42,564 research outputs found
The fully kinetic Biermann battery and associated generation of pressure anisotropy
The dynamical evolution of a fully kinetic, collisionless system with imposed
background density and temperature gradients is investigated analytically. The
temperature gradient leads to the generation of temperature anisotropy, with
the temperature along the gradient becoming larger than that in the direction
perpendicular to it. This causes the system to become unstable to pressure
anisotropy driven instabilities, dominantly to electron Weibel. When both
density and temperature gradients are present and non-parallel to each other,
we obtain a Biermann-like linear in time magnetic field growth. Accompanying
particle in cell numerical simulations are shown to confirm our analytical
results.Comment: 5 pages, 2 figures, + Supplementary materials (4 pages, 2 figures
Many-body interactions in a quantum wire in the integer quantum Hall regime: suppression of exchange-enhanced g factor
The collapse of Hall gaps in the integer quantum Hall liquid in a quantum
wire is investigated. Motivated by recent experiment [Pallecchi et al. PRB 65,
125303 (2002)] previous approaches are extended to treat confinement effects
and the exchanged enhanced g-factor in quantum wires. Two scenarios for the
collapse of the state are discussed. In the first one the
state becomes unstable at , due to the exchange interaction and
correlation effects, coming from the edge-states screening. In the second
scenario, a transition to the state occurs at , with a
smaller effective channel width, caused by the redistribution of the charge
density. This effect turns the Hartree interaction essential in calculating the
total energy and changes drastically. In both scenarios, the
exchange enhanced g-factor is suppressed for magnetic fields lower than
. Phase diagrams for the Hall gap collapse are determined. The critical
fields, activation energy, and optical -factor obtained are compared with
experiments. Within the accuracy of the available data, the first scenario is
most probable to be realized.Comment: 11 pages, 10 figure
Baryon loading and the Weibel instability in gamma-ray bursts
The dynamics of two counter-streaming electron-positron-ion unmagnetized
plasma shells with zero net charge is analyzed in the context of magnetic field
generation in GRB internal shocks due to the Weibel instability. The effects of
large thermal motion of plasma particles, arbitrary mixture of plasma species
and space charge effects are taken into account. We show that, although thermal
effects slow down the instability, baryon loading leads to a non-negligible
growth rate even for large temperatures and different shell velocities, thus
guaranteeing the robustness and the occurrence of the Weibel instability for a
wide range of scenarios.Comment: 6 pages, 4 figures. Accepted for publication in MNRA
Modelling radiation emission in the transition from the classical to the quantum regime
An emissivity formula is derived using the generalised
Fermi-Weizacker-Williams method of virtual photons which accounts for the
recoil the charged particle experiences as it emits radiation. It is found that
through this derivation the formula obtained by Sokolov et al using QED
perturbation theory is recovered. The corrected emissivity formula is applied
to nonlinear Thomson scattering scenarios in the transition from the classical
to the quantum regime, for small values of the nonlinear quantum parameter
\chi. Good agreement is found between this method and a QED probabilistic
approach for scenarios where both are valid. In addition, signatures of the
quantum corrections are identified and explored.Comment: 11 pages, 4 figures, submitted for publicatio
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