The Institute of History of The Academy of Sciences of The Republic of Uzbekistan

Abstract General relativity (GR) theory modifications include different scalar, vector, and tensor fields with non-minimal gravitational coupling. Kalb–Ramond (KR) gravity is a modified theory formulated based on the presence of the bosonic field. One astrophysical way to test gravity is by studying the motion of test particles in the spacetime of black holes (BHs) using observational data. In the present work, we aimed to test KR gravity through theoretical studies of epicyclic frequencies of particle oscillations using quasi-periodic oscillation (QPO) frequency data from microquasars. First, we derive equations of motion and analyze the effective potential for circular orbits. Also, we studied the energy and angular momentum of particles corresponding to circular orbits. In addition, we analyze the stability of circular orbits. It is shown that the radius of the innermost stable circular orbits is inversely proportional to the KR parameter. We are also interested in how the energy and angular momentum of test particles at ISCO behave around the KR BHs. We found that the Keplerian frequency for the test particles in KR gravity is the same as that in GR. Finally, we study the QPOs by applying epicyclic oscillations in the relativistic precession (RP), warped disc (WD), and epicyclic resonance (ER) models. We also analyze QPO orbits in the resonance cases of upper and lower frequencies 3:2, 4:3, and 5:4 in the QPO as mentioned above models. We obtain constraints on the KR gravity parameter and BH mass using a Monte Carlo Markov Chain simulation in the multidimensional parameter space for the microquasars GRO J1655-40 & XTE J1550-564, M82 X-1, and Sgr A*.

Abstract Quasiperiodic oscillations (QPOs) are a powerful tool for testing gravity theories, probing gravitational and electromagnetic field properties, and obtaining constraints on the black hole and field parameters. This work considers charged particle dynamics near uniformly magnetized black holes in braneworlds. First, we obtain the solution of the Maxwell equation for magnetic fields and calculate the radial and angular magnetic field components. We derive and analyze the effective potential of charged particles for circular orbits and investigate the energy and angular momentum for the circular orbits. We also analyze the combined effects of magnetic interaction and braneworlds on the charged particles’ innermost stable circular orbits (ISCOs). We calculate the angular momentum of charged particles in Keplerian orbits in the presence of an external magnetic field and braneworlds. Also, we investigate frequencies of the particle oscillations along vertical and angular directions. We applied our studies on particle oscillations to the QPO studies in the relativistic precession model. Finally, we obtain constraints on magnetic interaction and braneworld parameters together with the black hole mass and QPO orbits using Monte Carlo Markov Chain (MCMC) simulation in the four-dimensional parameter space for the QPOs observed in the microquasars XTE J1550-564, GRO J1655-40 & GRS 1915-105, and at the center of galaxies M82 and Milky Way.

Abstract General relativity (GR) is a well-tested theory of gravity in strong and weak field regimes. Many modifications to this theory were obtained, including different scalar, vector, and tensor fields to the GR with non-minimal coupling to gravity. Kalb–Ramond (KR) gravity is also a modified theory formulated in the presence of a bosonic field. One astrophysical way to test gravity is by studying the motion of test particles in the spacetime of black holes (BH). In this work, we study the circular motion of charged particles and explore energetic processes around charged BHs in KR theory. First, we investigated the event horizon radius and analyzed horizon-no horizon regions in the BH charge and KR parameter space. Considering the Coulomb interaction, we derive and analyze the effective potential for charged particles around a charged KR BH. We investigate charged particles’ angular momentum and energy corresponding to circular orbits. We also investigate how the KR non-minimal coupling parameter affects the radius of the innermost stable circular orbits, the corresponding energy, and the angular momentum. We also investigated the electric Penrose process and charged-particle collisions near the KR BH. The presence of the nonzero KR parameter results in a decrease in the energy efficiency of the Penrose process. Also obtained is that the KR parameter’s positive (negative) values cause a decrease (increase) in the center of mass energy of colliding particles near the BH horizon.

With the collapse of the Soviet Union in the 1991s Central Asian nations and Japan established diplomatic relations and partnership began to increase steadily as manifested by the level of official contacts. In 1997 the “Silk Road” Diplomacy concept was formulated for Japan's policy toward Central Asia. In the beginning of 21st century we see activization of new actors including India, Korea and Japan in Central Asia, which were mainly welcomed in the region. Tokyo recognized the growing strategic importance of Central Asia in the context of international security and sought to play a more active role as an Asian nation in Eurasia. During two decades Central Asian nations and Japan partnership began to increase steadily. Japan is one of the largest assistants to Central Asia in structural reforms and Japanese investments to the different aspects of region economy and transport communication add up to several billions. There are several areas of special interest to Japan in its relations with Central Asia, including cooperation in education, economic development of the region, political reforms, as well as energy resources. Japan's effort in creating the “Central Asia plus Japan” dialog is part of its multilateral diplomacy. At the same time there are some challenges and problems in Central Asia–Japan relations. However, there are potentialities for future bilateral and multilateral relations. Japan like Korea, India and other countries has a strong positive image in Central Asia, which could be regarded as an additional factor for fostering partnership of Central and East Asia as well as interregional relation with the vast Asian continent and beyond.

This paper scrutinizes main determinants of competitiveness and sustainable growth of priority industries in Uzbekistan. In particular, it investigates issues of rationale for strategic prioritization of industries within the structure of national economy by touching upon effective mechanisms that lend support in attracting foreign direct investment into these industries. The author concludes that the main strategic goal of industrial development of Uzbekistan should be not only reaching high rates of growth in this sector, but it should also involve relevant steps to develop priority industries which requires more rational use of untapped natural resource wealth of the country, formation of its modern structure, and boosting the competitiveness of country’s manufacturing industries in world markets.

Comprehensive Summary The rapid advancement of artificial intelligence and the Internet of Things has precipitated an urgent demand for renewable energy sources and portable electronic devices in contemporary society. Organic photovoltaic cells (OPVs), noted for their thinness, flexibility, and potential for large‐scale manufacturing, have emerged as a promising technology for the direct conversion of solar energy into electrical power. However, current research in OPVs predominantly focuses on enhancing power conversion efficiency (PCE), while the inherent mechanical brittleness of OPV films significantly constrains their applicability in stretchable electronics, thereby impeding their further development and practical implementation. To address this challenge, we show an elastic additive with high fracture strain and low modulus to make both polymer:small molecule (PM6:PY‐IT) and all‐polymer (PM6:N2200) OPV films stretchy. The resulting intrinsically stretchable OPVs derived from these delicately tuned films demonstrate exceptional photovoltaic performance, with a top PCE of 13.84%, alongside remarkable stretchable stability (strain at 80% efficiency breaking 50%), indicated by the ability to maintain efficiency retention up to 0.8 fold even after 500 cycles of stretching at 30% tensile strain. This work not only offers a new strategy for enhancing the mechanical and photovoltaic properties of multifunctional organic electronic systems but also provides a concrete pathway for advancing OPVs toward practical employment.

Abstract In this work, we study metric-Palatini gravity extended by the antisymmetric part of the affine curvature. This gravity theory leads to general relativity plus a geometric Proca field. Using our previous construction of its static spherically-symmetric AdS solution (Eur Phys J. C 83(4):318, 2023), we perform a detailed analysis in this work using the observational quasiperiodic oscillations (QPOs) data. To this end, we use the latest data from stellar-mass black hole GRO J1655-40, intermediate-mass black hole in M82-X1, and the super-massive black hole in SgA* (our Milky Way) and perform a Monte-Carlo-Markov-Chain (MCMC) analysis to determine or bound the model parameters. Our results shed light on the allowed ranges of the Proca mass and other parameters. The results imply that our solutions can cover all three astrophysical black holes. Our analysis can also be extended to more general metric-affine gravity theories.

Abstract In the present work, we first regularize a black hole spacetime in modified gravity (MOG) in the presence of the scalar-tensor-vector (STV) field, called the Schwarzschild MOG black hole, under the transformation $$r^2 \rightarrow r^2 + a^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>r</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>r</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>+</mml:mo> <mml:msup> <mml:mi>a</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> , known as the Simpson–Visser (SV) spacetime (where a is regularization or black-bounce parameter). The spacetime can represent a black hole and a wormhole. We analyze horizon properties and calculate the effective mass of the spacetime. Also, we find black hole-wormhole regions in black-bounce and MOG parameter spacetime. We also analyze scalar invariants of spacetime, such as the Ricci scalar, the square of the Ricci tensor, and the Kretchmann scalar. We study test particle motion in the SV-MOG spacetime by considering the interaction between the particle and the STV field. We investigate how the STV fields change the innermost stable circular orbits (ISCOs), energy, and angular momentum of the test particle’s ISCO. It is shown that the ISCO decreases in the presence of the black bounce parameter and increases in the STV field. We also study the collisions of test particles and analyze how the MOG and black-bounce parameters influence the critical angular momentum of colliding particles and their center of mass energy.

This article explores the prospects of using solar energy for hydrogen production as an alternative energy source. The author discusses the limitations of hydrogen energy, including the economic inefficiency of hydrogen production. The main objective of the study is to increase profitability and address the environmental and energy issues associated with hydrogen production. The use of modern heliotechnologies and heliomaterials is proposed to optimize the hydrogen production process. The article also examines technological problems related to hydrogen combustion in the presence of nitrogen and emphasizes the need for further research to create environmentally safe and economically efficient hydrogen energy. The issue of hydrogen’s environmental cleanliness is discussed, and the necessity of using environmentally clean and conditionally clean energy sources for hydrogen production is noted. In conclusion, the article emphasizes that hydrogen has the potential to become a clean energy source through the development of heliomaterials science, which requires further research and technological improvements for its commercialization.

Four irrigation regimes were established, varying the amount of irrigation water applied: 60%, 65%, 70%, and 75% of the soil moisture. The fields were left without mulch or covered with white and black polyethylene films. Prior to irrigation, the soil moisture in this case ranged from 60% to 75% in the 0-20 cm soil layer during the “sowing -shatrik” phase and in the 0-40 cm soil layer during the “shatrik -bloom” period, according to the experimental alternatives. During the time of “bloom fruit formation,” the soil layer from 0 to 50 cm was maintained at levels of 70%, 75%, 80%, and 85%. Similarly, during the “fruit formation ripening” period, the soil layer from 0 to 50 cm was maintained at levels of 60%, 65%, 70%, and 75%. One of the study options was the use of drip irrigation, which maintained soil moisture levels at 70%, 80%, or 70% depending on the phenophases of the watermelon plant. This approach led to a significant increase in both the production and quality of the watermelon crop.

Abstract One of the possible ways to test gravity theories and get constraints on parameters of a gravity theory and a black hole is based on studies of black hole shadow applying Event Horizon Telescope (EHT) data from the shadow sizes of M87* and Sgr A*. In this sense, we study the shadow of rotating charged black holes in Einstein–Maxwell scalar (EMS) theory. First, we obtain a rotating EMS black hole solution and analyze the horizon properties. We derive the effective potential for the circular motion of photons along null geodesics around the rotating black hole and obtain the black hole shadow using celestial coordinates. The effects of the black charge and spin and EMS theory parameters on the shape of the black hole shadow, its radius, and distortion parameters are analyzed in detail. We have obtained upper and lower limits for spin and black hole charges of Sgr A* and M87* using their shadow size for various values of EMS parameters. Lastly, we computed and examined the standard shadow radius, equatorial, and polar quasinormal modes using the geometric-optic relationship between the parameters of the quasinormal mode and the conserved values along the geodesics.

mediated nanoparticles of Ni/Fe and Ni/Fe/Zn could be further explored as alternative therapeutic agents for cancer and diabetes.

Abstract In the twentieth century, the Central Asian countries of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan passed through a complex historical period. They were originally founded as republics of the Soviet Union in the 1920s-30s as a result of national and territorial state delimitation. The process of the creation of new national state formations began after the Soviet Union disintegrated and these republics achieved independence. At the same time, the region's nations are facing complex problems of transition and the creation of new societies. Nevertheless, these countries have to continue the process of political and economic reforms, as well as development of civic institutions. The Central Asian nations established contacts with foreign states and international organizations and started to form a system of interstate relations between the countries of the region. There are potentials for development of regional integration of Central Asia. Future integration will depend on the readiness of the nations to carry out political and economic reforms, introduce forms and methods of economic regulation compatible with global norms, and most important, international support of political reforms and regional integration.

This article explores the prospects of synthesizing materials with a complex of specified properties using the pulsed tunneling effect (PTE) and concentrated solar radiation. The mechanisms of formation of metastable phases and the emergence of unique electrical and magnetic properties due to numerous structural distortions are described. The concept of using such materials as “artificial dopants” is proposed. Promising application areas are considered, ranging from the creation of extremely strong materials to the achievement of non-standard superconducting and magnetic effects.

This study focuses on investigating the potential of modified ceramic technology methods for producing composition materials with nano-level heterogeneity, approximating the properties of functional ceramics (FC) obtained through helio-technology. Three different powder synthesis methods were utilized: oxide method, ceramic technology, and sol-gel technology. X-ray diffraction and electron microscopy analyses were employed to compare the microstructure of powders obtained by these methods with samples synthesized using helio-technology. The results revealed that powders obtained through modified ceramic technology methods exhibited a more homogeneous structure and smaller particle size compared to those obtained through helio-technology. Nano-sized, metastable, and amorphous phases formed at the boundaries of such powders are considered responsible for the generation of pulsed infrared radiation. These findings have significant practical implications in various fields that require composition materials with controlled properties and the ability to generate pulsed infrared radiation.

This article presents the results of full-scale tests of a polyethylene-ceramic composite in real conditions, at an altitude of 1100 meters above sea level. This is due to the fact that at this height the level of UV, which destroys polyethylene, is significantly higher than at sea level. In parallel, the results of testing a conventional polyethylene film were also carried out, for a comparative assessment of effectiveness.

This article examines the use of fractals to estimate the probability of classical events controlled by quantum processes. A hypothesis explaining the opposite charges of the positron and electron is discussed, as well as the relationship with the main modern theories of quantum mechanics, such as quantum electrodynamics (QED), string theory, etc. The relationship with the tunnel effect and the pulsed tunnel effect is considered. Examples of practical application of fractals are given, for example, in photocatalysts. The concepts of the effective mass of a photon and the quantum nature of elementary particles, the idea of their internal structure and the formation of matter from the point of view of quantum mechanics are touched upon. Particular attention is paid to the fractal structure of the quantum field as a probability associated with the formation of a positron or electron, and the mathematical connection with the Dirac equation, QED and the Schrödinger equation.

In this paper the author explores the strategy of politics of memory in Samarkand, the hometown of the First President of Uzbekistan I.A. Karimov, in the post-Soviet period. The analysis concerns the traditions of Samarkand's memory culture chosen, invented or forgotten in independent Uzbekistan, to form ideas about the past using historical figures, monuments, holy places and renamed streets in Samarkand as examples. In this complex process it is important to take into consideration how the central authorities interacted with the local cultural elite of Samarkand. President Sh.Mirziyoyev formulated new trends in Uzbekistan's foreign policy, which was reflected in the politics of memory in Samarkand. These changes have become symbolic in the new politics of memory in Samarkand aimed at demonstrating the historical roots of the ethnic and religious tolerance in the society and highlighting Samarkand as a key place in the history of the Islamic world and the birthplace of the First President of Uzbekistan I. Karimov.Keywords: Samarkand, memory, identity, shrines, streets, memorials, cultural elites, Uzbekistan, Nation-building, urban studies.

Quantum mechanics based on the probabilistic approach provides a powerful tool for accurate prediction and interpretation of quantum phenomena, allowing statistically sound predictions about the behavior of microparticles and quantum systems. This statement emphasizes the probabilistic nature of quantum mechanics, its applicability to quantum phenomena and microparticles, as well as the statistical nature of its predictions when applied to the macro effects of classical physics. In addition, the role of statistics and probability in various fields of science, such as particle physics, thermodynamics, biology, sociology, psychology, economics and finance, is discussed. The philosophical implications of the probabilistic approach and the associated limitations and challenges are also considered.

In this work, a mathematical model of industrial wastewater treatment technology was formed. First, wastewater treatment technologies were analyzed and the technology of ion-exchange resin treatment was selected. A water purification device using ion-exchange resins was made, and tested on the Kungrad soda plant and the results were obtained. According to these results, it was determined that the cleaning coefficient of the device is up to 98-99%. In this article, a mathematical model of a wastewater treatment device using ion-exchange resins was developed using the stoichiometric matrix method. After the mathematical model of the process was found, a graph of the concentration change over time was constructed using the MATLAB program. With the help of the obtained results, we can monitor the changes in the concentration of each component participating in the process, and through this, we can optimally control the process.