This is the 4th post in our series in which we have asked a number of leading scientists in our field to identify the 3-5 most important challenges which the field of hot and dense QCD matter theory has to address (click for the previous posts by Larry McLerran, Carsten Greiner and Nu Xu).
- What are the dynamical degrees of freedom in quark-gluon matter in the vicinity of the deconfinement phase transition? Is a quasi-particle description applicable in this region at all? What is the role of extended field configurations of QCD in the plasma? Does topology play a role? if yes, what are the experimental signatures?
- How does the transition from the initial gluon fields to a thermalized plasma occur? Is the plasma really fully thermalized? How to describe a real-time dynamics of non-Abelian gauge fields at strong coupling?
- What are the transport properties of the quark-gluon plasma? How do we extract, with a reasonable accuracy, the transport coefficients of plasma (e.g. shear and bulk viscosities) from the data? What is the microscopic origin of the perfect liquid behavior?
- What is the true mechanism of parton energy loss? Is it perturbative? If not, how to describe it? At what transverse momentum (centrality, mass number, …) does the transition from strong to weak coupling occur?