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Register a new userCovariant Kinetic Theory with an Application to the Coma Cluster
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In this paper, we introduce a novel solution to the covariant Landau equation for a pure electron plasma. The method conserves energy and particle number, and reduces smoothly to the Rosenbluth potentials of non-relativistic theory. In addition, we find that a fully relativistic plasma equilibrates in only 1/100th of a Spitzer time--much faster than in the non-relativistic limit--a factor of significant import to situations in which distortions to a Maxwellian distribution are produced by anomalous methods of acceleration. To demonstrate the power of our solution in dealing with hot, astrophysical plasmas, we use this technique to show that one of the currently considered models--continuous stochastic acceleration--for the hard X-ray emission in the Coma cluster actually cannot work because the energy gained by the particles is distributed to the {it whole} plasma on a time scale much shorter than that of the acceleration process itself.
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We develop a covariant kinetic theory for massive fermions in curved spacetime and external electromagnetic field based on quantum field theory. We derive four coupled semi-classical kinetic equations accurate at $O(hbar)$, which describe the transports of particle number and spin degrees of freedom. The relation with the chiral kinetic theory is discussed. As an application, we study the spin polarization in the presence of finite Riemann curvature and electromagnetic field in both local and global equilibrium states.
The first order hydrodynamic evolution equations for the shear stress tensor, the bulk viscous pressure and the charge current have been studied for a system of quarks and gluons, with a non-vanishing quark chemical potential and finite quark mass. The first order transport coefficients have been obtained by solving an effective Boltzmann equation for the grand-canonical ensemble of quasiquarks and quasigluons. We adopted temperature dependent effective fugacity for the quasiparticles to encode the hot QCD medium effects. The non-trivial energy dispersion of the quasiparticles induces mean field contributions to the transport coefficients whose origin could be directly related to the realization of conservation laws from the effective kinetic theory. Both the QCD equation of state and chemical potential are seen to have a significant impact on the quark-gluon plasma evolution. The shear and bulk viscous corrections to the entropy-four current have been investigated in the framework of the effective kinetic theory. The effect of viscous corrections to the entropy density have been quantified in the case of one dimensional boost-invariant expansion of the system. Further, the first order viscous corrections to the time evolution of temperature along with the description of pressure anisotropy and Reynolds number of the system have been explored for the longitudinal boost-invariant expansion.volution of temperature along with the description of pressure anisotropy of the system have also been explored.
We construct and study several semilocal density functional approximations for the positive Kohn-Sham kinetic energy density. These functionals fit the kinetic energy density of the Airy gas and they can be accurate for integrated kinetic energies of atoms, molecules, jellium clusters and jellium surfaces. We find that these functionals are the most accurate ones for atomization kinetic energies of molecules and for fragmentation of jellium clusters. We also report that local and semilocal kinetic energy functionals can show binding when the density of a spin unrestricted Kohn-Sham calculation is used.
We have developed a numerical model for the temporal evolution of particle and photon spectra resulting from nonthermal processes at the shock fronts formed in merging clusters of galaxies. Fermi acceleration is approximated by injecting power-law distributions of particles during a merger event, subject to constraints on maximum particle energies. We consider synchrotron, bremsstrahlung, Compton, and Coulomb processes for the electrons, nuclear, photomeson, and Coulomb processes for the protons, and knock-on electron production during the merging process. The broadband radio through $gamma$-ray emission radiated by nonthermal protons and primary and secondary electrons is calculated both during and after the merger event. To test the ability of the computer model to accurately calculate the nonthermal emission expected from a cluster merger event, we apply the model to the Coma cluster of galaxies, and show that the centrally located radio emission and the Hard X-ray excess observed at 40-80$kev$ is well fit by our model. If our model is correct, then the Coma cluster will be significantly detected with GLAST and ground-based air Cherenkov telescopes.
Coulomb collisions in plasmas are typically modeled using the Boltzmann collision operator, or its variants, which apply to weakly magnetized plasmas in which the typical gyroradius of particles significantly exceeds the Debye length. Conversely, ONeil has developed a kinetic theory to treat plasmas that are so strongly magnetized that the typical gyroradius of particles is much smaller than the distance of closest approach in a binary collision. Here, we develop a generalized collision operator that applies across the full range of magnetization strength. To demonstrate novel physics associated with strong magnetization, it is used to compute the friction force on a massive test charge. In addition to the traditional stopping power component, this is found to exhibit a transverse component that is perpendicular to both the velocity and Lorentz force vectors in the strongly magnetized regime, as was predicted recently using linear response theory. Good agreement is found between the collision theory and linear response theory in the regime in which both apply, but the new collision theory also applies to stronger magnetization strength regimes than the linear response theory is expected to apply in.
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