Mini-Workshop on Algebra and Geometry
Workshop at Linköping University on the occasion of Axel Tiger Norkvist's PhD defense.
The talks before lunch will be held in room ``Kompakta rummet'' and
the talks after lunch will be held in room ``Hopningspunkten''.
Program
(Click on the title below to show the abstract.)
Friday 17 November
09:00 - 09:40
Real calculi and avenues of future research
(Axel Tiger Norkvist)
Buiding upon Thursday's seminar, "The Noncommutative Geometry
of Real Calculi," this presentation explores the future of real
calculi. By considering what has already been accomplished we
shall discuss several interesting prospects for future research
and discuss the hurdles that may lie ahead, offering a roadmap
for the next phase in our exploration of this algebraic
framework for noncommutative geometry.
09:40 - 10:10
Coffee break
10:10 - 10:50
Noncommutative soldering forms and their applications to pseudo-Riemannian calculi
(Stefan Wagner)
A soldering form on a principal G-bundle P over a manifold M is
a horizontal and G-equivariant differential 1-form on P with
values in a linear representation V of G that solders (or
attaches) P to M by identifying the associated vector bundle
(PxV)/G with the tangent bundle TM. This allows one, among
other things, to introduce the notion of torsion (of a
connection on P) which is a way of characterizing a twist or
screw of a moving frame around a curve. In this talk we reason
that derivation-based differential calculus d’après
Dubois-Violette provides a natural framework for generalizing
the theory of soldering forms to the noncommutative setting.
Furthermore, we explain how our findings may be utilized to
construct new examples of pseudo-Riemannian calculi.
11:00 - 11:40
P. Ševera's proof (2016) of the quantization of Lie bialgebras
(Martin Bordemann)
P. Ševera's approach in Sel. Math. 22 (2016) to the
quantization of Lie bialgebras is an important simplification
and precision of the classical results by Etingof-Kazhdan's in
1996. The result is used as a tool in some approaches of
deformation quantization. In my talk I also sketch a pedestrian
way to the understanding of the Drinfel'd associator and its
identities. Our work is in collaboration with Andrea Rivezzi
and Thomas Weigel from Milano-Bicocca.
13:00 - 13:40
Nonassociative algebras with identities and the universality of 1/2
(Vladimir Tkachev)
We will explain the following remarkable fact. For any
commutative nonassociative algebra over a field satisfying a
univariate identity and any its idempotent c, its Peirce
spectrum necessarily contains the universal eigenvalue 1/2.
Furthermore, the corresponding Peirce 1/2-subspace satisfies
the Jordan algebra fusion rules.
13:50 - 14:30
Finite order automorphisms and related Poisson-commutative subalgebras
(Oksana Yakimova)
The symmetric algebra S(g) of a lie algebra
g=Lie G carries the standard Lie-Poisson
structure. A subalgebra C of S(g) is Poisson-commutative, if
the Poisson brackets vanishes on it. The interest in these
objects appeared initially because of their role in complete
integrability of Hamiltonian systems. Poisson-commutative
subalgebras of S(g) are also important tools for the study of
geometry of the coadjoint representation of G. We present a
construction of a Poisson-commutative subalgebra associated with
a finite order automorphism of g. Then discuss finite order
automorphisms of reductive Lie algebras, in particular,
classification in terms of Kac’s diagrams.
14:30 - 15:00
Coffee break
15:50 - 16:30
Noncommutative Riemannian geometry of Kronecker algebras
(Joakim Arnlind)
Differential calculus in noncommutative geometry come in several
different flavors, and one of the more concrete versions goes by
the name of derivation based differential calculus. This
calculus is built from a disinguished Lie algebra of
derivations, and lead to the formulation of differential forms,
cohomology and connections. A fundamental question in
noncommutative Riemannian geometry is the existence and
uniqueness of a torsion free and metric compatible connection;
i.e a Levi-Civita connection. For the moment, there are no
general results addressing this question in this context, and I
will present a case study based on a simple quiver path algebra,
and show how the existence of a Levi-Civita connection depend on
the choice of a Lie algebra of derivations.
Participants
Joakim Arnlind | (Linköping University) |
Martin Bordemann | (Universite de Haute-Alsace) |
Sergei Silvestrov | (Mälardalen University) |
Axel Tiger Norkvist | (Linköping University) |
Vladimir Tkachev | (Linköping University) |
Stefan Wagner | (Blekinge Institute of Technology) |
Oksana Yakimova | (Friedrich-Schiller-Universität Jena) |