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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

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…

Representation Theory · Mathematics 2016-03-15 Anton Evseev , Alexander Kleshchev

Slattery has generalized Brauer's theory of p-blocks of finite groups to pi-blocks of pi-separable groups where pi is a set of primes. In this setting we show that the order of a defect group of a pi-block B is bounded in terms of the…

Representation Theory · Mathematics 2018-10-16 Benjamin Sambale

In by now classical work, K. Erdmann classified blocks of finite groups with dihedral defect groups (and more generally algebras of dihedral type) up to Morita equivalence. In the explicit description by quivers and relations of such…

Representation Theory · Mathematics 2008-09-09 Thorsten Holm , Guodong Zhou

In this paper, we classify all $2$-blocks for which the defect groups are abelian and the inertial quotient has prime order. As a consequence, we prove that Brou\'e's abelian defect group conjecture holds for all blocks under consideration…

Group Theory · Mathematics 2026-04-14 Qianhu Zhou , Kun Zhang

We study the Brauer groups of regular conic bundles over elliptic curves defined over a number field $k$. We explicitly compute the Brauer group of the conic bundle when the singular fibres lie above $k$-points that are divisible by $2$ in…

Algebraic Geometry · Mathematics 2025-09-22 Abdulmuhsin Alfaraj

In this short note we study the center ZB of a block B of a finite group over an algebraically closed field of prime characteristic through its Loewy length llZB. A result of Okuyama in 1981 gave an upper bound for llZB in terms of defect…

Representation Theory · Mathematics 2016-11-21 Yoshihiro Otokita

Let $\chi(x)\in \mathbb{Z}[x]$ be a monic polynomial whose roots are distinct integers. We study the ideal class monoid and the ideal class group of the ring $\mathbb{Z}[x]/(\chi(x))$. We obtain formulas for the orders of these objects, and…

Number Theory · Mathematics 2025-12-01 Ruben Hambardzumyan , Mihran Papikian

We investigate random connected graphs from a block-stable class whose distribution is weighted based on the number of $2$-connected components, or blocks. This includes the class of planar graphs. For this, we develop a notion of a…

Combinatorics · Mathematics 2026-04-28 Mihyun Kang , Zéphyr Salvy , Ronen Wdowinski

By using the structure and some properties of extraspecial and generalized/almost extraspecial $p$-groups, we explicitly determine the number of elements of specific orders in such groups. As a consequence, one may find the number of cyclic…

Group Theory · Mathematics 2024-05-08 Mihai-Silviu Lazorec

Any Schur ring is uniquely determined by a partition of the elements of the group. In this paper we present a general technique for enumerating Schur rings over cyclic groups using traditional Schur rings. We also survey recent efforts to…

Group Theory · Mathematics 2021-12-08 Andrew Misseldine

We consider a block $B$ of a finite group with defect group $D \cong (C_{2^m})^n$ and inertial quotient $\mathbb{E}$ containing a Singer cycle (an element of order $2^n-1$). This implies $\mathbb{E} = E \rtimes F$, where $E \cong…

Representation Theory · Mathematics 2020-01-09 Elliot Mckernon

We find representation type of the cyclotomic quiver Hecke algebras of level two in affine type A. In particular, we have determined representation type for all the block algebras of Hecke algebras of classical type (except for…

Representation Theory · Mathematics 2017-06-05 Susumu Ariki

Using Mackey functors, we provide a general framework for classifying torsors of algebraic tori in terms of Brauer groups of finite field extensions of the base field. This generalizes Blunk's description of the tori associated to del Pezzo…

Algebraic Geometry · Mathematics 2025-09-12 Alexander Duncan , Pankaj Singh

Recently, Kleshchev and Livesey proved the existence of RoCK $p$-blocks for double covers of symmetric and alternating groups over large enough coefficient rings. They proved that these RoCK blocks of double covers are Morita equivalent to…

Representation Theory · Mathematics 2025-10-24 Yucong Du , Xin Huang

We define and study RoCK blocks for double covers of symmetric groups. We prove that RoCK blocks of double covers are Morita equivalent to standard `local' blocks. The analogous result for blocks of symmetric groups, a theorem of Chuang and…

Representation Theory · Mathematics 2022-12-01 Alexander Kleshchev , Michael Livesey

We prove a conjecture of Broue about the Jordan decomposition of blocks of finite reductive groups. We show that a block of a finite connected reductive group, in non-describing characteristic, is Morita-equivalent to a quasi-isolated block…

Representation Theory · Mathematics 2007-05-23 Cedric Bonnafe , Raphael Rouquier

Suppose that all nontrivial subsections of a $p$-block $B$ are conjugate (where $p$ is a prime). By using the classification of the finite simple groups, we prove that the defect groups of $B$ are either extraspecial of order $p^3$ with $p…

Representation Theory · Mathematics 2014-10-22 Lázló Héthelyi , Radha Kessar , Burkhard Külshammer , Benjamin Sambale

We prove the existence of Morita equivalences between the spin blocks at the extremal points of strings in the block-reduced crystal graph. When the parities of the core partitions are not preserved, these equivalences require crossovers,…

Representation Theory · Mathematics 2009-10-28 R. Leabovich , M. Schaps

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 Brou\'e.…

Representation Theory · Mathematics 2015-09-01 Benjamin Sambale