6,368 research outputs found
On the time spent in the red by a refracted L\'evy risk process
In this paper, we introduce an insurance ruin model with adaptive premium
rate, thereafter refered to as restructuring/refraction, in which classical
ruin and bankruptcy are distinguished. In this model, the premium rate is
increased as soon as the wealth process falls into the red zone and is brought
back to its regular level when the process recovers. The analysis is mainly
focused on the time a refracted L\'evy risk process spends in the red zone
(analogous to the duration of the negative surplus). Building on results from
Kyprianou and Loeffen (2010) and Loeffen et al. (2012), we identify the
distribution of various functionals related to occupation times of refracted
spectrally negative L\'evy processes. For example, these results are used to
compute the probability of bankruptcy and the probability of Parisian ruin in
this model with restructuring
Hydrothermal coupling in a rough fracture
Heat exchange during laminar flow is studied at the fracture scale on the
basis of the Stokes equation. We used a synthetic aperture model (a self-affine
model) that has been shown to be a realistic geometrical description of the
fracture morphology. We developed a numerical modelling using a finite
difference scheme of the hydrodynamic flow and its coupling with an
advection/conduction description of the fluid heat. As a first step,
temperature within the surrounding rock is supposed to be constant. Influence
of the fracture roughness on the heat flux through the wall, is estimated and a
thermalization length is shown to emerge. Implications for the
Soultz-sous-For\^{e}ts geothermal project are discussed
Between order and disorder: a 'weak law' on recent electoral behavior among urban voters?
A new viewpoint on electoral involvement is proposed from the study of the
statistics of the proportions of abstentionists, blank and null, and votes
according to list of choices, in a large number of national elections in
different countries. Considering 11 countries without compulsory voting
(Austria, Canada, Czech Republic, France, Germany, Italy, Mexico, Poland,
Romania, Spain and Switzerland), a stylized fact emerges for the most populated
cities when one computes the entropy associated to the three ratios, which we
call the entropy of civic involvement of the electorate. The distribution of
this entropy (over all elections and countries) appears to be sharply peaked
near a common value. This almost common value is typically shared since the
1970's by electorates of the most populated municipalities, and this despite
the wide disparities between voting systems and types of elections. Performing
different statistical analyses, we notably show that this stylized fact reveals
particular correlations between the blank/null votes and abstentionists ratios.
We suggest that the existence of this hidden regularity, which we propose to
coin as a `weak law on recent electoral behavior among urban voters', reveals
an emerging collective behavioral norm characteristic of urban citizen voting
behavior in modern democracies. Analyzing exceptions to the rule provide
insights into the conditions under which this normative behavior can be
expected to occur.Comment: Version 1: main text 19 pages, 13 figures, 2 tables; Supporting
Information: 19 pages. Version 2: minor correction
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