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Abstract In classical texts, equations for fields are proposed without derivation of right-hand sides. Below, the right-hand sides of the Maxwell and Einstein equations are derived within the framework of the Vlasov–Maxwell–Einstein equations from a classical, but slightly more general principle of least action and Hamilton–Jacobi equations are used to obtain cosmological solutions.

In classical works, equations for fields are proposed without derivation of the right-hand sides. Here we give a derivation of the right-hand sides of the Maxwell and Einstein equations in the framework of the Vlasov-Maxwell-Einstein equations from the classical, but more general principle of least action. Moreover, in the case of Friedman's model of the Universe, one possibility is obtained to explain the mysterious accelerated expansion of the Universe. The accelerated expansion of the Universe, marked by the 2011 Nobel Prize in Physics, is receiving close attention. The generally accepted explanation now is the addition of Einstein's lambda term to the relativistic action. And it is well known that in the nonrelativistic theory this corresponds to the addition of a repulsive quadratic potential.

An Erratum to this paper has been published: https://doi.org/10.1134/S106456242207002X

The problem of justification of gravitation and electrodynamic equations with the help of the minimal action principle is a classical one. A derivation of the Vlasov–Maxwell–Einstein equation is proposed from the classical principle, but the little more general principle of minimal action. So we get new derivation of the right-hand side of the Maxwell and Einstein equations and we get a closed system of equations for gravitation and electrodynamics.

A potassium titanyl arsenate (KTiOAsO4, KTA) crystal 50 × 80 × 60 mm in size has been grown by upgraded Czochralski method from flux (TGGS) with a decrease in temperature from 900 to 770 °C during pulling. It is shown that the spectroscopic properties of the parts of KTA crystals grown at 900 and 770 °C are close, whereas the electrical conductivity of the low-temperature (770 °C) KTA part turned out to be an order of magnitude lower than that of the high-temperature part. Visualisation of the domain structure by second-harmonic generation microscopy revealed a more efficient domain intergrowth (throughout the sample) in the low-temperature KTA, which is important for forming a regular domain structure (RDS) in a KTA-based nonlinear optical element. It is established that the quantum efficiency of parametric generation of light in the RDS formed in low-temperature KTA is several times higher than in the case of high-temperature KTA. The results obtained are important for optimising RDS parameters.

The article is devoted to the issues of merging ontologies. These ontologies are used in the design of subsystems included in the corporate information system. This problem arises when it is necessary to build a united ontology for the design of information systems in the process of integrating various information solutions, as well as in the step-by-step design of a corporate information system created by different developers in different times. It is assumed that ontologies are built based on the same principles and on the basis of one thesaurus. But nevertheless, the task of a merged ontology may have significant difficulties in combining different ontologies that describe different subsystems of an enterprise. The authors investigated the formal determination of the possibility to merge ontologies without their preliminary revision. The article proposes a criterion for the possibility of merging. The method based on expert opinions for calculating the criterion is proposed. Various examples of merging different ontologies with the calculation of the proposed criterion are also considered. The novelty of the presented material lies in developing the principle and criterion for merging ontologies and a methodology for the application of this criterion.

We present the results of analysis of the switching current during polarization reversal in wide field range in KTA single crystals. According to previously revealed stages of domain structure evol...

The history of the cooperation between the staff of the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences and S.K. Godunov is described. Numerous novel and interesting results in the theory of kinetic equations and computational mathematics were obtained in the course of this cooperation.

Using the classical Lorentz-Hilbert-Einstein action, we derive the kinetic Vlasov-Maxwell-Einstein equation for particles in the gravitational and electromagnetic fields. The method of synchronization of intrinsic times of different particles is proposed. Based on the obtained expressions for actions (including in the post-Newtonian approximation), we analyze the connection of the cosmological lambda-term and dark energy.

The gravitational Lagrangian of general relativity is considered together with the Lagrangian of electromagnetism. Vlasov-type equations are derived from the former in the general, nonrelativistic, and weakly relativistic limits. Expressions for the resulting corrections to the Poisson equation are proposed, which may contribute to the effective action of dark matter and dark energy.

Optical parametric oscillator based on a periodically poled MgO:LiNbO3 crystal pumped by a repetitevely pulsed Tm3+:Lu2O3 ceramics laser at 1966 nm was studied. The OPO average output power up to 530 mW at wavelength of 3.7–4.2 μm was achieved at the ceramics laser power of 7.9 W. The optical-to-optical efficiency of OPO energy conversion was up to 6.7%, and the slope efficiency was up to 8%.

Social media data mining is rapidly developing to be a mainstream tool for marketing insights in today’s world, due to the abundance of data and often freely accessed information. In this paper, we propose a framework for market research purposes called the Disruptometer. The algorithm uses keywords to provide different types of market insights from data crawling. The preliminary algorithm data-mines information from Twitter and outputs 2 parameters-Product-to-Market Fit and Disruption Quotient, which is obtained from a brand’s customer value proposition, problem space, and incumbent space. The algorithm has been tested with a venture capitalist portfolio company and market research firm to show high correlated results. Out of 4 brand use cases, 3 obtained identical results with the analysts ‘studies.

A derivation of the Vlasov-Poisson-Poisson equation is proposed for studying stationary solutions of a system of gravitating charged particles in vicinity of triangular libration points (Kordylevsky cloud). Stationary solutions are sought as functions of integrals, which leads to elliptic nonlinear equations for the potentials of the gravitational and electrostatic fields. This gives a critical mass: for bodies with large masses dominates gravitation forces, and for bodies with smaller masses - electrostatic forces.

The Vlasov–Poisson–Poisson equation is derived to study stationary solutions for a system of gravitating charged particles in a neighborhood of triangular libration points (Kordylewski clouds). Stationary solutions are sought in the form of functions of integrals, which leads to elliptic nonlinear equations for the gravitational and electrostatic field potentials. This yields a critical mass: gravitation dominates for bodies with large masses, while electrostatics dominates for bodies with smaller masses.