Adrien Florio, “Dynamics of the O(4) critical point in QCD”, 12.03.2023

Abstract:

There are indications that the deconfinement phase transition of QCD with two-massless flavors is a second-order phase transition, likely to be in the O(4) universality class.  The real-world QCD deconfinement transition is a crossover, but the smallness of the up and down quark masses makes it plausible to be in the critical region of the O(4) critical point. This hypothesis is supported by recent lattice QCD simulations, which were able to model static QCD properties using the O(4) scaling functions.

In this talk, I will review the notion of dynamical universality class. I will then introduce a hydrodynamic theory with the order parameter of the QCD phase transition as an additional hydrodynamical variable. I will explain why it shares the same dynamical universality class of 2-flavor QCD ("Model G") and as a result why it can be used to gain insight into the dynamics of QCD.  I will the present some of our recent results obtained from classical real-time simulations (2111.03640) of this hydrodynamic theory and some more work in progress. I will discuss the emergence of pion pseudo-particles in the broken phase and their impact on the dynamics. I will also discuss our extraction of the dynamical critical exponent 𝜁 and some more results at finite momentum.