Annual Report 2005 - Fields Institute - University of Toronto

the property (T) in 2001.)
The workshop was attended by 33 registered participants,
including 18 graduate students and postdocs, and was supported
by the Fields Institute and the University of Ottawa.
Bachir Bekka introduced Property (T) in his first lecture
and gave applications of it in his second lecture. In the
third, he presented some new developments of the theory.
Alain Valette’s three lectures centered on the relations
between Property (T) and affine actions. In particular, in
his first lecture he showed that Property (T) is equivalent
to the fixed point property for affine actions (Delorme-
Guichardet theorem). In his second lecture, he gave
Shalom’s characterization of property (T) and in the third
he linked finite presentability and property (T).
Claire Anantharaman presented the links between von
Neumann algebras and Property (T). In her first lecture,
she presented the basic definitions of type II 1 -factors and
gave examples constructed from discrete groups and discrete
measured equivalence relations. In her second lecture,
she introduced Property (T) for type II 1 factors and showed
in particular that the fundamental group of such a factor
is countable. In her third talk, Claire introduced Relative
property (T), Haagerup approximation property (H) and
the notion of (HT) Cartan subalgebra. Using these notions,
she then presented the recent developments of the theory of
type II 1 von Neumann factors.
At the first short communications session on August 25,
Talia Farnos gave a talk: New examples of group pairs with
Kazhdan’s Relative Property (T). The result she presented
is very interesting due to the scarcity of examples of group
pairs with Kazhdan’s Relative Property (T).
During the second short communications session on
August 26, Stefaan Vaes presented a new proof of Nicoara,
Popa, and Sasykk of Osawa’s result on the non-existence of
a universal II 1 factor: a (separable) II 1 factor that contains
any (separable) II 1 factor as a subfactor.
In the last session of the workshop, the main speakers presented
a list of very interesting open problems.
Overall, the workshop was a remarkably coherent event.
The main speakers did a marvelous job not only in the
quality of their lectures but also in the coordination of the
materials they presented. Its impact on the directions of
research pursued by younger attendees should be considerable.
G e n e r a l S c i e n t i f i c A c t i v i t i e s
Speakers:
Bachir Bekka (Metz)
Introduction to Property (T)
Applications of Property (T)
Some new developments
Claire Anantharaman-Delaroche (Orléans)
Type II 1 factors in relation with group and ergodic theory
Property (T) for type II 1 factors
(HT) type II1 factors
Talia Fernos (UIC)
New examples of group pairs with Kazhdan’s Relative Property
(T)
Stefaan Vaes (CNRS, Paris)
There is no universal II 1 factor
Alain Valette (Neuchâtel)
Property (T) and affine actions I, II, and III
Mini-symposium on Influenza: Models and Data
September 8, 2004
Held at the Fields Institute
Organizer: David Earn (McMaster)
Picture: Influenza_Earn.jpeg
Caption: David Earn
On the afternoon of September 8, 2004, the Fields Institute
hosted a mini-symposium on Influenza: Models and Data.
An audience of about 40 participants heard presentations
from five applied mathematicians and mathematical biologists
who have been working together in an effort to make
progress on understanding the epidemiology of influenza.
David Earn
Fields Institute 2005 ANNUAL REPORT 63