arXiv subjects

Christian Beck

Publications and source records attributed to Christian Beck.

At least 109 records · Page 6Linked to original sources

arXiv2011

Dynamical modelling of superstatistical complex systems

We show how to construct the optimum superstatistical dynamical model for a given experimentally measured time series. For this purpose we generalise the superstatistics concept and study a Langevin equation with a memory kernel whose parameters fluctuate on a large time scale. It is shown how to construct a synthetic dynamical model with the same invariant density and correlation function as the experimental data. As a main example we apply our method to velocity time series measured in high-Reynolds number turbulent Taylor-Couette flow, but the method can be applied to many other complex systems in a similar way.

cond-mat.stat-mech↗

arXiv2010

Skewed superstatistical distributions from a Langevin and Fokker-Planck approach

The superstatistics concept is a useful statistical method to describe inhomogeneous complex systems for which a system parameter $β$ fluctuates on a large spatio-temporal scale. In this paper we analyze a measured time series of wind speed fluctuations and extract the superstatistical distribution function $f(β)$ directly from the data. We construct suitable Langevin and Fokker-Planck models with a position dependent $β$-field and show that they reduce to standard type of superstatistics in the overdamped limit.

cond-mat.stat-mech↗

arXiv2010

Multifractal information production of the human genome

We determine the Renyi entropies K_q of symbol sequences generated by human chromosomes. These exhibit nontrivial behaviour as a function of the scanning parameter q. In the thermodynamic formalism, there are phase transition-like phenomena close to the q=1 region. We develop a theoretical model for this based on the superposition of two multifractal sets, which can be associated with the different statistical properties of coding and non-coding DNA sequences. This model is in good agreement with the human chromosome data.

cond-mat.stat-mech↗

arXiv2010

Generalized statistical mechanics for superstatistical systems

Mesoscopic systems in a slowly fluctuating environment are often well described by superstatistical models. We develop a generalized statistical mechanics formalism for superstatistical systems, by mapping the superstatistical complex system onto a system of ordinary statistical mechanics with modified energy levels. We also briefly review recent examples of applications of the superstatistics concept for three very different subject areas, namely train delay statistics, turbulent tracer dynamics, and cancer survival statistics.

cond-mat.stat-mech↗

arXiv2009

Superstatistical fluctuations in time series: Applications to share-price dynamics and turbulence

We report a general technique to study a given experimental time series with superstatistics. Crucial for the applicability of the superstatistics concept is the existence of a parameter $β$ that fluctuates on a large time scale as compared to the other time scales of the complex system under consideration. The proposed method extracts the main superstatistical parameters out of a given data set and examines the validity of the superstatistical model assumptions. We test the method thoroughly with surrogate data sets. Then the applicability of the superstatistical approach is illustrated using real experimental data. We study two examples, velocity time series measured in turbulent Taylor-Couette flows and time series of log returns of the closing prices of some stock market indices.

physics.data-an↗

arXiv2009

Comment on ``Proposed central limit behavior in deterministic dynamical systems''

In a recent Brief Report [Phys. Rev. E 79 (2009) 057201], Grassberger re-investigates probability densities of sums of iterates of the logistic map near the critical point and claims that his simulation results are inconsistent with previous results obtained by us [U. Tirnakli et al., Phys. Rev. E 75 (2007) 040106(R) and Phys Rev. E 79 (2009) 056209]. In this comment we point out several errors in Grassberger's paper. We clarify that Grassberger's numerical simulations were mainly performed in a parameter region that was explicitly excluded in our 2009 paper and that his number of iterations is insufficient for the region chosen. We also show that, contrary to what is claimed by the author, (i) Levy distributions are irrelevant for this problem, and that (ii) the probability distributions of sums that focus on transients are unlikely to be universal.

cond-mat.stat-mech↗

arXiv2009

Recent developments in superstatistics

We provide an overview on superstatistical techniques applied to complex systems with time scale separation. Three examples of recent applications are dealt with in somewhat more detail: the statistics of small-scale velocity differences in Lagrangian turbulence experiments, train delay statistics on the British rail network, and survival statistics of cancer patients once diagnosed with cancer. These examples correspond to three different universality classes: Lognormal superstatistics, chi-square superstatistics and inverse chi-square superstatistics.

cond-mat.stat-mech↗

arXiv2009

Generalized information and entropy measures in physics

The formalism of statistical mechanics can be generalized by starting from more general measures of information than the Shannon entropy and maximizing those subject to suitable constraints. We discuss some of the most important examples of information measures that are useful for the description of complex systems. Examples treated are the Renyi entropy, Tsallis entropy, Abe entropy, Kaniadakis entropy, Sharma-Mittal entropies, and a few more. Important concepts such as the axiomatic foundations, composability and Lesche stability of information measures are briefly discussed. Potential applications in physics include complex systems with long-range interactions and metastable states, scattering processes in particle physics, hydrodynamic turbulence, defect turbulence, optical lattices, and quite generally driven nonequilibrium systems with fluctuations of temperature.

cond-mat.stat-mech↗

arXiv2009

Superstatistics in high energy physics: Application to cosmic ray energy spectra and e+e- annihilation

We work out a superstatistical description of high-energy scattering processes that takes into account temperature fluctuations in small volume elements. For Gamma-distributed fluctuations of the inverse temperature one effectively obtains formulas similar to those used in nonextensive statistical mechanics, whereas for other temperature distributions more general superstatistical models arise. We consider two main examples: Scattering processes of cosmic ray particles and e+e- annihilation processes. In both cases one obtains excellent fits of experimentally measured energy spectra and cross sections.

hep-ph↗

arXiv2008

A closer look at time averages of the logistic map at the edge of chaos

The probability distribution of sums of iterates of the logistic map at the edge of chaos has been recently shown [see U. Tirnakli, C. Beck and C. Tsallis, Phys. Rev. E 75, 040106(R) (2007)] to be numerically consistent with a q-Gaussian, the distribution which, under appropriate constraints, maximizes the nonadditive entropy S_q, the basis of nonextensive statistical mechanics. This analysis was based on a study of the tails of the distribution. We now check the entire distribution, in particular its central part. This is important in view of a recent q-generalization of the Central Limit Theorem, which states that for certain classes of strongly correlated random variables the rescaled sum approaches a q-Gaussian limit distribution. We numerically investigate for the logistic map with a parameter in a small vicinity of the critical point under which conditions there is convergence to a q-Gaussian both in the central region and in the tail region, and find a scaling law involving the Feigenbaum constant delta. Our results are consistent with a large number of already available analytical and numerical evidences that the edge of chaos is well described in terms of the entropy S_q and its associated concepts.

cond-mat.stat-mech↗

arXiv2008

Superstatistical distributions from a maximum entropy principle

We deal with a generalized statistical description of nonequilibrium complex systems based on least biased distributions given some prior information. A maximum entropy principle is introduced that allows for the determination of the distribution of the fluctuating intensive parameter $β$ of a superstatistical system, given certain constraints on the complex system under consideration. We apply the theory to three examples: The superstatistical quantum mechanical harmonic oscillator, the superstatistical classical ideal gas, and velocity time series as measured in a turbulent Taylor-Couette flow.

cond-mat.stat-mech↗

arXiv2008

Axiomatic approach to the cosmological constant

A theory of the cosmological constant Lambda is currently out of reach. Still, one can start from a set of axioms that describe the most desirable properties a cosmological constant should have. This can be seen in certain analogy to the Khinchin axioms in information theory, which fix the most desirable properties an information measure should have and that ultimately lead to the Shannon entropy as the fundamental information measure on which statistical mechanics is based. Here we formulate a set of axioms for the cosmological constant in close analogy to the Khinchin axioms, formally replacing the dependency of the information measure on probabilities of events by a dependency of the cosmological constant on the fundamental constants of nature. Evaluating this set of axioms one finally arrives at a formula for the cosmological constant that is given by Lambda = (G^2/hbar^4) (m_e/alpha_el)^6, where G is the gravitational constant, m_e is the electron mass, and alpha_el is the low energy limit of the fine structure constant. This formula is in perfect agreement with current WMAP data. Our approach gives physical meaning to the Eddington-Dirac large number hypothesis and suggests that the observed value of the cosmological constant is not at all unnatural.

gr-qc↗

arXiv2008

Scaling properties of invariant densities of coupled Tchebyscheff maps

We study 1-dimensional coupled map lattices consisting of diffusively coupled Tchebyscheff maps of N-th order. For small coupling constants a we determine the invariant 1-point and 2-point densities of these nonhyperbolic systems in a perturbative way. For arbitrarily small couplings a>0 the densities exhibit a selfsimilar cascade of patterns, which we analyse in detail. We prove that there are log-periodic oscillations of the density both in phase space as well as in parameter space. We show that expectations of arbitrary observables scale with \sqrt{a} in the low-coupling limit, contrasting the case of hyperbolic maps where one has scaling with a. Moreover we prove that there are log-periodic oscillations of period \log N^2 modulating the \sqrt{a}-dependence of the expectation value of any given observable.

nlin.CD↗

arXiv2008

The dark energy scale in superconductors: Innovative theoretical and experimental concepts

We revisit the cosmological constant problem using the viewpoint that the observed value of dark energy density in the universe actually represents a rather natural value arising as the geometric mean of two vacuum energy densities, one being extremely large and the other one being extremely small. The corresponding mean energy scale is the Planck-Einstein scale l_PE = (l_P l_E)^1/2 = (hbar G/ c^3 Lambda)^1/4 ~ 0.037 mm, a natural scale both for dark energy and the physics of superconductors. We deal with the statistics of quantum fluctuations underlying dark energy in superconductors and consider a scale transformation from the Planck scale to the Planck-Einstein scale which leaves the quantum physics invariant. Our approach unifies various experimentally confirmed or conjectured effects in superconductors into a common framework: Cutoff of vacuum fluctuation spectra, formation of Tao balls, anomalous gravitomagnetic fields, non-classical inertia, and time uncertainties in radioactive superconductors. We propose several new experiments which may further elucidate the role of the Planck-Einstein scale in superconductors.

gr-qc↗

arXiv2008

Discrete symmetries of chaotic strings

Chaotic strings are particular classes of coupled map lattices that can serve as models for vacuum fluctuations in stochastically quantized field theories. They have been previously shown to distinguish standard model coupling parameters as corresponding to states of strongest possible chaotic behaviour and vanishing nearest-neighbour correlation. In this paper we look at discrete symmetry transformations for chaotic strings. We show that several of the chaotic string dynamics can be transformed into each other by simple discrete coordinate transformations. We investigate how expectation values converge in the various coupling parameter regions and single out those stable zeros of the correlation function that correspond to ergodic states with well-defined convergence properties.

nlin.CD↗

arXiv2008

Chaotic quantization and the mass spectrum of fermions

In order to understand the parameters of the standard model of electroweak and strong interactions, one needs to embed the standard model into some larger theory that accounts for the observed values. This means some additional sector is needed that fixes and stabilizes the values of the fundamental constants of nature. We describe how such a sector can be constructed using the so-called chaotic quantization method applied to a system of coupled map lattices. We restrict ourselves in this short note on verifying how our model correctly yields the numerical values of Yukawa and gravitational coupling constants of a collection of heavy and light fermions using a simple principle, the local minimization of vacuum energy.

hep-th↗

arXiv2007

A superstatistical model of metastasis and cancer survival

We introduce a superstatistical model for the progression statistics of malignant cancer cells. The metastatic cascade is modeled as a complex nonequilibrium system with several macroscopic pathways and inverse-chi-square distributed parameters of the underlying Poisson processes. The predictions of the model are in excellent agreement with observed survival time probability distributions of breast cancer patients.

physics.med-ph↗

arXiv2007

Correlations in superstatistical systems

We review some of the properties of higher-dimensional superstatistical stochastic models. As an example, we analyse the stochastic properties of a superstatistical model of 3-dimensional Lagrangian turbulence, and compare with experimental data. Excellent agreement is obtained for various measured quantities, such as acceleration probability densities, Lagrangian scaling exponents, correlations between acceleration components, and time decay of correlations. We comment on how to proceed from superstatistics to a thermodynamic description.

cond-mat.stat-mech↗