Boundless Skepticism and the Five Modes

There is a difference between the tasks of interpreting Sextus Empiricus and contesting his arguments. Usually, one does the latter relying on some version of the former. Though this seems obvious, it is easy to make mistakes in this endeavor. From this point, I draw two basic recommendations which we should follow, lest we take Sextus to hold implausible positions regarding his Five Modes. However, these recommendations lead us to interpret Sextus’ Pyrrhonism as a limited skepticism. In the final section, as I suggest a counter-example to this commitment, I reconsider the notion of infinite in the Five Modes to better explain interpretation and criticism of Sextus’ arguments

What constrains Africa's exports?

This paper examines the effects of transit, documentation, and ports and customs delays on Africa’s exports. The authors find that transit delays have the most economically and statically significant effect on exports. A one-day reduction in inland travel times leads to a 7 percent increase in exports. Put another way, a one-day reduction in inland travel times translates to a 1.5 percentage point decrease in all importing-country tariffs. By contrast, longer delays in the other areas have a far smaller impact on trade. The analysis controls for the possibility that greater trade leads to shorter delays in three ways. First, it examines the effect of trade times on exports of new products. Second, it evaluates the effect of delays in a transit country on the exports of landlocked countries. Third, it examines whether delays affect time-sensitive goods relatively more. The authors show that large transit delays are relatively more harmful because of high within-country variation

New Spinor Fields on Lorentzian 7-Manifolds

This paper deals with the classification of spinor fields according to the bilinear covariants in 7 dimensions. The previously investigated Riemannian case is characterized by either one spinor field class, in the real case of Majorana spinors, or three non-trivial classes in the most general complex case. In this paper we show that by imposing appropriate conditions on spinor fields in 7d manifolds with Lorentzian metric, the formerly obtained obstructions for new classes of spinor fields can be circumvented. New spinor fields classes are then explicitly constructed. In particular, on 7-manifolds with asymptotically flat black hole background, these spinors can define a generalized current density which further defines a time Killing vector at the spatial infinity.Comment: 13 pages, improved, to match the final version accepted in JHE

Study of models of the sine-Gordon type in flat and curved spacetime

We study a new family of models of the sine-Gordon type, starting from the sine-Gordon model, including the double sine-Gordon, the triple one, and so on. The models appears as deformations of the starting model, with the deformation controlled by two parameters, one very small, used to control a linear expansion on it, and the other, which specifies the particular model in the family of models. We investigate the presence of topological defects, showing how the solutions can be constructed explicitly from the topological defects of the sine-Gordon model itself. In particular, we delve into the double sine-Gordon model in a braneworld scenario with a single extra dimension of infinite extent, showing that a stable gravity scenario is admissible. Also, we briefly show that the deformation procedure can be used iteratively, leading to a diversity of possibilities to construct families of models of the sine-Gordon type.Comment: 8 pages, 7 figures; Title changed, author and new results included; version to appear in EPJ