**Lecturer: **Vašek Chvátal

**Institute: **Concordia University, Montreal

**Date and time: **12.05.2014 - 14:00

**Details:**

The notion of lines in a Euclidean space can be generalized to a definition of lines in metric spaces in at least two distinct ways. The classical Sylvester-Gallai theorem of Euclidean geometry has been generalized to all metric spaces with one of the two definitions of lines; its corollary, customarily and not quite correctly referred to as a De Bruijn-Erdos theorem, has been conjectured to allow a generalization to all metric spaces with the other definition of lines.