Matching the heavy-quark fields in QCD and HQET at four loops

The QCD/HQET matching coefficient for the heavy-quark field is calculated up to four loops. It must be finite; this requirement produces analytical results for some terms in the four-loop on-shell heavy-quark field renormalization constant which were previously only known numerically. The effect of a non-zero lighter-flavor mass is calculated up to three loops. A class of on-shell integrals with two masses is analyzed in detail. By specifying our result to QED, we obtain the relation between the electron field and the Bloch--Nordsieck field with four-loop accuracy.Comment: 20 pages. v2: ref. [48] added, small changes in the text, corresponds to the journal versio

Hecke Transformations of Conformal Blocks in WZW Theory. I. KZB Equations for Non-Trivial Bundles

We describe new families of the Knizhnik-Zamolodchikov-Bernard (KZB) equations related to the WZW-theory corresponding to the adjoint $G$-bundles of different topological types over complex curves $\Sigma_{g,n}$ of genus $g$ with $n$ marked points. The bundles are defined by their characteristic classes - elements of $H^2(\Sigma_{g,n},\mathcal{Z}(G))$, where $\mathcal{Z}(G)$ is a center of the simple complex Lie group $G$. The KZB equations are the horizontality condition for the projectively flat connection (the KZB connection) defined on the bundle of conformal blocks over the moduli space of curves. The space of conformal blocks has been known to be decomposed into a few sectors corresponding to the characteristic classes of the underlying bundles. The KZB connection preserves these sectors. In this paper we construct the connection explicitly for elliptic curves with marked points and prove its flatness

Digital Demography Methods for Forecasting Migration Processes

The nature and intensity of migration processes are constantly changing. Demographic statistics are not suitable for obtaining up-to-date information and making timely decisions in the field of demographic and social policy. Thus, digital demography is becoming increasingly important, as this area of population research uses new methods and data sources resulting from the Internet expansion and the digitalisation of society. Using digital demography methods and emerging data sources, the study aims to identify current migration trends in Russia at the municipal level. The duality of the object (real and virtual population) and methods (demographic and data science methods) of digital demography is demonstrated. Digital data sources for studying migration and relevant processing methods were considered. Further, it was proposed to assess migration flows by examining social network information and graphs of migration routes. The analysis of data obtained from the “Virtual population of Russia” project for 2356 urban and municipal regions revealed the features of inter-municipal migration and the centres of migration attraction in the country. An indicator for assessing the potential of future migrations based on the graphs of migration routes was presented. The analysis results show that balanced spatial development of Russia requires the stimulation of human capital development in local centres characterised by high migration potential. These include regional capitals, “second” cities in terms of population, and some research and industrial centres. The study findings can be used to consider demographic processes at the municipal level and elaborate strategic documents in the field of regional spatial development. Therefore, future research should focus on improving digital demography methods for studying and forecasting demographic processes

Digital Demography Methods for Forecasting Migration Processes

The nature and intensity of migration processes are constantly changing. Demographic statistics are not suitable for obtaining up-to-date information and making timely decisions in the field of demographic and social policy. Thus, digital demography is becoming increasingly important, as this area of population research uses new methods and data sources resulting from the Internet expansion and the digitalisation of society. Using digital demography methods and emerging data sources, the study aims to identify current migration trends in Russia at the municipal level. The duality of the object (real and virtual population) and methods (demographic and data science methods) of digital demography is demonstrated. Digital data sources for studying migration and relevant processing methods were considered. Further, it was proposed to assess migration flows by examining social network information and graphs of migration routes. The analysis of data obtained from the “Virtual population of Russia” project for 2356 urban and municipal regions revealed the features of inter-municipal migration and the centres of migration attraction in the country. An indicator for assessing the potential of future migrations based on the graphs of migration routes was presented. The analysis results show that balanced spatial development of Russia requires the stimulation of human capital development in local centres characterised by high migration potential. These include regional capitals, “second” cities in terms of population, and some research and industrial centres. The study findings can be used to consider demographic processes at the municipal level and elaborate strategic documents in the field of regional spatial development. Therefore, future research should focus on improving digital demography methods for studying and forecasting demographic processes

The Arctic Population: Dynamics and Centers of the Settlement System

The article presents an estimate of the Arctic population in 1900–2019 by country and macro-region, obtained using official statistics of eight Arctic States. Analysis of spatial and temporal data revealed the main patterns of the Arctic population formation. Calculations show the world’s Arctic population in-creased from 1.3 million in 1900 to 6.1 million in 1989, and then declined to 5.4 million in 2019. The share of Russia varied from 22% to 58%. The data show that interregional migration in the Russian Arctic had a decisive influence on the demographic dynamics of the Arctic in general. The main reasons for the decline in the Arctic population in different periods were the completion of cycles of natural resource development and lower quality of life in comparison with the central regions. To smooth out differences in national statistical accounting systems, the article examines the dynamics of the population in 17 major centers of settlement in the Arctic, where more than two-thirds of the population lives. Calculations show that urbanization and population concentration in several of the most attractive areas of the Arctic continue. Administrative and educational centers, which are points of attraction for residents of other Arctic territories, get an advantage. The results of the study allow us to predict the further evolution of the Arctic settlement system. They can be used in the development of strategies and programs for the spatial development of the North and the Arctic

Decoupling of heavy quarks in HQET

Decoupling of c-quark loops in b-quark HQET is considered. The decoupling coefficients for the HQET heavy-quark field and the heavy-light quark current are calculated with the three-loop accuracy. The last result can be used to improve the accuracy of extracting f_B from HQET lattice simulations (without c-quark loops). The decoupling coefficient for the flavour-nonsinglet QCD current with n antisymmetrized gamma-matrices is also obtained at three loops; the result for the tensor current (n=2) is new.Comment: JHEP3 documentclass; the results in a computer-readable form can be found at http://www-ttp.physik.uni-karlsruhe.de/Progdata/ttp06/ttp06-25/ V2: a few typos corrected, a few minor text improvements, a few references added; V3: several typos in formulas fixe

The adventive species community changes in the Cheboksary reservoir during 2001-2021

Generally publications devoted to invasive fish species in the Volga-Kama cascade of reservoirs represents relative indicators and do not provide data on the abundance, numbers and invasive communities’ single species dynamics. It does not allow providing a correct assessment of population’s state and changes in the nonindigenous species composition. In this work, changes in the abundance and species structure of the Cheboksary reservoir’s invasive fish community during 2001-2021 were estimated. The total fish count was determined on data of active fishing gears catches and precise reservoir area. Differentiation into mass, widespread and relatively numerous and locally found with a small average abundance species was noted. A decrease in the species evenness of the invasive community was recorded in consequence of the Black Sea-Caspian sprat Clupeonella cultriventris (Nordmann, 1840) and the round goby Neogobius melanostomus (Pallas, 1814) domination rise. The Black Sea-Caspian sprat and the round goby put together for 98.7% of the total number of invasive fish in the current period. Due to this two dominant species there is a tendency to increase the relative abundance of invasive fish species in the reservoir up to 561 unit/ha despite a significant decrease in the abundance of some other invaders

Expulsions in the Russian North: migration processes and neoliberal policy

The article summarizes the results of a long-term study of changes in living conditions of the population in the North during the formation of trade capitalism and the spread of neoliberal policy. Expulsion is considered as an institutionally organized way of exception in the form of state policy, actively supporting social polarization, contributing to consumer way of natural resource development and extensive use of before-built infrastructure, and accompanied by the isolation of the experience, disregard of the interests and violation of the rights of residents. The article proves that Soviet policy, interested in attracting labor to develop the Russian North and used a distribution system of goods for these purposes, did not contribute much to the consolidation of labor migrants in the northern territories as it initiated their return to the homeland at the end of their labor biography. The position of a “temporary worker” was formed by the proposed privileges, which served a compensation for work in adverse climatic conditions but did not contribute to the prospects for the development of the northern territories. At the same time, the interests of residents, who turned out to be cut off from prestigious jobs and found themselves in worse living conditions, were regularly ignored, and their rights were unrecognized. If, through vertical mobility and integration into the Soviet distribution system, it was possible to smooth out the inequities in the distribution of benefits, it became more difficult to hide this with the country's transition to the market and the beginning of a new phase of natural resource extraction. Moreover, considering the exclusion processes have become more widespread. Now not only the indigenous peoples of the North but also the second generation of migrants are among the vulnerable groups. The focus of the conflict has shifted and expressed itself in the relations between the residents of the Center and the regions

Influence of Kerr nonlinearity on PT-transition in coupled fibre lasers

This work investigates a concept of coupled fiber lasers exhibiting PT-symmetry and a PT-transition between PTsymmetric and PT-broken lasing states. We consider a system operated via Raman gain comprising two fiber loops (ring cavities) connected to each other by means of two fiber couplers with adjustable phase shift between them. By changing the phase shift or/and amplification (loss) in fiber loops, one can switch between generation regimes, realizing either PTsymmetric or PT-broken solution. In the PT-symmetric lasing regime, equal powers are generated in both cavities despite only active one is pumped. We make theoretical and numerical description of the proposed coupled fiber lasers starting with the simple discrete matrix model taking into account coupling, phase delays, gain (which is assumed to be saturated), losses and nonlinear phase shift. We show how the PT-transition is affected by self-phase modulation inside the fiber cavity and investigate requirements that should be met in order to observe PT-transition experimentally despite Kerr effect that violates exact symmetry conditions. In particular, we show that PT-transition may be observable only near lasing threshold. Further on we adopt more sophisticated model based on Nonlinear Schrödinger equation for PT fiber laser. Taking into account quasi-CW polychromatic radiation with typical spectral bandwidth of fiber Raman lasers, chromatic dispersion and Kerr nonlinearity, we demonstrate both PT-symmetric and PT-broken lasing in a fiber laser

Development of the concept of an innovative laboratory installation for the study of dust-forming surfaces

Currently, the determination of the emission rate of suspended solids from a unit of the surface area of a man-made mass at various parameters of the wind flow is not sufficiently described. The analysis of the world experience of researchers shows that existing laboratory installations have various design features that do not allow to correctly determine the mass of the dust being flapped and wind-blown. Based on the analysis results, the concept of an innovative laboratory installation for the study of dust-forming surfaces has been developed. It takes into account the influence of wind shadows, the deturbulization of an artificially created air flow, the possibility of regulating not only the flow velocity mode, but also the creation of a vacuum or disturbance in the area of sample placement, as well as the formation of a certain angle of wind flow attack relative to the surface. The concept provides for the possibility of determining the volume of dust emissions by the values of the lost dust masses in the sample and by the values of dust concentrations in the outgoing stream. The calculation of the main basic elements of the installation using the ANSYS FLUENT software package was carried out. The model and configuration of the wind tunnel have been developed and calculated, the main geometric parameters and functional elements for the possibility of use in scientific work have been determined. For practical use of the empirical roughness value of the underlying surface, its values are recommended in a wide range – from zero for the water surface to 0.44 for large cities with tall buildings and skyscrapers