660 research outputs found
Equivalence between the Lovelock-Cartan action and a constrained gauge theory
We show that the four-dimensional Lovelock-Cartan action can be derived from
a massless gauge theory for the group with an additional BRST trivial
part. The model is originally composed by a topological sector and a BRST exact
piece and has no explicit dependence on the metric, the vierbein or a mass
parameter. The vierbein is introduced together with a mass parameter through
some BRST trivial constraints. The effect of the constraints is to identify the
vierbein with some of the additional fields, transforming the original action
into the Lovelock-Cartan one. In this scenario, the mass parameter is
identified with Newton's constant while the gauge field is identified with the
spin-connection. The symmetries of the model are also explored. Moreover, the
extension of the model to a quantum version is qualitatively discussed.Comment: 17 pages. No figures. Final version accepted for publication at the
EPJ
Quintais agroflorestais como estratégia de sustentabilidade ecológica e econômica.
Resumo: Um estudo preliminar no contexto sócio-histórico do Assentamento Fazenda Pirituba, na região de Itapeva-SP, evidenciou que os quintais agroflorestais (QAs), são alternativas criadas autonomamente pelos agricultores familiares assentados na busca da reprodução social das famílias (alimentação e acesso ao mercado através do PAA). O estudo dos QAs, na medida em que os resgata da invisibilidade, poderá qualificar seu desenho e manejo, além de subsidiar políticas públicas para assentamentos rurais
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