Antisymmetric tensor propagator with spontaneous Lorentz violation

In this work, we study the spontaneous Lorentz symmetry breaking due to an antisymmetric 2-tensor field in Minkowski spacetime. For a smooth quadratic potential, the spectrum of the theory exhibits massless and massive excitations. We show that the equations of motion for the free field obey some constraints which lead to the massive mode be non-propagating at leading order. Besides, there exists a massless mode in the theory which can be identified with the usual Kalb-Ramond field, carrying only one on-shell degree of freedom. The same conclusion holds when one analyses the pole structure of its Feynman propagator. A new complete set of spin-type operators is found, which was the requirement to evaluate the propagator of the Kalb-Ramond field modified by the presence of a nonzero vacuum expectation value responsible for the Lorentz violation.Comment: 13 pages. Some modifications to match published version in EuroPhysics Letter

Electromagnetic Structure of the Pion

In this work, we analyze the electromagnetic structure of the pion. We calculate its electromagnetic radius and electromagnetic form factor in low and intermediate momentum range. Such observables are determined by means of a theoretical model that takes into account the constituent quark and antiquark of the pion within the formalism of light-front field theory. In particular, we consider a nonsymmetrical vertex in this model, with which we calculate the electromagnetic form factor of the pion in an optimized way, so that we obtain a value closer to the experimental charge radius of the pion. The theoretical calculations are also compared with the most recent experimental data involving the pion electromagnetic form factor and the results show very good agreement.Comment: Paper with 4 pages, 1 figure, presented in XII HADRON PHYSICS Conference - to appear in AIP Conference Proceeding

Soft Law and competition policy: promoting competition through guidelines in Brazil

This paper examines the use of soft law in competition policy. The focus is on the guidelines issued by the Brazilian competition authority in order to foster a better understanding of the competition law and enforcement approaches. The economic agents and their legal advisors benefit from these measures, as they increase the predictability and transparency of competition enforcement, facilitate self-assessment, and improve legal certainty for business transactions that often involve high monetary sums. From previous experience, these guidelines are often well perceived by local competition community as there is an increasingly concern with the objective of gathering information from interested parties to facilitate the drafting of higher quality documents through public consultations.This paper examines the use of soft law in competition policy. The focus is on the guidelines issued by the Brazilian competition authority in order to foster a better understanding of the competition law and enforcement approaches. The economic agents and their legal advisors benefit from these measures, as they increase the predictability and transparency of competition enforcement, facilitate self-assessment, and improve legal certainty for business transactions that often involve high monetary sums. From previous experience, these guidelines are often well perceived by local competition community as there is an increasingly concern with the objective of gathering information from interested parties to facilitate the drafting of higher quality documents through public consultations

Cultivo do milho: plantio, espaçamento, densidade, quantidade de sementes.

bitstream/CNPMS/15602/1/Com_46.pd

Cultivares.

4. ed

Milho: como escolher a cultivar certa entre tantas alternativas.

bitstream/item/61040/1/Milho-escolher.pd