Lista referatów

• 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...

• 2022-11-02, godz. 17:15, 405 IMPAN & ZOOM

  SØREN EILERS (Københavns Universitet)

  EQUIVARIANT ISOMORPHISMS OF QUANTUM LENS SPACES

  Since their inception two decades ago, the quantum lens spaces of Hong and Szymański have been studied very successfully, due in no small part to the fact — established from the outset — that they are graph C*-algebras. Every quantum lens space comes with a natural circle action, leadin...

• 2022-10-26, godz. 17:15, ZOOM

  PIOTR M. HAJAC (IMPAN)

  COUNTING PATHS IN DIRECTED GRAPHS

  We consider the class of directed graphs with N edges and without loops shorter than k. Using the concept of a labelled graph and a recent result of Alexandru Chirvasitu, I will show how to determine graphs from this class (they can be viewed as graphs labelled by the semiring of n...

• 2022-10-19, godz. 17:15, ZOOM

  ALEXANDRU CHIRVASITU (SUNY Buffalo)

  CENTERS AS UNIVERSAL GRADING GROUPS OF REPRESENTATION CATEGORIES

  It is a result of Müger that, for a compact group G, associating to every irreducible G-representation its central character identifies the Pontryagin dual of the center Z(G) with the universal group that, in a certain sense, labels the grading of the category...

• 2022-10-12, godz. 17:15, ZOOM

  FRANCESCO D'ANDREA (Università degli Studi di Napoli Federico II)

  THE CONVOLUTION ALGEBRA OF A TOLERANCE RELATION

  It is well known that a "bad" quotient space can be studied by associating to it the groupoid C*-algebra of its defining equivalence relation. A similar procedure for relations that are reflexive and symmetric but fail to be transitive leads to non-associat...

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