The isomeric Heisenberg category acts naturally on a number of abelian categories appearing in the representation theory of the isomeric supergroup Q(n), and also on representations of Sergeev’s algebra which is related to the double covers of symmetric groups. I will explain an efficient way to convert an action of the isomeric Heisenberg category on these and other abelian categories into an action of a corresponding super Kac–Moody 2-category. To properly understand the odd simple root indexed by the element zero of the ground field requires the theory of odd symmetric functions developed by Ellis, Khovanov and Lauda, the quiver Hecke superalgebras of Kang, Kashiwara and Tsuchioka, and the covering quantum groups defined and studied by Clark and Wang.
Seminars in KLR Algebras
For the quiver Hecke algebra R associated with a simple Lie algebra, let R-gmod be the category of finite-dimensional graded R-modules. It is well known that it categorifies the unipotent quantum coordinate ring 𝒜q, that is, the Grothendieck ring 𝒦(R-gmod) is isomorphic to 𝒜q. For the localization of R-gmod, denoted by R̃-gmod, its Grothendieck ring 𝒦(R̃-gmod) defines the localized (unipotent) quantum coordinate ring 𝒜̃q. We shall give a certain crystal structure on the localized quantum coordinate ring 𝒜̃q by regarding the set of self-dual simple objects 𝔹(R̃-gmod) in R̃-gmod.
We also give the isomorphism of crystals from 𝔹(R̃-gmod) to the cellular crystal 𝔹i=Bi1⊗ . . . ⊗BiN for an arbitrary reduced word i=i1 . . . iN of the longest Weyl group element. This result can be seen as a localized version for the categorification of the crystal B(∞) by Lauda-Vazirani since the crystal B(∞) is realized as a subset of the cellular crystal 𝔹i.
KLR algebras of type A have been a revolution in the representation theory of Hecke algebras of a type A flavour, thanks to the the Brundan-Kleshchev-Rouquier isomorphism relating them explicitly to the affine Hecke algebra of type A. KLR algebras of other types exist but are not related to affine Hecke algebras of other types. In this talk I will present a generalisation of the KLR presentation for the affine Hecke algebra of type B and I will discuss some applications.
In 1901 Young gave an explicit construction of the ordinary irreducible representations of the symmetric groups. In doing this, he introduced content functions for partitions, which are now a key statistic in the semisimple representation theory of the symmetric groups. In this talk I will describe a generalization of Young's ideas to the cyclotomic KLR algebras of affine types A and C. This is quite surprising because Young's seminormal forms are creatures from the semisimple world whereas the cyclotomic KLR algebras are rarely semisimple. As an application, we show that these algebras are cellular and construct their irreducible representations. A special case of these results gives new information about the symmetric groups in characteristic p > 0. If time permits, I will describe how these results lead to an explicit categorification of the corresponding integrable highest weight modules.
Weighted KLRW algebras are diagram algebras that depend on continuous parameters. Varying these parameters gives a way to interpolate between various algebras that appear in (categorical) representation theory such as semisimple algebras, KLR algebras, quiver Schur algebras and diagrammatic Cherednik algebras. This talk is a friendly (and diagrammatic!) introduction explaining these algebras, with no prior knowledge about any of these assumed.
One ever-recurring goal of Lie theory is the quest for effective and elegant descriptions of collections of simple objects in categories of interest. A cornerstone feat achieved by Zelevinsky in that regard, was the combinatorial explication of the Langlands classification for smooth irreducible representations of p-adic GLn. It was a forerunner for an exploration of similar classifications for various categories of similar nature, such as modules over affine Hecke algebras or quantum affine algebras, to name a few. A next step - reaching an effective understanding of all reducible finite-length representations remains largely a difficult task throughout these settings.
Recently, joint with Erez Lapid, we have revisited the original Zelevinsky setting by suggesting a refined construction of all irreducible representations, with the hope of shedding light on standing decomposition problems. This construction applies the Robinson-Schensted-Knuth transform, while categorifying the determinantal Doubilet-Rota-Stein basis for matrix polynomial rings appearing in invariant theory. In this talk, I would like to introduce the new construction into the setting of modules over quiver Hecke (KLR) algebras. In type A, this category may be viewed as a quantization/gradation of the category of representations of p-adic groups. I will explain how adopting that point of view and exploiting recent developments in the subject (such as the normal sequence notion of Kashiwara-Kim) brings some conjectural properties of the RSK construction (back in the p-adic setting) into resolution. Time permits, I will discuss the relevance of the RSK construction to the representation theory of cyclotomic Hecke algebras.
Representation theory of Khovanov-Lauda-Rouquier (KLR) algebras in affine type A can be studied through the lens of Specht modules, associated with the cellular structure of cyclotomic KLR algebras, or through the lens of cuspidal modules, associated with categorified PBW bases for the quantum group of affine type A. Cuspidal ribbons provide a sort of combinatorial bridge between these approaches. I will describe some recent results on cuspidal ribbon tableaux, and some implications in the world of KLR representation theory, such as bounds on labels of simple factors of Specht modules, and the presentation of cuspidal modules.
We discuss a new explicit isomorphism between (truncations of) quiver Hecke algebras and Elias-Williamson’s diagrammatic endomorphism algebras of Bott-Samelson bimodules. This allows us to deduce that the decomposition numbers of these algebras (including as examples the symmetric groups and generalised blob algebras) are tautologically equal to the associated p-Kazhdan-Lusztig polynomials, provided that the characteristic is greater than the Coxeter number. This allows us to give an elementary and explicit proof of the main theorem of Riche-Williamson’s recent monograph and extend their categorical equivalence to cyclotomic Hecke algebras, thus solving Libedinsky-Plaza’s categorical blob conjecture.
