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PRODID:https://www.math.uni-bielefeld.de/birep/
 meetings/wcb2021/programme.php
METHOD:PUBLISH
BEGIN:VEVENT
UID:keller@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Bernhard Keller
DESCRIPTION:Bernhard Keller (Paris VII)\n\n
 Title. On Amiot's conjecture\n\n
 Abstract.
  In 2010\, Claire Amiot conjectured that algebraic 2-Calabi-Yau
 categories with cluster-tilting object must come from quivers with
 potential. This would extend a structure theorem obtained with Idun
 Reiten in the case where the endomorphism algebra of the
 cluster-tilting object is hereditary. Many other classes of examples
 are also known. We will report on recent progress in the general case.
CLASS:PUBLIC
DTSTART:20210901T100000Z
DTEND:20210901T110000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:plamondon@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Pierre-Guy Plamondon
DESCRIPTION:Pierre-Guy Plamondon (UVSQ/Paris-Saclay)\n\n
 Title. On g-vector fans of associative algebras\n\n
 Abstract.
  The g-vector fan of an algebra is a polytopal object defined from
 tau-tilting theory.  In this talk\, we will study the case when the
 fan has finitely many cones: we will see that\, under certain
 conditions on the algebra\, the fan is related to a set of generators
 of the Grothendieck group of the extriangulated category of 2-term
 complexes of projective modules.  We will then give applications to
 the theory of finite type cluster algebras.  Finally\, we will look at
 some cases where the fan is not finite\, and in particular at tame
 algebras.  This is a report on joint works with A.Padrol\, Y.Palu\,
 V.Pilaud and T.Yurikusa.
CLASS:PUBLIC
DTSTART:20210901T120000Z
DTEND:20210901T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:jasso@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Gustavo Jasso
DESCRIPTION:Gustavo Jasso (Bonn)\n\n
 Title. Homotopical algebra in exact (infinity-)categories\n\n
 Abstract.
  Exact categories were introduced by Quillen in 1973 as part of his
 foundational work on higher algebraic K-theory. Exact categories are
 ubiquitous in representation theory of rings and algebras: they arise
 as module categories\, categories of Gorenstein projective modules\,
 categories of cochain complexes\, etc. Much more recently\, in 2015\,
 Barwick introduced the class of exact infinity-categories in order to
 prove an infinity-categorical version of Neeman's Theorem of the
 Heart. Rouhgly speaking\, Barwick's exact infinity-categories are a
 simultaneous generalisation of Quillen's exact categories and of
 Lurie's stable infinity-categories (the latter can be thought of as
 enhancements of Verdier's triangulated categories).  In this talk\, I
 will explain the role of Barwick's exact infinity- categories in
 representation theory of rings and algebras. I will also explain how
 Cisinki's results on infinity-categorical homotopical algebra can be
 leveraged to study localisations of exact (infinity-)categories and
 their derived infinity-categories.  This is a report on joint work in
 progress with Sondre Kvamme (Uppsala)\, Yann Palu (Amiens) and Tashi
 Walde (TU Munich).
CLASS:PUBLIC
DTSTART:20210901T131500Z
DTEND:20210901T141500Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:neeman@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Amnon Neeman
DESCRIPTION:Amnon Neeman (ANU)\n\n
 Title. Finite approximations as a tool for studying triangulated
 categories\n\n
 Abstract.
  A metric on a category assigns lengths to morphisms\, with the
 triangle inequality holding. This notion goes back to a 1974 article
 by Lawvere. We'll begin with a quick review of some basic
 constructions\, like forming the Cauchy completion of a category with
 respect to a metric. And then will begin a string of surprising new
 results. It turns out that\, in a triangulated category with a
 metric\, there is a reasonable notion of Taylor series\, and an
 approximable triangulated category can be thought of as a category
 where many objects are the limits of their Taylor expansions. And then
 come two types of theorems: (1) theorems providing examples\, meaning
 showing that some category you might naturally want to look at is
 approximable\, and (2) general structure theorems about approximable
 triangulated categories. And what makes it all interesting is (3)
 applications. These turn out to include the proof of a conjecture by
 Bondal and Van den Bergh\, a major generalization of a theorem of
 Rouquier's\, and a short\, sweet proof of Serre's GAGA theorem.
CLASS:PUBLIC
DTSTART:20210902T080000Z
DTEND:20210902T090000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:minamoto@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Hiroyuki Minamoto
DESCRIPTION:Hiroyuki Minamoto (Osaka)\n\n
 Title. Quiver Heisenberg algebras and approximation with respect to
 the powers of the radical functors.\n\n
 Abstract.
  This talk is a report on a joint work with M. Herschend in which we
 study a class of central extensions of the preprojective algebras
 under the name “quiver Heisenberg algebras (QHA)”. We note that
 QHA is special case of “central extensions of the preprojective
 algebras” introduced by Etingof-Rains\, which is a special case of
 $N=1$ quiver algebras introduced by Cachazo-Katz-Vafa\, which is
 obtained as a pull-back of the deformation family of the preprojective
 algebas introduced by Crawley-Boevey-Holland. In the previous talks
 about QHA\, I gave a description of QHA as a modules over the path
 algebra KQ\, which implies the dimension formula by Etingof-Rains in
 the case where Q is Dynkin. The central aim of this talk is to provide
 an understaunding of the description.  Recall that left almost split
 map is nothing but a left approximation with respect to the radical
 functor $rad$. Thus\, universal Auslander-Reiten triangle given in the
 previous talks tells that degree 1-part of QHA provides left minimal
 approximation with respect $rad$ of KQ-modules. The main theorem of
 this talk tells that degree n-part of QHA provides left minimal
 approximation with respect to the n-th power of radical functor
 $rad^{n}$ of KQ-modules. From this result the above mentioned
 description of QHA immediately follows.
CLASS:PUBLIC
DTSTART:20210902T090000Z
DTEND:20210902T100000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:hausel@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Tamas Hausel
DESCRIPTION:Tamas Hausel (IST Austria)\n\n
 Title. Three stories about commutative Frobenius algebras\n\n
 Abstract.
  I will discuss three occurances of Frobenius algebras. First in joint
 work with Letellier and Villegas on quiver representations over
 Frobenius algebras. Second is an analogue of McWilliams identity for
 dual codes over finite graded commutative Frobenius algebras. Finally
 in joint work with Hitchin we study multiplicity algebras of the
 Hitchin integrable system on certain Lagrangians\, which in the very
 stable case are graded commutative Frobenius algebras.
CLASS:PUBLIC
DTSTART:20210902T103000Z
DTEND:20210902T113000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:hubery@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Andrew Hubery
DESCRIPTION:Andrew Hubery (Bielefeld)\n\n
 Title. The Deligne-Simpson Problem\n\n
 Abstract.
  The Deligne-Simpson Problem arises from the study of regular
 differential equations on the Riemann sphere\, and via the
 Riemann-Hilbert Correspondence can be expressed in terms of
 connections on locally-free sheaves on the projective line. We will
 review Bill Crawley-Boevey's work on the Deligne-Simpson Problem\,
 including his proof of the additive version\, his results on the
 multiplicative version\, as well as our joint work towards completing
 the classification of the irreducible solutions. This important
 achievement of Crawley-Boevey draws on his earlier work concerning
 deformed preprojective algebras\, their multiplicative analogues
 (joint with P. Shaw)\, as well as his reformulation of the problem in
 terms of connections on sheaves on weighted projective lines.
CLASS:PUBLIC
DTSTART:20210903T100000Z
DTEND:20210903T110000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:bennett-tennenhaus@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Raphael Bennett-Tennenhaus
DESCRIPTION:Raphael Bennett-Tennenhaus (Bielefeld)\n\n
 Title. Characterisations of $\Sigma$-pure-injective objects in
 triangulated categories.\n\n
 Abstract.
  The model theory of modules involves interpreting model theoretic
 notions in terms of module theory. For example\, an injective module
 embedding is pure provided solutions to certain formulas (called
 pp-formulas) are reflected. A module is $\Sigma$-pure-injective
 provided any set-indexed coproduct of it is pure-injective: that is\,
 injective with respect to pure embeddings. There are various
 well-known ways to characterise both pure-injective and
 $\Sigma$-pure-injective modules.  In this talk\, I will begin by
 replacing the category of modules with a compactly generated
 triangulated category. The notions of purity in this setting were
 defined by Krause\, and the canonical model theoretic language here
 was defined by Garkusha and Prest. I will then present some ways to
 characterise $\Sigma$-pure-injective objects here\, analogous to the
 module category setting. Time permitting\, I will try to say something
 about the proof\, and motivate the consideration of endocoperfect
 objects. This talk is based on the arxiv preprint 2004.06854.
CLASS:PUBLIC
DTSTART:20210903T120000Z
DTEND:20210903T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:laking@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Rosanna Laking
DESCRIPTION:Rosanna Laking (Verona)\n\n
 Title. Mutation in large silting theory\n\n
 Abstract.
  In this talk we will consider a large class of t-structures in
 compactly generated triangulated categories called cosilting
 t-structures.  In particular\, we will consider those determined by
 pure-injective cosilting objects\, which have the desirable property
 that the heart is a Grothendieck abelian category.  Examples of such
 t-structures in the derived category of a finite-dimensional algebra
 include those induced by derived equivalences with Grothendieck
 categories and those “lifted” from bounded t-structures in the
 bounded derived category (in the sense of Marks-Zvonereva).  In this
 talk we will define and explore a mutation operation on such
 t-structures that naturally extends the mutation operation on silting
 t-structures in the bounded derived category of a finite-dimensional
 algebra. This is a report on joint work with Lidia Angeleri Hügel\,
 Jan Stovicek and Jorge Vitória.
CLASS:PUBLIC
DTSTART:20210903T131500Z
DTEND:20210903T141500Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:spenko@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Špela Špenko
DESCRIPTION:Špela Špenko (VUB)\n\n
 Title. HMS symmetries and hypergeometric system\n\n
 Abstract.
  The derived category of an algebraic variety might be a source of its
 myriad new (categorical) symmetries. Some are predicted by homological
 mirror symmetry\, as representations of the fundamental group of
 complex structures of its mirror pair. These finally lead to
 differential equations. We will explain that in the case of (a class
 of) toric varieties we get GKZ hypergeometric systems. This is a joint
 work with Michel Van den Bergh.
CLASS:PUBLIC
DTSTART:20210906T123000Z
DTEND:20210906T133000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:derksen@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Harm Derksen
DESCRIPTION:Harm Derksen (Northeastern)\n\n
 Title. Generating Semi-Invariants for Quiver Representations\n\n
 Abstract.
  For a fixed quiver and a given dimension vector\, we can consider the
 ring of semi-invariants on the representation space. We will give
 degree bounds for generators of this ring that are polynomial in the
 dimension vector. There are also interesting applications to
 theoretical computer science. This is joint work with Visu Makam.
CLASS:PUBLIC
DTSTART:20210906T133000Z
DTEND:20210906T143000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:ginzburg@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Victor Ginzburg
DESCRIPTION:Victor Ginzburg (Chicago)\n\n
 Title. Chern classes of quantizable sheaves and characteristic
 cycles\n\n
 Abstract.
  Let X  be an algebraic symplectic manifold and A a formal deformation
 quantization of O_X. We show that the existence of a quantization of a
 coherent sheaf E on X to an A-module E_A forces the vanishing of
 homogeneous components of the Chern character ch(E) in a certain range
 of degrees. In the special case where the support of E  is a (possibly
 singular) Lagrangian subvariety\, this implies that  the image of
 ch(E) in the Borel-Moore homology reduces to the  support cycle of E. 
 To prove our vanishing result we obtain a formula for the Chern
 character of the quantized A-module E_A in the negative cyclic
 homology in terms of the ordinary Chern character of E. Let X be a
 conical symplectic resolution and B the algebra of global sections of
 a filtered quantization of X. We use the vanishing result to prove
 that the characteristic cycles of finite dimensional simple B-modules
 are linearly independent.
CLASS:PUBLIC
DTSTART:20210906T150000Z
DTEND:20210906T160000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:bauer@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Ulrich Bauer
DESCRIPTION:Ulrich Bauer (TUM)\n\n
 Title. Persistence in functional topology and data analysis\n\n
 Abstract.
  Topological persistence is a cornerstone of applied topology\,
 enabling the use of methods from algebraic topology in novel and
 powerful techniques of data analysis. In my talk\, I will illustrate
 the central role and the historical development of persistent homology
 in different incarnations\, connecting recent developments in
 topological data analysis with classical results in critical point
 theory and the calculus of variations. Presenting recent work with M.
 Schmahl and A. Medina-Mardones [1]\, I will explain how modern
 persistence theory\, in particular recent fundamental structural
 results by Crawley-Boevey et al. [2\,3]\, provide a new and clarifying
 perspective on Morse‘s theory of functional topology\, which has
 been instrumental in the first proof of the existence of unstable
 minimal surfaces by Morse and Tompkins.
CLASS:PUBLIC
DTSTART:20210907T120000Z
DTEND:20210907T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:baur@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Karin Baur
DESCRIPTION:Karin Baur (Leeds)\n\n
 Title. Surface combinatorics and module categories\n\n
 Abstract.
  Surface combinatorics have been instrumental in describing algebraic
 structures such as cluster algebras and cluster categories\, gentle
 algebras\, etc. In this talk\, I will present some of these and then
 concentrate on combinatorial approaches to cluster structures on the
 coordinate ring of the Grassmannians.
CLASS:PUBLIC
DTSTART:20210907T131500Z
DTEND:20210907T141500Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:king@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Alastair King
DESCRIPTION:Alastair King (Bath)\n\n
 Title. Categorification of perfect matchings\n\n
 Abstract.
  In the context of dimer models on a disc\, I will explain how treating
 perfect matchings as modules for the associated dimer algebra can shed
 some light on the cluster combinatorics of Grassmannians.
CLASS:PUBLIC
DTSTART:20210908T100000Z
DTEND:20210908T110000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:august@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Jenny August
DESCRIPTION:Jenny August (MPI Bonn)\n\n
 Title. Higher torsion classes and $𝜏_n$-tilting theory\n\n
 Abstract.
  Higher Auslander-Reiten theory provides “higher” versions of many
 of the classical concepts in representation theory\, such as abelian
 categories\, torsion classes and the Auslander-Reiten translation. In
 this talk\, I will present joint work with J. Haugland\, K. Jacobsen\,
 S. Kvamme\, Y. Palu and H. Treffinger where we explore the connection
 between $n$-torsion classes and $𝜏_n$ tilting theory (where $n=1$
 is the classical setup). We show that a higher analogue of the
 classical bijection between torsion classes and support tau-tilting
 pairs exists\, as well as providing a useful characterisation of
 $n$-torsion classes.
CLASS:PUBLIC
DTSTART:20210908T120000Z
DTEND:20210908T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:gnedin@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Wassilij Gnedin
DESCRIPTION:Wassilij Gnedin (Bochum)\n\n
 Title. Silting theory under change of rings\n\n
 Abstract.
  At the beginning of the nineties\, Rickard showed that the derived
 representation theory of an $\mathsf{R}$-free Noetherian algebra
 $\Lambda$ over a complete  local ring $\mathsf{R}$ is closely related
 to that of its quotient $\Lambda/\mathfrak{m} \Lambda$\, where
 $\mathfrak{m}$ denotes the maximal ideal of the local ring
 $\mathsf{R}$. More precisely\, he established a bijection between
 certain tilting complexes of the algebra $\Lambda$ and tilting
 complexes of the algebra $\Lambda/\mathfrak{m}\Lambda$. The broader
 notion of silting complexes  has attracted much interest recently\,
 after Aihara and Iyama have shown that silting complexes can always be
 mutated to produce new ones. My talk is motivated by the question how
 the silting theory of the ring $\Lambda$ differs from that of  one of
 its quotients $\overline{\Lambda}$ or its tensor product $\Lambda
 \otimes \Gamma$ with another $\mathsf{R}$-algebra $\Gamma$. It turns
 out that there is a bijection between silting complexes of the 
 $\mathsf{R}$-free Noetherian algebra $\Lambda$ and silting complexes
 of its quotient $\Lambda /\mathfrak{a} \Lambda$ for any proper ideal
 $\mathfrak{a}$ of the ring $\mathsf{R}$\, as well as an embedding of
 silting complexes in the context of faithfully flat base change. Using
 a variation of the silting bijection\, the problem to classify silting
 complexes of certain derived-wild rings\, which include some affine
 preprojective algebras and all Brauer graph algebras\, can be reduced
 to the classification problem of silting complexes of certain
 derived-tame rings\, which are nodal orders.
CLASS:PUBLIC
DTSTART:20210908T131500Z
DTEND:20210908T141500Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:burban@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Igor Burban
DESCRIPTION:Igor Burban (Paderborn)\n\n
 Title. Tame non-commutative nodal curves and related finite
 dimensional algebras\n\n
 Abstract.
  Nodal orders are  appropriate non-commutative generalizations of the
 ring $\mathbb{k}[\![ x\, y]\!]/(xy)$. They are characterized by the
 property to be  the only orders of tame (and even derived-tame)
 representation type. A non-commutative (projective) nodal curve is a
 ringed space $\mathbb{X} = (X\, \mathcal{A})$\, where $X$ is a
 conventional (projective) curve (over a field $\mathbb{k}$) and
 $\mathcal{A}$ is a sheaf of nodal orders on $X$. I shall make a review
 of results concerning the tameness of the derived category of coherent
 sheaves $D^b\bigl(\mathsf{Coh}(\mathbb{X})\bigr)$ of a non-commutative
 nodal curve $\mathbb{X}$. For any such $\mathbb{X}$ there exists a
 derived-tame finite dimensional $\mathbb{k}$-algebra $\Lambda$ of
 global dimension two and an exact  fully faithful functor
 $\mathsf{Perf}(\mathbb{X}) \longrightarrow D^b(\Lambda-\mathsf{mod}).
 $ This correspondence will be illustrated by concrete examples and
 some applications will be given. My talk is based on joint works with
 Yuriy Drozd.
CLASS:PUBLIC
DTSTART:20210909T090000Z
DTEND:20210909T100000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:kuelshammer@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Julian Külshammer
DESCRIPTION:Julian Külshammer (Uppsala)\n\n
 Title. Uniqueness of exact Borel subalgebras and bocses\n\n
 Abstract.
  One of Bill's earliest contributions to representation theory is the
 theorem that for a tame algebra all but finitely many modules of each
 dimension lie in homogeneous tubes. Its proof relies on the theory of
 bocses (bimodules over a category with coalgebra structure). In joint
 work with Koenig and Ovsienko we used this theory\, together with
 A-infinity-Koszul duality\, to construct an exact Borel subalgebra for
 every quasi-hereditary algebra up to Morita equivalence. In this talk
 I will present a uniqueness result of these subalgebras. This is joint
 work with Vanessa Miemietz.
CLASS:PUBLIC
DTSTART:20210909T100000Z
DTEND:20210909T110000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:schroll@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Sibylle Schroll
DESCRIPTION:Sibylle Schroll (Cologne)\n\n
 Title. Algebra and Module Varieties\n\n
 Abstract.
  In this talk on joint work in progress with Ed Green and Eduardo
 Marcos we will introduce varieties of finite dimensional modules over
 the path algebra of a quiver with relations. Modules in the same
 variety have the same dimension vector and share certain homological
 properties. The construction of the module varieties is closely
 related to the construction of varieties of algebras defined in
 earlier work with Ed Green and Lutz Hille.
CLASS:PUBLIC
DTSTART:20210909T120000Z
DTEND:20210909T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:erdmann@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Karin Erdmann
DESCRIPTION:Karin Erdmann (Oxford)\n\n
 Title. Hybrid algebras\n\n
 Abstract.
  Hybrid algebras\, introduced in [Hy]\, form a large class of tame 
 symmetric algebras. As extremes they include  weighted surface
 algebras (which are periodic of period four)\, but also Brauer graph
 algebras (which are special biserial). Intermediate versions have 
 ‘clannish’ representations\, as  in [CB-II] and [CB-III]. With
 these we get  new information on stable Auslander-Reiten components of
 hybrid algebras.
CLASS:PUBLIC
DTSTART:20210910T100000Z
DTEND:20210910T110000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:davison@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Ben Davison
DESCRIPTION:Ben Davison (Edinburgh)\n\n
 Title. Fermionizing Yangians via central extensions of preprojective
 algebras\n\n
 Abstract.
  The Hall algebra $A_Q$ built out of the Borel-Moore homology of the
 stack of representations of a preprojective algebra $\Pi_Q$ contains
 one half of the Kac-Moody Lie algebra $g_Q$ associated to $Q$\, and
 indeed one half of the Yangian of $Q$.  Moreover\, this BM homology is
 entirely situated in even cohomological degrees\, and can be shown to
 contain the universal enveloping algebra of the BPS Lie algebra
 associated to $Q$\, a cohomologically graded Lie algebra\,
 concentrated entirely in even degrees\, which recovers all of the Kac
 polynomials of $Q$ via the taking of characteristic polynomials. In
 this talk I will review these results\, and then introduce a
 construction of partially fermionized versions of the above algebras. 
 These new algebras also arise as cohomological Hall algebras\, this
 time built out of the vanishing cycle cohomology of certain central
 extensions of $\Pi_Q$ considered by Etingof and Rains.  These central
 extensions are determined by a parameter in the Cartan algebra of
 $g_Q$\, which also determines the extent of fermionization that the
 new algebra exhibits\, when compared to $A_Q$.
CLASS:PUBLIC
DTSTART:20210910T120000Z
DTEND:20210910T130000Z
DTSTAMP:20260412T152428Z
END:VEVENT
BEGIN:VEVENT
UID:etingof@math.uni-bielefeld.de/birep/meetings/wcb2021
LOCATION:Zoom
STATUS:CONFIRMED
SUMMARY:Talk of Pavel Etingof
DESCRIPTION:Pavel Etingof (MIT)\n\n
 Title. Frobenius exact symmetric tensor categories\n\n
 Abstract.
  I will report on a joint work with K. Coulembier and V. Ostrik. We
 show that a symmetric tensor category in characteristic $p>0$ admits a
 fiber functor to the Verlinde category (semisimplification of
 $Rep(Z/p)$) if and only if it has moderate growth and its Frobenius
 functor (an analog of the classical Frobenius in the representation
 theory of algebraic group) is exact. For example\, for $p=2$ and $3$
 this implies that any such category is (super)-Tannakian. We also give
 a characterization of super-Tannakian categories for $p>3$. This
 generalizes Deligne's theorem that any symmetric tensor category over
 C of moderate growth is super-Tannakian to characteristic $p$. At the
 end I'll discuss applications of this result to modular representation
 theory.
CLASS:PUBLIC
DTSTART:20210910T131500Z
DTEND:20210910T141500Z
DTSTAMP:20260412T152428Z
END:VEVENT
END:VCALENDAR