Turbulent Thermalization

We study, analytically and with lattice simulations, the decay of coherent field oscillations and the subsequent thermalization of the resulting stochastic classical wave-field. The problem of reheating of the Universe after inflation constitutes our prime motivation and application of the results. We identify three different stages of these processes. During the initial stage of ``parametric resonance'', only a small fraction of the initial inflaton energy is transferred to fluctuations in the physically relevant case of sufficiently large couplings. A major fraction is transfered in the prompt regime of driven turbulence. The subsequent long stage of thermalization classifies as free turbulence. During the turbulent stages, the evolution of particle distribution functions is self-similar. We show that wave kinetic theory successfully describes the late stages of our lattice calculation. Our analytical results are general and give estimates of reheating time and temperature in terms of coupling constants and initial inflaton amplitude.Comment: 27 pages, 13 figure

Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect

Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set, allowing off equatorial plane plasma extraordinary wave probing from high magnetic field side, was installed. A separate line less than 1.5 MHz wide and shifted by up to 2 MHz is routinely observed in the backscattering spectrum under condition of accessible upper hybrid resonance. The enhanced frequency shift is explained by the growth of poloidal wave number of the probing wave in the resonance. Development of a new scheme for local diagnostics of fluctuations poloidal rotation based on this effect is started.У статті описуються спостереження посиленого ефекту Доплера в спектрі сигналу розсіяного назад у верхньому гібридному резонансі зондувальної хвилі. Експеримент виконаний на токамаці ФТ-2, на якому недавно були встановлені рухливі антени, що дозволяють здійснювати зондування плазми електромагнітними хвилями в незвичайній поляризації з боку сильного магнітного поля. За умови доступного верхнього гібридного резонансу в спектрі розсіювання спостерігалася лінія шириною менш 1.5 МГц, зрушена до 2 МГц. Ефект пояснений ростом полоідального хвильового числа зондувальної хвилі в резонансі. Почато розвиток нової схеми локальної діагностики обертання плазмових флуктуацій, заснованої на цьому ефекті.В статье описываются наблюдения усиленного эффекта Доплера в спектре сигнала рассеянного назад в верхнем гибридном резонансе зондирующей волны. Эксперимент выполнен на токамаке ФТ-2, на котором недавно были установлены подвижные антенны, позволяющие осуществлять зондирование плазмы электромагнитными волнами в необыкновенной поляризации со стороны сильного магнитного поля. При условии доступного верхнего гибридного резонанса в спектре рассеяния наблюдалась линия шириной менее 1.5 МГц, сдвинутая до 2 МГц. Эффект объяснён ростом полоидального волнового числа зондирующей волны в резонансе. Начато развитие новой схемы локальной диагностики вращения плазменных флуктуаций, основанной на этом эффекте

From Coherent Modes to Turbulence and Granulation of Trapped Gases

The process of exciting the gas of trapped bosons from an equilibrium initial state to strongly nonequilibrium states is described as a procedure of symmetry restoration caused by external perturbations. Initially, the trapped gas is cooled down to such low temperatures, when practically all atoms are in Bose-Einstein condensed state, which implies the broken global gauge symmetry. Excitations are realized either by imposing external alternating fields, modulating the trapping potential and shaking the cloud of trapped atoms, or it can be done by varying atomic interactions by means of Feshbach resonance techniques. Gradually increasing the amount of energy pumped into the system, which is realized either by strengthening the modulation amplitude or by increasing the excitation time, produces a series of nonequilibrium states, with the growing fraction of atoms for which the gauge symmetry is restored. In this way, the initial equilibrium system, with the broken gauge symmetry and all atoms condensed, can be excited to the state, where all atoms are in the normal state, with completely restored gauge symmetry. In this process, the system, starting from the regular superfluid state, passes through the states of vortex superfluid, turbulent superfluid, heterophase granular fluid, to the state of normal chaotic fluid in turbulent regime. Both theoretical and experimental studies are presented.Comment: Latex file, 25 pages, 4 figure

A stress or migration marker (a study of the auditory canal exostosis in the skeleton material of the Middle Bronze Age population from the Lower Volga region burial grounds)

The paper attempts to analyze the incidences of ear exostoses revealed in the skeletal remains of the Middle Bronze Age population of the Lower Volga region. In total, we have revealed 4 incidences of bone (skeletal) formations in the ear canal. The pathologies were observed predominantly in men over 20 years old. The paper presents a description of paleoanthropological material and provides a detailed interpretation of archaeological sites the skeletal remains originated from. We have examined hypothesis of ear exostosis occurrence in the Middle Bronze Age people of the Lower Volga region. The condition may be caused by stress arising from exposure to climatic factors, a specific lifestyle and regular natural inflammatory ear processes. However, the appearance of ear exostoses in the Middle Bronze Age population in the Lower Volga region is most likely to be explained by relocation of some groups from the Trans-Caucasian, Northern Caucasian or Northern Black sea regions. This assumption corresponds to the results of the paleoecological, archaeological and craniological analysis confirming the likely migration of the population of the Trans-Caucasian, Northern Caucasian and the Northern Black sea regions as a result of an ecological crisis at the end of the III — the beginning of the II millennium BC to the territory of the Lower Volga region

Investigation of rutilizing additive influence in hydrated titanium dioxide at thermal processing

The influence of a rutilizing additive in hydrated titanium dioxide is studied at its dehydration within the range of temperatures from 100 to 230° С. The quantity of major impurities is determined using an atom-emission spectrometer. Also, the X-ray diffraction analysis of obtained samplesis performed

The Research of (NH4)2BeF4 Solution Purification Effectiveness

AbstractThe research work topicality is based on necessity of beryllium production from fluorine containing raw materials technology optimization, beryllium losses minimization and environmental impact decrease by beryllium and materials based on beryllium production. The goal of research is identification of beryllium containing solutions produced in the result of beryllium concentrate fluorineammonium processing purification possibility (clarification of iron, aluminum, calcium and silicon) and conditions provided maximum impurity removal from solution, which do not cause beryllium hydrolysis

Investigation of rutilizing additive influence in hydrated titanium dioxide at thermal processing

The influence of a rutilizing additive in hydrated titanium dioxide is studied at its dehydration within the range of temperatures from 100 to 230° С. The quantity of major impurities is determined using an atom-emission spectrometer. Also, the X-ray diffraction analysis of obtained samplesis performed