Gravitational Model of High Energy Particles in a Collimated Jet

Observations suggest that relativistic particles play a fundamental role in the dynamics of jets emerging from active galactic nuclei as well as in their interaction with the intracluster medium. However, no general consensus exists concerning the acceleration mechanism of those high energy particles. A gravitational acceleration mechanism is here proposed, in which particles leaving precise regions within the ergosphere of a rotating supermassive black hole produce a highly collimated flow. These particles follow unbound geodesics which are asymptotically parallel to the spin axis of the black hole and are characterized by the energy $E$, the Carter constant ${\cal Q}$ and zero angular momentum of the component $L_z$. If environmental effects are neglected, the present model predicts at distances of about 140 kpc from the ergosphere the presence of electrons with energies around 9.4 GeV. The present mechanism can also accelerate protons up to the highest energies observed in cosmic rays by the present experiments.Comment: 27 pages and 5 figures. Accepted for publication in Astrophysical Journal. arXiv admin note: text overlap with arXiv:1011.654

Field-induced phase transitions of repulsive spin-1 bosons in optical lattices

We study the phase diagram of repulsively interacting spin-1 bosons in optical lattices at unit filling, showing that an externally induced quadratic Zeeman effect may lead to a rich physics characterized by various phases and phase transitions. We find that the main properties of the system may be described by an effective field model, which provides the precise location of the phase boundaries for any dimension, being in excellent agreement with our numerical calculations for one-dimensional systems. Our work provides a quantitative guide for the experimental analysis of various types of field-induced quantum phase transitions in spin-1 lattice bosons. These transitions, which are precluded in spin-1/2 systems, may be realized using an externally modified quadratic Zeeman coupling, similar to recent experiments with spinor condensates in the continuum.Comment: 4 pages, 2 figure

The role of pressure anisotropy in the turbulent intracluster medium

In low-density plasma environments, such as the intracluster medium (ICM), the Larmour frequency is much larger than the ion-ion collision frequency. In such a case, the thermal pressure becomes anisotropic with respect to the magnetic field orientation and the evolution of the turbulent gas is more correctly described by a kinetic approach. A possible description of these collisionless scenarios is given by the so-called kinetic magnetohydrodynamic (KMHD) formalism, in which particles freely stream along the field lines, while moving with the field lines in the perpendicular direction. In this way a fluid-like behavior in the perpendicular plane is restored. In this work, we study fast growing magnetic fluctuations in the smallest scales which operate in the collisionless plasma that fills the ICM. In particular, we focus on the impact of a particular evolution of the pressure anisotropy and its implications for the turbulent dynamics of observables under the conditions prevailing in the ICM. We present results from numerical simulations and compare the results which those obtained using an MHD formalism.Comment: 7 pages, 14 figures, Journal of Physics: Conference Serie

Competição de linhagens de feijão-caupi avaliadas na área de influência de Petrolina e Juazeiro.

O objetivo deste trabalho foi avaliar o comportamento de 64 genótipos de feijão-caupi, em dois experimentos de densidades populacionais diferentes, em vários ambientes da região, tanto em regime irrigado, como de sequeiro, de forma a identificar e recomendar cultivares promissores para a região de influência do dipolo Petrolina, PE e Juazeiro, BA. Observou-se forte interação genótipo x ambiente para as variáveis analisadas. A média observada no experimento irrigado foi mais do que o dobro em relação aos experimentos de sequeiro, nas duas densidades populacionais, sendo de 693, 1.419 e 1.018 kg ha-1 para o cultivo em regime de sequeiro, irrigado e o conjunto dos ambientes na população de 200.000 plantas ha-1, respectivamente, enquanto as médias observadas para o experimento de 100.000 plantas ha-1 foram de 552, 1.313 e 823 kg ha-1, para as mesmas situações, respectivamente. O peso médio de 100 grãos foi de 19,8 g e de 20 g nas densidades de 200.000 e 100.000 plantas ha-1, respectivamente. A média para o caráter dias para a maturação foi em torno de 70 dias. Os genótipos BR 17 Gurguéia e Canapu foram os mais atacados por vírus. Linhagens que apresentavam valores próximos de 1,0 para as viroses, produtividade próxima dos valores superiores observados, peso de 100 grãos superior a 20 g e boa aparência de grãos foram selecionadas para avaliações em áreas de produtores, o que poderá resultar na recomendação de uma cultivar específica para a região

Comportamento agronômico e qualidade culinária de feijão-caupi no Vale do São Francisco.

Neste trabalho avaliou-se o comportamento de 64 linhagens e de quatro cultivares de feijão-caupi, em dois experimentos de densidades populacionais, em vários ambientes do Vale do São Francisco nos anos de 2004 e 2005, tanto em regime irrigado, como de sequeiro, visando a recomendação de cultivares para a região

Constraining the evolution of the CMB temperature with SZ measurements from Planck data

The CMB temperature-redshift relation, T_CMB(z)=T_0(1+z), is a key prediction of the standard cosmology, but is violated in many non standard models. Constraining possible deviations to this law is an effective way to test the LambdaCDM paradigm and to search for hints of new physics. We have determined T_CMB(z), with a precision up to 3%, for a subsample (104 clusters) of the Planck SZ cluster catalog, at redshift in the range 0.01-- 0.94, using measurements of the spectrum of the Sunyaev Zel'dovich effect obtained from Planck temperature maps at frequencies from 70 to 353 GHz. The method adopted to provide individual determinations of T_CMB(z) at cluster redshift relies on the use of SZ intensity change, Delta I_SZ(nu), at different frequencies, and on a Monte-Carlo Markov Chain approach. By applying this method to the sample of 104 clusters, we limit possible deviations of the form T_CMB(z)=T_0(1+z)^(1-beta) to be beta= 0.022 +/- 0.018, at 1 sigma uncertainty, consistent with the prediction of the standard model. Combining these measurements with previously published results we get beta=0.016+/-0.012.Comment: submitted to JCAP, 21 pages, 8 figure