Dear colleagues,

We are pleased to announce the 20th IAP colloquium on Cosmic Microwave Background physics and observation, to be held at the Institut d'Astrophysique de Paris, from Monday June 28 to Friday July 2nd 2004.

This meeting will conclude the successful European network CMBNET, and we hope it will serve as a kick-off meeting of its successor, CMB-Planet, in case it is funded.

After a series of observational results that culminated in the WMAP results of last year, CMB observations have dramatically sharpened our view of the Universe in the last five years. In the mean time, the recently discovered CMB polarization, bearing new cosmological information, is getting increasing attention, and indeed most of the upcoming CMB experiments are targetting polarization. The second release of WMAP is also now imminent.

It should be a good time to assess what we have learnt as of today, both from the theoretical and experimental points of view, from this very rich period; to discuss the likely stumbling block on the way forward, and new physics that the future CMB experiments will be able to help reveal, and the new experimental and data-processing techniques that need to be developped in their context.

The meeting will focus namely on the following topics: Early Universe theory and CMB physics, main CMB experiments (past and future), cosmological parameters extraction, Sunyaev-Zeldovich effect, CMB and gravitational lensing, Integrated Sachs-Wolf detection, reionisation, Galactic and extragalactic foregrounds, data processing methods and experimental developments.

F. R. Bouchet
Chair