Parametric amplification of waves during gravitational collapse: a first investigation

We study the dynamical evolution of perturbations in the gravitational field of a collapsing fluid star. Specifically, we consider the initial value problem for a massless scalar field in a spacetime similar to the Oppenheimer-Snyder collapse model, and numerically evolve in time the relevant wave equation. Our main objective is to examine whether the phenomenon of parametric amplification, known to be responsible for the strong amplification of primordial perturbations in the expanding Universe, can efficiently operate during gravitational collapse. Although the time-varying gravitational field inside the star can, in principle, support such a process, we nevertheless find that the perturbing field escapes from the star too early for amplification to become significant. To put an upper limit in the efficiency of the amplification mechanism (for a scalar field) we furthermore consider the case of perturbations trapped inside the star for the entire duration of the collapse. In this extreme case, the field energy is typically amplified at the level ~ 1% when the star is about to cross its Schwarszchild radius. Significant amplification is observed at later stages when the star has even smaller radius. Therefore, the conclusion emerging from our simple model is that parametric amplification is unlikely to be of significance during gravitational collapse. Further work, based on more realistic collapse models, is required in order to fully assess the astrophysical importance of parametric amplification.Comment: 14 pages, revtex, 9 eps figure

Nuclear classical dynamics of H2_2 in intense laser field

In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization respectively. In the second part of the paper, the time dependent Schr\"{o}dinger and Newton equations are solved simultaneously for the electrons and the nuclei of H$_2$ respectively. The electrons and nuclei dynamics are separated on the base of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390 nm, 532 nm and 780 nm) and intensities ($5\times10^{14}$ $Wcm^{-2}$ and $5\times10^{15}$ $Wcm^{-2}$) of the ultrashort intense laser pulses with a sinus second order envelope function are used. The behaviour of the time dependent classical nuclear dynamics in the absence and present of the laser field are investigated and compared. In the absence of the laser field, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.Comment: 16 pages, 7 figure

Research of mandrelling process of technological holes in the aviation alloy Д16чT

Розглянуто спосіб обробки отворів для відповідальних деталей з алюмінієвого сплаву Д16чТ шляхом дорнування з різними величинами натягу. Представлені результати розрахунків методом скінченних елементів в програмному комплексі DEFORM. Розрахунковим шляхом встановлено вплив натягу, при дорнувані, на напружено-деформований стан, розподіл пошкоджуваності в матеріалі навколо отвору і кінцеві форму і розмір після дорнування. Для перевірки результатів чисельного моделювання були проведені експериментальні дослідження дорнування отворів в заготовках з алюмінієвого сплаву Д16чТ з використанням для змащення суміші індустріального мастила И40, графіту (дрібного помелу) та дисульфід молібдену.Purpose. The impact of the magnitude of interference in the mandrelling processes of holes in workpieces made of aluminum alloy Д16чТ T on the stress-strain state, energy-power parameters of the process and quality characteristics of processed holes was determined. Design/methodology/approach. A method of processing holes for critical parts made of Д16чТ by mandrelling with different tightness values was proposed. The results of finite element analysis in the software package DEFORM were obtained. The impact of interference magnitude during mandrelling on the stress-strain state, the distribution of damage in the material around the hole and the final shape and size after mandrelling was determined by calculated method. For verification of numerical results the experimental studies of mandrelling of holes in workpieces made of aluminum alloy Д16чТ was carried out. Findings. The effect of a tension in the energy-power parameters of the mandrelling process of holes in workpieces made of aluminum alloy Д16чТ, the uneven spread of damage to the material, the stress-strain state of the material after burnishing and distortion of the geometry of the workpiece in the place of the mandrel entrance into the hole and exit from the hole was calculated and experimentally established. The lubricant is the mixture of industrial oil I-40A, graphite (fine grinding) and molybdenum disulfide was taken for experimental study. Originality/value. These materials are intended for the study of processes that allow improving the reliability and durability of aircraft details and designs with high reliability requirements.Рассмотрен способ обработки отверстий для ответственных деталей из алюминиевого сплава Д16чТ путем дорнования с разными величинами натяга. Представлены результаты расчетов методом конечных элементов в программном комплексе DEFORM. Расчётным путем установлено влияния величины натяга при дорновании на напряженно-деформированное состояние, распределение поврежденности в материале вокруг отверстия и конечные форму и размер отверстия после дорнования. Для проверки результатов численного моделирования были проведены экспериментальные исследования дорнования отверстий в заготовках из алюминиевого сплава Д16чТ с использованием для смазки смеси индустриального масла И40, гранита (мелкого помола) и дисульфид молибдена

Confusion background from compact binaries

URL to conference site: http://www.amaldi8.org/index.htmlDouble neutron stars are one of the most promizing sources for terrestrial gravitational wave interferometers. For actual interferometers and their planned upgrades, the probability of having a signal present in the data is small, but as the sensitivity improves, the detection rate increases and the waveforms may start to overlap, creating a confusion background, ultimately limiting the capabilities of future detectors. The third generation Einstein Telescope, with an horizon of z > 1 and very low frequency "seismic wall" may be affected by such confusion noise. At a minimum, careful data analysis will be require to separate signals which will appear confused. This result should be borne in mind when designing highly advanced future instruments

Testing Alternative Theories of Gravity using LISA

We investigate the possible bounds which could be placed on alternative theories of gravity using gravitational wave detection from inspiralling compact binaries with the proposed LISA space interferometer. Specifically, we estimate lower bounds on the coupling parameter \omega of scalar-tensor theories of the Brans-Dicke type and on the Compton wavelength of the graviton \lambda_g in hypothetical massive graviton theories. In these theories, modifications of the gravitational radiation damping formulae or of the propagation of the waves translate into a change in the phase evolution of the observed gravitational waveform. We obtain the bounds through the technique of matched filtering, employing the LISA Sensitivity Curve Generator (SCG), available online. For a neutron star inspiralling into a 10^3 M_sun black hole in the Virgo Cluster, in a two-year integration, we find a lower bound \omega > 3 * 10^5. For lower-mass black holes, the bound could be as large as 2 * 10^6. The bound is independent of LISA arm length, but is inversely proportional to the LISA position noise error. Lower bounds on the graviton Compton wavelength ranging from 10^15 km to 5 * 10^16 km can be obtained from one-year observations of massive binary black hole inspirals at cosmological distances (3 Gpc), for masses ranging from 10^4 to 10^7 M_sun. For the highest-mass systems (10^7 M_sun), the bound is proportional to (LISA arm length)^{1/2} and to (LISA acceleration noise)^{-1/2}. For the others, the bound is independent of these parameters because of the dominance of white-dwarf confusion noise in the relevant part of the frequency spectrum. These bounds improve and extend earlier work which used analytic formulae for the noise curves.Comment: 16 pages, 9 figures, submitted to Classical & Quantum Gravit

LISA as a dark energy probe

Recently it was shown that the inclusion of higher signal harmonics in the inspiral signals of binary supermassive black holes (SMBH) leads to dramatic improvements in parameter estimation with the Laser Interferometer Space Antenna (LISA). In particular, the angular resolution becomes good enough to identify the host galaxy or galaxy cluster, in which case the redshift can be determined by electromagnetic means. The gravitational wave signal also provides the luminosity distance with high accuracy, and the relationship between this and the redshift depends sensitively on the cosmological parameters, such as the equation-of-state parameter $w=p_{\rm DE}/\rho_{\rm DE}$ of dark energy. With a single binary SMBH event at $z < 1$ having appropriate masses and orientation, one would be able to constrain $w$ to within a few percent. We show that, if the measured sky location is folded into the error analysis, the uncertainty on $w$ goes down by an additional factor of 2-3, leaving weak lensing as the only limiting factor in using LISA as a dark energy probe.Comment: 11pages, 1 Table, minor changes in text, accepted for publication in Classical and Quantum Gravity (special issue for proceedings of 7th LISA symposium

Binary black hole spectroscopy

We study parameter estimation with post-Newtonian (PN) gravitational waveforms for the quasi-circular, adiabatic inspiral of spinning binary compact objects. The performance of amplitude-corrected waveforms is compared with that of the more commonly used restricted waveforms, in Advanced LIGO and EGO. With restricted waveforms, the properties of the source can only be extracted from the phasing. For amplitude-corrected waveforms, the spectrum encodes a wealth of additional information, which leads to dramatic improvements in parameter estimation. At distances of $\sim 100$ Mpc, the full PN waveforms allow for high-accuracy parameter extraction for total mass up to several hundred solar masses, while with the restricted ones the errors are steep functions of mass, and accurate parameter estimation is only possible for relatively light stellar mass binaries. At the low-mass end, the inclusion of amplitude corrections reduces the error on the time of coalescence by an order of magnitude in Advanced LIGO and a factor of 5 in EGO compared to the restricted waveforms; at higher masses these differences are much larger. The individual component masses, which are very poorly determined with restricted waveforms, become measurable with high accuracy if amplitude-corrected waveforms are used, with errors as low as a few percent in Advanced LIGO and a few tenths of a percent in EGO. The usual spin-orbit parameter $\beta$ is also poorly determined with restricted waveforms (except for low-mass systems in EGO), but the full waveforms give errors that are small compared to the largest possible value consistent with the Kerr bound. This suggests a way of finding out if one or both of the component objects violate this bound. We also briefly discuss the effect of amplitude corrections on parameter estimation in Initial LIGO.Comment: 28 pages, many figures. Final version accepted by CQG. More in-depth treatment of component mass errors and detectability of Kerr bound violations; improved presentatio

Innovation activity of scientists as a factor in the development of academic entrepreneurship in Russia

The development of academic entrepreneurship as a way of transfer of innovation is an urgent task. One of the main factors in the development of academic entrepreneurship is innovation-oriented staff of higher education institutions. Insufficient attention of the scientific literature to importance of this factor is thwarting progress of various forms of academic entrepreneurship. In connection with this proposed study is aimed at determining the degree of scientific innovation activity influence on the development of academic entrepreneurship in Russia. Academic entrepreneurship in Russia has been chosen as the object of study. Analysis of the basic research in the field of academic entrepreneurship for the period of 2011-2016 years was used to achieve this goal. Analysis of publications was revealed that the innovative activity of the teaching staff of universities is a critical factor in the development of academic entrepreneurship. However, Russian scientists are characterized by low innovation activity, resulting in academic entrepreneurship in Russia is weak. The researchers suggest the following solutions to eliminate or minimize the effects of this problem: full awareness and moral training of the scientists involved in the innovation process of higher education institutions; profit payment; creating a psychological climate that will affect the scientific process of self-realization; continuous training of employees involved in the innovation process of higher education institutions; the creation of conditions that will contribute to the manifestation of creative activity of scientists; provide greater confidence to young scientists, graduate students and undergraduates; providing moral and material encouragement of initiatives, experimentation and creativity of scientific and pedagogical staff; the allocation of free time for scientists to research and search activities and others. The data obtained can be used by the guidance of Russian universities to enhance innovation activity of the teaching staff of universities

Molecular-genetic mechanisms underlying fruit and seed coloration in plants

Diverse patterns of plant fruit and seed coloration are determined by the presence of two main types of pigment, carotenoids (red, orange and yellow color) and anthocyanins (purple, blue, red). Thеy belong to two groups of secondary metabolites, isoprenoids and flavonoids. Interest towards the genetic mechanisms that control coloration in plants has recently increased due to the antioxidant and antimicrobial properties of some pigments and their colorless precursors consumed with plant-derived food. The genes encoding enzymes involved in step-bystep conversion of initial organic molecules to final pigmented compounds are referred to as structural genes, while regulatory genes are responsible for activation of the expression of structural genes and control the synthesis of pigments at certain times and in proper tissue. The data in plant genetics accumulated to date show that the inter- and intraspecies phenotypic diversity in coloration is mainly related with regulatory genes. Previously developed rich gene collections and precise genetic models for coloration traits in dicots and monocots as well as the rapid development of molecular genetic methods for studying plants allowed for studying genetic regulation of pigment synthesis at a molecular level. The peculiarities of the regulation of carotenoid biosynthesis are exemplified with Solanaceae fruits. The genetic mechanisms underlying the synthesis of various flavonoid pigments are exemplified with a study of seed color in Poaceae plants. In summary, prospects for the practical use of regulatory genes that control pigment synthesis are discussed and examples of their practical use in vegetable and cereal crop breeding are given

Assessing unmodified 70-mer oligonucleotide probe performance on glass-slide microarrays

BACKGROUND: Long oligonucleotide microarrays are potentially more cost- and management-efficient than cDNA microarrays, but there is little information on the relative performance of these two probe types. The feasibility of using unmodified oligonucleotides to accurately measure changes in gene expression is also unclear. RESULTS: Unmodified sense and antisense 70-mer oligonucleotides representing 75 known rat genes and 10 Arabidopsis control genes were synthesized, printed and UV cross-linked onto glass slides. Printed alongside were PCR-amplified cDNA clones corresponding to the same genes, enabling us to compare the two probe types simultaneously. Our study was designed to evaluate the mRNA profiles of heart and brain, along with Arabidopsis cRNA spiked into the labeling reaction at different relative copy number. Hybridization signal intensity did not correlate with probe type but depended on the extent of UV irradiation. To determine the effect of oligonucleotide concentration on hybridization signal, 70-mers were serially diluted. No significant change in gene-expression ratio or loss in hybridization signal was detected, even at the lowest concentration tested (6.25 μm). In many instances, signal intensity actually increased with decreasing concentration. The correlation coefficient between oligonucleotide and cDNA probes for identifying differentially expressed genes was 0.80, with an average coefficient of variation of 13.4%. Approximately 8% of the genes showed discordant results with the two probe types, and in each case the cDNA results were more accurate, as determined by real-time PCR. CONCLUSIONS: Microarrays of UV cross-linked unmodified oligonucleotides provided sensitive and specific measurements for most of the genes studied