Dark Energy: Observational Evidence and Theoretical Models

The book elucidates the current state of the dark energy problem and presents the results of the authors, who work in this area. It describes the observational evidence for the existence of dark energy, the methods and results of constraining of its parameters, modeling of dark energy by scalar fields, the space-times with extra spatial dimensions, especially Kaluza---Klein models, the braneworld models with a single extra dimension as well as the problems of positive definition of gravitational energy in General Relativity, energy conditions and consequences of their violation in the presence of dark energy. This monograph is intended for science professionals, educators and graduate students, specializing in general relativity, cosmology, field theory and particle physics.Comment: Book, 380 p., 88 figs., 7 tables; 1st volume of three-volume book "Dark energy and dark matter in the Universe", ed. V. Shulga, Kyiv, Academperiodyka, 2013; ISBN 978-966-360-239-4, ISBN 978-966-360-240-0 (vol. 1). arXiv admin note: text overlap with arXiv:0706.0033, arXiv:1104.3029 by other author

Integrable Multicomponent Perfect Fluid Multidimensional Cosmology II: Scalar Fields

We consider anisotropic cosmological models with an universe of dimension 4 or more, factorized into n>1 Ricci-flat spaces, containing an m-component perfect fluid of m non-interacting homogeneous minimally coupled scalar fields under special conditions. We describe the dynamics of the universe: It has a Kasner-like behaviour near the singularity and isotropizes during the expansion to infinity. Some of the considered models are integrable, and classical as well as quantum solutions are found. Some solutions produce inflation from "nothing". There exist classical asymptotically anti-de Sitter wormholes, and quantum wormholes with discrete spectrum.Comment: 28 pages, LaTeX, subm. to Gen. Rel. Gra

ПРОСТОРОВО-ЧАСОВИЙ РОЗПОДІЛ СМЕРЧІВ ТА ШКВАЛІВ У ПІВНІЧНО-ЗАХІДНОМУ ПРИЧОРНОМОР’Ї

Tornadoes and strong squalls are dangerous for almost all spheres of human life and the economy of the region. The degree of negative impact depends on their type, quantity, intensity, area of formation and geographical features of the territory. The article defines the dynamics of the number of tornadoes and strong squalls in the North-Western Black Sea region (Odessa, Nikolayev and Kherson regions of Ukraine) from 2006 to 2020.Geographical position of the south-west of Ukraine, synoptic processes and a variety of climatic conditions contribute to the frequent occurrence of severe convective phenomena and creating the extraordinary complexity of their space-time distribution. The study revealed current trends in the formation of dangerous convective phenomena in the south-west of Ukraine. One of the most squall-prone regions of Ukraine is the territory of the North-Western Black Sea region. During 2006-2020 there was an increase in the number of squalls and tornadoes in the North-Western Black Sea region in comparison with previous years.Tornadoes and strong squalls are dangerous for almost all spheres of human life and the economy of the region. The degree of negative impact depends on their type, quantity, intensity, area of formation and geographical features of the territory. The article defines the dynamics of the number of tornadoes and strong squalls in the North-Western Black Sea region (Odessa, Nikolayev and Kherson regions of Ukraine) from 2006 to 2020.Geographical position of the south-west of Ukraine, synoptic processes and a variety of climatic conditions contribute to the frequent occurrence of severe convective phenomena and creating the extraordinary complexity of their space-time distribution. The study revealed current trends in the formation of dangerous convective phenomena in the south-west of Ukraine. One of the most squall-prone regions of Ukraine is the territory of the North-Western Black Sea region. During 2006-2020 there was an increase in the number of squalls and tornadoes in the North-Western Black Sea region in comparison with previous years

Multidimensional perfect fluid cosmology with stable compactified internal dimensions

Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the parameters of the models are found to ensure dynamical behavior of the external (our) universe in agreement with observations.Comment: 11 pages, Latex2e, uses IOP packages, submitted to Class.Quant.Gra

AdS and stabilized extra dimensions in multidimensional gravitational models with nonlinear scalar curvature terms 1/R and R^4

We study multidimensional gravitational models with scalar curvature nonlinearities of the type 1/R and R^4. It is assumed that the corresponding higher dimensional spacetime manifolds undergo a spontaneous compactification to manifolds with warped product structure. Special attention is paid to the stability of the extra-dimensional factor spaces. It is shown that for certain parameter regions the systems allow for a freezing stabilization of these spaces. In particular, we find for the 1/R model that configurations with stabilized extra dimensions do not provide a late-time acceleration (they are AdS), whereas the solution branch which allows for accelerated expansion (the dS branch) is incompatible with stabilized factor spaces. In the case of the R^4 model, we obtain that the stability region in parameter space depends on the total dimension D=dim(M) of the higher dimensional spacetime M. For D>8 the stability region consists of a single (absolutely stable) sector which is shielded from a conformal singularity (and an antigravity sector beyond it) by a potential barrier of infinite height and width. This sector is smoothly connected with the stability region of a curvature-linear model. For D<8 an additional (metastable) sector exists which is separated from the conformal singularity by a potential barrier of finite height and width so that systems in this sector are prone to collapse into the conformal singularity. This second sector is not smoothly connected with the first (absolutely stable) one. Several limiting cases and the possibility for inflation are discussed for the R^4 model.Comment: 28 pages, minor cosmetic improvements, Refs. added; to appear in Class. Quantum Gra

Фазозарождение кремния на стеклоуглероде в расплаве KF-KCl-K2SiF6

Silicon nucleation process was invesigated in melt KF-KCl-K2SiF6 on glassy carbon substrates at 675 ºС by chronoamperometric method. Using data of the chronoamperograms the linear dependence I – τ3/2 was constructed. That fact testified the progressive nucleation mode of silicon. As seem from SEM micrographs silicon crystals obtained by a single pulse had different sizes, that also confirmed the progressive nucletion mode.Методом хроноамперометрии изучено зарождение кремния на стеклоуглеродной подложке в расплаве KF-KCl-K2SiF6 при температуре 675 ºС. Выявлено прогрессивное фазозарождение кремния. Из SEM-микрофотографий зародышей кремния, выращенных на стеклоуглеродной подложке в потенциостатическом режиме в интервале потенциалов от –0.005 до –0.03 В в расплаве KF-KCl-K2SiF6 при Т = 675 ºС, видно, что в условиях одного эксперимента они имеют размеры, различающиеся в несколько раз, что подтверждает прогрессирующий характер возникновения зародышей кремния. Показано, что когда к рабочему электроду при прочих равных условиях прикладывается более отрицательное значение потенциала относительно кремниевого электрода сравнения, то количество сформировавшихся зародышей на поверхности электрода растет

ОТОЗВАНО: Фазозарождение кремния на стеклоуглероде в расплаве KF-KCl-K2SiF6

Following the joint decision of the Editor-in-Chief and the journal's Ethics Committee, this article has been retracted. The article (its original Russian version) is an erroneously published duplicate of a paper that has already been published in Chimica Techno Acta 2014;1(2):67-72, doi:10.15826/chimtech.2014.1.2.1047. One of the conditions of submission of a paper for publication is that a paper has not been published previously. As such this article represents a severe abuse of the scientific publishing system. Our Editorial Board takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.Данная статья была отозвана по решению главного редактора и комитета по этике редколлегии журнала. Причиной этому является тот факт, что русскоязычная (непереведенная) версия данной статьи уже была опубликована в Chimica Techno Acta 2014;1(2):67-72, doi:10.15826/chimtech.2014.1.2.1047. Таким образом, данная статья нарушает этические нормы научных публикаций. Статьи, отправляемые на рассмотрение в журнал, не должны быть где-либо опубликованы ранее. Редколлегия журнала Chimica Techno Acta серьезно относится к данному требованию и приносит извинения читателям в связи с тем, что данный факт не был замечен ранее на этапе рассмотрения манускрипта

АЛГОРИТМЫ ОБРАБОТКИ ДАННЫХ, ПОЛУЧАЕМЫХ С ДАТЧИКОВ ДАВЛЕНИЯ ГИДРОЦИЛИНДРОВ ЗАБОЙНЫХ КРЕПЕЙ

Algorithms to analyze data produced by pressure sensors mounted on hydraulic cylinders of mine linings, which are exploited in lavas of the Starobin potash deposit, are presented. To build algorithms, data mining process has been represented by three general stages. First of them consists of data preprocessing. Based on data specifics, algorithms of removing outliers as well as determining characteristics independent of tunneling machine location and state of bottomhole supports were included in it. The second stage contains algorithms of finding in the preprocessed data of cycles, which were created by descent of mining supports, and phases of cycles that depend on location of the tunneling machine relative to those supports. Algorithms of the third stage were built to compute data characteristics connected with the found cycles and their phases. Besides, modifications of correlation algorithms for aggregated data were developed in order to investigate relationship between the characteristics, including their coupling with behavior of rock pressure. The algorithms are designed for use in automated monitoring systems of rock pressure in lavas of potash mines, including mines of the Joint Stock Company “Belaruskali”. The developed algorithms were programmed. Program realizations were seriously tested on big data supplied by pressure sensors mounted on hydraulic cylinders of bottomhole supports of the Starobin potash deposit. As an example of application of the developed algorithms, it is shown that acceleration of mining process increases the likelihood of rock blows to the supports.Построены алгоритмы анализа данных, получаемых с датчиков давления систем мониторинга, которые установлены на гидростойках забойных крепей, используемых в забоях Старобинского месторождения калийных солей. При разработке алгоритмов процесс анализа данных был разбит на несколько этапов, первый их которых заключается в первичной обработке данных. Исходя из их специфики созданы алгоритмы удаления выбросов и вычисления характеристик, не требующих оценки положения комбайна и состояния крепей. Алгоритмы второго этапа разработаны для выделения циклов в предобработанных данных, вызванных опусканием и передвижением крепей, а также фаз циклов, зависящих от расположения комбайна относительно каждой крепи. Алгоритмы третьего этапа построены для вычисления характеристик данных с горных крепей, связанных с выявленными циклами и их фазами. Для сравнительного анализа данных и выявления зависимостей между различными характеристиками, а также степени их влияния на проявления горного давления были разработаны модификации алгоритмов вычисления корреляции по сгруппированным данным с различными временными лагами. Алгоритмы предназначены для использования в автоматизированных системах мониторинга горного давления в лавах рудников месторождений калийных руд, в том числе рудников РУ ОАО «Беларуськалий». Разработанные алгоритмы были программно реализованы. Программные реализации прошли апробацию на больших объемах реальных данных, полученных с датчиков давления забойных крепей, установленных в лавах рудников Старобинского месторождения калийных руд. В качестве примера использования разработанных алгоритмов приведены результаты оценки зависимости риска проявления горных ударов от скорости проходки лавы. В частности показано, что увеличение скорости подвигания лавы повышает риск проявления ударов по крепям.

Diversity of universes created by pure gravity

We show that a number of problems of modern cosmology may be solved in the framework of multidimensional gravity with high-order curvature invariants, without invoking other fields. We use a method employing a slow-change approximation, able to work with rather a general form of the gravitational action, and consider Kaluza-Klein type space-times with one or several extra factor spaces. A vast choice of effective theories suggested by the present framework may be stressed: even if the initial Lagrangian is entirely fixed, one obtains quite different models for different numbers, dimensions and topologies of the extra factor spaces. As examples of problems addressed we consider (i) explanation of the present accelerated expansion of the Universe, with a reasonably small cosmological constant, and the problem of its fine tuning is considered from a new point of view; (ii) the mechanism of closed wall production in the early Universe; such walls are necessary for massive primordial black hole formation which is an important stage in some scenarios of cosmic structure formation; (iii) sufficient particle production rate at the end of inflation; (iv) it is shown that our Universe may contain spatial domains with a macroscopic size of extra dimensions. We also discuss chaotic attractors appearing at possible nodes of the kinetic term of the effective scalar field Lagrangian.Comment: 14 pages, 8 figures, revtex4. Final version, some considerations added in response to referee remark

Multidimensional cosmological models: cosmological and astrophysical implications and constraints

We investigate four-dimensional effective theories which are obtained by dimensional reduction of multidimensional cosmological models with factorizable geometry and consider the interaction between conformal excitations of the internal space (geometrical moduli excitations) and Abelian gauge fields. It is assumed that the internal space background can be stabilized by minima of an effective potential. The conformal excitations over such a background have the form of massive scalar fields (gravitational excitons) propagating in the external spacetime. We discuss cosmological and astrophysical implications of the interaction between gravexcitons and four-dimensional photons as well as constraints arising on multidimensional models of the type considered in our paper. In particular, we show that due to the experimental bounds on the variation of the fine structure constant, gravexcitons should decay before nucleosynthesis starts. For a successful nucleosynthesis the masses of the decaying gravexcitons should be m>10^4 GeV. Furthermore, we discuss the possible contribution of gravexcitons to UHECR. It is shown that, at energies of about 10^{20}eV, the decay length of gravexcitons with masses m>10^4 GeV is very small, but that for m <10^2 GeV it becomes much larger than the Greisen-Zatsepin-Kuzmin cut-off distance. Finally, we investigate the possibility for gravexciton-photon oscillations in strong magnetic fields of astrophysical objects. The corresponding estimates indicate that even the high magnetic field strengths of magnetars are not sufficient for an efficient and copious production of gravexcitons.Comment: 16 pages, LaTeX2e, minor changes, improved references, to appear in PR