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Search Results: 1 - 10 of 189890 matches for " G. Brodin "
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Spin quantum plasmas - new aspects of collective dynamics
M. Marklund,G. Brodin
Physics , 2008,
Abstract: Quantum plasmas is a rapidly expanding field of research, with applications ranging from nanoelectronics, nanoscale devices and ultracold plasmas, to inertial confinement fusion and astrophysics. Here we give a short systematic overview of quantum plasmas. In particular, we analyze the collective effects due to spin using fluid models. The introduction of an intrinsic magnetization due to the plasma electron (or positron) spin properties in the magnetohydrodynamic limit is discussed. Finally, a discussion of the theory and examples of applications is given.
Quantum, spin and QED effects in plasmas
G. Brodin,M. Marklund
Physics , 2008,
Abstract: Plasmas are usually described using classical equations. While this is often a good approximation, where are situations when a quantum description is motivated. In this paper we will include several quantum effects, ranging from particle dispersion, which give raise to the so called Bohm potential, to spin effects, and to quantum electrodynamical effects. The later effects appears when the field strength approaches the Schwinger critical field, which may occur in for example astrophysical systems. Examples of how to model such quantum effects will be presented, and the phenomena resulting from these models will be discussed.
Spin solitons in magnetized pair plasmas
G. Brodin,M. Marklund
Physics , 2007, DOI: 10.1063/1.2793744
Abstract: A set of fluid equations, taking into account the spin properties of the electrons and positrons in a magnetoplasma, are derived. The magnetohydrodynamic limit of the pair plasma is investigated. It is shown that the microscopic spin properties of the electrons and positrons can lead to interesting macroscopic and collective effects in strongly magnetized plasmas. In particular, it is found that new Alfvenic solitary structures, governed by a modified Korteweg-de Vries equation, are allowed in such plasmas. These solitary structures vanish if the quantum spin effects are neglected. Our results should be of relevance for astrophysical plasmas, e.g. in pulsar magnetospheres.
Spin magnetohydrodynamics
G. Brodin,M. Marklund
Physics , 2006, DOI: 10.1088/1367-2630/9/8/277
Abstract: Starting from the non-relativistic Pauli description of spin-1/2 particles, a set of fluid equations, governing the dynamics of such particles interacting with external fields and other particles, is derived. The equations describe electrons, positrons, holes, and similar conglomerates. In the case of electrons, the magnetohydrodynamic limit of an electron-ion plasma is investigated. The results should be of interest and relevance both to laboratory and astrophysical plasmas.
Dynamics of spin 1/2 quantum plasmas
M. Marklund,G. Brodin
Physics , 2006, DOI: 10.1103/PhysRevLett.98.025001
Abstract: The fully nonlinear governing equations for spin 1/2 quantum plasmas are presented. Starting from the Pauli equation, the relevant plasma equations are derived, and it is shown that nontrivial quantum spin couplings arise, enabling studies of the combined collective and spin dynamics. The linear response of the quantum plasma in an electron--ion system is obtained and analyzed. Applications of the theory to solid state and astrophysical systems as well as dusty plasmas are pointed out.
On the possibility of metamaterial properties in spin plasmas
G. Brodin,M. Marklund
Physics , 2008, DOI: 10.1088/1367-2630/10/11/115031
Abstract: The fluid theory of plasmas is extended to include the properties of electron spin. The linear theory of waves in a magnetized plasma is presented, and it is shown that the spin effects causes a change of the magnetic permeability. Furthemore, by changing the direction of the external magnetic field, the magnetic permability may become negative. This leads to instabilities in the long wavelength regimes. If these can be controlled, however, the spin plasma becomes a metamaterial for a broad range of frequencies, i.e. above the ion cyclotron frequency but below the electron cyclotron frequency. The consequences of our results are discussed.
Gravitational wave detection using electromagnetic modes in a resonance cavity
G. Brodin,M. Marklund
Physics , 2002,
Abstract: We present a proposal for a gravitational wave detector, based on the excitation of an electromagnetic mode in a resonance cavity. The mode is excited due to the interaction between a large amplitude electromagnetic mode and a quasi-monochromatic gravitational wave. The minimum metric perturbation needed for detection is estimated to the order 7.10^(-23) using current data on superconducting niobium cavities. Using this value together with different standard models predicting the occurrence of merging neutron star or black hole binaries, the corresponding detection rate is estimated to 1-20 events per year, with a `table top' cavity of a few meters length.
The three-wave coupling coefficients for a cold magnetized plasma
L. Stenflo,G. Brodin
Physics , 2006,
Abstract: The resonant interaction between three waves in a uniform magnetized plasma is considered. Using the somewhat inaccessible result of the general theory we deduce the explicit expressions for the coupling coefficients of a cold magnetized two-component plasma.
Ferromagnetic behavior in magnetized plasmas
G. Brodin,M. Marklund
Physics , 2007, DOI: 10.1103/PhysRevE.76.055403
Abstract: We consider a low-temperature plasma within a newly developed MHD Fluid model. In addition to the standard terms, the electron spin, quantum particle dispersion and degeneracy effects are included. It turns out that the electron spin properties can give rise to Ferromagnetic behavior in certain regimes. If additional conditions are fulfilled, a homogenous magnetized plasma can even be unstable. This happen in the low-temperature high-density regime, when the magnetic properties associated with the spin can overcome the stabilizing effects of the thermal and Fermi pressure, to cause a Jeans like instability.
Quantum plasma effects in the classical regime
G. Brodin,M. Marklund,G. Manfredi
Physics , 2008, DOI: 10.1103/PhysRevLett.100.175001
Abstract: For quantum effects to be significant in plasmas it is often assumed that the temperature over density ratio must be small. In this paper we challenge this assumption by considering the contribution to the dynamics from the electron spin properties. As a starting point we consider a multicomponent plasma model, where electrons with spin up and spin down are regarded as different fluids. By studying the propagation of Alfv\'{e}n wave solitons we demonstrate that quantum effects can survive in a relatively high-temperature plasma. The consequences of our results are discussed.
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