2,842 research outputs found
Scaling of energy spreading in strongly nonlinear disordered lattices
To characterize a destruction of Anderson localization by nonlinearity, we
study the spreading behavior of initially localized states in disordered,
strongly nonlinear lattices. Due to chaotic nonlinear interaction of localized
linear or nonlinear modes, energy spreads nearly subdiffusively. Based on a
phenomenological description by virtue of a nonlinear diffusion equation we
establish a one-parameter scaling relation between the velocity of spreading
and the density, which is confirmed numerically. From this scaling it follows
that for very low densities the spreading slows down compared to the pure power
law.Comment: 4 pages, 4 figure
CO oxidation on Pd(100) at technologically relevant pressure conditions: A first-principles kinetic Monte Carlo study
The possible importance of oxide formation for the catalytic activity of
transition metals in heterogenous oxidation catalysis has evoked a lively
discussion over the recent years. On the more noble transition metals (like Pd,
Pt or Ag) the low stability of the common bulk oxides suggests primarily
sub-nanometer thin oxide films, so-called surface oxides, as potential
candidates that may be stabilized under gas phase conditions representative of
technological oxidation catalysis. We address this issue for the Pd(100) model
catalyst surface with first-principles kinetic Monte Carlo (kMC) simulations
that assess the stability of the well-characterized (sqrt{5} x sqrt{5})R27
surface oxide during steady-state CO oxidation. Our results show that at
ambient pressure conditions the surface oxide is stabilized at the surface up
to CO:O2 partial pressure ratios just around the catalytically most relevant
stoichiometric feeds (p(CO):p(O2) = 2:1). The precise value depends sensitively
on temperature, so that both local pressure and temperature fluctuations may
induce a continuous formation and decomposition of oxidic phases during
steady-state operation under ambient stoichiometric conditions.Comment: 13 pages including 5 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
The Levantine Basin - crustal structure and origin
The origin of the Levantine Basin in the Southeastern Mediterranean Sea is related to the opening of the Neo-Tethys. The nature of its crust has been debated for decades. Therefore, we conducted a geophysical experiment in the Levantine Basin. We recorded two refraction seismic lines with 19 and 20 ocean bottom hydrophones, respectively, and developed velocity models. Additional seismic reflection data yield structural information about the upper layers in the first few kilometers. The crystalline basement in the Levantine Basin consists of two layers with a P-wave velocity of 6.06.4 km/s in the upper and 6.56.9 km/s in the lower crust. Towards the center of the basin, the Moho depth decreases from 27 to 22 km. Local variations of the velocity gradient can be attributed to previously postulated shear zones like the Pelusium Line, the DamiettaLatakia Line and the BaltimHecateus Line. Both layers of the crystalline crust are continuous and no indication for a transition from continental to oceanic crust is observed. These results are confirmed by gravity data. Comparison with other seismic refraction studies in prolongation of our profiles under Israel and Jordan and in the Mediterranean Sea near Greece and Sardinia reveal similarities between the crust in the Levantine Basin and thinned continental crust, which is found in that region. The presence of thinned continental crust under the Levantine Basin is therefore suggested. A β-factor of 2.33 is estimated. Based on these findings, we conclude that sea-floor spreading in the Eastern Mediterranean Sea only occurred north of the Eratosthenes Seamount, and the oceanic crust was later subducted at the Cyprus Arc
Analysis of a four-mirror cavity enhanced Michelson interferometer
We investigate the shot noise limited sensitivity of a four-mirror cavity
enhanced Michelson interferometer. The intention of this interferometer
topology is the reduction of thermal lensing and the impact of the
interferometers contrast although transmissive optics are used with high
circulating powers. The analytical expressions describing the light fields and
the frequency response are derived. Although the parameter space has 11
dimensions, a detailed analysis of the resonance feature gives boundary
conditions allowing systematic parameter studies
Avalanche Size Scaling in Sheared Three-Dimensional Amorphous Solid
We have studied the statistics of plastic rearrangement events in a simulated
amorphous solid at T=0. Events are characterized by the energy release and the
``slip volume'', the product of plastic strain and system volume. Their
distributions for a given system size appear to be exponential, but a
characteristic event size cannot be inferred, because the mean values of these
quantities increase as with . In contrast to
results obtained in 2D models, we do not see simply connected avalanches. The
exponent suggests a fractal shape of the avalanches, which is also evidenced by
the mean fractal dimension and participation ratio.Comment: Accepted for publication in Physical Review Letter
Normal origamis of Mumford curves
An origami (also known as square-tiled surface) is a Riemann surface covering
a torus with at most one branch point. Lifting two generators of the
fundamental group of the punctured torus decomposes the surface into finitely
many unit squares. By varying the complex structure of the torus one obtains
easily accessible examples of Teichm\"uller curves in the moduli space of
Riemann surfaces. The p-adic analogues of Riemann surfaces are Mumford curves.
A p-adic origami is defined as a covering of Mumford curves with at most one
branch point, where the bottom curve has genus one. A classification of all
normal non-trivial p-adic origamis is presented and used to calculate some
invariants. These can be used to describe p-adic origamis in terms of glueing
squares.Comment: 21 pages, to appear in manuscripta mathematica (Springer
Загрязнение мирового океана
Проблема загрязнения Мирового океана - одна из самых важных и актуальных. Возможно ли решить её в современных условиях. Океан, как известно, - это основа всего живого на нашей планете. Ведь именно в нём появились первые живые организмы в нашей геологической истории. Мировой океан занимает больше 70% поверхности планеты. Кроме того, в нём содержится около 95% всей воды. Вот почему загрязнение вод Мирового океана настолько опасно для географической оболочки планеты. И сегодня эта проблема всё более обостряется.The problem of ocean pollution is one of the most important and relevant. Is it possible to solve it in modern conditions? The ocean, as you know, is the basis of all life on our planet. After all, it appeared the first living organisms in our geological history. Oceans occupy more than 70% of the planet's surface. In addition, it contains about 95% of all water. That's why the pollution of the waters of the World ocean is so dangerous to the geographical envelope of the planet. And today this problem is becoming more acute
Nonequilibrium theory of Coulomb blockade in open quantum dots
We develop a non-equilibrium theory to describe weak Coulomb blockade effects
in open quantum dots. Working within the bosonized description of electrons in
the point contacts, we expose deficiencies in earlier applications of this
method, and address them using a 1/N expansion in the inverse number of
channels. At leading order this yields the self-consistent potential for the
charging interaction. Coulomb blockade effects arise as quantum corrections to
transport at the next order. Our approach unifies the phase functional and
bosonization approaches to the problem, as well as providing a simple picture
for the conductance corrections in terms of renormalization of the dot's
elastic scattering matrix, which is obtained also by elementary perturbation
theory. For the case of ideal contacts, a symmetry argument immediately allows
us to conclude that interactions give no signature in the averaged conductance.
Non-equilibrium applications to the pumped current in a quantum pump are worked
out in detail.Comment: Published versio
TransCom N2O model inter-comparison - Part 2:Atmospheric inversion estimates of N2O emissions
This study examines N2O emission estimates from five different atmospheric inversion frameworks based on chemistry transport models (CTMs). The five frameworks differ in the choice of CTM, meteorological data, prior uncertainties and inversion method but use the same prior emissions and observation data set. The posterior modelled atmospheric N2O mole fractions are compared to observations to assess the performance of the inversions and to help diagnose problems in the modelled transport. Additionally, the mean emissions for 2006 to 2008 are compared in terms of the spatial distribution and seasonality. Overall, there is a good agreement among the inversions for the mean global total emission, which ranges from 16.1 to 18.7 TgN yr(-1) and is consistent with previous estimates. Ocean emissions represent between 31 and 38% of the global total compared to widely varying previous estimates of 24 to 38%. Emissions from the northern mid- to high latitudes are likely to be more important, with a consistent shift in emissions from the tropics and subtropics to the mid- to high latitudes in the Northern Hemisphere; the emission ratio for 0-30A degrees N to 30-90A degrees N ranges from 1.5 to 1.9 compared with 2.9 to 3.0 in previous estimates. The largest discrepancies across inversions are seen for the regions of South and East Asia and for tropical and South America owing to the poor observational constraint for these areas and to considerable differences in the modelled transport, especially inter-hemispheric exchange rates and tropical convective mixing. Estimates of the seasonal cycle in N2O emissions are also sensitive to errors in modelled stratosphere-to-troposphere transport in the tropics and southern extratropics. Overall, the results show a convergence in the global and regional emissions compared to previous independent studies
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