43,179 research outputs found
Dirac's hole theory versus quantum field theory
Dirac's hole theory and quantum field theory are usually considered
equivalent to each other. For models of a certain type, however, the
equivalence may not hold as we discuss in this Letter. This problem is closely
related to the validity of the Pauli principle in intermediate states of
perturbation theory.Comment: No figure
Scaling relations for diversity of languages
The distribution of living languages is investigated and scaling relations
are found for the diversity of languages as a function of the country area and
population. These results are compared with data from Ecology and from computer
simulations of fragmentation dynamics where similar scalings appear. The
language size distribution is also studied and shown to display two scaling
regions: (i) one for the largest (in population) languages and (ii) another one
for intermediate-size languages. It is then argued that these two classes of
languages may have distinct growth dynamics, being distributed on the sets of
different fractal dimensions.Comment: 10 pages, 4 figure
Emerging from Crisis: the Mediterranean Neighborhood
So far, developing countries like the countries of the Mediterranean region seem to have been far less affected by the and started to recover earlier crisis than industrial countries. However, the region faces several problems like high unemployment and high inflation in the long term due to higher government consumption.Mediterranean countries, economic crisis, economic recovery
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