The First Moments of Nucleon Generalized Parton Distributions

We extrapolate the first moments of the generalized parton distributions using heavy baryon chiral perturbation theory. The calculation is based on the one loop level with the finite range regularization. The description of the lattice data is satisfactory and the extrapolated moments at physical pion mass are consistent with the results obtained with dimensional regularization, although the extrapolation in the momentum transfer to $t=0$ does show sensitivity to form factor effects which lie outside the realm of chiral perturbation theory. We discuss the significance of the results in the light of modern experiments as well as QCD inspired models.Comment: 14 pages, 9 figure

Coefficient of restitution for viscoelastic disks

The dissipative collision of two identical viscoelastic disks is studied. By using a known law for the elastic part of the interaction force and the viscoelastic damping model an analytical solution for the coefficient of restitution shall be given. The coefficient of restitution depends significantly on the impact velocity. It approaches one for small velocities and decreases for increasing velocities.Comment: 11 pages, 3 figure

Quark structure and nuclear effective forces

We formulate the quark meson coupling model as a many-body effective Hamiltonian. This leads naturally to the appearance of many-body forces. We investigate the zero range limit of the model and compare its Hartree-Fock Hamiltonian to that corresponding to the Skyrme effective force. By fixing the three parameters of the model to reproduce the binding and symmetry energy of nuclear matter, we find that it allows a very satisfactory interpretation of the Skyrme force.Comment: 4 pages, 1tabl

Phase transition from hadronic matter to quark matter

We study the phase transition from nuclear matter to quark matter within the SU(3) quark mean field model and NJL model. The SU(3) quark mean field model is used to give the equation of state for nuclear matter, while the equation of state for color superconducting quark matter is calculated within the NJL model. It is found that at low temperature, the phase transition from nuclear to color superconducting quark matter will take place when the density is of order 2.5$\rho_0$ - 5$\rho_0$. At zero density, the quark phase will appear when the temperature is larger than about 148 MeV. The phase transition from nuclear matter to quark matter is always first order, whereas the transition between color superconducting quark matter and normal quark matter is second order.Comment: 18 pages, 11 figure

The Alignment of Clusters using Large Scale Simulations

The alignment of clusters of galaxies with their nearest neighbours and between clusters within a supercluster is investigated using simulations of 512^{3} dark matter particles for \LambdaCDM and \tauCDM cosmological models. Strongly significant alignments are found for separations of up to 15h^{-1}Mpc in both cosmologies, but for the \LambdaCDM model the alignments extend up to separations of 30h^{-1}Mpc. The effect is strongest for nearest neighbours, but is not significant enough to be useful as an observational discriminant between cosmologies. As a check of whether this difference in alignments is present in other cosmologies, smaller simulations with 256^{3} particles are investigated for 4 different cosmological models. Because of poor number statistics, only the standard CDM model shows indications of having different alignments from the other models.Comment: 6 pages, 5 figures Submitted to MNRA

Combining Semi-Analytic Models of Galaxy Formation with Simulations of Galaxy Clusters: the Need for AGN Heating

We present hydrodynamical N-body simulations of clusters of galaxies with feedback taken from semi-analytic models of galaxy formation. The advantage of this technique is that the source of feedback in our simulations is a population of galaxies that closely resembles that found in the real universe. We demonstrate that, to achieve the high entropy levels found in clusters, active galactic nuclei must inject a large fraction of their energy into the intergalactic/intracluster media throughout the growth period of the central black hole. These simulations reinforce the argument of Bower et al. (2008), who arrived at the same conclusion on the basis of purely semi-analytic reasoning.Comment: 4 pages, 1 figure. To appear in the proceedings of "The Monster's Fiery Breath", Eds. Sebastian Heinz and Eric Wilcots (AIP conference series

Measuring mass moments and electromagnetic moments of a massive, axisymmetric body, through gravitational waves

The electrovacuum around a rotating massive body with electric charge density is described by its multipole moments (mass moments, mass-current moments, electric moments, and magnetic moments). A small uncharged test particle orbiting around such a body moves on geodesics if gravitational radiation is ignored. The waves emitted by the small body carry information about the geometry of the central object, and hence, in principle, we can infer all its multipole moments. Due to its axisymmetry the source is characterized now by four families of scalar multipole moments: its mass moments $M_l$, its mass-current moments $S_l$, its electrical moments $E_l$ and its magnetic moments $H_l$, where $l=0,1,2,...$. Four measurable quantities, the energy emitted by gravitational waves per logarithmic interval of frequency, the precession of the periastron (assuming almost circular orbits), the precession of the orbital plane (assuming almost equatorial orbits), and the number of cycles emitted per logarithmic interval of frequency, are presented as power series of the newtonian orbital velocity of the test body. The power series coefficients are simple polynomials of the various moments.Comment: Talk given by T. A. A. at Recent Advances in Astronomy and Astrophysics, Lixourion, Kefallinia island, Greece, 8-11 Sep 200

The role of active galactic nuclei in galaxy formation

We use Monte-Carlo Markov chain techniques to constrain acceptable parameter regions for the Munich L-Galaxies semi-analytic galaxy formation model. Feedback from active galactic nuclei (AGN) is required to limit star-formation in the most massive galaxies. However, we show that the introduction of tidal stripping of dwarf galaxies as they fall into and merge with their host systems can lead to a reduction in the required degree of AGN feedback. In addition, the new model correctly reproduces both the metallicity of large galaxies and the fraction of intracluster light.Comment: Monster's Fiery Breath Conference Proceedings, 4 page

Memristive switching of MgO based magnetic tunnel junctions

Here we demonstrate that both, tunnel magneto resistance (TMR) and resistive switching (RS), can be observed simultaneously in nano-scale magnetic tunnel junctions. The devices show bipolar RS of 6 % and TMR ratios of about 100 %. For each magnetic state, multiple resistive sates are created depending on the bias history which provides a method for multi-bit data storage and logic. The electronic transport measurements are discussed in the framework of a memristive system. Differently prepared MgO barriers are compared to gain insight into the switching mechanism