We discuss the situations under which Brownian yet non-Gaussian (BnG) diffusion can be observed in the model of a particle's motion in a random landscape of diffusion coefficients slowly varying in ...space (quenched disorder). Our conclusion is that such behavior is extremely unlikely in the situations when the particles, introduced into the system at random at t = 0, are observed from the preparation of the system on. However, it indeed may arise in the case when the diffusion (as described in Ito interpretation) is observed under equilibrated conditions. This paradigmatic situation can be translated into the model of the diffusion coefficient fluctuating in time along a trajectory, i.e. into a kind of the 'diffusing diffusivity' model.
In this work, the short-time dynamics of simple liquid is explored both analytically and numerically with the focus on the interplay between the density fluctuations in a volume surrounding a chosen ...particle and its random walk motion. The particles interact via the Lennard-Jones potential with parameters corresponding to liquid argon. For large times, analytical calculations based on the fluctuation theory provides an explicit expression reproducing isothermal change of the self-diffusion coefficient in liquid argon corresponding to the experimental data. These results lead to the conclusion that such behavior is based on the reduced mobility of particles reflected in their density fluctuations that can be equivalently achieved in the cases of either low temperatures and pressures (supercooling) or moderate temperatures and high pressures (overdamping).
The TAIGA experiment (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) combines heterogeneous arrays of imaging and non-imaging Cherenkov light detectors for registration of ...extensive air showers. Monte Carlo simulation of the whole detector response was carried out and is described in this article.
The relaxation of a dissipative system to its equilibrium state often shows a multiexponential pattern with relaxation rates, which are typically considered to be independent of the initial ...condition. The rates follow from the spectrum of a Hermitian operator obtained by a similarity transformation of the initial Fokker-Planck operator. However, some initial conditions are mapped by this similarity transformation to functions which grow at infinity. These cannot be expanded in terms of the eigenfunctions of a Hermitian operator, and show different relaxation patterns. Considering the exactly solvable examples of Gaussian and generalized Lévy Ornstein-Uhlenbeck processes (OUPs) we show that the relaxation rates belong to the Hermitian spectrum only if the initial condition belongs to the domain of attraction of the stable distribution defining the noise. While for an ordinary OUP initial conditions leading to nonspectral relaxation can be considered exotic, for generalized OUPs driven by Lévy noise, such initial conditions are the rule.
In this work we compare two open source machine learning libraries, PyTorch and TensorFlow, as software platforms for rejecting hadron background events detected by imaging air Cherenkov telescopes ...(IACTs). Monte Carlo simulation for the TAIGA-IACT telescope is used to estimate background rejection quality. A wide variety of neural network algorithms provided by both libraries can easily be tested on various types of data, which is useful for various imaging air Cherenkov experiments. The work is a component of the Astroparticle.online project, which collaborates with the TAIGA and KASCADE experiments and welcomes any astroparticle experiment to join.
Wavelet phase synchronization and chaoticity Postnikov, E B
Physical review. E, Statistical, nonlinear, and soft matter physics,
11/2009, Letnik:
80, Številka:
5 Pt 2
Journal Article
Recenzirano
It has been shown that the so-called "wavelet phase" (or "time-scale") synchronization of chaotic signals is actually synchronization of smoothed functions with reduced chaotic fluctuations. This ...fact is based on the representation of the wavelet transform with the Morlet wavelet as a solution of the Cauchy problem for a simple diffusion equation with initial condition in a form of harmonic function modulated by a given signal. The topological background of the resulting effect is discussed. It is argued that the wavelet phase synchronization provides information about the synchronization of an averaged motion described by bounding tori instead of the fine-level classical chaotic phase synchronization.
In this work, we present a measurement system based on the thin layer of magnetic fluid aimed at scanning either the non-uniform magnetic field distribution applicable for magnetic levitation systems ...(MagLev) or determining small excess gas pressure. The key idea is based on the photo registration of a transparent air-filled cavity formed in a thin magnetic fluid layer due to balancing the gas pressure and the pressure emerging due to magnetic forces. As a result, the contour of the magnetic field lines in 3D space is visible. It is shown that the theoretical analysis and numerical simulations are consistent with experimental results.
The findings of the experimental research of a phased air cavity capture in a flat channel with a magnetic fluid located along the axis of the annular magnet influenced by the changing in sign ...magnetic field are discussed. The research was carried out with four magnetic fluids with the magnetic phase concentrations of 1.93%; 2.70%; 4.34%; 9.08%. The analysis of the obtained results is presented within the framework of the electrodynamic model of “low magnetic bodies” based on the development of the system of isolines of the module of the magnetic field intensity. The provided data, first, clarify the conclusions of the previous interpretation of the air cavity capture with an opaque magnetic fluid column, and second, can be useful to solve practical issues of microhydraulics.
We proposed a method of discrimination between light (p+He) and heavy (C+Fe) groups of primary nuclei. It's based on parametric analysis of lateral distribution of Cherenkov light in the atmosphere ...with approximation by the 'knee-like' fitting function, proposed and studied earlier. Two parameters most sensitive to the depth of shower maximum were revealed and used for analysis of the bulk of experimental data obtained in the TAIGA-HiSCORE experiment in the energy range 300-3000 TeV for various incident angles of particles. It is shown that the method allows estimating the contribution of light and heavy groups of primary nuclei. In the interval 300-3000 TeV we do not see a rapid decrease of the light component flux, as it was seen in the ARGO-YBJ experiment. This result will be refined after a more detailed analysis.
This work is a methodical study of another option of the hybrid method originally aimed at gamma/hadron separation in the TAIGA experiment. In the present paper this technique was performed to ...distinguish between different mass groups of cosmic rays in the energy range 200 TeV - 500 TeV. The study was based on simulation data of TAIGA prototype and included analysis of geometrical form of images produced by different nuclei in the IACT simulation as well as shower core parameters reconstructed using timing array simulation. We show that the hybrid method can be sufficiently effective to precisely distinguish between mass groups of cosmic rays.
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