Foreword

The 27th Winter School `Geometry and Physics' took place at the usual place, the village Srni in the Czech Republic, in the period January 13 - January 20, 2007. The Winter School was organized by the Union of Czech Mathematicians and Physicists, together with the Charles University and the Masaryk University, with financial support by the International Erwin Schr\"odinger Institute for Mathematical Physics.

During the School, 6 invited lecture series were presented: Twisted cohomology and Dirac geometry by Anton Alekseev, Jet isomorphism for conformal geometry by Robin Graham, An introduction to vertex algebras by Victor Kac, Double affine Hecke algebras by Siddhartha Sahi, Algebroids and sigma models by Thomas Strobl and Small unitary representations by David Vogan. In the rest of the program, many further lectures, communications, and posters were presented in two sections.

The Proceedings of this School contain 12 contributions by the participants.

Martin Cadek

editor