Real Brauer characters

In this paper, we determine the structure of finite groups with a small number of real-valued irreducible Brauer characters.     

Zeros of Brauer characters

The authors obtain a sufficient condition to determine whether an element is a vanishing regular element of some Brauer character. More precisely, let G be a finite group and p be a fixed prime, and H = G′ O^p′ (G); if g ∈ G⁰ - H⁰ with o(gH) coprime to the number of irreducible p-Brauer characters of G, then there always exists a nonlinear irreducible p-Brauer character which vanishes on g. The authors also showin this note that the sums of certain irreducible p-Brauer characters take the value zero on every element of G⁰ - H⁰.     

Normal Sylow subgroups and monomial Brauer characters

Let G be a finite group, p be a prime divisor of |G|, and P be a Sylow p-subgroup of G. We prove that P is normal in a solvable group G if |G : ker φ|p' = φ(1)p' for every nonlinear irreducible monomial p-Brauer character φ of G, where ker φ is the kernel of φ and φ(1)p' is the p'-part of φ(1).     

Cartan矩阵的分解和Brauer特征标次数猜想

设G为有限群,N是G的正规子群.记J=J(F[N])为F[N]的Jacobson根,I=Ann(J)={α∈F[G]|Jα=0}为J在F[G]中的零化子.本文主要研究了,根据F[G/N]和F[G]/I的Cartan矩阵,分解F[G]的Cartan矩阵.这种分解在Cartan不变量和G的合成因子之间建立了一些联系.本文指出N中p-亏零块的存在性依赖于Cartan不变量或者I在F[G]中的性质,证明了Cartan矩阵的分解部分地依赖于B所覆盖的N中的块的性质.本文研究了b为N上的块且l(b)=1时,覆盖b的G中的块B的性质.在两类情形下,本文证明了块代数上关于Brauer特征标次数的猜想成立,涵盖了Holm和Willems研究的某些情形.进而对Holm和Willems提出的问题给出了肯定的回答.另外,本文还给出了Cartan不变量的一些其它结果.     

Projective Brauer Theory

In this article, we define and study a new concept of projective Brauer characters. Following the direct approach as taken in Navarro (1998 Navarro , G. ( 1998 ). Characters and Blocks of Finite Groups. Cambridge , UK : Cambridge University Press . [Google Scholar]) and Isaacs (1975 Isaacs , I. M. ( 1975 ). Character Theory of Finite Groups . New York : Academic Press . [Google Scholar]), we study the resulting projective blocks of projective Frobenius characters and projective Brauer characters of a given group determined by certain linkage condition as an introduction to a projective extension of classic Brauer theory.     

Zeros of Monomial Brauer Characters

Let G be a finite group and p be a fixed prime. A p-Brauer character of G is said to be monomial if it is induced from a linear p-Brauer character of some subgroup(not necessarily proper) of G. Denote by IBr_m(G) the set of irreducible monomial p-Brauer′characters of G. Let H = G′O~p′(G) be the smallest normal subgroup such that G/H is an abelian p′-group. Suppose that g ∈ G is a p-regular element and the order of gH in the factor group G/H does not divide |IBr_m(G)|. Then there exists ? ∈ IBr_m(G) such that ?(g) = 0.     

Brauer Characters of Finite Monoids

We introduce the concept of a Brauer character of a representation of a finite monoid M in characteristic p>0. When p does not divide the order of any subgroup of M, we develop a theory of p-monoid quivers. We apply our results to the full transformation semigroup.     

A semiorthogonal decomposition for Brauer–Severi schemes

A semiorthogonal decomposition for the bounded derived category of coherent sheaves on a Brauer–Severi scheme is given. It relies on bounded derived categories of suitably twisted coherent sheaves on the base (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relative Brauer groups of discrete valued fields

Let be a non-trivial finite Galois extension of a field . In this paper we investigate the role that valuation-theoretic properties of play in determining the non-triviality of the relative Brauer group, , of over . In particular, we show that when is finitely generated of transcendence degree 1 over a -adic field and is a prime dividing , then the following conditions are equivalent: (i) the -primary component, , is non-trivial, (ii) is infinite, and (iii) there exists a valuation of trivial on such that divides the order of the decomposition group of at .

     

Brauer groups and crepant resolutions

We suggest a twisted version of the categorical McKay correspondence and prove several results related to it.     

A scheme related to the Brauer loop model

We introduce the Brauer loop scheme, where • is a certain degeneration of the ordinary matrix product. Its components of top dimension, ⌊N²/2⌋, correspond to involutions π∈SN having one or no fixed points. In the case N even, this scheme contains the upper-upper scheme from [A. Knutson, Some schemes related to the commuting variety, J. Algebraic Geom., in press, math.AG/0306275] as a union of (N/2)! of its components. One of those is a degeneration of the commuting variety of pairs of commuting matrices.The Brauer loop model is an integrable stochastic process studied in [J. de Gier, B. Nienhuis, Brauer loops and the commuting variety, J. Stat. Mech. (2005) P01006, math.AG/0410392], based on earlier related work in [M.J. Martins, B. Nienhuis, R. Rietman, An intersecting loop model as a solvable super spin chain, Phys. Rev. Lett. 81 (1998) 504-507, cond-mat/9709051], and some of the entries of its Perron-Frobenius eigenvector were observed (conjecturally) to equal the degrees of the components of the upper-upper scheme.Our proof of this equality follows the program outlined in [P. Di Francesco, P. Zinn-Justin, Inhomogeneous model of crossing loops and multidegrees of some algebraic varieties, math-ph/0412031]. In that paper, the entries of the Perron-Frobenius eigenvector were generalized from numbers to polynomials, which allowed them to be calculated inductively using divided difference operators. We relate these polynomials to the multidegrees of the components of the Brauer loop scheme, defined using an evident torus action on E. As a consequence, we obtain a formula for the degree of the commuting variety, previously calculated up to 4×4 matrices.     

Brauer代数的中心维数问题

Brauer代数B_n(t)是一种在表示论,数学物理中重要的带一个参数t的有限维代数.当t取普通值时它们的结构已经了解得比较清楚,例如,不可约表示分类.当t取某些特殊值时有关它们还仍有些问题未探明.本文讨论任意参数时Brauer代数的中心的维数问题.主要结论是当t取某些特殊值时,Brauer代数中心的维数必定大于或等于t取普通值时它们的维数.     

The equivariant Brauer group of a group

We consider the Brauer group of a group (finite or infinite) over a commutative ring with identity. A split exact sequence

is obtained. This generalizes the Fröhlich-Wall exact sequence from the case of a field to the case of a commutative ring, and generalizes the Picco-Platzeck exact sequence from the finite case of to the infinite case of . Here is the Brauer-Taylor group of Azumaya algebras (not necessarily with unit). The method developed in this paper might provide a key to computing the equivariant Brauer group of an infinite quantum group.

     

Brauer对的局部熔合

本文引入Ｓｙｌｏｗｂ－对图的概念研究Ｂｒａｕｅｒ对的局部熔合，证明了下面主要结果：简化的ｂ－对族是共轭族．若Ｆ是Ｓｙｌｏｗｂ－对（Ｄ，ｂＤ）内的基本ｂ－对族，Ｆ１＝｛（Ｐ，ｂＰ）｜存在ｇ∈Ｇ使（Ｐ，ｂＰ）是同时含在（Ｄ，ｂＤ）及（Ｄ，ｂＤ）ｇ内的极大ｂ－对且（Ｐ，ｂｐ）在（Ｄ，ｂＤ）与（Ｄ，ｂＤ）ｇ内极端｝则Ｆ１也是共轭族．这些结果统一了Ａｌｐｅｒｉｎ－Ｂｒｏｕｅ及Ｐｕｉｇ的熔合定理．     

相关于Brauer图的若干例子

Brauer图对于刻画有限群的p-块是非常关键的．高零不可约（复）特征标在有限群模表示理论中的Brauer图中扮演着重要的角色．本文用若干例子阐述了关于高零不可约特征标的几个问题．     

Homogeneous Deformations of Brauer Tree Algebras

Abstract

Based on tilting theory, we demonstrate the existence of homogeneous deformations for the Brauer tree algebras, which are derived naturally from a tilting complex.     

Subgroups of the Brauer Group of a Cocommutative Coalgebra

We introduce Shur and projective Schur subgroup of the Brauer group of a cocommutative coalgebra by means of twisted cogroup coalgebras and we study their properties. In particular we show that these subgroups are always torsion (in contrast with the whole Brauer group). Moreover, when C is coreflexive and irreducible both subgroups coincide with the coradical ones. We illustrate the theory with several examples.