Colour Dipoles and Saturation

We employ values of the colour dipole cross section extracted from electroproduction and photoproduction data to show that gluon saturation effects are not required by the current HERA data but will become important in the THERA energy region.Comment: 3 pages, 2 figures. Talk given by G.S. at DIS 2000(Liverpool, April 2000

Predicting F2D(3) from the dipole cross-section

We employ a parameterisation of the proton dipole cross section previously extracted from electroproduction and photoproduction data to predict the diffractive structure function F2D(3)(Q^2, beta, xpom). Comparison with HERA H1 data yields good agreement.Comment: 5 pages,4 figures, Latex2e, uses espcrc1.sty. Presented at "Hadron 99" Beijing, August 1999. Reference added, erroneous citation correcte

Mass-radius relationships for exoplanets

For planets other than Earth, interpretation of the composition and structure depends largely on comparing the mass and radius with the composition expected given their distance from the parent star. The composition implies a mass-radius relation which relies heavily on equations of state calculated from electronic structure theory and measured experimentally on Earth. We lay out a method for deriving and testing equations of state, and deduce mass-radius and mass-pressure relations for key materials whose equation of state is reasonably well established, and for differentiated Fe/rock. We find that variations in the equation of state, such as may arise when extrapolating from low pressure data, can have significant effects on predicted mass- radius relations, and on planetary pressure profiles. The relations are compared with the observed masses and radii of planets and exoplanets. Kepler-10b is apparently 'Earth- like,' likely with a proportionately larger core than Earth's, nominally 2/3 of the mass of the planet. CoRoT-7b is consistent with a rocky mantle over an Fe-based core which is likely to be proportionately smaller than Earth's. GJ 1214b lies between the mass-radius curves for H2O and CH4, suggesting an 'icy' composition with a relatively large core or a relatively large proportion of H2O. CoRoT-2b is less dense than the hydrogen relation, which could be explained by an anomalously high degree of heating or by higher than assumed atmospheric opacity. HAT-P-2b is slightly denser than the mass-radius relation for hydrogen, suggesting the presence of a significant amount of matter of higher atomic number. CoRoT-3b lies close to the hydrogen relation. The pressure at the center of Kepler-10b is 1.5+1.2-1.0 TPa. The central pressure in CoRoT-7b is probably close to 0.8TPa, though may be up to 2TPa.Comment: Added more recent exoplanets. Tidied text and references. Added extra "rock" compositions. Responded to referee comment

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

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]

Dense plasmas in astrophysics: from giant planets to neutron stars

We briefly examine the properties of dense plasmas characteristic of the interior of giant planets and the atmospheres of neutron stars. Special attention is devoted to the equation of state of hydrogen and helium at high density and to the effect of magnetic fields on the properties of dense matter.Comment: Invited Review, Strongly Coupled Coulomb Systems, Moscow June 2005; to appear in Journal of Physics

Hadron formation in high energy photonuclear reactions

We present a new method to account for coherence length effects in a semi-classical transport model. This allows us to describe photo- and electroproduction at large nuclei (A>12) and high energies using a realistic coupled channel description of the final state interactions that goes beyond simple Glauber theory. We show that the purely absorptive treatment of the final state interactions can lead to wrong estimates of color transparency and formation time effects in particle production. As an example, we discuss exclusive rho^0 photoproduction on Pb at a photon energy of 7 GeV as well as K^+ production in the photon energy range 1-7 GeV.Comment: 14 pages, 6 figures, version published in Phys. Rev.

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

Hydrogen-Helium Mixtures at High Pressure

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of Giant planets e.g. whether Jupiter has a rocky core and did it emerge via core accretion? Using path integral Monte Carlo simulations, we study the properties of these mixtures as a function of temperature, density and composition. The equation of state is calculated and compared to chemical models. We probe the accuracy of the ideal mixing approximation commonly used in such models. Finally, we discuss the structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004

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&apos;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