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We classify up to Morita equivalence all blocks whose defect groups are Suzuki $2$-groups. The classification holds for blocks over a suitable discrete valuation ring as well as for those over an algebraically closed field, and in fact…

Group Theory · Mathematics 2024-09-16 Charles W. Eaton

Except for blocks with a cyclic or Klein four defect group, it is not known in general whether the Morita equivalence class of a block algebra over a field of prime characteristic determines that of the corresponding block algebra over a…

Representation Theory · Mathematics 2007-05-23 Thorsten Holm , Radha Kessar , Markus Linckelmann

We construct blocks of finite groups with arbitrarily large Morita Frobenius numbers, an invariant which determines the size of the minimal field of definition of the associated basic algebra. This answers a question of Benson and Kessar.…

Representation Theory · Mathematics 2020-06-26 Florian Eisele , Michael Livesey

We introduce a new type of equivalence between blocks of finite group algebras called an almost isotypy. An almost isotypy restricts to a weak isotypy in Brou\'{e}'s original definition, and it is slightly weaker than Linckelmann's version.…

Representation Theory · Mathematics 2025-02-26 Xin Huang

The extension dimensions of an Artin algebra give a reasonable way of measuring how far an algebra is from being representation-finite. In this paper we mainly study extension dimensions linked by recollements of derived module categories…

Representation Theory · Mathematics 2025-02-14 Jinbi Zhang , Junling Zheng

Given a dihedral $2$-group $P$ of order at least~8, we classify the splendid Morita equivalence classes of principal $2$-blocks with defect groups isomorphic to $P$. To this end we construct explicit stable equivalences of Morita type…

Representation Theory · Mathematics 2019-03-08 Shigeo Koshitani , Caroline Lassueur

Let $(\mathcal{K},\mathcal{O},k)$ be a $p$-modular system with $k$ algebraically closed, let $b$ be a block of the normal subgroup $H$ of $G$ having defect pointed group $Q_\delta$ in $H$ and $P_\gamma$ in $G$, and consider the block…

Representation Theory · Mathematics 2019-09-09 Tiberiu Coconet , Andrei Marcus , Constantin-Cosmin Todea

We discuss the notion of essential dimension of a finite group and explain its relation with birational algebraic geometry. We show how this leads to a (partial) classification of simple finite groups of essential dimension less than or…

Algebraic Geometry · Mathematics 2014-01-14 Arnaud Beauville

We discuss representations of finite groups having a common central $p$-subgroup $Z$, where $p$ is a prime number. For the principal $p$-blocks, we give a method of constructing a relative $Z$-stable equivalence of Morita type, which is a…

Representation Theory · Mathematics 2023-04-12 Naoko Kunugi , Kyoichi Suzuki

Two Hopf algebras are called monoidally Morita equivalent if module categories over them are equivalent as linear monoidal categories. We introduce monoidal Morita invariants for finite-dimensional Hopf algebras based on certain braid group…

Quantum Algebra · Mathematics 2009-10-20 Kenichi Shimizu

Let p be a prime, and k be a field of characteristic p. We investigate the algebra structure and the structure of the cohomology ring for the connected Hopf algebras of dimension p^3, which appear in the classification obtained in [V.C.…

Representation Theory · Mathematics 2017-11-01 Karin Erdmann , Oeyvind Solberg , Xingting Wang

We classify principal $2$-blocks of finite groups $G$ with Sylow $2$-subgroups isomorphic to a wreathed $2$-group $C_{2^n}\wr C_2$ with $n\geq 2$ up to Morita equivalence and up to splendid Morita equivalence. As a consequence, we obtain…

Representation Theory · Mathematics 2024-06-05 Shigeo Koshitani , Caroline Lassueur , Benjamin Sambale

We develop Morita theory for finitary additive 2-representations of finitary 2-categories. As an application we describe Morita equivalence classes for 2-categories of projective functors associated to finite dimensional algebras and for…

Representation Theory · Mathematics 2017-05-10 Volodymyr Mazorchuk , Vanessa Miemietz

By results of Rognerud, a source algebra equivalence between two $p$-blocks of finite groups induces an equivalence between the categories of cohomological Mackey functors associated with these blocks, and a splendid derived equivalence…

Group Theory · Mathematics 2015-10-07 Markus Linckelmann

We investigate Conjecture 1.6 introduced by Barker and Gelvin in [3], which says that any source algebra of a p-block (p is a prime) of finite group has the unit group containing a basis stabilized by left and right action of the defect…

Group Theory · Mathematics 2022-12-13 Tiberiu Coconet , Constantin-Cosmin Todea

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 Morita equivalence of unital locally matrix algebras in terms of their Steinitz parametrization. Two countable dimensional unital locally matrix algebras are Morita equivalent if and only if their Steinitz numbers are rationally…

Rings and Algebras · Mathematics 2020-02-18 Oksana Bezushchak , Bogdana Oliynyk

This note uses a variation of graded Morita theory for finite dimensional superalgebras to determine explicitly the graded basic superalgebras for all real and complex Clifford superalgebras. As an application, the Grothendieck groups of…

Rings and Algebras · Mathematics 2012-04-20 Deke Zhao

We calculate examples of Picard groups for 2-blocks with abelian defect groups with respect to a complete discrete valuation ring. These include all blocks with abelian 2-groups of 2-rank at most three with the exception of the principal…

Representation Theory · Mathematics 2019-06-28 Charles W. Eaton , Michael Livesey

In this paper we investigate gradings on tame blocks of group algebras whose defect group is dihedral. We classify gradings on an arbitrary dihedral block up to graded Morita equivalence. We do this by computing the group of outer…

Representation Theory · Mathematics 2010-04-21 Dusko Bogdanic