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We show that the 3-block of the sporadic simple Janko group J_4 with defect group C_3 x C_3, and the principal 3-block of the alternating group A_8 are Puig equivalent, answering a question posed in earlier work of Koshitani-Kunugi-Waki. To…

Representation Theory · Mathematics 2012-12-13 Shigeo Koshitani , Jürgen Müller , Felix Noeske

We describe the ordinary characters of trivial source modules lying in blocks with cyclic defect groups relying on their recent classification in terms of paths on the Brauer tree by G.~Hiss and the second author. In particular, we show how…

Representation Theory · Mathematics 2020-04-07 Shigeo Koshitani , Caroline Lassueur

For any grading by an abelian group $G$ on the exceptional simple Lie algebra $\mathcal{L}$ of type $E_6$ or $E_7$ over an algebraically closed field of characteristic zero, we compute the graded Brauer invariants of simple…

Representation Theory · Mathematics 2017-11-27 Cristina Draper , Alberto Elduque , Mikhail Kochetov

We show (among other things) that Brauer's k(B)-conjecture holds for defect groups with are central extensions of metacyclic 2-groups by cyclic groups. The same holds for defect groups which contain a central cyclic subgroup of index at…

Representation Theory · Mathematics 2010-12-21 Benjamin Sambale

Problem 21 of Brauer's list of problems from 1963 asks whether for any positive integer k there are finitely many isomorphism classes of groups that occur as the defect group of a block with k irreducible characters. We solve this problem…

Group Theory · Mathematics 2023-10-03 Alexander Moretó , Noelia Rizo , A. A. Schaeffer Fry

In this article, we will generalize an explicit formula proved by Quer for the Brauer class of the endomorphism algebra of abelian varieties associated to modular forms of weight 2 to the case of Hilbert modular forms of parallel weight 2,…

Number Theory · Mathematics 2024-10-29 Alireza Shavali

We determine which quasi-simple groups have a non-principal $2$-block that is stable under complex conjugation. As a corollary, we determine that the Mathieu group $M_{22}$ is the only simple group not possessing a nontrivial irreducible…

Representation Theory · Mathematics 2026-05-25 John Revere McHugh , A. A. Schaeffer Fry

We give a reduction of Donovan's conjecture for abelian groups to a similar statement for quasisimple groups. Consequently we show that Donovan's conjecture holds for abelian $2$-groups.

Representation Theory · Mathematics 2018-03-12 Charles Eaton , Michael Livesey

This series of papers is a contribution to the program of classifying $p$-blocks of finite groups up to source algebra equivalence, starting with the case of cyclic blocks. To any $p$-block $\mathbf{B}$ of a finite group with cyclic defect…

Representation Theory · Mathematics 2025-12-08 Gerhard Hiss , Caroline Lassueur

We describe a general technique to classify blocks of finite groups, and we apply it to determine Morita equivalence classes of blocks with elementary abelian defect groups of order 32 with respect to a complete discrete valuation ring with…

Representation Theory · Mathematics 2021-01-25 Cesare Giulio Ardito

We give a reduction to quasisimple groups for Donovan's conjecture for blocks with abelian defect groups defined with respect to a suitable discrete valuation ring $\mathcal{O}$. Consequences are that Donovan's conjecture holds for…

Representation Theory · Mathematics 2019-05-27 Charles W. Eaton , Florian Eisele , Michael Livesey

In this paper, we characterize a Rickard complex, which induces a Rickard equivalence between the block algebras of a block $b$ and its Brauer correspondent and whose vertices have the same order as defect groups of the block $b$. The…

Representation Theory · Mathematics 2013-05-23 Yuanyang Zhou

In representation theory of finite groups, there is a well-known and important conjecture due to M. Brou\'e. He conjectures that, for any prime $p$, if a $p$-block $A$ of a finite group $G$ has an abelian defect group $P$, then $A$ and its…

Representation Theory · Mathematics 2009-06-30 Shigeo Koshitani , Jürgen Müller

Necessary and sufficient conditions are given for a $G$-graded simple module over a unital associative algebra, graded by an abelian group $G$, to be isomorphic to a loop module of a simple module, as well as for two such loop modules to be…

Representation Theory · Mathematics 2016-09-12 Alberto Elduque , Mikhail Kochetov

Relying on the classification of the indecomposable liftable modules in arbitrary blocks with non-trivial cyclic defect groups we give a complete classification of the trivial source modules lying in such blocks, describing in particular…

Representation Theory · Mathematics 2020-04-08 Gerhard Hiss , Caroline Lassueur

The aim of this paper is to study a Lie conformal algebra of Block type. In this paper, conformal derivation, conformal module of rank 1 and low-dimensional comohology of the Lie conformal algebra of Block type are studied. Also, the vertex…

Rings and Algebras · Mathematics 2016-01-28 Lamei Yuan

In a paper of 2003, B. K\"ulshammer, 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…

Representation Theory · Mathematics 2014-02-26 Jean-Baptiste Gramain

We prove, for primes $p\ge5$, two inequalities between the fundamental invariants of Brauer $p$-blocks of finite quasi-simple groups: the number of characters in the block, the number of modular characters, the number of height zero…

Representation Theory · Mathematics 2018-04-04 Gunter Malle

We consider central simple $K$-algebras which happen to bedifferential graded $K$-algebras. Two such algebras $A$ and $B$are considered equivalent if there are bounded complexes of finite dimensional$K$-vector spaces $C_A$ and $C_B$ such…

Rings and Algebras · Mathematics 2023-08-21 Alexander Zimmermann

We concern the VIGRE's conjecture; namely the complexity of a Specht module is the p-weight of the corresponding partition if and only if the partition is not p by p. In abelian defect case, we calculate the cohomological variety of the…

Representation Theory · Mathematics 2011-02-15 Kay Jin Lim