impan seminar:

working group in applications of set theory



No more talks this semester. First talk next semester on March 14.

Previous talks this semester:


24.01.2013; Michał Wojciechowski (IMPAN)

On the paper of Sreider concerning maximal ideals in rings of measures with convolution 4


17.01.2013; Michał Wojciechowski (IMPAN)

On the paper of Sreider concerning maximal ideals in rings of measures with convolution 3

10.01.2013; Michał Wojciechowski (IMPAN)

On the paper of Sreider concerning maximal ideals in rings of measures with convolution 2

20.12.2012; Seminar Canceled. Professor Aleksander Pełczyński has passed away.


13.12.2012; Michał Wojciechowski (IMPAN)

On the paper of Sreider concerning maximal ideals in rings of measures with convolution
The paper in question is: Yu. Sreider; The structure of maximal ideals in rings of measures with convolution. (Russian) Mat. Sbornik N.S. 27(69), (1950). 297–318.

06.12.2012; Przemysław Ohrysko (IMPAN)

On the paper of Zafran concerning measures with natural spectrum II

22. 11. 2012; Przemysław Ohrysko (IMPAN)

On the paper of Zafran concerning measures with natural spectrum
The paper in question is: M. Zafran: On Spectra of Multipliers, Pacific Journal of Mathematics, vol. 47, no.2, 1973.

15. 11. 2012; Przemysław Ohrysko (IMPAN)

The second of the series of talks will be the continuation of an introduction to the general Gelfand theory.


08. 11. 2012; Przemysław Ohrysko (IMPAN)

The first of the series of talks will be devoted to an introduction to the general Gelfand theory.


This series of talks will be devoted to the Banach algebra M(T) of measures on the circle with the convolution of measures. This was the topic of Przemysław Ohrysko's M.A. project conducted at Warsaw University under the guidance of Michał Wojciechowski and concluded this year. Przemysław focused on the Wienner-Pitt phenomenon.


Our purpose would be to try to represent the multiplicative functionals on this Banach algebra in a combinatorial way. Like representing multiplicative funtionals on the Banach algebra ell-infty naturally leads to the points of the Cech-Stone compactification of the integers, i.e., ultraflters of subsets of the inegers, we expect here some related set-theoretic constructions.
The talks are designed to nonspecialists who want to learn about the beautiful subject and perhaps try to think about a better representation of the functionals mentioned above. To get acquainted with the subject you may want to have a look at the M.A. thesis of Przemysław Ohrysko.









Talks in the second semester of 2011-12.

Talks in the first semester of 2011-12.

Time and place: Thursdays 11.15- 13.30, room 105, Sniadeckich 8

The scope of the seminar: Set-theoretic methods in diverse fields of mathematics, in particular in Banach spaces, C*-algebras, topology, the structure of the real line, measure theory, Boolean algebras, topological groups. Here we include both the developing of such methods as forcing, descriptive set theory, Ramsey theory as well as their concrete applications in the fields mentioned above.

Working group style: We will make efforts so that this seminar has more a working character rather than the presentation style. This means that we encourage long digressions, discussions, background preparations and participation of everyone. To achive this, the duration of the seminar will not be rigidly fixed and may reach even 3 hours with the breaks. We would like to immerse ourselves into the details of the mathematical arguments studied. We hope that such a seminar may complement presentations at the Wednesday set theory seminar at the University of Warsaw.

Participants this semester:

  • Piotr Koszmider (IMPAN)
  • Mikołaj Krupski (Ph. D. student IMPAN)
  • Maciej Malicki (Łazarski)
  • Witold Marciszewski (UW)
  • Przemysław Ohrysko (Ph. D. student IMPAN)
  • Marcin Sabok (IMPAN)
  • Michał Wojciechowski (IMPAN)
Forthcoming talks:


  • 14.03., 21.03. Piotr Koszmider; On representaion of elements of the bidual to C(K) (and hence the dual to M(K))
  • 4.04., 11.04. visitors on Banach spaces and set theory
  • 9.05., 16.05. P.Ohrysko/M.Wojciechowski
  • June M.Malicki/M.Sabok