Two lectures on Two-Dimensional Gravity

(from the talk:) I shall here speak on gravity in (1+1)-dimensional space-time --- lineal gravity. The purpose of studying lower dimensional theories, and specifically lower dimensional gravity, is to gain insight into difficult conceptional issues, which are present and even more opaque in the physical (3+1)-dimensional world. Perhaps lessons learned in the lower-dimensional setting can be used to explicate physical problems. Moreover, if we are lucky, the lower-dimensional theories can have a direct physical relevance to modelling phenomena that is actually dynamically confined to the lower dimensionality. This is what happened with (2+1)-dimensional gravity: gravitational physics in the presence of cosmic strings (infinitely long, perpendicular to a plane) is adequately described planar gravity. Indeed the recently discussed causality puzzles raised by ``Gott time machines'' were resolved with the help of the lower-dimensional model...