Johannes Oberreuter (Institute for Theoretical Physics, University of Amsterdam, The Netherlands)
Abstract: Scale invariance in quantum physics is usually associated with critical points which occur at specific phase transitions. There, fluctuations occur on all length scales and the system is described by a conformal field theory. In this framework, scaling dimensions and correlation functions can be computed. A lot of systems of interest, however, like e.g. certain superconductors are strongly coupled and perturbative field theory breaks down.
In the last decade, it turned out that such conformal field theories are related to gravity in a fashion, that the gravitational theory is predictive if the field theory picture is not applicable. The theory lives on the boundary of the gravitational system but still reproduces the physics. Therefore, it's called holographic. I will motivate and introduce this correspondence between field theory and gravity and show how it can be used to do calculations around strongly coupled critical points. I will also use the correspondence to obtain some insights about gravity. In particular, I will show how the big bang, which is an unphysical singularity in gravity, can be understood from the point of view of field theory.