Collapse of Primordial Clouds

We present here studies of collapse of purely baryonic Population III objects with masses ranging from $10M_\odot$ to $10^6M_\odot$. A spherical Lagrangian hydrodynamic code has been written to study the formation and evolution of the primordial clouds, from the beginning of the recombination era ($z_{rec} \sim 1500$) until the redshift when the collapse occurs. All the relevant processes are included in the calculations, as well as, the expansion of the Universe. As initial condition we take different values for the Hubble constant and for the baryonic density parameter (considering however a purely baryonic Universe), as well as different density perturbation spectra, in order to see their influence on the behavior of the Population III objects evolution. We find, for example, that the first mass that collapses is $8.5\times10^4M_\odot$ for $h=1$, $\Omega=0.1$ and $\delta_i={\delta\rho / \rho}=(M / M_o)^{-1/3}(1+z_{rec})^{-1}$ with the mass scale $M_o=10^{15}M_\odot$. For $M_o=4\times10^{17}M_\odot$ we obtain $4.4\times10^{4}M_\odot$ for the first mass that collapses. The cooling-heating and photon drag processes have a key role in the collapse of the clouds and in their thermal history. Our results show, for example, that when we disregard the Compton cooling-heating, the collapse of the objects with masses $>8.5\times10^4M_\odot$ occurs earlier. On the other hand, disregarding the photon drag process, the collapse occurs at a higher redshift.Comment: 10 pages, MN plain TeX macros v1.6 file, 9 PS figures. Also available at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS" and then "ARTICLES"). MNRAS in pres

Collapse of Primordial Clouds II. The Role of Dark Matter

In this article we extend the study performed in our previous article on the collapse of primordial objects. We here analyze the behavior of the physical parameters for clouds ranging from $10^7M_\odot$ to $10^{15}M_\odot$. We studied the dynamical evolution of these clouds in two ways: purely baryonic clouds and clouds with non-baryonic dark matter included. We start the calculations at the beginning of the recombination era, following the evolution of the structure until the collapse (that we defined as the time when the density contrast of the baryonic matter is greater than $10^4$). We analyze the behavior of the several physical parameters of the clouds (as, e.g., the density contrast and the velocities of the baryonic matter and the dark matter) as a function of time and radial position in the cloud. In this study all physical processes that are relevant to the dynamical evolution of the primordial clouds, as for example photon-drag (due to the cosmic background radiation), hydrogen molecular production, besides the expansion of the Universe, are included in the calculations. In particular we find that the clouds, with dark matter, collapse at higher redshift when we compare the results with the purely baryonic models. As a general result we find that the distribution of the non-baryonic dark matter is more concentrated than the baryonic one. It is important to stress that we do not take into account the putative virialization of the non-baryonic dark matter, we just follow the time and spatial evolution of the cloud solving its hydrodynamical equations. We studied also the role of the cooling-heating processes in the purely baryonic clouds.Comment: 8 pages, MN plain TeX macros v1.6 file, 13 PS figures. Also available at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS" and then "ARTICLES"). MNRAS in pres

Obtenção de plântulas de híbridos de dendezeiro por cultivo in vitro.

Este trabalho teve como objetivo aplicar técnicas de cultura de tecidos em diferentes híbridos de dendezeiro (Elaeis guineensis Jacq.) para a conversão in vitro de embriões zigóticos em plântulas para produção de mudasviáveis para serem disponibilizadas no Estado do Pará. O experimento foi realizado na Embrapa Amazônia Oriental, Belém-PA. A metodologia foi a aplicação de práticas assépticas de isolamento embrionário, cultura de embriões, conversão em plântulas e aclimatação destas. Dezessete híbridos foram submetidos a desinfestação e assepsia, com posterior inoculação nos meios de cultura MS, ½ MS, Y3 e ½ Y3. Os frascos inoculados foram dispostos em sala de cultivo sob fotoperíodo de 16 h luz dia-1, com intensidade luminosa de 25 μmol s-1 e temperatura de 25±3 °C. O delineamento experimental foi o inteiramente casualizado em fatorial 3 x 4. Após avaliação da germinação e crescimento dos embriões, quanto à oxidação os genótipos CN 470, nos tratamentos MS e 1/2 Y3 não apresentaram oxidação, e esta apresentou-se mais adequada para o desenvolvimento do comprimento de raiz. Quanto ao genótipo indicado para a conversão de embriões zigóticos de híbridos de dendezeiro em plântulas viáveis à aclimatização, em extrato de vermiculita e solução nutritiva, o CN 514 em meio Y3 foi o mais viável. Aos três meses foi possível a conversão de embriões de híbridos de dendezeiro até a formação de plântulas

The conservation of energy-momentum and the mass for the graviton

In this work we give special attention to the bimetric theory of gravitation with massive gravitons proposed by Visser in 1998. In his theory, a prior background metric is necessary to take in account the massive term. Although in the great part of the astrophysical studies the Minkowski metric is the best choice to the background metric, it is not possible to consider this metric in cosmology. In order to keep the Minkowski metric as background in this case, we suggest an interpretation of the energy-momentum conservation in Visser's theory, which is in accordance with the equivalence principle and recovers naturally the special relativity in the absence of gravitational sources. Although we do not present a general proof of our hypothesis we show its validity in the simple case of a plane and dust-dominated universe, in which the `massive term' appears like an extra contribution for the energy density.Comment: 9 pages, accepted for publishing in GR

Can black hole MACHO binaries be detected by the Brazilian spherical antenna?

Different studies show that dark matter of non-baryonic origin might exist. There have been experimental evidences that at least one form of dark matter has been detected through microlensing effects. This form of dark matter is named MACHOs (Massive Astrophysical Compact Halo Objects). The MACHO collaboration estimated that the masses of these objects are to be in the range 0.15-0.95 solar masses, where the most probable mass is of 0.5 solar masses. Some authors argue that MACHOs could be black holes, and that they could form binary systems, BHMACHO binaries. As is well known binary systems are sources of gravitational waves. The Brazilian spherical antenna will operate in the frequency band of 3.0-3.4 kHz, sensitive to binaries of a pair of 0.5 solar mass black holes just before coalescing. In the present work we study the detectability of these putative BHMACHO binaries by the Brazilian spherical antenna Mario Schenberg.Comment: 7 pages, 2 figure

Extra polarization states of cosmological gravitational waves in alternative theories of gravity

Cosmological Gravitational Waves (GWs) are usually associated with the transverse-traceless part of the metric perturbations in the context of the theory of cosmological perturbations. These modes are just the usual polarizations `+' and `x' which appear in the general relativity theory. However, in the majority of the alternative theories of gravity, GWs can present more than these two polarization states. In this context, the Newman-Penrose formalism is particularly suitable for evaluating the number of non-null GW modes. In the present work we intend to take into account these extra polarization states for cosmological GWs in alternative theories of gravity. As an application, we derive the dynamical equations for cosmological GWs for two specific theories, namely, a general scalar-tensor theory which presents four polarization states and a massive bimetric theory which is in the most general case with six polarization states for GWs. The mathematical tool presented here is quite general, so it can be used to study cosmological perturbations in all metric theories of gravity.Comment: 26 pages, 1 figure. Accepted for publication in Classical and Quantum Gravity

Observational Constraints on Visser's Cosmological Model

Theories of gravity for which gravitons can be treated as massive particles have presently been studied as realistic modifications of General Relativity, and can be tested with cosmological observations. In this work, we study the ability of a recently proposed theory with massive gravitons, the so-called Visser theory, to explain the measurements of luminosity distance from the Union2 compilation, the most recent Type-Ia Supernovae (SNe Ia) dataset, adopting the current ratio of the total density of non-relativistic matter to the critical density ($\Omega_m$) as a free parameter. We also combine the SNe Ia data with constraints from Baryon Acoustic Oscillations (BAO) and CMB measurements. We find that, for the allowed interval of values for $\Omega_m$, a model based on Visser's theory can produce an accelerated expansion period without any dark energy component, but the combined analysis (SNe Ia + BAO + CMB) shows that the model is disfavored when compared with $\Lambda$CDM model.Comment: 6 pages, 4 figure

Balanço nitrogenado de caprinos alimentados com dietas contendo subproduto de urucum (Bixa orellana L.).

Foram avaliados os balanços nitrogenados de caprinos alimentados com dietas contendo subproduto de urucum em diferentes níveis de inclusão. Utilizaram-se doze caprinos com peso vivo inicial de 18,05 kg, distribuídos num delineamento inteiramente casualizado com quatro tratamentos e seis repetições no tempo. As inclusões de subproduto de urucum nas dietas foram de 18, 36, 46 e 72%. Os dados de consumo e digestibilidade, além dos dados de balanço nitrogenado, foram submetidos a análises de variância e regressão, em função da inclusão do subproduto na dieta. Os balanços nitrogenados em função do nível de inclusão do subproduto, apresentaram significância entre as dietas P(<0,05), apesar de todos os níveis apresentarem balanço nitrogenado positivo

The continuity of the inversion and the structure of maximal subgroups in countably compact topological semigroups

In this paper we search for conditions on a countably compact (pseudo-compact) topological semigroup under which: (i) each maximal subgroup $H(e)$ in $S$ is a (closed) topological subgroup in $S$; (ii) the Clifford part $H(S)$(i.e. the union of all maximal subgroups) of the semigroup $S$ is a closed subset in $S$; (iii) the inversion $\operatorname{inv}\colon H(S)\to H(S)$ is continuous; and (iv) the projection $\pi\colon H(S)\to E(S)$, $\pi\colon x\longmapsto xx^{-1}$, onto the subset of idempotents $E(S)$ of $S$, is continuous

Comportamento de cultivares de maracujazeiro quanto ao vírus do endurecimento do fruto (Passionfruit woodiness virus - PWV).

Edição dos resumos do Congresso Brasileiro de Fitopatologia, 43