Ramanujan Auditorium

The QCD critical point

Thomas Schaefer

North Carolina State University

I summarize arguments that suggest that the phase diagram of QCD, the
theory of quarks and gluons, has a critical endpoint which is analogous
to the endpoint of the water-vapor transition. This point marks the
onset of a first order phase transition between a quark-gluon vapor
and a hadronic liquid. I will argue that the critical point can be
searched for in collisions of relativistic heavy ions. The main
observables are fluctuation measurements, and the expected signatures
are related to critical opalescence. I summarize the ongoing theoretical
and experimental efforts devoted to observing signatures of critical
fluctuations. I argue that along the way, we have gained new insights
into an old theory, fluid dynamics.