Black holes and a scalar field in an expanding universe

We consider a model of an inhomogeneous universe including a massless scalar field, where the inhomogeneity is assumed to consist of many black holes. This model can be constructed by following Lindquist and Wheeler, which has already been investigated without including scalar field to show that an averaged scale factor coincides with that of the Friedmann model. In this work we construct the inhomogeneous universe with an massless scalar field, where we assume that the averaged scale factor and scalar field are given by those of the Friedmann model including a scalar field. All of our calculations are carried out in the framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous universe, we define the mass of a black hole in the Brans-Dicke expanding universe which is equivalent to ADM mass if the mass evolves adiabatically, and obtain an equation relating our mass to the averaged scalar field and scale factor. As the results we find that the mass has an adiabatic time dependence in a sufficiently late stage of the expansion of the universe, and that the time dependence is qualitatively diffenrent according to the sign of the curvature of the universe: the mass increases decelerating in the closed universe case, is constant in the flat case and decreases decelerating in the open case. It is also noted that the mass in the Einstein frame depends on time. Our results that the mass has a time dependence should be retained even in the general scalar-tensor gravitiy with a scalar field potential. Furthermore, we discuss the relation of our results to the uniqueness theorem of black hole spacetime and gravitational memory effect.Comment: 16 pages, 3 tables, 5 figure

Follow-Up Near-infrared Spectroscopy of Ultraluminous Infrared Galaxies observed by ISO

We present low resolution near-infrared spectroscopy of an unbiased sample of 24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously observed spectroscopically in the mid-infrared with the Infrared Space Observatory (ISO). Qualitatively, the near-infrared spectra resemble those of starbursts. Only in one ULIRG, IRAS 04114-5117E, do we find spectroscopic evidence for AGN activity. The spectroscopic classification in the near-infrared is in very good agreement with the mid-infrared one. For a subset of our sample for which extinction corrections can be derived from Pa-alpha and Br-gamma, we find rather high Pa-alpha luminosities, in accordance with the powering source of these galaxies being star formation.[Fe] emission is strong in ULIRGs and may be linked to starburst and superwind activity. Additionally, our sample includes two unusual objects. The first, IRAS F00183-7111, exhibits extreme [Fe] emission and the second, IRAS F23578-5307, is according to our knowledge one of the most luminous infrared galaxies in H2 rotation-vibration emission.Comment: Accepted for publication in A&A (12 pages, 4 figures). See http://www.mpia-hd.mpg.de/homes/dannerb/ for a version with higher quality figure

Industry Trade Effects Related to NAFTA

CRS ReportCRSIndustryTradeNAFTARL31386.pdf: 3834 downloads, before Oct. 1, 2020

Waiting-times and returns in high-frequency financial data: an empirical study

In financial markets, not only prices and returns can be considered as random variables, but also the waiting time between two transactions varies randomly. In the following, we analyse the statistical properties of General Electric stock prices, traded at NYSE, in October 1999. These properties are critically revised in the framework of theoretical predictions based on a continuous-time random walk model.Comment: 8 pages, 4 figure, presented at the International Workshop "Horizons in Complex Systems", Messina, Italy, December 200

Production and characterization of diatomaceous earth-based geopolymers and geopolymeric mortars

Mestrado de dupla diplomação com o Centro Federal de Educação Tecnológica de Minas Gerais – CEFET-MGSince 1980, the world has faced an increase in the earth's average surface temperature due to the high release of carbon dioxide into the atmosphere. One of the main responsible for this CO2 release is the manufacture of Portland Cement, associated with a carbon dioxide emission of around 7% of the world's total emissions. In this way, there is a need to find alternatives to Portland cement to reduce these emissions. This work aims to contribute to this endeavor, proposing the application of a solid waste used as a wine filtration agent in the wine industry, diatomaceous earth, containing high amounts of silicon, to produce geopolymers and geopolymeric mortars. A geopolymer is an inorganic polymer produced with an aluminosilicate precursor reacted with an alkaline solution that has been studied as an alternative to cement in the composition of mortars and concretes. Diatomaceous earth and alumina were employed in this work as aluminosilicate sources for the geopolymer precursor, while sodium hydroxide and sodium silicate were used as the alkaline solution. The production process involved mixing all these raw materials of the geopolymers to create a fresh geopolymer, which was then combined with sand and water to form a mortar. In some instances, a specific amount of cement was also added to the binder along with the geopolymer. Subsequently, the samples underwent a 28-day curing process, with the initial four days placed in an oven at 40 ºC and then transferred to room temperature. Following production, the geopolymers were characterized using XRD, FTIR, SEM-EDS, and pore property analysis. On the other hand, the mortar samples underwent compressive and flexural strength tests and a flow test. The results revealed that the most favorable mortar sample, sample 2 (S2), utilized the top-performing geopolymer sample, Geopolymer 2 (GP2), as the geopolymeric binder. GP2 featured a NaOH concentration of 10 M, and a Si/Al ratio of 3,5. In the case of the S2 mortar, it consisted of 75% GP and 25% Portland Cement in the binder. This combination resulted in a higher proportion of geopolymer phase, consequently improving mechanical properties.Desde 1980, o mundo vem enfrentando um aumento na temperatura média da superfície terrestre devido à alta emissão de dióxido de carbono na atmosfera, tendo como um dos principais responsáveis a indústria de cimento Portland (PC), que tem associada a sua produção uma emissão de CO2 responsável por cerca de 7% do total do mundo. Assim, é necessário encontrar alternativas ao PC a fim de reduzir essas emissões. Este trabalho tem como objetivo contribuir para esse esforço, propondo a aplicação de um resíduo sólido chamado terra diatomácea, utilizado como meio de filtração do vinho na indústria vinícola e que contém altas quantidades de silício, para produzir geopolímeros e argamassas geopoliméricas. Um geopolímero é um polímero inorgânico produzido com um precursor aluminossilicato reagido com uma solução alcalina que tem sido estudado como uma alternativa ao cimento na composição de argamassas e concretos. Neste trabalho, foram utilizadas a terra diatomácea e a alumina como fontes de aluminossilicato para o precursor do geopolímero, enquanto o hidróxido de sódio e o silicato de sódio foram usados como solução alcalina. O processo de produção envolveu inicialmente a mistura de todas essas matérias-primas para criar um geopolímero fresco, que foi então combinado com areia e água para formar uma argamassa. Em certos casos, uma quantidade específica de cimento também foi adicionada ao ligante juntamente com o geopolímero. Posteriormente, as amostras passaram por um processo de cura de 28 dias, sendo os quatro primeiros dias em um forno a 40 ºC e depois transferidas para a temperatura ambiente. Após a produção, os geopolímeros foram caracterizados por XRD, FTIR, SEM-EDS e análise das propriedades texturais. As amostras de argamassa, por sua vez, foram submetidas a testes de resistência à compressão e flexão, bem como a um teste de fluidez. Os resultados revelaram que a amostra de argamassa mais favorável, a amostra 2 (S2), utilizou o geopolímero de melhor desempenho, o Geopolímero 2 (GP2), como ligante geopolimérico. O GP2 apresentava uma concentração de NaOH de 10 M e uma relação Si/Al de 3,5. No caso da argamassa S2, ela era composta por 75% de GP e 25% de cimento Portland como ligante. Essa combinação resultou em uma proporção maior de fase geopolimérica, consequentemente levando a melhorias nas propriedades mecânicas

Randomized Tensor Ring Decomposition and Its Application to Large-scale Data Reconstruction

Dimensionality reduction is an essential technique for multi-way large-scale data, i.e., tensor. Tensor ring (TR) decomposition has become popular due to its high representation ability and flexibility. However, the traditional TR decomposition algorithms suffer from high computational cost when facing large-scale data. In this paper, taking advantages of the recently proposed tensor random projection method, we propose two TR decomposition algorithms. By employing random projection on every mode of the large-scale tensor, the TR decomposition can be processed at a much smaller scale. The simulation experiment shows that the proposed algorithms are $4-25$ times faster than traditional algorithms without loss of accuracy, and our algorithms show superior performance in deep learning dataset compression and hyperspectral image reconstruction experiments compared to other randomized algorithms.Comment: ICASSP submissio

Single production of excited electrons at future e^-e^+, ep and pp colliders

We analyzed the potential of the LC with $\sqrt{s}=0.5$ TeV, LC$\times$LHC based ep collider with $\sqrt{s}=3.74$ TeV and LHC with $\sqrt{s}=14$ TeV to search for excited electrons through transition magnetic type couplings with gauge bosons. The $e^{\star}\to e\gamma$ signal and corresponding backgrounds are studied in detail.Comment: 11 pages, 11 figures, 3 table

Waiting-times and returns in high-frequency financial data: an empirical study

In financial markets, not only prices and returns can be considered as random variables, but also the waiting time between two transactions varies randomly. In the following, we analyse the statistical properties of General Electric stock prices, traded at NYSE, in October 1999. These properties are critically revised in the framework of theoretical predictions based on a continuous-time random walk model.Duration; Continuous-time random walk; Fractional calculus; Statistical finance.