Previous talks this semester:
June 27 at 10.30-12.45, Room 106.
Marcin Sabok (IM PAN); Representations of oligomorphic groups
Abstract: We will talk about a recent paper by Todor Tsankov devoted to continuous unitary representations of oligomorphic permutation groups.
A Polish group G of permutations of the natural numbers N is called oligomorphic
if the natural action of G on the product N^n has only finitely many orbits for every n.
These groups include the full permutation group of N, the automorphism group of the countable dense linear order,
the homeomorphism group of the Cantor space, etc. Oligomorphic groups have also strong connections with model theory:
the automorphism group of a countable model M of a theory T over a countable language is oligomorphic iff T is omega-categorical.
In the paper, a complete classification of irreducible representations of oligomorphic groups is presented.
As an application, it is proved that many oligomorphic groups have Kazhdan's property (T).
June 25 at 10.45-12.45, Room 106.
Maciej Malicki (IM PAN); Representations of oligomorphic groups
Abstract: We will talk about a recent paper by Todor Tsankov devoted to continuous unitary representations of oligomorphic permutation groups.
A Polish group G of permutations of the natural numbers N is called oligomorphic
if the natural action of G on the product N^n has only finitely many orbits for every n.
These groups include the full permutation group of N, the automorphism group of the countable dense linear order,
the homeomorphism group of the Cantor space, etc. Oligomorphic groups have also strong connections with model theory:
the automorphism group of a countable model M of a theory T over a countable language is oligomorphic iff T is omega-categorical.
In the paper, a complete classification of irreducible representations of oligomorphic groups is presented.
As an application, it is proved that many oligomorphic groups have Kazhdan's property (T).
May 14 at 12.00, Room 105.
Michał Wojciechowski (IM PAN) and Przemysław Ohrysko.
Abstract: We will sum up the cycle of seminars devoted to the measure algebra with a panel discussion
April 16 at 12.00, Room 105.
Przemysław Ohrysko.
Abstract: I'm going to talk on paper "Spectra of independent power measures" published by W. J. Bailey, G. Brown and W. Moran.
As the title says it is concentreted on studying spectral properties of measures
which have independent convolution powers. Proofs of main results use generalized characters and relays on some kind of extensions conncected to them. The most important theorem which will be proved states that if continous measure has independent
convolution powers then its spectrum is whole spectral disc.
The latter can be applied to classical examples of singular measures such as Riesz products.
April 9 at 12.00, Room 105.
Przemysław Ohrysko.
Abstract: I'm going to talk on paper "Spectra of independent power measures" published by W. J. Bailey, G. Brown and W. Moran.
As the title says it is concentreted on studying spectral properties of measures
which have independent convolution powers. Proofs of main results use generalized characters and relays on some kind of extensions conncected to them. The most important theorem which will be proved states that if continous measure has independent
convolution powers then its spectrum is whole spectral disc.
The latter can be applied to classical examples of singular measures such as Riesz products.
March 26 at 12.00, Room 105.
Piotr Koszmider; Remarks on representations of the bidual to C(T).
Abstract: Continuing our attempts of understanding the space of multiplicative functionals
on M(T) (the measure algebra on the circle with convolution) with the weak* topology we will present
some classical results concerning the representation of the bidual of C(T) as some C(K).
We will also discuss another representation due to Mauldin which assumes CH:
D. Mauldin, A representation theorem for the second dual of C[0,1]. Studia Math. 46 (1973), 197 - 200.
March 19. at 12.00, Room 105.
Piotr Koszmider; Remarks on representations of the bidual to C(T).
Abstract: Continuing our attempts of understanding the space of multiplicative functionals
on M(T) (the measure algebra on the circle with convolution) with the weak* topology we will present
some classical results concerning the representation of the bidual of C(T) as some C(K).
Talks in the first semester of 2012-13.
Talks in the second semester of 2011-12.
Talks in the first semester of 2011-12.
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