arXiv subjects
Publications and source records attributed to Vladimir Yurovsky.
Nowadays, the calculation of the Galactic Cosmic Rays diffusion coefficient with direct microscopic numerical simulations is a widespread approach. In this work, we investigated the numerical limits for such calculations and demonstrated that modern computations are affected by the influence of numerical errors. We found that velocity errors have a greater impact on the result than spatial ones.
At present, there is no consensus on whether the spectral break in the cosmic-ray flux of all elements around 4 PeV is a general characteristic of the Milky Way or is determined by a combination of factors that significantly affect the energy position of the knee. We argue that considering the anisotropic propagation of cosmic rays within a realistically modeled Galactic magnetic field enables an accurate description of the spectral break without invoking a source-related cutoff energy, and naturally predicts a spatial dependence of this phenomenon. To demonstrate this, we constructed a 3D diffusion propagation model with a diffusion tensor within a two-component magnetic field and determined both the local cosmic-ray spectrum and the spectra for specific regions of the Milky Way. We found that the spectral break is well reproduced by the energy dependence of the diffusion tensor components and appears at different energies in various regions of the Galaxy due to the inclusion of the turbulent component of the magnetic field. Furthermore, the spectral slope is determined by the degree of anisotropy in cosmic-ray diffusion. The model is based on the calculation of the diffusion tensor components using the trajectory method and on the direct solution of the stationary diffusion equation with a fully anisotropic diffusion tensor that includes all nine components in the global Galactic coordinate system, accounting for off-diagonal terms arising from the projection of locally field-aligned diffusion. We calculated the integral flux of diffuse gamma rays in the inner and outer regions of the Galaxy based on the cosmic-ray proton and nuclei spectra obtained within our model, which features a spatially dependent position of the knee. The resulting spectral shape of the diffuse gamma-ray flux is consistent with experimental data from LHAASO and Fermi-LAT.
Two zero-range-interacting atoms in a circular, transversely harmonic waveguide are used as a test-bench for a quantitative description of the crossover between integrability and chaos in a quantum system with no selection rules. For such systems we show that the expectation value after relaxation of a generic observable is given by a linear interpolation between its initial and thermal expectation values. The variable of this interpolation is universal; it governs this simple law to cover the whole spectrum of the chaotic behavior from integrable regime through the well- developed quantum chaos. The predictions are confirmed for the waveguide system, where the mode occupations and the trapping energy were used as the observables of interest; a variety of the initial states and a full range of the interaction strengths have been tested.
In this Letter we pose the question of whether a many-body quantum system with a full set of conserved quantities can relax to an equilibrium state, and, if it can, what the properties of such state are. We confirm the relaxation hypothesis through a thorough ab initio numerical investigation of the dynamics of hard-core bosons on a one-dimensional lattice. Further, a natural extension of the Gibbs ensemble to integrable systems results in a theory that is able to predict the mean values of physical observables after relaxation. Finally, we show that our generalized equilibrium carries more memory of the initial conditions than the usual thermodynamic one. This effect may have many experimental consequences, some of which having already been observed in the recent experiment on the non-equilibrium dynamics of one-dimensional hard-core bosons in a harmonic potential [T. Kinoshita, T. Wenger, D. S. Weiss, Nature (London) 440, 900 (2006)].