11,024 research outputs found
Lensing Magnification and QSO-Galaxy Cross-Correlations: Observations, Theory and Simulations
We review observations and gravitational lensing theory related to the
magnification of background QSOs by intervening overdensities, and the induced
cross-correlation between sources and foreground galaxies. We pay special
attention to simulations, and present some preliminary results from high
resolution cluster simulations, which show the role of the halo core and
substructure on non-linear magnification. For massive clusters, deviations from
the weak gravitational lensing regime are significant on arcmin scales and
bellow. The accumulated knowledge in the field already shows that gravitational
lensing magnification is an important astrophysical and cosmological tool.Comment: 6 pages. Presented at "100 years of relativity -- international
conference on classical and quantum aspects of gravity and cosmology", 200
On duality of the noncommutative extension of the Maxwell-Chern-Simons model
We study issues of duality in 3D field theory models over a canonical
noncommutative spacetime and obtain the noncommutative extension of the
Self-Dual model induced by the Seiberg-Witten map. We apply the dual projection
technique to uncover some properties of the noncommutative Maxwell-Chern-Simons
theory up to first-order in the noncommutative parameter. A duality between
this theory and a model similar to the ordinary self-dual model is
estabilished. The correspondence of the basic fields is obtained and the
equivalence of algebras and equations of motion are directly verified. We also
comment on previous results in this subject.Comment: Revtex, 9 pages, accepted for publication PL
On the dimensional dependence of duality groups for massive p-forms
We study the soldering formalism in the context of abelian p-form theories.
We develop further the fusion process of massless antisymmetric tensors of
different ranks into a massive p-form and establish its duality properties. To
illustrate the formalism we consider two situations. First the soldering mass
generation mechanism is compared with the Higgs and Julia-Toulouse mechanisms
for mass generation due to condensation of electric and magnetic topological
defects. We show that the soldering mechanism interpolates between them for
even dimensional spacetimes, in this way confirming the Higgs/Julia-Toulouse
duality proposed by Quevedo and Trugenberger \cite{QT} a few years ago. Next,
soldering is applied to the study of duality group classification of the
massive forms. We show a dichotomy controlled by the parity of the operator
defining the symplectic structure of the theory and find their explicit
actions.Comment: Reference [8] has been properly place
Alternativas atuais e potenciais de suplementação alimentar de caprinos no semi-árido do Nordeste.
A caprinocultura na reglao semi-árida do Nordeste se caracteriza pela extensividade e por baixos nÃveis de produtividade decorrentes, principalmente, da acentuada variação estacional na oferta de forragem da caatinga, a qual constitui sua base alimentar. Existe um consenso quanto a necessidade de suplementar os animais nos perÃodos crÃticos, tanto com energia como com proteÃna. As alternativas atualmente disponÃveis, como a palma forrageira (Opuntia ficus indica Mill), os restolhos de cultura, e o capim buffel (Cenchrus ciliaris) sao volumosos de reduzido valor energético e são mais utilizados dentro de um enfoque de sobrevivência dos animais. Os suplementos de maior valor nutritivo são de uso limitado e apresentam problemas de economicidade. As perspectivas de uso da ureia, da leucena (Leucaena leucocephala (Lam.) de Wit) e do guandu (Cajanus cajan (L.) Millsp) na suplementaçao de caprinos no semi-árido, são discutidas com base no seu potencial como fontes de nutrientes e como alternativas adaptáveis à s condições agro-ecológicas e sócio-econômicas da região.bitstream/item/143279/1/07629.pdfTrabalho apresentado no II Seminário Nordestino de Caprinocultura, Recife, 1984
Fenotipagem para tolerância à deficiência hÃdrica.
Tem como objetivos: Identificar linhagens promissoras em condições de deficiência hÃdrica; Caracterizar os principais fatores fisiológicos e morfológicos responsáveis pela tolerância à deficiência hÃdrica; Conduzir populações segregantes e selecionar linhagens promissoras, em condições de deficiência hÃdrica; Fenotipar populações de mapeamento; e Avaliar a tolerância à deficiência hÃdrica das linhagens elites.Palestra - CONAFE
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