Title:  Heavy Ion Physics and How I Learned to Love Geometry
Fluctuations


Abstract:  One of the most striking characteristics of the quark-gluon
matter produced in heavy ion collisions is the fluid-like behavior.  In
fact, the flowing of the medium is nearly perfect as characterized by
the low shear viscosity to entropy density ratio.  We discuss in detail
how this nearly perfect fluid property changes as a function of
colliding energy and how this compares to theoretical expectations.  In
addition, quantitatively understanding this property is intricately
linked to the event-by-event geometry fluctuations.  We detail recent
results from the Relativistic Heavy Ion Collider and the Large Hadron
Collider and how they clarify our understanding of the medium.