5,415 research outputs found
Towards Relativistic Skyrmions
We revisit baryons in the Skyrme model. Starting from static baryons in the
helicity eigenstates, we generalize their wavefunctions to the non-static and
relativistic regime. A new representation for gamma matrices in the soliton
collective space is constructed and the corresponding Dirac equation is
obtained. As an example, we draw consideration on how to apply this new
representation on the calculus of vector current vacuum expectation values for
baryon states of spin and isospin half and arbitrary momenta and we show how
elastic form factors can be derived.Comment: 7 pages, 7th Conference Mathematical Methods in Physics - Londrina
2012, Rio de Janeiro, Brazi
Production of negative parity baryons in the holographic Sakai-Sugimoto model
We extend our investigation of resonance production in the Sakai-Sugimoto
model to the case of negative parity baryon resonances. Using holographic
techniques we extract the generalized Dirac and Pauli baryon form factors as
well as the helicity amplitudes for these baryonic states. Identifying the
first negative parity resonance with the experimentally observed S_{11}(1535),
we find reasonable agreement with experimental data from the JLab-CLAS
collaboration. We also estimate the contribution of negative parity baryons to
the proton structure functions.Comment: 1+30 pages, 8 figures. v3: typos corrected, references added, section
2 and 3 shortened, improved discussion of helicity amplitudes and comparison
with experimental result
Generalized baryon form factors and proton structure functions in the Sakai-Sugimoto model
We investigate the production of positive parity baryon resonances in proton
electromagnetic scattering within the Sakai-Sugimoto model. The latter is a
string model for the non-perturbative regime of large QCD. Using
holographic techniques we calculate the generalized Dirac and Pauli form
factors that describe resonance production. We use these results to estimate
the contribution of resonance production to the proton structure functions.
Interestingly, we find an approximate Callan-Gross relation for the structure
functions in a regime of intermediate values of the Bjorken variable.Comment: v3: 38 pages, 25 figures. We added a new subsection in order to
compare our results with experimental data. To appear in Nucl. Phys.
Relativistic baryons in the Skyrme model revisited
Starting from the static Skyrme model baryon wavefunctions in their helicity eigenstates, we generalize the wavefunctions to the non-static and relativistic regime. A new representation for gamma matrices in the SU(2) collective space is constructed and the corresponding Dirac equation is obtained. Finally, we comment on possible applications of our results to the calculation of matrix elements of baryonic currents and the corresponding form factors in the relativistic case
Competitividade do etanol em áreas tradicional e de expansão na região centro-sul.
A cadeia do agronegócio da cana-de-açúcar é uma das que mais tem contribuído para o crescimento econômico do Brasil, na safra de 2010-2011 foi plantado 8,1 milhões de hectares produzindo 28 bilhões de litros de etanol e para a safra de 2011-2012 a previsão é de 33 bilhões de litros de etanol, elevando o Brasil como o maior produtor mundial de etanol. Este trabalho tem como objetivo verificar a competitividade do etanol brasileiro através da Matriz de Análise Política- MAP considerando uma área de cultivo tradicional e outra área de expansão da cana-de-açúcar. O instrumental utilizado para essa análise foi a Matriz de Análise de Política - MAP desenvolvida por Monke e Pearson (1989), os resultados mostram que as lucratividades privada e social foram positivos, indicando competitividade e eficiência econômica, respectivamente, para as duas cadeias. A cadeia do etanol em área tradicional foi a mais competitiva e com maior eficiência econômica por apresentar maior valor em ambas lucratividades. As transferências associadas à produção para as cadeias apresentaram valores positivos. O maior valor positivo na cadeia da área de tradicional reflete os altos preços ou receitas privadas nessa cadeia, indicando que há transferência positiva da sociedade para o setor produtor
Toward an automated identification of Anastrepha fruit flies in the fraterculus group (Diptera, Tephritidae)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In this study, we assess image analysis techniques as automatic identifiers of three Anastrepha species of quarantine importance, Anastrepha fraterculus (Wiedemann), Anastrepha obliqua (Macquart), and Anastrepha sororcula Zucchi, based on wing and aculeus images. The right wing and aculeus of 100 individuals of each species were mounted on microscope slides, and images were captured with a stereomicroscope and light microscope. For wing image analysis, we used the color descriptor Local Color Histogram; for aculei, we used the contour descriptor Edge Orientation Autocorrelogram. A Support Vector Machine classifier was used in the final stage of wing and aculeus classification. Very accurate species identifications were obtained based on wing and aculeus images, with average accuracies of 94 and 95%, respectively. These results are comparable to previous identification results based on morphometric techniques and to the results achieved by experienced entomologists. Wing and aculeus images produced equally accurate classifications, greatly facilitating the identification of these species. The proposed technique is therefore a promising option for separating these three closely related species in the fraterculus group.In this study, we assess image analysis techniques as automatic identifiers of three Anastrepha species of quarantine importance, Anastrepha fraterculus (Wiedemann), Anastrepha obliqua (Macquart), and Anastrepha sororcula Zucchi, based on wing and aculeus455554558CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)09/54806-0; 14/16082-9sem informaçã
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