FEATURE · Far-from-Equilibrium ATtractors at Ultra-Relativistic Energies

Far-from-Equilibrium ATtractors at Ultra-Relativistic Energies

The goal of FEATURE is to better understand how hydrodynamic attractors emerge in theories at relativistically high energies and their interplay with known features of relativistic flows. Hydrodynamic attractors can be thought of simply in the analogy with the water cycle. Let's say you were interested in describing the motion of water in our environment from point A to B. It may be difficult to simulate the evolution of every single molecule of water directly. However, there are large attractors of water, rivers for example, which capture the behavior of a significant fraction of that water. Moreover, they are easily described by a simpler set of equations than in the case of treating each water drop alone. In a similar vein, the evolution equations for matter at high energies are known: microscopically, they are the equations of quantum chromodynamics. These are complicated to evolve from first principles without simplifying assumptions. Luckily, it has been observed that an important part of the violent aftermath of the collision of lead or gold nuclei can be described by relativistic hydrodynamics. This was more surprising as hydrodynamics was found to work even when gradients were large, outside of the usual domain of hydrodynamics. How does hydrodynamics work outside of its naive domain of applicability? The resolution to this tension was in part the discovery of hydrodynamic attractors, akin to rivers in the previous example. These particular solutions represent the system's approach to a theory described by hydrodynamics. Different initial conditions approach hydrodynamics at different times (tributaries can enter the river at different times), but it is almost guaranteed that some of the evolution will be described by the attractor. In this sense, the system seems to "forget" about its intial conditions. Despite this important step, a number of questions remain. Earlier studies focused on highly symmetric situations, whereas FEATURE expanded the picture by developing new approaches and solutions in systems with richer symmetries. It also addressed open questions about how phase transitions or the strong magnetic fields generated after the collision affect the attractor structure. FEATURE sits naturally within the broader effort to understand real-time QCD dynamics. This is a core objective of major European and international experimental programs, including ALICE at CERN and the upcoming FAIR facilities. These experiments rely on accurate theoretical modeling (including hydrodynamic) to interpret signals of the quark–gluon plasma, including phase transitions, thermalization and other effects. By advancing our understanding of hydrodynamic attractors and extending them to more realistic flow geometries, FEATURE supports this need directly. Improved modeling of extreme states of matter contributes to both the long-term goals of fundamental physics and the strategic development of theoretical tools used across high-energy research.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз