An equation of state from cool-dense fluids to hot gases for mixed elements

An equation of state for the domain extending from hot gases to cool-dense fluids is formulated for a hydrogen-helium mixture. The physical processes take account of temperature ionization and dissociation, electron degeneracy, Coulomb coupling and pressure ionization. Pressure ionization and Coulomb coupling are studied with simple and comprehensive modeling. A single and complete algorithm is achieved with explicit expressions available for the whole domain from hot gases to cool dense fluids ($T>10^2$). Pressure ionization and Coulomb coupling have been examined for their contributions to the pressure and internal energy. The result reveals that their contributions smooth the variation of the pressure and internal energy in the region of pressure ionization even at very low temperatures.Comment: 10 pages, 8 figures, ApJ, accepted, E-mail: [email protected]

Monte Carlo results for the hydrogen Hugoniot

We propose a theoretical Hugoniot obtained by combining results for the equation of state (EOS) from the Direct Path Integral Monte Carlo technique (DPIMC) and those from Reaction Ensemble Monte Carlo (REMC) simulations. The main idea of such proposal is based on the fact that DPMIC 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. For this region it is possible to use accurate REMC simulations where bound states (molecules) are treated on the Born-Oppenheimer level using a binding potential calculated by Kolos and Wolniewicz. The remaining interaction is then reduced to the scattering between neutral particles which is reliably treated classically applying effective potentials. The resulting Hugoniot is located between the experimental values of Knudson {\textit{et al.}} \cite{1} and Collins {\textit{et al.}} \cite{2}.Comment: 10 pges, 2 figures, 2 table

doi:10.1016/j.biocon.2007.06.018

Abstract: Successful conservation initiatives often lead to rapid increases in large carnivore densities to the extent that overpopulation occurs. Yet conservation managers have no way of knowing the carrying capacity of their reserves. Here we derived relationships between the preferred prey (species and weight range) of Africa's large predator guild and their population densities to predict their carrying capacity in ten South African conservation areas. Conservation managers intervened at several of these sites because of evidence of predator overpopulation and these provided independent tests of our predictions. Highly significant linear relationships were found between the biomass of the preferred prey species of lion, leopard, spotted hyaena and African wild dog, and the biomass of prey in the preferred weight range of cheetah. These relationships are more robust than previous work for lion, cheetah and leopard, and novel for spotted hyaena and African wild dog. These relationships predicted that several predators exceeded carrying capacity at four sites, two where managers expressed concerns about overpopulation due to a decline in wildlife abundance and two where carnivores were actively removed. The ability to predict the carrying capacity of large predators is fundamental to their conservation, particularly in small enclosed reserves. Every predator that preys on large, readily surveyed wildlife can have its carrying capacity predicted in this manner based on the abundance of its preferred prey. This will be beneficial for reintroduction attempts, threatened species management, overpopulation estimation, detecting poaching and in investigating intra-guild competition. Carrying capacity of large African predators: Predictions and tests vation managers intervened at several of these sites because of evidence of predator overpopulation and these provided independent tests of our predictions. Highly significant linear relationships were found between the biomass of the preferred prey species of lion, leopard, spotted hyaena and African wild dog, and the biomass of prey in the preferred weight range of cheetah. These relationships are more robust than previous work for lion, cheetah and leopard, and novel for spotted hyaena and African wild dog. These relationships predicted that several predators exceeded carrying capacity at four sites, two where managers expressed concerns about overpopulation due to a decline in wildlife abundance and two where carnivores were actively removed. The ability to predict the carrying capacity of large predators is fundamental to their conservation, particularly in small enclosed reserves. Every predator that preys on large, readily surveyed wildlife can have its carrying capacity predicted in this manner based on the abundance of its preferred prey. This will be beneficial for reintroduction attempts, threatened species management, overpopulation estimation, detecting poaching and in investigating intra-guild competition

Variational Density Matrix Method for Warm Condensed Matter and Application to Dense Hydrogen

A new variational principle for optimizing thermal density matrices is introduced. As a first application, the variational many body density matrix is written as a determinant of one body density matrices, which are approximated by Gaussians with the mean, width and amplitude as variational parameters. The method is illustrated for the particle in an external field problem, the hydrogen molecule and dense hydrogen where the molecular, the dissociated and the plasma regime are described. Structural and thermodynamic properties (energy, equation of state and shock Hugoniot) are presented.Comment: 26 pages, 13 figures. submitted to Phys. Rev. E, October 199

Calculation of a Deuterium Double Shock Hugoniot from Ab initio Simulations

We calculate the equation of state of dense deuterium with two ab initio simulations techniques, path integral Monte Carlo and density functional theory molecular dynamics, in the density range of 0.67 < rho < 1.60 g/cc. We derive the double shock Hugoniot and compare with the recent laser-driven double shock wave experiments by Mostovych et al. [1]. We find excellent agreement between the two types of microscopic simulations but a significant discrepancy with the laser-driven shock measurements.Comment: accept for publication in Phys. Rev. Lett., Nov. 2001, 4 pages, 4 figure

Thermodynamic properties and electrical conductivity of strongly correlated plasma media

We study thermodynamic properties and the electrical conductivity of dense hydrogen and deuterium using three methods: classical reactive Monte Carlo (REMC), direct path integral Monte Carlo (PIMC) and a quantum dynamics method in the Wigner representation of quantum mechanics. We report the calculation of the deuterium compression quasi-isentrope in good agreement with experiments. We also solve the Wigner-Liouville equation of dense degenerate hydrogen calculating the initial equilibrium state by the PIMC method. The obtained particle trajectories determine the momentum-momentum correlation functions and the electrical conductivity and are compared with available theories and simulations

The colour dipole approach to small-x processes

We explain why it is possible to formulate a wide variety of high energy (small-x) photon-proton processes in terms of a universal dipole cross section and compare and contrast various parameterizations of this function that exist in the literature.Comment: 6 pages, latex, 2 figures. Contribution to Durham Collider Workshop (Sept 99) proceeding

From Deep Inelastic Scattering to Photoproduction: A Unified Approach

The strikingly different high energy behaviours of real photoabsorption cross-sections with Q^2 = 0 and the low x proton structure function at large Q^2 are studied from a laboratory frame viewpoint, in which the x and Q^2 dependence reflects the space-time structure of the interaction. This is done using a simple model which incorporates hadron dominance, but attributes the striking enhancement observed at HERA at very low x and high Q^2 to contributions from heavy long-lived fluctuations of the incoming photon. Earlier published predictions of the model for the then unknown behaviour of the structure function at small x and intermediate Q^2 are shown to be strikingly confirmed by recent experimental data. A simultaneous analysis of real photoabsorption data and structure function data for 0 <= x < 0.1 and 0 <= Q^2 <= 15 GeV^2 is then reported. An excellent fit is obtained, with all parameters in the restricted ranges allowed by other physical requirements.Comment: 23 pages, LaTex, 11 figures, Submitted to Physical Revie