共查询到20条相似文献,搜索用时 31 毫秒
1.
A. K. Vidybida K. G. Kravchuk 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(2):279-287
A binding neuron (BN) with delayed feedback is considered. The neuron is fed externally with a Poisson stream of intensity λ. The neuron’s output spikes are fed back into its input with time delay Δ. The resulting output stream of the BN is not Poissonian. The main purpose of this paper is to find interspike intervals (ISI) distribution of the output stream. For BN with threshold 2 the exact mathematical expressions as functions of λ, Δ and BN’s internal memory, τ are derived for the ISI distribution and coefficient of variation. For higher thresholds these quantities are found numerically. The distributions found are characterized with jumps, derivative discontinuities and include singularity of Dirac’s δ-function type. The ISI coefficient of variation found is a unimodal function of input intensity, with the maximum value considerably bigger than unity. It is concluded that delayed feedback presence can radically alter neuronal output firing statistics. 相似文献
2.
S.M.S. da Costa M.H.F. Bettega 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):67-71
We report elastic integral, momentum transfer and differential cross sections for electron scattering by N2O for energies up to 50 eV. These results were obtained at the static-exchange approximation with the Schwinger Multichannel
Method with Pseudopotentials [M.H.F. Bettega, L.G. Ferreira and M.A.P. Lima, Phys. Rev. A 47, 1111 (1993)]. In general our results show good agreement with experimental data and with other theoretical results but some
discrepancies are found. We have also found a shape resonance around 4 eV in agreement with previous calculations using the R-matrix Method of Sarpal et al. [J. Phys. B 29, 857 (1996)]. On the other hand, the existence of a resonance at about 13 eV, clearly seen by the Schwinger Variational Iterative Method [Michelin et al., J. Phys. B 29, 2115 (1996)], can not be confirmed by our calculations. At this energy, our cross sections show a broad bump with no clear resonant behavior given by the eigenphase sum.
Received: 13 November 1997 / Revised: 13 March 1998 / Accepted: 9 April 1998 相似文献
3.
J. B. Satinover D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):369-384
Human beings like to believe they are in control of their
destiny. This ubiquitous trait seems to increase motivation and persistence,
and is probably evolutionarily adaptive [J.D. Taylor, S.E. Brown, Psych. Bull. 103, 193 (1988); A. Bandura,
Self-efficacy: the exercise of control (WH Freeman, New
York, 1997)]. But how good really is our
ability to control? How successful is our track record in these areas? There
is little understanding of when and under what circumstances we may
over-estimate [E. Langer, J. Pers. Soc. Psych. 7, 185 (1975)] or even lose our ability to control and optimize outcomes,
especially when they are the result of aggregations of individual
optimization processes. Here, we demonstrate analytically using the theory
of Markov Chains and by numerical simulations in two classes of games, the
Time-Horizon Minority Game [M.L. Hart, P. Jefferies, N.F. Johnson, Phys. A 311, 275 (2002)] and the Parrondo Game
[J.M.R. Parrondo, G.P. Harmer, D. Abbott, Phys. Rev. Lett.
85, 5226 (2000); J.M.R. Parrondo, How to cheat a bad mathematician (ISI, Italy, 1996)], that agents
who optimize their strategy based on past information may actually perform
worse than non-optimizing agents. In other words, low-entropy (more
informative) strategies under-perform high-entropy (or random) strategies.
This provides a precise definition of the “illusion of control” in certain
set-ups a priori defined to emphasize the importance of optimization.
An erratum to this article is available at . 相似文献
4.
Y.-X. Ping B. Zhang Z. Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):175-180
The generation of continuous variable entanglement via
atomic coherence in a two-mode three-level cascade atomic system
is discussed according to the entanglement criterion proposed by
Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)].
Atomic coherence between the top and bottom levels is induced with
two photons of a strong external pump field. It shows that
entanglement for the two-mode field in the cavity can be generated
under certain conditions. Moreover, by means of the input-output
theory, we show that the two-mode entanglement could also be
approached at the output. 相似文献
5.
A. Dıaz-Sánchez L.A. Braunstein R.C. Buceta 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):289-294
The roughening of interfaces moving in inhomogeneous media is investigated by numerical integration of the phenomenological
stochastic differential equation proposed by Kardar, Parisi, and Zhang [Phys. Rev. Lett. 56, 889 (1986)] with quenched noise (QKPZ) [Phys. Rev. Lett. 74, 920 (1995)]. We express the evolution equations for the mean height and the roughness into two contributions: the local
and the lateral one in order to compare them with the local and the lateral contributions obtained for the directed percolation
depinning models (DPD) introduced independently by Tang and Leschhorn [Phys. Rev A 45, R8309 (1992)] and Buldyrev et al. [Phys. Rev A 45, R8313 (1992)]. These models are classified in the same universality class of the QKPZ although the mechanisms of growth
are quite different. In the DPD models the lateral contribution is a coupled effect of the competition between the local growth
and the lateral one. In these models the lateral contribution leads to an increasing of the roughness near the criticality
while in the QKPZ equation this contribution always flattens the roughness.
Received 7 April 2000 and Received in final form 7 March 2001 相似文献
6.
G. Apaydın E. Tıraşoğlu Ö. Söğüt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):487-492
The M X-ray production differential cross sections in Re, Bi and U elements
have been measured at the 5.96 keV incident photon energy in an angular
range 135°–155°. The measurements were performed using a 55Fe
source and a Si(Li) detector. The present results contradict the predictions
of Cooper and Zare [Atomic Collision Processes, Gordon and Breach, New York (1969)]
and experimental results of Kumar et al. [J. Phys. B: At. Mol. Opt. 34,
613 (2001)]. that, after photoionization of inner shells, the vacancy state has equal
population of magnetic substates and the subsequent X-ray emission is
isotropic, but confirm the predictions of the calculations of Flügge et
al. [Phys. Rev. Lett. 29, 7 (1972)] and experimental results of Sharma and Allawadhi [J. Phys. B: At. Mol. Opt. 32, 2343 (1999)] and Ertugrul [Nucl. Instrum. Meth. B 119, 345 (1996)].
Total M X-ray production cross sections from the decay at the 5.96 keV
photon energies are found to be in good agreement with the calculated
theoretical results using the theoretical values of M shell photoionization
cross section. 相似文献
7.
O. Gomes V. M. Mendes D. A. Mendes J. Sousa Ramos 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):195-199
There is by now a large consensus in modern monetary policy. This consensus has
been built upon a dynamic general equilibrium model of optimal monetary policy as
developed by, e.g., Goodfriend and King [NBER Macroeconomics
Annual 1997 edited by B. Bernanke and J. Rotemberg (Cambridge, Mass.: MIT Press, 1997), pp. 231–282],
Clarida et al. [J. Econ. Lit. 37, 1661 (1999)],
Svensson [J. Mon. Econ. 43, 607 (1999)]
and Woodford [Interest and Prices: Foundations of a
Theory of Monetary Policy (Princeton, New Jersey, Princeton University
Press, 2003)].
In this paper we extend the standard optimal monetary policy model by introducing nonlinearity into the Phillips curve.
Under the specific form of nonlinearity proposed in our paper (which allows for convexity and concavity and secures
closed form solutions), we show that the introduction of a nonlinear Phillips curve into the structure of the standard
model in a discrete time and deterministic framework produces radical changes to the major conclusions regarding
stability and the efficiency of monetary policy.
We emphasize the following main results: (i) instead of a unique fixed point we end up with multiple equilibria; (ii) instead
of saddle-path stability, for different sets of parameter values we may have saddle stability, totally unstable
equilibria and chaotic attractors; (iii) for certain degrees of convexity and/or concavity of the Phillips curve, where
endogenous fluctuations arise, one is able to encounter various results that seem intuitively correct. Firstly, when the
Central Bank pays attention essentially to inflation targeting, the inflation rate has a lower mean and
is less volatile; secondly, when the degree of price stickiness is high, the inflation
rate displays a larger mean and higher volatility (but this is sensitive to the values
given to the parameters of the model); and thirdly, the higher the target value of the
output gap chosen by the Central Bank, the higher is the inflation rate and its
volatility. 相似文献
8.
I. M. Herbauts S. Bettelli H. Hübel M. Peev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):395-406
Some MIT researchers [Phys. Rev. A
75, 042327 (2007)] have recently claimed that
their implementation of the Slutsky-Brandt attack [Phys. Rev. A
57, 2383 (1998); Phys. Rev. A 71, 042312 (2005)] to
the BB84 quantum-key-distribution (QKD) protocol puts the security of this
protocol “to the test” by simulating “the most powerful
individual-photon attack” [Phys. Rev. A 73, 012315
(2006)].
A related unfortunate news feature by a
scientific journal [G. Brumfiel, Quantum cryptography is hacked, News @ Nature (april 2007); Nature 447, 372 (2007)]
has spurred some concern in the QKD community and among the general public
by misinterpreting the implications of this work. The present article
proves the existence of a stronger individual attack on QKD protocols with
encrypted error correction, for which tight bounds are shown, and clarifies
why the claims of the news feature incorrectly suggest a contradiction with
the established “old-style” theory of BB84 individual attacks.
The full implementation of a quantum cryptographic protocol includes a
reconciliation and a privacy-amplification stage, whose choice alters in
general both the maximum extractable secret and the optimal eavesdropping
attack. The authors of [Phys. Rev. A
75, 042327 (2007)] are concerned only with the error-free
part of the so-called sifted string, and do not consider faulty bits,
which, in the version of their protocol, are discarded. When using the
provably superior reconciliation approach of encrypted error correction
(instead of error discard), the Slutsky-Brandt attack is no more optimal
and does not “threaten” the security bound derived by Lütkenhaus [Phys. Rev. A 59, 3301 (1999)].
It is shown that the method of Slutsky and collaborators [Phys. Rev. A
57, 2383 (1998)] can
be adapted to reconciliation with error correction, and that the optimal
entangling probe can be explicitly found. Moreover, this attack fills
Lütkenhaus bound, proving that it is tight (a fact which was not
previously known). 相似文献
9.
J. P. Santos F. Parente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):339-350
Total ionization cross sections of neutral phosphorus, arsenic,
antimony, and bismuth atoms by electron impact are reported and
compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some
target atoms used in the experiments were in metastable states close
to the ground state, the excitation-autoionization of nsnp4
excited states may be substantial, and the ions produced in
experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based
on
the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)].
Plane-wave Born cross sections scaled by the method developed by Kim
[Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the
contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections
is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can
be
used to complete data tables needed for plasma or astrophysical
studies. 相似文献
10.
B. Eckhardt S. Grossmann D. Lohse 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):541-544
We interpret measurements of the Reynolds number dependence of the torque in Taylor-Couette flow by Lewis and Swinney [Phys.
Rev. E 59, 5457 (1999)] and of the pressure drop in pipe flow by Smits and Zagarola [Phys. Fluids 10, 1045 (1998)] within the scaling theory of Grossmann and Lohse [J. Fluid Mech. 407, 27 (2000)], developed in the context of thermal convection. The main idea is to split the energy dissipation into contributions
from a boundary layer and the turbulent bulk. This ansatz can account for the observed scaling in both cases if it is assumed
that the internal wind velocity introduced through the rotational or pressure forcing is related to the external (imposed) velocity U, by with and for the Taylor-Couette (U inner cylinder velocity) and pipe flow (U mean flow velocity) case, respectively. In contrast to the Rayleigh-Bénard case the scaling exponents cannot (yet) be derived
from the dynamical equations.
Received 9 September 2000 相似文献
11.
Lines of extrema along isotherms and isobars for the residual isochoric heat capacity, the residual isobaric heat capacity, the isobaric thermal expansivity, and the isothermal compressibility of the Lennard–Jones fluid have been studied from popular equations of state due to Johnson et al. [Mol. Phys. 78, 591 (1993)], Kolafa and Nezbeda [Fluid Phase Equilib. 100, 1 (1994)], and Mecke et al. [Int. J. Thermophys. 17, 391 (1996)]. On depicting such loci in the pressure–temperature plane, the characteristic behaviour of thermodynamic response functions in the ideal-gas limit (at high enough temperatures or low enough pressures), the close-packed-fluid limit (at low enough temperatures or high enough pressures) as well as in the liquid, critical, and supercritical regions is identified. The present analysis is informative itself, but it also stimulates further work in order to tackle more complicated cases of study including associated fluids. 相似文献
12.
J.A. Davies 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):445-447
Over the last five years or so, a number of studies have focussed on the distribution of `success' in physics and other sciences;
in these studies, `success' is measured by the number of times a paper, or an author, is cited. The distribution of citations
of individual papers approximates to a power-law [S. Redner, Eur. Phys. J. B 4, 131 (1998)], while lifetime total citations of the 1120 most-cited physicists follows a stretched exponential [J. Laherrère,
D. Sornette, Eur. Phys. J. B 2, 525 (1998)]. Here, I examine the distribution of success in popular music, a field of creativity that has social structures
very different from those of physics, and which is generally held to be controlled primarily by fashion. For this study, the
lifetime total success of bands was measured by the total number of weeks they were in the weekly `top 75' list of best-selling
recordings. Like the lifetime success of physicists reported by Laherrere and Sornette, the success of the 6107 bands that
appeared in the UK `top 75' from 1950 until 2000 follows a stretched exponential of the form P(x)dx = c(x
c - 1/x
0
c)exp[- (x/x
0)c]dx; for the music data, c = 0.5 and x
0 = 9.37.
Received 23 October 2001 Published online 25 June 2002 相似文献
13.
M. Patriarca E. Heinsalu A. Chakraborti 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(1):145-153
We review the basic kinetic wealth-exchange models of Angle [J. Angle, Social Forces 65, 293 (1986); J. Math. Sociol. 26, 217 (2002)], Bennati [E. Bennati, Rivista Internazionale di Scienze Economiche e Commerciali 35, 735 (1988)], Chakraborti and Chakrabarti [A. Chakraborti, B. K. Chakrabarti, Eur. Phys. J. B 17, 167 (2000)], and of Dragulescu and Yakovenko [A. Dragulescu, V.M. Yakovenko, Eur. Phys. J. B 17, 723 (2000)]. Analytical fitting forms for the equilibrium wealth distributions are proposed. The influence of heterogeneity is investigated, the appearance of the fat tail in the wealth distribution and the relaxation to equilibrium are discussed. A unified reformulation of the models considered is suggested. 相似文献
14.
A. K.F. Haque M. A. Uddin M. A.R. Patoary A. K. Basak M. R. Talukder B. C. Saha K. R. Karim F. B. Malik 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):203-210
The recently modified Kolbenstvedt (MKLV) model [Eur. Phys. J. D 37, 361 (2006)], developed for electron impact ionization (EII) of the K-shell atomic targets, has been extended to generalize
its two parameters in terms of the electronic orbitals nl. The generalized MKLV
(GKLV) with two sets of the species independent parameters for the same nl,
one set for the ionization of inner orbits and another for the outermost orbit, is found
profoundly successful in accounting for the EII cross section data of the K, L and M-shell neutral atoms with atomic numbers
Z = 1-92 for the incident energies up to 1000 MeV
in a consistent manner. 相似文献
15.
A. Banerjee M.K. Harbola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):265-269
Using density based perturbation theory [M.K. Harbola, A. Banerjee, Phys. Lett. A 222, 315 (1996)], we calculate the static hyperpolarizabilty for spherical atoms and ions from their ground-state densities. Since densities are being employed, calculations are performed
using approximate functionals for the kinetic and the exchange-correlation energies. Use of densities - instead of the wavefunctions
or Kohn-Sham orbitals - reduces the computational effort substantially. The results obtained are within of those calculated from the corresponding orbital-based calculations.
Received: 23 June 1997 / Revised: 25 September 1997 / Accepted: 24 December 1997 相似文献
16.
We show that when a three-level laser is excited by Poisson light the lasing remains sub-Poisson, as asserted by H. Ritsch,
M. A. M. Marte, and P. Zoller [Europhys. Lett. 19, 7 (1992)], only if there is no reciprocal action on the exciting laser (weak coupling). In cascade schemes in which each
three-level Λ-laser excites each succeeding Λ-laser with its light, any desired degree of shot-noise suppression can be achieved.
Zh. éksp. Teor. Fiz. 114, 1971–1992 (December 1998) 相似文献
17.
A. Sokolov T. Kieu A. Melatos 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(4):637-642
The gauge theory of arbitrage was introduced by Ilinski in [K. Ilinski, preprint arXiv:hep-th/9710148 (1997)]
and applied to fast money flows in [A. Ilinskaia, K. Ilinski, preprint arXiv:cond-mat/9902044 (1999); K. Ilinski,
Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. The theory of fast money flow dynamics
attempts to model the evolution of currency exchange rates and stock prices on short, e.g. intra-day, time scales.
It has been used to explain some of the heuristic trading rules, known as technical analysis, that are used by professional
traders in the equity and foreign exchange markets. A critique of some of the underlying assumptions of the gauge theory of
arbitrage was presented by Sornette in [D. Sornette, Int. J. Mod. Phys. C 9, 505 (1998)]. In this paper, we present a
critique of the theory of fast money flow dynamics, which was not examined by Sornette. We demonstrate that the choice of
the
input parameters used in [K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]
results in sinusoidal oscillations of the exchange rate, in conflict with the results presented in [K. Ilinski,
Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. We also find that the dynamics
predicted by the theory are generally unstable in most realistic situations, with the exchange rate tending to zero or
infinity exponentially. 相似文献
18.
P. H. Chavanis A. Naso B. Dubrulle 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(2):167-186
Using a Maximum Entropy Production Principle (MEPP), we
derive a new type of relaxation equations for two-dimensional
turbulent flows in the case where a prior vorticity distribution is
prescribed instead of the Casimir constraints [R. Ellis, K. Haven,
B. Turkington, Nonlinearity 15, 239 (2002)]. The particular case of
a Gaussian prior is specifically treated in connection to minimum
enstrophy states and Fofonoff flows. These relaxation equations are
compared with other relaxation equations proposed by Robert and
Sommeria [Phys. Rev. Lett. 69, 2776 (1992)] and Chavanis
[Physica D 237, 1998 (2008)]. They can serve as numerical
algorithms to compute maximum entropy states and
minimum enstrophy states with appropriate constraints. We perform
numerical simulations of these relaxation equations in order to
illustrate geometry induced phase transitions in geophysical flows. 相似文献
19.
D. H. Shi J. F. Sun Y. F. Liu Z. L. Zhu H. Ma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):43-50
Total cross sections of electron scattering by several
sulfur-containing molecules OCS, SO2, SF4, SF6,
SF5CF3, SO2Cl2 and SO2ClF are calculated
at the Hartree-Fork level employing the modified additivity rule
approach. The modified additivity rule approach, which was
proposed by Shi et al. [Eur. Phys. J. D 45, 253 (2007);
Nucl. Instrum. Meth. B 254, 205 (2007)], takes into
consideration that the contributions of the geometric shielding
effect vary as the energy of incident electrons, the target’s
molecular dimension and the atomic and electronic numbers in the
molecule. The present investigations cover the impact energies
ranging from 30 to 5000 eV. The quantitative total cross sections
are compared with those obtained by experiments and other
theories. Good agreement is observed even at energies of several
tens of eV. It shows that the modified additivity rule approach is
applicable to carry out the total cross section calculations of
electron scattering by these sulfur-containing molecules at
intermediate and high energies, especially over the energy range
above 100 eV or so. In the present calculations, the atoms are
still represented by the spherical complex optical potential,
which is composed of static, exchange, polarization and absorption
terms. 相似文献
20.
F. Thibault D. Cappelletti F. Pirani G. Blanquet M. Bartolomei 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):337-344
Integral cross sections and pressure broadening coefficients have been
measured for the acetylene — neon system by a molecular beam
scattering technique and by high infrared resolution spectroscopy,
respectively. We have performed quantal calculations using an ab-initio
potential energy surface (PES) [J. Chem. Phys. 109,
8968 (1998)]. Results are found to be in good agreement with both
measured integral cross sections and pressure broadening coefficients
for the two temperatures investigated (173 and 298 K). We have also
derived a semi-empirical PES parameterized using an atom-bond pairwise
additive scheme. This PES shows an isotropic component in agreement
with the ab-initio calculation, reproduces the scattering data but it
only leads to a reasonable agreement for the pressure broadening
coefficients. 相似文献