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

Anomalous Hall effect in the Co-based Heusler compounds Co2_{2}FeSi and Co2_{2}FeAl

The anomalous Hall effect (AHE) in the Heusler compounds Co$_{2}$FeSi and Co$_{2}$FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity $\rho_{xx}$ as well as the anomalous Hall resistivity $\rho_{ahe}$. Analyzing the scaling behavior of $\rho_{ahe}$ in terms of $\rho_{xx}$ points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds

From Trapped Atoms to Liberated Quarks

We discuss some aspects of cold atomic gases in the unitarity limit that are of interest in connection with the physics of dense hadronic matter. We consider, in particular, the equation of state at zero temperature, the magnitude of the pairing gap, and the phase diagram at non-zero polarization.Comment: 13 pages, 5 figures; to appear in the proceedings of the International Symposium on Heavy Ion Physics 2006, Frankfurt, Germany; International Journal of Modern Physics E, in pres

Enhancement of synchronization in a hybrid neural circuit by spike timing dependent plasticity

Synchronization of neural activity is fundamental for many functions of the brain. We demonstrate that spike-timing dependent plasticity (STDP) enhances synchronization (entrainment) in a hybrid circuit composed of a spike generator, a dynamic clamp emulating an excitatory plastic synapse, and a chemically isolated neuron from the Aplysia abdominal ganglion. Fixed-phase entrainment of the Aplysia neuron to the spike generator is possible for a much wider range of frequency ratios and is more precise and more robust with the plastic synapse than with a nonplastic synapse of comparable strength. Further analysis in a computational model of HodgkinHuxley-type neurons reveals the mechanism behind this significant enhancement in synchronization. The experimentally observed STDP plasticity curve appears to be designed to adjust synaptic strength to a value suitable for stable entrainment of the postsynaptic neuron. One functional role of STDP might therefore be to facilitate synchronization or entrainment of nonidentical neurons

Loop-Less Electric Dipole Moment of the Nucleon in the Standard Model

We point out that the electric dipole moment of the neutron in the Standard Model is generated already at tree level to the second order in the weak interactions due to bound-state effects, without short-distance Penguin loops. The related contribution has a regular nonvanishing chiral limit and does not depend on the mass splitting between s and d quarks. We estimate it to be roughly 10^(-31)e*cm and expect a more accurate evaluation in the future. We comment on the connection between d_n and the direct CP-violation in D decays.Comment: 10 pages, 2 figure

Projections for future radiocarbon content in dissolved inorganic carbon in hardwater lakes: a retrospective approach

Inland water bodies contain significant amounts of carbon in the form of dissolved inorganic carbon (DIC) derived from a mixture of modern atmospheric and pre-aged sources, which needs to be considered in radiocarbon-based dating and natural isotope tracer studies. While reservoir effects in hardwater lakes are generally considered to be constant through time, a comparison of recent and historical DI14C data from 2013 and 1969 for Lake Constance reveals that this is not a valid assumption. We hypothesize that changes in atmospheric carbon contributions to lake water DIC have taken place due to anthropogenically forced eutrophication in the 20th century. A return to more oligotrophic conditions in the lake led to reoxygenation and enhanced terrigenous organic matter remineralization, contributing to lake water DIC. Such comparisons using DI14C measurements from different points in time enable nonlinear changes in lake water DIC source and signature to be disentangled from concurrent anthropogenically induced changes in atmospheric 14C. In the future, coeval changes in lake dynamics due to climate change are expected to further perturb these balances. Depending on the scenario, Lake Constance DI14C is projected to decrease from the 2013 measured value of 0.856 Fm to 0.54–0.62 Fm by the end of the century

Algebroid Yang-Mills Theories

A framework for constructing new kinds of gauge theories is suggested. Essentially it consists in replacing Lie algebras by Lie or Courant algebroids. Besides presenting novel topological theories defined in arbitrary spacetime dimensions, we show that equipping Lie algebroids E with a fiber metric having sufficiently many E-Killing vectors leads to an astonishingly mild deformation of ordinary Yang-Mills theories: Additional fields turn out to carry no propagating modes. Instead they serve as moduli parameters gluing together in part different Yang-Mills theories. This leads to a symmetry enhancement at critical points of these fields, as is also typical for String effective field theories.Comment: 4 pages; v3: Minor rewording of v1, version to appear in Phys. Rev. Let