Archimedean-type force in a cosmic dark fluid: II. Qualitative and numerical study of a multistage Universe expansion

In this (second) part of the work we present the results of numerical and qualitative analysis, based on a new model of the Archimedean-type interaction between dark matter and dark energy. The Archimedean-type force is linear in the four-gradient of the dark energy pressure and plays a role of self-regulator of the energy redistribution in a cosmic dark fluid. Because of the Archimedean-type interaction the cosmological evolution is shown to have a multistage character. Depending on the choice of the values of the model guiding parameters,the Universe's expansion is shown to be perpetually accelerated, periodic or quasiperiodic with finite number of deceleration/acceleration epochs. We distinguished the models, which can be definitely characterized by the inflation in the early Universe, by the late-time accelerated expansion and nonsingular behavior in intermediate epochs, and classified them with respect to a number of transition points. Transition points appear, when the acceleration parameter changes the sign, providing the natural partition of the Universe's history into epochs of accelerated and decelerated expansion. The strategy and results of numerical calculations are advocated by the qualitative analysis of the instantaneous phase portraits of the dynamic system associated with the key equation for the dark energy pressure evolution.Comment: 15 pages, 12 figures, Part II, typos corrected, Fig.4 replaced, references correcte

Non-minimal electrodynamics and resonance interactions in relativistic plasma

A three-parameter toy-model, which describes a non-minimal coupling of gravity field with electromagnetic field of a relativistic two-component electrically neutral plasma, is discussed. Resonance interactions between particles and transversal waves in plasma are shown to take place due to the curvature coupling effect.Comment: 6 pages, no figures, the short version of the talk at RUSGRAV-13, to be published in Gravitation and Cosmology, 2009, No.

Cherenkov radiation in a gravitational wave background

A covariant criterion for the Cherenkov radiation emission in the field of a non-linear gravitational wave is considered in the framework of exact integrable models of particle dynamics and electromagnetic wave propagation. It is shown that vacuum interacting with curvature can give rise to Cherenkov radiation. The conically shaped spatial distribution of radiation is derived and its basic properties are discussed.Comment: LaTeX file, no figures, 19 page

Non-minimal Wu-Yang wormhole

We discuss exact solutions of three-parameter non-minimal Einstein-Yang-Mills model, which describe the wormholes of a new type. These wormholes are considered to be supported by SU(2)-symmetric Yang-Mills field, non-minimally coupled to gravity, the Wu-Yang ansatz for the gauge field being used. We distinguish between regular solutions, describing traversable non-minimal Wu-Yang wormholes, and black wormholes possessing one or two event horizons. The relation between the asymptotic mass of the regular traversable Wu-Yang wormhole and its throat radius is analysed.Comment: 9 pages, 2 figures, typos corrected, 2 references adde

Non-minimal coupling of photons and axions

We establish a new self-consistent system of equations accounting for a non-minimal interaction of gravitational, electromagnetic and axion fields. The procedure is based on a non-minimal extension of the standard Einstein-Maxwell-axion action. The general properties of a ten-parameter family of non-minimal linear models are discussed. We apply this theory to the models with pp-wave symmetry and consider propagation of electromagnetic waves non-minimally coupled to the gravitational and axion fields. We focus on exact solutions of electrodynamic equations, which describe quasi-minimal and non-minimal optical activity induced by the axion field. We also discuss empirical constraints on coupling parameters from astrophysical birefringence and polarization rotation observations.Comment: 31 pages, 2 Tables; replaced with the final version published in Classical and Quantum Gravit

Trends in the Russian economy development during the new anti-Russian sanctions

Objective: to identify trends in the development of the Russian economy during the new anti-Russian sanctions. To this end, the paper analyzes the impact of the new sanctions on the budgetary sphere, the development of economic sectors and industries and the Russian regions.Methods: the work uses data from the Federal State Statistics Service (Rosstat), the Federal Treasury, the Ministry of Economic Development of the Russian Federation (Ministry of Economic Development), the Central Bank of the Russian Federation (Bank of Russia), the Federal Tax Service (FTS), the Federal Customs Service (FCS), the Federal Antimonopoly Service (FAS). For their analysis, graphical, tabular, and analytical methods are used.Results: the new anti-Russian sanctions caused significant changes in the structure of the Russian exports and trade balance. The reduced inflow of foreign currency put significant pressure on the ruble exchange rate, which created inflation risks. The devaluation was restrained by the Bank of Russia new currency regime. The favorable situation in the energy market in 2022 led to an increase in budget revenues. In 2023, economic growth resulted from an active fiscal policy supported by moderate monetary expansion. However, it was achieved at the cost of an increase in the budget deficit and public debt. The response of different industries and regions to the sanctions shock was heterogeneous. The development of certain adaptive strategies by economic entities, as well as the response of the authorities played an important role. The new sanctions regime prompted a revision of the state economy regulation paradigm. Dirigisme manifested itself in the increase of state orders, subsidies and other support for protected industries with one-time withdrawals of opportunistic revenues of big business. Monetary and fiscal policy gradually acquired a hybrid character. Direct and indirect price regulation became an important instrument of state regulation during the sanctions.Scientific novelty: it consists in a comprehensive analysis of development trends during the new anti-Russian sanctions, their impact on foreign economic parameters, budgetary sphere, financial system, development of Russian industries and regions.Practical significance: statistical information on various aspects of the Russian economy development during the new antiRussian sanctions was summarized and analyzed. The work can be useful to researchers studying the functioning of the Russian economy under sanctions, as well as to businesspersons for assessing the risks, opportunities and prospects of their businesses development, and to government agencies for forming an effective anti-crisis policy

Intersectoral contagion effects in the Russian economy under the pandemic shock

Objective: to identify the presence/absence of transmission of financial contagion between sectors of the Russian economy during the 2020-2021 pandemic.Methods: the study is based on data on the inter-sessional average daily profitability of six industry indices of the Russian trading system for the period from 01.01.2019 to 23.02.2022. Using the calculation of the sliding coefficient of variation for the average industry index of the Russian trading system and the sliding growth rate of coronavirus infection, three periods of pandemic shock were identified: short-term (acute phase of the pandemic), medium-term (covering the first and second waves of infection), and long-term (up to the announcement of the Russian special military operation in Ukraine). Intersectoral contamination was identified on the basis of strengthening the relationships between the profitability of industry assets by analyzing three distribution points: the correlation coefficient adjusted for heteroscedasticity (Forbes–Rigobon test), tests for co-asymmetry and co-kurtosis of the distribution.Results: estimates of the scale and direction of financial contagion between the Russian economic sectors during the pandemic were obtained. Firstly, they indicate an increase in confirmed cases of intersectoral contagion in the medium and long term, which indicates a “long-term trace” of the pandemic. Secondly, the number of contagions increases closer to higher distribution points. Thirdly, the main branches of the Russian economy (metallurgy and oil industry), contrary to expectations, turned out to be the least connected with other branches of the Russian economy during the pandemic. The telecommunications sector demonstrated the greatest propensity to transmit contagion. The conclusion about the consumer sphere and trade being the most exposed to contagion is rather expected.Scientific novelty: for the first time, estimates of intersectoral financial contagion for the Russian economy during the pandemic have been obtained, which indicate the presence of both short-term and long-term effects of the pandemic, as well as the strengthened role of certain industries (in particular, the telecommunications industry) in the transmission of contagion under the economy digitalization.Practical significance: the data obtained can be useful in managing the financial stability of individual industries during pandemic-type crises

Clinical Application of New Immobilization System in Seated Position for Proton Therapy

In November 2015, the proton therapy complex “Prometheus”, developed at PhTC LPI RAS, started being used for the clinical treatment of patients with head and neck cancer. A special mobile patient positioning and immobilization device has been developed within the proton therapy complex “Prometheus”. The purpose of this paper is to report the first clinical experience of using new patient setup system in a seated treatment position. Keywords: proton therapy, ion therapy, pencil beam scanning

Nonminimal isotropic cosmological model with Yang-Mills and Higgs fields

We establish a nonminimal Einstein-Yang-Mills-Higgs model, which contains six coupling parameters. First three parameters relate to the nonminimal coupling of non-Abelian gauge field and gravity field, two parameters describe the so-called derivative nonminimal coupling of scalar multiplet with gravity field, and the sixth parameter introduces the standard coupling of scalar field with Ricci scalar. The formulated six-parameter nonminimal Einstein-Yang-Mills-Higgs model is applied to cosmology. We show that there exists a unique exact cosmological solution of the de Sitter type for a special choice of the coupling parameters. The nonminimally extended Yang-Mills and Higgs equations are satisfied for arbitrary gauge and scalar fields, when the coupling parameters are specifically related to the curvature constant of the isotropic spacetime. Basing on this special exact solution we discuss the problem of a hidden anisotropy of the Yang-Mills field, and give an explicit example, when the nonminimal coupling effectively screens the anisotropy induced by the Yang-Mills field and thus restores the isotropy of the model.Comment: 15 pages, revised version accepted to Int. J. Mod. Phys. D, typos correcte

Chaplygin gas with non-adiabatic pressure perturbations

Perturbations in a Chaplygin gas, characterized by an equation of state $p = -A/\rho$, may acquire non-adiabatic contributions if spatial variations of the parameter $A$ are admitted. This feature is shown to be related to a specific internal structure of the Chaplygin gas. We investigate how perturbations of this type modify the adiabatic sound speed and influence the time dependence of the gravitational potential which gives rise to the Integrated Sachs-Wolfe effect in the anisotropy spectrum of the cosmic microwave background.Comment: 16 pages, comments and references added, accepted for publication in Class.Quantum Gra