Noncommutative Geometry and Cosmology

We study some consequences of noncommutativity to homogeneous cosmologies by introducing a deformation of the commutation relation between the minisuperspace variables. The investigation is carried out for the Kantowski-Sachs model by means of a comparative study of the universe evolution in four different scenarios: the classical commutative, classical noncommutative, quantum commutative, and quantum noncommutative. The comparison is rendered transparent by the use of the Bohmian formalism of quantum trajectories. As a result of our analysis, we found that noncommutativity can modify significantly the universe evolution, but cannot alter its singular behavior in the classical context. Quantum effects, on the other hand, can originate non-singular periodic universes in both commutative and noncommutative cases. The quantum noncommutative model is shown to present interesting properties, as the capability to give rise to non-trivial dynamics in situations where its commutative counterpart is necessarily static.Comment: 22 pages, 5 figures, substantial changes in the presentation, results are the same, to appear in Physical Review

Sunyaev - Zel'dovich fluctuations from spatial correlations between clusters of galaxies

We present angular power spectra of the cosmic microwave background radiation anisotropy due to fluctuations of the Sunyaev-Zel'dovich (SZ) effect through clusters of galaxies. A contribution from the correlation among clusters is especially focused on, which has been neglected in the previous analyses. Employing the evolving linear bias factor based on the Press-Schechter formalism, we find that the clustering contribution amounts to 20-30% of the Poissonian one at degree angular scales. If we exclude clusters in the local universe, it even exceeds the Poissonian noise, and makes dominant contribution to the angular power spectrum. As a concrete example, we demonstrate the subtraction of the ROSAT X-ray flux-limited cluster samples. It indicates that we should include the clustering effect in the analysis of the SZ fluctuations. We further find that the degree scale spectra essentially depend upon the normalization of the density fluctuations, i.e., \sigma_8, and the gas mass fraction of the cluster, rather than the density parameter of the universe and details of cluster evolution models. Our results show that the SZ fluctuations at the degree scale will provide a possible measure of \sigma_8, while the arc-minute spectra a probe of the cluster evolution. In addition, the clustering spectrum will give us valuable information on the bias at high redshift, if we can detect it by removing X-ray luminous clusters.Comment: 11 pages, 4 figures, submitted to Astrophysical Journa

Danos provocados por Amblycerus dispar Sharp, 1885 (Coleoptera: Bruchidae) a semente de imbuzeiro (Spondias tuberosa Arruda).

O objetivo deste foi identificar o inseto que estava atacando as sementes de plantas nativas de imbuzeiro, como também avaliar os danos causados as sementes e a existência de plantas jovens na área de estudo

Aparente ausência de resistência cruzada entre algumas proteínas de Bacillus thuringiensis em Spodoptera frugiperda

Resumo

Lattice Model for water-solute mixtures

A lattice model for the study of mixtures of associating liquids is proposed. Solvent and solute are modeled by adapting the associating lattice gas (ALG) model. The nature of interaction solute/solvent is controlled by tuning the energy interactions between the patches of ALG model. We have studied three set of parameters, resulting on, hydrophilic, inert and hydrophobic interactions. Extensive Monte Carlo simulations were carried out and the behavior of pure components and the excess properties of the mixtures have been studied. The pure components: water (solvent) and solute, have quite similar phase diagrams, presenting: gas, low density liquid, and high density liquid phases. In the case of solute, the regions of coexistence are substantially reduced when compared with both the water and the standard ALG models. A numerical procedure has been developed in order to attain series of results at constant pressure from simulations of the lattice gas model in the grand canonical ensemble. The excess properties of the mixtures: volume and enthalpy as the function of the solute fraction have been studied for different interaction parameters of the model. Our model is able to reproduce qualitatively well the excess volume and enthalpy for different aqueous solutions. For the hydrophilic case, we show that the model is able to reproduce the excess volume and enthalpy of mixtures of small alcohols and amines. The inert case reproduces the behavior of large alcohols such as, propanol, butanol and pentanol. For last case (hydrophobic), the excess properties reproduce the behavior of ionic liquids in aqueous solution.Comment: 28 pages, 13 figure

Efeito do sistema de manejo sob o comportamento em pastejo de cabras leiteiras.

O experimento foi conduzido na Embrapa Caprinos para avaliar o efeito do pastejo restrito (8 às 16 horas)e do pastejo em período integral sobre o comportamento em pastejo de caprinos leiteiros. Foram utilizadas cabras das raças Saanen e Anglo-nubiana. As variáveis analisadas foram os tempos de pastejo, de ruminação, em ócio e de permanência no sol e na sombra. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2 x 2 (dois tipos de manejo e duas raças), com cinco repetições. O manejo e a raça influenciaram o tempo de permanência na sombra. As cabras submetidas ao pastejo integral passaram menos tempo na sombra do que as cabras em pastejo restrito. As cabras Saanen permaneceram 24% mais tempo na sombra que das cabras Anglonubianas (p<0,05). Não houve efeito significatico de manejo sobre os tempos de ruminação e ócio. As cabras mantidas 24 horas no pasto apresentaram 3,5 horas a mais de pastejo do que as cabras em pastejo restrito, possivelmente afetando de forma positiva o consumo e a produção de leite. Effect of managment systems on grazing behaviour in dairy goats. Abstract: The experiment was carried out at Embrapa Caprinos to evaluate the effect of restricted grazing (8-16hrs) and integral grazing period on grazing behaviour in dairy goats. Saanen and Anglo-nubian goats were used. The variables analized were grazing time, rumination time, idleness time and time under sun and time under natural shade. The experimental design was completely randomized in a 2 x 2 arrangment (managments and breeds), with five replications.The managment systems is affected the time of grazing under natural shade (p<0,05). The goats on restricted grazing spent more time on share than goat on integral grazing. The Saanen goats stayed 24% more time under natural shade than Anglo-nubian goats (p <0,05).The managment systems didn't effect the rumination and ideleness time. It was founf effect of managment systems under grazing time (p<0,05). The percentage of time spent grazing was 3,5 hour more on integral grazing than on restricted grazing (p<0,05).The increase in grazing time under integral grazing had a positive affect on intake and milk production

Noncommutative Conformally Coupled Scalar Field Cosmology and its Commutative Counterpart

We study the implications of a noncommutative geometry of the minisuperspace variables for the FRW universe with a conformally coupled scalar field. The investigation is carried out by means of a comparative study of the universe evolution in four different scenarios: classical commutative, classical noncommutative, quantum commutative, and quantum noncommutative, the last two employing the Bohmian formalism of quantum trajectories. The role of noncommutativity is discussed by drawing a parallel between its realizations in two possible frameworks for physical interpretation: the NC-frame, where it is manifest in the universe degrees of freedom, and in the C-frame, where it is manifest through theta-dependent terms in the Hamiltonian. As a result of our comparative analysis, we find that noncommutative geometry can remove singularities in the classical context for sufficiently large values of theta. Moreover, under special conditions, the classical noncommutative model can admit bouncing solutions characteristic of the commutative quantum FRW universe. In the quantum context, we find non-singular universe solutions containing bounces or being periodic in the quantum commutative model. When noncommutativity effects are turned on in the quantum scenario, they can introduce significant modifications that change the singular behavior of the universe solutions or that render them dynamical whenever they are static in the commutative case. The effects of noncommutativity are completely specified only when one of the frames for its realization is adopted as the physical one. Non-singular solutions in the NC-frame can be mapped into singular ones in the C-frame.Comment: explanations added, references include

Enhancing the Accuracy of Ab Initio Molecular Dynamics by Fine Tuning of Effective Two-Body Interactions: Acetonitrile as a Test Case

Grimme’s dispersion-corrected density functional theory (DFT-D) methods have emerged among the most practical approaches to perform accurate quantum mechanical calculations on molecular systems ranging from small clusters to microscopic and mesoscopic samples, i.e., including hundreds or thousands of molecules. Moreover, DFT-D functionals can be easily integrated into popular ab initio molecular dynamics (MD) software packages to carry out first-principles condensed-phase simulations at an affordable computational cost. Here, starting from the well-established D3 version of the dispersion-correction term, we present a simple protocol to improve the accurate description of the intermolecular interactions of molecular clusters of growing size, considering acetonitrile as a test case. Optimization of the interaction energy was performed with reference to diffusion quantum Monte Carlo calculations, successfully reaching the same inherent accuracy of the latter (statistical error of ∼0.1 kcal/mol per molecule). The refined DFT-D3 model was then used to perform ab initio MD simulations of liquid acetonitrile, again showing significant improvements toward available experimental data with respect to the default correction