒｓｉ...     

Uniform Boundedness of Torsion Subgroups of Linear Groups

The torsion conjecture says： for any abelian variety A defined over a number field k, the order of the torsion subgroup of A（k） is bounded by a constant C（k,d） which depends only on the number field k and the dimension d of the abelian variety. The torsion conjecture remains open in general. However, in this paper, a short argument shows that the conjecture is true for more general fields if we consider linear groups instead of abelian varieties. If G is a connected linear algebraic group defined over a field k which is finitely generated over Q,Г is a torsion subgroup of G（k）. Then the order of Г is bounded by a constant C＇（k, d） which depends only on k and the dimension d of G.     

On F-Abnormal Maximal Subgroups of Finite Groups

For any saturated formation F of finite groups containing all supersolvable groups, the groups in F are characterized by F-abnormal maximal subgroups.     

On θ*-completions of F-abnormal Subgroups

Let F be a saturated formation of finite groups. Given a proper subgroup H of a group G, a subgroup H of G is called F-normal in G if G/HG belongs to F;otherwise H is said to be F-abnormal in G. In this paper, we investigate the structure of a finite group byθ?-completions of F-abnormal subgroups.     

Free Subgroups in the Units of ℤ[K 8 × C p ]

Abstract

Marciniak and Sehgal (Marciniak, Z., Sehgal, S. K. (1997). Constructing free subgroups of integral group rings units. Proc. Amer. Math. Soc.125(4):1005–1009) constructed free subgroups in U(?[G]) whenever Ghas a non normal finite subgroup. In this paper we construct free subgroups in U(?[G]), where Gis a group whose subgroups are all normal.     

Theta Subgroups and the Solvability of FiniteGroups

§１．　ＩｎｔｒｏｄｕｃｔｉｏｎａｎｄＤｅｆｉｎｉｔｉｏｎＡｌｌｇｒｏｕｐｓｔｒｅａｔｅｄａｒｅｆｉｎｉｔｅ．Ｉｎ［１］，Ｎ．Ｐ．ＭｕｋｈｅｒｊｅｅａｎｄＰ．Ｂｈａｔｔａｃｈａｒｙａｄｅｆｉｎｅｄｔｈｅｃｏｎｃｅｐｔｏｆθ－ｐａｉｒｓａｓｓｏｃｉａｔｅｄｔｏａｍａｘｉｍａｌｓｕｂｇｒｏｕｐＭｏｆａｇｒｏｕｐＧａｓｆｏｌｌｏｗｓ：ａθ－ｐａｉｒｆｏｒＭｉｓａｎｙｐａｉｒｏｆｓｕｂｇｒｏｕｐｓ（Ｃ，Ｄ）ｏｆＧｓｕｃｈｔｈａｔ（１）ＤＧ，Ｄ＜Ｃ，（２）〈Ｍ，Ｃ〉＝Ｇ，〈Ｍ，Ｄ〉＝Ｍａｎｄ（３）Ｃ／Ｄ…     

On σ-semipermutable Subgroups of Finite Groups

Let σ = {σ_i|i ∈ I } be some partition of the set of all primes P, G a finite group andσ(G) = {σ_i |σ_i ∩π(G) = ?}. A set H of subgroups of G is said to be a complete Hall σ-set of G if every member = 1 of H is a Hall σ_i-subgroup of G for some σ_i ∈σ and H contains exactly one Hallσ_i-subgroup of G for every σ_i ∈σ(G). A subgroup H of G is said to be: σ-semipermutable in G with respect to H if H H_i~x= H_i~xH for all x ∈ G and all H_i ∈ H such that(|H|, |H_i|) = 1; σ-semipermutable in G if H is σ-semipermutable in G with respect to some complete Hall σ-set of G. We study the structure of G being based on the assumption that some subgroups of G are σ-semipermutable in G.     

RESEARCH ANNOUNCEMENTS Strong Discreteness of Subgroups of SL(2, Γ_n)

As in [1,6], let Г_n be the n-dimensional Clifford group, i.e., the set of all elements in ndimensional Clifford algebra An, which can be expressed as a finite product of non-zero-vectors and SL(2, Г_n) denote the group of n-dimensional Clifford matrices which satisfy: