On Centralizer Subalgebras of Group Algebras

Let G be a finite group, H ≤ G and R be a commutative ring with an identity 1R. Let CRG（H）={α ∈ RG｜αh = hα for all h ∈ H）, which is called the centralizer subalgebra of H in RG. Obviously, if H=G then CRG（H） is just the central subalgebra Z（RG） of RG. In this note, we show that the set of all H- conjugacy class sums of G forms an R-basis of CRG（H）. Furthermore, let N be a normal subgroup of G and γthe natural epimorphism from G to G to G/N. Then γ induces an epimorphism from RG to RG, also denoted by % We also show that if R is a field of characteristic zero, then γ induces an epimorphism from CRG（H） to CRG（H）, that is, 7（CRG（H）） = CRG（H）.     

(∈,∈∨q)-模糊正规化子与(∈,∈∨q)-模糊商子群

在(∈,∈∨q)-模糊子群的基础上,引入了(∈,∈∨q)-模糊正规化子与(∈,∈∨q)-模糊中心化子的概念,并讨论了它们的一些性质.同时,给出了(∈,∈∨q)-模糊商群与(∈,∈∨q)-模糊商子群的定义,建立了(∈,∈∨q)-模糊商群的同构定理.     

The Commutativity Relation in the Symmetric Semigroup

We compute the cardinality of the centralizer of an injection or surjection provided that the basic set is countable. We prove a formula for the cardinality of the set of conjugacy classes in the infinite symmetric group.     

Finite Groups with Character Degrees of Two Distinct Primes

0Introduction Characterdegreesoffinitegroupsandtheirsubgroupshavebeenrecentlystudied[16].Inthisnote,westudytherelationshipsbetweenthegroup theoreticalstructureofafinitegroupGandthearithmeticpropertyofthedegreesofthe irreduciblecharactersofG.Afundamentalfactisthatifafi nitegroupGhasanabeliannormalsubgroupA,thenthede greeofanyirreduciblecharacterofGdividesthequotientorder|G/A|;seeTheorem6.15ofRef.[2]andProperty24of Ref.[7].ForfinitesolvablegroupsG,It gaveapartialin verse.Heshownthatifthede…     

完全分配可交换子空间格代数上的中心化映射

基于Hilbert空间H上的一个完全分配可交换子空间格代数Alg L,考虑Alg L上的中心化映射.设为Alg L上的一个可加映射,用完全分配可交换子空间格代数的结构性质和代数分解,证明了:若存在正整数m,n≥1,使得A∈Alg L,(Am+n+1)-Am(A)An∈F I成立,则存在Alg L中心里的元素λ,满足A∈Alg L,有(A)=λA.     

On a Class of Projections on *-Rings

ABSTRACT

In this article we describe the structure of projections acting on semiprime *-rings and satisfying a certain functional identity. The main result is applied to bicircular projections on C *-algebras.     

Partially commutative metabelian groups: centralizers and elementary equivalence

For partially commutative metabelian groups, annihilators of elements of commutator subgroups are described; canonical representations of elements are defined; approximability by torsion-free nilpotent groups is proved; centralizers of elements are described. Also, it is proved that two partially commutative metabelian groups have equal elementary theories iff their defining graphs are isomorphic, and that every partially commutative metabelian group is embeddable in a metabelian group with decidable universal theory. Dedicated to V. N. Remeslennikov on the occasion of his 70th birthday Supported by RFBR (project No. 09-01-00099). Translated from Algebra i Logika, Vol. 48, No. 3, pp. 309–341, May–June, 2009.     

Derangements and Tensor Powers of Adjoint Modules for \mathfrak{s}\mathfrak{l}_n

We obtain the decomposition of the tensor space as a module for , find an explicit formula for the multiplicities of its irreducible summands, and (when n 2k) describe the centralizer algebra = ( ) and its representations. The multiplicities of the irreducible summands are derangement numbers in several important instances, and the dimension of is given by the number of derangements of a set of 2k elements.     

Second Centralizers of Partial Transformations

Second centralizers of partial transformations on a finite set are determined. In particular, it is shown that the second centralizer of any partial transformation consists of partial transformations that are locally powers of .