Last updated: Aug 03, 2022, 19:20 CEST
Conference Titles, Abstracts, Slides,
and Videos
All in-person talks will
take place in
Aula 3, Edificio de Ciencias de la Salud
Mohamed Barakat, Categorizing computer algebra:
Building and compiling towers of categories
Talk cancelled
Abstract: While set theory is by design a foundational
theory for mathematics where complex structures are built a
posteriori out of the unstructured notion of a set, category
theory is a highly expressive meta-theory of structures that
keep popping up in a wide range of mathematical disciplines
and at arbitrary high abstraction levels with the same syntax
but with completely different semantics. In this talk, I will
show how we use towers of category constructors to reorganize
computer algebra in the spirit of category theory. The
categorical organization of computer algebra helped us design
algorithms that would have never been possible to directly
implement. However, building such towers comes at the cost of
runtime. A category-theory-aware compiler becomes
indispensable for producing a highly performant code that
compiles away the abstraction introduced by the different
layers of the tower. I will demonstrate this modern,
unorthodox style of computer algebra by examples.
Vladimir Bavula, The PBW Theorem and simplicity
criteria for the Poisson enveloping algebra and the algebra
of Poisson differential operators.
Abstract: I will explain some of my recent results on Poisson
algebras: The PBW Theorem holds for the Poisson enveloping
algebra (PEA) of a Poisson algebra (an affirmative answer to a
long standing problem). The algebras of Poisson differential
operators (APDO) are introduced.
Explicit sets of generators and defining relations are given
for PEAs and APDOs as well as simplicity criteria. Explicit
formulae for the Gelfand-Kirillov dimension of the above
algebras are given. In the case when the Poisson algebra is a
regular domain of essentially finite type an explicit
simplecticity criterion for PEA is found and a criterion is
presented for PEA to be isomorphic to APDO.
Isaac Bird, Definable functors between triangulated
categories.
Abstract: I will discuss definable functors between
compactly generated triangulated categories. As in the
finitely accessible case, these are the functors which
preserve pure triangles and pure injective objects. I will
give several examples, and explain the relationship between
definable functors between triangulated categories and
definable functors between their corresponding functor
categories. This is based on ongoing joint work with Jordan
Williamson
Simion Breaz, Change of scalars functors and silting
complexes.
Abstract: I will present results about the transfer of the
(co)silting property of an object from the derived category of
a module category by using the (co)extension of scalars
functors induced by morphisms of commutative rings. In
particular, we will see that the derived versions of the
(co)extension of scalars functors preserve (co)silting objects
of (co)finite type. In the last part of the talk, I will
discuss some cases when these functors reflect the (co)silting
property. The talk is based on a joint work with Michal Hrbek
and George-Ciprian Modoi.
Thomas Brüstle, Homological approximations in
persistence theory.
Abstract: Multiparameter persistence modules are defined over
a wild algebra and therefore they do not admit a complete
discrete invariant. One thus tries in persistence theory to
“approximate” such a module by a more manageable class of
modules. Using that approach we define a class of invariants
for persistence modules based on ideas from homological
algebra. This is a report on joint work with Benjamin
Blanchette and Eric Hanson.
Manuel Cortés Izurdiaga, Rooted functor categories.
Abstract: First, we will see how the usual description of the
category of modules over a triangular matrix ring can be
extended to the category of all additive functors from a small
preadditive category to the category of abelian groups. Then,
we will define rooted small preadditive categories, so that we
will be able to apply methods from the representations (by
modules) of rooted quivers to the aforementioned functor
category. Finally, we will see how these methods can be
extended to study other functor categories.
Samuel Dean, Infinitary model theory of modules.
Abstract: Let λ be a regular infinite cardinal. Using
abelian functor categories, I will show that finitary pp
formulas for right R-modules, i.e. the classical objects of
study in the finitary model theory of modules, are sufficient
to describe the λ-ary model theory of a locally presentable
additive category C, where R is the category of λ-presented
objects in C. The cost is that we must interpret pp formulas
only among the right R-modules which preserve λ-small
products.
Alberto Facchini, Multiplicative lattices,
commutators, braces.
Abstract: The multiplicative lattices we will consider are
those defined in the paper [3], published in February 2022.
Multiplicative lattices yield the natural setting in which
several basic mathematical questions concerning algebraic
structures find their answer. We will consider the particular
cases of braces ([2] and [3]).
[1] D. Bourn, A. Facchini and M. Pompili, Aspects of the
Category SKB of Skew Braces, submitted for publication,
available in arXiv, 2022
[2] A. Facchini, Algebraic structures from the point of view
of complete multiplicative lattices, accepted for publication
in "Rings, Quadratic Forms, and their Applications in Coding
Theory", Contemporary Math., 2022, available at:
http://arxiv.org/abs/2201.03295
[3] A. Facchini, C. A. Finocchiaro and G. Janelidze,
Abstractly constructed prime spectra, Algebra universalis
83(1) (2022).
Grigory Garkusha, Recollements for
derived categories of enriched functors and triangulated
categories of motives.
Abstract: This is joint work with Darren Jones. We investigate
certain categorical aspects of Voevodsky's triangulated
categories of motives. For this, various recollements for
Grothendieck categories of enriched functors and their derived
categories are established. In order to extend these
recollements further with respect to Serre's localization, the
concept of the (strict) Voevodsky property for Serre
localizing subcategories is introduced. This concept is
inspired by the celebrated Voevodsky theorem on homotopy
invariant presheaves with transfers. As an application, it is
shown that Voevodsky's triangulated categories of motives fit
into recollements of derived categories of associated
Grothendieck categories of Nisnevich sheaves with specific
transfers.
Lorna Gregory, Model theory of modules over Prüfer
domains and dimensions on lattice ordered abelian groups.
Abstract: Much of the model theory of modules over a
Prüfer domain R is captured by its value group, that is, the
group of fractional ideals of R ordered by reverse inclusion.
This group is a lattice ordered abelian group and all lattice
ordered abelian groups occur as the value group of a Prüfer,
or even Bézout, domain.
In this talk I will explain how the principal invariants of
model theory of modules, m-dimension and breadth of the
lattice of pp-formulae, can be calculated (or bounded) for
Prüfer domains using their value groups. I will explain the
intended meaning of these invariants and, if there is time,
explain how to show that for Prüfer domains, they measure what
they are supposed to measure.
Alina Iacob, Ding injective envelopes.
Abstract: Among the generalizations of the Gorenstein
injective modules, the Ding injectives were probably studied
the most. The existence of the Ding injective envelopes is
known over coherent rings. We prove that, in fact, the Ding
injective modules form an enveloping class over any ring. We
also show that the result carries to the category of
complexes: for any ring R, the class of Ding injective
complexes is enveloping in Ch(R). This is joint work with J.
Gillespie.
Miodrag Iovanov, On some homological categories and
their underlying quantum group classification.
Abstract: Several categories, such as that of bounded or
arbitrary chain compelexes, double chain complexes or other
diagrams are at the core of homological algebra. Many of these
have natural monoidal rigid tensor category structure on them,
and they can in fact be regarded as the category of comodules
("rational representations") of a suitable quantum group, AKA
pointed Hopf algebras. It turns out such Hopf algebras posses
the interesting feature that "locally" they are of finite
representation type. We pursue the question of what are the
pointed Hopf algebras which have this property, equivalently,
pointed tensor categories so that there are only finitely many
objects having a fixed dimension vector. Important classical
quantum groups such as the Taft algebras and their
generalization are of these types. Our main result is a
classification of these, which morally says that, up to
deformations of all these examples, these are all the
examples.
Mamuka Jibladze, Lawvere distributions,
pseudolinear algebra and factorization structures.
Abstract: There are currently at least two approaches to
the algebraic description of structures arising in field
theory. Both of them use a certain "distortion" of monoidal
structures.
One approach uses several variations of multicategory
structures (like the Borcherds category Fin≢ , colored
operads, Beilinson-Drinfeld pseudo-tensor categories,
factorization monoids of Kapranov-Vasserot, and more recent
refined version of factorization algebras by Costello and
Gwilliam).
Another approach appeared in the work of Bakalov, D'Andrea and
Kac, where the formalism of pseudo-linear algebra was
developed to describe structures like dynamical Poisson
brackets using a version of Yetter-Drinfeld modules.
On the other hand, much earlier Lawvere worked on what would
be nowadays called categorification of the calculus of
distributions and the notion of Radon-Nicodym derivative in
the non-linear (set theoretic) context of the combination of
co- and contravariant set-valued functors, using his concept
of extensive and intensive quantities.
It seems that the Lawvere calculus relates to both of the
above approaches, which might provide further insight into
vertex algebras and the operator product expansion formalism
through his categorified calculus of distributions.
We will try to briefly survey all three notions and show
parallels between them. If time permits, we will also address
what could be the Lawvere calculus viewpoint on the
Chas-Sullivan string topology and planar algebras of V. F. R.
Jones.
Ilias Kaperonis, K-Absolutely pure complexes.
Abstract: Projective and injective resolutions of modules play
an important role in the study of Homological Algebra. However
we can view the category of modules over a ring as a
subcategory of the complexes of the ring. Spaltenstein in 1972
introduces the classes of K-Projective and K-Injective
complexes which can be used to generalize common resolutions.
In this talk we will introduce the class of K-Absolutely pure
complexes, we will study their basic properties and we will
compare them with the class of K-Flat complexes of
Spaltenstein.
George Ciprian Modoi, Not necessarily compact
approximability via silting theory.
Abstract: D be a triangulated category with coproducts.
The (quite technical) definition of approximability of D
involves a compact generator G and a t-structure (see
Definition 5.1 of A. Neeman, Approximable triangulated
categories, preprint, arXiv:1806.06995[math.CT]). One of the
main examples of approximable triangulated categories is
obtained when G is assumed, in addition, to be silting (case
in which the t-structure can be chosen to be the associated
silting t-structure). In this talk I will present an ongoing
project about a generalization of approximability in
triangulated categories via silting theory.
George Nadareishvili, Homological algebra in
noncommutative topology.
Abstract: We will give a brief introduction to homological
algebra in nonabelian setting of triangulated categories of
C*-algebras. Next, using these techniques, we will explain how
Universal Coefficient Theorems are a homological phenomenon.
Juan Orendain Almada, Reconstructing double
categories from End-indexings.
Abstract: Framed bicategories are double categories
satisfying a generalized operation of base change. Symmetric
monoidal structures on framed bicategories descend to
symmetric monoidal structures on horizontal bicategories. The
axioms defining symmetric monoidal double categories are
significantly more tractable than those defining symmetric
monoidal bicategories. It is thus convenient to study ways of
lifting a given bicategory into a framed bicategory along an
appropriate category of vertical morphisms. Solutions to the
problem of lifting bicategories to double categories have
classically been useful in expressing Kelly and Street's mates
correspondence and in proving the 2-dimensional Seifert-van
Kampen theorem of Brown et. al., amongst many other
applications.
Globularly generated double categories are minimal solutions
to lifting problems of bicategories into double categories
along given categories of vertical arrows. Globularly
generated double categories form a coreflective sub-2-category
of general double categories. This, together with an analysis
of the internal structure of globularly generated double
categories yields a numerical invariant on general double
categories. We call this invariant the length. The length of a
double category C measures the complexity of lifting decorated
bicategories into C.
It is conjectured that framed bicategories are of length 1.
Motivated by this I present a general method for constructing
globularly generated double categories of length 1 through
extra data in the form of what I will call End-monoidal
indexings of decoration categories. The methods presented are
related to Moeller and Vasilakopoulou's monoidal Grothendieck
construction, to Shulman's construction of framed bicategories
from monoidal fibrations on cocartesian categories, and in the
case of strict single object and single horizontal morphism
2-groupoids decorated by groups, specialize to semidirect
products.
Sebastian Posur, How to classify objects in
Krull-Schmidt categories.
Abstract: Krull-Schmidt categories are ubiquitous in
representation theory. In such categories every object can be
written as a finite direct sum of indecomposables in an
essentially unique way. In this talk, I discuss helpful tools
for the determination of the isomorphism classes in
Krull-Schmidt categories. These tools are direct
generalizations from ring theory to category theory, like
filtrations, gradings, or Galois descent. With the help of
these tools, I show how to classify the objects in Deligne's
interpolation category for the symmetric groups in arbitrary
characterstic, and how to classify the objects in
Khovanov–Sazdanovic's recent generalization of Deligne's
interpolation category. This is joint work with Johannes Flake
and Robert Laugwitz.
Mike Prest, Definability in monoidal additive
categories.
Abstract: Model theory and definability in additive, including
triangulated, categories is well-developed. I discuss some of
what we get when there is tensor structure on the categories.
In particular I will present some 2-category equivalences due
to Rose Wagstaffe.
Job Rock, Continuous Nakayama algebras.
Abstract: We construct a continuous analogue of Nakayama
algebras using representations of the real line and of the
circle. This is done with a combination of (pre-)Kupisch
functions (a continuous analogue of Kupisch series) and
functor categories. We classify the orthogonal components of
categories of Nakayama representations with regard to
connectedness using some analytic properties of the
(pre-)Kupisch functions. We conclude by relating continuous
Nakayama representations to their discrete counter part and to
dynamical systems. Joint with Shijie Zhu.
arXiv link
Philipp Rothmaler, Universal models and Bass
modules.
Abstract: For the purpose of this talk, I call a module Bass
module if it is the direct limit of a chain of order type of
the natural numbers of finitely presented modules. This term
is suggested by work of Trlifaj et al on Bass type phenomena.
Puninski suggested a model-theoretic proof of the Bass-Björk
result that all flat (left) modules are projective (i.e., the
ring is left perfect) if and only if it satisfies the dcc on
(pp formulas defining) finitely generated right ideals. In
this talk on joint work with Anand Pillay I show how this can
be done with any kind of descending chain of pp formulas and
their free realizations (i.e., associated f.p. modules) in
order to show that the corresponding Bass module is
pure-projective precisely when the category of left modules
enjoys the dcc on the pp chains in question. This gives a
self-contained proof of Bass’ theorem (and Björk’s) in case
all the f.p. modules in question are flat. The other end of
the spectrum, when all f.p. modules are considered at once,
one obtains a well-known result of Daniel Simson that a ring
is left pure-semisimple iff all left modules are
Sigma-pure-injective iff all left modules are Mittag-Leffler.
I will explain how this investigation may be viewed as a study
of universal models in certain classes of structures, resp.,
of certain theories. This talk is dedicated to the memory of
Professor Simson.
Kamal Saleh, Constructive category theory and
tilting equivalences via strong exceptional sequences.
Abstract: In this presentation, we'll demonstrate how to
implement categories on a computer using our software project
CAP - Categories, Algorithms, and Programming. We will discuss
how to construct the bounded homotopy category of an additive
or Abelian category, as well as the obstacles encountered and
their practical categorical solutions.
We use these homotopy categories to demonstrate some
applications to homological algebra: Given a bounded homotopy
category that is finitely generated as a triangulated
category, we can verify whether a given set of objects forms a
complete strong exceptional sequence and, if so, to implement
the associated tilting equivalences.
Manuel Saorín, Hearts which are Grothendieck
categories: a study through functor categories.
Abstract: Given a triangulated category with arbitrary
coproducts and a t-structure in it, it is a well-known fact
that the heart of the latter is an abelian category. A problem
that has deserved a lot of attention in recent times is that
of identifying the t-structures whose heart is a Grothendieck
category. In this talk we will give a short survey on the most
important related results, and will present some recent ones
based on joint work with Jan Stovicek, where the use of
functor categories is crucial.
Alex Sorokin, All concepts are defects.
Abstract: In the mid 1960s Auslander introduced a notion of
the defect of a finitely presented functor on a module
category. In 2021 Martsinkovsky generalized it to arbitrary
additive functors. In this talk I will show how to define a
defect of any enriched functor with a codomain a cosmos. Under
mild assumptions, the covariant (contravariant) defect functor
turns out to be a left covariant (right contravariant) adjoint
to the covariant (contravariant) Yoneda embedding. Both
defects can be defined for any profunctor enriched in a cosmos
V. They happen to be adjoints to the embeddings of V-Cat in
V-Prof. Moreover, the Isbell duals of a profunctor are
completely determined by the profunctor's covariant and
contravariant defects. Furthermore, Kan extensions can be
described as defects of certain profunctors, showing the
fundamental role of the defects. These results are based on
(co)end calculus.
Ashish Srivastava, On a quotient of face algebra.
Abstract: Hayashi introduced face algebras as a new class of
quantum groups inspired by the quantum inverse scattering
method and solvable lattice models of face type. In this talk,
we will discuss a quotient algebra of Hayashi's face algebra
over a quiver Q and its connection with the Leavitt path
algebra over Kronecker square of Q. We study structural
connection between Leavitt path algebra over a quiver and its
Kronecker square and category equivalence of modules over such
algebras.
Jan Šťovíček, The coderived category of a
locally coherent dg category.
Abstract: The homotopy category of complexes of injective
modules or injective quasi-coherent sheaves (aka the coderived
category) received a lot of attention in the last two decades
in connection with the Grothendieck duality in algebraic
geometry, the Koszul duality or representation theory of
finite groups. In the present joint work with Leonid
Positselski, we define the coderived category of a locally
coherent dg category, which generalizes coderived categories
both for complexes over usual locally coherent abelian
categories and for curved dg modules over curved dg rings.
Moreover, we prove that the coderived category is always
compactly generated in this setting and identify the compact
objects.
Alberto Tonolo, Injective envelopes of simple
modules over a family of Leavitt path algebras.
Abstract: I will quickly recall the definition of Leavitt path
algebras (LPA) associated to a graph E, giving some examples
and properties. Assuming the graph E is finite and that every
vertex in E is the base of at most one cycle, I will
explicitly construct the injective envelope of each simple
left module. The talk is based on some very recent results
obtained in collaboration with Francesca Mantese and Gene
Abrams.
Jan Trlifaj, Locality of quasi-coherent sheaves
associated with relative Mittag-Leffler modules.
Abstract: The ascent and descent of the Mittag-Leffler
property was instrumental in proving locality of the notion of
an (infinite dimensional) vector bundle in the classic work of
Raynaud and Gruson. More recently, relative Mittag-Leffler
modules were employed in the theory of (infinitely generated)
tilting modules and the associated quasi-coherent sheaves.
Here, we study the ascent and descent of the relative
Mittag-Leffler property. As an application, we prove locality
of the notions of an f-projective quasi-coherent sheaf for all
coherent schemes, and of an i-filtered quasi-coherent sheaf
for all integral schemes (based on joint work with Asmae Ben
Yassine).
arXiv link
Kristo Väljako, Tensor product rings and Morita
equivalence.
Abstract: In my talk I will introduce tensor product
rings Q ⊗R P, where QR and RP
are R-modules for an arbitrary associative ring R. I will
define pseudo-surjective mappings and show that if S is an
idempotent ring, then a pseudo-surjectively defined tensor
product ring Q ⊗S P is Morita equivalent to S.
Then I will define locally injective homomorphisms of rings
and strict local isomorphisms of rings. It turns out that a
locally injective homomorphism of rings arises naturally from
any Morita context between rings.
I will talk about rings of adjoint endomorphisms of modules
and their connections to Morita equivalence. I will introduce
dual mappings and show how they can be used to describe Morita
equivalence. Dual mappings also arise naturally form unitary
and surjective Morita context.
Finally, I will give a new necessary and sufficient condition
for firm rings to be Morita equivalent. Also I will give a
necessary and sufficient condition for s-unital rings to be
Morita equivalent, which is a generalization result that two R
and S with identity are Morita equivalent if and only if there
exists a progenerator QR with S ≅ End(QR).
My talk is based on the article Väljako, K., (2022). Tensor
product rings and Rees matrix rings. Comm. in Algebra,
published online.
Jordan Williamson, Duality and definability in
triangulated categories.
Abstract: In the category of modules over a ring, purity may
be viewed as a weakening of splitting - a short exact sequence
is pure if and only if it is split exact after applying the
character dual. The notion of purity in triangulated
categories was introduced by Krause, and it has since been
seen to be intimately related to many questions of interest in
representation theory and homotopy theory. In this talk, I
will explain a framework of duality pairs in triangulated
categories which provides an elementary way to check pure
closure properties, and describe an application to the study
of definable subcategories of triangulated categories.
Throughout I will explain some connections of this with
tensor-triangular geometry. This is joint work with Isaac
Bird.
arXiv link
Robert Wisbauer, An alternative approach to tilting
theory.
Comments and Table of Contents:
Abstract: We show that essentially an R-module P is tilting
provided a suitable restriction of the comparison functor for
Hom(P,-) is fully faithful. The latter constructions work for
objects P in any category, thus bringing elements of tilting
theory to any categories with suitable completeness
conditions, in fact to any adjoint pair of functors.
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