Singularities of the renormalization group flow for random elastic manifolds

We consider the singularities of the zero temperature renormalization group flow for random elastic manifolds. When starting from small scales, this flow goes through two particular points $l^{*}$ and $l_{c}$, where the average value of the random squared potential turnes negative ($l^{*}$) and where the fourth derivative of the potential correlator becomes infinite at the origin ($l_{c}$). The latter point sets the scale where simple perturbation theory breaks down as a consequence of the competition between many metastable states. We show that under physically well defined circumstances $l_{c} to negative values does not take place.Comment: RevTeX, 3 page

Sedimentation in an artificial lake -Lake Matahina, Bay of Plenty

Lake Matahina, an 8 km long hydroelectric storage reservoir, is a small (2.5 km2), 50 m deep, warm monomictic, gorge-type lake whose internal circulation is controlled by the inflowing Rangitaiki River which drains a greywacke and acid volcanic catchment. Three major proximal to distal subenvironments are defined for the lake on the basis of surficial sediment character and dominant depositional process: (a) fluvial-glassy, quartzofeld-spathic, and lithic gravel-sand mixtures deposited from contact and saltation loads in less than 3 m depth; (b) (pro-)deltaic-quartzofeldspathic and glassy sand-silt mixtures deposited from graded and uniform suspension loads in 3-20 m depth; and (c) basinal-diatomaceous, argillaceous, and glassy silt-clay mixtures deposited from uniform and pelagic suspension loads in 20-50 m depth. The delta face has been prograding into the lake at a rate of 35-40 m/year and vertical accretion rates in pro-delta areas are 15-20 cm/year. Basinal deposits are fed mainly from river plume dispersion involving overflows, interflows, and underflows, and by pelagic settling, and sedimentation rates behind the dam have averaged about 2 cm/year. Occasional fine sand layers in muds of basinal cores attest to density currents or underflows generated during river flooding flowing the length of the lake along a sublacustrine channel marking the position of the now submerged channel of the Rangitaiki River

Controlling surface statistical properties using bias voltage: Atomic force microscopy and stochastic analysis

The effect of bias voltages on the statistical properties of rough surfaces has been studied using atomic force microscopy technique and its stochastic analysis. We have characterized the complexity of the height fluctuation of a rough surface by the stochastic parameters such as roughness exponent, level crossing, and drift and diffusion coefficients as a function of the applied bias voltage. It is shown that these statistical as well as microstructural parameters can also explain the macroscopic property of a surface. Furthermore, the tip convolution effect on the stochastic parameters has been examined.Comment: 8 pages, 11 figures

Glassy Motion of Elastic Manifolds

We discuss the low-temperature dynamics of an elastic manifold driven through a random medium. For driving forces well below the $T=0$ depinning force, the medium advances via thermally activated hops over the energy barriers separating favorable metastable states. We show that the distribution of waiting times for these hopping processes scales as a power-law. This power-law distribution naturally yields a nonlinear glassy response for the driven medium, $v\sim\exp(-{\rm const}\times F^{-\mu})$.Comment: 4pages, revte

Ground state properties of fluxlines in a disordered environment

A new numerical method to calculate exact ground states of multi-fluxline systems with quenched disorder is presented, which is based on the minimum cost flow algorithm from combinatorial optimization. We discuss several models that can be studied with this method including their specific implementations, physically relevant observables and results: 1) the N-line model with N fluxlines (or directed polymers) in a d-dimensional environment with point and/or columnar disorder and hard or soft core repulsion; 2) the vortex glass model for a disordered superconductor in the strong screening limit and 3) the Sine-Gordon model with random pase shifts in the strong coupling limit.Comment: 4 pages RevTeX, 3 eps-figures include

Anomalous Roughness in Dimer-Type Surface Growth

We point out how geometric features affect the scaling properties of non-equilibrium dynamic processes, by a model for surface growth where particles can deposit and evaporate only in dimer form, but dissociate on the surface. Pinning valleys (hill tops) develop spontaneously and the surface facets for all growth (evaporation) biases. More intriguingly, the scaling properties of the rough one dimensional equilibrium surface are anomalous. Its width, $W\sim L^\alpha$, diverges with system size $L$, as $\alpha={1/3}$ instead of the conventional universal value $\alpha={1/2}$. This originates from a topological non-local evenness constraint on the surface configurations.Comment: Published version in PR

Energy Barriers for Flux Lines in 3 Dimensions

I determine the scaling behavior of the free energy barriers encountered by a flux line in moving through a three-dimensional random potential. A combination of numerical simulations and analytic arguments suggest that these barriers scale with the length of the line in the same way as the fluctuation in the free energy.Comment: 12 pages Latex, 4 postscript figures tarred, compressed, uuencoded using `uufiles', coming with a separate fil

Stochastic Analysis and Regeneration of Rough Surfaces

We investigate Markov property of rough surfaces. Using stochastic analysis we characterize the complexity of the surface roughness by means of a Fokker-Planck or Langevin equation. The obtained Langevin equation enables us to regenerate surfaces with similar statistical properties compared with the observed morphology by atomic force microscopy.Comment: 4 pages, 7 figure