21 research outputs found
Energy-Momentum Tensor for the Electromagnetic Field in a Dielectric
The total momentum of a thermodynamically closed system is unique, as is the
total energy. Nevertheless, there is continuing confusion concerning the
correct form of the momentum and the energy-momentum tensor for an
electromagnetic field interacting with a linear dielectric medium. Here we
investigate the energy and momentum in a closed system composed of a
propagating electromagnetic field and a negligibly reflecting dielectric. The
Gordon momentum is easily identified as the total momentum by the fact that it
is, by virtue of being invariant in time, conserved. We construct continuity
equations for the energy and the Gordon momentum and use the continuity
equations to construct an array that has the properties of a traceless,
diagonally symmetric energy-momentum tensor. Then the century-old
Abraham-Minkowski momentum controversy can be viewed as a consequence of
attempting to construct an energy-momentum tensor from continuity equations
that contain densities that correspond to nonconserved quantities.Comment: added publication informatio
Relativistic analysis of the dielectric Einstein box: Abraham, Minkowski and total energy-momentum tensors
We analyse the "Einstein box" thought experiment and the definition of the
momentum of light inside matter. We stress the importance of the total
energy-momentum tensor of the closed system (electromagnetic field plus
material medium) and derive in detail the relativistic expressions for the
Abraham and Minkowski momenta, together with the corresponding balance
equations for an isotropic and homogeneous medium. We identify some assumptions
hidden in the Einstein box argument, which make it weaker than it is usually
recognized. In particular, we show that the Abraham momentum is not uniquely
selected as the momentum of light in this case
Entropy Production in Relativistic Hydrodynamics
The entropy production occurring in relativistic hydrodynamical systems such
as the quark-gluon plasma (QGP) formed in high-energy nuclear collisions is
explored. We study mechanisms which change the composition of the fluid, i.e.
particle production and/or chemical reactions, along with chemo- and
thermo-diffusion. These effects complement the conventional dissipative effects
of shear viscosity, bulk viscosity, and heat conductivity.Comment: 15 pages; LaTex. Accepted for publication in Physics Letters B. - Two
typos corrected and one reference adde
Derivation of fluid dynamics from kinetic theory with the 14--moment approximation
We review the traditional derivation of the fluid-dynamical equations from
kinetic theory according to Israel and Stewart. We show that their procedure to
close the fluid-dynamical equations of motion is not unique. Their approach
contains two approximations, the first being the so-called 14-moment
approximation to truncate the single-particle distribution function. The second
consists in the choice of equations of motion for the dissipative currents.
Israel and Stewart used the second moment of the Boltzmann equation, but this
is not the only possible choice. In fact, there are infinitely many moments of
the Boltzmann equation which can serve as equations of motion for the
dissipative currents. All resulting equations of motion have the same form, but
the transport coefficients are different in each case.Comment: 15 pages, 3 figures, typos fixed and discussions added; EPJA: Topical
issue on "Relativistic Hydro- and Thermodynamics