The Autumn 2017 seminars will be held at Imperial College on Thursdays throughout the term, and will begin at 5pm unless otherwise stated. The room will be Huxley 130 unless otherwise stated. Organizer: John Britnell
October 12  Chris Bowman (Kent)  Complex reflection groups of type G(l,1,n) and their deformations  
October 19  John MacQuarrie (UFMG)  The path algebra as a left adjoint functor  
October 26  Alexander Molev (Sydney)  Vinberg’s problem for classical Lie algebras  
November 2  no colloquium  
November 9  Joanna Fawcett (Imperial)  TBA  
November 16  Dan Segal (Oxford)  Small profinite groups  
November 23  Jason Semeraro (Leicester)  TBA  
November 7  Dugald MacPherson (Leeds)  Model theory of profinite groups 
Previous seminars
Summer 2017
In Summer Term 2017, the LAC was held at City University, organized by Jorge Vittoria.
8th June (ELG04 City University)  Jay Taylor (Arizona)  HarishChandra Induction and Lusztig’s Jordan Decomposition of Characters 
22nd June (ELG04 City University)  Arik Wilbert (Bonn)  Twoblock Springer fibers and Springer representations in type D 
29th June (ELG08 City University)  Benjamin Briggs (Bonn)  The characteristic action of Hochschild cohomology, and Koszul duality 
4th July (ELG08 City University)  Andrew Mathas (Sydney)  Jantzen filtrations and graded Specht modules 
20th July (ELG08 City University)  Olaf Schnürer (Bonn)  Geometric applications of conservative descent for semiorthogonal decompositions 
Abstracts:
Title: Geometric applications of conservative descent for semiorthogonal decompositions
Motivated by the local flavor of several wellknown semiorthogonal decompositions in algebraic geometry we introduce a technique called “conservative descent” in order to establish such decompositions locally. The decompositions we have in mind are those for projective bundles, blowups and root constructions. Our technique simplifies the proof of these decompositions and establishes them in greater generality. We also discuss semiorthogonal decompositions for BrauerSeveri varieties.
This is joint work with Daniel Bergh (Copenhagen).
Title: Jantzen filtrations and graded Specht modules
The Jantzen sum formula is a classical result in the representation theory of the symmetric and general linear groups that describes a natural filtration of the modular reductions of the simple modules of these groups. Analogues of this result exist for many algebras including the cyclotomic Hecke algebras of type A. Quite remarkably, the cyclotomic Hecke algebras of type A are now know to admit a Zgrading because they are isomorphic to cyclotomic KLR algebras. I will explain how to give an easy proof of the Jantzen sum formula for the Specht modules of the cyclotomic Hecke algebras of type A using the KLR grading. I will discuss some consequences and applications of this approach.
Title: Twoblock Springer fibers and Springer representations in type D
Abstract: We explain how to construct an explicit topological model for
every twoblock Springer fiber of type D. These socalled topological
Springer fibers are homeomorphic to their corresponding algebrogeometric
Springer fiber. They are defined combinatorially using cup diagrams which
appear in the context of finding closed formulas for parabolic
KazhdanLusztig polynomials of type D with respect to a maximal parabolic
of type A. As an application it is discussed how the topological Springer
fibers can be used to reconstruct the famous Springer representation in an
elementary and combinatorial way.
Spring 2017
In Winter/Spring 2017 the LAC was hosted at Queen Mary, University of London, organized by John Bray. The seminars will usually begin at 4:45pm (the traditional LAC start time). They all take place in the Fogg Lecture Theatre, Fogg Building (SBCS).
19 January (5pm)  Alex Fink (Queen Mary)  Characteristic polynomials from reciprocal planes in two ways 
26 January  Ben Fairbairn (Birkbeck)  A Baby, Some Bathwater & What I Did on my Holidays 
2 February  Behrang Noohi (Queen Mary)  Explicit HRStilting 
9 February  Rieuwert J. Blok (Bowling Green State University, Ohio, visiting Birmingham (UK))  CANCELLED, owing to illness. 
16 February  Chimere S. Anabanti (Birkbeck)  Three questions of Bertram on locally maximal sumfree sets. 
23 February  Rieuwert J. Blok (Bowling Green State University, Ohio, visiting Birmingham (UK))  3spherical Curtis–Tits groups 
2 March  Michael Wibmer (University of Pennsylvania)  Differential Embedding Problems over Complex Function Fields 
16 March  Susama Agarwala (US Naval Academy)  Mixed Tate Motives from Graphs 
23 March  Ben Smith (QMUL)  An Algebraic Approach to Generalised Frobenius Numbers 
30 March  Alla Detinko (St Andrews)  TBA 
In Autumn 2016 the LAC was hosted at City University, organized by Chris BowmanScargill. The seminars began at 5pm. Room details will be added to the list of seminars below shortly.
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6 October ELG08  Michael Bate (York)  Geometric Invariant Theory without Etale Slices 
13 October EM01  Lewis Topley (Bristol)  Modular finite Walgebras and their applications 
20 October EM01  Jan Grabowski (Lancaster)  Recovering automorphisms of quantum spaces 
27 October EM01  Robert Marsh (Leeds)  Dimer models and cluster categories of Grassmannians 
3 November EM01  Jorge Vitoria (City)  Silting modules and ring epimorphisms 
10 November EM01  Florian Eisele (City)  Tame blocks 
17 November EM01  Neil Saunders (City) 
On the Exotic Springer Correspondence

24 November EM01  Kevin McGerty (Oxford)  Kirwan surjectivity for quiver varieties 
1 December ELG08  Mark Wildon (Royal Holloway)  Plethysms: permutations, weights and Schur functions 
8 December ELG08  Tim Burness (Bristol)  Generating simple groups and their subgroups 