Relativistic jets are major sources of radio-frequency radiation in the Universe. Their study is complicated by the fact that the relativistic gas flows interact with interstellar space, with the ...formation of complex flows that are smaller than the jets but can affect the evolution of the entire jets. Adaptive grids have traditionally been used to simulate such multi-scale phenomena with high spatial resolution in the zone of complex jets and low resolution to reproduce the unperturbed gas flows. In this paper, a Patch-Block-Structured Adaptive-Mesh-Refinement technique is proposed for modeling multi-scale relativistic jets. To use this technique, mathematical tools for numerically solving the equations of special relativistic hydrodynamics are updated in a particular manner. The approach is applied to the evolution of a jet in interstellar space.
The Rusanov solver for solving hydrodynamic equations is one of the most robust schemes in the class of Riemann solvers. For special relativistic hydrodynamics, the robustness condition of the scheme ...is the most important property, especially for sufficiently high values of the Lorentz factor. At the same time, the Rusanov solver is known to be very dissipative. It is proposed to use a piecewise parabolic representation of physical variables to reduce the dissipation of the Rusanov scheme. Using this approach has made it possible to obtain a scheme with the same dissipative properties as Roe-type schemes and the family of Harten–Lax–van Leer schemes. Using the problem of the decay of a relativistic hydrodynamic discontinuity, it is shown that the present author’s version of the Rusanov scheme is advantageous in terms of reproducing a contact discontinuity. The scheme is verified on classical problems of discontinuity decay and on the problem of the interaction of two relativistic jets in the three-dimensional formulation.
A low-dissipation modification of Godunov’s method based on a multidimensional piecewise-parabolic representation of numerical solutions on a local stencil is proposed. The modification is based on ...operator splitting approach for force term and for an advective term. To resolve the force term the linearized Riemann problem was used. The Rusanov scheme to solve the advective transport term was used. The method is verified by some classical hydrodynamic tests. Its order of accuracy is studied on discontinuous and differentiable solutions. The efficiency of a parallel implementation of the numerical method is investigated as well. The performance of the method is demonstrated with a model problem of multiignition explosion of a thermonuclear supernova.
In this paper, the construction of the original “Harten–Lax–van Leer” method using a piecewise-linear reconstruction of physical variables is described. The thus obtained numerical method makes it ...possible to reproduce the pressure, density, and velocity profiles with low dissipation at the discontinuities. To verify the method, classical problems of discontinuity breakdown are used with analytical solutions based on various configurations of shock waves, contact discontinuities, and rarefaction waves. The order of accuracy of the numerical method is studied using a Sod-type problem. It is shown that the greatest decrease in the order of accuracy is when a rarefaction wave is reproduced. The numerical method is verified by means of a three-dimensional Sedov test of a point explosion and a problem of a supernova Ia type explosion with two symmetric ignition points leading to the formation of a G1.9+0.3-type remnant.
Type Ia supernovae play a key role in astrophysics, but the study of the mechanisms of their explosion is still incomplete. The mathematical simulation is the main apparatus for studying known and ...all potentially new scenarios of explosion of the type Ia supernovae. All scenarios are based on the nuclear combustion of the white dwarf matter, first of all, the nuclear combustion of carbon and the subsequent detonation with the supernova explosion. For simulation of the explosion of type Ia supernovae, a subgrid model of carbon static combustion is used. This model does not take into account the previous evolution and dynamics of white dwarfs, which leads to lower values of the combustion energy and, consequently, the supernova explosion energy. We propose a mathematical model of the turbulent combustion of carbon which more adequately describes the matter combustion taking into account the white dwarfs dynamics. Computational experiments show that the supersonic turbulent combustion allows increasing the explosion energy by several times. This is achieved by “pumping” the kinetic energy obtained due to the nonzero velocity dispersion into internal energy and by more active course of the nuclear reactions of the alpha-chain from carbon to iron and nickel. In the future, the above model will be used as a subgrid model of the combustion of the white dwarf matter.
We propose some new computational model of gravitational hydrodynamics with consideration of radiation transfer in diffusion approximation on tetrahedral meshes. This model is a qualitative extension ...of the classical gravitational hydrodynamics model adapted to simulation of star formation and evolution of protoplanetary disks. We describe computational methods of solving this problem and provide the results of numerical simulation of the solar mass cloud collapse.
In this work, the development of a superconducting joint between GdBa2Cu3O7−x-based second-generation high temperature superconducting tapes using a thin YBa2Cu3O7−x intermediate layer is presented. ...The critical current of the superconducting joint was 18 A, which is about 30% of the current in the original tape. The persistent field decay of the one-turn loop showed a joint resistance of less than 6 10−13 at 77 K.
Abstract
The tin isotope
100
Sn is of singular interest for nuclear structure due to its closed-shell proton and neutron configurations. It is also the heaviest nucleus comprising protons and ...neutrons in equal numbers—a feature that enhances the contribution of the short-range proton–neutron pairing interaction and strongly influences its decay via the weak interaction. Decay studies in the region of
100
Sn have attempted to prove its doubly magic character
1
but few have studied it from an ab initio theoretical perspective
2,3
, and none of these has addressed the odd-proton neighbours, which are inherently more difficult to describe but crucial for a complete test of nuclear forces. Here we present direct mass measurements of the exotic odd-proton nuclide
100
In, the beta-decay daughter of
100
Sn, and of
99
In, with one proton less than
100
Sn. We use advanced mass spectrometry techniques to measure
99
In, which is produced at a rate of only a few ions per second, and to resolve the ground and isomeric states in
101
In. The experimental results are compared with ab initio many-body calculations. The 100-fold improvement in precision of the
100
In mass value highlights a discrepancy in the atomic-mass values of
100
Sn deduced from recent beta-decay results
4,5
.
The article presents a numerical technique for solving equations that describe the process of radiative transfer in protostellar disks. The proposed method expands the previously developed original ...computational gas-dust model of the star formation process using multi-level nested grids, which takes into account thermal radiation. In this article, we will consider three numerical schemes for three model equations describing the heat equation, the equilibrium and nonequilibrium radiative transfer models. All three model equations are parabolic, which, with the requirement to use a hydrodynamic time step, leads to the use of implicit schemes. In this work, to solve systems of linear algebraic equations, we used a fairly robust BiCGStab scheme with Jacobi preconditioning. Model problems demonstrate the robustness of the developed methodology.
This paper examines the mechanism of functioning of the artistic space of the Egyptian noble tomb of the Old Kingdom period as a system of pictorial and architectural components. The purpose of the ...burial and the mechanism of functioning of the system to a great extent determined the themes and content of the plots, which contributes a special relevance to the study. A systematic analysis of reliefs from more than a hundred burials of the necropolises of Giza and Saqqara is used, with a focus on the design of the large tombs of Yasen and Chi. The paper emphasizes the fact that the universal mechanism for the functioning of the level system “a large image of the owner – a nearby scene” is a stable correlation between the elements of the attribute set of the nobleman and the content of the plots. Moreover, a large image of the nobleman is valuable not only as an image itself, but also as a set of necessary attributes that allow one to engage in “contemplating” on the images corresponding to these attributes. A new unusual variant of correlation has been identified by depicting a nobleman without the required attribute, however in a certain pose in which this attribute is usually present. Thus, the combination of the necessary insignia, combined with the pose of the depicted nobleman, endowed the large image of the owner with additional functions, allowing it to correlate with several plots and scenes of different content.
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