Seminar in C*-algebras

The C*-seminar is usually held on

Talks in the seminar are announced on this site and via E-mail. If you want to be included in or deleted from the mailing list, please contact Ola Bratteli.

Here is more information about the Operator Algebra Group, QSNG, seminars in fields related to operator algebras, and the complete list of seminars at the institute.

For questions about this page, contact Nadia S. Larsen.

Prerequisites for participating in the seminar.

Coming talks.

Paul Arne Østvær: Homotopy of C*-algebras

Kjetil Røysland: Symmetries in Projective Multiresolution Analyses

The time of the talk is tentative. The talk is based on the paper
http://uk.arxiv.org/PS_cache/arxiv/pdf/0709/0709.4122v1.pdf

We give an equivariant version of Packer and Rieffel's theorem on sufficient conditions for the existence of orthonormal wavelets in projective multiresolution analyses. The scaling functions that generate a projective multiresolution analysis are supposed to be invariant with respect to some finite group action. We give sufficient conditions for the existence of wavelets with similar invariance.

Past talks this semester.

Erik Alfsen: A Markov kernel theorem for a class of functional calculi of operators.

The measurement theory of standard quantum mechanics is based on spectral theory, which provides a functional calculus for self-adjoint operators, and these spectral functional calculi are uniquely determined by projection valued measures (PVMs). But in many cases, more general functional calculi, associated with positive operator valued measures (POVMs), are a more effective tool.

The theme of this talk is a class of such calculi, referred to as Abelian functional calculi. These are linear functional calculi which are not necessarily multiplicative, but nevertheless take values in a commutative operator algebra. The class of Abelian functional calculi does not exhaust the class of all functional calculi associated with POVMs. In fact, the calculi associated with POVMs which are currently being used (for example in the context of quantum computation), are not Abelian in general. But the class of Abelian functional calculi may still be relevant for measurement theory, as these calculi have some important properties that are not enjoyed by all calculi associated with POVMs.

The key result in the talk will be a theorem by which every Abelian functional calculus can be represented by an explicit formula involving a Markov kernel which accounts for the extra uncertainty ("noise") that is added to the intrinsic quantum mechanical uncertainity by measuring devices other than the "ideal" ones of the standard theory.

Ola Bratteli: Approximately inner derivations

Joint work with Akitaka Kishimoto and Derek Robinson: http://front.math.ucdavis.edu/0703.5013

Erling Størmer: Separable tilstander og positive avbildninger

En tilstand på et tensorprodukt av to C*-algebraer kalles separabel hvis den er en norm grense for konvekse summer av produkttilstander. Jeg skal vise hvordan noen kjegler av positive avbildninger, som jeg studerte for ca. 25 år siden, passer inn i studiet av slike tilstander.

Sergey Neshveyev: On a class of II_1 factors with at most one Cartan subalgebra

The talk is based on this paper by Narutaka Ozawa and Sorin Popa:: http://front.math.ucdavis.edu/0706.3623

Nadia S. Larsen: Generalized multiresolution analyses with given multiplicity functions

I will discuss the main ideas in the
paper of the same title, joint
with Bagget, Merrill, Packer and Raeburn.

Past seminars (2007).

Past seminars (2006).

Past seminars (2005).

Past seminars (2004).

Past seminars (2003).