Bruno Scheihing Hitschfeld, [NT/RBRC Seminar] "An Adiabatic Description of Hydrodynamization in the Kinetic Theory of a Gluon Plasma"
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US/Eastern
Description
The far-from equilibrium dynamics of the pre-hydrodynamic quark-gluon plasma (QGP) formed in heavy ion collisions can be characterized by distinct stages, during each of which the system loses some memory of its initial condition, until only the hydrodynamic modes remain. This attractor behavior has been characterized previously in both strongly and weakly coupled descriptions. In particular, at weak coupling it has been found in kinetic theory descriptions in terms of self-similar scaling solutions for the particle distribution function, even at times well before hydrodynamization. However, even though it has been repeatedly observed, there has been an absence of an intuitive physical explanation of how and why attractor behavior occurs. The Adiabatic Hydrodynamization (AH) framework provides exactly such an explanation, showing that the attractor solution can be thought of as the ground state of an analog to quantum mechanical adiabatic evolution, provided we identify appropriate coordinate rescalings. In this talk, we analytically demonstrate that this is the case for the Baier-Mueller-Schiff-Son fixed point of the bottom-up thermalization scenario, finding explicit expressions for the aforementioned ground state and the rest of the spectrum in this stage of the hydrodynamization process of weakly coupled QCD matter. Furthermore, using the example of a simplified QCD kinetic theory in the small-angle scattering limit, we show how AH can explain both the early pre-hydrodynamic attractor and the later hydrodynamizing attractor in a longitudinally expanding gluon gas in a unified framework. By doing this, we provide a unified description of, and intuition for, all the stages of what in QCD would be bottom-up thermalization, starting from a pre-hydrodynamic attractor and ending with hydrodynamization.
