47,426 research outputs found
Comment on: "Estimating the Hartree-Fock limit from finite basis set calculations" [Jensen F (2005) Theor Chem Acc 113:267]
We demonstrate that a minor modification of the extrapolation proposed by
Jensen [(2005): Theor Chem Acc 113:267] yields very reliable estimates of the
Hartree-Fock limit in conjunction with correlation consistent basis sets.
Specifically, a two-point extrapolation of the form
yields HF limits
with an RMS error of 0.1 millihartree using aug-cc-pVQZ and
aug-cc-pV5Z basis sets, and of 0.01 millihartree using aug-cc-pV5Z and
aug-cc-pV6Z basis sets.Comment: Theoretical Chemistry Accounts, in pres
Inverse Statistics in the Foreign Exchange Market
We investigate intra-day foreign exchange (FX) time series using the inverse
statistic analysis developed in [1,2]. Specifically, we study the time-averaged
distributions of waiting times needed to obtain a certain increase (decrease)
in the price of an investment. The analysis is performed for the Deutsch
mark (DM) against the US. With high statistical
significance, the presence of "resonance peaks" in the waiting time
distributions is established. Such peaks are a consequence of the trading
habits of the markets participants as they are not present in the corresponding
tick (business) waiting time distributions. Furthermore, a new {\em stylized
fact}, is observed for the waiting time distribution in the form of a power law
Pdf. This result is achieved by rescaling of the physical waiting time by the
corresponding tick time thereby partially removing scale dependent features of
the market activity.Comment: 8 pages. Accepted Physica
Dimensional reduction in a model with infinitely many absorbing states
Using Monte Carlo method we study a two-dimensional model with infinitely
many absorbing states. Our estimation of the critical exponent beta=0.273(5)
suggests that the model belongs to the (1+1) rather than (2+1)
directed-percolation universality class. We also show that for a large class of
absorbing states the dynamic Monte Carlo method leads to spurious dynamical
transitions.Comment: 6 pages, 4 figures, Phys.Rev. E, Dec. 199
Secondary electron emission characteristics of molybdenum-masked, ion-textured OFHC copper
A method for producing a uniform, highly textured surface on oxygen-free, high conductivity (OFHC) copper by ion bombardment using sputtered molybdenum as a texture-inducing masking film was developed and used to provide samples for study. The purpose was to develop a basically OFHC copper surface having very low secondary electron emission characteristics. Surfaces having low secondary electron emission are a requirement for the electrodes of very high efficiency multistage depressed collectors (MDC's). Such MDC's are used in microwave amplifier traveling wave tubes for space communications and other applications. OFHC copper is the material most commonly used for MDC electrodes because it has high thermal conductivity, it is easy to machine, and its fabrication and brazing procedures are well established. However, its untreated surface displays relatively very high levels of secondary electron emissions. Textured OFHC copper samples were tested for true secondary electron emission and relative reflected primary electron yield at primary electron beam energy levels from 200 to 2000 eV and at direct (0 deg) to oblique (60 deg) beam impingement angles. The test results for three of the samples, each of which was processed in a slightly different way, are compared with each other and with test results for a machined OFHC copper sample. Although the textured samples are not represented here as having been processed optimally, their measured secondary electron emission characteristics are significantly lower than those of the untreated OFHC copper sample over the range of conditions studied. Importantly, the relative reflected primary electron yield of one of the textured samples is conspicuously lower than that of the others. Clearly, with further development, the molybdenum-masked ion-textured OFHC copper surface will be a promising material for high-efficiency MDC electrodes
Low-density series expansions for directed percolation III. Some two-dimensional lattices
We use very efficient algorithms to calculate low-density series for bond and
site percolation on the directed triangular, honeycomb, kagom\'e, and
lattices. Analysis of the series yields accurate estimates of the critical
point and various critical exponents. The exponent estimates differ only
in the digit, thus providing strong numerical evidence for the
expected universality of the critical exponents for directed percolation
problems. In addition we also study the non-physical singularities of the
series.Comment: 20 pages, 8 figure
One Dimensional Nonequilibrium Kinetic Ising Models with Branching Annihilating Random Walk
Nonequilibrium kinetic Ising models evolving under the competing effect of
spin flips at zero temperature and nearest neighbour spin exchanges at
are investigated numerically from the point of view of a phase
transition. Branching annihilating random walk of the ferromagnetic domain
boundaries determines the steady state of the system for a range of parameters
of the model. Critical exponents obtained by simulation are found to agree,
within error, with those in Grassberger's cellular automata.Comment: 10 pages, Latex, figures upon request, SZFKI 05/9
Universality of three-body systems in 2D: parametrization of the bound states energies
Universal properties of mass-imbalanced three-body systems in 2D are studied
using zero-range interactions in momentum space. The dependence of the
three-particle binding energy on the parameters (masses and two-body energies)
is highly non-trivial even in the simplest case of two identical particles and
a distinct one. This dependence is parametrized for ground and excited states
in terms of {\itshape supercircles} functions in the most general case of three
distinguishable particles.Comment: 3 pages, 1 figure, published versio
Scattering into Cones and Flux across Surfaces in Quantum Mechanics: a Pathwise Probabilistic Approach
We show how the scattering-into-cones and flux-across-surfaces theorems in
Quantum Mechanics have very intuitive pathwise probabilistic versions based on
some results by Carlen about large time behaviour of paths of Nelson
diffusions. The quantum mechanical results can be then recovered by taking
expectations in our pathwise statements.Comment: To appear in Journal of Mathematical Physic
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