5,945 research outputs found

    Galactic Collapse of Scalar Field Dark Matter

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    We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies.Comment: 4 pages, 3 figue

    Generalized Chaplygin Gas, Accelerated Expansion and Dark Energy-Matter Unification

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    We consider the scenario emerging from the dynamics of a generalized dd-brane in a (d+1,1)(d+1, 1) spacetime. The equation of state describing this system is given in terms of the energy density, ρ\rho, and pressure, pp, by the relationship p=A/ραp = - A/\rho^{\alpha}, where AA is a positive constant and 0<α10 < \alpha \le 1. We discuss the conditions under which homogeneity arises and show that this equation of state describes the evolution of a universe evolving from a phase dominated by non-relativistic matter to a phase dominated by a cosmological constant via an intermediate period where the effective equation of state is given by p=αρp = \alpha \rho.Comment: 5 pages, 4 figures, revte

    Back reaction of a long range force on a Friedmann-Robertson-Walker background

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    It is possible that there may exist long-range forces in addition to gravity. In this paper we construct a simple model for such a force based on exchange of a massless scalar field and analyze its effect on the evolution of a homogeneous Friedmann-Robertson-Walker cosmology. The presence of such an interaction leads to an equation of state characterized by positive pressure and to resonant particle production similar to that observed in preheating scenarios.Comment: 14 pages, 6 color Postscript figures, LaTe

    hCG administration in Saanem goats inseminated following synchronized estrus.

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    Proceedings of the 28th Annual Meeting of The Brazilian Embryo Technology Society - SBTE, Natal, RN, Brasil, ago. 2014

    Diversidade florística em quintais agroflorestais de agroecossistemas familiares da comunidade Nova Canaã, Rio Preto da Eva-AM.

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    Este trabalho teve por objetivo verificar a diversidade de espécies cultivadas em pomares caseiros de agroecossistemas, onde trabalhavam agricultores familiares da comunidade Vila Canaã

    Levantamento de espécies frutíferas em área de várzea do Município de Parintins - Amazonas.

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    Este trabalho buscou identificar as espécies frutíferas que são encontradas nos quintais florestais em áreas de várzeas e descrever a sua importância e a sua utilização pelos ribeirinhos e agricultores do município de Parintins ? AM
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