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.PACS numbers: 52.27.-h, 52.27. Gr, 67.57.Lm There is currently a great deal of interest in investigating collective plasma modes [1,2,3,4,5,6,7,8] in quantum plasmas, as such plasmas could be of relevance in nano-scale electro-mechanical systems [9,10,11], in microplasmas and dense laser-plasmas [12], and laser interactions with atomic systems [13,14]. For example, Refs.[1] and [3,4,5] used quantum transport models in order to derive modified dispersion relations for Langmuir and ion-acoustic waves, while Shukla & Stenflo [15] ionvestigated drift modes in nonuniform quantum magnetoplasmas. Moreover, it is known that cold quantum plasmas can support new dust modes [16,17]. In Ref.[8] it was shown that electron quantum plasmas could support highly stable dark solitons and vortices. Further examples of quantum plasmas and the range of validity of their descriptions has been discussed recently in Ref. [18]. The above studies of quantum plasmas have used models based on the Schrödinger description of the electron. It is expected that new and possible important effects could appear as further quantum effects are incorporated in models describing the quantum plasma particles. The coupling of spin to classical motion has attracted interest in the literature (see, e.g., [19,20,21,22,23,24,25,26,27,28,29,30,31]). Much work has been done concerning single particle spin effects in external field configurations, such as intense laser fields [22,23,24,25,26,27], and the possible experimental signatures thereof. However, there have also been interest in excitations of collective modes in spin systems, such as spin waves, in a wide scientific community. For example, in Refs. [19,20,21] hydrodynamical models including spin was presented, and further theory concerning spin, angular momentum, and the forces related to spin was discussed in Refs. [29] and [30]. Moreover, spin waves in spinor Bose condensates has recently been discussed in, e.g., Ref. [31]. The treatment of charged particles and plasmas using quantum theory has received attention in astrophysical settings, especially in strongly mag- * Electronic address: mattias.marklund@physics.umu.se † Electronic address: gert.brodin@physics.umu.se netized environments [32,33]. For example, effects of quantum field theory on the linear response of an electron gas has been analyzed [34], results concerning the spin-dependence of cyclotron decay on strong magnetic fields has been presented [35], and the propagation of quantum electrodynamical waves in strongly magnetized plasmas has been considered ...

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.

Starting from the Pauli Hamiltonian operator, we derive a scalar quantum kinetic equations for spin-1/2 systems. Here the regular Wigner two-state matrix is replaced by a scalar distribution function in extended phase space. Apart from being a formulation of principal interest, such scalar quantum kinetic equation makes the comparison to classical kinetic theory straightforward, and lends itself naturally to currently available numerical Vlasov and Boltzmann schemes. Moreover, while the quasi-distribution is a Wigner function in regular phase space, it is given by a Qfunction in spin space. As such, nonlinear and dynamical quantum plasma problems are readily handled. Moreover, the issue of gauge invariance is treated. Applications (e.g. ultra-dense laser compressed targets and their diagnostics), possible extensions, and future improvements of the presented quantum statistical model are discussed.

A kinetic theory for spin plasmas is put forward, generalizing those of previous authors. In the model, the ordinary phase space is extended to include the spin degrees of freedom. Together with Maxwell's equations, the system is shown to be energy conserving. Analyzing the linear properties, it is found that new types of wave-particle resonances are possible that depend directly on the anomalous magnetic moment of the electron. As a result, new wave modes, not present in the absence of spin, appear. The implications of our results are discussed.

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 Alfvén wave solitons we demonstrate that quantum effects can survive in a relatively high-temperature plasma. The consequences of our results are discussed.