Lista referatów

• 2023-01-25, godz. 17:15, 405 IMPAN & ZOOM

  Piotr M. Hajac (IMPAN)

  THE COVARIANT FUNCTORIALITY OF GRAPH ALGEBRAS

  In the standard category of directed graphs, morphisms respect the lengths of paths. However, this requirement is way too strong to present natural *-homomorphisms between graph C*-algebras as covariantly induced from morphisms of graphs, so we define a new category of directed graphs where morphism...

• 2023-01-18, godz. 17:15, 405 IMPAN & ZOOM

  HUA WANG (IMPAN)

  CONSTRUCTIONS OF QUANTUM GROUPS WITH THE RAPID DECAY PROPERTY

  Starting with Haagerup's seminal work, the rapid decay (RD) property was systematically studied by Jolissaint for discrete groups, and later by Vergnioux, in the setting of discrete quantum groups. Through the work of many hands, the RD property is nowadays an interesting approximation p...

• 2023-01-11, godz. 17:15, 405 IMPAN & ZOOM

  AHMAD REZA HAJ SAEEDI SADEGH (Northeastern University)

  DEFORMATION SPACES, GETZLER'S RESCALING, AND AN EQUIVARIANT INDEX THEOREM FOR LIE GROUPOIDS

  In recent work, Higson and Yi developed a new perspective on Getzler's symbol calculus, reinterpreting the latter in terms of a convolution algebra of sections of the rescaled bundle over the tangent groupoid of a spin manifold. We generalize the construction of the rescaled bundle to ...

• 2022-12-21, godz. 17:15, 405 IMPAN & ZOOM

  MARIUSZ TOBOLSKI (Uniwersytet Wrocławski)

  THE CONTRAVARIANT FUNCTORIALITY OF GRAPH ALGEBRAS

  We introduce a subcategory of directed graphs for which the construction of Leavitt path algebras induces a contravariant functor into the category of algebras. Then we prove a theorem stating under which conditions this functor turns pushouts of directed graphs into pullbacks of algebras. Finally, ...

• 2022-12-14, godz. 17:15, 405 IMPAN & ZOOM

  JACEK KRAJCZOK (University of Glasgow)

  APPROXIMATION PROPERTIES FOR LOCALLY COMPACT QUANTUM GROUPS

  One of the most widely studied properties of groups is the notion of amenability. In one of its many formulations, it gives us a way of approximating constant functions by functions in the Fourier algebra. The notion of amenability was relaxed in various directions. For instance, a very weak form of...

• 2022-12-07, godz. 17:15, 405 IMPAN & ZOOM

  JACK SPIELBERG (Arizona State University)

  RELATIVE GRAPHS AND PULLBACKS OF RELATIVE TOEPLITZ GRAPH ALGEBRAS

  We generalize a result from a recent paper of Hajac, Reznikoff and Tobolski. In that paper they give conditions they call "admissibility" on a pushout diagram in the category of directed graphs implying that the C*-algebras of the graphs form a pullback diagram. We consider a larger catego...

• 2022-11-30, godz. 17:15, 405 IMPAN & ZOOM

  MATTHIAS SCHÖTZ (IMPAN)

  GELFAND-NAIMARK THEOREMS OF ORDERED *-ALGEBRAS

  Ordered *-algebras (i.e. unital *-algebras endowed with a quadratic module of "positive&...

• 2022-11-23, godz. 17:15, 405 IMPAN & ZOOM

  MARC A. RIEFFEL (UC Berkeley)

  CONVERGENCE OF FOURIER TRUNCATIONS

  We generalize the Fejer-Riesz operator systems defined for the circle group by Connes and van Suijlekom to the setting of compact matrix quantum groups and their ergodic actions on C*-algebras. These truncations form filtrations of the containing C*-algebra. When the truncations and the containing C...

• 2022-11-16, godz. 17:15, 405 IMPAN & ZOOM

  LUDWIK DĄBROWSKI (SISSA)

  SPECTRAL METRIC AND EINSTEIN FUNCTIONALS

  Using the Wodzicki residue, in terms of the Laplace operator, we define two bilinear functionals on vector fields. Their densities yield, respectively, the metric tensor and the Einstein tensor on an even-dimensional Riemannian manifold. Then, in terms of the Dir...

• 2022-11-09, godz. 17:15, 405 IMPAN & ZOOM

  BRAM MESLAND (Universiteit Leiden)

  CURVATURE FOR DIFFERENTIABLE HILBERT MODULES

  In this talk, we introduce the curvature of densely defined universal connections on Hilbert C*-modules, relative to a spectral triple, leading to a well defined curvature operator. Algebraically, this curvature can be interpreted as the defect of the unbounded Kasparov product to commute with the o...

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