Towards the little bang standard model

Abstract. I review recent progress in developing a complete dynamical model for the evolution of the Little Bang fireballs created in relativistic heavy-ion collisions, and using the model to extract the transport properties and initial density fluctuations of the liquid quark-gluon plasma state of matter of which makes up these Little Bangs during the first half of their lives. 1. The Big Bang and the Little Bangs Ultra-relativistic heavy-ion collisions at RHIC and the LHC produce fireballs made of extraordinarily hot matter, at initial energy densities (at the time when the matter reaches approximate local thermal equilibrium) that exceed the energy density of atomic nuclei in their ground states by two to three orders of magnitude. Due to enormous pressure gradients between the fireball center and the surrounding vacuum, these fireballs undergo explosive collective expansion, cooling down rapidly through several different states of matter, finally fragmenting into thousands of free-streaming hadrons whose energy and momentum distributions can be detected in the detectors set up around the collider rings. The evolution history of these “Little Bangs ” has much similarity with the Big Bang that created our Universe (Fig. 1): Both undergo Hubble-like expansion,1 feature a hierarchy of decoupling processes that are driven b