24,605 research outputs found
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
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