Hydro+: hydrodynamics with parametric slowing down and fluctuations near the critical point

The search for the QCD critical point in heavy-ion collision experiments requires dynamical simulations of the bulk evolution of QCD matter as well as of fluctuations. We consider two essential ingredients of such a simulation: a generic extension of hydrodynamics by a_parametrically_ slow mode or modes ("Hydro+") and a description of fluctuations out of equilibrium. By combining the two ingredients we are able to describe the bulk evolution and the fluctutations within the same framework. Critical slowing down means that equilibration of fluctuations could be as slow as hydrodynamic evolution and thus fluctuations could significantly deviate from equilibrium near the critical point. We generalize hydrodynamics to partial-equilibrium conditions where the state of the system is characterized by the off-equilibrium magnitude of fluctuations in addition to the usual hydrodynamic variables -- conserved densities. We find that the key element of the new formalism -- the extended entropy taking into account the off-equilibrium fluctuations -- is remarkably similar to the 2PI action in quantum field theory. We show how the new Hydro+ formalism reproduces two major effects of critical fluctuations on the bulk evolution: the strong frequency dependence of the anomalously large bulk viscosity as well as the stiffening of the equation of state with increasing frequency or wave-number. While the agreement with known results confirms its validity, the fact that Hydro+ achieves this within a local and deterministic framework gives it significant advantages for dynamical simulations.Comment: 46 pages, 5 figure

Solidification/stabilisation of soil contaminated with metal: a review

Solidification/stabilisation (S/S) is generically defined as a chemical and physical alteration technique of reducing the mobility as well as solubility of contaminants in wastes in order to convert them into chemically inert form. The technique is specifically developed to confine the movement of contaminants in wastes so that their concentrations in the surrounding environment (e.g. subsurface soil matrices and groundwater) will not exceed stipulated environmental regulatory levels. This technique necessitates application of cementitious materials such as cement which also provides a favorable solidification effect on the stabilised wastes so that the end product can be easily transported to disposal sites or reused as construction materials. This paper reviews the S/S technology as applied to contaminated soil treatment with emphasis on its chemical binder systems, mechanisms, interferences and post-treatment leaching tests. S/S is an important soil contamination remediation technology as evident by its simplicity, technical and cost-effectiveness