Broue's Abelian Defect Group Conjecture for the Tits Group

Broué's Conjecture for 2-blocks with elementary abelian defect groups of order 32

The first author has recently classified the Morita equivalence classes of 2-blocks B of finite groups with elementary abelian defect group of order 32. In all but three cases he proved that the Morita equivalence class determines the inertial quotient of B. We finish the remaining cases by utilizing the theory of lower defect groups. As a corollary, we verify Broué's Abelian Defect Group Conjecture in this situation.

Broué's isotypy conjecture for the sporadic groups and their covers and automorphism groups

Let B be a p-block of a finite group G with abelian defect group D such that S\unlhd G, S'=S, G/Z(S)\le\Aut(S) and S/Z(S) is a sporadic simple group. We show that B is isotypic to its Brauer correspondent in N_G(D) in the sense of Broué. This has been done by [Rouquier, 1994] for principal blocks and it remains to deal with the non-principal blocks.

${\ m SL}(2,p^n)$ 与 ${\ m GL}(2,p^n)$ 的加强 Broué 阿贝尔亏群猜想

The strengthened Broué abelian defect group conjecture for ${\rm SL}(2,p^n)$ and ${\rm GL}(2,p^n)$

本文证明了 ${\ m SL}(2,p^n)$ 和 ${\ m GL}(2,p^n)$ 的每个 $p$-块与其 Brauer 对应块 splendidly Rickard 等价，为 Kessar-Linckelmann 的精细化 Broué 猜想提供新证据。

An algorithmic approach to perverse derived equivalences: Broué's Conjecture for $Ω^{+}_8(2)$

Following Craven and Rouquier's computational method to tackle Broué's abelian defect group conjecture, we present two algorithms implementing that procedure in the case of principal blocks of defect $D \cong C_{\ell} \times C_{\ell}$ for a prime $\ell$; the first describes a stable equivalence between $B_0(G)$ and $B_0(N_G(D))$, and the second tries to lift a such stable equivalence to a perverse derived equivalence. As an application, we show that Broué's conjecture holds for the principal $5$-block of the simple group $Ω^{+}_8(2)$.

Translation by the full twist and Deligne-Lusztig varieties

We prove several conjectures about the cohomology of Deligne-Lusztig varieties: invariance under conjugation in the braid group, behaviour with respect to translation by the full twist, parity vanishing of the cohomology for the variety associated with the full twist. In the case of split groups of type $A$, and using previous results of the second author, this implies Broué-Michel's conjecture on the disjointness of the cohomology for the variety associated to any good regular element. That conjecture was inspired by Broué's abelian defect group conjecture and the specific form Broué conjectu…

对称群与交错群的双覆盖的RoCK块的精细Broué猜想

The refined Broué conjecture for RoCK blocks of double covers of symmetric and alternating groups

本文针对对称群与交错群双覆盖的RoCK $p$-块，证明Kleshchev和Livesey构造的Morita等价与精彩Rickard等价可下降到$p$-进整数环，验证了Kessar与Linckelmann提出的精细Broué阿贝尔亏群猜想。

关于端分裂 $p$-置换分解与 $p$-可解群的 Broué 猜想

On endosplit $p$-permutation resolutions and Broué's conjecture for $p$-solvable groups

本文通过端分裂 $p$-置换分解的新刻画和 Galois 下降的约化，证明了 Kessar-Linckelmann 提出的 Broué 猜想细化版本对满足 $G = O_{p',p,p'}(G)$ 且具有交换 Sylow $p$-子群的某些块成立，这是 Harris-Linckelmann 验证所有 $p$-可解群的 Broué 猜想的关键约化步骤。

Perverse Equivalences and Broué's Conjecture II: The Cyclic Case

We study Broué's abelian defect group conjecture for groups of Lie type using the recent theory of perverse equivalences and Deligne--Lusztig varieties. Our approach is to analyze the perverse equivalence induced by certain Deligne--Lusztig varieties (the geometric form of Broué's conjecture) directly; this uses the cohomology of these varieties, together with information from the cyclotomic Hecke algebra. We start with a conjecture on the cohomology of these Deligne--Lusztig varieties, prove various desirable properties about it, and then use this to prove the existence of the perverse equiva…

$G$-spectra of cyclic defect

Broué's Abelian Defect Conjecture predicts interesting derived equivalences between derived categories of modular representations of finite groups. We investigate a generalization of Broué's Conjecture to ring spectrum coefficients and prove this generalization in the cyclic defect case, following an argument of Rouquier.

Morita equivalence classes of 2-blocks of defect three

We give a complete description of the Morita equivalence classes of blocks with elementary abelian defect groups of order 8 and of the derived equivalences between them. A consequence is the verification of Broué's abelian defect group conjecture for these blocks. It also completes the classification of Morita and derived equivalence classes of 2-blocks of defect at most three defined over a suitable field.

Infinitely many algebras derived equivalent to a block

We give a construction that in many cases gives a simple way to construct infinite families of algebras that are not Morita equivalent, but are all derived equivalent to the same block algebra of a finite group, and apply it to some small blocks. We make some remarks relating this construction to Donovan's Conjecture and Broue's Abelian Defect Group Conjecture.

Tits groups of Iwahori-Weyl groups and presentations of Hecke algebras

Let $G$ be a connected reductive group over a non-archimedean local field $F$ and $I$ be an Iwahori subgroup of $G(F)$. Let $I_n$ is the $n$-th Moy-Prasad filtration subgroup of $I$. The purpose of this paper is two-fold: to give some nice presentations of the Hecke algebra of connected, reductive groups with $I_n$-level structure; and to introduce the Tits group of the Iwahori-Weyl group of groups $G$ that split over an unramified extension of $F$. The first main result of this paper is a presentation of the Hecke algebra $\mathcal H(G(F),I_n)$, generalizing the previous work of Iwahori-Matsu…

Blocks of symmetric groups, semicuspidal KLR algebras and zigzag Schur-Weyl duality

We prove Turner's conjecture, which describes the blocks of the Hecke algebras of the symmetric groups up to derived equivalence as certain explicit Turner double algebras. Turner doubles are Schur-algebra-like `local' objects, which replace wreath products of Brauer tree algebras in the context of the Broué abelian defect group conjecture for blocks of symmetric groups with non-abelian defect groups. The main tools used in the proof are generalized Schur algebras corresponding to wreath products of zigzag algebras and imaginary semicuspidal quotients of affine KLR algebras.

Classifying blocks with abelian defect groups of rank $3$ for the prime $2$

In this paper we classify all blocks with defect group $C_{2^n}\times C_2\times C_2$ up to Morita equivalence. Together with a recent paper of Wu, Zhang and Zhou, this completes the classification of Morita equivalence classes of $2$-blocks with abelian defect groups of rank at most $3$. The classification holds for blocks over a suitable discrete valuation ring as well as for those over an algebraically closed field. The case considered in this paper is significant because it involves comparison of Morita equivalence classes between a group and a normal subgroup of index $2$, so requires nove…

On blocks stably equivalent to a quantum complete intersection of dimension 9 in characteristic 3 and a case of the abelian defect group conjecture

Using a stable equivalence due to Rouquier, we prove that Broue's abelian defect group conjecture holds for 3-blocks of defect 2 whose Brauer correspondent has a unique isomorphism class of simple modules. The proof makes use of the fact, also due to Rouquier, that a stable equivalence of Morita type between self-injective algebras induces an isomorphism between the connected components of the outer automorphism groups of the algebras.

On Rouquier Blocks for Finite Classical Groups at Linear Primes

H. Miyachi and W. Turner have independently proved that Broue's Abelian Defect Group Conjecture holds for certain unipotent blocks of the finite general linear group, the so-called Rouquier blocks. This together with A. Marcus and J. Chuang and R. Rouquier proves that the conjecture holds for all blocks of such groups. We prove that other finite classical groups also possess unipotent Rouquier blocks at linear primes.

Mod $\ell$ cohomology of some Deligne-Lusztig varieties for $\operatorname{GL}_n(q)$

In this article, we study the mod $\ell$ cohomology of some Deligne-Lusztig varieties for $\operatorname{GL}_n(q)$. We prove that the cohomology groups of these varieties are torsion-free under some conditions on the characteristic. Under the torsion-free assumption we can compute the cohomology groups explicitly and we prove that the cohomology complex satisfies partial-tilting condition, which is one of the necessary conditions in the geometric version of Broué's abelian defect group conjecture.

On Perverse Equivalences and Rationality

We show that perverse equivalences between module categories of finite-dimensional algebras preserve rationality. As an application, we give a connection between some famous conjectures from the modular representation theory of finite groups, namely Broué's Abelian Defect Group conjecture and Donovan's Finiteness conjectures.

On the Cohomology of Deligne-Lusztig Varieties

In this paper, we present a conjecture on the degree of unipotent characters in the cohomology of particular Deligne-Lusztig varieties for groups of Lie type, and derive consequences of it. These degrees are a necessary piece of data in the geometric version of Broué's abelian defect group conjecture, and can be used to verify this geometric conjecture in new cases. The geometric version of Broué's conjecture should produce a more combinatorially defined derived equivalence, called a perverse equivalence. We prove that our conjectural degree is an integer (which is not obvious) and has the cor…

On saturated fusion systems and Brauer indecomposability of Scott modules

Let $p$ be a prime number, $G$ a finite group, $P$ a $p$-subgroup of $G$ and $k$ an algebraically closed field of characteristic $p$. We study the relationship between the category $\Ff_P(G)$ and the behavior of $p$-permutation $kG$-modules with vertex $P$ under the Brauer construction. We give a sufficient condition for $\Ff_P(G)$ to be a saturated fusion system. We prove that for Scott modules with abelian vertex, our condition is also necessary. In order to obtain our results, we prove a criterion for the categories arising from the data of $(b, G)$-Brauer pairs in the sense of Alperin-Brou…

Derived equivalences for symmetric groups and sl\_2-categorification

We define and study sl\_2-categorifications on abelian categories. We show in particular that there is a self-derived (even homotopy) equivalence categorifying the adjoint action of the simple reflection. We construct categorifications for blocks of symmetric groups and deduce that two blocks are splendidly Rickard equivalent whenever they have isomorphic defect groups and we show that this implies Broué's abelian defect group conjecture for symmetric groups. We give similar results for general linear groups over finite fields. The constructions extend to cyclotomic Hecke algebras. We also con…

超焦点亚代数的超焦点阿贝尔弗罗贝尼乌斯块

Hyperfocal subalgebras of hyperfocal abelian Frobenius blocks

本文引入了超焦点阿贝尔弗罗贝尼乌斯块，研究其超焦点亚代数与弗罗贝尼乌斯群群代数的莫rita型稳定等价，探讨了超焦点子群为克莱因四元组和循环子群的块结构。

GL_n(q)中辉煌Rickard等价的下降

Descent of splendid Rickard equivalences in ${\rm GL}_n(q)$

本文证明Broué阿贝尔亏群猜想的精细版本对GL_n(q)的幂零ℓ-块成立，并给出一般ℓ-块满足该猜想的一个充分条件，同时举例说明该条件并非普遍成立。

On defect groups for generalized blocks of the symmetric group

In a paper of 2003, B. Külshammer, J. B. Olsson and G. R. Robinson defined $\ell$-blocks for the symmetric groups, where $\ell >1$ is an arbitrary integer. In this paper, we give a definition for the defect group of the principal $\ell$-block. We then check that, in the Abelian case, we have an analogue of one of M. Broué's conjectures.

The McKay conjecture and Brauer's induction theorem

Let $G$ be an arbitrary finite group. The McKay conjecture asserts that $G$ and the normaliser $N_G (P)$ of a Sylow $p$-subgroup $P$ in $G$ have the same number of characters of degree not divisible by $p$ (that is, of $p'$-degree). We propose a new refinement of the McKay conjecture, which suggests that one may choose a correspondence between the characters of $p'$-degree of $G$ and $N_G (P)$ to be compatible with induction and restriction in a certain sense. This refinement implies, in particular, a conjecture of Isaacs and Navarro. We also state a corresponding refinement of the Broué abeli…