4'th Íresund Symposium on
Non-commutative Geometry and Non-commutative Analysis

 

Lund, Sweden,

 

Thursday, November 25, 2004

 

Organisers 

Lund: Sergei Silvestrov    
Copenhagen:
S°ren Eilers, Frank Hansen, Gert Pedersen

 

Location

Centre for Mathematical Sciences, Lund University, Lund, Sweden
Third floor, Auditorium 332A, (10.00-15.00),   Auditorium 362D, (15.30-17.30)  
 

10.10-10.15   Welcome Address (Auditorium 332A)

10.15-11.05     Yacin Ameur, Kalmar university, Sweden 

 Calderon couples, interpolation functions and monotone matrix functions.

 

Abstract: Let $X_0$ and $X_1$ be banach spaces such that $X_0\cap X_1$

is dense in $X_0$ and in $X_1$. A basic goal of interpolation theory is

to characterize those spaces $X_*$ which fulfill

$X_0\cap X_1\subseteq X_*\subseteq X_0+X_1$ and the interpolation

inequality:

$$\|T\|_{{\cal L}(X_*)}\le \max(\|T\|_{{\cal L}(X_0)},\|T\|_{{\cal L}(X_1)})$$

whenever $T$ is an operator which is defined and bounded on $X_0$ and

on $X_1$.

 

In the case when $X_0$ and $X_1$ are Hilbert spaces, the corresponding

Banach spaces $X_*$ can be completely characterized, and they

generalize the monotone matrix functions of L÷wner. I will speak about this and

some realted results and problems. 

 

11.05-11.55   Gunnar Sparr, Lund University (LTH), Sweden.
                       Monotone matrix functions and the Foias-Lions interpolation problem

 

Abstract: The Foias-Lions problem concerns characterization of the exact

interpolation functions for weighted $L^p$-spaces, i.e. functions $h$

obeying

$$

||Tf||_{L^p_{w_i}} \le  ||f||_{L^p_{v_i}}, \ i=0,1 \Longrightarrow ||Tf||_{L^p_{h(w_0,w_1}} \le  ||f||_{L^p_{h(v_0,v_1)}}\ .

$$

For $p=2$, a characterization is provided by the L÷wner theorem for

monotone matrix functions.

 

The presentation will reveal this connection and discuss an

unsuccessful attempt 25 years ago to solve the Foias-Lions problem, starting by a

non-Hilbertian proof of L÷wner's theorem in the case $p=2$,

cf. G. Sparr, A new proof of L÷wner's theorem on monotone matrix

functions, Math. Scand. 1980.

 

12.00-13.10  Lunch

 

13.15-14.05  Sten Kaijser, Uppsala University, Sweden

Interpolation of Banach algebras and Hilbert spaces

 

14.10-15.00  Frank Hansen, University of Copenhagen, Denmark

Monotone trace functions of several variables.

 

15.00-15.30     Coffee at the department (in the lunch room at the 4:th floor)

 

Note change of room to Auditorium 362D  

15.30-16.20
     Niels Jakob Laustsen, University of Copenhagen, Denmark
                      Involutions on Banach algebra of operators on a Banach space

 

Abstract:  I shall report on ongoing joint work with Matt Daws (Oxford,

formerly Leeds) and Charles Read (Leeds), where we define and study

involutions on the Banach algebra $\mathcal{B}(E)$ of all bounded,

linear operators on a Banach space $E$. Our motivating example is the standard

involution on $\mathcal{B}(H)$ for a Hilbert space $H$.

 

16.25-17.15  Toke Carlsen, NTNU, Trondheim, Norway
                      On C*-algebras of actions of inverse semigroup

Abstract:  I will talk about C*-algebras associated with actions of inverse
semigroups on sets (without topology or any other structure).
These C*-algebras can be described as universal C*-algebras
generated by partial isometries subject to conditions given
by the inverse semigroup and a Boolean algebra.
I will describe how Cuntz-Krieger algebras (both for finite
and infinite matrices), C*-algebras associated to shift spaces
and C*-algebras of higher-rank graphs in a very natural
way can be constructed as C*-algebras of actions of inverse semigroups.
This allow us to make natural generalizations of these
C*-algebras.

 

18.00-                       If weather is enough good, then interested participants join for a walk

to a dinner in one of the restaurants in the centre of Lund