1,206 research outputs found
Spin-Orbital momentum decomposition and helicity exchange in a set of non-null knotted electromagnetic fields
We calculate analytically the spin-orbital decomposition of the angular
momentum using completely non-paraxial fields that have certain degree of
linkage of electric and magnetic lines. The split of the angular momentum into
spin-orbital components is worked out for non-null knotted electromagnetic
fields. The relation between magnetic and electric helicities and spin-orbital
decomposition of the angular momentum is considered. We demonstrate that even
if the total angular momentum and the values of the spin and orbital momentum
are the same, the behaviour of the local angular momentum density is rather
different. By taking cases with constant and non-constant electric and magnetic
helicities, we show that the total angular momentum density present different
characteristics during time evolution
A topological mechanism of discretization for the electric charge
We present a topological mechanism of discretization, which gives for the
fundamental electric charge a value equal to the square root of the Planck
constant times the velocity of light, which is about 3.3 times the electron
charge. Its basis is the following recently proved property of the standard
linear classical Maxwell equations: they can be obtained by change of variables
from an underlying topological theory, using two complex scalar fields, the
level curves of which coincide with the magnetic and the electric lines,
respectively.Comment: 10 pages, LaTeX fil
Ionization fronts in negative corona discharges
In this paper we use a hydrodynamic minimal streamer model to study negative
corona discharge. By reformulating the model in terms of a quantity called
shielding factor, we deduce laws for the evolution in time of both the radius
and the intensity of ionization fronts. We also compute the evolution of the
front thickness under the conditions for which it diffuses due to the geometry
of the problem and show its self-similar character.Comment: 4 pages, 4 figure
On the mechanism of branching in negative ionization fronts
We explain a mechanism for branching of a planar negative front. Branching
occurs as the result of a balance between the destabilizing effect of impact
ionization and the stabilizing effect of electron diffusion on ionization
fronts. The dispersion relation for transversal perturbation is obtained
analytically and reads: , where , which is
assumed to be small, is the ratio between the electron diffusion coefficient
and the intensity of the externally imposed electric field. We estimate the
spacing between streamers in a planar discharge and deduce a scaling
law
Power laws and self-similar behavior in negative ionization fronts
We study anode-directed ionization fronts in curved geometries. When the
magnetic effects can be neglected, an electric shielding factor determines the
behavior of the electric field and the charged particle densities. From a
minimal streamer model, a Burgers type equation which governs the dynamics of
the electric shielding factor is obtained. A Lagrangian formulation is then
derived to analyze the ionization fronts. Power laws for the velocity and the
amplitude of streamer fronts are observed numerically and calculated
analytically by using the shielding factor formulation. The phenomenon of
geometrical diffusion is explained and clarified, and a universal self-similar
asymptotic behavior is derived.Comment: 25 pages, 9 figure
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