Veneziano ghost, modified gluon propagator, and gauge copies in QCD

In this short note, we come back to the recent proposal put forward by Kharzeev and Levin [Phys. Rev. Lett. 114, 242001 (2015)], in which they phenomenologically couple the nonperturbative Veneziano ghost to the perturbative gluon, leading to a modified gluon propagator (the "glost") of the Gribov type, with complex poles. As such, a possible link was made between the QCD topological theta-vacuum (Veneziano ghost) and color confinement (no physically observable gluons). We discuss some subtleties concerning gauge (Becchi-Rouet-Stora-Tuytin) invariance of this proposal, related to the choice of Feynman gauge. We draw particular attention to the incompatibility in the longitudinal sector with available nonperturbative results for the linear covariant gauge. We furthermore provide an example in the Landau gauge of a similar phenomenological vertex that also describes the necessary Veneziano ghost but does not affect the Landau gauge gluon propagator

The state of Portuguese research in economics: an anlysis based on publications in international journals

In this paper I analyze the state of Portuguese research in Economics based on publications in international journals for the period of 1986 to 2000. I find that scientific production is increasing but productivity remains low. I also provide a revealing characterization of the production habits of Portuguese researchers by answering the following questions: where do Portuguese researchers publish? who are the most active publishers? how often do they publish? how much do they collaborate? what is their background? Finally, I analyze the impact of that research based on citation counts.research in economics, sociology of economics, citation analysis

Vulnerability of Currency Pegs: Evidence from Brazil

This paper analyses predictions of a simple model of currency crises in which the peg will be abandoned when the currency overvaluation hits a certain threshold, unknown to the agents. Due to learning about the threshold, some features usually observed in the data and identified with models with multiple equilibria arise in the model. But the model yields distinctive predictions about the behaviour of the probability and the expected magnitude of a currency devaluation. The paper identifies the probability and expected magnitude of a devaluation of Brazilian Real in the period leading up to the end of the Brazilian pegged exchange rate regime, using data on exchange rate options. The empirical results are consistent with model predictions.Currency crises, exchange rate, options, probability of devaluation, devaluation size

Light radioactive nuclei capture reactions with phenomenological potential models

Light radioactive nuclei play an important role in many astrophysical environments. Due to very low cross sections of some neutron and proton capture reactions by these radioactive nuclei at energies of astrophysical interest, direct laboratory measurements are very difficult. For radioactive nuclei such as 8Li and 8B, the direct measurement of neutron capture reactions is impossible. Indirect methods have been applied to overcome these difficulties. In this work we will report on the results and discussion of phenomenological potential models used to determine some proton and neutron capture reactions. As a test we show the results for the 16O(p,g)17F_gs(5/2+) and 16O(p,g)17F_ex(1/2+) capture reactions.We also computed the nucleosynthesis cross sections for the 7Li(n,g)8Li, 8Li(n,g)9Li and 8B(p,g)9C capture reactions.Comment: Invited talk at Nuclear Physics Meeting in Brazil (2009). To be published at AIP conference proceeding