Sebastiano Giambò

A model for relativistic fluid mixture with different pressure laws

In the present paper a model for a compressible relativistic fluid 2-component mixture with different temperature, and even different pressure laws, is obtained. Total pressure is then the sum of the two independent pressures, which are supposed to be described by an evolution equation formally analogous to the usual one governing the pressure of a simple fluid. The deduced system is able to describe different complex situations, like plasma physics where the temperature of the electrons must be different from the temperatures of the other species. Weak discontinuities compatible with such kind of mixtures are also studied. In the isentropic case the governing equations are put into symmetric hyperbolic form in which the dependent variables are the two pressures plus a generalized velocity vector defined by the fluids unit 4-velocity divided pointwise by the fluids index.

Modified Kadometsev-Petviashvili equation for ion-acoustic waves

In this paper we study the propagation of ion-acoustic waves in a collisionless plasma, when different scales of variation are imposed. A modified Reduction-Perturbation method is used to obtain a generalized Kadometsev-Petviashvili equation, which reduces to a KP when a plane simmetry is assumed.

On the generalized relativistic magnetohydrodynamics for a heat conducting fluid

SummaryA scheme for the relativistic magnetohydrodynamics for a heat conducting fluid, of infinite conductivity, is proposed, together with a generalized thermodynamical differential equation. Its main consequences, as far as the wave propagation is concerned, are examined under suitable compressibility hypotheses.

Non-equilibrium relativistic two-phase flow with heat exchange

We consider two different systems of hyperbolic balance laws governing relativistic two-phase flows with general equations of state. The phases are assumed to be immiscible. In the first one the thermal equilibrium is attained through a relaxation procedure consistent with the second law of thermodynamics, while the second is a fully relaxed model in which the two phases reach an equal temperature instantaneously. Finally, we deduce and compare the wave velocities for both the models: the hydrodynamical velocity of the relaxed system can never exceed that of the relaxation system.

Nonlinear waves in an ultrarelativistic heat-conducting fluid II (Eckart formulation)

In this paper a second-order theory for relativistic heat-conducting fluids is derived in the Eckart scheme, based on the assumption that the entropy 4-current should include quadratic terms in the heat flux. In the special case of ultrarelativistic fluids, the velocities of hydrodynamic and thermal weak discontinuity wave fronts are determined and, through the second-order compatibility conditions, the discontinuities associated to the waves and the transport equations for the amplitude of the discontinuities are found out. Finally, for heat wave, plane, cylindrical and spherical diverging waves are also investigated.

WEAKLY NONLINEAR INTERACTION OF TWO WAVES IN RADIATIVE GASDYNAMICS

The interaction of two weakly nonlinear waves in radiative gasdynamics is investigated following the perturbation analysis developed by He and Moodie. Explicit solutions are given and the two waves interactions are graphically shown.

An extended thermodynamic description of mass diffusion in elastic solids

We present here a non-conventional model for a themoelastic body, based on the Extended Irreversible Thermodynamics, of physical processes in which mass diffusion occurs.Then we linearize the field equations around a constant state in order to obtain the dispersion relation pointing out the interaction between diffusive field and thermal field.

Weakly non-linear high frequency waves for a first order quasi-linear system involving source-like terms

Making use of the method of asymptotic expansion of multiple scales, a study of weakly non-linear, high frequency waves, through “homogeneous” media characterized by dissipative or dispersive hyperbolic systems of partial differential equations, is proposed.Within the present theoretical framework, asymptotic waves in a heat-conducting fluid are considered.

Relativistic heat conducting magnetizable fluids: An extended thermodynamical approach

In the framework of the extended irreversible thermodynamics we examine the coupling between the magnetic field and the thermal field and their influence on the evolution of a heat conducting relativistic magnetizable fluid.

A model of heat conducting collisionless plasma

A model of heat conducting diluted and collisionless plasma embedded in a strong magnetic field is proposed in the framework of extended irreversible thermodynamics. Finally in the special case of polytropic fluid the dispersion relation for weak, plane disturbances is derived.