Publications by authors named "Kremp D"

The long-standing discrepancy in the equation of state of charge neutral plasmas, the occurrence of an e(2) direct term in the second virial coefficient, is dealt with. We state that such a contribution should not appear for a pure Coulomb interaction.

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Direct linear term in the equation of state of plasmas.

Phys Rev E Stat Nonlin Soft Matter Phys

January 2015

Article Synopsis
  • There is a long-standing issue regarding the equation of state for charge-neutral plasmas, specifically the role of a term labeled e(2) that affects the calculations.
  • The presence of this e(2) term seems to depend on how the average potential energy is calculated in the models used.
  • The study concludes that this e(2) term should not be included when only considering pure Coulombic interactions in the plasma.
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Collisional absorption of dense fully ionized plasmas in strong laser fields is investigated using quantum statistical methods as well as molecular dynamics simulations. For high-frequency fields, quantum statistical expressions for the electrical current density and the electron-ion collision frequency are presented. Strong correlations are taken into account and their influence on the absorption rate is discussed.

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We propose a theoretical Hugoniot relation obtained by combining results for the equation of state from the direct path integral Monte Carlo technique (DPIMC) and those from reaction ensemble Monte Carlo (REMC) simulations. The main idea of this proposal is based on the fact that the DPMIC technique provides first-principle results for a wide range of densities and temperatures including the region of partially ionized plasmas. On the other hand, for lower temperatures where the formation of molecules becomes dominant, DPIMC simulations become cumbersome and inefficient.

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In spite of the simple structure of hydrogen, up to now there is no unified theoretical and experimental description of hydrogen at high pressures. Recent results of Z-pinch experiments show a large deviation from those obtained by laser driven ones. Theoretical investigations including ab initio computer simulations show considerable differences at such extreme conditions from each other and from experimental values.

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Two-particle problem in a nonequilibrium many-particle system.

Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics

December 1999

The two-particle problem within a nonequilibrium many-particle system is investigated in the framework of real-time Green's functions. Starting from the nonequilibrium Bethe-Salpeter equation on the Keldysh contour, a Dyson equation is given for two-time two-particle Green's functions. Thereby the well-known Kadanoff-Baym equations are generalized to the case of two-particle functions.

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Quantum kinetic theory of plasmas in strong laser fields.

Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics

October 1999

A kinetic theory for quantum many-particle systems in time-dependent electromagnetic fields is developed based on a gauge-invariant formulation. The resulting kinetic equation generalizes previous results to quantum systems and includes many-body effects. It is, in particular, applicable to the interaction of strong laser fields with dense correlated plasmas.

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Collisional absorption of dense, fully ionized plasmas in strong laser fields is investigated starting from a quantum kinetic equation with non-Markovian and field-dependent collision integrals in dynamically screened Born approximation. This allows to find rather general balance equations for the energy and the current. For high-frequency laser fields, quantum statistical expressions for the electrical current density and the cycle-averaged electron-ion collision frequency in terms of the Lindhard dielectric function are derived.

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Anomalously high generation efficiency of coherent higher field harmonics in collisions between oppositely charged particles in the field of femtosecond lasers is predicted. This is based on rigorous numerical solutions of a quantum kinetic equation for dense laser plasmas that overcomes limitations of previous investigations.

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Classical Molecular Dynamics simulations for a one-component plasma are presented. Quantum effects are included in the form of the Kelbg potential. Results for the dynamical structure factor are compared with the Vlasov and random phase approximation theories.

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The short-time dynamics of correlated systems is strongly influenced by initial correlations, giving rise to an additional collision integral in the non-Markovian kinetic equation. Exact cancellation of the two integrals is found if the initial state is thermal equilibrium, which is an important consistency criterion. Analytical results are given for the time evolution of the correlation energy, which are confirmed by comparisons with molecular dynamics simulations.

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