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BEGIN:VEVENT
SUMMARY:Henning Krause (Bielefeld University)
DTSTART;VALUE=DATE-TIME:20221012T113000Z
DTEND;VALUE=DATE-TIME:20221012T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/1
DESCRIPTION:Title: Stratification of integral representations for finite groups\nby He
nning Krause (Bielefeld University) as part of RA Seminar\n\n\nAbstract\nW
e consider representations of finite groups over a commutative noetherian
ring and explain a classification of thick and localising tensor ideals vi
a group cohomology. Some focus will be on the definition of the appropriat
e categories of representations such that the existing machinery can be ap
plied. Another crucial ingredient is the passage to the finite dimensional
fibres for any group algebra. This is a report on joint work with Dave Be
nson\, Srikanth Iyengar\, and Julia Pevtsova.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bernhard Keller (Paris City University)
DTSTART;VALUE=DATE-TIME:20221109T113000Z
DTEND;VALUE=DATE-TIME:20221109T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/2
DESCRIPTION:Title: Hom-infinite Higgs categories\nby Bernhard Keller (Paris City Unive
rsity) as part of RA Seminar\n\n\nAbstract\nIn his thesis\, Yilin Wu has r
ealized every Jacobi-finite ice quiver with potential as the ice quiver as
sociated with a cluster-tilting object in the Higgs category\, a certain F
robenius extriangulated category which generalizes the category of represe
ntations of a preprojective algebra. We will report on joint work with Yil
in Wu where we extend his results to a large class of Jacobi-infinite ice
quivers with potential.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Amnon Neeman (Australian National University)
DTSTART;VALUE=DATE-TIME:20221214T113000Z
DTEND;VALUE=DATE-TIME:20221214T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/3
DESCRIPTION:Title: Vanishing negative K-theory and bounded t-structures\nby Amnon Neem
an (Australian National University) as part of RA Seminar\n\n\nAbstract\nW
e will begin with a quick reminder of algebraic K-theory\, and a few class
ical\, vanishing results for negative K-theory. The talk will then focus o
n a striking 2019 article by Antieau\, Gepner and Heller - it turns out th
at there are K-theoretic obstructions to the existence of bounded t-struct
ures. The result suggests many questions. A few have already been answered
\, but many remain open. We will concentrate on the many possible directio
ns for future research.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Volodymyr Mazorchuk (Uppsala University)
DTSTART;VALUE=DATE-TIME:20230111T113000Z
DTEND;VALUE=DATE-TIME:20230111T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/4
DESCRIPTION:Title: Homological invariants of category O\nby Volodymyr Mazorchuk (Uppsa
la University) as part of RA Seminar\n\n\nAbstract\nThis will be a survey
talk about homological\nproperties of the Bernstein-Gelfand-Gelfand\ncateg
ory O associated with a triangular\ndecomposition of a semi-simple complex
\nfinite dimensional Lie algebra. Blocks of O\nare module categories over
finite dimensional\nassociative algebras having many nice properties\nand
symmetries\, inclduing quasi-heredity\,\nRingel self-duality\, Koszul self
-duality\,\nAuslander regularity etc. I will try to\npresent a number of r
esults describing\nhomological properties and invariants\nfor these blocks
and describe both methods\nand tools which are used to establish these\nr
esults.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karin Baur (University of Leeds)
DTSTART;VALUE=DATE-TIME:20230208T113000Z
DTEND;VALUE=DATE-TIME:20230208T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/5
DESCRIPTION:Title: Frieze patterns and cluster theory\nby Karin Baur (University of Le
eds) as part of RA Seminar\n\n\nAbstract\nCluster categories and cluster a
lgebras can be described via triangulations of surfaces or via Postnikov d
iagrams. In type A\, such triangulations lead to frieze patterns or SL_2-f
riezes in the sense of Conway and Coxeter. We explain how infinite frieze
patterns arise and discuss their growth behaviour. In particular\, we show
that tame module categories yield friezes with linear growth.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Prest (University of Manchester)
DTSTART;VALUE=DATE-TIME:20230315T113000Z
DTEND;VALUE=DATE-TIME:20230315T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/6
DESCRIPTION:Title: Definable categories\nby Mike Prest (University of Manchester) as p
art of RA Seminar\n\n\nAbstract\nA definable subcategory of a module categ
ory is one which is closed under direct products\, directed colimits and p
ure submodules. Many interesting categories of this kind arise in homolog
ical algebra and representation theory. Definable categories have a rich
internal structure and the natural functors between them mirror exact func
tors between associated small abelian categories. I will give a variety of
examples and describe some of their features.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sophie Morier-Genoud (Université Reims Champagne Ardenne)
DTSTART;VALUE=DATE-TIME:20230412T113000Z
DTEND;VALUE=DATE-TIME:20230412T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/7
DESCRIPTION:Title: q-analogues of real numbers\nby Sophie Morier-Genoud (Université R
eims Champagne Ardenne) as part of RA Seminar\n\n\nAbstract\nThe most popu
lar q-analogues of numbers are certainly the q-integers and the q-binomial
coefficients of Gauss which both appear in various areas of mathematics a
nd physics. Most classical sequences of integers often have interesting q-
analogues. With Valentin Ovsienko we recently suggested a notion of q-anal
ogues for rational numbers. Our approach is based on combinatorial propert
ies and continued fraction expansions of the rationals. The definition of
q-rationals naturally extends the one of q-integers and leads to ratios of
polynomials with positive integer coefficients. A surprising phenomenon o
f stabilization allows us to define q-irrational numbers as formal power s
eries with integer coefficients. I will explain all the constructions and
give the main properties of these q-numbers. The subject can be developed
in connections with various topics such as the enumerative combinatorics\,
cluster algebras\, homological algebra\, Burau representation\, Jones pol
ynomials... I will briefly discuss some of these connections.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yann Palu (LAMFA\, Université UPJV Amiens)
DTSTART;VALUE=DATE-TIME:20230614T113000Z
DTEND;VALUE=DATE-TIME:20230614T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/11
DESCRIPTION:Title: Mutation of maximal rigid objects in 0-Auslander extriangulated catego
ries\nby Yann Palu (LAMFA\, Université UPJV Amiens) as part of RA Sem
inar\n\n\nAbstract\nWe introduce the notion of a 0-Auslander extriangulate
d categories in order to study mutations in representation theory. Our aim
in this talk is to show that many examples of known mutations can be inte
rpreted as mutations of maximal rigid objects in some 0-Auslander extriang
ulated category: cluster tilting mutation\, two-term silting mutation\, mu
tation of maximal almost-rigid modules\, mutation of intermediate co-t-str
uctures\, flips of dissections...\nThis is a collaboration with Mikhail Go
rsky and Hiroyuki Nakaoka.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Srikanth Iyengar (University of Utah)
DTSTART;VALUE=DATE-TIME:20230712T130000Z
DTEND;VALUE=DATE-TIME:20230712T140000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/12
DESCRIPTION:Title: Lattices over group algebras\nby Srikanth Iyengar (University of U
tah) as part of RA Seminar\n\n\nAbstract\nThis talk is based on an ongoing
collaboration with Barthel\, Benson\, Krause\, and Pevtsova\, concerning
the representation theory of a finite group over an arbitrary noetherian
commutative ring. Our goal is to understand the structure of the stable mo
dule categories of representations that arise in this context. In my talk
I will focus mostly on the construction and basic properties of the stable
categories. This part of our story can\, and is\, developed in the more g
eneral context of Frobenius algebras.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karin Erdmann (Mathematical Institute\, University of Oxford)
DTSTART;VALUE=DATE-TIME:20230913T113000Z
DTEND;VALUE=DATE-TIME:20230913T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/13
DESCRIPTION:Title: Tame Symmetric Algebras\nby Karin Erdmann (Mathematical Institute\
, University of Oxford) as part of RA Seminar\n\n\nAbstract\nWe give an ov
erview of Hybrid Algebras which we introduced in joint work with Andrzej S
kowro´nski. This is a large class of tame symmetric algebras\, which unif
ies weighted surface algebras and special biserial symmetric algebras and
other algebras. We discuss homological properties of tame symmetric algebr
as more generally\, in particular the graph structure of stable Auslander-
Reiten components.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ralf Schiffler (University of Connecticut)
DTSTART;VALUE=DATE-TIME:20231108T130000Z
DTEND;VALUE=DATE-TIME:20231108T140000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/14
DESCRIPTION:Title: On Gorenstein algebras of finite Cohen-Macaulay type\nby Ralf Schi
ffler (University of Connecticut) as part of RA Seminar\n\n\nAbstract\nThi
s is a report on joint work with Khrystyna Serhiyenko. We study the (stabl
e) category of Cohen-Macaulay modules over 2-Calabi-Yau tilted algebras\,
a class of non-commutative algebras given by a quiver with potential. We a
re particularly interested in the case where the CM category is finite. We
show the following.\n\n(a) For a particularly nice subclass\, which we ca
ll dimer tree algebras\, the stable CM-category is a 2-cluster category of
Dynkin type A.\n\n(d) Every dimer tree algebra gives rise to several skew
-group algebras\, and for each of these the stable CM-category is a 2-clus
ter category of Dynkin type D.\n\n(e) We have examples of Dynkin types E.\
n\nThe dimer tree algebras are characterized by two conditions on the quiv
er. For one\, we want that every arrow lies in an oriented (chordless) cyc
le\, and moreover\, the dual graph of the quiver is a tree. For dimer tree
algebras\, we obtain a combinatorial model for the CM category in terms o
f 2-diagonals in a regular polygon. For the type D\, we have a similar mod
el on a punctured polygon.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hiroyuki Nakaoka (Nagoya University)
DTSTART;VALUE=DATE-TIME:20231213T113000Z
DTEND;VALUE=DATE-TIME:20231213T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/15
DESCRIPTION:Title: Localization of extriangulated categories\nby Hiroyuki Nakaoka (Na
goya University) as part of RA Seminar\n\n\nAbstract\nThis talk is based o
n a joint work with Yasuaki Ogawa and Arashi Sakai.\nOur main theorem show
s that the localization of an extriangulated\ncategory by a class of morph
isms satisfying some conditions can be\nequipped with a natural structure
of an extriangulated category in a\nuniversal way. This construction unifi
es several localizations involving\nabelian/exact/triangulated categories
known in the literature\, the\nrelation with which is given via biresolvin
g/percolating thick\nsubcategories.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Markus Reineke (RUHR Universitat Bochum)
DTSTART;VALUE=DATE-TIME:20240110T113000Z
DTEND;VALUE=DATE-TIME:20240110T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/16
DESCRIPTION:Title: Homological properties of universal quiver representations\nby Mar
kus Reineke (RUHR Universitat Bochum) as part of RA Seminar\n\n\nAbstract\
nFine moduli spaces of quiver representations carry universal representati
ons in vector bundles. Under mild numerical conditions\, we prove that the
se are partial tilting bundles\, and discuss applications to the geometry
of the moduli spaces. Joint recent work with P. Belmans\, A. Brecan\, H. F
ranzen\, G. Petrella\, arXiv:2311.17003\, arXiv:2311.17004\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lidia Angeleri Hügel (University of Verona)
DTSTART;VALUE=DATE-TIME:20240214T113000Z
DTEND;VALUE=DATE-TIME:20240214T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/17
DESCRIPTION:Title: Torsion pairs via the Ziegler spectrum\nby Lidia Angeleri Hügel (
University of Verona) as part of RA Seminar\n\n\nAbstract\nThe torsion pai
rs in the category mod(A) of \nfinite dimensional modules over a finite\nd
imensional algebra A form a complete lattice tors(A) which encodes essenti
al information on\nA. Another important measure for the complexity of the
category mod(A) is given by the set\nbrick(A) of isomorphism classes of \n
finite dimensional bricks\, i.e. modules whose endomorphism\nring is a ske
w-field.\nA fundamental tool for studying tors(A) and brick(A) and their i
nterrelationship is provided by\nsilting theory. It was shown by Adachi\,
Iyama and Reiten that the poset formed by the functorially\nfinite torsion
pairs is isomorphic to the poset of compact 2-term silting complexes. Mor
eover\,\ncompact 2-term silting complexes can be represented by pairs (M\;
P) formed by a $\\tau$-rigid module\nM and a projective module P. The $\\
tau$-rigid modules also provide a link to the collection of bricks: a resu
lt by Demonet\, Iyama and Jasso establishes a bijection between the indeco
mposable $\\tau$-rigid modules and the set of bricks B having the property
that the smallest torsion class in mod(A) containing B is functorially \n
finite. The aim of my talk is to lift these finiteness conditions and desc
ribe the whole lattice tors(A) and the entire collection brick(A) in terms
of large silting theory. It is more convenient\, however\, to work with t
he dual concept of a cosilting complex\, since we can then take advantage
of the fact that cosilting complexes are pure-injective and work in the Zi
egler spectrum\, a topological space associated to A. We will see that the
lattice tors(A) is isomorphic to a lattice given by pairs (Z\; I) where Z
is a closed and rigid set in the Ziegler spectrum of Mod(A) and I is a se
t of indecomposable injective modules. Furthermore\, we will present a lar
ge counterpart to the brick-$\\tau$-rigid correspondence mentioned above.\
n\nThis is a report on joint work with Rosanna Laking and Francesco Sentie
ri.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Pauksztello (Lancaster University)
DTSTART;VALUE=DATE-TIME:20240313T113000Z
DTEND;VALUE=DATE-TIME:20240313T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/18
DESCRIPTION:Title: Tilting\, reduction and mutation for simple-minded objects\nby Dav
id Pauksztello (Lancaster University) as part of RA Seminar\n\n\nAbstract\
nModule categories have two important types of generators: projective modu
les and simple modules. Morita theory describes equivalences of module cat
egories in terms of images of projective modules. Tilting theory is the ge
neralisation of Morita theory to derived categories describing equivalence
s of derived categories in terms of tilting objects. Tilting\, silting and
cluster-tilting objects\, can be thought of as ‘projective-minded objec
ts’. \n\n\n‘Simple-minded objects’ are generalisations of simple mod
ules. They satisfy Schur’s lemma and a version of the Jordan-Holder theo
rem\, depending on context. Although the theory of simple-minded objects s
hows many parallels with that of projective-minded objects\, it remains re
latively undeveloped and is technically more challenging. It remains impor
tant to develop this theory because many natural classes of examples\, for
instance\, stable module categories\, have no projective-minded objects b
ut do have simple-minded objects. In this talk\, I will explain aspects of
the theory of simple-minded objects\, including mutation and reduction. I
will explain how this gives a conceptual understanding of why tilting alg
ebraic hearts at torsion pairs generated by simple modules always yields a
n algebraic heart\, which has applications for spaces of stability conditi
ons. This talk will be based on various joint works with Nathan Broomhead\
, Raquel Coelho Simoes\, David Ploog and Jon Woolf.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aslak Bakke Buan (Norwegian University of Science and Technology)
DTSTART;VALUE=DATE-TIME:20240508T113000Z
DTEND;VALUE=DATE-TIME:20240508T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/19
DESCRIPTION:Title: Mutation of $\\tau$-exceptional sequences\nby Aslak Bakke Buan (No
rwegian University of Science and Technology) as part of RA Seminar\n\n\nA
bstract\nWe first recall classical notions of exceptional sequences and th
eir mutations for module categories of hereditary algebras (e.g. path alge
bras). Next\, we discuss a generalization to all finite dimensional algebr
as\, motivated by $\\tau$-tilting theory\, by Adachi-Iyama-Reiten\; by Jas
so's reduction techniques for such modules and corresponding torsion pairs
\; and by the introduction of signed exceptional sequences by Igusa-Todoro
v.\nThe interplay between theories for $\\tau$-rigid modules\, torsion pai
rs and\nwide subcategories are central to our discussions.\nThis talk is b
ased on joint work with Eric Hanson and Bethany Marsh.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Brustle (Bishop's University and Université de Sherbrooke)
DTSTART;VALUE=DATE-TIME:20240612T113000Z
DTEND;VALUE=DATE-TIME:20240612T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/20
DESCRIPTION:Title: Homological algebra in persistence theory\nby Thomas Brustle (Bish
op's University and Université de Sherbrooke) as part of RA Seminar\n\n\n
Abstract\nMultiparameter persistence modules appear in topological data an
alysis when dealing with noisy data. They are defined over a wild poset al
gebra and therefore one cannot give a complete description of their indeco
mposables. The aim of persistence theory is to roughly describe these modu
les by linear invariants\, i.e. additive functions which are constant on i
somorphism classes. We discuss several examples of such invariants that ca
n be obtained from order embeddings\, or by using relative homological al
gebra. \nThis is a report on joint work with Claire Amiot and Eric Hanson.
No prior knowledge of topological data analysis is required.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hugh Thomas (Université du Québec à Montréal)
DTSTART;VALUE=DATE-TIME:20240710T123000Z
DTEND;VALUE=DATE-TIME:20240710T133000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/21
DESCRIPTION:Title: Flow polytopes and gentle algebras\nby Hugh Thomas (Université du
Québec à Montréal) as part of RA Seminar\n\n\nAbstract\nA recent paper
by von Bell\, Braun\, Bruegge\, Hanely\, Peterson\, Serhiyenko and Yip (a
rXiv:2203.01896) made an important connection between the tau-tilting theo
ry of (some) gentle algebras and the flow polytopes of (some) oriented gra
phs. We deepen the connection and relax the conditions on the oriented gra
phs. This is joint work with Abram\, Bastidas\, Brauner\, Dequêne\, Moral
es\, and Park.\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Stovicek (Charles University in Prague)
DTSTART;VALUE=DATE-TIME:20240814T113000Z
DTEND;VALUE=DATE-TIME:20240814T123000Z
DTSTAMP;VALUE=DATE-TIME:20240719T153105Z
UID:RA-Seminar/22
DESCRIPTION:by Jan Stovicek (Charles University in Prague) as part of RA S
eminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/RA-Seminar/22/
END:VEVENT
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