Finite groups in which Sylow normalizers have nilpotent Hall supplements

The normalizer of each Sylow subgroup of a finite group G has a nilpotent Hall supplement in G if and only if G is soluble and every tri-primary Hall subgroup H (if exists) of G satisfies either of the following two statements: (i) H has a nilpotent bi-primary Hall subgroup; (ii) Let π(H) = {p, q, r}. Then there exist Sylow p-, q-, r-subgroups H _p , H _q , and H _r of H such that H _q ? N _H (H _p ), H _r ? N _H (H _q ), and H _p ? N _H (H _r ).     

The average number of Sylow subgroups of a finite group

We prove that if the average Sylow number (ignoring the Sylow numbers that are one) of a finite group G is ?7, then G is solvable.     

Pure quantitative characterization of finite projective special unitary groups

We prove that each projective special unitary group G can be characterized using only the set of element orders of G and the order of G.     

Finite groups in which the normalizers of Sylow 3-subgroups are of odd or primary index

We determine the composition factors of the finite groups in which the normalizers of Sylow 3-subgroups are of odd or primary index.     

Symmetric designs and four dimensional projective special unitary groups

In this article, we study symmetric $(v,k,\lambda )$ designs admitting a flag-transitive and point-primitive automorphism group $G$ whose socle is ${\mathrm{PSU}}_4\left(q\right)$. We prove that there exist eight non-isomorphic such designs for which $\lambda \in \{3,6,18\}$ and $G$ is either ${\mathrm{PSU}}_4\left(2\right)$, or ${\mathrm{PSU}}_4\left(2\right):2$.     

On g-s-supplemented subgroups of finite groups

A subgroup H of a group G is said to be g-s-supplemented in G if there exists a subgroup K of G such that HK⊴G and H ∩ K ⩽ H _sG , where H_sG is the largest s-permutable subgroup of G contained in H. By using this new concept, we establish some new criteria for a group G to be soluble.     

On the Sylow graph of a group and Sylow normalizers

Let G be a finite group and G _p be a Sylow p-subgroup of G for a prime p in π(G), the set of all prime divisors of the order of G. The automiser A _p (G) is defined to be the group N _G (G _p )/G _p C _G (G _p ). We define the Sylow graph Γ _A (G) of the group G, with set of vertices π(G), as follows: Two vertices p, q ∈ π(G) form an edge of Γ _A (G) if either q ∈ π(A _p (G)) or p ∈ π(A _q (G)). The following result is obtained Theorem: Let G be a finite almost simple group. Then the graph Γ _A (G) is connected and has diameter at most 5. We also show how this result can be applied to derive information on the structure of a group from the normalizers of its Sylow subgroups.     

Locally Transitive Graphs Admitting a Group with Cyclic Sylow Subgroups

All graphs are finite simple undirected and of no isolated vertices in this paper. Using the theory of coset graphs and permutation groups, it is completed that a classification of locally transitive graphs admitting a non-Abelian group with cyclic Sylow subgroups. They are either the union of the family of arc-transitive graphs, or the union of the family of bipartite edge-transitive graphs.     

A new characterization of L 2(r) by their Sylow numbers

Let G be a finite centerless group, let π(G) be the set of prime divisors of the order of G, and let np(G) be the number of Sylow p-subgroups of G, that is, n_p(G) = |Sylp(G)|. Set NS(G) := {n_p(G)| p ∈π(G)}. In this paper, we are investigating whether L_2(r) is determined up to isomorphism by NS(L_2(r)) when r is prime.     

有限交换环上典型群的Sylow子群

令Ｒ为有限交换局部环，Ｍ表其唯一的极大理想，ｋ表其剩余类域．本文定出了Ｒ上的一般线性群ＧＬｎＲ，辛群Ｓｐ２ｎＲ及双曲正交群Ｏ２ｎＲ的Ｓｙｌｏｗ子群．一般讲，若ｃｈａｒｘ＝ｐ，上述三类典型群的Ｓｙｌｏｗ ｐ－子群分别同构于由某些特殊形式的矩阵生成的子群；若ｃｈａｒｋ≠ｐ，上述三类典型群的Ｓｙｌｏｗｐ－子群分别同构于一循环群或半二面体群与若干Ｚｐ型循环群的圈积。     

The Existence of p-Blocks with a Submaximal-Subgroup of a Sylow p-Subgroup as Defect Group

Abstract

In this paper,we will determine the existence of blocks with submaximal subgroups of Sylow p-subgroups of a finite group G as defect groups.     

A modified Brauer algebra as centralizer algebra of the unitary group

The centralizer algebra of the action of on the real tensor powers of its natural module, , is described by means of a modification in the multiplication of the signed Brauer algebras. The relationships of this algebra with the invariants for and with the decomposition of into irreducible submodules is considered.

     

The generic character table of a Sylow p-subgroup of a finite Chevalley group of type D4

Let U be a Sylow p-subgroup of the finite Chevalley group of type D₄ over the field of q elements, where q is a power of a prime p. We describe a construction of the generic character table of U.     

The order of elements in Sylow p-subgroups of the symmetric group

Define a random variable ξ_n by choosing a conjugacy class C of the Sylow p-subgroup of S_pn by random, and let ξ_n be the logarithm of the order of an element in C. We show that ξ_n has bounded variance and mean order log n /log p +O(1), which differs greatly from the average order of elements chosen with equal probability. This revised version was published online in June 2006 with corrections to the Cover Date.     

有限特殊射影酉群U4(q)与U5(q)的一个特征性质

设G为有限群,如对每个质数r都有|N_G(R₁)|=|N_(Un(q))(R₂)|,那么G≌U_n(q),此处R₁∈Syl_r(G),R₂∈Syl_r(U_n(q)),n=4或5.     

Maximal and Sylow Subgroups of Solvable Finite Groups

The structure of finite solvable groups in which any Sylow subgroup is the product of two cyclic subgroups is studied. In particular, it is proved that the nilpotent length of such a group is no greater than 4. It is also proved that the nilpotent length of a finite solvable group in which the index of any maximal subgroup is either a prime or the square of a prime or the cube of a prime does not exceed 5.     

A characterization ofL n (q) by the normalizers' orders of their sylow subgroups

LetG be a finite group. If for every primer, whereR ₁ Syl _r G andR ₂ Syl _r (L _n (q)), thenG L _n (q).     

有限特殊射影酉群U_4(q)与U_5(q)的一个特征性质

间; 设G为有限群,如对每个质数r都有那么 此处 n=4或5,     

On generalized m-S-permutable subgroups of a finite group

In this paper, we give some new conditions under which a normal subgroup E of a finite group G is hypercyclically embedded in G, that is, every chief factor of G below E is cyclic.