Generalised effective cosmology from group field theory

We extend various recent results regarding the derivation of effective cosmological Friedmann equations from the dynamics of group field theory (GFT). Restricting ourselves to a single GFT field mode (or fixed values of Peter–Weyl representation labels), we first consider dynamics given by a quadratic Hamiltonian, which takes the form of a squeezing operator, and then add a quartic interaction that can be seen as a toy model for interactions in full GFT. Our derivation of effective Friedmann equations does not require a mean-field approximation; we mostly follow a general approach in which these equations in fact hold for any state. The resulting cosmological equations exhibit corrections to classical Friedmann dynamics similar to those of loop quantum cosmology, leading to generic singularity resolution, but also involve further state-dependent terms. We then specify these equations to various types of coherent states, such as Fock coherent states or Perelomov–Gilmore states based on the su(1, 1) structure of harmonic quantum cosmology. We compute relative uncertainties of volume and energy in these states, clarifying whether they can be interpreted as semiclassical. In the interacting case, both analytical and numerical approximations are used to obtain modified cosmological dynamics. Our results clarify how effective cosmological equations derived from GFT can provide reliable approximations to the full dynamics

Estimation of corrosion resistance of curing mixtures based on coal-bearing rocks from Western Donbass

Purpose. Substantiation of possible use of coal-bearing rocks as a replacement for a part of the filler in the preparation of shotcrete for lining of mine workings in the conditions of mineralized mine water. Methods. The research is based on carrying out corrosion testing of concrete specimens by dipping them into mine water. Chemical analysis of mine waters composition has been completed. A scanning microscope was used to study the state of concrete specimens microstructure. Findings. A comparative analysis was conducted to evaluate of the cement rock resistance to mineralized water, depending on the composition of the starting components for the grouting and shotcrete mixtures is carried out. The change in the chemical composition of mine water after soaking concrete specimens in it is defined. Photographs of concrete specimens microstructure after soaking in ordinary and mineralized water for 6 and 8 months are shown. Originality. Curing mixtures based on coal-bearing rocks from Western Donbass are mineralized water resistant and can act as a quality protection from aggressive water filtrationdue to the properties of rocks used as a filler. Practical implications. The results can be used for the rational choice of the composition of the concrete mixture with the replacement of filler part with mine rock. That will enhance the long-term stability of the mine working lined by these compositions.Мета. Обґрунтування можливості використання вуглевміщуючих порід у якості заміни частини заповнювача в процесі приготування бетону для кріплення гірничих виробок в умовах мінералізованих шахтних вод. Методика. Робота базується на проведенні корозійних випробувань бетонних зразків шляхом занурення їх у шахтну воду. Виконано хімічний аналіз складу шахтних вод. Використаний растровий мікроскоп для дослідження стану мікроструктури бетонних зразків. Результати. Виконано порівняльний аналіз оцінки стійкості цементного каменю до впливу мінералізованої води залежно від складу вихідних компонентів для тампонажних, торкрет-бетонних і набризкбетонних сумішей. Визначено зміну хімічного складу шахтної води після витримки у ній бетонних зразків. Наведено фотографії мікроструктури бетонних зразків після витримки у нормальних умовах та мінералізованої води протягом 6 і 8 місяців. Наукова новизна. Твердіючі суміші на основі вуглевміщуючих порід Західного Донбасу достатньо стійкі до впливу мінералізованих вод та є якісною протифільтраційною завісою завдяки властивостям порід, використаних у якості заповнювача. Практична значимість. Отримані результати можуть бути використані для раціонального підбору складу бетонної суміші із заміною частини заповнювача шахтної породою, що дозволить підвищити тривалу стійкість гірничої виробки, закріпленої з використанням даних складів.Цель. Обоснование возможности использование углевмещающих пород в качестве замены части заполнителя в процессе приготовления бетона для крепления горных выработок в условиях минерализованных шахтных вод. Методика. Работа базируется на проведении коррозионных испытаний бетонных образцов путем погружения их в шахтную воду. Выполнен химический анализ состава шахтных вод. Использован растровый микроскоп для исследования состояния микроструктуры бетонных образцов. Результаты. Выполнен сравнительный анализ оценки устойчивости цементного камня к воздействию минерализованной воды в зависимости от состава исходных компонентов для тампонажных, торкрет-бетонных и набрызгбетонных смесей. Определено изменение химического состава шахтной воды после выдержки в ней бетонных образцов. Представлены фотографии микроструктуры бетонных образцов после выдержки в нормальных условиях и минерализованной воде в течение 6 и 8 месяцев. Научная новизна. Твердеющие смеси на основе углевмещающих пород Западного Донбасса устойчивы к влиянию минерализованных вод и являются качественной противофильтрационной завесой благодаря свойствам пород, использованных в качестве заполнителя. Практическая значимость. Полученные результаты могут быть использованы для рационального подбора состава бетонной смеси с заменой части заполнителя шахтной породой, что позволит повысить длительную устойчивость горной выработки, закрепленной с использованием данных составов.The authors express their gratitude to the administration of the Department of Construction, Geotechnics and Geomechanics of the National Mining University (Dnipropetrovsk, Ukraine), represented by O. Shashenko and A. Solodiankin, as well as to all those who helped in carrying out works related to preparation of this paper

Hamiltonian group field theory with multiple scalar matter fields

One approach to defining dynamics for quantum gravity in a naturally timeless setting is to select a suitable matter degree of freedom as a “clock” before quantization. This idea of deparametrization was recently introduced in group field theory leading to a Hamiltonian formulation in which states or operators evolve with respect to the clock given by a free massless scalar field, similar to what happens in deparametrized models in quantum cosmology. Here we extend the construction of Hamiltonian group field theory to models with multiple scalar matter fields, encountering new features and technical subtleties compared with the previously studied case. We show that the effective cosmological dynamics for these more general models reduce to the Friedmann dynamics of general relativity with multiple scalar fields in the limit of large volume, if suitable (nongeneric) initial conditions are chosen. At high energy, we find corrections to the classical Friedmann equations whose form is similar to what is found in loop quantum cosmology. These corrections lead to generic singularity resolution by a bounce. For generic initial conditions, the effective cosmological dynamics treat the clock field and other matter fields differently, in disagreement with the Friedmann dynamics of general relativity. We speculate on a possible interpretation in terms of inhomogeneities

Эволюция информационных технологий и их роль в развитии экономики и общества

In Russia there is a problem of formation of information economy is one of the most pressing problems of our time. The information economy is needed for further stable development of the country and the subsequent introduction of Russia into the global economy

Addendum to "Relational Hamiltonian for group field theory"

In this addendum to E. Wilson-Ewing, [Phys. Rev. D 99, 086017 (2019)], we extend the construction of a Hamiltonian formalism to a new class of group field theory actions with a kinetic term that is local in the group variables and depends only on their derivatives; such a kinetic term will couple magnetic indices of opposite sign in the Peter-Weyl decomposition. The main results of that Wilson-Ewing paper for the resulting cosmology extend to this case

Wood characteristics of Ceiba pentandra cultivated in upland and floodplain ecosystem.

The present work was carried out with tree sumauma's tree (nativa, adult and young trees) cultivated in floodplains (varzeas) and uplands (terra firme) ecosystem, having as objective, obtain information about growth patterns of the species and to correlate them into different environmental conditions (floodplain and upland) as well as investigate anatomic and physical parameters of the wood, purposing correlate the wood quality of adult native trees, with young tree's wood, cultivated in floodplain and upland.bitstream/item/180970/1/ID-3837-2-Apendix-1.pd

LAS BATALLAS FESTIVAS DE ESPANA

Serving individual customer needs at reasonable prices can be a profitable target market in high-wage countries. The dilemma between scale and scope-oriented production is one major research topic within the Cluster of Excellence "Integrative Production Technology for High-Wage Countries" at the RWTH Aachen University. One main objective of this project is to bridge the existing gap between individual manufacturing and mass production. Modularization is a widely accepted approach in tool-based manufacturing processes. In this paper, we propose a flexible design methodology for modular tools and dies. The methodology will assist the design engineer in setting up a series of modularized tools in a conceptually closed manner. The described methodology covers modularization in a broad sense, i.e. it includes hardware modularization as well as modularization of the construction process. The methodology consists of three phases: initiation, analysis and design phase

Влияние CaO на синтез и микроструктуру керамики на основе бората алюминия

Осуществлен синтез бората алюминия на основе природных сырьевых материалов, изучено влияние добавки CaO на структуру и свойства материала. Было выявлено, что введение CaO в состав исходной сырьевой смеси способствует формированию игольчатых кристаллов и увеличению выхода фазы бората алюминия, а также снижению плотности материала. Показано, что двухстадийный обжиг позволяет повысить прочность образцов с добавкой CaO с сохранением низкой плотности

Исследование температурного состояния графитовой кладки реактора РБМК-1000

The usual way of realizing microstructured features on metallic surfaces is to generate the designated pattern on each single part by means of laser ablation, electro discharge machining or micro milling. A disadvantage of these process chains is the limited productivity due to the additional processing of each part. The approach taken by this project is to replicate microstructured surfaces via investment casting. The main research objective deals with the investigation of single process steps of the investment casting process with regard to the molding accuracy. To demonstrate the potential of microcast surfaces, current results for the casting of a microstructured hydrophobic surface will be shown