Relativistic fluid dynamics and the theory of relativistic detonation fronts are used to estimate the space-time dynamics of the burning of the D-T fuel in Laser driven pellet fusion experiments. The initial High foot heating of the fuel makes the co
mpressed target transparent to radiation, and then a rapid ignition pulse can penetrate and heat up the whole target to supercritical temperatures in a short time, so that most of the interior of the target ignites almost simultaneously and instabilities will have no time to develop. In these relativistic, radiation dominated processes both the interior, time-like burning front and the surrounding space-like part of the front will be stable against Rayleigh-Taylor instabilities. To achieve this rapid, volume ignition the pulse heating up the target to supercritical temperature should provide the required energy in less than ~ 10 ps.
Fluid dynamical models preceded the first heavy ion accelerator experiments, and led to the main trend of this research since then. In recent years fluid dynamical processes became a dominant direction of research in high energy heavy ion reactions.
The Quark-gluon Plasma formed in these reactions has low viscosity, which leads to significant fluctuations and turbulent instabilities. One has to study and separate these two effects, but this is not done yet in a systematic way. Here we present a few selected points of the early developments, the most interesting collective flow instabilities, their origins, their possible ways of detection and separation form random fluctuations arising from different origins, among these the most studied is the randomness of the initial configuration in the transverse plane.
Substantial collective flow is observed in collisions between Lead nuclei at LHC as evidenced by the azimuthal correlations in the transverse momentum distributions of the produced particles. Our calculations indicate that the Global v1-flow, which a
t RHIC peaked at negative rapidities (named as 3rd flow component or anti-flow), now at LHC is going to turn toward forward rapidities (to the same side and direction as the projectile residue). Potentially this can provide a sensitive barometer to estimate the pressure and transport properties of the Quark-Gluon Plasma. Our calculations also take into account the initial state Center of Mass rapidity fluctuations, and demonstrate that these are crucial for v1 simulations. In order to better study the transverse momentum flow dependence we suggest a new symmetrized v1S flow component; and we also propose a new method to disentangle Global v1 flow from the contribution generated by the random fluctuations in the initial state. This will enhance the possibilities of studying the collective Global v1 flow both at the STAR Beam Energy Scan program and at LHC.
Heavy ion reactions and other collective dynamical processes are frequently described by different theoretical approaches for the different stages of the process, like initial equilibration stage, intermediate locally equilibrated fluid dynamical sta
ge and final freeze-out stage. For the last stage the best known is the Cooper-Frye description used to generate the phase space distribution of emitted, non-interacting, particles from a fluid dynamical expansion/explosion, assuming a final ideal gas distribution, or (less frequently) an out of equilibrium distribution. In this work we do not want to replace the Cooper-Frye description, rather clarify the ways how to use it and how to choose the parameters of the distribution, eventually how to choose the form of the phase space distribution used in the Cooper-Frye formula. Moreover, the Cooper-Frye formula is used in connection with the freeze-out problem, while the discussion of transition between different stages of the collision is applicable to other transitions also. More recently hadronization and molecular dynamics models are matched to the end of a fluid dynamical stage to describe hadronization and freeze-out. The stages of the model description can be matched to each other on spacetime hypersurfaces (just like through the frequently used freeze-out hypersurface). This work presents a generalized description of how to match the stages of the description of a reaction to each other, extending the methodology used at freeze-out, in simple covariant form which is easily applicable in its simplest version for most applications.
