5,765 research outputs found
Radiation from low-momentum zoom-whirl orbits
We study zoom-whirl behaviour of equal mass, non-spinning black hole binaries
in full general relativity. The magnitude of the linear momentum of the initial
data is fixed to that of a quasi-circular orbit, and its direction is varied.
We find a global maximum in radiated energy for a configuration which completes
roughly one orbit. The radiated energy in this case exceeds the value of a
quasi-circular binary with the same momentum by 15%. The direction parameter
only requires minor tuning for the localization of the maximum. There is
non-trivial dependence of the energy radiated on eccentricity (several local
maxima and minima). Correlations with orbital dynamics shortly before merger
are discussed. While being strongly gauge dependent, these findings are
intuitive from a physical point of view and support basic ideas about the
efficiency of gravitational radiation from a binary system.Comment: 9 pages, 6 figures, Amaldi8 conference proceedings as publishe
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
Collective Behavior of Asperities in Dry Friction at Small Velocities
We investigate a simple model of dry friction based on extremal dynamics of
asperities. At small velocities, correlations develop between the asperities,
whose range becomes infinite in the limit of infinitely slow driving, where the
system is self-organized critical. This collective phenomenon leads to
effective aging of the asperities and results in velocity dependence of the
friction force in the form .Comment: 7 pages, 8 figures, revtex, submitted to Phys. Rev.
Quenched Averages for self-avoiding walks and polygons on deterministic fractals
We study rooted self avoiding polygons and self avoiding walks on
deterministic fractal lattices of finite ramification index. Different sites on
such lattices are not equivalent, and the number of rooted open walks W_n(S),
and rooted self-avoiding polygons P_n(S) of n steps depend on the root S. We
use exact recursion equations on the fractal to determine the generating
functions for P_n(S), and W_n(S) for an arbitrary point S on the lattice. These
are used to compute the averages and over different positions of S. We find that the connectivity constant
, and the radius of gyration exponent are the same for the annealed
and quenched averages. However, , and , where the exponents
and take values different from the annealed case. These
are expressed as the Lyapunov exponents of random product of finite-dimensional
matrices. For the 3-simplex lattice, our numerical estimation gives ; and , to be
compared with the annealed values and .Comment: 17 pages, 10 figures, submitted to Journal of Statistical Physic
Training, Retention, and Transfer of Data Entry Perceptual and Motoric Processes Over Long Retention Intervals
Subjects trained in a standard data entry task, which involved typing numbers (e.g., 5421) using their right hands. At test (6 months post-training), subjects completed the standard task, followed by a left-hand variant (typing with their left hands) that involved the same perceptual, but different motoric, processes as the standard task. At a second test (8 months post-training), subjects completed the standard task, followed by a code variant (translating letters into digits, then typing the digits with their right hands) that involved different perceptual, but the same motoric, processes as the standard task. For each of the three tasks, half the trials were trained numbers (old) and half were new. Repetition priming (faster response times to old than new numbers) was found for each task. Repetition priming for the standard task reflects retention of trained numbers; for the left-hand variant reflects transfer of perceptual processes; and for the code variant reflects transfer of motoric processes. There was thus evidence for both specificity and generalizability of training data entry perceptual and motoric processes over very long retention intervals
Soliton effects in dangling-bond wires on Si(001)
Dangling bond wires on Si(001) are prototypical one dimensional wires, which
are expected to show polaronic and solitonic effects. We present electronic
structure calculations, using the tight binding model, of solitons in
dangling-bond wires, and demonstrate that these defects are stable in
even-length wires, although approximately 0.1 eV higher in energy than a
perfect wire. We also note that in contrast to conjugated polymer systems,
there are two types of soliton and that the type of soliton has strong effects
on the energetics of the bandgap edges, with formation of intra-gap states
between 0.1 eV and 0.2 eV from the band edges. These intra-gap states are
localised on the atoms comprising the soliton.Comment: 6 pages, 3 figures, 3 tables, submitted to Phys. Rev.
Exact Analysis of Level-Crossing Statistics for (d+1)-Dimensional Fluctuating Surfaces
We carry out an exact analysis of the average frequency
in the direction of positive-slope crossing of a given level
such that, , of growing surfaces in spatial
dimension . Here, is the surface height at time , and
is its mean value. We analyze the problem when the surface growth
dynamics is governed by the Kardar-Parisi-Zhang (KPZ) equation without surface
tension, in the time regime prior to appearance of cusp singularities (sharp
valleys), as well as in the random deposition (RD) model. The total number
of such level-crossings with positive slope in all the directions is then
shown to scale with time as for both the KPZ equation and the RD
model.Comment: 22 pages, 3 figure
- …