51 research outputs found
Brain neurons as quantum computers: {\it in vivo} support of background physics
The question: whether quantum coherent states can sustain decoherence,
heating and dissipation over time scales comparable to the dynamical timescales
of the brain neurons, is actively discussed in the last years. Positive answer
on this question is crucial, in particular, for consideration of brain neurons
as quantum computers. This discussion was mainly based on theoretical
arguments. In present paper nonlinear statistical properties of the Ventral
Tegmental Area (VTA) of genetically depressive limbic brain are studied {\it in
vivo} on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in
generation of pleasure and in development of psychological drug addiction. We
found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal
properties for interspike frequencies on the scales where healthy VTA
dopaminergic neurons exhibit bursting activity. For high moments the observed
multifractal (generalized dimensions) spectrum coincides with the generalized
dimensions spectrum calculated for a spectral measure of a {\it quantum} system
(so-called kicked Harper model, actively used as a model of quantum chaos).
This observation can be considered as a first experimental ({\it in vivo})
indication in the favour of the quantum (at least partially) nature of the
brain neurons activity
Chaos from turbulence: stochastic-chaotic equilibrium in turbulent convection at high Rayleigh numbers
It is shown that correlation function of the mean wind velocity generated by
a turbulent thermal convection (Rayleigh number ) exhibits
exponential decay with a very long correlation time, while corresponding
largest Lyapunov exponent is certainly positive. These results together with
the reconstructed phase portrait indicate presence of chaotic component in the
examined mean wind. Telegraph approximation is also used to study relative
contribution of the chaotic and stochastic components to the mean wind
fluctuations and an equilibrium between these components has been studied in
detail
Components of multifractality in high-frequency stock returns
We analyzed multifractal properties of 5-minute stock returns from a period
of over two years for 100 highly capitalized American companies. The two
sources: fat-tailed probability distributions and nonlinear temporal
correlations, vitally contribute to the observed multifractal dynamics of the
returns. For majority of the companies the temporal correlations constitute a
much more significant related factor, however.Comment: to appear in Physica
Fluctuations of temperature gradients in turbulent thermal convection
Broad theoretical arguments are proposed to show, formally, that the
magnitude G of the temperature gradients in turbulent thermal convection at
high Rayleigh numbers obeys the same advection-diffusion equation that governs
the temperature fluctuation T, except that the velocity field in the new
equation is substantially smoothed. This smoothed field leads to a -1 scaling
of the spectrum of G in the same range of scales for which the spectral
exponent of T lies between -7/5 and -5/3. This result is confirmed by
measurements in a confined container with cryogenic helium gas as the working
fluid for Rayleigh number Ra=1.5x10^{11}. Also confirmed is the logarithmic
form of the autocorrelation function of G. The anomalous scaling of
dissipation-like quantities of T and G are identical in the inertial range,
showing that the analogy between the two fields is quite deep
Multiscaling of galactic cosmic ray flux
Multiscaling analysis of differential flux dissipation rate of galactic
cosmic rays (Carbon nuclei) is performed in the energy ranges: 56.3-73.4
Mev/nucleon and 183.1-198.7 MeV/nucleon, using the data collected by ACE/CRIS
spacecraft instrument for 2000 year. The analysis reveals strong
(turbulence-like) intermittency of the flux dissipation rate for the short-term
intervals: 1-30 hours. It is also found that type of the intermittency can be
different in different energy ranges
Critical Fluctuation of Wind Reversals in Convective Turbulence
The irregular reversals of wind direction in convective turbulence are found
to have fluctuating intervals that can be related to critical behavior. It is
shown that the net magnetization of a 2D Ising lattice of finite size
fluctuates in the same way. Detrended fluctuation analysis of the wind reversal
time series results in a scaling behavior that agrees with that of the Ising
problem. The properties found suggest that the wind reversal phenomenon
exhibits signs of self-organized criticality.Comment: 4 RevTeX pages + 3 figures in ep
Multifractality in the stock market: price increments versus waiting times
By applying the multifractal detrended fluctuation analysis to the
high-frequency tick-by-tick data from Deutsche B\"orse both in the price and in
the time domains, we investigate multifractal properties of the time series of
logarithmic price increments and inter-trade intervals of time. We show that
both quantities reveal multiscaling and that this result holds across different
stocks. The origin of the multifractal character of the corresponding dynamics
is, among others, the long-range correlations in price increments and in
inter-trade time intervals as well as the non-Gaussian distributions of the
fluctuations. Since the transaction-to-transaction price increments do not
strongly depend on or are almost independent of the inter-trade waiting times,
both can be sources of the observed multifractal behaviour of the fixed-delay
returns and volatility. The results presented also allow one to evaluate the
applicability of the Multifractal Model of Asset Returns in the case of
tick-by-tick data.Comment: Physica A, in prin
Directed Fixed Energy Sandpile Model
We numerically study the directed version of the fixed energy sandpile. On a
closed square lattice, the dynamical evolution of a fixed density of sand
grains is studied. The activity of the system shows a continuous phase
transition around a critical density. While the deterministic version has the
set of nontrivial exponents, the stochastic model is characterized by mean
field like exponents.Comment: 5 pages, 6 figures, to be published in Phys. Rev.
Intermittency and the passive nature of the magnitude of the magnetic field
It is shown that the statistical properties of the magnitude of the magnetic
field in turbulent electrically conducting media resemble, in the inertial
range, those of passive scalars in fully developed three-dimensional fluid
turbulence. This conclusion, suggested by the data from Advanced Composition
Explorer, is supported by a brief analysis of the appropriate
magnetohydrodynamic equations
Beyond scaling and locality in turbulence
An analytic perturbation theory is suggested in order to find finite-size
corrections to the scaling power laws. In the frame of this theory it is shown
that the first order finite-size correction to the scaling power laws has
following form , where
is a finite-size scale (in particular for turbulence, it can be the Kolmogorov
dissipation scale). Using data of laboratory experiments and numerical
simulations it is shown shown that a degenerate case with can
describe turbulence statistics in the near-dissipation range , where
the ordinary (power-law) scaling does not apply. For moderate Reynolds numbers
the degenerate scaling range covers almost the entire range of scales of
velocity structure functions (the log-corrections apply to finite Reynolds
number). Interplay between local and non-local regimes has been considered as a
possible hydrodynamic mechanism providing the basis for the degenerate scaling
of structure functions and extended self-similarity. These results have been
also expanded on passive scalar mixing in turbulence. Overlapping phenomenon
between local and non-local regimes and a relation between position of maximum
of the generalized energy input rate and the actual crossover scale between
these regimes are briefly discussed.Comment: extended versio
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