Scandinavian Operator Algebra Workshop (ScaOAW)
Scandinavian Operator Algebra Workshop (ScaOAW)
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The next Scandinavian Operator Algebra Workshop will take place September 23-24, 2025 in Odense.
The next Scandinavian Operator Algebra Workshop will take place September 23-24, 2025 in Odense.
Information about the next Scandinavian Operator Algebra Workshop
Information about the next Scandinavian Operator Algebra Workshop
This meeting of the Scandinavian noncommutative geometers and operator algebraists is going take place at University of Southern Denmark in Odense on September 23rd & 24th 2025.
Registration is closed, but if you want to come just send an email to an organizer.
The dinner for the workshop takes place at District 13 at 18.30 on September (at your own expense). Please make sure you are registered to make sure there are enough seats.
Possible hotels to choose from in Odense include Comwell, City Hotel, and Odeon.
Tuesday, September 23
Tuesday, September 23
13.30-14.15: David Kyed (University of Southern Denmark)
13.30-14.15: David Kyed (University of Southern Denmark)
Title: Quantum metrics on q-deformations
Abstract: Click to expand →
Title: Quantum metrics on q-deformations
Abstract: Click to expand →
Abstract:
Abstract:
The q-deformations of classical spaces, such as SU(2) and the 2-sphere, is at the heart of non-commutative geometry, but despite a consistent effort, it remains an open problem to fully reconcile these with Connes’ approach to non-commutative differential geometry. However, the quantum metric geometry has turned out to be much more accessible, and in my talk I will survey the progress made within this area in recent years.
14.15-15.00 Coffee break
14.15-15.00 Coffee break
15.00-15.45: Spyridon Petrakos (Chalmers/University of Gothenburg)
15.00-15.45: Spyridon Petrakos (Chalmers/University of Gothenburg)
Title: Almost finiteness and groups of dynamical origin
Abstract: Click to expand →
Title: Almost finiteness and groups of dynamical origin
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Abstract:
Abstract:
With the conclusion of the Elliott Classification Programme about a decade ago, a lot of research has been conducted on determining which C*-algebras are classifiable, i.e. satisfy the conditions of the classification theorem. After reviewing some of the relevant machinery developed to address this problem for crossed products, I will present some recent results on actions of several groups of dynamical origin. This is joint work with Petr Naryshkin.
16.15-17.00: Valerio Proietti (University of Oslo)
16.15-17.00: Valerio Proietti (University of Oslo)
Title: Base change, groupoid homology, and hyperbolic dynamics
Abstract: Click to expand →
Title: Base change, groupoid homology, and hyperbolic dynamics
Abstract: Click to expand →
Abstract:
Abstract:
In sheaf theory, base change theorems relate the direct image and the inverse image of sheaves. I will introduce a simple base change result in the context of ample groupoid modules and homology. As an application, I will explain that groupoid homology can recover Putnam's homology groups of Smale spaces. These are hyperbolic topological dynamical systems akin to the basic sets of Axiom A diffeomorphisms, orginally studied by Smale. The groupoids of Smale spaces produce several examples of interesting C*-algebras, and their K-theory groups are suitably approximated by groupoid homology. This approximation property can be used to show that K-theory groups of Smale space C*-algebras have finite rank, which in turn invalidates a conjecture that Smale spaces exhaust the range of K-theory on classifiable real rank zero C*-algebras.
Wednesday, September 24
Wednesday, September 24
9.00-9.45: Ian Thompson (University of Copenhagen)
9.00-9.45: Ian Thompson (University of Copenhagen)
Title: Reduced gauge dynamics for Cuntz-Pimsner C*-algebras
Abstract: Click to expand →
Title: Reduced gauge dynamics for Cuntz-Pimsner C*-algebras
Abstract: Click to expand →
Abstract:
Abstract:
Cuntz-Pimsner algebras define a wide range of C*-algebras that, in a sense, encode the dynamics of a C*-correspondence. A recurring technique is to capture a Cuntz-Pimsner algebra at the level of its correspondence and, in joint work with Adam Dor-On, we accomplish this for reduced crossed products. This was first proven by Hao and Ng for amenable groups and has since seen several improvements in the following decade. Our proof leans heavily on C*-envelope techniques popularized by Katsoulis and Ramsey, rather than the C*-algebra theory that appears in the formulation of the problem itself.
10.00-10.45: Johannes Christensen (Aarhus University)
10.00-10.45: Johannes Christensen (Aarhus University)
Title: Weights on crossed product C*-algebras by abelian groups
Abstract: Click to expand →
Title: Weights on crossed product C*-algebras by abelian groups
Abstract: Click to expand →
Abstract:
Abstract:
In this talk, I will discuss some ongoing work with R. Neagu and G. Szabó concerning weights on crossed product C*-algebras by abelian groups. There are several results in literature that construct either KMS weights or tracial weights on crossed product C*-algebras using some kind of invariant states or weights of the underlying C*-algebra. When the acting group is the real numbers, one important such construction was introduced by Kishimoto and Kumjian. I will present new results on constructing weights on crossed product C*-algebras and illustrate that these new results naturally generalize and connect several constructions in literature, including that of Kishimoto and Kumjian. Subsequently, I will discuss when we can describe all extremal tracial weights on a crossed product C*-algebra from our new results.
10.45-11.15 Coffee break
10.45-11.15 Coffee break
11.15-12.00: Gabor Szabo (KU Leuven)
11.15-12.00: Gabor Szabo (KU Leuven)
Title: Flows on stably projectionless C*-algebras
Abstract: Click to expand →
Title: Flows on stably projectionless C*-algebras
Abstract: Click to expand →
Abstract:
Abstract:
In this talk I would like to present ongoing joint work with J. Christensen and R. Neagu. Our main goal is to construct a wealth of completely new examples of flows (i.e. actions of the reals R) on classifiable stably projectionless C*-algebras. It has been relatively unexplored how rich the class of flows on such algebras truly is. The only published result about this topic is an article by Kishimoto-Kumjian, who show that for certain UHF-stable, stable, projectionless C*-algebras with a unique unbounded trace (up to multiples), there exists a trace-scaling flow. However, it is a priori completely open if one can find flows on C*-algebras with more traces that scale different extremal traces at different speeds. Another open issue, which has only been studied in the unital case in a sole article of Kishimoto, is what possible pairings between invariant traces and the K_1-group can arise as Connes' rotation map associated to a flow on the C*-algebra. The main result of our work in progress is that any combination of these two abstract invariants is realized when the underlying C*-algebra A is classifiable, stable, and has trivial pairing map between traces and K_0. I shall make both the involved concepts and the statement of our result more rigorous during the talk.
Current organizers and contact:
Current organizers and contact:
Chalmers/University of Gothenburg
Chalmers/University of Gothenburg
Lyudmila Turowsska
University of Copenhagen:
University of Copenhagen:
Søren Eilers
Lund University:
Lund University:
Magnus Goffeng [magnus dot goffeng (at) math dot lth dot se (responsible for the homepage)]
University of Southern Denmark (Odense):
University of Southern Denmark (Odense):
Kevin Aguyar Brix
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