ACTION FUNCTIONALS FOR RELATIVISTIC PERFECT FLUIDS

Action functionals describing relativistic perfect fluids are presente d. Two of these actions apply to fluids whose equations of state are s pecified by giving the fluid energy density as a function of particle number density and entropy per particle. Other actions apply to fluids whose equations of state are specified in terms of other choices of d ependent and independent fluid variables. Particular cases include act ions for isentropic fluids and pressureless dust. The canonical Hamilt onian forms of these actions are derived, symmetries and conserved cha rges are identified, and the boundary value and initial value problems are discussed. As in previous works on perfect fluid actions, the act ion functionals considered here depend on certain Lagrange multipliers and Lagrangian coordinate fields. Particular attention is paid to the interpretations of these variables and to their relationships to the physical properties of the fluid.