Quantum Singularities in Horava-Lifshitz Cosmology

The recently proposed Horava-Lifshitz (HL) theory of gravity is analyzed from the quantum cosmology point of view. By employing usual quantum cosmology techniques, we study the quantum Friedmann-Lemaitre-Robertson-Walker (FLRW) universe filled with radiation in the context of HL gravity. We find that this universe is quantum mechanically nonsingular in two different ways: the expectation value of the scale factor $(t)$ never vanishes and, if we abandon the detailed balance condition suggested by Horava, the quantum dynamics of the universe is uniquely determined by the initial wave packet and no boundary condition at $a=0$ is indeed necessary.Comment: 13 pages, revtex, 1 figure. Final version to appear in PR

Quantum singularities in a model of f(R) Gravity

The formation of a naked singularity in a model of f(R) gravity having as source a linear electromagnetic field is considered in view of quantum mechanics. Quantum test fields obeying the Klein-Gordon, Dirac and Maxwell equations are used to probe the classical timelike naked singularity developed at r=0. We prove that the spatial derivative operator of the fields fails to be essentially self-adjoint. As a result, the classical timelike naked singularity remains quantum mechanically singular when it is probed with quantum fields having different spin structures.Comment: 12 pages, final version. Accepted for publication in EPJ

n-Dimensional FLRW Quantum Cosmology

We introduce the formalism of quantum cosmology in a Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe of arbitrary dimension filled with a perfect fluid with $p=\alpha\rho$ equation of state. First we show that the Schutz formalism, developed in four dimensions, can be extended to a n-dimensional universe. We compute the quantum representant of the scale factor $a(t)$, in the Many-Worlds, as well as, in the de Broglie-Bohm interpretation of quantum mechanics. We show that the singularities, which are still present in the n-dimensional generalization of FLRW universe, are excluded with the introduction of quantum theory. We quantize, via the de Broglie-Bohm interpretation of quantum mechanics, the components of the Riemann curvature tensor in a tetrad basis in a n-dimensional FLRW universe filled with radiation ($p=\frac{1}{n-1}\rho$). We show that the quantized version of the Ricci scalar are perfectly regular for all time $t$. We also study the behavior of the energy density and pressure and show that the ratio $_L/_L$ tends to the classical value $1/(n-1)$ only for $n=4$, showing that $n=4$ is somewhat privileged among the other dimensions. Besides that, as $n\to\infty$, $_L/_L\to 1$.Comment: 12 pages, revtex, minor modification

Classical and Quantum Equations of Motion for a BTZ Black String in AdS Space

We investigate gravitational collapse of a $(3+1)$-dimensional BTZ black string in AdS space in the context of both classical and quantum mechanics. This is done by first deriving the conserved mass per unit length of the cylindrically symmetric domain wall, which is taken as the classical Hamiltonian of the black string. In the quantum mechanical context, we take primary interest in the behavior of the collapse near the horizon and near the origin (classical singularity) from the point of view of an infalling observer. In the absence of radiation, quantum effects near the horizon do not change the classical conclusions for an infalling observer, meaning that the horizon is not an obstacle for him/her. The most interesting quantum mechanical effect comes in when investigating near the origin. First, quantum effects are able to remove the classical singularity at the origin, since the wave function is non-singular at the origin. Second, the Schr\"odinger equation describing the behavior near the origin displays non-local effects, which depend on the energy density of the domain wall. This is manifest in that derivatives of the wavefunction at one point are related to the value of the wavefunction at some other distant point.Comment: 9 pages, 1 figure. Minor Clarification and corrections. Accepted for Publication in JHE

Manual de identificação de plantas daninhas da cultura da soja.

Família Amaranthaceae: Alternanthera tenella; Amaranthus deflexus; Amaranthus hybridus; Amaranthus spinosus; Amaranthus viridis. Família Asteraceae (Compositae): Acanthospermum hispidum; Acanthospermum australe; Ageratum conyzoides; Emilia sonchifolia; Conyza spp.; Bidens spp.; Galinsoga parviflora; Melampodium perfoliatum; Parthenium hysterophorus; Porophyllum ruderale; Senecio brasiliensis; Siegesbeckia orientalis; Sonchus oleraceus; Tridax procumbens; Família Brassicaceae: Coronopus didymus; Raphanus raphanistrum; Família Commelinaceae: Commelina benghalensis; Murdannia nudiflora. Família Convolvulaceae: Ipomoea grandifolia; Ipomoea nil; Ipomoea purpúrea; Família Euphorbiaceae: Chamaesyce hirta; Chamaesyce hyssopifolia; Croton glandulosus; Euphorbia heterophylla; Phyllanthus tenellus. Família Fabaceae; Desmodium tortuosum; Senna obtusifolia. Família Lamiaceae: Hyptys suaveolens; Leonotis nepetifolia; Leonurus sibiricus; Família Malvaceae; Sida rhombifolia. Família Poaceae: Avena fátua; Brachiaria brizantha; Brachiaria decumbens; Brachiaria plantaginea; Cenchrus echinatus; Chloris spp.; Digitaria insularis; Digitaria spp.; Echinochloa colonum; Eleusine indica; Lolium multiflorum; Panicum maximum; Pennisetum setosum; Rhynchelytrum repens; Setaria geniculata; Sorghum halepense; Família Portulacaceae: Portulaca oleracea; Talinum paniculatum. Família Rubiaceae: Richardia brasiliensis; Spermacoce latifólia; Spermacoce vertticilata; Família Sapindaceae Cardiospermum halicacabum; Família Solanaceae ; Nicandra physaloides; Solanum americanum. Plantas Daninhas resistentes a herbicidas. Espécies resistentes a herbicidas de diferentes mecanismos de ação, relatadas no Brasil. Glossário de termos botânicos.bitstream/item/126196/1/manual-de-identificacao-de-plantas-daninhas.pdf2. ed

Avaliação fitossociológica da comunidade infestante em áreas de transição para o café orgânico.

Objetivou-se com este trabalho verificar os efeitos dos insumos orgânicos e convencionais na dinâmica de plantas daninhas da lavoura durante o primeiro e o segundo ano de transição agroecológica. Para isso, montou-se um experimento em um cafezal de seis anos, onde iniciou-se a transição para o sistema de cultivo orgânico. A espécie mais importante no primeiro ano da transição, na maioria das áreas avaliadas, foi Ageratum conyzoides; no segundo ano ocorreu considerável mudança na relação de dominância entre as espécies, destacando-se Leunurus sibiricus na maior parte das áreas estudadas. Ocorreu também aumento do número de espécies presentes na maioria das áreas de um ano para o outro. No segundo ano de transição observou-se decréscimo na diversidade de espécies em relação ao primeiro ano. Dessa forma, pode-se concluir que nos dois anos de avaliação verificaram-se mudanças no número, na diversidade e na relação de importância entre as espécies de um ano para o outro