Simple stochastic models showing strong anomalous diffusion

We show that {\it strong} anomalous diffusion, i.e. \mean{|x(t)|^q} \sim t^{q \nu(q)} where $q \nu(q)$ is a nonlinear function of $q$, is a generic phenomenon within a class of generalized continuous-time random walks. For such class of systems it is possible to compute analytically nu(2n) where n is an integer number. The presence of strong anomalous diffusion implies that the data collapse of the probability density function P(x,t)=t^{-nu}F(x/t^nu) cannot hold, a part (sometimes) in the limit of very small x/t^\nu, now nu=lim_{q to 0} nu(q). Moreover the comparison with previous numerical results shows that the shape of F(x/t^nu) is not universal, i.e., one can have systems with the same nu but different F.Comment: Final versio

Application of satellite data for snow mapping in Norway

The author has identified the following significant results. A close quantitative relationship was found between snow covered areas and subsequent runoff for different parts of the country despite climate differences. Digital LANDSAT data can be used for areas down to approximately 10 sq km to 20 sq km for accurate measurement of snow cover extent. On large watersheds (more than 500 sq km), digital NOAA/TIROS imagery can be used for snow mapping if the area/runoff relationship is determined by using observations from previous years

Signatures of orbital loop currents in the spatially resolved local density of states

Polarized neutron scattering measurements have suggested that intra-unit cell antiferromagnetism may be associated with the pseudogap phase. Assuming that loop current order is responsible for the observed magnetism, we calculate some signatures of such circulating currents in the local density of states around a single non-magnetic impurity in a coexistence phase with superconductivity. We find a distinct C4 symmetry breaking near the disorder which is also detectable in the resulting quasi-particle interference patterns.Comment: 5 pages, 3 figure

Infrared properties of SiC particles

We present basic laboratory infrared data on a large number of SiC particulate samples, which should be of great value for the interpretation of the 11.3 micron feature observed in the spectra of carbon-rich stars. The laboratory spectra show a wide variety of the SiC phonon features in the 10-13 micron wavelength range, both in peak wavelength and band shape. The main parameters determining the band profile are morphological factors as grain size and shape and, in many cases, impurities in the material. We discovered the interesting fact that free charge carriers, generated e.g. by nitrogen doping, are a very common characteristics of many SiC particle samples. These free charge carriers produce very strong plasmon absorption in the near and middle infrared, which may also heavily influence the 10-13 micron feature profile via plasmon-phonon coupling. We also found that there is no systematic dependence of the band profile on the crystal type (alpha- vs. beta-SiC). This is proven both experimentally and by theoretical calculations based on a study of the SiC phonon frequencies. Further, we give optical constants of amorphous SiC. We discuss the implications of the new laboratory results for the interpretation of the spectra of carbon stars.Comment: 17 pages, 12 figures. To appear in A&

Multimodal Representation of Space in the Posterior Parietal Cortex and its use in Planning Movements

Recent experiments are reviewed that indicate that sensory signals from many modalities, as well as efference copy signals from motor structures, converge in the posterior parietal cortex in order to code the spatial locations of goals for movement. These signals are combined using a specific gain mechanism that enables the different coordinate frames of the various input signals to be combined into common, distributed spatial representations. These distributed representations can be used to convert the sensory locations of stimuli into the appropriate motor coordinates required for making directed movements. Within these spatial representations of the posterior parietal cortex are neural activities related to higher cognitive functions, including attention. We review recent studies showing that the encoding of intentions to make movements is also among the cognitive functions of this area

Pinning of stripes by local structural distortions in cuprate high-Tc superconductors

We study the spin-density wave (stripe) instability in lattices with mixed low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal symmetry. Within an explicit mean-field model it is shown how local LTT regions act as pinning centers for static stripe formation. We calculate the modulations in the local density of states near these local stripe regions and find that mainly the coherence peaks and the van Hove singularity (VHS) are spatially modulated. Lastly, we use the real-space approach to simulate recent tunneling data in the overdoped regime where the VHS has been detected by utilizing local normal state regions.Comment: Conference proceedings for Stripes1

Coupled Magnetic Excitations in Single Crystal PrBa2Cu3O6.2

The dispersion of the low-energy magnetic excitations of the Pr sublattice in PrBa2Cu3O6.2 is determined by inelastic neutron scattering measurements on a single crystal. The dispersion, which shows the effect of interactions with the Cu spin-waves, is well described by a model of the coupled Cu-Pr magnetic system. This enables values for the principal exchange constants to be determined, which suggest that both Pr-Pr and Cu-Pr interactions are important in producing the anomalously high ordering temperature of the Pr sublattice. Measurements of the Cu optic spin wave mode show that the inter-layer Cu-Cu exchange is significantly lower than in YBa2Cu3O6.2.Comment: To be published Phys. Rev. Let