60 research outputs found
Jeans instability in the linearized Burnett regime
Jeans instability is derived for the case of a low density self-gravitating
gas beyond the Navier-Stokes equations. The Jeans instability criterium is
shown to depend on a Burnett coefficient if the formalism is taken up to fourth
order in the wave number. It is also shown that previously known viscosity
corrections to the Jeans wave-number are enhanced if the full fourth order
formalism is applied to the stability analysis.Comment: 8 pages, no figures. Submitted to Physica
Light Cone analysis of relativistic first-order in the gradients hydrodynamics
This work applies a Rayleigh-Brillouin light spectrum analysis in order to
establish a causality test by means of a frequency cone. This technique allows
to identify forbidden and unforbidden regions in light scattering experiments
and establishes if a set of linearized transport equations admits causal
solutions. It is shown that, when studying a relativistic fluid with its
acoustic modes interacting with light, Eckart's formalism yields a non causal
behavior. In this case the solutions describing temperature, density and
pressure fluctuations are located outside the frequency cone. In contrast, the
set of equations that arises from modified Eckart's theory (based on
relativistic kinetic theory) yields solutions that lie within the cone, so that
they are causal.Comment: 6 pages, no figure
Kaluza's theory in generalized coordinates
Maxwell's equations can be obtained in generalized coordinates by considering
the electromagnetic field as an external agent. The work here presented shows
how to obtain the electrodynamics for a charged particle in generalized
coordinates eliminating the concept of external force. Based on Kaluza's
formalism, the one here presented extends the 5x5 metric into a 6x6 space-time
giving enough room to include magnetic monopoles in a very natural way.Comment: 11 pages, RevTex. Accepted for publication in the Journal of
Matematical Physic
On the Statistical Foundations of Kaluza's Magnetohydrodynamics
The introduction of electromagnetic fields into the Boltzmann equation
following a 5D general relativistic approach is considered in order to
establish the transport equations for dilute charged fluids in the presence of
a weak electromagnetic field. The conserved 5D stress-energy tensor is
evaluated using the J\"uttner function for non-degenerate relativistic gases in
local equilibrium, and the evolution equations for the local thermodynamic
variables are established by means of relativistic kinetic theory. An outline
of the possibilities offered by the Kaluza-type approach to MHD is also
included.Comment: 10 page
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