Vertex operators and soliton solutions of affine Toda model with U(2) symmetry

The symmetry structure of the non-Abelian affine Toda model based on the coset SL(3)/SL(2) circle times U(1) is studied. It is shown that the model possess non-Abelian Noether symmetry closing into a q-deformed SL(2) circle times U(1) algebra. Specific two-vertex soliton solutions are constructed.

Pure spinor vertex operators in Siegel gauge and loop amplitude regularization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Finite dimensional vertex

The spectrum of linearized excitations of the Type IIB SUGRA on AdS(5) x S-5 contains both unitary and non-unitary representations. Among the non-unitary, some are finite-dimensional. We explicitly construct the pure spinor vertex operators for a family of such finite-dimensional representations. The construction can also be applied to in finite-dimensional representations, including unitary, although it becomes in this case somewhat less explicit.

Cornering the unphysical vertex

In the classical pure spinor worldsheet theory of AdS(5) x S-5 there are some vertex operators which do not correspond to any physical excitations. We study their flat space limit. We find that the BRST operator of the worldsheet theory in flat space-time can be nontrivially deformed without deforming the worldsheet action. Some of these deformations describe the linear dilaton background. But the deformation corresponding to the nonphysical vertex differs from the linear dilaton in not being worldsheet parity even. The nonphysically deformed worldsheet theory has nonzero beta-function at one loop. This means that the classical Type IIB SUGRA backgrounds are not completely characterized by requiring the BRST symmetry of the classical worldsheet theory; it is also necessary to require the vanishing of the one-loop beta-function.

Measurement of B(B)over-bar angular correlations based on secondary vertex reconstruction at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Upland rice yield as affected by previous summer crop rotation (soybean or upland rice) and glyphosate management on cover crops

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Historical land-cover/use in different slope and riparian buffer zones in watersheds of the state of São Paulo, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

GHOST POLES IN THE NUCLEON PROPAGATOR - VERTEX CORRECTIONS AND FORM-FACTORS

Vertex corrections are taken into account in the Schwinger-Dyson equation for the nucleon propagator in a relativistic field theory of fermions and mesons. The usual Hartree-Fock approximation for the nucleon propagator is known to produce the appearance of complex (ghost) poles which violate basic theorems of quantum field theory. In a theory with vector mesons there are vertex corrections that produce a strongly damped vertex function in the ultraviolet. One set of such corrections is known as the Sudakov form factor in quantum electrodynamics. When the Sudakov form factor generated by massive neutral vector mesons is included in the Hartree-Fock approximation to the Schwinger-Dyson equation for the nucleon propagator, the ghost poles disappear and consistency with basic requirements of quantum field theory is recovered.

Nitrogen management in maize cover crop rotations

Winter cover crops can affect N nutrition of the following maize crop. Although legumes have been recommend for maize rotations, in tropical areas grasses may be more interesting because they provide a longer protection of soil surface. Legumes can add N to the system and grasses can compete with maize for the available nutrient. An experiment was conducted in Botucatu, São Paulo State, Brazil, to study N dynamics in the soil surface straw-maize system as affected by N fertilization management and species included in the no-till rotation. Treatments were fallow, black oat (Avena strigosa), pearl millet (Pennisetum glaucum), white lupins (Lupinus albus), black oat fertilized with N. and pearl millet fertilized with N. Maize was grown afterwards in the same plots, receiving 0.0, 60.0 and 120.0 kg ha(-1) of N sidedressed 30 days after plant emergence. Soil, straw and maize samples were taken periodically. The highest corn yields were observed when it was cropped after pearl millet fertilized with N. Nitrogen side dressed application up to 120 kg ha(-1) was not able to avoid corn yield decrease caused by black oat. Grasses can be recommended in maize rotations in tropical areas, provided they receive nitrogen fertilizer and show no allelopathy. Due to its higher ON ratio and dry matter yield they are better than legumes, protecting the soil surface for a longer period. Pearl millet is particularly interesting because it enhances N use efficiency by the following maize crop. For a better N availability/demand synchronism, the cover crops should be desiccated right before maize planting.

Early development and nutrition of cover crop species as affected by soil compaction

A good cover crop should have a vigorous early development and a high potential for nutrient uptake that can be made available to the next crop. In tropical areas with relatively dry winters drought tolerance is also very important. An experiment was conducted to evaluate the early development and nutrition of six species used as cover crops as affected by sub-superficial compaction of the soil. The plants (oats, pigeon pea, pearl millet, black mucuna, grain sorghum, and blue lupin) were grown in pots filled with soil subjected to different subsurface compaction levels (bulk densities of 1.12, 1.16, and 1.60 mg m(-3)) for 39 days. The pots had an internal diameter of 10 cm and were 33.5 cm deep. Grasses were more sensitive to soil compaction than leguminous plants during the initial development. Irrespective of compaction rates, pearl millet and grain sorghum were more efficient in recycling nutrients. These two species proved to be more appropriate as cover crops in tropical regions with dry winters, especially if planted shortly before spring.

Leaching of nitrate and ammonium from cover crop straws as affected by rainfall

Nitrogen (N) mineralization dynamics in no-till systems is affected, among other factors, by N amount and quality in the mulch and by climatic conditions. Leaching of NO3-N and NH4-N from six plant species used as soil cover crops in tropical environments were evaluated when the straw was submitted to rainfall after chemical desiccation. Millet (Pennisetum glaucum), guinea sorghum (Sorghum vulgare), black oat (Avena strigosa), triticale (Triticum secale), Indian hemp (Crotalaria juncea), and brachiaria (Brachiaria decumbens) were grown in a greenhouse, in Botucatu-SP, Brazil. Forty-five days after emergence, the plants were cut at the root collar, oven-dried, and submitted to simulated rainfalls of 4.4, 8.7, 17.04, 34.9, and 69.8 mm, considering an amount of straw equivalent to 8 t ha(-1) of dry matter. The amounts of N-NO3- extracted from the straw by rainwater were very small. However, accumulated rainfall around 70 mm caused ammonium leaching ranging from 2.5 to 9.5kg ha(-1), depending on the species. Plant residues of triticale and black oat (grasses) and Indian hemp (legume) showed high N leaching intensity with the first rains after chemical desiccation. The amount of N leached from straw was highly correlated with N tissue content.

The use of U-isotopes on the study of a weathered cover in Parana basin, Brazil

This paper describes the results of a study involving the sampling of a soil profile developed over sandstone from Itarare Sub-Group at the Parana sedimentary basin, Brazil. It was carried out to integrate chemical and U-isotopes data in order to improve the knowledge of the weathering processes acting in the area. U-238 and its daughter U-234 proved to be important tools for evaluating physical and chemical alteration, allowing to suggest a possible timescale for the development of the more superficial soil horizons.

Estimation of water transit time in soils under Amazon forest cover using variations in sigma18O values.

In an attempt to estimate the soil-water transit time using the variation in 18O values, a statistical model was used. This model is based on linear regression analysis applied to the values observed for soil water and rain water. The time obtained from these correlations represents the mean time necessary for the water to run from one collecting point to the next.-from Authors